钙敏感受体在高血压发病中作用和机制的研究

Essential hypertension (EH) is a serious disease which is harmful to human health, and the renin-angiotensin system (RAS) plays an important role in the pathogenesis processes of EH. The extracellular calcium-sensing receptor (CaSR) is a G protein-coupled receptors and the data suggest that CaSR may have a role in regulating blood pressure. However, the underlying pathologic mechanisms are poorly understood.The investigations demonstrated that stimulating CaSR of renal juxtaglomerular (JG) cells could activate G(q) leading to the generation of inositol 1,4,5-trisphophate (IP3),and the release of Ca2+ from the endoplasmic reticulum (ER),increasing intracellular calcium concentration ([Ca2+]i), and resulting in calcium-mediated renin inhibition by inhibition of adenylate cyclase V (adenylyl cyclase isoform V, AC-V) and to reduce the cyclic adenosine monophosphate (cAMP) formation. Our preliminary experiment results show that CaSR activation can reduce spontaneous hypertensive rats (SHR) blood pressure; CaSR expression and the response to CaSR agonist were decreased in SHR vascular smooth muscle cells (VSMC). Therefore, we hypothesized that in SHR, because of CaSR expression and/or function impairment resulted in [Ca2+]i decrease by PLC/IP3 pathway, weakening of AC-V inhibition and increased cAMP formation and renin release. RAS activation proceeds and evokes vasoconstriction,vascular smooth muscle proliferation and remodeling, promoting the development of hypertension. To prove this hypothesis, based on vivo, tissue ,cell and molecular levels, we intend to study the relationship between CaSR and hypertension, its roles in decrease SHR blood pressure,regulation angiotasis and vascular smooth muscle proliferation and remodeling as well as cAMP contents and RAS activity change. Eventually, we clarify the effects of CaSR on hypertension and its mechanisms and to provide a new clinical target for the prevention and treatment of hypertension.

高血压病是严重危害人类健康疾病，肾素-血管紧张素系统(RAS)在其中起重要作用。研究提示作为G蛋白偶联受体的钙敏感受体(CaSR)可能有调节血压作用，机制不明。而肾小球球旁细胞CaSR激活经细胞内钙离子浓度（[Ca2+]i）增加，可抑制腺苷酸环化酶(AC)，减少cAMP形成和肾素释放。预实验发现：CaSR激活可降低自发性高血压大鼠(SHR)血压，SHR血管平滑肌细胞CaSR表达降低且对CaSR激动剂反应减弱。我们推测：在SHR体内，由于CaSR表达下降或功能缺陷使[Ca2+]i降低，对AC抑制作用减弱，使cAMP和肾素增加，激活RAS介导了血管收缩及平滑肌增殖重塑，促进了高血压发生。为证实此假说，本项目拟在整体、组织和细胞分子三个层面研究CaSR与高血压相关性及在SHR降血压、调节血管张力等方面作用及与AC和RAS活性变化关系，阐明CaSR在高血压发病中作用和机制，为高血压防治提供新标靶。

高血压病是严重危害人类健康疾病，肾素-血管紧张素系统(RAS)在其中起重要作用。研究显示作为G蛋白偶联受体的钙敏感受体(CaSR)通过磷脂酶C(PLC)/1，4，5-三磷酸肌醇增加(IP3)途径增加细胞内钙离子([Ca2+]i)，抑制腺苷酸环化酶V(AC-V)，减少环磷酸腺苷（cAMP）的形成和RAS激活，但是否参与高血压及靶器官损害发生发展尚不清楚。本项目拟从RAS角度部分阐明CaSR在高血压发病中作用和机制。研究证实：(1) CaSR表达降低参与了高血压及血管和心肌重塑的发生发展，其机制与CaSR低表达经cAMP途径激活循环及血管和心肌局部经典RAS有关；(2) R568激活CaSR在降低血压的同时可以改善血管和心肌重塑，其作用机制是通过抑制心肌和血管局部经典RAS活性实现，在心肌还与激活新型RAS有关；(3) SHR血管收缩反应增强，而舒张反应减弱，且不依赖血管内皮的完整性；(4) CaSR激动剂NPSR568可浓度依赖性的引起SHR大鼠血管舒张，且依赖血管内皮的完整性；其抑制剂NPS2143可浓度依赖性的引起血压正常和SHR大鼠同等程度收缩作用；(5)CaSR参与SHR和正常血压大鼠血管张力的调节，但存在差异：NPSR568可抑制SHR血管收缩反应，增强血管舒张反应，且依赖血管内皮的完整性；NPS2143减弱正常血压大鼠血管收缩反应作用强于SHR，而增强SHR血管舒张反应，抑制正常血压大鼠血管舒张反应，此调节作用部分依赖于血管内皮的完整性，并由PLC/IP3/AC-V/cAMP/RAS信号通路介导；(6)CaSR低表达促进SHR VSMCs的增殖、抑制凋亡，此作用机制与CaSR低表达经PLC/IP3 /Ca2+/AC-V/cAMP途径激活经典RAS有关。该研究成果进一步从RAS角度阐明了CaSR在高血压发病中的作用和机制，为临床高血压防治提供新思路和药物作用新靶标。