Morphine inhibits AP-1 activity and CD14 expression in leukocytes by a nitric oxide and opioid receptor-dependent mechanism.
BACKGROUND
Activator protein 1 is a transcription factor involved in the regulation of proinflammatory mediators. Activation of phagocytes by lipopolysaccharide depends on the expression of CD14 on the cell surface. In this study, we investigated the effects of morphine and nitric oxide on CD14 expression and activator protein 1 activation in human blood monocytes and neutrophils as well as the leukocyte cell line HL-60.


METHODS
Whole blood was incubated with morphine, the nitric oxide donor S-nitroso-N-acetyl-penicillamine, naloxone or nitric oxide synthase inhibitors Nomega-nitro-l-arginine and Nomega-nitro-l-arginine-methylester and stimulated with lipopolysaccharide. Activator protein 1 nuclear content was determined by flow cytometry in human blood neutrophils and monocytes. CD14 expression on neutrophils was measured after incubation with fluorescein isothiocyanate-labelled antibodies. Electric mobility shift assay served for evaluation of activator protein 1 nuclear binding in HL-60 cells.


RESULTS
Incubation of whole blood with morphine and subsequent stimulation with lipopolysaccharide decreased activator protein 1 nuclear content. Exposure to naloxone before morphine treatment abolished morphine-induced inhibition of activator protein 1 activity in human blood monocytes and neutrophils. Nitric oxide synthase inhibitors also reversed morphine's effects. CD14 expression on neutrophils was reduced after morphine treatment. These effects were antagonized by nitric oxide synthase inhibitors and naloxone.


CONCLUSIONS
Morphine inhibits activator protein 1 activation by a mu opioid receptor pathway coupled to nitric oxide as second messenger. The decrease in CD14 expression caused by morphine may play a role in inhibition of activator protein 1 activation following lipopolysaccharide treatment of phagocytes.
Welters
I D
ID
University of liverpool, Division of Clinical Sciences, Liverpool, UK. I.Welters@chiru.med.uni-giessen.de
Menzebach
A
A
Goumon
Y
Y
Langefeld
T W
TW
Harbach
H
H
Mühling
J
J
Cadet
P
P
Stefano
G B
GB
D000701:Analgesics, Opioid / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects; D002467:Cell Nucleus / Q000737:chemistry / Q000187:drug effects; D024202:Electrophoretic Mobility Shift Assay; D005434:Flow Cytometry; D018922:HL-60 Cells; D006801:Humans; D007202:Indicators and Reagents; D007962:Leukocytes / Q000187:drug effects / Q000378:metabolism*; D018950:Lipopolysaccharide Receptors / Q000096:biosynthesis*; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors / Q000494:pharmacology; D009020:Morphine / Q000494:pharmacology*; D009569:Nitric Oxide / Q000494:pharmacology*; D010586:Phagocytes / Q000187:drug effects; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D011957:Receptors, Opioid / Q000187:drug effects*; D017450:Receptors, Opioid, mu / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D014212:Tretinoin / Q000494:pharmacology
D000701:Analgesics, Opioid; D007202:Indicators and Reagents; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D011957:Receptors, Opioid; D017450:Receptors, Opioid, mu; D018808:Transcription Factor AP-1; D009569:Nitric Oxide; D014212:Tretinoin; D012313:RNA; D009020:Morphine