Interferon-γ down-regulates transcription of the μ-opioid receptor gene in neuronal and immune cells

Earlier investigations demonstrated up-regulated μ-opioid receptor expression in neuronal and immune cells in response to IL-1, IL-4, IL-6 and TNF-α. We herein report that μ-opioid receptor expression is down-regulated in SH SY5Y neuroblastoma cells by IFN-γ, and that IL-4-mediated induction of μ-opioid receptor expression is inhibited in Jurkat T cells by IFN-γ. Additionally, μ-opioid receptor transcripts were found in IL-4-expressing human primary T helper cells type 2, but not in type 1 cells, which typically express IFN-γ. This indicates that μ-opioid receptor expression may be altered under conditions like inflammation, viral infections or neurological diseases associated with imbalanced cytokine expression.