Search

Heat shock protein (HSP) 72 is released by cells during stress and injury. HSP-72 also stimulates the release of cytokines in macrophages by binding to Toll-like receptors (TLR) 2 and 4. Circulating levels of HSP-72 increase during hepatic ischemia-reperfusion injury. The role of extracellular HSP-72 (eHSP-72) in the injury response to ischemia-reperfusion is unknown. Therefore, the objective of the present study was to determine whether eHSP-72 has any direct effects on hepatocytes. Primary mouse hepatocytes were treated with purified human recombinant HSP-72. Conditioned media were evaluated by ELISA for the cytokines, TNF-[alpha], IL-6, and macrophage inflammatory protein 2 (MIP-2). Stimulation of hepatocytes with eHSP-72 did not induce production of TNF[alpha] or IL-6 but resulted in dose-dependent increases in MIP-2 production. To evaluate the pathway responsible for this response, expression of TLR2 and TLR4 was confirmed on hepatocytes by immunohistochemistry. Hepatocyte production of MIP-2 was significantly decreased in hepatocytes obtained from TLR2 or TLR4 knockout mice. MIP-2 production was found to be partially dependent on NF-[kappa]B because inhibition of NF-K[kappa] with Bay 11-7085 significantly decreased eHSP-72-induced MIP-2 production. Inhibitors of p38 mitogen-activated protein kinase or c-Jun [NH.sub.2]-terminal kinase had no effect on production of MIP-2 induced by eHSP-72. The data suggest that eHSP-72 binds to TLR2 and TLR4 on hepatocytes and signals through NF-[kappa]B to increase MIP-2 production. The fact that eHSP-72 did not increase TNF-[alpha] or IL-6 production may be indicative of a highly regulated signaling pathway downstream from TLR. liver; chemokines; Toll-like receptors; nuclear factor-[kappa]B; inflammation

It is well established that liver ischemia-reperfusion induces the expression of heat shock protein (HSP) 70. However, the biological function of HSP70 in this injury is unclear. In this study, we sought to determine the role of HSP70 in hepatic ischemia-reperfusion injury in mice. Male mice were subjected to 90 rain of partial hepatic ischemia followed by up to 8 h of reperfusion. HSP70 was rapidly upregulated after reperfusion. To explore the function of HSP70, sodium arsenite (8 mg/kg iv) was injected before surgery. We found that this dose induced HSP70 expression within 6 h of treatment. Induction of HSP70 with arsenite resulted in a >50% reduction in liver injury as determined by serum transaminases and histology. In addition, arsenite similarly reduced liver neutrophil recruitment and liver nuclear factor-[kappa]B activation, and attenuated serum levels of tumor necrosis factor-[alpha] and macrophage inflammatory protein-2, but increased levels of interleukin (IL)-6. In HSP70 knockout mice, arsenite did not protect against liver injury but did reduce liver neutrophil accumulation. Arsenite-induced reductions in neutrophil accumulation in HSP70 knockout mice were found to be mediated by IL-6. To determine whether extracelullar HSP70 contributed to the injury, recombinant HSP70 was injected before surgery. Intravenous injection of 10 [micro]g of recombinant HSP70 had no effect on liver injury after ischemia-reperfusion. The data suggest that intracellular HSP70 is directly hepatoprotective during ischemia-reperfusion injury and that extracellular HSP70 is not a significant contributor to the injury response in this model. Targeted induction of HSP70 may represent a potential therapeutic option for postischemic liver injury. liver; inflammation; neutrophils; cytokines

The present study examined the role of hepatocyte NF-[kappa]B activation during ischemia-reperfusion injury. Second, we evaluated the effects of ischemic hypothermia on NF-[kappa]B activation and liver injury. C57BL/6 mice underwent 90 min of partial hepatic ischemia and up to 8 h of reperfusion. Body temperature was regulated during the ischemic period between 35 and 37[degrees]C, 33 and 35[degrees]C, 29 and 33[degrees]C or unregulated, where temperature fell to liver inflammation; nuclear factor-[kappa]B p65; Pin1

The present study examined the role of hepatocyte NF-κB activation during ischemia-reperfusion injury. Second, we evaluated the effects of ischemic hypothermia on NF-κB activation and liver injury. C57BL/6 mice underwent 90 mm of partial hepatic ischemia and up to 8 h of reperfusion. Body temperature was regulated during the ischemic period between 35 and 37°C, 33 and 35°C, 29 and 33°C or unregulated, where temperature fell to <29°C. Liver injury, as measured by serum alanine aminotransferase as well as liver histopathology, was inversely proportional to regulated body temperature, with the unregulated group (<29°C) being highly protected and the normothermic group (35-37°C) displaying the greatest injury. Inflammation, as measured by production of TNF-α and liver recruitment of neutrophils, was greatest in the normothermic groups and lowest in the ischemic hypothermia groups. Interestingly, hepatocyte NF-κB activation was highest in the hypothermic group and least in the normothermic group. Paradoxically, degradation of IκB proteins, IκB-α and IκB-β, was greatest in the normothermic group, suggesting an alternate NF-κB regulatory mechanism during ischemia-reperfusion injury. Subsequently, we found that NF-κB p65 protein was increasingly degraded in normothermic versus hypothermic groups, and this degradation was specific for hepatocytes and was associated with decreased expression of the peptidyl-prolyl isomerase Pin1. The data suggest that NF-κB activation in hepatocytes is a protective response during ischemia-reperfusion and can be augmented by ischemic hypothermia. Furthermore, it appears that Pin1 promotes NF-κB p65 protein stability such that decreased expression of Pin1 during ischemia-reperfusion results in p65 degradation, reduced nuclear translocation of NF-κB, and enhanced hepatocellular injury. [ABSTRACT FROM AUTHOR]

The role of stromal cell-derived factor-1 (SDF-1 or CXCL12) and its receptor CXC chemokine receptor-4 (CXCR4) in ischemic liver injury and recovery has not been studied. Some reports suggest that this chemokine may aid in liver regeneration, but others suggest that it may be profibrotic through its activation of hepatic stellate cells. In this study we sought to elucidate the role of SDF-1 and its receptor CXCR4 during liver injury, recovery, and regeneration after ischemia-reperfusion (I/R). A murine model of partial (70%) I/R was used to induce liver injury and study the reparative and regenerative response. CXCR4 was expressed constitutively in the liver, and hepatic levels of SDF-1 peaked 8 h after reperfusion but remained significantly increased for 96 h. Treatment of mice with the CXCR4 antagonist AMD3100 or agonist SDF-1 had no effect on acute liver injury assessed 8 h after I/R. However, treatment with AMD3100 increased hepatocyte proliferation after 72 and 96 h of reperfusion and reduced the amount of liver necrosis. In contrast, treatment with SDF-1 significantly decreased hepatocyte proliferation. These effects appeared to be dependent on the presence of liver injury, as AMD3100 and SDF-1 had no effect on hepatocyte proliferation or liver mass in mice undergoing 70% partial hepatectomy. The data suggest that signaling through CXCR4 is detrimental to liver recovery and regeneration after I/R and that clinical therapy with a CXCR4 antagonist may improve hepatic recovery following acute liver injury., (Copyright © 2015 the American Physiological Society.)