Inhibitory activities

DL-threo-b-Benzyloxyaspartate (DL-TBOA) was synthesized and examined as an inhibitor of sodium-dependent glutamate/aspartate (excitatory amino acid) transporters. DL-TBOA inhibited the uptake of glutamate in COS-1 cells expressing the human excitatory amino acid transporter-1 (EAAT1) (Ki=42 mM). With regard to the human excitatory amino acid transporter-2(EAAT2), the Ki of DL-TBOA 5.7 mM.

Cell lines

COS-1 cells

Preparation method

The solubility of this compound in DMSO is >10 mM. General tips for obtaining a higher concentration: Please warm the tube at 37℃ for 10 minutes and/or shake it in the ultrasonic bath for a while. Stock solution can be stored below -20℃ for several months.

Reacting condition

Measurements of glutamate uptake in transfected COS-1 cells assey: 37℃ for 12 min.

Applications

DL-TBOA markedly inhibited glutamate (1 mM) uptake in transfected cells in a dosedependent manner. The subconfluent cells were washed two times with 300 μl of modified phosphate-buffered saline that contained 137 mM NaCl, 2.7 mM KCl, 8.1 mM Na2HPO4, 1.5 mM KH2PO4,1mM MgCl2, 1mM CaCl2, and 10 mM D-glucose, pH 7.4, and preincubated in 300 μl of the same buffer at 37℃ for 12 min. After aspiration of the buffer, cells were incubated with 1 μM L-glutamate in 100 μl of modified phosphate-buffered saline in the absence or presence of DL-TBOA at various concentrations at 37℃ for 12 min.

Animal models

Males Wistar rats

Dosage form

500 μM DL-TBOA

Preparation method

Dissolved in Ringer Krebs medium which containing (in mM): NaCl 118, KCl 4.5, MgSO4 1.18, KH2PO4 1.2, CaCl2 2.5, NaHCO3 25.

Application

Microdialysis administration of 500μM DL-TBOA into the hippocampus increased 3.4- and nine-fold the extracellular levels of aspartate and glutamate, respectively.

Other notes

Please test the solubility of all compounds indoor, and the actual solubility may slightly differ with the theoretical value. This is caused by an experimental system error and it is normal.

Ki: 42 μM for EAAT1; 5.7 μM for EAAT2

Glutamate acts as an excitatory neurotransmitter in the mammalian central nervous system and a potent neurotoxin. Glutamate transporters also play an important role in maintaining the extracellular glutamate concentration below neurotoxic levels and therefore contribute to the prevention of neuronal damage. DL-TBOA was synthesized and examined as an inhibitor of sodium-dependent glutamate/aspartate transporters(excitatory amino acid transporters).

In vitro: DL-TBOA inhibited the uptake of [14C]glutamate in COS-1 cells overexpressing the human excitatory amino acid transporter-1 (EAAT1) (Ki = 42 μM) with almost the same potency as DL-threo-b-hydroxyaspartate (Ki = 58 μM). With regard to the human excitatory amino acid transporter-2 (EAAT2), the inhibitory effect of DL-TBOA (Ki = 5.7 μM) was much more potent than that of dihydrokainate (Ki = 79 μM), which is well known as a selective blocker of this subtype. [1].

In vivo: Microdialysis administration of 500 μM DL-TBOA into the hippocampus increased 3.4- and nine-fold the extracellular levels of aspartate and glutamate, respectively. Upon stereotaxic administration it induced neuronal damage dose-dependently in CA1 and dentate gyrus, and convulsive behavior. Electroencephalographic recording showed limbic seizures appearance in the hippocampus after DL-TBOA infusion. [2].

Clinical trial: Up to now, DL-TBOA is still in the preclinical development stage.

Reference:
[1] Shimamoto K, Lebrun B, Yasuda-Kamatani Y, Sakaitani M, Shigeri Y, Yumoto N, Nakajima T.  DL-threo-beta-benzyloxyaspartate, a potent blocker of excitatory amino acid transporters. Mol Pharmacol. 1998 Feb;53(2):195-201.
[2] Montiel T, Camacho A, Estrada-Sánchez AM, Massieu L.  Differential effects of the substrate inhibitor l-trans-pyrrolidine-2,4-dicarboxylate (PDC) and the non-substrate inhibitor DL-threo-beta-benzyloxyaspartate (DL-TBOA) of glutamate transporters on neuronal damage and extracellular amino acid levels in rat brain in vivo. Neuroscience. 2005;133(3):667-78.