title: Activation of μ-opioid receptor and Toll-like receptor 4 by plasma from morphine-treated mice.
abstract: In this study, we quantified the ability of opioids present in biological samples to activate the μ-opioid receptor and TLR4 using cell-based assays. Each assay was standardised, in the presence of plasma, using morphine, its μ receptor-active metabolite morphine-6 glucuronide (M6G) and its μ receptor-inactive, but TLR4-active metabolite morphine-3 glucuronide (M3G). Specificity was verified using antagonists. Morphine- and M6G-spiked plasma samples exhibited μ receptor activation, which M3G-spiked plasma lacked. In contrast, M3G showed moderate but consistent activation of TLR-4. Plasma samples were collected at a number of time points from mice administered morphine (1 or 10mg/kg every 12h for 3days) or saline. Morphine administration led to intermittent μ receptor activation, reversed by μ receptor antagonists, and to TRL4 activation at time points where M3G is measured in plasma. Interestingly, this protocol of morphine administration also led to TLR4-independent NF-κB activation, at time points where M3G was not detected, presumably via elevation of circulating cytokines including, but not limited to, TNFα. Circulating TNFα was increased after three days of morphine administration, and TNFα mRNA elevated in the spleen of morphine-treated mice.
authors.affiliation: School of Pharmacy, The University of Queensland, St Lucia, QLD 4072, Australia.
authors.forename: Nan
authors.initials: N
authors.lastname: Xie
authors.affiliation: School of Pharmacy, The University of Queensland, St Lucia, QLD 4072, Australia.
authors.forename: Fabio P
authors.initials: FP
authors.lastname: Gomes
authors.affiliation: School of Pharmacy, The University of Queensland, St Lucia, QLD 4072, Australia.
authors.forename: Vandana
authors.initials: V
authors.lastname: Deora
authors.affiliation: Mater Research Institute (MRI-UQ), The University of Queensland, Brisbane, Australia.
authors.forename: Kye
authors.initials: K
authors.lastname: Gregory
authors.affiliation: Mater Research Institute (MRI-UQ), The University of Queensland, Brisbane, Australia.
authors.forename: Tharindu
authors.initials: T
authors.lastname: Vithanage
authors.affiliation: School of Pharmacy, The University of Queensland, St Lucia, QLD 4072, Australia.
authors.forename: Zeyad D
authors.initials: ZD
authors.lastname: Nassar
authors.affiliation: School of Pharmacy, The University of Queensland, St Lucia, QLD 4072, Australia.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Cabot
authors.affiliation: Mater Research Institute (MRI-UQ), The University of Queensland, Brisbane, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Sturgess
authors.affiliation: School of Pharmacy, The University of Queensland, St Lucia, QLD 4072, Australia.
authors.forename: Paul N
authors.initials: PN
authors.lastname: Shaw
authors.affiliation: School of Pharmacy, The University of Queensland, St Lucia, QLD 4072, Australia. Electronic address: m.parat@uq.edu.au.
authors.forename: Marie-Odile
authors.initials: MO
authors.lastname: Parat
mesh_terms: D000818:Animals; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D009022:Morphine Derivatives / Q000494:pharmacology*; D010949:Plasma / Q000187:drug effects*; D017450:Receptors, Opioid, mu / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
chemical_list: D009022:Morphine Derivatives; D017450:Receptors, Opioid, mu; D051197:Toll-Like Receptor 4; D009020:Morphine
keywords: Morphine; TLR-4; TNFα; μ-Opioid receptor