CPB Procedure

The rats were anesthetized by intraperitoneal injection of 3% pentobarbital (50 mg/kg). The right external jugular vein and right internal carotid artery were exposed through a longitudinal incision of the neck, and the right femoral artery was exposed through an incision in the right groin. The right femoral artery was catheterized and connected with a pressure sensor to measure blood pressure. The right carotid artery was catheterized and perfused with an indwelling venous catheter needle (20G). The right external jugular vein central venous catheter was used to establish a vein channel. Heparin (500 IU/kg) was injected into the right external jugular vein for systemic heparinization. Then, the rats were connected with the CPB apparatus, pre-charged with the solution: 10 mL substitute plasma (Hess), 0.5 mL 5% NaHCO₃, and 0.5 mL 20% mannitol. The deep hypothermia circulatory arrest procedure was induced in rats. Briefly, after cooling down the body temperature to 20–25°C for 30 min by using a heat exchanger and topical cooling with ice bags and a cooling blanket, DHCA confirmed by asystole were maintained for 30 min. After DHCA, CPB was reinstituted, and rats were rewarmed to rectal temperatures of at least 35.5°C over 40 min as previously described.22 Electrocardiogram (ECG) and anal temperature were routinely monitored during the operation. When stable respiration, hemodynamics, and an anal temperature of 36°C were achieved, the machine was stopped and protamine and heparin were injected intravenously. The rats were allowed to feed freely in an oxygen-sufficient environment for 2 h, and heart rate and mean arterial pressure were monitored during the surgery. Two hours after operation, the rats were decapitated and the lung tissues were collected for further analysis. After transfection, SD rats were injected with 4 mg/kg LPS through the tail vein. Follow-up experiments were carried out 4 h after the injection.