The first peak of the UVB irradiation-dependent biphasic induction of vascular endothelial growth factor (VEGF) is due to phosphorylation of the epidermal growth factor receptor and independent of autocrine transforming growth factor alpha

Ultraviolet B (UVB) irradiation, the major damaging component of sunlight, has earlier been reported to enhance cutaneous angiogenesis in chronically sun-exposed skin. We herein provide first evidence for a biphasic induction of the vascular endothelial growth factor (VEGF) following UVB irradiation of the human epidermal cell line HaCaT. The first VEGF peak occurred on mR NA level at 1 h and on protein level at 4 h postirradiation and is fully me diated by the UVB-dependent phosphorylation of the epidermal growth factor receptor, which subsequent to its phosphorylation also initiates at least i n part the synthesis of transforming growth factor alpha that confers as sh own previously the second late VEGF peak at 8 h on mRNA and at 24 h on prot ein level, (C) 2000 Federation of European Biochemical Societies.