UV Released Factors Induce Antioxidant Defense in A375 Cells

UV light leads to release of different secretory factors from irradiated cells of which some of them have been characterized. We have reported earlier that cells exposed to the supernatant medium from irradiated cells were resistant to killing by some genotoxic agents. In this study, we present our finding that demonstrates DNA damage induced by UV or H2O2 is lowered on prior exposure to the UV released factors (UVRF). Production of ROS in cells and lipid peroxidation was also lowered. It was found that treatment of unexposed cells with UVRF present in the supernatant medium altered the antioxidant defense activity in cells. Significant was the increase in catalase (CAT) and Cu–Zn superoxide dismutase (SOD) activity, whereas glutathione peroxidase (GPx) and reduced glutathione (GSH) levels remained unaffected. Cells exposed to UVRF prior to UV or H2O2 treatment also experienced such upregulation; however, the remarkable increase in the GPx activity exhibited by these cells was not observed in cells exposed to H2O2 or UV alone. It appears that exposure to UVRF tinkered with antioxidant defense in cells to facilitate its proliferation upon assault by an agent that can produce oxidative damage. UV‐irradiated cells transmit signals to nonirradiated cells through secretory factors (UVRF) that can produce a variety of responses. We have found that cells exposed to these factors were less sensitive to killing by UVC or H2O2, but not to MNNG. For UVC and H2O2 treatment oxidative damage was lowered because UVRF exposed cells have elevated CAT and SOD activities. The ability of these cells to counter the assaults by oxidants through a considerable increase in GPx activity is significant for its ability to provide protection to cells.