硝酸甘油（NTG）经生物转化后释放一氧化氮（NO），扩张血管。NO能对蛋白质半胱氨酸上的巯基进行亚硝基化修饰而影响蛋白质的功能。前列环素（PGI2）是花生四烯酸的一种代谢产物，具有显著的扩血管作用，由前列环素合酶（PGIS）催化合成。研究发现NTG能抑制PGIS的活性，减少PGI2的生物合成，其机制有待阐明。预实验发现NTG能增加PGIS的亚硝基化，NO抑制剂能恢复PGIS的活性和PGI2的合成。据此，我们推测“NTG可能通过NO对PGIS进行亚硝基化修饰而抑制PGI2的合成，从而引起NTG耐受”。本课题拟运用药理学、生理学、分子生物学等实验方法，体外与体内研究相结合，确定NO对PGIS的亚硝基化修饰作用并鉴定相关分子靶点，明确PGIS亚硝基化在NTG耐受中的作用，初步探讨阿司匹林等药物能否改善NTG耐受。该课题将从新的角度阐明NTG耐受的机制，为临床防治NTG耐受提供新思路。

Nitroglycerin (NTG) is still widely used in the management of coronary artery disease, including patients with stable and unstable angina, acute myocardial infarction, and congestive heart failure. It is assumed that NTG induces vasorelaxation by releasing the vasoactive principle nitric oxide (NO) via an enzymatic biotransformation step. Long-term administration of NTG is frequently associated with a progressive reduction of hemodynamic and antiaggregatory effects, which is called NTG tolerance. The molecular mechanism needs to be further defined. Prostacyclin (PGI2) is an end product derived from the sequential metabolism of arachidonic acid via cyclooxygenase and PGI2 synthase (PGIS). As such, PGI2 has been understood to play a role in cardiovascular health specifically inhibiting platelet aggregation and having powerful vasodilatory effects via relaxation of smooth muscle. S-nitrosylation, as a post-translational modification of protein, the addition of an NO group to a cysteine thiol to form an S-nitrosylated protein, regulates a broad spectrum of proteins in all functional protein classes and cell types examined. However, dysregulation of S-nitrosylation produces potential clinical coimplications. Our exciting preliminary data indicated that treatment of endothelial cells with NTG increased PGIS S-nitrosylation and reduced PGI2 biosynthesis, which were reversed by PTIO, an NO scavenger. Thus, we propose that NO mediated PGIS S-nitrosylation is a critical step contributing to NTG tolerance. To test this hypothesis, we setup the following specific aims to support this hypothesis: Aim 1 is to identify the PGIS S-nitrosylation by NO in tube and in vitro. Aim 2 is to determine the role of PGIS S-nitrosylation in NTG tolerance in vitro and in vivo. Aim 3 is to investigate the effects of COX inhibition by aspirin, supplement of PGI2 by Beraprost, and antagonists of TPr by SQ29548 on NTG tolerance. This multidisciplinary, integrative, and translational approach to investigate the central hypothesis that PGIS S-nitrosylation is critical in NTG tolerance is technically and conceptually innovative. The proposed studies will provide new insights into how NTG tolerance happens via NO-mediated PGIS S-nitrosylation and a subsequent reduction of PGI2 and prove that specific modulation of arachidonic acid metabolizes might be a novel approach to prevent NTG tolerance.