TNF Alpha Production in Morphine-Treated Human Neural Cells Is NF-κB-Dependent

The cytokine tumor necrosis factor alpha (TNF alpha) is a key factor in several inflammatory diseases and its levels increase in response to a variety of internal or external stimuli. The regulation of the TNF alpha promoter is mediated by several transcription factors including the nuclear factor kappa B protein (NF-kappa B). This study examines the role of NF-kappa B in the regulation of TNF alpha production by morphine in microglia. Using reverse transcriptase polymerase chain reaction, we demonstrated the presence of morphine receptors in these cells. We next demonstrated the ability of morphine to promote TNF alpha production and secretion by these cells using a cytokine array assay. Transient transfection experiments led to the identification of the region located between nucleotides -751 and -615 within the TNF alpha promoter as being responsive to morphine treatment. The DNA sequence of this region contains a motif indicative of a potential NF-kappa B binding site. The use of a small interfering RNA directed against p65, a subunit of NF-kappa B, demonstrated that TNF alpha induction by morphine is NF-kappa B-dependent. All of the effects of morphine were reversed by the morphine inhibitor, naloxone. These data provide important insights into the effects of morphine on microglia.