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Infect. Immun., Sep 1997, 3644-3647, Vol 65, No. 9
Y Nozaki, Y Hasegawa, S Ichiyama, I Nakashima and K Shimokata
We demonstrated that products of the L-arginine-dependent pathway of human
alveolar macrophages (AM) effectively kill the Mycobacterium bovis bacillus
Calmette-Guerin (BCG) in vitro. The formation of products was triggered by
inoculation with BCG itself. Many reports have shown that activated rodent
AM could produce an amount of nitric oxide (NO) sufficient to suppress the
growth of mycobacteria. However, there have been no definitive results as
to whether human AM might have the NO-dependent mechanism for the killing
of mycobacteria. Therefore, we have undertaken some experiments to answer
this question. Immunofluorescence assays showed an increased production of
inducible nitric oxide synthase (iNOS) and peroxynitrite in BCG-inoculated
AM from patients with pulmonary fibrosis. Reverse transcriptase-PCR also
revealed the higher expression of iNOS-coding mRNA. Colony assays
demonstrated that these human AM effectively killed BCG in their cytoplasm.
However, treatment of AM with N(G)-monomethyl-L-arginine monoacetate
resulted in markedly reduced killing activity. These results clearly show
that BCG-induced NO and its reactive product with the oxygen radical
peroxynitrite could play an important role in the killing of BCG in human
AM.
Copyright © 1997, American Society for Microbiology
Mechanism of nitric oxide-dependent killing of Mycobacterium bovis BCG in human alveolar macrophages
First Department of Internal Medicine, Nagoya University School of Medicine, Japan.
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