Effects of quercetin on apoptosis of alveolar polymorphonuclear neutrophils in severe acute pancreatitis rats with lung injury

AIM：To explore the effects of quercetin (Que) on the apoptosis of alveolar polymorphonuclear neutrophils (PMN) isolated from severe acute pancreatitis (SAP) rats with lung injury. METHODS：Forty-eight SD rats were randomly divided into 4 groups：sham group, SAP group, low-dose (50 mg/kg) Que group and high-dose (100 mg/kg) Que group. SAP was induced by retrograde administration of 5% sodium taurocholate into the biliary pancreatic duct. The SAP rats in Que groups were given quercetin, while the rats in sham group and SAP group received an infusion of physiological saline. Alveolar PMN were harvested by the collection of bronchoalveolar lavage fluid. The cell morphological changes were observed under fluorescent microscope. The cell apoptotic index was analyzed by flow cytometry. The protein levels of Bax and Bcl-2 were examined by Western blotting. Caspase-3 activity was measured by fluorescence spectrophotometry. RESULTS：Cell shrinkage and condensation of chromosomes were observed in alveolar PMN from SAP rats. Compared with sham group, the apoptotic index of alveolar PMN reduced in SAP group. The protein expression of Bax was significantly reduced, that of Bcl-2 was significantly enhanced, and caspase-3 activity was attenuated. After Que pretreatment, the apoptotic index of alveolar PMN increased, the protein expression of Bax was significantly enhanced, that of Bcl-2 was significantly reduced, and caspase-3 activity increased. The effects of Que presented a concentration-dependent manner, indicating that Que alleviated SAP-induced lung injury. CONCLUSION：The apoptosis of alveoar PMN is delayed in SAP rats. Quercetin induces apoptosis of alveolar PMN by up-regulating the expression of Bax and down-regulating the expression of Bcl-2.