Zn2+ entry produces oxidative neuronal necrosis in cortical cell cultures

Evidence has accumulated that Zn²⁺ plays a central role in neurodegenerative processes following brain injuries including ischaemia or epilepsy. In the present study, we examined patterns and possible mechanisms of Zn²⁺ neurotoxicity. Inclusion of 30–300 μm Zn²⁺ for 30 min caused neuronal necrosis apparent by cell body and mitochondrial swelling in cortical cell cultures. This Zn²⁺ neurotoxicity was not attenuated by antiapoptosis agents, inhibitors of protein synthesis or caspase. Blockade of glutamate receptors or nitric oxide synthase showed no beneficial effect against Zn²⁺ neurotoxicity. Interestingly, antioxidants, trolox or SKF38393, attenuated Zn²⁺-induced neuronal necrosis. Pretreatment with insulin or brain-derived neurotrophic factor increased the Zn²⁺-induced free radical injury. Kainate or AMPA facilitated Zn²⁺ entry and potentiated Zn²⁺ neurotoxicity in a way sensitive to trolox. Reactive oxygen species and lipid peroxidation were generated in the early phase of Zn²⁺ neurotoxicity. These findings indicate that entry and accumulation of Zn²⁺ result in generation of toxic free radicals and then cause necrotic neuronal degeneration under certain pathological conditions in the brain.