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目的:探讨Toll样受体4（TLR4）通路在脓毒症大鼠心肌损伤和心功能障碍中的作用。方法:将18只雄性SD大鼠按照随机数字表法分为对照组、脂多糖（LPS）组和TLR4特异性抑制剂TAK242预处理组（TAK242+LPS组），每组6只。通过腹腔注射LPS 15 mg/kg诱导脓毒性心脏功能障碍大鼠模型；对照组给予等量生理盐水。TAK242+LPS组在给予LPS刺激前3 h腹腔注射3 mg/kg TAK242〔以0.2 g/L溶于10%二甲基亚砜（DMSO）+90%玉米油中〕；对照组和LPS组给予等量10% DMSO+90%玉米油。注射LPS后14 h采用心脏多普勒超声检查各组大鼠心功能。取腹主动脉血，采用酶联免疫吸附试验（ELISA）检测血清心肌肌钙蛋白（cTn）水平。取心肌组织，苏木素-伊红（HE）染色后，光镜下观察大鼠心肌组织形态学改变；采用实时荧光定量聚合酶链反应（qPCR）检测心肌组织中白细胞介素-6（IL-6）和肿瘤坏死因子-α（TNF-α）的mRNA表达；采用免疫组化法观察心肌组织中TLR4的表达；采用蛋白质免疫印迹试验（Western blotting）检测心肌组织中TLR4、核转录因子-κB p65（NF-κB p65）及其磷酸化（p-NF-κB p65）水平。结果:①心功能及心肌损伤：心脏多普勒超声显示，LPS组大鼠左室舒张期末容积（LVEDV）、左室收缩期末容积（LVESV）明显高于对照组，左室射血分数（LVEF）、左室短轴缩短率（LVFS）明显低于对照组；光镜下可见心肌细胞变性坏死和炎性细胞浸润，且血清cTn水平均较对照组明显升高，说明LPS诱导的脓毒症可引起心功能障碍和心肌损伤。而给予TAK242预处理阻断TLR4通路对脓毒症时的心功能和心肌有保护作用，表现为TAK242+LPS组LVEDV和LVESV均较LPS组明显降低〔LVEDV（μL）：71.25±21.16比118.01±11.89，LVESV（μL）：9.57±5.75比32.70±9.22，均n P<0.01〕，LVEF、LVFS较LPS组明显升高〔LVEF：0.868±0.075比0.722±0.095，LVFS：（59.88±8.46）%比（42.37±8.71）%，均n P<0.05〕，心肌组织损伤明显减轻，且血清cTn水平较LPS组明显降低（μg/L：107.85±21.38比152.25±27.46，n P<0.05）。②炎症指标：qPCR、Western blotting及免疫组化显示，LPS组大鼠心肌组织中IL-6和TNF-α的mRNA表达、TLR4蛋白表达及p-NF-κB p65/NF-κB p65比值均明显高于对照组，说明LPS诱导的脓毒症可激活心肌组织中TLR4/NF-κB通路介导的炎症反应。给予TAK242阻断TLR4通路可抑制TLR4/NF-κB通路，从而减轻脓毒症大鼠心肌组织炎症反应，表现为TAK242+LPS组心肌组织IL-6和TNF-α的mRNA表达、TLR4蛋白表达及p-NF-κB p65/NF-κB p65比值均较LPS组明显降低〔IL-6 mRNA（2n -ΔΔCT）：10.44±3.30比107.50±29.48，TNF-α mRNA（2n -ΔΔCT）：2.38±0.68比3.77±0.56，TLR4蛋白（TLR4/GAPDH）：0.39±0.01比0.58±0.04，p-NF-κB p65/NF-κB p65比值：1.21±0.11比2.10±0.18，均n P<0.05〕。n 结论:TAK242可通过阻断TLR4信号通路介导的炎症反应来保护LPS诱导的脓毒性心功能障碍和心肌损伤。“,”Objective:To investigate the role of Toll-like receptor 4 (TLR4) pathway on myocardial injury and cardiac dysfunction in septic rats.Methods:According to the random number table, 18 male Sprague-Dawley (SD) rats were divided into control group, lipopolysaccharide (LPS) group and TLR4 specific inhibitor TAK242 pretreatment group (TAK242+LPS group) with 6 rats in each group. The rat model of septic cardiac dysfunction was induced by intraperitoneal injection of LPS 15 mg/kg, and the control group was given the same amount of normal saline. The TAK242+LPS group was intraperitoneally given injection of TAK242 [it was injected intraperitoneally at a dose of 3 mg/kg and dissolved in 10% dimethyl sulfoxide (DMSO) and 90% corn oil according to the concentration of 0.2 g/L] 3 hours before LPS stimulation. The control group and LPS group were given the same amount of 10% DMSO and 90% corn oil. The cardiac function of rats in each group was examined by Doppler echocardiography 14 hours after injection of LPS. The blood of abdominal aorta was taken and the level of serum troponin (cTn) was measured by enzyme linked immunosorbent assay (ELISA). Myocardial tissue was harvested for hematoxylin-eosin (HE) staining, and the morphological changes of myocardial tissue were observed under light microscope. The mRNA expressions of interleukin-6 (IL-6) and tumor necrosis factor-α(TNF-α) in myocardial tissue were detected by real-time fluorescence quantitative polymerase chain reaction (qPCR). The protein expression of TLR4 in myocardial tissue was observed by immunohistochemical method. Western blotting was used to detect the levels of TLR4, nuclear factor-κB p65 (NF-κB p65) and its phosphorylation (p-NF-κB p65) in myocardial tissue.Results:① The cardiac function and myocardial injury: Doppler echocardiography showed that the levels of left ventricular end-diastolic volume (LVEDV) and left ventricular end-systolic volume (LVESV) in the LPS group were significantly higher than those in the control group, while left ventricular ejection fraction (LVEF) and left ventricular shortened fraction (LVFS) were significantly lower than those in the control group. The degeneration, necrosis and inflammatory cell infiltration of cardiomyocytes were found with light microscope in the LPS group, and the levels of serum cTn were significantly higher than those in the control group, indicating that LPS-induced sepsis could cause cardiac dysfunction and myocardial injury. TAK242 blocking TLR4 pathway had a protective effect on cardiac function and myocardium during sepsis. LVEDV and LVESV in the TAK242+LPS group were significantly lower than those in the LPS group [LVEDV (μL): 71.25±21.16 vs. 118.01±11.89, LVESV (μL): 9.57±5.75 vs. 32.70±9.22, bothn P < 0.01]. LVEF and LVFS were significantly higher than those in the LPS group [LVEF: 0.868±0.075 vs. 0.722±0.095, LVFS: (59.88±8.46)% vs. (42.37±8.71)%, both n P < 0.05]. Myocardial tissue injury was significantly reduced, and the serum cTn level was significantly lower than that in the LPS group (μg/L: 107.85±21.38 vs. 152.25±27.46, n P < 0.05). ② Inflammatory parameters: the results of qPCR, Western blotting and immunohistochemistry showed that the mRNA expressions of IL-6 and TNF-α, the expression of TLR4 protein and the p-NF-κB p65/NF-κB p65 ratio in the LPS group were significantly higher than those in the control group, indicating that LPS-induced sepsis could activate the inflammatory response mediated by TLR4/NF-κB pathway in the heart. However, blocking the TLR4 pathway by TAK242 could inhibit the TLR4/NF-κB pathway and reduce the myocardial inflammation in septic rats. The mRNA expressions of IL-6 and TNF-α, the expression of TLR4 protein and the p-NF-κB p65/NF-κB p65 ratio in the TAK242+LPS group were significantly lower than those in the LPS group [IL-6 mRNA (2 n -ΔΔCT): 10.44±3.30 vs. 107.50±29.48, TNF-α mRNA (2n -ΔΔCT): 2.38±0.68 vs. 3.77±0.56, TLR4 protein (TLR4/GAPDH): 0.39±0.01 vs. 0.58±0.04, p-NF-κB p65/NF-κB p65 ratio: 1.21±0.11 vs. 2.10±0.18, alln P < 0.05].n Conclusion:TAK242 can protect LPS-induced cardiac dysfunction and myocardial injury by blocking the TLR4 mediated inflammatory response.