Chloroquine Alone and Combined with Antifungal Drug Against Candida albicans Biofilms In Vitro and In Vivo via Autophagy Inhibition.

OBJECTIVES

Candida albicans (C. albicans) is a common opportunistic fungal pathogen that poses a serious threat to human health. Autophagy inhibition decreased the resistance of C. albicans. This study investigated the antifungal activity of autophagy inhibitor chloroquine (CQ) against C. albicans biofilms and its synergistic potential with antifungal drug, and the underlying mechanisms.

METHODS

The inhibitory effect of CQ on C. albicans biofilms was determined using the XTT assay. The interactions between CQ and antifungal drugs were evaluated using the FICI and ΔE models. The in vivo efficacy and biosafety were assessed in a murine model with oral candidiasis. The antifungal effects were further evaluated through time-kill assays, live/dead staining, and scanning electron microscopy. The autophagic regulation was analyzed using the expression of autophagy-related genes and proteins, reactive oxygen species (ROS), and alkaline phosphatase (ALP), and an ATG9 deletion strain was used to confirm the involvement.

RESULTS

CQ exhibited antifungal activity against both standard and drug-resistant C. albicans strains, and showed significant synergy with amphotericin B (AmB). In vivo, CQ alone or in combination with AmB effectively against oral candidiasis in mice with good biosafety. Mechanistically, CQ alone or combined with AmB downregulated autophagy-related gene and protein expression, elevated ROS levels, and suppressed ALP activity. Consistently, ATG9 deletion reduced CQ efficacy in vitro and vivo, confirming CQ's antifungal effect via autophagy inhibition.

CONCLUSIONS

CQ enhances antifungal activity against C. albicans biofilms in vitro and in vivo by inducing oxidative stress and inhibiting autophagy, and exhibits synergistic effects with AmB.