Hypertension: Contribution of Arterial Wall Changes

描述(由申请人提供)：天然血管平滑肌细胞(VSMC)的电压门控K+(Kv)电流受到胞内游离钙增加的抑制，继之于细胞内钙释放或细胞外钙内流。与正常血压的大鼠相比，高血压大鼠的VSMCs对阻力动脉和高血压大鼠的这种抑制作用增强。因此，钙离子介导的Kv电流抑制可能参与了小动脉张力的调节和高血压病的发病机制。在我们以往的研究中发现：1)Kv1.2和Kv1.5是大鼠肠系膜小动脉(SMA)上主要的Shaker通道，在高血压动脉中的表达水平较高；2)细胞内钙离子抑制Kv1.2、Kv1.5和Kv1.2-1.5异构体通道在非洲爪哇卵母细胞和CHO细胞中的表达；3)这种钙抑制作用可被钙调素(CaM)增强，但不受蛋白激酶A、G和C的抑制剂Staruosporine的影响；以及4)钙离子介导的Kv抑制可能涉及多种机制。我们的数据还表明，Kv1.2和Kv1.5以异构体结构共同组装，形成功能性的Kv1.2-1.5通道，而仅有Kv1.2和Kv1.5的特性不足以代表大鼠SMA VSMCs中Kv电流的特性。基于这些发现，这一新的应用将检验以下假设：1)多个Kv通道组合(α和β亚基)参与SMA的Kv电流和收缩功能；2)只有Shaker KV1通道被钙抑制；3)钙抑制Kv通道的多种机制涉及CaM；以及4)这些过程在高血压动物的VSMC中被增强。这些假说将用正常(WKY)和高血压(SHR)动物的SMA进行检验。我们认为，这一过程将细胞内钙离子的变化与膜电位和电压门控钙通道活性的变化相结合，从而有助于调节动脉力量维持和血管阻力。SHR和WKY这一效应在VSMC中的差异“表达”将有助于确认候选机制。这些研究将为基于钙-Kv通道调控机制(S)的降压药物开发提供新的治疗靶点。

DESCRIPTION (provided by applicant): Voltage-gated K+ (Kv) currents in native vascular smooth muscle cells (VSMC) are inhibited by an increase in cytosolic free Ca2+, secondary to intracellular Ca 2+ release or extracellular Ca2+ influx. This inhibitory effect is enhanced in VSMCs from resistance versus conduit arteries and from hypertensive compared to normotensive rats. Thus, Ca2+-mediated inhibition of Kv currents may contribute to the regulation of tone in small arteries and to the pathogenesis of hypertensive disease. In our previous studies to identify the molecular mechanisms responsible for this effect, we found that 1) Kv1.2 and Kv1.5 are the dominant Shaker channels in rat small mesenteric arteries (SMA) and expression of these proteins is higher in hypertensive arteries; 2) intracellular Ca2+ inhibits Kv1.2, Kv1.5 and Kv1.2-1.5 heteromeric channels expressed in Xenopus laevis oocytes and in CHO cells; 3) this Ca2+ inhibition is enhanced by added calmodulin (CaM) but is not affected by staruosporine, an inhibitor of protein kinases A, G and C; and 4) more than one mechanism may be involved in Ca2+-mediated Kv inhibition. Our data also suggest that Kv1.2 and Kv1.5 are coassembled in a heterotetramic structure to form functional Kv1.2-1.5 channels, and that the properties of Kv1.2 and Kv1.5 alone are not sufficient to represent those of Kv currents in rat SMA VSMCs. Based on these findings, this renewal application will test the hypotheses that 1) multiple Kv channel assemblies (alpha and beta subunits) contribute to Kv current and to contractile function in SMA; 2) only Shaker Kv1 channels are inhibited by Ca2+; 3) Ca2+ inhibition of Kv channels is mediated by multiple mechanisms involving CaM; and 4) these processes are enhanced in VSMC from hypertensive animals. These hypotheses will be tested using SMA from normal (WKY) and hypertensive (SHR) animals. We suggest that this process couples changes in intracellular Ca2+ to changes in membrane potential and voltage-gated Ca2+ channel activity thereby contributing to the regulation of arterial force maintenance and vascular resistance. The differential "expression" of this effect in VSMCs from SHR versus WKY will aid in confirming candidate mechanisms. These studies will define a novel therapeutic target for antihypertensive drug development based upon the mechanism(s) of Ca2+-Kv channel modulation.