Antifungal activity of the WSP1267, an inhibitor of the squalene synthase, on Candida spp. isolates: Effects on growth, cell cycle and ultrastructure

Ishida K., Fernandes Rodriguez J.C., Urbina J., Gilbert I., de Souza W., Rozental S.

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Sterol biosynthesis inhibitors targeting fungal sterol C14- alfa-demethylase (CYP51) are frequently used in the candidiasis treatment. However, the increase of resistance and pharmacological proprieties has become important issue for therapeutic failure. Therefore, other targets in the sterol biosynthesis pathway could be useful to inhibit fungal growth. In this work, we evaluated the antifungal activity of WSP1267, a squalene synthase (SQS) inhibitor, against Candida spp. The minimum inhibitory concentration (MIC) of WSP1267 was determined for 65 clinical isolates of Candida (21 C. albicans, 19 C. parapsilosis, 14 C. tropicalis, 3 C. guilliermondii, 2 C. glabrata, 1 C. krusei, 1 C. lusitaneae, 1 C. zeylanoides, 1 C. rugosa, 1 C. dubliniensis e 1 C. lipolytica) by broth microdilution method according to the CLSI (M27-A3, 2008). Fluconazole (a CYP51 inhibitor) was used as standard antifungal. Three of the isolates were resistant to fluconazole (2 C. tropicalis and 1 C. krusei). The MTC value for WSP1267 ranged from 0.5 to 8 microg/mL and 50% of isolates had MIC values below 2 microg/mL, including strains f1uconazole-resistant. C. dubliniensis e C. lipolytica were the species less susceptible (MIC = 8 microg/mL). To evaluate morphological alterations, fluorescence microscopy by DAPT staining and transmission electron microscopy of the C. albicans treated with MIC value were performed. Treatment with WSP1267 leads to several ultrastructural alterations, including alteration in cell wall shape and thickness, a pronounced discontinuity of cytoplasm membrane and detachment from the cell wall, small vesicles budding from the cytoplasm membranes migrating through the periplasmatic region and the presence of electron-dense vacuoles. In addition, fluorescence microscopy analyses indicated alterations of the yeasts' cell cycle and abnormal chromatin condensation. Taken together, these results suggest that inhibition of SQS may be a novel approach to control Candida spp. infections, and could be considered as an alternative for the development new antifungals.

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17th International Society for Human and Animal Mycology
    • ISHAM 17th (2009)