AUTOCRINE/PARACRINE REGULATION OF RENAL MICROCIRCULATION

肾微循环的自分泌/旁分泌调节

• 批准号: 6649479
• 负责人: Oscar A. Carretero
• 金额: $ 7.35万
• 依托单位: HENRY FORD HEALTH SYSTEM
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-01 至 2007-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6649479
• 关键词: adenosine; adenosine triphosphate; angiotensin receptor; angiotensins; autocrine; calcium flux; glomerular filtration rate; hormone regulation /control mechanism; kidney circulation; laboratory rabbit; microcirculation; nitric oxide; nitric oxide synthase; paracrine; receptor expression; renal glomerulus; renal tubular transport; renal tubule; tissue /cell culture; transforming growth factors; vascular resistance; vasoactive agent; vasomotion

DESCRIPTION: (provided by applicant) In hypertension, regardless of its cause, renal vascular resistance increases, shifting the pressure natriuresis curve to the right. The afferent (Af-Art) and efferent arterioles (Ef-Art) account for most renal vascular resistance; they control glomerular filtration rate (GFR) and peritubular pressure, and consequently renal function. Af- and Ef-Art resistances are regulated by a balance between vasopressors (angiotensin, adenosine via the A1 receptor, reactive oxygen species) and vasodepressors (kinins, NO, adenosine via the A2 receptor). The Af-Art is also controlled by tubuloglomerular feedback (TGF). TGF operates via the macula densa, which senses Cl-, Na+ and/or solute load and sends a paracrine signal to the extraglomerular mesangial cells and/or the effectors of TGF, which are the Af-Art and Ef-Art. In addition to the TGF signal itself, the macula densa produces autocrine and paracrine factors that alter TGF either by acting on the macula densa or the Af- and Ef-Art, respectively. NO produced by macula densa neuronal NO synthase (nNOS), which attenuates TGF, is one such autacoid. We have evidence that the Ef-Art dilates rather than constricts during TGF and that the Ef-Art response to vasoactive hormones is modulated by paracrine factors produced by the glomerulus. Thus control of the renal microcirculation is complex and difficult to examine in vivo. For this reason, we propose to use a technique we developed that consists of in vitro perfusion of a microdissected Af- or Ef-Art and adherent tubular segment containing the macula densa. Using this preparation, we hypothesize that different and efferent resistance are regulated by autocrine and paracrine factors released from the glomerulus and the macula densa. Factors that promote dilatation include NO, prostaglandins (PGs) and 5,6 epoxyeicosatrienoic acid (EET). These are counterbalanced by factors that promote vasoconstriction including Ang II, thromboxane, 20- hydroxyeicosatetraenoic acid (HETE) and reactive oxygen species. Paracrine factors such as adenosine may have dilator or constrictor actions depending on whether A1 or A2 receptors are expressed on the target tissue. In Aim 1 we will test the hypothesis that when macula densa nNOS is increased, such as during low salt intake, NO released by the macula densa regulates basal Af-Art resistance even when the NaCl level in the macula densa is very low. In this situation, NO acts not only at the macula densa but also by diffusing from the macula densa to the Af-Art where it causes dilatation, thus preserving renal blood flow despite high renin. In Aim 2 we will test the hypothesis that by quenching NO released by macula densa nNOS, O2- determines a) the magnitude of TGF and b) whether NO acts only in an autocrine manner in the macula densa itself, or also in a paracrine mode by diffusing to the Af-Art and causing dilatation. In Aim 3 we will test the hypothesis that increased intracellular calcium in the macula densa acts as both a positive regulator by contributing to macula densa release of ATP and formation of adenosine in the interstitial space and a negative regulator of TGF by activating nNOS. In Aim 4 we will test the hypothesis that the glomerulus releases paracrine factors that control downstream Ef-Art resistance and consequently its own filtration pressure. In Aim 5 we will test the hypothesis that the mechanism of Ef-Art TGF is similar to Af-Art TGF, save that adenosine acts on the Ef-Art A2 receptor, causing dilatation. Thus reducing NO by inhibiting nNOS in the macula densa will potentiate Ef-Art TGF (greater dilatation).

描述：(申请人提供) 在高血压中，无论其原因如何，肾血管阻力增加， 将压力排钠曲线向右移动。传入者(Af-Art) 传出小动脉(EF-Art)是肾血管阻力的主要来源； 它们控制肾小球滤过率(GFR)和肾小管周围压力，以及 因此，肾功能。AF-和EF-Art电阻由 血管加压素(血管紧张素，通过A1受体的腺苷， 活性氧)和血管抑制剂(激动素，一氧化氮，通过A2的腺苷 受体)。Af-Art还受肾小管小球反馈(TGF)的控制。 转化生长因子通过致密斑区起作用，致密斑区感知氯、钠和/或溶质负荷。 并将旁分泌信号发送到肾小球外系膜细胞和/或 转化生长因子的效应物，即Af-Art和EF-Art。除了转化生长因子 信号本身，致密斑会产生自分泌和旁分泌因子， 通过作用于致密黄斑或Af-和EF-Art改变转化生长因子， 分别进行了分析。致密斑神经元型一氧化氮合酶(NNOS)产生的NO 抗转化生长因子，就是这样的一种海绵体。我们有证据表明EF-ART扩大了 而不是在转化生长因子期间收缩，EF-ART对血管活性的反应 激素受肾小球产生的旁分泌因子的调节。因此， 肾微循环的控制是复杂的，很难检查。 活着。出于这个原因，我们建议使用我们开发的一种技术 包括体外灌流显微解剖的Af-或EF-Art和粘附物 含有致密黄斑的管状节段。利用这种准备，我们 假设不同的传出阻力由自分泌调节 肾小球和致密黄斑释放旁分泌因子。 促进扩张的因素包括一氧化氮、前列腺素(PGs)和5，6 环氧二十碳三烯酸(EET)。这些都被一些因素抵消了 促进血管收缩，包括血管紧张素II、血栓素、20- 羟基二十碳四烯酸(HETE)和活性氧物种。旁分泌 腺苷等因子可能具有扩张或收缩作用，具体取决于 靶组织是否表达A1或A2受体。在目标1中，我们 将检验这样的假设，即当致密黄斑nNOS增加时，例如 在低盐摄入期间，致密黄斑释放的NO调节基础Af-Art 即使在致密斑内的氯化钠水平非常低的情况下也是如此。在这 在这种情况下，NO不仅作用于致密黄斑，而且还通过从 致密黄斑至Af-ART，导致扩张，从而保护肾脏 血液流动，尽管肾素很高。在目标2中，我们将通过以下方式测试假设 致密黄斑释放的NO猝灭，O2-决定a) 转化生长因子和b)致密黄斑中NO是否仅以自分泌方式起作用 本身，或者也以旁分泌模式扩散到Af-Art并引起 扩张。在目标3中，我们将检验细胞内增加的假设 致密黄斑中的钙既是一种积极的调节剂，也是一种 致黄斑间质中ATP的释放和腺苷的形成 通过激活nNOS，对转化生长因子起负调控作用。在《目标4》中我们将 检验肾小球释放旁分泌因子的假设 控制下游EF-Art阻力，从而控制其自身过滤 压力。在目标5中，我们将检验EF-ART机制的假设 转化生长因子类似于Af-Art转化生长因子，不同之处在于腺苷作用于EF-ArtA2 受体，导致扩张。从而通过抑制脑组织中的nNOS来减少NO 致密黄斑会增强EF-Art的转化生长因子(更大的扩张)。