Objective:To evaluate the effects of dexmedetomidine on alveolar epithelial barrier function in rats with ventilator-induced lung injury (VILI), and the role of protein kinase C (PKC).Methods:One hundred clean-grade male Sprague-Dawley rats, weighing 270-320 g, aged 4-5 months, were divided into 5 groups ( n=20 each) using a random number table method: control group (group C), VILI group (group V), PKC inhibitor group (group B), dexmedetomidine group (group D), and dexmedetomidine plus PKC agonist group (DP group). The VILI model was developed by mechanical ventilation with a tidal volume of 40 ml/kg for 4 h in anesthetized animals.Group C breathed air autonomously for 4 h without mechanical ventilation.Group V was mechanically ventilated for 4 h. In group B, bisindolvlmaleimide I 0.12 mg/kg was injected intramuscularly 1 h before mechanical ventilation.In D and DP groups, dxmedetomidine 5.0 μg/kg was injected intravenously at 20 min before mechanical ventilation, and dexmedetomidine was intravenously infused at the rate of 5.0 μg·kg -1·h -1 during mechanical ventilation.In group DP, PKC agonist phorbol-12-myristic acid-13-acetate 15 μg/kg was intraperitoneally injected at 30 min before mechanical ventilation.At 4 h of mechanical ventilation, oxygenation index (OI), lung permeability index (LPI) and wet/dry lung weight (W/D) ratio were measured, the pathological changes of lung tissues were observed, and lung injury was assessed and scored.The expression of PKC, occludin and ZO-1 protein was detected by Western blot, and the expression of PKC mRNA, occludin mRNA and ZO-1 mRNA was determined by real-time polymerase chain reaction. Results:Compared with group C, OI was significantly decreased, LPI, W/D ratio and lung injury score were increased, the expression of PKC protein and mRNA was up-regulated, and the expression of occludin and ZO-1 protein and mRNA was down-regulated in V and DP groups ( P<0.05), and no significant change was found in the parameters mentioned above in B and D groups ( P>0.05). Compared with group V, OI was significantly increased, LPI, W/D ratio and lung injury score were decreased, the expression of PKC protein and mRNA was down-regulated, and the expression of occludin and ZO-1 protein and mRNA was up-regulated in B, D and DP groups ( P<0.05). Compared with group D, OI was significantly decreased, LPI, W/D ratio and lung injury score were increased, the expression of PKC protein and mRNA was up-regulated, and the expression of occludin and ZO-1 protein and mRNA was down-regulated in group DP ( P<0.05). Conclusions:Dexmedetomidine can reduce the damage to alveolar epithelial barrier function in rats with VILI, and the mechanism is related to inhibition of PKC activation and up-regulation of the expression of occludin and ZO-1.

Objective:To evaluate the effect of dexmedetomidine on the extracellular signal-regulated kinase(ERK)/sodium-potassium ATPase(Na + -K + -ATPase)signaing pathway in lung tissues of rats with mechanical ventilation-induced lung injury (VILI). Methods:Forty-eighty clean-grade male Sprague-Dawley rats, weighing 270-320 g, aged 4-5 months, were divided into 4 groups ( n=12 each) using a random number table method: control group (group C), VILI (alpha2-adrenergic receptor antagonist) group (group V), dexmedetomidine group (group D), and dexmedetomidine plus yohimbine group (group DY). Group C underwent no mechanical ventilation and breathed air spontaneously for 4 h. Mechanical ventilation (respiratory rate 40 breaths/min, tidal volume 40 ml/kg, inspiratory/expiratory ratio 1∶1, PEEP 0, fraction of inspired oxygen 21%) lasted 4 h in group V. Dexmedetomidine was infused intravenously in a dose of 5.0 μg/kg at 20 min before ventilation followed by an infusion of 5.0 μg·kg -1· h -1 throughout ventilation in group D. In group DY, yohimbine 0.1 mg/kg was injected intravenously at 10 min before dexmedetomidine, and the other treatments were similar to these previously described in group D. Blood samples and lung tissues were taken at 4 h of mechanical ventilation to determine the wet/dry weight ratio (W/D ratio), lung permeability index (LPI), alveolar fluid clearance rate (AFC), and expression of extracellular signal-regulated kinase (ERK), phosphorylated extracellular signal-regulated kinase (p-ERK), and Na + -K + -ATPase in lung tissues (by Western blot) and to observe pathological changes of lung tissues. Results:Compared with group C, LPI and W/D ratio were significantly increased, AFC was decreased, p-ERK expression was up-regulated, and Na + -K + -ATPase expression was down-regulated in group V and group DY ( P<0.05), and no significant change was found in the incidence of the parameters mentioned above in group D ( P>0.05). Compared with group V, LPI and W/D ratio were significantly decreased, AFC was increased, p-ERK expression was down-regulated, Na + -K + -ATPase expression was up-regulated ( P<0.05), and the pathological changes of lung tissues were significantly attenuated in group D, and no significant change was found in the incidence of the parameters mentioned above in group DY ( P>0.05). Compared with group D, LPI and W/D ratio were significantly increased, AFC was decreased, p-ERK expression was up-regulated, Na + -K + -ATPase expression was down-regulated ( P<0.05), and the pathological changes of lung tissues were accentuated in group DY. Conclusion:The mechanism by which dexmedetomidine alleviates VILI may be related to activating alpha2-adrenergic receptors and inhibiting ERK/Na + -K + -ATPase signaling pathway in rats.

Objective:To evaluate the role of transient receptor potential vanilloid receptor 1 (TRPV1)/nuclear factor-κB (NF-κB) signaling pathway in dexmedetomidine-induced alleviation of ventilator-induced lung injury (VILI) in rats.Methods:One hundred clean-grade healthy male Sprague-Dawley rats, weighing 270-320 g, aged 4-5 months, were divided into 5 groups ( n=20 each) using a random number table method: control group (group C), VILI group (group V), AMG9810 group (group A), dexmedetomidine group (group D), and dexmedetomidine + RTX group (group DR). VILI model was prepared by mechanical ventilation with a tidal volume of 40 ml/kg for 4 h. In group A, TRPV1 inhibitor AMG9810 30 mg/kg was intraperitoneally injected at 1 h before mechanical ventilation.Dexmedetomidine 5.0 μg/kg was intravenously infused at 20 min before mechanical ventilation, and dexmedetomidine was intravenously infused at the rate of 5.0 μ g·kg -1·h -1 during ventilation in group D and group DR.In group DR, RTX 70 μ g/kg was intraperitoneally injected for 3 consecutive days before mechanical ventilation.At 4 h of mechanical ventilation, the concentrations of interleukin-1beta (IL-1β), tumor necrosis factor-alpha (TNF-α) and IL-6 in bronchoalveolar lavage fluid (BALF) were detected, oxygenation index (OI) and wet/dry lung weight (W/D) ratio were measured, the histopathological changes of lung tissues were observed, and lung injury was assessed and scored.The expression of TRPV1 and NF-κB in lung tissues was detected by Western blot, and real-time polymerase chain reaction was used to detect the expression of TRPV1 and NF-κB mRNA. Results:Compared with group C, the concentrations of IL-1β, TNF-α and IL-6 in BALF were significantly increased, OI was decreased, the W/D ratio and lung injury scores were increased, and the expression of TRPV1 and NF-κB protein and mRNA was up-regulated in group V ( P<0.05). Compared with group V, the concentrations of IL-1β, TNF-α and IL-6 in BALF were significantly decreased, OI was increased, the W/D ratio and lung injury scores were decreased, and the expression of TRPV1 and NF-κB protein and mRNA was down-regulated in A, D and DR groups ( P<0.05). Compared with group D, the concentrations of IL-1β, TNF-α and IL-6 in BALF were significantly increased, OI was decreased, the W/D ratio and lung injury scores were increased, and the expression of TRPV1 and NF-κB protein and mRNA was up-regulated in group DR ( P<0.05). Conclusions:The mechanism by which dexmedetomidine alleviates VILI is partially related to inhibition of the activation of TRPV1/NF-κB signaling pathway and inhibition of the inflammatory responses in lung tissues of rats.