基于肾上腺素β2受体调控主动脉瓣钙化的分子机制研究

The prevalence of aortic valve calcification increases with age, as the most common valvular abnormality. It is caused by an active cellular process involving bone formation concerning valve interstitial cells differentiation toward an osteoblast-like cell phenotype. The processes are all modulated by autonomic system the same. It was found that the depression in calcification of VICs was related to the stimulation of β2 Adrenergic receptors. Simultaneously, in the calcified heart valve, the expression of HIF-1αproteins was elevated, then activation of HIF-1 by 3% hypoxia could weaken the depression in calcification byβ2 Adrenergic receptors, which resemble the β2 Adrenergic blockade. We hypothesize that activation of the 2-ARs may regulate calcification of the aortic valve by preventing the differentiation of valve ICs into an osteoblast-like cell phenotype with HIF in combination. Four aspects will be addressed in detail: β2 AR, concerning active oxygen( O2, NO), HIF-1 subtypes and the related osteogenic genes. It is postulated that we will determine the level and pattern of expression ofβ2ARs and HIF in human aortic valve leaflets and to investigate the effect of the β2ARs stimulation on the osteogenic differentiation of human valve ICs.

主动脉瓣钙化狭窄已然成为流行的心脏瓣膜疾病，为最主要的心脏手术病因，缺乏有效的药物干预，主要源于其分子机制知之甚少。主动脉瓣钙化和成骨发生有着诸多相似之处，主要涉及瓣膜间质细胞的成骨表型转化，同样接受自主神经调控。我们前期试验发现β2受体激动对瓣膜细胞钙化的特异性抑制作用，以及钙化心脏瓣膜中HIF-1α明显上调，且HIF-1活化（3%低氧环境）可模拟β受体阻滞剂，减弱β2受体激动对细胞成骨分化的抑制作用。因而本课题构想：肾上腺素β2受体介导HIF-1，实现对瓣膜间质细胞成骨表型转化的调控，是主动脉瓣钙化的调控机制之一。我们将从β2R密度/G蛋白/AC酶活性；相关氧化物质代谢（O2、NO）；HIF-1各亚基表达，转位，降解；以及核内钙化基因的转录4个方面进行分子调控信号及反馈机制的研究。从而率先明确特异的β2AR-HIF-calcification分子通路，阐释β2受体调控瓣膜钙化的分子机制

瓣膜间质细胞（VICs）发生成骨分化是主动脉瓣发生钙化的重要病理基础。在各种病理因素作用下，VICs发生成骨分化，表达骨化相关基因表达，促进钙盐沉积。本研究发现，在钙化的主动脉瓣组织中，VICs存在细胞内缺氧和HIF-1α高表达；抑制其表达可减少病理环境下VICs表达骨化相关基因、减少钙盐沉积。我们进一步发现，HIF-1α可直接与TLR-4基因promoter区结合，促进TLR-4的高表达及下游信号通路的过度激活，进而引起骨化相关基因的大量转录表达，促进VICs发生成骨分化。而β-2AR的激活剂沙美特罗可通过Gi蛋白，从HIF-1α表达和入核两个水平抑制HIF-1α促进钙化的作用，从而起到减轻瓣膜钙化的作用。本研究首次发现HIF-1α参与瓣膜钙化的发病过程，并揭示其作为核心因子，连接和促进了G蛋白偶联受体通路β2-AR信号通路和模式识别受体TLR4信号通路的交互通话。本研究通过描绘HIF-1α促进瓣膜钙化发生机制及β2-AR的干预机制，为多重层面抑制主动脉瓣钙化提供治疗新思路。