B. Aladegbami1, J. Guo1, B. W. Warner1 1Washington University,Pediatric Surgery,St. Louis, MO, USA
Introduction: Following massive small bowel resection (SBR), an important programmed compensatory process takes place in the remaining bowel termed adaptation. This adaptive response is characterized by increased enterocyte proliferation leading to taller villi, deeper crypts, and an expanded mucosal surface area. The magnitude of adaptation is regulated at least in part by intact epidermal growth factor receptor (EGFR) signaling. Recently, we have found that adaptation is also associated with diminished oxygen delivery, increased hypoxia-inducing factor (HIF1α) expression, and subsequent enhanced angiogenesis within the villi and submucosal layer in the remnant bowel. The aim of this study is to elucidate the potential role for EGFR signaling as a regulator of HIF1α expression in both enterocytes and endothelial cells.
Methods: Rat Intestinal Epithelial Cells (RIEC) and Human Intestinal Endothelial Cells (HIMEC) were serum-starved for 24 hours. The cells were then treated with either EGF (50ng/ml) alone, EGF plus EGFR inhibitors (Geftinib (ZD1839) or Analinoquinazolin (AG1478)) or the EGFR inhibitors alone for 1 hour. This was followed by a period of either normoxia or hypoxia (0.5 % Fi02) for another 4 hours. Cells were washed and harvested directly into 1X SDS sample loading buffer. A Western blot was then performed to assess the effects of EGFR signaling manipulation and expressions of HIF1α in these cell lines
Results: HIF1α expression could be detected only under hypoxic condition in both epithelial and endothelial cells. EGFR is activated at both normoxia and hypoxia conditions as demonstrated by EGFR phosphorylation in both cells. EGFR inhibitors effectively diminished EGFR and MAP-Kinase activity in both normoxia and hypoxia cells upon EGF stimulation. Interestingly HIF1α expression is also reduced in those cells with blunted EGFR activation.
Conclusion: EGFR signaling appears to play a role in the stimulation of HIF1α expression in both enterocytes and endothelial cells. These findings illuminate a novel mechanism for enhanced angiogenesis associated with resection-induced intestinal adaptation.
