Nitric oxide expression in airway epithelial cells in response to tubercle bacilli stimulation

Abstract

In order to investigate the role of airway epithelial cells in pulmonary tuberculosis, inducible nitric oxide synthetase (iNOS) expression and nitric oxide (NO) production were studied in A549 cells. Peripheral blood mononuclear cells (PBMC) from normal volunteers were separated and cultured for 24 h with LPS or tubercle bacilli (H37Rv, H37Ra). Thereafter, A549 cells were stimulated for another 24 h with culture supernatant fluids of PBMC. iNOS messenger RNA (mRNA) expression was measured with Northern blot analysis and NO production was measured with the Griess reaction, which can measure nitrite concentration. iNOS mRNA expression and NO production were minimal in the control cells. iNOS mRNA expression and NO production were significantly increased with LPS (P < 0.05) or tubercle bacilli (P < 0.01) stimulation. However, there was no difference in iNOS mRNA expression and NO production between H37Rv and H37Ra stimulations. Interestingly, iNOS mRNA expression and NO production were greater in A549 cells stimulated with tubercle bacilli-conditioned media than in the cells stimulated with LPS-conditioned media. IL-1beta, tumour necrosis factor-alpha and interferon gamma concentrations were increased in culture supernatant fluids of PBMC stimulated with tubercle bacilli. These findings suggest that airway epithelial cells may play a certain role in the pathogenesis of pulmonary tuberculosis by producing NO. However, the role of airway epithelial cells, regarding the virulence of tubercle bacilli, was not clear in this study.

The source and role of RANTES in interstitial lung disease

“…This hypothesis is supported by reports of the localization of RANTES mRNA to macrophages within the granulomas related to sarcoidosis or tuberculosis [25]. In this context, it is interesting that Mycobacterium tuberculosis, which is considered to be a possible antigenic trigger in sarcoidosis, can induce RANTES production [29]. By contrast with sarcoidosis, patients with FA did not show a significant difference from controls with regard to the total number of cells expressing RANTES protein or the levels of RANTES mRNA in BAL cell pellets.…”

Nitric Oxide InhibitsCoxiella burnetiiReplication and Parasitophorous Vacuole Maturation

“…When produced at high levels for an extended period, nitric oxide and/or resulting reactive nitrogen intermediates are cytotoxic and can inhibit the replication of a variety of intracellular parasites in animal models of infection, including the aerosol-borne bacterial pathogens Mycobacterium tuberculosis (7) and Legionella pneumophila (31). Accumulating evidence also suggests that nitric oxide controls human infection by intracellular parasites, with the most compelling evidence coming from studies of infection by mycobacteria (24,30). Inducible NOS (iNOS), encoded by nos2, is the NOS isoform responsible for producing sustained bactericidal-bacteriostatic levels of nitric oxide in macrophages and other cell types (21).…”

Relative Efficacy of Uptake and Presentation of Mycobacterium bovis BCG Antigens by Type I Mouse Lung Epithelial Cells and Peritoneal Macrophages

“…in response to pathogens (20,21,26), and such nonspecific toxic mediators may be responsible for the reduced recovery of BCG-treated macrophages. Lung epithelial cells, unlike macrophages, produce no or low levels of nitric oxide in response to mycobacterial antigens (13,32). In our own experiments, BCG-treated PMs secreted 10-fold-larger amounts of TNF-␣ than those secreted by the similarly treated PLE cells (results not shown).…”