Han Jibo, Zou Chunpeng, Mei Liqin, Zhang Yali, Qian Yuanyuan, You Shengban, Pan Yong, Xu Zheng, Bai Bin, Huang Weijian, Liang Guang
Chemical Biology Research Center, School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, 325035, Zhejiang, China.
Department of Cardiology, The First Affiliated Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China.
Basic Res Cardiol. 2017 Jan;112(1):9. doi: 10.1007/s00395-016-0599-5. Epub 2016 Dec 24.
Angiotensin II (Ang II) induces cardiac inflammation and remodeling. Emerging evidence indicates that Ang II may utilize the Toll-like receptor 4 (TLR4) signaling pathway in mediating pro-inflammatory and pro-fibrotic activities. However, the precise mechanism is poorly understood. Myeloid differentiation 2 (MD2), a molecule that physically binds to TLR4, confers lipopolysaccharide responsiveness and may also be involved in mediating the actions of Ang II. We hypothesize that MD2 plays an essential role in cardiac inflammation and remodeling induced by local Ang II, and inhibition of MD2 can attenuate Ang II-induced cardiac dysfunction. Using a specific small molecule MD2 blocker L6H21 and the MD2 knockout mice, we show that MD2 deficiency significantly reduces cardiac inflammation and subsequent fibrosis, hypertrophy, and dysfunction in mice challenged with subcutaneous injection of Ang II. In rat cardiomyocyte-like H9c2 cells as well as rat primary cardiomyocytes, inhibition of MD2 by L6H21 or siRNA knockdown suppressed the Ang II-induced TLR4 signaling pathway activation including MyD88 recruitment, and reduced cardiomyocyte hypertrophy and matrix protein expression. These pro-inflammatory activities of Ang II were independent of the AT1 receptor. Finally, we demonstrated the direct interaction between Ang II and MD2 protein via hydrogen bonds on Arg-90, Glu-92, and Asp-100. Ang II produces an inflammatory response and cardiac remodeling by directly binding to MD2, activating MD2/TLR4 complex, and recruiting MyD88. MD2 may be a new therapeutic target for Ang II-mediated cardiac inflammation and remodeling.
血管紧张素 II（Ang II）可诱发心脏炎症和重塑。新出现的证据表明，Ang II 可能利用 Toll 样受体 4（TLR4）信号通路介导促炎和促纤维化活动。然而，其确切机制尚不清楚。髓样分化蛋白 2（MD2）是一种与 TLR4 物理结合的分子，赋予脂多糖反应性，也可能参与介导 Ang II 的作用。我们假设 MD2 在局部 Ang II 诱导的心脏炎症和重塑中起关键作用，抑制 MD2 可减轻 Ang II 诱导的心脏功能障碍。使用特异性小分子 MD2 阻滞剂 L6H21 和 MD2 基因敲除小鼠，我们发现 MD2 缺陷显著减轻皮下注射 Ang II 攻击的小鼠的心脏炎症以及随后的纤维化、肥大和功能障碍。在大鼠心肌样 H9c2 细胞以及大鼠原代心肌细胞中，L6H21 或 siRNA 敲低抑制 MD2 可抑制 Ang II 诱导的 TLR4 信号通路激活，包括 MyD88 募集，并减少心肌细胞肥大和基质蛋白表达。Ang II 的这些促炎活性独立于 AT1 受体。最后，我们通过 Arg-90、Glu-92 和 Asp-100 上的氢键证明了 Ang II 与 MD2 蛋白之间的直接相互作用。Ang II 通过直接结合 MD2、激活 MD2/TLR4 复合物并募集 MyD88 产生炎症反应和心脏重塑。MD2 可能是 Ang II 介导的心脏炎症和重塑的新治疗靶点。
