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The Wound Healing Potential of Komodo Dragons
Inspired by the discovery of an antimicrobial protein in Komodo dragon plasma, researchers have synthesized a peptide called DRGN-1 that demonstrated potent antimicrobial and wound healing activity.
Researchers at George Mason University have synthesized a peptide called DRGN-1 that demonstrated potent antimicrobial and wound healing activity. Study results, recently published in Biofilms and Microbiomes, indicated that “peptides such as DRGN-1 that have multiple modes of action against bacteria are of significant interest for potential future development,” the researchers wrote.
The emergence of multidrug-resistant bacteria has complicated wound treatment. Antimicrobial peptides (AMPs), particularly cationic AMPs (CAMPs), present a promising treatment alternative. AMPs are believed to target the cytoplasmic membrane and various intracellular functions; bacteria, in turn, have difficulty developing resistance to AMPs. These peptides have previously demonstrated potent antimicrobial, anti-biofilm, and host-directed immunomodulatory activity.
Animals, particularly reptiles, could be a source of CAMPs. For example, Komodo dragon saliva contains sepsis-causing bacteria; however, these animals do not get sickened by their saliva, suggesting that peptides in Komodo dragon saliva or blood have antimicrobial activity.
Researchers first identified a peptide from Komodo dragon plasma, naming it VK25. To synthesize DRGN-1, they reversed the order of two amino acids at VK25’s N-terminal. Using strains of Staphylococcus aureus and Pseudomonas aeruginosa, the researchers performed experiments to evaluate the peptides’ antimicrobial, anti-biofilm, and wound healing activities.
Antimicrobial and Anti-biofilm Activity
In a half maximal effective concentration (EC50 =) assay, DRGN-1 demonstrated marked antimicrobial activity against S. aureus and P. aeruginosa. VK25’s antimicrobial activity against these two bacteria was much weaker.
Crystal violet staining in test tubes containing S. aureus and P. aeruginosa biofilms revealed concentration-dependent biofilm inhibition by DRGN-1. Using confocal microscopy of individual and mixed bacterial cultures, researchers observed significant biofilm reduction with DRGN-1 treatment.
Activity Within Infected Cells
Researchers infected human epidermal keratinocytes-adult (HEKa) with P. aeruginosa, then treated them with DRGN-1, VK25, or LL-37 (a cathelicidin-related AMP). Compared with VK25, DRGN-1 enhanced cell survival; DRGN-1 and LL-37 significantly reduced bacterial survival within the infected cells. Notably, DRGN-1 and VK25, but not LL-37, were minimally cytotoxic across a wide concentration range.
The researchers used an ethidium bromide fluorescent probe to measure membrane permeability of P. aeruginosa cells by the peptides. Fluorescence was significantly greater with DRGN-1 and LL-37 than VK25, indicating significant cytoplasmic membrane disruption.
Using spectroscopy, the researchers analyzed VK25 and DRGN-1 conformation to determine why N-terminal amino acid reversal markedly increased antimicrobial activity and membrane permeability. Both peptide conformations changed from a random coil to a more organized α-helix in a membrane-mimicking media that supports α-helical peptide structures. Although DRGN-1’s α-helix was slightly more organized than that of VK25, this difference “may not be sufficient to explain the significantly different antimicrobial activity of these peptides,” the researchers wrote.
A mouse model of wound healing showed that DRGN-1 treatment enhanced wound healing and closure in uninfected wounds and wounds infected with S. aureus and P. aeruginosa. In particular, wound size was markedly more reduced with DRGN-1 than with VK25 or LL-37 by day 11 of treatment.
DRGN-1 stimulated HEKa migration in a scratch wound closure assay, indicating that keratinocyte migration is a host-directed wound healing function of DRGN-1. Western blotting results confirmed that DRGN-1’s HEKa migration function is induced by EGFR-STAT1/3 pathway activation; previous studies have reported that this pathway stimulates cell migration.
Researchers concluded that DRGN-1’s potent antimicrobial, anti-biofilm, and wound closure activities with minimal cytotoxicity make this peptide a potential topical wound treatment. Because of DRGN-1’s multiple mechanisms of action, researchers suspect that bacterial resistance to the peptide is less likely.
Dr. JoAnna Pendergrass received her Doctor of Veterinary Medicine degree from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory University’s Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner of JPen Communications, a medical communications company.