Requirement for Ergosterol in Berberine Tolerance Underlies Synergism of Fluconazole and Berberine against Fluconazole-Resistant Candida albicans Isolates

Abstract

Candida albicans is one of the most common fungal pathogens. Our previous study demonstrated that concomitant use of berberine (BBR) and fluconazole (FLC) showed a synergistic action against FLC-resistant C. albicans in vitro and BBR had a major antifungal effect in the synergism, while FLC played a role of increasing the intracellular BBR concentration. Since the antifungal activity of BBR alone is very weak (MIC > 128 μg/mL), it was assumed that FLC-resistant C. albicans was naturally tolerant to BBR, and this tolerance could be reversed by FLC. The present study aimed to elucidate the mechanism underlying BBR tolerance in FLC-resistant C. albicans and its disruption by FLC. The ergosterol quantitative analysis showed that the BBR monotreatment could increase the content of cellular ergosterol. Real-time RT-PCR revealed a global upregulation of ergosterol synthesis genes in response to BBR exposure. In addition, exogenous ergosterol could decrease intracellular BBR concentration and increase the expression of drug efflux pump genes, further reducing the susceptibility of C. albicans to BBR. Similar to FLC, other antifungal agents acting on ergosterol were able to synergize with BBR against FLC-resistant C. albicans. However, the antifungal agents not acting on ergosterol were not synergistic with BBR. These results suggested that ergosterol was required for BBR tolerance, and FLC could enhance the susceptibility of FLC-resistant C. albicans to BBR by inhibiting ergosterol synthesis.

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

“…This result in agreement with the observation made by Ahmad et al (2010) wherein ergosterol synthesis was inhibited in C. albicans by eugenol and methyl eugenol in a dose dependent manner. Conversely, Xu et al (2017) have reported that the berberine treatment in fluconazole-resistant C. albicans increased the ergosterol content and up regulated the genes involved in ergosterol biosynthesis.…”

Eucalyptal D Enhances the Antifungal Effect of Fluconazole on Fluconazole-Resistant Candida albicans by Competitively Inhibiting Efflux Pump

“…qRT-PCR was carried out on the QuantStudio ® 3 real-time PCR System (Applied Biosystems). Primers used in this study referred to Yi et al (2017) and were listed in Supplementary Table 1. The relative expression levels of target genes were calculated by the 2 −ΔΔ CT method (Livak and Schmittgen, 2001; Rybak et al, 2017).…”

<p>Synergistic Effect of Pseudolaric Acid B with Fluconazole Against Resistant Isolates and Biofilm of <em>Candida tropicalis</em></p>

“…Such similar synergistic phenomenon has been reported on palmatine, berberine, and calcium channel blockers. 17 , 24 , 25 …”

“…Growth curve assay was used to dynamically monitor the synergistic effect of PAB with FLC against planktonic C. tropicalis isolates. 17 The fungal supernatant (10 3 CFU/mL) containing agents (1 µg/mL PAB, 2 µg/mL FLC, and 1µg/mL PAB + 2µg/mL FLC) was grown with constant shaking at 37 ◦ C. The control was free of FLC and PAB. At designated time points (0, 12, 24, 48 h), the cell broths were pipetted out to determine the OD with microplate reader at 495 nm.…”