Atsushi Kato

Interleukin-10 inhibits pulmonary NF-κB activation and lung injury induced by hepatic ischemia-reperfusion

Hepatic ischemia and reperfusion cause local and remote organ injury. This injury culminates from an integrated cascade of proinflammatory cytokines, chemokines, and adhesion molecules, many of which are regulated by the transcription factor nuclear factor-kappaB (NF-kappaB). The anti-inflammatory cytokine interleukin-10 (IL-10) has been shown to have inhibitory effects on NF-kappaB. The objective of the current study was to determine whether IL-10 could suppress pulmonary NF-kappaB activation and ensuing lung injury induced by hepatic ischemia-reperfusion. C57BL/6 mice underwent partial hepatic ischemia with or without intravenous administration of IL-10. Hepatic ischemia-reperfusion resulted in pulmonary NF-kappaB activation, increased mRNA expression of tumor necrosis factor-alpha (TNF-alpha), and macrophage inflammatory protein-2 (MIP-2), as well as increased pulmonary neutrophil accumulation and lung edema. Administration of IL-10 suppressed lung NF-kappaB activation, reduced TNF-alpha and MIP-2 mRNA expression, and decreased pulmonary neutrophil recruitment and lung injury. The data suggest that IL-10 protects against hepatic ischemia and reperfusion-induced lung injury by inhibiting lung NF-kappaB activation and the resulting pulmonary production of proinflammatory mediators.

Reduced hepatic ischemia/reperfusion injury by IL-4: potential anti-inflammatory role of STAT6

Objective and Design: The ability of interleukin-4 (IL-4) to modulate activation of the transcription factors, NF-κB and STAT6, reduce proinflammatory cytokine expression and protect against liver injury induced by ischemia/ reperfusion was assessed.¶Materials and Subjects: C57BL/6 mice underwent 90 minutes of partial hepatic ischemia followed by 1 or 8 h of reperfusion with or without intravenous administration of 1 μg (0.5 μg just prior to ischemia, 0.5 μg at reperfusion) recombinant murine IL-4. Liver expression of TNFα mRNA was determined by RT-PCR. Activation of NF-κB and STAT6 in liver nuclear extracts was assessed by mobility shift assay.¶Results: Hepatic ischemia/reperfusion increased hepatic expression of tumor necrosis factor-α (TNFα), induced significant neutrophil accumulation and liver injury. Treatment with IL-4 greatly suppressed liver TNFα mRNA expression, neutrophil accumulation and liver injury. IL-4 had no effect on liver NF-κB activation, but greatly increased the activation of STAT6.¶Conclusions: The data suggest that STAT6 activation by IL-4 may be responsible for the protective effects of this cytokine.

IL-13 Activates STAT6 and Inhibits Liver Injury Induced by Ischemia/Reperfusion

Hepatic ischemia/reperfusion injury is initiated by the activation of Kupffer cells and their subsequent release of proinflammatory mediators, including tumor necrosis factor-alpha (TNFalpha). These mediators stimulate a cascade of events including up-regulation of CXC chemokines and vascular endothelial adhesion molecules, leading to hepatic neutrophil recruitment and tissue injury. Interleukin-13 (IL-13) is a cytokine that has been shown to suppress macrophage production of proinflammatory mediators. The objective of the current study was to determine whether IL-13 could regulate the liver inflammatory injury induced by ischemia and reperfusion. C57BL/6 mice underwent 90 minutes of partial hepatic ischemia followed by reperfusion with or without intravenous administration of recombinant murine IL-13. Hepatic ischemia/reperfusion increased expression of TNFalpha and macrophage inflammatory protein-2 (MIP-2), leading to hepatic neutrophil recruitment, hepatocellular injury, and liver edema. Administration of IL-13 reduced the production of TNFalpha and MIP-2 mRNA and protein. IL-13 suppressed liver neutrophil recruitment by up to 72% and hepatocellular injury and liver edema were each reduced by >60%. Administration of IL-13 had no effect on liver NFkappaB activation, but greatly increased the activation of STAT6. The data suggest that the hepatoprotective effects of IL-13 may be a result of STAT6 activation.

Gene deletion of NF-κB p50 does not alter the hepatic inflammatory response to ischemia/reperfusion

BACKGROUND/AIMSnNuclear factor kappa B (NF-kappa B) is a primary regulator of gene expression and is activated during hepatic ischemia/reperfusion injury. The objective of the present study was to determine whether activation of NF-kappa B is causally related to the induction of the acute inflammatory response induced by hepatic ischemia/reperfusion.nnnMETHODSnWild-type (p50(+/+)) and NF-kappa B p50-deficient (p50(-/-)) mice underwent hepatic ischemia/reperfusion. NF-kappa B activation was determined by electrophoretic mobility shift assay. Hepatic neutrophil accumulation was measured by liver myeloperoxidase content. Hepatocellular injury was assessed by serum level of alanine aminotransferase and liver histology.nnnRESULTSnIn p50(+/+) mice, ischemia/reperfusion induced marked activation of NF-kappa B consisting of p50/p65 heterodimers. In contrast, NF-kappa B activation in livers from p50(-/-) mice was abrogated, but p65 was observed in nuclear extracts. Despite amelioration of NF-kappa B activation there was no significant difference between p50(+/+) and p50(-/-) mice in expression of TNF alpha and MIP-2, liver accumulation of neutrophils or hepatocellular injury.nnnCONCLUSIONSnGene deletion of NF-kappa B p50 does not alter the hepatic inflammatory response to ischemia/reperfusion. Despite abrogation of DNA-binding by the NF-kappa B p50/p65 complex, p65 was still observed in nuclear extracts suggesting that there may be functional redundancy amongst members of the Rel protein family in order to preserve the inflammatory response.

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-kappaB, increased production of tumor necrosis factor-alpha (TNFalpha), 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 wild-type and STAT6 knockout mice significantly increased (P < 0.05) NF-kappaB activation, serum levels of TNFalpha, 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 microg of IL-4 or IL-13 at reperfusion reduced serum TNFalpha, liver neutrophil accumulation, and hepatocellular injury in wild-type mice. Treatment with IL-4 or IL-13 had no effect on liver NF-kappaB activation but significantly increased activation of STAT6. In STAT6 knockout mice, neither IL-4 nor IL-13 had any effect on TNFalpha, 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.