The Catestatin-Derived Peptides Are New Actors to Fight the Development of Oral Candidosis

Abstract

Resistance to antifungal therapy of Candida albicans and non-albicans Candida strains, frequently associated with oral candidosis, is on the rise. In this context, host-defense peptides have emerged as new promising candidates to overcome antifungal resistance. Thus, the aim of this study was to assess the effectiveness against Candida species of different Catestatin-derived peptides, as well as the combined effect with serum albumin. Among Catestatin-derived peptides, the most active against sensitive and resistant strains of C. albicans, C. tropicalis and C. glabrata was the D-isomer of Cateslytin (D-bCtl) whereas the efficiency of the L-isomer (L-bCtl) significantly decreases against C. glabrata strains. Images obtained by transmission electron microscopy clearly demonstrated fungal membrane lysis and the leakage of the intracellular material induced by the L-bCtl and D-bCtl peptides. The possible synergistic effect of albumin on Catestatin-derived peptides activity was investigated too. Our finding showed that bovine serum albumin (BSA) when combined with the L- isomer of Catestatin (L-bCts) had a synergistic effect against Candida albicans especially at low concentrations of BSA; however, no synergistic effect was detected when BSA interacted with L-bCtl, suggesting the importance of the C-terminal end of L-bCts (GPGLQL) for the interaction with BSA. In this context in vitro D-bCtl, as well as the combination of BSA with L-bCts are potential candidates for the development of new antifungal drugs for the treatment of oral candidosis due to Candida and non-Candida albicans, without detrimental side effects.

Keywords: Catestatin; antifungal; antimicrobial peptides; candidosis; resistance.

Figure 1

Transmission electron microscopy images of cells from “S” C. albicans, treated with D-bCtl or L-bCtl at different concentrations, compared to untreated cells. D-bCtl or L-bCtl were used at concentrations of 1 × MIC and 10 × MIC and incubated for 1 h at 37 °C with minimal shaking. White stars indicate which cell is magnified at 10,000×. Black arrows localize lysed cells.

Figure 2

Transmission electron microscopy images of cells from a resistant strain of Candida albicans, treated with D-Ctl or L-Ctl at different concentrations, compared to untreated cells. D-Ctl or L-Ctl were used at concentrations of 1 × MIC and 10 × MIC and incubated for 1 h at 37 °C with minimal shaking. White stars indicate which cell is magnified at 10,000×. Black arrows localize lysed cells.

Figure 3

Antimicrobial activity of L-bCtl and L-bCts with BSA against C. albicans. BSA was used with a molar concentration of 30, 6, and 1.5 nM for Ctl (1 µM) or 120, 24 and 6 nM for L-bCts (4 µM). The growth inhibition of BSA (controls) is reported only for the concentrations used with L-bCts where we obtained synergistic antimicrobial effects. No antimicrobial effects were obtained for BSA combined with L-bCtl., *** p ≤ 0.001 with 1 way ANOVA comparing peptide only to BSA plus peptide treatments.

Figure 4

Non-toxicity of BSA/L-bCts complex. Hemolytic assays of erythrocytes with BSA (120, 24, and 6 nM) plus L-bCts (40 and 80 µM). All the treatments were statistically significant compared to the positive control of the hemolytic test with One way ANOVA.

Figure 5

Quartz Crystal Microbalance (QCM) analysis of the interaction BSA with L-bCts or L-bCtl. The analysis was performed at 37 °C in PBS pH 7.2 with a first injection of 2 mg/mL BSA (400 µL,) and a second injection of 1 mg/mL L-bCts or L-bCtl (400 µL).