Acacetin ameliorates alveolar epithelial cell damage caused by Streptococcus pneumoniae infection by regulating Sirt1-mediated AMPK/Nrf2 signaling pathway
Objective:To investigate effect of acacetin on alveolar epithelial cell damage caused by Streptococcus pneumoniae(SP)infection by regulating sirtuin 1(Sirt1)-mediated 5'-AMP activated protein kinase(AMPK)/nuclear factor erythroid-2 related factor 2(Nrf2)signaling pathway.Methods:Alveolar epithelial cells A549 cultured in vitro were infected with SP to establish a cell damage model.After treatment with acacetin at final concentrations of 0,5,25,50,100,150,200 µmol/L,CCK-8 was performed to detect cell viability of each treatment group and optimal concentration of acacetin was screened.A549 cells cultured in vitro were ran-domly separated into five groups:control group,model group,acacetin(150 µmol/L)group,EX527(Sirt1 inhibitor,40 µmol/L)group,acacetin(150 µmol/L)+EX527(40 µmol/L)group,control group was not treated,other groups were infected with SP to establish a cell damage model,and then treated with 150 µmol/L acacetin and 40 µmol/L EX527,CCK-8 and flow cytometry were performed to measure cell viability and apoptosis rate in each group;kits were performed to measure levels of reactive oxygen species(ROS),superoxide dismutase(SOD),malondialdehyde(MDA),lactate dehydrogenase(LDH)and IL-10,IL-1β,TNF-α levels of cells in each group;Western blot was performed to measure proliferation-related proteins Ki-67,proliferating cell nuclear antigen(PCNA),apoptosis-related proteins caspase-9,Bax,Sirt1 and AMPK/Nrf2 signaling pathway proteins p-AMPK/AMPK,Nrf2 expres-sions of cells in each group.Results:Model group had decreased A549 cell viability,SOD and IL-10 levels,p-AMPK/AMPK,Sirt1,Nrf2,Ki-67 and PCNA protein expressions(P<0.05),and increased apoptosis rate,MDA,LDH,ROS,IL-1β and TNF-α levels than control group(P<0.05).Compared with model group and acacetin+EX527 group,acacetin group had increased A549 cell viability,SOD and IL-10 levels,p-AMPK/AMPK,Sirt1,Nrf2,Ki-67 and PCNA protein expressions(P<0.05),and decreased apoptosis rate,MDA,LDH,ROS,IL-1β and TNF-α levels(P<0.05);EX527 group had decreased A549 cell viability,SOD and IL-10 levels,p-AMPK/AMPK,Sirt1,Nrf2,Ki-67 and PCNA protein expressions(P<0.05),and increased apoptosis rate,MDA,LDH,ROS,IL-1β and TNF-α levels(P<0.05).Conclusion:Acnestin can activate AMPK/Nrf2 signaling by up-regulating Sirt1 expression,thereby promoting secretion of anti-inflammatory factors,reducing production of ROS and pro-inflammatory factors,reducing inflammation and oxidative stress,and finally alleviating neuronal damage.
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