Analyses of polymorphisms of intron 2 of OPRK1 (kappa-opioid receptor gene) in association with opioid and cocaine dependence diagnoses in an African-American population

OPRM1 rs2075572 has potential to affect plasma buprenorphine level in opioid users, but not OPRM1 rs562859

OPRM1 gene encoding mu-opioid receptor (MOR) is the primary candidate gene for buprenorphine (BUP) pharmacogenetics. OPRM1 undergoes alternative splicing leading to multiple MOR subtypes. Thus, in the current study 2 SNPs (rs1799972 and rs562859) were selected due to evidence for their contribution to alternative splicing of OPRM1. The effects of 2 SNPs of OPRM1 gene on plasma buprenorphine and norbuprenorphine levels in a sample of 233 OUD patients receiving BUP/naloxone were examined. Polymorphisms were analyzed by PCR and RFLP. BUP and norbuprenorphine concentrations in plasma were measured by LC-MS/MS. OPRM1 rs2075572 GC + CC (0.12 ng/ml) had significantly higher plasma BUP level compared to GG (0.084 ng/ml) (p = 0.043). Although there was not a statistically significant difference between OPRM1 rs562859 genotypes (p = 0.46), patients with OPRM1 rs562859 CT + TT had higher plasma BUP and BUP-related values as compared to those with CC. In conclusion, the effect of OPRM1 rs2075572 on BUP levels in opioid users' plasma was shown in a Caucasian population for the first time. On the other hand, OPRM1 rs562859 seems not to influence the BUP pharmacology.

Endogenous opiates and behavior: 2022

This paper is the forty-fifth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2022 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Effect of PDYN and OPRK1 polymorphisms on the risk of alcohol use disorder and the intensity of depressive symptoms

AIMS

The dynorphin (DYN)/Kappa Opioid Receptor (KOR) system has been suggested to be involved in both negative affective states and the action of alcohol. The present study was undertaken to explore whether the DYN/KOR system genes, PDYN and OPRK1, influence on individual differences in the intensity of depressive symptoms at admission as well as the risk of alcohol use disorder (AUD) risk in a sample of 101 individuals with AUD and 100 controls.

METHODS

PDYN (rs2281285, rs2225749 and rs910080) and OPRK1 (rs6473797, rs963549 and rs997917) polymorphisms were analyzed by PCR-RFLP. The intensity of depressive and anxiety symptoms and craving were measured by the Beck Depression Inventory-II (BDI-II), Beck Anxiety Inventory (BAI), and Penn Alcohol Craving Scale, respectively.

RESULTS

A significant association between the risk of AUD and OPRK1 rs6473797 (P < 0.05) at the gene level. OPRK1 rs6473797 CC genotype was found to lead to a 3.11 times greater alcohol dependence risk. In addition, the BDI-II score of the OPRK1 rs963549 CC genotype was found to be significantly lower (20.9 ± 11.2, min: 1.0, max: 48.0) than that of the CT + TT genotypes (27.04 ± 12.7, min: 0.0, max: 49.0) (t: -2.332, P = 0.022). None of the PDYN polymorphisms were associated with BDI-II score.

CONCLUSION

Variations in the KOR are associated with the risk of AUD and the intensity of depressive symptoms at admission at the gene level in Turkish males. On the other hand, PDYN gene seemed not to be associated with AUD, depression, anxiety, and craving.

OPRD1 rs569356 polymorphism has an effect on plasma norbuprenorphine levels and dose/kg-normalized norbuprenorphine values in individuals with opioid use disorder

This study aimed to determine the effects of nine OPRM1, OPRD1 and OPRK1 polymorphisms on plasma BUP and norbuprenorphine (norBUP) concentrations and various treatment responses in a sample of 122 patients receiving BUP/naloxone. Plasma concentrations of BUP and norBUP were detected by LC-MS/MS. PCR-RFLP method was used to genotype polymorphisms. OPRD1 rs569356 GG had significantly lower plasma norBUP concentration (p=0.018), dose- (p=0.049) and dose/kg-normalized norBUP values (p=0.036) compared with AA. Craving and withdrawal symptoms were significantly higher in OPRD1 rs569356 AG+GG relative to AA. There was a statistically significant difference between the OPRD1 rs678849 genotypes in the intensity of anxiety (13.5 for CT+TT and 7.5 for TT). OPRM1 rs648893 TT (18.8±10.8) was significantly different to CC+CT (14.82±11.3; p=0.049) in view of the intensity of depression. This current study provides the first data on a prominent effect of the OPRD1 rs569356 variation on BUP pharmacology due to its metabolite norBUP.

[Polymorphisms of OPRM1, OPRK1, DCC genes and non-suicidal self-injuries in adults]

OBJECTIVE

To investigate the associations of OPRM1 gene rs179971, OPRK1 gene rs6473797 and DCC gene rs8084280 polymorphisms with non-suicidal self-injury (NSSI) characteristics and motivations in adults.

MATERIAL AND METHODS

A pilot sample included 28 adult patients with history of NSSI (89.3% (n=25) women, median age (Q1-Q3) - 23 (21.25-25) years). Most patients (78.6%, n=20) had a diagnosis of bipolar disorder. NSSI characteristics and motivations were assessed using the Inventory of Statements about Self-Injury (ISAS) scale. The Childhood Trauma Questionnaire (CTQ) was used to control for childhood trauma - one of the most important environmental factors associated with NSSI. The Baratt Impulsivity Scale (BIS) and the Buss-Perry Aggression Questionnaire (BPAQ) were also used to assess impulsivity and aggression, respectively. RT-PCR was used for genotyping, a genetic effect was assessed using the dominant model. Mann-Whitney U-test, Pearson χ2-test and multiple linear regression were used for statistical analysis.

RESULTS

Carriers of the minor G allele of OPRM1 gene rs1779971 had a higher level of aggression assessed by BPAQ (p=0.02). The minor C allele of OPRK1 gene rs6473797 was associated with an increase of the subjective importance of «Affect regulation» (B=2.23; CI 95% [0.39-4.06]; p=0.022) and «Anti-dissociation» (B=3.31; CI 95% [0.18-6.44]; p=0.039) motivations, whereas the minor T allele of DCC gene rs8084280, on the contrary, was associated with a decrease of the importance of «Affect regulation» (B=-1.74; CI 95% [-3.30 - -0.18]; p=0.032). Moreover, this effect was found after adjusting for diagnosis, sex, age, and the presence of childhood trauma.

CONCLUSIONS

To our knowledge, this is the first study on the association of genetic markers with NSSI motivations. The results of this pilot study demonstrate that OPRK1 and DCC gene polymorphisms can determine differences in motivations for self-harm, however, these results require confirmation in large samples.

CpH methylome analysis in human cortical neurons identifies novel gene pathways and drug targets for opioid use disorder

INTRODUCTION

DNA methylation (DNAm), an epigenetic mechanism, has been associated with opioid use disorder (OUD) in preclinical and human studies. However, most of the studies have focused on DNAm at CpG sites. DNAm at non-CpG sites (mCpHs, where H indicates A, T, or C) has been recently shown to have a role in gene regulation and to be highly abundant in neurons. However, its role in OUD is unknown. This work aims to evaluate mCpHs in the human postmortem orbital frontal cortex (OFC) in the context of OUD.

METHODS

A total of 38 Postmortem OFC samples were obtained from the VA Brain Bank (OUD = 12; Control = 26). mCpHs were assessed using reduced representation oxidative bisulfite sequencing in neuronal nuclei. Differential analysis was performed using the "methylkit" R package. Age, ancestry, postmortem interval, PTSD, and smoking status were included as covariates. Significant mCpHs were set at q-value < 0.05. Gene Ontology (GO) and KEGG enrichment analyses were performed for the annotated genes of all differential mCpH loci using String, ShinyGO, and amiGO software. Further, all annotated genes were analyzed using the Drug gene interaction database (DGIdb).

RESULTS

A total of 2,352 differentially methylated genome-wide significant mCpHs were identified in OUD, mapping to 2,081 genes. GO analysis of genes with differential mCpH loci showed enrichment for nervous system development (p-value = 2.32E-19). KEGG enrichment analysis identified axon guidance and glutamatergic synapse (FDR 9E-4-2.1E-2). Drug interaction analysis found 3,420 interactions between the annotated genes and drugs, identifying interactions with 15 opioid-related drugs, including lofexidine and tizanidine, both previously used for the treatment of OUD-related symptoms.

CONCLUSION

Our findings suggest a role of mCpHs for OUD in cortical neurons and reveal important biological pathways and drug targets associated with the disorder.