Nicotine inhibits UV-induced activation of the apoptotic pathway.

Although nicotine has been implicated as a potential factor in the pathogenesis of cancer in humans, its mechanism of action in the development of cancer remains largely unknown. Growing evidence indicates that the induction of apoptosis is an important mechanism in the prevention of cancer development. In the study presented here, we examined the effects of nicotine on the process of apoptosis. Preincubation of human cells with nicotine completely inhibited ultraviolet light (UV)-induced apoptosis. The inhibition of apoptosis by nicotine was correlated with the prevention of cytochrome c release and caspase activation, which are essential components of the UV-induced apoptotic pathway. Thus, our results suggest that the inhibition of apoptosis by nicotine contributes to the increased incidence of cancer in smokers.