Inhibitors of phospholipase C prevent glutamate neurotoxicity in primary cultures of cerebellar neurons.

The role of phospholipase C in the molecular mechanism of glutamate neurotoxicity was assessed in primary cultures of cerebellar neurons. It is shown that 1-[6-[[(17b)-3-methoxyestra-1,3, 5(10)-trien-17-yl]amino] hexyl]-1H-pyrrole-2,5-dione (U-73122) and 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphorylcholine (Et-18-OCH(3)), two agents that inhibit phospholipase C, prevent glutamate and N-methyl-D-aspartic acid (NMDA) neurotoxicity. It is shown that both compounds prevent glutamate neurotoxicity at concentrations lower than those required to inhibit carbachol-induced hydrolysis of inositol phospholipids. In contrast, it was a good correlation between the concentrations of U-73122 and Et-18-OCH(3) required to inhibit NMDA-induced hydrolysis of phospholipids and those required to prevent glutamate and NMDA neurotoxicity. NMDA-induced hydrolysis of phospholipids is inhibited by nitroarginine, an inhibitor of nitric-oxide synthase, and is mimicked by the nitric oxide-generating agent S-nitroso-N-acetylpenicillamine. The results reported indicate that glutamate neurotoxicity would be mediated by activation of NMDA receptors, leading to activation of nitric-oxide synthase and increased formation of nitric oxide, which results in increased activity of phospholipase C. Inhibition of phospholipase C by U-73122 or Et-18-OCH(3) prevents glutamate-induced neuronal death.