Crystal structure of glutamate dehydrogenase 3 from Candida albicans.

Glutamate dehydrogenase 3 from Candida albicans (CaGdh3) catalyzes the reversible oxidative deamination of l-glutamate, playing an important role in the yeast-to-hyphal transition of C. albicans. Here we report the crystal structures of CaGdh3 and its complex with α-ketoglutarate and NADPH. CaGdh3 exists as a hexamer, with each subunit containing two domains. The substrate and coenzyme bind in the cleft between the two domains and their binding induces a conformational change in CaGdh3. Our results will help to understand the catalytic mechanism of CaGdh3 and will provide a structural basis for the design of antifungal drugs targeting the CaGdh3 pathway.

Green synthesized silver nanoparticles demonstrating enhanced in vitro and in vivo antibiofilm activity against Candida spp.

Candida species are opportunistic fungal pathogens, which are known for their biofilm associated infections on implanted medical devices in clinical settings. Broad spectrum usage of azole groups and other antifungal agents leads to the occurrence of drug resistance among Candida species. Most of the antifungal agents have failed to treat the biofilm mediated Candida infections. In the present study, silver nanoparticles (AgNPs) were synthesized using Dodonaea viscosa and Hyptis suoveolens methanolic leaf extracts and characterized by ultraviolet-visible absorption spectroscopy, X-ray diffraction analysis, Fourier transform infrared spectroscopy and Scanning electron microscopy, Dynamic light scattering, and Zeta potential analysis. The main goal of this study was to assess the AgNPs for their antibiofilm efficacy against Candida spp. through microscopic analysis and in vitro virulence assays. The results revealed that AgNPs strongly inhibited more than 80% biofilm formed by Candida spp. Furthermore, the AgNPs also reduced the yeast-to-hyphal transition, exopolysaccharide biosynthesis, secreted aspartyl proteinase production which are the major virulence factors of Candida species. This study reveals that biosynthesized AgNPs can be considered for the treatment of biofilm related Candida infections.

Piperine Impedes Biofilm Formation and Hyphal Morphogenesis of Candida albicans.

Candida albicans is the primary etiological agent associated with the pathogenesis of candidiasis. Unrestricted growth of C. albicans in the oral cavity may lead to oral candidiasis, which can progress to systemic infections in worst scenarios. Biofilm of C. albicans encompasses yeast and hyphal forms, where hyphal formation and yeast to hyphal morphological transitions are contemplated as the key virulence elements. Current clinical repercussions necessitate the identification of therapeutic agent that can limit the biofilm formation and escalating the susceptibility of C. albicans to immune system and conventional antifungals. In the present study, a plant-derived alkaloid molecule, piperine, was investigated for the antibiofilm and antihyphal activities against C. albicans. Piperine demonstrated a concentration-dependent antibiofilm activity without exerting negative impact on growth and metabolic activity. Inhibition in the hyphal development was witnessed through confocal laser-scanning microscopy and scanning electron microscopy. Interestingly, piperine displayed a tremendous potential to inhibit the virulence-associated colony morphologies, such as filamentation and wrinkling. Furthermore, piperine regulated morphological transitions between yeast and hyphal forms by inhibiting hyphal extension and swapping hyphal phase to yeast forms yet under filamentation-inducing circumstances. Remarkably, piperine-challenged C. albicans exhibited low potential for spontaneous antibiofilm resistance development. In addition, piperine effectively reduced in vivo colonization and prolonged survival of C. albicans-infected Caenorhabditis elegans, thereby expounding the distinct antivirulent potential. Transcriptomic analysis revealed piperine significantly downregulating the expression of several biofilm related and hyphal-specific genes (ALS3, HWP1, EFG1, CPH1, etc.). Furthermore, no acute toxicity was observed in the HBECs and nematodes exposed to piperine. Altogether, results from this study reveals the potential of piperine to inhibit biofilm and hyphal morphogenesis, and its in vivo efficacy and innocuous nature to HBECs suggests that piperine may be considered as a potential candidate for the treatment of biofilm-associated C. albicans infection, especially for oral candidiasis.

Are the Statins promising antifungal agents against invasive candidiasis?

The medical importance of intra-abdominal candidiasis (IAC) contrasts with the limited number of pharmacological treatment options available and the increasing rate of resistance to antifungal drugs. Thus, the repositioning of compounds in clinical use can contribute to the broadening of treatment possibilities for this infection. Statins, a class of drugs used to reduce cardiovascular event risk, have shown antiparasitic, antibacterial, and antiviral activities; however, their antifungal effects remain poorly studied. In this context, the present study aimed to elucidate the antifungal potential of six statins in vitro, as well as to evaluate the therapeutic use of fluvastatin in a mouse model of IAC. The biological effects of statins were evaluated against Candida spp., through the determination of the minimum inhibitory concentration (MIC). For the statins that showed activity, the fungicidal concentration, toxicity/selectivity, synergism with azoles and polyenes, phenotypic effects, and activity against virulence factors were also determined. Atorvastatin, rosuvastatin and fluvastatin were highly active, especially against C. albicans (MIC < 1-128 µg.mL-1) and C. glabrata (MIC 32-64 µg.mL-1). Fluvastatin and atorvastatin were selective for C. albicans in baby hamster kidney (BHK) cells. Moreover, all active statins in the antifungal assay showed high selectivity for fungal cells over bacteria. The combination of atorvastatin, rosuvastatin, and fluvastatin with azoles was associated with a synergistic effect. Active statins do not act on the fungal membrane or wall, but instead stimulate farnesol-dependent pathogenicity factors such as yeast-to-hyphal transition and biofilm generation. Fluvastatin treatment was evaluated in a mouse model of IAC, showing stimulation of the extra-hepatic dissemination of C. albicans but improvements in renal, splenic, and hepatic histological aspects. In conclusion, statins have potent antifungal activity in vitro, but the therapeutic effect in vivo is restricted to their anti-inflammatory activity.

The Dietary Food Components Capric Acid and Caprylic Acid Inhibit Virulence Factors in Candida albicans Through Multitargeting.

Capric acid and caprylic acid are the dietary food components. They are found to inhibit the virulence factors like morphogenesis, adhesion, and biofilm formation in the human pathogenic yeast Candida albicans. Our study demonstrated that yeast-to-hyphal signal transduction pathways were affected by capric acid and caprylic acid. The expression profile of genes associated with serum-induced morphogenesis showed reduced expressions of Cdc35, Hwp1, Hst7, and Cph1 by the treatment with both the fatty acids. Cell elongation gene, Ece1, was surprisingly downregulated by 5208-fold by the treatment of caprylic acid. Nrg1 and Tup1, negative regulators of hyphal formation, were overexpressed in presence of capric or caprylic acid. Cell cycle studies revealed that capric and caprylic acids arrested cell cycle at G2/M and S phase. Targeting the virulence factors like yeast-to-hyphal transition is efficacious for treatment of opportunistic fungal infections. This research suggests that both capric and caprylic acid may be effective interventions for treating C. albicans yeast infections.