TY - JOUR T1 - Neuroprotective Effects of the Novel Glutamate Transporter Inhibitor (–)-3-Hydroxy-4,5,6,6<em>a</em>-tetrahydro-3<em>aH</em>-pyrrolo[3,4-<em>d</em>]-isoxazole-4-carboxylic Acid, Which Preferentially Inhibits Reverse Transport (Glutamate Release) Compared with Glutamate Reuptake JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 646 LP - 656 DO - 10.1124/jpet.107.135251 VL - 326 IS - 2 AU - Simona Colleoni AU - Anders A. Jensen AU - Elisa Landucci AU - Elena Fumagalli AU - Paola Conti AU - Andrea Pinto AU - Marco De Amici AU - Domenico E. Pellegrini-Giampietro AU - Carlo De Micheli AU - Tiziana Mennini AU - Marco Gobbi Y1 - 2008/08/01 UR - http://jpet.aspetjournals.org/content/326/2/646.abstract N2 - (±)-3-Hydroxy-4,5,6,6a-tetrahydro-3aH-pyrrolo [3,4 -d]-isoxazole-4-carboxylic acid (HIP-A) and (±)-3-hydroxy-4,5,6, 6a-tetrahydro-3aH-pyrrolo[3,4-d]isoxazole-6-carboxylic acid (HIP-B) are selective inhibitors of excitatory amino acid transporters (EAATs), as potent as dl-threo-β-benzyloxyaspartic acid (TBOA). We report here that the active isomers are (–)-HIP-A and (+)-HIP-B, being approximately 150- and 10-fold more potent than the corresponding enantiomers as inhibitors of [3H]aspartate uptake in rat brain synaptosomes and hEAAT1–3-expressing cells. Comparable IC50 values were found on the three hEAAT subtypes. (–)-HIP-A maintained the remarkable property, previously reported with the racemates, of inhibiting synaptosomal glutamate-induced [3H]d-aspartate release (reverse transport) at concentrations significantly lower than those inhibiting [3H]l-glutamate uptake. New data suggest that the noncompetitive-like interaction described previously is probably the consequence of an insurmountable, long-lasting impairment of EAAT's function. Some minutes of preincubation are required to induce this impairment, the duration of preincubation having more effect on inhibition of glutamate-induced release than of glutamate uptake. In organotypic rat hippocampal slices and mixed mouse brain cortical cultures, TBOA, but not (–)-HIP-A, had toxic effects. Under ischemic conditions, a neuroprotective effect was found with 10 to 30 μM (–)-HIP-A, but not with 10 to 30 μM TBOA or 100 μM (–)-HIP-A. The effect of (–)-HIP-A suggests that, under ischemia, EAATs mediate both release (reverse transport) and uptake of glutamate. The neuroprotection with the lower (–)-HIP-A concentrations may indicate a selective inhibition of the reverse transport confirming the data obtained in synaptosomes. The selective interference with glutamate-induced glutamate release might offer a new strategy for neuroprotective action. The American Society for Pharmacology and Experimental Therapeutics ER -