MULTIFACTOR REGULATION OF PROSTAGLANDIN-H SYNTHASE-2 IN MURINE KERATINOCYTES

Prostaglandin H synthase (PGHS) is the rate-limiting enzyme responsibl e for the formation of the prostaglandins from arachidonic acid. Prost aglandins (and other metabolites) elicit signals for inflammation, whi ch is thought to be required for tumor promotion in the mouse skin car cinogenesis model. This study was designed to examine the effect of pr otein kinase C (PKC)-activating tumor promoters (4 beta-12-O-tetradeca noylphorbol-13-acetate (TPA)), non-PKC-type promoters (anthralin, benz oyl peroxide, okadaic acid), and mitogens (epidermal growth factor (EG F)) on the levels of the constitutive (PGHS-1) and inducible (PGHS-2) forms of PGHS in murine keratinocytes. Northern analysis of mRNA isola ted from cultures treated with TPA (1 mu g/ml) showed that a single tr eatment of TPA produced a sevenfold increase in PGHS-2 mRNA by 1 h tha t decreased by 6 h after treatment. PGHS-2 protein levels were elevate d threefold by 3 h and remained elevated through 9 h. Downregulation o f PKC with a second TPA treatment 15 h after the first resulted in dim inished induction of PGHS-2 expression. Of the other promoters examine d, anthralin (5 mu M), benzoyl peroxide (10 mu M), and okadaic acid (1 mu M) induced PGHS-2 mRNA with different kinetics and to different ex tents. Additionally, the nontumor-promoting phorbol ester analogue 4 a lpha-12-O-tetradecanoylphorbol-13-acetate induced PGHS-2 mRNA signific antly by 1 h, and this response remained elevated up to 6 h after trea tment. Elevated PGHS-2 expression was also observed by 3 h in response to EGF (10 ng/mL) treatment. Collectively, these observations indicat e that there are several different signaling pathways by which PGHS-2 can be upregulated in murine keratinocytes. (C) 1996 Wiley-Liss, Inc.