Role of microRNA-125b in ventilator-induced lung injury in mice

Objective To evaluate the role of microRNA-125b (miR-125b) on ventilator-induced lung injury (VILI) in mice. Methods Forty healthy male C57BL/6 male mice, weighing 25-30 g, aged 2-3 months, were divided into 4 groups (n=10 each) using a random number table method: sham operation group (group Sham), group VILI, VILI plus miR-125b negative control group (group VILI+ NC), and VILI plus miR-125b overexpression group (group VILI+ miR-125b agomir). In VILI+ NC and VILI+ miR-125b agomir groups, miR-125b negative control and miR-125b agomir transfection complex 50 μl were intratracheally instilled, respectively, and 48 h later VILI model was established.The animals were mechanically ventilated for 4 h with high tidal volume (40 ml/kg) to induce VILI.Blood samples were obtained from the femoral artery at 4 h of mechanical ventilation for detection of PaO2, then animals were sacrificed, lungs were removed for determination of wet to dry weight ratio (W/D ratio) and for examination of pathological changes (with a light microscope), and lung injury was scored.In VILI+ NC and VILI+ miR-125b agomir groups, bronchoalveolar lavage fluid (BALF) was collected to measure the concentrations of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) by enzyme-linked immunosorbent assay.The cell apoptosis of lung tissues was measured using TUNEL, apoptosis index was calculated, the caspase-3 expression was detected by Western blot, and the miR-125b expression was detected by real-time polymerase chain reaction. Results Compared with Sham group, PaO2 was significantly decreased, and W/D ratio and lung injury score were increased in VILI, VILI+ NC and VILI+ miR-125b agomir groups, and the expression of miR-125b was down-regulated in VILI and VILI+ NC groups (P<0.05). Compared with VILI group, PaO2 was significantly increased, W/D ratio and lung injury score were decreased, the expression of miR-125b was up-regulated (P<0.05), the pathological changes of lung tissues were significantly attenuated in group VILI+ miR-125b agomir, and no significant change was found in the parameters mentioned above in group VILI+ NC (P<0.05). Compared with group VILI+ NC, the concentrations of TNF-α and IL-6 in BALF and apoptotic index were significantly decreased, and the expression of caspase-3 was down regulated in group VILI+ miR-125b agomir (P<0.05). Conclusion MiR-125b is involved in the endogenous protective mechanism of VILI in mice. Key words: MicroRNAs; Ventilator-induced lung injury