Reduction in oxalate-induced renal tubular epithelial cell injury by an extract from Quercus salicina Blume/Quercus stenophylla Makino.

Urocalun, a herbal medicine prepared from an extract of Quercus salicina Blume/Quercus stenophylla Makino (QS extract), has been clinically used for the treatment of urolithiasis in Japan since 1969. In the present study, the effects of QS extract on oxalate-induced cell injury and NADPH-induced superoxide anion (O(2) (-)) production in the injured cells were investigated. Oxalate-induced cell injury was assessed by mitochondrial reduction of 3-(4,5-dimethyl-2-thiazol)-2,5-diphenyltetrazolium bromide and leakage of lactate dehydrogenase into the extracellular fluid. When NRK-52E cells were injured by exposure to oxalate for 24 h, QS extract prevented the injury in a dose-dependent manner. In addition, QS extract suppressed the increase in NADPH-induced O(2) (-) production, or NADPH oxidase activity, in the homogenate of cells injured by oxalate exposure. These findings suggest that the reduction in oxalate-induced O(2) (-) production contributes to the cytoprotective effect of QS extract.