Synergistic Effects of Cepharanthine and Amphotericin B Against Candida Albicans by Targeting PMP3-Mediated Sphingolipid Biosynthesis and Membrane Disruption

Candida albicans is a major opportunistic fungal pathogen causing various mucosal infections, including oral candidiasis, poses challenges in current antifungal therapy because of limited number of drugs, increased pathogen resistance, and notable toxicity associated with existing medications. Combination therapy is crucial for optimizing treatment outcomes. In this study, cepharanthine (CEP) was explored as an adjunct to amphotericin B (AmB) to elucidate the potential mechanism of action of drug combinations against Candida albicans. The minimum inhibitory concentration (MIC) was determined using the checkerboard method, and the fractional inhibitory concentration index (FICI) was computed. The combination of cepharanthine and amphotericin B had a synergistic effect (FICI < 0.5) on both standard strains and 73 clinical strains of Candida albicans, leading to significant inhibition of metabolism, hyphal growth, and biofilm formation. Transcriptome sequencing, membrane permeability studies, assessment of mitochondrial membrane potential, and scanning electron microscopy revealed that cepharanthine primarily targeted the membrane structure of Candida albicans. RT‒qPCR analysis demonstrated that cepharanthine in combination with amphotericin B suppressed sphingolipid synthesis by downregulating the expression of the plasma membrane-associated gene PMP3, thereby compromising cell membrane integrity. Molecular docking model analysis further supported the binding affinity of both drugs to the PMP3 protein. The combined use of cepharanthine and amphotericin B presents a promising approach for the clinical management of oral candidiasis.