Heparin-binding epidermal-growth-factor-like growth factor gene expression is induced by scrape-wounding epithelial cell monolayers: Involvement of mitogen-activated protein kinase cascades

Abstract

Peptide growth factors can promote the cell migration and proliferation that is needed to repair epithelia after mechanical or chemical injury. We report here that scrape-wounding rat intestinal epithelial (RIE-1) cell monolayers caused a rapid increase in levels of heparin-binding epidermal-growth-factor-like growth factor (HB-EGF) mRNA, with a maximal response at approx, 1 h. Hybridization in situ showed that transcript induction occurred primarily in cells at or near wound borders. The increase in HB-EGF mRNA was preceded by activation of the p42 mitogen-activated protein kinase (MAPK) in the wounded cell cultures. Moreover, the induction of HB-EGF mRNA was blocked by PD098059 and U0126, inhibitors that prevent the activation of p42/p44 MAPKs and extracellular signal-regulated protein kinase 5 (ERK5). Both p42 MAPK activation and HB-EGF mRNA induction were inhibited by genistein, indicating a requirement for an upstream tyrosine kinase activity. In contrast, neither response was affected by inhibition of phosphoinositide 3-kinase activity, down-regulation of protein kinase C, or disruption of the actin cytoskeleton with cytochalasin B. We conclude that scrape-wounding epithelial cell monolayers induces HB-EGF mRNA expression by a mechanism that most probably requires p42/p44 MAPK activation, although we cannot exclude a role for ERK5. Our results suggest a physiological role for locally synthesized HB-EGF in promoting epithelial repair after injury.