Pharmacological modulation of circadian rhythms: a new drug target in psychotherapeutics

Mechanisms underlying the association between insomnia, anxiety, and depression in adolescence: Implications for behavioral sleep interventions

There is robust evidence of an association between insomnia, anxiety, and depression in adolescence. The aim of this review is to describe and synthesize potential mechanisms underlying this association and explore implications for the design of adolescent behavioral sleep interventions. Specifically, we examine whether insomnia symptoms are a mechanism for the development of internalizing symptoms in adolescence and whether sleep interventions are an effective treatment for both insomnia and internalizing symptoms in adolescence because they target the shared mechanisms underlying these disorders. Research using different methodologies points to the role of sequential, parallel, and interacting mechanisms. In this paper, we review a wide range of relevant biological (i.e., polymorphisms and dysregulation in serotonin, dopamine, and circadian clock genes; alterations in corticolimbic and mesolimbic brain circuits; cortisol reactivity to stress; inflammatory cytokine dysregulation; biased memory consolidation; changes in sleep architecture), psychological (i.e., cognitive inflexibility, interpretational biases, judgment biases, negative attribution styles, worry, rumination, biased attention to threat, dysfunctional beliefs and attitudes about sleep, misperception of sleep deficit), and social mechanisms (i.e., reduced and impaired social interactions, unhelpful parenting behaviors, family stress) and propose an integrative multilevel model of how these phenomena may interact to increase vulnerability to both insomnia and internalizing disorders. Several 'biopsychosocial' mechanisms hold promise as viable treatment targets for adolescent behavioral sleep interventions, which may reduce both insomnia and internalizing symptoms.

Regulation of bone mass through pineal-derived melatonin-MT2 receptor pathway

Tryptophan, an essential amino acid through a series of enzymatic reactions gives rise to various metabolites, viz. serotonin and melatonin, that regulate distinct biological functions. We show here that tryptophan metabolism in the pineal gland favors bone mass accrual through production of melatonin, a pineal-derived neurohormone. Pineal gland-specific deletion of Tph1, the enzyme that catalyzes the first step in the melatonin biosynthesis lead to a decrease in melatonin levels and a low bone mass due to an isolated decrease in bone formation while bone resorption parameters remained unaffected. Skeletal analysis of the mice deficient in MT1 or MT2 melatonin receptors showed a low bone mass in MT2-/- mice while MT1-/- mice had a normal bone mass compared to the WT mice. This low bone mass in the MT2-/- mice was due to an isolated decrease in osteoblast numbers and bone formation. In vitro assays of the osteoblast cultures derived from the MT1-/- and MT2-/- mice showed a cell intrinsic defect in the proliferation, differentiation and mineralization abilities of MT2-/- osteoblasts compared to WT counterparts, and the mutant cells did not respond to melatonin addition. Finally, we demonstrate that daily oral administration of melatonin can increase bone accrual during growth and can cure ovariectomy-induced structural and functional degeneration of bone by specifically increasing bone formation. By identifying pineal-derived melatonin as a regulator of bone mass through MT2 receptors, this study expands the role played by tryptophan derivatives in the regulation of bone mass and underscores its therapeutic relevance in postmenopausal osteoporosis.

Systems Chronotherapeutics

Chronotherapeutics aim at treating illnesses according to the endogenous biologic rhythms, which moderate xenobiotic metabolism and cellular drug response. The molecular clocks present in individual cells involve approximately fifteen clock genes interconnected in regulatory feedback loops. They are coordinated by the suprachiasmatic nuclei, a hypothalamic pacemaker, which also adjusts the circadian rhythms to environmental cycles. As a result, many mechanisms of diseases and drug effects are controlled by the circadian timing system. Thus, the tolerability of nearly 500 medications varies by up to fivefold according to circadian scheduling, both in experimental models and/or patients. Moreover, treatment itself disrupted, maintained, or improved the circadian timing system as a function of drug timing. Improved patient outcomes on circadian-based treatments (chronotherapy) have been demonstrated in randomized clinical trials, especially for cancer and inflammatory diseases. However, recent technological advances have highlighted large interpatient differences in circadian functions resulting in significant variability in chronotherapy response. Such findings advocate for the advancement of personalized chronotherapeutics through interdisciplinary systems approaches. Thus, the combination of mathematical, statistical, technological, experimental, and clinical expertise is now shaping the development of dedicated devices and diagnostic and delivery algorithms enabling treatment individualization. In particular, multiscale systems chronopharmacology approaches currently combine mathematical modeling based on cellular and whole-body physiology to preclinical and clinical investigations toward the design of patient-tailored chronotherapies. We review recent systems research works aiming to the individualization of disease treatment, with emphasis on both cancer management and circadian timing system–resetting strategies for improving chronic disease control and patient outcomes.

Do Circadian Rhythms Draw the Patterns of Sustained Mental Vigor and Ailment?

Preclinical Research Circadian rhythms are fundamental processes in all cells that coordinate a variety of cellular functions related to a specific time of the day. Disruption of circadian rhythms markedly impacts homeostasis. In this Commentary, we present data that disruption of circadian rhythm may lead to the pathogenesis of neurodegenerative states. In this context, we further argue that there is an urgent need of developing new generations of compounds, chronobiotics, to modulate the molecular substrates of circadian timing system. Chronobiotics conceptually offer an effective way for restoration and protection from the consequences of the circadian disruption. We also briefly discuss whether dysfunctional circadian rhythms are a major driver of aging. Drug Dev Res 77 : 469-473, 2016. © 2016 Wiley Periodicals, Inc.

Selective pharmacological blockade of the 5-HT7 receptor attenuates light and 8-OH-DPAT induced phase shifts of mouse circadian wheel running activity

Recent reports have illustrated a reciprocal relationship between circadian rhythm disruption and mood disorders. The 5-HT7 receptor may provide a crucial link between the two sides of this equation since the receptor plays a critical role in sleep, depression, and circadian rhythm regulation. To further define the role of the 5-HT7 receptor as a potential pharmacotherapy to correct circadian rhythm disruptions, the current study utilized the selective 5-HT7 antagonist JNJ-18038683 (10 mg/kg) in three different circadian paradigms. While JNJ-18038683 was ineffective at phase shifting the onset of wheel running activity in mice when administered at different circadian time (CT) points across the circadian cycle, pretreatment with JNJ-18038683 blocked non-photic phase advance (CT6) induced by the 5-HT1A/7 receptor agonist 8-OH-DPAT (3 mg/kg). Since light induced phase shifts in mammals are partially mediated via the modulation of the serotonergic system, we determined if JNJ-18038683 altered phase shifts induced by a light pulse at times known to phase delay (CT15) or advance (CT22) wheel running activity in free running mice. Light exposure resulted in a robust shift in the onset of activity in vehicle treated animals at both times tested. Administration of JNJ-18038683 significantly attenuated the light induced phase delay and completely blocked the phase advance. The current study demonstrates that pharmacological blockade of the 5-HT7 receptor by JNJ-18038683 blunts both non-photic and photic phase shifts of circadian wheel running activity in mice. These findings highlight the importance of the 5-HT7 receptor in modulating circadian rhythms. Due to the opposite modulating effects of light resetting between diurnal and nocturnal species, pharmacotherapy targeting the 5-HT7 receptor in conjunction with bright light therapy may prove therapeutically beneficial by correcting the desynchronization of internal rhythms observed in depressed individuals.

Time-restricted feeding and the realignment of biological rhythms: translational opportunities and challenges

It has been argued that circadian dysregulation is not only a critical inducer and promoter of adverse health effects, exacerbating symptom burden, but also hampers recovery. Therefore understanding the health-promoting roles of regulating (i.e., restoring) circadian rhythms, thus suppressing harmful effects of circadian dysregulation, would likely improve treatment. At a critical care setting it has been argued that studies are warranted to determine whether there is any use in restoring circadian rhythms in critically ill patients, what therapeutic goals should be targeted, and how these could be achieved. Particularly interesting are interventional approaches aiming at optimizing the time of feeding in relation to individualized day-night cycles for patients receiving enteral nutrition, in an attempt to re-establish circadian patterns of molecular expression. In this short review we wish to explore the idea of transiently imposing (appropriate, but yet to be determined) circadian rhythmicity via regulation of food intake as a means of exploring rhythm-setting properties of metabolic cues in the context of improving immune response. We highlight some of the key elements associated with his complex question particularly as they relate to: a) stress and rhythmic variability; and b) metabolic entrainment of peripheral tissues as a possible intervention strategy through time-restricted feeding. Finally, we discuss the challenges and opportunities for translating these ideas to the bedside.

Antidepressant chronotherapeutics for bipolar depression

Chronotherapeutics refers to treatments based on the principles of circadian rhythm organization and sleep physiology, which control the exposure to environmental stimuli that act on biological rhythms, in order to achieve therapeutic effects in the treatment of psychiatric conditions. It includes manipulations of the sleep-wake cycle such as sleep deprivation and sleep phase advance, and controlled exposure to light and dark. The antidepressant effects of chronotherapeutics are evident in difficult-to-treat conditions such as bipolar depression, which has been associated with extremely low success rates of antidepressant drugs in naturalistic settings and with stable antidepressant response to chronotherapeutics in more than half of the patients. Recent advances in the study of the effects of chronotherapeutics on neurotransmitter systems, and on the biological clock machinery, allow us to pinpoint its mechanism of action and to transform it from a neglected or “orphan” treatment to a powerful clinical instrument in everyday psychiatric practice.

The mammalian clock and chronopharmacology

Increases in our understanding of the molecular control of circadian rhythms and subsequent signaling pathways has allowed for new therapeutic drug targets to be identified as well as for a better understanding of how to more efficaciously and safely utilize current drugs. Here, we review recent advances in targeting components of the molecular clock in mammals for the development of novel therapeutics as well as describe the impact of the circadian rhythm on drug efficacy and toxicity.

Sleep disturbance as transdiagnostic: consideration of neurobiological mechanisms

Sleep disturbance is increasingly recognized as an important, but understudied, mechanism in the complex and multi-factorial causation of the symptoms and functional disability associated with psychiatric disorders. This review proposes that it is biologically plausible for sleep disturbance to be mechanistically transdiagnostic. More specifically, we propose that sleep disturbance is aetiologically linked to various forms of psychopathology through: its reciprocal relationship with emotion regulation and its shared/interacting neurobiological substrates in (a) genetics--genes known to be important in the generation and regulation of circadian rhythms have been linked to a range of disorders and (b) dopaminergic and serotonergic function--we review evidence for the interplay between these systems and sleep/circadian biology. The clinical implications include potentially powerful and inexpensive interventions including interventions targeting light exposure, dark exposure, the regulation of social rhythms and the reduction of anxiety. We also consider the possibility of developing a 'transdiagnostic' treatment; one treatment that would reduce sleep disturbance across psychiatric disorders.

Rapid changes in night eating: considering mechanisms

This paper considers possible mechanisms for the Night Eating Syndrome (NES). NES is a disorder characterized by a delay in the circadian rhythm of meals and of several neuroendocrine factors. The disorder occurs in genetically vulnerable people when exposed to stress. No convincing mechanism of the NES has been reported until now. To search for the mechanisms of NES, the long term treatment of two highly perceptive patients with rapid onset of the disorder are described. Disruption of three neuroendocrine systems compatible with these histories are discussed: the glucocorticoid system, the melanocortin [corrected] system, and the serotonergic system. Current evidence favors the serotonergic system and this view is strongly supported by the great effectiveness of selective serotonin reuptake inhibitors (SSRIs) in the treatment of NES.

Circadian Disruption, Fatigue, and Anorexia Clustering in Advanced Cancer Patients: Implications for Innovative Therapeutic Approaches

A disruption of the circadian timing system, as identified by monitoring of marker biorhythms, is common in cancer patients. The recording of the rest—activity rhythm with a wrist actigraph has been commonly used. This noninvasive monitoring allows a robust estimation of circadian disruption. The authors have previously found that altered patterns of circadian rest—activity rhythms are significantly and independently associated with the severity of fatigue and anorexia in patients with metastatic colorectal cancer. Elevated proinflammatory cytokines could partly account for this circadian disruption and its associated constitutional symptoms. Here, the authors present and discuss the data supporting the hypothesis that circadian disruption is often associated with fatigue and anorexia, which in turn further alter and dampen circadian synchronization, thus, creating a vicious cycle. This body of evidence paves the path for innovative therapeutic approaches targeting the circadian timing system in an effort to diminish constitutional symptoms induced by cancer and some anticancer treatments.

Circadian disruption accelerates liver carcinogenesis in mice

BACKGROUND

The circadian timing system rhythmically controls behavior, physiology, cellular proliferation and xenobiotic metabolism over the 24-h period. The suprachiasmatic nuclei in the hypothalamus coordinate the molecular clocks in most mammalian cells through an array of circadian physiological rhythms including rest-activity, body temperature, feeding patterns and hormonal secretions. As a result, shift work that involves circadian disruption is probably carcinogenic in humans. In experimental models, chronic jet-lag (CJL) suppresses rest-activity and body temperature rhythms and accelerates growth of two transplantable tumors in mice. CJL also suppresses or significantly alters the expression rhythms of clock genes in liver and tumors. Circadian clock disruption from CJL downregulates p53 and upregulates c-Myc, thus favoring cellular proliferation. Here, we investigate the role of CJL as a tumor promoter in mice exposed to the hepatic carcinogen, diethylnitrosamine (DEN).

METHODS

In experiment 1 (Exp 1), the dose-dependent carcinogenicity of chronic intraperitoneal (i.p.) administration of DEN was explored in mice. In Exp 2, mice received DEN at 10 mg/kg/day (cumulative dose: 243 mg/kg), then were randomized to remain in a photoperiodic regimen where 12 h of light alternates with 12 h of darkness (LD 12:12) or to be submitted to CJL (8-h advance of light onset every 2 days). Rest-activity and body temperature were monitored. Serum liver enzymes were determined repeatedly. Mice were sacrificed and examined for neoplastic lesions at 10 months.

RESULTS

In Exp 1, DEN produced liver cancers in all the mice receiving 10 mg/kg/day. In Exp 2, mice on CJL had increased mean plasma levels of aspartate aminotransferase and more liver tumors as compared to LD mice at approximately 10 months (p = 0.005 and 0.028, respectively). The mean diameter of the largest liver tumor was twice as large in CJL vs LD mice (8.5 vs 4.4 mm, p = 0.027). In LD, a single histologic tumor type per liver was observed. In CJL, up to four different types were associated in the same liver (hepatocellular- or cholangio-carcinomas, sarcomas or mixed tumors). DEN itself markedly disrupted the circadian rhythms in rest-activity and body temperature in all the mice. DEN-induced disruption was prolonged for >or= 3 months by CJL exposure.

CONCLUSIONS

The association of circadian disruption with chronic DEN exposure suggests that circadian clocks actively control the mechanisms of liver carcinogenesis in mice. Persistent circadian coordination may further be critical for slowing down and/or reverting cancer development after carcinogen exposure.

Inhibition of casein kinase I epsilon/delta produces phase shifts in the circadian rhythms of Cynomolgus monkeys

INTRODUCTION

Circadian rhythms in mammals depend upon the cyclic oscillations of transcriptional/translational feedback loops in pacemaker cells of the suprachiasmatic nucleus. The rise and fall of clock-related proteins is a function of synthesis and degradation, the latter involving phosphorylation by casein kinase Iepsilon and delta.

OBJECTIVE

Earlier studies by our lab described the actions of a selective CKIepsilon/delta inhibitor, PF-670462, on circadian behavior in rats; the present work extended these studies to a diurnal species, Cynomolgus monkeys.

MATERIALS AND METHODS

General cage activity was used to estimate the circadian rhythms of eight telemeterized monkeys under baseline conditions and following s.c. doses of PF-670462.

RESULTS AND DISCUSSION

Consolidated bouts of activity were noted during periods of light with a repeating period length of roughly 24 h based on their onset. Reassessment in constant dim light (42 vs. 450 lx) again yielded period lengths of 24 h, in this instance revealing the animals' endogenous rhythm. PF-670462 (10-100 mg/kg s.c.) produced a dose-dependent phase delay in much the same manner as that observed previously in rats. Dosing occurred 1.5 h prior to lights-off, roughly coincident with peaking levels of PER protein, a primary substrate of CKIepsilon/delta.

CONCLUSIONS

These findings suggest that the time of dosing, when held constant in both the monkey and rat studies, produced nearly identical effects despite the subjects' diurnal or nocturnal preference. Importantly, these changes in rhythm occurred in the presence of light, revealing the drug as a powerful zeitgeber in a non-human primate and, by extension, in man.

An Inhibitor of Casein Kinase Iϵ Induces Phase Delays in Circadian Rhythms under Free-Running and Entrained Conditions

Casein kinase Iepsilon (CKIepsilon) is an essential component of the biological clock, phosphorylating PER proteins, and in doing so regulating their turnover and nuclear entry in oscillator cells of the suprachiasmatic nucleus (SCN). Although hereditary decreases in PER phosphorylation have been well characterized, little is known about the consequences of acute enzyme inhibition by pharmacological means. A novel reagent, 4-[3-cyclohexyl-5-(4-fluoro-phenyl)-3H-imidazol-4-yl]-pyrimidin-2-ylamine (PF-670462), proved to be both a potent (IC(50) = 7.7 +/- 2.2 nM) and selective (>30-fold with respect to 42 additional kinases) inhibitor of CKIepsilon in isolated enzyme preparations; in transfected whole cell assays, it caused a concentration-related redistribution of nuclear versus cytosolic PER. When tested in free-running animals, 50 mg/kg s.c. PF-670462 produced robust phase delays when dosed at circadian time (CT)9 (-1.97 +/- 0.17 h). Entrained rats dosed in normal light-dark (LD) and then released to constant darkness also experienced phase delays that were dose- and time of dosing-dependent. PF-670462 yielded only phase delays across the circadian cycle with the most sensitive time at CT12 when PER levels are near their peak in the SCN. Most importantly, these drug-induced phase delays persisted in animals entrained and maintained in LD throughout the entire experiment; re-entrainment to the prevailing LD required days in contrast to the rapid elimination of the drug (t(1/2) = 0.46 +/- 0.04 h). Together, these results suggest that inhibition of CKIepsilon yields a perturbation of oscillator function that forestalls light as a zeitgeber, and they demonstrate that pharmacological tools such as PF-670462 may yield valuable insight into clock function.

5-HT7 receptor inhibition and inactivation induce antidepressantlike behavior and sleep pattern

BACKGROUND

The 5-hydroxytryptamine7 receptor (5-HT7) is implicated in circadian rhythm phase resetting, and 5-HT7 receptor-selective antagonists alter rapid eye movement (REM) sleep parameters in a pattern opposite from those in patients with clinical depression.

METHODS

As sleep, circadian rhythm, and mood regulation are related, we examined 5-HT7 receptor knockout mice in two behavioral models of depression. The forced swim and tail suspension tests are highly predictive for antidepressant drug activity.

RESULTS

Unmedicated 5-HT7-/- mice showed decreased immobility in both tests, consistent with an antidepressantlike behavior. The selective 5-HT7 receptor antagonist SB-269970 also decreased immobility. The selective serotonin reuptake inhibitor citalopram, a widely used antidepressant, decreased immobility in both 5-HT7+/+ and 5-HT7-/- mice in the tail suspension test, suggesting that it utilizes an independent mechanism. The 5-HT7-/- mice spent less time in and had less frequent episodes of REM sleep, also consistent with an antidepressantlike state.

CONCLUSIONS

The 5-HT7 receptor might have a role in mood disorders and antagonists might have therapeutic value as antidepressants.