Anti- Pseudomonas Activity of Frog Skin Antimicrobial Peptides in a Caenorhabditis elegans Infection Model: a Plausible Mode of Action In Vitro and In Vivo

Abstract

The emergence of multidrug-resistant (MDR) microorganisms makes it increasingly difficult to treat infections. These infections include those associated with Pseudomonas aeruginosa, which are hard to eradicate, especially in patients with a compromised immune system. Naturally occurring membrane-active cationic antimicrobial peptides (CAMPs) serve as attractive candidates for the development of new therapeutic agents. Amphibian skin is one of the richest sources for such peptides, but only a few studies on their in vivo activities and modes of action have been reported. We investigated (i) the activity and mechanism underlying the killing of short CAMPs from frog skin (e.g., temporins and esculentin fragments) on an MDR clinical isolate of P. aeruginosa and (ii) their in vivo antibacterial activities and modes of action, using the minihost model of Caenorhabditis elegans. Our data revealed that in vivo, both temporin-1Tb and esculentin(1-18) were highly active in promoting the survival of Pseudomonas-infected nematodes, although temporin-1Tb did not show significant activity in vitro under the experimental conditions used. Importantly, esculentin(1-18) permeated the membrane of Pseudomonas cells within the infected nematode. To the best of our knowledge, this is the first report showing the ability of a CAMP to permeate the microbial membrane within a living organism. Besides shedding light on a plausible mode of action of frog skin CAMPs in vivo, our data suggest that temporins and esculentins would be attractive molecules as templates for the development of new therapeutics against life-threatening infections.

Short native antimicrobial peptides and engineered ultrashort lipopeptides: similarities and differences in cell specificities and modes of action

“…Treated animals exhibited a clear and fast decrease in fluorescence intensity along the entire intestine already within the first 90 min incubation with the peptide, due to the death of GFP-expressing Pseudomonas. This finding suggests that the mode of action used by this peptide to promote worm survival is based on its direct effect on the pathogen growth, rather than making bacteria avirulent and therefore harmless [137].…”

“…The peptide increased worm survival by approximately fourfold after 40 h of peptide treatment. Furthermore, the number of Pseudomonas colonies in the intestinal lumen of the animal dropped fivefold in comparison to untreated infected worms, within 1 day of peptide treatment [137]. The ability of this temporin to reduce Pseudomonas cells within the worm gut was also visualized by fluorescence microscopy, using nematodes infected with a strain of P. aeruginosa expressing the green-fluorescent protein (GFP).…”

Temporins A and B Stimulate Migration of HaCaT Keratinocytes and Kill Intracellular Staphylococcus aureus

“…Ta and Tb are short (13 residues long), linear, and mildly cationic (net charge, ϩ3 at neutral pH) AMPs particularly active against Gram-positive bacteria and Leishmania parasites (30). They both adopt an ␣-helical conformation in a membrane-mimicking environment (31-33); they are able to perturb the membrane of microbial cells (34), and in contrast with the highly cytotoxic isoform temporin L (35), Ta and Tb are practically nonhemolytic up to concentrations (i.e., 12 M and 32 M, respectively) 5-fold higher than their MICs against Gram-positive bacteria (34,36).…”

Use of Peptide Libraries for Identification and Optimization of Novel Antimicrobial Peptides

“…Perhaps most importantly is the fact that they have shown activity towards a wide spectrum of pathogens including gram positive and gram negative bacteria [14], fungi [15] viruses [16], protozoa [17] and organisms with multidrugresistant phenotypes [18]- [20]. This is coupled with the fact that antimicrobial peptides (AMP's) have shown a lower propensity for inducing bacterial resistance compared to other antibiotics [21] and they also have the ability to target metabolically inert cells e.g.…”