Nicotine switches the form of H(2)O(2)-induced cell death from apoptosis to necrosis in U937 cells

Cigarette smoking is a major risk factor for lung diseases and oral diseases. The present study examined the effect of nicotine on H(2)O(2)-induced apoptosis in U937 cells. In the presence of 1 microg/ml nicotine, cell viability was not affected, but the cells were unable to undergo H(2)O(2)-induced apoptosis and instead died as a result of necrosis. Nicotine reduced the intracellular level of ATP, which is an important determinant of the form of cell death. These results suggest that nicotine can alter the cell death pathway by reducing the level of intracellular ATP, and that this effect may contribute to cigarette smoke-induced tissue destruction.