Contribution of UVB and UVA to UV-dependent stimulation of cyclooxygenase-2 expression in artificial epidermis

Both UVB (280 - 320 nm) and UVA (320 - 400 nm) radiation lead to an enhanced expression of cyclooxygenase-2 (COX-2) in epidermal cells in various in-vitro and in-vivo models. It is demonstrated here that the expression of COX-2 is induced in artificial human epidermis exposed to simulated solar light (> 290 nm). Employing filters eliminating specified regions from the simulated solar spectrum, the UVB and UVA-2 ( 320 - 350 nm) regions are shown to fully account for induction of COX- 2 mRNA and protein as well as the enhanced production of prostaglandin E-2 after irradiation. At the protein level, approximately 70% of the total induction by solar light is due to light in the UVA-2 region. UVA-1 (350 - 400 nm), visible light and IR radiation are practically ineffective. COX- 2 induction by simulated solar light is attenuated in the presence of inhibitors of p38(MAPK) or of c-Jun-N-terminal kinases (JNK), whereas COX-2 induction by UVA is blocked only by inhibition of JNK. UV-induced COX- 2 expression is not affected by inhibition of the MEK 1,2/ERK 1,2 pathways.