Differential effects of psychoactive substances on human wildtype and polymorphic T356M dopamine transporters (DAT)

Anne Zwartsen,Carlijn H.C Litjens,Laura Hondebrink,Jeroen J.M.W Van Den Heuvel,Rick Greupink,Frans G.M Russel,Dylan W De Lange,Juliette Legler,Jan B Koenderink,Remco H.S Westerink

doi:10.1016/j.tox.2019.04.012

Anne Zwartsen, Carlijn H.C Litjens + Show 8 more

Open Access

https://doi.org/10.1016/j.tox.2019.04.012

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Abstract

Many psychoactive substances affect the human dopamine (DA) reuptake transporter (hDAT). Polymorphisms in the encoding gene could affect the functionality of the transporter and consequently alter effects of psychotropic and recreational drugs. Recently, a T356 M single nucleotide polymorphism in the human SLC6A3 gene was described, which resulted in functional impairments of DA uptake. Therefore, we investigated the effects of 10 psychoactive substances (0.01–1000 μM)) on DA uptake in human embryonic kidney (HEK) 293 cells transiently overexpressing wildtype (WT) or T356 M hDAT.Our data shows that T356 M hDAT has a 3 times lower Vmax and a 3 times higher Km compared to WT hDAT. Additionally, all psychoactive substances inhibited DA uptake by T356 M and WT hDAT. The DA reuptake inhibitors (methylphenidate, cocaine, and bupropion) inhibited DA uptake by WT hDAT most potently, followed by amphetamine-type stimulants [4-fluoroamphetamine (4-FA), amphetamine and MDMA], selective serotonin reuptake inhibitors (SSRI; fluoxetine and citalopram) and arylcyclohexylamines [methoxetamine (MXE) and ketamine].Compared to DA uptake by WT hDAT, bupropion, methylphenidate, cocaine, and MXE less potently inhibited DA uptake by T356 M hDAT, while citalopram more potently inhibited uptake. The differences in IC50 values between T356 M and WT hDAT were considerable (3–45 fold). As such, the presence of this polymorphism could affect treatment efficiency with these substances as well as susceptibly for toxicity and addiction for individuals carrying this polymorphism.

Highlights

Over half of the adult American population uses at least one prescription drug and 1 in 7 is considered a polydrug user (≥5 different prescription drugs)
Transport activity of the wild type (WT) hDAT and T356 M hDAT variant was measured at the predetermined optimal incubation time of 2 min (Supplemental Fig. 1)
The current study extends on the earlier observation that T356 M hDAT impairs DA uptake and alters sensitivity to certain psychoactive substances (Herborg et al, 2018)

Summary

Introduction

Over half of the adult American population uses at least one prescription drug and 1 in 7 is considered a polydrug user (≥5 different prescription drugs) Many of these prescription drugs involve psychotropic medication. (prescribed or illicit) psychoactive compounds likely have multiple mechanisms of action, their effects are at least partly attributable to increased concentrations of monoamine neurotransmitters in the brain. This increase in monoamines is caused by the inhibition of neurotransmitter reuptake via inhibition of the dopamine (DA), norepinephrine (NE) or serotonin (5-HT) reuptake transporters (DAT, NET, and SERT).

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