Decreased expression of nociceptin/orphanin FQ in the dorsal anterior cingulate cortex of suicides

Imaging Nociceptin Opioid Peptide Receptors in Alcohol Use Disorder With [11C]NOP-1A and Positron Emission Tomography: Findings From a Second Cohort

BACKGROUND

Nociceptin, which binds to the nociceptin opioid peptide receptor (NOP), regulates stress and reward in addiction. In a previous [11C]NOP-1A positron emission tomography (PET) study, we found no differences in NOP in non-treatment-seeking individuals with alcohol use disorder (AUD) relative to healthy control subjects Here, we evaluated NOP in treatment-seeking individuals with AUD to document its relationship with relapse to alcohol.

METHODS

[11C]NOP-1A distribution volume (VT) was measured in recently abstinent individuals with AUD and healthy control subjects (n = 27/group) using an arterial input function-based kinetic analysis in brain regions that regulate reward and stress behaviors. Recent heavy drinking before PET was quantified using hair ethyl glucuronide (≥30 pg/mg was defined as heavy drinking). To document relapse, 22 subjects with AUD were followed with urine ethyl glucoronide tests (3/week) for 12 weeks after PET, where they were incentivized with money to abstain.

RESULTS

There were no differences in [11C]NOP-1A VT between individuals with AUD and healthy control subjects. Individuals with AUD who drank heavily before the study had significantly lower VT than those with no recent heavy drinking history. Significant negative correlations between VT and the number of drinking days and the number of drinks consumed per drinking day in the 30 days before enrollment were also present. Individuals with AUD who relapsed (and dropped out) had significantly lower VT than those who abstained for 12 weeks.

CONCLUSIONS

Lower NOP VT in heavy drinking AUD predicted relapse to alcohol during a 12-week follow-up period. The results of this PET study support the need to investigate medications that act at NOP to prevent relapse in individuals with AUD.

Novel Targets to Treat Depression: Opioid-Based Therapeutics

After participating in this activity, learners should be better able to:• Identify the effects of dysregulated opioid signalling in depression• Evaluate the use of opioid compounds and ketamine in patients with depression ABSTRACT: Major depressive disorder (MDD) remains one of the leading causes of disability and functional impairment worldwide. Current antidepressant therapeutics require weeks to months of treatment prior to the onset of clinical efficacy on depressed mood but remain ineffective in treating suicidal ideation and cognitive impairment. Moreover, 30%-40% of individuals fail to respond to currently available antidepressant medications. MDD is a heterogeneous disorder with an unknown etiology; novel strategies must be developed to treat MDD more effectively. Emerging evidence suggests that targeting one or more of the four opioid receptors-mu (MOR), kappa (KOR), delta (DOR), and the nociceptin/orphanin FQ receptor (NOP)-may yield effective therapeutics for stress-related psychiatric disorders. Furthermore, the effects of the rapidly acting antidepressant ketamine may involve opioid receptors. This review highlights dysregulated opioid signaling in depression, evaluates clinical trials with opioid compounds, and considers the role of opioid mechanisms in rapidly acting antidepressants.

Neural and molecular correlates of psychological pain during major depression, and its link with suicidal ideas

OBJECTIVES

Psychological pain increases the risk of suicidal ideas and acts, and represents a potential therapeutic target. However, the mechanisms of mental pain remain unclear. Here, we assessed the peripheral transcriptomic and central neural correlates of mental pain during a depressive episode.

METHODS

172 adult un-medicated depressed patients were recruited. Leucocytes were extracted for RNA quantification at baseline (T0) and after 8 weeks (T8) of an antidepressant treatment. Ninety-nine genes of the cortisol, immune, opioid, serotonergic, and kynurenine systems were a priori selected, and 41 were sufficiently expressed to be analyzed. At both T0 and T8, mean level of mental pain over the last 15 days was measured with a visual analog scale. A subset of 38 patients was additionally scanned with Magnetic Resonance Imaging at T0. Resting-state sequences of 4 networks (default-mode, basal ganglia, central executive, salience) were examined.

RESULTS

Mean psychological pain scores significantly decreased between T0 and T8. At conservative p-corrected levels, T0 mental pain was significantly correlated with 11 brain clusters encompassing the prefrontal, parietal, and temporal cortices, the striatum, and the cerebellum. There was no direct association between peripheral gene expression and mean mental pain at any time points or in terms of temporal changes. However, expressions of 5HTR2B at p-corrected levels, and 5HTR3A, TPH1, and OPRL1 were correlated with the activity of several identified brain clusters at T0. Finally, while suicidal ideas and mental pain were correlated, the neural and molecular correlates of suicidal ideas were not the same.

CONCLUSION

Our study suggests that the serotonergic and nociceptin systems are associated with the activity of a cortico-subcortical brain network underlying the perception of mental pain during depression. Mental pain may be a necessary but insufficient condition for the emergence of suicidal ideation during depression.

The Nociceptin/Orphanin FQ System and the Regulation of Memory

Nociceptin/orphanin FQ (N/OFQ) is an endogenous neuropeptide of 17 amino acids, related to opioid peptides but with its own receptor, distinct from conventional opioid receptors, the ORL1 or NOP receptor. The NOP receptor is a G protein-coupled receptor which activates Gi/o proteins and thus induces an inhibition of neuronal activity. The peptide and its receptor are widely expressed in the central nervous system with a high density of receptors in regions involved in learning and memory. This review describes the consequences of the pharmacological manipulation of the N/OFQ system by NOP receptor ligands on learning processes and on the consolidation of various types of long-term memory. We also discuss the role of endogenous N/OFQ release in the modulation of learning and memory. Finally we propose several putative neuronal mechanisms taking place at the level of the hippocampus and amygdala and possibly underlying the behavioral amnestic or promnesic effects of NOP ligands.

Molecular Imaging of Opioid and Dopamine Systems: Insights Into the Pharmacogenetics of Opioid Use Disorders

Opioid use in the United States has steadily risen since the 1990s, along with staggering increases in addiction and overdose fatalities. With this surge in prescription and illicit opioid abuse, it is paramount to understand the genetic risk factors and neuropsychological effects of opioid use disorder (OUD). Polymorphisms disrupting the opioid and dopamine systems have been associated with increased risk for developing substance use disorders. Molecular imaging studies have revealed how these polymorphisms impact the brain and contribute to cognitive and behavioral differences across individuals. Here, we review the current molecular imaging literature to assess how genetic variations in the opioid and dopamine systems affect function in the brain's reward, cognition, and stress pathways, potentially resulting in vulnerabilities to OUD. Continued research of the functional consequences of genetic variants and corresponding alterations in neural mechanisms will inform prevention and treatment of OUD.

Analysis of key genes and micro-RNA-mRNA regulatory networks in women with ulcerative interstitial cystitis/pain bladder syndrome

INTRODUCTION AND HYPOTHESIS

This aim of this study was to better understand ulcerative interstitial cystitis/painful bladder syndrome (IC/PBS) at the molecular level and provide new clues related to diagnosis and treatment.

METHODS

The microarray data set GSE11783, including the mRNA and miRNA profiles of bladder tissue obtained at cystoscopic biopsy from patients with ulcerative IC/PBS (presence of at least one Hunner's ulcer) and normal controls, was downloaded from the GEO (Gene Expression Omnibus) database (National Center for Biotechnology Information). These were evaluated using Greenspring GX and Ingenuity Pathway Analysis (IPA) software. The differentially expressed genes (DEGs) and miRNAs (DEMs) in these two groups were identified. Subsequently, the DEGs were subjected to functional analysis, and a protein-protein interaction (PPI) network was constructed. Finally, the miRNA-mRNA regulatory network was visualized using Cystoscope software.

RESULTS

Four DEMs and 1521 DEGs were identified between the ulcerative IC/PBS and control groups. The PPI network of the DEGs was constructed by STRING, which was composed of 393 nodes and 1039 edges, including 221 upregulated genes and 172 downregulated genes. Moreover, 27 genes in the PPI network were identified as hub genes in the IC/PBS group, e.g., PNOC, SSTR1, FPR3, GPR18 and APLNR. Subsequently, 27 clusters were selected from the PPI network using MCODE. It was shown that the most significant cluster consisted of 22 nodes and 231 edges. Moreover, miR-21 was the most significantly upregulated miRNA and was predicted to target one upregulated gene (RASGRP1) and two downregulated genes (KLF5 and SC5D).

CONCLUSIONS

The results of this data mining and integration provide further information on the possible molecular basis of IC/PBS pathogenesis as well as potential biomarkers and therapeutic targets for ulcerative IC/PBS diagnosis and treatment.

Epigenetic Regulation of the Kappa Opioid Receptor by Child Abuse

BACKGROUND

Experiences of abuse and neglect during childhood are major predictors of the emergence of depressive and suicidal behaviors throughout life. The underlying biological mechanisms, however, remain poorly understood. Here, we focused on the opioid system as a potential brain substrate mediating these effects.

METHODS

Postmortem samples from three brain structures regulating social bonds and emotions were analyzed. Groups were constituted of depressed individuals who died by suicide, with or without a history of severe child abuse, and of psychiatrically healthy control subjects. Expression of opioid peptides and receptors was measured using real-time polymerase chain reaction. DNA methylation, a major epigenetic mark, was investigated using targeted bisulfite sequencing and characterized at functional level using in vitro reporter assays. Finally, oxidative bisulfite sequencing was used to differentiate methylation and hydroxymethylation of DNA.

RESULTS

A history of child abuse specifically associated in the anterior insula with a downregulation of the kappa opioid receptor (Kappa), as well as decreased DNA methylation in the second intron of the Kappa gene. In vitro assays further showed that this intron functions as a genomic enhancer where glucocorticoid receptor binding regulates Kappa expression, unraveling a new mechanism mediating the well-established interactions between endogenous opioids and stress. Finally, results showed that child abuse is associated in the Kappa intron with a selective reduction in levels of DNA hydroxymethylation, likely mediating the observed downregulation of the receptor.

CONCLUSIONS

Altogether, our findings uncover new facets of Kappa physiology, whereby this receptor may be epigenetically regulated by stressful experiences, in particular as a function of early social life.

Nociceptin Receptors in Alcohol Use Disorders: A Positron Emission Tomography Study Using [11C]NOP-1A

BACKGROUND

The neuropeptide transmitter nociceptin, which binds to the nociceptin/orphanin FQ peptide (NOP) receptor, is a core component of the brain's antistress system. Nociceptin exerts its antistress effect by counteracting the functions of corticotropin-releasing factor, the primary stress-mediating neuropeptide in the brain. Basic investigations support a role for medications that target nociceptin receptors in the treatment of alcohol use disorders. Thus, it is of high interest to measure the in vivo status of NOP receptors in individuals with alcohol use disorders.

METHODS

Here, we used [11C]NOP-1A and positron emission tomography to measure the in vivo binding to NOP receptors in 15 alcohol-dependent humans as identified by DSM-IV and 15 healthy control subjects matched for age, sex, and smoking status. Alcohol-dependent individuals with no comorbid psychiatric, medical, or drug abuse disorders were scanned following 2 weeks of outpatient monitored abstinence (confirmed with three times per week urine alcohol metabolite testing). [11C]NOP-1A distribution volume in regions of interest (including the amygdala, hippocampus, and midbrain, striatal, and prefrontal cortical subdivisions) was measured with kinetic analysis using the arterial input function.

RESULTS

Regional [11C]NOP-1A distribution volume in alcohol dependence was not significantly different compared with healthy control subjects. No relationship between [11C]NOP-1A distribution volume and other clinical measures (including duration and severity of alcohol abuse, craving, and anxiety or depressive symptoms) were significant after correction for the multiple hypotheses tested.

CONCLUSIONS

The results of this study do not support alterations in the binding to NOP receptors in alcohol dependence. However, this finding does not necessarily rule out alterations in nociceptin transmission in alcohol dependence.

Global long non-coding RNA expression in the rostral anterior cingulate cortex of depressed suicides

Long non-coding RNAs (lncRNAs) are an emerging class of regulatory RNA that may be implicated in psychiatric disorders. Here we performed RNA-sequencing in the rostral anterior cingulate cortex of 26 depressed suicides and 24 matched controls. We first performed differential lncRNA expression analysis, and then conducted Weighted Gene Co-expression Network Analysis (WGCNA) to identify co-expression modules associating with depression and suicide. We identified 23 differentially expressed lncRNAs (FDR < 0.1) as well as their differentially expressed overlapping and antisense protein-coding genes. Several of these overlapping or antisense genes were associated with interferon signaling, which is a component of the innate immune response. Using WGCNA, we identified modules of highly co-expressed genes associated with depression and suicide and found protein-coding genes highly connected to differentially expressed lncRNAs within these modules. These protein-coding genes were located distal to their associated lncRNAs and were found to be part of several GO terms enriched in the significant modules, which include: cytoskeleton organization, plasma membrane, cell adhesion, nucleus, DNA-binding, and regulation of dendrite development and morphology. Altogether, we report that lncRNAs are differentially expressed in the brains of depressed individuals who died by suicide and may represent regulators of important molecular functions and biological processes.

Epigenetic regulation of the kappa opioid receptor gene by an insertion-deletion in the promoter region

Preclinical and clinical studies have demonstrated that the kappa opioid receptor (KOR) regulates reward, hedonic tone and emotions. At therapeutic level, on-going clinical trials are assessing the potential of targeting the KOR for the management of depression, anxiety disorders and substance use disorders. However, genetic polymorphisms in the KOR gene that potentially contribute to its implication in these phenotypes have been poorly studied. Here we investigated an insertion-deletion in the promoter region of KOR (rs35566036), recently associated with alcohol addiction, in a cohort of depressed subjects who died by suicide, as well as psychiatrically healthy individuals. Focusing on 3 brain regions (anterior insula, anterior cingulate cortex, and mediodorsal thalamus), we characterized the functional impact of this structural variant on the expression and patterns of DNA methylation of the KOR gene, using qPCR and targeted Bisulfite-Sequencing, respectively. While there was no significant change in the expression of KOR as a function of the insertion-deletion, or as a function of disease status in any brain region, we found that this variant strongly determines DNA methylation in KOR promoter, leading to a significant decrease in methylation levels of 8 nearby CpG dinucleotides located approximately 500 base pairs upstream the transcription start site. In addition, our results suggest a possible association between the insertion-deletion and depression; however, this result should be tested in larger populations. In sum, in this study we uncovered an epigenetic mechanism potentially contributing to KOR dysfunction in carriers of the insertion-deletion.

Neuropathology of suicide: recent findings and future directions

Suicide is a major public health concern and a leading cause of death in most societies. Suicidal behaviour is complex and heterogeneous, likely resulting from several causes. It associates with multiple factors, including psychopathology, personality traits, early-life adversity and stressful life events, among others. Over the past decades, studies in fields ranging from neuroanatomy, genetics and molecular psychiatry have led to a model whereby behavioural dysregulation, including suicidal behaviour (SB), develops as a function of biological adaptations in key brain systems. More recently, the unravelling of the unique epigenetic processes that occur in the brain has opened promising avenues in suicide research. The present review explores the various facets of the current knowledge on suicidality and discusses how the rapidly evolving field of neurobehavioural epigenetics may fuel our ability to understand, and potentially prevent, SB.

Neuropathic pain promotes adaptive changes in gene expression in brain networks involved in stress and depression

Neuropathic pain is a complex chronic condition characterized by various sensory, cognitive, and affective symptoms. A large percentage of patients with neuropathic pain are also afflicted with depression and anxiety disorders, a pattern that is also seen in animal models. Furthermore, clinical and preclinical studies indicate that chronic pain corresponds with adaptations in several brain networks involved in mood, motivation, and reward. Chronic stress is also a major risk factor for depression. We investigated whether chronic pain and stress affect similar molecular mechanisms and whether chronic pain can affect gene expression patterns that are involved in depression. Using two mouse models of neuropathic pain and depression [spared nerve injury (SNI) and chronic unpredictable stress (CUS)], we performed next-generation RNA sequencing and pathway analysis to monitor changes in gene expression in the nucleus accumbens (NAc), the medial prefrontal cortex (mPFC), and the periaqueductal gray (PAG). In addition to finding unique transcriptome profiles across these regions, we identified a substantial number of signaling pathway-associated genes with similar changes in expression in both SNI and CUS mice. Many of these genes have been implicated in depression, anxiety, and chronic pain in patients. Our study provides a resource of the changes in gene expression induced by long-term neuropathic pain in three distinct brain regions and reveals molecular connections between pain and chronic stress.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.