3-nitrotyrosine and Tuberculosis--Pulmonary

Topics: Animals; Humans; Immunohistochemistry; In Vitro Techniques; Lung; Macrophages, Alveolar; Mice; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Tuberculosis, Pulmonary; Tyrosine

The role of nitric oxide (NO) in the host-defense against human tuberculosis (TB) is controversial. Although experimental evidence indicates that NO may play an important role in controlling TB, its expression in human tuberculous lungs has not been systematically characterized. We therefore investigated the expression of NO synthases (NOS) and of nitrotyrosine, the latter a marker of NO expression, in surgically resected lungs of eight patients with TB. Immunohistochemical and morphometric analyses revealed that, compared with control subjects, inducible NOS, endothelial NOS, and nitrotyrosine, but not neuronal NOS, were significantly elevated in the inflammatory zone of the tuberculous granulomas, and in the nongranulomatous pneumonitis zone. Tumor necrosis factor-alpha (TNF-alpha) was also significantly increased in tuberculous lungs and was principally localized to the necrotic, and to a lesser extent, the inflammatory and fibrotic areas of the granulomas. The NOS isoforms, nitrotyrosine, and TNF-alpha were expressed by the epithelioid macrophages and giant cells within the granulomas and in alveolar macrophages and epithelial cells in pneumonitis areas. This descriptive study provides evidence that in human TB, NOS isoenzymes and NO are present in specialized areas of the tuberculous granulomas; their precise role in human TB remains to be determined.

Topics: Epithelium; Humans; Immunohistochemistry; Lung; Lymphocytes; Macrophages; Macrophages, Alveolar; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Tuberculosis, Pulmonary; Tumor Necrosis Factor-alpha; Tyrosine

Nitric oxide (NO) is a relevant antimycobacterial factor in mouse macrophages. NO is a product of inducible nitric oxide synthase (iNOS). NO toxicity is greatly enhanced by reacting with superoxide to form peroxynitrite that reacts with many biological molecules. Tyrosine is one of the molecules with which NO reacts and the product is nitrotyrosine (NT). The production of peroxynitrite and the nitrosylation of proteins might play a role in bacterial killing and also in mediating host injury. In this study, we used a well-characterized mouse model of pulmonary tuberculosis to examine the local kinetics of expression and cellular distribution of iNOS and NT at the cellular and subcellular level. The histopathological study showed two phases of the disease: early and late. The early phase was characterized by mononuclear inflammation and granuloma formation. During this phase, high percentages of activated macrophages were observed that were immunostained for iNOS and NT. Immuno-electronmicroscopy showed NT immunoreactivity in lysosomes and mycobacterial wall and cytoplasm. The concentration of iNOS mRNA and NO metabolites were also elevated. The late phase was characterized by progressive pneumonia with focal necrosis and a decrease of iNOS mRNA and NO metabolites. The strongest NT immunostained areas were the necrotic tissue. Macrophages became foamy cells with scarce iNOS immunostaining but strong NT immunoreactivity. At the ultrastructural level, these cells showed NT immunolabeling in cytoskeleton, mitochondria, lysosomes and cell membrane. NT was also located in bronchial epithelial cell mitochondria, in cell membranes and cytoplasm of endothelial cells and in actin bundles within smooth muscle cells. These results suggest an important role of NO in mycobacterial killing, particularly during the early phase of the infection. They also suggest an important participation by NO in tissue damage during the late phase of the disease.

Topics: Animals; Cell Count; Disease Models, Animal; Immunoenzyme Techniques; Lung; Macrophages, Alveolar; Male; Mice; Mice, Inbred BALB C; Microscopy, Immunoelectron; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Tuberculosis, Pulmonary; Tyrosine