Wavelength specific activation of PI 3‐kinase by UVB irradiation

We investigated the effect of UVB irradiation on phospholipid metabolism using normal human diploid skin fibroblasts. When cells were exposed to monochromatic UV light, the intracellular PIP3 level was increased within 1 min in a wavelength-specific manner. The increase was most marked in the UVB range and was inhibited by a PI 3-kinase inhibitor, tyrosine kinase inhibitor, or antioxidant reagents. Furthermore, the decrease of cell viability induced by UVB irradiation was significantly blocked by wortmannin. These results suggest that PI 3-kinase activation is involved in novel cellular responses specific for UVB that lead to cell death.