Gomes-Junior Rafael Araújo, da Silva Roberto Santana, de Lima Renata Galvão, Vannier-Santos Marcos A
Gonçalo Moniz Institute, Oswaldo Cruz Foundation (FIOCRUZ), Salvador, CEP 40295-00, BA, Brazil.
Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. do Café s/n, 14040-903, Ribeirão Preto, SP, Brazil.
FEMS Microbiol Lett. 2017 May 1;364(9). doi: 10.1093/femsle/fnx073.
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.
念珠菌病是由念珠菌属引起的一种主要的机会性真菌病，可能包括危及生命的全身感染。非白色念珠菌的发病率正在上升，尤其是在南美洲，并且它们常常具有耐药性，导致出现难以治疗的病例。因此，需要新型抗真菌药物。在此，我们测试了[RuIII(NH3)4儿茶酚]+复合物（RuCat）对氟康唑耐药的热带念珠菌的抗真菌活性，并探讨了其可能的作用机制。RuCat显著（P < 0.05）剂量依赖性地抑制热带念珠菌的生长和活力（IC50为20.3 μM）。RuCat对小鼠脾细胞的细胞毒性较低（选择性指数 = 16）。扫描电子显微镜分析显示有假菌丝形成、酵母聚集和表面损伤。通过透射电子显微镜研究RuCat处理的样品显示黑色素颗粒向细胞表面和细胞外环境运输。还观察到表面附着的膜碎片和细胞外碎片。RuCat处理产生强烈的H2DCFDA标记，表明产生活性氧（ROS），这导致脂质过氧化增加。由于N-乙酰-L-半胱氨酸完全恢复了细胞活力，因此ROS参与了杀菌作用。荧光增白剂几丁质染色表明，用70或140 μM RuCat处理2小时会影响细胞壁结构。PI标记表明细胞发生坏死性死亡。目前的数据表明，RuCat触发ROS产生、脂质过氧化和细胞表面损伤，最终导致耐药热带念珠菌选择性坏死死亡。
