title: Antifungal mechanism of [RuIII(NH3)4catechol]+ complex on fluconazole-resistant Candida tropicalis.
abstract: Candidiasis, a major opportunistic mycosis caused by Candida sp., may comprise life-threatening systemic infections. The incidence of non-albicans species is rising, particularly in South America and they are frequently drug resistant, causing unresponsive cases. Thus, novel antimycotic agents are required. Here we tested the antifungal activity of [RuIII(NH3)4catechol]+ complex (RuCat), approaching possible action mechanisms on fluconazole-resistant Candida tropicalis. RuCat significantly (P < 0.05) inhibited the growth and viability of C. tropicalis dose-dependently (IC50 20.3 μM). Cytotoxicity of RuCat upon murine splenocytes was lower (Selectivity Index = 16). Scanning electron microscopy analysis showed pseudohyphae formation, yeast aggregation and surface damage. RuCat-treated samples investigated by transmission electron microscopy showed melanin granule trafficking to cell surfaces and extracellular milieu. Surface-adherent membrane fragments and extracellular debris were also observed. RuCat treatment produced intense H2DCFDA labeling, indicating reactive oxygen species (ROS) production which caused increased lipoperoxidation. ROS are involved in the fungicidal effect as N-acetyl-L-cysteine completely restored cell viability. Calcofluor White chitin staining suggests that 70 or 140 μM RuCat treatment for 2 h affected cell-wall structure. PI labeling indicated necrotic cell death. The present data indicate that RuCat triggers ROS production, lipoperoxidation and cell surface damage, culminating in selective necrotic death of drug-resistant C. tropicalis.
authors.affiliation: Gonçalo Moniz Institute, Oswaldo Cruz Foundation (FIOCRUZ), Salvador, CEP 40295-00, BA, Brazil.
authors.forename: Rafael Araújo
authors.initials: RA
authors.lastname: Gomes-Junior
authors.affiliation: Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. do Café s/n, 14040-903, Ribeirão Preto, SP, Brazil.
authors.forename: Roberto Santana
authors.initials: RS
authors.lastname: da Silva
authors.affiliation: Faculdade de Ciências Integradas do Pontal, Universidade Federal de Uberlândia, Rua Vinte, 1600, Tupã, Ituiutaba, MG, Brazil.
authors.forename: Renata Galvão
authors.initials: RG
authors.lastname: de Lima
authors.affiliation: Gonçalo Moniz Institute, Oswaldo Cruz Foundation (FIOCRUZ), Salvador, CEP 40295-00, BA, Brazil.
authors.forename: Marcos A
authors.initials: MA
authors.lastname: Vannier-Santos
mesh_terms: D000818:Animals; D000935:Antifungal Agents / Q000737:chemistry / Q000494:pharmacology*; D041022:Candida tropicalis / Q000187:drug effects* / Q000254:growth & development / Q000648:ultrastructure; D016923:Cell Death; D002473:Cell Wall / Q000187:drug effects; D056831:Coordination Complexes / Q000494:pharmacology*; D025141:Drug Resistance, Fungal; D015725:Fluconazole / Q000494:pharmacology*; D006801:Humans; D020128:Inhibitory Concentration 50; D051379:Mice; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D013154:Spleen / Q000166:cytology / Q000187:drug effects / Q000382:microbiology
chemical_list: D000935:Antifungal Agents; D056831:Coordination Complexes; D017382:Reactive Oxygen Species; C000625674:tetraammine(catechol)ruthenium(III); D015725:Fluconazole
keywords: Candida tropicalis; antifungal agents; candidiasis; catechol; fluconazole-resistant; ruthenium complex