血管紧张素Ⅱ和机械应力协同上调压力超负荷小鼠心脏表达HMGB1的作用及机制

The mechanisms of pressure overload-induced cardiac remodeling are complex. We have previously found that a proinflammatory factor, high mobility group box 1 (HMGB1), which was upregulated in the myocardium under pressure overload, promoted cardiac hypertrophy and deteriorated cardiac function. However, the underlying mechanisms of producing and releasing HMGB1 are unclear. Meanwhile, we found that mechanical stress directly induced cardiac hypertrophy via AT1 receptor-MAPKs signaling pathway in an angiotensin II (Ang II)-independent manner. Combining these with the fact that Ang II plays a pro-inflammatory role via AT1/AT2 receptors, which might be mediated by the intracellular ROS-MAPKs-NFκB signaling pathway, we propose the hypothesis that Ang II and mechanical stress may have synergistic effect on both expression and activation of HMGB1 in myocardium under pressure overload via the signaling pathway mentioned above. To validate the hypothesis and to identify the types of cells that release HMGB1 in myocardium, the models of pressure overload-induced cardiac hypertrophy will be built in angiotensinogen knock-out mice, meanwhile, relative gene-absent cells and the equipments for exerting mechanical stress to the cultured cells will be used. Moreover, the relative receptors and proteins in the signaling pathway will be inhibited either in vivo or in vitro to explore the mechanisms of Ang II and mechanical stress in regulating HMGB1 in myocardium under pressure overload. Overall, this study will give great impetus to the full understanding of the roles of HMGB1 in pressure overload-induced cardiac remodeling, and may provide novel viewpoint for the management of the disease.

压力超负荷心肌重构病理机制错综复杂。我们发现，致炎因子高迁移率族蛋白B1（HMGB1）在压力超负荷心肌表达上调并促进心肌肥厚、加速心功能恶化，但未阐明其产生和释放机制。已证实，血管紧张素Ⅱ(AngⅡ)通过AT1/AT2受体发挥促炎作用，ROS-MAPKs-NFκB信号通路可能介导该作用；机械应力可不依赖AngⅡ而直接激活AT1受体及MAPKs通路并导致心肌肥厚。故推测AngⅡ和机械应力通过激活上述受体信号通路，既而协同调节压力超负荷心脏HMGB1表达和活化。本项目拟利用血管紧张素原基因敲除小鼠构建压力超负荷模型，同时应用相关基因缺失细胞及细胞牵张培养装置，通过体内外阻断相应受体和信号蛋白，探讨AngⅡ和机械应力对压力超负荷心脏HMGB1的调节作用及受体信号通路机制，并观察HMGB1的细胞来源。本研究有助于全面认识HMGB1参与压力超负荷心肌重构的病理机制，为疾病防治提供新的理论依据。

压力超负荷心肌重构病理机制错综复杂。我们前期研究发现致炎因子高迁移率族蛋白B1（HMGB1）在压力超负荷心肌表达上调并促进心肌肥厚、加速心功能恶化，但未阐明其产生和释放机制。血管紧张素Ⅱ(AngⅡ)可通过AT1/AT2受体发挥促炎作用，故推测AngⅡ通过激活上述受体信号通路，既而调节压力超负荷心脏HMGB1表达和活化。本项目通过构建压力超负荷小鼠模型并观察1-14天发现，压力超负荷心脏组织HMGB1、IL-6、TNF-a表达水平升高，且HMGB1升高部分来源于心肌细胞本身；血清中HMGB1、IL-6、TNF-a水平呈先升高后恢复至正常的变化过程。此外，在术前3天及术后每天对压力超负荷小鼠分别给予生理盐水、氯沙坦（AT1受体拮抗剂）、PD123319（AT2受体拮抗剂）干预并观察1-14天发现，氯沙坦在不同时期可以有效降低小鼠心脏组织及血清中因压力超负荷而引起的HMGB1升高，而PD123319无该抑制作用；氯沙坦在压力超负荷14天时可以有效减轻小鼠心肌肥厚，而PD123319对心肌肥厚无明显改善作用。用10-6mol/L AngⅡ干预体外培养心肌细胞，动态观察（5分钟、10分钟、30分钟、1小时、2小时、4小时、8小时、12小时、24小时、48小时）其对细胞内、外HMGB1表达的影响并发现，AngⅡ可明显增加心肌细胞内HMGB1表达，且表达量随着时间延长而增加；氯沙坦可明显降低AngⅡ引起的HMGB1升高，而PD123319无明显抑制作用。上述研究结果提示压力超负荷条件下由心肌细胞合成并分泌的HMGB1参与心肌重构病理机制；AngⅡ受体拮抗剂改善心肌重构的药理作用可能与HMGB1及其相关的炎症反应有关，且AT1受体信号通路在其中发挥重要作用。本项目有助于全面认识HMGB1参与压力超负荷心肌重构的病理机制，为疾病防治提供新的理论依据。