Pharmacogenomics of the human µ-opioid receptor

Opioid Receptor Mu 1 Gene (OPRM1) A118G Polymorphism and Emotional Modulation of Pain

Purpose

The A118G polymorphism in the opioid receptor mu 1 gene (OPRM1) is associated with decreased opioid receptor availability, altered emotion, and increased pain. Given that emotions modulate pain (positive emotions inhibit pain, negative emotions enhance pain), we predicted that G allele carriers would experience impaired emotional modulation of pain compared to non-G allele carriers.

Patients and Methods

Emotional pictures (ie, erotica, neutral, attack) from the International Affective Picture System were used by permission from the authors to experimentally manipulate emotions in 64 adult participants while painful electrocutaneous stimulations were delivered in a cross-sectional study. Ratings of arousal and valence/pleasure were made in response to pictures, and pain ratings and a physiological measure of spinal nociception (ie, nociceptive flexion reflex, NFR) were collected in response to painful stimulations. Secondary analyses were conducted to examine the relationship between the A118G polymorphism and emotional modulation of pain/NFR.

Results

Exposure to emotional pictures elicited similar changes in valence, but G-carriers rated erotic pictures as more arousing. In non-carriers, pain was facilitated by attack pictures and pain and NFR were inhibited by erotic pictures relative to neutral pictures. Among G-carriers, pain was facilitated by negative emotional pictures but there was no pain or NFR inhibition by positive emotional pictures.

Conclusion

The altered response to pleasant stimuli further supports the role of opioids in appetitive behavior and describes how the A118G polymorphism may prevent carriers from inhibiting pain during pleasure.

The µ-Opioid Receptor in Cancer and Its Role in Perineural Invasion: A Short Review and New Evidence

Cancer is a significant public health problem worldwide. While there has been a steady decrease in the cancer death rate over the last two decades, the number of survivors has increased and, thus, cancer-related sequela. Pain affects the life of patients with cancer and survivors. Prescription opioids continue as the analgesic of choice to treat moderate-to-severe cancer-related pain. There has been controversy on whether opioids impact cancer progression by acting on cancer cells or the tumor microenvironment. The μ-opioid receptor is the site of action of prescription opioids. This receptor can participate in an important mechanism of cancer spread, such as perineural invasion. In this review, current evidence on the role of the μ-opioid receptor in cancer growth is summarized and preliminary evidence about its effect on the cross-talk between sensory neurons and malignant cells is provided.

Impact of SLCO1B1*5 on Flucloxacillin and Co-Amoxiclav-Related Liver Injury

Background: Idiosyncratic drug-induced liver injury (DILI) is a serious uncommon disease that may develop as a result of the intake of certain drugs such as the antimicrobials flucloxacillin and co-amoxiclav. The reported cases showed significant associations between DILI and various human leukocyte (HLA) markers. The solute carrier organic anion transporter 1B1 (SLCO1B1), a non-HLA candidate gene, was previously reported as a risk factor for liver injury induced by rifampin and methimazole. This study presumed that SLCO1B1 may play a general role in the DILI susceptibility and therefore investigated the association of rs4149056 (SLCO1B1*5, T521C) polymorphism with flucloxacillin- and co-amoxiclav-induced liver injury. Methodology: We recruited 155 and 165 DILI cases of white ancestral origin from various European countries but mainly from the United Kingdom owing to flucloxacillin and co-amoxiclav, respectively. Only adult patients (≥18 years) who were diagnosed with liver injury and who showed i) clinical jaundice or bilirubin >2x the upper limit of normal (ULN), ii) alanine aminotransferase (ALT) >5x ULN or iii) alkaline phosphatase (ALP) >2x ULN and bilirubin > ULN were selected. The population reference sample (POPRES), a European control group (n = 282), was used in comparison with the investigated cases. TaqMan SNP genotyping custom assay designed by Applied Biosystems was used to genotype both DILI cohorts for SLCO1B1 polymorphism (rs4149056). Allelic discrimination analysis was performed using a step one real-time PCR machine. Genotype differences between cases and controls were examined using Fisher's exact test. GraphPad Prism version 5.0 was used to determine the p-value, odds ratio, and 95% confidence interval. Compliance of the control group with Hardy-Weinberg equilibrium was proven using a web-based calculator available at https://wpcalc.com/en/equilibrium-hardy-weinberg/. Results: A small number of cases failed genotyping in each cohort. Thus, only 149 flucloxacillin and 162 co-amoxiclav DILI cases were analyzed. Genotyping of both DILI cohorts did not show evidence of association with the variant rs4149056 (T521C) (OR = 0.71, 95% CI = 0.46-1.12; p = 0.17 for flucloxacillin cases and OR = 0.87, 95% CI = 0.56-1.33; p = 0.58 for co-amoxiclav), although slightly lower frequency (22.8%) of positive flucloxacillin cases was noticed than that of POPRES controls (29.4%). Conclusion: Carriage of the examined allele SLCO1B1*5 is not considered a risk factor for flucloxacillin DILI or co-amoxiclav DILI as presumed. Testing a different allele (SLCO1B1*1B) and another family member gene (SLCO1B3) may still be needed to provide a clearer role of SLCO1B drug transporters in DILI development-related to the chosen antimicrobials.

Solid Tumor Opioid Receptor Expression and Oncologic Outcomes: Analysis of the Cancer Genome Atlas and Genotype Tissue Expression Project

Background

Opioid receptors are expressed not only by neural cells in the central nervous system, but also by many solid tumor cancer cells. Whether perioperative opioids given for analgesia after tumor resection surgery might inadvertently activate tumor cells, promoting recurrence or metastasis, remains controversial. We analysed large public gene repositories of solid tumors to investigate differences in opioid receptor expression between normal and tumor tissues and their association with long-term oncologic outcomes.

Methods

We investigated the normalized gene expression of µ, κ, δ opioid receptors (MOR, KOR, DOR), Opioid Growth Factor (OGFR), and Toll-Like 4 (TLR4) receptors in normal and tumor samples from twelve solid tumor types. We carried out mixed multivariable logistic and Cox regression analysis on whether there was an association between these receptors' gene expression and the tissue where found, i.e., tumor or normal tissue. We also evaluated the association between tumor opioid receptor gene expression and patient disease-free interval (DFI) and overall survival (OS).

Results

We retrieved 8,780 tissue samples, 5,852 from tumor and 2,928 from normal tissue, of which 2,252 were from the Genotype Tissue Expression Project (GTEx) and 672 from the Cancer Genome Atlas (TCGA) repository. The Odds Ratio (OR) [95%CI] for gene expression of the specific opioid receptors in the examined tumors varied: MOR: 0.74 [0.63-0.87], KOR: 1.27 [1.17-1.37], DOR: 1.66 [1.48-1.87], TLR4: 0.29 [0.26-0.32], OGFR: 2.39 [2.05-2.78]. After controlling all confounding variables, including age and cancer stage, there was no association between tumor opioid receptor expression and long-term oncologic outcomes.

Conclusion

Opioid receptor gene expression varies between different solid tumor types. There was no association between tumor opioid receptor expression and recurrence. Understanding the significance of opioid receptor expression on tumor cells remains elusive.

Short Tandem Repeat Variation in the CNR1 Gene Associated With Analgesic Requirements of Opioids in Postoperative Pain Management

Short tandem repeats (STRs) and variable number of tandem repeats (VNTRs) that have been identified at approximately 0.7 and 0.5 million loci in the human genome, respectively, are highly multi-allelic variations rather than single-nucleotide polymorphisms. The number of repeats of more than a few thousand STRs was associated with the expression of nearby genes, indicating that STRs are influential genetic variations in human traits. Analgesics act on the central nervous system via their intrinsic receptors to produce analgesic effects. In the present study, we focused on STRs and VNTRs in the CNR1, GRIN2A, PENK, and PDYN genes and analyzed two peripheral pain sensation-related traits and seven analgesia-related traits in postoperative pain management. A total of 192 volunteers who underwent the peripheral pain sensation tests and 139 and 252 patients who underwent open abdominal and orthognathic cosmetic surgeries, respectively, were included in the study. None of the four STRs or VNTRs were associated with peripheral pain sensation. Short tandem repeats in the CNR1, GRIN2A, and PENK genes were associated with the frequency of fentanyl use, fentanyl dose, and visual analog scale pain scores 3 h after orthognathic cosmetic surgery (Spearman’s rank correlation coefficient ρ = 0.199, p = 0.002, ρ = 0.174, p = 0.006, and ρ = 0.135, p = 0.033, respectively), analgesic dose, including epidural analgesics after open abdominal surgery (ρ = −0.200, p = 0.018), and visual analog scale pain scores 24 h after orthognathic cosmetic surgery (ρ = 0.143, p = 0.023), respectively. The associations between STRs in the CNR1 gene and the frequency of fentanyl use and fentanyl dose after orthognathic cosmetic surgery were confirmed by Holm’s multiple-testing correction. These findings indicate that STRs in the CNR1 gene influence analgesia in the orofacial region.

Genetic Polymorphisms as Predictors of Survival in Breast Cancer: Future Lessons in Historical Data

Introduction

Breast cancer is the most common cancer among women worldwide and one of the main causes of death in the female sex. Genetic polymorphisms in the mu-opioid receptor (OPRM1) and catechol-o-methyltransferase (COMT) genes have been shown to increase breast cancer risk. Variants in these genes may carry a prognostic impact in breast cancer. Long follow-up intervals are critical to adequately analyze prognosis in diseases with prolonged survival times and late relapses.

Objective

To analyze the impact of genetic polymorphisms on the survival of a cohort of breast cancer patients with very long follow-up.

Methods

This was a retrospective study of patients treated at Portuguese Oncology Institute of Porto (IPO Porto), a Portuguese comprehensive cancer center, with invasive carcinoma of the breast with very long follow-up, with analysis of genetic polymorphisms OPMR1 rs1799971 (AA vs. G allele) and COMT rs4680 (CC vs T allele) on biological samples. Statistical analysis of survival was performed using the Kaplan-Meier method, log-rank test, and Cox regression method.

Results

A total of 143 patients with invasive breast cancer were included, with a median follow-up of 21.5 years. There was a statistically significant difference in overall survival (OS) at 30 years according to the OPMR1 polymorphism, with lower survival in patients with the AA genotype (p<0.05). The difference in OS according to the COMT polymorphism was also statistically significant, with worse survival in patients with genotype T allele (p<0.05). The genetic variants were not associated with patient age, stage at diagnosis, or tumor grade.

Discussion

The genetic polymorphisms of OPRM1 and COMT affected the overall survival of breast cancer patients, in concordance with previous research. Further investigation is needed in order to clarify the prognostic impact of these genetic alterations on breast cancer.

Opioid-free anesthesia versus opioid-inclusive anesthesia for breast cancer surgery: a retrospective study

Background

Breast cancer surgery is usually managed using opioid-inclusive anesthesia (OIA), although opioids are associated with several adverse events, including nausea, vomiting, and constipation. Multimodal opioid-free anesthesia (OFA) has been introduced to reduce the incidence of these side effects. In this single-center retrospective study, we investigated whether ketamine, combined with magnesium and clonidine, could effectively control postoperative pain in patients undergoing quadrantectomy, while reducing postoperative nausea and vomiting (PONV).

Results

A total of 89 patients submitted to quadrantectomy were included and divided into an OFA group (38 patients) and an OIA group (51 patients) according to the received anesthetic technique. Analgesia in the OIA group was based on an intraoperative infusion of remifentanil, and analgesia in the OFA consisted of an intraoperative infusion of ketamine and magnesium sulfate. Postoperative pain in both groups was managed with nonsteroidal anti-inflammatory drugs (NSAIDs) and paracetamol. Postoperative pain, assessed with the numeric rating scale (NRS), requirements for additional analgesics, the incidence of PONV, and patient satisfaction evaluated using a QoR-40 questionnaire were compared between the two groups. Levels of pain at 30 min and 6, 12, and 24 h after surgery; number of paracetamol rescue doses; and the incidence of PONV were lower in the OFA group (p <0.05). Patient satisfaction was comparable in the two groups.

Conclusions

A combination of ketamine, magnesium, and clonidine could be more effective than opioid-based analgesia in reducing postoperative pain and lowering PONV occurrence after quadrantectomy for breast cancer.

Systematic elucidation of the pharmacological mechanisms of Rhynchophylline for treating epilepsy via network pharmacology

Background

Epilepsy, one of the most common neurological disorders, affects over 70 million people worldwide. Rhynchophylline displays a wide variety of pharmacologic actives. However, the pharmacologic effects of rhynchophylline and its mechanisms against epilepsy have not been systematically elucidated.

Methods

The oral bioavailability and druglikeness of rhynchophylline were evaluated using the Traditional Chinese Medicine Systems Pharmacology Database. Rhynchophylline target genes to treat epilepsy were identified using PharmMapper, SwissTargetPrediction and DrugBank databases integration. Protein-protein interaction analysis was carried out by utilizing the GeneMANIA database. WebGestalt was employed to perform Gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses. The drug-disease-target-Gene Ontology-pathway network was constructed using Cytoscape.

Results

The oral bioavailability and druglikeness of rhynchophylline were calculated to be 41.82% and 0.57, respectively. A total of 20 rhynchophylline target genes related to epilepsy were chosen. Among the 20 genes and their interacting genes, 54.00% shared protein domains and 16.61% displayed co-expression characteristics. Gene ontology, Kyoto Encyclopedia of Genes and Genomes and network analyses illustrate that these targets were significantly enriched in regulation of sensory perception, morphine addiction, neuroactive ligand-receptor interaction and other pathways or biological processes.

Conclusion

In short, rhynchophylline targets multiple genes or proteins, biological processes and pathways. It shapes a multiple-layer network that exerts systematic pharmacologic activities on epilepsy.

Aberrant Feeding and Growth in Neonates With Prenatal Opioid Exposure: Evidence of Neuromodulation and Behavioral Changes

Opioid use disorder (OUD) among pregnant women over the last decade has led to more than a fivefold increase in the number of neonates born with withdrawal signs known as Neonatal Abstinence Syndrome (NAS) or Neonatal Opioid Withdrawal Syndrome (NOWS). The impact of prenatal opioid exposure on these neonates remains a public health and research priority due to both its short and long-term effects on offspring. Among the adverse long-term effects associated with OUD is a metabolic syndrome with accompanying cardiovascular comorbidities. The susceptibility to metabolic diseases may begin as early as conception. Neonates born in a setting of prenatal opioid exposure are known to have aberrant early growth, e.g., lower birth weight and smaller head size, and dysregulated feeding behavior that ranges from feeding difficulty to hyperphagia which may predispose these neonates to metabolic syndrome in adulthood. However, studies on this topic are lacking. In this article, we describe the reported association between OUD and metabolic syndrome in adults, animal data linking opioid receptors with the development of diet-induced obesity, the inflammatory modulation of opioids and finally, neonatal salivary transcriptomic data from our laboratory that highlighted the sex-specific impact of opioids on the hypothalamic and reward receptors that regulate feeding behavior in opioid-exposed neonates. There is a great need for future research linking opioids with epigenetic and gene expression changes, as well as neuromodulatory effects in the developing brain, that may underlie the dysregulated feeding, growth, and long-term metabolic and cardiovascular risks for these neonates.

Long non-coding RNA MIR4300HG polymorphisms are associated with postoperative nausea and vomiting: a genome-wide association study

Background

Genetic factors such as single-nucleotide polymorphisms (SNPs) play a key role in the development of postoperative nausea and vomiting (PONV). However, previous findings are not widely applicable to different populations because of population-specific genetic variation. We developed a Japanese-specific DNA microarray for high-throughput genotyping. The aim of the current study was to identify SNPs associated with PONV on a genome-wide scale using this microarray in a sample of Japanese surgical patients.

Methods

Associations between 659,636 SNPs and the incidence of PONV 24 h after surgery in a limited sample of 24 female patients were assessed using the microarray. After imputation of genotypes at 24,330,529 SNPs, 78 SNPs were found to be associated with the incidence of PONV. We chose 4 of the 78 SNPs to focus on by in silico functional annotation. Finally, we genotyped these 4 candidate SNPs in 255 patients using real-time PCR to verify association with the incidence of PONV.

Results

The T > C variant of rs11232965 in the long non-coding RNA MIR4300HG was significantly associated with reduced incidence of PONV among genotypes and between alleles (p = 0.01 and 0.007).

Conclusions

We identified a novel SNP (rs11232965) in the long non-coding RNA MIR4300HG that is associated with PONV. The rs11232965-SNP variant (T > C) is protective against the incidence of PONV.

Trial registration

This study was registered at the UMIN Clinical Trials Registry (Identifier: UMIN000022903, date of registration: June 27, 2016, retrospectively registered.

Metabolic and Addiction Indices in Patients on Opioid Agonist Medication-Assisted Treatment: A Comparison of Buprenorphine and Methadone

Metabolic hormones stabilize brain reward and motivational circuits, whereas excessive opioid consumption counteracts this effect and may impair metabolic function. Here we addressed the role of metabolic processes in the course of the agonist medication-assisted treatment for opioid use disorder (OUD) with buprenorphine or methadone. Plasma lipids, hemoglobin A1C, body composition, the oral glucose tolerance test (oGTT) and the Sweet Taste Test (STT) were measured in buprenorphine- (n = 26) or methadone (n = 32)- treated subjects with OUD. On the whole, the subjects in both groups were overweight or obese and insulin resistant; they displayed similar oGTT and STT performance. As compared to methadone-treated subjects, those on buprenorphine had significantly lower rates of metabolic syndrome (MetS) along with better values of the high-density lipoproteins (HDL). Subjects with- vs. without MetS tended to have greater addiction severity. Correlative analyses revealed that more buprenorphine exposure duration was associated with better HDL and opioid craving values. In contrast, more methadone exposure duration was associated with worse triglycerides-, HDL-, blood pressure-, fasting glucose- and hemoglobin A1C values. Buprenorphine appears to produce beneficial HDL- and craving effects and, contrary to methadone, its role in the metabolic derangements is not obvious. Our data call for further research aimed at understanding the distinctive features of buprenorphine metabolic effects vis-à-vis those of methadone and their potential role in these drugs' unique therapeutic profiles.

Association Between Polymorphisms in the Purinergic P2Y12 Receptor Gene and Severity of Both Cancer Pain and Postoperative Pain

Background

Despite the widespread use of opioids for the treatment of cancer pain, results from several surveys consistently show that pain is still prevalent in some patients with malignant diseases. The purinergic P2Y12 receptor is a primary site leading to microglial activation and hyperalgesic pain behaviors and is considered a key regulator in the prevention of the aggravation of clinical pain conditions. Genetic variability in the P2RY12 gene may contribute to individual differences in pain and opioid sensitivity.

Methods

We genotyped 31 single nucleotide polymorphisms (SNPs) throughout the P2RY12 gene and compared genotypes against pain measurements and opioid requirements in Japanese cancer pain patients (N = 90). The most promising SNP association with pain severity was validated by genotyping an additional postoperative pain patient cohort (N = 355).

Results

Five SNPs (rs3732765, rs9859538, rs17283010, rs11713504, and rs10935840) of the P2RY12 gene were significantly associated with cancer pain severity, although opioid requirements were comparable in each genotype of the five SNPs. The alleles of these SNPs represented one absolute linkage disequilibrium block of the P2RY12 gene. In the second association study of postoperative pain, subjects carrying the minor T allele of the rs3732765 SNP demonstrated more intense 24-hour postoperative pain compared with subjects not carrying this allele although total 24-hour postoperative opioid consumptions based on weight were comparable.

Conclusions

Polymorphisms of the P2RY12 gene may predict individual differences in both cancer and postoperative pain severity; this might be caused by functional alteration of nociceptive neurons through neuron-glia interaction.

Candidate gene analyses for acute pain and morphine analgesia after pediatric day surgery: African American versus European Caucasian ancestry and dose prediction limits

Acute pain and opioid analgesia demonstrate inter-individual variability and polygenic influence. In 241 children of African American and 277 of European Caucasian ancestry, we sought to replicate select candidate gene associations with morphine dose and postoperative pain and then to estimate dose prediction limits. Twenty-seven single-nucleotide polymorphisms (SNPs) from nine genes (ABCB1, ARRB2, COMT, DRD2, KCNJ6, MC1R, OPRD1, OPRM1, and UGT2B7) met selection criteria and were analyzed along with TAOK3. Few associations replicated: morphine dose (mcg/kg) in African American children and ABCB1 rs1045642 (A allele, β = -9.30, 95% CI: -17.25 to -1.35, p = 0.02) and OPRM1 rs1799971 (G allele, β = 23.19, 95% CI: 3.27-43.11, p = 0.02); KCNJ6 rs2211843 and high pain in African American subjects (T allele, OR 2.08, 95% CI: 1.17-3.71, p = 0.01) and in congruent European Caucasian pain phenotypes; and COMT rs740603 for high pain in European Caucasian subjects (A allele, OR: 0.69, 95% CI: 0.48-0.99, p = 0.046). With age, body mass index, and physical status as covariates, simple top SNP candidate gene models could explain theoretical maximums of 24.2% (European Caucasian) and 14.6% (African American) of morphine dose variances.

The HECT ubiquitin E3 ligase Smurf2 degrades μ-opioid receptor 1 in the ubiquitin-proteasome system in lung epithelial cells

Opioids are widely used for relieving clinical acute or chronic pain. The biological effects of opioids are through activating μ-opioid receptor 1 (MOR1). Most studies have focused on the consequences of agonist-induced MOR1 phosphorylation, ubiquitination, and internalization. Agonist-mediated MOR1 degradation, which is crucial for receptor stability and responsiveness, has not been well studied. E3 ubiquitin-protein ligase SMURF2 (Smurf2), a homolog to E6AP carboxy terminus (HECT) ubiquitin E3 ligase, has been shown to regulate MOR1 ubiquitination and internalization; however, its role in MOR1 degradation has not been studied. Here, we demonstrate that Smurf2 mediates [d-Ala²,N-MePhe⁴,Gly⁵-ol]-enkephalin (DAMGO, an agonist of MOR1)-induced MOR1 ubiquitination and degradation. DAMGO decreased MOR1 levels in the ubiquitin-proteasome system. MOR1 was modified by a Lys48-linked polyubiquitin chain. Overexpression of Smurf2 induced MOR1 ubiquitination and accelerated DAMGO-induced MOR1 degradation, whereas downregulation of Smurf2 attenuated MOR1 degradation. Furthermore, DAMGO increased lung epithelial cell migration and proliferation, and the effect was attenuated by overexpressing Smurf2. Collectively, these data unveil that Smurf2 negatively regulates MOR1 activity by reducing its stability. We also demonstrate an unrevealed biological function of MOR1 in lung epithelial cells. DAMGO-MOR1 promote cell migration and proliferation in lung epithelial cells, suggesting a potential effect of DAMGO in lung repair and remodeling after lung injury.

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.

When the Safe Alternative Is Not That Safe: Tramadol Prescribing in Children

Children represent a vulnerable population in which management of nociceptive pain is complex. Drug responses in children differ from adults due to age-related differences. Moreover, therapeutic choices are limited by the lack of indication for a number of analgesic drugs due to the challenge of conducting clinical trials in children. Furthermore the assessment of efficacy as well as tolerance may be complicated by children's inability to communicate properly. According to the World Health Organization, weak opioids such as tramadol and codeine, may be used in addition to paracetamol and ibuprofen for moderate nociceptive pain in both children and adults. However, codeine prescription has been restricted for the last 5 years in children because of the risk of fatal overdoses linked to the variable activity of cytochrome P450 (CYP) 2D6 which bioactivates codeine. Even though tramadol has been considered a safe alternative to codeine, it is well established that tramadol pharmacodynamic opioid effects, efficacy and safety, are also largely influenced by CYP2D6 activity. For this reason, the US Food and Drug Administration recently released a boxed warning regarding the use of tramadol in children. To provide safe and effective tramadol prescription in children, a personalized approach, with dose adaptation according to CYP2D6 activity, would certainly be the safest method. We therefore recommend this approach in children requiring chronic or recurrent nociceptive pain treatment with tramadol. In case of acute inpatients nociceptive pain management, prescribing tramadol at the minimal effective dose, in a child appropriate dosage form and after clear instructions are given to the parents, remains reasonable based on current data. In all other situations, morphine should be preferred for moderate to severe nociceptive pain conditions.

In Vitro Chondrotoxicity of Nonsteroidal Anti-inflammatory Drugs and Opioid Medications

BACKGROUND

A variety of medications are administered to the intra-articular space for the relief of joint pain. While amide-type local anesthetics have been extensively studied, there is minimal information regarding the potential chondrotoxicity of nonsteroidal anti-inflammatory drugs (NSAIDs) and opioid medications.

PURPOSE

To investigate the in vitro chondrotoxicity of single-dose equivalent concentrations of ketorolac, morphine, meperidine, and fentanyl on human chondrocytes.

STUDY DESIGN

Controlled laboratory study.

METHODS

Human cartilage was arthroscopically harvested from the intercondylar notch and expanded in vitro. Gene expression of cultured chondrocytes before treatment was performed with quantitative polymerase chain reaction for type I collagen, type II collagen, aggrecan, and SOX9. Chondrocytes were then exposed to 0.01%, 0.02%, and 0.04% morphine sulfate; 0.3% and 0.6% ketorolac tromethamine; 0.5%, 1.0%, and 1.5% meperidine hydrochloride; 0.0005% and 0.001% fentanyl citrate; and saline. A custom bioreactor was used to constantly deliver medications, with the dosage of each medication and the duration of exposure based on standard dose equivalents, medication half-lives, and differences in the surface area between the 6-well plates and the native joint surface. After treatment, a live/dead assay was used to assess chondrocyte viability and if minimal cell death was detected. A subset of samples after treatment was maintained to analyze for possible delayed cell death.

RESULTS

All tested concentrations of ketorolac and meperidine caused significantly increased cell death versus the saline control, demonstrating a dose-response relationship. The morphine and fentanyl groups did not show increased chondrotoxicity compared with the saline group, even after 2 weeks of additional culture.

CONCLUSION

In vitro exposure of chondrocytes to single-dose equivalent concentrations of either ketorolac or meperidine demonstrated significant chondrotoxicity, while exposure to morphine or fentanyl did not lead to increased cell death.

Does Opioid Use Cause Angiogenesis and Metastasis?

Objective

To provide a comprehensive overview of the potential for morphine to lead to angiogenesis and metastasis.

Background

Morphine is often the treatment of choice for severe cancer-related pain. Small studies have been emerging that indicate that opioids may influence angiogenesis and metastasis, but this has not yet been comprehensively synthesized.

Purpose

To highlight morphine's relationship with angiogenesis and metastasis in in vitro models.

Method

A review of the literature was conducted using PubMed (1966 to 2015) and Cochrane Library (1987 to 2015) electronic databases. The search, as well as consultation with experts, yielded 84 articles for initial review, 12 of which met inclusion for review. Possible theories of the underlying etiology of the metastasis and angiogenesis were recorded.

Results

All studies were assessed using the PRISMA checklist.

Conclusion

This systematic review demonstrates that morphine has a potential causal relationship with angiogenesis and metastasis. This is likely due to multiple etiologies, including immunosuppressive, pro-inflammatory, and pro-angiogenetic.

Nociceptin/orphanin FQ receptor gene variation is associated with smoking status in Japanese

Aim: The endogenous opioid system has been reportedly implicated in tobacco/nicotine dependence. Materials & methods: We examined the genetic effects of eight SNPs in opioid receptor-related genes on smoking status and smoking-related traits in Japanese. Results: The genotypic and allelic variations of the rs2229205 SNP in the OPRL1 gene were significantly associated with smoking status, but no significant differences were found in the genetic variations of any of the SNPs with regard to smoking-related traits. The rs2229205 SNP did not show high linkage disequilibrium with the other SNPs in the linkage disequilibrium block that contained the SNP. Conclusion: The rs2229205 SNP in the OPRL1 gene may be a genetic factor that contributes to individual differences in the vulnerability to smoking in Japanese individuals.

Anesthetic use in newborn infants: the urgent need for rigorous evaluation

Approximately 1.5 million neonates receive general anesthesia each year for a surgical procedure. Despite this being an essential practice, a number of recent studies now indicate that anesthetic exposure could cause toxicity and neuronal apoptosis in the developing brain. This could potentially influence long-term neurodevelopmental outcome, especially premature infants in need of multiple surgical procedures. Most anesthetic drugs routinely administered to neonates have not been adequately tested for safety or efficacy. Given the number of confounders, dosing is often extrapolated from adults. This is concerning since many different drugs can be administered concurrently, with few of these agents actually approved for use by the Food and Drug Administration. Since 1997, legislation has been passed in the United States and abroad encouraging more drug investigation in infants and children. This has resulted in over 500 labeling changes to products regarding safety and efficacy in various pediatric age groups. However, only three drugs routinely used as anesthetic agents in newborn infants have had any updated labeling (none in very premature infants). This "off-label" use without adequate testing must be addressed. Therefore, more clinical trials of common anesthetic agents used alone and in combination in neonates are urgently needed.

μ-Opioid receptor gene (OPRM1) polymorphism in patients with breast cancer

Structure-dependent μ-opioid receptor (MOR) activity is an important element in cancer opioid analgesic effectiveness. It is widely accepted that guanine (G) substitution for adenine (A) at OPRM1 gene sequence position 118 changes receptor glycosylation pattern. This is associated with decreased binding ability in both exogenous and endogenous opioids, resulting in increased human pain resistance. The endogenous opioid system's function in body homeostasis maintenance is considered mainly regulatory, so its participation in breast tumor formation and progression is identified herein. We examine the association of the most frequent MOR (A118G) gene polymorphism on breast cancer risk in a Northeastern Polish population by PCR-RFLP comparison of A and G allele frequency at OPRM1 gene A118G polymorphic site in breast cancer-diagnosed patients with healthy control group frequencies. Our results highlight a strong association between G allele presence at μ-opioid receptor A118G and increased breast cancer incidence (OR = 3.3, 95 % CI 2.2-5.0, p < 0.0001) and female gender (OR = 2.0, 95 % CI 1.4-2.9, p = 0.0004). Consequently, OPRM1 G allele presence at that site is a highly significant risk factor in breast cancer development.

Rescue morphine in mechanically ventilated newborns associated with combined OPRM1 and COMT genotype

AIM

Determine whether SNPs of OPRM1 118A>G (asn(40)asp), COMT 472G>A (val(158)met) and ARRB2 8622C>T are associated with morphine rescue in newborns on mechanical ventilation.

MATERIALS & METHODS

This is a pharmacogenetic analysis of a randomized controlled trial in (pre)term newborns (n = 64) at a level III Neonatal Intensive Care Unit (NICU) who received placebo infusion and for whom need and dose for rescue morphine was documented.

RESULTS

For OPRM1 and COMT separately, the expected risk for rescue morphine or morphine dose was not significantly increased. However, the combined OPRM1/COMT 'high-risk' genotype lead to a significant association with the need for rescue (OR: 5.12; 95% CI: 1.12-23.3; p = 0.035). No association was found between OPRM1/COMT 'high-risk' genotype and total morphine dose administered.

CONCLUSION

Combined OPRM1 118A>G and COMT 472G>A genotype might serve as a predictor for the need of rescue morphine in premature and term newborns on mechanical ventilation.

Association of mu-opioid receptor expression with lymph node metastasis in esophageal squamous cell carcinoma

The mu-opioid receptor (MOR), a membrane-bound G protein-coupled receptor, is the main target for opioids in the nervous system. MOR1 has been found in several types of cancer cells and reported to be involved in tumor progression and metastasis. However, the expression and clinical significance of MOR1 in esophageal squamous cell carcinoma (ESCC) remain unclear. In our study, the expression of MOR1 was confirmed in ESCC cell lines (KYSE180, KYSE150, and EC109) by Western blot. MOR1 was also detected on tissue microarrays of ESCC samples in 239 cases using immunohistochemical staining. We found that MOR1 was mainly located in the cytoplasm and occasionally occurred in the membrane or nucleus of ESCC cells. Moreover, results indicated that MOR1 expression in the cytoplasm was associated with lymph node metastasis (R = 0.164, P = 0.008, Kendall's tau-b-test). No more associations were found between MOR1 expression status and other clinical parameters. However, no statistical significant differences were found between MOR1 expression in the cytoplasm, nucleus/membrane, and the overall survival of ESCC patients (P = 0.848; P = 0.167; P = 0.428, respectively, log-rank test). Our results suggest that the cytoplasmic MOR1 may be a high-risk factor for lymph node metastasis of ESCC patients. We also hypothesize that MOR1 agonists used in ESCC patients should be prudent, and opioid receptor antagonists may be novel therapeutic drugs for ESCC patients.

Pharmacogenetics of chemotherapy-induced nausea and vomiting

Chemotherapy-induced nausea and vomiting (CINV) is associated with distressing adverse effects observed in patients during cytotoxic chemotherapy. One of the potential factors explaining suboptimal response to currently used antiemetics is variability in genes encoding enzymes and proteins that play a role in the action of antiemetic drugs. Pharmacogenomics studies of CINV are sparse and focus mainly on polymorphisms associated with serotonin receptor, drug metabolism and drug transport. Currently, the role of pharmacogenetics in mechanisms of CINV has not been fully unraveled, and it is premature to implement results of pharmacogenetic association studies of antiemetic drugs in clinical practice. More uniform studies, with genetic profiles and biomarkers relevant for the proposed target and transporter mechanisms, are needed.

Haplotypes of P2RX7 gene polymorphisms are associated with both cold pain sensitivity and analgesic effect of fentanyl

Background

The P2X₇ receptor is a member of the P2X family of adenosine 5′-triphosphate-gated cation channels. Several recent studies have demonstrated that this receptor is involved in mechanisms related to pain and inflammation. However, unknown is whether polymorphisms of the P2RX7 gene that encodes the human P2X₇ receptor influence pain sensitivity and analgesic effects of opioids. The P2RX7 gene is known to be highly polymorphic. Thus, the present study examined associations between fentanyl sensitivity and polymorphisms in the P2RX7 gene in 355 Japanese patients who underwent painful orofacial cosmetic surgery.

Results

We first conducted linkage disequilibrium (LD) analyses for 55 reported single-nucleotide polymorphisms (SNPs) in the region within and around the P2RX7 gene using genomic samples from 100 patients. In our samples, 42 SNPs were polymorphic, and a total of five LD blocks with six Tag SNPs (rs2708092, rs1180012, rs1718125, rs208293, rs1718136, and rs7132846) were observed. Thus, we further analyzed associations between genotypes/haplotypes of these Tag SNPs and clinical data using a total of 355 samples. In the genotype-based association study, only the rs1718125 G > A SNP tended to be associated with higher pain scores on a visual analog scale 24 h after surgery (VAS24). The haplotype-based association study showed that subjects with homozygous haplotype No.3 (GTAAAC; estimated frequency: 15.0%) exhibited significantly higher cold pain sensitivity and lower analgesic effects of fentanyl for acute cold pain in the cold pressor test. Conversely, subjects who carried haplotype No.1 (ACGGAC; estimated frequency: 24.5%) tended to exhibit lower cold pain sensitivity and higher analgesic effects of fentanyl. Furthermore, subjects with homozygous haplotype No.2 (GCGGAC; estimated frequency: 22.9%) exhibited significantly lower VAS24 scores.

Conclusions

Cold pain sensitivity and analgesic effects of fentanyl were related to the SNP and haplotypes of the P2RX7 gene. The patients with the rs1718125 G>A SNP tended to show higher VAS24 scores. Moreover, the combination of polymorphisms from the 5′-flanking region to exon 5 recessively affected cold pain sensitivity and analgesic effects of opioids for acute cold pain. The present findings shed light on the involvement of P2RX7 gene polymorphisms in naive cold pain sensitivity and analgesic effects of fentanyl.

Electronic supplementary material

The online version of this article (doi:10.1186/1744-8069-10-75) contains supplementary material, which is available to authorized users.

Association between the A107V substitution in the δ-opioid receptors and ethanol drinking in mice selected for high and low analgesia

Experimental evidence suggests that endogenous opioids play an important role in the development of ethanol addiction. In this study, we employed two mouse lines divergently bred for opioid-mediated stress-induced analgesia. In comparison with HA (high analgesia line) mice, LA (low analgesia line) mice, having lower opioid receptor system activity, manifest enhanced basal as well as stress-induced ethanol drinking. Here, we found that recently discovered C320T transition in exon 2 of the δ-opioid receptor gene (EU446125.1), which results in an A107V substitution (ACA23171.1), leads to higher ethanol preference in CT mice compared with CC homozygotes. This genetic association is particularly evident under chronic mild stress (CMS) conditions. The interaction between stress and ethanol intake was significantly stronger in HA than in LA mice. Ethanol almost completely attenuated the pro-depressive effect of CMS (assessed with the tail suspension test) in both the CC and CT genotypes in the HA line. In the LA mice, a lack of response to ethanol was observed in the CC genotype, whereas ethanol consumption strengthened depressive-like behaviours in CT individuals. Our results suggest that constitutively active A107V substitution in δ-opioid receptors may be involved in stress-enhanced vulnerability to ethanol abuse and in the risk of ethanol dependence.

OPRM1 rs1799971 polymorphism and opioid dependence: evidence from a meta-analysis

The OPRM1 gene encodes the µ-opioid receptor, which is the primary site of action of most opioids. Several studies and three meta-analyses have examined a possible link between the exonic OPRM1 A118G (rs1799971) polymorphism and opioid dependence; however, results have been inconclusive. Therefore, a systematic review and meta-analysis have been carried out to examine whether this polymorphism is associated with opioid dependence. Thirteen studies (n = 9385), comprising 4601 opioid dependents and 4784 controls, which evaluated association of the OPRM1 rs1799971 polymorphism with susceptibility to opioids, were included in this study. Our meta-analysis showed significant association between this polymorphism and susceptibility to opioid dependence in overall studies under a codominant model, as well as susceptibility to opioid dependence or heroin dependence in Asians under an autosomal dominant model. The nonsynonymous OPRM1 rs1799971 might be a risk factor for addiction to opioids or heroin in an Asian population.

Transforming pain medicine: adapting to science and society

The field of chronic pain medicine is currently facing enormous challenges. The incidence of chronic pain is increasing worldwide, particularly in the developed world. As a result, chronic pain is imposing a growing burden on Western societies in terms of cost of medical care and lost productivity. This burden is exacerbated by the fact that despite research efforts and a huge expenditure on treatment for chronic pain, clinicians have no highly effective treatments or definitive diagnostic measures for patients. The lack of an objective measure for pain impedes basic research into the biological and psychological mechanisms of chronic pain and clinical research into treatment efficacy. The development of objective measurements of pain and ability to predict treatment responses in the individual patient is critical to improving pain management. Finally, pain medicine must embrace the development of a new evidence-based therapeutic model that recognizes the highly individual nature of responsiveness to pain treatments, integrates bio-psycho-behavioural approaches, and requires proof of clinical effectiveness for the various treatments we offer our patients. In the long-term these approaches will contribute to providing better diagnoses and more effective treatments to lessen the current challenges in pain medicine.

Association between genetic polymorphisms in Ca(v)2.3 (R-type) Ca2+ channels and fentanyl sensitivity in patients undergoing painful cosmetic surgery

Individual differences in the sensitivity to fentanyl, a widely used opioid analgesic, lead to different proper doses of fentanyl, which can hamper effective pain treatment. Voltage-activated Ca(2+) channels (VACCs) play a crucial role in the nervous system by controlling membrane excitability and calcium signaling. Ca(v)2.3 (R-type) VACCs have been especially thought to play critical roles in pain pathways and the analgesic effects of opioids. However, unknown is whether single-nucleotide polymorphisms (SNPs) of the human CACNA1E (calcium channel, voltage-dependent, R type, alpha 1E subunit) gene that encodes Cav2.3 VACCs influence the analgesic effects of opioids. Thus, the present study examined associations between fentanyl sensitivity and SNPs in the human CACNA1E gene in 355 Japanese patients who underwent painful orofacial cosmetic surgery, including bone dissection. We first conducted linkage disequilibrium (LD) analyses of 223 SNPs in a region that contains the CACNA1E gene using genomic samples from 100 patients, and a total of 13 LD blocks with 42 Tag SNPs were observed within and around the CACNA1E gene region. In the preliminary study using the same 100 genomic samples, only the rs3845446 A/G SNP was significantly associated with perioperative fentanyl use among these 42 Tag SNPs. In a confirmatory study using the other 255 genomic samples, this SNP was also significantly associated with perioperative fentanyl use. Thus, we further analyzed associations between genotypes of this SNP and all of the clinical data using a total of 355 samples. The rs3845446 A/G SNP was associated with intraoperative fentanyl use, 24 h postoperative fentanyl requirements, and perioperative fentanyl use. Subjects who carried the minor G allele required significantly less fentanyl for pain control compared with subjects who did not carry this allele. Although further validation is needed, the present findings show the possibility of the involvement of CACNA1E gene polymorphisms in fentanyl sensitivity.

Association analysis between the A118G polymorphism in the OPRM1 gene and treatment response to venlafaxine XR in generalized anxiety disorder

Patients diagnosed with generalized anxiety disorder (GAD) exhibit differential responses to standard antidepressant pharmacotherapy. Mounting evidence demonstrates that genetic differences may be implicated in treatment response in disorders like GAD. In this study, we examined whether the OPRM1 gene, which has been implicated in antidepressant treatment response in major depressive disorder, also has an effect in GAD. In our study, 156 patients diagnosed with GAD received venlafaxine XR treatment as part of an 18-month relapse prevention study. Genotypes were obtained for the OPRM1 functional variant A118G for the entire sample (n = 151); however, only the European American population was considered (n = 108) for pharmacogenetic analysis. We found no significant association between A118G and antidepressant treatment response in our GAD population. Future studies that include different single nucleotide polymorphisms of the OPRM1 gene as well as larger populations will need to be conducted to further elucidate the pharmacogenetic role of the endogenous opioid system in anxiety disorders.

Reduced supraspinal nociceptive responses and distinct gene expression profile in CXBH recombinant inbred mice

CXBH mice, known as an "opioid receptor-rich" strain, are a recombinant inbred mouse strain established by crossing the C57BL/6By and BALB/cBy strains. In the present study, we investigated nociceptive and antinociceptive sensitivity in CXBH mice and elucidated the underlying molecular mechanisms. CXBH mice exhibited slightly higher morphine-induced antinociception compared with C57BL/6J and BALB/cBy mice in the hot-plate test but not tail-flick test. CXBH mice exhibited a marked reduction of nociceptive sensitivity, regardless of the type of nociceptive stimulus, with the exception of tail stimulation. Changes in gene expression that corresponded to reduced nociceptive sensitivity in the brains of CXBH mice were observed in 62 transcripts, including pain- and analgesia-related transcripts, in a whole-genome expression assay. The total mRNA expression of opioid receptors was higher in CXBH mice than in C57BL/6J and BALB/cBy mice. However, the expression levels of MOR-1 mRNA, a major transcript of the μ opioid receptor gene, were not different among the C57BL/6J, BALB/cBy, and CXBH strains. In conclusion, supraspinal nociceptive responses were reduced in the CXBH mouse strain, and the expression levels of transcripts were altered in the brain of this strain.

PERSPECTIVE

This article presents the nociceptive and antinociceptive properties of CXBH recombinant inbred mice and gene expression differences that may underlie nociceptive tolerance in the strain. The CXBH mouse strain may be a useful animal model to investigate the molecular basis of individual differences in supraspinal pain sensitivity.

The correlation between post-operative fentanyl requirements and μ-opioid receptor gene A118G polymorphism in patients undergoing radical gastrectomy

The aim of this study was to investigate the effect of the μ-opioid receptor gene (OPRM1) A118G polymorphism on the requirement for post-operative fentanyl analgesia in patients undergoing radical gastrectomy. One hundred and twenty-eight gastric cancer patients scheduled to undergo radical gastrectomy under general anesthesia were enrolled in the study. Post-operative, patient-controlled intravenous analgesia of fentanyl was provided for satisfactory analgesia until 48 h after surgery. OPRM1 A118G was screened by DNA sequence analysis of polymerase chain reaction (PCR)-amplified DNA. Differences in fentanyl consumption and adverse effects were compared among the different genotypes at 24 and 48 h after surgery. The ranges of fentanyl dose in the 128 patients at 24 and 48 h after surgery were 5.4-17.3 μg/kg and 12.4-29.9 μg/kg, respectively. Among these patients, there were 54 wild-type homozygotes (AA), 53 heterozygotes (AG) and 21 mutant homozygotes (GG). The frequency of the G allele was 0.371 in the OPRM1 polymorphism. There were no significant differences in fentanyl dose or adverse effects, including nausea, vomiting and dizziness, for the OPRM1 A118G polymorphism (P>0.05). The OPRM1 A118G polymorphism does not play a significant role in post-operative fentanyl analgesic dose or post-operative nausea, vomiting and dizziness in patients undergoing radical gastrectomy.

Polymorphism of A118G in μ-opioid receptor gene is associated with risk of esophageal squamous cell carcinoma in a Chinese population

BACKGROUND

Previous studies have indicated a direct effect of μ-opioid receptors on tumor progression or recurrence. An A118G polymorphism in the μ-opioid receptor gene was believed to play an important role in this carcinogenic process. The aim of the present study was to investigate the association between the A118G polymorphism and the risk of esophageal squamous cell carcinoma (ESCC) in a Chinese population.

METHOD

The case-control study included 260 cancer patients and 291 controls from a Chinese Han and Chinese TuJia population in Enshi region, China. Genotypes were determined by TaqMan platform. Odds ratios (ORs) and 95 % confidence intervals (CIs) were calculated using multivariate unconditional logistic regression.

RESULTS

Compared with the G/G genotype, the A/A genotype exhibited a significantly elevated risk for ESCC (OR = 3.12, 95 % CI [1], 1.11-6.01). A significant interaction between the A118G polymorphism and age, smoking status, and family history of cancer was also found (OR = 2.25, 95 % CI 1.36-4.12; OR = 1.75, 95 % CI 1.23-2.32; OR = 3.14, 95 % CI 1.31-7.28, respectively).

CONCLUSION

The A118G polymorphism in the μ-opioid receptor gene might be associated with the risk of ESCC in Chinese population.

ABCB1 haplotype and OPRM1 118A > G genotype interaction in methadone maintenance treatment pharmacogenetics

BACKGROUND

Genetic variability in ABCB1, encoding the P-glycoprotein efflux transporter, has been linked to altered methadone maintenance treatment dose requirements. However, subsequent studies have indicated that additional environmental or genetic factors may confound ABCB1 pharmacogenetics in different methadone maintenance treatment settings. There is evidence that genetic variability in OPRM1, encoding the mu opioid receptor, and ABCB1 may interact to affect morphine response in opposite ways. This study aimed to examine whether a similar gene-gene interaction occurs for methadone in methadone maintenance treatment.

METHODS

Opioid-dependent subjects (n = 119) maintained on methadone (15-300 mg/day) were genotyped for five single nucleotide polymorphisms of ABCB1 (61A > G; 1199G > A; 1236C > T; 2677G > T; 3435C > T), as well as for the OPRM1 118A > G single nucleotide polymorphism. Subjects' methadone doses and trough plasma (R)-methadone concentrations (C(trough)) were compared between ABCB1 haplotypes (with and without controlling for OPRM1 genotype), and between OPRM1 genotypes (with and without controlling for ABCB1 haplotype).

RESULTS

Among wild-type OPRM1 subjects, an ABCB1 variant haplotype group (subjects with a wild-type and 61A:1199G:1236C:2677T:3435T haplotype combination, or homozygous for the 61A:1199G:1236C:2677T:3435T haplotype) had significantly lower doses (median ± standard deviation 35 ± 5 versus 180 ± 65 mg/day, P < 0.01) and C(trough) (78 ± 22 versus 177 ± 97 ng/mL, P < 0.05) than ABCB1 wild-type subjects. Among subjects with the most common ABCB1 haplotype combination (wild-type with 61A:1199G:1236T:2677T:3435T), the OPRM1 118 A/G genotype was associated with a significantly higher C(trough) than 118 A/A (250 ± 126 versus 108 ± 36 ng/mL, P = 0.016). No ABCB1 haplotype group or OPRM1 genotype was associated with dose or C(trough) without taking into account confounding genetic variability at the other locus. Therefore, two interacting pharmacogenetic determinants of methadone maintenance treatment response were identified, ie, ABCB1, where variants are associated with lower methadone requirements, and OPRM1, where the variant is associated with higher methadone requirements.

CONCLUSION

These opposing pharmacogenetic effects therefore need to be considered in combination when assessing methadone maintenance treatment pharmacogenetics.