Cellular localization of the organic cation transporters, OCT1 and OCT2, in brain microvessel endothelial cells and its implication for MPTP transport across the blood-brain barrier and MPTP-induced dopaminergic toxicity in rodents.
The cellular localization of organic cation transporter (OCT) 1 and OCT2 in isolated brain microvessel endothelial cells from humans, rats, and mice and in cultured adult rat brain endothelial cells was examined by confocal microscopy and in isolated luminal and abluminal membrane fractions by Western blot analysis. Cellular uptake of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was measured with or without OCT1/OCT2 silencing. The interaction between MPTP and amantadine was studied by in vitro kinetic analysis and in vivo brain microdialysis. MPTP-induced dopaminergic toxicity was examined by measuring dopamine levels in the brain striatum and by positron emission tomography scanning. The results showed that both OCT1 and OCT2 were mainly expressed on the luminal side of brain microvessel endothelial cells and adult rat brain endothelial cells. Cellular uptake of MPTP was significantly (p < 0.05) decreased by about 53%, 60%, or 91% following silencing of OCT1, OCT2, or both, respectively. Amantadine competitively inhibited MPTP uptake in vitro and significantly (p < 0.05) reduced the area under the time-concentration curve for MPTP and MPP(+) in the brain extracellular fluid in rats and mice by 65-70% and 35-85%, respectively. MPTP-induced dopaminergic toxicity in mice was ameliorated by amantadine without stimulating dopamine turnover. In conclusion, OCT1 and OCT2 are important for MPTP transfer across the blood-brain barrier and amantadine reduces the blood-brain barrier transfer of MPTP and MPTP-induced dopaminergic toxicity in rodents.
Lin
Chun-Jung
CJ
School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan. clementumich@ntu.edu.tw
Tai
Ying
Y
Huang
Miao-Tzu
MT
Tsai
Yuan-Feen
YF
Hsu
Hao-Jui
HJ
Tzen
Kai-Yuan
KY
Liou
Horng-Huei
HH
D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine / Q000493:pharmacokinetics*; D000818:Animals; D001667:Binding, Competitive / Q000502:physiology; D001693:Biological Transport, Active; D001812:Blood-Brain Barrier / Q000378:metabolism*; D002196:Capillaries / Q000166:cytology / Q000378:metabolism; D002478:Cells, Cultured; D004298:Dopamine / Q000502:physiology* / Q000633:toxicity; D042783:Endothelial Cells / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009498:Neurotoxins / Q000493:pharmacokinetics; D050811:Octamer Transcription Factor-1 / Q000378:metabolism*; D027701:Organic Cation Transport Proteins / Q000378:metabolism*; D000075102:Organic Cation Transporter 2; D020734:Parkinsonian Disorders / Q000378:metabolism / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar
D009498:Neurotoxins; D050811:Octamer Transcription Factor-1; D027701:Organic Cation Transport Proteins; D000075102:Organic Cation Transporter 2; C494166:Pou2f1 protein, mouse; C491012:Slc22a2 protein, mouse; D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; D004298:Dopamine