Lee Hansol, Hwang Yun-Jin, Park Jung-Hyun, Cho Du-Hyong
Department of Pharmacology, Yeungnam University College of Medicine, 170 Hyunchung-ro, Nam-gu, Daegu, 42415, South Korea.
AbT R&D Center, Azothbio Inc., 520 Misa-daero, Hanam-si, Gyeonggi-do, 12925, South Korea.
Biochem Biophys Res Commun. 2022 May 28;606:94-99. doi: 10.1016/j.bbrc.2022.03.100. Epub 2022 Mar 22.
Valproic acid (VPA) has been used to treat epilepsy and bipolar disorder. Although the abnormal proliferation of vascular smooth muscle cells (VSMCs) is a well-established contributor to the development of various vascular diseases including atherosclerosis, the effect of VPA on VSMC proliferation and its mechanism of action have not been fully revealed. Herein, we investigated the molecular mechanism by which VPA inhibits rat VSMC proliferation. VPA dose-dependently decreased VSMC proliferation, which was accompanied by the dose-dependent decrease in phosphorylation of p70 S6 kinase (p70S6K) at Thr389 (p-p70S6K-Thr), and overexpression of the p70S6K-T389E mutant gene significantly reversed VPA-inhibited VSMC proliferation. Co-treatment with okadaic acid, a specific protein phosphatase 2A (PP2A) inhibitor, significantly restored p-p70S6K-Thr. Furthermore, knockdown of PP2Ac gene expression by siRNA significantly reversed VPA-inhibited p-p70S6K-Thr and VSMC proliferation. Confocal microscopic analyses and co-immunoprecipitation results clearly showed that the physical binding of p70S6K and PP2Ac was promoted by VPA. Valpromide, a VPA's structural derivative with no histone deacetylase (HDAC) inhibition activity, as well as VPA and sodium butyrate, an HDAC inhibitor similar to VPA, decreased VSMC proliferation and p-p70S6K-Thr, indicating that HDAC is not involved in VPA-inhibited VSMC proliferation. Finally, the inhibitory effects of VPA on p-p70S6K-Thr and VSMC proliferation were reiterated in a platelet-derived growth factor (PDGF)-induced in vitro atherosclerosis model. In conclusion, our results demonstrate that VPA decreased cell proliferation via PP2A-mediated inhibition of p-p70S6K-Thr in basal and PDGF-stimulated VSMCs. The results suggest that VPA could be used in the treatment and prevention of atherosclerosis and in-stent restenosis.
丙戊酸（VPA）已被用于治疗癫痫和双相情感障碍。尽管血管平滑肌细胞（VSMC）的异常增殖是包括动脉粥样硬化在内的各种血管疾病发展的一个公认因素，但VPA对VSMC增殖的影响及其作用机制尚未完全阐明。在此，我们研究了VPA抑制大鼠VSMC增殖的分子机制。VPA剂量依赖性地降低VSMC增殖，同时伴有苏氨酸389（p-p70S6K-Thr）处p70 S6激酶（p70S6K）磷酸化的剂量依赖性降低，并且p70S6K-T389E突变基因的过表达显著逆转了VPA抑制的VSMC增殖。用冈田酸（一种特异性蛋白磷酸酶2A（PP2A）抑制剂）共同处理可显著恢复p-p70S6K-Thr。此外，通过小干扰RNA（siRNA）敲低PP2Ac基因表达可显著逆转VPA抑制的p-p70S6K-Thr和VSMC增殖。共聚焦显微镜分析和免疫共沉淀结果清楚地表明，VPA促进了p70S6K与PP2Ac的物理结合。丙戊酰胺是一种没有组蛋白去乙酰化酶（HDAC）抑制活性的VPA结构衍生物，以及VPA和丁酸钠（一种与VPA类似的HDAC抑制剂），均可降低VSMC增殖和p-p70S6K-Thr，表明HDAC不参与VPA抑制VSMC增殖。最后，在血小板衍生生长因子（PDGF）诱导的体外动脉粥样硬化模型中，再次证实了VPA对p-p70S及VSMC增殖的抑制作用。总之，我们的结果表明，VPA通过PP2A介导的对基础状态和PDGF刺激的VSMC中p-p70S6K-Thr的抑制作用来降低细胞增殖。这些结果表明，VPA可用于动脉粥样硬化和支架内再狭窄的治疗和预防。
