The acute and temporary modulation of PERIOD genes by hydrocortisone in healthy subjects

Stroke in the Time of Circadian Medicine

Time-of-day significantly influences the severity and incidence of stroke. Evidence has emerged not only for circadian governance over stroke risk factors, but also for important determinants of clinical outcome. In this review, we provide a comprehensive overview of the interplay between chronobiology and cerebrovascular disease. We discuss circadian regulation of pathophysiological mechanisms underlying stroke onset or tolerance as well as in vascular dementia. This includes cell death mechanisms, metabolism, mitochondrial function, and inflammation/immunity. Furthermore, we present clinical evidence supporting the link between disrupted circadian rhythms and increased susceptibility to stroke and dementia. We propose that circadian regulation of biochemical and physiological pathways in the brain increase susceptibility to damage after stroke in sleep and attenuate treatment effectiveness during the active phase. This review underscores the importance of considering circadian biology for understanding the pathology and treatment choice for stroke and vascular dementia and speculates that considering a patient's chronotype may be an important factor in developing precision treatment following stroke.

Effect of acute stress on working memory in pilots: Investigating the modulatory role of memory load

Many practitioners, such as pilots, frequently face working memory (WM) demands under acute stress environments, while the effect of acute stress on WM has not been conclusively studied because it is moderated by a variety of factors. The current study investigated how acute stress affects pilots' WM under different memory load conditions. There are 42 pilots conducting the experiments, consisting of 21 stress group participants experiencing the Trier Social Stress Test (TSST) and 21 control group participants experiencing the controlled TSST (C-TSST). Subsequently, both groups performed N-back tasks under three memory load conditions (0-back, 1-back, and 2-back). State Anxiety Inventory (S-AI), heart rate (HR), and salivary cortisol concentrations (SCC) were collected to analyze acute stress induction. The results revealed that (1) the TSST could effectively induce acute stress with higher S-AI, HR, and SCC; (2) higher memory load reduces WM accuracy (ACC) and delays response times (RT); (3) acute stress increases WM ACC under moderate load conditions (1-back task). These results suggest that acute stress may not necessarily impair WM and even improve WM performance under certain memory load conditions. Potential mechanisms of acute stress effects on WM and alternative explanations for the modulatory role of memory load consistent with the emotion and motivation regulation theory are discussed. These findings not only provide insight into the field of acute stress and WM but are also beneficial for pilot training and the development of stress management strategies.

Association of Circadian Clock Gene Expression with Pediatric/Adolescent Asthma and Its Comorbidities

The pathology of asthma is characterized by marked day-night variation, which is likely controlled by circadian clock activity. This study aimed to clarify the association of core circadian clock gene expression with clinical features of asthma. For this purpose, we accessed the National Center for Biotechnology Information database and analyzed transcriptomes of peripheral blood mononuclear cells and clinical characteristics of 134 pediatric/adolescent patients with asthma. Based on the expression patterns of seven core circadian clock genes (CLOCK, BMAL1, PER1-3, CRY1-2), we identified three circadian clusters (CCs) with distinct comorbidities and transcriptomic expressions. In the three CC subtypes, allergic rhinitis, and atopic dermatitis, both asthma comorbidities occurred in different proportions: CC1 had a high proportion of allergic rhinitis and atopic dermatitis; CC2 had a high proportion of atopic dermatitis but a low proportion of allergic rhinitis; and CC3 had a high proportion of allergic rhinitis but a low proportion of atopic dermatitis. This might be associated with the low activity of the FcεRI signaling pathway in CC2 and the cytokine-cytokine receptor interaction pathways in CC3. This is the first report to consider circadian clock gene expression in subcategories of patients with asthma and to explore their contribution to pathophysiology and comorbidity.

Circadian Clock, Glucocorticoids and NF-κB Signaling in Neuroinflammation- Implicating Glucocorticoid Induced Leucine Zipper as a Molecular Link

Inflammation including neuroinflammation is considered a protective response and is directed to repair, regenerate, and restore damaged tissues in the central nervous system. Persistent inflammation due to chronic stress, age related accrual of free radicals, subclinical infections or other factors lead to reduced survival and increased neuronal death. Circadian abnormalities secondary to altered sleep/wake cycles is one of the earliest signs of neurodegenerative diseases. Brain specific or global deficiency of core circadian trans-activator brain and muscle ARNT (Arylhydrocarbon Receptor Nuclear Translocator)-like protein 1 (BMAL1) or that of the transrepressor REV-ERBα, impaired neural function and cognitive performance in rodents. Consistently, transcripts of inflammatory cytokines and host immune responses have been shown to exhibit diurnal variation, in parallel with the disruption of the circadian rhythm. Glucocorticoids that exhibit both a circadian rhythm similar to that of the core clock transactivator BMAL1 and tissue specific ultradian rhythm are critical in the control of neuroinflammation and re-establishment of homeostasis. It is widely accepted that the glucocorticoids suppress nuclear factor-kappa B (NF-κB) mediated transactivation and suppress inflammation. Recent mechanistic elucidations suggest that the core clock components also modulate NF-κB mediated transactivation in the brain and peripheral tissues. In this review we discuss evidence for interactions between the circadian clock components, glucocorticoids and NF-κB signaling responses in the brain and propose glucocorticoid induced leucine zipper (GILZ) encoded by Tsc22d3, as a molecular link that connect all three pathways in the maintenance of CNS homeostasis as well as in the pathogenesis of neuroinflammation-neurodegeneration.

Molecular regulations of circadian rhythm and implications for physiology and diseases

The term “circadian rhythms” describes endogenous oscillations with ca. 24-h period associated with the earth’s daily rotation and light/dark cycle. Such rhythms reflect the existence of an intrinsic circadian clock that temporally orchestrates physiological processes to adapt the internal environment with the external cues. At the molecular level, the circadian clock consists of multiple sets of transcription factors resulting in autoregulatory transcription-translation feedback loops. Notably, in addition to their primary role as generator of circadian rhythm, the biological clock plays a key role in controlling physiological functions of almost all tissues and organs. It regulates several intracellular signaling pathways, ranging from cell proliferation, DNA damage repair and response, angiogenesis, metabolic and redox homeostasis, to inflammatory and immune response. In this review, we summarize findings showing the crosstalk between the circadian molecular clock and some key intracellular pathways, describing a scenario wherein their reciprocal regulation impinges upon several aspects of mammalian physiology. Moreover, based on evidence indicating that circadian rhythms can be challenged by environmental factors, social behaviors, as well as pre-existing pathological conditions, we discuss implications of circadian misalignment in human pathologies, such as cancer and inflammatory diseases. Accordingly, disruption of circadian rhythm has been reported to affect several physiological processes that are relevant to human diseases. Expanding our understanding of this field represents an intriguing and transversal medicine challenge in order to establish a circadian precision medicine.

Circadian clock genes as promising therapeutic targets for autoimmune diseases

Circadian rhythm is a natural, endogenous process whose physiological functions are controlled by a set of clock genes. Disturbance of the clock genes have detrimental effects on both innate and adaptive immunity, which significantly enhance pro-inflammatory responses and susceptibility to autoimmune diseases via strictly controlling the individual cellular components of the immune system that initiate and perpetuate the inflammation pathways. Autoimmune diseases, especially rheumatoid arthritis (RA), often exhibit substantial circadian oscillations, and circadian rhythm is involved in the onset and progression of autoimmune diseases. Mounting evidence indicate that the synthetic ligands of circadian clock genes have the property of reducing the susceptibility and clinical severity of subjects. This review supplies an overview of the roles of circadian clock genes in the pathology of autoimmune diseases, including BMAL1, CLOCK, PER, CRY, REV-ERBα, and ROR. Furthermore, summarized some circadian clock genes as candidate genes for autoimmune diseases and current advancement on therapy of autoimmune diseases with synthetic ligands of circadian clock genes. The existing body of knowledge demonstrates that circadian clock genes are inextricably linked to autoimmune diseases. Future research should pay attention to improve the quality of life of patients with autoimmune diseases and reduce the effects of drug preparation on the normal circadian rhythms.

Multidimensional informatic deconvolution defines gender-specific roles of hypothalamic GIT2 in aging trajectories

In most species, females live longer than males. An understanding of this female longevity advantage will likely uncover novel anti-aging therapeutic targets. Here we investigated the transcriptomic responses in the hypothalamus - a key organ for somatic aging control - to the introduction of a simple aging-related molecular perturbation, i.e. GIT2 heterozygosity. Our previous work has demonstrated that GIT2 acts as a network controller of aging. A similar number of both total (1079-female, 1006-male) and gender-unique (577-female, 527-male) transcripts were significantly altered in response to GIT2 heterozygosity in early life-stage (2 month-old) mice. Despite a similar volume of transcriptomic disruption in females and males, a considerably stronger dataset coherency and functional annotation representation was observed for females. It was also evident that female mice possessed a greater resilience to pro-aging signaling pathways compared to males. Using a highly data-dependent natural language processing informatics pipeline, we identified novel functional data clusters that were connected by a coherent group of multifunctional transcripts. From these it was clear that females prioritized metabolic activity preservation compared to males to mitigate this pro-aging perturbation. These findings were corroborated by somatic metabolism analyses of living animals, demonstrating the efficacy of our new informatics pipeline.

Insulin/IGF-1 Drives PERIOD Synthesis to Entrain Circadian Rhythms with Feeding Time

In mammals, endogenous circadian clocks sense and respond to daily feeding and lighting cues, adjusting internal ∼24 h rhythms to resonate with, and anticipate, external cycles of day and night. The mechanism underlying circadian entrainment to feeding time is critical for understanding why mistimed feeding, as occurs during shift work, disrupts circadian physiology, a state that is associated with increased incidence of chronic diseases such as type 2 (T2) diabetes. We show that feeding-regulated hormones insulin and insulin-like growth factor 1 (IGF-1) reset circadian clocks in vivo and in vitro by induction of PERIOD proteins, and mistimed insulin signaling disrupts circadian organization of mouse behavior and clock gene expression. Insulin and IGF-1 receptor signaling is sufficient to determine essential circadian parameters, principally via increased PERIOD protein synthesis. This requires coincident mechanistic target of rapamycin (mTOR) activation, increased phosphoinositide signaling, and microRNA downregulation. Besides its well-known homeostatic functions, we propose insulin and IGF-1 are primary signals of feeding time to cellular clocks throughout the body.

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Insulin and IGF-1 are a systemic synchronizing cue for circadian rhythms in mammals

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Insulin and IGF-1 signaling rapidly upregulates translation of PERIOD clock proteins

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Coincident signaling facilitates selective induction of PERIOD synthesis

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Circadian disruption is recapitulated by mistimed insulin in cell and animal models

Temporal dynamics of cortisol-associated changes in mRNA expression of glucocorticoid responsive genes FKBP5, GILZ, SDPR, PER1, PER2 and PER3 in healthy humans

Secretion of the stress hormone cortisol follows a circadian rhythm and is stimulated following stress exposure. Cortisol regulates the transcription of several genes, primarily through activation of the glucocorticoid receptor (GR). Previously, we showed an upregulation of PERIOD genes PER1 and PER3 after pharmacological/glucocorticoid challenge in vivo and in vitro. The current study aims to investigate the temporal association between unstimulated, diurnal cortisol secretion and the expression of selected GR-target genes (PER1, PER2, PER3, FKBP5, GILZ and SDPR) in vivo to determine the timing of the most pronounced coupling between cortisol and mRNA expression. Unstimulated plasma and saliva cortisol concentrations and gene expression levels in whole blood were measured every 15 min from early morning until 16:00 h in 18 healthy men. Time-lagged correlations of cortisol concentrations with mRNA expression levels were assessed allowing lags between -240 and + 240 min. Strong positive correlations at non-zero lags between cortisol levels and the expression of FKBP5 (plasma: r = 0.74 (CI = 0.65-0.81), p <  0.001, lag + 90 min; saliva: r = 0.71 (CI = 0.61-0.78), p <  0.001, lag + 75 min), and GILZ (plasma: r = 0.59 (CI = 0.46-0.69), p <  0.001, lag + 30 min; saliva r = 0.53 (CI = 0.41-0.63), p <  0.001, lag +15 min) were observed. Expressions of PERIOD genes and SDPR correlated only weakly with cortisol (all |r| < 0.25). Our findings demonstrate strong correlations between cortisol secretion and gene expression in humans under unstimulated conditions. The observed time-lags can guide future research aiming to characterize glucocorticoid-dependent gene expression in clinical samples with stress-related disorders.

Coupling the Circadian Clock to Homeostasis: The Role of Period in Timing Physiology

A plethora of physiological processes show stable and synchronized daily oscillations that are either driven or modulated by biological clocks. A circadian pacemaker located in the suprachiasmatic nucleus of the ventral hypothalamus coordinates 24-hour oscillations of central and peripheral physiology with the environment. The circadian clockwork involved in driving rhythmic physiology is composed of various clock genes that are interlocked via a complex feedback loop to generate precise yet plastic oscillations of ∼24 hours. This review focuses on the specific role of the core clockwork gene Period1 and its paralogs on intra-oscillator and extra-oscillator functions, including, but not limited to, hippocampus-dependent processes, cardiovascular function, appetite control, as well as glucose and lipid homeostasis. Alterations in Period gene function have been implicated in a wide range of physical and mental disorders. At the same time, a variety of conditions including metabolic disorders also impact clock gene expression, resulting in circadian disruptions, which in turn often exacerbates the disease state.

Glucocorticoid hormones are both a major circadian signal and major stress signal: How this shared signal contributes to a dynamic relationship between the circadian and stress systems

Glucocorticoid hormones are a powerful mammalian systemic hormonal signal that exerts regulatory effects on almost every cell and system of the body. Glucocorticoids act in a circadian and stress-directed manner to aid in adaptation to an ever-changing environment. Circadian glucocorticoid secretion provides for a daily waxing and waning influence on target cell function. In addition, the daily circadian peak of glucocorticoid secretion serves as a timing signal that helps entrain intrinsic molecular clock phase in tissue cells distributed throughout the body. Stress-induced glucocorticoid secretion also modulates the state of these same cells in response to both physiological and psychological stressors. We review the strong functional interrelationships between glucocorticoids and the circadian system, and discuss how these interactions optimize the appropriate cellular and systems response to stress throughout the day. We also discuss clinical implications of this dual aspect of glucocorticoid signaling, especially for conditions of circadian and HPA axis dysregulation.

Time-dependent glucocorticoid administration differently affects peripheral circadian rhythm in rats

There is a growing recognition that glucocorticoid (GC) acts as an internal timing signal for peripheral circadian oscillators. However, the transcription process of GC-related clock gene in the peripheral tissues is not fully understood. The present study was designed to explore the potential role of clock genes in the GC-induced peripheral circadian gene expression in vivo. Real-time RT-PCR analysis indicated that the transcript levels of Per1 and Dec1 were rapidly up-regulated within 0.5 and 1 h in the heart and kidney respectively after stimulation with dexamethasone (Dex). These results suggest that Per1 and Dec1 serve as the primary and secondary responsers respectively in initiating the GC-induced peripheral circadian gene expression. By comparing the effects of the different GC administration schedules on the circadian rhythm of clock genes in peripheral tissues in rats, we found that the circadian phases of Bmal1 and Per1 were shifted more in the ZT0 (endogenous valley time) Dex stimulation group than in the ZT12 (endogenous peak time) Dex stimulation group in heart and kidney under the normal LD cycle. Under the jet lag condition, the circadian phases of Bmal1 and Per1 were also shifted more in the ZT0 Dex stimulation group than in the ZT12 Dex stimulation group. Therefore, the GC stimulation in the endogenous valley time caused circadian disorder in the normal LD cycle, but it might benefit the circadian resetting of peripheral clocks under the LD reversal condition.