Abstract:

BACKGROUND: Retina ganglion cell (RGC) degeneration in glaucoma is irreversible and tropomyosin-related kinase receptor B (TrkB) associated signaling pathways were implicated in this process. Our study thus examined whether imipramine (Imip), a tricyclic antidepressant, may protect RGC degeneration through the activation of TrkB pathway.
METHODS: Retinal ganglion cell 5 (RGC-5) cell line was cultured in vitro. Various concentrations of Imip were added in the culture and the activation of TrkB pathway was examined by western blot on phosphorylation of ERK and TrkB proteins. H2O2 was applied in the culture to introduce oxidative stress in RGC-5 cells. Imip was then added to examine its protection on oxidative stress induced RGC-5 apoptosis by a TUNEL staining assay. Finally, the functional association of TrkB pathway and Imip protection against apoptosis was examined by adding functional TrkB blocking antibody, TrkB-IgG, into the RGC-5 culture.
RESULTS: In the in vitro RGC-5 culture, western blot showed Imip activated TrkB pathways through ERK/TrkB phosphorylation. TUNEL staining assay demonstrated that H2O2 induced severe oxidative stress-related apoptosis in RGC-5 culture, and the addition of Imip ameliorated H2O2-induced apoptosis. Finally, TrkB-IgG was able to reverse the protective effect of Imip on H2O2-induced RGC-5 apoptosis. 
CONCLUSION: We discovered a novel mechanism of tricyclic antidepressant Imip protecting oxidative stress induced apoptosis in retinal ganglion cells.