title: Effect of melanin and carotenoids of Exophiala (Wangiella) dermatitidis on phagocytosis, oxidative burst, and killing by human neutrophils.
abstract: The black yeast Exophiala (Wangiella) dermatitidis is an increasingly recognized pathogen and a leading cause of severe pheohyphomycosis. Melanin is thought to contribute to the virulence of E. dermatitidis. Whereas the synthesis and the redox properties of melanin have been studied intensively, the influence of melanin and carotenoids on the phagocytosis, the oxidative burst, and the killing of E. dermatitidis by human neutrophils has not been studied. To study their effects on these phenomena, we applied a combination of flow cytometry and a colony-count-dependent method. Using E. dermatitidis wild-type strain 8565 and several melanin-deficient mutants that have been described previously, we demonstrate that melanin prevents this pathogen from being killed in the phagolysosome of the neutrophils. Melanin did not influence the phagocytosis or the oxidative burst of the neutrophils involved. The carotenoids torulene and torularhodine were not found to contribute to the prevention of killing. The ability of E. dermatitidis to block the effects of the neutrophil oxidative burst may critically impair the potential of the host to sufficiently eliminate this fungal pathogen and thus may play an important role in the pathogenesis of phaeohyphomycosis.
authors.affiliation: Institute of Medical Immunology, University Hospital RWTH Aachen, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Schnitzler
authors.forename: H
authors.initials: H
authors.lastname: Peltroche-Llacsahuanga
authors.forename: N
authors.initials: N
authors.lastname: Bestier
authors.forename: J
authors.initials: J
authors.lastname: Zündorf
authors.forename: R
authors.initials: R
authors.lastname: Lütticken
authors.forename: G
authors.initials: G
authors.lastname: Haase
mesh_terms: D000328:Adult; D001770:Blood Bactericidal Activity / Q000276:immunology*; D002338:Carotenoids / Q000502:physiology*; D005093:Exophiala / Q000235:genetics / Q000254:growth & development / Q000276:immunology*; D005452:Fluoresceins; D005456:Fluorescent Dyes; D017353:Gene Deletion; D006801:Humans; D008543:Melanins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D009504:Neutrophils / Q000276:immunology / Q000378:metabolism / Q000382:microbiology*; D010587:Phagocytosis / Q000235:genetics / Q000276:immunology*; D017382:Reactive Oxygen Species / Q000276:immunology; D016897:Respiratory Burst / Q000276:immunology*; D013194:Staining and Labeling
chemical_list: D005452:Fluoresceins; D005456:Fluorescent Dyes; D008543:Melanins; D017382:Reactive Oxygen Species; D002338:Carotenoids; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein