Hsieh Cheng-Ying, Hsiao George, Hsu Ming-Jen, Wang Yi-Hsuan, Sheu Joen-Rong
Department of Pharmacology, School of Medicine, Taipei Medical University, Taipei, Taiwan.
J Cell Mol Med. 2014 Jul;18(7):1278-89. doi: 10.1111/jcmm.12277. Epub 2014 Apr 13.
The hydrophilic α-tocopherol derivative, 2,2,5,7,8-pentamethyl-6-hydroxychromane (PMC), is a promising alternative to vitamin E in clinical applications. Critical vascular inflammation leads to vascular dysfunction and vascular diseases, including atherosclerosis, hypertension and abdominal aortic aneurysms. In this study, we investigated the mechanisms of the inhibitory effects of PMC in vascular smooth muscle cells (VSMCs) exposed to pro-inflammatory stimuli, lipopolysaccharide (LPS) combined with interferon (IFN)-γ. Treatment of LPS/IFN-γ-stimulated VSMCs with PMC suppressed the expression of inducible nitric oxide synthase (iNOS) and matrix metalloproteinase-9 in a concentration-dependent manner. A reduction in LPS/IFN-γ-induced nuclear factor (NF)-κB activation was also observed in PMC-treated VSMCs. The translocation and phosphorylation of p65, protein phosphatase 2A (PP2A) inactivation and the formation of reactive oxygen species (ROS) were significantly inhibited by PMC in LPS/IFN-γ-activated VSMCs. However, neither IκBα degradation nor IκB kinase (IKK) or ribosomal s6 kinase-1 phosphorylation was affected by PMC under these conditions. Both treatments with okadaic acid, a PP2A-selective inhibitor, and transfection with PP2A siRNA markedly reversed the PMC-mediated inhibition of iNOS expression, NF-κB-promoter activity and p65 phosphorylation. Immunoprecipitation analysis of the cellular extracts of LPS/IFN-γ-stimulated VSMCs revealed that p65 colocalizes with PP2A. In addition, p65 phosphorylation and PP2A inactivation were induced in VSMCs by treatment with H(2)O(2), but neither IκBα degradation nor IKK phosphorylation was observed. These results collectively indicate that the PMC-mediated inhibition of NF-κB activity in LPS/IFN-γ-stimulated VSMCs occurs through the ROS-PP2A-p65 signalling cascade, an IKK-IκBα-independent mechanism. Therapeutic interventions using PMC may therefore be beneficial for the treatment of vascular inflammatory diseases.
亲水性α-生育酚衍生物2,2,5,7,8-五甲基-6-羟基色满（PMC）在临床应用中是维生素E的一种有前景的替代物。严重的血管炎症会导致血管功能障碍和血管疾病，包括动脉粥样硬化、高血压和腹主动脉瘤。在本研究中，我们调查了PMC对暴露于促炎刺激物脂多糖（LPS）联合干扰素（IFN）-γ的血管平滑肌细胞（VSMC）的抑制作用机制。用PMC处理LPS/IFN-γ刺激的VSMC以浓度依赖的方式抑制了诱导型一氧化氮合酶（iNOS）和基质金属蛋白酶-9的表达。在经PMC处理的VSMC中也观察到LPS/IFN-γ诱导的核因子（NF）-κB活化降低。在LPS/IFN-γ激活的VSMC中，PMC显著抑制了p65的易位和磷酸化、蛋白磷酸酶2A（PP2A）失活以及活性氧（ROS）的形成。然而，在这些条件下，PMC对IκBα降解、IκB激酶（IKK）或核糖体s6激酶-1磷酸化均无影响。用PP2A选择性抑制剂冈田酸处理以及用PP2A小干扰RNA转染均显著逆转了PMC介导的对iNOS表达、NF-κB启动子活性和p65磷酸化 的抑制作用。对LPS/IFN-γ刺激的VSMC细胞提取物进行免疫沉淀分析显示，p65与PP2A共定位。此外，用H(2)O(2)处理VSMC诱导了p
