State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Acta Pharmacol Sin. 2020 Mar;41(3):327-335. doi: 10.1038/s41401-019-0274-0. Epub 2019 Jul 29.
23,24-Dihydrocucurbitacin B (designated as C95 in this article) is a cucurbitane triterpenoid that has been shown to possess a variety of pharmacological activities, such as anti-inflammatory and anti-HIV-1 activities etc. In this study, we investigated the effects of 23,24-dihydrocucurbitacin B on lipid regulation. We showed that 23,24-dihydrocucurbitacin B (1-5 μM) dose-dependently promoted DiI-LDL uptake in HepG2 cells by upregulating low-density lipoprotein receptor (LDLR) protein. In HepG2 cells, 23,24-dihydrocucurbitacin B (1-10 μM) dose-dependently enhanced LDLR promoter activity by elevating the mature form of SREBP2 (sterol regulatory element binding protein 2) protein levels on one hand, and inhibited PCSK9 (proprotein convertase subtilisin/kexin type 9) promoter activity by attenuating HNF1α (hepatocyte nuclear factor-1α) protein levels in nuclei on the other hand. Consequently, the expression of LDLR protein markedly increased, whereas the PCSK9-mediated LDLR protein degradation decreased. In a high-cholesterol LVG golden Syrian Hamster model, administration of 23,24-dihydrocucurbitacin B (30 mg · kg⋅ d, intragastric, for 3 weeks) significantly decreased the serum LDL-cholesterol (LDL-C) levels. PCSK9 protein levels in the serum and liver tissues were significantly decreased, whereas LDLR protein levels in liver tissues were significantly increased in the treated animals as compared with the control animals. In conclusion, our study demonstrates for the first time that 23,24-dihydrocucurbitacin B exhibits dual transcriptional regulation of LDLR and PCSK9 in HepG2 cells by increasing SREBP2 protein levels and decreasing HNF1α protein levels in the nuclei. These results propose a new strategy to simultaneously manage LDLR and PCSK9 protein expression and provide a promising lead compound for drug development.
23,24-二氢葫芦素 B（本文中指定为 C95）是一种葫芦烷三萜，已被证明具有多种药理活性，如抗炎和抗 HIV-1 等。在这项研究中，我们研究了 23,24-二氢葫芦素 B 对脂质调节的影响。我们表明，23,24-二氢葫芦素 B（1-5μM）剂量依赖性地通过上调低密度脂蛋白受体（LDLR）蛋白促进 HepG2 细胞摄取 DiI-LDL。在 HepG2 细胞中，23,24-二氢葫芦素 B（1-10μM）一方面通过提高成熟形式的 SREBP2（固醇调节元件结合蛋白 2）蛋白水平，另一方面通过降低核内 HNF1α（肝细胞核因子-1α）蛋白水平，剂量依赖性地增强 LDLR 启动子活性。因此，LDLR 蛋白的表达显著增加，而 PCSK9 介导的 LDLR 蛋白降解减少。在高胆固醇 LVG 金黄叙利亚仓鼠模型中，给予 23,24-二氢葫芦素 B（30mg·kg·d，灌胃，持续 3 周）可显著降低血清 LDL-胆固醇（LDL-C）水平。与对照组相比，治疗组动物血清和肝组织中的 PCSK9 蛋白水平显著降低，而肝组织中的 LDLR 蛋白水平显著升高。总之，我们的研究首次表明，23,24-二氢葫芦素 B 通过增加 SREBP2 蛋白水平和降低核内 HNF1α 蛋白水平，在 HepG2 细胞中对 LDLR 和 PCSK9 进行双重转录调控。这些结果提出了一种新的策略，可同时管理 LDLR 和 PCSK9 蛋白的表达，并为药物开发提供了一种有前途的先导化合物。
