title: Blastomyces dermatitidis yeast cells inhibit nitric oxide production by alveolar macrophage inducible nitric oxide synthase.
abstract: The ability of pathogens to evade host antimicrobial mechanisms is crucial to their virulence. The dimorphic fungal pathogen Blastomyces dermatitidis can infect immunocompetent patients, producing a primary pulmonary infection that can later disseminate to other organs. B. dermatitidis possesses a remarkable ability to resist killing by alveolar macrophages. To date, no mechanism to explain this resistance has been described. Here, we focus on macrophage production of the toxic molecule nitric oxide as a potential target of subversion by B. dermatitidis yeast cells. We report that B. dermatitidis yeast cells reduce nitric oxide levels in the supernatants of activated alveolar macrophages. This reduction is not due to detoxification of nitric oxide, but rather to suppression of macrophage nitric oxide production. We show that B. dermatitidis yeast cells do not block upregulation of macrophage inducible nitric oxide synthase (iNOS) expression or limit iNOS access to its arginine substrate. Instead, B. dermatitidis yeast cells appear to inhibit iNOS enzymatic activity. Further investigation into the genetic basis of this potential virulence mechanism could lead to the identification of novel antifungal drug targets.
authors: Microbiology Doctoral Training Program, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53792, USA.
authors: Nicole M
authors: NM
authors: Rocco
authors: John C
authors: JC
authors: Carmen
authors: Bruce S
authors: BS
authors: Klein
mesh_terms: D000818:Animals; D001758:Blastomyces / Q000378:metabolism*; D001759:Blastomycosis / Q000378:metabolism*; D015153:Blotting, Western; D002460:Cell Line; D054884:Host-Pathogen Interactions; D016676:Macrophages, Alveolar / Q000201:enzymology* / Q000378:metabolism / Q000382:microbiology; D051379:Mice; D009569:Nitric Oxide / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse