Background. Endothelial dysfunction and apoptosis resulting from oxidative stress can lead to the development of atherosclerosis. Our group has previously showed that CD137 signaling contributes to the progression of atherosclerosis and the vulnerability of plaques. The aim of this study is to investigate the effects of CD137 signaling in atherosclerosis on endothelial cells (ECs) apoptosis and to explore the underlying mechanisms. Methods. Serum samples were collected from 11 patients with acute myocardial infarction and 4 controls. Peritoneal injection of agonist-CD137 recombinant protein in ApoE^−/− mice was used to determine whether CD137 signaling can promote apoptosis in vivo, and human umbilical vein endothelial cells treated with agonist-CD137 recombinant protein, M5580 (a Nrf2 pathway agonist) and CAPE (a NF-κB pathway inhibitor) were used to explore the effect of Nrf2 and NF-κB pathway in CD137 signaling-induced ECs apoptosis in vitro. Results. ELISA showed that Bcl-2 in the serum of AMI patients was lower than that of the control group, while TNF-α and sCD137 were higher than that of the control group. Confocal microscopy and Western blot analysis showed that the nuclear translocation of Nrf2 in the agonist-CD137 group was significantly inhibited, and the expression of its downstream antioxidant enzymes was also decreased when compared with control. Immunofluorescence and Western blot results showed that the nuclear translocation of NF-κB in the agonist-CD137 group was enhanced, and ELISA results showed that the secretion of proinflammatory cytokines in the agonist-CD137 group was increased. Immunofluorescence results revealed that ROS production in the agonist-CD137 group was higher than that in control, M5580 (a Nrf2 pathway agonist) and CAPE (a NF-κB pathway inhibitor) groups. In vitro studies using HUVECs and in vivo studies using high-fat-fed ApoE^−/− mice showed that the number of apoptotic endothelial cells was the highest in the agonist-CD137 group. By contrast, both M5580 and CAPE treatments were able to reduce CD137 induced ECs apoptosis. Conclusions. Our results showed that CD137 signaling promotes ECs apoptosis through prooxidative and proinflammatory mechanisms, mediated by Nrf2 and NF-κB pathways, respectively.

中文翻译：

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CD137 信号通过抑制 Nrf2 通路和上调 NF-κB 通路促进内皮细胞凋亡。

背景。氧化应激引起的内皮功能障碍和细胞凋亡可导致动脉粥样硬化的发展。我们小组之前已经表明，CD137 信号传导有助于动脉粥样硬化的进展和斑块的易损性。本研究的目的是研究 CD137 信号在动脉粥样硬化中对内皮细胞 (ECs) 凋亡的影响，并探索其潜在机制。方法。血清样本采集自 11 名急性心肌梗死患者和 4 名对照者。腹腔注射 ApoE 激动剂-CD137 重组蛋白^-/-小鼠用于确定CD137信号在体内是否可以促进细胞凋亡，并使用激动剂-CD137重组蛋白、M5580（一种Nrf2通路激动剂）和CAPE（一种NF-κB通路抑制剂）处理人脐静脉内皮细胞来探索Nrf2和NF-κB通路在体外CD137信号诱导ECs凋亡中的作用。结果。ELISA 显示 AMI 患者血清中 Bcl-2 低于对照组，而 TNF -α和sCD137均高于对照组。共聚焦显微镜和Western blot分析显示，激动剂-CD137组Nrf2的核转位明显受到抑制，其下游抗氧化酶的表达也较对照组降低。免疫荧光和Western blot结果显示激动剂-CD137组NF-κB核转位增强，ELISA结果显示激动剂-CD137组促炎细胞因子分泌增加。免疫荧光结果显示激动剂-CD137 组的 ROS 产生高于对照组、M5580（一种 Nrf2 通路激动剂）和 CAPE（一种 NF- κB途径抑制剂）组。使用 HUVEC 的体外研究和使用高脂喂养的 ApoE ^-/-小鼠的体内研究表明，激动剂-CD137 组中凋亡内皮细胞的数量最多。相比之下，M5580 和 CAPE 处理都能够减少 CD137 诱导的 ECs 细胞凋亡。结论。我们的研究结果表明，CD137 信号通过促氧化和促炎机制促进 ECs 凋亡，分别由 Nrf2 和 NF-κB 通路介导。