Oxidative stress and neuronal apoptosis play crucial roles in secondary brain injury (SBI) after intracerebral hemorrhage (ICH). Recently, Nle4-D-Phe7-α-melanocyte-stimulating hormone (NDP-MSH), a synthetic agonist of the melanocortin-1 receptor (Mc1r), has been proved to inhibit neuroinflammatory in several diseases. This study is aimed at exploring if NDP-MSH could reduce oxidative stress and neuronal apoptosis following ICH, as well as the potential mechanism. A mouse ICH model was induced by autologous blood injection. NDP-MSH was intraperitoneally injected at 1 h after ICH. Mc1r siRNA and PI3K inhibitor LY294002 were administrated to inhibit the expression of Mc1r and phosphorylation of PI3K, respectively. Neurological test, brain water content, enzyme-linked immunosorbent assay (ELISA), terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL), immunofluorescence, and Western blot analysis were utilized in this study. The results exhibited that Mc1r was mainly expressed in neurons, and its level in the ipsilateral hemisphere was significantly elevated after ICH. NDP-MSH treatment significantly attenuated the neurological deficits and brain water content 24 hours after ICH, which was accompanied by the inhibition of oxidative stress and neuronal apoptosis. The administration of NDP-MSH after ICH significantly promoted the expression of Mc1r, p-PI3K, p-Akt, and p-Nrf2, followed by an increase of Bcl-2 and reduction of cleaved caspase-3. Conversely, downregulating the expression of Mc1r and phosphorylation of PI3K aggravated the neurological deficits and brain edema at 24 hours after ICH, meanwhile, the effect of NDP-MSH on the expression of Mc1r, p-PI3K, p-Akt, p-Nrf2, Bcl-2, and cleaved caspase 3 was also abolished. In conclusion, our data suggest that the activation of Mc1r by NDP-MSH ameliorates oxidative stress and neuronal apoptosis through the PI3K/Akt/Nrf2 signaling pathway after ICH in mice.

中文翻译：

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NDP-MSH激活Melanocortin-1受体可通过小鼠脑出血后PI3K / Akt / Nrf2途径减轻氧化应激和神经元凋亡。

氧化应激和神经元凋亡在脑出血（ICH）后继发性脑损伤（SBI）中起着关键作用。最近，Nle4-D-Phe7- αβ-黑素细胞刺激激素（NDP-MSH）是melanocortin-1受体（Mc1r）的合成激动剂，已被证明可以抑制多种疾病的神经炎症。这项研究旨在探讨NDP-MSH是否可以减轻ICH后的氧化应激和神经元凋亡以及其潜在机制。通过自体血液注射诱导小鼠ICH模型。ICH后1 h腹膜内注射NDP-MSH。施用Mc1r siRNA和PI3K抑制剂LY294002以分别抑制Mc1r的表达和PI3K的磷酸化。在这项研究中使用了神经学测试，脑含水量，酶联免疫吸附测定（ELISA），末端脱氧核苷酸转移酶介导的dUTP-生物素缺口末端标记（TUNEL），免疫荧光和蛋白质印迹分析。结果表明，ICH后，Mc1r主要在神经元中表达，同侧半球中的Mc1r水平明显升高。NDP-MSH治疗可显着减轻ICH后24小时的神经功能缺损和脑含水量，并伴有氧化应激和神经细胞凋亡的抑制作用。ICH后NDP-MSH的给药显着促进了Mc1r，p-PI3K，p-Akt和p-Nrf2的表达，随后增加了Bcl-2并减少了裂解的caspase-3。相反，下调ICH后24小时，Mc1r的表达和PI3K的磷酸化加剧了神经功能缺损和脑水肿，同时，NDP-MSH对Mc1r，p-PI3K，p-Akt，p-Nrf2， Bcl-2，和裂解的胱天蛋白酶3也被废除了。结论，