title: Interactions of 1-methyl-4-phenylpyridinium and other compounds with P-glycoprotein: relevance to toxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine.
abstract: The vesicular monoamine transporter 2 (VMAT2) has sequence homology with bacterial multidrug transporters which in turn share homology with mammalian P-glycoprotein (P-GP). Both VMAT2 and P-GP can detoxify cells. 1-Methyl-4-phenylpyridinium (MPP(+)), the toxic metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), is a substrate for VMAT2 that has several structural features in common with P-GP substrates and inhibitors. The present studies investigated whether P-GP is responsible for the elimination of MPP(+) from the brain. Additionally, VMAT2 and P-GP are inhibited by many of the same compounds. Thus we also investigated whether VMAT2 inhibitors could block P-GP in vitro and vice versa whether P-GP inhibitors could block VMAT2 mediated transport of [3H]-DA into synaptic vesicles. In mice treated with MPTP and a P-GP inhibitor (quinidine, trans-flupentixol or cyclosporine A), the elimination of MPP(+) from the striatum was significantly delayed. However, in experiments using various cell lines expressing either mouse or human P-GP, MPP(+) did not reverse the P-GP mediated resistance to vincristine, suggesting that MPP(+) is a poor substrate for P-GP. Additional experiments were performed using mdr1a/b double knockout mice which lack functional P-GP encoded by these two genes. Data from mdr1a/b knockout mice treated with MPTP also suggest that MPP(+) is not extruded from the brain by P-GP. In other studies, we demonstrated that the VMAT2 inhibitors tetrabenazine and Ro 4-1284 inhibit P-GP and that the P-GP inhibitors trans-flupentixol and quinidine inhibit VMAT2. Thus, several new drugs can be added to the list of compounds that are able to inhibit both VMAT2 and P-GP, providing further evidence of the similarity between these two transporters.
authors.affiliation: Department of Neurology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854-4535, USA.
authors.forename: R G
authors.initials: RG
authors.lastname: Staal
authors.forename: J M
authors.initials: JM
authors.lastname: Yang
authors.forename: W N
authors.initials: WN
authors.lastname: Hait
authors.forename: P K
authors.initials: PK
authors.lastname: Sonsalla
mesh_terms: D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine / Q000378:metabolism / Q000493:pharmacokinetics*; D015655:1-Methyl-4-phenylpyridinium / Q000031:analogs & derivatives / Q000378:metabolism*; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D001921:Brain / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D004298:Dopamine / Q000378:metabolism; D018492:Dopamine Antagonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008297:Male; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D026901:Membrane Transport Proteins; D051379:Mice; D018345:Mice, Knockout; D009479:Neuropeptides; D020734:Parkinsonian Disorders / Q000378:metabolism* / Q000503:physiopathology; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D014407:Tumor Cells, Cultured; D050492:Vesicular Biogenic Amine Transport Proteins; D050493:Vesicular Monoamine Transport Proteins
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000889:Anti-Arrhythmia Agents; D002121:Calcium Channel Blockers; D018492:Dopamine Antagonists; D004791:Enzyme Inhibitors; D007166:Immunosuppressive Agents; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009479:Neuropeptides; C493453:Slc18a2 protein, mouse; D050492:Vesicular Biogenic Amine Transport Proteins; D050493:Vesicular Monoamine Transport Proteins; D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; D015655:1-Methyl-4-phenylpyridinium; D004298:Dopamine