A mechanism of retinal protection from light-induced degeneration by hydrogen sulfide

Figures & data

Figure 1. When retinal photoreceptor cells are exposed to light, cGMP-gated channels are closed and the cell membrane is hyperpolarized. The intracellular concentrations of Ca²⁺ in photoreceptor cells are decreased to approximately 10 nM, which activates 3MST/CAT to produce H₂S. H₂S activates vacuolar-type H⁺-ATPase in horizontal cells to released H⁺ that suppresses the activity of voltage gated Ca²⁺ channels in photoreceptor cells. By this mechanism H₂S maintains intracellular Ca²⁺ in low levels. Excessive light exposure leads to photoreceptor degeneration caused by reactive oxygen species and elevated intracellular concentrations of Ca²⁺. The regulation of Ca²⁺ by endogenous H₂S may fail by the excessive levels of light, and the photoreceptor cell degeneration occurs. Even under such conditions the enhancement of 3MST/CAT pathway or the administration of H₂S may have clinical benefit for diseases with retinal cell degeneration.