Emerald Health Biotechnology, Cordoba, Spain.
Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), Cordoba, Spain.
Neurotherapeutics. 2021 Jul;18(3):1849-1861. doi: 10.1007/s13311-021-01089-4. Epub 2021 Aug 2.
Huntington's disease (HD) is a neurodegenerative disorder characterized by unwanted choreatic movements, behavioral and psychiatric disturbances, and dementia. The activation of the hypoxic response pathway through the pharmacological inhibition of hypoxia-inducing factor (HIF) prolyl-hydroxylases (PHDs) is a promising approach for neurodegenerative diseases, including HD. Herein, we have studied the mechanism of action of the compound Betulinic acid hydroxamate (BAH), a hypoximimetic derivative of betulinic acid, and its efficacy against striatal neurodegeneration using complementary approaches. Firstly, we showed the molecular mechanisms through which BAH modifies the activity of the PHD2 prolyl hydroxylase, thus directly affecting HIF-1α stability. BAH treatment reduces PHD2 phosphorylation on Ser-125 residue, responsible for the control of its hydrolase activity. HIF activation by BAH is inhibited by okadaic acid and LB-100 indicating that a protein phosphatase 2A (PP2A) is implicated in the mechanism of action of BAH. Furthermore, in striatal cells bearing a mutated form of the huntingtin protein, BAH stabilized HIF-1α protein, induced Vegf and Bnip3 gene expression and protected against mitochondrial toxin-induced cytotoxicity. Pharmacokinetic analyses showed that BAH has a good brain penetrability and experiments performed in a mouse model of striatal neurodegeneration induced by 3-nitropropionic acid showed that BAH improved the clinical symptoms. In addition, BAH also prevented neuronal loss, decreased reactive astrogliosis and microglial activation, inhibited the upregulation of proinflammatory markers, and improved antioxidant defenses in the brain. Taken together, our results show BAH's ability to activate the PP2A/PHD2/HIF pathway, which may have important implications in the treatment of HD and perhaps other neurodegenerative diseases.
亨廷顿病（HD）是一种神经退行性疾病，其特征为不自主的舞蹈运动、行为和精神障碍以及痴呆。通过药理学抑制缺氧诱导因子（HIF）脯氨酰羟化酶（PHD）来激活低氧反应途径，是包括 HD 在内的神经退行性疾病的一种有前途的方法。在此，我们使用互补方法研究了白桦脂酸羟肟酸（BAH），即白桦脂酸的低氧模拟衍生物的作用机制及其对纹状体神经退行性变的疗效。首先，我们展示了 BAH 修饰 PHD2 脯氨酰羟化酶活性的分子机制，从而直接影响 HIF-1α 的稳定性。BAH 处理会减少 Ser-125 残基上 PHD2 的磷酸化，这负责控制其水解酶活性。BAH 对 HIF 的激活被 okadaic acid 和 LB-100 抑制，表明蛋白磷酸酶 2A（PP2A）参与了 BAH 的作用机制。此外，在携带突变型亨廷顿蛋白的纹状体细胞中，BAH 稳定了 HIF-1α 蛋白，诱导了 Vegf 和 Bnip3 基因的表达，并能抵抗线粒体毒素诱导的细胞毒性。药代动力学分析表明，BAH 具有良好的脑渗透性，并且在由 3-硝基丙酸诱导的纹状体神经退行性变的小鼠模型中进行的实验表明，BAH 改善了临床症状。此外，BAH 还能防止神经元丢失，减少反应性星形胶质细胞和小胶质细胞的激活，抑制促炎标志物的上调，并改善大脑中的抗氧化防御。综上所述，我们的结果表明 BAH 能够激活 PP2A/PHD2/HIF 途径，这可能对 HD 及其他神经退行性疾病的治疗具有重要意义。
