Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX 77204, USA.
Int J Mol Sci. 2019 Jul 22;20(14):3570. doi: 10.3390/ijms20143570.
The intestinal microbe-derived metabolite trimethylamine N-oxide (TMAO) is implicated in the pathogenesis of cardiovascular diseases (CVDs). The molecular mechanisms of how TMAO induces atherosclerosis and CVDs' progression are still unclear. In this regard, high-mobility group box protein 1 (HMGB1), an inflammatory mediator, has been reported to disrupt cell-cell junctions, resulting in vascular endothelial hyper permeability leading to endothelial dysfunction. The present study tested whether TMAO associated endothelial dysfunction results via HMGB1 activation. Biochemical and RT-PCR analysis showed that TMAO increased the HMGB1 expression in a dose-dependent manner in endothelial cells. However, prior treatment with glycyrrhizin, an HMGB1 binder, abolished the TMAO-induced HMGB1 production in endothelial cells. Furthermore, Western blot and immunofluorescent analysis showed significant decrease in the expression of cell-cell junction proteins ZO-2, Occludin, and VE-cadherin in TMAO treated endothelial cells compared with control cells. However, prior treatment with glycyrrhizin attenuated the TMAO-induced cell-cell junction proteins' disruption. TMAO increased toll-like receptor 4 (TLR4) expression in endothelial cells. Inhibition of TLR4 expression by TLR4 siRNA protected the endothelial cells from TMAO associated tight junction protein disruption via HMGB1. In conclusion, our results demonstrate that HMGB1 is one of the important mediators of TMAO-induced endothelial dysfunction.
肠道微生物衍生的代谢产物三甲胺 N-氧化物（TMAO）与心血管疾病（CVDs）的发病机制有关。TMAO 如何诱导动脉粥样硬化和 CVDs 进展的分子机制尚不清楚。在这方面，高迁移率族蛋白 B1（HMGB1）作为一种炎症介质，据报道可破坏细胞-细胞连接，导致血管内皮通透性增加，从而导致内皮功能障碍。本研究测试了 TMAO 是否通过 HMGB1 激活导致内皮功能障碍。生化和 RT-PCR 分析表明，TMAO 以剂量依赖性方式增加内皮细胞中 HMGB1 的表达。然而，HMGB1 结合物甘草甜素的预先处理消除了内皮细胞中 TMAO 诱导的 HMGB1 产生。此外，Western blot 和免疫荧光分析显示，与对照细胞相比，TMAO 处理的内皮细胞中细胞-细胞连接蛋白 ZO-2、Occludin 和 VE-cadherin 的表达明显下降。然而，甘草甜素的预先处理减轻了 TMAO 诱导的细胞-细胞连接蛋白的破坏。TMAO 增加了内皮细胞中 Toll 样受体 4（TLR4）的表达。通过 TLR4 siRNA 抑制 TLR4 表达可通过 HMGB1 保护内皮细胞免受 TMAO 相关紧密连接蛋白破坏。总之，我们的结果表明，HMGB1 是 TMAO 诱导的内皮功能障碍的重要介质之一。
