Research reportOrphanin FQ/nociceptin blocks chronic morphine-induced tyrosine hydroxylase upregulation
Introduction
Orphanin FQ/Nociceptin (OFQ/N) displays high affinity for the opioid receptor-like 1 (ORL1) receptor, but very low affinity for μ, δ or κ receptors [39]. ORL1 receptor activation by OFQ/N initiates pertussis toxin-sensitive intracellular events including inhibition of adenylyl cyclase, activation of extracellular signal-regulated kinases (ERKs), ERK1 and ERK2, and modulation of calcium and potassium channel conductances [20]. OFQ/N potently produces analgesia after spinal [20] as well as supraspinal administration [41], however it exhibits ‘anti-opioid activity’ supraspinally by antagonizing μ-, δ- and κ-opioid receptor-mediated analgesia [30].
The ‘anti-μ opioid’ actions of OFQ/N are not limited to blockade of morphine analgesia, as supraspinal OFQ/N also inhibits morphine-induced conditioned place preference [6], [32], suggesting that OFQ/N blocks the positive reinforcing effects of morphine. The establishment of conditioned place preference involves facilitation of dopaminergic transmission in the nucleus accumbens [44], [14]. Chronic morphine administration increases mesolimbic dopaminergic transmission by upregulating tyrosine hydroxylase (TH; the rate-limiting enzyme in catecholamine biosynthesis) in the neurons of the ventral tegmental area (VTA) [2], [5]. Chronic morphine-induced TH upregulation in the locus coeruleus (LC) is implicated in morphine dependence and withdrawal, where this upregulation could increase the capacity of LC neurons to synthesize and release norepinephrine [5], [16], [26]. Interestingly, OFQ/N also has been found to inhibit morphine withdrawal [23], [25].
As ORL1 and μ opioid receptors are both densely expressed [33] and co-expressed [10] on LC neurons, and ORL1 mRNA is found in TH-containing neurons of the VTA and substantia nigra [34], we hypothesized that the ability of OFQ/N to block the reinforcing and withdrawal effects of morphine may result from its ability to block morphine-induced TH upregulation. Two different human neuroblastoma cell lines, BE(2)-C and SH-SY5Y, endogenously expressing TH [8], and ORL1 [28], [9], [38] and μ opioid receptors [45], [22] were utilized to determine the mechanism(s) by which OFQ/N could modulate the intracellular changes resulting from chronic morphine.
One of the mechanisms by which chronic administration of morphine in rats produces TH upregulation, particularly in the VTA, is via activation of ERKs [3]. ERK levels are elevated in the LC and caudate putamen following chronic morphine exposure in rats [36]. Furthermore, naloxone-precipitated withdrawal in morphine-dependent rats stimulates ERK activation in the LC and the nucleus of the solitary tract, brain regions associated with the aversive components of the opioid withdrawal syndrome [42]. These studies strongly suggest an important role for ERKs in mediating the long-term adaptations in the brain that result in profound behavioral effects following chronic morphine exposure. Similar to those in vivo studies, we find that ERKs also mediate chronic morphine-induced TH upregulation in human neuroblastoma cells wherein natively expressed μ and ORL1 receptors are functionally coupled to the activation of ERKs. Besides directly interfering with the pathway through which morphine stimulates TH upregulation, the other possible mechanism for a negative modulation of TH is via induction of Oct-2 protein. Oct-2 is a POU (Pit-Oct-Unc) family transcription factor that binds to the heptamer sequence 5′-CTAATGG-3′ in the TH promoter to repress TH gene expression and reduce the endogenous levels of TH in neuronal cells [11]. The present study suggests that OFQ/N blocks chronic morphine-induced TH upregulation by upregulating the levels of Oct-2 protein.
Section snippets
Materials
The following drugs and materials were purchased from, or kindly provided by, the sources indicated: cell culture media, penicillin G, streptomycin sulfate (Gibco BRL, Grand Island, NY, USA); fetal bovine sera (Atlanta Biologicals, Norcross, GA, USA); OFQ/N, PL-017 and morphine sulfate (Research Technology Branch of the National Institute on Drug Abuse, Rockville, MD, USA); peptide III BTD (Neosystem, Strasbourg, France); PD98059, phospho-specific ERK1 and ERK2, and ERK1 and ERK2 antisera (Cell
μ and ORL1 receptor-mediated activation of ERK
To illustrate the functional coupling of natively expressed μ and ORL1 receptors to ERK activation in human neuroblastoma cells, phospho-specific ERK antiserum was used for immunoblotting. This antiserum recognizes ERK1 and ERK2 only when the enzymes are phosphorylated at both tyrosine and threonine residues, representing the fully activated state of ERKs [40]. Cells were serum-deprived for 24 h to decrease basal ERK activation in order to facilitate the quantification of opioid-induced ERK
Discussion
Recent studies have unveiled the differential role of OFQ/N in modulating the long-term deleterious effects of morphine [20], clearly demonstrating the inhibitory effect of OFQ/N on morphine-induced conditioned place preference and withdrawal [6], [32], [23]. Although ORL1 and μ opioid receptors are co-localized on several populations of neuronal cells, including the locus coeruleus [10], very little is known about how morphine and OFQ/N may modulate each others actions at the cellular level [7]
Acknowledgements
This work was supported in part, by grants from the US Public Health Service (DA10738) and the Texas Advanced Research Program (003652-0114-1999) to K.M.S.
References (48)
- et al.
Ligands for κ-opioid, and ORL1 receptors identified from a conformationally constrained peptide combinatorial library
J. Biol. Chem.
(1999) - et al.
Effect of nociceptin/orphanin FQ on the rewarding properties of morphine
Eur. J. Pharmacol.
(2000) - et al.
Nociceptin/orphanin FQ and drugs of abuse
Peptides
(2000) - et al.
The novel neuropeptide orphanin FQ fails to produce conditioned place preference or aversion
Brain Res.
(1996) The role of dopamine in drug abuse viewed from the perspective of its role in motivation
Drug Alcohol Depend.
(1995)- et al.
Nociceptin differentially affects morphine-induced dopamine release from the nucleus accumbens and nucleus caudate in rats
Peptides
(2000) - et al.
Lack of cross-tolerance between the antinociceptive effect of intrathecal orphanin FQ and morphine in the rat
Neurosci. Lett.
(1997) - et al.
Opiate modulating properties of nociceptin/orphanin FQ
Peptides
(2000) - et al.
Morphine tolerance and dependence in nociceptin/orphanin FQ transgenic knock-out mice
Neuroscience
(2001) - et al.
μ- and δ-opioid receptor agonists induce mitogen-activated protein kinase (MAPK) activation in the absence of receptor internalization
Neuropharmacology
(2000)
Protein measurement with the folin phenol reagent
J. Biol. Chem.
Orphanin FQ/nociceptin and naloxone benzoylhydrazone activate distinct receptors in BE(2)-C human neuroblastoma cells
Neurosci. Lett.
Functional antagonism of μ-, δ- and κ-opioid antinociception by orphanin FQ
Neurosci. Lett.
Orphanin FQ/nociceptin blocks acquisition of morphine place preference
Brain Res.
Rat central ORL-1 receptor uncouples from adenylyl cyclase during membrane preparation
Neurosci. Lett.
A cellular mechanism for the bidirectional pain-modulating actions of orphanin FQ/nociceptin
Neuron
Orphanin FQ/nociceptin binds to functionally coupled ORL1 receptors on human immune cell lines and alters peripheral blood mononuclear cell proliferation
Brain Res. Bull.
Structures that delineate orphanin FQ and dynorphin A pharmacological selectivities
J. Biol. Chem.
Regulation and properties of extracellular signal-regulated protein kinases 1 and 2 in vitro
J. Biol. Chem.
Orphanin FQ/nociceptin analgesia in the rat
Brain Res.
The dopamine hypothesis of reward: past and current status
Trends Neurosci.
Opioid receptor endocytosis and activation of MAP kinase pathway
Mol. Brain Res.
Accelerated release and production of orphanin FQ in brain of chronic morphine tolerant rats
Brain Res.
Morphine and cocaine exert common chronic actions on tyrosine hydroxylase in dopaminergic brain reward regions
J. Neurochem.
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