Cytoprotective and cytotoxic effects of curcumin: dual action on H2O2-induced oxidative cell damage in NG108-15 cells.

The ability of curcumin, a natural antioxidant isolated from Curcuma longa, to inhibit hydrogen peroxide (H(2)O(2))-induced cell damage in NG108-15 cells was examined. When added simultaneously with 500 microM H(2)O(2), curcumin (25-100 microM) effectively protected cells from oxidative damage. However, when the cells were pretreated with curcumin (25-100 microM) for 1.5 h before H(2)O(2) exposure, curcumin was unable to inhibit H(2)O(2)-induced cell damage. Instead, it caused a significant concentration-dependent decrease in cell viability after H(2)O(2) exposure. This dual action of curcumin suggests that pretreatment with curcumin by itself did not have any significant effect on the viability of the NG108-15 cells, but it sensitized them to oxidative damage induced by H(2)O(2) under our experimental conditions. It appears that these events may not relate to the antioxidant and free radical scavenging activities of curcumin.