Changes of MAO-A and MAO-B Expressions in the Placenta of MPTP or MPP+ Treated Mice

In the present study, we evaluated the influence of intraperitoneal administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or 1-methyl-4-phenylpyridinium (MPP+) on the placenta. There was no increase in apoptotic cells in the placentas of C57BL/6 mice treated with 25.0 mg/kg MPTP or 17.1 mg/kg MPP+, indicating that a single injection of the chemicals may induce very slight cytotoxicity in the placenta at 12 hr after administration. The decrease in the expression of monoamine oxidase (MAO)-A in the labyrinth zone and that of MAO-B in the basal zone may be due to the decrease in cell activity, whereas the increase of MAO-B expression in the labyrinth zone after MPTP treatment may be due to a responsive reaction caused by MPTP, one of the substrates of MAO-B. The results represent histological evidence that MAO-B may be involved in the metabolism of MPTP to MPP+ in the labyrinth zone of the mouse placenta. In the present study, no increase in apoptotic cells indicates that MPTP and MPP+ are hardly toxic to the placenta, and the histological change in MAO-B expression may indicate the possibility of involvement of placental MAO-B in MPTP metabolism. (DOI: 10.1293/tox.26.73; J Toxicol Pathol 2013; 26: 73-77)