Antifungal Activity and Potential Mechanism of N-Butylphthalide Alone and in Combination With Fluconazole Against Candida albicans

Abstract

Candida albicans is a common opportunistic fungal pathogen that may cause nosocomial fungal infections. The resistance of Candida albicans to traditional antifungal drugs has been increasing rapidly in recent years, and it brings a great challenge in clinical treatment. N-butylphthalide is originally extracted from the seed of Apium graveolens and is currently used for the treatment of ischemic stroke in the clinic. This study demonstrated that n-butylphthalide exhibited antifungal activity against Candida albicans with minimum inhibitory concentrations of 128 μg/ml; moreover, n-butylphthalide combined with fluconazole showed synergistic antifungal effects against resistant Candida albicans , resulting in a decrease in the minimum inhibitory concentrations of fluconazole from >512 to 0.25–1 μg/ml. Time-killing curves verified the antifungal activity in dynamic. Besides, n-butylphthalide exhibited anti-biofilm activity against Candida albicans , biofilms preformed <12 h with sessile minimum inhibitory concentrations of 128–256 μg/ml and synergism was observed when n-butylphthalide combined with fluconazole against resistant Candida albicans biofilms preformed <12 h, resulting in a decrease in the sessile minimum inhibitory concentrations of fluconazole from >1,024 to 0.5–8 μg/ml. Furthermore, in vitro antifungal effects of n-butylphthalide were confirmed in vivo . N-butylphthalide prolonged survival rate of larvae infected by Candida albicans , reduced the fungal burden in larvae and caused less damage to larval tissues. Notably, n-butylphthalide inhibited hyphal growth and induced intracellular reactive oxygen species accumulation and a loss in mitochondrial membrane potential, which was a potential antifungal mechanism. Besides, the synergistic effects between n-butylphthalide and fluconazole potentially relied on the mechanism that n-butylphthalide significantly promoted drug uptake, and suppressed drug efflux via down-regulating the drug transporter encoding genes CDR1 and CDR2 . These findings demonstrated the antifungal effects and mechanisms of n-butylphthalide against Candida albicans for the first time, which might provide broad prospects for the identification of new potential antifungal targets.

Antifungal Activity and Potential Mechanism of Panobinostat in Combination With Fluconazole Against Candida albicans

“…The hyphal growth and the overexpression of drug efflux pumps are both major mechanisms of drug resistance ( Nobile and Johnson, 2015 ). According to a series of previous researches, some drugs had synergistic effects with FLC against C. albicans strains because the combination could inhibit adhesion, inhibit hyphal formation, and suppress drug efflux ( Gong et al, 2019b ; Li Y. et al, 2019 ; Dwivedi et al, 2020 ). We previously studied the azole resistance of the strains in this study that was associated with overexpression of efflux pumps and high production of biofilms ( Li et al, 2016 ; Lu et al, 2018 ; Gong et al, 2019b ).…”

“…Plates were incubated at 35°C for 24 h. The growth inhibition was determined by an XTT reduction assay, and the optical density was determined at 492 nm using a microplate reader. The MIC was defined as the lowest concentration required to support 80% growth inhibition compared with the growth in the control group ( Khan and Ahmad, 2012 ; Gong et al, 2019b ; Li Y. et al, 2019 ). The fractional inhibitory concentration index (FICI) was used to assess the in vitro interaction of the drug combination ( Odds, 2003 ).…”

“…According to a series of previous researches, some drugs had synergistic effects with FLC against C. albicans strains because the combination could inhibit adhesion, inhibit hyphal formation, and suppress drug efflux (Gong et al, 2019b;Dwivedi et al, 2020). We previously studied the azole resistance of the strains in this study that was associated with overexpression of efflux pumps and high production of biofilms Lu et al, 2018;Gong et al, 2019b). Based on these studies, we first measured the effects of the drug combination on hyphal growth.…”

“…Combination drug therapy is a promising strategy to increase effectiveness of antifungals and alleviate the emergence of drug resistance ( Spitzer et al, 2017 ; Arita et al, 2019 ). Over the past few years, many efforts have been made to prove that drug combination is an optional approach for overcoming drug resistance and treatment of invasive fungal infections, and the results indicate that non-antifungal drugs can significantly increase the sensitivity of azoles regardless of whether they have antifungal effects or not by themselves ( Li et al, 2017 ; Li Y. et al, 2019 ; Gong et al, 2019b ).…”

SWL-1 Reverses Fluconazole Resistance in Candida albicans by Regulating the Glycolytic Pathway

“…Thus, new therapeutic drugs and antifungal methods are urgently required. Efflux pump-mediated resistance is the most ubiquitous pathway among the variety of molecular mechanisms underlying fungal resistance (Kontoyiannis, 2000;Gong et al, 2019). The efflux protein mainly comprises two different types proteins.…”