Effects of ultraviolet A and antioxidant defense in cultured fibroblasts and keratinocytes

Lipid peroxidation, measured by the thiobarbituric acid-reactive substances assay, was evaluated for cultured human skin fibroblasts and keratinocytes exposed to ultraviolet A radiation (320-400 nm, UVA). Peroxidation increases with increasing UVA doses and is much lower for keratinocytes than for fibroblasts. Immediate UVA-induced cytotoxicity, monitored by the trypan blue exclusion assay, is also lower for keratinocytes. Thus, cultured human skin keratinocytes are less sensitive than fibroblasts to the immediate deleterious effects of UVA with respect to membrane damage and lipid peroxidation. As a first attempt to understand this lower sensitivity of keratinocytes, basal levels of antioxidant defenses including total glutathione, superoxide dismutase, glutathione peroxidase and catalase were evaluated in both keratinocytes and fibroblasts from the same donors. We failed to correlate this lower susceptibility of keratinocyte to UVA-induced lipid peroxidation and cytotocixity with a higher antioxidant status.