Department of Biotechnology, Chonnam National University, Gwangju 61186, Korea.
School of Food Science and Biotechnology, Kyungpook National University, Daegu 41566, Korea.
Molecules. 2021 May 1;26(9):2659. doi: 10.3390/molecules26092659.
Betulinic acid (BA) is a major constituent of Zizyphus seeds that have been long used as therapeutic agents for sleep-related issues in Asia. BA is a pentacyclic triterpenoid. It also possesses various anti-cancer and anti-inflammatory effects. Current commercially available sleep aids typically use GABAergic regulation, for which many studies are being actively conducted. However, few studies have focused on acetylcholine receptors that regulate wakefulness. In this study, we utilized BA as an antagonist of α3β4 nicotinic acetylcholine receptors (α3β4 nAChRs) known to regulate rapid-eye-movement (REM) sleep and wakefulness. Effects of BA on α3β4 nAChRs were concentration-dependent, reversible, voltage-independent, and non-competitive. Site-directed mutagenesis and molecular-docking studies confirmed the binding of BA at the molecular level and showed that the α3 subunit L257 and the β4 subunit I263 residues affected BA binding. These data demonstrate that BA can bind to a binding site different from the site for the receptor's ligand, acetylcholine (ACh). This suggests that BA may be an effective antagonist that is unaffected by large amounts of ACh released during wakefulness and REM sleep. Based on the above experimental results, BA is likely to be a therapeutically useful sleep aid and sedative.
白桦脂酸（BA）是酸枣仁的主要成分之一，在亚洲，酸枣仁一直被用作治疗与睡眠相关问题的药物。BA 是一种五环三萜。它还具有多种抗癌和抗炎作用。目前市售的助眠药物通常采用 GABA 能调节，许多研究正在积极进行。然而，很少有研究关注调节觉醒的乙酰胆碱受体。在这项研究中，我们利用 BA 作为已知调节快速眼动（REM）睡眠和觉醒的α3β4 烟碱型乙酰胆碱受体（α3β4 nAChRs）的拮抗剂。BA 对 α3β4 nAChRs 的作用具有浓度依赖性、可逆转、电压独立性和非竞争性。定点突变和分子对接研究证实了 BA 在分子水平上的结合，并表明 α3 亚基 L257 和 β4 亚基 I263 残基影响 BA 的结合。这些数据表明，BA 可以结合到与受体配体乙酰胆碱（ACh）不同的结合位点。这表明 BA 可能是一种有效的拮抗剂，不受觉醒和 REM 睡眠期间大量释放的 ACh 的影响。基于上述实验结果，BA 可能是一种有治疗价值的助眠和镇静药物。
