Oxidative stress induced by UV-B and sunlight mediated photoactivation of carbazole inhibits normal human skin cells physiology

Solar ultraviolet (UV) radiation causes skin cancer after prolongs exposure. Carbazole (CBZ) has a tricyclic structure and is produced from fossil fuels, cigarette smoke, eye kohl, black tattoo ink, coal and wood combustion. We have studied the photomodification of CBZ under UV-B (0.9mw/cm 2 ) and sunlight. Phototoxicity of CBZ was done on human skin keratinocytes (HaCaT) through MTT, NRU and cell migration assays. CBZ generates reactive oxygen species (ROS) through type-I photodynamic reaction and measured through H2DCFDA and DHE fluorescence in cells. Photosensitized CBZ induced apoptosis which was confirmed through sub-G1 fraction, morphological changes, cytochrome c and caspase-12 release from mitochondria and ER, PS translocation, CPDs/6,4PPs/MN formation. Our RT-PCR and western blot results strongly supports our view point of apoptotic cell death through up-regulation of pro-apoptotic genes followed by antioxidant genes keap-1, nrf-2 and hmox-1. Therefore, much attention should be paid to concomitant exposure of carbazole and UV-R for its total environmental impact.