Department of Child and Adolescent Psychiatry and Psychotherapy, University Hospital of Psychiatry Zurich, University of Zurich, Switzerland.
Department of Chemistry and Applied Biosciences, Eidgenössische Technische Hochschule (ETH) Zurich, 8093 Zurich, Switzerland; Facoltà di Informatica, Istituto di Scienze Computazionali, Università della Svizzera Italiana, 6900 Lugano, Switzerland.
Prog Neuropsychopharmacol Biol Psychiatry. 2017 Oct 3;79(Pt B):281-288. doi: 10.1016/j.pnpbp.2017.07.002. Epub 2017 Jul 8.
Methylphenidate (MPH), a psychostimulant, is an effective first-line treatment for the symptoms associated with Attention-Deficit/Hyperactivity Disorder (ADHD). Although most MPH formulations are composed of the racemic 1:1 mixture of the two enantiomers (d- and l-threo), converging lines of evidence indicate that d-threo MPH seems to be superior to the l-isomer. We aimed to investigate whether MPH racemic mixture or pure enantiomers influence the enzyme activity of tyrosine hydroxylase (TH), monoamine oxidase B (MAO-B), catechol-O-methyltransferase (COMT), and aldehyde dehydrogenase (ALDH) in vitro in homogenates of rat PC12 cells incubated with racemic, d- and l-threo MPH (1nM up to 100μM), or a vehicle for control. We could observe dose dependent enhancement of TH activity with d-threo MPH, probably due to its higher affinity to the enzyme, which we could confirm for d-threo versus l-threo MPH via docking and molecular dynamic simulations analysis. MAO-B enzyme activity was found to be enhanced when incubated with both d- and l-isomers but not with the racemic mixture. This conflicting result was hypothesized to be due to possible aggregation of the two enantiomers or other molecular conformations. Such a possible interaction was observed indirectly, when TH was incubated with constant d-threo MPH while increasing l-isomer (increasing total MPH concentrations). Hence, TH activity was slightly decreased with increased l-isomer. In conclusion, the current in vitro investigation points to the stereoselectivity of the investigated enzymes and pharmacological effects of MPH enantiomers.
哌醋甲酯（MPH）是一种精神兴奋剂，是治疗注意力缺陷多动障碍（ADHD）相关症状的有效一线治疗药物。尽管大多数 MPH 制剂由两种对映异构体（d-和 l-苏）的 1:1 外消旋混合物组成，但越来越多的证据表明，d-苏式 MPH 似乎优于 l-对映异构体。我们旨在研究 MPH 外消旋混合物或纯对映异构体是否会影响在与外消旋、d-和 l-苏式 MPH（1nM 至 100μM）孵育的大鼠 PC12 细胞匀浆中酪氨酸羟化酶（TH）、单胺氧化酶 B（MAO-B）、儿茶酚-O-甲基转移酶（COMT）和醛脱氢酶（ALDH）的酶活性，或用载体作为对照。我们可以观察到 d-苏式 MPH 剂量依赖性地增强 TH 活性，这可能是由于其与酶的亲和力更高，通过对接和分子动力学模拟分析，我们可以确认 d-苏式 MPH 与 l-苏式 MPH 相比。当与两种对映异构体孵育时，MAO-B 酶活性被发现增强，但与外消旋混合物没有增强。这种相互矛盾的结果据推测是由于两种对映异构体可能的聚集或其他分子构象。当 TH 与恒定的 d-苏式 MPH 孵育而增加 l-异构体（增加总 MPH 浓度）时，观察到了这种可能的相互作用。因此，TH 活性随着 l-异构体的增加而略有降低。总之，目前的体外研究指出了所研究酶的立体选择性和 MPH 对映异构体的药理学效应。
