Redox-Redux and NADPH Oxidase (NOX): Even More Complicated than We Thought it Might Be.

The NOX (nicotinamide adenine dinucleotide phosphate oxidase) family includes seven unique members that are involved in a multitude of physiological functions, including extensive interaction with UVR and the skin. NOX1 is uniquely present and activated by UVB radiation with biphasic expression of the enzyme immediately and then after a several-hour delay. Specific inhibition of both early and late NOX1 activation leads to evidence of decreased photocarcinogenesis in in vitro keratinocytes and in well-characterized mouse models in which antitumor efficacy has been shown; inhibiting only late NOX activation does not exhibit such effects. These results suggest a crucial function of early NOX activation in transducing a signal for cellular protection after UVB carcinogenesis provocation. We term this an intrinsic cellular ROS priming function for quenching DNA damage and promoting survival. Evolutionally, this type of priming function may be essential for addressing various types of stimuli from adverse environments.