Regulation of the susceptibility to oxidative stress by cysteine availability in pancreatic [beta]-cells

Pancreatic 13-cells are susceptible to oxidative stress, which is related closely to the islet dysfunction. In the present study, using the pancreatic cell lines HIT-T15 and RINm5F as known in vitro models of impaired [beta]-cell function as well as primary rat islet [beta]-cells, we observed a relationship between intracellular glutathione levels and oxidative stress-mediated cell dysfunction. Hydrogen peroxide and 4-hydroxy2-nonenal caused cell death in HIT-T15 and RINm5F cells at lower concentrations compared with non-[beta]-cells, such as HepG2 and NRK49F cells. The extent of the cytotoxicity caused by the model oxidants was inversely correlated well with intracellular glutathione levels in the cell lines used. Treatment of HIT-T15 and RINm5F cells with L-cysteine or L-cystine significantly augmented the glutathione contents, surpassing the effect of N-acetylcysteine, and abrogated 4-hydroxy-2-nonenal-mediated cytotoxicity almost completely. L-Cysteine increased intracellular glutathione levels in primary [beta]-cells as well. Supplementation of L-cysteine to the RINm5F cell culture inhibited 4-hydroxy-2-nonenal-mediated cytosolic translocation of PDX-1, a key transcription factor for [beta]-cell function. Intrinsic transport activities ([V.sub.max]/[K.sub.m]) of the L-cystine/L-glutamate exchanger in HIT-T15 and RINm5F cells were considerably lower than that in NRK-49F cells, although gene expressions of the exchanger were similar in these cells. Results obtained from the present study suggest that the restricted activity of the L-cystine/L-glutamate exchanger controls the levels of intracellular glutathione, thereby making [beta]-cells become susceptible to oxidative stress. system [x.sup.-.sub.c]; glutathione; hydrogen peroxide; reactive oxygen species; PDX-1