N-methylation underlying Parkinson's disease

Kazuo Matsubara, Koji Aoyama, Manabu Suno, Toshio Awaya

Research output: Contribution to journalReview articlepeer-review

36 Citations (Scopus)


The discovery of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) leads to the hypothesis that Parkinson's disease (PD) is maybe initiated or precipitated by environmental or endogenous toxins by the mechanism similar to that of MPTP in genetically-predisposed individuals. Endogenous analogs of MPTP, such as β-carbolines (βCs) and tetrahydroisoquinolines, have been proposed as possible causative candidates causing PD and are bioactivated into potential neurotoxins by N-methylation enzyme(s). These N-methylated βCs and tetrahydroisoquinoline have been higher cerebrospinal levels in parkinsonian patients than age-matched controls. Thus, there is a hypotheses to influence the pathogenesis of PD, that is, the excess enzyme activity to activate neurotoxins, such as N-methyltransferase, might be higher in PDs. Indeed, simple βCs, via N-methylation steps, induced bradykinesia with the decreased dopamine contents in the striatum and midbrain in C57/BL mice. In younger (65 years old) PD patients, the excretion amount of N1-methyl-nicotinamaide was significantly higher than that in younger controls. The protein amount of nicotinamide N-methyltransferase (NNMT) was also significantly higher in younger PD patients than that in younger controls. These findings described here would indicate that the excess N-methylation ability for azaheterocyclic amines, such as βCs, before the onset had been implicated in PD pathogenesis. On the other hand, the contribution of aberrant cytochrome P450 or aldehyde oxidase activity acting on the pyridine ring, that could act as detoxification routes of endogenous neurotoxins, would be small in the etiology of PD.

Original languageEnglish
Pages (from-to)593-598
Number of pages6
JournalNeurotoxicology and Teratology
Issue number5
Publication statusPublished - Sept 2002
Externally publishedYes


  • Cerebrospinal fluid
  • N-methylation
  • Neurotoxin
  • Parkinson's disease
  • β-Carboline

ASJC Scopus subject areas

  • Toxicology
  • Developmental Neuroscience
  • Cellular and Molecular Neuroscience


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