Study on the mechanisms of action of berberine combined with fluconazole against fluconazole-resistant strains of Talaromyces marneffei

Inhibitory effects of berberine on fungal growth, biofilm formation, virulence, and drug resistance as an antifungal drug and adjuvant with prospects for future applications

Berberine (BBR), an isoquinoline alkaloid found in medicinal plants such as Coptidis rhizoma, Berberis sp., and Hydrastis canadensis, is a distinctive compound known for its dual ability to exhibit broad-spectrum antifungal activity while offering beneficial effects to the host. These attributes make it a highly valuable candidate for antifungal therapy and as an antibiotic adjuvant. This review provides a comprehensive evaluation of BBR's antifungal properties, focusing on its in vitro and in vivo activity, underlying mechanisms, and its influence on fungal pathogenicity, including virulence, biofilm formation, and resistance. Additionally, the antifungal potential of BBR extracts, derivatives, and nanoformulations is examined in detail. BBR demonstrates fungicidal effects through multiple mechanisms. It targets critical fungal components such as mitochondria, cell membranes, and cell walls, while also inhibiting enzymatic activity and transcription processes. Furthermore, it suppresses the expression of virulence factors, effectively diminishing fungal pathogenicity. Beyond its direct antifungal activity, BBR exerts beneficial effects on the host by modulating gut microbiota, thereby bolstering host defenses against fungal infections and reducing potential adverse effects. BBR's interaction with conventional antifungal drugs presents a unique complexity, particularly in the context of resistance mechanisms. When used in combination therapies, conventional antifungal drugs enhance the intracellular accumulation of BBR, thereby amplifying its antifungal potency as the primary active agent. These synergistic effects position BBR as a promising candidate for combination strategies, especially in addressing drug-resistant fungal infections and persistent biofilms. As antifungal resistance and biofilm-associated infections continue to rise, the multifaceted properties of BBR and its advanced formulations highlight their significant therapeutic potential. However, the scarcity of robust in vivo and clinical studies limits a full understanding of its efficacy and safety profile. To bridge this gap, future investigations should prioritize well-designed in vivo and clinical trials to thoroughly evaluate the therapeutic effectiveness and safety of BBR in diverse clinical settings. This approach could pave the way for its broader application in combating fungal infections.

Antifungal activity of bamemacrolactine C against Talaromyces marneffei and its possible mechanisms of action

AIMS

The present study aims to investigate the in vitro antifungal activity and mechanism of action of bamemacrolactine C (BAC), a new 24-membered macrolide compound, against Talaromyces marneffei.

METHODS AND RESULTS

The test drug BAC initially demonstrated antifungal activity through a paper disk diffusion assay, followed by determination of the minimum inhibitory concentration value of 35.29 μg ml-1 using microdilution. The association study revealed that combination therapy exhibited additive effects (0.5 < FICI < 1.0) when combined BAC with either amphotericin B or fluconazole. A time-growth assay confirmed that treatment with 35.29 μg ml-1 of BAC completely inhibited the growth of T. marneffei and exhibited antifungal effects. Micromorphological analysis using scanning electron microscopy and transmission electron microscopy photomicrographs revealed that BAC treatment induced morphological damage in fungal cells compared to the control group. Transmembrane protein assays showed a significant reduction in the levels of Na+/K+-ATPase (P < .05) and Ca2+-ATPase (P < .01) compared to the control group. Intracellular enzyme assays demonstrated that BAC treatment significantly decreased ATP, malate dehydrogenase, and succinate dehydrogenase content (P < .01). The combination of proteomics and parallel reaction monitoring (PRM) verification indicated that BAC exhibits an antifungal mechanism against T. marneffei by downregulating ATP citric acid lyase (ACLY) levels , potentially affecting the tricarboxylic acid (TCA) cycle. Besides, the binding model of BAC and the ACLY also shows a good docking score.

CONCLUSIONS

The findings suggest that BAC exhibits antifungal activity against T. marneffei, elucidating its multifaceted mechanism of action involving disruption of cell membranes' integrity and inhibition of intracellular enzyme activities, in which the modulation of ACLY in the TCA cycle may play an important role.

Diagnosis of Human Endemic Mycoses Caused by Thermally Dimorphic Fungi: From Classical to Molecular Methods

Human endemic mycoses are potentially fatal diseases caused by a diverse group of fungi that can alter their morphology in response to an increase in temperature. These thermally dimorphic fungi affect both healthy and immunocompromised hosts, causing a substantial health and economic burden. Despite this, the diagnosis of endemic mycoses is still a formidable challenge for several reasons, including similar symptomatology, limited utility of classical diagnostic methods, inaccessibility to reliable molecular approaches in most endemic areas, and a lack of clinical suspicion out of these regions. This review summarizes essential knowledge on thermally dimorphic fungi and the life-threatening diseases they cause. The principle, advantages and limitations of the methods traditionally used for their diagnosis are also described, along with the application status and future directions for the development of alternative diagnostic strategies, which could help to reduce the disease burden in endemic areas.

New Polyene Macrolide Compounds from Mangrove-Derived Strain Streptomyces hiroshimensis GXIMD 06359: Isolation, Antifungal Activity, and Mechanism against Talaromyces marneffei

Mangrove-derived actinomycetes represent a rich source of novel bioactive natural products in drug discovery. In this study, four new polyene macrolide antibiotics antifungalmycin B-E (1-4), along with seven known analogs (5-11), were isolated from the fermentation broth of the mangrove strain Streptomyces hiroshimensis GXIMD 06359. All compounds from this strain were purified using semi-preparative HPLC and Sephadex LH-20 gel filtration while following an antifungal activity-guided fractionation. Their structures were elucidated through spectroscopic techniques including UV, HR-ESI-MS, and NMR. These compounds exhibited broad-spectrum antifungal activity against Talaromyces marneffei with minimum inhibitory concentration (MIC) values being in the range of 2-128 μg/mL except compound 2. This is the first report of polyene derivatives produced by S. hiroshimensis as bioactive compounds against T. marneffei. In vitro studies showed that compound 1 exerted a significantly stronger antifungal activity against T. marneffei than other new compounds, and the antifungal mechanism of compound 1 may be related to the disrupted cell membrane, which causes mitochondrial dysfunction, resulting in leakage of intracellular biological components, and subsequently, cell death. Taken together, this study provides a basis for compound 1 preventing and controlling talaromycosis.