Screening A Novel Carbohydrate Mimicary Peptide With Anti-inflammation Activity Bases On The Model Of Acute Peritonitis In Mice Induced By Zymosan A

The inflammation reactions do great damage to the body in many diseases such as asthma, myocardial infarction and so on. So the searching of one effective method to ant-inflammation is important to reduce the damage. The inflammation reaction depends on the function of the members of selectin family and their glycosylated ligand. There are three members in the selectin family, P(Platelet)-, E(Endothelium)-, L(Leukocyte)- selecting. E-selectin is expressed on endothelial cell of inflammation part. E-selectin combines with sleX located in glycoprotein or glycolipid on the surface of white blood cells (WBCs)( neutrophil , Monocyte, CD4+ remember cell) through C-type lectin-like domain and makes WBCs be detained and roll on the surface of endothelial cell, then migrate to the part of inflammation. So using something to block the reaction between E-selectin and sleX can inhibit neutrophils' adherent to endothelium cell. So the inflammation will be inhibited.Some peptides are called oligosaccharide mimic peptides that have the similar structure with the oligosaccharide. The peptide's sequences that combine with it tightly can be screened from the peptides' library with the oligosaccharide monoclone antibody. So they must have some similar structure. As they have the similar structure, it can be concluded that they may have the similar function. It suggests that mimic peptides can compete with oligosaccharides binding to the E-selectin in vivo. Thus neutrophils cannot adhere to endothelium and migrate. So the inflammation will be inhibited.As shown above, experiments were designed to inhibit the happening and development of peritonitis in mice with the mimic peptide. Lewis A has the similar structure with Lewis X, The peptides were used were phages screened from phage display libraries expressing the sequences with high affinity to monoclone antibodies of the saccharide and synthesized peptides. The controls were phages that do not display the saccharide and BSA.Zymosan A can induce inflammation in mice. Mice were injected intraperitoneally with 1ml of saline containing 0.5mg/ml Zymosan A and it will induce peritonitis in mice.In order to observe the inhibition of peritonitis in mice by the mimic peptide, mice injected Zymosan A were divided into 2 groups with random.3 hours after injected Zymosan A ip, mice were injected mimic peptide or phage expressing the peptide and control respectively in tail vein. Mice were sacrificed 1h after iv injection and the cells from peritoneal cavity were collected by lavage with 10 ml of ice-cold PBS containing 10 mM EDTA and counted in a hemocytometer. Compared with control experiments, statistically significant reduction of neutrophils' recruitment into the intraperitoneal cavity was observed on administration of mimic peptide or phage expressing the peptide in a murine acute inflammation model in vivo. To confirm these results, myeloperoxidase(MPO) activity, an enzymatic marker for neutrophils, which is about 5% of the neutrophil's weight, was measured spectrophotometrically as an absorbance rate in the homogenates of cells collected from peritoneal cavity. The reduction of enzymatic activity was observed in parallel with decrease of neutrophils counting.Together with above results, Zymosan A can induce peritonitis in mice as a chemokine. Injection of the mimic peptides of Lewis A or Lewis X can inhibit exuding of neutrophils and alleviate damage. It can be concluded that peritonitis in mice were made by Zymosan A through inducing the expression of E-selectin and the mimic peptides of Lewis A or Lewis X compete with carbohydrate ligand expressed on neutrophils for E-selectin. This inhibits the adherence of neutrophils to endothelial cell and alleviates damage induced by inflammation.