Neuroprotective effects of the novel glutamate transporter inhibitor (-)-3-hydroxy-4,5,6,6a-tetrahydro-3aH-pyrrolo[3,4-d]-isoxazole-4-carboxylic acid, which preferentially inhibits reverse transport (glutamate release) compared with glutamate reuptake

Simona Colleoni, Anders A. Jensen, Elisa Landucci, Elena Fumagalli, Paola Conti, Andrea Pinto, Marco De Amici, Domenico E. Pellegrini-Giampietro, Carlo De Micheli, Tiziana Mennini, Marco Gobbi

Research output: Contribution to journalArticlepeer-review

Abstract

(±)-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.

Original languageEnglish
Pages (from-to)646-656
Number of pages11
JournalJournal of Pharmacology and Experimental Therapeutics
Volume326
Issue number2
DOIs
Publication statusPublished - Aug 2008

ASJC Scopus subject areas

  • Pharmacology

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