Research on a novel mechanism for oxidative stress mediated by NO-induced nucleic acid nitration.

一氧化氮(NO)在微生物感染、炎症、心血管和神经退行性疾病以及癌症等多种疾病的发病机制和防御机制中发挥着重要作用。目前，我们研究了NO诱导的核酸修饰，重点是鸟嘌呤硝化(如8-硝基鸟嘌呤的形成)及其在宿主防御微生物病原体中的信号潜力(Akaike T.等人，100：685-690,2003)。用8-硝基鸟苷抗体免疫化学方法检测了8-硝基鸟苷及其相关化合物在体内和培养细胞中的形成。野生型和产仔鼠感染流感病毒和沙门氏菌等多种病原体。野生型小鼠感染灶内8-硝基鸟苷免疫反应较强，炎性细胞如渗出的巨噬细胞等胞浆中8-硝基鸟苷免疫染色较强，但未见诱导型一氧化氮合酶缺陷的…更多的NT小鼠。这种染色通常与iNOS免疫染色在组织和细胞中共同定位。野生型小鼠产生过量的NO，而iNOS缺陷小鼠在感染后被消除；这一结果与8-硝基鸟苷的形成也有很好的相关性。类似的8-硝基鸟苷的免疫染色也很明显，不同的细胞在培养中依赖于内源性和外源性NO的产生。有趣的是，8-硝基鸟苷表现出独特的氧化还原活性，影响NADPH依赖的还原酶，包括NADPH-细胞色素P450还原酶和所有NOS同功酶来产生超氧化物。更重要的是，8-硝基鸟苷刺激培养的细胞显著增加细胞保护酶血红素加氧酶-1的表达，从而使细胞对感染相关的细胞毒性和营养饥饿诱导的细胞凋亡和死亡具有抵抗力。本研究结果提示我们通过氧化和硝化应激引起的鸟嘌呤硝化(即硝化信号)来研究氧化还原信号的新范式，这可能在许多疾病过程中发生的细胞保护和宿主防御中起关键作用。较少

Nitric oxide(NO) plays important roles in the pathogenesis and defense mechanism involved in various diseases, including microbial infections, inflammation, cardiovascular and neurodegenerative diseases, and cancer.We currently explored NO-induced nucleic acid modifications with a focus on guanine nitration(e.g., 8-nitroguanine formation) and its signaling potential contributing to host defense against microbial pathogens(Akaike T.et al.Proc.Natl.Acad.Sci.USA,100:685-690,2003). Formation of 8-nitroguanine and its related compounds in vivo and in cultured cells was assessed immunochemically with an antibody for 8-nitroguanosine. Wild-type mice and littermate mice deficient in inducible NO synthase(iNOS) were infected with various pathogens including influenza virus and Salm onella.Strong 8-nitroguanosine immunostaining was observed primarily in the cytosol of epithelial cells and inflammatory cells such as exudate macrophages in the infectious foci of wild-type mice but not iNOS-deficie … More nt mice. This staining generally co-localized with iNOS immunostaining in the tissues and cells. NO was generated in excess in wild-type mice but was eliminated in iNOS-deficient mice after infections ; this result also correlated well with formation of 8-nitroguanosine. Similar immunostaining for 8-nitroguanosine was evident with various cells in culture depending on endogenous and exogenous NO production. It is intriguing that 8-nitroguanosine shows unique redox activity affecting NADPH-dependent reductases including NADPH-cytochrome P450 reductase and all isoforms of NOS to produce superoxide. More importantly, 8-nitroguanosine stimulated the cultured cells to significantly increase the expression of a cytoprotective enzyme heme oxygenase-1, so that the cells became resistant to apoptosis and cell death induced by infection-associated cytotoxicity and nutrient starvation.The present results prompt us a new paradigm for redox signaling via guanine nitration caused by oxidative and nitrative stress(i.e., nitrative signaling), which may thus contribute in a critical way to the cytoprotection and host defense occurring during many disease processes. Less