Research On TLR4/NF-κB Expression Of Cardiac Cells And Signal-transduction Pathway Of ADR In Newborn Rats And The Intervention Of Dexamethasone

Objective:To observe the effect of adriamycin(ADR) on the Toll-like receptor 4(TLR4),Nuclear factor-kappa B(NF-κB),Tumor necrosis factor-alpha(TNF-a) expression of cardiac cells in newborn rats,and to discuss the possible effects of adriamycin on myocardial damage and the intervention effects and possible mechanism of dexamethasone(DXM) on adriamycin-injured cardiac cells.Methods:Adriamycin was administered to establish the injury model of primary cultured cardiomyocytes in newborn rats.Primary cultured cardiomyocytes were randomly divided into three groups:1) control group:myocardial cell suspension was continue cultivated with serum-free medium and no drugs put into;2) ADR group:with adriamycin lmg/L in cultured fluid;3) DXM + ADR group:with dexamethasone 32mg/L and ADR1 mg/L half an hour later in cultured fluid.They were operated for 2 hours,4 hours and 24 hours respectively.The expression of TLR4,TNF- a protein in cardiac cells was checked with immunohistochemical.The semiquantitative analysis of TLR4,NF-kB,TNF-a protein was checked with Western blot and the activity of LDH was checked in cultured fluid with colorimetry.Results:The TLR4,NF-κB,TNF- a expression of the cardiac cells in ADR group are markedly increased when compared with control group(p＜0.01).The TLR4,NF-κB,TNF-a expression of cardiac cells in DXM+ADR group are considerably decreased compared with ADR group(p＜0.01).Activity of LDH:Compared with control group,the activity of LDH was increased significantly in ADR group(135.8±5.44 v 80.8±3.83u/L,p＜0.01,6h group).Compared with ADR group,the activity of LDH was decreased in ADR+DXM group significantly(98.8±6.09 v 135.8±5.44u/L,p＜0.01,6h group).Compared with control group,the activity of LDH was increased slighty in ADR+DXM group(98.8±6.09 v 80.8±3.83u/L,p＜0.05,6h group)Conclusion:From this research,TLR4 of cardiac cells under ADR is over expressed,activating the downstream signal-transduction system, making cytokine TNF-a expressed.This is one of the cardiac cells injuring mechanism.DXM could interfere in the over expression of TLR4 in cardiac cells and its downstream signal-transduction NF-κB and TNF-a,thus protect the cardiac muscle invariably.These offer theoretical and experimental bases for clinical preservation of myocardial damage when using ADR.