Susceptibility of three different strains of Mycobacterium avium complex (MAC), i.e., one strain of M. avium (Mino) and two strains of M. intracellulare (31F093T and KUMS 9007), to nitric oxide (NO) generated by rat alveolar macrophages (Mφ) or NO generated chemically by acidification of NO2- was examined in vitro. We also investigated the effects of NO on phagocytosis and superoxide anion (O2-) generation by Mφ. The intracellular growth of M. avium Mino was significantly suppressed by NO generated by gamma interferon (IFN-γ)-stimulated Mφ, whereas that of two strains of M. intracellulare (31F093T and KUMS 9007) was not. M. avium Mino was also more susceptible to NO generated chemically by acidification of NO2/- than the two M. intracellulare strains. In L-arginine (1 mM)- containing medium, NO release from the Mφ assessed by measuring NO2/- increased as the concentration of IFN-γ increased. The enhancing potential of IFN-γ for NO release became more pronounced when Mφ were infected with 31F093T, an NO-resistant strain. A large amount of NO generated by IFN-γ- stimulated Mφ suppressed both phagocytosis and O2- generation by the Mφ, especially after infection of the Mφ with strain 31F093T. These results indicate that the intracellular growth of MAC is not always inhibited by NO generated by immunologically activated Mφ; rather, NO generation induced by infection with an NO-resistant MAC strain suppresses phagocytosis of the Mφ, which may allow extracellular spreading of such NO-resistant mycobacteria. Therefore, the pathogenic potential of MAC may be partly attributed to its resistance to NO.
|Number of pages||10|
|Journal||Infection and immunity|
|Publication status||Published - 1993 Jan 1|
ASJC Scopus subject areas
- Infectious Diseases