Effect of dexmedetomidine on expression of Semaphorin 7A during lung ischemia-reperfusion in rats

Objective To evaluate the effect of dexmedetomidine on the expression of Semaphorin 7A during lung ischemia-reperfusion(I/R)in rats. Methods Thirty healthy clean-grade adult male Sprague-Dawley rats, aged 8-12 weeks, weighing 200-240 g, were divided into 3 groups (n=10 each) using a random number table method: sham operation group (S group), I/R group and dexmedetomidine group (D group). Only sternotomy was performed, and the left hilum of lung was not clamped in S group.The model of lung I/R injury was established by clamping the left hilum of lung for 45 min followed by 120 min of reperfusion in I/R group.Dexmedetomidine 50 μg/kg was intraperitoneally injected at 30 min before ischemia, and then the model was established in D group.The rats were sacrificed at the end of reperfusion, and the lungs were removed for examination of the pathological changes(using haematoxylin and eosin staining)which were scored and for determination of the wet to dry weight ratio (W/D ratio), expression of Semaphorin 7A protein and mRNA (by Western blot or real-time polymerase chain reaction), and contents of tumor necrosis factor-alpha (TNF-α) and interleukin-1beta (IL-1β) in lung tissues (by enzyme-linked immunosorbent assay). Results Compared with S group, W/D ratio and pathological scores were significantly increased, the expression of Semaphorin 7A protein and mRNA was up-regulated, and the contents of TNF-α and IL-1β were increased in I/R and D groups (P<0.05). Compared with I/R group, W/D ratio and pathological scores were significantly decreased, the expression of Semaphorin 7A protein and mRNA was down-regulated, and the contents of TNF-α and IL-1β were decreased in D group (P<0.05). Conclusion The mechanism by which dexmedetomidine reduces lung I/R injury may be related to down-regulating Semaphorin 7A expression, thus inhibiting inflammatory responses of rats. Key words: Semaphorins; Dexmedetomidine; Reperfusion injury; Lung