Objective To investigate the changes and potential roles of the expression of apoptosis signal-regulating kinase 1(ASK1),thioredoxin(Trx)and thioredoxin reductase(TrxR)in the pathogenesis of lung injury of premature newborn rats exposed to hyperoxia. Methods In the first day after delivery,preterm SD rats were randomly divided into air group and hyperoxia group with 64 rats in each.The rats were respectively sacrificed at 1,4,7,10 and 14 days after air or hyperoxia exposure.Sections of 1ungs were stained with HE to observe the histologic changes.Trx and TrxR mRNA were detected by reverse transcription-polymerase chain reaction(RT-PCR).Immunohistochemistry was used to detect the expression and distribution of ASK1.Western blot was used to detect the expression of ASK1 protein. Results Rats in hyperoxia group showed typical lung injury,which was characterized by alveolitis and delayed of lung development.Immunohistochemistry detected that ASK1 expressed generally in the cytoplasm of both alveolar epithelial cells and vascular endothelial cells:ASK1 protein expression in hyperoxia group at 1th and 4th day were 0.4382±0.0227 and 0.5270±0.0432,higher than in the air group(0.3458±0.0263 and 0.3760±0.0058)(P<0.01),and it was until 7th day that the expression became weaker(0.4343±0.0254),but still higher compared with the air group(0.3473±0.0220)(P<0.01).Compared with the air group,Trx and TrxR mRNA of the hyperoxia group increased significantly and peaked at lOth day(0.6860±0.0811)and 7th day(2.0351±0.1600),respectively(P<0.05).ASK1 protein expressions resulting

Objective To explore the effects of expression of thioredoxin-2(Trx-2) suppressed by small interference RNA(SiRNA) in A549 cells exposed to hyperoxia on expression of nicotinamide adenine dinucleotide(NADH) dehydrogenase subunit 1(ND1)and cytochrome C oxidase Ⅰ(COX Ⅰ). Methods A549 cells were gained by serial subcultivation in vitro and transfered with synthetic Trx-2 sequence-specific SiRNA and then were randomly divided into air group without interference,hyperoxia group without interference,air group after interference,and hyperoxia group after interference.After exposure to oxygen or room air for 12,24 and 48 h,expressions of Trx-2,ND1 and COX Ⅰ mRNA of these cells were detected by reverse transcription-polymerase chain reaction (RT-PCR),and Trx-2 protein was detected by Western blot. Results (1)Sequence-specific SiRNAtargeting Trx-2 could significantly down-regulate its expression in A549 cells.(2)Trx-2 mRNA levds inhyperoxia group without interference at 24 h was higher than those in air group without interference(0.7799±0.1249 VS 0.4424±Ⅰ.1140,P<0.05).Th-2 mRNA levels in hyperoxia group after ireedcrence at 24 hand 48 h were 0.2774±0.0174 and 0.2587±0.0069,lower than those in air group after interference andhyperoxia group without interference (P<0.05).(3)ND1 mRNA levels in hyperoxia group without interference at 24 h was 0.6609±0.0368,lower than those in air group without interference(0.8898±0.1049)(P<0.05).ND1 mRNA levels in hyperoxia group after interference at 12 h was 0.8848±0.0135,higher than those in air group after imederence(P<0.05).ND1 mRNA levels in hypemxia group afterinterference at 48 h was 0.3808±0.0937,lower than those in air group after imerference and hyperoxiagroup without interference(P<0.05).(4)COXI mRNA levels in hypemxia group without inteference at 12,24 and 48 h were 1.7313±0.4331,2.1929±0.6722 and 2.0754±0.2584,higher than those in air group witheUt interference,respectively (P<0.05). Conclusions ND1 and COXⅠ participate in thedevelopment of hyperoxia indUCed lung.injury,and Trx-2 is likely to have protective effect on mitochondria ofA549 cells in hyperoxia lung injury.