Regulation of Renal Hemodynamics by Adenosine Mediated Coincident Signaling

描述（由申请方提供）：利尿剂用作高血压、心力衰竭、肝功能障碍和慢性肾病等疾病的药物治疗干预。这些疾病状态与肾交感神经张力增加相关，这反过来最终导致肾血流量（RBF）和肾小球滤过率（GFR）降低。不幸的是，利尿剂治疗也显示出增加肾交感神经张力，从而增加了在这些患者中已经存在的对肾血流动力学的观察到的有害影响。这种作用可能是利尿剂抵抗和不耐受的潜在机制，限制了当前利尿剂的治疗潜力。为了解决这一重大的公共卫生问题，正在努力开发新的利尿药物，适合于慢性治疗，保持肾血流动力学。我们实验室的观察结果表明，选择性A1腺苷受体（A1 AR）拮抗剂BG 9928可减少肾交感神经刺激（RSNS）诱导的肾血管收缩。这些发现表明，肾神经效应器接头中的A1 AR激活增强肾交感神经传递。RSNS已被证明可增加神经效应器接头中去甲肾上腺素（NE）和ATP（也是将ATP代谢为腺苷的酶）的浓度。由于腺苷在调节肾交感神经传递中的确切作用尚未确定，我们的总体目标是研究腺苷增强RSNS血管收缩反应的机制。同时，我们将证明选择性A1 AR拮抗剂发挥其利尿作用，同时保持良好的肾脏血流动力学的手段。由于连接前A1 ARs是抑制性的，我们在这里建议，这是连接后A1 ARs是腺苷在RSNS反应的主要作用部位。还提出腺苷通过同步信号（途径的会聚）增强NE的血管收缩作用。为了验证我们的假设，我们将使用多种方法/技术，为该奖学金申请提供相当大的培训潜力。1)我们将证明，只有A1 AR亚型的拮抗作用将减少RSNS诱导的血管收缩在释放NE的存在下。2)我们将使用A1 AR敲除动物证明，仅重建连接后受体可恢复对RSNS的野生型反应。3)使用离体肾脏和体外实验，我们将证明腺苷和NE之间的一致信号，增加RSNS的血管收缩反应的精确机制。该项目的完成，除了显着的培训潜力，将确定一个以前不受重视的机制，腺苷在调节肾血流动力学和支持使用A1 AR拮抗剂的条件下，肾交感神经紧张。从这些实验中获得的信息将引起广大受众的兴趣，从研究肾脏生理学的基础科学家到评估利尿剂治疗的潜在治疗益处和/或并发症的临床医生。 公共卫生相关性：长期使用利尿剂作为心脏、肝脏和肾脏疾病的治疗干预，是公共卫生的一个重大问题。目前类别的利尿剂，虽然在短期疾病管理中相对有效，但具有不期望的副作用，因此限制了它们的治疗潜力。这项奖学金申请研究了内源性分子腺苷在调节肾交感神经传递中的作用，并将阐明一种新兴的利尿剂的作用机制，这种利尿剂靶向肾脏中腺苷介导的信号传导。

DESCRIPTION (provided by applicant): Diuretics are used as a pharmacological therapeutic intervention in diseases including hypertension, heart failure, liver dysfunction and chronic kidney disease. These disease states are associated with increased renal sympathetic tone, which in turn, ultimately leads to decreases in both renal blood flows (RBF) and glomerular filtration rate (GFR). Unfortunately, diuretic treatment has been shown to also increase renal sympathetic tone thus adding to the observed deleterious effects on kidney hemodynamics already present in these patients. This effect could be a contributing mechanism underlying the conditions of diuretic resistance and intolerance which limit the therapeutic potential of the current diuretics. To address this significant public health issue, effort is being put forth to develop new diuretic drugs suitable for chronic treatment that preserve renal hemodynamics. Observations from our laboratory demonstrate that BG9928, a selective A1 adenosine receptor (A1AR) antagonist, reduces renal sympathetic nerve stimulation (RSNS)-induced renal vasoconstriction. These findings suggest that A1AR activation in the renal neuroeffector junction potentiates renal sympathetic neurotransmission. RSNS has been shown to increase the concentration of norepinephrine (NE) and ATP (also the enzymes that metabolize ATP to adenosine) in the neuroeffector junction. Since the precise role that adenosine plays in modulating renal sympathetic neurotransmission remains undefined, our overall objective is to examine the mechanism by which adenosine enhances the vasoconstrictive response to RSNS. In conjunction, we will demonstrate the means by which selective A1AR antagonists exert their diuretic effects while preserving favorable renal hemodynamics. Since pre-junctional A1ARs are inhibitory, we suggest here that it is the post-junctional A1ARs that are the predominant site of action of adenosine in response to RSNS. Also propose that adenosine potentiates NE's vasoconstrictive actions via coincident signaling (convergence of pathways). To test our hypothesis, we will use multiple approaches/techniques providing considerable training potential for this fellowship application. 1) We will demonstrate that antagonism of only the A1AR subtype will reduce RSNS-induced vasoconstriction in the presence of released NE. 2) We will show using A1AR knock-out animals that reconstitution of only the post-junction receptors restores the wild-type response to RSNS. 3) Using isolated kidneys and in vitro experiments, we will demonstrate the precise mechanism of coincident signaling between adenosine and NE that increases the vasoconstrictive response to RSNS. The completion of this project, in addition to the significant training potential, will identify a previously unappreciated mechanism for adenosine in regulating renal hemodynamics and support for the use of A1AR antagonists in conditions with elevated renal sympathetic tone. The information obtained from these experiments will be of interest to a broad audience, ranging from basic scientists studying renal physiology to clinical physicians evaluating potential therapeutic benefit and/or complications of diuretic treatment. PUBLIC HEALTH RELEVANCE: The long-term use of diuretics as a therapeutic intervention for diseases of the heart, liver and kidney represents a significant concern for public health. The current classes of diuretics, although relatively effective in short-term disease management, possess undesired side effects thus limiting their therapeutic potential. This fellowship grant application examines the role of the endogenous molecule adenosine in modulating renal sympathetic neurotransmission and will elucidate the mechanism of action of an emerging class of diuretics that target adenosine-mediated signaling in the kidney.