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.
Translational Medicine Research Center, Affiliated Jiangning Hospital and Liver Transplantation Center, First Affiliated Hospital of Nanjing Medical University, Nanjing, China.|Changzhou No. 2 People's Hospital, Affiliated Hospital of Nanjing Medical University, Changzhou, China.
Haojun
H
Yang
Translational Medicine Research Center, Affiliated Jiangning Hospital and Liver Transplantation Center, First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
Haoming
H
Zhou
Translational Medicine Research Center, Affiliated Jiangning Hospital and Liver Transplantation Center, First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
Lin
L
Zhuang
Metabolic Signaling, Institute of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
Johan
J
Auwerx
Metabolic Signaling, Institute of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
Kristina
K
Schoonjans
Translational Medicine Research Center, Affiliated Jiangning Hospital and Liver Transplantation Center, First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
Xuehao
X
Wang
Translational Medicine Research Center, Affiliated Jiangning Hospital and Liver Transplantation Center, First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
Cheng
C
Feng
Translational Medicine Research Center, Affiliated Jiangning Hospital and Liver Transplantation Center, First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
Ling
L
Lu
D000410:Alanine Transaminase / Q000097:blood; D000818:Animals; D017209:Apoptosis; D001219:Aspartate Aminotransferases / Q000097:blood; D053181:Caspase 8 / Q000378:metabolism; D002462:Cell Membrane; D002793:Cholic Acids / Q000494:pharmacology; D004195:Disease Models, Animal; D015536:Down-Regulation; D007150:Immunohistochemistry; D015850:Interleukin-6 / Q000378:metabolism; D008099:Liver / Q000473:pathology; D016031:Liver Transplantation / Q000009:adverse effects*; D008264:Macrophages / Q000378:metabolism / Q000648:ultrastructure; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016328:NF-kappa B / Q000378:metabolism; D061251:Primary Cell Culture; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D015427:Reperfusion Injury / Q000097:blood / Q000378:metabolism*; D015398:Signal Transduction; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D015854:Up-Regulation; D052096:Warm Ischemia / Q000009:adverse effects*
C545501:6alpha-ethyl-23(S)-methylcholic acid; D002793:Cholic Acids; C513561:Gpbar1 protein, mouse; D015850:Interleukin-6; D016328:NF-kappa B; D043562:Receptors, G-Protein-Coupled; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; C577686:interleukin-6, mouse; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase; C505526:Casp8 protein, mouse; D053181:Caspase 8