Antifungal activity and potential mechanism of berberine hydrochloride against fluconazole-resistant Candida albicans

Abstract

<b>Introduction.</b> The emergence of resistance to fluconazole in <i>Candida albicans</i> has made the clinical treatment of this microbe difficult. A potential strategy to address this problem involves diminishing fungal resistance to antimicrobial drugs.<b>Hypothesis.</b> Berberine hydrochloride (BH), the primary active ingredient of the traditional Chinese medicine (TCM) Coptis, inhibits the growth of fluconazole-resistant <i>C. albicans</i> through its action on the high-osmolarity glycerol mitogen-activated protein kinase (HOG-MAPK) pathway.<b>Aim.</b> To examine the effect of BH on the HOG-MAPK pathway to assess the potential molecular mechanism by which BH inhibits fluconazole-resistant <i>C. albicans</i>.<b>Methodology.</b> The minimum inhibitory concentration (MIC) of BH to fluconazole-resistant <i>C. albicans</i> was measured using the broth microdilution approach to determine the concentration of effective drug intervention. Changes in physiological functions regulated by the HOG-MAPK pathway in response to BH treatment were measured, as well as the expression of central signalling pathway genes and key downstream factors by qRT-PCR and Western blotting, respectively.<b>Results.</b> BH inhibited fluconazole-resistant <i>C. albicans</i> and the sensitivity to fluconazole increased after BH treatment. At a concentration of 256 and 64 μg ml^-1 BH may affect key downstream factors that regulate several physiological functions of <i>C. albicans</i> by upregulating the core genes expression of <i>SLN1</i>, <i>SSK2</i>, <i>HOG1</i>, and <i>PBS2</i> in the HOG-MAPK pathway. Upregulation of <i>GPD1</i>, the key gene for glycerol synthesis, increased cell osmotic pressure. BH treatment increased the accumulation of reactive oxygen species by upregulating the expression of the key respiratory metabolism gene <i>ATP11</i> and downregulating the expression of the superoxide dismutase gene <i>SOD2</i>. Furthermore, downregulation of mycelial-specific <i>HWP1</i> hindered the morphological transformation of <i>C. albicans</i> and inhibition of the chitin synthase gene <i>CHS3</i> and the β-(1,3) glucan synthase gene <i>GSC1</i> impaired cytoderm integrity.<b>Conclusion.</b> BH affects multiple target genes in diminishing the resistance of <i>C. albicans</i> strains to fluconazole. This effect may be related to the action of BH on the HOG-MAPK pathway.