Bowles Center for Alcohol Studies, University of North Carolina Medical School, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
Gastroenterology and Hepatology, Hospital Marques de Valdecilla, Research Institute Valdecilla, Santander, Spain.
Alcohol Clin Exp Res. 2018 Nov;42(11):2107-2122. doi: 10.1111/acer.13871. Epub 2018 Sep 10.
Toll-like receptor 7 (TLR7) is an endosomal TLR that is activated by single-stranded RNA, including endogenous microRNAs (e.g., let-7b). Increased hepatic expression of TLRs, microRNAs, and inflammatory mediators is linked to ethanol (EtOH) exposure and to alcoholic liver disease (ALD). ALD invovles chronic hepatic inflammation that can progress to alcoholic hepatitis (AH), a particularly severe form of ALD. This study aimed to investigate TLR7 expression in patients with different liver disease phenotypes and in mouse liver following alcohol exposure.
Hepatic mRNA expression was determined by RNA sequencing of liver tissue from patients with liver disease or normal liver tissue. Mice were exposed to subchronic EtOH followed by administration of the TLR7 agonist imiquimod. Primary human hepatocytes were exposed to EtOH or imiquimod in vitro.
RNAseq analysis revealed that hepatic expression of TLR7 and let-7b microRNA, an endogenous TLR7 ligand, was significantly increased in AH patients. Hepatic expression of TLR7 and let-7b positively correlated with hepatic IL-8 mRNA expression. In mice, EtOH increased hepatic TLR7 mRNA expression and enhanced imiquimod-induced expression of the pro-inflammatory mediators TNFα, MCP-1, and iNOS. In vitro, EtOH significantly increased hepatocyte TLR7 mRNA and the TLR7 agonist, imiquimod, induced hepatocyte expression of TNFα and IL-8 mRNA. EtOH also increased the release of let-7b in microvesicles from hepatocytes, suggesting that EtOH can increase the expression of both the receptor and its endogenous ligand.
These studies suggest that increased TLR7 signaling caused by increased expression of TLR7 and its endogenous ligand let-7b may contribute to the enhanced inflammatory response associated with AH.
Toll 样受体 7（TLR7）是一种内体 TLR，可被单链 RNA 激活，包括内源性 microRNA（例如 let-7b）。TLR、microRNA 和炎症介质在肝内的表达增加与乙醇（EtOH）暴露和酒精性肝病（ALD）有关。ALD 涉及慢性肝炎症，可进展为酒精性肝炎（AH），这是一种特别严重的 ALD 形式。本研究旨在探讨 TLR7 在不同肝病表型患者和酒精暴露后小鼠肝中的表达。
通过对肝病患者或正常肝组织的肝组织进行 RNA 测序，确定肝内 mRNA 表达。用亚慢性 EtOH 处理小鼠，然后用 TLR7 激动剂咪喹莫特处理。在体外将乙醇或咪喹莫特暴露于人原代肝细胞。
RNAseq 分析显示，AH 患者肝内 TLR7 和内源性 TLR7 配体 let-7b microRNA 的表达显著增加。TLR7 和 let-7b 在肝内的表达与肝内 IL-8 mRNA 的表达呈正相关。在小鼠中，EtOH 增加了肝内 TLR7 mRNA 的表达，并增强了咪喹莫特诱导的促炎介质 TNFα、MCP-1 和 iNOS 的表达。在体外，EtOH 显著增加了肝细胞 TLR7 mRNA 的表达，TLR7 激动剂咪喹莫特诱导了 TNFα 和 IL-8 mRNA 在肝细胞中的表达。EtOH 还增加了微囊泡中 let-7b 的释放，这表明 EtOH 可以增加受体及其内源性配体的表达。
这些研究表明，TLR7 和其内源性配体 let-7b 表达增加引起的 TLR7 信号转导增强可能导致与 AH 相关的炎症反应增强。
