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Objective To investigate the effect of melatonin on mice with ischemia-reperfusion via a silent information regulator 1 (SIRT1) reducing mitochondrial oxidative stress mechanism. Methods A transient middle cerebral artery occlusion ( MCAO) cerebral ischemia-reperfusion ( IR) model in mice was established by the suture-occluded method. One hundred and ninety mice were injected with melatonin intraperitoneally or the SIRT1 inhibitor (EX527) intracerebroventricularly,30 dead and model failure mice were excluded. They were divided into IR,melatonin,melatonin +EX527,and EX527 groups (n =40 in each group ) according to the random number table. The cerebral infarct volume was detected by the triphenyltetrazolium chloride (TTC) method,the brain edema was measured by the wet and dry weight method and the neurological deficit scores were measured. Western blot was used to detect SIRT1,Ac-P53, acetylated-nuclear factorκB (Ac-NF-κB),BCl2,Bax proteins in the mitochondria and cytoplasm,as well as the cytochrome C protein expression. A single factor analysis of variance was used for comparison among the groups. Results ( 1 ) There were significant differences in cerebral infarction volume, neurological dysfunction scores and cerebral edema among the four groups ( F values,16. 452,23. 622,and 18. 786, respectively (all P<0. 05). There were significant differences in the expression levels of SIRT1,Ac-P53, Ac-NF-κB,BCl2, and Bax among the four groups ( F values, 2348. 158, 1434. 841, 7042. 563, 14627. 128,and 691. 475,respectively,all P<0. 05). There were significant differences in mitochondrial membrane potential,mitochondrial reactive oxygen species,and complex I activity in mice among the four groups (F value,28. 454,33. 728 and 29. 716,respectively,all P <0. 05). (2) Compared with the IR group,the infarct volume was reduced (32 ± 5 mm3 vs. 57 ± 5 mm3,P<0. 05),neurological deficit scores were decreased (2. 4 ± 0. 3 vs. 3. 5 ± 0. 3,P<0. 05);brain edema was reduced (80. 2 ± 0. 9% vs. 83. 9 ± 1. 2%,P<0. 05);the expression levels of SIRT1 and anti-apoptosis protein BCL2 were increased in the melatonin group (P<0. 05);the expression levels of pro-apoptotic protein BAX and Ac-P53,Ac-NF-κB were reduced ( P <0. 05 );the mitochondrial membrane potential, mitochondrial complex I activity and cytochrome C level were increased (P<0. 05);and the cytoplasmic reactive oxygen species and cytochrome C level were decreased (P < 0. 05). (3) Compared with the melatonin group,cerebral infarction volume were increased (42 ± 5 mm3 vs. 32 ± 5 mm3,P < 0. 05);nerve dysfunction scores were increased(3. 2 ± 0. 3 vs. 2. 4 ± 0. 3,P<0. 05);cerebral edema was aggravated (83. 4 ± 0. 8% vs. 80. 2 ± 0. 9%, P < 0. 05 );the expression levels of SIRT1 and anti-apoptotic protein BCL2 were reduced (P <0. 05);the pro-apoptotic protein BAX,Ac-P53,and Ac-NF-κB expression levels were increased (P<0. 05);the mitochondrial membrane potential and mitochondrial complex I activity and cytochrome C level were decreased (P<0. 05);and the cytoplasmic reactive oxygen species and cytoplasmic cytochrome C level were increased in the melatonin+EX527 group (P<0. 05). Conclusion In ischemic stroke model mice, melatonin plays a neuroprotective role by activating the SIRT1 signaling pathway and reducing oxidative stress injury and cell death in mitochondria,thus plays a role in cerebral protection.