Melanin in <it>Fonsecaea pedrosoi</it>: a trap for oxidative radicals

• Main Authors: de Souza Wanderley, Borba Luana P, Vugman Ney V, Herbst Marcelo H, Seabra Sergio H, Franzen Anderson J, Cunha Marcel ML, Rozental Sonia
• Format: Article
• Language: English
• Published: BMC 2010-03-01
• Series: BMC Microbiology
• Online Access: http://www.biomedcentral.com/1471-2180/10/80

<p>Abstract</p> <p>Background</p> <p>The pathogenic fungus <it>Fonsecaea pedrosoi </it>constitutively produces the pigment melanin, an important virulence factor in fungi. Melanin is incorporated in the cell wall structure and provides chemical and physical protection for the fungus.</p> <p>We evaluated the production of nitric oxide (NO) in macrophages, the oxidative burst and the inducible nitric oxide synthase (i-NOS) activity in interactions between activated murine macrophages and <it>F. pedrosoi</it>. Experiments were carried out with or without tricyclazole (TC) treatment, a selective inhibitor of the dihydroxynaphthalene (DHN)-melanin biosynthesis pathway in <it>F. pedrosoi</it>. The paramagnetisms of melanin and the TC-melanin were analysed by electron spin resonance. The fungal growth responses to H₂O₂and to S-nitroso-N-acetylpenicillamine (SNAP), a nitric oxide donor, were also evaluated.</p> <p>Results</p> <p>Melanised <it>F. pedrosoi </it>cells were more resistant to both H₂O₂and NO. Nitrite was not detected in the supernatant of macrophages incubated with melanised fungal cells. However, i-NOS expression was unaffected by the presence of either untreated control <it>F. pedrosoi </it>or TC-treated <it>F. pedrosoi</it>. In addition, the inhibition of the DHN-melanin pathway by TC improved the oxidative burst capability of the macrophages.</p> <p>Conclusion</p> <p>The NO-trapping ability of <it>F. pedrosoi </it>melanin is an important mechanism to escape the oxidative burst of macrophages.</p>