The protective effects and mechanisms of metformin against oxidative stress were evaluated both in vivo and in vitro. ARPE-19 cells comprised the normal group, the glyoxal-treated group (0.5 mM glyoxal), and the glyoxal+metformin group (0.5 mM glyoxal and 0.1 mM metformin). In the in vitro model, differences in cell viability, ROS production, NO products, cellular apoptosis, and the expressions of phospho-AMPKα, total-AMPKα, Sirt1, Nrf2, TXNIP, ZO-1, and Occludin were assessed. In the glyoxal-treated group, cell viability and NO production were decreased, while ROS production and cell apoptosis were increased (), compared with the control group. These changes were prevented by metformin treatment. Protein expressions of phospho-AMPKα, Sirt1, TXNIP, ZO-1, and Occludin, but not Nrf2, were decreased significantly in the glyoxal-treated group compared to normal controls. Metformin treatment significantly increased the above protein expressions and slightly increased TXNIP expression. Immunofluorescence showed that metformin prevented the glyoxal-induced, disorganized tight junctions in ARPE-19 cells. To confirm metformin’s protection, Sprague-Dawley rats were injected intravenously with sodium iodate (SI) to induce oxidative stress in the retinal pigment epithelium (RPE). Metformin was then delivered intraperitoneally or intravitreally. One day and three days after SI and metformin treatments, the RPE-Bruch’s membrane-choriocapillaris complex was isolated and immune-stained with ZO-1 antibodies. The morphology of the RPE showed enlarged cellular bodies and disorganized ZO-1 staining in SI-treated rats. Metformin treatment prevented these changes. The results indicated that metformin maintained the barrier functions of RPE cells both in vivo and in vitro. Metformin exerted its protection against oxidative stress possibly via activating AMPK/Sirt1 and increasing TXNIP. Metformin has been proposed as a candidate drug for age-related macular degeneration (AMD) by both preclinical and clinical studies. The cellular and animal models used in this study might be useful for the interpretation of the molecular mechanisms involved in the drug activity.

中文翻译：

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二甲双胍可保护ARPE-19细胞免受乙二醛诱导的氧化应激。

在体内和体外评估二甲双胍对氧化应激的保护作用和机制。ARPE-19细胞包括正常组，乙二醛处理组（0.5 mM乙二醛）和乙二醛+二甲双胍组（0.5 mM乙二醛和0.1 mM二甲双胍）。在体外模型中，在细胞生存力，ROS的产生，NO产品，细胞凋亡，和磷酸AMPK的表达差异α，总-AMPK α，Sirt1的，Nrf2的，TXNIP，ZO-1，和Occludin蛋白进行了评估。在乙二醛治疗组中，细胞活力和NO产生降低，而ROS产生和细胞凋亡增加（），与对照组相比。二甲双胍治疗可预防这些变化。磷酸化AMPK蛋白表达α与正常对照组相比，乙二醛治疗组的Sirt1，TXNIP，ZO-1和Occludin（而非Nrf2）显着降低。二甲双胍治疗显着增加上述蛋白质表达，并略微增加TXNIP表达。免疫荧光显示，二甲双胍可防止ARPE-19细胞中乙二醛诱导的，紊乱的紧密连接。为了证实二甲双胍的保护作用，向Sprague-Dawley大鼠静脉注射碘酸钠（SI），以诱导视网膜色素上皮（RPE）的氧化应激。然后将二甲双胍腹膜内或玻璃体内给药。SI和二甲双胍治疗后的第一天和第三天，分离出RPE-Bruch的膜-脉络膜毛细血管复合物，并用ZO-1抗体免疫染色。RPE的形态在SI处理的大鼠中显示出增大的细胞体和无序的ZO-1染色。二甲双胍治疗可预防这些变化。结果表明二甲双胍均维持RPE细胞的屏障功能体内和体外。二甲双胍可能通过激活AMPK / Sirt1和增加TXNIP发挥抗氧化应激的作用。临床前和临床研究均已提议将二甲双胍作为年龄相关性黄斑变性（AMD）的候选药物。在这项研究中使用的细胞和动物模型可能有助于解释参与药物活性的分子机制。