INHIBITION OF NADPH OXIDASE REDUCES ENDOPLASMIC RETICULUM STRESS AND AMELIORATES ACUTE PANCREATITIS

Abstract

Background & Aims: Endoplasmic reticulum stress and its conserved rejoinder -the unfolded protein response (UPR)- have been found to play critical roles in several diseases. We previously showed that all major UPR pathways are activated early in acute pancreatitis. Here we present evidence that oxidative stress mediated by NADPH oxidase is necessary for both ER stress and the development of acute pancreatitis in this model. Methods: Necrohemmoragic pancreatitis was induced in rats by a single ip injection of 4.0 g/kg bw arginine. Pancreatitis severity was assessed at 4 and 24 h by analysis of serum amylase, pancreatic trypsin activity, edema formation and histology. ER stress related phosphorylation of PKR-like ER kinase (PERK) and posttranslational splicing of X-Box binding protein (XBP-1) into sXBP-1 were analyzed. To examine the influence of the NADPH oxidase inhibitors on ER stress and pancreatitis animals were pre-treated 20 min before arginine administration with 1 mg/kg diphenylene iodonium (DPI) iv, or 50 mg/kg aminoethyl benzenesulfonyl fluoride (pefabloc) ip. The data were compared to saline or arginine treatment alone. Results: Arginine treatment rapidly induced pancreatitis, indicated by increased serum amylase, pancreatic edema, and acinar cell damage within 4 h. Arginine also activated ER stress, as shown by phosphorylation of PERK at 4 and 24 h and XBP-1 splicing at 24 h. Inhibition of NADPH oxidase with either DPI or pefabloc reduced ER stress as shown by reduction of PERK phosphorylation and sXBP-1 to control levels of saline treated pancreases. The inhibitors also profoundly reduced serum amylase, tissue edema, trypsin activation and histological damage after L-arginine administration compared to arginine treatment alone. Conclusions: These results indicate that ER stress is activated downstream of oxidative stress in the arginine model of acute pancreatitis and suggests that ER stress mechanisms may contribute to the development and severity of this disease.