Neurotoxicity of 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP) as a parkinson's disease model

Abstract

Administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to susceptible animals is the most popular means for modeling the destruction of the nigrostriatal dopaminergic neurons seen in Parkinson's disease (PD). MPTP causes a damage to the substantia nigra pars compacta (SNpc) dopaminergic neurons and depletes striatal dopamine secretion in nonhuman primates and rodents. MPTP passes through the blood-brain barrier (BBB) and is converted, mainly in glial cells, into its active form, 1-methyl-4-phenylpyridinium (MPP+), by an enzyme, monoamine oxidase B (MAO-B). MPP+ is selectively transported into dopaminergic nerve terminals through dopamine transporter (DAT) and finally induces dopaminergic cell loss. The selective neurotoxicity of MPTP to neural tissues other than the dopaminergic system, such as the subventricular zone (SVZ) and rostral migratory stream (RMS) in the adult brain, has been indicated. The cells undergoing apoptosis in the SVZ are A cells and MAO-B inhibitors completely protected against the neurotoxicity, suggesting that the MPTP neurotoxicity to A cells is mediated by the conversion of MPTP into MPP+ by MAO-B. The neurotoxicity of MPTP to neuroblasts in the SVZ does not require DAT or other monoamine transporters. There is a strain difference in the susceptibility of the MPTP neurotoxicity between susceptible C57BL/6 and resistant BALB/c mice. However, MAO-B, DAT, neural NOS (nNOS), and inducible NOS (iNOS) expression levels do not influence the strain susceptibility to MPTP. MPTP and MPP+ can pass through the placenta and embryonic or newborn BBB, and finally reach the brain. The number of MAO-B-positive glial cells in the brain increases in MPTP-treated embryonic and newborn mice, indicating the involvement of MAO-B in the acute neurotoxicity. MPTP or MPP+ administration into embryonic and newborn mice causes a loss of TH-positive cells and fibers in the nigrostriatal system and increases the number of apoptotic cells in the SVZ. Delayed regeneration of dopaminergic neurons due to the loss of SVZ A cells may be one of possible causes of the pathological condition. With increased attention to dopaminergic neurogenesis in MPTP-induced animal models, such animals become useful as a tool for establishing the contact to PD on neurogenesis.