Abstract
BackgroundThionins are a family of plant antimicrobial peptides (AMPs), which participate in plant defense system against pathogens. Here we describe some aspects of the CaThi thionin-like action mechanism, previously isolated from Capsicum annuum fruits. Thionin-like peptide was submitted to antimicrobial activity assays against Candida species for IC50 determination and synergism with fluconazole evaluation. Viability and plasma membrane permeabilization assays, induction of intracellular ROS production analysis and CaThi localization in yeast cells were also investigated.ResultsCaThi had strong antimicrobial activity against six tested pathogenic Candida species, with IC50 ranging from 10 to 40 μg.mL−1. CaThi antimicrobial activity on Candida species was candidacidal. Moreover, CaThi caused plasma membrane permeabilization in all yeasts tested and induces oxidative stresses only in Candida tropicalis. CaThi was intracellularly localized in C. albicans and C. tropicalis, however localized in nuclei in C. tropicalis, suggesting a possible nuclear target. CaThi performed synergistically with fluconazole inhibiting all tested yeasts, reaching 100 % inhibition in C. parapsilosis. The inhibiting concentrations for the synergic pair ranged from 1.3 to 4.0 times below CaThi IC50 and from zero to 2.0 times below fluconazole IC50.ConclusionThe results reported herein may ultimately contribute to future efforts aiming to employ this plant-derived AMP as a new therapeutic substance against yeasts.
Highlights
Thionins are a family of plant antimicrobial peptides (AMPs), which participate in plant defense system against pathogens
The most susceptible species to Capsicum annuum Thionin (CaThi) were C. buinensis, C. parapsilosis and C. albicans with 99.2, 98.9 and 80.3 % of viability loss, respectively, and the less susceptible was C. tropicalis with 47.9 % of viability loss (Fig. 1b). These results indicated that inhibitory effect of CaThi was candidacidal
Prompted by the considerable increase in the incidence of human infections by Candida species, we investigated the potential of CaThi, a plant-derived thionin peptide, as a novel therapeutic drug against six Candida strains of clinical interest: C. albicans, C. tropicalis, C. parapsilosis, C. pelliculosa, C. buinensis, and C. mogii
Summary
Thionins are a family of plant antimicrobial peptides (AMPs), which participate in plant defense system against pathogens. Thionin-like peptide was submitted to antimicrobial activity assays against Candida species for IC50 determination and synergism with fluconazole evaluation. A significant global public health threat is the emergence of pathogenic bacteria, fungi, and yeasts that are resistant to multiple antimicrobial agents. Alternatives to chemotherapies include antimicrobial peptides (AMPs), small molecules produced by all living organisms, which have gained considerable attention. Promising AMPs include plant-derived thionins, a family of basic, low molecular weight (~5 kDa), cysteinerich peptides. Taveira et al BMC Microbiology (2016) 16:12 are toxic against yeasts, pathogenic fungi, Gram-positive and Gram-negative bacteria, protozoa, and insects [7,8,9,10]. Like other AMPS, thionins’ antimicrobial activity relies on their interaction with phospholipids to cause membrane instability [10]
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