Cationic Amino Acid Transporters and Lung NO Production

说明书(申请人提供)：一氧化氮(NO)是一种参与多种生理功能的重要分子。在肺动脉高压疾病中，NO的产生减少，导致血管收缩和血管重塑。而在肺部炎症性疾病中，NO的产生增加，导致组织损伤。一氧化氮是由L精氨酸(L精氨酸)通过一氧化氮合酶(NOS)产生的。L精氨酸对一氧化氮合酶的细胞生物利用度在很大程度上取决于细胞外L精氨酸通过阳离子氨基酸转运体(CAT)的摄取。初步研究表明，在高度脆弱的患者群体中，操纵L-精氨酸摄取改变了临床重要参数。因此，本申请中描述的研究集中在阐明CAT摄取L-精氨酸的功能和机制方面，以及它在调节肺内NO产生中的作用。这些研究的长期目标是开发治疗方法，在肺动脉高压疾病中通过促进CAT介导的L-精氨酸摄取来增加NO的产生，在炎症性肺部疾病中通过抑制CAT介导的L-精氨酸摄取来减少NO的产生。工作假说是，通过改变CAT介导的L-精氨酸转运，可以通过控制L-精氨酸对一氧化氮合酶的生物利用度来调节一氧化氮的产生。这些研究将针对三个特定目的提出假设：1)检验CAT活性的变化通过改变L-精氨酸对一氧化氮合酶的生物利用度来调节NO产生的假说；2)检验Src家族酪氨酸激酶和丝裂原激活的蛋白激酶介导炎症诱导的CAT和/或NOS表达改变的假说；以及3)检验体内调控CAT表达的基因转移将影响肺中NO的产生，从而影响肺血管舒缩张力和肺损伤的假说。相关性：针对肺部疾病的NO介导效应的治疗主要集中在药物抑制NO的产生或吸入外源性NO上，然而这些危重患者中的大多数对这些治疗没有反应。摄取L-精氨酸是肺内NO生成的限速步骤。本提案将为设计合理的临床试验提供必要的翻译数据，以确定在ARDS和肺动脉高压等严重肺部疾病中，安全有效的药理和遗传操作对L-精氨酸摄取率的影响，从而不产生任何产品。

DESCRIPTION (provided by applicant): Nitric oxide (NO) is an important molecule involved in a myriad of physiological functions. In pulmonary hypertensive diseases, NO production is decreased resulting in vasoconstriction and vascular remodeling. While in pulmonary inflammatory diseases, NO production is increased resulting in tissue damage. NO is generated from L-arginine (L-arg) by the NO synthases (NOS). The cellular bioavailability of L-arg to NOS is determined in large part by uptake of extracellular L-arg via the cationic amino acid transporters (CAT). Preliminary studies suggest that manipulation of L-arg uptake modifies clinically important parameters in highly vulnerable patient populations. Thus, the studies described in the present application are focused on elucidation of the functional and mechanistic aspects of endothelial cell uptake of L-arg by CAT and its role in regulation of NO production in the lung. The long-term goals of these studies are to develop therapies that increase NO production by facilitating CAT-mediated L-arg uptake in pulmonary hypertensive diseases, and that decrease NO production by inhibiting CAT-mediated L-arg uptake in inflammatory lung diseases. The working hypothesis is that NO production can be modulated by control of L-arg bioavailability to NOS through alterations in CAT-mediated L-arg transport. The studies will address the hypothesis in three specific aims: 1) to test the hypothesis that alterations in CAT activities regulate NO production by altering the bioavailability of L-arg to NOS; 2) to test the hypothesis that Src-family tyrosine kinases and mitogen-activated protein kinases mediate inflammation-induced alterations in the expression of CAT and/or NOS; and 3) to test the hypothesis that gene transfer to regulate CAT expression in vivo will affect NO production in the lung, and thereby affect pulmonary vasomotor tone and lung injury. RELEVANCE: Therapies aimed at manipulating NO-mediated effects in lung diseases have centered on pharmacological inhibition of NO production or inhalation of exogenous NO, however a majority of these critically ill patients do not respond to these therapies. L-arg uptake represents a rate-limiting step in lung NO production. The present proposal will provide translational data necessary for the design of rational clinical trials to determine safe and effective pharmacological and genetic manipulations of L-arg uptake rates, and thereby NO production, in severe pulmonary diseases, such as ARDS and pulmonary hypertension.