Regulation of liver inflammatory injury by signal transducer and activator of transcription-6

Liver Injury induced by hepatic ischemia/reperfusion is characterized by activation of the transcription factor NF-KB, increased production of tumor necrosis factor-alpha (TNF alpha), liver neutrophil accumulation, and hepatocellular damage. Exogenous administration of interleukin-4 (IL-4) or IL-13 was recently shown to regulate this inflammatory Injury in association with activation of signal transducer and activator of transcription-6 (STAT6), The objective of the present study was to determine whether STAT6 was required for the regulation of liver inflammation by IL-4 and IL-13. Wild-type and STAT6 knockout mice underwent 90 minutes of hepatic ischemia followed by 8 hours of reperfusion, Hepatic ischemia/reperfusion in wildtype and STAT6 knockout mice significantly Increased (P < 0.05) NF-kappa B activation, serum levels of TNF alpha, liver accumulation of neutrophils [measured by myeloperoxidase (MPO) content], and hepatocellular damage [measured by serum alanine aminotransferase (ALT)] compared to sham controls. In wild-type mice, activation of STAT6 was not observed after ischemia/reperfusion, Administration of 1 mu g of IL-4 or IL-13 at reperfusion reduced serum TNF alpha, liver neutrophil accumulation, and hepatocellular injury in wild-type mice, Treatment with IL-4 or IL-13 had no effect on liver NF-kappa B activation but significantly Increased activation of STAT6, In STAT6 knockout mice, neither IL-4 nor IL-13 had any effect on TNF alpha, MPO, or ALT values, the regulatory effects of these cytokines being completely abolished. The data suggest that activation of STAT6 may regulate liver inflammatory injury.