title: Cryptococcus neoformans inhibits nitric oxide synthesis caused by CpG-oligodeoxynucleotide-stimulated macrophages in a fashion independent of capsular polysaccharides.
abstract: Cryptococcus neoformans is eradicated by macrophages via production of NO. Unmethylated CpG-ODN protect mice from infection with this fungal pathogen by inducing IFN-gamma. The present study was designed to elucidate the effect of C. neoformans on the synthesis of NO by alveolar macrophages. For this purpose, MH-S, an alveolar macrophage cell line, was stimulated with CpG-ODN in the presence of IFN-gamma. A highly virulent strain of C. neoformans with thick capsule suppressed the production of NO. Capsular polysaccharides were not essential for this suppression, because there was no difference between acapsular mutant (Cap67) and its parent strain. Physical or close interaction of Cap67 with MH-S was necessary, as shown by the loss of such effect when direct contact was interfered by nitrocellulose membrane. Similar effects were observed by disrupted as well as intact Cap67. Whereas the inhibitory effect of intact Cap67 was completely abrogated by heat treatment, disrupted Cap67 did not receive such influence. Finally, disrupted Cap67 did not show any inhibitory effect on the TLR9-mediated activation of NF-kappaB in a luciferase reporter assay with HEK293T cells, although the TLR4-mediated activation was suppressed. These results revealed that C. neoformans suppressed the synthesis of NO by CpG-ODN and IFN-gamma-stimulated macrophages in a fashion independent of capsular polysaccharides, although the precise mechanism remains to be elucidated.
authors.affiliation: Microbiology and Immunology, Department of Medical Technology, School of Health Sciences, Faculty of Medicine, Tohoku University, Sendai, Japan.
authors.forename: Gang
authors.initials: G
authors.lastname: Xiao
authors.forename: Akiko
authors.initials: A
authors.lastname: Miyazato
authors.forename: Ken
authors.initials: K
authors.lastname: Inden
authors.forename: Kiwamu
authors.initials: K
authors.lastname: Nakamura
authors.forename: Kohei
authors.initials: K
authors.lastname: Shiratori
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Nakagawa
authors.forename: Teruo
authors.initials: T
authors.lastname: Miyazawa
authors.forename: Kazuo
authors.initials: K
authors.lastname: Suzuki
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Kaku
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Kawakami
mesh_terms: D000818:Animals; D002460:Cell Line; D003455:Cryptococcus neoformans / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007371:Interferon-gamma / Q000276:immunology; D016676:Macrophages, Alveolar / Q000276:immunology*; D051379:Mice; D009569:Nitric Oxide / Q000037:antagonists & inhibitors*; D009838:Oligodeoxyribonucleotides / Q000276:immunology*; D011134:Polysaccharides / Q000235:genetics / Q000276:immunology*
chemical_list: C408982:CPG-oligonucleotide; D009838:Oligodeoxyribonucleotides; D011134:Polysaccharides; D009569:Nitric Oxide; D007371:Interferon-gamma