Department of Pharmacology, College of Medicine (C.-H.L., T.-J.L.), Department of Life Sciences, College of Medicine (H.-J.H., W.-H.W.), and Ph.D program in Pharmacology and Toxicology, Department of Medicine, School of Medicine (C.-H.L., T.-J.L.), Tzu Chi University, Hualien, Taiwan; Department of Medical Research (T.-L.T., M.-F.C., T.J.-F.L.) and Cardiovascular Research Center (C.-H.L., T.-L.T., M.-F.C., T.J.-F.L.), Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan; and Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, Illinois (T.J.-F.L.).
Department of Pharmacology, College of Medicine (C.-H.L., T.-J.L.), Department of Life Sciences, College of Medicine (H.-J.H., W.-H.W.), and Ph.D program in Pharmacology and Toxicology, Department of Medicine, School of Medicine (C.-H.L., T.-J.L.), Tzu Chi University, Hualien, Taiwan; Department of Medical Research (T.-L.T., M.-F.C., T.J.-F.L.) and Cardiovascular Research Center (C.-H.L., T.-L.T., M.-F.C., T.J.-F.L.), Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan; and Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, Illinois (T.J.-F.L.)
J Pharmacol Exp Ther. 2020 May;373(2):175-183. doi: 10.1124/jpet.119.263517. Epub 2020 Feb 18.
Decreased release of palmitic acid methyl ester (PAME), a vasodilator, from perivascular adipose tissue (PVAT) might contribute to hypertension pathogenesis. However, the PAME biosynthetic pathway remains unclear. In this study, we hypothesized that PAME is biosynthesized from palmitic acid (PA) via human catechol-O-methyltransferase (COMT) catalysis and that decreased PAME biosynthesis plays a role in hypertension pathogenesis. We compared PAME biosynthesis between age-matched normotensive Wistar Kyoto (WKY) rats and hypertensive spontaneously hypertensive rats (SHRs) and investigated the effects of losartan treatment on PAME biosynthesis. Computational molecular modeling indicated that PA binds well at the active site of COMT. Furthermore, in enzymatic assays in the presence of COMT and -5'-adenosyl--methionine (AdoMet), the stable isotope [C]-PA was methylated to form [C]-PAME in incubation medium or the Krebs-Henseleit solution containing 3T3-L1 adipocytes or rat PVAT. The adipocytes and PVATs expressed membrane-bound (MB)-COMT and soluble (S)-COMT proteins. [C]-PA methylation to form [C]-PAME in 3T3-L1 adipocytes and rat PVAT was blocked by various COMT inhibitors, such as -(5'-adenosyl)--homocysteine, adenosine-2',3'-dialdehyde, and tolcapone. MB- and S-COMT levels in PVATs of established SHRs were significantly lower than those in PVATs of age-matched normotensive WKY rats, with decreased [C]-PA methylation to form [C]-PAME. This decrease was reversed by losartan, an angiotensin II (Ang II) type 1 receptor antagonist. Therefore, PAME biosynthesis in rat PVAT is dependent on AdoMet, catalyzed by COMT, and decreased in SHRs, further supporting the role of PVAT/PAME in hypertension pathogenesis. Moreover, the antihypertensive effect of losartan might be due partly to its increased PAME biosynthesis. SIGNIFICANCE STATEMENT: PAME is a key PVAT-derived relaxing factor. We for the first time demonstrate that PAME is synthesized through PA methylation via the -5'-adenosyl--methionine-dependent COMT catalyzation pathway. Moreover, we confirmed PVAT dysfunction in the hypertensive state. COMT-dependent PAME biosynthesis is involved in Ang II receptor type 1-mediated blood pressure regulation, as evidenced by the reversal of decreased PAME biosynthesis in PVAT by losartan in hypertensive rats. This finding might help in developing novel therapeutic or preventive strategies against hypertension.
从血管周围脂肪组织 (PVAT) 释放的棕榈酸甲酯 (PAME) 减少，一种血管舒张剂，可能导致高血压发病机制。然而，PAME 的生物合成途径尚不清楚。在这项研究中，我们假设 PAME 是由棕榈酸 (PA) 通过人儿茶酚-O-甲基转移酶 (COMT) 催化合成的，并且 PAME 生物合成减少在高血压发病机制中起作用。我们比较了年龄匹配的正常血压 Wistar Kyoto (WKY) 大鼠和高血压自发性高血压大鼠 (SHR) 之间的 PAME 生物合成，并研究了氯沙坦对 PAME 生物合成的影响。计算分子建模表明 PA 很好地结合在 COMT 的活性部位。此外，在存在 COMT 和 -5'-腺嘌呤核苷 -S-腺苷甲硫氨酸 (AdoMet) 的酶促测定中，稳定同位素 [C]-PA 在孵育介质或含有 3T3-L1 脂肪细胞或大鼠 PVAT 的 Krebs-Henseleit 溶液中被甲基化为形成 [C]-PAME。脂肪细胞和 PVAT 表达膜结合 (MB)-COMT 和可溶性 (S)-COMT 蛋白。各种 COMT 抑制剂，如 -(5'-腺嘌呤核苷)-同型半胱氨酸、腺苷-2',3'-二醛和托卡朋，可阻断 [C]-PA 甲基化为形成 [C]-PAME 在 3T3-L1 脂肪细胞和大鼠 PVAT 中。与年龄匹配的正常血压 WKY 大鼠的 PVAT 相比，已建立的 SHR 中 PVAT 的 MB-和 S-COMT 水平显著降低，并且 [C]-PA 甲基化为形成 [C]-PAME。氯沙坦，血管紧张素 II (Ang II) 1 型受体拮抗剂，可逆转这种降低。因此，大鼠 PVAT 中的 PAME 生物合成依赖于 AdoMet，由 COMT 催化，在 SHR 中减少，进一步支持了 PVAT/PAME 在高血压发病机制中的作用。此外，氯沙坦的降压作用部分可能与其增加的 PAME 生物合成有关。意义声明：PAME 是一种关键的 PVAT 衍生的放松因子。我们首次证明 PAME 通过 PA 甲基化通过 -5'-腺嘌呤核苷 -S-腺苷甲硫氨酸依赖性 COMT 催化途径合成。此外，我们证实了高血压状态下的 PVAT 功能障碍。COMT 依赖性 PAME 生物合成参与了血管紧张素 II 受体 1 介导的血压调节，这一点从氯沙坦在高血压大鼠中逆转 PVAT 中 PAME 生物合成减少得到证实。这一发现可能有助于开发针对高血压的新的治疗或预防策略。
