Department of BioMolecular Sciences and National Center for Natural Products Research, Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University, MS 38677, United States.
National Center for Natural Products Research, Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University, MS 38677, United States.
Biochem Pharmacol. 2018 Sep;155:82-91. doi: 10.1016/j.bcp.2018.06.024. Epub 2018 Jun 26.
The endocannabinoid system plays an important role in the pathophysiology of various neurological disorders, such as anxiety, depression, neurodegenerative diseases, and schizophrenia; however, little information is available on the coupling of the endocannabinoid system with the monoaminergic systems in the brain. In the present study, we tested four endocannabinoids and two anandamide analogs for inhibition of recombinant human MAO-A and -B (monoamine oxidase). Virodhamine inhibited both MAO-A and -B (IC values of 38.70 and 0.71 μM, respectively) with ∼55-fold greater inhibition of MAO-B. Two other endocannabinoids (noladin ether and anandamide) also showed good inhibition of MAO-B with IC values of 18.18 and 39.98 μM, respectively. Virodhamine was further evaluated for kinetic characteristics and mechanism of inhibition of human MAO-B. Virodhamine inhibited MAO-B (K value of 0.258 ± 0.037 μM) through a mixed mechanism/irreversible binding and showed a time-dependent irreversible mechanism. Treatment of Neuroscreen-1 (NS-1) cells with virodhamine produced significant inhibition of MAO activity. This observation confirms potential uptake of virodhamine by neuronal cells. A molecular modeling study of virodhamine with MAO-B and its cofactor flavin adenine dinucleotide (FAD) predicted virodhamine's terminal -NH group to be positioned near the N5 position of FAD, but for docking to MAO-A, virodhamine's terminal -NH group was far away (∼6.52 Å) from the N5 position of FAD, and encountered bad contacts with nearby water molecules. This difference could explain virodhamine's higher potency and preference for MAO-B. The binding free energies for the computationally-predicted poses also showed that virodhamine was selective for MAO-B. These findings suggest potential therapeutic applications of virodhamine for the treatment of neurological disorders.
内源性大麻素系统在各种神经障碍的病理生理学中发挥着重要作用，如焦虑、抑郁、神经退行性疾病和精神分裂症；然而，关于内源性大麻素系统与大脑中单胺能系统的偶联，信息很少。在本研究中，我们测试了四种内源性大麻素和两种大麻素类似物对重组人 MAO-A 和 -B（单胺氧化酶）的抑制作用。维罗达明抑制 MAO-A 和 -B（IC 值分别为 38.70 和 0.71 μM），对 MAO-B 的抑制作用约为 55 倍。另外两种内源性大麻素（诺拉迪恩醚和大麻素）对 MAO-B 的抑制作用也很好，IC 值分别为 18.18 和 39.98 μM。进一步评价了维罗达明对人 MAO-B 的动力学特征和抑制机制。维罗达明通过混合机制/不可逆结合抑制 MAO-B（K 值为 0.258 ± 0.037 μM），并表现出时间依赖性的不可逆机制。用维罗达明处理 Neuroscreen-1（NS-1）细胞可显著抑制 MAO 活性。这一观察结果证实了维罗达明可能被神经元细胞摄取。维罗达明与 MAO-B 及其辅因子黄素腺嘌呤二核苷酸（FAD）的分子建模研究预测，维罗达明的末端 -NH 基团将位于 FAD 的 N5 位置附近，但对于与 MAO-A 对接，维罗达明的末端 -NH 基团距离 FAD 的 N5 位置很远（约 6.52 Å），并与附近的水分子发生不良接触。这种差异可以解释维罗达明对 MAO-B 的更高效力和偏好。计算预测构象的结合自由能也表明，维罗达明对 MAO-B 具有选择性。这些发现表明维罗达明可能在治疗神经障碍方面有应用潜力。
