Preclinical Study Of Cathelicidin-DM From Duttaphrynus Melanostictus

Cathehcidins are a family of structurally diverse antimicrobial peptides found in mammals, reptiles, fish, birds and other animals, which are the important and effectivehost-defense molecules of innate immunity. Cathehcidins consist of a N-terminal conserved signal peptide, a pro sequence "cathelin" and mature peptide at the C-terminus, which play an important role in natural defense system in most vertebrates. Cathelicidins not only possess broad-spectrum antimicrobial activity, but also possess many other biological activities, such as immune cell chemotaxis,inducing mast cell degrannlation andhistamine release, angiogenesis, promoting woundhealing, lymphocyte activation and cell apoptosis of variation. Further studies evaluating their biologic activities and clinical purposes are beneficial to the development of novel therapeutic agents to battle the increasing antibiotics resistance.In our previous study, a Cathelicidin antimicrobial peptide, Cathelicidin-DM were found in the Duttaphrynus melanostictus. In this study, preclinical studies, including antibacterial activity in vitro, animal model of anti-systemic infection and local infection, trauma and pharmacokinetics, were performed.Cathelicidin-DM have potent antibacterial activity both for gram-positive bacteria and gram-negative bacteria in vitro, even stronger than do the classic antibacterial effect of antibiotics,in vivo and in vitro but there is no synergy in combination with antibiotics; in vitro melittin is used to do research on sterilization mechanism which can be speculated that the site of action Cathelicidin-DM is the cell membrane whose bactericidal capacity can reach to be about 80% as melittin does. In vivo experiments done peritonitis model of systemic infection and local infection model of trauma, internal use Cathelicidin-DM treatment of bacterial peritonitis group was a larger number of reduced trauma alsohave significanthealing; and gentamicin sulfate compared found in vitro antibacterial effect Cathelicidin-DM stronger in vivo antibacterial effect of gentamicin is stronger. Treatment were measured in three different forms of administration, among which oral is the worst, intravenous is the strongest.In Pharmacokinetic aspects, it is determined byhigh performance liquid chromatography with in-vivo plasma concentration, cytokines, and the distribution of drugs in different times with a small animal imaging system observed with FITC-Cathelicidin-DM in mice. HPLC describes Cathelicidin-DM standard curve with a good linear relationship, which is calculated at different time points after injection. Blood samples were obtained from mice plasma concentration curve drawnhalf Cathelicidin-DM found in about 50 min, when the blood concentration begins to drop quickly, gradually slowed down behind, until 360 min is totally metabolized completedly. In order to demonstrate the ability to target the polypeptide near the wound pathogens more vividly, this experiment vein injected with FITC-Cathelicidin-DM on mice tail, and the use the vivo imaging system and make the appropriate tracer.60 min after the administration, Cathelicidin-DM is mainly distributed in the affected organs and trauma which is proved that Cathelicidin-DMhas a cumulative effect of the target site, but also fully explained Cathelicidin-DMhas a good reason for trauma treatment capacity. Cytokine measurement results also reflect Cathelicidin-DM effects in the body from the side.