Microvessel O2 Responses in Salt-Sensitive Hypertension

描述(申请人提供)：细胞色素P450-4A(细胞色素P450-4A)w-羟基酶，催化花生四烯酸形成20-羟基二十碳四烯酸(20-HETE)，可作为血管氧气感受器，在氧气供应增加和减少期间调节血管张力起关键作用。我们的研究表明，在盐敏感型高血压的发展过程中，CYP450-20-HETE系统的活性增强是提高血管阻力的主要候选因素，它通过感知O2的可用性和介导外周循环中O2依赖的血管收缩来实现。这项建议代表了一系列成功研究的继续，这些研究调查了20-HETE和CYP450-4A w-羟基酶在介导Dahl盐敏感(SS)大鼠对O2供应变化的改变反应中的作用。本研究要检验的总体假设是，Dahl SS高血压大鼠小动脉对PO2升高的反应增强是由于三个因素中的一个或三个因素的组合：20-HETE的产生增加，血管对20-HETE的血管收缩作用更敏感，和/或细胞色素P450-4A w-羟基酶的表达改变，该酶催化从花生四烯酸合成20-HETE。为了验证这一假说，本研究有以下具体目的：1)利用同系和同系大鼠模型，评价细胞色素P450酶和20-HETE在高盐饮食引起SS大鼠血管O2反应改变中的作用；2)确定HS饮食是否改变SS大鼠小动脉和阻力动脉P450-4A w-羟化酶亚型的表达模式，增加CYP-4504A蛋白的表达；3)与正常血压的SS大鼠和缺乏SS CYP450-4A等位基因的SS大鼠相比，HS饮食的SS大鼠小动脉和阻力动脉中20-HETE的产生是否增加；以及4)确定HS饮食是否增加SS大鼠小动脉对20-HETE的敏感性，以及从缺乏SS CYP450-4A等位基因的大鼠品系中导入的CYP450基因是否可以防止盐诱导的小动脉20-HETE敏感性的增强。这些研究应该为人类，特别是非裔美国人在盐敏感型高血压期间血管控制机制如何改变提供有价值的见解，他们表现出一种与Dahl SS大鼠惊人相似的盐敏感型高血压。

DESCRIPTION (provided by applicant): Cytochrome P450-4A (CYP450-4A) w-hydroxylase, which catalyzes the formation of 20-hydroxy- eicosatetraenoic acid (20-HETE) from arachidonic acid, may act as a vascular O2 sensor, with a crucial role n regulating vascular tone during both increases and decreases in O2 availability. Our studies indicate that enhanced activity of the CYP450-20-HETE system is a major candidate to elevate vascular resistance during the development of salt sensitive forms of hypertension by sensing O2 availability and mediating O2- dependent vasoconstriction in the peripheral circulation. This proposal represents a continuation of a successful line of studies investigating the role of 20-HETE and CYP450-4A w-hydroxylase in mediating altered responses to changes in O2 availability in the Dahl salt-sensitive (SS) rat. The overall hypothesis to be tested in this study is that the enhanced response of arterioles to elevated PO2 in Dahl SS hypertensive rats is due to one or a combination of three factors: increases in the production of 20-HETE, an increased sensitivity of the vessels to the vasoconstrictor effects of 20-HETE, and/or an altered expression of cytochrome P450-4A w-hydroxylase, the enzyme that catalyzes the synthesis of 20-HETE from arachidonic acid. To test this hypothesis, the proposed study has the following Specific Aims: 1) To utilize consomic and congenic rat models to evaluate the role of cytochrome P450 (CYP450) enzymes and 20-HETE in contributing to altered vascular O2 responses in SS rats on high salt (HS) diet; 2) To determine whether HS diet changes the expression pattern of individual P450-4A w-hydroxylase isoforms and increases CYP- 4504A protein expression in arterioles and resistance arteries of SS rats; 3): To determine whether 20-HETE production is elevated in arterioles and resistance arteries of SS rats on HS diet compared to normotensive SS rats on LS diet and rat strains lacking the SS CYP450-4A alleles; and 4) To determine whether HS diet increases 20-HETE sensitivity in arterioles of SS rats, and whether any salt-induced potentiation of arteriolar 20-HETE sensitivity is prevented by introgression of CYP450 genes from rat strains lacking the SS CYP450- 4A alleles. These studies should provide valuable insight into how vascular control mechanisms are altered during salt-sensitive hypertension in humans, particularly in members of the African-American population, who exhibit a form of salt sensitive hypertension that is strikingly similar to that occurring in the Dahl SS rat.