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A Simplified Derivative of Human Defensin 5 with Potent and Efficient Activity against Multidrug-Resistant
Cheng Wang1, Gaomei Zhao1, Song Wang1
1State Key Laboratory of Trauma, Burns and Combined Injury, Institute of Combined Injury of PLA, Chongqing Engineering Research Center for Nanomedicine, College of Preventive Medicine, Third Military Medical University, Shapingba, Chongqing, People's Republic of China.
Abstract:
The increasing incidence of multidrug-resistant Acinetobacter baumannii (MDRAb) infections worldwide has necessitated the development of novel antibiotics. Human defensin 5 (HD5) is an endogenous peptide with a complex architecture and antibacterial activity against MDRAb In the present study, we attempted to simplify the structure of HD5 by removing disulfide bonds. We found that the Cys2-4 bond was most indispensable for HD5 to inactivate MDRAb, although the antibacterial activity of the derivative was significantly attenuated. We then replaced the noncationic and nonhydrophobic residues with electropositive Arg to increase the antibacterial activity of HD5 derivative that contains a Cys2-4 bond, obtaining another derivative termed HD5d5. The in vitro antibacterial assay and irradiation-wound-infection animal experiment both showed that HD5d5 was much more effective than HD5 at eliminating MDRAb Further investigations revealed that HD5d5 efficiently bound to outer membrane lipid A and penetrated membranes, leading to bacterial collapse and peptide translocation. Compared to HD5, more HD5d5 molecules were located in the cytoplasm of MDRAb, and HD5d5 was more efficient at reducing the activities of superoxide dismutase and catalase, causing the accumulation of reactive oxygen species that are detrimental to microbes. In addition, HD5 failed to suppress the pathogenic outer membrane protein A of Acinetobacter baumannii (AbOmpA) at concentrations up to 50 μg/ml, whereas HD5d5 strongly bound to AbOmpA and exhibited a dramatic toxin-neutralizing ability, thus expanding the repertoire of drugs that is available to treat MDRAb infections.
Insights
Researchers modified human defensin 5 (HD5) to create a potent new antibiotic, HD5d5, effective against multidrug-resistant Acinetobacter baumannii (MDR Ab). HD5d5 shows enhanced bacterial membrane penetration and toxin neutralization capabilities.
Area of Science:
- Microbiology
- Infectious Diseases
- Drug Discovery
Background:
- Multidrug-resistant Acinetobacter baumannii (MDR Ab) infections pose a growing global health threat.
- Human defensin 5 (HD5) exhibits antibacterial properties but requires structural optimization for enhanced efficacy.
- Novel therapeutic strategies are urgently needed to combat MDR Ab.
Purpose of the Study:
- To develop a simplified and more potent derivative of HD5 for treating MDR Ab infections.
- To investigate the structure-activity relationship of HD5 in combating MDR Ab.
- To evaluate the efficacy of the novel HD5 derivative (HD5d5) in vitro and in vivo.
Main Methods:
- Structural modification of HD5 by removing disulfide bonds and replacing residues with arginine.
- In vitro antibacterial assays to determine the efficacy of HD5 and HD5d5 against MDR Ab.
- In vivo irradiation-wound-infection animal model to assess therapeutic potential.
- Mechanistic studies involving membrane penetration, reactive oxygen species generation, and AbOmpA binding.
Main Results:
- A modified HD5 derivative, HD5d5, demonstrated significantly enhanced antibacterial activity against MDR Ab compared to native HD5.
- HD5d5 effectively penetrated bacterial membranes, induced bacterial collapse, and accumulated in the cytoplasm.
- HD5d5 showed increased efficacy in reducing bacterial antioxidant enzyme activity and neutralizing the pathogenic AbOmpA.
- In vivo experiments confirmed HD5d5's superior performance in clearing MDR Ab infections.
Conclusions:
- HD5d5 represents a promising novel antibiotic candidate for treating multidrug-resistant Acinetobacter baumannii infections.
- Structural simplification and targeted modifications of HD5 can lead to enhanced antibacterial potency and broader therapeutic applications.
- HD5d5's mechanism involves membrane disruption, oxidative stress induction, and virulence factor neutralization.
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