Solar-simulated radiation induces secretion of IL-6 and production of isoprostanes in human skin in vivo

Cytokines represent an integral part of the large group of mediators involved in dermal inflammation. In this in vivo study, ultraviolet light which is one of the major environmental factors affecting cytokine release patterns in the skin was employed. The effects of repeated versus one-time irradiation with solar-simulated ultraviolet light was studied regarding the secretion of proinflammatory cytokines with a Bio-Plex cytokine assay using suction blisters as a model for localized inflammatory processes. The IL-6 concentration increased markedly after 24 h in skin areas irradiated with a twofold minimal erythemal dose (MED) compared to areas challenged repeatedly with 0.3 MED. In addition, we investigated the concentration of 8-isoprostane in the suction blister fluid as a marker of lipid peroxidation due to a UV-induced increase in free radical production. 8-Isoprostane was increased immediately after treatment but declined after 24 h with the exception of the skin area exposed to 2 MED. The differential expression and release of cytokines, and the extent of oxidative damage might therefore depend on the dose and regimen of exposure to solar-simulated radiation.