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    15 October 2021, Volume 16 Issue 10 Previous Issue   
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    Axonal regeneration and sprouting as a potential therapeutic target for nervous system disorders
    Katherine L. Marshall, Mohamed H. Farah
    2021, 16 (10):  1901-1910.  doi: 10.4103/1673-5374.308077
    Abstract ( 293 )   PDF (2291KB) ( 221 )   Save
    Nervous system disorders are prevalent health issues that will only continue to increase in frequency as the population ages. Dying-back axonopathy is a hallmark of many neurologic diseases and leads to axonal disconnection from their targets, which in turn leads to functional impairment. During the course of many of neurologic diseases, axons can regenerate or sprout in an attempt to reconnect with the target and restore synapse function. In amyotrophic lateral sclerosis (ALS), distal motor axons retract from neuromuscular junctions early in the disease-course before significant motor neuron death. There is evidence of compensatory motor axon sprouting and reinnervation of neuromuscular junctions in ALS that is usually quickly overtaken by the disease course. Potential drugs that enhance compensatory sprouting and encourage reinnervation may slow symptom progression and retain muscle function for a longer period of time in ALS and in other diseases that exhibit dying-back axonopathy. There remain many outstanding questions as to the impact of distinct disease-causing mutations on axonal outgrowth and regeneration, especially in regards to motor neurons derived from patient induced pluripotent stem cells. Compartmentalized microfluidic chambers are powerful tools for studying the distal axons of human induced pluripotent stem cells-derived motor neurons, and have recently been used to demonstrate striking regeneration defects in human motor neurons harboring ALS disease-causing mutations. Modeling the human neuromuscular circuit with human induced pluripotent stem cells-derived motor neurons will be critical for developing drugs that enhance axonal regeneration, sprouting, and reinnervation of neuromuscular junctions. In this review we will discuss compensatory axonal sprouting as a potential therapeutic target for ALS, and the use of compartmentalized microfluidic devices to find drugs that enhance regeneration and axonal sprouting of motor axons. 
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    The role of gap junctions in cell death and neuromodulation in the retina
    Gergely Szarka, Márton Balogh, Ádám J. Tengölics, Alma Ganczer, Béla Völgyi, Tamás Kovács-Öller
    2021, 16 (10):  1911-1920.  doi: 10.4103/1673-5374.308069
    Abstract ( 132 )   PDF (684KB) ( 151 )   Save
    Vision altering diseases, such as glaucoma, diabetic retinopathy, age-related macular degeneration, myopia, retinal vascular disease, traumatic brain injuries and others cripple many lives and are projected to continue to cause anguish in the foreseeable future. Gap junctions serve as an emerging target for neuromodulation and possible regeneration as they directly connect healthy and/or diseased cells, thereby playing a crucial role in pathophysiology. Since they are permeable for macromolecules, able to cross the cellular barriers, they show duality in illness as a cause and as a therapeutic target. In this review, we take recent advancements in gap junction neuromodulation (pharmacological blockade, gene therapy, electrical and light stimulation) into account, to show the gap junction’s role in neuronal cell death and the possible routes of rescuing neuronal and glial cells in the retina succeeding illness or injury.
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    Don’t know what you got till it’s gone: microglial depletion and neurodegeneration
    David Graykowski, Eiron Cudaback
    2021, 16 (10):  1921-1927.  doi: 10.4103/1673-5374.308078
    Abstract ( 322 )   PDF (436KB) ( 217 )   Save
    In the central nervous system, immunologic surveillance and response are carried out, in large part, by microglia. These resident macrophages derive from myeloid precursors in the embryonic yolk sac, migrating to the brain and eventually populating local tissue prior to blood-brain barrier formation. Preserved for the duration of lifespan, microglia serve the host as more than just a central arm of innate immunity, also contributing significantly to the development and maintenance of neurons and neural networks, as well as neuroregeneration. The critical nature of these varied functions makes the characterization of key roles played by microglia in neurodegenerative disorders, especially Alzheimer’s disease, of paramount importance. While genetic models and rudimentary pharmacologic approaches for microglial manipulation have greatly improved our understanding of central nervous system health and disease, significant advances in the selective and near complete in vitro and in vivo depletion of microglia for neuroscience application continue to push the boundaries of research. Here we discuss the research efficacy and utility of various microglial depletion strategies, including the highly effective CSF1R inhibitor models, noteworthy insights into the relationship between microglia and neurodegeneration, and the potential for therapeutic repurposing of microglial depletion and repopulation.
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    Low-dose lipopolysaccharide as an immune regulator for homeostasis maintenance in the central nervous system through transformation to neuroprotective microglia
    Haruka Mizobuchi, Gen-Ichiro Soma
    2021, 16 (10):  1928-1934.  doi: 10.4103/1673-5374.308067
    Abstract ( 99 )   PDF (806KB) ( 198 )   Save
    Microglia, which are tissue-resident macrophages in the brain, play a central role in the brain innate immunity and contribute to the maintenance of brain homeostasis. Lipopolysaccharide is a component of the outer membrane of gram-negative bacteria, and activates immune cells including microglia via Toll-like receptor 4 signaling. Lipopolysaccharide is generally known as an endotoxin, as administration of high-dose lipopolysaccharide induces potent systemic inflammation. Also, it has long been recognized that lipopolysaccharide exacerbates neuroinflammation. In contrast, our study revealed that oral administration of lipopolysaccharide ameliorates Alzheimer’s disease pathology and suggested that neuroprotective microglia are involved in this phenomenon. Additionally, other recent studies have accumulated evidence demonstrating that controlled immune training with low-dose lipopolysaccharide prevents neuronal damage by transforming the microglia into a neuroprotective phenotype. Therefore, lipopolysaccharide may not a mere inflammatory inducer, but an immunomodulator that can lead to neuroprotective effects in the brain. In this review, we summarized current studies regarding neuroprotective microglia transformed by immune training with lipopolysaccharide. We state that microglia transformed by lipopolysaccharide preconditioning cannot simply be characterized by their general suppression of proinflammatory mediators and general promotion of anti-inflammatory mediators, but instead must be described by their complex profile comprising various molecules related to inflammatory regulation, phagocytosis, neuroprotection, anti-apoptosis, and antioxidation. In addition, microglial transformation seems to depend on the dose of lipopolysaccharide used during immune training. Immune training of neuroprotective microglia using low-dose lipopolysaccharide, especially through oral lipopolysaccharide administration, may represent an innovative prevention or treatment for neurological diseases; however more vigorous studies are still required to properly modulate these treatments.
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    Protein post-translational modifications after spinal cord injury
    Shuang Zhu, Bing-Sheng Yang, Si-Jing Li, Ge Tong, Jian-Ye Tan, Guo-Feng Wu, Lin Li, Guo-Li Chen, Qian Chen, Li-Jun Lin
    2021, 16 (10):  1935-1943.  doi: 10.4103/1673-5374.308068
    Abstract ( 127 )   PDF (952KB) ( 182 )   Save
    Deficits in intrinsic neuronal capacities in the spinal cord, a lack of growth support, and suppression of axonal outgrowth by inhibitory molecules mean that spinal cord injury almost always has devastating consequences. As such, one of the primary targets for the treatment of spinal cord injury is to develop strategies to antagonize extrinsic or intrinsic axonal growth-inhibitory factors or enhance the factors that support axonal growth. Among these factors, a series of individual protein level disorders have been identified during the generation of axons following spinal cord injury. Moreover, an increasing number of studies have indicated that post-translational modifications of these proteins have important implications for axonal growth. Some researchers have discovered a variety of post-translational modifications after spinal cord injury, such as tyrosination, acetylation, and phosphorylation. In this review, we reviewed the post-translational modifications for axonal growth, functional recovery, and neuropathic pain after spinal cord injury, a better understanding of which may elucidate the dynamic change of spinal cord injury-related molecules and facilitate the development of a new therapeutic strategy for spinal cord injury.
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    Proteolysis targeting chimera technology: a novel strategy for treating diseases of the central nervous system
    Ke Ma, Xiao-Xiao Han, Xiao-Ming Yang, Song-Lin Zhou
    2021, 16 (10):  1944-1949.  doi: 10.4103/1673-5374.308075
    Abstract ( 229 )   PDF (893KB) ( 213 )   Save
    Neurological diseases such as stroke, Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease are among the intractable diseases for which appropriate drugs and treatments are lacking. Proteolysis targeting chimera (PROTAC) technology is a novel strategy to solve this problem. PROTAC technology uses the ubiquitin-protease system to eliminate mutated, denatured, and harmful proteins in cells. It can be reused, and utilizes the protein destruction mechanism of the cells, thus making up for the deficiencies of traditional protein degradation methods. It can effectively target and degrade proteins, including proteins that are difficult to identify and bind. Therefore, it has extremely important implications for drug development and the treatment of neurological diseases. At present, the targeted degradation of mutant BTK, mHTT, Tau, EGFR, and other proteins using PROTAC technology is gaining attention. It is expected that corresponding treatment of nervous system diseases can be achieved. This review first focuses on the recent developments in PROTAC technology in terms of protein degradation, drug production, and treatment of central nervous system diseases, and then discusses its limitations. This review will provide a brief overview of the recent application of PROTAC technology in the treatment of central nervous system diseases. 
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    Axonal mRNA localization and local translation in neurodegenerative disease
    Jin-Xin Lu, Yang Wang, Yi-Jie Zhang, Mei-Fen Shen, Hai-Ying Li, Zheng-Quan Yu, Gang Chen
    2021, 16 (10):  1950-1957.  doi: 10.4103/1673-5374.308074
    Abstract ( 256 )   PDF (807KB) ( 174 )   Save
    The regulation of mRNA localization and local translation play vital roles in the maintenance of cellular structure and function. Many human neurodegenerative diseases, such as fragile X syndrome, amyotrophic lateral sclerosis, Alzheimer’s disease, and spinal muscular atrophy, have been characterized by pathological changes in neuronal axons, including abnormal mRNA translation, the loss of protein expression, or abnormal axon transport. Moreover, the same protein and mRNA molecules have been associated with variable functions in different diseases due to differences in their interaction networks. In this review, we briefly examine fragile X syndrome, amyotrophic lateral sclerosis, Alzheimer’s disease, and spinal muscular atrophy, with a focus on disease pathogenesis with regard to local mRNA translation and axon transport, suggesting possible treatment directions.
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    Alzheimer’s disease: a tale of two diseases?
    Eleonora Nardini, Ryan Hogan, Anthony Flamier, Gilbert Bernier
    2021, 16 (10):  1958-1964.  doi: 10.4103/1673-5374.308070
    Abstract ( 116 )   PDF (919KB) ( 144 )   Save
    Sporadic late-onset Alzheimer’s disease (SLOAD) and familial early-onset Alzheimer’s disease (FEOAD) associated with dominant mutations in APP, PSEN1 and PSEN2, are thought to represent a spectrum of the same disorder based on near identical behavioral and histopathological features. Hence, FEOAD transgenic mouse models have been used in past decades as a surrogate to study SLOAD pathogenic mechanisms and as the gold standard to validate drugs used in clinical trials. Unfortunately, such research has yielded little output in terms of therapeutics targeting the disease’s development and progression. In this short review, we interrogate the widely accepted view of one, dimorphic disease through the prism of the Bmi1+/– mouse model and the distinct chromatin signatures observed between SLOAD and FEOAD brains.
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    Sleep disorders in Alzheimer’s disease: the predictive roles and potential mechanisms
    Huang Kuang, Yu-Ge Zhu, Zhi-Feng Zhou, Mei-Wen Yang, Fen-Fang Hong, Shu-Long Yang
    2021, 16 (10):  1965-1972.  doi: 10.4103/1673-5374.308071
    Abstract ( 126 )   PDF (774KB) ( 222 )   Save
    Sleep disorders are common in patients with Alzheimer’s disease, and can even occur in patients with amnestic mild cognitive impairment, which appears before Alzheimer’s disease. Sleep disorders further impair cognitive function and accelerate the accumulation of amyloid-β and tau in patients with Alzheimer’s disease. At present, sleep disorders are considered as a risk factor for, and may be a predictor of, Alzheimer’s disease development. Given that sleep disorders are encountered in other types of dementia and psychiatric conditions, sleep-related biomarkers to predict Alzheimer’s disease need to have high specificity and sensitivity. Here, we summarize the major Alzheimer’s disease-specific sleep changes, including abnormal non-rapid eye movement sleep, sleep fragmentation, and sleep-disordered breathing, and describe their ability to predict the onset of Alzheimer’s disease at its earliest stages. Understanding the mechanisms underlying these sleep changes is also crucial if we are to clarify the role of sleep in Alzheimer’s disease. This paper therefore explores some potential mechanisms that may contribute to sleep disorders, including dysregulation of the orexinergic, glutamatergic, and γ-aminobutyric acid systems and the circadian rhythm, together with amyloid-β accumulation. This review could provide a theoretical basis for the development of drugs to treat Alzheimer’s disease based on sleep disorders in future work.
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    The plasminogen activating system in the pathogenesis of Alzheimer’s disease
    Manuel Yepes
    2021, 16 (10):  1973-1977.  doi: 10.4103/1673-5374.308076
    Abstract ( 109 )   PDF (469KB) ( 129 )   Save
    Dementia is a clinical syndrome that affects approximately 47 million people worldwide and is characterized by progressive and irreversible decline of cognitive, behavioral and sesorimotor functions. Alzheimer’s disease (AD) accounts for approximately 60–80% of all cases of dementia, and neuropathologically is characterized by extracellular deposits of insoluble amyloid-β (Aβ) and intracellular aggregates of hyperphosphorylated tau. Significantly, although for a long time it was believed that the extracellular accumulation of Aβ was the culprit of the symptoms observed in these patients, more recent studies have shown that cognitive decline in people suffering this disease is associated with soluble Aβ-induced synaptic dysfunction instead of the formation of insoluble Aβ-containing extracellular plaques. These observations are translationally relevant because soluble Aβ-induced synaptic dysfunction is an early event in AD that precedes neuronal death, and thus is amenable to therapeutic interventions to prevent cognitive decline before the progression to irreversible brain damage. The plasminogen activating (PA) system is an enzymatic cascade that triggers the degradation of fibrin by catalyzing the conversion of plasminogen into plasmin via two serine proteinases: tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA). Experimental evidence reported over the last three decades has shown that tPA and uPA play a role in the pathogenesis of AD. However, these studies have focused on the ability of these plasminogen activators to trigger plasmin-induced cleavage of insoluble Aβ-containing extracellular plaques. In contrast, recent evidence indicates that activity-dependent release of uPA from the presynaptic terminal of cerebral cortical neurons protects the synapse from the deleterious effects of soluble Aβ via a mechanism that does not require plasmin generation or the cleavage of Aβ fibrils. Below we discuss the role of the PA system in the pathogenesis of AD and the translational relevance of data published to this date. 
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    Emerging concepts underlying selective neuromuscular dysfunction in infantile-onset spinal muscular atrophy
    Kishore Gollapalli, Jeong-Ki Kim, Umrao R. Monani
    2021, 16 (10):  1978-1984.  doi: 10.4103/1673-5374.308073
    Abstract ( 90 )   PDF (2197KB) ( 107 )   Save
    Infantile-onset spinal muscular atrophy is the quintessential example of a disorder characterized by a predominantly neurodegenerative phenotype that nevertheless stems from perturbations in a housekeeping protein. Resulting from low levels of the Survival of Motor Neuron (SMN) protein, spinal muscular atrophy manifests mainly as a lower motor neuron disease. Why this is so and whether other cell types contribute to the classic spinal muscular atrophy phenotype continue to be the subject of intense investigation and are only now gaining appreciation. Yet, what is emerging is sometimes as puzzling as it is instructive, arguing for a careful re-examination of recent study outcomes, raising questions about established dogma in the field and making the case for a greater focus on milder spinal muscular atrophy models as tools to identify key mechanisms driving selective neuromuscular dysfunction in the disease. This review examines the evidence for novel molecular and cellular mechanisms that have recently been implicated in spinal muscular atrophy, highlights breakthroughs, points out caveats and poses questions that ought to serve as the basis of new investigations to better understand and treat this and other more common neurodegenerative disorders. 
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    Current application of neurofilaments in amyotrophic lateral sclerosis and future perspectives
    Yuri Matteo Falzone, Tommaso Russo, Teuta Domi, Laura Pozzi, Angelo Quattrini, Massimo Filippi, Nilo Riva
    2021, 16 (10):  1985-1991.  doi: 10.4103/1673-5374.308072
    Abstract ( 106 )   PDF (1052KB) ( 989 )   Save
    Motor neuron disease includes a heterogeneous group of relentless progressive neurological disorders defined and characterized by the degeneration of motor neurons. Amyotrophic lateral sclerosis is the most common and aggressive form of motor neuron disease with no effective treatment so far. Unfortunately, diagnostic and prognostic biomarkers are lacking in clinical practice. Neurofilaments are fundamental structural components of the axons and neurofilament light chain and phosphorylated neurofilament heavy chain can be measured in both cerebrospinal fluid and serum. Neurofilament light chain and phosphorylated neurofilament heavy chain levels are elevated in amyotrophic lateral sclerosis, reflecting the extensive damage of motor neurons and axons. Hence, neurofilaments are now increasingly recognized as the most promising candidate biomarker in amyotrophic lateral sclerosis. The potential usefulness of neurofilaments regards various aspects, including diagnosis, prognosis, patient stratification in clinical trials and evaluation of treatment response. In this review paper, we review the body of literature about neurofilaments measurement in amyotrophic lateral sclerosis. We also discuss the open issues concerning the use of  neurofilaments clinical practice, as no overall guideline exists to date; finally, we address the most recent evidence and future perspectives.
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    A paradigm shift: emerging roles of microglia, a non-neuronal cell, in learning and memory
    Neelima Gupta, S. Thameem Dheen
    2021, 16 (10):  1992-1993.  doi: 10.4103/1673-5374.308082
    Abstract ( 89 )   PDF (531KB) ( 113 )   Save
    Microglial cells are non-neuronal cells which serve as the first line of defence against various injuries and insults in the central nervous system (CNS). They act as sentinels that constantly patrol the surrounding parenchyma through their ramified processes in the CNS. In response to any pathological insult, microglia become activated, undergo proliferation, migrate to the site of injury or infection, and release chemokines and cytokines followed by the phagocytosis of dead cells and debris.    
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    Slc7a5 regulation of neural development
    Aidan M. Sokolov, David M. Feliciano
    2021, 16 (10):  1994-1995.  doi: 10.4103/1673-5374.308086
    Abstract ( 125 )   PDF (449KB) ( 162 )   Save
    Membrane transport proteins are appreciated for their ability to transport molecules across biological membranes and have received a renewed focus for their role in nervous system disorders. One such group of transporters are members of the solute carrier (SLC) family. SLC transporters shuttle various molecules, including neurotransmitters, fatty acids, amino acids, and inorganic ions. As such, they play an integral role in supplying cells with essential resources. An example is that amino acids are transported by SLC family members. Slc7a5 is a SLC family member that transports essential amino acids important for neuronal development, as well as other biological molecules including thyroid hormones T3, T4, and L-Dopa. Slc7a5 forms a heterodimer with Slc3a2 that facilitates the subcellular distribution of Slc7a5. Amino acids including leucine, glutamine, and arginine support cell growth by activating the protein kinase, mammalian target of rapamycin complex 1 (mTORC1) (Liu et al., 2020). Consistent with this notion is that Slc7a5 transport of amino acids regulates mTORC1 activity in numerous cell types (Nicklin et al., 2009). A recent manuscript expands upon these findings to demonstrate that Slc7a5 plays a previously unrecognized and critical role in the regulation of mTORC1 activity and neuron development (Sokolov et al., 2020).
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    MicroRNA-based therapeutics for optic neuropathy: opportunities and challenges
    Heather K. Mak, Christopher K. S. Leung
    2021, 16 (10):  1996-1997.  doi: 10.4103/1673-5374.308081
    Abstract ( 96 )   PDF (515KB) ( 96 )   Save
    Optic nerve degeneration is a major cause of irreversible blindness worldwide with glaucoma being the most common optic neuropathy, affecting approximately 76 million people worldwide in 2020. The optic nerve comprises axons of retinal ganglion cells (RGCs), the output neurons of the inner retina. Protecting RGCs and axons from degeneration and regenerating RGC axons to preserve and recover vision in patients with progressive optic neuropathy is an unmet need. Unlike embryonic neurons, mature neurons of the mammalian central nervous system fail to regenerate their axons following injury. The age-related loss of axon regenerative capacity of RGCs over time renders vision loss from optic neuropathy irreversible. The failure of injured RGCs to regenerate axons is largely attributed to inhibitory molecules in the extrinsic environment and a change in the intrinsic molecular makeup of aging cells. Early studies have demonstrated that RGCs require specific molecular signals for the stimulation of axon growth even without inhibitory molecules in the extrinsic environment, leading successive efforts to focus on uncovering the intrinsic signaling pathways that control axon extension during RGC development. Phosphatase and tensin homolog (PTEN), suppressor of cytokine signaling 3 (SOCS3), dual leucine zipper kinase, and krüppel-like factor (KLF) family members are some of the transcription factors and proteins that have been demonstrated to govern the intrinsic signaling pathways of axon regeneration (He and Jin, 2016). Whereas the molecular signatures that contribute to the differential axon regenerative potential between young and mature RGCs remain poorly understood, increasing evidence has revealed that microRNAs play a critical role in orchestrating the expression of transcription factors for axon growth in neurons of the central nervous system. A recent study has unveiled a previously unrecognized involvement of the miR-19a/PTEN axis in regulating the developmental decline of axon regenerative capacity in RGCs, highlighting the potential of microRNA-based therapeutics to rejuvenate aged RGCs and promote optic nerve regeneration (Mak et al., 2019). 
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    In vivo direct reprogramming as a therapeutic strategy for brain and retina repair
    Haruka Sekiryu, Taito Matsuda
    2021, 16 (10):  1998-1999.  doi: 10.4103/1673-5374.308093
    Abstract ( 92 )   PDF (732KB) ( 130 )   Save
    Once neurons are lost because of injury or degeneration, they hardly ever regenerate in most mammalian central nervous system (CNS) regions. In adult rodents, some brain regions, such as the subventricular zone of the lateral ventricle and the subgranular zone of the dentate gyrus, retain neural stem cells (NSCs) and generate new neurons. Although a small population of new neurons derived from NSCs migrate toward lesion sites after brain injury, they are insufficient to completely restore neuronal functions. Cell transplantation using induced pluripotent stem cells (iPSCs) or embryonic stem cells (ESCs) has become an attractive therapeutic strategy for nerve injury or degeneration (Barker et al., 2015; Huang and Zhang, 2019). For Parkinson’s disease, transplantation of dopaminergic neurons from human ESCs or iPSCs is emerging as a therapeutic approach (Li and Chen, 2016). However, the risks of immune rejection and tumorigenesis remain substantial drawbacks of this therapeutic approach.
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    Intravitreal fluorogold tracing as a method to label retinal neurons and the retinal pigment epithelium
    Francisco Javier Valiente-Soriano, Fernando Lucas-Ruiz, Juan A. Miralles de Imperial-Ollero, Manuel Vidal-Sanz, Marta Agudo-Barriuso
    2021, 16 (10):  2000-2001.  doi: 10.4103/1673-5374.308084
    Abstract ( 80 )   PDF (1861KB) ( 136 )   Save
    Techniques to label the neuroretina and the retinal pigment epithelium (RPE) have been the topic of many studies for years. The reliability and reproducibility of these techniques are essential to investigate retinal alterations of ocular pathologies and possible treatments. In particular, the study of the integrity of the RPE is of great importance in pathologies such as retinitis pigmentosa or age-related macular degeneration (Gu et al., 2012; Fisher and Ferrington, 2018; Zhang et al., 2019). The most common approaches use antibodies to identify different cell populations. Recently, we have described a novel technique to study the integrity of the neuroretina and the RPE, as well as the functionality of the RPE in rats (Valiente-Soriano et al., 2020). 
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    OTX2 signaling in retinal dysfunction, degeneration and regeneration
    Kenneth. L. Moya, Raoul Torero Ibad
    2021, 16 (10):  2002-2003.  doi: 10.4103/1673-5374.308094
    Abstract ( 109 )   PDF (659KB) ( 92 )   Save
    The protein OTX2 in the retina is necessary for the maintenance of normal physiologic processes, and may be a promising therapeutic agent for some ophthalmic diseases. In this Perspective, we first shortly introduce the organization of the retina and the importance of OTX2 expression. We then present an example of reduced OTX2 activity in the developed retina associated with structural and functional consequences. We next show that homeoproteins can have neuroprotective functions. We finally review several clear examples of OTX2 non-cell autonomous activity in the retina and the effects of diminishing or providing extracellular OTX2.
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    Modulation of brainstem reflexes induced by non-invasive brain stimulation: is there a future?
    Hatice Kumru, Markus Kofler, Josep Valls-Sole
    2021, 16 (10):  2004-2005.  doi: 10.4103/1673-5374.308083
    Abstract ( 83 )   PDF (314KB) ( 95 )   Save
    Kumru et al. (2019) have recently reported significant reduction of the R2 component of the trigeminal blink reflex following high-frequency (20 Hz) repetitive transcranial magnetic stimulation (rTMS) over the vertex in both, healthy subjects and in patients with spinal cord injury (SCI) (Figure 1). The modulatory influence of non-invasive brain stimulation (NIBS) on brainstem reflexes has been only scarcely studied.
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    High mobility group box-1 protein as a therapeutic target in perinatal hypoxic-ischemic brain injury
    Kazuki Hatayama, Barbara S. Stonestreet
    2021, 16 (10):  2006-2007.  doi: 10.4103/1673-5374.308092
    Abstract ( 90 )   PDF (604KB) ( 189 )   Save
    Perinatal hypoxic-ischemic (HI) brain injury is a leading cause of morbidity and long-standing disability in newborns (Millar et al., 2017). Improved neonatal intensive care has increased survival in infants with pregnancy and birth related complications.  Nonetheless, many surviving neonates exhibit neurological abnormalities that can persist throughout life (Millar et al., 2017). Early neuroprotective strategies have the potential to improve neurological outcomes and attenuate developmental delay in neonates. However, hypothermia is the only currently approved intervention for HI encephalopathy in full-term infants, which is only partially protective (Millar et al., 2017). Findings in preterm and full-term infants suggest that elevations in pro-inflammatory cytokines are important in the pathogenesis of HI-related brain injury (Millar et al., 2017). The high mobility group box-1 (HMGB1), a representative damage associated-molecular pattern (DAMP) protein, has been reported to be implicated in a variety of brain related inflammatory diseases including traumatic brain injury, epilepsy, and stroke (Nishibori et al., 2019). Anti-HMGB1 therapies have gained increasing interest to treat inflammation related disorders in the brain (Nishibori et al., 2019). However, there is a paucity of information regarding the pathology of HMGB1 in HI-related brain injury during the perinatal period. The current perspective discusses the potential contributions of HMGB1 to HI-related brain injury during the perinatal period and also addresses the potential of HMGB1 as a therapeutic target of the brain injury. Furthermore, this perspective emphasizes the potential for combinational therapeutics for hypothermia with anti-HMGB1 monoclonal antibodies (mAb) in perinatal HI brain injury.
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    Regulating autophagy: a novel role for SETX (Senataxin)
    Patricia Richard, Emanuel Rosonina
    2021, 16 (10):  2008-2009.  doi: 10.4103/1673-5374.308091
    Abstract ( 255 )   PDF (447KB) ( 106 )   Save
    Mutations in the gene encoding SETX, also known as Senataxin, are mainly linked to two distinct neurodegenerative diseases, a cerebellar ataxia known as oculomotor apraxia type 2 (AOA2) and a form of juvenile amyotrophic lateral sclerosis, ALS4 (Chen et al., 2004; Moreira et al., 2004). SETX is an RNA/DNA helicase that functions in multiple events related to RNA metabolism and DNA maintenance, including transcriptional termination at certain genes and the DNA damage response at replication stress foci. A key role attributed to SETX in both of these functions is in the resolution of R loops, potentially deleterious DNA:RNA hybrid structures that form during transcription (Aguilera and Garcia-Muse, 2012). As abnormal levels of R loops are frequently observed in neurological disorders, this role has been proposed as a link between SETX dysfunction and neurodegeneration (Richard and Manley, 2016). In a recently published study, however, we demonstrated that SETX plays critical roles in the progression of autophagy, the process employed by cells to eliminate defective proteins and organelles, through its effects on expression of autophagy-related genes (Richard et al., 2020). A hallmark of neurodegenerative disease is the abnormal accumulation of protein aggregates that eventually lead to cellular dysfunction and degeneration of neuronal tissues (Kurtishi et al., 2019). Not surprisingly, defective autophagy is strongly implicated in the development of such disorders (Finkbeiner, 2020). As described in this perspective, we now suggest that this novel role for SETX provides an additional pathway by which transcriptional and gene expression defects caused by mutations in SETX can lead to neurological disease. Indeed, in preliminary analyses, we have detected perturbed autophagy in samples from AOA2 and ALS4 patients harboring SETX mutations.
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    Biomarker-guided drug therapy: personalized medicine for treating Alzheimer’s disease
    Charvi Syal, Jing Wang
    2021, 16 (10):  2010-2011.  doi: 10.4103/1673-5374.308079
    Abstract ( 128 )   PDF (500KB) ( 91 )   Save
    Alzheimer’s disease (AD) is a progressive neurodegenerative disorder associated with significant memory decline and cognitive impairment. AD is characterized by two classical neuropathological hallmarks, namely the amyloid-beta (Aβ) plaques and neurofibril tangles. Currently, there are no disease-modifying treatments available for AD, except for a couple of the US Food and Drug Administration (FDA)-approved drugs to improve cognitive function by blocking N-methyl-D-aspartate receptors or cholinesterase activity (Panza et al., 2019). While these drugs offer some symptomatic relief against AD, they do little to halt the progression of the disease. For over two decades, the amyloid cascade hypothesis of AD has been the central focus for the development of biomarkers and disease-modifying therapeutic strategies, supported by strong genetic, biochemical and histopathological evidence. Unfortunately, over 15 years of clinical failure with several classes of anti-Aβ drugs that affect the formation, aggregation and clearance of Aβ have made the research community rethink the strategies to develop appropriate treatments for AD (Panza et al., 2019). AD is characterized by a vast heterogeneity in its pathophysiology that is influenced by several risk factors such as aging, lifestyle, and genetic and environmental changes. The complex etiology of the disease, coupled with the failure of past clinical interventions directed at a “fit-for-all” therapy, demands a change in therapeutic strategies for an effective and more favourable outcome against AD. There is thus, a need for the development of tailored/targeted therapy for specific AD subpopulations that share distinct genetic, molecular or pathological properties. In this regard, our perspective discusses three potential molecular biomarkers, namely monoacylglycerol lipase (Mgll), apolipoprotein E4 (APOE4) and the phosphatidylinositol 3-kinase (PIK3)/protein kinase (AKT)/glycogen synthase kinase-3β (GSK-3β) signaling pathway, as prime candidates for targeted therapy.

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    How would preclinical Alzheimer’s disease (AD pathology) occur? An insight from a genomic instability mouse model
    Chinthalapally V. Rao, Hiroshi Y. Yamada
    2021, 16 (10):  2012-2014.  doi: 10.4103/1673-5374.308096
    Abstract ( 82 )   PDF (936KB) ( 136 )   Save
    More than 95% of Alzheimer’s disease (AD) is late-onset, in which patients show clinical cognition/behavior symptoms after age 65. Unlike early-onset AD that comes with mutations in genes directly involved in amyloid metabolism (APP, PSEN), genetic predispositions associated with late-onset AD are harder to pinpoint, and their mechanistic links to AD development need further investigation. Although the development mechanism of late-onset AD remains controversial, amyloid-beta accumulation, initiated in middle age, is widely accepted as the triggering event for early AD pathology (Du Bois et al., 2010; Sterling et al., 2011). In 2018, we reported a genomic instability mouse model (Sgo1–/+) in which amyloid-beta accumulates in the brain in old age without early-onset AD mutation (Rao et al., 2018). The identification led us to anticipate that the model may reveal the development mechanism of late-onset AD. In a new study that appeared in Aging Cell (Rao et al., 2020a), we identified GSK3 inactivation in middle age as a cause for triggering the amyloid-beta accumulation. Inactivation of GSK3 appeared to affect amyloid-beta generation in two ways: (i) via increasing ARC/Arg3.1, which can generate amyloid-beta in an activity-dependent manner, and (ii) via activating canonical Wnt signaling and driving the cell cycle in the brain, thus activating the “amyloid-beta accumulation cycle” (Rao et al., 2020b). Since the Sgo1–/+ condition prolongs mitosis, during which amyloid-beta generation and accumulation is facilitated, Sgo1–/+ may be mimicking the aneuploid condition prevalent in patients with mild cognitive impairment (MCI) and AD (Potter et al., 2019). Our studies (a) support the notion of the critical roles of genomic instability and aneuploidy in AD development, (b) suggest a role of GSK3 in the onset of amyloid-beta accumulation and onset of AD pathology in middle age, and (c) suggest the usefulness of the mouse model for testing drug candidates for late-onset AD.
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    Short-chain fatty acids in the context of Parkinson’s disease
    Judith Metzdorf, Lars Tönges
    2021, 16 (10):  2015-2016.  doi: 10.4103/1673-5374.308089
    Abstract ( 104 )   PDF (422KB) ( 114 )   Save
    Research on neurodegenerative diseases such as Alzheimer’s disease, Parkinson´s disease (PD), Huntington’s disease or amyotrophic lateral sclerosis is becoming increasingly important in our society. Due to the ageing of the population, the prevalence of these diseases continue to rise worldwide, and causal cures are not yet available (Erkkinen et al., 2018). This Perspective focusses on PD, a movement disorder of the central nervous system with an estimated prevalence between 65 and 1250/100,000 in Europe, affecting about 1 percent of the population older than 60 years. The clinical symptoms include motor symptoms like bradykinesia, tremor or rigidity which are associated with loss of dopaminergic neurons in the substantia nigra and their innervating axonal fibers to the striatum. Additional non-motor symptoms may consist in depression, hyposmia, cognitive decline or constipation due to impaired motility of the gastrointestinal tract. The aggregation and dysfunction of the protein α-Synuclein (αSyn) in dopaminergic and surrounding cells is the major pathological hallmark of the disease. Its course is significantly influenced by inflammatory processes that also involve non-neuronal cell types such as astroglia, microglia and T cells. Currently, several environmental factors are discussed to influence the development and progression of PD such as the microbiome composition of the gastrointestinal tract. The human gut contains about 160 bacterial species which are essential for the digestion of dietary fibers and the synthesis of several proteins or vitamins. Therefore, the microbiome contributes to the human enteral metabolism and several direct effects on human health have been demonstrated (Rowland et al., 2018).
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    Non-coding RNAs and stem cells: the dream team for neural regeneration in Parkinson’s disease?
    Shubhra Acharya, Andrew I. Lumley, Yvan Devaux
    2021, 16 (10):  2017-2018.  doi: 10.4103/1673-5374.308090
    Abstract ( 120 )   PDF (433KB) ( 95 )   Save
    Parkinson’s disease (PD) is a widely spread neurodegenerative movement disorder, affecting approximately 10 million people worldwide. It is primarily caused by the loss of dopaminergic neurons in the substantia nigra, which causes decreased secretion of dopamine leading to tremors, bradykinesia and rigid muscle movement. The development of PD is complex and needs to be better understood. Current treatment strategies primarily involve targeting disease symptoms, however, since there is a continuous loss of dopaminergic neurons in the brain, PD appears to be incurable. Moreover, treatment strategies often carry severe side effects related to dopamine production, where too little or too much can cause debilitating issues such as dyskinesia. The pool of neural stem/progenitor cells (NSCs) located in sub-ventricular zone and hippocampal dentate gyrus, proliferate and are responsible to give rise to neurons and glia in response to any cellular damage. Though this activation of NSCs is highly regulated, it is insufficient to overcome the loss of dopaminergic neurons in PD. In this line, non-coding RNAs (ncRNAs) are involved in the underlying mechanisms of PD and are known to have important functional roles in neural regeneration (Acharya et al., 2020). Thus, the study of ncRNAs in NSC activation and adult neurogenesis post PD development is an extremely attractive area of research with significant clinical application potential.
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    The dual role of necrostatin-1 in Parkinson’s disease models
    Eva Alegre-Cortés, Guadalupe Martínez-Chacón, José M. Fuentes, Sokhna M. S. Yakhine-Diop
    2021, 16 (10):  2019-2020.  doi: 10.4103/1673-5374.308080
    Abstract ( 92 )   PDF (495KB) ( 100 )   Save
    Neuronal cell death is the main hallmark of Parkinson’s disease (PD). It is an irreversible process promoted by neurotoxins and/or genetic mutations. Different types of cell death have been associated with PD. The mechanisms by which neurons decide to specific type of cell death remain elusive. However, it is well known that cell death can be either programmed or not. Apoptosis is a programmed cell death that involves the release of cytochrome c from damaged mitochondria to cytosol and the activation of caspases leading to nuclear condensation. Necrosis is a caspase-independent cell death characterized by a gain in cell volume, rupture of plasma membrane and leak of cell contents, inflammation, and affects neighbouring cells. It was classified as a non-programmed cell death, but there are types of necrotic death triggered by a protein activation cascade, including necroptosis.
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    Potential role of biofeedback therapy for Parkinson’s diseas
    Naoya Kotani, Takashi Morishita, Tooru Inoue
    2021, 16 (10):  2021-2022.  doi: 10.4103/1673-5374.308095
    Abstract ( 127 )   PDF (413KB) ( 116 )   Save
    Parkinson’s disease (PD) is a neurological disorder characterized by rigidity, tremor, bradykinesia, and postural instability. Gait disturbance is one of cardinal symptoms of PD and affects the activities of daily living and quality of life. This symptom in advanced PD patients is usually refractory to medication and surgical intervention such as deep brain stimulation (Morishita et al., 2016). Therefore, physical therapy with an efficient exercise program is important to maintain or improve gait ability. Among the various rehabilitation programs, biofeedback therapy is drawing attention as a rehabilitation method. Biofeedback is a technique that aims to make unconscious or involuntary bodily processes perceptible so that patients can control them consciously. We recently reported the effect of biofeedback therapy using a robot suit hybrid assistive limb (HAL) on PD patients (Kotani et al., 2020). HAL is a robotic exoskeleton designed to facilitate movements and was developed based on the “interactive biofeedback” theory (Morishita and Inoue, 2016). Specifically, the movement of the robot is triggered by bioelectric signals detected by surface electrodes. It supports the spontaneous movement of impaired muscles and generates sensory feedback. In our study, we used the HAL lumbar type. Eight patients with advanced PD participated in this study. The participants performed HAL-assisted core exercises and squats, one session per day, for a total of five sessions. In our study, exercise with HAL improved walking ability after the short period of the five sessions, and the effect was maintained for 3 months. We considered that the HAL exercises were successful because the biofeedback of HAL is predominantly via the proprioceptive receptors. The robot enables patients to achieve repetitive movements.
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    Pharmacological interventions targeting nuclear factor-kappa B signaling in multiple sclerosis
    Kim M. A. De Kleijn, Gerard J. M. Martens
    2021, 16 (10):  2023-2025.  doi: 10.4103/1673-5374.308088
    Abstract ( 143 )   PDF (801KB) ( 97 )   Save
    Multiple sclerosis (MS) is an inflammatory neurodegenerative disease of the central nervous system (CNS). Pathological characteristics of the disease include activation of CNS-intrinsic immune cells, such as microglia and astrocytes, and loss of neuronal connections, myelin and blood-brain barrier (BBB) integrity as well as peripheral immune cell infiltration into the brain. MS has long been considered a predominantly immunological disease, which has led to the development of essentially only immune-directed medications. Within this traditional “outside-in” MS hypothesis, a dysregulation of the peripheral immune system causes immune cell infiltration into the CNS, leading to autoreactivity against myelin sheath components and secondary BBB dysfunction. However, recent findings indicate that overactivation of microglia and astrocytes represents an important first step in MS pathology, as appears to be the case for other neurodegenerative diseases such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). Within this new hypothesis of CNS-intrinsic neuroinflammation in MS – also known as the “inside-out” model (Titus et al., 2020), the transcription factor nuclear factor-kappa B (NFκB) plays a central role in the brain. In CNS cells, various triggers, such as bacterial and viral infections, oxidative stress and other cellular stressors like protein misfolding and DNA damage, lead to NFκB activation in CNS-immune cells and subsequent production of pro-inflammatory cytokines and adhesion molecules, activation of the inflammasome complex, apoptosis and cell cycle arrest. The production of pro-inflammatory molecules causes a microenvironment which provokes CNS-cell degeneration, and is detrimental for (re)myelination by oligodendrocytes and neuronal regeneration. Neuroinflammatory cascades in the CNS also prevent microglia and astrocytes from exerting their regenerative effects on oligodendrocytes and neurons. In addition, microglia and astrocytes reinforce each other’s negative effects via cytokine-mediated feedback mechanisms, which create a negative loop that further affects the environment for CNS-cell regeneration. Targeting the NFκB pathway may be especially attractive for the treatment of MS as this transcription factor is also involved in regulating inflammatory processes within both the innate and the adaptive peripheral immune systems.
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    Therapeutic potential of trehalose in neurodegenerative diseases: the knowns and unknowns
    Masoomeh Khalifeh, George E. Barreto, Amirhossein Sahebkar
    2021, 16 (10):  2026-2027.  doi: 10.4103/1673-5374.308085
    Abstract ( 315 )   PDF (729KB) ( 136 )   Save
    Neurodegenerative diseases (NDs) are a growing health problem associated with a high burden due to destructive and long-term clinical effects. Cellular aggregations of misfolded proteins are the most common pathological hallmark of many late-onset NDs called proteinopathies including Parkinson’s disease (PD), Alzheimer’s disease (AD), tauopathies, amyotrophic lateral sclerosis (ALS), and polyglutamine (polyQ) expansion diseases such as Huntington’s disease (HD) and various spinocerebellar ataxias (SCA) such as SCA3 (Renna et al., 2010). Misfolded proteins can be generated by posttranslational conjugation (e.g., hyperphosphorylated tau in AD), or endoproteolytic cleavage (e.g., amyloid β peptides) or genetic mutations in specific proteins (such as HTT in HD, α-synuclein in PD, PrPC in prion disease and SOD1 and TDP-43 in ALS) leading to the formation of oligomers. 
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    Nuclear sphingomyelin in neurodegenerative diseases
    Elisabetta Albi, Alice V. Alessenko
    2021, 16 (10):  2028-2029.  doi: 10.4103/1673-5374.308087
    Abstract ( 113 )   PDF (400KB) ( 329 )   Save
    Introduction: Recently, sphingolipids (SphLs) have become increasingly appreciated as a family of molecules involved in the growth, differentiation, and death of the central nervous system  cells. The disequilibrium among the different SphLs leads to changes in the neuronal cell physiology and induces the development of neurodegenerative diseases (Alessenko and Albi, 2020). Sphingomyelin (SM), sphinganin (Sphn), sphingosine (Sph), sphingosine-1-phosphate (S1P) and ceramide (Cer) are the most well-studied group of SphLs responsible for neurodegeneration, as well as derived molecules such as glucosylceramide or cerebroside (GCer) and galactosylceramide (GalCer) and finally more complex molecules such as as gangliosides.
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    Arbutin effectively ameliorates the symptoms of Parkinson’s disease: the role of adenosine receptors and cyclic adenosine monophosphate
    Jie Zhao, Manish Kumar, Jeevan Sharma, Zhihai Yuan
    2021, 16 (10):  2030-2040.  doi: 10.4103/1673-5374.308102
    Abstract ( 179 )   PDF (5122KB) ( 192 )   Save
    An antagonistic communication exists between adenosinergic and dopaminergic signaling in the basal ganglia, which suggests that the suppression of adenosine A2A receptors-cyclic adenosine monophosphate pathway may be able to restore the disrupted dopamine transmission that results in motor symptoms in Parkinson’s disease (PD). Arbutin is a natural glycoside that possesses antioxidant, anti-inflammatory, and neuroprotective properties. The purpose of this study was to investigate whether arbutin could ameliorate the symptoms of PD and to examine the underlying mechanism. In this study, Swiss albino mouse models of PD were established by the intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine for 4 successive days, with the concurrent intraperitoneal administration of arbutin (50 and 100 mg/kg) for 7 days. The results showed that arbutin significantly reduced lipid peroxidation, total nitrite levels, and inflammation in the substantia nigra and striatum of PD mouse models. In addition, arbutin decreased the activity of endogenous antioxidants, reduced the levels of dopamine, 3,4-dihydroxyphenylacetic acid, homovanillic acid, and γ-aminobutyric acid, and minimized neurodegeneration in the striatum. Arbutin also reduced the abnormal performance of PD mouse models in the open field test, bar test, pole test, and rotarod test. The therapeutic efficacy of arbutin was similar to that of madopar. The intraperitoneal injection of the A2AR agonist CGS21680 (0.5 mg/kg) 
    attenuated the therapeutic effects of arbutin, whereas the intraperitoneal injection of forskolin (3 mg/kg) enhanced arbutin-mediated improvements. These findings suggest that arbutin can improve the performance of PD mouse models by inhibiting the function of the A2AR and enhancing the effects of cyclic adenosine monophosphate. This study was approved by the Institutional Animal Ethics Committee (1616/PO/Re/S/12/CPCSEA) on November 17, 2019 (approval No. IAEC/2019/010).
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    β2 and α2 adrenergic receptors mediate the proneurogenic in vitro effects of norquetiapine
    Valeria Bortolotto, Pier Luigi Canonico, Mariagrazia Grilli
    2021, 16 (10):  2041-2047.  doi: 10.4103/1673-5374.308097
    Abstract ( 126 )   PDF (1488KB) ( 195 )   Save
    Positive modulation of adult hippocampal neurogenesis may contribute to the therapeutic effects of clinically relevant antidepressant drugs, including atypical antipsychotics. Quetiapine, an antipsychotic which represents a therapeutic option in patients who are resistant to classical antidepressants, promotes adult hippocampal neurogenesis in preclinical studies. Norquetiapine, the key active metabolite of quetiapine in humans, has a distinctive receptor profile than the parent compound. The drug is indeed a high affinity norepinephrine transporter inhibitor and such activity has been proposed to contribute to its antidepressant effect. At present, no information is available on the effects of norquetiapine on adult neurogenesis. We extensively investigated the activity of quetiapine and norquetiapine on adult murine neural stem/progenitor cells and their progeny. Additionally, selective antagonists for β2/α2 adrenergic receptors allowed us to evaluate if these receptors could mediate quetiapine and norquetiapine effects. We demonstrated that both drugs elicit in vitro proneurogenic effects but also that norquetiapine had distinctive properties which may depend on its ability to inhibit norepinephrine transporter and involve β2/α2 adrenergic receptors. Animal care and experimental procedures were approved by the Institutional Animal Care and Use Committees (IACUC) at University of Piemonte Orientale, Italy (approval No. 1033/2015PR) on September 29, 2015.  
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    Role of circular RNA expression in the pathological progression after spinal cord injury
    Wen-Zhao Wang, Jun Li, Lei Liu, Zheng-Dong Zhang, Ming-Xin Li, Qin Li, Hui-Xu Ma, Hai Yang, Xiao-Ling Hou
    2021, 16 (10):  2048-2055.  doi: 10.4103/1673-5374.308100
    Abstract ( 95 )   PDF (2540KB) ( 146 )   Save
    Differential expression of non-coding RNA after traumatic spinal cord injury (TSCI) is closely related to the pathophysiological process. The purposes of this study were to systematically profile and characterize expression of circular RNA (circRNA) in the lesion epicenter of spinal tissues after TSCI, and predict the structure and potential function of the regulatory circRNA/miRNA network. Forty-eight C57BL/6 mice were randomly and equally assigned to two groups: one subjected to TSCI at T8–10 with an Allen’s drop impactor, and a second subjected to laminectomy without TSCI. Spinal cord samples were stained with hematoxylin and eosin, sequenced, and validated. RNA-Seq, Gene Ontology analysis, Kyoto Encyclopedia of Genes and Genomes analysis, and network analyses (Targetscan and miRanda) were used to predict and annotate the circRNA/miRNA/mRNA network. Luciferase reporter, quantitative reverse transcription polymerase chain reaction, and western blot assays were used to profile expression and regulation patterns of the network in mouse models of TSCI. Hematoxylin-eosin staining revealed severe damage to the blood-spinal cord barrier after TSCI. Differentially expressed circRNA and miRNA profiles were obtained after TSCI; differentially expressed circRNAs, which were abundant in the cytoplasm, were involved in positive regulation of transcription and protein phosphorylation. miR-135b-5p was the most significantly downregulated miRNA after TSCI; circRNAAbca1 and KLF4 were predicted to be its target circRNA and mRNA, respectively. Subsequently, the circAbca1/miR-135b-5P/KLF4 regulatory axis was predicted and constructed, and its targeted binding was verified. After inhibiting circAbca1, GAP43 expression was upregulated. Differential expression of circRNAs might play an important role after TSCI. circAbca1 plays a neuroinhibitory role by targeted binding of the miR-135b-5P/KLF4 axis. The identified circRNA/miRNA/mRNA network could provide the basis for understanding pathophysiological mechanisms underlying TSCI, as well as guide the formulation of related therapeutic strategies. All animal protocols were approved by the Research Ethics Committee of West China Hospital of China (approval No. 2017128) on May 16, 2017. 
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    Methylene blue enhances polyethylene glycol-fusion repair of completely severed rat sciatic nerves
    Cameron L. Ghergherehchi, Jaimie T. Shores, Joseph Alderete, Erik K. Weitzel, George D. Bittner
    2021, 16 (10):  2056-2063.  doi: 10.4103/1673-5374.308099
    Abstract ( 117 )   PDF (2514KB) ( 181 )   Save
    Complete transection of peripheral mixed nerves immediately produces loss of sensory perception, muscle contractions and voluntary behavior mediated by the severed distal axons. In contrast to natural regeneration (~1 mm/d) of proximal axons that may eventually reinnervate denervated targets, re-innervation is restored within minutes by PEG-fusion that consists of  neurorrhaphy and a sequence of well specified hypo- and isotonic calcium-free or calcium-containing solutions, the anti-oxidant methylene blue (MB) and the membrane fusogen polyethylene glycol (PEG). In this study, we examined the relative efficacy of PEG-fusion with no MB (0%), 0.5% MB, or 1% MB on the recovery of voluntary behaviors by female Sprague-Dawley rats with a complete mid-thigh severance of their sciatic nerve bathed in extracellular fluid or calcium-containing isotonic saline. The recovery of voluntary behaviors is the most relevant measure of success of any technique to repair peripheral nerve injuries. We assessed recovery by the sciatic functional index, a commonly used measure of voluntary hindlimb behaviors following complete sciatic transections. We reported that both 1% MB and 0.5% MB in sterile distilled water in our PEG-fusion protocol with neurorrhaphy significantly increased the rate and extent of behavioral recovery compared to PEG plus neurorrhaphy alone. Furthermore, 0.5% MB was as effective as 1% MB in voluntary behavioral recovery as assessed by the sciatic functional index. Since sterile 1% MB is no longer clinically available, we therefore recommend that 0.5% MB be included in upcoming human clinical trials to evaluate the safety and efficacy of PEG-fusion. All animal procedures were approved by the University of Texas Institutional Animal Care and Use Committee (AUP-2019-00225) on September 9, 2020.
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    Exosomes derived from human induced pluripotent stem cell-derived neural progenitor cells protect neuronal function under ischemic conditions
    Wen-Yu Li, Qiong-Bin Zhu, Lu-Ya Jin, Yi Yang, Xiao-Yan Xu, Xing-Yue Hu
    2021, 16 (10):  2064-2070.  doi: 10.4103/1673-5374.308665
    Abstract ( 128 )   PDF (1830KB) ( 160 )   Save
    Compared with other stem cells, human induced pluripotent stem cells-derived neural progenitor cells (iPSC-NPCs) are more similar to cortical neurons in morphology and immunohistochemistry. Thus, they have greater potential for promoting the survival and growth of neurons and alleviating the proliferation of astrocytes. Transplantation of stem cell exosomes and stem cells themselves have both been shown to effectively repair nerve injury. However, there is no study on the protective effects of exosomes derived from iPSC-NPCs on oxygen and glucose deprived neurons. In this study, we established an oxygen-glucose deprivation model in embryonic cortical neurons of the rat by culturing the neurons in an atmosphere of 95% N2 and 5% CO2 for 1 hour and then treated them with iPSC-NPC-derived exosomes for 30 minutes. Our results showed that iPSC-NPC-derived exosomes increased the survival of oxygen- and glucose-deprived neurons and the level of brain-derived neurotrophic factor in the culture medium. Additionally, it attenuated oxygen and glucose deprivation-induced changes in the expression of the PTEN/AKT signaling pathway as well as synaptic plasticity-related proteins in the neurons. Further, it increased the length of the longest neurite in the oxygen- and glucose-deprived neurons. These findings validate the hypothesis that exosomes from iPSC-NPCs exhibit a neuroprotective effect on oxygen- and glucose-deprived neurons by regulating the PTEN/AKT signaling pathway and neurite outgrowth. This study was approved by the Animal Ethics Committee of Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, China (approval No. SRRSH20191010) on October 10, 2019.
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    The role of pineal microRNA-325 in regulating circadian rhythms after neonatal hypoxic-ischemic brain damage
    Ning Sha, Hua-Wei Wang, Bin Sun, Min Gong, Po Miao, Xiao-Lu Jiang, Xiao-Feng Yang, Mei Li, Li-Xiao Xu, Chen-Xi Feng, Yuan-Yuan Yang, Jie Zhang, Wen-Jing Zhu, Yuan-Yuan Gao, Xing Feng, Xin Ding
    2021, 16 (10):  2071-2077.  doi: 10.4103/1673-5374.308101
    Abstract ( 133 )   PDF (1859KB) ( 140 )   Save
    Circadian rhythm disorder is a common, but often neglected, consequence of neonatal hypoxic-ischemic brain damage (HIBD). However, the underlying molecular mechanisms remain largely unknown. We previously showed that, in a rat model of HIBD, up-regulation of microRNA-325 (miR-325) in the pineal gland is responsible for the suppression of Aanat, a key enzyme involved in melatonin synthesis and circadian rhythm regulation. To better understand the mechanism by which miR-325 affects circadian rhythms in neonates with HIBD, we compared clinical samples from neonates with HIBD and samples from healthy neonates recruited from the First Affiliated Hospital of Soochow University (Dushuhu Branch) in 2019. We found that circulating miR-325 levels correlated positively with the severity of sleep and circadian rhythm disorders in neonates with HIBD. Furthermore, a luciferase reporter gene assay revealed that LIM homeobox 3 (LHX3) is a novel downstream target of miR-325. In addition, in miR-325 knock-down mice, the transcription factor LHX3 exhibited an miR-325-dependent circadian pattern of expression in the pineal gland. We established a neonatal mouse model of HIBD by performing double-layer ligation of the left common carotid artery and exposing the pups to a low-oxygen environment for 2 hours. Lhx3 mRNA expression was significantly down-regulated in these mice and partially rescued in miR-325 knockout mice subjected to the same conditions. Finally, we showed that improvement in circadian rhythm-related behaviors in animals with HIBD was dependent on both miR-325 and LHX3. Taken together, our findings suggest that the miR-325-LHX3 axis is responsible for regulating circadian rhythms and provide novel insights into the identification of potential therapeutic targets for circadian rhythm disorders in patients with neonatal HIBD. The clinical trial was approved by Institutional Review Board of Children’s Hospital of Soochow University (approval No. 2015028) on July 20, 2015. Animal experiments were approved by Animal Care and Use Committee, School of Medicine, Soochow University, China (approval No. XD-2016-1) on January 15, 2016.
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    Combined treatment with valproic acid and estrogen has neuroprotective effects in ovariectomized mice with Alzheimer’s disease
    Yan-Zhen Li, Yuan-Jie Liu, Wei Zhang, Shi-Fang Luo, Xin Zhou, Gui-Qiong He
    2021, 16 (10):  2078-2085.  doi: 10.4103/1673-5374.308103
    Abstract ( 127 )   PDF (4161KB) ( 169 )   Save
    Postmenopausal women with Alzheimer’s disease (AD) exhibit dramatically reduced sensitivity to estrogen replacement therapy, which is though to be related to an estrogen receptor (ER)α/ERβ ratio imbalance arising from a significantly decreased level of ERs of the brain. The aim of our study was to investigate whether valproic acid (VPA) can enhance the beneficial effects of estrogen on cognitive function through restoration of ERα and ERβ expression in the brain. We removed the ovaries of female APP/PS1 mice to simulate the low estrogen levels present in postmenopausal women and then administered VPA (30 mg/kg, intraperitoneal injection, once daily), 17β-estradiol (E2) (2.4 μg, intraperitoneal injection, once daily), liquiritigenin (LG) (50 μg/kg, intragastric infusion, once daily), VPA + E2, or VPA + LG for 4 successive weeks. Compared with treatment with a single drug, treatment with VPA + E2 or VPA + LG significantly increased the level of glycogen synthase kinase 3β, increased the expression of estrogen receptor α, reduced the expression of small ubiquitin-like modifiers, and increased the level of estrogen receptor β. This resulted in enhanced sensitivity to estrogen therapy, reduced amyloid β aggregation, reduced abnormal phosphorylation of the tau protein, reduced neuronal loss, increased dendritic spine and postsynaptic density, and significantly alleviated memory loss and learning impairment in mice. This study was approved by the Chongqing Medical University Animal Protection and Ethics Committee, China on March 6, 2013. 
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    Markers for neural degeneration and regeneration: novel highly sensitive methods for the measurement of thrombin and activated protein C in human cerebrospinal fluid
    Alexandra Gerasimov, Valery Golderman, Shany Guly Gofrit, Shay Anat Aharoni, Daniela Noa Zohar, Ze’ev Itsekson-Hayosh, Tsviya Fay-Karmon, Sharon Hassin-Baer, Joab Chapman, Nicola Maggio, Efrat Shavit-Stein
    2021, 16 (10):  2086-2092.  doi: 10.4103/1673-5374.308098
    Abstract ( 113 )   PDF (1157KB) ( 125 )   Save
    Inflammation and coagulation are tightly interconnected in the pathophysiology of neuronal diseases. Thrombin, a pro-coagulant serine protease is associated with neurodegeneration and its indirect inhibitor, activated protein C (aPC), is considered neuroprotective. While levels of thrombin and aPC activity are readily measured in the blood, similar assays in the cerebrospinal fluid (CSF) have not been described. The aim of this study was to establish a specific and sensitive enzymatic assay to measure both thrombin and aPC activity in the CSF. CSF was collected from 14 patients with suspected normal pressure hydrocephalus served as a control group, while seven patients with central nervous system infections served as an acute neuro-inflammatory study group and one sample of CSF following traumatic lumbar puncture served as a positive control. Thrombin and aPC activities were measured by fluorescence released by specific proteolytic cleavage in the presence of endopeptidase and amino-peptidase inhibitors to ensure specificity. Specificity of the method was verified by thrombin and serine-protease inhibitors N-alpha-((2-naphthylsulfinyl)glycyl)-DL-p-amidinophenylalanylpiperidine and phenylmethanesulfonyl fluoride. Inhibition of thrombin activity by CSF samples and levels of specific thrombin inhibitors were also assessed. Thrombin and aPC activities were reliably measured and were significantly higher in the CSF of patients with central nervous system infections compared to normal pressure hydrocephalus controls, suggesting the involvement of these factors in neuro-inflammation. CSF thrombin activity levels in the presence of known thrombin concentration were high in patients with central nervous system infections, and low in normal pressure hydrocephalus patients. Quantification of endogenous thrombin inhibitors protease nexin 1, amyloid precursor protein and anti-thrombin III in CSF by western blot indicated a significant elevation of amyloid precursor protein in infectious CSF. In conclusion, this study describes a novel and sensitive assay aimed at the detection of thrombin and aPC activity in CSF. This method may be useful for measuring these factors that reflect degenerative and protective influences of coagulation on neurological disorders. The study procedure was approved by the Ethics Committee of the Chaim Sheba Medical Center (approval No. 4245-17-SMC) on October 18, 2018.
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    Fluoxetine, a selective serotonin reuptake inhibitor used clinically, improves bladder function in a mouse model of moderate spinal cord injury 
    Long Ma, Jing-Yuan Tang, Jin-Yong Zhou, Chen Zhu, Xin Zhang, Ping Zhou, Qiu Yu, Yan Wang, Xiao-Jian Gu
    2021, 16 (10):  2093-2098.  doi: 10.4103/1673-5374.308667
    Abstract ( 106 )   PDF (2048KB) ( 164 )   Save
    After spinal cord injury, the upward conduction of the spinal cord is lost, resulting in the loss of micturition control, which manifests as detrusor sphincter dyssynergia and insufficient micturition. Studies have shown that serotonergic axons play important roles in the control of the descending urination tract. In this study, mouse models of moderate spinal cord contusions were established. The serotonin agonists quipazine (0.2 mg/kg), 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DAPT, 0.1 mg/kg), buspirone (1 mg/kg), sumatriptan (1 mg/kg), and rizatriptan (50 mg/kg), the serotonin reuptake inhibitors fluoxetine (20 mg/kg) and duloxetine (1 mg/kg), and the dopamine receptor agonist SKF-82197 (0.1 mg/kg) were intraperitoneally administered to the model mice 35 days post-injury in an acute manner. The voided stain on paper method and urodynamics revealed that fluoxetine reduced the amount of residual urine in the bladder and decreased bladder and external urethral sphincter pressure in a mouse model of moderate spinal cord injury. However, fluoxetine did not improve the micturition function in a mouse model of severe spinal cord injury. In contrast, the other serotonergic drugs had no effects on the micturition functions of spinal cord injury model mice. This study was ethically approved by the Institutional Animal Care and Use Committee of Jiangsu Province Hospital of Chinese Medicine (approval No. 2020DW-20-02) on September 11, 2020.
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    MicroRNA and mRNA profiling of cerebral cortex in a transgenic mouse model of Alzheimer’s disease by RNA sequencing
    Li Zeng, Hai-Lun Jiang, Ghulam Md Ashraf, Zhuo-Rong Li, Rui Liu
    2021, 16 (10):  2099-2108.  doi: 10.4103/1673-5374.308104
    Abstract ( 134 )   PDF (3378KB) ( 132 )   Save
    In a previous study, we found that long non-coding genes in Alzheimer’s disease (AD) are a result of endogenous gene disorders caused by the recruitment of microRNA (miRNA) and mRNA, and that miR-200a-3p and other representative miRNAs can mediate cognitive impairment and thus serve as new biomarkers for AD. In this study, we investigated the abnormal expression of miRNA and mRNA and the pathogenesis of AD at the epigenetic level. To this aim, we performed RNA sequencing and an integrative analysis of the cerebral cortex of the widely used amyloid precursor protein and presenilin-1 double transgenic mouse model of AD. Overall, 129 mRNAs and 68 miRNAs were aberrantly expressed. Among these, eight down-regulated miRNAs and seven up-regulated miRNAs appeared as promising noninvasive biomarkers and therapeutic targets. The main enriched signaling pathways involved mitogen-activated kinase protein, phosphatidylinositol 3-kinase-protein kinase B, mechanistic target of rapamycin kinase, forkhead box O, and autophagy. An miRNA-mRNA network between dysregulated miRNAs and corresponding target genes connected with AD progression was also constructed. These miRNAs and mRNAs are potential biomarkers and therapeutic targets for new treatment strategies, early diagnosis, and prevention of AD. The present results provide a novel perspective on the role of miRNAs and mRNAs in AD. This study was approved by the Experimental Animal Care and Use Committee of Institute of Medicinal Biotechnology of Beijing, China (approval No. IMB-201909-D6) on September 6, 2019.
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    Luteolin delays photoreceptor degeneration in a mouse model of retinitis pigmentosa
    Xiao-Bin Liu, Feng Liu, Yi-Yao Liang, Gang Yin, Hui-Jun Zhang, Xue-Song Mi, Zai-Jun Zhang, Kwok-Fai So, Ang Li, Ying Xu
    2021, 16 (10):  2109-2120.  doi: 10.4103/1673-5374.303537
    Abstract ( 199 )   PDF (4627KB) ( 176 )   Save
    Luteolin is neuroprotective for retinal ganglion cells and retinal pigment epithelial cells after oxidative injury, whereby it can inhibit microglial neurotoxicity. Therefore, luteolin holds the potential to be useful for treatment of retinal diseases. The purpose of this study was to investigate whether luteolin exhibits neuroprotective effects on rod cells in rd10 mice, a slow photoreceptor-degenerative model of retinitis pigmentosa. Luteolin (100 mg/kg) intraperitoneally injected daily from postnatal day 14 (P14) to P25 significantly enhanced the visual performance and retinal light responses of rd10 mice at P25. Moreover, it increased the survival of photoreceptors and improved retinal structure. Mechanistically, luteolin treatment attenuated increases in reactive oxygen species, photoreceptor apoptosis, and reactive gliosis; increased mRNA levels of anti-inflammatory cytokines while lowering that of pro-inflammatory and chemoattractant cytokines; and lowered the ratio of phospho-JNK/JNK. Application of the JNK inhibitor SP600125 exerted a similar protective effect to luteolin, suggesting that luteolin delays photoreceptor degeneration and functional deterioration in rd10 mice through regulation of retinal oxidation and inflammation by inhibiting the JNK pathway. Therefore, luteolin may be useful as a supplementary treatment for retinitis pigmentosa. This study was approved by the Qualified Ethics Committee of Jinan University, China (approval No. IACUC-20181217-02) on December 17, 2018.
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