The effect of desferoxamine (DFO)-induced hypoxia on neuronal human mu-opioid receptor (hMOR) gene expression was investigated using NMB cells. DFO decreased cell viability and increased cellular glutathione levels in a dose- and time-dependent manner. Confocal analysis using annexin-V-fluorescein and propidium iodide staining revealed that surviving/attached cells under DFO challenge were morphologically similar to control (vehicle-treated) cells. RT-PCR analysis demonstrated that the hypoxia inducible factor-1 alpha (HIF-1 alpha) mRNA level was augmented in these surviving neurons. DFO treatment for 8 h or longer down-regulated the hMOR message, but not that of the delta-opioid receptor. Functional analysis using luciferase reporter assay showed that the hMOR 5'-regulatory region, from 357 bp to translational initiation site (+1), contains the active promoter with an inhibitory region located in the 422 to 357 bp region. DFO decreased hMOR promoter activity as compared to control. Mutation analysis suggested the existence of both dsDNA and ssDNA elements, located in a CT-rich region of hMOR, mediating the DFO-response. RT-PCR further revealed that DFO exhibited no effect on hMOR mRNA stability. In conclusion, DFO-induced hypoxia specifically affects neuronal hMOR gene expression at the transcriptional, not post-transcriptional, level. (C) 2010 Elsevier Inc. All rights reserved.