Effect of ulinastatin pretreatment on expression of p-ERK during ventilator-induced lung injury in rats

Abstract

Objective To evaluate the effect of ulinastatin pretreatment on the expression of phosphorylated extracellular signal-regulated kinase (p-ERK) during ventilator-induced lung injury (VILI) in the rats. Methods Forty-five pathogen-free healthy adult male Sprague-Dawley rats, weighing 200-250 g, were randomly divided into 3 groups using a random number table: control group (group C), group VILI and ulinastatin pretreatment group (group UP), with 15 rats in each group.Ulinastatin 200 000 U/kg was injected via the jugular vein at 10 min prior to mechanical ventilation in group UP.The equal volume of normal saline was injected via the jugular vein at 10 min prior to mechanical ventilation in C and VILI groups.Bilateral lungs were ventilated in volume-controlled mode in the 3 groups.Ventilator settings were adjusted to volume-controlled mode with a fixed tidal volume 40 ml/kg, inspiratory/expiratory ratio 1∶1, respiratory rate 40 breaths/min, and fraction of inspired oxygen 50%.The rats were anesthetized at 4 h of ventilation and sacrificed, and lungs were removed for determination of wet/dry lung weight ratio (W/D ratio), total lung water content (TLW) and cell apoptosis (using TUNEL) and for examination of the pathologic changes (with light microscope) and ultrastructure of lung tissues (with electron microscope). The injured alveolus rate (IAR) and apoptosis index (AI) were calculated.The expression of ERK mRNA and p-ERK in lung tissues was detected by real-time polymerase chain reaction and by Western blot, respectively.The expression of B-cell lymphoma/leukemia-2 (Bcl-2) and Bcl-2-associated X protein (Bax) in lung tissues was detected by Western blot. Results Compared to group C, the W/D ratio, TLW, IAR and AI were significantly increased, and the expression of p-ERK, Bcl-2 and Bax in lung tissues was significantly up-regulated in group VILI (P<0.01). Compared to group VILI, the W/D ratio, TLW, IAR and AI were significantly decreased, the expression of Bax in lung tissues was significantly down-regulated, and the expression of p-ERK and Bcl-2 in lung tissues was significantly up-regulated in group UP (P<0.01). The pathological changes of lung tissues were significantly attenuated in group UP as compared with group VILI. Conclusion The mechanism by which ulinastatin pretreatment mitigates VILI is related to activation of ERK signaling pathway and inhibition of cell apoptosis in rats. Key words: Trypsin inhibitors; Pneumonia, ventilator-associated; Extracellular signal-regulated MAP kinases; Apoptosis