Effects of an Anti‐Methamphetamine Antibody Fragment on Markers of Methamphetamine Neurotoxicity

Abstract

Methamphetamine (METH) is considered one of the top drug problems in the United States today, yet there are no FDA approved pharmacological treatments available for METH abuse. To this end, we have designed and produced an anti-METH single chain antibody fragment (scFv7F9Cys) and a PEGylated scFv (scFv7F9Cys-PEG) as anti-METH pharmacological treatments. However, the effects of these pharmacokinetic antagonists on methamphetamine neurotoxicity markers have not been previously tested. Therefore, the purpose of this study was to determine the effects of chronic administration of METH and treatment with an anti-METH scFv on three makers in the dopaminergic system: dopamine transporter (DAT), tyrosine hydroxylase (TH), and VMAT2; and three markers in the glutamatergic system: NMDA receptor (NR2A), AMPA receptor (GluR2), and PSD-95. Rats received 3.2 mg/kg/day of METH from an osmotic pump (s.c.) for a total of 144 hours. Approximately 48 hours after pump implantation, scFv7F9Cys or scF7F9Cys-PEG was administered (30 mg/kg, i.v.). Brain samples were harvested 144 hours post-pump implantation, flash frozen, and pulverized into a fine powder. The pulverized brain tissue was then processed for qRT-PCR and Western blot analysis for all six markers (DAT, TH, VMAT2, NR2A, GluR2, PSD-95). qRT-PCR results showed a significant reduction in TH, NMDA, AMPA receptors and PSD-95 mRNA levels in the scFv7F9Cys and scFv7F9Cys-PEG treatment groups. However, Western blotting revealed that only TH protein levels were significantly reduced in the scFv7F9Cys-PEG group. These unexpected findings will be the basis for further study of the relationship of anti-METH scFvs and neuronal markers of toxicity.