Department of Pharmacology, Yeungnam University College of Medicine, Daegu, Korea.
Department of Molecular Medicine, Ewha Womans University College of Medicine, Seoul, Korea.
J Korean Med Sci. 2020 Sep 7;35(35):e289. doi: 10.3346/jkms.2020.35.e289.
Telmisartan, an angiotensin II type 1 receptor blocker (ARB), is widely used to treat hypertension by blocking the renin-angiotensin-aldosterone system. Although abnormal proliferation of vascular smooth muscle cells (VSMCs) is a well-established contributor to the development of various vascular diseases, such as atherosclerosis, the effect of telmisartan on VSMC proliferation and its mechanism of action have not been fully revealed. Herein, we investigated the molecular mechanism whereby telmisartan inhibits rat VSMC proliferation.
We measured VSMC proliferation by MTT assay, and performed inhibitor studies and western blot analyses using basal and platelet-derived growth factor (PDGF)-stimulated rat VSMCs. To elucidate the role of AMP-activated protein kinase (AMPK), we introduced dominant-negative (dn)-AMPKα1 gene into VSMCs.
Telmisartan decreased VSMC proliferation, which was accompanied by decreased phosphorylations of mammalian target of rapamycin (mTOR) at Ser2448 (p-mTOR-Ser) and p70 S6 kinase (p70S6K) at Thr389 (p-p70S6K-Thr) in dose- and time-dependent manners. Telmisartan dose- and time-dependently increased phosphorylation of AMPK at Thr172 (p-AMPK-Thr). Co-treatment with compound C, a specific AMPK inhibitor, or ectopic expression of the dn-AMPKα1 gene, significantly reversed telmisartan-inhibited VSMC proliferation, p-mTOR-Ser and p-p70S6K-Thr levels. Among the ARBs tested (including losartan and fimasartan), only telmisartan increased p-AMPK-Thr and decreased p-mTOR-Ser, p-p70S6K-Thr, and VSMC proliferation. Furthermore, GW9662, a specific and irreversible peroxisome proliferator-activated receptor γ (PPARγ) antagonist, did not affect any of the telmisartan-induced changes. Finally, telmisartan also exhibited inhibitory effects on VSMC proliferation by increasing p-AMPK-Thr and decreasing p-mTOR-Ser and p-p70S6K-Thr in a PDGF-induced in vitro atherosclerosis model.
These results demonstrated that telmisartan-activated AMPK inhibited basal and PDGF-stimulated VSMC proliferation, at least in part, by downregulating the mTOR/p70S6K signaling axis in a PPARγ-independent manner. These observations suggest that telmisartan could be used to treat arterial narrowing diseases such as atherosclerosis and restenosis.
替米沙坦是一种血管紧张素 II 型 1 型受体阻滞剂（ARB），通过阻断肾素-血管紧张素-醛固酮系统广泛用于治疗高血压。尽管血管平滑肌细胞（VSMC）的异常增殖是各种血管疾病（如动脉粥样硬化）发展的一个公认因素，但替米沙坦对 VSMC 增殖的影响及其作用机制尚未完全阐明。在此，我们研究了替米沙坦抑制大鼠 VSMC 增殖的分子机制。
我们通过 MTT 测定法测量 VSMC 的增殖，并使用基础和血小板衍生生长因子（PDGF）刺激的大鼠 VSMC 进行抑制剂研究和 Western blot 分析。为了阐明 AMP 激活的蛋白激酶（AMPK）的作用，我们将显性失活（dn）-AMPKα1 基因引入 VSMC。
替米沙坦降低了 VSMC 的增殖，这伴随着哺乳动物靶标雷帕霉素（mTOR）在丝氨酸 2448 处的磷酸化（p-mTOR-Ser）和 p70 S6 激酶（p70S6K）在苏氨酸 389 处的磷酸化（p-p70S6K-Thr）呈剂量和时间依赖性降低。替米沙坦呈剂量和时间依赖性地增加 AMPK 在苏氨酸 172 处的磷酸化（p-AMPK-Thr）。用特定的 AMPK 抑制剂化合物 C 或异位表达 dn-AMPKα1 基因共同处理，可显著逆转替米沙坦抑制的 VSMC 增殖、p-mTOR-Ser 和 p-p70S6K-Thr 水平。在所测试的 ARB 中（包括氯沙坦和非那司他），只有替米沙坦增加了 p-AMPK-Thr，降低了 p-mTOR-Ser、p-p70S6K-Thr 和 VSMC 增殖。此外，PPARγ的特异性和不可逆激动剂 GW9662 不影响替米沙坦诱导的任何变化。最后，替米沙坦还通过增加 p-AMPK-Thr 和降低 p-mTOR-Ser 和 p-p70S6K-Thr 在 PDGF 诱导的体外动脉粥样硬化模型中抑制 VSMC 增殖。
这些结果表明，替米沙坦激活的 AMPK 通过下调 mTOR/p70S6K 信号通路，至少部分抑制了基础和 PDGF 刺激的 VSMC 增殖，这种作用是 PPARγ 独立的。这些观察结果表明，替米沙坦可用于治疗动脉狭窄疾病，如动脉粥样硬化和再狭窄。
