Nitric oxide mediates glutamate neurotoxicity in primary cortical cultures.

TLDR

Nitric oxide mediates diverse physiological processes—including vascular relaxation, macrophage cytotoxicity, and cGMP production via glutamate receptors—and its synthase localizes to neurons that are resistant to toxic insults. In primary cortical cultures, inhibition of nitric oxide synthase or removal of arginine blocks NMDA‑induced neurotoxicity, hemoglobin scavenging of NO likewise prevents cell death, thereby establishing NO as the mediator of glutamate‑induced neuronal injury.

Abstract

Nitric oxide (NO) mediates several biological actions, including relaxation of blood vessels, cytotoxicity of activated macrophages, and formation of cGMP by activation of glutamate receptors in cerebellar slices. Nitric oxide synthase (EC 1.14.23.-) immunoreactivity is colocalized with nicotinamide adenine di-nucleotide phosphate diaphorase in neurons that are uniquely resistant to toxic insults. We show that the nitric oxide synthase inhibitors, N omega-nitro-L-arginine (EC50 = 20 microM) and N omega-monomethyl-L-arginine (EC50 = 170 microM), prevent neurotoxicity elicited by N-methyl-D-aspartate and related excitatory amino acids. This effect is competitively reversed by L-arginine. Depletion of the culture medium of arginine by arginase or arginine-free growth medium completely attenuates N-methyl-D-aspartate toxicity. Sodium nitroprusside, which spontaneously releases NO, produces dose-dependent cell death that parallels cGMP formation. Hemoglobin, which complexes NO, prevents neurotoxic effects of both N-methyl-D-aspartate and sodium nitroprusside. These data establish that NO mediates the neurotoxicity of glutamate.