Plasma membrane-bound G protein-coupled bile acid receptor attenuates liver ischemia/reperfusion injury via the inhibition of toll-like receptor 4 signaling in mice.

The plasma membrane-bound G protein-coupled bile acid receptor (TGR5) displays varied levels of expression in different tissues. TGR5-induced liver protection has been demonstrated during several liver diseases, except during ischemia/reperfusion injury (IRI). Male adult wild-type and TGR5 knockout (KO) mice were subjected to liver partial warm ischemia/reperfusion. Hepatic injury was evaluated based on serum alanine aminotransferase and serum aspartate aminotransferase. Liver histological injury and inflammatory cell infiltration were evaluated in tissue sections using liver immunohistochemical analysis. We used quantitative real-time polymerase chain reaction to analyze the liver expression of inflammatory cytokines. The toll-like receptor 4 (TLR4) signaling pathway and its related apoptotic molecules were investigated after reperfusion. Moreover, the effect of TGR5 on inflammation was determined with TGR5+/+ or TGR5-/- primary bone marrow-derived macrophages in vitro. TGR5 significantly attenuated liver damage after IRI. As demonstrated by in vivo experiments, TGR5 significantly reduced the up-regulation of the TLR4-nuclear factor kappa B (NF-κB) pathway and inhibited caspase 8 activation after IRI. Later experiments showed that TGR5 KO significantly increased the expression of TLR4-NF-κB signaling molecules and promoted hepatocellular apoptosis. In addition, in vitro experiments showed that overexpression of 6alpha-ethyl-23(S)-methylcholic acid (INT-777)-activated TGR5 directly down-regulated tumor necrosis factor α (TNF-α) and interleukin (IL) 6 expression but up-regulated IL10 expression in hypoxia/reoxygenation-induced primary TGR5+/+ macrophages. Moreover, the expression of TLR4-NF-κB signaling molecules was significantly inhibited by the activation of TGR5. Importantly, these results were completely reversed in primary TGR5-/- macrophages. This work is the first to provide evidence for a TGR5-inhibited inflammatory response in IRI through suppression of the TLR4-NF-κB pathway, which may be critical in reducing related inflammatory molecules and modulating innate inflammation. Liver Transplantation 23:63-74 2017 AASLD.

Yang H ，Zhou H ，Zhuang L ，Auwerx J ，Schoonjans K ，Wang X ，Feng C ，Lu L ... -  《-》

TGR5 Attenuated Liver Ischemia-Reperfusion Injury by Activating the Keap1-Nrf2 Signaling Pathway in Mice.

Zhuang L ，Ding W ，Zhang Q ，Ding W ，Xu X ，Yu X ，Xi D ... -  《-》

Resveratrol preconditioning protects hepatocytes against hepatic ischemia reperfusion injury via Toll-like receptor 4/nuclear factor-κB signaling pathway in vitro and in vivo.

The purpose of this study was to investigate the protective effect of resveratrol against hepatic ischemia reperfusion injury (HIRI) and explore the potential underlying mechanism. Resveratrol-pretreated BRL-3A (rat liver) cells and rats underwent hypoxia/reoxygenation and hepatic ischemia/reperfusion, respectively. BRL-3A cell damage was evaluated, and the mRNA and protein expression of related signal molecules was assessed in cell model. The protein expression of related signal molecules was also assessed in rat model. Inflammatory cytokines levels were determined in the cell supernatant and rat serum while rat liver function and hepatocyte apoptosis were assessed. The results revealed that resveratrol significantly enhanced cell viability, inhibited cell apoptosis, and decreased levels of lactate dehydrogenase (LDH) and production of tumor necrosis factor-α (TNF-α) and interleukin-(IL)-1β in the cell supernatant. In addition, resveratrol ameliorated elevated Toll-like receptor 4 (TLR4) and nuclear factor (NF)-κB, and the depressed inhibitor of NF-κB (IκB)-α caused by hypoxia/reoxygenation stimulation in BRL-3A cells. Moreover, resveratrol inhibited the translocation of NF-κB p65 after the stimulation of hypoxia/reoxygenation in BRL-3A cells. In vivo assays revealed that resveratrol reduced levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), and liver pathological changes, while it alleviated hepatocyte apoptosis, negatively mediated the production of TNF-α and IL-1β in serum, and reversed TLR4/NF-κB signaling pathway caused by hepatic ischemia/reperfusion stimulation in liver tissues. The results indicate that resveratrol protected hepatocytes against HIRI, which may be mediated in part via the TLR4/NF-κB signaling pathway.

He D ，Guo Z ，Pu JL ，Zheng DF ，Wei XF ，Liu R ，Tang CY ，Wu ZJ ... -  《-》

Ischemia and reperfusion liver injury is reduced in the absence of Toll-like receptor 4.

Toll-like receptor 4 (TLR4) is expressed on hepatic non-parenchymal cells and hepatocytes. Hepatic signaling through TLR4 is critical in the pathogenesis of ischemia reperfusion injury (IRI) and leads to the release of cytokines. The role of bone marrow-derived TLR4 in the early reperfusion stage is unclear. We used wild type mice (WT), TLR4deficient (TLR4ko) mice and chimeras to dissociate between the role of TLR4 expression in the liver (TLR4ko/WT) and in the immuno-hematopoietic system (WT/TLR4ko) in mouse hepatic IR injury model. Mice were subjected to in vivo partial IRI (70% for 60 min). Compared with WT IR livers, TLR4ko IRI mice (4 hours) showed a significant reduction in serum liver enzyme, hepatic TNF-α and interleukin-1β levels. Fewer apoptotic hepatocytes cells were identified by morphological criteria and immunohistochemistry for caspase-3. In TLR4ko mice, decreased hepatic CJUN and NF-ĸB expression during IRI was noted compared with WT mice. Chimeric mice having either TLR4 bone-marrow or non-bone marrow derived cells following IRI exhibited almost similar hepatic injury as WT mice in the immediate reperfusion stage. Both TLR4 bone marrow-derived and non-bone marrow-derived cells are necessary in the initial process of hepatic injury. Activating TLR4-dependent signaling is required for IRI. The absence of the TLR4 gene plays a pivotal role in reducing hepatic IR injury.

Ben-Ari Z ，Avlas O ，Fallach R ，Schmilovitz-Weiss H ，Chepurko Y ，Pappo O ，Hochhauser E ... -  《-》

Endogenous danger signals trigger hepatic ischemia/reperfusion injury through toll-like receptor 4/nuclear factor-kappa B pathway.

Wang H ，Li ZY ，Wu HS ，Wang Y ，Jiang CF ，Zheng QC ，Zhang JX ... -  《CHINESE MEDICAL JOURNAL》