Abstract:

Disruption of the blood–brain barrier and blood-spinal cord barrier is a fundamental pathological feature of multiple sclerosis progression. The ketogenic diet has a high therapeutic potential for patients with multiple sclerosis. We previously reported that treating experimental autoimmune encephalomyelitis mice with ketogenic diet results in anti-neuroinflammation and neuroprotection. However, the impact of ketogenic diet administration on the blood–brain barrier/blood–spinal cord barrier in MS remains unclear. Here, we investigated the effects of ketogenic diet on the blood–brain barrier/blood–spinal cord barrier integrity and the possible underlying mechanisms. We established a 24-day continuous experimental autoimmune encephalomyelitis mouse model with or without ketogenic diet and performed β-hydroxybutyrate assay kit histological analysis, quantitative reverse transcription-polymerase chain reaction, and western blot to examine experimental autoimmune encephalomyelitis pathological hallmarks, glial cell activation status, and intracellular signaling pathway alterations. Our results showed that ketogenic diet inhibited demyelination, suppressed astrocyte and microglial activation, and modulated the balance of matrix metalloproteinases/tissue inhibitors of metalloproteinases in the central nervous system of experimental autoimmune encephalomyelitis mice. Ketogenic diet upregulated tight junction proteins (occludin, claudin-1, and ZO-1) and adherens junction proteins (VE-cadherin and β-catenin) in the spinal cord, cerebellum, and cortex of experimental autoimmune encephalomyelitis mice. Notably, we found that ketogenic diet protects the blood–brain barrier/blood–spinal cord barrier integrity by modulating astrocyte polarization from the A1 phenotype to A2 phenotype and modifying the inflammatory milieu (downregulating pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, and interleukin-6, and upregulating anti-inflammatory cytokines such as transforming growth factor-β and interleukin-4) by inhibition of class I histone deacetylase 3/STAT3/nuclear factor kappa B (NF-κB)/NOD-, LRR- and pyrin domain-containing protein 3 and activation of PI3K/AKT signaling pathways. Furthermore, ketogenic diet downregulated key chemokines (C–X–C motif chemokine ligand 10, C–X–C motif chemokine ligand 12, C–C motif chemokine ligand 2, and C–C motif chemokine ligand 5) and receptor C–C motif chemokine receptor 2 expression throughout the central nervous system, suggesting an impaired capacity for leukocyte recruitment. Ketogenic diet suppressed astrocytic NOD-, LRR- and pyrin domain-containing protein 3 inflammasome activation, as evidenced by reduced NOD-, LRR- and pyrin domain-containing protein 3/glial fibrillary acidic protein co-localization. In summary, the ketogenic diet promotes neuroprotection in the experimental autoimmune encephalomyelitis model by inhibiting A1 astrogliogenesis and protecting the integrity of the blood–brain barrier/blood-spinal cord barrier.

Key words: A1 astrocytesl A2 astrocytesl blood–brain barrierl blood–spinal cord barrierl experimental autoimmune encephalomyelitisl ketogenic dietl multiple sclerosisl nerve regenerationl neuroinflammationl NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome