Study The Expression And Its Possible Mechanism Of HMGB1 In Mycoplasma Pneumoniae Infection

Objective:Study the expression of HMGB1 in the peripheral blood and THP-1 cell level after Mycoplasma pneumoniae infection.To investigate the possible mechanism of HMGB1 and its related receptors in the immune response after Mycoplasma pneumoniae infection.Methods:1.108 cases of hospitalized children with refractory Mycoplasma pneumoniae pneumonia（RMPP group）were collected from January 2013 to December2015 in Children’s Hospital Affiliated to Suzhou University.344 cases of hospitalized children with non-refractory Mycoplasma pneumoniae pneumonia were collected as control group（NRMPP group）in the same period.Analyzing the clinical data and laboratory examination between refractory Mycoplasma pneumoniae pneumonia（RMPP）and refractory Mycoplasma pneumoniae pneumonia（NRMPP）retrospectively to find the difference.2.Detect the expression of TNF-α,IL-6 in peripheral blood from samples of 58cases of MPP（24 cases of RMPP,34 cases of NRMPP）and 24 cases of healthy children as control by ELISA assay and the expression of HMGB1 by RT-qPCR assay.Analyzing the sensitivity and specificity of the different indexes in RMPP and NRMPP by receiver operator characteristics curve.3.The lipid-associated membrane proteins（LAMPs）were extracted from Mycoplasma pneumoniae strains.THP-1 cells were stimulated with different concentrations of LAMPs.Detect the expressions of TNF-α,IL-6,HMGB1,RAGE,TLR2 and TLR4 from THP-1cells by RT-qPCR assay.Analyse the relationship of the expression of HMGB1 and INF-α,IL-6,RAGE,TLR2 and TLR4.Results:1.The average age of RMPP group was older than that of NRMPP group.There were more symptoms of cough,body characters,longer duration of fever and longer time in hospital in RMPP group.WBC and neutrophil counts,CRP,CK,IgA,IgG,IgM of RMPP group were higher than those of NRMPP group in the peripheral blood.However,Lymphocyte counts,CD3+,CD4+,CD4+/CD8+,CD3-CD19+,CD3-CD（16+56+）+,CD19+CD23+of RMPP group were lower than those of NRMPP group.2.The expression of TNF-α,IL-6 and HMGB1 in the peripheral blood of RMPP group increased compared with NRMPP group（P<0.05）.Using a cut-off level of 5.25×10^-3,HMGB1 expression had a sensitivity of 83.3%and a specificity of 82.4%in distinguishing RMPP from NRMPP patients.Using a cut-off level of 6.278x10⁹/L,neutrophil counts had a sensitivity of 87.5%and a specificity of 94.1%in distinguishing RMPP from NRMPP patients.3.The expression of TNF-αwas higher in 2μg/ml,4μg/ml,6μg/ml,8μg/ml,10μg/ml than that of the blank group respectively.The expression of IL-6 was higherin 4μg/ml,6μg/ml,8μg/ml,10μg/ml than that of the blank group respectively.The expression of HMGB1 was higher in 10μg/ml than that of the blank group.The expression of RAGE was higher in 8μg/ml than that of the blank group.The expression of TLR2 was higher in6μg/ml,8μg/ml,10μg/ml than that of the blank group respectively.There was no significant difference in the expression of TLR4 in each group compared with the control group（P>0.05）.Correlation analysis showed that the expression of HMGB1 was positively correlated with the expression of TNF-α,IL-6 and TLR2.Conclusions:1.RMPP tended to occur in older children.Children with RMPP proned to cough,have a long duration of fever,long time in hospital and have lung rales.The incidence of myocardial damage was higher.2.The counts of white blood cells,neutrophils and CRP were obviously increased in RMPP patients with serious inflammation and immune dysfunction.3.HMGB1 may participate in the development of RMPP,which may be used to identify RMPP from NRMPP.4.TNF-α,IL-6,HMGB1and TLR2 may participate in the inflammatory reaction of Mycoplasma pneumoniae lipid membrane associated proteins stimulating THP-1 cells.HMGB1 may partly take part in the inflammatory process by TLR2.