钙敏感受体在新生鼠内毒素性心肌损伤中的作用及机制

Endotoxin-induced myocardial injury in neonatal can increase mortality and increase the financial burden of families. A lot of studies demonstrated that the overproduction of proinflammatory cytokines, abnormal calcium cycling in cardiomyocytes are associated with endotoxin -induced myocardial dysfunction, but the mechanisms underlying endotoxin-induced myocardial depression remain elusive.. Calcium-sensing receptor (CaSR) is a G protein-coupled receptors. In 2003,it was first found in myocardial tissue by Wang and Xu et al. It is confirmed that it is involved in myocardial ischemia - reperfusion injury, apoptosis, and the occurrence of cardiac hypertrophy. However, the role of CaSR in myocardial injury induced by endotoxemia is unclear. In the previous study, we found that LPS-induced myocardial injury in neonatal rats increased the expression of CaSR. We speculate that CaSR may be involved in intracellular calcium overload and the release of inflammatory cytokines in endotoxemia cardiomycyte. Increased expression of CaSR in myocardial may be a new mechanism of endotoxin myocardial injury. To confirm this hypothesis, we will replicate neonatal rat cardiomycyte injury model induced by endotoxin, use molecular biology, flow cytometry technology, from the whole - myocardium - cardiomycyte, the three levels, observe the effect of activation of CaSR in endotoxin induced myocardial injury and the signal transduction pathway. The issue will clarify the new mechanism and provide new targets in treatment of myocardial injury induced by endotoxin.

内毒素性心肌损伤可增加患儿死亡率，增加家属经济负担，其确切机制尚未阐明，多认为与炎症反应有关。钙敏感受体（CaSR）是G蛋白偶联受体。2003年本人博士导师首次发现心肌组织有CaSR存在，并证实它参与心肌缺血/再灌注损伤、细胞凋亡和心肌肥大的发生。但是，CaSR与内毒素性心肌损伤发生、发展的关系，迄今国内外尚无报道。在前期研究中，我们发现脂多糖诱导新生鼠心肌损伤中CaSR的表达增加，我们推测内毒素血症心肌细胞CaSR表达增加可能参与心肌细胞内钙超载及炎症因子释放，这可能是内毒素心肌损伤的一个新机制。为证实这一假说，我们将复制新生鼠大体和细胞内毒素心肌损伤模型，采用分子生物学、流式细胞仪等技术，从整体-心肌组织-心肌细胞三个层次，观察CaSR表达增加或活化对内毒素心肌细胞损伤的影响及其信号传导通路。本课题将从新的视觉阐明内毒素心肌损伤发生的分子机制，并为内毒素心肌损伤的防治提供新靶点。

项目的背景：革兰氏阴性菌败血症导致新生儿的心肌损伤，严重威胁着新生儿的生命健康，本课题通过制作内毒素心肌损伤模型，观察钙敏感受体在内毒素心肌损伤中的作用及机制，从而为内毒素心肌损伤的防治提供理论依据。.主要研究内容：通过制作乳鼠内毒素心肌损伤模型，透射电镜观察心肌细胞超微结构变化，Western Blot检测CaSR、JNK、GRP78、LC3B、Bcl-2、Cyt-C等蛋白表达变化。.结果：结果显示内毒素乳鼠心肌细胞CaSR表达增多，在给予CaSR激动剂后，CaSR的蛋白表达进一步增加，心肌损伤进一步加重；而给予CaSR抑制剂后，CaSR的蛋白表达下降，心肌细胞损伤减轻。给予CaSR激动剂后，GRP78、LC3B、Cyt-C、JNK表达增加，Bcl-2蛋白表达减少；而CaSR抑制剂则相反。.结论：CaSR可能是通过激活内质网应激、自噬、参与细胞凋亡来诱导心肌细胞损伤；CaSR可能通过JNK途径参与了内毒素心肌细胞损伤。