Activation of neutrophil membrane-associated oxidative metabolism by ultraviolet radiation

Exposure of human neutrophils to ultraviolet radiation (UVR) in vitro was accompanied by activation of superoxide generation and preferential release of secondary granules. These pro-oxidative interactions of UVR with neutrophils were dependent on intact cellular membrane-associated oxidative metabolism and were mediated almost exclusively by the UVB component of UVR. Irradiation of neutrophils was also associated with release of arachidonic acid from membrane phospholipids, implicating involvement of phospholipase A2 (PLA2) in the pro-oxidative activity of UVR. The pro-oxidative interactions of UVR with neutrophils were mimicked by coincubation of the cells with reagent arachidonate or lysophosphatidylcholine (LPC), whereas the PLA2 inhibitor 4-p-bromophenacyl bromide, as well as the LPC- and arachidonate complex-forming agent alpha-tocopherol, inhibited these pro-oxidative interactions of UVR with phagocytes. Because phagocyte-derived reactive oxidants are cytotoxic, immunosuppressive, and carcinogenic, these agents are potential mediators of UVR-mediated tissue damage and tumorigenesis.