Effect of genetic factors on opioid action

Genetic Factors Associated with Morphine Consumption in Women Undergoing Laparoscopic Cholecystectomy: A Prospective Cohort Study

Introduction

Morphine has been a crucial analgesic agent used perioperatively in various surgical procedures. Genetic factors can lead to morphine dose requirement interpatient variability. Our objective was to determine the contribution of genetic polymorphisms in human μ-opioid receptor gene (OPRM1), ATP binding cassette gene (ABCB1) and rs2952768 to the variation of the perioperative morphine consumption in women undergoing laparoscopic cholecystectomy.

Methods

This is a prospective cohort study that included 102 adult Arab females undergoing laparoscopic cholecystectomy. The exposures were carrying the genetic variants of OPRM1, ABCB1 and rs2952768. Our primary outcome was total morphine or morphine equivalent dose required perioperatively. The secondary outcomes were pain score during the first 24 hours and adverse drug reactions. A standardized, general anaesthesia was used for all subjects. In addition to the genetic factors, we also investigated non-genetic factors influencing post-operative pain sensitivity and morphine consumption.

Results

Both (rs1799971, A>G) in OPRM1 and (rs2952768, T>C) showed statistically significant association with intra-operative total morphine dose requirements. Patients carrying the "G" allele in OPRM1 had a significantly higher total morphine mean rank dose compared to the AA genotype [62.9 vs 47.1, p=0.008]. Furthermore, patients homozygous for the rs2952768 (T>C) minor allele "CC" had a higher mean rank compared to the other genotypes [72.7 vs 50.1, p=0.046].

Conclusion

OPRM1 (rs1799971) and rs2952768 are associated with variation of intra-operative morphine consumption in laparoscopic cholecystectomy.

Clinical Trial Identifier

This study was registered at ClinicalTrials.gov, NCT04621864. https://clinicaltrials.gov/ct2/show/NCT04621864.

The Associations of Single Nucleotide Polymorphisms with Risk and Symptoms of Irritable Bowel Syndrome

Although several risk single nucleotide polymorphisms (SNPs) have been found to play an important role in etiology of irritable bowel syndrome (IBS), the findings are inconsistent. A descriptive correlational design was used to analyze the baseline data of a randomized controlled trial including participants with IBS and healthy controls (HC). Pain severity and interference, anxiety, sleep, and fatigue were measured using the Brief Pain Inventory (BPI) and patient-reported outcomes measurement information system (PROMIS). Fisher’s exact test and multivariate linear regression were used to investigate the associations between IBS risk alleles and IBS symptoms. Participants were predominantly female, white, and had an average age of 21.13 ± 2.42 years. Polymorphisms within TNFSF15 (rs4263839), SLC6A4 5-HTTLPR, HTR3A (rs1062613), and OXTR (rs2254298) were associated with IBS risk, and TNFSF15 (rs4263839), COMT (rs6269), SLC6A4 5-HTTLPR polymorphisms were associated with pain severity. TNFSF15 (rs4263839) and COMT (rs4680; rs4633) genotypes were associated with sleep disturbance, and the ADRA1D SNP rs1556832 was associated with fatigue in both IBS and HC groups. Genotypic differences were associated with IBS risk and symptoms including abdominal pain, sleep disturbance, and fatigue. Further investigation is warranted to reveal the mechanisms by which these genetic variations influence the dynamic nature of IBS symptoms over time.

Genetic Polymorphisms of Cytokines Might Affect Postoperative Sufentanil Dosage for Analgesia in Patients

Objective

To explore the effect of genetic polymorphisms of cytokines on the dosage of sufentanil for patient-controlled intravenous analgesia (PCIA) after radical lung cancer surgery.

Methods

A total of 100 patients, aged 18 years and above, with ASA grade Ⅰ-Ⅱ and body mass index (BMI) 18.5 to 30, and who were scheduled for radical lung cancer surgery under total intravenous anaesthesia with PCIA of sufentanil from September 2015 to March 2016, were selected. DNA was collected from peripheral blood samples before surgery, and the iMLDRTM multiple single-nucleotide polymorphism typing kit was used to detect 16 related single-nucleotide polymorphism (SNP) sites of interleukin-1A (IL-1A), interleukin-1β (IL-1β), interleukin-1RN (IL-1RN), interleukin-6 (IL-6), C-X-C motif chemokine ligand 8 (CXCL8), interleukin-10 (IL-10), tumour necrosis factor (TNF), nuclear factor kappa-B1 (NFκB1), REL (REL proto-oncogene, NF-kB subunit), and nuclear factor kappa-B inhibitor alpha (NFκBIA). The general characteristics of patients, surgery and anaesthesia data, postoperative resting VAS pain scores, postoperative opioid dosages of sufentanil for PCIA and opioid-related adverse events were recorded. The effects of the examined genetic polymorphisms of the cytokines on the dosage of sufentanil were analysed.

Results

Eight of 100 patients withdrew for various reasons, and, eventually, 92 patients were included. The patients’ resting visual analogue scale (VAS) scores at 24 h, 48 h, and 72 h after surgery were 2.3 ± 1.2, 2.0 ± 0.9, and 1.9 ± 1.0, respectively. The total amounts of sufentanil used were 34.7 ± 10.5 μg, 65.2 ± 13.7 μg, and 94.7 ± 11.6 μg, respectively. We found that the TT genotype of NFκBIA rs696 had higher PCIA sufentanil dosages than the CC genotype and the CT genotype at 48–72 h postoperation (p=0.023, p=0.025, respectively).

Conclusion

The genetic polymorphisms of the cytokine NFκBIA rs696 might affect the dosage of sufentanil for PCIA after radical lung cancer surgery. The specific mechanism needs further study.

Post-tonsillectomy pain control: consensus or controversy?

Pediatric post-tonsillectomy analgesia continues to be highly debated and an area of active research. Tonsillectomy pain can lead to significant patient morbidity, and incur potentially avoidable healthcare costs. Moreover, the various analgesic classes, each present their own risk profiles and unique side effects when used in children post-tonsillectomy. This review delineates the clinical and pathophysiological basis for post-tonsillectomy pain, types of analgesics and their risk profiles, as well as special considerations in this clinical population and a review of alternative analgesic treatment options. This article presents a summary of recent literature and discusses evidence-based management options to aid medical and allied health professionals who may encounter these patients.

Maternal and Neonatal Effects of Remifentanil in Women Undergoing Cesarean Section in Relation to ABCB1 and OPRM1 Polymorphisms

The aim of our study was to evaluate possible effect of ABCB1, and OPRM1 polymorphisms on the efficacy and safety of remifentanil in women undergoing elective cesarean section under general anesthesia. Women received remifentanil (1 µg/kg i.v.) 30 s prior to the induction to standardized general anesthesia. The ABCB1 (rs2032582, rs1045642) and OPRM1 (rs1799971) polymorphisms were analyzed from maternal peripheral blood. The basal hemodynamic and demographic parameters in the study population (n=54) were similar in all the subgroups. The median ± SD increase of systolic blood pressure at 5 min from the baseline was practically completely abolished in homozygous carriers of ABCB1 variants in comparison with wild-type subjects -2.67±25.0 vs. 16.57±15.7 mm Hg, p<0.05 for rs2032582, and 2.00±23.9 vs. 22.13±16.8 mm Hg, p<0.05, for rs1045642, respectively. While no neonate belonging to ABCB1 wild-type homozygous or OPRM1 variant carrying mothers needed any resuscitative measure, 10.5 % of the neonates belonging to OPRM1 wild-type homozygous mothers received resuscitative support similarly as 11.1 %, and 12.5 % of neonates of mothers carrying variants of rs2032582, and rs1045642, respectively. Decreased stabilizing effects of remifentanil on maternal hemodynamics has been observed in ABCB1 wild type mothers, while the adaptation of the neonates was clinically worse in OPRM1 wild type, and ABCB1 variant allele carriers.

Influence of UGT2B7, CYP3A4, and OPRM1 Gene Polymorphisms on Transdermal Buprenorphine Pain Control in Patients with Critical Lower Limb Ischemia Awaiting Revascularization

BACKGROUND

Pain control in critical limb ischemia (CLI) varies considerably between individuals.

OBJECTIVE

To evaluate pharmacogenetically the response to transdermal buprenorphine (BUP-TTS) in patients with CLI who are awaiting revascularization.

METHODS

One hundred and seven patients with CLI were treated with BUP-TTS. The following were analyzed: (1) pain perception (visual analog scale (VAS) before and 4 days after treatment) and (2) genetics: glucuronosyltransferase (UGT2B7), cytochrome (CYP3A4), and μ-opioid receptor (OPRM1) gene polymorphisms.

RESULTS

Ninety-three patients completed the study. The VAS score by the fourth day of analgesia dropped from 6.82 to 3.38 (P < 0.05). The analgesic response to BUP-TTS was greater in men than in women (P = 0.019). Patients who were AA homozygotes for the CYP3A4 gene showed the best response to analgesic treatment (P = 0.003). The combination of the CYP3A4 gene with UGT2B7 or OPRM1 was favorable to the effect of the CYP3A4 gene (P = 0.045 and P = 0.026, respectively). The combination of UGT2B7 with OPRM1 was ineffective (P = 0.648). The 3 polymorphisms together had no effect on response to treatment (P = 0.461).

CONCLUSIONS

BUP-TTS is efficacious in the control of pain in patients with CLI. The homozygous AA carriers of the CYP3A4 gene respond better to treatment with BUP-TTS.

The search for novel analgesics: targets and mechanisms

The management of the pain state is of great therapeutic relevance to virtually every medical specialty. Failure to manage its expression has deleterious consequence to the well-being of the organism. An understanding of the complex biology of the mechanisms underlying the processing of nociceptive information provides an important pathway towards development of novel and robust therapeutics. Importantly, preclinical models have been of considerable use in determining the linkage between mechanism and the associated behaviorally defined pain state. This review seeks to provide an overview of current thinking targeting pain biology, the use of preclinical models and the development of novel pain therapeutics. Issues pertinent to the strengths and weaknesses of current development strategies for analgesics are considered.

Physiology, signaling, and pharmacology of opioid receptors and their ligands in the gastrointestinal tract: current concepts and future perspectives

Opioid receptors are widely distributed in the human body and are crucially involved in numerous physiological processes. These include pain signaling in the central and the peripheral nervous system, reproduction, growth, respiration, and immunological response. Opioid receptors additionally play a major role in the gastrointestinal (GI) tract in physiological and pathophysiological conditions. This review discusses the physiology and pharmacology of the opioid system in the GI tract. We additionally focus on GI disorders and malfunctions, where pathophysiology involves the endogenous opioid system, such as opioid-induced bowel dysfunction, opioid-induced constipation or abdominal pain. Based on recent reports in the field of pharmacology and medicinal chemistry, we will also discuss the opportunities of targeting the opioid system, suggesting future treatment options for functional disorders and inflammatory states of the GI tract.

Association between ABCB1 gene polymorphisms and fentanyl's adverse effects in Turkish patients undergoing spinal anesthesia

The ATP-binding cassette transporter (ABCB1) gene product, P-glycoprotein plays an important role in the prevention of intracellular accumulation of potentially toxic substances and metabolites in various tissues. Single nucleotide polymorphisms in this gene are claimed to be correlated with changes in the function of P-glycoprotein. There is evidence that fentanyl, may be a substrate for P-glycoprotein. The aim of the study was to assess whether an association exists between ABCB1 gene polymorphism and early respiratory and sedative adverse effects of intravenous fentanyl in Turkish patients who underwent spinal anesthesia In all 83 unrelated Turkish patients were enrolled in this study. In this study, spinal anesthesia was provided and a single dose of intravenous fentanyl (2.5μg.kg(-1)) at the beginning of surgery was used as a sedative agent. Bispectral index, respiration rate and peripheral oxygen saturation were measured continuously and recorded throughout the study. The allele and genotype frequencies were similar to previous data from Turkish population. Respiratory rate (RR) and SpO(2) parameters of the patients did not show any significant difference according to the genotype distribution for C1236T and C3435T SNPs. Fentanyl-induced decrease in respiration rate was most remarkable at 15min (23%) in CC genotype of C1236T, whereas in TT genotype of C3435T (18%) polymorphism. SpO(2) parameters in allele distribution were also not significant among the groups (p=0.374, p=0.985, respectively). For the C1236T polymorphism, patients carrying T allele showed a significant decrease in pH, and a significant increase in pCO(2) (p<0.001). ABCB1 polymorphisms did not seem to have a significant effect on sedation and respiratory depression caused by intravenous fentanyl in spinal anesthesia in Turkish patients.

Genome sequencing and comparison of two nonhuman primate animal models, the cynomolgus and Chinese rhesus macaques

The nonhuman primates most commonly used in medical research are from the genus Macaca. To better understand the genetic differences between these animal models, we present high-quality draft genome sequences from two macaque species, the cynomolgus/crab-eating macaque and the Chinese rhesus macaque. Comparison with the previously sequenced Indian rhesus macaque reveals that all three macaques maintain abundant genetic heterogeneity, including millions of single-nucleotide substitutions and many insertions, deletions and gross chromosomal rearrangements. By assessing genetic regions with reduced variability, we identify genes in each macaque species that may have experienced positive selection. Genetic divergence patterns suggest that the cynomolgus macaque genome has been shaped by introgression after hybridization with the Chinese rhesus macaque. Macaque genes display a high degree of sequence similarity with human disease gene orthologs and drug targets. However, we identify several putatively dysfunctional genetic differences between the three macaque species, which may explain functional differences between them previously observed in clinical studies.

Can the chronic administration of the combination of buprenorphine and naloxone block dopaminergic activity causing anti-reward and relapse potential?

Opiate addiction is associated with many adverse health and social harms, fatal overdose, infectious disease transmission, elevated health care costs, public disorder, and crime. Although community-based addiction treatment programs continue to reduce the harms of opiate addiction with narcotic substitution therapy such as methadone maintenance, there remains a need to find a substance that not only blocks opiate-type receptors (mu, delta, etc.) but also provides agonistic activity; hence, the impetus arose for the development of a combination of narcotic antagonism and mu receptor agonist therapy. After three decades of extensive research, the federal Drug Abuse Treatment Act 2000 (DATA) opened a window of opportunity for patients with addiction disorders by providing increased access to options for treatment. DATA allows physicians who complete a brief specialty-training course to become certified to prescribe buprenorphine and buprenorphine/naloxone (Subutex, Suboxone) for treatment of patients with opioid dependence. Clinical studies indicate that buprenorphine maintenance is as effective as methadone maintenance in retaining patients in substance abuse treatment and in reducing illicit opioid use. With that stated, we must consider the long-term benefits or potential toxicity attributed to Subutex or Suboxone. We describe a mechanism whereby chronic blockade of opiate receptors, in spite of only partial opiate agonist action, may ultimately block dopaminergic activity causing anti-reward and relapse potential. While the direct comparison is not as yet available, toxicity to buprenorphine can be found in the scientific literature. In considering our cautionary note in this commentary, we are cognizant that, to date, this is what we have available, and until such a time when the real magic bullet is discovered, we will have to endure. However, more than anything else this commentary should at least encourage the development of thoughtful new strategies to target the specific brain regions responsible for relapse prevention.

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.

Genetic polymorphism and toxicology--with emphasis on cytochrome p450

Individual susceptibility to environmental, chemical, and drug toxicity is to some extent determined by polymorphism in drug-metabolizing enzymes, in particular the cytochromes P450 (CYPs). This polymorphism is in particular translated into risk differences concerning drugs metabolized by the highly polymorphic enzymes CYP2C9, CYP2C19, and CYP2D6, whereas CYP enzymes active in procarcinogen activation are relatively well conserved without important functional polymorphisms. Examples of drug toxicities that can be predicted by P450 polymorphism include those exerted by codeine, tramadol, warfarin, acenocoumarol, and clopidogrel. The polymorphic CYP2A6 has a role in nicotine metabolism and smoking behavior. Besides this genetic variation, genome-wide association studies now allow for the identification of an increasing number of predictive genetic biomarkers among, e.g., human leukocyte antigens and to some extent drug transporters that provide useful information regarding the choice of the drug and drug dosage in order to avoid toxicity. The translation of this information into the clinical practice has been slow; however, an increasing number of pharmacogenomic drug labels are assigned, where the predictive genotyping before drug treatment can be mandatory, recommended, or only for informational purposes. In this review, we provide an update of the field with emphasis on CYP polymorphism.

Genetics of pain, opioids, and opioid responsiveness

Pain is an integral part of the defense mechanisms required for survival. Several hereditary syndromes of complete or almost complete insensitivity to pain have been identified and include channelopathy-associated pain insensitivity, of which the most likely candidate gene is the α-subunit of the voltage-gated sodium channel known as Na(v)1.7. Five hereditary sensory and autonomic neuropathy syndromes have been described. Variable pain sensitivity in the general population has been linked to common variants of the μ-opioid receptor and of the catecholamine-O-methyltransferase genes potentially leading to increased opioid tonus. Variants of the guanosine triphosphate cyclohydrolase 1/dopa-responsive dystonia gene appear to regulate nociception. Other candidate genes are the transient receptor potential cation channel, subfamily 5 member 1, gene and the melanocortin-1 receptor gene. Candidate genes for predicting opioid efficacy are drug-metabolizing enzymes and transporters-including cytochrome P450, uridine 5'-diphosphate-glucuronosyltransferases, and adenosine triphosphate-binding cassette transporters-that are involved in opioid metabolism. Most current knowledge on the genetic regulation of pain has been derived from animal models developed mainly in mice. Genomics has the potential to contribute to therapeutic advances with the promising approach of using small interfering RNA in the control of neuropathic pain. Knowledge of the genetic factors that affect opioid efficacy, metabolism, and adverse effects has the potential for personalizing both acute and chronic pain management, and for designing more useful opiate pain medications with lower adverse event profiles.

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.