Neuroprotection produced by the NAALADase inhibitor 2-PMPA in rat cerebellar neurons

The present study examined the neuroprotective actions of the N- acetylated-α-linked-acidic dipeptidase (NAALADase) inhibitor 2- (phosphonomethyl)pentanedioic acid (2-PMPA) in four in vitro models of neurotoxicity. Using neuron-enriched primary cultures derived from rat embryo (E15) cerebellum, 2-PMPA afforded 100% neuroprotection from injuries induced by hypoxia (EC₅₀ = 8.4 μM). In contrast, against glutamate or N-methyl-D- aspartate (NMDA) injury, 2-PMPA was less potent and its efficacy limited to a maximum of 46% and 16%, respectively. 2-PMPA was not effective against veratridine-induced injury. Also, the less potent analog of 2-PMPA, 2- [phosphonomethyl]succinic acid (2-PMSA), was ineffective. Unlike 2-PMPA, the endogenous NAALADase substrate and mGlu₃ receptor agonist N-acetyl-aspartyl- glutamate (NAAG) was neuroprotective against all four injury mechanisms and compared to 2-PMPA, exhibited a different 'phosphate effect' on neuroprotection. These results confirm the superior efficacy of 2-PMPA to protect against injury caused by cellular anoxia, and are discussed relative to upstream modulation of hyperglutamatergic activity vs. downstream modulation of metabotropic receptors as possible targets for ischemia/stroke therapy. (C) 2000 Elsevier Science B.V.