Miller D R, Collier J M, Billings R E
Department of Environmental Health, Colorado State University, Fort Collins 80523, USA.
Am J Physiol. 1997 Feb;272(2 Pt 1):G207-14. doi: 10.1152/ajpgi.1997.272.2.G207.
Regulation of induced nitric oxide synthase (NOS) in isolated rat hepatocytes is poorly understood. The specific protein tyrosine kinase inhibitor genistein was used to determine if NOS induction is dependent on protein tyrosine kinase activation. Genistein inhibited tumor necrosis factor-alpha (TNF-alpha)-stimulated induction of NOS activity and NOS protein in a dose-dependent manner. Genistein also impaired TNF-alpha-induced NOS mRNA accumulation, suggesting protein tyrosine kinase regulation of NOS induction occurred at the level of transcription-translation. Like TNF-alpha, genistein inhibited induction of NOS protein by a second proinflammatory cytokine, interleukin-1beta, suggesting similar activation mechanisms by proinflammatory cytokines. NOS induction by other stimuli, including phorbol 12-myristate 13-acetate and the superoxide-generating system xanthine/xanthine oxidase, was also inhibited by genistein. Finally, cytokine-stimulated protein tyrosine kinase activity in hepatocytes was demonstrated by increased tyrosine phosphorylation of five high molecular mass protein bands. Genistein inhibited this cytokine-induced phosphotyrosine increase. The commonality of genistein inhibition suggests that protein tyrosine kinase activity is critical for NOS induction by a variety of stimuli.
对分离的大鼠肝细胞中诱导型一氧化氮合酶（NOS）的调节了解甚少。使用特异性蛋白酪氨酸激酶抑制剂染料木黄酮来确定一氧化氮合酶的诱导是否依赖于蛋白酪氨酸激酶的激活。染料木黄酮以剂量依赖的方式抑制肿瘤坏死因子-α（TNF-α）刺激的一氧化氮合酶活性和一氧化氮合酶蛋白的诱导。染料木黄酮还损害了TNF-α诱导的一氧化氮合酶mRNA积累，提示蛋白酪氨酸激酶对一氧化氮合酶诱导的调节发生在转录-翻译水平。与TNF-α一样，染料木黄酮抑制了第二种促炎细胞因子白细胞介素-1β对一氧化氮合酶蛋白的诱导，提示促炎细胞因子有相似的激活机制。染料木黄酮也抑制了其他刺激物诱导的一氧化氮合酶，这些刺激物包括佛波醇12-肉豆蔻酸酯13-乙酸酯和超氧化物生成系统黄嘌呤/黄嘌呤氧化酶。最后，通过五条高分子量蛋白条带酪氨酸磷酸化增加证明了肝细胞中细胞因子刺激的蛋白酪氨酸激酶活性。染料木黄酮抑制了这种细胞因子诱导的磷酸酪氨酸增加。染料木黄酮抑制作用的共性表明，蛋白酪氨酸激酶活性对于多种刺激诱导一氧化氮合酶至关重要。
