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

Abstract

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 µM), and to TPEN plus zinc sulfate (5 µM) 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 µM) 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.