Micafungin Enhances the Human Macrophage Response to Candida albicans through β-Glucan Exposure

Physical impediment to sodium houttuyfonate conversely reinforces β-glucan exposure stimulated innate immune response to Candida albicans

Candida albicans is a dimorphic opportunistic pathogen in immunocompromised individuals. We have previously demonstrated that sodium houttuyfonate (SH), a derivative of medicinal herb Houttuynia cordata Thunb, was effective for antifungal purposes. However, the physical impediment of SH by C. albicans β-glucan may weaken the antifungal activity of SH. In this study, the interactions of SH with cell wall (CW), extracellular matrix (EM), CW β-glucan, and a commercial β-glucan zymosan A (ZY) were inspected by XTT assay and total plate count in a standard reference C. albicans SC5314 as well as two clinical fluconazole-resistant strains Z4935 and Z5172. After treatment with SH, the content and exposure of CW β-glucan, chitin, and mannan were detected, the fungal clearance by phagocytosis of RAW264.7 and THP-1 was examined, and the gene expressions and levels of cytokines TNF-ɑ and IL-10 were also monitored. The results showed that SH could be physically impeded by β-glucan in CW, EM, and ZY. This impediment subsequently triggered the exposure of CW β-glucan and chitin with mannan masked in a time-dependent manner. SH-induced β-glucan exposure could significantly enhance the phagocytosis and inhibit the growth of C. albicans. Meanwhile, the SH-pretreated fungal cells could greatly stimulate the cytokine gene expressions and levels of TNF-ɑ and IL-10 in the macrophages. In sum, the strategy that the instant physical impediment of C. albicans CW to SH, which can induce the exposure of CW β-glucan may be universal for C. albicans in response to physical deterrent by antifungal drugs.

The antifungal effect induced by itraconazole in Candida parapsilosis largely depends on the oxidative stress generated at the mitochondria

In Candida parapsilosis, homozygous disruption of the two genes encoding trehalase activity increased the susceptibility to Itraconazole compared with the isogenic parental strain. The fungicidal effect of this azole can largely be counteracted by preincubating growing cells with rotenone and the protonophore 2,4-Dinitrophenol. In turn, measurement of endogenous reactive oxygen species formation by flow cytometry confirmed that Itraconazole clearly induced an internal oxidative stress, which can be significantly abolished in rotenone-exposed cells. Analysis of the antioxidant enzymatic activities of catalase and superoxide dismutase pointed to a moderate decrease of catalase in trehalase-deficient mutant cells compared to the wild type, with an additional increase upon addition of rotenone. These enzymatic changes were imperceptible in the case of superoxide dismutase. Alternative assays with Voriconazole led to a similar profile in the results regarding cell growth and antioxidant activities. Collectively, our data suggest that the antifungal action of Itraconazole on C. parapsilosis is dependent on a functional mitochondrial activity. They also suggest that the central metabolic pathways in pathogenic fungi should be considered as preferential antifungal targets in new research.

Potential of Sulforaphane and Broccoli Membrane Vesicles as Regulators of M1/M2 Human Macrophage Activity

Macrophages have emerged as important therapeutic targets in many human diseases. The aim of this study was to analyze the effect of broccoli membrane vesicles and sulphoraphane (SFN), either free or encapsulated, on the activity of human monocyte-derived M1 and M2 macrophage primary culture. Our results show that exposure for 24 h to SFN 25 µM, free and encapsulated, induced a potent reduction on the activity of human M1 and M2 macrophages, downregulating proinflammatory and anti-inflammatory cytokines and phagocytic capability on C. albicans. The broccoli membrane vesicles do not represent inert nanocarriers, as they have low amounts of bioactive compounds, being able to modulate the cytokine production, depending on the inflammatory state of the cells. They could induce opposite effects to that of higher doses of SFN, reflecting its hormetic effect. These data reinforce the potential use of broccoli compounds as therapeutic agents not only for inflammatory diseases, but they also open new clinical possibilities for applications in other diseases related to immunodeficiency, autoimmunity, or in cancer therapy. Considering the variability of their biological effects in different scenarios, a proper therapeutic strategy with Brassica bioactive compounds should be designed for each pathology.

Development and Evaluation of a Film Forming System Containing Myricetin and Miconazole Nitrate for Preventing Candida albicans Catheter-Related Infection

Background: Candida albicans catheter-related infection (CRI) is a great challenge in clinic now, mainly due to the difficulty in eradicating the biofilms. Purpose: In this study, the mechanism of the antibiofilm effect of myricetin (MY) on C. albicans was illustrated. A film forming system (FFS) containing MY and miconazole nitrate (MN) was developed, optimized, and evaluated. The anti-infection effect of MY+MN@FFS against C. albicans CRI was investigated in vivo. Study Design and Methods: To clarify the mechanism of the action of MY, the influence of MY on each key process of the formation of C. albicans biofilms was evaluated. To deliver MY and MN into the skin and form a drug reservoir on the surface of the skin, the FFS was used as a carrier and MY+MN@FFS was developed, optimized, and evaluated. After preliminary confirmation of drug safety, a percutaneously inserted C. albicans CRI mouse model was established to investigate the in vivo anti-infection effect of MY+MN@FFS by fluorescence microscopy and scanning electron microscopy on the outer surface of the catheters, hematoxylin/eosin staining, and periodic acid-Schiff staining of the mice skin tissues. Results: MY was found to inhibit the morphological transition of C. albicans and the secretion of exopolysaccharides, resulting in a reduction in biofilms. MY+MN@FFS exhibited excellent properties and no irritation to mice skin. In an in vivo anti-infection study, MY+MN@FFS exhibited an excellent preventive effect against percutaneously inserted C. albicans CRI. Conclusion: MY+MN@FFS might be a potential approach for effectively preventing percutaneously inserted C. albicans CRI in clinic.

Echinocandins - structure, mechanism of action and use in antifungal therapy

With increasing number of immunocompromised patients as well as drug resistance in fungi, the risk of fatal fungal infections in humans increases as well. The action of echinocandins is based on the inhibition of β-(1,3)-d-glucan synthesis that builds the fungal cell wall. Caspofungin, micafungin, anidulafungin and rezafungin are semi-synthetic cyclic lipopeptides. Their specific chemical structure possess a potential to obtain novel derivatives with better pharmacological properties resulting in more effective treatment, especially in infections caused by Candida and Aspergillus species. In this review we summarise information about echinocandins with closer look on their chemical structure, mechanism of action, drug resistance and usage in clinical practice. We also introduce actual trends in modification of this antifungals as well as new methods of their administration, and additional use in viral and bacterial infections.

Sodium houttuyfonate enhances the mono-therapy of fluconazole on oropharyngeal candidiasis (OPC) through HIF-1α/IL-17 axis by inhibiting cAMP mediated filamentation in Candida albicans-Candida glabrata dual biofilms

Candida albicans and Candida glabrata are two common opportunistic fungi that can be co-isolated in oropharyngeal candidiasis (OPC). Hypha is a hallmark of the biofilm formation of C. albicans, indispensable for the attachment of C. glabrata, which is seldom in mycelial morphology. Increasing evidence reveals a hypoxic microenvironment in interior fungal biofilms, reminding of a fact that inflammation is usually accompanied by oxygen deprivation. As a result, it is assumed that the disaggregation of hypha-mediated hypoxia of biofilms might be a solution to alleviate OPC. Based on this hypothesis, sodium houttuyfonate (SH), a well-identified traditional herbal compound with antifungal activity, is used in combination with fluconazole (FLU), a well-informed synthesized antimycotics, to investigate their impact on filamentation in C. albicans and C. glabrata dual biofilms and the underlying mechanism of their combined treatment on OPC. The results show that compared with the single therapy, SH plus FLU can inhibit the hyphal growth in the mixed biofilms in vitro, decrease the fungal burden of oral tissues and internal organs, restore mucosal epithelial integrity and function, and reduce hypoxic microenvironment and inflammation in a mice OPC model. The possible mechanism of the combined therapy of SH plus FLU can be attributed to the regulation of HIF-1α/IL-17A axis through direct abrogation of the dual Candida biofilm formation. This study highlights the role of HIF-1α/IL-17A axis and the promising application of SH as a sensitizer of conventional antifungals in the treatment of OPC.

In vitro and in vivo analysis of monotherapy and dual therapy with ethyl caffeate and fluconazole on virulence factors of Candida albicans and systemic candidiasis

OBJECTIVES

Candida albicans is the most clinically prevalent cause of systemic fungal infections in the immunocompromised population. The biofilm-forming ability of C. albicans confers resistance to conventional antifungal agents. The main aim of this study was to investigate the antifungal effects of ethyl caffeate (EC) alone and in combination with fluconazole (FLU) against C. albicans isolates.

METHODS

The single and combined antifungal activities of EC and FLU were evaluated against planktonic and biofilm cells of C. albicans by the checkerboard assay, time-kill test, crystal violet assay, live/dead staining, rhodamine 6G (R6G) efflux analysis and hydrolase activity. Monotherapy and dual therapy of EC and FLU against systemic candidiasis in a mouse model was also evaluated.

RESULTS

The results showed that EC+FLU displayed synergism in 14/26 planktonic C. albicans isolates and 11/26 C. albicans biofilms with fractional inhibitory concentration index (FICI) values ranging between 0.06-0.49 and 0.02-0.38, respectively. Compared with monotherapy, the combination of EC+FLU can markedly inhibit adhesion, yeast-to-hyphae transition, premature and mature biofilm metabolism, hydrolase secretion and drug efflux function of C. albicans Z1407 and Z4935. Moreover, EC can potentiate the antifungal activity of FLU to improve mouse survival, reduce fungal burden and alleviate pathological damage in both C. albicans isolates compared with EC or FLU used alone.

CONCLUSION

EC exhibits a moderate antifungal potential but can be a strong synergist with FLU against C. albicans, highlighting the potential of EC in clinical antifungal therapy as a sensitiser.

Paeonol assists fluconazole and amphotericin B to inhibit virulence factors and pathogenicity of Candida albicans

This study aimed to evaluate the mono- and dual- antifungal activities of paeonol (PAE) and fluconazole (FLZ)/amphotericin B (AmB). To this end, the effects of PAE and FLZ/AmB on cell surface hydrophobicity, hydrolase activity, morphological transition were investigated in vitro and in a Galleria mellonella infection model. The results showed a relatively high minimum inhibitory concentration (MIC) and sessile MIC (SMIC) of PAE alone. However, compared with the single drug, the combined use of PAE and FLZ/AmB had a potent synergistic potential to inhibit the virulence factors for Candida. The concomitant use of two drugs was consistently more effective than either drug alone for increasing survival rate, decreasing the fungal burden, and alleviating the pathological features of G. mellonella infected by the fungus. Taken together, these findings demonstrate the anti-Candida effects of PAE plus FLZ/AmB and their potential to increase the sensitivity of C. albicans to FLZ/AmB of PAE.

Intermittent micafungin for prophylaxis in a rat model of chronic Candida albicans gut colonization

BACKGROUND

During antifungal prophylaxis, micafungin is generally infused IV once daily over 1 h. In practice, less-frequent dosing could improve the quality of life in patients requiring long-term treatment or prophylaxis. The feasibility of this approach was assessed using humanized doses of daily or infrequent micafungin regimens.

OBJECTIVES

To evaluate the effectiveness of intermittent high-dose micafungin, simulating human exposure, for prophylaxis of invasive candidiasis in a rat model of chronic Candida albicans gastrointestinal colonization and systemic dissemination.

METHODS

Two weeks post-infection with an oral challenge of C. albicans, Sprague-Dawley rats were immunocompromised with a cytotoxic drug and a steroid. Rats received IV infusions of: daily vehicle control; daily subcutaneous micafungin (20 mg/kg SC); high-dose micafungin (20 mg/kg bolus SC + 80 mg/kg infusion/72 h, to simulate intermittent human dosing of 300 mg/72 h); or daily fluconazole by mouth (10 mg/kg PO). The effects of antifungal prophylaxis on faecal fungal burden and systemic C. albicans dissemination were evaluated.

RESULTS

A rat model of chronic C. albicans gastrointestinal colonization and systemic dissemination was established, characterized by a sustained microbiological burden over 29 days and fungal recovery from normally sterile tissues. Using this model, intermittent high-dose micafungin (delivered via iPrecio pumps) to simulate humanized doses of 300 mg/72 h was significantly more effective than vehicle control, as effective as once-daily micafungin and similar to daily fluconazole at reducing faecal burden and preventing systemic dissemination.

CONCLUSIONS

These data indicate that intermittent high-dose micafungin can be as effective as daily therapy, supporting clinical assessment in high-risk patients requiring long-term antifungal prophylaxis.

Sodium houttuyfonate attenuates dextran sulfate sodium associated colitis precolonized with Candida albicans through inducing β-glucan exposure

Inflammatory bowel disease (IBD) including Crohn's disease and ulcerative colitis is a chronic intestinal disease most likely associated with gut dysbiosis. Candida related mycobiota has been demonstrated to play a role in IBD progression. Traditional Chinese herbal medicines (TCHMs) with antifungal activity have a potential in prevention and treatment of fungi-related IBD. Sodium houttuyfonate (SH) is a promising anti-Candida TCHMs. In this study, a dextran sulfate sodium induced colitis model with Candida albicans precolonization is established. SH gavage can significantly decrease the fungal burdens in feces and colon tissues, reduce disease activity index score, elongate colon length, and attenuate colonic damages. Moreover, SH markedly inhibits the levels of anti-Saccharomyces cerevisiae antibodies, β-glucan, and proinflammatory cytokine (IL-1β, IL-6, IL-8, TNF-α), and increases anti-inflammatory factor IL-10 level in serum and colon tissue. Further experiments demonstrate that SH could induce β-glucan exposure, priming intestinal macrophages to get rid of colonized C. albicans through the collaboration of Dectin-1 and TLR2/4. With the decreased fungal burden, the protein levels of Dectin-1, TLR2, TLR4, and NF-κBp65 are fallen back, indicating the primed macrophages calm down and the colitis is alleviated. Collectively, these results manifest that SH can attenuate C. albicans associated colitis via β-glucan exposure, deepening our understanding of TCHMs in the prevention and treatment of fungi associated IBD.

Antifungal evaluation of traditional herbal monomers and their potential for inducing cell wall remodeling in Candida albicans and Candida auris

Traditional herbal monomers (THMs) are widely distributed in many traditional Chinese formulas (TCFs) and decoctions (TCDs) and are frequently used for the prevention and treatment of fungal infections. The antifungal activities of five common THMs, including sodium houttuyfonate (SH), berberine (BER), palmatine (PAL), jatrorrhizine (JAT) and cinnamaldehyde (CIN), and their potential for inducing cell wall remodeling (CWR), were evaluated against Candida albicans SC5314 and Candida auris 12372. SH/CIN plus BER/PAL/JAT showed synergistic antifungal activity against both Candida isolates. Furthermore, SH-associated combinations (SH plus BER/PAL/JAT) induced stronger exposure of β-glucan and chitin than their counterparts, while CIN triggered more marked exposure compared with CIN-associated combinations (CIN plus BER/PAL/JAT). Collectively, this study demonstrated the anti-Candida effect and the CWR induction potential of the five THMs and their associated combinations, providing a possibility of their in vivo application against fungal-associated infections.

Physical Interaction of Sodium Houttuyfonate With β-1,3-Glucan Evokes Candida albicans Cell Wall Remodeling

Candida albicans is a commonly isolated opportunistic yeast and can endanger immune-compromised human health. As increasingly isolated strains present resistance to currently used antifungals, it is necessary to develop novel antimycotics. In a previous study, sodium houttuyfonate (SH) alone or in combination with fluconazole revealed relatively strong antifungal potential against C. albicans, and the underlying mechanism might be likely to be associated with β-glucan synthesis and transportation (Shao et al., 2017). In the present experiment, we used a standard C. albicans isolate and a phr1 mutant (phr1−/−) to investigate the interaction of SH with β-glucan, one of the critical components in cell wall and biofilm matrix. We showed that lyticase was the most effective enzyme that could significantly increase the antifungal inhibition of SH at 64 μg/mL in C. albicans SC5314 but became futile in phr1−/−. Although the minimum inhibitory concentrations (MICs) of SH were comparable in the two Candida strains used, phr1−/− appeared to be more susceptible to SH compared with C. albicans SC5314 in biofilms (64 versus 512 μg/mL). The peak areas of SH decreased markedly by 71.6, 38.2, and 62.6% in C. albicans SC5314 and by 70% and 53.2% in phr1−/− by ultra-performance liquid chromatography (UPLC) analysis after co-incubation of SH with laminarin, extracellular matrix (EM) and cell wall. The chitin appeared to not interact with SH. We further demonstrated that sub-MIC SH (8 μg/mL) was able to induce cell wall remodeling by unmasking β-1,3-glucan and chitin in both C. albicans SC5314 and phr1−/−. Based on these findings, we propose that β-1,3-glucan can block the entrance of SH through non-specific absorption, and then the fungus senses the interaction of SH with β-1,3-glucan and exposes more β-1,3-glucan that contributes to SH blocking in turn.