Virulence Of Candida Albicans Research Articles

Modulation of Candida albicans virulence in invitro biofilms by oral bacteria.

Candida‐associated denture stomatitis presents as erythema of the palatal mucosa and is caused by biofilms containing the fungus Candida albicans that co‐reside with oral bacteria on the denture‐fitting surface. This study aimed to assess the effect of several frequently encountered oral bacteria on the expression of C. albicans virulence factors in in vitro polymicrobial biofilms. Biofilms containing C. albicans and selected bacterial species were grown on denture acrylic, and analysed by microscopy and by qPCR for expression of putative virulence genes. Candida albicans‐only biofilms showed limited hyphal production. Hyphal development was significantly (P < 0·001) increased when biofilms also contained four species of oral bacteria (Streptococcus sanguinis, Streptococcus gordonii, Actinomyces odontolyticus and Actinomyces viscosus), as was the expression of virulence genes (P < 0·05). Importantly, inclusion of Porphyromonas gingivalis in the biofilm consortium resulted in significant (P < 0·05) inhibition of virulence gene expression and production of hyphae. The in vitro expression of C. albicans virulence factors was modulated in polymicrobial biofilms. The complexity of this modulation was highlighted by the reversal of effects following introduction of a single bacterial species into a biofilm community.Significance and Impact of the StudyThe impact of individual bacterial species on Candida albicans virulence highlights both the complexity of predicting infection mediated by polymicrobial communities and the potential for management through pro‐ or prebiotic therapy. The possibility to selectively modulate microbial virulence by addition of, or treatment with pro‐ or prebiotics avoids the use of conventional antimicrobial compounds, thus reducing the contribution to potential drug resistance. Understanding which bacterial species modulate virulence, and the mechanisms by which this occurs, particularly in biofilms, provides excellent foundations for further research questions, and the potential for novel clinical interventions.

An analysis of the role of statins in reducing the virulence of Candida albicans

The yeast Candida albicans has the ability to induce several systematic and superficial diseases in the immunocompromised or immunosuppressed host. Statins are widely used drugs for the control of cholesterol biosynthesis in the body and are therefore used in treatment of hypercholesterolemia. There is increasing evidence for the potential use of statins in preventing and treating fungal infections. The aim of this study was to assess the effect of statins on C. albicans and to characterize the proteomic alterations occurring in C. albicans in response to statin. Pre-growth of C. albicans in the presence of statin lead to lower levels of ergosterol, reduced adherence to buccal epithelial cells and decreased virulence in Galleria mellonella larvae. Cells also showed increased permeability as measured by elevated amino acid and protein leakage. Proteomic analysis of C. albicans exposed to statin revealed differential abundance of proteins related to ergosterol biosynthesis such as squalene monooxygenase (4.52 fold increase), and lanosterol synthase (2.84 fold increase). Proteins involved in oxidative stress response such as small heat shock protein 21 (6.33 fold decrease) and glutathione peroxidase (2.05 fold decrease) and adherence related proteins such as yeast-form wall protein 1 (6.26 fold decrease) and Ecm33p protein (2.06 fold decrease) were also altered in abundance. These results indicate that statins have the ability to reduce the growth of C. albicans and induce an oxidative stress response. Statins may have potential to control fungal infections in vivo if used alone or in combination with conventional antifungal agents.

Hexokinase and Glucokinases Are Essential for Fitness and Virulence in the Pathogenic Yeast Candida albicans.

The pathogenic yeast Candida albicans is both a powerful commensal and a pathogen of humans that can infect wide range of organs and body sites. Metabolic flexibility promotes infection and commensal colonization by this opportunistic pathogen. Yeast cell survival depends upon assimilation of fermentable and non-fermentable locally available carbon sources. Physiologically relevant sugars like glucose and fructose are present at low levels in host niches. However, because glucose is the preferred substrate for energy and biosynthesis of structural components, its efficient detection and metabolism are fundamental for the metabolic adaptation of the pathogen. We explored and characterized the C. albicans hexose kinase system composed of one hexokinase (CaHxk2) and two glucokinases (CaGlk1 and CaGlk4). Using a set of mutant strains, we found that hexose phosphorylation is mostly performed by CaHxk2, which sustains growth on hexoses. Our data on hexokinase and glucokinase expression point out an absence of cross regulation mechanisms at the transcription level and different regulatory pathways. In the presence of glucose, CaHxk2 migrates in the nucleus and contributes to the glucose repression signaling pathway. In addition, CaHxk2 participates in oxidative, osmotic and cell wall stress responses, while glucokinases are overexpressed under hypoxia. Hexose phosphorylation is a key step necessary for filamentation that is affected in the hexokinase mutant. Virulence of this mutant is clearly impacted in the Galleria mellonella and macrophage models. Filamentation, glucose phosphorylation and stress response defects of the hexokinase mutant prevent host killing by C. albicans. By contributing to metabolic flexibility, stress response and morphogenesis, hexose kinase enzymes play an essential role in the virulence of C. albicans.

Genetically Compromising Phospholipid Metabolism Limits Candida albicans' Virulence.

Perturbing ergosterol synthesis has been previously shown to reduce the virulence of Candida albicans. We tested the hypothesis that further altering cell membrane composition by limiting phospholipid synthesis or remodeling will have the same effect. To model partial inhibition, C. albicans strains independently harboring heterozygous deletion of four genes that encode for enzymes that mediate phospholipid synthesis or modification were generated. Quantitative PCR determined that heterozygous deletion routinely caused a nearly 50% reduction in the respective gene's transcript abundance. Compensatory increased transcript abundance was only found with the deletion of LRO1, a homolog of phospholipid diacylglycerol acyltransferases. Virulence of the mutants was assayed in a Caenorhabditis elegans host model. Even modestly reduced expression of LRO1, phosphatidylserine synthase (CHO1), and lysophospholipid acyltransferase (LPT1) significantly reduced virulence by 23-38%. Reintroducing a second functional allele, respectively, to all three mutants restored virulence. Heterozygous deletion of SLC1, a homolog of 1-acylglycerol-3-phosphate O-acyltransferases, did not significantly reduce virulence. Electrospray ionization tandem mass spectrometry analysis of phospholipid composition followed by principal component analysis identified comprehensive changes in the LRO1 and CHO1 deletion heterozygotes. Strikingly (p < 0.001), univariate comparisons found that both deletion heterozygotes had 20% more phosphatidylinositol, 75% less lysophosphatidylcholine, and 35% less lysophosphatidylethanolamine compared to wild type. Heterozygous deletion of LPT1 also significantly increased phosphatidylinositol abundance. No growth phenotype, including filamentation, was affected by any mutation. Together, these data predict that even partial pharmacological inhibition of Lro1p, Cho1p, and Lpt1p will limit C. albicans virulence through altering phospholipid composition.

Magnesium deprivation affects cellular circuitry involved in drug resistance and virulence in Candida albicans.

Candida albicans has to struggle for the limited micronutrients present in the hostile host niche, including magnesium (Mg). The aim of this study was to examine the effect of Mg deprivation on drug resistance mechanisms and virulence traits of C. albicans. The drug susceptibility of C. albicans strain SC5314 was determined by broth microdilution and spot assay. Efflux pump activity was measured using the substrate rhodamine 6G. Membrane intactness was studied by propidium iodide influx, and ergosterol levels were determined by the alcoholic KOH method. Metabolic flexibility was examined by studying the activity of glyoxylate cycle enzymes. Virulence factors were assessed by yeast-to-hyphae transition, biofilm formation and cell adherence. An in vivo study was also performed in a Caenorhabditis elegans infection model. Mg chelation leads to potentiation of membrane-targeting antifungals. The role of Mg on membrane homeostasis was explored and significant differences in ergosterol levels were found. Interestingly, it was also observed that Mg deprivation impedes the metabolic flexibility of C. albicans SC5314 by inhibiting glyoxylate cycle enzymes. Furthermore, Mg deprivation inhibited potential virulence traits, including morphological transition, biofilm formation and buccal epithelial cell adherence. All of the disrupted gene targets were validated by reverse transcription PCR. Lastly, enhanced survival of C. elegans infected with C. albicans SC5314 under Mg deprivation was observed. In view of the restricted growth of C. albicans in a Mg-deficient environment, approaches could be utilised to boost the effectiveness of existing antifungals thereby improving the management of fungal infections.

Blocking β-1,6-glucan synthesis by deleting KRE6 and SKN1 attenuates the virulence of Candida albicans.

β-1,6-glucan is an important component of the fungal cell wall. The β-1,6-glucan synthase gene KRE6 was thought to be essential in the fungal pathogen Candida albicans because it could not be deleted in previous efforts. Also, the role of its homolog SKN1 was unclear because its deletion caused no defects. Here, we report the construction and characterization of kre6Δ/Δ, skn1Δ/Δ and kre6Δ/Δ skn1Δ/Δ mutants in C. albicans. While deleting KRE6 or SKN1 had no obvious phenotypic consequence, deleting both caused slow growth, cell separation failure, cell wall abnormalities, diminished hyphal growth, poor biofilm formation and loss of virulence in mice. Furthermore, the GPI-linked cell surface proteins Hwp1 and the invasin Als3 or Ssa1 were not detected in kre6Δ/Δ skn1Δ/Δ mutant. In GMM medium, RT-qPCR and western blotting revealed a constitutive expression of KRE6 and growth conditions-associated activation of SKN1. Like many hypha-specific genes, SKN1 is repressed by Nrg1, but its activation does not involve the transcription factor Efg1. Dysregulation of SKN1 reduces C. albicans ability to damage epithelial and endothelial cells and attenuates its virulence. Given the vital role of β-1,6-glucan synthesis in C. albicans physiology and virulence, Kre6 and Skn1 are worthy targets for developing antifungal agents.

Phosphatidate phosphatase Pah1 has a role in the hyphal growth and virulence of Candida albicans

Phosphatidate phosphatases play essential roles in lipid metabolism by converting phosphatidic acid to diacylglycerol. Here, we have investigated the roles of a phosphatidate phosphatase, Pah1, in the fungal pathogen Candida albicans. Deleting PAH1 causes multiple phenotypes, especially severe hyphal defects, increased sensitivity to cell wall stress, and reduced virulence in mice. By qPCR, we detected a significant downregulation of hyphal-specific genes including two key hyphal-promoting genes UME6 and HGC1. Overexpression of UME6 in pah1Δ/Δ cells largely restored the hyphal growth, indicating that the reduced expression of UME6 is primarily responsible for the hyphal defects. We also detected decreased expression of three hyphal-promoting transcription factors EFG1, FLO8, and CPH1 in pah1 mutants, consistent with the reduced expression of UME6. Furthermore, the pah1Δ/Δ mutant exhibited increased sensitivity to cell wall stress. During systemic infection of mice, the mutant showed significantly impaired ability to colonize the kidney and to kill the host. Together, C. albicans PAH1 plays an important role in hyphal growth, adaptability to environmental stresses, and virulence. Thus, Pah1 could be targeted for the development of new antifungal drugs.

Silencing of OCH1 unveils the role of Sporothrix schenckii N-linked glycans during the host-fungus interaction.

BackgroundSporothrix schenckii is a neglected fungal pathogen for the human being and other mammals. In several fungal systems, Och1 is a Golgi α1,6-mannosyltransferase with a key function in the synthesis of N-linked glycans; which are important elements during the host-fungus interplay. The role of OCH1 in fungal virulence seems to be species-specific, being an essential component for Candida albicans virulence and dispensable during the interaction of Aspergillus fumigatus with the host.MethodsHere, we silenced S. schenckii OCH1 and characterized the phenotype of the mutant strains.ResultsThe mutant strains did not show defects in the cell or colony morphology, the growth rate or the ability to undergo dimorphism; but the cell wall changed in both composition and exposure of inner components at the surface. When interacting with human monocytes, the silenced strains had a reduced ability to stimulate TNFα and IL-6 but stimulated higher levels of IL-10. The interaction with human macrophages was also altered, with reduced numbers of silenced cells phagocytosed. These strains showed virulence attenuation in both Galleria mellonella and in the mouse model of sporotrichosis. Nonetheless, the cytokine levels in infected organs did not vary significantly when compared with the wild-type strain.ConclusionOur data demonstrate that OCH1 silencing affects different aspects of the S. schenckii-host interaction.

Antifungal activity of magnoflorine against Candida strains.

Candida albicans is a major invasive pathogen, and the development of strains resistant to conventional antifungal agents has been reported in recent years. We evaluated the antifungal activity of 44 compounds against Candida strains. Magnoflorine showed the highest growth inhibitory activity of the tested Candida strains, with a minimum inhibitory concentration (MIC) of 50μg/mL based on microdilution antifungal susceptibility testing. Disk diffusion assay confirmed the antifungal activity of magnoflorine and revealed that this activity was stable over 3days compared to those of berberine and cinnamaldehyde. Cytotoxicity testing showed that magnoflorine could potentially be used in a clinical setting because it didn't have any toxicity to HaCaT cells even in 200μg/mL of treatment. Magnoflorine at 50μg/mL inhibited 55.91 ± 7.17% of alpha-glucosidase activity which is required for normal cell wall composition and virulence of Candida albicans. Magnoflorine also reduced the formation of C. albicans' biofilm. Combined treatment with magnoflorine and miconazole decreased the amount of miconazole required to kill various Candida albicans. Therefore, magnoflorine is a good candidate lead compound for novel antifungal agents.

Histone acetylation increases in response to ferulic, gallic, and sinapic acids acting synergistically in vitro to inhibit Candida albicans yeast-to-hyphae transition.

Novel treatments are needed to prevent candidiasis/candidemia infection due to the emergence of Candida species resistant to current antifungals. Considering the yeast-to-hyphae switch is a critical factor to Candida albicans virulence, phenols common in plant sources have been reported to demonstrating their ability to prevent dimorphism. Therefore, phenols present in many agricultural waste stress (ferulic (FA) and gallic (GA) acid) were initially screened in isolation for their yeast-to-hyphae inhibitory properties at times 3, 6, and 24hr. Both FA and GA inhibited 50% of hyphae formation inhibitory concentration (IC50 ) but at a concentration of 8.0±0.09 and 90.6±1.05mM, respectively, at 24hr. However, the inhibitory effect of FA increased by 1.9-2.6 fold when combined with different GA concentrations. GA and FA values decreased even lower when sinapic acid (SA) was added as a third component. As evidenced by concave isobolograms and combination indexes less than 1, both GA:F A and GA:FA:SA combinations acted synergistically to inhibit 50% hyphae formation at 24hr. Lastly, acetylation of histone H3 lysine 56 acetylation (H3K56) was higher in response to the triple phenolic cocktail (using the IC50 24hr inhibitory concentration level) comparable with the nontreated samples, indicating that the phenols inhibited hyphal growth in part by targeting H3K56 acetylation.

Mannich base limits Candida albicans virulence by inactivating Ras-cAMP-PKA pathway

Mannich bases and its derivatives are regarded as supreme pharmacophores in therapeutics. The study investigates the antimycotic potential of Mannich bases, 1-((1H-benzimidazol-1-yl) methyl) urea (C1) and 1-((3-hydroxynapthalen-2-yl) methyl) thiourea (C2), against Candida albicans. Biofilm and hyphal inhibitory activities of the Mannich bases were tested by crystal violet quantification, fluorescence imaging cAMP rescue, qRT PCR, and by molecular docking analysis. The compounds inhibited the biofilms of C. albicans and restrained the filamentation abilities of the pathogen. Structure-activity relationship studies revealed that the presence of urea or thiourea moiety in the tail section is essential for interacting with adenylate cyclase (AC). The Mannich bases seemed to block Ras-cAMP-PKA pathway by inhibiting second messenger activity required for hyphal induction and biofilm formation. In conclusion, the study warrants point-of-care testing of C1/C2 and provides a starting point for deriving several structurally modified Mannich bases which might plausibly replace the prevailing antimycotic drugs in future.

Influence of Streptococcus mitis and Streptococcus sanguinis on virulence of Candida albicans: in vitro and in vivo studies.

The aim was to evaluate in vitro possible interactions, gene expression, and biofilm formation in species of Candida albicans, Streptococcus mitis, and Streptococcus sanguinis and their in vivo pathogenicity. The in vitro analysis evaluated the effects of S. mitis and S. sanguinis on C. albicans's biofilm formation by CFU count, filamentation capacity, and adhesion (ALS1, ALS3, HWP1) and transcriptional regulatory gene (BCR1, CPH1, EFG1) expression. In vivo studies evaluated the pathogenicity of the interaction of the microorganisms on Galleria mellonella, with analyses of the CFU per milliliter count and filamentation. In vitro results indicated that there was an observed decrease in CFU (79.4-71.5%) in multi-species biofilms. The interaction with S. mitis inhibited filamentation, which seems to increase its virulence factor with over-expression of genes ALS1, ALS3, and HWP1 as well the interaction with S. sanguinis as ALS3 and HWP1. S. mitis upregulated BRC1, CPH1, and EFG1. The histological images of in vivo study indicate an increase in the filamentation of C. albicans when in interaction with the other species. It was concluded that S. mitis interaction suggests increased virulence factors of C. albicans, with periods of lower virulence and proto-cooperation in the interaction with S. sanguinis.

Mgm1 is required for maintenance of mitochondrial function and virulence in Candida albicans

Mitochondria are dynamic organelles, and their shapes and sizes are regulated by mitochondrial fusion and fission. The proteins essential for mitochondrial fusion in Candida albicans have not been clearly characterized. In this study, Mgm1 was explored for its roles in mitochondrial function, cell cycle, hyphal growth and virulence in this pathogen. The deletion of MGM1 led to mitochondrial fragmentation and mtDNA loss and activated the checkpoint pathway to arrest the cell cycle in G1 phase. Moreover, loss of MGM1 led to defects in hyphal development and attenuation of virulence in a macrophage cell line and a mouse model of disseminated infection. These results reveal that Mgm1 plays an important role in mitochondrial dynamics and function, cell cycle progression, hyphal development and virulence in C. albicans.

(1-aryloxy-2-hydroxypropyl)-phenylpiperazine derivatives suppress Candida albicans virulence by interfering with morphological transition.

SummaryClinical treatment of Candida albicans infections has become more difficult due to the limited development of antifungal agents and the rapid emergence of drug resistance. In this study, we demonstrate the synthesis of a series of piperazine derivatives and the evaluation of their inhibitory activity against C. albicans virulence. Thirty‐four (1‐aryloxy‐2‐hydroxypropyl)‐phenylpiperazine derivatives, including 25 new compounds, were synthesized and assessed for their efficacy against the physiology and pathogenesis of C. albicans. Several compounds strongly inhibited the morphological transition and virulence of C. albicans cells, although they did not influence the growth rate of the fungal pathogen. A leading novel compound, (1‐(4‐ethoxyphenyl)‐4‐(1‐biphenylol‐2‐hydroxypropyl)‐piperazine), significantly attenuated C. albicans virulence by interfering with the process of hyphal development, but it showed no cytotoxicity against human cells at a micromolar level. These findings suggest that (1‐aryloxy‐2‐hydroxypropyl)‐phenylpiperazine derivatives could potentially be developed as novel therapeutic agents for the clinical treatment of C. albicans infections by interfering with morphological transition and virulence.

SDH2 is involved in proper hypha formation and virulence in Candida albicans.

To investigate the role of SDH2 in Candida albicans filamentation and virulence. Caenorhabditis elegans and mouse candidiasis models were used to assess the virulence of a sdh2Δ/Δ mutant. Various hypha-inducing media were used to evaluate the hyphal development of C. albicans. DCFH-DA was used to measure intracellular Reactive Oxygen Species (ROS) levels. The sdh2Δ/Δ mutant was avirulent in the C. elegans model, hypovirulent in a murine candidiasis model, and defective to form filaments both in vitro and in vivo. Intracellular ROS level increased in the sdh2Δ/Δ mutant, and the filamentation defects of sdh2Δ/Δ were rescued by decreasing intracellular ROS. SDH2 plays an important role in C. albicans filamentation and virulence probably through affecting intracellular ROS. [Formula: see text].

Intersection of phosphate transport, oxidative stress and TOR signalling in Candida albicans virulence.

Phosphate is an essential macronutrient required for cell growth and division. Pho84 is the major high-affinity cell-surface phosphate importer of Saccharomyces cerevisiae and a crucial element in the phosphate homeostatic system of this model yeast. We found that loss of Candida albicans Pho84 attenuated virulence in Drosophila and murine oropharyngeal and disseminated models of invasive infection, and conferred hypersensitivity to neutrophil killing. Susceptibility of cells lacking Pho84 to neutrophil attack depended on reactive oxygen species (ROS): pho84-/- cells were no more susceptible than wild type C. albicans to neutrophils from a patient with chronic granulomatous disease, or to those whose oxidative burst was pharmacologically inhibited or neutralized. pho84-/- mutants hyperactivated oxidative stress signalling. They accumulated intracellular ROS in the absence of extrinsic oxidative stress, in high as well as low ambient phosphate conditions. ROS accumulation correlated with diminished levels of the unique superoxide dismutase Sod3 in pho84-/- cells, while SOD3 overexpression from a conditional promoter substantially restored these cells’ oxidative stress resistance in vitro. Repression of SOD3 expression sharply increased their oxidative stress hypersensitivity. Neither of these oxidative stress management effects of manipulating SOD3 transcription was observed in PHO84 wild type cells. Sod3 levels were not the only factor driving oxidative stress effects on pho84-/- cells, though, because overexpressing SOD3 did not ameliorate these cells’ hypersensitivity to neutrophil killing ex vivo, indicating Pho84 has further roles in oxidative stress resistance and virulence. Measurement of cellular metal concentrations demonstrated that diminished Sod3 expression was not due to decreased import of its metal cofactor manganese, as predicted from the function of S. cerevisiae Pho84 as a low-affinity manganese transporter. Instead of a role of Pho84 in metal transport, we found its role in TORC1 activation to impact oxidative stress management: overexpression of the TORC1-activating GTPase Gtr1 relieved the Sod3 deficit and ROS excess in pho84-/- null mutant cells, though it did not suppress their hypersensitivity to neutrophil killing or hyphal growth defect. Pharmacologic inhibition of Pho84 by small molecules including the FDA-approved drug foscarnet also induced ROS accumulation. Inhibiting Pho84 could hence support host defenses by sensitizing C. albicans to oxidative stress.

Identification of genome-wide binding sites of heat shock factor 1, Hsf1, under basal conditions in the human pathogenic yeast, Candida albicans

The master regulator of thermal stress response, Hsf1, is also an essential determinant for viability and virulence in Candida albicans. Our recent studies highlighted that apart from ubiquitous roles of Hsf1 at higher temperatures, it also has myriad non-heat shock responsive roles essential under iron deprivation and drug defense. Here, we further explored its implications in the normal cellular functioning, by profiling its genome-wide occupancy using chromatin immuno-precipitation coupled to high-density tiling arrays under basal and iron deprived conditions. Hsf1 recruitment profiles revealed that it binds to promoters of 660 genes of varied functions, under both the conditions, however, elicited variability in intensity of binding. For instance, Hsf1 binding was observed on several genes of oxidative and osmotic stress response, cell wall integrity, iron homeostasis, mitochondrial, hyphal and multidrug transporters. Additionally, the present study divulged a novel motif under basal conditions comprising, -GTGn3GTGn3GTG- where, Hsf1 displays strong occupancy at significant number of sites on several promoters distinct from the heat induced motif. Hence, by binding to and regulating major chaperones, stress responsive genes and drug resistance regulators, Hsf1 is imperative in regulating various cellular machineries. The current study provides a framework for understanding novel aspects of how Hsf1 coordinates diverse cellular functions.

ERG11 couples oxidative stress adaptation, hyphal elongation and virulence in Candida albicans.

Candida albicans is a major fungal opportunistic pathogen for humans. In the treatment of C. albicans, azole drugs target the sterol 14α-demethylase (CYP51) encoded by ERG11 gene. Most studies have focused on the fact that the ERG11 mutant results in drug resistance, but its mechanism of action as a drug target has not been described yet. Our results showed that deletion of ERG11 reduced filamentous and invasive growth, and impaired hyphal elongation in sensing serum. Lack of ERG11 increased susceptibility to H2O2 and was defective in clearing reactive oxygen species. ERG11 may affect oxidative stress adaptation by specifically downregulating CAT1 expression. In addition, C. albicans cells lacking ERG11 were more efficiently killed by macrophages and became avirulent in vivo. This study is the first to indicate that ERG11 plays an essential role in hyphal elongation, oxidative stress adaptation and virulence in C. albicans. We speculated that azole drugs not only inhibit the growth of C. albicans, but also assist the host immune system in clearing the fungal organism. The new understanding of mechanisms of action of antifungal drugs should facilitate the development of treatment strategies for resistant fungal infections.

Functions of CaPhm7 in the regulation of ion homeostasis, drug tolerance, filamentation and virulence in Candida albicans

BackgroundCalcium-permeable transient receptor potential (TRP) channels exist in eukaryotic cells from yeasts to animals and plants. and they act as sensors for various stresses. Arabidopsis thalianacalcium permeable stress-gated cation channel 1 (AtCSC1) was the first plant calcium-permeable TRP to be described and can be activated by hyperosmotic shock. Candida albicans CaPHM7 is one of the sequence homologs of AtCSC1, but its function remains unknown.ResultsWe show here that CaPhm7 is localized to the plasma membrane in both the yeast and hyphal cells of C. albicans. C. albicans cells lacking CaPHM7 are sensitive to SDS and ketoconazole but tolerant to rapamycin and zinc. In addition, deletion of CaPHM7 leads to a filamentation defect, reduced colony growth and attenuated virulence in the mouse model of systemic infection.ConclusionsCaPhm7 is involved in the regulation of ion homeostasis, drug tolerance, filamentation and virulence in this important human fungal pathogen. CaPhm7 could be a potential target of antifungal drugs.

β-lapachone and α-nor-lapachone modulate Candida albicans viability and virulence factors

BackgroundCandida albicans is the most important fungal pathogen that causes infections in humans, and the search for new therapeutic strategies for its treatment is essential. ObjectiveThe aim of this study was to evaluate the activity of seven naphthoquinones (β-lapachone, β-nor-lapachone, bromide-β-lapachone, hydroxy-β-lapachone, α-lapachone, α-nor-lapachone and α-xyloidone) on the growth of a fluconazole-resistant C. albicans oral clinical isolate and the effects of these compounds on the viability of mammalian cells, on yeast's morphogenesis, biofilm formation and cell wall mannoproteins availability. ResultsAll the compounds were able to completely inhibit the yeast growth. β-lapachone and α-nor-lapachone were the less cytotoxic compounds against L929 and RAW 264.7 cells. At IC50, β-lapachone inhibited morphogenesis in 92%, while the treatment of yeast cells with α-nor-lapachone decreased yeast-to-hyphae transition in 42%. At 50μg/ml, β-lapachone inhibited biofilm formation by 84%, whereas α-nor-lapachone reduced biofilm formation by 64%. The treatment of yeast cells with β-lapachone decreased cell wall mannoproteins availability in 28.5%, while α-nor-lapachone was not able to interfere on this virulence factor. Taken together, data show that β-lapachone and α-nor-lapachone exhibited in vitro cytotoxicity against a fluconazole-resistant C. albicans strain, thus demonstrating to be promising candidates to be used in the treatment of infections caused by this fungus.