IFN-γ protects cerulein-induced acute pancreatitis by repressing NF-κB activation

We explored the pathophysiological roles of IFN-gamma in cerulein-induced acute pancreatitis. In wild-type (WT) mice, cerulein injection caused acute pancreatitis as evidenced by increased serum amylase levels and pathological changes such as interstitial edema, vacuolization, acinar cell necrosis, and neutrophil infiltration in pancreas. Concomitantly, cerulein treatment augmented intrapancreatic gene expression of TNF-alpha, KC/CXCL1, MIP-2/CXCL2, cyclooxygenase-2 (COX-2), and IFN-gamma in WT mice. In situ hybridization combined with immunofluorescence analyses demonstrated that infiltrating neutrophils expressed IFN-gamma mRNA. Unexpectedly, IFN-gamma(-/-) mice exhibited exacerbated cerulein-induced pancreatic injury, with enhanced neutrophil recruitment. Moreover, intrapancreatic gene expression of TNF-a, KC/CXCL1, MIP-2/CXCL2, and COX-2 were significantly exaggerated in IFN-gamma(-/-) mice, compared with WT mice. Cerulein activated NF-kappa B, an indispensable transcription factor for gene transcription of TNF-alpha, KC/CXCL1, MIP-2/CXCL2, and COX-2, in pancreas of cerulein-treated WT mice as evidenced by the increases in nuclear amount and DNA-binding activity of NF-kappa B p65. In comparison with WT mice, IFN-gamma(-/-) mice exhibited exaggerated and prolonged NF-kappa B activation, probably due to reduced acetylation of Stat1, a main signal transducer of IFN-gamma, because acetylated Stall can inhibit NF-kappa B activation. Indeed, IFN-gamma acetylated Stat1 and reciprocally reduced NF-kappa B activation and COX-2 expression in neutrophils. Finally, even when administered 4 h after the first cerulein injection, IFN-gamma remarkably attenuated acute pancreatitis in both WT and IFN-gamma(-/-) mice, with reduced NF-kappa B activation and COX-2 expression. Thus, IFN-gamma can have anti-inflammatory effects on acute pancreatitis by depressing the proinflammatory consequences of NF-kappa B activation.