title: Inhibition of Large Neutral Amino Acid Transporters Suppresses Kynurenic Acid Production Via Inhibition of Kynurenine Uptake in Rodent Brain.
abstract: The tryptophan metabolite, kynurenic acid (KYNA), is a preferential antagonist of the α7 nicotinic acetylcholine receptor and N-methyl-D-aspartic acid receptor at endogenous brain concentrations. Recent studies have suggested that increases of brain KYNA levels are involved in psychiatric disorders such as schizophrenia and depression, and regulation of KYNA production has become a new target for treatment of these diseases. Kynurenine (KYN), the immediate precursor of KYNA, is transported into astrocytes via large neutral amino acid transporters (LATs). In the present study, the effect of LATs regulation on KYN uptake and KYNA production was investigated in vitro and in vivo using an LATs inhibitor, 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH). In the in vitro study, cortical slices of rat brain were incubated with a physiological concentration of KYN and 3 µmol/L-3 mmol/L BCH. BCH inhibited KYNA production and KYN uptake in a dose-dependent manner, and their IC50 values were 90.7 and 97.4 µmol/L, respectively. In the in vivo study, mice were administered KYN (50 mg/kg BW) orally and BCH (200 mg/kg BW) intravenously. Administration of KYN increased brain KYN and KYNA levels compared with the mice treated with vehicle, whereas additional administration of BCH suppressed KYN-induced elevations in KYN and KYNA levels to 50 and 70 % in the brain. These results suggest that inhibition of LATs prevented the increase of KYNA production via blockade of KYN uptake in the brain in vitro and in vivo. LATs can be a target to modulate brain function by regulation of KYNA production in the brain.
authors.affiliation: Department of Nutrition, School of Human Cultures, The University of Shiga Prefecture, 2500 Hassaka, Hikone, Shiga, 522-8533, Japan.
authors.forename: Airi
authors.initials: A
authors.lastname: Sekine
authors.affiliation: Department of Nutrition, School of Human Cultures, The University of Shiga Prefecture, 2500 Hassaka, Hikone, Shiga, 522-8533, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kuroki
authors.affiliation: Department of Nutrition, School of Human Cultures, The University of Shiga Prefecture, 2500 Hassaka, Hikone, Shiga, 522-8533, Japan.
authors.forename: Tomomi
authors.initials: T
authors.lastname: Urata
authors.affiliation: Department of Nutrition, School of Human Cultures, The University of Shiga Prefecture, 2500 Hassaka, Hikone, Shiga, 522-8533, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Mori
authors.affiliation: Department of Nutrition, School of Human Cultures, The University of Shiga Prefecture, 2500 Hassaka, Hikone, Shiga, 522-8533, Japan. fukkie@shc.usp.ac.jp.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Fukuwatari
mesh_terms: D026921:Amino Acid Transport Systems, Neutral / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D007736:Kynurenic Acid / Q000378:metabolism*; D007737:Kynurenine / Q000378:metabolism* / Q000494:pharmacology*; D008297:Male; D017208:Rats, Wistar; D012559:Schizophrenia / Q000378:metabolism; D014364:Tryptophan / Q000378:metabolism; D064569:alpha7 Nicotinic Acetylcholine Receptor / Q000378:metabolism
chemical_list: D026921:Amino Acid Transport Systems, Neutral; D064569:alpha7 Nicotinic Acetylcholine Receptor; D007737:Kynurenine; D014364:Tryptophan; D007736:Kynurenic Acid
keywords: Amino acids; Dopamine; Kynurenic acid; Kynurenine; Large neutral amino acid transporter; Neuropsychiatric disorders; α7 Nicotinic acetylcholine receptor