Basidiomycete metabolites attenuate virulence properties of Candida albicans in vitro

Secreted Aspartic Proteinases: Key Factors in Candida Infections and Host-Pathogen Interactions

Extracellular proteases are key factors contributing to the virulence of pathogenic fungi from the genus Candida. Their proteolytic activities are crucial for extracting nutrients from the external environment, degrading host defenses, and destabilizing the internal balance of the human organism. Currently, the enzymes most frequently described in this context are secreted aspartic proteases (Saps). This review comprehensively explores the multifaceted roles of Saps, highlighting their importance in biofilm formation, tissue invasion through the degradation of extracellular matrix proteins and components of the coagulation cascade, modulation of host immune responses via impairment of neutrophil and monocyte/macrophage functions, and their contribution to antifungal resistance. Additionally, the diagnostic challenges associated with Candida infections and the potential of Saps as biomarkers were discussed. Furthermore, we examined the prospects of developing vaccines based on Saps and the use of protease inhibitors as adjunctive therapies for candidiasis. Given the complex biology of Saps and their central role in Candida pathogenicity, a multidisciplinary approach may pave the way for innovative diagnostic strategies and open new opportunities for innovative clinical interventions against candidiasis.

Farnesol, a fungal quorum-sensing molecule triggers Candida albicans morphological changes by downregulating the expression of different secreted aspartyl proteinase genes

The aim of this study was to determine the effect of exogenous farnesol in yeast-to-hyphae morphogenesis, and Saps (2, 4, 5 and 6) mRNA expressions by a Candida strain that does not produce endogenous farnesol. C. albicans was cultured in the absence and presence of farnesol at various concentrations (10, 100, and 300 µM), in proteinase induction medium, and then used to determine yeast-to- hyphae changes, Candida ultrastructure and to determine Saps 2, 4, 5 and 6 expressions using q-TR-PCR and ELISA (for Sap2). Data demonstrated that farnesol greatly reduced the yeast-to-hyphae morphogenesis of a Candida strain that does not produce endogenous farnesol. Farnesol induced several ultrastructural alterations, including changes in the cell-wall shape, a visible disconnection between the cell wall and cytoplasm with an electron-lucent zone between them, and the presence of electron-dense vacuoles. Tested on gene expressions, farnesol was able to significantly (p < 0.01) decrease Sap2 secretion and mRNA expression. Farnesol downregulated also Sap4-6 mRNA expression. These results demonstrated for the first time that farnesol modules Candida morphogenesis through a downregulation of Saps 2, 4, 5 and 6 expressions. Overall these data point to the potential use of farnesol as an antifungal molecule

Obionin B: An o-pyranonaphthoquinone decaketide from an unidentified fungus (MSX 63619) from the Order Pleosporales

A fungal extract (MSX 63619), from the Mycosynthetix library of over 50,000 fungi, displayed promising cytotoxicity against a human tumor cell panel. Bioactivity-directed fractionation led to the isolation of an o-pyranonaphthoquinone decaketide, which we termed obionin B (1). The structure of 1 was deduced via spectroscopic and spectrometric techniques. The IC(50) value of 1 was moderate, ranging from 3 to 13 μM, depending on the cell line tested.