Genomic variations and transcriptional regulation of the human mu-opioid receptor gene

Single nucleus transcriptomics of ventral midbrain identifies glial activation associated with chronic opioid use disorder

Dynamic interactions of neurons and glia in the ventral midbrain mediate reward and addiction behavior. We studied gene expression in 212,713 ventral midbrain single nuclei from 95 individuals with history of opioid misuse, and individuals without drug exposure. Chronic exposure to opioids was not associated with change in proportions of glial and neuronal subtypes, however glial transcriptomes were broadly altered, involving 9.5 - 6.2% of expressed genes within microglia, oligodendrocytes, and astrocytes. Genes associated with activation of the immune response including interferon, NFkB signaling, and cell motility pathways were upregulated, contrasting with down-regulated expression of synaptic signaling and plasticity genes in ventral midbrain non-dopaminergic neurons. Ventral midbrain transcriptomic reprogramming in the context of chronic opioid exposure included 325 genes that previous genome-wide studies had linked to risk of substance use traits in the broader population, thereby pointing to heritable risk architectures in the genomic organization of the brain's reward circuitry.

Single Nucleus Transcriptomics Reveals Pervasive Glial Activation in Opioid Overdose Cases

Dynamic interactions of neurons and glia in the ventral midbrain (VM) mediate reward and addiction behavior. We studied gene expression in 212,713 VM single nuclei from 95 human opioid overdose cases and drug-free controls. Chronic exposure to opioids left numerical proportions of VM glial and neuronal subtypes unaltered, while broadly affecting glial transcriptomes, involving 9.5 - 6.2% of expressed genes within microglia, oligodendrocytes, and astrocytes, with prominent activation of the immune response including interferon, NFkB signaling, and cell motility pathways, sharply contrasting with down-regulated expression of synaptic signaling and plasticity genes in VM non-dopaminergic neurons. VM transcriptomic reprogramming in the context of opioid exposure and overdose included 325 genes with genetic variation linked to substance use traits in the broader population, thereby pointing to heritable risk architectures in the genomic organization of the brain's reward circuitry.

The NFKB1 polymorphism (rs4648068) is associated with the cell proliferation and motility in gastric cancer

BACKGROUND

We have demonstrated previously that NFKB1 single nucleotide polymorphism (SNP) rs4648068 GG homozygote was associated with the increased risk of gastric cancer in Chinese Han population. In this study, we constructed the recombinant plasmid pGL3-AA, pGL3-GG, pGL3-AA-NFKB and pGL3-GG-NFKB to investigate the function of rs4648068 by cell biology experiments.

METHODS

Quantitative real-time PCR was used to detect NFKB1 SNP rs4648068 genotype in the patients with gastric cancer. Anti-NF-κB1 p50 polyclonal antibodies were used for immunohistochemical analysis of the tissue specimens. The subsection of NFKB1 containing the promoter site and adjacent three consecutive exons were obtained by PCR technique and subcloned into the vector pGL3-Basic. Dual-Luciferase reporter assay was used to detect the transcriptional activity of the constructed promoter. Effects of transcription factor NFKB1 on C/EBPβ expression were determined by chromatin immunoprecipitation and Western analysis. Furthermore, proliferation and invasion ability of the transduced cell were also measured and compared.

RESULTS

Intensive staining for p50 expression was observed in the tissues of GG genotype patients, compared with those of GA group and AA genotype patients. The transcriptional activity of rs4648068 (A > G) by dual-Luciferase reporter assay suggested that the luciferase activity of homozygote group (pGL3-GG) was greater than that of the control (pGL3-AA), especially at the stimulation of LPS. We found that the luciferase activity was also influenced by pGL3-GG levels. The effects of NFKB1 rs4648068 were enhanced by rs4648065 on the transduced cells. The interaction between NFKB1 promoter nucleotide sequence and C/EBPβ was regulated by the functional SNP rs4648068 in SGC-7901 cells. Our data indicated that the transduction of pGL3 expression plasmid pGL3-GG-NFKB improved the proliferation and motility of gastric cancer cells. Correspondingly, the homozygote GG of SNP rs4648068 strengthened the transcriptional activity of NFKB1 and influenced the cell biological activity.

CONCLUSION

The transcriptional activity of NFKB1 was associated with SNP rs4648068, and this functional SNP site has the important effects on cell proliferation and motility.

A heroin addiction severity-associated intronic single nucleotide polymorphism modulates alternative pre-mRNA splicing of the μ opioid receptor gene OPRM1 via hnRNPH interactions

Single nucleotide polymorphisms (SNPs) in the OPRM1 gene have been associated with vulnerability to opioid dependence. The current study identifies an association of an intronic SNP (rs9479757) with the severity of heroin addiction among Han-Chinese male heroin addicts. Individual SNP analysis and haplotype-based analysis with additional SNPs in the OPRM1 locus showed that mild heroin addiction was associated with the AG genotype, whereas severe heroin addiction was associated with the GG genotype. In vitro studies such as electrophoretic mobility shift assay, minigene, siRNA, and antisense morpholino oligonucleotide studies have identified heterogeneous nuclear ribonucleoprotein H (hnRNPH) as the major binding partner for the G-containing SNP site. The G-to-A transition weakens hnRNPH binding and facilitates exon 2 skipping, leading to altered expressions of OPRM1 splice-variant mRNAs and hMOR-1 proteins. Similar changes in splicing and hMOR-1 proteins were observed in human postmortem prefrontal cortex with the AG genotype of this SNP when compared with the GG genotype. Interestingly, the altered splicing led to an increase in hMOR-1 protein levels despite decreased hMOR-1 mRNA levels, which is likely contributed by a concurrent increase in single transmembrane domain variants that have a chaperone-like function on MOR-1 protein stability. Our studies delineate the role of this SNP as a modifier of OPRM1 alternative splicing via hnRNPH interactions, and suggest a functional link between an SNP-containing splicing modifier and the severity of heroin addiction.

Mu opioids and their receptors: evolution of a concept

Opiates are among the oldest medications available to manage a number of medical problems. Although pain is the current focus, early use initially focused upon the treatment of dysentery. Opium contains high concentrations of both morphine and codeine, along with thebaine, which is used in the synthesis of a number of semisynthetic opioid analgesics. Thus, it is not surprising that new agents were initially based upon the morphine scaffold. The concept of multiple opioid receptors was first suggested almost 50 years ago (Martin, 1967), opening the possibility of new classes of drugs, but the morphine-like agents have remained the mainstay in the medical management of pain. Termed mu, our understanding of these morphine-like agents and their receptors has undergone an evolution in thinking over the past 35 years. Early pharmacological studies identified three major classes of receptors, helped by the discovery of endogenous opioid peptides and receptor subtypes-primarily through the synthesis of novel agents. These chemical biologic approaches were then eclipsed by the molecular biology revolution, which now reveals a complexity of the morphine-like agents and their receptors that had not been previously appreciated.

An intronic variant in OPRD1 predicts treatment outcome for opioid dependence in African-Americans

Although buprenorphine and methadone are both effective treatments for opioid dependence, their efficacy can vary significantly among patients. Genetic differences may explain some of the variability in treatment outcome. Understanding the interactions between genetic background and pharmacotherapy may result in more informed treatment decisions. This study is a pharmacogenetic analysis of the effects of genetic variants in OPRD1, the gene encoding the δ-opioid receptor, on the prevalence of opioid-positive urine tests in African-Americans (n=77) or European-Americans (n=566) undergoing treatment for opioid dependence. Patients were randomly assigned to treatment with either methadone or buprenorphine/naloxone (Suboxone) over a 24-week open-label clinical trial, in which illicit opioid use was measured by weekly urinalysis. In African-Americans, the intronic SNP rs678849 predicted treatment outcome for both medications. Methadone patients with the CC genotype were less likely to have opioid-positive urine tests than those in the combined CT and TT genotypes group (relative risk (RR)=0.52, 95% confidence interval (CI)=0.44-0.60, p=0.001). In the buprenorphine treatment group, however, individuals with the CC genotype were more likely to have positive opioid drug screens than individuals in the combined CT and TT genotypes group (RR=2.17, 95% CI=1.95-2.68, p=0.008). These findings indicate that the genotype at rs678849 predicts African-American patient response to two common treatments for opioid dependence, suggesting that matching patients to treatment type based on the genotype at this locus may improve overall treatment efficacy. This observation requires confirmation in an independent population.

Combined analysis of circulating β-endorphin with gene polymorphisms in OPRM1, CACNAD2 and ABCB1 reveals correlation with pain, opioid sensitivity and opioid-related side effects

Background

Opioids are associated with wide inter-individual variability in the analgesic response and a narrow therapeutic index. This may be partly explained by the presence of single nucleotide polymorphisms (SNPs) in genes encoding molecular entities involved in opioid metabolism and receptor activation. This paper describes the investigation of SNPs in three genes that have a functional impact on the opioid response: OPRM1, which codes for the μ-opioid receptor; ABCB1 for the ATP-binding cassette B1 transporter enzyme; and the calcium channel complex subunit CACNA2D2. The genotyping was combined with an analysis of plasma levels of the opioid peptide β-endorphin in 80 well-defined patients with chronic low back pain scheduled for spinal fusion surgery, and with differential sensitivity to the opioid analgesic remifentanil. This patient group was compared with 56 healthy controls.

Results

The plasma β-endorphin levels were significantly higher in controls than in pain patients.

A higher incidence of opioid-related side effects and sex differences was found in patients with the minor allele of the ABCB1 gene. Further, a correlation between increased opioid sensitivity and the major CACNA2D2 allele was confirmed. A tendency of a relationship between opioid sensitivity and the minor allele of OPRM1 was also found.

Conclusions

Although the sample cohort in this study was limited to 80 patients it appears that it was possible to observe significant correlations between polymorphism in relevant genes and various items related to pain sensitivity and opioid response. Of particular interest is the new finding of a correlation between increased opioid sensitivity and the major CACNA2D2 allele. These observations may open for improved strategies in the clinical treatment of chronic pain with opioids.

The genetics of the opioid system and specific drug addictions

Addiction to drugs is a chronic, relapsing brain disease that has major medical, social, and economic complications. It has been established that genetic factors contribute to the vulnerability to develop drug addiction and to the effectiveness of its treatment. Identification of these factors may increase our understanding of the disorders, help in the development of new treatments and advance personalized medicine. In this review, we will describe the genetics of the major genes of the opioid system (opioid receptors and their endogenous ligands) in connection to addiction to opioids, cocaine, alcohol and methamphetamines. Particular emphasis is given to association and functional studies of specific variants. We will provide information on the sample populations and the size of each study, as well as a list of the variants implicated in association with addiction-related phenotypes, and with the effectiveness of pharmacotherapy for addiction.

Haplotype block structure of the genomic region of the mu opioid receptor gene

The opioid system is involved in the action of opiate drugs, opioid addiction, pain experience and analgesia. Individual differences in opioid effect may be attributed in part to genetic variations. Long-range cis regulatory elements and intronic variants are potential sources of functional diversity. Recently, we have detected association of two intronic OPRM1 variants with heroin addiction in European Americans. In this study, we analyzed the genetic variations in the OPRM1 100 kb 5'-flanking region and intron 1 in the HapMap Caucasian population. Four major linkage disequilibrium blocks were identified, consisting of 28, 22, 15 and 42 single-nucleotide polymorphisms (SNPs), respectively. The locations of these blocks are (-100 to -90), (-90 to -67), (-20 to -1) and (+1 to +44) kb, respectively. The two intronic variants, indicated in our recent study, are part of a distinct haplogroup that includes SNPs from intron 1, and the proximal 5' region. The 118G (rs1799971) allele is part of a different haplogroup that includes several variants in the distal 5' region that may have a regulatory potential. These findings were corroborated by genotyping eight SNPs in a sample of European Americans and suggest an extended OPRM1 locus with potential new regulatory regions.

OPRM1 SNP (A118G): involvement in disease development, treatment response, and animal models

Endogenous opioids acting at mu-opioid receptors mediate many biological functions. Pharmacological intervention at these receptors has greatly aided in the treatment of acute and chronic pain, in addition to other uses. However, the development of tolerance and dependence has made it difficult to adequately prescribe these therapeutics. A common single nucleotide polymorphism (SNP), A118G, in the mu-opioid receptor gene can affect opioid function and, consequently, has been suggested to contribute to individual variability in pain management and drug addiction. Investigation into the role of A118G in human disease and treatment response has generated a large number of association studies across various disease states as well as physiological responses. However, characterizing the functional consequences of this SNP and establishing if it causes or contributes to disease phenotypes have been significant challenges. In this manuscript, we will review a number of association studies as well as investigations of the functional impact of this gene variant. In addition, we will describe a novel mouse model that was generated to recapitulate this SNP in mice. Evaluation of models that incorporate known human genetic variants into a tractable system, like the mouse, will facilitate the understanding of discrete contributions of SNPs to human disease.

Search for genetic markers and functional variants involved in the development of opiate and cocaine addiction and treatment

Addiction to opiates and illicit use of psychostimulants is a chronic, relapsing brain disease that, if left untreated, can cause major medical, social, and economic problems. This article reviews recent progress in studies of association of gene variants with vulnerability to develop opiate and cocaine addictions, focusing primarily on genes of the opioid and monoaminergic systems. In addition, we provide the first evidence of a cis-acting polymorphism and a functional haplotype in the PDYN gene, of significantly higher DNA methylation rate of the OPRM1 gene in the lymphocytes of heroin addicts, and significant differences in genotype frequencies of three single-nucleotide polymorphisms of the P-glycoprotein gene (ABCB1) between "higher" and "lower" methadone doses in methadone-maintained patients. In genomewide and multigene association studies, we found association of several new genes and new variants of known genes with heroin addiction. Finally, we describe the development and application of a novel technique: molecular haplotyping for studies in genetics of drug addiction.

[Role of genetics in anaesthesia-related variability]

OBJECTIVE

This review discusses variability among patients in anesthesia, due to genetic polymorphisms.

DATA SOURCES

Articles in French and English languages were retrieved from PubMed database. The initial request was "anesth* and (genotyp* or polymorphism* or genetic*)".

STUDY SELECTION

Original articles, general reviews and one case report. Letters were excluded.

DATA EXTRACTION

Rare genetic diseases were excluded from the scope of this review. We stressed on frequent genetic polymorphisms that may have a daily impact in anesthesiology.

DATA SYNTHESIS

Most results were related to pain studies. We selected various examples to describe how genetic polymorphisms impacts the pharmacology of a given drug, and what are the clinical consequences.

CONCLUSION

There is a growing field of pharmacogenetic related evidences in anesthesiology. The results from various animal and human studies underline the genetic origin of variability among individuals. How anaesthesists have to integrate these parameters for their daily practice is still unclear, but pharmacogenetic will obviously be a leading field of anesthesia research in the future.

Positive transcriptional regulation of the human micro opioid receptor gene by poly(ADP-ribose) polymerase-1 and increase of its DNA binding affinity based on polymorphism of G-172 -> T

Micro opioid receptor (MOR) agonists such as morphine are applied widely in clinical practice as pain therapy. The effects of morphine through MOR, such as analgesia and development of tolerance and dependence, are influenced by individual specificity. Recently, we analyzed single nucleotide polymorphisms on the human MOR gene to investigate the factors that contribute to individual specificity. In process of single nucleotide polymorphisms analysis, we found that specific nuclear proteins bound to G(-172) --> T region in exon 1 in MOR gene, and its affinity to DNA was increased by base substitution from G(-172) to T(-172). The isolated protein was identified by mass spectrometry and was confirmed by Western blotting to be poly(ADP-ribose) polymerase-1 (PARP-1). The overexpressed PARP-1 bound to G(-172) --> T and enhanced the transcription of reporter vectors containing G(-172) and T(-172). Furthermore, PARP-1 inhibitor (benzamide) decreased PARP-1 binding to G(-172) --> T without affecting mRNA or protein expression level of PARP-1 and down-regulated the subsequent MOR gene expression in SH-SY5Y cells. Moreover, we found that tumor necrosis factor-alpha enhanced MOR gene expression as well as increased PARP-1 binding to the G(-172) --> T region and G(-172) --> T-dependent transcription in SH-SY5Y cells. These effects were also inhibited by benzamide. In this study, our data suggest that PARP-1 positively regulates MOR gene transcription via G(-172) --> T, which might influence individual specificity in therapeutic opioid effects.

OPRM1 Asn40Asp predicts response to naltrexone treatment: a haplotype-based approach

BACKGROUND

Individualized pharmacotherapy requires identification of genetic variants predictive of treatment response. In OPRM1, Asn40Asp has been reported to be predictive of response to naltrexone treatment. Nevertheless, the in vitro function of the polymorphism remains elusive and over 300 OPRM1 sequence variants have been identified to date. Therefore we used a haplotype-based approach to capture information of other genetic variants that might predict treatment response to naltrexone in the COMBINE Study.

METHODS

5' nuclease genotyping assays (TaqMan) were applied for 10 SNPs. Five-locus haplotypes in 2 OPRM1 haplotype blocks were assigned to Caucasian participants. The relationship of the haplotypes to medication reflected by "good clinical outcome" was analyzed in 306 Caucasians treated without Combined Behavioral Intervention and with either naltrexone or placebo.

RESULTS

A significant haplotype by medication interaction (p = 0.03) was found in OPRM1 block 1. Naltrexone-treated alcoholics with haplotype AGCCC, the single haplotype carrying the Asp40 allele had the highest percent of good clinical outcome. When interaction of genotypes at each of the 5 loci comprising block 1 with medication was examined, only the Asn40/Asp40 and Asp40/Asp40 genotypes were found to significantly interact with naltrexone treatment. No haplotype by medication interaction was documented in OPRM1 block 2.

CONCLUSIONS

Our haplotype-based approach confirms that the single OPRM1 locus predictive of response to naltrexone treatment is Asn40Asp in exon 1. A substantial contribution of any other OPRM1 genetic variant to interindividual variations in response to naltrexone treatment (at least in terms of good clinical outcome) is not supported by our findings.

The evolution of vertebrate opioid receptors

The proteins that mediate the analgesic and other effects of opioid drugs and endogenous opioid peptides are known as opioid receptors. Opioid receptors consist of a family of four closely-related proteins belonging to the large superfamily of G-protein coupled receptors. The three types of opioid receptors shown unequivocally to mediate analgesia in animal models are the mu (MOR), delta (DOR), and kappa (KOR) opioid receptor proteins. The role of the fourth member of the opioid receptor family, the nociceptin or orphanin FQ receptor (ORL), is not as clear as hyperalgesia, analgesia, and no effect was reported after administration of ORL agonists. There are now cDNA sequences for all four types of opioid receptors that are expressed in the brain of six species from three different classes of vertebrates. This review presents a comparative analysis of vertebrate opioid receptors using bioinformatics and data from recent human genome studies. Results indicate that opioid receptors arose by gene duplication, that there is a vector of opioid receptor divergence, and that MOR shows evidence of rapid evolution.

Endogenous opiates and behavior: 2007

This paper is the thirtieth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2007 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; alcohol and drugs of abuse; 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.