Effect of mechanical ventilation preconditioning on expression of Rho-associated kinase 1 in lung tissues in a rat model of ventilator-induced lung injury

Abstract

Objective To evaluate the effects of mechanical ventilation preconditioning on the expression of Rho-associated kinase 1 (ROCK1) in the lung tissue in a rat model of ventilator-induced lung injury. Methods Forty-eight male Sprague-Dawley, aged 8–12 weeks, weighing 250–300 g, were randomly assigned into 6 groups (n= 8 each) using a random number table: control group (group C); normal mechanical ventilation group (group N); mechanical ventilation with large tidal volume (VT) group (group L); preconditioning with mechanical ventilation with different VT groups (P1, P2 and P3 groups). The animals were anesthetized with intraperitoneal pentobarbital sodium, and tracheostomized.In group C, the animals kept spontaneous breathing after intubation.In group N, the animals were mechanically ventilated for 3 h with the VT of 8–10 ml/kg.In group L, the animals were mechanically ventilated for 3 h with the VT of 40 ml/kg.In P1, P2 and P3 groups, the animals were mechanically ventilated for 30 min with the VT of 6–7, 20 and 30 ml/kg, respectively, and then were mechanically ventilated for 3 h with the VT of 40 ml/kg.The respiratory rate was 40 breaths/min, and inspiratory/expiratory ratio was 1∶1.The animals were sacrificed at the end of ventilation.Broncho-alveolar lavage fluid was collected, and pulmonary permeability index (PPI) was calculated.Lungs were removed for examination of pathological changes which were scored, and for detection of the wet to dry lung weight ratio (W/D ratio), apoptosis in alveolar epithelial cells, and expression of ROCK1 (by immunohistochemistry and Western blot). Apoptosis index (AI) was calculated. Results Compared with group C, the pathological scores, W/D ratio, PPI and AI were significantly increased, and the expression of ROCK1 was up-regulated in L, P1, P2 and P3 groups (P 0.05). Compared with group L, the pathological scores, W/D ratio, PPI and AI were significantly decreased, and the expression of ROCK1 was down-regulated in group P1 (P 0.05). Conclusion The mechanism by which mechanical ventilation preconditioning decreases ventilator-induced lung injury may be related to inhibition of the expression of ROCK1 in lung tissues of rats. Key words: Respiration, artificial; Respiration distress syndrome, adult; rho-associated kinases