Will Widespread Synthetic Opioid Consumption Induce Epigenetic Consequences in Future Generations?

Maternal exposure to buprenorphine, but not methadone, during pregnancy reduces social play behavior across two generations of offspring

RATIONALE

The prevalence of newborns exposed to medications for opioid use disorder (MOUD), such as methadone or buprenorphine, during pregnancy is increasing. The opioid system plays a crucial role in regulating and shaping social behavior, and children prenatally exposed to opioids face an increased risk of developing behavioral problems. However, the impact of prenatal exposure to MOUD on offspring's social behavior during adolescence and adulthood, as well as potential intergenerational effects, remains largely unexplored.

OBJECTIVES

Our study employed a translationally relevant animal model to investigate how maternal (F0) exposure to MOUD during pregnancy affects social behavior in young and adult rats across the first (F1) and second (F2) generation of offspring.

METHODS

Female Sprague-Dawley rats were implanted with an osmotic minipump delivering methadone (10 mg/kg/day), buprenorphine (1 mg/kg/day), or sterile water, prior to mating with drug-naïve males. Adult F1 females were mated with treatment-matched F1 males to generate F2 offspring. We assessed social play behavior in juvenile offspring, and social interaction behavior in a three-chamber social interaction test in young adults of the F1 and F2 generations.

RESULTS

Maternal exposure to buprenorphine, but not methadone, during pregnancy reduced social play behavior in both F1 and F2 offspring, expressed by a reduced number of pounces and pins, which are the two most characteristic parameters of social play in rats. Adult social interactions were unaffected by prenatal MOUD exposure across both generations.

CONCLUSIONS

Maternal exposure to buprenorphine during pregnancy may have adverse effects on social play behavior across two generations of offspring.

Transgenerational inheritance and its modulation by environmental cues

The epigenome plays an important role in shaping phenotypes. However, whether the environment can alter an organism's phenotype across several generations through epigenetic remodeling in the germline is still a highly debated topic. In this chapter, we briefly review the mechanisms of epigenetic inheritance and their connection with germline development before highlighting specific developmental windows of susceptibility to environmental cues. We further discuss the evidence of transgenerational inheritance to a range of different environmental cues, both epidemiological in humans and experimental in rodent models. Doing so, we pinpoint the current challenges in demonstrating transgenerational inheritance to environmental cues and offer insight in how recent technological advances may help deciphering the epigenetic mechanisms at play. Together, we draw a detailed picture of how our environment can influence our epigenomes, ultimately reshaping our phenotypes, in an extended theory of inheritance.

Development of anxiety-like behaviors during adolescence: Persistent effects of adolescent morphine exposure in male rats

Epidemiological studies show the prevalence of opioid use, misuse and abuse in adolescents, which imposes social and economic accountability worldwide. Chronic opioid exposure, especially in adolescents, may have lasting effects on emotional behaviors that persist into adulthood. The current experiments were therefore designed to study the effects of sustained opioid exposure during adolescence on anxiety-like behaviors. Adolescent male Wistar rats underwent increasing doses of morphine for 10 days (PNDs 31-40). After that the open field test (OFT) and elevated plus maze (EPM) test were performed over a 4-week postmorphine treatment from adolescence to adulthood. Moreover, the weight of the animals was measured at these time points. We found that chronic adolescent morphine exposure reduces the weight gain during the period of morphine treatment and 4 weeks after that. It had no significant effect on the locomotor activity in the animals. Moreover, anxiolytic-like behavior was observed in the rats exposed to morphine during adolescence evaluated by OFT and EPM test. Thus, long-term exposure to morphine during adolescence has the profound potential of altering the anxiety-like behavior profile in the period from adolescence to adulthood. The maturation of the nervous system can be affected by drug abuse during the developmental window of adolescence and these effects may lead to behaviorally stable alterations.

Opioid use, misuse, and abuse: a narrative review about interventions to reduce opioid consumption and related adverse events in the perioperative setting

Opioids remain the most potent and predictable drug available for perioperative analgesia and moderate-to-severe cancer-related pain. However, their efficacy has been questioned in other clinical settings. Moreover, opioids are associated with a wide variety of dose-dependent adverse events, limiting their use. The indiscriminate prescription of opioids has fueled the so-called "opioid epidemic" in the United States and other developed countries. Thus, there has been a significant effort to develop strategies to curtail their unnecessary prescription. Here, we summarize the history, current trends, and new directions in perioperative opioid prescription in an unbiased manner.

Epigenetic Alterations in Prescription Opioid Misuse: New Strategies for Precision Pain Management

Prescription opioids are used for some chronic pain conditions. However, generally, long-term therapy has unwanted side effects which may trigger addiction, overdose, and eventually cause deaths. Opioid addiction and chronic pain conditions have both been associated with evidence of genetic and epigenetic alterations. Despite intense research interest, many questions about the contribution of epigenetic changes to this typology of addiction vulnerability and development remain unanswered. The aim of this review was to summarize the epigenetic modifications detected in specific tissues or brain areas and associated with opioid prescription and misuse in patients who have initiated prescribed opioid management for chronic non-cancer pain. The review considers the effects of opioid exposure on the epigenome in central and peripheral tissues in animal models and human subjects and highlights the mechanisms in which opioid epigenetics may be involved. This will improve our current understanding, provide the basis for targeted, personalized pain management, and thus balance opioid risks and benefits in managing chronic pain.

Cohort-based analysis of paternal opioid use in relation to offspring's BMI and plasma lipid profile

A growing body of evidence suggests that opioid use may affect consumer’s offspring by second-hand passive smoke exposure, as well as by transgenerational impacts mediated by genetic and epigenetic alterations of paternal gametes. In human studies, these effects are limited to investigating the neural, behavioral and cognitive characteristics of offspring. Only animal studies have investigated the metabolic parameters influenced by passive opium smoke exposure. Here, we conducted population-based analyses aimed to estimate the association of paternal opioid consumption, started before or after child birth, with BMI status and plasma lipid profile of young adult offspring. The present study includes 840 parents-offspring trios (offspring aged 15–35, parents aged 35–70) who participated in the prospective Rafsanjan Cohort Study (RCS)—a city in the south-east of Iran—as one of the district areas of the PERSIAN cohort (Prospective Epidemiological Research Studies in IrAN). All procedures for interviews, anthropometric measurements and physical examinations, biological sample collection and laboratory tests for blood biochemical parameters were conducted according to the PERSIAN cohort protocol, and in the well-established RCS setting. Crude and adjusted multiple logistic regression analysis were conducted to assess the relationship of paternal regular opioid use with offspring’s BMI status, and plasma lipid factors. The prevalence of fathers who use opioids regularly among the studied trios was 42.8% (360/840). Our regression analyses demonstrated that paternal opioid use started pre-fatherhood is associated with 76% higher adjusted odds ratio (OR) of overweight/obesity in young offspring (adjusted OR 1.76 (95% CI 1.15–2.71)), adjusting for sex, age, parental BMIs, paternal smoking status and socioeconomic status index (WSI). This relationship persisted when fathers who used opioid by routes other than inhaling (oral) were excluded from logistic analysis (adjusted OR 1.73 (95% CI 1.12–2.68)). Interestingly, sex stratified analysis displayed a 201% increased odds ratio of overweight/obesity in sons of fathers who use opioid regularly, started after child birth (Adjusted OR 3.01 (95% CI 1.68–5.39), while no significant association was found in daughters (adjusted OR 0.74 (95% CI 0.35–1.54)). Additionally, increasing exposure–response relationships were observed between odds ratios of overweight/obesity and the number of years of paternal opioid use after birth (p-trend = 0.0008). Paternal regular opioid use started pre-fatherhood was associated with 54% lowered risk of underweight [adjusted OR 0.46 (95% CI 0.24–0.86)]. Finally, paternal opioid consumption started either before or after child birth did not show a significant association with the high level of the three parameters of plasma lipid factors (triglyceride, cholesterol and HDL-cholesterol) in offspring. Our results suggest that the environmental impacts of paternal regular opioid use may be sufficient to make an effect on male offspring metabolism independent of genetic and epigenetic impact on gametes.

Enriched environment and social isolation differentially modulate addiction-related behaviors in male offspring of morphine-addicted dams: The possible role of μ-opioid receptors and ΔFosB in the brain reward pathway

Prenatal opioids exposure negatively affects the neurobehavioral abilities of children born from dependence dams. Adolescent housing conditions can buffer the detrimental impacts of early life experiences or contradictory can worsen individual psychosocial functions. The present study investigated the effects of maternal morphine dependence and different rearing conditions on behaviors and protein expression in brain reward circuits of male pups. Female Wistar rats a week before conception, during pregnancy and lactation were injected twice daily with escalating doses of morphine or saline. On a postnatal day 21, male pups were weaned and subjected to three different environments for two months: standard (STD), isolated (ISO), or enriched environment (EE). The anxiety and drug-related reward were measured using elevated plus maze, open field test, and conditioned place preference. Western blotting was used to determine the protein level of ΔFosB and μ-opioid receptor proteins in the striatum and the midbrain of male offspring, respectively. Results showed that maternal morphine administration dramatically increased anxiety-like and morphine place preference behaviors in offspring. Also, ISO condition aggravated these behavioral outcomes. While, rearing in EE could attenuate anxiety and morphine conditioning in pups. At molecular levels, maternal morphine exposure and social isolation markedly increased both of ΔFosB and μ-opioid receptor proteins expression. However, rearing in the EE declined ΔFosB protein expression. Together, these findings help to elucidate long lasting impacts of early life morphine exposure and rearing environment on the behavioral and molecular profile of addicted individuals.

Transgenerational effects on anxiety-like behavior following adolescent morphine exposure in female rats

Global opioid use and misuse remains high, despite efforts to decrease rates of prescribing and diversion. Chronic exposure to opioids, particularly during critical periods of development, can lead to long-lasting effects, including effects that may extend to future generations. Using a rodent model, we have demonstrated significant transgenerational effects of female adolescent morphine exposure, despite the absence of in utero drug exposure. While these effects have been observed in both sexes, effects on anxiety-like behavior were only observed in F1 females. The current study was designed to examine both inter- and transgenerational effects of adolescent morphine exposure on anxiety-like behavior. Female Sprague Dawley rats were administered increasing doses of morphine (5-25 mg/kg s.c.) or saline for 10 days during adolescence (PND30-39). Adult diestrous female offspring (MORF1 or SALF1) and grand offspring (F2) were tested for anxiety-like behavior using the elevated plus maze (EPM). F1 females cross-fostered to donor mothers were also examined. The results show that MORF1 and MORF2 females spend significantly more time on the open arms of the EPM compared to SALF1 controls, an effect that persisted in cross-fostered females. Additional studies demonstrate that this effect is estrous cycle dependent, as decreased anxiety-like behavior was observed in diestrus, while increased anxiety-like behavior was observed in estrus. These behavioral effects were not associated with any differences in circulating corticosterone either at baseline or following EPM testing. Thus, female adolescent morphine exposure alters the regulation of anxiety-like behavior in an estrous-dependent manner and this effect persists in the F2 generation.

Cross-generational THC Exposure Weakly Attenuates Cocaine's Rewarding Effects in Adult Male Offspring

Adolescents represent a large demographic of marijuana consumers. Regrettably, use during this developmental period has been associated with above average health risks. A growing body of evidence suggests that adolescent drug use in the lifetime of a parent can modify behavior and neurochemistry in descendants without direct exposure. The current study was designed to evaluate the effects of pre-conception THC during adolescence on vulnerability to cocaine in adult male offspring. Male and female rats were given an intermittent THC (0 or 1.5 mg/kg) exposure regimen during the adolescent window and mated with drug group conspecifics in adulthood. F1-THC and F1-Veh pups were cross fostered to drug naïve control dams. In Experiment 1, adult offspring underwent cocaine (0 or 15 mg/kg) locomotor sensitization procedures and showed no effect of parental THC exposure on locomotor activity. In Experiment 2, intravenous catheters were implanted and subjects were tested under a number of reinforcement schedules with cocaine (FR1, FR5, FR10, PR, dose-response, extinction, cue + stress induced reinstatement). F1-THC subjects exhibited a slight decrease in cocaine responding during acquisition and a more rapid extinction, but they failed to produce significant differences on any other measure. These findings indicate that adolescent cannabis use likely has minimal effects on cocaine abuse liability in the next generation.

Novel Opioids: Systematic Web Crawling Within the e-Psychonauts' Scenario

Background

A wide range of novel psychoactive substances (NPSs) are regularly searched and discussed online by e-psychonauts. Among NPSs, the range of prescription/non-prescription opioids (fentanyl and non-fentanyl analogs) and herbal derivatives currently represents a challenge for governments and clinicians.

Methods

Using a web crawler (i.e., NPS.Finder^®), the present study aimed at assessing psychonaut fora/platforms to better understand the online situation regarding opioids.

Results

The open-web crawling/navigating software identified some 426 opioids, including 234 fentanyl analogs. Of these, 176 substances (162 were very potent fentanyls, including two ohmefentanyl and seven carfentanyl analogs) were not listed in either international or European NPS databases.

Conclusion

A web crawling approach helped in identifying a large number, indeed higher than that listed by European/international agencies, of unknown opioids likely to possess a significant misuse potential. Most of these novel/emerging substances are still relatively unknown. This is a reason of concern; each of these analogs potentially presents with different toxicodynamic profiles, and there is a lack of docking, preclinical, and clinical observations. Strengthening multidisciplinary collaboration between clinicians and bioinformatics may prove useful in better assessing public health risks associated with opioids.

Prenatal drug exposure and neurodevelopmental programming of glucocorticoid signalling

Prenatal neurodevelopment is dependent on precise functioning of multiple signalling pathways in the brain, including those mobilised by glucocorticoids (GC) and endocannabinoids (eCBs). Prenatal exposure to drugs of abuse, including opioids, alcohol, cocaine and cannabis, has been shown to not only impact GC signalling, but also alter functioning of the hypothalamic-pituitary-adrenal (HPA) axis. Such exposures can have long-lasting neurobehavioural consequences, including alterations in the stress response in the offspring. Furthermore, cannabis contains cannabinoids that signal via the eCB pathway, which is linked to some components of GC signalling in the adult brain. Given that GCs are frequently used in pregnancy to prevent complications of prematurity, and also that rates of cannabis use in pregnancy are increasing, the likelihood of foetal co-exposure to these compounds is high and may have additional implications for long-term neurodevelopment. Here, we present a discussion of GC signalling and the HPA axis, as well as the effects of prenatal drug exposure on these pathways and the stress response, and we explore the interactions between GC and EC signalling in the developing brain and potential for neurodevelopmental consequences.

General anesthesia, germ cells and the missing heritability of autism: an urgent need for research

Agents of general anesthesia (GA) are commonly employed in surgical, dental and diagnostic procedures to effectuate global suppression of the nervous system, but in addition to somatic targets, the subject's germ cells-from the embryonic primordial stage to the mature gametes-may likewise be exposed. Although GA is generally considered safe for most patients, evidence has accumulated that various compounds, in particular the synthetic volatile anesthetic gases (SVAGs) such as sevoflurane, can exert neurotoxic, genotoxic and epigenotoxic effects, with adverse consequences for cellular and genomic function in both somatic and germline cells. The purpose of this paper is to review the evidence demonstrating that GA, and in particular, SVAGs, may in some circumstances adversely impact the molecular program of germ cells, resulting in brain and behavioral pathology in the progeny born of the exposed cells. Further, we exhort the medical and scientific communities to undertake comprehensive experimental and epidemiological research programs to address this critical gap in risk assessment.

Mental health in youth prenatally exposed to opioids and poly-drugs and raised in permanent foster/adoptive homes: A prospective longitudinal study

BACKGROUND

Little is known about the mental health of prenatally opioid- and polydrug-exposed youth raised in foster/adoptive families.

AIM

To compare mental health problems among two groups of youth, one prenatally drug-exposed group with participants who were mainly placed in permanent foster or adoptive homes in early infancy and a group without known prenatal risk factors who were raised by their birth parents.

METHODS

The sample consisted of 45 drug-exposed and 48 nonexposed youth between 17 and 22 years old from an original sample of 136 followed since birth. An extended version of the Mini International Neuropsychiatric Interview was used to assess lifetime psychiatric disorder, and participants completed the Achenbach Adult Self-Report form and Cantril's Ladder of Life Satisfaction Scale.

RESULTS

A higher proportion of the youth in the drug-exposed group had lifetime experiences with major depressive episodes, alcohol abuse and attention deficit, hyperactivity disorder (OR > 3, p ≤ .030). They scored higher on the aggressive behavior scale, had more sexual partners and were younger at their sexual debut (p ≤ .030). There were no group differences in current self-reported satisfaction with life.

CONCLUSION

Youth exposed to drugs prenatally continue to represent a risk group despite early placement in permanent foster and adoptive homes. The factors contributing to this elevated risk may be multifaceted and involve adverse prenatal conditions including but not limited to drug exposure, genetics, and postnatal environmental conditions. The results highlight the need for longitudinal follow-up in the transition to adulthood as well as qualified service provision for these youth and their families.