Synergistic action of synthetic peptides and amphotericin B causes disruption of the plasma membrane and cell wall in Candida albicans

The objective of this work was to evaluate the combination of synthetic peptides based on the gamma-core motif of defensin PvD1 with amphotericin B (AmB) at different concentrations against Candida albicans. We applied the checkerboard assay using different concentrations of the commercial drug AmB and the synthetic peptides gamma 31-45PvD1++ and gamma 33-41PvD1++ against C. albicans, aiming to find combinations with synergistic interactions. Between these two interactions involving gamma 31-45PvD1++ and AmB, an additive effect was observed. One such interaction occurred at concentrations of 0.009 mu M of peptide gamma 31-45PvD1++ and 13.23 mu M of AmB and another condition of 0.019 mu M of peptide gamma 31-45PvD1++ and 6.61 mu M of AmB. The other two concentrations of the interaction showed a synergistic effect in the combination of synthetic peptide gamma 31-45PvD1++ and AmB, where the concentrations were 1.40 mu M peptide gamma 31-45PvD1++ and 0.004 mu M AmB and 0.70 mu M gamma 31-45PvD1++ peptide and 0.002 mu M AmB. We proceeded with analysis of the mechanism of action involving synergistic effects. This examination unveiled a range of impactful outcomes, including the impairment of mitochondrial functionality, compromise of cell wall integrity, DNA degradation, and a consequential decline in cell viability. We also observed that both synergistic combinations were capable of causing damage to the plasma membrane and cell wall, causing leakage of intracellular components. This discovery demonstrates for the first time that the synergistic combinations found between the synthetic peptide gamma 31-45PvD1++ and AmB have an antifungal effect against C. albicans, acting on the integrity of the plasma membrane and cell wall.