Phorbol-12-myristate-13-acetate induces nociceptin in human Mono Mac 6 cells via multiple transduction signalling pathways.
BACKGROUND
Nociceptin in the peripheral circulation has been proposed to have an immunoregulatory role with regards to inflammation and pain. However, the mechanisms involved in its regulation are still not clear. The aim of this study was to investigate signalling pathways contributing to the regulation of the expression of nociceptin under inflammatory conditions.


METHODS
Mono Mac 6 cells (MM6) were cultured with or without phorbol-12-myristate-13-acetate (PMA). Prepronociceptin (ppNOC) mRNA was detected by RT-qPCR and extracellular nociceptin by fluorescent-enzyme immunoassay. Intracellular nociceptin and phosphorylated kinases were measured using flow cytometry. To evaluate the contribution of various signalling pathways to the regulation of ppNOC mRNA and nociceptin protein, cells were pre-treated with specific kinase inhibitors before co-culturing with PMA.


RESULTS
ppNOC mRNA was expressed in untreated MM6 at low concentrations. Exposure of cells to PMA upregulated ppNOC after nine h compared with controls without PMA (median normalized ratio with IQR: 0.18 (0.15-0.26) vs. 0 (0-0.02), P<0.01). Inhibition of mitogen-activated protein kinases specific for signal transduction reversed the PMA effects (all P<0.001). Induction of nociceptin protein concentrations in PMA stimulated MM6 was prevented predominantly by identity of ERK inhibitor (P<0.05).


CONCLUSIONS
Upregulation of nociceptin expression by PMA in MM6 cells involves several pathways. Underlying mechanisms involved in nociceptin expression may lead to new insights in the treatment of pain and inflammatory diseases.
Department of Anaesthesiology and Pain Medicine, Inselspital and Department of Clinical Research, University of Bern, Bern, Switzerland lan.zhang@dkf.unibe.ch.
L
L
Zhang
Department of Anaesthesiology and Pain Medicine, Inselspital and Department of Clinical Research, University of Bern, Bern, Switzerland.
F
F
Stuber
Department of Anaesthesiology and Pain Medicine, Inselspital and Department of Clinical Research, University of Bern, Bern, Switzerland.
C
C
Lippuner
Department of Anaesthesiology and Pain Medicine, Inselspital and Department of Clinical Research, University of Bern, Bern, Switzerland.
M
M
Schiff
Department of Anaesthesiology and Pain Medicine, Inselspital and Department of Clinical Research, University of Bern, Bern, Switzerland.
U M
UM
Stamer
D045744:Cell Line, Tumor; D002470:Cell Survival; D004305:Dose-Response Relationship, Drug; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D018847:Opioid Peptides / Q000096:biosynthesis*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D000097629:Nociceptin
D018847:Opioid Peptides; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D013755:Tetradecanoylphorbol Acetate; D000097629:Nociceptin
RNA, messenger; monocytes; nociceptin; phorbol-12-myristate; signal transduction