Effects of intracellular zinc depletion on the expression of VDAC in cultured hippocampal neurons

An experiment was conducted to investigate whether intracellular zinc depletion can actually change expression of voltage-dependent anion channel 1 (VDAC1) and VPAC2 in cultured hippocampal neurons as well as their significance. Hippocampal neurons were obtained by primary culture from hippocampus of newborn Wistar rats. Cultured hippocampal neurons were exposed to a cell membrane-permeable zinc chelator N,N,N',N'-tetrakis (2-pyridyl methyl) ethylenediamine (TPEN) (2 mu M), and to TPEN plus zinc sulfate (5 mu M) for 1 or 24 hours. Cultures were then processed to detect neuronal injury by lactate dehydrogenase (LDH) assay, intracellular Ca2+ with the fluorescent probe fluo-3/AM, reactive oxygen species (ROS) generation using 2',7'-dichlorofluorescein diacetate (DCFH-DA) assay, nuclear morphology by Hoechst 33342, VDAC1, and VDAC2 protein levels by western blot, and VDAC1 and VDAC2 mRNA levels by RT-PCR. The results demonstrated that exposure of hippocampal neurons to TPEN (2 mu M) for 24 hours induced notably neuronal injury, significantly increased the number of apoptotic nuclei, up-regulated the expression of VDAC1 protein level and down-regulated the expression of VDAC2 protein level. Significant down-regulation of mRNA levels for VDAC1 and VDAC2 were observed in TPEN-treated neurons. Co-addition of zinc almost completely reversed TPEN-induced neuronal injury and above alterations in VDAC1 and VDAC2 protein levels and mRNA levels. Present results implicate a possibility that up-regulation of VDAC1 and down-regulation of VDAC2 may participate in hippocampal neuron injury induced by zinc deficiency.