ABSTRACT
Objective:To investigate the protective mechanism of TAK242, a specific inhibitor of Toll-like receptor 4 (TLR4), on the liver of septic rats.Methods:Eighteen male Sprague-Dawley (SD) rats were randomly divided into three groups ( n = 6 in each group). The septic model was established by intraperitoneal injection of lipopolysaccharide (LPS) 15 mg/kg. The rats in the TAK242 intervention group received intraperitoneal injection of TAK242 (5 mg/kg) before modeling, while the rats in the septic model group and the control group were injected with the same amount of solvent [10% dimethyl sulfoxide (DMSO) + 90% corn oil]. Six hours later, the blood of abdominal aorta was collected and the levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured by enzyme linked immunosorbent assay (ELISA). The rats were sacrificed to obtain liver, the expression levels of TLR4, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), cysteinyl aspartate-specific proteinase-3 (caspase-3), nuclear factor-κB p65 (NF-κB p65) and phosphorylated NF-κB p65 (p-NF-κB p65) were detected by Western blotting. Immunohistochemical staining was used to observe NF-κB p65 protein expression in liver, and hepatocyte injury was assessed by hematoxylin-eosin (HE) staining. Results:Serum ALT and AST levels in the septic model group were significantly higher than those in the control group [ALT (μg/L): 26.639±7.814 vs. 2.847±2.150, AST (μg/L): 28.442±8.417 vs. 5.779±3.019, both P < 0.01]. The ALT and AST levels in the TAK242 intervention group were significantly lower than those in septic model group [ALT (μg/L): 7.269±3.398 vs. 26.639±7.814, AST (μg/L): 3.580±3.115 vs. 28.442±8.417, both P < 0.01]. Light microscopy showed that the hepatocytes in the septic model group were disordered, with obvious cell edema and increased inflammatory cells infiltration; the hepatocytes in the TAK242 intervention group were more neatly arranged, with significantly reduced hepatocyte edema and reduced inflammatory cells infiltration. Western blotting results showed that caspase-3 protein expression in hepatic tissue of septic model group was significantly higher than that in the control group (caspase-3/GAPDH: 0.794±0.164 vs. 0.482±0.055, P < 0.05), and caspase-3 protein expression in the TAK242 intervention group significantly decreased than that in the septic model group (caspase-3/GAPDH: 0.482±0.056 vs. 0.794±0.164, P < 0.05), which indicated that TAK242 could attenuate hepatocytes apoptosis of septic rats. The expression of IL-6, TNF-α and TLR4 protein and the ratio of p-NF-κB p65/NF-κB p65 in hepatic tissue of septic model group were significantly higher than those in control group (IL-6/GAPDH: 1.442±0.204 vs. 1.019±0.024, TNF-α/GAPDH: 1.089±0.098 vs. 0.806±0.005, TLR4/GAPDH: 1.292±0.085 vs. 0.941±0.087, p-NF-κB p65/NF-κB p65 ratio: 1.936±0.081 vs. 1.579±0.183, all P < 0.05), IL-6, TNF-α and TLR4 protein expression and p-NF-κB p65/NF-κB p65 ratio in the TAK242 intervention group were significantly lower than those in septic model group (IL-6/GAPDH: 1.035±0.042 vs. 1.442±0.204, TNF-α/GAPDH: 0.572±0.096 vs. 1.089±0.098, TLR4/GAPDH: 0.984±0.078 vs. 1.292±0.085, p-NF-κB p65/NF-κB p65 ratio: 1.484±0.255 vs. 1.936±0.081, all P < 0.05), it is suggested that LPS-induced sepsis could activate the inflammatory response mediated by TLR4/NF-κB pathway in liver, and the activation of TLR4/NF-κB pathway was inhibited by TAK242 through the TLR4 pathway, therefore, the inflammation of liver in septic rats was reduced. Immunohistochemical staining showed that the positive expression of NF-κB p65 in liver was significantly increased in the septic model group compared with the control group; the positive expression of NF-κB p65 was significantly reduced in the TAK242 intervention group compared with the septic model group, and there was almost no positive expression in the nucleus. Conclusion:TAK242 could reduce liver function injury and protect the liver by inhibition TLR4/NF-κB pathway in septic rats.
ABSTRACT
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, both 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 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, 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 -ΔΔCT): 10.44±3.30 vs. 107.50±29.48, TNF-α mRNA (2 -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, all P < 0.05]. Conclusion:TAK242 can protect LPS-induced cardiac dysfunction and myocardial injury by blocking the TLR4 mediated inflammatory response.