The etiology of Parkinson's disease (PD), a neurodegenerative disorder linked to aging, remains unclear. We initially proposed that (N)- methylated beta-carbolinium (MeBC) compounds, metabolic derivatives of physiological indoleamines, may be causative factors. MeBCs structurally mirror N-methyl-4-phenyl-pyridinium (MPP+), the mitochondrially toxic metabolite of N-methyl-4-phenyl-tetrahydro-pyridine, a parkinsonism- inducing contaminant in illicit street drugs. Supporting our proposal, we find that normethyl BCs reported in vivo undergo methylation on the 2- nitrogen and, more surprisingly, the 9(indole)-nitrogen by S- adenosylmethionine-dependent transferase(s) in guinea pig or rat brain. Further, like MPP+, the 7-oxygenated 2-MeBCs and particularly the simple 2,9-Me2BCs are effective mitochondrial respiratory inhibitors, but notably, because they cannot N-deprotonate, only the 2,9-Me2BCs are mitochondrially sequestered like MPP+ (PNAS, 1990). Consistent with these results, certain MeBCs have neurotoxic potencies approaching MPP+ in vitro (PC12 cells) and in vivo (striatal microdialysis or nigral injections in rats); importantly, for simple 2-MeBCs, 9(indole)-methylation markedly enhances toxicity (Science, submitted). The main aim of this application focuses on a key analytical question: are MeBCs -- and especially the unique 2,9-Me2BCs -- present and possibly increased in the human CNS during early or late PD? To answer this we will examine both cerebrospinal fluid and postmortem brain from PD subjects and controls employing HPLC/fluorescence detection; with Dr. Faull's collaboration at UCLA, mass spectrometry will be used for structural and quantitative confirmation. The objective of a 2nd aim is to partially characterize the N-methyltransferase(s) effecting 2-MeBC and 2,9-Me2BC formation in human brain regions, in order to clarify relationships between regional brain MeBC levels and N-methylation activity. In our 3rd aim, to better understand the toxic mechanisms, we will compare selected 2,9-MeBCs, 2-BCs and MPP+ using fetal rat mesencephalic cultures and, in ongoing collaboration with Dr. H. Rollema, in vivo striatal microdialysis in rats. This overall approach should provide definitive answers about the possible involvement of MeBCs in PD.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
2R01NS023891-04A3
Application #
3407915
Study Section
Neurological Sciences Subcommittee 1 (NLS)
Project Start
1986-09-01
Project End
1995-06-30
Budget Start
1992-07-01
Budget End
1993-06-30
Support Year
4
Fiscal Year
1992
Total Cost
Indirect Cost
Name
Loyola University Chicago
Department
Type
Schools of Medicine
DUNS #
791277940
City
Maywood
State
IL
Country
United States
Zip Code
60153
Gearhart, Debra A; Neafsey, Edward J; Collins, Michael A (2002) Phenylethanolamine N-methyltransferase has beta-carboline 2N-methyltransferase activity: hypothetical relevance to Parkinson's disease. Neurochem Int 40:611-20
Collins, Michael A (2002) Alkaloids, alcohol and Parkinson's disease. Parkinsonism Relat Disord 8:417-22
Gearhart, D A; Collins, M A; Lee, J M et al. (2000) Increased beta-carboline 9N-methyltransferase activity in the frontal cortex in Parkinson's disease. Neurobiol Dis 7:201-11
Gearhart, D A; Neafsey, E J; Collins, M A (1997) Characterization of brain beta-carboline-2-N-methyltransferase, an enzyme that may play a role in idiopathic Parkinson's disease. Neurochem Res 22:113-21
Neafsey, E J; Albores, R; Gearhart, D et al. (1995) Methyl-beta-carbolinium analogs of MPP+ cause nigrostriatal toxicity after substantia nigra injections in rats. Brain Res 675:279-88
Collins, M A (1994) Potential parkinsonian protoxicants within and without. Neurobiol Aging 15:277-8
Cobuzzi Jr, R J; Neafsey, E J; Collins, M A (1994) Differential cytotoxicities of N-methyl-beta-carbolinium analogues of MPP+ in PC12 cells: insights into potential neurotoxicants in Parkinson's disease. J Neurochem 62:1503-10
Fields, J Z; Albores, R R; Neafsey, E J et al. (1992) Inhibition of mitochondrial succinate oxidation--similarities and differences between N-methylated beta-carbolines and MPP+. Arch Biochem Biophys 294:539-43
Fields, J Z; Albores, R; Neafsey, E J et al. (1992) Similar inhibition of mitochondrial respiration by 1-methyl-4-phenyl-pyridinium (MPP+) and by a unique N-methylated beta-carboline analogue, 2,9-dimethyl-norharman (2,9Me2NH). Ann N Y Acad Sci 648:272-4
Matsubara, K; Neafsey, E J; Collins, M A (1992) Novel S-adenosylmethionine-dependent indole-N-methylation of beta-carbolines in brain particulate fractions. J Neurochem 59:511-8

Showing the most recent 10 out of 14 publications