Dexmedetomidine exerts its protective effect on cerebral ischemia reperfusion injury in mice by inhibiting ferroptosis. / å³ç¾Žæ‰˜å’ªå®šé€šè¿‡æŠ‘åˆ¶é“æ­»äº¡å‘æŒ¥å¯¹å°é¼ è„‘ç¼ºè¡€å†çŒæ³¨æŸä¼¤çš„ä¿æŠ¤ä½œç”¨.

OBJECTIVES: Stroke is one of the major diseases that can threaten human life and health. The incidence of ischemic stroke accounts for more than 70% of stroke. The mechanism of ischemia reperfusion (IR) injury caused by ischemic stroke is extremely complex. In recent years, dexmedetomidine has been increasingly studied in anti-cerebral IR injury as a common clinical anesthetic adjunct, but its specific mechanism is not fully understood. Therefore, this study aims to explore the effects and mechanisms of dexmedetomidine on cerebral IR injury in mice. METHODS: The mouse middle cerebral artery occlusion (MCAO) model was prepared by modified suture method. Male ICR mice were randomly divided into a sham group, an IR group, an IR+D1 group (IR+administered 25 µg/kg dexmedetomidine), an IR+D2 group(IR+administered 50 µg/kg dexmedetomidine), an IR+D3 group (IR+administered 100 µg/kg dexmedetomidine), and an IR+D2+ML385 group (IR+administered 50 µg/kg dexmedetomidine and 30 mg/kg ML385). The neurologic behavior of mice was evaluated by Longa's five-point method. 2,3,5-triphenyltetrazolium chloride (TTC) staining was used to detect the percentage of cerebral infarct volume in mice. The protein expressions of nuclear factor erythroid 2-related factor 2 (Nrf2), transferrin receptor 1 (TFR1), glutathione peroxidase 4 (GPX4), and solute carrier family 7 member 11 (SLC7A11) in the cerebral tissues of mice were detected by Western blotting.Mitochondrial morphology was observed under the transmission electron microscope. The contents of MDA, Fe2+, and GSH in the cerebral tissues of mice were detected. RESULTS: Compared with the sham group, neurobehavioral scores, cerebral infarct volume, the contents of MDA and Fe2+, as well as the protein expression of TFR1 were significantly increased; the contents of GSH and the protein expression of SLC7A11 and GPX4 were significantly reduced (all P<0.05); mitochondria in cerebral tissue were wrinkled, cristae were reduced, and membrane density was increased in the IR group. Compared with the IR group, neurobehavioral scores, cerebral infarction volume, MDA and Fe2+ contents, as well as the protein expression of TFR1 were significantly reduced; the contents of GSH and the protein expression of SLC7A11 and GPX4 were significantly increased (all P<0.05); mitochondrial damage in cerebral tissue was significantly relieved with the pre-treatment of dexmedetomidine. Compared with the IR+D2 group, neurobehavioral scores, cerebral infarction volume, MDA and Fe2+ contents, as well as the protein expression of TFR1 were significantly increased; the contents of GSH and the protein expression of SLC7A11 and GPX4 were significantly reduced (all P<0.05);mitochondria reappeared significantly damaged with the ML385 on the basis of dexmedetomidine pre-treatment. CONCLUSIONS: The protective effect of dexmedetomidine on cerebral IR injury mice is related to its inhibition of ferroptosis, and the mechanism might be related to its regulation of Nrf2 expression.

[Role of mitochondrial fusion and fission in protective effects of dexmedetomidine against cerebral ischemia/reperfusion injury in mice].

OBJECTIVE: To investigate the protective effects of dexmedetomidine (DEX) against cerebral ischemia/reperfusion (I/R) injury in mice and its relation with mitochondrial fusion and fission. METHODS: Male ICR mice were randomly divided into sham-operated group, I/R group, I/R+DEX group and I/R+DEX+dorsomorphin group. Mouse models of cerebral I/R injury were established by modified thread occlusion of the middle cerebral artery. DEX (50 µg/kg) was injected intraperitoneally at 30 min before cerebral ischemia, which lasted for 1 h followed by reperfusion for 24 h. The neurobehavioral deficits of the mice were evaluated based on Longa's scores. The volume of cerebral infarction was detected by TTC staining. The changes in mitochondrial morphology of the brain cells were observed with transmission electron microscopy. Western blotting was performed to detect the expressions of phosphorylated AMP-activated protein kinase (p-AMPK), mitochondrial fusion protein (Mfn2) and mitochondrial fission protein (p-Drp1) in the brain tissues. RESULTS: DEX pretreatment significantly reduced the neurobehavioral score and the percent volume of cerebral infarction in mice with cerebral I/R injury. Treatment with dorsomorphin (an AMPK inhibitor) in addition to DEX significantly increased the neurobehavioral score and the percent volume of cerebral infarction in the mouse models. Transmission electron microscopy showed that DEX obviously reduced mitochondrial damage caused by cerebral I/R injury and restored mitochondrial morphology of the brain cells, and such effects were abolished by dorsomorphin treatment. Western blotting showed that DEX pretreatment significantly increased the expressions of p-AMPK and Mfn2 protein and decreased the expression of p-Drp1 protein in the brain tissue of the mice, and these changes were also reversed by dorsomorphin treatment. CONCLUSIONS: Preconditioning with DEX produces protective effects against cerebral I/R injury in mice possibly by activating AMPK signaling to regulate mitochondrial fusion and fission in the brain cells.

[Inhibitory effect of connexin43 protein on autophagy in cisplatin-resistant testicular cancer I-10 cells].

OBJECTIVE: To investigate the effect of connexin43 (Cx43) protein on autophagy in cisplatin (DDP)-resistant testicular cancer I-10 cells. METHODS: The expression of Cx43 proteins in testicular cancer I-10 cells and I-10/DDP cells were detected with Western blotting. I-10/DDP cells were transfected with a full- length mouse Cx43 vector (mCx43) via Lipofectamine2000, the empty vector or Lipofectamine2000 (blank control group), and the changes in the expressions of LC3 and p62 proteins were determined with Western blotting. mCherry-GFP-LC3B transfection and transmission electron microscopy were used to analyze the changes in autophagy of the cells with Cx43 overexpression. RESULTS: Cx43 was significantly decreased in I-10/DDP cells compared with I-10 cells (P < 0.01). Transfection of the I-10/DDP cells with mCx43 vector resulted in significantly increased Cx43 expression in the cells (P < 0.01) and caused significantly decreased expression of LC3-Ⅱ (P < 0.01) and increased expression of p62 (P < 0.05) as compared with the negative control cells. Both transmission electron microscopy and mCherry-GFP-LC3B transfection showed that the number of autophagosomes was obviously reduced in mCx43-transfected cells as compared with the negative control cells. CONCLUSIONS: Cx43 inhibits autophagy in cisplatin-resistant testicular cancer I-10 /DDP cells.