Role of Toll like receptor 4/nuclear factor-κB signal pathway on the pathogenesis of acute myocardial dysfunction after cardiopulmonary resuscitation in pigs

Abstract

Objective To investigate the role of Toll like receptor 4/nuclear factor-κB (TLR4/NF-κB) signal pathway on myocardial dysfunction after cardiac arrest-cardiopulmonary resuscitation (CA-CPR) in animal model. Methods Twenty-six pigs were randomly divided into sham group (n = 6), CA-CPR 12 hours group (n = 10) and CA-CPR 24 hours group (n = 10). The model of CA-CPR was reproduced by endocardial electrical stimulation for 8 minutes followed by CPR, and the pigs in sham group were only given anesthesia and tracheal intubation. The changes in hemodynamics including mean arterial pressure (MAP) and cardiac output (CO), as well as morphology and ultrastructure of myocardial cells were observed before and after CPR. The levels of serum tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were determined by enzyme linked immunosorbent assay (ELISA), and protein and mRNA expressions of TLR4/NF-κB in the myocardium were determined by Western Blot and real-time fluorescence quantitative reverse transcription-polymerase chain reaction (RT-PCR), respectively. Results Hemodynamic disturbance and myocardial serious injury were observed in CA-CPR groups. Compared with sham group, the levels of serum TNF-α were markedly increased 0.5 hour after return of spontaneous circulation (ROSC) in CA-CPR 12 hours and 24 hours groups (pg/L: 62.49±6.66, 48.39±2.37 vs. 10.75±0.74, both P < 0.05), and peaked at 2 hours (pg/L: 70.93±5.51, 66.03±2.60 vs. 10.87±0.91, both P < 0.05) followed by a gradual decline. The levels of serum IL-6 at 0.5 hours after ROSC in CA-CPR 12 hours and 24 hours groups were markedly higher than those of sham group (pg/L: 14.42±1.99, 11.23±1.12 vs. 8.75±0.74, both P < 0.05), and peaked at 12 hours (pg/L: 36.50±2.91, 38.15±1.26 vs. 8.88±0.62, both P < 0.05) followed by a gradual decline. The protein expressions of TLR4 and NF-κB in the myocardium were significantly increased in CA-CPR 12 hours and 24 hours groups as compared with sham group [TLR4 protein (gray value): 0.11±0.03, 0.24±0.05 vs. 0.05±0.02; NF-κB protein (gray value): 0.27±0.04, 0.24±0.03 vs. 0.09±0.02, all P < 0.05]. The mRNA levels of TLR4 in CA-CPR 12 hours and 24 hours groups were increased by approximately (9.93±1.07) folds and (9.21±1.27) folds of sham group respectively, and NF-κB mRNA expressions were increased by (4.44±0.96) folds and (6.09±0.81) folds of sham group respectively (all P < 0.01). Conclusion Activation of TLR4/NF-κB signal pathway may be one of the main pathological mechanisms of post resuscitation myocardial injury in a porcine model of CA-CPR. Key words: Cardiopulmonary resuscitation; Myocardial dysfunction; Toll like receptor 4/nuclear factor-κB signal pathway; Interleukin-6; Tumor necrosis factor-α