Curcumin potentiates the fungicidal effect of dodecanol by inhibiting drug efflux in wild‐type budding yeast

Drug resistance commonly occurs when treating immunocompromised patients who have fungal infections. Curcumin, is a compound isolated from Curcuma longa, has been reported to inhibit drug efflux in several human cell lines and nonpathogenic budding yeast Saccharomyces cerevisiae cells that overexpresses the ATP‐binding cassette (ABC) transporters S. cerevisiae Pdr5p and pathogenic Candida albicans Cdr1p and Cdr2p. The aim of this study was to examine the effects of curcumin on multidrug resistance in a wild‐type strain of the budding yeast with an intrinsic expression system of multidrug efflux‐related genes. The antifungal activity of dodecanol alone was temporary against S. cerevisiae; however, restoration of cell viability was completely inhibited when the cells were co‐treated with dodecanol and curcumin. Furthermore, restriction of rhodamine 6G (R6G) efflux from the cells and intracellular accumulation of R6G were observed with curcumin treatment. Reverse transcription‐polymerase chain reaction analysis revealed that curcumin reduced the dodecanol‐induced overexpression of the ABC transporter‐related genes PDR1, PDR3 and PDR5 to their control levels in untreated cells. Curcumin can directly restrict the glucose‐induced drug efflux and inhibits the expression of the ABC transporter gene PDR5, and can thereby inhibit the efflux of dodecanol from S. cerevisiae cells. Curcumin is effective in potentiating the efficacy of antifungal drugs via its effects on ABC transporters. SIGNIFICANCE AND IMPACT OF THE STUDY: Drug resistance is common in immunocompromised patients with fungal infections. Curcumin, isolated from Curcuma longa, inhibits drug efflux in nonpathogenic budding yeast Saccharomyces cerevisiae cells overexpressing ABC transporters S. cerevisiae Pdr5p and pathogenic Candida albicans Cdr1p and Cdr2p. We examined the effects of curcumin on multidrug resistance in a wild‐type strain of the budding yeast with an intrinsic expression system of multidrug efflux‐related genes. Curcumin directly inhibited drug efflux and also suppressed the PDR5 expression, thereby enhancing the antifungal effects. Thus, curcumin potentially promotes the efficacy of antifungals via its effects on ABC transporters in wild‐type fungal strains.