Caveolae/RhoA/BKCa复合体作为功能性细胞表面缓冲系统在模拟失重所致动脉重建中的作用和机制研究

The mechanisms underlying simulated microgravity-induced artery remodeling are still not fully understood, the initial factor of which might be transmural pressure alterations secondary to hemodynamic changes. Recent studies have demonstrated the protective role of buffering system at cell surface in the detrimental cellular effects of mechanical stimulus, which contributes to artery remodeling. Previous studies investigating buffering system at cell surface were mainly focused on the structural buffering system, few studies payed special attention to the functional buffering system. Thus, it’s still not clear whether the functional buffering system played a role in simulated microgravity-induced artery remodeling or what kind of role it was. The present study adopted hindlimb unweighted rat as the animal model to simulate the main physiological effects of simulated microgravity on the cardiovascular system, and investigated the possibility of Caveolae/RhoA/BKCa complex as functional buffering system at cell surface and the role of this complex in simulated microgravity-induced artery remodeling. We intended to observe: ① co-localization of Caveolae/RhoA/BKCa; ② functional relationship among Caveolae/RhoA/BKCa; ③ the role of Caveolae/RhoA/BKCa complex in buffering transmural pressure changes and simulated microgravity-induced artery remodeling. Our study supplies significant importance for illuminating the mechanisms underlying artery remodeling induced by microgravity and enriching the theoretical research of buffering system at cell surface in the field of vascular biology.

模拟失重所致动脉重建的机理尚未完全阐明，其始动因素可能为血流动力学变化所致血管跨壁压力改变。近年研究表明，细胞表面缓冲系统可缓冲外界机械刺激对细胞的不利影响，进而参与动脉重建。目前，有关细胞表面缓冲系统的研究主要集中于结构性缓冲系统，而针对功能性缓冲系统的研究较少，故其在模拟失重所致动脉重建中的作用亦不明确。本研究以大鼠尾部悬吊模拟失重影响，从动物整体、离体动脉培养及细胞水平研究Caveolae/RhoA/大电导钙激活钾离子通道（BKCa）复合体作为功能性细胞表面缓冲系统的可能性及其在模拟失重致动脉重建中的作用，拟观察：①Caveolae/RhoA/BKCa之间的共定位关系；②Caveolae/RhoA/BKCa之间的功能联系；③上述复合体在缓冲血管跨壁压力变化及模拟失重所致动脉重建中的作用。本工作对阐明航天失重下动脉重建的机理并丰富血管生物学领域细胞表面缓冲系统的理论研究均具有重要意义。

模拟失重所致动脉重建的机理尚未完全阐明。近年研究表明，细胞表面缓冲系统可缓冲外界机械刺激对细胞的不利影响，进而参与动脉重建。目前，有关细胞表面缓冲系统的研究主要集中于结构性缓冲系统，而针对功能性缓冲系统的研究较少，故其在模拟失重所致动脉重建中的作用亦不明确。本研究以尾部悬吊大鼠作为动物模型模拟失重对心血管系统的影响，从多个层面深入研究Caveolae/RhoA/大电导钙激活钾离子通道（large conductance calcium activated potassium channel, BKCa）复合体及其相关通路作为功能性细胞表面缓冲系统的可能性及其在模拟失重致动脉重建中的作用。本工作主要结果如下：1）28天模拟失重显著降低RhoA-Rho激酶（ROCK）通路的表达及其对下游靶通路的作用，包括与股动脉收缩反应性直接相关的肌球蛋白轻链磷酸酶（myosin light chain phosphatase, MLCP）/肌球蛋白轻链（myosin light chain, MLC）通路，以及间接相关的核因子-κB（nuclear factor-κB, NF-κB）/诱导型一氧化氮合酶（inducible nitric oxide synthase, iNOS）/一氧化氮（nitric oxide, NO）通路，二者可能共同导致模拟失重大鼠股动脉收缩功能降低；2）RhoA与BKCa通道之间存在共定位结合关系，且模拟失重可能通过改变二者之间结合方式以及结合程度的形式代偿大鼠阻力动脉功能重建；3）BKCa可能通过激活RhoA-ROCK通路发挥代偿模拟失重所致冠状动脉收缩功能降低的作用；4）Caveolae/RhoA/BKCa通道可能作为经典的血管平滑肌细胞（vascular smooth muscle cells, VSMCs）表面缓冲系统的补充，共同发挥代偿外界应力改变对VSMCs不利刺激的保护性作用。