RESUMO
Objective:To investigate the protective effect of β- blocker (esmolol) on myocardia and toll-like receptor 4 (TLR4) inflammatory pathway in septic rats.Methods:Sixty male Wistar rats were randomly (random number) divided into the shame group, sepsis group (CLP group), esmolol group (CLP+ES group) and TLR4 inhibitor group (CLP+TAK-242 group) with 15 rats in each group. Cecal exploration was performed in the shame group, and cecal ligation and perforation (CLP) was performed in the CLP group, CLP+ES group and CLP+TAK-242 group. The CLP+ES group received intraperitoneal injection of esmolol diluent 20 mg/kg 12 h after CLP. The CLP+TAK-242 group was given intraperitoneal injection of TAK-242 3 mg/kg at the same time point as above. The shame group and CLP group were given the same amount of normal saline. Rats in all groups were sacrificed 24 h after operation, and the samples were collected and processed. The pathological changes of myocardium were observed by hematoxylin - eosin staining. The expression of TLR4, myeloid differentiation protein 88 (MyD88) and nuclear factor -κB (NF-κB) in myocardial tissue were observed by immunohistochemistry. Masson staining was used to observe the expression of fibers and inflammatory factors in myocardial tissue. The protein expressions of TLR4, MyD88, NF-κB and aspartic acid specific cysteine protease 1 (caspase-1) were detected by Western blot. Serum levels of cardiac troponin I (cTn-I), tumor necrosis factor α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) were detected by enzyme-linked immunosorbent assay (ELISA).Results:Compared with the shame group, myocardial injury, fibrosis and inflammatory cell infiltration were significantly aggravated in the CLP group, and the levels of myocardial injury index cTn-I and inflammatory mediators TNF-α, IL-6 and IL-1β were significantly increased [(8.70±0.22) vs. (4.41±0.31), (445.57±9.13) vs. (219.60±5.52), (165.55±2.18) vs. (93.47±3.37), (124.12±2.59) vs. (67.63±6.04),all P<0.05]. Compared with the CLP group, myocardial injury was significantly reduced in the CLP+ES group and CLP+TAK-242 group, and the levels of inflammatory transmitters were significantly reduced [(5.38±0.18) and (5.37±0.13) vs. (8.70±0.22), (322.73±7.63) and (300.58±17.47) vs. (445.57±9.13), (121.28±5.44) and (120.30±4.95) vs. (165.55±2.18), (102.60±4.09) and (105.08±7.21) vs. (124.12±2.59), all P<0.05]. Western blot analysis showed that the protein expression levels of TLR4, MyD88, NF-κB and caspase-1 in the CLP group were significantly higher than those in the shame group [(1.79±0.15) vs. (1.15±0.04), (4.70±0.30) vs. (3.87±0.10), (0.35±0.04) vs. (0.18±0.02), (2.27±0.29) vs. (1.15±0.07), all P<0.05], while the protein expression levels in the CLP+ES group and CLP+TAK-242 group were significantly lower than those in the CLP group [(1.31±0.16) and (1.18±0.14) vs. (1.79±0.15), (1.50±0.16) and (1.46±0.19) vs. (2.27±0.29), (0.27±0.02) and (0.24±0.01) vs. (0.35±0.04), (1.50±0.16) and (1.46±0.19) vs. (2.27±0.29), all P<0.05]. Conclusions:β-blocker can reduce myocardial injury and inhibit the expression of inflammatory mediators in septic rats by blocking the inflammatory response mediated by TLR4 signaling pathway.