PROSTAGLANDIN SYNTHASE 2 EXPRESSION IN EPIDERMAL GROWTH FACTOR-DEPENDENT PROLIFERATION OF MOUSE KERATINOCYTES

BALB/c mouse keratinocytes (BALB/MK) are nontumorigenic epithelial cel ls which are dependent on mouse epidermal growth factor (EGF) for main taining proliferation in culture, In BALB/MK the oxygenation of both a rachidonic acid and linoleic acid was dependent on EGF. EGF stimulated the formation of prostaglandin E(2) and prostaglandin F-2 alpha from arachidonic acid and 9- and 13-hydroxyoctadecadienoic acid (HODE) from linoleic acid, Analysis of the linoleic acid metabolites determined t he ratio of 9-HODE to 13-HODE was approximately 6 to 4, and the 9-HODE was the (R) enantiomer, consistent with metabolism by prostaglandin G /H synthase (PGHS). The formation of these linoleic acid metabolites w as sensitive to indomethacin, a PGHS inhibitor. EGF induced the expres sion of PGHS-2 mRNA after 30 min, which peaked after 1 h, and remained expressed for at least 24 h after the addition of EGF. A less signifi cant increase in the expression of PGHS-1 mRNA occurred 4 h after EGF stimulation, Immunoblot analysis did not detect expression of PGHS-1 p rotein. However, PGHS-2 protein expression was increased 2 h after EGF exposure and was dependent on EGF. PGHS-2 protein was not transiently expressed as reported with other cell types, but was continually expr essed in proliferating cells maintained with EGF at a subconfluent den sity, Indomethacin significantly attenuated EGF-dependent mitogenesis and cell proliferation. These results suggest that PGHS-2 activity con tributes to the proliferative response of BALB/MK to EGF. (C) 1996 Aca demic Press, Inc.