Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, IN 46202-5113, USA.
Am J Respir Cell Mol Biol. 2011 Apr;44(4):540-7. doi: 10.1165/rcmb.2009-0367OC. Epub 2010 Jun 17.
The effect of nitric oxide (NO) on Pneumocystis (Pc) organisms, the role of NO in the defense against infection with Pc, and the production of NO by alveolar macrophages (AMs) during Pneumocystis pneumonia (PCP) were investigated. The results indicate that NO was toxic to Pc organisms and inhibited their proliferation in culture. When the production of NO was inhibited by intraperitoneal injection of rats with the nitric oxide synthase inhibitor L-N(5)-(1-iminoethyl) ornithine, progression of Pc infection in immunocompetent rats was enhanced. Concentrations of NO in bronchoalveolar lavage fluids from immunosuppressed, Pc-infected rats and mice were greatly reduced, compared with those from uninfected animals, and AMs from these animals were defective in NO production. However, inducible nitric oxide synthase (iNOS) mRNA and protein concentrations were high in AMs from Pc-infected rats and mice. Immunoblot analysis showed that iNOS in AMs from Pc-infected rats existed primarily as a monomer, but the homo-dimerization of iNOS monomers was required for the production of NO. When iNOS dimerization cofactors, including calmodulin, were added to macrophage lysates, iNOS dimerization increased, whereas incubation of the same lysates with all cofactors except calmodulin did not rescue iNOS dimer formation. These data suggest that NO is important in the defense against Pc infection, but that the production of NO in AMs during PCP is defective because of the reduced dimerization of iNOS.
研究了一氧化氮（NO）对卡氏肺孢子虫（Pc）生物体的影响、NO 在防御卡氏肺孢子虫感染中的作用，以及肺泡巨噬细胞（AMs）在卡氏肺孢子虫肺炎（PCP）期间产生的 NO。结果表明，NO 对 Pc 生物体有毒，抑制其在培养物中的增殖。当通过腹腔注射大鼠一氧化氮合酶抑制剂 L-N（5）-（1-亚氨基乙基）鸟氨酸抑制 NO 的产生时，免疫功能正常的大鼠的 Pc 感染进展增强。与未感染动物相比，免疫抑制、Pc 感染的大鼠和小鼠的支气管肺泡灌洗液中的 NO 浓度大大降低，并且这些动物的 AMs 产生 NO 的能力受损。然而，Pc 感染的大鼠和小鼠的 AMs 中诱导型一氧化氮合酶（iNOS）mRNA 和蛋白浓度很高。免疫印迹分析表明，来自 Pc 感染大鼠的 AMs 中的 iNOS 主要以单体形式存在，但 iNOS 单体的同二聚化是产生 NO 的必需条件。当将 iNOS 二聚化辅助因子（包括钙调蛋白）添加到巨噬细胞裂解物中时，iNOS 二聚化增加，而用除钙调蛋白之外的所有辅助因子孵育相同的裂解物不能挽救 iNOS 二聚体形成。这些数据表明，NO 对 Pc 感染的防御很重要，但由于 iNOS 的二聚化减少，AMs 中 PCp 期间的 NO 产生存在缺陷。
