Role of type I & type II reactions in DNA damage and activation of caspase 3 via mitochondrial pathway induced by photosensitized benzophenone.

Sunscreen users have been increased, since excessive sun exposure increased the risk of skin diseases. Benzophenone (BP) and its derivatives are commonly used in sunscreens as UV blocker. Its photosafety is concern for human health. Our study showed the role of type-I and type-II radicals in activation of caspase 3 and phototoxicity of BP under sunlight/UV radiation. BP photodegraded and formed two photoproducts. BP generates reactive oxygen species (ROS) singlet oxygen ((1)O2), superoxide anion (O2˙(-)) and hydroxyl radical (˙OH) through type-I and type-II photodynamic mechanisms. Photocytotoxicity significantly reduced cell viability under sunlight, UVB and UVA. DCF fluorescence confirmed intracellular ROS generation. BP showed single strand DNA breakage, further proved by cyclobutane pyrimidine dimmers (CPDs) formation. Lipid peroxidation and LDH leakage were enhanced by BP. P21 dependent cell cycle study showed sub G1 population which advocates apoptotic cell death, confirmed through AO/EB and annexin V/PI staining. BP decreased mitochondrial membrane potential, death protein released and activated caspase. We proposed cytochrome c regulated caspase 3 dependent apoptosis in HaCaT cell line through down regulation of Bcl2/Bax ratio. Phototoxicity potential of its photoproducts is essential to understand its total environmental fate. Hence, we conclude that BP may replace from cosmetics preparation of topical application.