title: The intracellular environment of human macrophages that produce nitric oxide promotes growth of mycobacteria.
abstract: Nitric oxide (NO) is a diffusible radical gas produced from the activity of nitric oxide synthase (NOS). NOS activity in murine macrophages has a protective role against mycobacteria through generation of reactive nitrogen intermediates (RNIs). However, the production of NO by human macrophages has remained unclear due to the lack of sensitive reagents to detect NO directly. The purpose of this study was to investigate NO production and the consequence to mycobacteria in primary human macrophages. We found that Mycobacterium bovis BCG or Mycobacterium tuberculosis infection of human macrophages induced expression of NOS2 and NOS3 that resulted in detectable production of NO. Treatment with gamma interferon (IFN-γ), l-arginine, and tetrahydrobiopterin enhanced expression of NOS2 and NOS3 isoforms, as well as NO production. Both of these enzymes were shown to contribute to NO production. The maximal level of NO produced by human macrophages was not bactericidal or bacteriostatic to M. tuberculosis or BCG. The number of viable mycobacteria was increased in macrophages that produced NO, and this requires expression of nitrate reductase. An narG mutant of M. tuberculosis persisted but was unable to grow in human macrophages. Taken together, these data (i) enhance our understanding of primary human macrophage potential to produce NO, (ii) demonstrate that the level of RNIs produced in response to IFN-γ in vitro is not sufficient to limit intracellular mycobacterial growth, and (iii) suggest that mycobacteria may use RNIs to enhance their survival in human macrophages.
authors.affiliation: Department of Pathology, University of South Carolina, School of Medicine, Columbia, South Carolina, USA.
authors.forename: Joo-Yong
authors.initials: JY
authors.lastname: Jung
authors.forename: Ranjna
authors.initials: R
authors.lastname: Madan-Lala
authors.forename: Maria
authors.initials: M
authors.lastname: Georgieva
authors.forename: Jyothi
authors.initials: J
authors.lastname: Rengarajan
authors.forename: Charles D
authors.initials: CD
authors.lastname: Sohaskey
authors.forename: Franz-Christoph
authors.initials: FC
authors.lastname: Bange
authors.forename: Cory M
authors.initials: CM
authors.lastname: Robinson
mesh_terms: D001120:Arginine / Q000494:pharmacology; D001708:Biopterins / Q000031:analogs & derivatives / Q000494:pharmacology; D002460:Cell Line; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D009163:Mycobacterium bovis / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D026361:Reactive Nitrogen Species / Q000378:metabolism
chemical_list: D026361:Reactive Nitrogen Species; D001708:Biopterins; D009569:Nitric Oxide; D007371:Interferon-gamma; D001120:Arginine; C496319:NOS2 protein, human; C496314:NOS3 protein, human; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C003402:sapropterin