CYTOSTATIC ROLE OF THE ARGININE-NITRIC OXIDE PATHWAY

一氧化氮(NO)被认为干扰了细胞的增殖， 虽然其细胞抑制作用的机制在很大程度上是未知的。这 观点是基于观察到没有供体代理或诱导 培养细胞中没有合酶与伴随的 细胞增殖的减弱。我们发现N/G-羟基-L- 精氨酸(Noha)，精氨酸氧化成NO的中间体 瓜氨酸，是在培养的细胞中合成和释放的。诺哈是一位 有效的竞争性抑制物或精氨酸酶(Ki=10微米)并关闭 鸟氨酸尿素在细胞中的生产。鸟氨酸是鸟氨酸的前身 腐胺和其他细胞增殖所需的多胺。我们有 还发现NO抑制鸟氨酸脱羧酶的活性。这个 拟议研究的主要目标是确定是否没有 合成酶通过NOHA和NO的生物作用，发挥着生理性的作用。 或在调节血管平滑生长中的病理生理作用 肌肉细胞和肿瘤细胞，并阐明其机制 细胞生长受到抑制。推动这一点的核心假设是 推测是NO合成酶反应的两个产物，Noha和NO， 通过抑制两种生物效应来减缓细胞的增殖 连续的酶步骤(NoHA抑制精氨酸酶；NO抑制精氨酸酶 鸟氨酸脱羧酶)在导致产生 精氨酸中的多胺。这些额外的细胞抑制机制 由于一氧化氮合酶活性的增加而导致的 已知的NO细胞抑制机制，如鸟苷酸环化酶激活 环状GMP介导的DNA合成障碍。这两个具体的 将被用来严格检验所提出的假设的目标是： (A)确定NOHA、NO和NO合酶的机制 生理或生理状态下的活动干扰细胞的增殖 以及(B)通过以下方式阐明其机制： 一氧化氮抑制鸟氨酸脱羧酶。拟议的研究应 促进我们对一氧化氮合酶在体内的生物学作用的理解 调节细胞增殖。

Nitric oxide (NO) is believed to interfere with cell proliferation, although its mechanism of cytostatic action is largely unknown. This view is based on the observations that NO donor agents or induction of NO synthase in cultured cells is associated with the concomitant attenuation of cell proliferation. We have found that N/G-hydroxy-L- arginine (NOHA), an intermediate in the oxidation of arginine to NO + citrulline, is synthesized and released from cells in culture. NOHA is a potent competitive inhibitor or arginase (Ki = 10 muM) and turns off production of ornithine + urea in cells. Ornithine is the precursor to putrescine and other polyamines required for cell proliferation. We have also found that NO inhibits ornithine decarboxylase activity. The principal objective of the proposed research is to determine whether NO synthase, via the biologic actions of NOHA and NO, plays a physiological or pathophysiological role in regulating the growth of vascular smooth muscle cells and tumor cells, and to elucidate the mechanisms by which cell growth is inhibited. The central hypothesis that drives this proposal is that two products of the NO synthase reaction, NOHA and NO, function biologically to slow cell proliferation by inhibiting two sequential enzymatic steps (NOHA inhibits arginase; NO inhibits ornithine decarboxylase) in the pathway leading to the production of polyamines from arginine. These additional cytostatic mechanisms resulting from increased NO synthase activity would complement other known cytostatic mechanisms of NO such as guanylyl cyclase activation and cyclic GMP-mediated impairment of DNA synthesis. The two specific aims that will be taken to rigorously test the proposed hypothesis are: (a) to ascertain the mechanisms by which NOHA, NO and NO synthase activity interfere with cell proliferation under physiological or pathophysiological conditions and (b) to elucidate the mechanism by which NO inhibits ornithine decarboxylase. The proposed research should advance our understanding of the biological role of NO synthase in regulating cell proliferation.