Peroxynitrite inhibits epidermal growth factor receptor signaling in Caco-2 cells

Intestinal mucosa serves as an important barrier that may be disrupted by inflammation. A complex system of cellular and humoral factors, including epidermal growth factor ( EGF), maintains the integrity of this barrier. We hypothesized that peroxynitrite, generated in inflamed intestinal epithelium, can alter the EGF receptor function by nitrating tyrosine residues and blocking ligand- activated tyrosine autophosphorylation. Caco- 2 cells or A431 cell membranes were treated with peroxynitrite or its decomposed form. Cell proliferation was measured by [ H-3] thymidine uptake. Immunoblot and immunoprecipitation were used to assess the tyrosine phosphorylation and nitration. Binding of epidermal growth factor to its receptor was detected by affinity labeling with I-125- EGF. Peroxynitrite inhibited EGF- induced Caco- 2 cell proliferation and binding of EGF to its receptor in a concentration- dependent manner. Peroxynitrite abolished EGF- stimulated receptor autophosphorylation and nitrated EGF receptor tyrosine residues. Peroxynitrite generated during inflammation may disrupt the EGF- induced signaling in intestinal epithelial cells.