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GASTROINTESTINAL, HEPATIC, PULMONARY, AND RENAL

Angiotensin II Type 1 Receptor-Dependent Nuclear Factor-B Activation-Mediated Proinflammatory Actions in a Rat Model of Obstructive Acute Pancreatitis

Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China

Angiotensin II is a key mediator of inflammation, and nuclear factor-B (NF-B) plays a critical role in various inflammatory diseases, including acute pancreatitis (AP). This study sought to elucidate the mechanism mediating angiotensin II involvement in angiotensin II type 1 (AT₁) receptor-mediated NF-B activation, and ultimately in proinflammatory actions of AP pathogenesis. A rat model of obstructive pancreatitis was induced by ligation of the common biliopancreatic duct. Pancreatic injury was determined by assessing pancreatic histology, myeloperoxidase activity, and serum interleukin-6. Protein levels of pancreatic angiotensinogen and AT₁ receptor as well as NF-B inhibitory subunits (IB and IB) and phospho-NF-B p65, B-related proteins (intercellular adhesion molecule-1, cyclooxygenas-2, and interleukin-1), and NADPH oxidase isoforms p67 and p22 were examined by Western blot. Nuclear B binding activity and degree of oxidative stress were determined by electrophoretic mobility shift assay and glutathione/nitrotyrosine examination, respectively. The effects of losartan, an AT₁ receptor antagonist, on NF-B-mediated proinflammatory actions were also assessed. Induction of AP was associated with a time-dependent increase in pancreatic angiotensinogen levels. AT₁ receptor blockade with losartan improved the pancreatic histological damage, myeloperoxidase activity, and serum interleukin-6. Losartan treatment also reduced AP-associated depletion of IB and elevation of phospho-NF-B p65 protein expression as well as the enhanced nuclear B binding activity and elevated levels of B-related proteins. In addition, losartan treatment suppressed pancreatic glutathione and nitrotyrosine levels, which were consistent with decreased NADPH oxidase expression. These data provide substantial evidence that angiotensin II is involved in AT₁ receptor-mediated NADPH oxidase-dependent NF-B activation; thus, it might ultimately promote proinflammatory actions during AP pathogenesis.

Address correspondence to: Dr. Po Sing Leung, Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China. E-mail: psleung{at}cuhk.edu.hk