Ewart Marie-Ann, Kennedy Simon, Macmillan Debbi, Raja Abhirami L N, Watt Ian M, Currie Susan
Institute of Cardiovascular & Medical Sciences, University of Glasgow, G12 8QQ, UK.
Institute of Cardiovascular & Medical Sciences, University of Glasgow, G12 8QQ, UK.
Atherosclerosis. 2014 May;234(1):154-61. doi: 10.1016/j.atherosclerosis.2014.02.014. Epub 2014 Mar 12.
Relaxation of vascular smooth muscle (VSM) requires re-uptake of cytosolic Ca(2+) into the sarcoplasmic reticulum (SR) via the Sarco/Endoplasmic Reticulum Ca(2+) ATPase (SERCA), or extrusion via the Plasma Membrane Ca(2+) ATPase (PMCA) or sodium Ca(2+) exchanger (NCX). Peroxynitrite, a reactive species formed in vascular inflammatory diseases, upregulates SERCA activity to induce relaxation but, chronically, can contribute to atherogenesis and altered vascular function by escalating endoplasmic reticulum stress. Our objectives were to determine if peroxynitrite-induced relaxation and Ca(2+) handling processes within vascular smooth muscle cells were altered as atherosclerosis develops.
Aortae from control and ApoE(-/-) mice were studied histologically, functionally and for protein expression levels of SERCA and PMCA. Ca(2+) responses were assessed in dissociated aortic smooth muscle cells in the presence and absence of extracellular Ca(2+).
Relaxation to peroxynitrite was concentration-dependent and endothelium-independent. The abilities of the SERCA blocker thapsigargin and the PMCA inhibitor carboxyeosin to block this relaxation were altered during fat feeding and plaque progression. SERCA levels were progressively reduced, while PMCA expression was upregulated. In ApoE(-/-) VSM cells, increases in cytosolic Ca(2+) [Ca(2+)]c in response to SERCA blockade were reduced, while SERCA-independent Ca(2+) clearance was faster compared to control.
As atherosclerosis develops in the ApoE(-/-) mouse, expression and function of Ca(2+) handling proteins are altered. Up-regulation of Ca(2+) removal via PMCA may offer a potential compensatory mechanism to help normalise the dysfunctional relaxation observed during disease progression.
血管平滑肌（VSM）的舒张需要通过肌浆网/内质网Ca²⁺ATP酶（SERCA）将胞浆Ca²⁺重新摄取到肌浆网（SR）中，或通过质膜Ca²⁺ATP酶（PMCA）或钠钙交换体（NCX）将其排出。过氧亚硝酸盐是血管炎症性疾病中形成的一种活性物质，它上调SERCA活性以诱导舒张，但长期来看，可通过加剧内质网应激促进动脉粥样硬化的发生和血管功能改变。我们的目的是确定随着动脉粥样硬化的发展，血管平滑肌细胞内过氧亚硝酸盐诱导的舒张和Ca²⁺处理过程是否发生改变。
对对照小鼠和载脂蛋白E基因敲除（ApoE⁻/⁻）小鼠的主动脉进行组织学、功能研究，并检测SERCA和PMCA的蛋白表达水平。在有无细胞外Ca²⁺存在的情况下，评估分离的主动脉平滑肌细胞中的Ca²⁺反应。
对过氧亚硝酸盐的舒张反应呈浓度依赖性且不依赖于内皮。在高脂喂养和斑块进展过程中，SERCA阻滞剂毒胡萝卜素和PMCA抑制剂羧基曙红阻断这种舒张的能力发生了改变。SERCA水平逐渐降低，而PMCA表达上调。在ApoE⁻/⁻血管平滑肌细胞中，对SERCA阻断的胞浆Ca²⁺[Ca²⁺]c升高反应减弱，而与对照相比，不依赖SERCA的Ca²⁺清除更快。
随着ApoE⁻/⁻小鼠动脉粥样硬化的发展，Ca²⁺处理蛋白的表达和功能发生改变。通过PMCA增加Ca²⁺清除可能提供一种潜在的代偿机制，有助于使疾病进展过程中观察到的功能失调性舒张正常化。
