Giardina SF, Beart PM. Excitotoxic profiles of novel, low-affinity kainate receptor agonists in primary cultures of murine cerebellar granule cells.
Neuropharmacology 2001;
41:421-32. [PMID:
11543762 DOI:
10.1016/s0028-3908(01)00086-7]
[Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The involvement of low-affinity kainate (KA) receptors in neuronal injury was investigated by employing a variety of agonists active at GluR5-7. Their excitotoxic profiles were determined in primary cultures of cerebellar granule cells, which abundantly expressed low-affinity KA receptors, and in the absence of any AMPA receptor-mediated neurotoxicity. Neurotoxicity induced by these compounds was analysed by phase contrast microscopy, a cell viability assay, the TUNEL technique (apoptosis), and by employing propidium iodide (PI; necrosis). All agonists induced concentration-dependent neurotoxicity, with rank order (EC(50) values; microM): (S)-iodowillardiine (IW) 0.2>(2S,4R)-4-methylglutamate (4-MG) 36>(2S,4R,6E)-2-amino-4-carboxy-7-(2-naphthyl)hept-6-enoic acid (LY339434) 46>KA 74>(RS)-2-amino-3-(hydroxy-5-tert-butylisoxazol-4yl)propanoic acid (ATPA) 88. IW exposure resulted in apoptosis at lower concentrations (<30 microM) and necrosis at higher concentrations, both of which were attenuated by CNQX (50 microM), but not MK-801 (10 microM). ATPA-mediated neurotoxicity was purely apoptotic and was attenuated by the non-NMDA receptor antagonists. Both IW and ATPA induced injury with the morphological characteristics of apoptosis shown by the presence of TUNEL-positive neurones. LY339434-mediated neuronal injury was only attenuated by MK-801 and was necrotic in nature. Similarly, 4-MG (>30 microM) exposure caused necrosis that was partially attenuated by MK-801 (10 microM) and CNQX (50 microM). The patterns of neurotoxicity possessed a complex pharmacological profile, demonstrated an apoptotic-necrotic continuum and were inconsistent with past findings, further outlining the importance of characterizing novel compounds at native receptors. ATPA and to a lesser extent IW appear to be suitable drugs for low-affinity KA receptors. Since toxicity-mediated by low-affinity KA receptors seem likely to contribute to neurodegenerative conditions, our study importantly examines the excitotoxic profile of these novel agonists.
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