Involvement of Redox-Sensitive Extracellular-Regulated Kinases in Angiotensin II-Induced Interleukin-6 Expression in Pancreatic Acinar Cells

Abstract

Angiotensin II has been shown to play a role in the pathogenesis of acute pancreatitis (AP). The present investigation aimed at elucidating redox-sensitive mechanistic pathway involved in proinflammatory actions of angiotensin II during an episode of AP; in particular, the regulation of expression of cytokine interleukin (IL)-6. Exogenous angiotensin II induced IL-6 expression, activation of extracellular-regulated kinase (ERK) 1/2, and superoxide generation in pancreatic acinar cell line AR42J, which were reversed by the angiotensin II type 1 (AT(1)) receptor antagonist, losartan (2-butyl-4-chloro-1-[p-(o-1H-tetrazol-5-ylphenyl) benzyl] imidazole-5-methanol monopotassium salt, C(22)H(23)ClN(6)O). Pharmacological blockade of ERK1/2 improved angiotensin II-induced IL-6 expression. Moreover, angiotensin II-induced ERK1/2 activation was suppressed by antioxidant, indicating that redox-regulated ERK1/2 mediates the cytokine expression. cAMP-responsive element-binding protein (CREB) might be involved in ERK1/2-induced IL-6 expression because phosphorylation of CREB was observed after angiotensin II treatment, which was reversed by losartan and the ERK1/2 inhibitor. These results were in close agreement with the in vivo findings using an obstructive model of AP. Obstruction of the common biliopancreatic duct time-dependently enhanced angiotensinogen levels, which correlated well with superoxide generation, ERK1/2 and CREB phosphorylation, and subsequent IL-6 expression. It is more important that changes in these parameters were antagonized by prophylactic administration of losartan. These in vitro and in vivo results indicate that angiotensin II induces redox-regulated ERK1/2 and CREB activation, thus leading to IL-6 expression in an AT(1) receptor-mediated manner in pancreatic acinar cells during the pathogenesis of AP.