(834.9) Atorvastatin Modulates the Function and Trafficking of Dopamine Transporters

Poster Board Number: B36

Jonté Roberts (Wake Forest University), Sherry Wang (Wake Forest University), Mar Medrano (Wake Forest University), Haigou Sun (Wake Forest), Rong Chen (Wake Forest University)

Introduction: Dopaminergic signaling is involved in learning, memory, reward, movement, and emotion. The dopamine transporter (DAT) is the primary mechanism for terminating this signaling via DA uptake. A few lines of evidence indicate that DAT function is regulated by membrane cholesterol. Cholesterol is a critical component of plasma membranes and plays an essential role in regulating membrane fluidity, protein compartmentalization, and function. Statins are cholesterol-lowering medications that have been linked to mild cognitive impairment. The goal of this project was to examine the effects of atorvastatin-mediated reductions in cholesterol content on DAT function and trafficking.

Methods: Cultured cells amp; cholesterol measurement: HA-tagged human DAT (hDAT) was stably expressed in neuroblastoma 2a (N2A) cells using G418 as selection. Cells were treated with atorvastatin (0.1, 0.3, 1.0, or 10 μM) and membrane cholesterol content was measured using Amplex Red.

[3H]DA Uptake: After 24hr atorvastatin or vehicle treatment, cells were incubated with 15 nM [3H]DA in the presence of various concentrations of non-labeled DA and [3H]DA uptake was measured to determine Vmax and Km.

Cocaine inhibition of DA uptake amp; cholesterol replenishment: Cells were treated for 24hr with atorvastatin (1 μM) or vehicle and incubated with 15 nM [3H]DA and increasing concentrations of cocaine (100 nM-10 μM). To determine if there was a causal effect of reduced cholesterol content and cocaine inhibition of DA uptake, atorvastatin-treated cells were replenished with water soluble cholesterol (~40 mg per gram solid; MβCD) prior to cocaine inhibition.

Amphetamine-induced, DAT-mediated DA efflux: Cells treated for 24hrs with either atorvastatin (1 μM) or vehicle were preloaded with 30 nM of [3H]DA. Then, cells were incubated with amphetamine (1 or 10 μM). AMPH-induced DA efflux was determined by measuring DA content in the medium across time.

Surface DAT Biotinylation: Basal surface levels of DAT in atorvastatin and vehicle treated cells, as well as DA-induced DAT internalization, were measured by surface biotinylation using membrane non-permeable sulfo-NHS-SS biotin.

Immunocytochemistry: We measured levels of F-actin and G-actin to determine the effects of atorvastatin treatment on actin dynamics using immunocytochemistry.

Results: We found that atorvastatin dose dependently reduced membrane cholesterol content. This reduction was accompanied by decreases in the maximal rate of DA uptake and by decreases in the potency of cocaine to inhibit [3H]DA uptake. In contrast, atorvastatin treatment did not significantly alter AMPH-induced DA efflux. Importantly, the reduced ability of cocaine to inhibit DA uptake was reversed by replenishing cholesterol in atorvastatin-treated cells, suggesting a direct causal effect of reduced cholesterol content and cocaine inhibition. Lastly, we found that atorvastatin disrupted actin dynamics and abolished DA-induced DAT internalization. The present study provides evidence for the first time that atorvastatin dysregulates DAT function and trafficking. Furthermore, this dysregulation may be associated with the cognitive deficits observed in patients receiving atorvastatin treatment.

NIDA R01DA042862,T32DA041349