Department of Neurobiology, Key Laboratory for Neurodegenerative Disease of the Ministry of Education, Capital Medical University, Beijing 100069, China.
Department of Medical Genetics, Capital Medical University, Beijing 100069, China.
Biochem Pharmacol. 2015 Jan 15;93(2):221-31. doi: 10.1016/j.bcp.2014.12.001. Epub 2014 Dec 13.
Adiponectin blocks hepatocellular carcinoma (HCC) progression by inducing cell apoptosis through the modulation of C-Jun N-terminal kinase and mammalian target of rapamycin. However, the precise upstream signaling pathways or molecules remain elusive. In the present study, we analyzed the role of antioxidant protein thioredoxin (Trx) in adiponectin-induced apoptosis in HCC. Adiponectin treatment decreased the viabilities of both HepG2 and Huh7 HCC cells accompanied by increased accumulation of intracellular reactive oxygen species, as evidenced by 2',7'-dichlorodihydrofluorescein diacetate staining. Pretreatment of these cells with the deoxidant N-acetylcysteine blocked the inhibitory effect of adiponectin. Levels of Trx2 protein in both HCC cells were significantly decreased, and the level of Trx1 was significantly inhibited in Huh7 cells while unchanged in HepG2 cells. However, the redox state of Trx1 was altered from reduced to the oxidized form following adiponectin treatment in HepG2 cells. Overexpression of both Trx proteins rescued adiponectin-induced cell apoptosis, whereas mutated Trx proteins were less effective. Further analysis suggested that both ASK1 and JNK signaling are involved in this process. Trx1 and Trx2 proteins also manifested protective effects on HCC cells in response to adiponectin treatment in a xenograft tumor model. Furthermore, high levels of Trx proteins and low adiponectin expression levels were found in primary human HCC samples compared with paracancerous tissues. These results suggest that Trx proteins play important roles in mediating adiponectin-induced HCC cell apoptosis, thus providing new insights into the pathogenesis of HCC and identifying adiponectin and Trx proteins as potential combinational therapeutic targets for the treatment of HCC.
脂联素通过调节 C-Jun N 端激酶和哺乳动物雷帕霉素靶蛋白诱导细胞凋亡来阻止肝细胞癌 (HCC) 的进展。然而，确切的上游信号通路或分子仍不清楚。在本研究中，我们分析了抗氧化蛋白硫氧还蛋白 (Trx) 在脂联素诱导 HCC 细胞凋亡中的作用。脂联素处理降低了 HepG2 和 Huh7 HCC 细胞的活力，同时伴随着细胞内活性氧的积累增加，这一点通过 2'，7'-二氯二氢荧光素二乙酸酯染色得到证明。用抗氧化剂 N-乙酰半胱氨酸预处理这些细胞可阻断脂联素的抑制作用。两种 HCC 细胞中的 Trx2 蛋白水平显著降低，而 Huh7 细胞中的 Trx1 水平显著抑制而 HepG2 细胞中不变。然而，脂联素处理后 HepG2 细胞中 Trx1 的氧化还原状态从还原态转变为氧化态。过表达两种 Trx 蛋白均可挽救脂联素诱导的细胞凋亡，而突变 Trx 蛋白的效果则较差。进一步的分析表明，ASK1 和 JNK 信号通路均参与了这一过程。Trx1 和 Trx2 蛋白在异种移植肿瘤模型中也对 HCC 细胞对脂联素处理的反应表现出保护作用。此外，与癌旁组织相比，原发性人 HCC 样本中 Trx 蛋白水平较高，而脂联素表达水平较低。这些结果表明，Trx 蛋白在介导脂联素诱导的 HCC 细胞凋亡中发挥重要作用，从而为 HCC 的发病机制提供了新的见解，并确定脂联素和 Trx 蛋白作为治疗 HCC 的潜在联合治疗靶点。
