Inhibition of yeast-to-filamentous growth transitions in Candida albicans by a small molecule inducer of mammalian apoptosis

Antifungal efficacy of scorpion derived peptide K1K8 against Candida albicans in vitro and in vivo

As an alternative class of antimicrobial agents, antimicrobial peptides (AMPs) have gained significant attention. In this study, K1K8, a scorpion AMP derivative, showed effective activity against Candida albicans including clinically resistant strains. K1K8 killed C. albicans cells mainly by damaging the cell membrane and inducing necrosis via an ROS-related pathway. K1K8 could also interact with DNA after damaging the nuclear envelope. Moreover, K1K8 inhibited hyphal development and biofilm formation of C. albicans in a dose-dependent manner. In the mouse skin infection model, K1K8 significantly decreased the counts of C. albicans cells in the infection area. Overall, K1K8 is a potential anti-infective agent against skin infections caused by C. albicans.

In vitro and in vivo Activity of Phibilin Against Candida albicans

The increase in the occurrence of antifungal-resistant Candida albicans infections necessitates more research to explore alternative effective and safe agents against this fungus. In this work, Phibilin, a new antimicrobial peptide obtained from Philomycus bilineatus and used in traditional Chinese medicine, effectively inhibits the growth and activities of C. albicans, including the clinical resistant strains. Phibilin is a fungicidal antimicrobial peptide that exhibited its antimicrobial effect against C. albicans mainly by disrupting the membrane and interacting with the DNA of the fungi. In particular, Phibilin induces the necrosis of C. albicans via the ROS-related pathway. Moreover, this antifungal compound inhibited the biofilm formation of C. albicans by preventing the development of hyphae in a dose-dependent manner. Furthermore, Phibilin and clotrimazole displayed a synergistic effect in inhibiting the growth of the fungi. In the mouse cutaneous infection model, Phibilin significantly inhibited the formation of skin abscesses and decreased the counts of C. albicans cells in the infected area. Overall, Phibilin is potentially an effective agent against skin infections caused by C. albicans.

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.

Quorum Sensing Activity and Hyphal Growth by External Stimuli in the Entomopathogenic Fungus Ophiocordyceps sinensis

The entomopathogenic fungus Ophiocordyceps sinensis is one of the best known and most precious medicines and health food in China. The blastospores-hyphae (dimorphism) transition of this fungus in host hemolymph is critical for the virulence and the mummification of host larvae. To regulate this transition, the effects of inoculum density and fifteen chemicals including fungal nutrients, fungal metabolites, quorum-sensing molecules (QSMs) and insect hormones on the dimorphism in O. sinensis were investigated in vitro. The blastospores tended to exhibit budding growth when inoculated at 10⁷ blastospores per mL, and hyphal growth at concentrations lower than 10⁶ blastospores per mL. At 10⁵ blastospores per mL, the percentage of hyphal formation decreased with the addition of filtered spent medium containing 10⁷ blastospores per mL, indicating the quorum-sensing effect. Blastospores-hyphae transition in this fungus by fifteen chemicals was varied from no response to dimorphic reversion. The addition of N-acetylglucosamine at three concentrations significantly stimulated hyphal formation while inhibiting budding growth. For the first time, insect hormone 20-hydroxyecdysone was found to be involved in the hyphal formation in fungi. These results open new possibilities to regulate the dimorphism, which would be beneficial for the cultivation of the Chinese cordyceps.

Global proteomic analysis deciphers the mechanism of action of plant derived oleic acid against Candida albicans virulence and biofilm formation

Candida albicans is a commensal fungus in humans, mostly found on the mucosal surfaces of the mouth, gut, vagina and skin. Incidence of ever increasing invasive candidiasis in immunocompromised patients, alarming occurrence of antifungal resistance and insufficient diagnostic methods demand more focused research into C. albicans pathogenicity. Consequently, in the present study, oleic acid from Murraya koenigii was shown to have the efficacy to inhibit biofilm formation and virulence of Candida spp. Results of in vitro virulence assays and gene expression analysis, impelled to study the protein targets which are involved in the molecular pathways of C. albicans pathogenicity. Proteomic studies of differentially expressed proteins reveals that oleic acid induces oxidative stress responses and mainly targets the proteins involved in glucose metabolism, ergosterol biosynthesis, lipase production, iron homeostasis and amino acid biosynthesis. The current study emphasizes anti-virulent potential of oleic acid which can be used as a therapeutic agent to treat Candida infections.

Linking Cellular Morphogenesis with Antifungal Treatment and Susceptibility in Candida Pathogens

Fungal infections are a growing public health concern, and an increasingly important cause of human mortality, with Candida species being amongst the most frequently encountered of these opportunistic fungal pathogens. Several Candida species are polymorphic, and able to transition between distinct morphological states, including yeast, hyphal, and pseudohyphal forms. While not all Candida pathogens are polymorphic, the ability to undergo morphogenesis is linked with the virulence of many of these pathogens. There are also many connections between Candida morphogenesis and antifungal drug treatment and susceptibility. Here, we review how Candida morphogenesis-a key virulence trait-is linked with antifungal drugs and antifungal drug resistance. We highlight how antifungal therapeutics are able to modulate morphogenesis in both sensitive and drug-resistant Candida strains, the shared signaling pathways that mediate both morphogenesis and the cellular response to antifungal drugs and drug resistance, and the connection between Candida morphology, drug resistance, and biofilm growth. We further review the development of anti-virulence drugs, and targeting Candida morphogenesis as a novel therapeutic strategy to target fungal pathogens. Together, this review highlights important connections between fungal morphogenesis, virulence, and susceptibility to antifungals.

Synergistic Effect of Quinic Acid Derived From Syzygium cumini and Undecanoic Acid Against Candida spp. Biofilm and Virulence

In recent decades, fungal infections have incredibly increased with Candida genus as the major cause of morbidity and mortality in hospitalized and immunocompromised patients. Most of the Candida species are proficient in biofilm formation on implanted medical devices as well as human tissues. Biofilm related Candida infections are very difficult to treat using common antifungal agents owing to their increased drug resistance. To address these issues, the present study investigated the antibiofilm and antivirulent properties of Syzygium cumini derived quinic acid in combination with known antifungal compound undecanoic acid. Initially, antibiofilm potential of S. cumini leaf extract was assessed and the active principles were identified through gas chromatography and mass spectrometry analysis. Among the compounds identified, quinic acid was one of the major compounds. The interaction between quinic acid and undecanoic acid was found to be synergistic in the Fractional inhibitory concentration index (≤0.5). Results of in vitro assays and gene expression analysis suggested that the synergistic combinations of quinic acid and undecanoic acid significantly inhibited virulence traits of Candida spp. such as the biofilm formation, yeast-to-hyphal transition, extracellular polymeric substances production, filamentation, secreted hydrolases production and ergosterol biosynthesis. In addition, result of in vivo studies using Caenorhabditis elegans demonstrated the non-toxic nature of QA-UDA combination and antivirulence effect against Candida spp. For the first time, synergistic antivirulence ability of quinic acid and undecanoic acid was explored against Candida spp. Thus, results obtained from the present study suggest that combination of phytochemicals might be used an alternate therapeutic strategy for the prevention and treatment of biofilm associated Candida infection.

A phenotypic small-molecule screen identifies halogenated salicylanilides as inhibitors of fungal morphogenesis, biofilm formation and host cell invasion

A poorly exploited paradigm in the antimicrobial therapy field is to target virulence traits for drug development. In contrast to target-focused approaches, antivirulence phenotypic screens enable identification of bioactive molecules that induce a desirable biological readout without making a priori assumption about the cellular target. Here, we screened a chemical library of 678 small molecules against the invasive hyphal growth of the human opportunistic yeast Candida albicans. We found that a halogenated salicylanilide (N1-(3,5-dichlorophenyl)-5-chloro-2-hydroxybenzamide) and one of its analogs, Niclosamide, an FDA-approved anthelmintic in humans, exhibited both antifilamentation and antibiofilm activities against C. albicans and the multi-resistant yeast C. auris. The antivirulence activity of halogenated salicylanilides were also expanded to C. albicans resistant strains with different resistance mechanisms. We also found that Niclosamide protected the intestinal epithelial cells against invasion by C. albicans. Transcriptional profiling of C. albicans challenged with Niclosamide exhibited a signature that is characteristic of the mitochondria-to-nucleus retrograde response. Our chemogenomic analysis showed that halogenated salicylanilides compromise the potential-dependant mitochondrial protein translocon machinery. Given the fact that the safety of Niclosamide is well established in humans, this molecule could represent the first clinically approved antivirulence agent against a pathogenic fungus.