Stability, toxicity, and biological activity of host defense peptide BMAP28 and its inversed and retro-inversed isomers

• Published in: Biopolymers Vol. 96; no. 1; pp. 14 - 24
• Main Authors: Kindrachuk, Jason, Scruten, Erin, Attah-Poku, Sam, Bell, Kelli, Potter, Andrew, Babiuk, Lorne A., Griebel, Philip J., Napper, Scott
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 2011
• Subjects: Amino Acid Sequence; Animals; Anti-Infective Agents - chemistry; Anti-Infective Agents - metabolism; Anti-Infective Agents - pharmacology; antimicrobial; Antimicrobial Cationic Peptides - chemistry; Antimicrobial Cationic Peptides - metabolism; Antimicrobial Cationic Peptides - pharmacology; Bacteria - drug effects; Bacteria - growth & development; Bacterial Infections - microbiology; Bacterial Infections - prevention & control; Cattle; Cell Survival - drug effects; Cells, Cultured; Circular Dichroism; Dose-Response Relationship, Drug; Female; Hemolysis - drug effects; host defense peptide; Male; Mice; Mice, Inbred BALB C; Microbial Sensitivity Tests; Molecular Sequence Data; Monocytes - cytology; Monocytes - drug effects; Monocytes - microbiology; Peptide Hydrolases - metabolism; peptide modification; Phagocytes - cytology; Phagocytes - drug effects; Phagocytes - microbiology; Phagocytosis - drug effects; Protein Isoforms; Protein Stability; Proteins - chemical synthesis; Proteins - metabolism; Proteins - pharmacology; toxicity
• ISSN: 0006-3525; 1097-0282
• DOI: 10.1002/bip.21441

Host defense peptides (HDPs) contribute to immune defense through direct antimicrobial activity as well as modulation of host immune responses. While the antimicrobial activity of HDPs has been successfully exploited as topical antibiotics, their use as systemic immunomodulatory antimicrobials has been limited by their toxicity and biological instability. Peptide modification strategies to address these characteristics, while maintaining biological activity, are likely essential to capture the full therapeutic potential of HDPs. Here we investigate the stability, toxicity, and biological activity of the L, inversed (D), and retro‐inversed (RI) isomers of BMAP28. The D and RI isomers both form symmetrically related structures to L BMAP28 and resist proteolytic degradation. With respect to toxicity, the considerable hemolytic activity of L BMAP28 is approximately halved with the D isomer and eliminated with RI BMAP28. Furthermore, while D BMAP28 maintains the same cytotoxicity profile against epithelial cells and monocytes as the natural peptide, RI BMAP28 is markedly less toxic against these cell types. As prophylactic antimicrobials, all three isomers significantly reduced bacterial loads [99.99% bacterial clearance by each peptide at the highest dose (20 mg kg−1)], when administered 18 h prior to challenge in a mouse model of peritoneal infection. This protection appears to be mediated through neutrophil recruitment and activation of macrophages for bacterial clearance. Collectively, the increased stability and retained biological activity of D and RI BMAP28 make these isomers attractive as antimicrobial therapeutics. In particular, the protection conferred by RI BMAP28, combined with its reduced toxicities, make it a strong candidate for further consideration. © 2010 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 96: 14–24, 2011.