Zinc Regulation of Cobalt-Induced Apoptosis in Cultured Human Neurons

Abstract

While it is clear that hypoxic-ischemic injury leads to neuronal death, the type of cell death and the molecular mechanisms involved are not fully understood. This study was designed to test the hypothesis that cobalt-induced hypoxia induces neuronal apoptosis and that high concentrations of the nutrient zinc protects neurons. Treatment of cultured postmitotic human neurons (NT2-N) with cobalt to mimic hypoxia resulted in a significant reduction in the number of viable NT2-N neurons. Cellular and nuclear morphology suggested that hypoxic NT2-N neurons die as a result of apoptosis. Northern analysis and immunocytochemistry revealed increases in p53 mRNA and p53. Cobalt also resulted in translocation of p53 to the nucleus of apoptotic neurons. Treatment with high concentrations of zinc (700 μM) not only reduced the morphological evidence of apoptosis, but also appeared to inhibit nuclear translocation of p53. Hsp 70, a chaperone protein that has been associated with cellular protection, was increased by cobalt. Additional increases in the nuclear translocation of Hsp 70 were observed following zinc treatment of hypoxic neurons suggesting that at high concentrations zinc may act to protect neurons from cobalt-induced hypoxia by decreasing nuclear p53 and increasing Hsp 70 in vitro.

Keywords:

• Hypoxia
• p53
• Hsp 70
• Apoptosis
• Ischemia
• Brain