title: Effects of lipopolysaccharide on the expression of plasma membrane monoamine transporter (PMAT) at the blood-brain barrier and its implications to the transport of neurotoxins.
abstract: Plasma membrane monoamine transporter (PMAT) is a polyspecific organic cation transporter that is highly expressed in the central nervous system. This study aimed to investigate the effect of lipopolysaccharide on PMAT expression at the blood-brain barrier and the interaction between PMAT and neurotoxins. As a result, PMAT mRNA was identified in brain microvessels (BMVs), brain microvascular endothelial cells (BMECs), astrocytes, and pericytes isolated from C57BL/6 mice and/or Wistar rats using RT-qPCR. The immunofluorescence staining confirmed the expression of PMAT protein in BMVs and striatum of C57BL/6 mice. Western blotting demonstrated its localization at the luminal and abluminal sides of BMECs. In C57BL/6 mice, PMAT protein was significantly increased in BMVs 24 h after an intraperitoneal injection of 3 mg/kg lipopolysaccharide. Lipopolysaccharide treatment also significantly increased PMAT expression in cerebral cortex and the striatum in a time-dependent manner, as well as the brain-to-plasma ratio of 1-benzyl-1,2,3,4-tetrahydroisoquinoline (1-benzyl-TIQ). In isolated cells, lipopolysaccharide treatment significantly increased PMAT mRNA in brain astrocytes and the BMECs co-cultured with astrocytes. In addition to 1-methyl-4-phenylpyridinium, the kinetic study indicated that both 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and 1-benzyl-TIQ are substrates of human PMAT. These findings suggest that inflammation can change PMAT expression at the blood-brain barrier, which may affect PMAT-mediated transport of neurotoxins. We demonstrated the expression of plasma membrane monoamine transporter (PMAT; mRNA or protein) at several subunits of the blood-brain barrier. Lipopolysaccharide treatment can significantly increase the expression of PMAT in vivo (in brain microvessels, cerebral cortex, and the striatum of C57BL/6 mice) and in vitro (in brain astrocytes and brain microvascular endothelial cells co-cultured with astrocytes). Lipopolysaccharide treatment also increased the brain-to-plasma ratio of 1-benzyl-1,2,3,4-tetrahydroisoquinoline (1-benzyl-TIQ) in mice, where 1-benzyl-TIQ competitively inhibited 1-methyl-4-phenylpyridinium (MPP(+)) uptake in MDCK-human PMAT (hPMAT) cells and its uptake in MDCK-hPMAT is concentration dependent.
authors.affiliation: School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Kuo-Chen
authors.initials: KC
authors.lastname: Wu
authors.affiliation: School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Ya-Hsuan
authors.initials: YH
authors.lastname: Lu
authors.affiliation: School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Yi-Hsuan
authors.initials: YH
authors.lastname: Peng
authors.affiliation: School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Lih-Ching
authors.initials: LC
authors.lastname: Hsu
authors.affiliation: School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Chun-Jung
authors.initials: CJ
authors.lastname: Lin
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000378:metabolism*; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D033705:Equilibrative Nucleoside Transport Proteins / Q000378:metabolism*; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D008810:Mice, Inbred C57BL; D009498:Neurotoxins / Q000378:metabolism*; D027701:Organic Cation Transport Proteins / Q000378:metabolism; D017208:Rats, Wistar
chemical_list: D033705:Equilibrative Nucleoside Transport Proteins; D008070:Lipopolysaccharides; D009498:Neurotoxins; D027701:Organic Cation Transport Proteins; C495988:SLC29A4 protein, human
keywords: Blood-brain barrier; PMAT; lipopolysaccharide; neurotoxin