Bacterial Lipoprotein Tolerance Mechanism Of The Protective Effect Of Cardiac Function In Septic Mice

Objective:To study the effect of bacterial lipoprotein(BLP) on the expression of Toll-like receptor 2(TLR2)and myeloid differentiation factor 88(MyD88)and production of TNF-αby stimulating with different ways in THP-1 cell line.Methods:Human THP-1 cells were stimulated with 10 ng/ml BLP for 24h to achieve BLP tolerance,then stimulated with 1000 ng/ml BLP for 2h.TLR2 and MyD88 protein concentration were detected using Western Blot analysis, while TNF-αwas detected using available ELISA kit.Results:The production of TNF-αin THP-1 cells after stimulated with a low-dose BLP and a following high-dose BLP was significant lower than that in THP-1 cells after stimulated with a high-dose BLP challenge directly, whereas no significant differences in TLR2 and MyD88 expression was observed.Conclusion:Pretreatment of THP-1 cells with a low-dose BLP induced BLP tolerance,suppressed TNF-αoverexpression,and different doses of BLP had no effect on the expression of TLR2 and MyD88 protein. Objective:To observe the effect of sepsis on cardiac function of mice and investigate the protection of BLP tolerance to cardiac function in mice with sepsis.Methods:55 adult,male C57BL/6 mice were randomly divided into four groups:normal control(N),sham surgery control(S),BLP tolerance +sepsis(B+C)and sepsis group(sepsis induced by cecal ligation and puncture)(C).At time Oh,2h,6h and 12h after CLP,heart rate(HR),left ventricle shortening fraction(FS)were measured by echocardiography,and ejection fraction(EF)and cardiac output(CO)and left ventricular posterior wall thickness diastolic (LVPWd)were calculated respectively for all groups.The levels of TLR2-MyD88-dependent signaling molecules and TNF-α,IL-10 in the myocardium were detected.The expression of macrophage in the myocardiac tissue was detected by immunohistochemistry.Apoptosis in cadiocyte was determined by the TUNEL assay.Results:HR,FS,EF and LVPWd in the sham surgery group were tending upwards between 0h and 6h,and was higher at 6h compared with the normal control group,and then declined to the baseline at 12h,CO decreased between 0h and 2h, and returned to the baseline level at 12h.In the sepsis group,HR and FS increased between 0h and 2h,and decreased from 2h onwards.EF increased since 0h and decreased after 6h.CO continuously decreased since 0h to the lowest at 12h.LVPWd had no any change between 2h and 6h,and increased from 6h and was significantly higher than the sham surgery group at 12h(P≤0.05).HR,FS,EF and CO in the BLP tolerance + sepsis group had similar tendencies with the sepsis group between 0h and 6h,which in former were lower than ones in the later(P≤0.05).It then increased from 6h and was significantly higher than the sepsis group at 12h(P≤0.05,respectively).LVPWd increased from 0h to 12h and was significantly higher than the sham surgery group at 12h(P≤0.05)and had no difference with the sepsis group.The expression of TLR2-MyD88-dependent signaling molecules on myocardiac cells and the levels of TNF-αand IL-10 in the myocardial cytoplasmic proteins had no significant changes among all groups.Macrophagic infiltration to myocardiac tissue were observed at 12h in the sepsis group and 2h in the BLP tolerance + sepsis group respectively,the rest were negative.The number of apoptosis positive myocardial cells was significantly increased in BLP tolerance + sepsis group as compared with the sepsis group and sham group at different time points,respectively.But apoptosis in cadiocyte had no differences in BLP tolerance +sepsis mice at different times.Conclusion:Operation affects cardiac function in mice,sepsis markedly suppress cardiac function,BLP tolerance has the protection to cardiac function in mice with sepsis;The change in cardiac function at early stage of sepsis may have no relationship with inflammation in myocardiac cell.Apoptosis in cadiocyte is delayed by BLP tolerance.