Synthetic organotelluride compounds induce the reversal of Pdr5p mediated fluconazole resistance in Saccharomyces cerevisiae

Abstract

BackgroundResistance to fluconazole, a commonly used azole antifungal, is a challenge for the treatment of fungal infections. Resistance can be mediated by overexpression of ABC transporters, which promote drug efflux that requires ATP hydrolysis. The Pdr5p ABC transporter of Saccharomyces cerevisiae is a well-known model used to study this mechanism of antifungal resistance. The present study investigated the effects of 13 synthetic compounds on Pdr5p.ResultsAmong the tested compounds, four contained a tellurium-butane group and shared structural similarities that were absent in the other tested compounds: a lateral hydrocarbon chain and an amide group. These four compounds were capable of inhibiting Pdr5p ATPase activity by more than 90%, they demonstrated IC50 values less than 2 μM and had an uncompetitive pattern of Pdr5p ATPase activity inhibition. These organotellurides did not demonstrate cytotoxicity against human erythrocytes or S. cerevisiae mutant strains (a strain that overexpress Pdr5p and a null mutant strain) even in concentrations above 100 μM. When tested at 100 μM, they could reverse the fluconazole resistance expressed by both the S. cerevisiae mutant strain that overexpress Pdr5p and a clinical isolate of Candida albicans.ConclusionsWe have identified four organotellurides that are promising candidates for the reversal of drug resistance mediated by drug efflux pumps. These molecules will act as scaffolds for the development of more efficient and effective efflux pump inhibitors that can be used in combination therapy with available antifungals.

Synthetic Organotellurium Compounds Sensitize Drug-Resistant Candida albicans Clinical Isolates to Fluconazole

“…Reis de Sá et al recently demonstrated that synthetic organotellurium compounds also inhibit the fungal multidrug ABC efflux pump S. cerevisiae Pdr5p, a homolog of C. albicans Cdr1p (27). The present study is an extension of that study ]).…”

“…The chemosensitization assays were performed as described previously (20,27). In brief, 5-l aliquots of undiluted and three 5-fold serial dilutions of logarithmic (optical density at 600 nm [OD 600 ] ϭ 0.1 ϫ 10 6 or ϳ1 ϫ 10 6 cells/ml) S. cerevisiae cell suspensions were placed onto sterile polystyrene six-well YPD agar plates that were supplemented with synthetic organotellurium compounds in the presence or absence of subinhibitory (ϳ1/2 to ϳ1/4 of the MIC) fluconazole concentrations.…”

“…The inhibitory effects of individual test compounds on the CaCdr1p ATPase activity were assessed as previously described (27). To determine the CaCdr1p-specific ATPase activities …”

“…Examples of Mdr1p inhibitors are cerulenin analogues (24), the monoamine oxidase A inhibitor clorgyline (which inhibits a broad range of fungal ABC multidrug efflux transporters, as well as Mdr1p) (25), and compounds with a core cyclobutene-dione ring (26). A recent study by Reis de Sá et al (27) demonstrated that synthetic organotelluride compounds inhibited the prototype Saccharomyces cerevisiae ABC multidrug efflux pump Pdr5p, a homolog of C. albicans Cdr1p. We sought here to evaluate the inhibitory potential of these organotellurides on the major C. albicans multidrug efflux pumps and to test their ability to reverse the fluconazole resistance of C. albicans clinical isolates known to overexpress variations of these efflux pumps.…”

Characterisation of an ABC transporter of a resistant Candida glabrata clinical isolate

“…Evaluation of azole resistance reversion by FK506 - FK506 is a classical ABC transporter inhibitor ( Egner & Kuchler 2000 ) and is used as a screening for resistance mediated by these efflux proteins. The “spot test” was used as a measure of growth as previously described by ( de Sá et al 2014 ). Screenings of azole resistance concentrations were previously performed in order to observe the highest azole concentrations that did not affect yeast viability.…”