Ultraviolet radiation alters choline phospholipid metabolism in human keratinocytes

Ultraviolet radiation B (UVB-290-320 nm) induces inflammation and hyperproliferation in human epidermis. This response is associated with the recovery from irradiated skin of inflammatory mediators derived from membrane phospholipids. We have previously reported that UVB stimulates the production of such mediators by human keratinocytes (HK) in culture. In these studies we examined the effect of UVB on the metabolism of choline containing phospholipids in HK prelabeled with [3H] choline. UVB (400-1600J/m2) stimulated a dose dependent release of [3H] choline from HK within minutes of irradiation. Examination of media extracts by paper chromatography revealed that the released [3H] choline was predominately in the form of glycerophosphorylcholine. Examination of label remaining in membranes of cells after irradiation by acid precipitation and HPLC revealed that the origin of the released [3H] choline was the membrane phosphatidylcholine/lysophosphatidylcholine. These data support a concept of UVB stimulation of both a phospholipase A (1 or 2) and a lysophospholipase. These UVB induced alterations of HK membrane phospholipid metabolism likely have profound effects on UVB-induced inflammation and control of cell growth in human skin.