Vitamin D Attenuates Hypoxia-Induced Injury in Rat Primary Neuron Cells through Downregulation of the Dual Oxidase 1 (DUOX1) Gene

BACKGROUND: This study aimed to investigate the mechanisms underlying the neuroprotective effects of vitamin D. MATERIAL/METHODS: Rat primary neuron cells were incubated under a hypoxia condition [a hypoxic chamber mixed with anaerobic gas (90% N(2), 5% CO(2)) and 5% O(2)] to induce cell injury. Cell transfection was performed to overexpress or suppress the expression of dual oxidase 1 (DUOX1). The malondialdehyde (MDA) and superoxide dismutase (SOD) levels were detected using a MDA (A003-2) or SOD (A001-1) kit. DUOX1 mRNA levels were detected using RT-PCR. Hypoxia-inducible factor-1α (HIF-1α), DUOX1, vitamin D receptor (VDR), NF-κB protein expressions were determined by western blotting. Cell apoptosis and reactive oxygen species (ROS) were evaluated by flow cytometry. RESULTS: ROS increased significantly after hypoxic treatment. The expressions of HIF-1α and DUOX1 were significantly increased after hypoxic treatment. Vitamin D could decrease ROS level, apoptotic neuron cells and DUOX1 expression, and increase VDR expression. Downregulation of DUOX1 significantly decreased MDA level and apoptotic percentages of neuron cells, increased SOD level, and counteracted the hypoxia-induced increase of NF-κB signal. Further study showed that overexpression of DUOX1 significantly increased MDA level, ROS level, apoptotic percentages of neuron cells, and NF-κB nuclear signaling, while decreased SOD level. Vitamin D significantly counteracted the effects of DUOX1 overexpression induced injury in rat primary neuron cells. CONCLUSIONS: Our study indicated that vitamin D may protect neuron cells from hypoxia-induced injury by regulating DUOX1 via the NF-κB signaling pathway.