WMR Peptide as Antifungal and Antibiofilm against Albicans and Non-Albicans Candida Species: Shreds of Evidence on the Mechanism of Action

Abstract

Candida species are the most common fungal pathogens infecting humans and can cause severe illnesses in immunocompromised individuals. The increased resistance of Candida to traditional antifungal drugs represents a great challenge in clinical settings. Therefore, novel approaches to overcome antifungal resistance are desired. Here, we investigated the use of an antimicrobial peptide WMR against Candida albicans and non-albicans Candida species in vitro and in vivo. Results showed a WMR antifungal activity on all Candida planktonic cells at concentrations between 25 μM to >50 μM and exhibited activity at sub-MIC concentrations to inhibit biofilm formation and eradicate mature biofilm. Furthermore, in vitro antifungal effects of WMR were confirmed in vivo as demonstrated by a prolonged survival rate of larvae infected by Candida species when the peptide was administered before or after infection. Additional experiments to unravel the antifungal mechanism were performed on C. albicans and C. parapsilosis. The time-killing curves showed their antifungal activity, which was further confirmed by the induced intracellular and mitochondrial reactive oxygen species accumulation; WMR significantly suppressed drug efflux, down-regulating the drug transporter encoding genes CDR1. Moreover, the ability of WMR to penetrate within the cells was demonstrated by confocal laser scanning microscopy. These findings provide novel insights for the antifungal mechanism of WMR against Candida albicans and non-albicans, providing fascinating scenarios for the identification of new potential antifungal targets.

Competitiveness during Dual-Species Biofilm Formation of Fusarium oxysporum and Candida albicans and a Novel Treatment Strategy

“…The susceptibility of F. oxysporum and C. albicans planktonic cells to antifungal agents is shown in Table 1. While WMR exhibited good antifungal activity against C. albicans, as also reported in our previous study [17], the complete growth inhibition of F. oxysporum was not found since MIC values were higher than 150 µM. All the two species indiscriminately showed high MIC values for fluconazole > 150 µM (corresponding to 46 µg mL −1 ).…”

“…WMR (NH 2 -WGIRRILKYGKRSK-CONH 2 ) was synthesized based on ultrasonicassisted solid-phase peptide synthesis (US-SPPS) methodology) as previously reported [17]. Briefly, Fmoc deprotection (20% piperidine in dimethylformamide (DMF, Merk Life Science S.r.l., Milano, Italy), 0.5 + 1 min) and the coupling (HOBt/HBTU, purchased by Merk Life Science S.r.l., Milano, Italy as additive reagents (3 equiv), and DIPEA (purchased by Merk Life Science S.r.l., Milano, Italy 6 equiv) as basis, 2 × 10 min) reactions, were cyclically performed until the obtainment of peptide sequence.…”

“…Efficacy of WMR and FLC, alone or in combination, in G. mellonella larvae infected with C. albicans, F. oxysporum, or the mixture of the two species, was evaluated by survival assays, as described previously [17].…”

“…Therefore, AMPs have been considered a promising treatment option to combat the increasing number of drug-resistant pathogens. The WMR peptide, a modified version of the myxinidin sequence developed in our laboratory, has shown a high antimicrobial activity not only against Gram-positive and Gram-negative bacteria [16] but also antifungal activity against several Candida species [17]. WMR displays a versatile mechanism of action that varies from cell membrane damage to interactions with intracellular targets, and it is also effective towards biofilms.…”

COVID-19-Associated Fungal Infections: An Urgent Need for Alternative Therapeutic Approach?

“…Myxidin, originated from the epidermal mucus of hagfish ( Myxine glutinosa L.), was modified (WMR) by Maione et al (2022) to increase the number of positively charged amino acids in the original sequence. The peptide previously represented antimicrobial activity against Gram-positive and Gram-negative bacteria.…”