Evaluation of resveratrol and piceatannol cytotoxicity in macrophages, T cells, and skin cells.

The cytotoxicity of resveratrol and of piceatannol, a structural analog of resveratrol, was examined in cultured cells. Using a MTT-based assay, which measures the conversion of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) to a colored formazan product in living cells, resveratrol was found to inhibit the viability of transformed mouse macrophages, tumor-derived human T cells and human epidermoid carcinoma cells in a concentration-dependent manner, with the effect decreasing in the order: T cells (LC50 approximately 27 micromol L(-1), 24 h; approximately 9 micromol L(-1); 48 h)>macrophages (LC50 approximately 29 micromol L(-1), 24 h; 39 micromol L(-1), 48 h)>skin cells (LC50 approximately 91 micromol L(-1), 24 h; approximately 66 micromol L(-1), 48 h). Paradoxically, a high concentration of resveratrol (50 micromol L(-1)) inhibited the proliferation of all three cell types, and a low concentration (5 micromol L(-1)) stimulated the proliferation of macrophages. The viability of macrophages was also decreased by piceatannol in a concentration-dependent manner. The stimulation of macrophages with zymosan lowered the cytotoxicity of both resveratrol and piceatannol. Scanning electron microscopy of cells treated with resveratrol revealed changes in cellular morphology that were consistent with toxicity. In macrophages and skin cells, resveratrol (50 micromol L(-1)) induced a time-dependent increase in reduced glutathione levels but did not alter the background levels of thiobarbituric acid-reactive substances. Taken together, the present data indicate that resveratrol is toxic to cultured macrophages, T cells and skin cells at concentrations>or=25 micromol L(-1), and that the cytotoxicity occurs via a mechanism that does not involve oxidative stress. Furthermore, the degree of toxicity of both resveratrol and piceatannol towards macrophages depends on the activation status of these cells, with zymosan-activated cells appearing more resistant than nonstimulated cells.