[To explore the preventive and therapeutic effects of Xuebijing injection on acute lung injury induced by cardiopulmonary bypass in rats by regulating the expression of microRNA-17-5p and its mechanism].

OBJECTIVE

To investigate the preventive effect of Xuebijing injection on acute lung injury induced by cardiopulmonary bypass (CPB) and the underlying mechanism.

METHODS

(1) In vivo experiment: 30 Sprague-Dawley (SD) rats were randomly divided into sham group, CPB group, Xuebijing pretreatment group (XBJ+CPB group) with 10 rats in each group. CPB model was reproduced in rats; and CPB was not performed in sham group, but only through arteriovenous puncture. In the XBJ+CPB group, 4 mL/kg Xuebijing injection was injected intraperitoneally 2 hours before CPB, sham group and CPB group were injected with equal volume of normal saline at the same time. The blood from femoral artery was analyzed 4 hours after operation, and the oxygenation index (PaO/FiO) was calculated. Then the rats were sacrificed to collect bronchoalveolar lavage fluid (BALF), and the lung permeability index (PPI) was calculated. The lung tissues were harvested, and the wet/dry weight ratio (W/D) of lung tissue was measured. The index of quantitative evaluation of alveolar injury (IQA) was measured. The levels of interleukins (IL-1, IL-6) and tumor necrosis factor-α (TNF-α) in lung tissue and BALF were measured by enzyme-linked immunosorbent assay (ELISA). The content of malondialdehyde (MDA) and the activities of myeloperoxidase (MPO) and superoxide dismutase (SOD) in lung tissue were detected by biochemical method. The microRNA-17-5p (miR-17-5p) expression in lung tissue was determined by quantitative reverse transcription-polymerase chain reaction (RT-qPCR). (2) In vitro experiments: type II alveolar epithelial cells (AEC II) were cultured in vitro, and they were randomly divided into control group (the cells were treated by preoperative serum of CPB in patients with ventricular septal defect), CPB group (the cells were treated by serum after CPB in patients), and XBJ+CPB group (Xuebijing injection 10 g/L+serum after CPB in patients). After 12 hours of culture in each group, the expression of miR-17-5p was detected by RT-qPCR. AEC II cells were transfected with miR-17-5p mimic, inhibitor or corresponding control oligonucleotide (negative control), respectively, to observe the effect of miR-17-5p on Xuebijing regulating CPB-induced apoptosis rate and caspase-3 activity.

RESULTS

(1) In vivo experiment: compared with the sham group, the PPI, lung W/D ratio, IQA, and IL-1, IL-6, TNF-α in lung tissue and BALF, as well as MDA content and MPO activity in lung tissue were significantly increased, PaO/FiO and SOD activity in lung tissue were significantly decreased. The parameters of the XBJ+CPB group were significantly improved, suggesting that Xuebijing pretreatment could improve CPB-induced ALI in rats. The expression of miR-17-5p in lung tissue of the CPB group was significantly down-regulated as compared with sham group (2: 0.48±0.13 vs. 1.00±0.11, P < 0.05); while the expression of miR-17-5p in the XBJ group was significantly up-regulated as compared with the CPB group (2: 1.37±0.09 vs. 0.48±0.13, P < 0.05), indicating that the improvement of Xuebijing injection on lung injury after CPB might be related to miR-17-5p. (2) In vitro experiment: the changes in miR-17-5p expression in each group of AEC II cells confirmed in vivo results. After transfection of miR-17-5p mimic, the apoptotic rate and caspase-3 activity of each group were significantly lower than those transfected with negative control, and the decrease was more significant in the XBJ+CPB group [apoptotic rate: (7.37±0.95)% vs. (12.60±1.90)%, caspase-3 (A value): 0.82±0.09 vs. 1.37±0.08, both P < 0.05]. After transfection of miR-17-5p inhibitor, the apoptotic rate and caspase-3 activity of each group were significantly more than those transfected with negative control [in the XBJ+CPB group: apoptotic rate was (16.30±1.86)% vs. (12.60±1.90)%, caspase-3 (A value) was 1.78±0.13 vs. 1.37±0.08, both P < 0.05]. This indicated that the apoptosis of AEC II cells cultured in serum after CPB was significantly reduced by miR-17-5p, and further reduced by the pretreatment with Xuebijing.

CONCLUSIONS

Xuebiing injection can reduce the inflammatory reaction and oxidative stress of lung tissue in rats with ALI induced by CPB, and improve oxygenation. The mechanism may be related to up-regulation of miR-17-5p expression in AEC II cells and inhibition of apoptosis of AEC II cells.