Niello Marco, Cintulová Daniela, Raithmayr Philip, Holy Marion, Jäntsch Kathrin, Colas Claire, Ecker Gerhard F, Sitte Harald H, Mihovilovic Marko D
Institute of Pharmacology, Medical University, Vienna, Austria.
Institute of Applied Synthetic Chemistry, TU Wien, Vienna, Austria.
Front Pharmacol. 2021 Apr 9;12:654061. doi: 10.3389/fphar.2021.654061. eCollection 2021.
Mephedrone is a largely abused psychostimulant. It elicits the release of monoamines via the high affinity transporters for dopamine (DAT), norepinephrine (NET) and serotonin (SERT). Stereoselective metabolic reactions are involved in the inactivation and the elimination of its chemical structure. However, during these processes, several structures are generated and some of them have been reported to be still pharmacologically active. In this study 1) we have newly synthetized several putative mephedrone metabolites, 2) compared their activity at monoamine transporters, 3) generated quantitative structure activity relationships, and 4) exploited the chemical structure of the putative metabolites to screen a urine sample from a drug user and dissect mephedrone metabolism. We have found that most of the tested metabolites are weak inhibitors of monoamine transporters and that all of them are more potent at DAT and NET in comparison to SERT. The only exception is represented by the COOH-metabolite which shows no pharmacological activity at all three monoamine transporters. The enantioselectivity of mephedrone and its metabolites is present mainly at SERT, with only minor effects at DAT and NET being introduced when the β-keto group is reduced to an OH-group. Importantly, while at DAT the putative metabolites did not show changes in inhibitory potencies, but rather changes in their substrate/blocker profile, at SERT they showed mainly changes in inhibitory potencies. Molecular modeling suggests that the hydrophobic nature of a specific SERT subpocket may be involved in such loss of affinity. Finally, the assessment of the putative metabolites in one urine sample of mephedrone user displayed two previously uncharacterized metabolites, 4-COOH-nor-mephedrone (4-COOH-MC) and dihydro-4- nor-mephedrone (dihydro-4-MC). These results confirm and expand previous studies highlighting the importance of the stereochemistry in the pharmacodynamics of phase-1 metabolites of mephedrone, established their structure-activity relationships at DAT, NET and SERT and pave the way for a systematic dissection of mephedrone metabolic routes. Given the number of structures found having residual and modified pharmacological profiles, these findings may help in understanding the complex subjective effects of administered mephedrone. Moreover, the dissection of mephedrone metabolic routes may help in developing new therapies for treating psychostimulants acute intoxications.
4-甲基甲卡西酮是一种被大量滥用的精神兴奋剂。它通过对多巴胺（DAT）、去甲肾上腺素（NET）和5-羟色胺（SERT）具有高亲和力的转运体引发单胺的释放。立体选择性代谢反应参与其化学结构的失活和消除。然而，在这些过程中，会产生几种结构，其中一些据报道仍具有药理活性。在本研究中，1）我们新合成了几种假定的4-甲基甲卡西酮代谢物，2）比较了它们对单胺转运体的活性，3）建立了定量构效关系，4）利用假定代谢物的化学结构筛选一名吸毒者的尿液样本并剖析4-甲基甲卡西酮的代谢情况。我们发现，大多数测试的代谢物是单胺转运体的弱抑制剂，并且与SERT相比，它们对DAT和NET的抑制作用更强。唯一的例外是COOH-代谢物，它在所有三种单胺转运体上均无药理活性。4-甲基甲卡西酮及其代谢物的对映选择性主要存在于SERT，当β-酮基还原为OH-基团时，对DAT和NET的影响较小。重要的是，虽然在DAT上，假定的代谢物在抑制效力上没有变化，而是在其底物/阻断剂谱上有变化，但在SERT上，它们主要表现为抑制效力的变化。分子建模表明，特定SERT亚口袋的疏水性可能与这种亲和力丧失有关。最后，对一名4-甲基甲卡西酮使用者的一份尿液样本中假定代谢物的评估显示出两种以前未鉴定的代谢物，4-COOH-去甲-4-甲基甲卡西酮（4-COOH-MC）和二氢-4-去甲-4-甲基甲卡西酮（二氢-4-MC）。这些结果证实并扩展了先前的研究，突出了立体化学在4-甲基甲卡西酮1期代谢物药效学中的重要性，确立了它们在DAT、NET和SERT上的构效关系，并为系统剖析4-甲基甲卡西酮的代谢途径铺平了道路。鉴于发现有残留和修饰药理特征的结构数量，这些发现可能有助于理解服用4-甲基甲卡西酮后的复杂主观效应。此外，剖析4-甲基甲卡西酮的代谢途径可能有助于开发治疗精神兴奋剂急性中毒的新疗法。
