CXCR1/CXCR2 Antagonist-G31P's Therapeutic Effect On Pseudomonas Aeruginosa Pneumonia

Objective: Chemokines are a family of small, structurally related molecules that play a fundamental role in the homeostasis and function of the immune system. It is universally recognized that ELR+CXC chemokine as a kind of CXC chemokines exert a significant part in the initiation, development and progression of neutrophil inflammation. G31P, an ELR+CXC chemokine antagonist, can bind both CXCR1 and CXCR2 effectively so as to inhibit inflammation by blocking the ability of ELR+CXC chemokine to activate and chemoattract neutrophils. Pseudomonas Aeruginosa is ubiquitous in the natural environment and it can secrete many kinds of virulence such as exotoxin, endotoxin and elastase, etc. Therefore, in this experiment we are trying to find out whether G31P also works very well in the Pseudomonas Aeruginosa pneumonia model on BL mice.Methods: For the preparation of the bacteria, we chose the optimal growth stage by drawing the time-growth curve of bacterium and diluted it with sterile saline. G31P is from a human IL-8 gene which is modified in two sites, K11R and G31P, by site-directed mutagenesis. The gene is then inserted into expressing vector pGEX-2T and expressed by recombinant bacteria E.Coli HB101 and finally, G31P is extracted and analyzed by Western Blotting. Then mice were challenged with 107 cfu by intranasal injection meanwhile administrated G31P (500μg/kg) or the same volume sterile saline as positive control by subcutaneously injection on the back. The temperature was monitored by thermometer for rectal use and the mice were sacrificed 18h later and the number of white blood cells (WBC) and neutrophil response, the release of myeloperoxidase (MPO) by both lung tissue and in the bronchoalveolar lavage fluid (BALF), the observation of appearance of lung tissue and lung histopathology were accessed respectively.Results: The results show that, compared with the control group, the total WBC and the ratio of neutrophil in total WBC decreased to some extent, the secretion of MPO in both lung tissue and BALF dropped, and there is much difference in histopathology in G31P treatment group.Conclusion: In a word, G31P can partly block neutrophil influx and tissue hemorrhage so as to exert a certain effect on this pneumonia model.