Who's your daddy? Behavioral and epigenetic consequences of paternal drug exposure

Paternal exposure to antiseizure medications and offspring outcomes: a systematic review

BACKGROUND

Concerns have recently been raised about risks to the fetus resulting from paternal exposure to antiseizure medications (ASMs). To address these concerns, we conducted a systematic review of the literature to assess neurodevelopmental and anatomical outcomes in offspring born to fathers taking ASMs at the time of conception.

METHODS

Electronic searches of MEDLINE, PsycINFO, and Embase were conducted to identify human studies published in English that reported on outcomes, comprising neurodevelopmental disorders, major congenital malformations, small-for-gestational age or low birth weight, in offspring of fathers taking ASMs at conception. Quality analysis of included studies was undertaken using the Newcastle-Ottawa Scale. A narrative synthesis was used to report study findings.

RESULTS

Of 923 studies identified by the search and screened by title and abstract, 26 underwent full-text review and 10 met eligibility criteria. There was limited evidence available, but there appeared to be no clear evidence for an adverse impact of paternal ASM use on offspring outcomes. Few isolated adverse findings were not replicated by other investigations. Several methodological limitations prevented meta-analysis, including failure by most studies to report outcomes separately for each individual ASM, heterogeneity in measurement and outcome reporting, and small numbers of monotherapy exposures.

CONCLUSIONS

Although there were limited data available, this systematic review provides reassuring evidence that paternal exposure to ASMs at conception is unlikely to pose any major risk of adverse outcomes for the offspring. Further research is needed to examine the relationship between preconception ASM use in males and offspring outcomes at birth and postnatally.

Beyond a simple cause and effect relationship: Exploring the long-term outcomes of children prenatally exposed to opioids and other substances

The long-term outcomes of children exposed to opioids and other substances in utero, specifically those diagnosed with Neonatal Abstinence Syndrome (NAS), present a complex interaction of different factors. First, NAS and its clinical presentation will be defined, then summarized will be an overview of NAS prevalence, recent trends, and significance of NAS in the context of the rising synthetic opioid and polysubstance use. Highlighted will also be the identified risk factors for NAS, especially regarding the role of environmental and psychosocial stressors during pregnancy. Finally, reviewed will be the existing NAS literature, including its gaps and limitations, and suggested recommendations for future research and policy considerations for improving care for children and families impacted by NAS.

Influence of substance use on male reproductive health and offspring outcomes

The prevalence of substance use globally is rising and is highest among men of reproductive age. In Africa, and South and Central America, cannabis use disorder is most prevalent and in Eastern and South-Eastern Europe, Central America, Canada and the USA, opioid use disorder predominates. Substance use might be contributing to the ongoing global decline in male fertility, and emerging evidence has linked paternal substance use with short-term and long-term adverse effects on offspring development and outcomes. This trend is concerning given that substance use is increasing, including during the COVID-19 pandemic. Preclinical studies have shown that male preconception substance use can influence offspring brain development and neurobehaviour through epigenetic mechanisms. Additionally, human studies investigating paternal health behaviours during the prenatal period suggest that paternal tobacco, opioid, cannabis and alcohol use is associated with reduced offspring mental health, in particular hyperactivity and attention-deficit hyperactivity disorder. The potential effects of paternal substance use are areas in which to focus public health efforts and health-care provider counselling of couples or individuals interested in conceiving.

METH exposure alters sperm DNA methylation in F0 mice and mPFC transcriptome in male F1 mice

RATIONALE

Methamphetamine (METH) exposure has toxicity in sperm epigenetic phenotype and increases the risk for developing addiction in their offspring. However, the underlying transgenerational mechanism remains unclear.

OBJECTIVES

The current study aims to investigate the profiles of sperm epigenetic modifications in male METH-exposed mice (F0) and medial prefrontal cortex (mPFC) transcriptome in their male first-generation offspring (F1).

METHODS

METH-related male F0 and F1 mice model was established to investigate the effects of paternal METH exposure on reproductive functions and sperm DNA methylation in F0 and mPFC transcriptomic profile in F1. During adulthood, F1 was subjected to a conditioned place preference (CPP) test to evaluate sensitivity to METH. The gene levels were verified with qPCR.

RESULTS

METH exposure obviously altered F0 sperms DNA methylated profile and male F1 mPFC transcriptomic profile, many of which being related to neuronal system and brain development. In METH-sired male F1, subthreshold dose of METH administration effectively elicited CPP, along with more mPFC activation. After qPCR verification, Sort1 and Shank2 were at higher levels in F0 sperm and F1 mPFC.

CONCLUSIONS

Our findings put new insights into paternal METH exposure-altered profiles of F0 sperm DNA methylation and male F1 mPFC transcriptomics. Several genes, such as Sort1 and Shank2, might be used as potential molecules for further research on the transgenerational vulnerability to drug addiction in offspring by paternal drug exposure.

Oxidative Stress Biomarkers in Male Infertility: Established Methodologies and Future Perspectives

Male fertility can be affected by oxidative stress (OS), which occurs when an imbalance between the production of reactive oxygen species (ROS) and the body's ability to neutralize them arises. OS can damage cells and influence sperm production. High levels of lipid peroxidation have been linked to reduced sperm motility and decreased fertilization ability. This literature review discusses the most commonly used biomarkers to measure sperm damage caused by ROS, such as the high level of OS in seminal plasma as an indicator of imbalance in antioxidant activity. The investigated biomarkers include 8-hydroxy-2-deoxyguanosine acid (8-OHdG), a marker of DNA damage caused by ROS, and F2 isoprostanoids (8-isoprostanes) produced by lipid peroxidation. Furthermore, this review focuses on recent methodologies including the NGS polymorphisms and differentially expressed gene (DEG) analysis, as well as the epigenetic mechanisms linked to ROS during spermatogenesis along with new methodologies developed to evaluate OS biomarkers. Finally, this review addresses a valuable insight into the mechanisms of male infertility provided by these advances and how they have led to new treatment possibilities. Overall, the use of biomarkers to evaluate OS in male infertility has supplied innovative diagnostic and therapeutic approaches, enhancing our understanding of male infertility mechanisms.

Paternal alcohol exposure attenuates maintenance and reinstated operant responding for alcohol in the offspring of rats

BACKGROUND

The heritability of alcohol use disorder is close to 50%, yet common genetic variants account for less than 5% of risk. The missing heritability may reflect environmental exposure in the parents prior to conception. Indeed, paternal alcohol exposure has many behavioral and biological consequences for rodent offspring. We recently found that paternal alcohol exposure attenuated the acquisition of operant alcohol self-administration in offspring of rats of both sexes. Here we test whether this effect extends to other phases of operant self-administration thought to model motivation, craving, and relapse.

METHODS

Wistar male rats exposed to alcohol vapors or air for 6 weeks were mated with alcohol-naïve females 8 weeks later. The adult offspring were trained to lever press for alcohol and tested under several conditions: (1) maintenance responding under a progressive ratio schedule, (2) extinction responding due to removal of the alcohol delivery contingency, (3) reinstatement of extinguished responding in the presence of alcohol-associated cues, and (4) reinitiation of lever press responding for alcohol delivery under fixed and progressive ratio schedules.

RESULTS

Alcohol-sired offspring showed reduced responding under the progressive ratio schedule and blunted cue-induced reinstatement of extinguished responding. Alcohol-sired offspring also emitted fewer responses during extinction sessions and did not reinitiate responding to the same extent as control-sired rats after alcohol delivery was restored.

CONCLUSIONS

Across all conditions, paternal alcohol exposure led to a reduction in the reinforcing effects of alcohol in offspring. These results are consistent with studies conducted with paternal cocaine exposure except that here we find effects in rats of both sexes.

Developmental origins of health and disease: Impact of paternal nutrition and lifestyle

Most epidemiological and experimental studies have focused on maternal influences on offspring's health. The impact of maternal undernutrition, overnutrition, hypoxia, and stress is linked to adverse offspring outcomes across a range of systems including cardiometabolic, respiratory, endocrine, and reproduction among others. During the past decade, it has become evident that paternal environmental factors are also linked to the development of diseases in offspring. In this article, we aim to outline the current understanding of the impact of male health and environmental exposure on offspring development, health, and disease and explore the mechanisms underlying the paternal programming of offspring health. The available evidence suggests that poor paternal pre-conceptional nutrition and lifestyle, and advanced age can increase the risk of negative outcomes in offspring, via both direct (genetic/epigenetic) and indirect (maternal uterine environment) effects. Beginning at preconception, and during utero and the early life after birth, cells acquire an epigenetic memory of the early exposure which can be influential across the entire lifespan and program a child's health. Potentially not only mothers but also fathers should be advised that maintaining a healthy diet and lifestyle is important to improve offspring health as well as the parental health status. However, the evidence is mostly based on animal studies, and well-designed human studies are urgently needed to verify findings from animal data.

An epigenetic synopsis of parental substance use

The rate of substance use is rising, especially among reproductive-age individuals. Emerging evidence suggests that paternal pre-conception and maternal prenatal substance use may alter offspring epigenetic regulation (changes to gene expression without modifying DNA) and outcomes later in life, including neurodevelopment and mental health. However, relatively little is known due to the complexities and limitations of existing studies, making causal interpretations challenging. This review examines the contributions and influence of parental substance use on the gametes and potential transmissibility to the offspring's epigenome as possible areas to target public health warnings and healthcare provider counseling of individuals or couples in the pre-conception and prenatal periods to ultimately mitigate short- and long-term offspring morbidity and mortality.

Paternal alcohol exposure has task- and sex-dependent behavioral effect in offspring

BACKGROUND

Endophenotypes for alcohol use disorder are well known and may reflect paternal exposure effects passed down to offspring via epigenetic mechanisms. Previously, we showed that paternal alcohol exposure prior to conception attenuates the acquisition of operant alcohol self-administration. We now test whether paternal alcohol exposure alters their offsprings' behavioral responses to alcohol (endophenotypes) and global DNA methylation levels in reward-related brain regions.

METHODS

Adult male rats were exposed to alcohol vapors or air for 6 weeks and mated with alcohol-naïve females 8 weeks later. Adult male and female offspring of the alcohol- and control-sired litters were tested on three behaviors 30 m after gavage with water or alcohol (1.5 g/kg): open field, elevated plus maze, and accelerating rotarod. Global DNA methylation levels in sperm, nucleus accumbens, and prefrontal cortex were examined in male sires and in another group of offspring.

RESULTS

Alcohol-sired males showed less anxiety-like behavior in the elevated plus maze that was not affected by alcohol administration. By contrast, alcohol had anxiolytic effects in the open field in male offspring only with no paternal alcohol effect. Neither paternal alcohol exposure nor alcohol administration altered locomotor activity in either sex. Sex-specific effects of paternal alcohol exposure were seen in the rotarod test. Alcohol-sired male offspring showed blunted sensitivity to the alcohol's motor-impairing effects, whereas alcohol-sired female offspring showed enhanced sensitivity. Global DNA methylation was altered in the sperm of alcohol-exposed males, but no changes were seen in their offspring.

CONCLUSIONS

Paternal alcohol exposure prior to conception has sex- and task-dependent effects on unconditioned behaviors in their offspring.

Situating the Father: Strengthening Interdisciplinary Collaborations between Sociology, History and the Emerging POHaD Paradigm

(1) Background: Albeit the main focus remains largely on mothers, in recent years Developmental Origins of Health and Disease (DOHaD) scientists, including epigeneticists, have started to examine how a father's environment affects disease risk in children and argued that more attention needs to be given to father's health-related behaviors for their influence on offspring at preconception (i.e., sperm health) as well as paternal lifestyle influences over the first 1000 days. This research ushers in a new paternal origins of health and disease (POHaD) paradigm and is considered a welcome equalization to the overemphasis on maternal influences. Epigeneticists are excited by the possibilities of the POHaD paradigm but are also cautious about how to interpret data and avoid biased impression of socio-biological reality. (2) Methods: We review sociological and historical literatures on the intersection of gender, food and diet across different social and historical contexts to enrich our understanding of the father; (3) Results: Sociological and historical research on family food practices and diet show that there are no "fathers" in the abstract or vacuum, but they are differently classed, racialized and exist in socially stratified situations where choices may be constrained or unavailable. This confirms that epigeneticists researching POHaD need to be cautious in interpreting paternal and maternal dietary influences on offspring health; (4) Conclusions: We suggest that interdisciplinary approach to this new paradigm, which draws on sociology, history and public health, can help provide the social and historical context for interpreting and critically understanding paternal lifestyles and influences on offspring health.

Sex-specific neurobehavioural outcomes and brain stimulation pattern in adult offspring paternally exposed to methamphetamine

Paternal methamphetamine (METH) exposure results in long-term behavioural deficits in the sub-generations with a sex difference. Here, we aim to investigate the sex-specific neurobehavioural outcomes in the first-generation offspring mice (F1 mice) paternally exposed to METH prior to conception and explore the underlying brain mechanisms. We found that paternal METH exposure increased anxiety-like behaviours and spatial memory deficits only in female F1 mice and caused depression-like behaviours in the offspring without sex-specific differences. In parallel, METH-sired F1 mice exhibited sex-specific brain activity pattern in response to mild stimulus (in water at room temperature for 3 min). Overall, paternal METH exposure caused a blunting phenomenon of prelimbic cortex (PrL), infralimbic cortex (IL) and nucleus accumbens (NAc) core in both male and female F1 mice, as indicated by the decreased c-Fos levels under mild stimulus. Of note, the activity of central nucleus of the amygdala (CeA) by mild stimulus was triggered in male but suppressed in female F1 mice, whereas the neurons of orbitofrontal cortex (OFC), cingulate cortex (Cg1), NAc shell, medial habenula (mHb), dorsal hippocampal CA1 (dCA1) and ventral hippocampal CA1 (vCA1) were only blunted in female F1 mice. Taken together, the distinct brain stimulation patterns between male and female F1 mice might contribute to the sex-specific behavioural outcomes by paternal METH exposure, which indicate that sex differences should be considered in the treatment of offspring paternally exposed drugs.

Paternal alcohol exposure reduces acquisition of operant alcohol self-administration and affects Bdnf DNA methylation in male and female offspring

Familial transmission of alcohol use disorder reflects genetic and environmental factors. Paternal alcohol exposure may affect rodent offspring via epigenetic modifications transmitted through the male germ line. While such exposure alters alcohol sensitivity in mouse offspring, no studies examined if it impacts the development of operant alcohol self-administration in rats. We exposed male (sires) Wistar rats to chronic intermittent ethanol in vapour chambers (16 h/day; 5 days/week) or to air for 6 weeks. Eight weeks later, rats were mated with alcohol-naive females. Adult alcohol- and control-sired F1 offspring were assessed in acquisition of alcohol self-administration in which increasing alcohol concentrations (2.5%, 5% and 10%, v/v) were delivered after one lever press (fixed ratio 1 or FR1). Prior to alcohol sessions, rats were trained to lever press for food delivery under an FR1 schedule of reinforcement. DNA methylation levels of the brain derived neurotrophic factor (Bdnf) gene were measured in sperm, nucleus accumbens (NAc) and medial prefrontal cortex (mPFC) in sires and in offspring. Alcohol-exposed sires had lower Bdnf DNA methylation levels in NAc and greater methylation levels in mPFC. Although this pattern was not recapitulated in offspring, alcohol-sired offspring of both sexes did show aberrant Bdnf DNA methylation patterns compared to control-sired offspring. Alcohol-sired offspring self-administered less alcohol (5% and 10%) with no group differences in food responding. Results indicate that paternal alcohol exposure prior to conception protects against alcohol's initial reinforcing effects but the pattern of dysregulated Bdnf methylation in reward-related circuitry did not mimic changes seen in sires.

Epigenetics of Male Infertility: The Role of DNA Methylation

In recent years, a number of studies focused on the role of epigenetics, including DNA methylation, in spermatogenesis and male infertility. We aimed to provide an overview of the knowledge concerning the gene and genome methylation and its regulation during spermatogenesis, specifically in the context of male infertility etiopathogenesis. Overall, the findings support the hypothesis that sperm DNA methylation is associated with sperm alterations and infertility. Several genes have been found to be differentially methylated in relation to impaired spermatogenesis and/or reproductive dysfunction. Particularly, DNA methylation defects of MEST and H19 within imprinted genes and MTHFR within non-imprinted genes have been repeatedly linked with male infertility. A deep knowledge of sperm DNA methylation status in association with reduced reproductive potential could improve the development of novel diagnostic tools for this disease. Further studies are needed to better elucidate the mechanisms affecting methylation in sperm and their impact on male infertility.

Repeated ethanol intoxications of Drosophila melanogaster adults increases the resistance to ethanol of their progeny

BACKGROUND

For decades, Drosophila melanogaster has been used as a model organism to understand the genetics and neurobiology of ethanol intoxication and tolerance. Previous research has shown that acute and chronic pre-exposures to ethanol can trigger the development of functional ethanol tolerance in flies and has unveiled some of the genetic pathways involved in the process. To our knowledge, however, no previous work has systematically explored whether repeated intoxications of adult flies can affect the ethanol tolerance of their progeny.

METHODS

Adult flies were intoxicated several times (once daily, over several days), and their F1 and F2 progeny were subjected to a functional tolerance test in which flies are exposed to ethanol and video recorded twice within 5 hr. Their behavior was subsequently analyzed to determine how long it took them to become sedated during the first and second exposures. One- and 2-way ANOVAs were used to determine whether parental treatment had an effect on their progeny's baseline resistance and/or acquired functional tolerance to ethanol.

RESULTS

Parental flies that were intoxicated several times produced F1 and F2 progeny with a significantly higher resistance to ethanol than progeny from unexposed controls. Further, parental intoxications inconsistently increased the progeny's capacity to develop rapid functional tolerance upon re-exposure to ethanol. The transmission of increased ethanol resistance to progeny lasted several days after the last parental intoxication.

CONCLUSION

To our knowledge, this is the first demonstration that repeated parental daily intoxications affect the progeny's response to ethanol in fruit flies. Our findings support the use of D. melanogaster to explore conserved pathways underlying the transmission of ethanol tolerance and can help in the identificaton of novel strategies for managing alcohol use disorder.

Epigenetics of the developing and aging brain: Mechanisms that regulate onset and outcomes of brain reorganization

Brain development is a life-long process that encompasses several critical periods of transition, during which significant cognitive changes occur. Embryonic development, puberty, and reproductive senescence are all periods of transition that are hypersensitive to environmental factors. Rather than isolated episodes, each transition builds upon the last and is influenced by consequential changes that occur in the transition before it. Epigenetic marks, such as DNA methylation and histone modifications, provide mechanisms by which early events can influence development, cognition, and health outcomes. For example, parental environment influences imprinting patterns in gamete cells, which ultimately impacts gene expression in the embryo which may result in hypersensitivity to poor maternal nutrition during pregnancy, raising the risks for cognitive impairment later in life. This review explores how epigenetics induce and regulate critical periods, and also discusses how early environmental interactions prime a system towards a particular health outcome and influence susceptibility to disease or cognitive impairment throughout life.

Food Addiction and Psychosocial Adversity: Biological Embedding, Contextual Factors, and Public Health Implications

The role of stress, trauma, and adversity particularly early in life has been identified as a contributing factor in both drug and food addictions. While links between traumatic stress and substance use disorders are well documented, the pathways to food addiction and obesity are less established. This review focuses on psychosocial and neurobiological factors that may increase risk for addiction-like behaviors and ultimately increase BMI over the lifespan. Early childhood and adolescent adversity can induce long-lasting alterations in the glucocorticoid and dopamine systems that lead to increased addiction vulnerability later in life. Allostatic load, the hypothalamic-pituitary-adrenal axis, and emerging data on epigenetics in the context of biological embedding are highlighted. A conceptual model for food addiction is proposed, which integrates data on the biological embedding of adversity as well as upstream psychological, social, and environmental factors. Dietary restraint as a feature of disordered eating is discussed as an important contextual factor related to food addiction. Discussion of various public health and policy considerations are based on the concept that improved knowledge of biopsychosocial mechanisms contributing to food addiction may decrease stigma associated with obesity and disordered eating behavior.