Fungal NOX is an essential factor for induction of TG2 in human hepatocytes

Antifungal activity and mechanism of novel peptide Glycine max antimicrobial peptide (GmAMP) against fluconazole-resistant Candida tropicalis

Background

There is a pressing need to create innovative alternative treatment approaches considering the overuse of antifungal drugs causes the number of clinically isolated fluconazole-resistant Candida species to increase. Glycine max antimicrobial peptide (GmAMP) is a novel peptide screened by us using artificial intelligence modeling techniques, and pre-tests showed its strong antimicrobial activity against clinically fluconazole-resistant Candida tropicalis.

Methods

The study aimed to comprehensively investigate the antimicrobial activity and mechanisms of GmAMP against fluconazole-resistant C. tropicalis. The antifungal activity of GmAMP against fluconazole-resistant C. tropicalis was assessed by using broth microdilution method, growth and fungicidal kinetics, hypha transformation, and antibiofilm assay. To further uncover the potential mechanisms of action of GmAMP, we performed scanning electron microscopy, flow cytometry, cell membrane potential probe 3, 3'-Dipropylthiadicarbocyanine Iodide (DiSC3(5)), and reactive oxygen species (ROS) probe 2', 7'-Dichlorodihydrofluorescein diacetate (DCFH-DA) detection to assess the cellular morphology and structure, membrane permeability, membrane depolarization, and ROS accumulation, respectively. At the same time, we used cytotoxicity and degree of erythrocyte hemolysis assays to assess GmAMP's toxicity in vitro. Cytotoxicity and treatment efficacy were evaluated in vivo by utilizing the Galleria mellonella larvae infection model.

Results

GmAMP exhibited significant antifungal activity against fluconazole-resistant C. tropicalis with a minimum inhibitory concentration (MIC) of 25 µM and demonstrated fungicidal effects at 100 µM within 2 h. GmAMP prevented the transition from yeast to hypha morphology, inhibited the biofilm formation rate of 88.32%, and eradicated the mature biofilm rate of 58.28%. Additionally, GmAMP treatment at 100 µM caused cell structure damage in fluconazole-resistant C. tropicalis, whereas GmAMP treatment at concentrations ranging from 25 to 100 µM caused membrane permeability, depolarization of cell membrane potential, and intracellular ROS accumulation. Moreover, GmAMP enhanced the survival rate of 75% for G. mellonella with fluconazole-resistant C. tropicalis infection as well as reduced fungal burden in vivo by approximately 1.0 × 102 colony forming units per larva (CFU per larva).

Conclusion

GmAMP can disrupt the cell membrane of fluconazole-resistant C. tropicalis and also shows favorable safety and therapeutic efficacy in vivo. Accordingly, GmAMP has the potential to be an agent against drug-resistant fungi.

Activity and mechanism of action of antimicrobial peptide ACPs against Candida albicans

AIMS

Candida albicans is the most prevalent pathogenic fungus, exhibiting escalating multidrug resistance (MDR). Antimicrobial peptides (AMPs) represent promising candidates for addressing this issue. In this research, five antimicrobial peptides, ACP1 to ACP5 which named ACPs were studied as alternative fungicidal molecules.

MAIN METHODS

CD assay was used to analyze the 2D structures, Absorbance method was used to test the antimicrobial activity, haemolytic activity, time-kill kinetics, biofilm inhibition and reduction activity, resistance induction activity and assessment against fluconazole-resistant C. albicans. SEM, TEM, CLSM, flow cytometer and FM were carried out to provide insight into the mechanisms of anti-Candida action.

KEY FINDINGS

ACPs possessed an α-helical structure and strong anti-Candida activities, with minimum inhibitory concentrations (MICs) from 3.9 to 15.6 μg/mL. In addition, ACPs did not produce hemolysis at concentrations lower than 10 or 62 × MIC, indicating their low cytotoxicity. Fungicidal kinetics showed that they completely killed C. albicans within 8 h at 2 to 4 × MIC. Notably, ACPs were highly fungicidal against fluconazole-resistant C. albicans and showed low resistance. In addition, they were effective in inhibiting mycelium and biofilm formation. Fluorescence microscopy revealed that while fluconazole had minimal to no inhibitory effect on biofilm-forming cells, ACPs induced apoptosis in all of them. The research on mechanism of action revealed that ACPs disrupted the cell membranes, with ROS increasing and cellular mitochondrial membrane potential decreasing.

SIGNIFICANCE

ACPs could be promising candidates for combating fluconazole-resistant C. albicans infections.

Novel Splicing Variants in the ARR3 Gene Cause the Female-Limited Early-Onset High Myopia

Purpose

Variants in the ARR3 gene have been linked to early-onset high myopia (eoHM) with a unique X-linked female-limited inheritance. However, the clinical validity of this gene-disease association has not been systematically evaluated.

Methods

We identified two Chinese families with novel ARR3 splicing variants associated with eoHM. Minigene constructs were generated to assess the effects of the variants on splicing. We integrated previous evidence to curate the clinical validity of ARR3 and eoHM using the ClinGen framework.

Results

The variants c.39+1G>A and c.100+4A>G were identified in the two families. Minigene analysis showed both variants resulted in abnormal splicing and introduction of premature termination codons. Based on genetic and experimental evidence, the ARR3-eoHM relationship was classified as "definitive."

Conclusions

Our study identified two novel splicing variants of the ARR3 gene linked to eoHM and confirmed their functional validity via minigene assay. This research expanded the mutational spectrum of ARR3 and confirmed the minigene assay technique as an effective tool for understanding variant effects on splicing mechanisms.

A Putative NADPH Oxidase Gene in Unicellular Pathogenic Candida glabrata Is Required for Fungal ROS Production and Oxidative Stress Response

Most previous studies on fungal NADPH oxidases (Nox) focused on multicellular fungi and highlighted the important roles of Nox-derived reactive oxygen species (ROS) in cellular differentiation and signaling communication. However, there are few reports about Nox in unicellular fungi. A novel NOX ortholog, CAGL0K05863g (named CgNOX1), in Candida glabrata was investigated in this study. Deletion of CgNOX1 led to a decrease in both intracellular and extracellular ROS production. In addition, the Cgnox1∆ mutant exhibited hypersensitivity to hydrogen peroxide and menadione. Also, the wild-type strain showed higher levels of both CgNOX1 mRNA expression and ROS production under oxidative stress. Moreover, the absence of CgNOX1 resulted in impaired ferric reductase activity. Although there was no effect on in vitro biofilm formation, the CgNOX1 mutant did not produce hepatic apoptosis, which might be mediated by fungal Nox-derived ROS during co-incubation. Together, these results indicated that the novel NOX gene plays important roles in unicellular pathogenic C. glabrata and its interaction with host cells.