Protection By Resveratrol Against Seawater-Drowning-Induced Lung Injury In Rats

Objective:1.To improve the seawater-drowning-induced lung injury model in rats.2.To study the pathophysiological process and mechanism of seawater-drowning-induced acute lung injury in rats.3.To investigate the protective effect of resveratrol against seawater-drowning-induced lung injury and its mechanism.Methods:A total of 112 Sprague-Dawley healthy male rats were randomly assigned into 5 groups:control group（Group C,n=8）,seawater drowning group（Group S,n=32）,resveratrol prophylactic treatment group（Group S+R,n=32）,resveratrol group（Group R,n=8）,and endotracheal intubation group（Group E,n=32）.Groups S,S+R and E were further divided into four subgroups according to the sampling time,namely,0.5h,1h,2h and 4h,with 8 rats in each.Endotracheal intubation models were improved as follows:The rats were fixed on the operating table in the supine position with the head elevated 45°;endotracheal intubation was performed directly through the mouth（depth of insertion:5～6cm from the upper teeth）,and the secretions on the glottis were intermittently cleansed with small cotton swabs.The SWD-ALI animal model was constructed with a1.0ml syringe connected to the endotracheal tube to infuse seawater（2ml/kg）into the trachea at a constant rate within 1 minute.Groups S and S+R were injected through the trachea with 2ml/kg seawater within 1min;Group E was intubated for 1 minute,then the tube was removed.At the above-mentioned sampling time points,abdominal aortic blood was taken from these 3 groups for blood gas analysis;then the rats were sacrificed to obtain their lungs;lung wet-to-dry ratio（W/D）,MDA,SOD,MPO,and caspase-3 were measured by ELISA,and the histological sections of rat lungs were stained with haematoxylin-eosin.Groups S+R and R were pretreated with resveratrol（50mg/kg）through intragastric administration for 3 days;then models were established and the rats were sacrificed 24 hours after the last intragastric administration.Results:1.ModelThe model of seawater-drowning-induced lung injury in rats was successfully constructed.2.Arterial blood gas resultsIn Group S,after seawater perfusion,PO₂ significantly decreased and PCO2significantly increased,but both gradually recovered after 60min.There was no statistical difference between Group S and Group C at 4h.The PO₂ decrease and PCO2increase were minor in Group S+R than in Group S,and they returned to normal quickly.There was no statistical difference in the values of PO₂ and PCO₂in Groups C,R,and E.3.SOD and MPO activity,MDA and caspase-3 content in lung tissueThe activity of SOD and MPO in Group S decreased significantly after seawater perfusion,while the content of MDA and caspase-3 increased.This trend also appeared in Group S+R,but less severe than in Group S.60 minutes later,in both groups,the activity of SOD and MPO slowly increased,while the content of MDA and caspase-3slowly decreased,and Group S+R recovered significantly faster than Group S.There was no significant difference among Groups C,R and E in SOD and MPO activity,or in MDA and caspase-3 content.4.W/D of lung tissueAfter seawater perfusion,the lung tissue W/D of Group S increased significantly,decreased slowly after 60min,and was still higher than that of Group C after 240min.The lung tissue W/D of Group S+C was lower than that of Group S at the same time points.There was no significant difference in W/D values among Groups C,R and E.5.Pathological changes of lung tissueAfter seawater perfusion,the lungs in Group S were hyperemic and edematous.On the surface of the lungs,there were dots and patches of different sizes,some of which were fused.In severe cases,there were hepatogenic changes,and the low-hanging parts were obvious.The lung injury was most obvious at 0.5h and 1h after perfusion,and the lung swelling was reduced at 4h after perfusion,with occasional scattered bleeding points but no obvious hemorrhagic foci.However,the lung tissue swelling and bleeding in Group S+R was less severe than that in Group S.Microscopically,the pulmonary tissue structure in Group S was disordered,with thickened alveolar walls,structural destruction,and a large number of red blood cells.Focal lymphocytic infiltration and exfoliation of bronchial epithelial cells were observed.The damage in Group S+R was less serious than that in Group S.There was no significant difference in the appearance and microscopic appearance of the lung tissues in Groups C,R and E.Conclusion:1.After seawater perfusion,Pa CO₂,Pa O₂,W/D and lung histological HE staining in Groups S and S+R were changed,suggesting that resveratrol can improve the hypoxia condition of the lung tissue,reduce the degree of pulmonary edema,and finally achieve the therapeutic effect.2.After seawater perfusion,SOD,MPO and MDA in Groups S and S+R were changed,suggesting that SOD,MDA and MPO may be involved in the pathogenesis of SWD-ALI,and that resveratrol may reduce the oxidation reaction by regulating SOD,MDA and MPO,leading to the recovery from lung injury.3.After seawater perfusion,caspase-3 in groups S and S+R were changed,indicating that the apoptosis of lung tissue might occur in seawater-drowning-induced lung injury,and that resveratrol might achieve the protective effect by regulating the apoptosis of lung tissue.