S100B/RAGE通路对心衰小鼠室性心律失常及电重构的影响及机制研究

Chronic heart failure (CHF) is a serious threat to safety and quality of life. Complex ventricular arrhythmias associated with CHF patients, as well as non-sustained ventricular tachycardia higher morbidity, leaded to mortality up to 50 %. Therefore, prevention of arrhythmia after heart failure is critical. Currently arrhythmia research and therapeutic targets focused on ion channels has certain limitations. Therefore, it is essential for the understanding of cardiac electrical activity to find the upstream regulatory targets of ion flow. S100B protein, which has a wide range of biological effects, mediated hypertrophy and apoptosis of myocardial by the receptor of advanced glycation end products (RAGE), and promoted the development of HF. RAGE, a membrane protein, is closely related to cardiovascular disease. Recent researches had shown that the RAGE system upregulated connexin43 expression in rat cardiomyocytes, and promoted the occurrence of atrial fibrillation. From these studies, we infer that S100B/RAGE may play an important role in electrical remodeling after CHF. We will use S100B knockout mice and cardiac-specific S100B transgenic mouse to observe the effects of S100B on electrical remodeling after CHF, and to explore possible mechanisms involved, that is provided new ideas for prevention and treatment of arrhythmia after CHF.

慢性心力衰竭发生心律失常的主要机制是心衰电活动的异常，目前针对心衰合并心律失常并无确切有效地治疗手段。因此，寻找离子通道等电学基质的上游调控靶点可能是未来防治心衰后发生的新思路。S100B蛋白在正常心肌细胞不表达，在心衰心肌细胞表达及分泌却显著升高，与心功能呈负相关。S100B生物学效应主要是通过与RAGE结合来发挥的。RAGE与其配体结合后，激活下游信号通路可上调cx43的表达，增加糖尿病大鼠心律失常的发生，还可促进房颤的发生。然而S100B/RAGE通路对于心衰后室性心律失常及电重构的影响却不明确，尚无国内外报道。本课题通过分别干预S100B及RAGE蛋白功功能，即构建S100B基因敲除和心脏特异性转基因心衰小鼠及给予RAGE抑制剂，探讨S100B/RAGE通路对心衰后室性心律失常及电重构的影响，以明确心衰合并心律失常治疗的最佳靶点，为临床防治心衰后心律失常的发生提供新思路及实验依据。

慢性心力衰竭发生心律失常的主要机制是心衰电活动的异常，寻找离子通道等电学基质的上游调控靶点可能是未来防治心衰后发生的新思路。本课题通过构建S100B基因敲除小鼠，观察S100B蛋白对心力衰竭小鼠心脏电生理及室性心律失常发生的影响并探讨其可能机制。主要方法：实验分组为4组C57+Sham组、S100B-/- +Sham组、C57+AF组、S100B-/- +AF组。通过主动脉缩窄术造成70%的血管缩窄，诱导压力负荷，构建小鼠心力衰竭模型。术后8周评估心衰模型，实时定量PCR检测心肌肥厚与心肌纤维化的分子标志物的mRNA表达水平，一部分小鼠采用Langendorff-离体心脏灌流及全细胞膜片钳技术行电生理检测，采用Real-time PCR和Western blot 技术检测心肌细胞钾通道蛋白及mRNA 表达水平。重要结果与关键数据：1.术后8周C57+AF组与S100B-/- +AF组较假手术组小鼠左室心功能恶化；S100B-/- +AF组小鼠心功能较C57+AF组小鼠得到明显改善；C57+AF组与S100B-/- +AF组小鼠心肌肥厚及心肌纤维化标志物的mRNA表达水平均高于假手术组小鼠。S100B-/- +AF组小鼠心室肌中的这些指标与C57+AF组比较得到了明显的改善。2. 术后8周C57+AF组与S100B-/- +AF组较假手术组小鼠QRS波增宽、J波低平以及QT和QTc间期延长，MAP复极10%-90%（APD10-APD90）时间和ERP均发生显著延长；S100B-/- +AF组小鼠上述指标较C57+AF组小鼠得到明显改善。在低起搏频率(5Hz和2.5Hz)下于C57+AF组与S100B-/- +AF组可观察到早期后除极现象发生，同时其室性心律失常的诱发率增加；S100B-/- +AF-组的这些现象与C57+AF组比较发生率明显降低。C57+AF组与S100B-/- +AF组心室肌细胞Ipeak、Ito、IKur以及Iss较假手术组发生显著降低，并且其蛋白和mRNA表达水平也发生下调。S100B-/- +AF组较C57+AF组Ipeak、Ito、IKur电流密度增加，Iss无显著改变。科学意义：S100B蛋白可能参与心力衰竭过程中电生理的重构，这些可能改变可能促进室性心律失常的发生，为临床防治心衰后心律失常的发生提供新思路及实验依据。