Study Of Antibacterial Activity And In Vivo Distribution Of Cation-bridged Antibacterial Peptides

The widespread multi-drug resistance of bacteria makes it urgent to develop new antibiotics.Antibiotics have saved countless lives since their introduction,but in recent years the problem of antibiotic abuse has become increasingly serious.New drug-resistant bacteria are emerging all over the world,but the pace of novel antibiotic research and development is slowing down at present,and drug-resistant strains were often found in a very short period of time after marketed new antibiotic drugs,leading to the increasingly serious problem of antimicrobial treatment,and in some urgent cases,there is even no drugs available clinically.Therefore,there is an urgent need for new antibiotic drugs to treat infectious diseases related to multi-drug resistant bacteria.Antimicrobial peptides(AMPs)are a class of endogenous peptides composed of 10-50 amino acids with broad antimicrobial and immunomodulatory activities.It is expected to be developed as a new antibiotic because of its wide antibacterial spectrum and low risk to develop drug resistance.Currently,many antimicrobial peptides are under preclinical and clinical development,but to date,only few have been approved for clinical use.Investigate its reason,antimicrobial peptides have strong toxicity of hemolysis to eukaryotic cells,and poor plasma stability and short half-life in vivo,which lead to the low correlation of antibacterial activity in vitro and in vivo efficacy of AMPs,and greatly influenced the PK/PD of antimicrobial peptides in vivo.Therefore,how to improve the physiological activity and in vivo pharmacokinetics of antimicrobial peptides is a major challenge for the development of novel antimicrobial peptides.In our previous study,we found that modification of OH-CM6,a antimimicrobial peptide found from the venom of King-Cobra,by introducing a cationic bridged-staple structure crosslinked with the side chain of lysine,could improve the protease stability of the antibacterial peptide and reduce its hemolytic toxicity.In addition,of the new cationbridged antimicrobial peptides has been found through activity screening in the early stage,which has a good broad-spectrum antimicrobial activity against MRSA and Escherichia coli.In this research we will further study this novel cation-bridged antimicrobial peptide,mainly including the following aspects:(1)antimicrobial activity to clinically isolated multiple drug-resistant bacteria ESKAPE(Enterococcus faecium,Staphylococcus aureus,Klebsiella pneumonia,Acinetobacter baumannii,Pseudomonas aeruginosa and Enterobacter),which have severe challenges in a variety of clinical treatments;(2)drug resistance development of bacteria toward these novel cation-bridged antimicrobial peptides.(3)study the distribution of the cation-bridged antimicrobial peptide at cell level in vitro and animal level in vivo by fluorescent labeling,which will help to investigate its action mode,metabolic stability and tissue distribution in vivo.In this study,we found that the new cation-bridged antimicrobial peptide had good antimicrobial activity against ESKAPE bacteria,and it was found that the new cationbridged antimicrobial peptide had better antimicrobial activity than OH-CM6 and was not easy to develop drug resistance.In addition using solid phase peptide synthesis,successful fluorescent labeling of OH-CM6 and cation-bridged antimicrobial peptide was achieved.Further research of these fluorescent labeled antimicrobial peptides at cell and animal levelshowed that the antimicrobial peptides acted mainly on the cell membrane of bacteria,and the cation-bridged antimicrobial peptide has better metabolic stability in vivo.These results layed a foundation for the subsequent preclinical study and therapeutic transformation of the cation-bridged antimicrobial peptide for treating diseases related to multi-drug resistant bacteria.