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Role of blood–brain barrier organic anion transporter 3 (OAT3) in the efflux of indoxyl sulfate, a uremic toxin: its involvement in neurotransmitter metabolite clearance from the brain
Author(s) -
Ohtsuki Sumio,
Asaba Hiroshi,
Takanaga Hitomi,
Deguchi Tsuneo,
Hosoya Kenichi,
Otagiri Masaki,
Terasaki Tetsuya
Publication year - 2002
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2002.01108.x
Subject(s) - chemistry , probenecid , organic anion transporter 1 , efflux , blood–brain barrier , neurotransmitter , pharmacology , biochemistry , metabolite , transporter , endocrinology , central nervous system , biology , receptor , gene
Renal impairment is associated with CNS dysfunctions and the accumulation of uremic toxins, such as indoxyl sulfate, in blood. To evaluate the relevance of indoxyl sulfate to CNS dysfunctions, we investigated the brain‐to‐blood transport of indoxyl sulfate at the blood–brain barrier (BBB) using the Brain Efflux Index method. [ 3 H]Indoxyl sulfate undergoes efflux transport with an efflux transport rate of 1.08 × 10 −2 /min, and the process is saturable with a K m of 298 µ m . This process is inhibited by para ‐aminohippuric acid, probenecid, benzylpenicillin, cimetidine and uremic toxinins, such as hippuric acidand 3‐carboxy‐4‐methyl‐5‐propyl‐2‐furanpropanoic acid. RT–PCR revealed that an OAT3 mRNA is expressed in conditionally immortalized rat brain capillary endothelial cell lines and rat brain capillary fraction. Xenopus oocytes expressing OAT3 were found to exhibit [ 3 H]indoxyl sulfate uptake, which was significantly inhibited by neurotransmitter metabolites, such as homovanillic acid and 3‐methoxy‐4‐hydroxymandelic acid, and by acyclovir, cefazolin, baclofen, 6‐mercaptopurine, benzoic acid, and ketoprofen. These results suggest that OAT3 mediates the brain‐to‐blood transport of indoxyl sulfate, and is also involved in the efflux transport of neurotransmitter metabolites and drugs. Therefore, inhibition of the brain‐to‐blood transport involving OAT3 would occur in uremia and lead to the accumulation of neurotransmitter metabolites and drugs in the brain.