Antimicrobial peptides RI8 and RW8 target bacterial membranes and genomic DNA to overcome drug resistance

Area of Science:

• Biochemistry and Molecular Biology
• Antimicrobial Drug Discovery
• Nanotechnology and Biomaterials

Background:

• The rise of multidrug-resistant (MDR) pathogens necessitates novel therapeutic strategies beyond conventional antibiotics.
• Natural antimicrobial peptides (AMPs) face limitations in proteolytic stability and targeted delivery.
• Developing stable and effective AMPs is crucial for combating infectious diseases.

Purpose of the Study:

• To design and characterize a protease-resistant, symmetric peptide scaffold for dual bacterial membrane and genomic DNA targeting.
• To evaluate the antimicrobial activity, stability, and therapeutic potential of derived peptides RI8 and RW8 against MDR pathogens and biofilms.
• To investigate the mechanism of action and in vivo efficacy of these novel peptides.

Main Methods:

• Design of a symmetric peptide scaffold (RRYY)2P(YYRR)2 with alternating cationic-hydrophobic repeats and palindromic topology.
• Characterization of derived peptides RI8 and RW8 for antimicrobial activity (MIC), hemolysis, protease resistance, and biofilm inhibition.
• Mechanism of action studies including bacterial membrane disruption, genomic DNA binding, and molecular dynamics simulations.
• In vivo efficacy evaluation in murine models of MDR-infected wounds and Staphylococcus aureus pneumonia.

Main Results:

• RI8 exhibited broad-spectrum activity against MDR pathogens (MIC: 2-16 μg/mL) with a high therapeutic index and negligible hemolysis.
• RW8 demonstrated robust protease resistance and significant inhibition of Staphylococcus aureus biofilms by downregulating key virulence genes.
• Both peptides effectively disrupted bacterial membranes and bound genomic DNA, with simulations confirming membrane insertion.
• In vivo studies showed RI8/RW8 accelerated wound healing, reduced bacterial burdens, and outperformed levofloxacin in a pneumonia model, while restoring immune function.

Conclusions:

• A rationally designed, protease-resistant symmetric peptide scaffold offers a versatile platform for developing novel antimicrobial agents.
• Peptide RI8 shows promise for treating systemic MDR infections, while RW8 is effective against localized biofilm-associated infections.
• This strategy addresses key translational limitations of AMPs and provides a potential solution to the growing threat of antibiotic resistance.