Modulation of nociceptin receptor and nociceptin/orphanin FQ mRNA expression in whole blood cultures

Abstract

Background: Expression of the nociceptin receptor (NOP) and its endogenous ligand nociceptin/orphanin FQ (N/OFQ) in peripheral blood cells have been described, however, their regulation is not yet known. In this study the influence of by inflammatory mediators on mRNA expression of NOP and N/OFQ in human whole blood was investigated. Methods: Peripheral whole blood from 30 healthy volunteers was cultured for 0, 3, 6 and 24 hours with or without lipopolysaccharide (LPS) 10 ng/ml, tumor necrosis factor alpha (TNFα) 3 ng/ml, IL- (interleukin)-1β 3 ng/ml, IL-10 50 ng/ml or interferon-γ (IFN-γ) 10 ng/ml. NOP and N/OFQ mRNA levels were detected by quantitative RT-PCR. Concentrations of TNFα, IL-1β and IL-10 were measured by enzyme-linked immunosorbent assay in the supernatants of blood cultures. In addition, an intervention study with neutralizing antibodies to TNF-α, IL-β, IFN-γ and IL-10 were performed. Results: NOP and pN/OFQ were constitutively detected at mRNA level in human peripheral blood cells. LPS significantly suppressed both, NOP and pN/OFQ expression. TNF-α, IL-1β, IL-10 and IFN-γ attenuated NOP and pN/OFQ mRNA levels to varying extents. LPS induced a significant increase in cytokines measured in the supernatants of the blood cultures. Inhibition of the LPS-induced increase in TNF-α and IL-1β by respective antibodies partially antagonized the down-regulation of NOP at 3 hours. Conclusion: Inflammatory mediators regulate NOP and N/OFQ expression in a human whole blood culture. The role of cytokine induced changes in NOP and pN/OFQ expression in different disease states has to be determined.