Epigenetic variation in the mu-opioid receptor gene in infants with neonatal abstinence syndrome

Infants Born to Opioid-Dependent Women in Ontario, 2002-2014

BACKGROUND

There is a paucity of data characterizing mother-infant pairs with prenatal opioid dependence in Canada. We therefore conducted a study of relevant births in Ontario from 2002 to 2014.

METHODS

We used data from the Institute for Clinical Evaluative Sciences, the linked databases of coded population-based Ontario health services records. Differences in characteristics of opioid-dependent mother-neonate pairs and infant hospital costs by year were assessed using linear regression, and we calculated rates of preterm birth, low birth weight, birth defects, mortality, and neonatal abstinence syndrome.

RESULTS

The number of infants born to opioid-dependent women in Ontario rose from 46 in 2002 to almost 800 in 2014. Methadone was most frequently used for prenatal opioid dependence; there was little buprenorphine or buprenorphine + naloxone use. Rates of preterm birth and low birth weight were high. The proportion of neonates with neonatal abstinence syndrome (58%) was stable over the study period. The mean length of neonatal hospital stay was 13.96 days. Infant hospital costs increased from $724 774 in 2003 to $10 539 988 in 2013, and the mean cost per infant grew from $9928 to $12 917. Birth defect prevalence was 75.84/1000 live births (95% CI 68.12/1000 to 84.10/1000). The stillbirth rate was 11.39/1000 births (95% CI 8.47/1000 to 14.99/1000), and the infant mortality rate was 12.21/1000 live births (95% CI 9.16/1000 to 15.95/1000).

CONCLUSION

We observed a 16-fold increase in the number of mother-infant pairs affected by opioid dependence in Ontario over the past decade. Adverse birth outcome rates were high. Expanded services for opioid-dependent women and their children are needed.

Opioid Use in Pregnancy, Neonatal Abstinence Syndrome, and Childhood Outcomes: Executive Summary of a Joint Workshop by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, American College of Obstetricians and Gynecologists, American Academy of Pediatrics, Society for Maternal-Fetal Medicine, Centers for Disease Control and Prevention, and the March of Dimes Foundation

In April 2016, the Eunice Kennedy Shriver National Institute of Child Health and Human Development invited experts to a workshop to address numerous knowledge gaps and to review the evidence for the screening and management of opioid use in pregnancy and neonatal abstinence syndrome. The rising prevalence of opioid use in pregnancy has led to a concomitant dramatic fivefold increase in neonatal abstinence syndrome over the past decade. Experts from diverse disciplines addressed research gaps in the following areas: 1) optimal screening for opioid use in pregnancy; 2) complications of pregnancy associated with opioid use; 3) appropriate treatments for pregnant women with opioid use disorders; 4) the best approaches for detecting, treating, and managing newborns with neonatal abstinence syndrome; and 5) the long-term effects of prenatal opioid exposure on children. Workshop participants identified key scientific opportunities to advance the understanding of opioid use disorders in pregnancy and to improve outcomes for affected women, their children, and their families. This article provides a summary of the workshop presentations and discussions.

Neonatal abstinence syndrome: where are we, and where do we go from here?

PURPOSE OF REVIEW

Over the last 15 years the prevalence of neonatal abstinence syndrome (NAS) increased almost five-fold. A considerable diversity seems to prevail in the management of NAS. This review provides an overview of factors affecting the expression and course of NAS, and recent developments in NAS assessment and treatment.

RECENT FINDINGS

Apart from different pharmacological and nonpharmacological treatment modalities, maturity of the infant and genetic variations likely are (co)responsible for interpatient variability in NAS severity, despite similar maternal exposure. Recent efforts concerning the further development of NAS severity scoring systems focus on the development of brief screening measures; in addition, pupil diameter and skin conductance have been proposed as complements to observer-rated scales. The decrease in incidence of NAS begins in the appropriate management of medication assisted treatment of the mother.

SUMMARY

Mitigating the negative outcomes for infants affected by NAS, their mothers and the healthcare system implies, first and foremost, developing and implementing an organized protocol for the management of NAS, and the homogenous use of a standardized scoring system utilizing interobserver reliability and a guide for medication initiation, maintenance, and weaning which is consistent with traditional methods of treatment for neonates.

Neonatal abstinence syndrome: Neurobehavior at 6 weeks of age in infants with or without pharmacological treatment for withdrawal

Use and abuse of prescription opioids and concomitant increase in Neonatal Abstinence Syndrome (NAS), a condition that may lead to protracted pharmacological treatment in more than 60% of infants, has tripled since 2000. This study assessed neurobehavioral development using the NICU Network Neurobehavioral Scale in 6-week old infants with prenatal methadone exposure who did (NAS+; n = 23) or did not (NAS-; n = 16) require pharmacological treatment for NAS severity determined by Finnegan Scale. An unexposed, demographically similar group of infants matched for age served as comparison (COMP; n = 21). NAS+, but not NAS- group, had significantly lower scores on the regulation (p < .01) and quality of movement (p < .01) summary scales than the COMP group. The NAS+ and NAS- groups had higher scores on the stress-abstinence scale than the COMP group (p < .05). NAS diagnosis (NAS +) was associated with poorer regulation and quality of movement at 6 weeks of age compared to infants without prenatal methadone exposure from the same demographic.

DNA methylation at the mu-1 opioid receptor gene (OPRM1) promoter predicts preoperative, acute, and chronic postsurgical pain after spine fusion

Introduction

The perioperative pain experience shows great interindividual variability and is difficult to predict. The mu-1 opioid receptor gene (OPRM1) is known to play an important role in opioid-pain pathways. Since deoxyribonucleic acid (DNA) methylation is a potent repressor of gene expression, DNA methylation was evaluated at the OPRM1 promoter, as a predictor of preoperative, acute, and chronic postsurgical pain (CPSP).

Methods

A prospective observational cohort study was conducted in 133 adolescents with idiopathic scoliosis undergoing spine fusion under standard protocols. Data regarding pain, opioid consumption, anxiety, and catastrophizing (using validated questionnaires) were collected before and 2–3 months postsurgery. Outcomes evaluated were preoperative pain, acute postoperative pain (area under curve [AUC] for pain scores over 48 hours), and CPSP (numerical rating scale >3/10 at 2–3 months postsurgery). Blood samples collected preoperatively were analyzed for DNA methylation by pyrosequencing of 22 CpG sites at the OPRM1 gene promoter. The association of each pain outcome with the methylation percentage of each CpG site was assessed using multivariable regression, adjusting for significant (P<0.05) nongenetic variables.

Results

Majority (83%) of the patients reported no pain preoperatively, while CPSP occurred in 36% of the subjects (44/121). Regression on dichotomized preoperative pain outcome showed association with methylation at six CpG sites (1, 3, 4, 9, 11, and 17) (P<0.05). Methylation at CpG sites 4, 17, and 18 was associated with higher AUC after adjusting for opioid consumption and preoperative pain score (P<0.05). After adjusting for postoperative opioid consumption and preoperative pain score, methylation at CpG sites 13 and 22 was associated with CPSP (P<0.05).

Discussion

Novel CPSP biomarkers were identified in an active regulatory region of the OPRM1 gene that binds multiple transcription factors. Inhibition of binding by DNA methylation potentially decreases the OPRM1 gene expression, leading to a decreased response to endogenous and exogenous opioids, and an increased pain experience.

Elevated OPRD1 promoter methylation in Alzheimer's disease patients

Aberrant DNA methylation has been observed in the patients with Alzheimer’s disease (AD), a common neurodegenerative disorder in the elderly. OPRD1 encodes the delta opioid receptor, a member of the opioid family of G-protein-coupled receptors. In the current study, we compare the DNA methylation levels of OPRD1 promoter CpG sites (CpG1, CpG2, and CpG3) between 51 AD cases and 63 controls using the bisulfite pyrosequencing technology. Our results show that significantly higher CpG3 methylation is found in AD cases than controls. Significant associations are found between several biochemical parameters (including HDL-C and ALP) and CpG3 methylation. Subsequent luciferase reporter gene assay shows that DNA fragment containing the three OPRD1 promoter CpGs is able to regulate gene expression. In summary, our results suggest that OPRD1 promoter hypermethylation is associated with the risk of AD.

Pharmacogenetics in obstetric anesthesia

The 21st century has been billed as the era of "precision/personalized medicine." Genetic investigation of clinical syndromes may guide therapy as well as reveal previously unknown biological or pharmacological pathways that may result in novel drug therapies. Several clinical issues in obstetrics and obstetric anesthesiology have been targets for genetic investigations. These include evaluation of the genetic effects on preterm labor and the progression of labor, spinal anesthesia-induced hypotension and the response to medications used to treat hypotension, and the effect of gene variants on pain and analgesic responses. Most studies have examined specific single nucleotide polymorphisms. Findings have revealed modest effects of genetic variation without tangible impact on current clinical practice. Over the next decade, increased availability of whole exome and genome sequencing, epigenetics, large genetic databases, computational biology and other information technology, and more rapid methods of real-time genotyping may increase the impact of genetics in the clinical arena of obstetrics and obstetric anesthesia.

Decreasing Total Medication Exposure and Length of Stay While Completing Withdrawal for Neonatal Abstinence Syndrome during the Neonatal Hospital Stay

INTRODUCTION

Neonatal abstinence syndrome (NAS) is a rapidly growing public health concern that has considerably increased health-care utilization and health-care costs. In an effort to curtail costs, attempts have been made to complete withdrawal as an outpatient. Outpatient therapy has been shown to prolong exposure to medications, which may negatively impact neurodevelopmental and behavioral outcomes. We hypothesized that the implementation of a modified NAS protocol would decrease total drug exposure and length of stay while allowing for complete acute drug withdrawal during the neonatal hospital stay.

METHODS

Data were derived retrospectively from medical records of term (≥37 0/7) infants with NAS who were treated with pharmacologic therapy in the University of Louisville Hospital Neonatal Intensive Care Unit from 2005 to 2015. The pharmacologic protocol (SP1) for infants treated between 2005 and March 2014 (n = 146) dosed oral morphine every 4 h and utilized phenobarbital as adjuvant therapy. Protocol 2 (SP2) initiated after March 2014 (n = 44) dosed morphine every 3 h and used clonidine as adjuvant therapy. Charts were reviewed for demographic information and maternal drug history. Maternal and infant toxicology screens were recorded. The length of morphine therapy and need for adjuvant drug therapy were noted. Length of stay was derived from admission and discharge dates.

RESULTS

The length of morphine therapy was decreased by 8.5 days from 35 to 26.5 days (95% CI 4.5-12 days) for infants treated with SP2 vs. SP1 (p < 0.001). The need for adjuvant pharmacologic therapy was decreased by 24% in patients treated with SP2 vs. SP1 (p = 0.004). The length of stay was decreased by 9 days from 42 to 33 days (95% CI 5.1-13 days) for infants treated with SP2 vs. SP1 (p < 0.001). The decreased length of stay resulted in an average reduction of hospital charges by $27,090 per patient in adjusted 2015 US Dollars.

CONCLUSION

This study demonstrates that total drug exposure and length of stay can be reduced while successfully completing acute withdrawal during the neonatal hospital stay.

Neonatal abstinence syndrome and the gastrointestinal tract

Development of a healthy gut microbiome is essential in newborns to establish immunity and protection from pathogens. Recent studies suggest that infants who develop dysbiosis may be at risk for lifelong adverse health consequences. Exposure to opioid drugs during pregnancy is a factor of potential importance for microbiome health that has not yet been investigated. Since these infants are born after an entire gestation exposed to mu opioid receptor agonists and have severe gastrointestinal and neurological symptoms, we hypothesize that these infants are at risk for dysbiosis. We speculate that opioid exposure during gestation and development of NAS at birth may lead to a dysbiotic gut microbiome, which may impair normal microbiome succession and development, and impact future health of these children.

Clinical pharmacology of analgosedatives in neonates: ways to improve their safe and effective use

OBJECTIVES

To propose approaches tailored to the specific needs of neonates, such as structured product development programmes, with the ultimate goal to improve the safe and effective use of analgosedatives in these fragile patients.

KEY FINDINGS

The feasibility and relevance of a structured product development programme in neonates (optimal study design based on preliminary data; model development; internal, external and prospective evaluation; an individualized dosing regimen; long-term safety; pharmacogenetics) are illustrated for the use of morphine. Based on changes in clinical practices, similar development plans are in progress for short-acting analgosedatives such as propofol, but are in need of tailored pharmacodynamic tools to assess and quantify effects. Furthermore, for drugs like paracetamol where there is already sufficient clinical pharmacology knowledge, attention needs to be given to long-term safety aspects. Finally, new covariates such as pharmacogenetics might further improve neonatal pain management, but clearly need to be integrated with other well-established covariates like age or weight.

SUMMARY

Product development programmes for analgosedatives in neonates are needed. These programmes should be tailored to their specific needs (short-acting sedation, pain relief), should include long-term safety and should incorporate the exploration of newer covariates like pharmacogenetics.

Behavior and Attention Problems in Eight-Year-Old Children with Prenatal Opiate and Poly-Substance Exposure: A Longitudinal Study

Multiple studies have found that children born to mothers with opioid or poly-substance use during pregnancy have more behavior and attention problems and lower cognitive functioning than non-exposed children. The present study aimed to investigate whether behavior and attention problems are more prominent than general cognitive deficits in this risk group and whether the problems wane or increase over time. This prospective longitudinal cross-informant study compared 72 children who were prenatally exposed to heroin and multiple drugs with a group of 58 children without known prenatal risk factors. Group differences in caregivers' and teachers' reports of the children's behavior and attention problems based on the Child Behavior Check List and the ADHD Rating Scale were compared based on group differences in general cognitive functioning at 4 ½ and 8 ½ years of age. Both parent and teacher reports suggest that the exposed group has significantly more problems in several behavioral areas than the comparison group, particularly with regard to attention problems. The preschool teachers had already reported these problems when the children were 4 ½ years old, whereas the caregivers reported these problems mainly when the children were 8 ½ years old. The group differences in behavioral and attentional problems were not significantly greater and some were even significantly smaller than the group differences in general cognitive abilities. These findings suggest that children subject to prenatally drug exposure have increasing problems in multiple areas related to behavior from preschool age to 8 ½ years but that these problems do not seem to be specific; i.e., they are not more severe than the problems with general cognitive abilities found for this group.

Neonatal abstinence syndrome: Pharmacologic strategies for the mother and infant

Opioid use in pregnancy has increased dramatically over the past decade. Since prenatal opioid use is associated with numerous obstetrical and neonatal complications, this now has become a major public health problem. In particular, in utero opioid exposure can result in neonatal abstinence syndrome (NAS) which is a serious condition characterized by central nervous system hyperirritability and autonomic nervous system dysfunction. The present review seeks to define current practices regarding the approach to the pregnant mother and neonate with prenatal opiate exposure. Although the cornerstone of prenatal management of opioid dependence is opioid maintenance therapy, the ideal agent has yet to be definitively established. Pharmacologic management of NAS is also highly variable and may include an opioid, barbiturate, and/or α-agonist. Genetic factors appear to be associated with the incidence and severity of NAS. Establishing pharmacogenetic risk factors for the development of NAS has the potential for creating opportunities for "personalized genomic medicine" and novel, individualized therapeutic interventions.

Off-Target drug effects resulting in altered gene expression events with epigenetic and "Quasi-Epigenetic" origins

This review synthesizes examples of pharmacological agents who have off-target effects of an epigenetic nature. We expand upon the paradigm of epigenetics to include "quasi-epigenetic" mechanisms. Quasi-epigenetics includes mechanisms of drugs acting upstream of epigenetic machinery or may themselves impact transcription factor regulation on a more global scale. We explore these avenues with four examples of conventional pharmaceuticals and their unintended, but not necessarily adverse, biological effects. The quasi-epigenetic drugs identified in this review include the use of beta-lactam antibiotics to alter glutamate receptor activity and the action of cyclosporine on multiple transcription factors. In addition, we report on more canonical epigenome changes associated with pharmacological agents such as lithium impacting autophagy of aberrant proteins, and opioid drugs whose chronic use increases the expression of genes associated with addictive phenotypes. By expanding our appreciation of transcriptomic regulation and the effects these drugs have on the epigenome, it is possible to enhance therapeutic applications by exploiting off-target effects and even repurposing established pharmaceuticals. That is, exploration of "pharmacoepigenetic" mechanisms can expand the breadth of the useful activity of a drug beyond the traditional drug targets such as receptors and enzymes.

Endogenous opiates and behavior: 2014

This paper is the thirty-seventh consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2014 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 (endogenous opioids and receptors), and the roles of these opioid peptides and receptors in pain and analgesia (pain and analgesia); stress and social status (human studies); tolerance and dependence (opioid mediation of other analgesic responses); learning and memory (stress and social status); eating and drinking (stress-induced analgesia); alcohol and drugs of abuse (emotional responses in opioid-mediated behaviors); sexual activity and hormones, pregnancy, development and endocrinology (opioid involvement in stress response regulation); mental illness and mood (tolerance and dependence); seizures and neurologic disorders (learning and memory); electrical-related activity and neurophysiology (opiates and conditioned place preferences (CPP)); general activity and locomotion (eating and drinking); gastrointestinal, renal and hepatic functions (alcohol and drugs of abuse); cardiovascular responses (opiates and ethanol); respiration and thermoregulation (opiates and THC); and immunological responses (opiates and stimulants). This paper is the thirty-seventh consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2014 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 (endogenous opioids and receptors), and the roles of these opioid peptides and receptors in pain and analgesia (pain and analgesia); stress and social status (human studies); tolerance and dependence (opioid mediation of other analgesic responses); learning and memory (stress and social status); eating and drinking (stress-induced analgesia); alcohol and drugs of abuse (emotional responses in opioid-mediated behaviors); sexual activity and hormones, pregnancy, development and endocrinology (opioid involvement in stress response regulation); mental illness and mood (tolerance and dependence); seizures and neurologic disorders (learning and memory); electrical-related activity and neurophysiology (opiates and conditioned place preferences (CPP)); general activity and locomotion (eating and drinking); gastrointestinal, renal and hepatic functions (alcohol and drugs of abuse); cardiovascular responses (opiates and ethanol); respiration and thermoregulation (opiates and THC); and immunological responses (opiates and stimulants).

Long-Term Outcomes of Infants with Neonatal Abstinence Syndrome

Parents of infants with neonatal abstinence syndrome (NAS) in the NICU may have questions about the long-term consequences of prenatal exposure to methadone, both asked and unasked. Although the signs of withdrawal will abate relatively quickly, parents should be aware of potential vision, motor, and behavioral/cognitive problems, as well as sleeping disturbances and ear infections so their infants can be followed closely and monitored by their pediatrician with appropriate referrals made. Furthermore, this knowledge may inspire parents to enroll their infants in an early intervention program to help optimize their outcomes. There are still many unanswered questions about epigenetic consequences, risk for child abuse/neglect, and risk of future substance abuse in this population.

DNA Methylation Modulates Nociceptive Sensitization after Incision

DNA methylation is a key epigenetic mechanism controlling DNA accessibility and gene expression. Blockade of DNA methylation can significantly affect pain behaviors implicated in neuropathic and inflammatory pain. However, the role of DNA methylation with regard to postoperative pain has not yet been explored. In this study we sought to investigate the role of DNA methylation in modulating incisional pain and identify possible targets under DNA methylation and contributing to incisional pain. DNA methyltranferase (DNMT) inhibitor 5-Aza-2′-deoxycytidine significantly reduced incision-induced mechanical allodynia and thermal sensitivity. Aza-2′-deoxycytidine also reduced hindpaw swelling after incision, suggesting an anti-inflammatory effect. Global DNA methylation and DNMT3b expression were increased in skin after incision, but none of DNMT1, DNMT3a or DNMT3b was altered in spinal cord or DRG. The expression of proopiomelanocortin Pomc encoding β-endorphin and Oprm1 encoding the mu-opioid receptor were upregulated peripherally after incision; moreover, Oprm1 expression was further increased under DNMT inhibitor treatment. Finally, local peripheral injection of the opioid receptor antagonist naloxone significantly exacerbated incision-induced mechanical hypersensitivity. These results suggest that DNA methylation is functionally relevant to incisional nociceptive sensitization, and that mu-opioid receptor signaling might be one methylation regulated pathway controlling sensitization after incision.

Opioids in pregnancy and neonatal abstinence syndrome

Opiate use in pregnancy has increased dramatically over the past decade and now represents a major public health problem. More women are using prescription opioids, illegal opioids, and opioid-substitution therapy. These drugs have been associated with numerous obstetrical complications including intrauterine growth restriction, placental abruption, preterm delivery, oligohydramnios, stillbirth, and maternal death. Neonatal complications are also significant, such as an increased risk of mortality as well as neonatal abstinence syndrome (NAS). NAS is a serious and highly variable condition characterized by central nervous system hyperirritability and autonomic nervous system dysfunction. The present review seeks to define current practices regarding the management of opiate dependence in pregnancy and care of the neonate with prenatal opiate exposure. Since genetic factors appear to be associated with the incidence and severity of NAS, opportunities for "personalized genomic medicine" and unique therapeutic interventions could be developed in the future.

Variations in opioid receptor genes in neonatal abstinence syndrome

BACKGROUND

There is significant variability in the severity of neonatal abstinence syndrome (NAS) due to in-utero opioid exposure. We wanted to determine if single nucleotide polymorphisms (SNPs) in key candidate genes contribute to this variability.

METHODS

Full-term opioid-exposed newborns and their mothers (n=86 pairs) were studied. DNA was genotyped for 80 SNPs from 14 genes utilizing a custom designed microarray. The association of each SNP with NAS outcomes was evaluated.

RESULTS

SNPs in two opioid receptor genes in the infants were associated with worse NAS severity: (1) The PNOC rs732636 A allele (OR=3.8, p=0.004) for treatment with 2 medications and a longer hospital stay (LOS) of 5.8 days (p=0.01), and (2) The OPRK1 rs702764 C allele (OR=4.1, p=0.003) for treatment with 2 medications. The OPRM1 rs1799971 G allele (β=-6.9 days, p=0.02) and COMT rs740603 A allele (β=-5.3 days, p=0.01) were associated with shorter LOS. The OPRD1 rs204076 A allele in the mothers was associated with a longer LOS by 6.6 days (p=0.008). Results were significant point-wise but did not meet the experiment-wide significance level.

CONCLUSIONS

These findings suggest that SNPs in opioid receptor and the PNOC genes are associated with NAS severity. However, further testing in a large sample is warranted. This has important implications for prenatal prediction and personalized treatment regimens for infants at highest risk for severe NAS.

Methadone versus morphine for treatment of neonatal abstinence syndrome: a prospective randomized clinical trial

OBJECTIVE

Compare duration of treatment of neonatal abstinence syndrome between methadone and morphine.

STUDY DESIGN

A prospective, double-masked, randomized trial at a single site. Randomization of methadone or morphine was stratified for maternal treatment with methadone or buprenorphine. Inclusion criteria were (i) maternal treatment with prescribed methadone or buprenorphine, (ii) withdrawal treatment criteria, (iii) adjusted gestational age ⩾35(0/7) weeks and (iv) medically stable. Primary outcome was length of opioid treatment.

RESULT

From January 2011 through October 2012, 78 infants were eligible for the study: 41 methadone-exposed and 37 buprenorphine-exposed. Consent was obtained from 31 mothers, 13/41 (32%) methadone-treated and 18/37 (49%) buprenorphine-treated. Length of opioid treatment was significantly shorter for methadone than morphine treatment, median 14 versus 21 days (P=0.008).

CONCLUSION

Methadone had a shorter length of neonatal withdrawal treatment compared with morphine. Owing to the smaller sample size and single site, a larger randomized study is needed.