Targeting and synergistic action of an antifungal peptide in an antibiotic drug-delivery system.

Amphotericin B (AmB) has been widely used against fungal infections throughout almost the entire body, including the skin, nails, oral cavity, respiratory tract, and urinary tract. However, the development of AmB-loaded nanoparticles demands a novel technique that reduces its toxicity and other associated problems. Here, we developed a pH-responsive and redox-sensitive polymer-based AmB-delivery carrier system. In particular, this system was functionalized by conjugation with the antifungal peptide histatin 5, which acts both as a targeting ligand and a synergistic antifungal molecule against Candida albicans, a major systemic fungal pathogen of humans. Our results in vitro and in vivo suggest that this drug-delivery system may serve as a novel tool to facilitate the use of antimicrobial peptides as targeting ligands to pathogenic microbes, which would open new avenues of investigation in the field of drug delivery.

Functional characterization of alpha-synuclein protein with antimicrobial activity.

Alpha-synuclein (α-Syn), a small (14 kDa) protein associated with Parkinson's disease, is abundant in human neural tissues. α-Syn plays an important role in maintaining a supply of synaptic vesicles in presynaptic terminals; however, the mechanism by which it performs this function are not well understood. In addition, there is a correlation between α-Syn over-expression and upregulation of an innate immune response. Given the growing body of literature surrounding antimicrobial peptides (AMPs) in the brain, and the similarities between α-Syn and a previously characterized AMP, Amyloid-ß, we set out to investigate if α-Syn shares AMP-like properties. Here we demonstrate that α-Syn exhibits antibacterial activity against Escherichia coli and Staphylococcus aureus. In addition, we demonstrate a role for α-Syn in inhibiting various pathogenic fungal strains such as Aspergillus flavus, Aspergillus fumigatus and Rhizoctonia solani. We also analyzed localizations of recombinant α-Syn protein in E. coli and Candida albicans. These results suggest that in addition to α-Syn's role in neurotransmitter release, it appears to be a natural AMP.

Algicidal effect of hybrid peptides as potential inhibitors of harmful algal blooms.

OBJECTIVES: To biochemically characterize synthetic peptides to control harmful algal blooms (HABs) that cause red tides in marine water ecosystems. RESULTS: We present an analysis of several short synthetic peptides and their efficacy as algicidal agents. By altering the amino acid composition of the peptides we addressed the mode of algicidal action and determine the optimal balance of cationic and hydrophobic content for killing. In a controlled setting, these synthetic peptides disrupted both plasma and chloroplast membranes of several species known to result in HABs. This disruption was a direct result of the hydrophobic and cationic content of the peptide. Furthermore, by using an anti-HAB bioassay in scallops, we determined that these peptides were algicidal without being cytotoxic to other marine organisms. CONCLUSIONS: These synthetic peptides may prove promising for general marine ecosystem remediation where HABs have become widespread and resulted in serious economic loss.

Polymeric micellar nanoplatforms for Fenton reaction as a new class of antibacterial agents.

Reactive oxygen species (ROS) produced by host phagocytes exert antibacterial action against a variety of pathogens and ROS-induced oxidative stress is the governing mechanism for the antibacterial activity of major bactericidal antibiotics. In particular, hydroxyl radical is a strong and nonselective oxidant which can damage biomolecules such as DNA, proteins and lipids. Ferrous ion is known to convert mild oxidant hydrogen peroxide (H2O2) into highly reactive and toxic hydroxyl radicals, referred to as Fenton reaction. Herein, we report a new class of antibacterial agents based on Fenton reaction-performing nanostructures, composed of H2O2-generating polymer (PCAE) and iron-containing ferrocene. Amphiphilic PCAE was designed to incorporate H2O2-generating cinnamaldehyde through acid-cleavable linkages and self-assemble to form thermodynamically stable micelles which could encapsulate ferrocene in their hydrophobic core. All the experiments in vitro display that ferrocene-loaded PCAE micelles produce hydroxyl radicals to kill Escherichia coli and Pseudomonas aeruginosa through membrane damages. Intraperitoneally injected ferrocene-loaded PCAE micelles significantly reduced the lung damages and therefore increased the survival rate of mice infected with drug resistant P. aeruginosa. Given their potent antibacterial activity, ferrocene-loaded PCAE micelles hold great potential as a new class of ROS-manipulating antibacterial agents.

Novel chimeric peptide with enhanced cell specificity and anti-inflammatory activity.

An antimicrobial peptide (AMP), Hn-Mc, was designed by combining the N-terminus of HPA3NT3 and the C-terminus of melittin. This chimeric AMP exhibited potent antibacterial activity with low minimal inhibitory concentrations (MICs), ranging from 1 to 2 µM against four drug-susceptible bacteria and ten drug-resistant bacteria. Moreover, the hemolysis and cytotoxicity was reduced significantly compared to those of the parent peptides, highlighting its high cell selectivity. The morphological changes in the giant unilamellar vesicles and bacterial cell surfaces caused by the Hn-Mc peptide suggested that it killed the microbial cells by damaging the membrane envelope. An in vivo study also demonstrated the antibacterial activity of the Hn-Mc peptide in a mouse model infected with drug-resistant bacteria. In addition, the chimeric peptide inhibited the expression of lipopolysaccharide (LPS)-induced cytokines in RAW 264.7 cells by preventing the interaction between LPS and Toll-like receptors. These results suggest that this chimeric peptide is an antimicrobial and anti-inflammatory candidate as a pharmaceutic agent.