Inhibitory effect of green tea tannin on free radical-induced injury to the renal epithelial cell line, LLC-PK₁

Green tea is an antioxidant with radical-scavenging activity. To investigate these properties we examined the effect of green tea tannin on the viability of renal epithelial LLC-PK₁ cells treated with 3-morpholinosydnonimine (SIN-1), sodium nitroprusside or pyrogallol. SIN-1 treatment significantly decreased cell viability, while a mixture of tannin and SIN1 led to a recovery of viability from the cellular damage induced by free radicals generated by SIN-1. Moreover, (-)-epigallocatechin 3-O-gallate (EGCg) and (-)-epigallocatechin (EGC), the main components of tannin, produced higher activity than tannin alone. Caffeine and theanine, also components of green tea, did not show activity. However, tannin did not protect the cell against nitric oxide (NO) or superoxide anion (02^-) (produced by sodium nitroprusside and pyrogallol, respectively). This result suggests that green tea tannin protects LLC-PK₁ cells from oxidative stress caused by free radicals generated by SIN-1, but not from stress induced by either NO or O₂^-. Moreover, and its components, EGCg and EGC.