Prenatal ethanol exposure alters the expression of period genes governing the circadian function of beta-endorphin neurons in the hypothalamus

Characteristics of sleep in children with heavy prenatal alcohol exposure

BACKGROUND

Sleep plays an important role in neurodevelopment. However, the effects of prenatal alcohol exposure on sleep quality have been understudied, despite reports of sleep disturbance in infants prenatally exposed to alcohol and elevated levels of sleep problems reported by caregivers of children with fetal alcohol spectrum disorders. The current study characterizes sleep in children with prenatal alcohol exposure using both objective (actigraphy) and subjective (questionnaires, sleep diaries) methods.

METHODS

Participants aged 6-10 years, with and without prenatal alcohol exposure, were included in the study (alcohol-exposed [AE]: n = 35; control [CON]: n = 39). Objective sleep was measured via 24-h actigraphy for 2 weeks. Parents completed sleep diaries and sleep questionnaires (Children's Sleep Habits Questionnaire, Pediatric Sleep Questionnaire). Multivariate analysis of variance was used to characterize the sleep profile (objective, subjective) and examine group differences.

RESULTS

There were no group differences on actigraphy metrics averaged across 2 weeks. However, the AE group showed significantly greater intraindividual variability on most actigraphy measures, particularly total sleep time, percent sleep, wake after sleep onset, and number of wake bouts. Parents reported significantly more sleep problems in the AE group than in the CON group, primarily driven by night wakings, parasomnias (e.g., sleepwalking), snoring, and daytime sleepiness. These effects were more severe in children >8.5 years of age.

CONCLUSIONS

Despite similar 2-week average sleep outcomes, children with prenatal alcohol exposure showed greater intraindividual sleep variability and parents reported more sleep problems related to sleep behavior and snoring. These difficulties with sleep may be related to other cognitive and behavioral outcomes. Importantly, sleep is a modifiable behavior, and interventions that focus on variability in sleep, particularly in sleep duration, can impact the quality of life in children with prenatal alcohol exposure and their families.

Sexually dimorphic role of circadian clock genes in alcohol drinking behavior

Sex differences in alcohol use and abuse are pervasive and carry important implications for the prevention and treatment of alcohol use disorder (AUD), yet insight into underlying sexually dimorphic mechanisms is limited. Growing experimental and clinical evidence points to an important influence of circadian rhythms and circadian clock genes in the control of alcohol drinking behavior and AUD. Sex differences in the expression of circadian rhythms and in the molecular circadian clock that drive these rhythms have been reported in humans and animals. While studying the role of striatal circadian clock gene expression in the control of affective and goal-directed behaviors, we uncovered a novel sexually dimorphic function of the clock genes Bmal1 and Per2 in the control of voluntary alcohol consumption in mice, which may contribute to sex differences in alcohol drinking behavior. In this mini review, we briefly discuss relevant literature on AUD, circadian rhythms and clock genes, and on sex differences in these domains, and describe our own findings on clock genes as sexually dimorphic regulators of alcohol drinking behavior in mice.

Epigenetic insight into effects of prenatal alcohol exposure on stress axis development: Systematic review with meta-analytic approaches

We conducted a systematic review with meta-analytic elements using publicly available Gene Expression Omnibus (GEO) datasets to determine the role of epigenetic mechanisms in prenatal alcohol exposure (PAE)-induced hypothalamic-pituitary-adrenal (HPA) axis dysfunctions in offspring. Several studies have demonstrated that PAE has long-term consequences on HPA axis functions in offspring. Some studies determined that alcohol-induced epigenetic alterations during fetal development persist in adulthood. However, additional research is needed to understand the major epigenetic events leading to alcohol-induced teratogenesis of the HPA axis. Our network analysis of GEO datasets identified key pathways relevant to alcohol-mediated histone modifications, DNA methylation, and miRNA involvement associated with PAE-induced alterations of the HPA axis. Our analysis indicated that PAE perturbated the epigenetic machinery to activate corticotrophin-releasing hormone, while it suppressed opioid, glucocorticoid receptor, and circadian clock genes. These results help to further our understanding of the epigenetic basis of alcohol's effects on HPA axis development.

Disrupted circadian expression of beta-arrestin 2 affects reward-related µ-opioid receptor function in alcohol dependence

There is increasing evidence for a daily rhythm of μ-opioid receptor (MOR) efficacy and the development of alcohol dependence. Previous studies show that beta-Arrestin 2 (bArr2) has an impact on alcohol intake, at least partially mediated via modulation of MOR signaling, which in turn mediates the alcohol rewarding effects. Considering the interplay of circadian rhythms on MOR and alcohol dependence, we aimed to investigate bArr2 in alcohol dependence at different time-points of the day/light cycle on the level of bArr2 mRNA (in situ hybridization), MOR availability (receptor autoradiography) and MOR signaling (Damgo-stimulated G-protein coupling) in the nucleus accumbens of alcohol-dependent and non-dependent Wistar rats. Using a microarray data set we found that bArr2, but not bArr1, shows a diurnal transcription pattern in the accumbens of naïve rats with higher expression levels during the active cycle. In three-week abstinent rats, bArr2 is upregulated in the accumbens at the beginning of the active cycle (ZT15), whereas no differences were found at the beginning of the inactive cycle (ZT3), compared to controls. This effect was accompanied with a specific downregulation of MOR binding in the active cycle. Additionally, we detect a higher receptor coupling during the inactive cycle compared to the active cycle in alcohol-dependent animals. Together, we report a daily rhythmicity for bArr2 expression linked to an inverse pattern of MOR, suggesting an involvement for bArr2 on circadian regulation of G-protein coupled receptors in alcohol dependence. The presented data may have implications for the development of novel bArr2-related treatment targets for alcoholism.

Sleep problems among children with Fetal Alcohol Spectrum Disorders (FASD)- an explorative study

BACKGROUND

Fetal alcohol spectrum disorders (FASD) is a group of conditions resulting from prenatal alcohol exposure (PAE). Patients with FASD experience a variety of neuropsychological symptoms resulting from central nervous system impairment. Little is known about sleep disorders associated with PAE. The objective of this study was to investigate sleep problems related to FASD.

METHODS

Forty patients (median age 8 years (6; 11)) diagnosed with FASD and forty typically developing children (median age 10 years (8; 13)) were recruited for the 1st phase of the study. In the 1st phase, the screening of sleep problems was performed with Child Sleep Habit Questionnaire (CSHQ) filled in by a caregiver. Those of the FASD group who scored above 41 points were qualified to the 2nd phase of the study and had an in-lab attended polysomnography (PSG) performed. The measurements consisted of electroencephalogram, electrooculograms, chin and tibial electromyogram, electrocardiogram, ventilatory monitoring, breathing effort, pulse oximetry, snoring and body position. Their results were compared to PSG laboratory reference data.

RESULTS

The number of participants with sleep disturbances was markedly higher in the FASD group as compared to typically developing children (55% vs. 20%). The age-adjusted odds ratio for a positive result in CSHQ was 4.31 (95% CI: 1.54-12.11; p = 0.005) for FASD patients as compared to the control group. Significant differences between the FASD as compared to the typically developing children were observed in the following subscales: sleep onset delay, night wakings, parasomnias, sleep disordered breathing, and daytime sleepiness. Children from the FASD group who underwent PSG experienced more arousals during the sleep as compared with the PSG laboratory reference data. The respiratory indices in FASD group appear higher than previously published data from typically developing children.

CONCLUSION

The results support the clinical observation that sleep disorders appear to be an important health problem in individuals with FASD. In particular distorted sleep architecture and apneic/hypopneic events need further attention.

Persistent Changes in Stress-Regulatory Genes in Pregnant Women or Children Exposed Prenatally to Alcohol

BACKGROUND

We have recently shown that binge or heavy levels of alcohol drinking increase deoxyribonucleic acid (DNA) methylation and reduce gene expression of proopiomelanocortin (POMC) and period 2 (PER2) in adult human subjects (Gangisetty et al., Alcohol Clin Exp Res, 43, 2019, 212). One hypothesis would be that methylation of these 2 genes is consistently associated with alcohol exposure and could be used as biomarkers to predict risk of prenatal alcohol exposure (PAE). Results of the present study provided some support for this hypothesis.

METHODS

We conducted a series of studies to determine DNA methylation changes in stress regulatory genes proopiomelanocortin (POMC) and period 2 (PER2) using biological samples from 3 separate cohorts of patients: (i) pregnant women who consumed moderate-to-high levels of alcohol or low/unexposed controls, (ii) children with PAE and non-alcohol-exposed controls, and (iii) children with PAE treated with or without choline.

RESULTS

We found pregnant women who consumed moderate-to-high levels of alcohol and gave birth to PAE children had higher DNA methylation of POMC and PER2. PAE children also had increased methylation of POMC and PER2. The differences in the gene methylation of PER2 and POMC between PAE and controls did not differ by maternal smoking status. PAE children had increased levels of stress hormone cortisol and adrenocorticotropic hormone. Choline supplementation reduced DNA hypermethylation and increased expression of POMC and PER2 in children with PAE.

CONCLUSIONS

These data suggest that PAE significantly elevates DNA methylation of POMC and PER2 and increases levels of stress hormones. Furthermore, these results suggest the possibility that measuring DNA methylation levels of PER2 and POMC in biological samples from pregnant women or from children may be useful for identification of a woman or a child with PAE.

Sleep in Infants and Children with Prenatal Alcohol Exposure

Prenatal exposure to alcohol can result in a range of neurobehavioral impairments and physical abnormalities. The term "fetal alcohol spectrum disorders (FASD)" encompasses the outcomes of prenatal alcohol exposure (PAE), the most severe of which is fetal alcohol syndrome. These effects have lifelong consequences, placing a significant burden on affected individuals, caregivers, and communities. Caregivers of affected children often report that their child has sleep problems, and many symptoms of sleep deprivation overlap with the cognitive and behavioral deficits characteristic of FASD. Alcohol-exposed infants and children demonstrate poor sleep quality based on measures of electroencephalography, actigraphy, and questionnaires. These sleep studies indicate a common theme of disrupted sleep pattern, more frequent awakenings, and reduced total sleep time. However, relatively little is known about circadian rhythm disruption and the neurobehavioral correlates of sleep disturbance in individuals with PAE. Furthermore, there is limited information available to healthcare providers about identification and treatment of sleep disorders in patients with FASD. This review consolidates the findings from studies of infant and pediatric sleep in this population, providing an overview of typical sleep characteristics, neurobehavioral correlates of sleep disruption, and potential avenues for intervention in the context of PAE.

The Impact of Traditional Food and Lifestyle Behavior on Epigenetic Burden of Chronic Disease

Noncommunicable chronic diseases (NCCDs) are the leading causes of morbidity and mortality globally. The mismatch between present day diets and ancestral genome is suggested to contribute to the NCCDs burden, which is promoted by traditional risk factors like unhealthy diets, physical inactivity, alcohol and tobacco. However, epigenetic evidence now suggests that cumulatively inherited epigenetic modifications may have made humans more prone to the effects of present day lifestyle factors. Perinatal starvation was widespread in the 19th century. This together with more recent events like increasing consumption of western and low fiber diets, smoking, harmful use of alcohol, physical inactivity, and environmental pollutants may have programed the human epigenome for higher NCCDs risk. In this review, on the basis of available epigenetic data it is hypothesized that transgenerational effects of lifestyle factors may be contributing to the current global burden of NCCDs. Thus, there is a need to reconsider prevention strategies so that the subsequent generations will not have to pay for our sins and those of our ancestors.

Circadian behavior of adult mice exposed to stress and fluoxetine during development

INTRODUCTION

Women of child-bearing age are the population at greatest risk for depression. The stress experienced during pregnancy and the associated antidepressant treatments can both affect fetal development. Fluoxetine (FLX) is among the most common antidepressants used by pregnant women. We have previously demonstrated that perinatal exposure to FLX can alter expression of circadian rhythms in adulthood. Here, we examine the combined effects of maternal stress during pregnancy and perinatal exposure to the antidepressant FLX on the circadian behavior of mice as adults.

METHODS

Mouse dams were exposed to chronic unpredictable stress (embryonic (E) day 7 to E18), FLX (E15 to postnatal day 12), a combination of both stress and FLX, or were left untreated. At 2 months of age, male offspring were placed in recording chambers and circadian organization of wheel running rhythms and phase shifts to photic and non-photic stimuli were assessed.

RESULTS

Mice exposed to prenatal stress (PS) had smaller light-induced phase delays. Mice exposed to perinatal FLX required more days to re-entrainment to an 8-h phase advance of their light-dark cycle. Mice subjected to either perinatal FLX or to PS had larger light-induced phase advances and smaller phase advances to 8-OH-DPAT. FLX treatment partially reversed the effect of PS on phase shifts to late-night light exposure and to 8-OH-DPAT.

CONCLUSIONS

Our results suggest that, in mice, perinatal exposure to either FLX, or PS, or their combination, leads to discernible, persistent changes in their circadian systems as adults.

Chronic Alcohol Consumption in Rats Leads to Desynchrony in Diurnal Rhythms and Molecular Clocks

BACKGROUND

Circadian rhythms are essential for adapting to the environment. Chronic alcohol consumption often leads to sleep and circadian disruptions, which may impair the life quality of individuals with alcohol use disorders and contribute to the morbidity associated with alcoholism.

METHODS

We used a pair-feeding liquid diet alcohol exposure protocol (6 weeks duration) in PER1::LUC transgenic rats to examine the effects of chronic alcohol exposure on: (i) diurnal rhythms of core body temperature and locomotor activity, (ii) plasma corticosterone (CORT) concentrations, and (iii) rhythms of ex vivo Period1 (Per1) expression in the suprachiasmatic nucleus (SCN), pituitary, and adrenal glands. We followed multiple circadian outputs not only to examine individual components, but also to assess the relative phase relationships among rhythms.

RESULTS

We found that chronic alcohol consumption: (i) reduced 24-hour body temperature and locomotor activity counts in the dark period, (ii) advanced the acrophase of diurnal rhythms of body temperature and locomotor activity, (iii) abolished the phase difference between temperature and activity rhythms, (iv) blunted and advanced the diurnal CORT rhythm, and (v) advanced Per1 expression in the adrenal and pituitary glands but not in the SCN. We found that chronic alcohol altered the phase relationships among diurnal rhythms and between the central (SCN) and peripheral (adrenal and pituitary) molecular clocks.

CONCLUSIONS

Our findings suggest that desynchrony among internal rhythms is an important and overlooked aspect of alcohol-induced circadian disruptions. The misalignment of phases among rhythms may compromise normal physiological functions and put individuals with chronic alcohol use at greater risk for developing other physical and mental health issues. How this desynchrony occurs and the extent to which it participates in alcohol-related pathologies requires further investigation.

Sleep and melatonin secretion abnormalities in children and adolescents with fetal alcohol spectrum disorders

OBJECTIVES

Caregivers describe significant sleep disturbances in the vast majority of children and adolescents, which is diagnosed as fetal alcohol spectrum disorders (FASD), but objective data on sleep disorders in this population are almost completely lacking. Animal models suggest that intrauterine alcohol exposure may disrupt sleep wake patterns, cause sleep fragmentation, and specifically affect the suprachiasmatic nucleus, thus disrupting melatonin secretion. The objective of this pioneering study was to evaluate sleep and melatonin abnormalities in children with FASD using objective, gold-standard measures.

METHODS

Children and adolescents (N = 36, 6-18 years) with FASD participated in clinical assessments by sleep specialists, overnight polysomnography (PSG), and a dim light melatonin onset (DLMO) test in a pediatric sleep laboratory. PSG was analyzed according to standardized scoring guidelines and sleep architecture was compared with normative data. DLMOs were determined and melatonin secretion curves were evaluated qualitatively to classify melatonin profiles. Sleep disorders were evaluated according to international diagnostic criteria.

RESULTS

There was a high prevalence (58%) of sleep disorders. The most common sleep problems were parasomnias (27.9%) and insomnia (16.8%). The sleep studies showed lower than normal sleep efficiency and high rates of sleep fragmentation. Most participants (79%) had an abnormal melatonin profile.

CONCLUSIONS

This study led to the recognition that both sleep and melatonin secretion abnormalities are present in children with FASD. Therefore, to be effective in managing the sleep problems in children with FASD, one needs to consider both the sleep per se and a possible malfunction of the circadian regulation.

Mutations in the circadian gene period alter behavioral and biochemical responses to ethanol in Drosophila

Clock genes, such as period, which maintain an organism's circadian rhythm, can have profound effects on metabolic activity, including ethanol metabolism. In turn, ethanol exposure has been shown in Drosophila and mammals to cause disruptions of the circadian rhythm. Previous studies from our labs have shown that larval ethanol exposure disrupted the free-running period and period expression of Drosophila. In addition, a recent study has shown that arrhythmic flies show no tolerance to ethanol exposure. As such, Drosophila period mutants, which have either a shorter than wild-type free-running period (perS) or a longer one (perL), may also exhibit altered responses to ethanol due to their intrinsic circadian differences. In this study, we tested the initial sensitivity and tolerance of ethanol exposure on Canton-S, perS, and perL, and then measured their Alcohol Dehydrogenase (ADH) and body ethanol levels. We showed that perL flies had slower sedation rate, longer recovery from ethanol sedation, and generated higher tolerance for sedation upon repeated ethanol exposure compared to Canton-S wild-type flies. Furthermore, perL flies had lower ADH activity and had a slower ethanol clearance compared to wild-type flies. The findings of this study suggest that period mutations influence ethanol induced behavior and ethanol metabolism in Drosophila and that flies with longer circadian periods are more sensitive to ethanol exposure.

Male germline transmits fetal alcohol epigenetic marks for multiple generations: a review

Alcohol exposure during fetal and early postnatal development can lead to an increased incidence of later life adult-onset diseases. Examples include central nervous system dysfunction, depression, anxiety, hyperactivity, and an inability to deal with stressful situations, increased infection and cancer. Direct effects of alcohol leading to developmental abnormalities often involve epigenetic modifications of genes that regulate cellular functions. Epigenetic marks carried over from the parents are known to undergo molecular programming events that happen early in embryonic development by a wave of DNA demethylation, which leaves the embryo with a fresh genomic composition. The proopiomelanocortin (Pomc) gene controls neuroendocrine-immune functions and is imprinted by fetal alcohol exposure. Recently, this gene has been shown to be hypermethylated through three generations. Additionally, the alcohol epigenetic marks on the Pomc gene are maintained in the male but not in the female germline during this transgenerational transmission. These data suggest that the male-specific chromosome might be involved in transmitting alcohol epigenetic marks through multiple generations.

Clock genes × stress × reward interactions in alcohol and substance use disorders

Adverse life events and highly stressful environments have deleterious consequences for mental health. Those environmental factors can potentiate alcohol and drug abuse in vulnerable individuals carrying specific genetic risk factors, hence producing the final risk for alcohol- and substance-use disorders development. The nature of these genes remains to be fully determined, but studies indicate their direct or indirect relation to the stress hypothalamo-pituitary-adrenal (HPA) axis and/or reward systems. Over the past decade, clock genes have been revealed to be key-players in influencing acute and chronic alcohol/drug effects. In parallel, the influence of chronic stress and stressful life events in promoting alcohol and substance use and abuse has been demonstrated. Furthermore, the reciprocal interaction of clock genes with various HPA-axis components, as well as the evidence for an implication of clock genes in stress-induced alcohol abuse, have led to the idea that clock genes, and Period genes in particular, may represent key genetic factors to consider when examining gene × environment interaction in the etiology of addiction. The aim of the present review is to summarize findings linking clock genes, stress, and alcohol and substance abuse, and to propose potential underlying neurobiological mechanisms.

Alcohol disrupts sleep homeostasis

Alcohol is a potent somnogen and one of the most commonly used "over the counter" sleep aids. In healthy non-alcoholics, acute alcohol decreases sleep latency, consolidates and increases the quality (delta power) and quantity of NREM sleep during the first half of the night. However, sleep is disrupted during the second half. Alcoholics, both during drinking periods and during abstinences, suffer from a multitude of sleep disruptions manifested by profound insomnia, excessive daytime sleepiness, and altered sleep architecture. Furthermore, subjective and objective indicators of sleep disturbances are predictors of relapse. Finally, within the USA, it is estimated that societal costs of alcohol-related sleep disorders exceeds $18 billion. Thus, although alcohol-associated sleep problems have significant economic and clinical consequences, very little is known about how and where alcohol acts to affect sleep. In this review, we have described our attempts to unravel the mechanism of alcohol-induced sleep disruptions. We have conducted a series of experiments using two different species, rats and mice, as animal models. We performed microdialysis, immunohistochemical, pharmacological, sleep deprivation and lesion studies which suggest that the sleep-promoting effects of alcohol may be mediated via alcohol's action on the mediators of sleep homeostasis: adenosine (AD) and the wake-promoting cholinergic neurons of the basal forebrain (BF). Alcohol, via its action on AD uptake, increases extracellular AD resulting in the inhibition of BF wake-promoting neurons. Since binge alcohol consumption is a highly prevalent pattern of alcohol consumption and disrupts sleep, we examined the effects of binge drinking on sleep-wakefulness. Our results suggest that disrupted sleep homeostasis may be the primary cause of sleep disruption observed following binge drinking. Finally, we have also shown that sleep disruptions observed during acute withdrawal, are caused due to impaired sleep homeostasis. In conclusion, we suggest that alcohol may disrupt sleep homeostasis to cause sleep disruptions.

Fetal alcohol exposure increases susceptibility to carcinogenesis and promotes tumor progression in prostate gland

The idea that exposure to adverse environmental conditions and lifestyle choices during pregnancy can result in fetal programming that underlies disease susceptibility in adulthood is now widely accepted. Fetal alcohol exposed offspring displays many behavioral and physiological abnormalities including neuroendocrine-immune functions, which often carry over into their adult life. Since the neuroendocrine-immune system plays an important role in controlling tumor surveillance, fetal alcohol exposed offspring can be vulnerable to develop cancer. Animal studies have recently showed increased cancer growth and progression in various tissues of fetal alcohol exposed offspring. I will detail in this chapter the recent evidence for increased prostate carcinogenesis in fetal alcohol exposed rats. I will also provide evidence for a role of excessive estrogenization during prostatic development in the increased incidence of prostatic carcinoma in these animals. Furthermore, I will discuss the additional possibility of the involvement of impaired stress regulation and resulting immune incompetence in the increased prostatic neoplasia in the fetal alcohol exposed offspring.

Third trimester-equivalent ethanol exposure is characterized by an acute cellular stress response and an ontogenetic disruption of genes critical for synaptic establishment and function in mice

The developing brain is remarkably sensitive to alcohol exposure, resulting in the wide range of cognitive and neurobehavioral characteristics categorized under the term fetal alcohol spectrum disorders (FASD). The brain is particularly susceptible to alcohol during synaptogenesis, a process that occurs heavily during the third trimester and is characterized by the establishment and pruning of neural circuitry; however, the molecular response of the brain to ethanol during synaptogenesis has not been documented. To model a binge-like exposure during the third-trimester neurodevelopmental equivalent, neonate mice were given a high (5 g/kg over 2 h) dose of ethanol at postnatal day 7. Acute transcript changes within the brain were assessed using expression arrays and analyzed for associations with gene ontology functional categories, canonical pathways, and gene network interactions. The short-term effect of ethanol was characterized by an acute stress response and a downregulation of energetically costly cellular processes. Further, alterations to a number of genes with roles in synaptic transmission and hormonal signaling, particularly those associated with the neuroendocrine development and function, were evident. Ethanol exposure during synaptogenesis was also associated with altered histone deacetylase and microRNA transcript levels, suggesting that abnormal epigenetic patterning may maintain some of the persistent molecular consequences of developmental ethanol exposure. The results shed insight into the sensitivity of the brain to ethanol during the third-trimester equivalent and outline how ethanol-induced alterations to genes associated with neural connectivity may contribute to FASD phenotypes.

Fetal alcohol exposure disrupts metabolic signaling in hypothalamic proopiomelanocortin neurons via a circadian mechanism in male mice

Early-life ethanol feeding (ELAF) alters the metabolic function of proopiomelanocortin (POMC)-producing neurons and the circadian expression of clock regulatory genes in the hypothalamus. We investigated whether the circadian mechanisms control the action of ELAF on metabolic signaling genes in POMC neurons. Gene expression measurements of Pomc and a selected group of metabolic signaling genes, Stat3, Sirt1, Pgc1-α, and Asb4 in laser-captured microdissected POMC neurons in the hypothalamus of POMC-enhanced green fluorescent protein mice showed circadian oscillations under light/dark and constant darkness conditions. Ethanol programmed these neurons such that the adult expression of Pomc, Stat3, Sirt, and Asb4 gene transcripts became arrhythmic. In addition, ELAF dampened the circadian peak of gene expression of Bmal1, Per1, and Per2 in POMC neurons. We crossed Per2 mutant mice with transgenic POMC-enhanced green fluorescent protein mice to determine the role of circadian mechanism in ELAF-altered metabolic signaling in POMC neurons. We found that ELAF failed to alter arrhythmic expression of most circadian genes, with the exception of the Bmal1 gene and metabolic signaling regulating genes in Per2 mutant mice. Comparison of the ELAF effects on the circadian blood glucose in wild-type and Per2 mutant mice revealed that ELAF dampened the circadian peak of glucose, whereas the Per2 mutation shifted the circadian cycle and prevented the ELAF dampening of the glucose peak. These data suggest the possibility that the Per2 gene mutation may regulate the ethanol actions on Pomc and the metabolic signaling genes in POMC neurons in the hypothalamus by blocking circadian mechanisms.

Long-term genomic and epigenomic dysregulation as a consequence of prenatal alcohol exposure: a model for fetal alcohol spectrum disorders

There is abundant evidence that prenatal alcohol exposure leads to a range of behavioral and cognitive impairments, categorized under the term fetal alcohol spectrum disorders (FASDs). These disorders are pervasive in Western cultures and represent the most common preventable source of neurodevelopmental disabilities. The genetic and epigenetic etiology of these phenotypes, including those factors that may maintain these phenotypes throughout the lifetime of an affected individual, has become a recent topic of investigation. This review integrates recent data that has progressed our understanding FASD as a continuum of molecular events, beginning with cellular stress response and ending with a long-term “footprint” of epigenetic dysregulation across the genome. It reports on data from multiple ethanol-treatment paradigms in mouse models that identify changes in gene expression that occur with respect to neurodevelopmental timing of exposure and ethanol dose. These studies have identified patterns of genomic alteration that are dependent on the biological processes occurring at the time of ethanol exposure. This review also adds to evidence that epigenetic processes such as DNA methylation, histone modifications, and non-coding RNA regulation may underlie long-term changes to gene expression patterns. These may be initiated by ethanol-induced alterations to DNA and histone methylation, particularly in imprinted regions of the genome, affecting transcription which is further fine-tuned by altered microRNA expression. These processes are likely complex, genome-wide, and interrelated. The proposed model suggests a potential for intervention, given that epigenetic changes are malleable and may be altered by postnatal environment. This review accentuates the value of mouse models in deciphering the molecular etiology of FASD, including those processes that may provide a target for the ammelioration of this common yet entirely preventable disorder.

Circadian rhythms and addiction: mechanistic insights and future directions

Circadian rhythms are prominent in many physiological and behavioral functions. Circadian disruptions either by environmental or molecular perturbation can have profound health consequences, including the development and progression of addiction. Both animal and humans studies indicate extensive bidirectional relationships between the circadian system and drugs of abuse. Addicted individuals display disrupted rhythms, and chronic disruption or particular chronotypes may increase the risk for substance abuse and relapse. Moreover, polymorphisms in circadian genes and an evening chronotype have been linked to mood and addiction disorders, and recent efforts suggest an association with the function of reward neurocircuitry. Animal studies are beginning to determine how altered circadian gene function results in drug-induced neuroplasticity and behaviors. Many studies suggest a critical role for circadian rhythms in reward-related pathways in the brain and indicate that drugs of abuse directly affect the central circadian pacemaker. In this review, we highlight key findings demonstrating the importance of circadian rhythms in addiction and how future studies will reveal important mechanistic insights into the involvement of circadian rhythms in drug addiction.

Neurobehavioral, neurologic, and neuroimaging characteristics of fetal alcohol spectrum disorders

Alcohol consumption during pregnancy can have deleterious consequences for the fetus, including changes in central nervous system development leading to permanent neurologic alterations and cognitive and behavioral deficits. Individuals affected by prenatal alcohol exposure, including those with and without fetal alcohol syndrome, are identified under the umbrella of fetal alcohol spectrum disorders (FASD). While studies of humans and animal models confirm that even low to moderate levels of exposure can have detrimental effects, critical doses of such exposure have yet to be specified and the most clinically significant and consistent consequences occur following heavy exposure. These consequences are pervasive, devastating, and can result in long-term dysfunction. This chapter summarizes the neurobehavioral, neurologic, and neuroimaging characteristics of FASD, focusing primarily on clinical research of individuals with histories of heavy prenatal alcohol exposure, although studies of lower levels of exposure, particularly prospective, longitudinal studies, will be discussed where relevant.

Circadian rhythms in liver physiology and liver diseases

In mammals, circadian rhythms function to coordinate a diverse panel of physiological processes with environmental conditions such as food and light. As the driving force for circadian rhythmicity, the molecular clock is a self-sustained transcription-translational feedback loop system consisting of transcription factors, epigenetic modulators, kinases/phosphatases, and ubiquitin E3 ligases. The molecular clock exists not only in the suprachiasmatic nuclei of the hypothalamus but also in the peripheral tissues to regulate cellular and physiological function in a tissue-specific manner. The circadian clock system in the liver plays important roles in regulating metabolism and energy homeostasis. Clock gene mutant animals display impaired glucose and lipid metabolism and are susceptible to diet-induced obesity and metabolic dysfunction, providing strong evidence for the connection between the circadian clock and metabolic homeostasis. Circadian-controlled hepatic metabolism is partially achieved by controlling the expression and/or activity of key metabolic enzymes, transcription factors, signaling molecules, and transporters. Reciprocally, intracellular metabolites modulate the molecular clock activity in response to the energy status. Although still at the early stage, circadian clock dysfunction has been implicated in common chronic liver diseases. Circadian dysregulation of lipid metabolism, detoxification, reactive oxygen species (ROS) production, and cell-cycle control might contribute to the onset and progression of liver steatosis, fibrosis, and even carcinogenesis. In summary, these findings call for a comprehensive study of the function and mechanisms of hepatic circadian clock to gain better understanding of liver physiology and diseases.

Cyclic adenosine monophosphate and brain-derived neurotrophic factor decreased oxidative stress and apoptosis in developing hypothalamic neuronal cells: role of microglia

BACKGROUND

We have previously shown that ethanol (EtOH) increases cellular apoptosis to developing neurons via the effects on oxidative stress of neurons directly and via increasing production of microglia-derived factors. To study further the mechanism of EtOH action on neuronal apoptosis, we determined the effects of 2 well-known PKA activators, dibutyryl cAMP (dbcAMP) and brain-derived neurotrophic factor (BDNF), on EtOH-activated oxidative stress and apoptotic processes in the hypothalamic neurons in the presence and absence of microglial cells' influence.

METHODS

In enriched neuronal cells from fetal rat hypothalami treated with EtOH or with conditioned medium from EtOH-treated microglia, we measured cellular apoptosis by the free nucleosome assay and the levels of cAMP, BDNF, O²⁻, reactive oxygen species (ROS), nitrite, glutathione (GSH), and catalase following treatment with EtOH or EtOH-treated microglial culture conditioned medium. Additionally, we tested the effectiveness of dbcAMP and BDNF in preventing EtOH or EtOH-treated microglial conditioned medium on cellular apoptosis and oxidative stress in enriched hypothalamic neuronal cell in primary cultures.

RESULTS

Neuronal cell cultures following treatment with EtOH or EtOH-activated microglial conditioned medium showed decreased production levels of cAMP and BDNF. EtOH also increased apoptotic death as well as oxidative status, as demonstrated by higher cellular levels of oxidants but lower levels of antioxidants, in neuronal cells. These effects of EtOH on oxidative stress and cell death were enhanced by the presence of microglia. Treatment with BDNF or dbcAMP decreased EtOH or EtOH-activated microglial conditioned medium-induced changes in the levels of intracellular free radicals, ROS and O²⁻, nitrite, GSH, and catalase.

CONCLUSIONS

These data support the possibility that EtOH by acting directly and via increasing the production of microglial-derived factors reduces cellular levels of cAMP and BDNF to increase cellular oxidative status and apoptosis in hypothalamic neuronal cells in primary cultures.

Neurodevelopmental alcohol exposure elicits long-term changes to gene expression that alter distinct molecular pathways dependent on timing of exposure

BACKGROUND

Maternal alcohol consumption is known to adversely affect fetal neurodevelopment. While it is known that alcohol dose and timing play a role in the cognitive and behavioral changes associated with prenatal alcohol exposure, it is unclear what developmental processes are disrupted that may lead to these phenotypes.

METHODS

Mice (n=6 per treatment per developmental time) were exposed to two acute doses of alcohol (5 g/kg) at neurodevelopmental times representing the human first, second, or third trimester equivalent. Mice were reared to adulthood and changes to their adult brain transcriptome were assessed using expression arrays. These were then categorized based on Gene Ontology annotations, canonical pathway associations, and relationships to interacting molecules.

RESULTS

The results suggest that ethanol disrupts biological processes that are actively occurring at the time of exposure. These include cell proliferation during trimester one, cell migration and differentiation during trimester two, and cellular communication and neurotransmission during trimester three. Further, although ethanol altered a distinct set of genes depending on developmental timing, many of these show interrelatedness and can be associated with one another via 'hub' molecules and pathways such as those related to huntingtin and brain-derived neurotrophic factor.

CONCLUSIONS

These changes to brain gene expression represent a 'molecular footprint' of neurodevelopmental alcohol exposure that is long-lasting and correlates with active processes disrupted at the time of exposure. This study provides further support that there is no neurodevelopmental time when alcohol cannot adversely affect the developing brain.

Larval ethanol exposure alters free-running circadian rhythm and per Locus transcription in adult D. melanogaster period mutants

Alcohol consumption causes disruptions in a variety of daily rhythms, including the circadian free-running rhythm. A previous study conducted in our laboratories has shown that larval ethanol exposure alters the free-running period in adult Canton-S Drosophila melanogaster. Few studies, however, have explored the effect of alcohol exposure on organisms exhibiting circadian periods radically different than (normal) 24-h. We reared Canton-S, period long, and period short Drosophila melanogaster larvae on 10%-ethanol supplemented food, and assessed their adult free-running locomotor activity and period transcript at ZT 12. We demonstrate that in Canton-S larval ethanol exposure shortens the adult free-running locomotor activity but does not significantly alter period mRNA levels at ZT 12. Period long mutants exposed to larval ethanol had significantly shortened adult free-running locomotor activity rhythms and decreased period mRNA levels, while period short mutants lengthened their free-running rhythm and showed increased period mRNA levels at ZT 12 after being exposed to larval ethanol. These results indicate that the effects of ethanol on the circadian clock might depend upon the baseline circadian period of the organism or that period mutant gene expression is sensitive to developmental ethanol treatment.

Male germline transmits fetal alcohol adverse effect on hypothalamic proopiomelanocortin gene across generations

BACKGROUND

Neurons containing proopiomelanocortin (POMC)-derived peptides, known to control stress axis, metabolic, and immune functions, have a lower function in patients with a family history of alcoholism, raising the possibility that alcohol effects on the POMC system may transmit through generations. Here we describe epigenetic modifications of Pomc gene that transmit through generation via male germline and may be critically involved in alcoholism-inherited diseases.

METHODS

Whether an epigenetic mechanism is involved in causing a Pomc expression deficit in fetal alcohol-exposed rats is studied by determining Pomc gene methylation, expression, and functional abnormalities and their normalization following suppression of DNA methylation or histone acetylation. Additionally, transgenerational studies were conducted to evaluate the germline-transmitted effect of alcohol.

RESULTS

Fetal alcohol-exposed male and female rat offspring showed a significant deficit in POMC neuronal functions. Associated with this was an increased methylation status of several CpG dinucleotides in the proximal part of the Pomc promoter region and altered level of histone-modifying proteins and DNA methyltransferases levels in POMC neurons. Suppression of histone deacetylation and DNA methylation normalized Pomc expression and functional abnormalities. Fetal alcohol-induced Pomc gene methylation, expression, and functional defects persisted in the F2 and F3 male but not in female germline. Additionally, the hypermethylated Pomc gene was detected in sperm of fetal alcohol-exposed F1 offspring that was transmitted through F3 generation via male germline.

CONCLUSIONS

Trangenerational epigenetic studies should spur new insight into the biological mechanisms that influence the sex-dependent difference in genetic risk of alcoholism-inherited diseases.

Evidence for possible period 2 gene mediation of the effects of alcohol exposure during the postnatal period on genes associated with maintaining metabolic signaling in the mouse hypothalamus

BACKGROUND

Animals exposed to alcohol during the developmental period develop circadian disturbances and metabolic problems that often persist during their adult period. In order to study whether alcohol and the circadian clock interact to alter metabolic signaling in the hypothalamus, we determined whether postnatal alcohol feeding in mice permanently alters metabolic sensing in the hypothalamus. Furthermore, we evaluated whether the effect of circadian disruption via Period 2 (Per2) gene mutation prevents alcohol's effects on metabolic signaling in the hypothalamus.

METHODS

Per2 mutant and wild-type male and female mice of the same genetic background were given a milk formula containing ethanol (EtOH; 11.34% vol/vol) from postnatal day (PD) 2 to 7 and used for gene expression and peptide level determinations in the hypothalamus at PD7 and PD90.

RESULTS

We report here that postnatal alcohol feeding reduces the expression of proopiomelanocortin (Pomc) gene and production of β-endorphin and α-melanocyte stimulating hormone (α-MSH) in the hypothalamus that persists into adulthood. In addition, expressions of metabolic sensing genes in the hypothalamus were also reduced as a consequence of postnatal alcohol exposure. These effects were not sex-specific and were observed in both males and females. Mice carrying a mutation of the Per2 gene did not show any reductions in hypothalamic levels of Pomc and metabolic genes and β-endorphin and α-MSH peptides following alcohol exposure.

CONCLUSIONS

These data suggest that early-life exposure to alcohol alters metabolic sensing to the hypothalamus possibly via regulating Per2 gene and/or the cellular circadian clock mechanism.

Microglia play a role in ethanol-induced oxidative stress and apoptosis in developing hypothalamic neurons

BACKGROUND

Animals exposed to alcohol during the developmental period develop many physiological and behavioral problems because of neuronal loss in various brain areas including the hypothalamus. Because alcohol exposure is known to induce oxidative stress in developing neurons, we tested whether hypothalamic cells from the fetal brain exposed to ethanol (EtOH) may alter the cell-cell communication between neurons and microglia, thereby leading to increased oxidative stress and the activation of apoptotic processes in the neuronal population in the hypothalamus.

METHODS

Using enriched neuronal and microglial cells from fetal rat hypothalami, we measured cellular levels of various oxidants (O2 -, reactive oxygen species, nitrite), antioxidants (glutathione [GSH]), antioxidative enzymes (glutathione peroxidase [GSH-Px], catalase, superoxide dismutase) and apoptotic death in neurons in the presence and absence of EtOH or EtOH-treated microglial culture medium. Additionally, we tested the effectiveness of antioxidative agents in preventing EtOH or EtOH-treated microglial conditioned medium actions on oxidative stress and apoptosis in neuronal cell cultures.

RESULTS

Neuronal cell cultures showed increased oxidative stress, as demonstrated by higher cellular levels of oxidants but lower levels of antioxidant and antioxidative enzymes, as well as, increased apoptotic death following treatment with EtOH. These effects of EtOH on oxidative stress and cell death were enhanced by the presence of microglia. Antioxidative agents protected developing hypothalamic neurons from oxidative stress and cellular apoptosis which is caused by EtOH or EtOH-treated microglial culture medium.

CONCLUSIONS

These data suggest that exposure of developing hypothalamic neurons to EtOH increases cellular apoptosis via the effects on oxidative stress of neurons directly and via increasing production of microglial-derived factor(s).

Period 2 gene deletion abolishes beta-endorphin neuronal response to ethanol

BACKGROUND

Ethanol exposure during early life has been shown to permanently alter the circadian expression of clock regulatory genes and the beta-endorphin precursor proopiomelanocortin (POMC) gene in the hypothalamus. Ethanol also alters the stress- and immune-regulatory functions of beta-endorphin neurons in laboratory rodents. Our aim was to determine whether the circadian clock regulatory Per2 gene modulates the action of ethanol on beta-endorphin neurons in mice.

METHODS

Per2 mutant (mPer2(Brdml)) and wild type (C57BL/6J) mice were used to determine the effect of Per2 mutation on ethanol-regulated beta-endorphin neuronal activity during neonatal period using an in vitro mediobasal hypothalamic (MBH) cell culture model and an in vivo milk formula feeding animal model. The beta-endorphin neuronal activity following acute and chronic ethanol treatments was evaluated by measuring the peptide released from cultured cells or peptide levels in the MBH tissues, using enzyme-linked immunosorbent assay (ELISA).

RESULTS

Per2 mutant mice showed a higher basal level of beta-endorphin release from cultured MBH cells and a moderate increase in the peptide content in the MBH in comparison with control mice. However, unlike wild type mice, Per2 mutant mice showed no stimulatory or inhibitory beta-endorphin-secretory responses to acute and chronic ethanol challenges in vitro. Furthermore, Per2 mutant mice, but not wild type mice, failed to show the stimulatory and inhibitory responses of MBH beta-endorphin levels to acute and chronic ethanol challenges in vivo.

CONCLUSIONS

These results suggest for the first time that the Per2 gene may be critically involved in regulating beta-endorphin neuronal function. Furthermore, the data revealed an involvement of the Per2 gene in regulating beta-endorphin neuronal responses to ethanol.

Alcoholism: A Systems Approach From Molecular Physiology to Addictive Behavior

Alcohol consumption is an integral part of daily life in many societies. The benefits associated with the production, sale, and use of alcoholic beverages come at an enormous cost to these societies. The World Health Organization ranks alcohol as one of the primary causes of the global burden of disease in industrialized countries. Alcohol-related diseases, especially alcoholism, are the result of cumulative responses to alcohol exposure, the genetic make-up of an individual, and the environmental perturbations over time. This complex gene × environment interaction, which has to be seen in a life-span perspective, leads to a large heterogeneity among alcohol-dependent patients, in terms of both the symptom dimensions and the severity of this disorder. Therefore, a reductionistic approach is not very practical if a better understanding of the pathological processes leading to an addictive behavior is to be achieved. Instead, a systems-oriented perspective in which the interactions and dynamics of all endogenous and environmental factors involved are centrally integrated, will lead to further progress in alcohol research. This review adheres to a systems biology perspective such that the interaction of alcohol with primary and secondary targets within the brain is described in relation to the behavioral consequences. As a result of the interaction of alcohol with these targets, alterations in gene expression and synaptic plasticity take place that lead to long-lasting alteration in neuronal network activity. As a subsequent consequence, alcohol-seeking responses ensue that can finally lead via complex environmental interactions to an addictive behavior.

Effects of developmental exposure to ethanol on Caenorhabditis elegans

BACKGROUND

We investigated the effects of chronic ethanol exposure on physical development, reproduction, and life expectancy of Caenorhabditis elegans, a microscopic nematode worm. It has a small nervous system of 302 neurons and a short lifespan of 2 to 3 weeks.

METHODS

In this study, the worms were chronically exposed to varying concentrations of ethanol for different periods of their life: for their entire lifespan, during larval development only, and during adulthood only. In addition, the worms were exposed to ethanol acutely during different stages of embryonic development.

RESULTS

Chronic exposure to ethanol during larval development temporarily delayed physical growth, slowed development, delayed the onset of reproductive maturity, and decreased both reproductive fecundity and longevity. Chronic exposure to ethanol beginning when worms completed development and reached reproductive maturity resulted in reduced C. elegans body length, decreased reproductive fecundity, and life expectancy. Finally, acute embryonic exposure of C. elegans eggs to high concentrations of ethanol at different stages of development resulted in a lower probability of exposed eggs hatching into larval worms depending on when eggs were exposed during development. Furthermore, some of the worms that did hatch displayed distinct physical dysmorphologies as a consequence of acute ethanol exposure during embryonic development.

CONCLUSIONS

These data suggest that exposing C. elegans to ethanol during critical development periods results in characteristic phenotypic outcomes. Thus, C. elegans offers a novel model for exploring the mechanisms by which ethanol exposure affects development.

Neonatal alcohol exposure differentially alters clock gene oscillations within the suprachiasmatic nucleus, cerebellum, and liver of adult rats

BACKGROUND

In rats, alcohol exposure during the period of rapid brain growth produces long-term changes in the free-running period, photoentrainment and phase-shifting responses of the circadian rhythm in wheel-running behavior. To determine whether these alterations in circadian behavior are associated with permanent damage to the circadian timekeeping mechanism or reconfiguration of its molecular components, we examined the long-term effects of neonatal alcohol exposure on clock gene rhythms in the pacemaker located in the suprachiasmatic nucleus (SCN) and in other brain or peripheral tissues of adult rats.

METHODS

Artificially reared male rat pups were exposed to alcohol (4.5 g/kg/d) or isocaloric milk formula (gastrostomy control; GC) on postnatal days 4 to 9. At 3 months of age, animals were exposed to constant darkness and then SCN, cerebellum, and liver tissue were harvested at 6-hour intervals for subsequent analysis of Period1 (Per1), Per2, Cryptochrome1 (Cry1), Bmal1, and Rev-erbalpha mRNA levels by quantitative PCR.

RESULTS

In the SCN, cerebellum and liver, Per1, Per2, Cry1, Bmal1, and Rev-erbalpha expression oscillated with a similar amplitude (peak-to-trough differences of 2- to 9-fold) and phase in the suckle control (SC) and GC groups. These clock gene rhythms in control animals were marked by peak expression of Per1, Per2, Cry1, and Rev-erbalpha during the subjective day and of Bmal1 during the subjective night. The EtOH group was distinguished by altered rhythms in the expression of specific clock genes within the SCN, cerebellum and liver. In EtOH-treated rats, the SCN rhythm in Cry1 expression was strongly damped and the Per2 rhythms in the cerebellum and liver were phase-advanced such that peak expression occurred during the mid-subjective day.

CONCLUSIONS

These results demonstrate alcohol exposure during the brain growth spurt alters the circadian regulation of some molecular components of the clock mechanism in the rat SCN, cerebellum, and liver. The observed alterations in the temporal configuration of essential "gears" of the molecular clockworks may play a role in the long-term effects of neonatal alcohol exposure on the regulation of circadian behavior.

Prenatal ethanol exposure alters core body temperature and corticosterone rhythms in adult male rats

Ethanol's effects on the developing brain include alterations in morphology and biochemistry of the hypothalamus. To examine the potential functional consequences of ethanol's interference with hypothalamic differentiation, we studied the long-term effects of prenatal ethanol exposure on basal circadian rhythms of core body temperature (CBT) and heart rate (HR). We also examined the late afternoon surge in corticosterone (CORT). Core body temperature and HR rhythms were studied in separate groups of animals at 4, 8, and 20 months of age. The normal late afternoon rise in plasma CORT was examined in freely moving male rats at 6 months of age via an indwelling right atrial cannula. Results showed that the CBT circadian rhythm exhibited an earlier rise after the nadir of the rhythm in fetal alcohol-exposed (FAE) males at all ages compared to controls. At 8 months of age, the amplitude of the CBT circadian rhythm in FAE males was significantly reduced to the level observed in controls at 20 months. No significant effects of prenatal ethanol exposure were observed on basal HR rhythm at any age. The diurnal rise in CORT secretion was blunted and prolonged in 6-month-old FAE males compared to controls. Both control groups exhibited a robust surge in CORT secretion around the onset of the dark phase of the light cycle, which peaked at 7:30 p.m. Whereas FAE males exhibited a linear rise beginning in mid afternoon, which peaked at 9:30 p.m. These results indicate that exposure to ethanol during the period of hypothalamic development can alter the long-term regulation of circadian rhythms in specific physiological systems.

Endogenous opiates and behavior: 2006

This paper is the 29th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning 30 years of research. It summarizes papers published during 2006 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 (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurological disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Neuroendocrine-immune correlates of circadian physiology: studies in experimental models of arthritis, ethanol feeding, aging, social isolation, and calorie restriction

Virtually all neuroendocrine and immunological variables investigated in animals and humans display biological periodicity. Circadian rhythmicity is revealed for every hormone in circulation as well as for circulating immune cells, lymphocyte metabolism and transformability, cytokines, receptors, and adhesion molecules. Clock genes, notably the three Period (Per1/Per2/Per3) genes and two Cryptochrome (Cry1/Cry2) genes, are present in immune and endocrine cells and are expressed in a circadian manner in human cells. This review discusses the circadian disruption of hormone release and immune-related mechanisms in several animal models in which circulating cytokines are modified including rat adjuvant arthritis, social isolation in rats and rabbits and alcoholism, the aging process and calorie restriction in rats. In every case the experimental manipulation used perturbed the temporal organization by affecting the shape and amplitude of a rhythm or by modifying the intrinsic oscillatory mechanism itself.