REGULATION OF EXPRESSION OF NO SYNTHASE

一氧化氮 (NO) 是介导哺乳动物生理和病理生理过程的关键分子，其中许多过程涉及血管系统。 NO的许多生理作用都是由环鸟苷酸介导的，并且NO和环鸟苷酸的作用持续时间都相对较短。 NO 不稳定，不能通过常规机制储存、释放或失活。 NO 与活性氧以及含铁和硫的分子的反应性导致 NO 快速失活。由于特定磷酸二酯酶的水解，环状 GMP 也不稳定。 因此，NO 会被自然发生的化学过程快速失活，而环 GMP 会被细胞中的磷酸二酯酶快速失活，每个半衰期不到 1 秒。 因此，NO 的作用高度依赖于 NO 合酶 (NOS) 从 L-精氨酸生物合成。 因此，NO生物合成的调节或调节是决定NO药效学的最重要过程。 本研究的主要目的是阐明控制 NO 生物合成的几种潜在新机制。 这些靶向机制涉及 NOS mRNA 表达、NOS 蛋白表达和稳定性、精氨酸酶表达和催化活性、精氨酸底物可用性以及 NOS 产生的活性氧的变化。 待检验的中心假设是细胞 NO 的产生受到影响 NOS 亚型转录、翻译和翻译后表达的各种内源性因素的严格调控。为实现这一目标，提出了三个具体目标：（1）阐明NO下调诱导型NOS（iNOS）和内皮型NOS（eNOS）表达的分子机制； (2)阐明精氨酸酶上调iNOS和eNOS表达的机制； (3)阐明精氨酸酶在调节iNOS和eNOS产生超氧阴离子和过氧化氢中的作用。 拟议的研究代表了阐明影响一氧化氮在健康和疾病中的血管和相关作用的生物因素的持续长期努力。

Nitric oxide (NO) is a key molecule mediating physiological and pathophysiological processes in mammals, many of which involve the vascular system. Many physiological actions of NO are mediated by cyclic GMP, and both NO and cyclic GMP have relatively short durations of action. NO is labile and is not stored, released, or inactivated by conventional mechanisms. Reactivity of NO with reactive oxygen species and with iron and sulfur containing molecules causes rapid inactivation of NO. Cyclic GMP is also unstable due to hydrolysis by specific phosphodiesterases. Thus, NO is rapidly inactivated by naturally-occurring chemical processes and cyclic GMP is rapidly inactivated by phosphodiesterases in cells, yielding half lives for each of less than 1-second. Therefore, the actions of NO are highly dependent on its biosynthesis from L-arginine by NO synthase (NOS). Accordingly, the regulation or modulation of NO biosynthesis is the most important process dictating the pharmacodynamics of NO. The principal objective of the proposed studies is to elucidate several potentially novel mechanisms by which NO biosynthesis may be controlled. These targeted mechanisms involve changes in NOS mRNA expression, NOS protein expression and stability, arginase expression and catalytic activity, arginine substrate availability, and the production of reactive oxygen species by NOS. The central hypothesis to be tested is that cellular NO production is tightly regulated by various endogenous factors affecting transcriptional, translational and posttranslational expression of NOS isoforms. Three Specific Aims are proposed to achieve this objective: (1) to elucidate the molecular mechanisms by which NO downregulates the expression of inducible NOS (iNOS) and endothelial NOS (eNOS); (2) to elucidate the mechanisms by which arginase upregulates the expression of iNOS and eNOS; and (3) to elucidate the role of arginase in modulating the production of superoxide anion and hydrogen peroxide by iNOS and eNOS. The proposed research represents a continuing long-term effort to elucidate the biological factors influencing the vascular and related actions of NO in health and disease.