Comparison of mycobacteria-induced cytotoxicity and inflammatory responsesin human and mouse cell lines

Environmental mycobacteria, which are ubiquitous in nature, are also detect ed in moisture-damaged buildings. Their potential role inducing the adverse health effects associated with living in moisture damaged buildings requir es clarification. To establish a model for these studies, we evaluated infl ammatory responsiveness in different cell lines exposed to environmental my cobacterial species. Four mycobacterial isolates belonging to Mycobacterium avium complex and Mycobacterium terrae, recovered from the indoor air samp led when a moldy building was being demolished, were studied for their cyto toxicity and ability to stimulate the production of inflammatory mediators in mouse RAW264.7 and human 28SC macrophage cell lines, and human A549 lung epithelial cell line. Lipopolysaccharide (LPS) was used as a positive cont rol. Production of cytokines (tumor necrosis factor alpha, TNF-alpha; inter leukin 6, IL-6; and interleukin beta, IL-1 beta) was analyzed immunochemica lly, nitric oxide (NO) by the Griess method, expression of inducible NO syn thase with Western blot analysis, and cytotoxicity with the MTT test. Both human and mouse cells produced NO and IL-6 after mycobacterial exposure. Mo use macrophages also showed production of TNF-alpha induced by both mycobac teria and LPS, whereas the human cell lines failed to produce TNF-alpha aft er mycobacterial exposure and the human epithelial cell line also failed to respond to LPS. Similarly, only mouse macrophages produced IL-1 beta. Myco bacterial exposure was not cytotoxic to human cells and was only slightly c ytotoxic to mouse macrophages. The results indicate that environmental myco bacterial isolates from moldy buildings are capable of activating inflammat ory mechanisms in both human and murine cells. The human and mouse cell lin es, however, differ significantly in the grade and type of the responses.