Regulation of Blood Pressure Circadian Rhythm by Vascular Smooth Muscle BMAL1

描述（由申请人提供）：众所周知的血压（BP）昼夜节律对人类健康很重要，糖尿病患者的BP昼夜节律紊乱正成为未来靶器官损伤和心血管结局的指标。最近的研究发现，生物钟基因在所有被检查的组织中都有表达，这挑战了BP昼夜节律仅由中央起搏器控制的教条。然而，目前尚不清楚外周组织中哪些特定的时钟基因对BP昼夜节律起重要作用。我们培育了一种新的平滑肌特异性时钟基因BMAL1敲除小鼠SM-bmal1-/-来研究生理和糖尿病条件下血管平滑肌在血压昼夜节律中的作用。我们发现血管平滑肌BMAL1对于正常的血压昼夜节律以及正常的血管平滑肌收缩昼夜节律变化至关重要。此外，我们的初步研究表明rho激酶ROCK2与BMAL1与收缩有关。重要的是，我们发现，在2型糖尿病小鼠db/db中，BMAL1蛋白和活动昼夜节律振荡的丧失与血管平滑肌昼夜节律变化和血压昼夜节律的丧失有关。因此，我们假设BMAL1调节ROCK2，从而控制血管平滑肌收缩的昼夜节律变化，从而在糖尿病患者中显著促进正常的血压昼夜节律及其破坏。我们建议采用体外和体内的方法来验证这一假设，具体有三个目的：1)验证在生理条件下BMAL1通过ROCK2调节血管平滑肌收缩昼夜变化和BP昼夜节律的假设。2)验证在糖尿病条件下，BMAL1是血管平滑肌收缩昼夜变化中断所必需的假设。3)确定血管平滑肌BMAL1在糖尿病相关血压昼夜节律紊乱中的作用。这些研究的结果首次提供了外周血管平滑肌BMAL1发挥重要作用的直接实验证据，可能会改变中枢起搏器仅负责生理血压昼夜节律的教条。此外，我们的研究结果可能通过提供证据来确定血管平滑肌BMAL1作为糖尿病患者控制24小时血压的潜在治疗靶点

DESCRIPTION (provided by applicant): The well-known blood pressure (BP) circadian rhythm is important to human health and BP circadian rhythm disruption in diabetes is emerging as an index for future target organ damage and cardiovascular outcomes. Recent discoveries that clock genes are expressed in all of the tissues examined challenges the dogma that BP circadian rhythm is solely controlled by central pacemaker. However, it is completely unknown which specific clock gene(s) in which peripheral tissue(s) are important for BP circadian rhythm. We have generated a novel smooth muscle specific clock gene BMAL1 knockout mice SM-bmal1-/- to investigate the role of vascular smooth muscle in BP circadian rhythm under physiological and diabetic conditions. We found that vascular smooth muscle BMAL1 is essential for normal BP circadian rhythm as well as normal vascular smooth muscle contractile circadian variation. Moreover, our preliminary study implicates rho kinase, ROCK2, links BMAL1 to contraction. Importantly, we found that, in type 2 diabetic db/db mice, loss of BMAL1 protein and activity circadian oscillations is associated with loss of vascular smooth muscle circadian variation and BP circadian rhythm. Thus we hypothesize that BMAL1 regulates ROCK2, thus controlling vascular smooth muscle contractile circadian variation, thereby significantly contributing to normal BP circadian rhythm and its disruption in diabetes. We propose to use in vitro and in vivo approaches to test the hypothesis in three specific aims: 1) test the hypothesis that, under physiological conditions, BMAL1 regulates the vascular smooth muscle contractile circadian variation and BP circadian rhythm via ROCK2. 2) Test the hypothesis that, under diabetic conditions, BMAL1 is required for disruptions in vascular smooth muscle contractile circadian variation. 3) Determine the role of vascular smooth muscle BMAL1 in diabetes-associated disruption of BP circadian rhythm. Results from the proposed studies may modify the dogma that central pacemaker is solely responsible for the physiological BP circadian rhythm by providing the first direct experimental evidence that peripheral vascular smooth muscle BMAL1 play an important role. Moreover, our results may identify vascular smooth muscle BMAL1 as a potential therapeutic target for control of 24-h BP in diabetic patients by providing evidence that BMAL1 is a significant contributor linking diabetes to disruptions of BP circadian rhythm.