P58: Cystathionine-gamma-lyase is essential in maintaining retinal redox balance.

Retina is one of the tissues that exposed to highest oxidative stress due to its high metabolic rate, abundant photosensitizing activity and visible light exposure. With these high chances of oxidative damage, antioxidative capacity of retinal tissues is essential for maintaining the proper functions of retina. Cytoprotective roles of hydrogen sulfide (H2S) have been documented and were largely attributed to its antioxidative activity. However, whether are these three H2S-producing enzymes (cystathionine-gamma-lyase (CSE), cystathionine-beta-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (MPST) plays antioxidative roles in retinal tissue is unclear. In this study, we examined the role of CSE, CBS and MPST enzymes in human retinal pigmented epithelial cell line ARPE19. ARPE19 expressed comparatively similar protein levels of the three enzymes. Surprisingly, gene silencing of CSE sensitized the cells to hydrogen peroxide (H2O2) challenge to a much greater extent as compared to gene silencing in CBS or MPST. We also observed that loss of CSE in ARPE19 resulted in decreased level of glutathione, higher oxidative stress and accelerated senescence. Taken together, our data suggest that CSE is essential for retinal functions by maintaining its redox balance. [ABSTRACT FROM AUTHOR]