Role of the Toll-like receptor 3 signaling pathway in the neuroprotective effect of sevoflurane pre-conditioning during cardiopulmonary bypass in rats

The aim of the present study was to explore the roles and possible molecular mechanism of the alleviating effect of sevoflurane pre‑treatment on the extracorporeal circulation and to investigate the possible involvement of the Toll‑like receptor (TLR3) signaling pathway. A total of 64 male Sprague Dawley rats were randomly divided into three groups: The sham operation group (H group; n=8), cardiopulmonary bypass (CPB) group (C group; n=24) and sevoflurane pre‑conditioning group (S group; n=32). The C group was subjected to tracheal intubation and mechanical ventilation, vessel puncture and catheter placement in the right femoral artery and right internal jugular vein, while no CPB was performed in the H group. The S group was pre‑treated with 2.4% sevoflurane for 1 h prior to establishing the CPB model. The CPB in the C and S groups was performed for 1 h. Blood of the rats was analyzed and clinical parameters were detected prior to, during and at various time‑points after CPB. In addition, eight rats from the C and S groups each were sacrificed at these time‑points and brain tissue samples were analyzed. The levels of the brain damage‑specific protein S100‑β as well as IL‑6 and IFN‑β in the serum were detected by ELISA; furthermore, the expression levels of TLR3 and TIR‑domain‑containing adapter‑inducing interferon‑β (TRIF) in the left hippocampus were assessed by ELISA and/or western blot analysis. The right hippocampus was assessed for neuronal apoptosis by terminal deoxynucleotidyl transferase dUTP nick end labeling assay. The mean arterial pressure, heart rate and hematocrit were significantly decreased following CPB (P