Epidermal Growth Factor Regulation of Linoleic Acid Metabolism in Syrian Hamster Embryo Fibroblasts

Abstract

Epidermal growth factor (EGF) stimulates the lipoxygenase metabolism of linoleic acid to 13- and 9- hydroxyoctadecadienoic acid (HODE) in Syrian hamster embryo (SHE) fibroblasts. Lipoxygenase inhibitors are potent blockers of EGF dependent mitogenesis in SHE cells, while addition of these linoleate compounds (10–11 to 10–6M) produce a 2–4 fold enhancement of EGF-stimulated DNA synthesis. This activity appears to be specific for the linoleate metabolites as mono-hydroxy dervatives of arachidonic acid have no mitogenic acitivtity in these fibroblasts. Moreover, in testing 13(S)-HODE vs. 13(R)-HODE, only the S isomer was found to be active. Chiral phase HPLC analyses of cellular derived 13-HODE revealed the compound to be in the S configuration. In studies on the mechanism of EGF regulation of linoleic acid metabolism, inhibitors of EGF-receptortyrosine kinase activity were observed to block EGF-stimulated HODE biosynthesis. These inhibitors did not alter lipoxygenase activity in vitro. In addition, both cyclohexamide and actinomycin D attenuated the ability of EGF to increase linoleic acid metabolism in SHE cells. EGF induction of the linoleate pathway appears to be linked to activation of the EGF receptor and may be modulated at the transcriptional and translational level.