Functional characterization of Candida glabrata ORF, CAGL0M02233g for its role in stress tolerance and virulence

Recent Advances in Understanding the Human Fungal Pathogen Hypoxia Response in Disease Progression

Fungal-mediated disease progression and antifungal drug efficacy are significantly impacted by the dynamic infection microenvironment. At the site of infection, oxygen often becomes limiting and induces a hypoxia response in both the fungal pathogen and host cells. The fungal hypoxia response impacts several important aspects of fungal biology that contribute to pathogenesis, virulence, antifungal drug susceptibility, and ultimately infection outcomes. In this review, we summarize recent advances in understanding the molecular mechanisms of the hypoxia response in the most common human fungal pathogens, discuss potential therapeutic opportunities, and highlight important areas for future research.

Elucidating the lactic acid tolerance mechanism in vaginal clinical isolates of Candida glabrata

Incidence of vulvovaginal candidiasis are strikingly high and treatment options are limited with nearly 50% Candida glabrata cases left untreated or experience treatment failures. The vaginal microenvironment is rich in lactic acid, and the adaptation of C. glabrata to lactic acid (LA) is the main reason for clinical treatment failure. In the present study, C. glabrata and its vaginal clinical isolates were comprehensively investigated for their growth response, metabolic adaptation and altered cellular pathway to LA using different biochemical techniques, metabolic profiling and transcriptional studies. C. glabrata shown considerable variations in its topological and biochemical features without compromising growth in LA media. Chemical profiling data highlighted involvement of cell wall/membrane, ergosterol and oxidative stress related pathways in mediating adaptative response of C. glabrata towards LA. Further, one dimensional proton (1H) NMR spectroscopy based metabolic profiling revealed significant modulation in 19 metabolites of C. glabrata cells upon growth in LA. Interestingly myo-inositol, xylose, putrescine and betaine which are key metabolites for cell growth and viability were found to be differentially expressed by clinical isolates. These observations were supported by the transcriptional expression study of selected genes evidencing cell wall/membrane re-organisation, altered oxidative stress, and reprogramming of carbon metabolic pathways. Collectively, the study advances our understanding on adaptative response of C. glabrata in vaginal microenvironment to lactic acid for survival and virulence.

Molecular investigations on Candida glabrata clinical isolates for pharmacological targeting

Prevalence of drug resistant C. glabrata strains in hospitalized immune-compromised patients with invasive fungal infections has increased at an unexpected pace. This has greatly pushed researchers in identification of mutations/variations in clinical isolates for better assessment of the prevailing drug resistance trends and also for updating of antifungal therapy regime. In the present investigation, the clinical isolates of C. glabrata were comprehensively characterized at a molecular level using metabolic profiling and transcriptional expression analysis approaches in combination with biochemical, morphological and chemical profiling methods. Biochemically, significant variations in azole susceptibility, surface hydrophobicity, and oxidative stress generation were observed among the isolates as compared to wild-type. The ¹H NMR profiling identified 18 differential metabolites in clinical strains compared to wild-type and were classified into five categories, that include: sugars (7), amino acids and their derivatives (7), nitrogen bases (3) and coenzymes (1). Transcriptional analysis of selective metabolic and regulatory enzymes established that the major differences were found in cell membrane stress, carbohydrate metabolism, amino acid biosynthesis, ergosterol pathway and turnover of nitrogen bases. This detailed molecular level/metabolic fingerprint study is a useful approach for differentiating pathogenic/clinical isolates to that of wild-type. This study comprehensively delineated the differential cellular pathways at a molecular level that have been re-wired by the pathogenic clinical isolates for enhanced pathogenicity and virulence traits.

The clinical isolates of Candida glabrata were characterized and found to be different in terms of metabolic pathways that could be targeted for drug development.

Elucidating the Eradication Mechanism of Perillyl Alcohol against Candida glabrata Biofilms: Insights into the Synergistic Effect with Azole Drugs

Increased incidences of fungal infections and associated mortality have accelerated the need for effective and alternative therapeutics. Perillyl alcohol (PA) is a terpene produced by the hydroxylation of limonene via the mevalonate pathway. In pursuit of an alternative antifungal agent, we studied the effect of PA on the biofilm community of Candida glabrata and on different cellular pathways to decipher its mode of action. PA efficiently inhibited growth and eradicated biofilms by reducing carbohydrate and eDNA content in the extracellular matrix. PA reduced the activity of hydrolytic enzymes in the ECM of C. glabrata biofilm. The chemical profiling study has given insights into the overall mode of action of PA in C. glabrata and the marked involvement of the cell wall and membrane, ergosterol biosynthesis, oxidative stress, and DNA replication. The spectroscopic and RT-PCR studies suggested a strong interaction of PA with chitin, β-glucan, ergosterol, and efflux pump, thus indicating increased membrane fluidity in C. glabrata. Furthermore, the microscopic and flow cytometry analysis emphasized that PA facilitated the change in mitochondrial activity, increased Ca²⁺ influx via overexpression of voltage-gated Ca²⁺ channels, and enhanced cytochrome C release from mitochondria. In addition, PA interferes with DNA replication and thus hinders the cell cycle progression at the S-phase. All these studies together established that PA mitigates the C. glabrata biofilms by targeting multiple cellular pathways. Interestingly, PA also potentiated the efficacy of azole drugs, particularly miconazole, against C. glabrata and its clinical isolates. Conclusively, the study demonstrated the use of PA as an effective antifungal agent alone or in combination with FDA-approved conventional drugs for fungal biofilm eradication.

DNA damage checkpoint and repair: From the budding yeast Saccharomyces cerevisiae to the pathogenic fungus Candida albicans

Cells are constantly challenged by internal or external genotoxic assaults, which may induce a high frequency of DNA lesions, leading to genome instability. Accumulation of damaged DNA is severe or even lethal to cells and can result in abnormal proliferation that can cause cancer in multicellular organisms, aging or cell death. Eukaryotic cells have evolved a comprehensive defence system termed the DNA damage response (DDR) to monitor and remove lesions in their DNA. The DDR has been extensively studied in the budding yeast Saccharomyces cerevisiae. Emerging evidence indicates that DDR genes in the pathogenic fungus Candida albicans show functional consistency with their orthologs in S. cerevisiae, but may act through distinct mechanisms. In particular, the DDR in C. albicans appears critical for resisting DNA damage stress induced by reactive oxygen species (ROS) produced from immune cells, and this plays a vital role in pathogenicity. Therefore, DDR genes could be considered as potential targets for clinical therapies. This review summarizes the identified DNA damage checkpoint and repair genes in C. albicans based on their orthologs in S. cerevisiae, and discusses their contribution to pathogenicity in C. albicans.

Eugenol-acacia gum-based bifunctional nanofibers as a potent antifungal transdermal substitute

Aim: Fungal biofilms interfere with the wound healing processes. Henceforth, the study aims to fabricate a biomaterial-based nano-scaffold with the dual functionalities of wound healing and antibiofilm activity. Methods: Nanofibers comprising acacia gum, polyvinyl alcohol and inclusion complex of eugenol in β-cyclodextrin (EG-NF) were synthesized using electrospinning. Antibiofilm studies were performed on Candida species, and the wound-healing activity was evaluated through an in vivo excision wound rat model. Results: The EG-NF potentially eradicated the mature biofilm of Candida species and their clinical isolates. Further, EG-NF also enhanced the re-epithelization and speed of wound healing in in vivo rat experiments. Conclusion: The study established the bifunctional applications of eugenol nanofibers as a transdermal substitute with antifungal potency.

Geraniol eradicates Candida glabrata biofilm by targeting multiple cellular pathways

Global burden of fungal infections and associated health risk has accelerated at an incredible pace and needs to be attended at the earliest with an unbeatable therapeutic intervention. Candida glabrata is clinically the most relevant and least drug susceptible Candida species. In the pursuit of mining alternative novel drug candidates, the antifungal activity of a monoterpene phytoactive molecule geraniol (GR) against C. glabrata biofilm was evaluated. Biofilm inhibitory and eradication ability of GR evaluated against C. glabrata along with its clinical isolates. Impact of GR on various cellular pathways was evaluated to delineate its antifungal mode of action. GR has inhibited both planktonic and sessile growth of all the studied C. glabrata strains and eradicated the mature biofilm. GR reduced the carbohydrate and eDNA content, as well as hydrolytic enzyme activity in extracellular matrix of C. glabrata. The chemical profiling, microscopic, and spectroscopic studies revealed that GR targets chitin and β-glucan in cell wall. Further, results highlighted the reduction of cell membrane ergosterol content, and blocking of ABC drug efflux pump by GR which was also confirmed by RT-PCR where expression of CDR1 and ERG4 was downregulated in GR exposed C. glabrata cells. The fluorescence microscopy and flow cytometry results emphasized the alteration in mitochondrial activity, increased Ca⁺² uptake, thus changing the membrane permeability ensuing increased cytochrome C release from mitochondria to cytoplasm. Indeed, GR also has arrested cell cycle in G1/S phase and interfered with DNA replication. These observations suggest GR targets multiple cellular pathways and mediated killing of C. glabrata cells via apoptosis. In conclusion, the present study strengthens the candidacy of GR as novel antifungal therapeutic. Key points • GR inhibits growth and eradicates biofilm of C. glabrata and its clinical isolates. • GR inactivates the hydrolytic enzymes in extracellular matrix. • GR mediates C. glabrata apoptosis by interfering with multiple signaling pathways.

Mechanistic insights into Candida biofilm eradication potential of eucalyptol

AIM

Candida-associated fungal infections are prevalent in hospitalized and immune-compromised patients. Their biofilm architecture and high rate of antifungal resistance make treatment challenging. Eucalyptol (EPTL), a monoterpene majorly present in the essential oil of eucalyptus is well known for curing respiratory infections. Hence, the present study investigated the anti-biofilm efficacy of EPTL against the laboratory strains and clinical isolates of Candida to delineate its mode of action.

METHODS

The effect of EPTL on the viability, biofilm formation, and mature biofilm of Candida strains was studied. Furthermore, its effect on cell cycle arrest, mitochondrial membrane potential (MMP), ROS generation, germ tube formation, ergosterol content and transcriptional expression of selected genes was also investigated.

RESULTS

EPTL exhibited anti-biofilm activity against mature and developing biofilm of Candida albicans and Candida glabrata along with their clinical isolates. The biochemical components and enzyme activity were differentially modulated in EPTL-treated biofilm extracellular matrix. EPTL generated ROS and arrested cell cycle at the G₁ /S phase in both the species, while altered MMP was recorded in C. glabrata. Transcriptional analysis evidenced for differential gene expression of selected ABC transporters, secreted hydrolytic enzymes, and cell wall biogenesis in C. albicans/C. glabrata upon treating with EPTL.

CONCLUSION

The current data on anti-biofilm activity of EPTL establish its candidacy for drug development or as an adjuvant with existing antifungal formulations.

SIGNIFICANCE AND IMPACT OF THE STUDY

Present investigation elucidates the mode of action of Eucalyptol as antifungal agent and would stand as a candidate for management of topical fungal infection.