Comparative neurotoxicity profiles of drugs of abuse, METH and MDMA, and selective dopaminergic neurotoxicants MPP+ and MPTP in three different cell culture models
Syed Ali1*, Susan LantzMcPeak1, Bonnie Robinson1, Glenn Newport1, Saber Hussain2, Merle Paule1, William Trickler1.
1Neurochemistry Laboratory, Division of Neurotoxicology, National Center of Toxicological Research/FDA, Jefferson, AR 72079 USA;
2Applied Biotechnology Branch, Human Effectiveness Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Dayton, OH 45433 USA
The purpose of this study was to evaluate and compare the neurotoxicity profiles of two common drugs of abuse and two dopaminergic neurotoxicants in three neuronal cell culture models. Two murine cell lines, MN9D and Cath.a, and one rat cell line, PC12, were exposed to methamphetamine (METH), 3,4 methylene dioxymethamphetamine (MDMA), 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and its metabolite 1-methyl-4-phenylpyridinium (MPP+) at various concentrations (0.001-10 mM). Cell viability and mitochondrial function were evaluated using lactate dehydrogenase (LDH) and 2, 3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT) assays following 24-hour exposure. High performance liquid chromatography (HPLC) was used to determine intracellular levels of dopamine. The results demonstrate that neuronal exposure to METH, MDMA, or MPTP significantly decreased neuronal cell viability at concentrations above 1 mM, as indicated by LDH release and decreased mitochondrial function. However, MPP+ significantly decreased mitochondrial function starting at 1mM in MN9D cells. In PC12 cells, MPP+ produced significant LDH release at 10 μM, with no effects observed in XTT assays. In contrast, the release of LDH following MPP+ exposure was not increased in MN9D or Cath.a cells. METH, MDMA, MPTP and MPP+ significantly decreased intracellular levels of dopamine in a dose-dependent manner in all three cell culture models. In Cath.a cells, the observed EC50 for METH (8.5 µM) was 8-fold lower than MDMA, 11-fold lower than MPTP, and 41-fold lower than MPP+. In contrast, for MN9D cells, the observed EC50 for METH and MPP+ (60µM) was two-fold higher than MDMA and 6-fold higher than MPTP. In PC12 cells, the observed EC50 for METH (70µM) was 2-fold higher than MDMA, 1.5-fold lower than MPTP, and more than 7-fold higher than MPP+. These results suggest that drugs of abuse such as METH and MDMA, and the dopaminergic neurotoxicants MPP+ and MPTP induce neuronal cytotoxicity in these cell culture models, with varying vulnerability of each cell line, likely due to differences in ability to metabolize these neurotoxicants.