Restoring Antiendotoxin Activities of Inactive Antimicrobial Peptides

Abstract

Gram‐negative bacteria cell wall is composed of two layers: the inner phospholipid membrane and the outer membrane with a highly conserved unique lipid called lipopolysaccharide (LPS; endotoxin). LPS acts as a permeability barrier against a number of bactericidal agents. Furthermore, LPS is well known as a potent inducer of the immune system when it is released to blood and often causes septic shock syndromes in human. Some but not every antimicrobial peptide can neutralize LPS stimulated proinflammatory responses. We have developed an easy method to restore antiendotoxin activities of inactive antimicrobial peptides by linking two inactive α‐helical peptides with the AGP sequence. Antibacterial activities were determined by the standard broth micro‐dilution method of National Committee for Clinical Laboratory Standards. Toxicities of the peptides were determined from measuring cell death by the MTT assay against human fibroblast (HFW cells). Dynamic light scattering (DLS) was used to measure the size increase of LPS in the presence of the peptides. The ability of LPS neutralization in vitro was measured by Limulus Amebocyte Lysate (LAL) assay. LPS can induce nitrite oxide (NO) and TNF‐α production in macrophage cells. Experimental mouse endotoxemia model was used to test the antiendotoxin activities of the peptides. Significant antiendotoxin effects were observed in vitro and in vivo with the AGP linked variant of the short α‐helical peptides KR12 and WR6. The results will be used to help us design more potent antimicrobial peptides for clinical application in the future.Support or Funding InformationGrant Number 103‐2113‐M‐007‐009‐MY2, Ministry of Science and Technology, Taiwan