Lack of Functional Trehalase Activity in Candida parapsilosis Increases Susceptibility to Itraconazole

Abstract

Central metabolic pathways may play a major role in the virulence of pathogenic fungi. Here, we have investigated the susceptibility of a Candida parapsilosis mutant deficient in trehalase activity (atc1Δ/ntc1Δ strain) to the azolic compounds fluconazole and itraconazole. A time-course exposure to itraconazole but not fluconazole induced a significant degree of cell killing in mutant cells compared to the parental strain. Flow cytometry determinations indicated that itraconazole was able to induce a marked production of endogenous ROS together with a simultaneous increase in membrane potential, these effects being irrelevant after fluconazole addition. Furthermore, only itraconazole induced a significant synthesis of endogenous trehalose. The recorded impaired capacity of mutant cells to produce structured biofilms was further increased in the presence of both azoles, with itraconazole being more effective than fluconazole. Our results in the opportunistic pathogen yeast C. parapsilosis reinforce the study of trehalose metabolism as an attractive therapeutic target and allow extending the hypothesis that the generation of internal oxidative stress may be a component of the antifungal action exerted by the compounds currently available in medical practice.

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

“…3 . As it has been previously reported (Sánchez-Fresneda et al 2022 ) the atc1Δ/ntc1Δ mutant produced a lower basal level of endogenous ROS (Fig. 3 ).…”

“…Furthermore, the atc1Δ/ntc1Δ null mutant always displayed higher susceptibility to ITC respect to the parental strain (Fig. 2 ; Sánchez-Fresneda et al 2022 ). Hence, these results suggest that the antifungal effect triggered by ITC on C. parapsilosis is, at least in part, dependent on a functional mitochondrial activity.…”

“…It has previously shown that treatment with Itraconazole (ITC) induced a significant toxic action on YPD-grown exponential cells of C. parapsilosis , recorded both as a decrease in the percentage of cell viability and the macroscopic formation of colonies (Sánchez-Fresneda et al 2022 ). Indeed, the addition of 0.3 µg/ml ITC (equivalent 2 × MIC) also caused a prominent time-course reduction of the optical density (Fig.…”

“…1 ), suggesting that several azoles share a similar pattern of toxicity against C. parapsilosis . Although no experiments were followed beyond 24 h here, exposed cells were able to resume active growth after that time, since these compounds are essentially fungistatic (Sánchez-Fresneda et al 2022 ).…”

“…Thus, the homozygous atc1Δ/ntc1Δ null mutant, besides its inability to mobilize trehalose, displays a pleiotropic phenotype that includes the impairment of cell growth, resistance to nutrient starvation and oxidative stress, together with a reduction of virulence and the capacity to form biofilms (Sánchez-Fresneda et al 2015 ). A recent analysis of azole susceptibility showed that atc1Δ/ntc1Δ cells were more sensitive to itraconazole (ITC) than the parental strain (Sánchez-Fresneda et al 2022 ). We report here that the ITC-induced fungicidal effect is dependent on a functional mitochondrial activity.…”