髓样分化蛋白2介导的炎症反应在糖尿病心肌病中的作用机制研究

Myocardial chronic inflammation induced by hyperglycemia plays an important role in the progress and development of diabetic cardiomyopathy (DCM). However, it is still unclear how hyperglycemia stimulates the myocardial chronic inflammation. Myeloid differentiation protein-2(MD2) is an assistant protein of toll-like receptor 4 (TLR4), which directly binds to the lipopolysaccharide (LPS). Thus, MD2 is an important mediator in LPS-induced acute inflammation. However, it is unknown if MD2 could mediate the inflammation induced by other stimulators including hyperglycemia. In the previous studies, we found that L6H21, a specific MD2 small-molecule inhibitor, significantly attenuated hyperglycemia-induced cardiac injuries in type 1 diabetic mice, which was accompanied with a marked reduction in myocardial inflammatory response. Based on these results, we hypothesize that, MD2 may play an important role in the development of hyperglycemia-induced myocardial inflammation and DCM. MD2 may become a therapeutic target for the treatment of DCM. In this study, a series of experiments are designed to evaluate and confirm the above hypothesis. We plan to 1) investigate the effects and mechanism of MD2 in mediating high glucose concentration-induced inflammation and injuries in cultured cardiac cells, 2) validate the key role of MD2 in regulating hyperglycemia-induced inflammation and DCM in isolated hearts, MD2 wide-type mice, and MD2 knockout mice, 3) probe the relationship between MD2 and DCM using clinical blood samples from patients with or without DCM. The completion of these studies will demonstrate the MD2-involved mechanism in hyperglycemia-induced cardiac inflammation and DCM, providing a new target for the treatment of DCM.

心肌慢性炎症反应是糖尿病心肌病（DCM）的重要病理过程之一，但高血糖如何引起心肌炎症反应尚未被阐明。髓样分化蛋白2（MD2）是Toll样受体4（TLR4）的辅助蛋白，一般认为，它直接结合LPS，是LPS-TLR4炎症反应的直接介导物。但尚不清楚MD2是否能介导其他刺激物引起炎症反应。我们前期工作发现特异性MD2小分子抑制剂L6H21在1型糖尿病小鼠中显著缓解高血糖导致的心肌损伤，并伴随着心肌炎症反应的降低。基于此，我们假设：MD2在高血糖诱导的心肌炎症和DCM发生中有着重要介导作用。本项目中，我们拟利用心肌细胞探索MD2在高糖诱导炎症和损伤中的介导作用与分子机制；利用离体心脏、普通小鼠和MD2敲除小鼠，确证MD2在DCM发生发展中的重要性；利用临床样本，探讨MD2与DCM的相关性。本项目预期解决MD2介导的糖尿病-心肌炎症-心肌病的机制问题，为防治DCM提供新的治疗靶点。

心肌慢性炎症反应是糖尿病心肌病（DCM）的重要病理过程之一，但高血糖如何引起心肌炎症反应尚不完全清楚。髓样分化蛋白2（MD2）是Toll样受体4（TLR4）的辅助蛋白，一般认为，它直接结合LPS，是LPS-TLR4炎症反应的直接介导物。但尚不清楚MD2是否能介导其他刺激物引起的炎症反应。我们前期工作发现特异性的MD2小分子抑制剂L6H21在1型糖尿病小鼠中显著缓解高血糖导致的心肌损伤，并伴随着心肌炎症反应的降低。基于此，我们假设：MD2在高血糖诱导的心肌炎症和DCM发生中有着重要介导作用。本项目中，我们利用心肌细胞探索MD2在高糖诱导炎症和损伤中的介导作用与分子机制；利用C57BL/6小鼠（MD2野生型小鼠）和MD2敲除小鼠，确证MD2在DCM发生发展中的重要性；利用临床样本，探讨MD2与DCM的相关性。我们的研究结果发现，MD2在糖尿病小鼠心脏组织和糖尿病人血清中均有升高。MD2敲除显著抑制促炎TLR4通路的激活，而TLR4通路的抑制与心肌重构的减少和心功能的改善相关。在机制上，我们发现高糖可诱导细胞外快速生成晚期糖基化终产物(AGEs)，它直接与MD2蛋白结合，形成AGEs-MD2-TLR4复合物，并启动下游促炎信号通路。我们进一步检测发现DCM患者血清和糖尿病小鼠心脏组织及血清中AGE-MD2复合物水平升高。总之，我们为高糖诱导炎症反应和心肌损伤提供了一个新的致病机制，并为糖尿病心肌病的治疗提供了新的思路。