title: The role of oxidative and nitrosative bursts caused by azoles and amphotericin B against the fungal pathogen Cryptococcus gattii.
abstract: OBJECTIVE
  Although the most accepted mechanisms of action of amphotericin B and azoles are related to ergosterol, it is possible that these drugs have other effects on the fungal cell. In the present study, the role of endogenous reactive oxygen species (ROS) and peroxynitrite produced by azoles and amphotericin B in the fungus Cryptococcus gattii were examined.
  
  
  METHODS
  We studied distinct parameters to evaluate the effect of oxidative and nitrosative stresses induced by these drugs in C. gattii cells: lipid peroxidation, ergosterol content, ROS and peroxynitrite production, enzymatic activity of the antioxidant system and the in vitro interaction of antifungal drugs with a peroxidase inhibitor, a superoxide dismutase inhibitor and a peroxynitrite scavenger.
  
  
  RESULTS
  The data demonstrated that itraconazole led to ROS formation and lipid peroxidation in C. gattii cells in the early stages of the treatment; this did not occur with fluconazole. This phenomenon strongly increased the activities of enzymes of the antioxidant system. These results were confirmed by synergism observed between the catalase inhibitor and itraconazole. Amphotericin B caused lipid peroxidation in C. gattii cells through a greatly enhanced production of oxidative and nitrosative radicals with increased peroxidase activity. These data were confirmed by the synergism between the catalase/superoxide dismutase inhibitors and amphotericin B. In addition, the effect of this antifungal was antagonized by the peroxynitrite scavenger.
  
  
  CONCLUSIONS
  Oxidative and nitrosative bursts play an important role in the antifungal activity of itraconazole and amphotericin B against C. gattii.
authors.affiliation: Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, MG, Brazil.
authors.forename: Gabriella Freitas
authors.initials: GF
authors.lastname: Ferreira
authors.forename: Ludmila de Matos
authors.initials: Lde M
authors.lastname: Baltazar
authors.forename: Julliana Ribeiro Alves
authors.initials: JR
authors.lastname: Santos
authors.forename: Andrea Souza
authors.initials: AS
authors.lastname: Monteiro
authors.forename: Lucia Alves de Oliveira
authors.initials: LA
authors.lastname: Fraga
authors.forename: Maria Aparecida
authors.initials: MA
authors.lastname: Resende-Stoianoff
authors.forename: Daniel Assis
authors.initials: DA
authors.lastname: Santos
mesh_terms: D000666:Amphotericin B / Q000494:pharmacology*; D000935:Antifungal Agents / Q000494:pharmacology*; D056285:Cryptococcus gattii / Q000187:drug effects* / Q000378:metabolism; D017964:Itraconazole / Q000494:pharmacology*; D015538:Nitrosation; D030421:Peroxynitrous Acid / Q000378:metabolism / Q000633:toxicity; D017382:Reactive Oxygen Species / Q000378:metabolism / Q000633:toxicity; D016897:Respiratory Burst
chemical_list: D000935:Antifungal Agents; D017382:Reactive Oxygen Species; D030421:Peroxynitrous Acid; D017964:Itraconazole; D000666:Amphotericin B
keywords: antifungal drugs; cryptococcosis; peroxynitrite; reactive oxygen species