The Protective Effect Of Alpha7nAChR Against CPB-induced ALI

Objective: Acute lung injury(ALI)is a common pathophysiological phenomenon after cardiopulmonary bypass(CPB).In this study,to study the role of cholinergic receptor activation in acute lung injury and its relationship with HMGB1,the acute lung injury model induced by CPB in rats and theoxygen-glucose derivation-reglucose and reoxygenation(OGD/R&R)model of alveolar macrophages were used.To further explore its potential mechanism,the specific agonist of alpha7 nicotinic acetylcholine receptor(alpha7nAChR)PNU-282987 or the antagonist bungarotoxin was adoptedas an intervention.Methods: Animal experiment part: Forty two Sprague-Dawley(SD)rats weighed 400-450 g were randomly divided into 7 groups as follows: normal group,sham group,CPB group,PNU-282987 plus CPB group,PNU-282987 plus sham group,BGT plus sham group,BGT plus PNU-282987 plus CPB group.Rats were subjected to CPB at the rate of 100ml/kg/min under anesthesia for 60 min.PNU-282987(4.8mg/kg)was administratered via arterial inflow as soon as CPB began.Bungarotoxin was performed intraperitoneal injected 30 minutes before the beginning of cardiopulmonary bypass or sham operation.Two hours post-CPB,samples of blood,bronchoalveolar lavage fluid(BALF)and lung tissues were processed for investigations.Cell experiment part: Rat alveolar macrophage cell line NR8383 for oxygen and glucose deprivation(OGD)for respectively 2h,4h,6h,8h,12 h,and re-glucose and reoxygenation for 4h.The expression of alpha7 nAChR and HMGB1 were evaluated by western-blot detection.The release of HMGB1,TNF-alpha and IL-1 beta were detected by ELISA.PNU-282987 was adopted to investigate the protective mechanism of cholinergic receptor activation on the inflammatory response induced by OGD/Re-glucose and Reoxygenation.Results: In CPB rats,structural damage in the lung was marked,density of alpha7 nAChR of the lung in the CPB group was significantly less than all other groups,while lung edema,inflammatory markers in serum and lung,protein concentrations in BALF were significantly higher.In the PNU-282987 plus CPB group,by all the above measures the CPB-associated effects were significantly ameliorared by were not identical to the control groups.The expression of alpha7 nAChR was decreased with OGD time prolonging.The expression of HMGB1 in the cytoplasm and the secretion of HMGB1 were both increased with the prolongation of OGD time.The concentration of HMGB1,TNF-alpha and IL-1 beta in the supernatant after PNU-282987 treatment were much lower than that in model group.Conclusion: Our results suggest that PNU-282987 affords protective effect against CPB-induced ALI,and inhibits HMGB1.