Studies fro the role of nitric oxide in bronchial asthma

我们研究了一氧化氮(NO)在麻醉和机械通气猫气道反应性调节中的作用。为了评估气道反应性，我们测量了NW-硝基-L-精氨酸甲酯(L-NAME)或神经节细胞阻滞剂六甲溴铵(据报道阻断I-NANC)前后向呼吸道输送5-羟色胺气雾剂所产生的总肺阻力(RL)的变化。之所以选择5-羟色胺，是因为它会引起支气管收缩，部分原因是神经反射。为了进一步阐明其作用机制(S)，我们还观察了吸入辣椒素对阿托品和心得安治疗后5-羟色胺引起的持续性支气管收缩动物的影响。L-NAME抑制一氧化氮合酶或六甲基溴铵阻断i-NANC神经元可显著增加气道反应性。然而，添加L-NAME并没有进一步增加用六甲溴铵治疗的动物的呼吸道反应性。在阿托品和心得安…存在的情况下在5-羟色胺诱导的持续支气管收缩过程中，吸入更多的辣椒素可引起明显的支气管扩张。辣椒素引起的支气管扩张可被六甲溴铵或L所显著抑制。这些结果表明，I-NANC神经元释放的NO在调节猫活体气道反应性中起重要作用。另一方面，哮喘患者呼出的空气中NO含量增加。我们推测内源性NO参与了气道炎症和高反应性，白介素8(IL-8)可能参与了这一机制。在体外转化的人支气管上皮细胞中，NO供体可剂量依赖性地增加IL-8的产生。此外，肿瘤坏死因子-a+IL-1b+干扰素-g可增加上皮细胞培养上清液中IL-8的含量，而一氧化氮合酶抑制剂氨基胍+N-硝基-L-精氨酸甲酯(L-NAME)可减弱细胞因子诱导的上皮细胞产生IL-8。在活体豚鼠中，臭氧暴露可引起气道对乙酰胆碱的高反应性和支气管肺泡灌洗液中中性粒细胞的增加，并持续至少5h，NO合酶抑制剂对臭氧后即刻的气道高反应性和中性粒细胞聚集无影响，但显著抑制臭氧后5h的变化。NO合酶抑制剂还可抑制臭氧作用5h后支气管肺泡灌洗液中亚硝酸盐/硝酸盐水平的升高以及豚鼠呼吸道上皮细胞和中性粒细胞中IL-8mRNA的表达。这些结果表明，内源性NO可能在臭氧暴露后持续的气道炎症和高反应性中发挥重要作用，可能部分是通过上调IL-8来实现的。较少

We studied the role of nitric oxide (NO) in the regulation of airway responsiveness in anesthetized and mechanically ventilated cats. To assess airway responsiveness, we measured the changes in total pulmonary resistance (RL) produced by delivering serotonin aerosol to the airways before and after Nw-nitro-L-arginine methyl ester (L-NAME), or ganglionic blocker, hexamethonium which was reported to block I-NANC. Serotonin was chosen because it causes bronchoconstriction in part by neural reflex. To further clarify the mechanism (s) involved, we also determined the effect of inhaled capsaicn in the animals with sustained bronchoconstriction induced by serotonin after treatment with atropine and propranolol. Inhibition of NO synthase by L-NAME or blockade of I-NANC neurons by hexamethonium significantly increased airway responsiveness. However, addition of L-NAME did not further increase airway responsiveness in animals treated with hexamethonium. In the presence of atropine and propranol … More ol, inhaled capsaicin caused a marked bronchodilation during serotonin-induced sustained bronchoconstriction. The bronchodilation induced by capsaicin was significantly suppressed by hexamethonium or by L-NAME. These results suggest that the NO released from I-NANC neurons is important in modulating the airway responsiveness of cats in vivo.On the other hand, NO is increased in exhaled air of asthmatics. We hypothesized that endogenous NO contributes to airway inflammation and hyperresponsiveness, and that interleukin-8 (IL-8) might be involved in this mechanism. In human transformed bronchial epithelial cells in vitro, NO donors increased IL-8 production dose-dependently. In addition, tumor necrosis factor-a plus IL-1b plus interferon-g increased IL-8 in culture supernatant of epithelial cells ; the combination of NO synthase inhibitors, aminoguanidine plus NG-nitro-L-argiine methyl ester (L-NAME), attenuated the cytokines-induced IL-8 production in epithelial cells. In guinea pigs in vivo, ozone exposure induced airway hyperresponsiveness to acetylcholine and increased neutrophils in bronchoalveolar lavage fluid, and these changes were persisted for at least 5 h. Pretreatment with NO synthase inhibitors had no effect on airway hyperresponsiveness or neutrophil accumulation immediately after ozone, but significantly inhibited the changes 5 h after ozone. NO synthase inhibitors also attenuated the increases of nitrite/nitrate levels in bronchoalveolar lavage fluid and the IL-8 mRNA expression in epithelial cells and in neutrophils in guinea pig airways 5 h after ozone. These results suggest that endogenous NO may play an important role in the persistent airway inflammation and hyperresponsiveness after ozone exposure, presumably partly through the upregulation of IL-8. Less