The effect of intraperitoneally injection of S100A9 protein on the early immune function in mice with sepsis

Abstract

Objective To investigate the effect of S100A9 protein when injected intraperitoneally on early immune function in mice with sepsis.Methods Experimental sepsis was induced by cecal ligation and puncture (CLP).36 C57BL/6 mice were randomly divided into 3 groups (n=12):a Sham group,a CLP group and a S100A9 group.1 h after the CLP operation,S100A9 protein was injected intraperitoneally into mice in the S100A9 group,while the same volume of normal saline was given to the mice of Sham and CLP group.24 h after surgery,the peripheral blood and peritoneal lavage fluid(PLF) were collected for detection of bacterial loads,while the livers and lungs were harvested from the living mice from each group.The levels of inflammatory factors tumor necrosis factor-α (TNF-α) and interleukin-10 (IL-10) in blood were measured using enzyme linked immunosorbent assay.Counts of polymorphonuclear neutrophils (PMN),CD4+ and CD8+T cells in PLF were assayed using flow cytometry.The sections of liver and lung tisssues were stained by hematoxylin and eosin for histopathological examination.Results Bacterial loads in the blood and PLF after CLP were (179-±52)×103 and (247±50)×107 clonal formation unit(CFU) respectively,and they were significantly higher compared to Sham group (P＜0.01).Bacterial loads in blood and PLF from the S100A9 group were (20±8)×103 and (48±19)×107 CFU respectively,and they were significantly lower when compared to the CLP group (P＜0.01).The level of anti-inflammatory cytokine IL-10 in CLP group was (296±7) ng/L,and (907±93) ng/L in S100A9 group(P＜0.01),while the level of TNF-α was almost similar in these two groups.In CLP group only the number of PMN in PLF,as (767±142) cells/μl,increased significantly when compared with sham group(P＜0.01).Number of PMN in PLF increased even more in S100A9 group as (1 569±195) cells/μl(P＜0.01).Moreover,CD4+ and CD8+T cells in the S100A9 group also increased significantly when compared with CLP group,as (702±167) cells/μl and(287± 115) cells/μl (P＜0.05 and ＜0.01) respectively.Histopathology results also showed less severe injuries in liver and lung tissues in S100A9 group.Conclusions Intraperitoneally injection of S100A9 could enhance the ability of clearing pathogens in peritoneal cavity,inhibit the over-aggressive inflammatory response,and attenuate liver and lung injury in mice with sepsis. Key words: S100A9; Sepsis; Cecal ligation and puncture; Polymorphonuclear neutrophil; Inflammation