Circadian variation in plasma 5-hydroxyindoleacetic acid level during and after alcohol withdrawal: phase advances in alcoholic patients compared with normal subjects

GPR35 promotes neutrophil recruitment in response to serotonin metabolite 5-HIAA

Rapid neutrophil recruitment to sites of inflammation is crucial for innate immune responses. Here, we reveal that the G-protein-coupled receptor GPR35 is upregulated in activated neutrophils, and it promotes their migration. GPR35-deficient neutrophils are less recruited from blood vessels into inflamed tissue, and the mice are less efficient in clearing peritoneal bacteria. Using a bioassay, we find that serum and activated platelet supernatant stimulate GPR35, and we identify the platelet-derived serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) as a GPR35 ligand. GPR35 function in neutrophil recruitment is strongly dependent on platelets, with the receptor promoting transmigration across platelet-coated endothelium. Mast cells also attract GPR35+ cells via 5-HIAA. Mice deficient in 5-HIAA show a loss of GPR35-mediated neutrophil recruitment to inflamed tissue. These findings identify 5-HIAA as a GPR35 ligand and neutrophil chemoattractant and establish a role for platelet- and mast cell-produced 5-HIAA in cell recruitment to the sites of inflammation and bacterial clearance.

Racing the clock: The role of circadian rhythmicity in addiction across the lifespan

Although potent effects of psychoactive drugs on circadian rhythms were first described over 30 years ago, research into the reciprocal relationship between the reward system and the circadian system - and the impact of this relationship on addiction - has only become a focus in the last decade. Nonetheless, great progress has been made in that short time toward understanding how drugs of abuse impact the molecular and physiological circadian clocks, as well as how disruption of normal circadian rhythm biology may contribute to addiction and ameliorate the efficacy of treatments for addiction. In particular, data have emerged demonstrating that disrupted circadian rhythms, such as those observed in shift workers and adolescents, increase susceptibility to addiction. Furthermore, circadian rhythms and addiction impact one another longitudinally - specifically from adolescence to the elderly. In this review, the current understanding of how the circadian clock interacts with substances of abuse within the context of age-dependent changes in rhythmicity, including the potential existence of a drug-sensitive clock, the correlation between chronotype and addiction vulnerability, and the importance of rhythmicity in the mesocorticolimbic dopamine system, is discussed. The primary focus is on alcohol addiction, as the preponderance of research is in this area, with references to other addictions as warranted. The implications of clock-drug interactions for the treatment of addiction will also be reviewed, and the potential of therapeutics that reset the circadian rhythm will be highlighted.

Circadian clock genes: effects on dopamine, reward and addiction

Addiction is a widespread public health issue with social and economic ramifications. Substance abuse disorders are often accompanied by disruptions in circadian rhythms including sleep/wake cycles, which can exacerbate symptoms of addiction and dependence. Additionally, genetic disturbance of circadian molecular mechanisms can predispose some individuals to substance abuse disorders. In this review, we will discuss how circadian genes can regulate midbrain dopaminergic activity and subsequently, drug intake and reward. We will also suggest future directions for research on circadian genes and drugs of abuse.

Alcohol and the sleeping brain

Alcohol acts as a sedative that interacts with several neurotransmitter systems important in the regulation of sleep. Acute administration of large amounts of alcohol prior to sleep leads to decreased sleep-onset latency and changes in sleep architecture early in the night, when blood alcohol levels are high, with subsequent disrupted, poor-quality sleep later in the night. Alcohol abuse and dependence are associated with chronic sleep disturbance, lower slow-wave sleep, and more rapid-eye-movement sleep than normal, that last long into periods of abstinence and may play a role in relapse. This chapter outlines the evidence for acute and chronic alcohol effects on sleep architecture and sleep electroencephalogram, evidence for tolerance with repeated administration, and possible underlying neurochemical mechanisms for alcohol's effects on sleep. Also discussed are sex differences as well as effects of alcohol on sleep homeostasis and circadian regulation. Evidence for the role of sleep disruption as a risk factor for developing alcohol dependence is discussed in the context of research conducted in adolescents. The utility of sleep-evoked potentials in the assessment of the effects of alcoholism on sleep and the brain and in abstinence-mediated recovery is also outlined. The chapter concludes with a series of questions that need to be answered to determine the role of sleep and sleep disturbance in the development and maintenance of problem drinking and the potential beneficial effects of the treatment of sleep disorders for maintenance of abstinence in alcoholism.

The role of clock in ethanol-related behaviors

Mice with a mutation in the Clock gene (ClockΔ19) exhibit increased preference for stimulant rewards and sucrose. They also have an increase in dopaminergic activity in the ventral tegmental area (VTA) and a general increase in glutamatergic tone that might underlie these behaviors. However, it is unclear if their phenotype would extend to a very different class of drug (ethanol), and if so, whether these systems might be involved in their response. Continuous access voluntary ethanol intake was evaluated in ClockΔ19 mutants and wild-type (WT) mice. We found that ClockΔ19 mice exhibited significantly increased ethanol intake in a two-bottle choice paradigm. Interestingly, this effect was more robust in female mice. Moreover, chronic ethanol experience resulted in a long-lasting decrease in VTA Clock expression. To determine the importance of VTA Clock expression in ethanol intake, we knocked down Clock expression in the VTA of WT mice via RNA interference. We found that reducing Clock expression in the VTA resulted in significantly increased ethanol intake similar to the ClockΔ19 mice. Interestingly, we also discovered that ClockΔ19 mice exhibit significantly augmented responses to the sedative effects of ethanol and ketamine, but not pentobarbital. However, their drinking behavior was not affected by acamprosate, an FDA-approved drug for the treatment of alcoholism, suggesting that their increased glutamatergic tone might underlie the increased sensitivity to the sedative/hypnotic properties of ethanol but not the rewarding properties of ethanol. Taken together, we have identified a significant role for Clock in the VTA as a negative regulator of ethanol intake and implicate the VTA dopamine system in this response.

Reduced expression of circadian clock genes in male alcoholic patients

BACKGROUND

 There are clear interactions between chronic alcohol consumption and circadian rhythmicity that is regulated by several circadian clock genes. The altered expressions of these genes have been mainly described in animals. The mammalian master clock in the suprachiasmatic nuclei orchestrates the biological rhythms in peripheral tissues. As peripheral blood mononuclear cells (PBMCs) are the most accessible tissue clinically, we assessed the mRNA levels of these genes in patients with alcohol dependence (AD) undergoing alcohol-withdrawal (AW) treatment.

METHODS

 Twenty-two male patients fulfilled the DSM-IV diagnostic criteria of AD, and 12 comparison healthy control subjects were recruited. The patients with AD were further divided by the presence of delirium tremens (DTs), the most severe form of AW syndrome, into DT group and non-DT group. All the participants received blood withdrawal at 9 am, while the patients with AD had blood collection twice: on the next morning of admission (baseline) and on the seventh day. PBMCs were isolated from whole blood, and the mRNA expression profiles of hClock1, hBmal1, hPer1, hPer2, hCry1, and hCry2 were determined by quantitative real-time PCR.

RESULTS

The baseline mRNA levels of the target circadian clock genes were markedly lower in patients with AD than in control subjects. After 1 week of alcohol detoxification, there were very limited restorations of discrete circadian gene expressions. DT group did not differ in the expression patterns of circadian clock genes from non-DT group.

CONCLUSIONS

This is the first study demonstrating the overall lowering of circadian clock genes among patients with AD. The expression pattern is comparable between patients with and without DTs. Although preliminary with data at only one single time point, the observation of strikingly reduced mRNA levels supports the association between circadian clock gene dysregulation and chronic alcohol intake.

Chronic ethanol intake alters circadian phase shifting and free-running period in mice

Chronic alcohol intake is associated with widespread disruptions in sleep and circadian rhythms in both human alcoholics and in experimental animals. Recent studies have demonstrated that chronic and acute ethanol treatments alter fundamental properties of the circadian pacemaker--including free-running period and responsiveness to photic and nonphotic phase-shifting stimuli--in rats and hamsters. In the present work, the authors extend these observations to the C57BL/6J mouse, an inbred strain characterized by very high levels of voluntary ethanol intake and by reliable and stable free-running circadian activity rhythms. Mice were housed individually in running-wheel cages under conditions of either voluntary or forced ethanol intake, whereas controls were maintained on plain water. Forced ethanol intake significantly attenuated photic phase delays (but not phase advances) and shortened free-running period in constant darkness, but voluntary ethanol intake failed to affect either of these parameters. Thus, high levels of chronic ethanol intake, beyond those normally achieved under voluntary drinking conditions, are required to alter fundamental circadian pacemaker properties in C57BL/6J mice. These observations may be related to the relative ethanol insensitivity displayed by this strain in several other phenotypic domains, including ethanol-induced sedation, ataxia, and withdrawal. Additional experiments will investigate chronobiological sensitivity to ethanol in a range of inbred strains showing diverse ethanol-related phenotypes.

The genetics of deliria

Delirium not induced by alcohol or other psychoactive substance and alcohol withdrawal delirium (or delirium tremens) are both cerebral syndromes with similar presentations and are associated with various adverse outcomes. Recently, interest in identifying genetic predisposing factors that influence the occurrence or the outcome of delirium has become a prominent point of delirium research. We systematically searched published articles concerning genetic associations and the occurrence and outcome of delirium. Of 33 identified articles, six investigated non-alcohol withdrawal delirium, and from those six, five evaluated an association with apolipoprotein E (APOE). One association of APOE genotype with the emergence of delirium and two associations of APOE genotype with the duration of delirium were reported. The remaining 27 identified articles investigated genetic associations with alcohol withdrawal delirium and were mainly related to dopamine. Two studies reported a significant association of alcohol withdrawal delirium with the dopamine transporter gene (SLC6A3) and the dopamine receptor 3 (DRD3). Results are inconclusive, and no hard evidence exists due primarily to insufficiently powered studies and other methodological issues. Prospective studies incorporating systematic and rigorous diagnostic criteria and involving long term follow up are needed to advance understanding of this field.

The effect of curcumin on ethanol induced changes in suprachiasmatic nucleus (SCN) and pineal

(1) Circadian clocks have been localized to discrete sites within the nervous system of several organisms and in mammals to the suprachiasmatic nucleus (SCN) in the anterior hypothalamus. The SCN controls and regulates the production and discharge of melatonin (hormonal message of darkness) from the pineal gland via a multisynaptic efferent pathway. The nocturnal rise in melatonin production from serotonin results due to an increased activity of serotonin N-acetyl transferase (NAT). (2) The complex interaction between alcohol and biological clock need to be understood as alcoholism results in various clock linked neuronal disorders especially loss of memory and amnesia like state of consciousness, sleep disorders, insomnia, dementia etc. (3) Serotonin, 5-Hydroxy-tryptamine (5-HT) plays an important role in mediating alcohol's effects on the brain. Understanding the impact of alcohol consumption on circadian system is a pre-requisite to help in treatment of alcohol induced neurological disorders. We, therefore, studied the effect of ethanol drinking and ethanol withdrawal on daily rhythms of serotonin and its metabolite, 5-hydroxy-indole acetic acid (5-HIAA) in SCN and Pineal of adult male Wistar rats maintained under light-dark (LD, 12:12) conditions. (4) Curcumin is well known for its protective properties such as antioxidant, anti-carcinogenic, anti-viral and anti-infectious etc. Hence, we studied the effect of curcumin on ethanol induced changes on 5-HT and 5-HIAA levels and rhythms in SCN and Pineal. (5) Ethanol withdrawal could not restore either rhythmicity or phases or levels of 5-HT and 5-HIAA. Curcumin administration resulted in partial restoration of daily 5-HT/5-HIAA ratio, with phase shifts in SCN and in Pineal. Understanding the impact of alcohol consumption on circadian system and the role of herbal medication on alcohol withdrawal will help in treatment of alcohol induced neurological disorders.

Alcohol consumption and the body's biological clock

This review summarizes new findings on the bidirectional interactions between alcohol and the clock genes, underlying the generation of circadian rhythmicity. At the behavioral level, both adult and perinatal ethanol treatments after the free-running period and light response of the circadian clock in rodents; genetic ethanol preference in alcohol-preferring rat lines is also associated with alterations in circadian pacemaker function. At the neuronal level, it has been shown that ethanol consumption alters the circadian expression patterns of period (per) genes in various brain regions, including the suprachiasmatic nucleus. Notably, circadian functions of beta-endorphin-containing neurons that participate in the control of alcohol reinforcement become disturbed after chronic alcohol intake. In turn, per2 gene activity regulates alcohol intake through its effects on the glutamatergic system through glutamate reuptake mechanisms and thereby may affect a variety of physiological processes that are governed by our internal clock. In summary, a new pathologic chain has been identified that contributes to the negative health consequences of chronic alcohol intake. Thus, chronic alcohol intake alters the expression of per genes, and as a consequence, a variety of neurochemical and neuroendocrine functions become disturbed. Further steps in this pathologic chain are alterations in physiological and immune functions that are under circadian control, and, as a final consequence, addictive behavior might be triggered or sustained by this cascade.

Chronic ethanol intake alters circadian period-responses to brief light pulses in rats

Although chronic alcohol intake is associated with widespread disruptions of sleep-wake cycles and other daily biological rhythms in both human alcoholics and experimental animals, the extent to which the chronobiological effects of alcohol are mediated by effects on the underlying circadian pacemaker remains unknown. Nevertheless, recent studies indicate that both adult and perinatal ethanol treatments may alter the free-running period and photic responsiveness of the circadian pacemaker. The present experiment was designed to further characterize the effects of chronic ethanol intake on the response of the rat circadian pacemaker to brief light pulses. Ethanol-treated and control animals were exposed to 15-min light pulses during either early or late subjective night on the first day of constant darkness following entrainment to a 12:12 light-dark cycle. Relative to pulses delivered during early subjective night and to "no-pulse" conditions, light pulses delivered during late subjective night resulted in period-shortening after-effects under constant darkness, but only in control animals, not in ethanol-treated animals. These results indicate that chronic ethanol intake reduces the responsiveness of the circadian pacemaker to acute photic stimulation, and suggest that the chronobiological disruptions seen in human alcoholics are due in part to alterations in circadian pacemaker function.

Circadian activity rhythms in selectively bred ethanol-preferring and nonpreferring rats

Chronic alcohol intake is associated with dramatic disruptions in sleep and other circadian biological rhythms in both humans and experimental animals. In human alcoholics, these disruptions persist during extended abstinence and appear to promote relapse to drinking. Whereas chronic ethanol intake alters fundamental properties of the circadian pacemaker in unselected rats, nothing is known concerning circadian pacemaker function in selectively bred ethanol-preferring and nonpreferring rats, which are the most widely accepted animal models of genetic predisposition to alcoholism. The present experiments were designed to characterize free-running circadian activity (wheel-running) rhythms under both constant darkness and constant light in selectively bred ethanol-preferring (P, HAD2) and nonpreferring (NP, LAD2) rats. Differences in circadian organization between ethanol-preferring and nonpreferring animals were seen for both pairs of selected lines (P vs. NP; HAD2 vs. LAD2), but these differences were not identical in the two line pairs. For example, although P rats showed shorter free-running periods than NP rats only in constant light, HAD2 rats showed shorter free-running periods than LAD2 rats only in constant darkness. In addition, ethanol-preferring HAD2 rats showed a high rate of rhythm "splitting" that was not seen in any of the other three lines. Taken together, these results suggest that the circadian pacemakers of P and NP rats differ mainly in light sensitivity, whereas those of HAD2 and LAD2 rats differ in their intrinsic period.

5-Hydroxyindolacetic acid and homovanillic acid are not involved in the cerebrospinal fluid after a seizure in patients with Delirium Tremens

Little is known about 5-hydroxyindolacetic acid (5-HIAA) and homovanillic acid (HVA) levels in cerebrospinal fluid of patients with Delirium Tremens revealed at onset by seizures. The aim of the study is to understand the biochemical abnormalities induced by seizures in the cerebrospinal fluid of patients involved by Delirium Tremens. Nine patients 42-62 years of age, who had experienced a Delirium Tremens after alcohol withdrawal, with one or two seizures at onset, were included in this study. The lumbar puncture (and a CT scan) were performed after the last seizure. Nine patients with neither Delirium Tremens nor seizure, needing a lumbar puncture for their medical problem, were matched by sex and by age. For the measures of 5-HIAA and HVA, we systematically took the first cm3. The mean value of 5-HIAA levels were 12.70 ng ml(-1) in the group of nine patients with Delirium Tremens versus 13.45 ng ml(-1) in the control group. The mean value of HVA levels were 19.81 ng ml(-1) in the group of nine patients with Delirium Tremens versus 25.25 ng ml(-1) in the control group. The differences were not statistically significant. During a Delirium Tremens with seizure at onset, there are no statistically significant changes in 5-HIAA and HVA levels in the cerebrospinal fluid. Our work raises the question of the role of Delirium Tremens in the normalization of the levels of neuro-mediators that usually decrease soon after seizures.

5-Hydroxy-indolacetic-acid (5-HIAA) serum levels in depressive patients and ECT

In 31 drug and ECT naive melancholic patients, serum levels of the major metabolite of serotonin 5-hydroxy-indolacetic-acid (5-HIAA) were estimated in the first and third ECT of a course. Plasma samples were taken before ECT and 1, 60 and 120 min thereafter. The estimations were done by a new high performance liquid chromatography method (HPLC). After the seizure, a statistically significant decrease of 5-HIAA serum levels was observed over both ECTs. There was a significant increase in 5-HIAA serum levels from the first to the third ECT. ECT was found to influence serotonin turnover. It might be interpreted that ECT improves serotonergic responsiveness and neurotransmission. There was no significant correlation between 5-HIAA levels and gender, or age of the patients, or seizure duration. Furthermore, the severity of depression and treatment response did not correlate with certain 5-HIAA serum level patterns.

The reduction of alcohol consumption with novel pharmacological intervention

The development of pharmacological agents in treating alcoholism represents one of many different ways to suppress alcohol intake. Regarding the hypothetical involvement of different neurochemical systems in "alcohol craving", specific substances have been examined in animals models (especially rats) and increasingly in man. Promising results in reducing "alcohol craving" were described in the use of different kinds of chemical substances. "Craving" therefore can hardly be explained on the basis of a deficit in only one neurochemical (neurotransmitter) system. This conclusion is supported by the data. The efficiacy of many anti-craving substances described in smaller studies must first be confirmed in clinical studies on a wider scale.

Psychotropic analgesic nitrous oxide and neurotransmitter mechanisms involved in the alcohol withdrawal state

We relate the extremely rapid and lasting beneficial effects of psychotropic analgesic nitrous oxide (PAN) on the alcohol withdrawal state (AWS) to the underlying neurotransmitter system disturbances and clinical findings. PAN is an opioid and its main therapeutic effects are produced by stimulating the underactive endogenous opioid system (EOS) found in the AWS. In common with other opioids, PAN also acts on other neurotransmitter systems. While controlling the cholinergic and adrenergic overactivity and the concomitant stress state, through its opioid agonism, it simultaneously stimulates the underactive serotonergic and GABA-ergic systems found in the AWS. PAN also ameliorates disturbances in corticotropin-releasing factor (CRF) dopaminergic, glutaminergic and second messenger function. This unique combination of stimulation and inhibition enables a single 20 minute administration of PAN to rapidly restore the patients' homeostatic balance with lasting effect, and almost no other medication requirements during the entire detoxification period. Unlike other currently available therapies this is achieved without sedation.