Diurnal transcriptome atlas of a primate across major neural and peripheral tissues

Chronopharmacokinetics of the antidepressant paroxetine: An in vitro and in vivo approach

The circadian rhythm influences homeostatic functions such as sleep, physical activity and food intake as well as pharmacotherapy, namely pharmacokinetics. To investigate the impact of the circadian rhythm on the pharmacokinetics of paroxetine, in vitro synchronized permeability studies were carried out in a tri-culture blood-brain barrier model. Paroxetine demonstrated lower apparent permeability when the cells were incubated at 24 h post-synchronization than at 36 h. Additionally, in vivo chronopharmacokinetic studies were performed in CD-1 female mice administered with paroxetine (5 mg/kg) by intranasal route in the early morning or evening. Paroxetine exposure in the brain was higher when it was administered at the beginning of the active phase (ZT13) compared with the rest phase (ZT1) (p < 0.001), probably owing to the lower levels of P-glycoprotein expressed in the brain at the active phase (p < 0.05). Since melatonin production depends on serotonin, its plasma concentrations were also assessed in vivo. The results demonstrated that melatonin concentrations increased 12 h after paroxetine nasal instillation at ZT13 (p < 0.05), but remained unchanged at ZT1, suggesting that the drug effect is influenced by administration time. In conclusion, the circadian rhythm impacted the pharmacokinetics of paroxetine, especially its distribution into the brain, the target organ. This emphasizes the importance of the time of administration in antidepressant dosing, highlighting its relevance for future studies.

Harnessing the circadian nature of the choroid plexus and cerebrospinal fluid

Cerebrospinal fluid (CSF) exchanges with the central nervous system's immediate environment and interfaces with systemic circulation at the blood-CSF barrier. CSF composition reflects brain states, contributes to brain health and disease, is modulated by circadian rhythms and behaviors, and turns over multiple times per day, enabling rapid signal relay. Mechanisms of how CSF elements change over circadian time and influence function can be harnessed for diagnostic biomarkers and therapeutic intervention.

Genome-wide allele-specific expression in multi-tissue samples from healthy male baboons reveals the transcriptional complexity of mammals

Allele-specific expression (ASE) is pivotal in understanding the genetic underpinnings of phenotypic variation within species, differences in disease susceptibility, and responses to environmental factors. We processed 11 different tissue types collected from 12 age-matched healthy olive baboons (Papio anubis) for genome-wide ASE analysis. By sequencing their genomes at a minimum depth of 30×, we identified over 16 million single-nucleotide variants (SNVs). We also generated long-read sequencing data, enabling the phasing of all variants present within the coding regions of 96.5% of assayable protein-coding genes as a single haplotype block. Given the extensive heterozygosity of baboons relative to humans, we could quantify ASE across 72% of the total annotated protein-coding gene set. We identified genes that exhibit ASE and affect specific tissues and genotypes. We discovered ASE SNVs that also exist in human populations with identical alleles and that are designated as pathogenic by both the PrimateAI-3D and AlphaMissense models.

Circadian Biology in Obstructive Sleep Apnea-Associated Cardiovascular Disease

A dysregulated circadian system is independently associated with both Obstructive Sleep Apnea (OSA) and cardiovascular disease (CVD). OSA and CVD coexistence is often seen in patients with prolonged untreated OSA. However, the role of circadian dysregulation in their relationship is unclear. Half of the human genes, associated biological pathways, and physiological functions exhibit circadian rhythms, including blood pressure and heart rate regulation. Mechanisms related to circadian dysregulation and heart function are potentially involved in the coexistence of OSA and CVD. In this article, we provide a comprehensive overview of circadian dysregulation in OSA and associated CVD. We also discuss feasible animal models and new avenues for future research to understand their relationship. Oxygen-sensing pathways, inflammation, dysregulation of cardiovascular processes, oxidative stress, metabolic regulation, hormone signaling, and epigenetics are potential clock-regulated mechanisms connecting OSA and CVD.

Long-term variable photoperiod exposure impairs hippocampal synapse involving of the glutamate system and leads to memory deficits in male Wistar rats

Excessive artificial light at night can induce the human circadian misalignment, potentially impairing memory consolidation and the rhythms of hippocampal clock genes. To investigate the impact of circadian misalignment on hippocampal function, we measured various field excitatory postsynaptic potentials (fEPSP) and golgi staining in the CA1 and dentate gyrus (DG) regions in Wistar rats. Our findings revealed that circadian misalignment resulted in a leftward shift in the input-output (I-O) curve within the CA1 region, decreased long-term potentiation (LTP), multi-time interval paired-pulse ratio (PPR), as well as dendritic spines and complexity across both CA1 and DG regions. Additionally, magnetic resonance spectroscopy (MRS) showed that circadian misalignment downregulated glutamate-related neurotransmitters (Glu + Gln) in the hippocampus, contributing to impaired synaptic function. Furthermore, disruptions to glutamate receptor subunits due to circadian misalignment led to reduced expression of AMPA receptor and NMDA receptor subunits in the hippocampus. In summary, our results suggest that memory impairments resulting from circadian misalignment are associated with diminished functionality within the glutamatergic system; this includes reductions in both Glx levels and availability of glutamate receptor subunits-key factors contributing to compromised synaptic function within the hippocampus.

Spatiotemporal Control Over Circadian Rhythms With Light

Circadian rhythms are endogenous biological oscillators that synchronize internal physiological processes and behaviors with external environmental changes, sustaining homeostasis and health. Disruption of circadian rhythms leads to numerous diseases, including cardiovascular and metabolic diseases, cancer, diabetes, and neurological disorders. Despite the potential to restore healthy rhythms in the organism, pharmacological chronotherapy lacks spatial and temporal resolution. Addressing this challenge, chrono-photopharmacology, the approach that employs small molecules with light-controlled activity, enables the modulation of circadian rhythms when and where needed. Two approaches-relying on irreversible and reversible drug activation-have been proposed for this purpose. These methodologies are based on photoremovable protecting groups and photoswitches, respectively. Designing photoresponsive bioactive molecules requires meticulous structural optimization to obtain the desired chemical and photophysical properties, and the design principles, detailed guidelines and challenges are summarized here. In this review, we also analyze all the known circadian modulators responsive to light and dissect the rationale following their construction and application to control circadian biology from the protein level to living organisms. Finally, we present the strength of a reversible approach in allowing the modulation of the circadian period and the phase.

Adropin: A cardio-metabolic hormone in the periphery, a neurohormone in the brain?

Whole-body metabolic homeostasis is regulated by physiological responses across organs and tissues to proteins and peptides (<50 amino acids) released into the interstitial and circulatory spaces. These secreted factors integrate signals of metabolic status at both the cellular and systemic level, regulate the intake and distribution of ingested and stored energy substrates across tissues, and minimize toxicity from excessive excursions in circulating concentrations of energy substrates (for example, glucotoxicity and lipotoxicity). The proteins and peptides that are known to be secreted into circulation that are involved in regulating metabolic processes represent a fraction of the secretome predicted by the Human Proteome Atlas. Many undiscovered leads for targeting new therapies for metabolic diseases may therefore exist. In this review, we discuss the biology of adropin, the peptide encoded by the Energy Homeostasis Associated (ENHO) gene. First described as a feeding-responsive, liver-secreted peptide ("hepatokine") involved in metabolic homeostasis, > 2 decades of research indicate adropin is a stress-responsive peptide acting across multiple tissues, vascular, and organ systems. Adropin modulates the responses of liver and muscle to insulin and glucagon in regulating glucose homeostasis. Adropin inhibits hepatic glucose production and stimulates glycolysis but also inhibits tissue fibrosis and maintains vascular health in aging and metabolic disease states. Adropin is also highly expressed in the central nervous system where recent data suggest neuroprotective actions. Collectively, these results suggest the potential for targeting adropin in reducing risk of both metabolic (metabolic syndrome/type-2 diabetes) and neurodegenerative diseases in the context of aging and obesity.

Non-human primate seasonal transcriptome atlas reveals seasonal changes in physiology and diseases

The metabolic, immune, and endocrine systems show profound seasonal changes in animals, including humans. In addition, morbidity from cardiovascular and psychiatric diseases is more severe and mortality rate is higher in winter. However, their molecular mechanisms remain unknown. Here we report the seasonal transcriptome of 80 tissues collected over 1 year from male and female rhesus macaques kept in a semi-natural outdoor environment. We find seasonal changes in plasma metabolites and hormones. Transcriptome analysis identifies sex differences in seasonally oscillating genes (SOGs) in all tissues studied, and we generate the web database 'Non-Human Primate Seasonal Transcriptome Atlas (NHPSTA).' Transcriptional regulatory network analysis, siRNA knockdown, and mutant mouse analyses reveal regulation of SOGs by GA-binding protein (GABP). We also demonstrate seasonal oscillations in the expression of disease risk factor genes and drug interacting genes. NHPSTA provides a molecular resource for seasonally regulated physiology and targets for therapeutic interventions for seasonally regulated diseases.

Circadian clock disruption promotes retinal photoreceptor degeneration

Daily rhythms are a central hallmark of vision, in particular by adapting retinal physiology and light response to the day-night cycle. These cyclic processes are regulated by retinal circadian clocks, molecular machineries regulating gene expression across the 24-h cycle. Although hundreds of genes associated with genetic retinal disorders have been identified, no direct link has been established with the clock. Hence, we investigated the hypothesis that a poorly functioning circadian clock aggravates retinal photoreceptor disease. We performed this study in the P23H rhodopsin-mutated mouse model (P23H Rho) that mimics one major cause of human autosomal dominant retinitis pigmentosa. We also used the rod-specific knockout (rod-Bmal1KO) of Bmal1, a key clock component. More specifically, we used either heterozygous P23H Rho mice or rod-Bmal1KO alone, as well as double mutants of these strains and control mice. We showed by structural (histology, immunohistochemistry) and functional (electroretinography: ERG) analyses that the retinitis pigmentosa phenotype is exacerbated in the double mutant line compared to the P23H Rho mutation alone. Indeed, we observed marked ERG amplitude reduction and more photoreceptor cell loss in double mutants with respect to simple P23H Rho mutants. These observations were further corroborated by transcriptome analysis revealing major gene expression differences between these genotypes. In this data, we identified unique gene expression sets implicating neurogenesis, phototransduction cascade, and metabolism, associated with enhanced photoreceptor degeneration. Thus, our results establish a link between clock dysfunction and retinal degeneration and suggest underlying molecular mechanisms, together providing new concepts for understanding and managing blinding diseases.

Circadian clock features define novel subtypes among breast cancer cells and shape drug sensitivity

The circadian clock regulates key physiological processes, including cellular responses to DNA damage. Circadian-based therapeutic strategies optimize treatment timing to enhance drug efficacy and minimize side effects, offering potential for precision cancer treatment. However, applying these strategies in cancer remains limited due to a lack of understanding of the clock's function across cancer types and incomplete insights into how the circadian clock affects drug responses. To address this, we conducted deep circadian phenotyping across a panel of breast cancer cell lines. Observing diverse circadian dynamics, we characterized metrics to assess circadian rhythm strength and stability in vitro. This led to the identification of four distinct circadian-based phenotypes among 14 breast cancer cell models: functional, weak, unstable, and dysfunctional clocks. Furthermore, we demonstrate that the circadian clock plays a critical role in shaping pharmacological responses to various anti-cancer drugs and we identify circadian features descriptive of drug sensitivity. Collectively, our findings establish a foundation for implementing circadian-based treatment strategies in breast cancer, leveraging clock phenotypes and drug sensitivity patterns to optimize therapeutic outcomes.

Circadian clockwork controls the balance between mitochondrial turnover and dynamics: What is life … without time marking?

Circadian rhythms driven by biological clocks regulate physiological processes in all living organisms by anticipating daily geophysical changes, thus enhancing environmental adaptation. Time-resolved serial multi-omic analyses in vivo, ex vivo, and in synchronized cell cultures have revealed rhythmic changes in the transcriptome, proteome, and metabolome, involving up to 50 % of the mammalian genome. Mitochondrial oxidative metabolism is central to cellular bioenergetics, and many nuclear genes encoding mitochondrial proteins exhibit both circadian and ultradian oscillatory expression. However, studies on mitochondrial DNA (mtDNA) gene expression remain incomplete. Using a well-established in vitro synchronization protocol, we investigated the time-resolved expression of mtDNA genes coding for respiratory chain complex subunits, revealing a rhythmic profile dependent on BMAL1, the master circadian clock transcription factor. Additionally, the expression of genes coding for key mitochondrial biogenesis transcription factors, PGC1a, NRF1, and TFAM, showed BMAL1-dependent circadian oscillations. Notably, LC3-II, involved in mitophagy, displayed a similar in-phase circadian expression, thereby maintaining stable respiratory chain complex levels. Moreover, we found that simultaneous mitochondrial biogenesis and degradation occur in a coordinated manner with cycles in organelle dynamics, leading to rhythmic changes in mitochondrial fission and fusion. This study provides new insights into circadian clock regulation of mitochondrial turnover, emphasizing the importance of temporal regulation in cellular metabolism. Understanding these mechanisms opens potential therapeutic avenues for targeting mitochondrial dysfunctions and related metabolic disorders.

Circadian clock communication during homeostasis and ageing

Maintaining homeostasis is essential for continued health, and the progressive decay of homeostatic processes is a hallmark of ageing. Daily environmental rhythms threaten homeostasis, and circadian clocks have evolved to execute physiological processes in a manner that anticipates, and thus mitigates, their effects on the organism. Clocks are active in almost all cell types; their rhythmicity and functional output are determined by a combination of tissue-intrinsic and systemic inputs. Numerous inputs for a specific tissue are produced by the activity of circadian clocks of other tissues or cell types, generating a form of crosstalk known as clock communication. In mammals, the central clock in the hypothalamus integrates signals from external light-dark cycles to align peripheral clocks elsewhere in the body. This regulation is complemented by a tissue-specific milieu of external, systemic and niche inputs that modulate and cooperate with the cellular circadian clock machinery of a tissue to tailor its functional output. These mechanisms of clock communication decay during ageing, and growing evidence suggests that this decline might drive ageing-related morbidities. Dietary, behavioural and pharmacological interventions may offer the possibility to overcome these changes and in turn improve healthspan.

Beyond vision: effects of light on the circadian clock and mood-related behaviours

Light is a crucial environmental factor that influences various aspects of life, including physiological and psychological processes. While light is well-known for its role in enabling humans and other animals to perceive their surroundings, its influence extends beyond vision. Importantly, light affects our internal time-keeping system, the circadian clock, which regulates daily rhythms of biochemical and physiological processes, ultimately impacting mood and behaviour. The 24-h availability of light can have profound effects on our well-being, both physically and mentally, as seen in cases of jet lag and shift work. This review summarizes the intricate relationships between light, the circadian clock, and mood-related behaviours, exploring the underlying mechanisms and its implications for health.

The circadian rhythm as therapeutic target in inflammatory bowel disease

The primary objectives of the management of patients with inflammatory bowel disease (IBD) are to prevent IBD flares, prevent/delay disease progression and improve patients' quality of life. To this end, one needs to identify risk factor(s) associated with flare-ups and disease progression. We posit that disruption of circadian rhythms is one of the key factors that is associated with risk of flare-up and disease progression. This hypothesis is based on published studies that show: (1) The circadian rhythm regulates many biological processes including multiple IBD-relevant biological processes that are critical in inflammatory/immune processes such as environment/microbe interaction, microbe/host interaction, intestinal barrier integrity and mucosal immunity-all central in the pathogenesis of IBD, and (2) Circadian machinery is the primary tool for the host to interact with the environment. Circadian misalignment results in a loss of preparedness of the host to respond and adjust to the environmental changes that could make the host more vulnerable to IBD flare-ups. In this review, we first provide an overview of circadian rhythms and its role in healthy and disease states. Then we present data to support our hypothesis that: (1) IBD patients have disrupted circadian rhythms ("social jet lag") and (2) circadian misalignment and associated disrupted sleep decreases the resiliency of IBD patients resulting in microbiota dysbiosis, more disrupted intestinal barrier integrity and a more aggressive disease phenotype. We also show that circadian-directed interventions have a potential to mitigate the deleterious impact of disrupted circadian and improve IBD disease course.

The main sources of molecular organization in the cell. Atlas of self-organized and self-regulated dynamic biostructures

One of the most important goals of contemporary biology is to understand the principles of the molecular order underlying the complex dynamic architecture of cells. Here, we present an overview of the main driving forces involved in the cellular molecular complexity and in the emergent functional dynamic structures, spanning from the most basic molecular organization levels to the complex emergent integrative systemic behaviors. First, we address the molecular information processing which is essential in many complex fundamental mechanisms such as the epigenetic memory, alternative splicing, regulation of transcriptional system, and the adequate self-regulatory adaptation to the extracellular environment. Next, we approach the biochemical self-organization, which is central to understand the emergency of metabolic rhythms, circadian oscillations, and spatial traveling waves. Such a complex behavior is also fundamental to understand the temporal compartmentalization of the cellular metabolism and the dynamic regulation of many physiological activities. Numerous examples of biochemical self-organization are considered here, which show that practically all the main physiological processes in the cell exhibit this type of dynamic molecular organization. Finally, we focus on the biochemical self-assembly which, at a primary level of organization, is a basic but important mechanism for the order in the cell allowing biomolecules in a disorganized state to form complex aggregates necessary for a plethora of essential structures and physiological functions. In total, more than 500 references have been compiled in this review. Due to these main sources of order, systemic functional structures emerge in the cell, driving the metabolic functionality towards the biological complexity.

The circadian clock orchestrates spermatogonial differentiation and fertilization by regulating retinoic acid signaling in vertebrates

The circadian clock generates and maintains ∼24-hour oscillations in almost all organs. The testis, however, remains mysterious, without a clear understanding of its circadian functions. Our time-series transcriptome analysis reveals more than 1000 rhythmically expressed genes in the zebrafish and mouse testes, respectively. Canonical circadian clock genes are rhythmically expressed in Sertoli cells and regulate retinoic acid (RA) production, which is also evidenced by their co-expression with RA synthesis genes in single Sertoli cells. Genetic and pharmacological manipulations and temporal desynchronization revealed that the circadian clock-regulated RA signaling synchronizes spermatogonial differentiation via zbtb16a and promotes fertilization via izumo1 in zebrafish. Our findings indicate that the testicular circadian clock contributes to reproduction in a cell-specific manner through RA signaling, highlighting circadian roles in male fertility.

Relationship between shift type and sleep quality in rotating-shift nurses with chronotype as a moderator variable

BACKGROUND

Rotating-shift nurses are susceptible to sleep disorders due to numerous factors, such as their biological clock, emotions, and age. At present, a lack of research exists on whether chronotype and shift type jointly influence the sleep quality of nurses.

AIM

To verify whether chronotype is a moderator variable of the relationship between shift type and sleep quality in nurses in order to provide empirical evidence for future mental and physical health improvement.

METHOD

Clinical rotating-shift nurses at a medical center in northern Taiwan were recruited as participants between November 1, 2023, and December 13, 2023. All of the nurses were working a monthly rotating shift schedule. Hierarchical multiple regression analysis was employed to investigate whether the influence of shift type on sleep quality in nurses varied with chronotype. The STROBE checklist was used for reporting this study.

RESULTS

The participants were 255 rotating-shift nurses in this study. Hierarchical multiple regression results revealed that rotating-shift nurses who were older (B = 0.19, p = 0.029), had greater physical fatigue (B = 0.27, p = 0.016), and had more negative emotions (B = 0.17, p = 0.011) suffered from poorer sleep quality. After controlling the above factors, we further found that chronotype indeed had moderating effects on the influence of shift type on sleep quality (B = -1.83, p = 0.049).

CONCLUSIONS

This study demonstrates that early- and intermediate-type nurses are more suitable for working the day and evening shifts, whereas late-type nurses are more suitable for working the night shift.

IMPLICATION FOR NURSING AND HEALTH POLICY

Coordinating chronotype with shift type will ensure that shift schedules better match the biological clocks of nurses; such individual considerations could help to improve their sleep quality.

Association between the degree of nonalcoholic fatty liver disease and nocturnal hypertension

Nighttime blood pressure (BP) decreases have prognostic significance owing to circadian patterns. The prevalence of nonalcoholic fatty liver disease (NAFLD) has rapidly increased in recent years. We aimed to investigate circadian blood pressure changes in patients with NAFLD. The present study included 114 patients diagnosed with nonalcoholic fatty liver disease and no previous hypertension diagnosis. Thirty patients comprised the control group (no hepatosteatosis and no hypertension). The patients were divided into 3 groups based on nocturnal BP dipping. Blood pressure patterns using night-day ratios were classified as dipper (ratio ≤ 0, 9), nondipper (0, 9 < ratio ≤ 1, 0), or nocturnal hypertension (ratio > 1, 0). There were no significant differences in sex, age, presence of diabetes, or biochemical test results between the groups. According to the blood pressure pattern, the nondipper rate in the hepatosteatosis group was significantly higher than that in the control group. Patients were compared in terms of the presence and severity of hepatosteatosis according to night blood pressure patterns. A significant difference was observed between the groups (P < .001 and P = .001, respectively). We found an association between hepatosteatosis severity and night blood pressure patterns. Patients with nonalcoholic fatty liver disease have a higher incidence of nocturnal hypertension. We observed impaired circadian blood pressure changes in patients with nonalcoholic fatty liver disease.

Rev-erb-α antagonism in alveolar macrophages protects against pneumococcal infection in elderly mice

Circadian rhythms control the diurnal nature of many physiological, metabolic, and immune processes. We hypothesized that age-related impairments in circadian rhythms are associated with high susceptibility to bacterial respiratory tract infections. Our data show that the time-of-day difference in the control of Streptococcus pneumoniae infection is altered in elderly mice. A lung circadian transcriptome analysis revealed that aging alters the daily oscillations in the expression of a specific set of genes and that some pathways that are rhythmic in young-adult mice are non-rhythmic or time shifted in elderly mice. In particular, the circadian expression of the clock component Rev-erb-α and apelin/apelin receptor was altered in elderly mice. In young-adult mice, we discovered an interaction between Rev-erb-α and the apelinergic axis that controls host defenses against S. pneumoniae via alveolar macrophages. Pharmacological repression of Rev-erb-α in elderly mice resulted in greater resistance to pneumococcal infection. These data suggest the causative role of age-associated impairments in circadian rhythms on respiratory infections and have clinical relevance.

Circadian rhythms in stem cells and their therapeutic potential

Circadian rhythms are present in almost all cells, but their existence in stem cells has remains not well established. Circadian clock appears to be closely associated with differentiated mature cells and rarely detected in immature embryonic stem cells. Recent evidence reveals the presence of circadian genes and rhythmic physiologic activities in stem cells as well as stem cell-derived extracellular vesicle (EV) characteristics. The circadian clock entails diverse physiologic and pathological mechanisms underlying cell fate. Integration of circadian rhythm to clinical applications, such as chronotherapy, chrono-biomarker, and environment modification, may facilitate therapeutic outcomes of stem cell-based regenerative medicine. Understanding circadian rhythms in stem cells can optimize stem cell-based therapies by determining the best times for harvesting and administering stem cells, thereby enhancing therapeutic efficacy. Further research into the circadian properties of stem cells will refine stem cell-based therapies, contributing to advancements in regenerative medicine.

Mental health and sleep correlates of self-reported outdoor daylight exposure in over 13,000 adults with depression

BACKGROUND

Increasing daylight exposure might be a simple way to improve mental health. However, little is known about daylight-symptom associations in depressive disorders.

METHODS

In a subset of the Australian Genetics of Depression Study (N = 13,480; 75% female), we explored associations between self-reported number of hours spent in daylight on a typical workday and free day and seven symptom dimensions: depressive (overall, somatic, psychological); hypo-manic-like; psychotic-like; insomnia; and daytime sleepiness. Polygenic scores for major depressive disorder (MDD); bipolar disorder (BD); and schizophrenia (SCZ) were calculated. Models were adjusted for age, sex, shift work status, employment status, season, and educational attainment. Exploratory analyses examined age-stratified associations (18-24 years; 25-34 years; 35-64 years; 65 and older). Bonferroni-corrected associations (p < 0.004) are discussed.

RESULTS

Adults with depression reported spending a median of one hour in daylight on workdays and three hours on free days. More daylight exposure on workdays and free days was associated with lower depressive (overall, psychological, somatic) and insomnia symptoms (p's<0.001), but higher hypo-manic-like symptoms (p's<0.002). Genetic loading for MDD and SCZ were associated with less daylight exposure in unadjusted correlational analyses (effect sizes were not meaningful). Exploratory analyses revealed age-related heterogeneity. Among 18-24-year-olds, no symptom dimensions were associated with daylight. By contrast, for the older age groups, there was a pattern of more daylight exposure and lower insomnia symptoms (p < 0.003) (except for 25-34-year-olds on free days, p = 0.019); and lower depressive symptoms with more daylight on free days, and to some extent workdays (depending on the age-group).

CONCLUSIONS

Exploration of the causal status of daylight in depression is warranted.

Circatidal control of gene expression in the deep-sea hot vent shrimp Rimicaris leurokolos

Biological clocks are a ubiquitous feature of all life, enabling the use of natural environmental cycles to track time. Although studies on circadian rhythms have contributed greatly to the knowledge of chronobiology, biological rhythms in dark biospheres such as the deep sea remain poorly understood. Here, based on a free-running experiment in the laboratory, we reveal potentially endogenous rhythms in the gene expression of the deep-sea hydrothermal vent shrimp Rimicaris leurokolos. Oscillations with approximately 12 h periods, probably reflecting tidal influence, greatly prevail over others in the temporal transcriptome, indicating R. leurokolos probably depends on a circatidal clock consisting of at least some components independent from the circadian clocks. The tidal transcripts exhibit an antiphased expression pattern divided into two internally synchronized clusters, correlated with wide-ranging biological processes that occur in the nucleus and cytoplasm, respectively. In addition, the tidal transcripts showed great similarities with genes in fruit flies and mice exhibiting approximately 12 h ultradian rhythms, indicating that the tide probably had a broad impact on the evolution of approximately 12 h oscillations found across the Metazoa. These findings not only provide new insights into the temporal adaptations in deep-sea organisms but also highlight hydrothermal vent organisms as intriguing models for chronobiological studies, particularly those linked to approximately 12 h ultradian rhythms.

Understanding the intricacies of cellular mechanisms in remyelination: The role of circadian rhythm

The term "circadian rhythm" refers to the 24-h oscillations found in various physiological processes in organisms, responsible for maintaining bodily homeostasis. Many neurological diseases mainly involve the process of demyelination, and remyelination is crucial for the treatment of neurological diseases. Current research mainly focuses on the key role of circadian clocks in the pathophysiological mechanisms of multiple sclerosis. Various studies have shown that the circadian rhythm regulates various cellular molecular mechanisms and signaling pathways involved in remyelination. The process of remyelination is primarily mediated by oligodendrocyte precursor cells (OPCs), oligodendrocytes, microglia, and astrocytes. OPCs are activated, proliferate, migrate, and ultimately differentiate into oligodendrocytes after demyelination, involving many key signaling pathway and regulatory factors. Activated microglia secretes important cytokines and chemokines, promoting OPC proliferation and differentiation, and phagocytoses myelin debris that inhibits remyelination. Astrocytes play a crucial role in supporting remyelination by secreting signals that promote remyelination or facilitate the phagocytosis of myelin debris by microglia. Additionally, cell-to-cell communication via gap junctions allows for intimate contact between astrocytes and oligodendrocytes, providing metabolic support for oligodendrocytes. Therefore, gaining a deeper understanding of the mechanisms and molecular pathways of the circadian rhythm at various stages of remyelination can help elucidate the fundamental characteristics of remyelination and provide insights into treating demyelinating disorders.

Daily glucocorticoids promote glioblastoma growth and circadian synchrony to the host

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults with a poor prognosis despite aggressive therapy. Here, we hypothesized that daily host signaling regulates tumor growth and synchronizes circadian rhythms in GBM. We find daily glucocorticoids promote or suppress GBM growth through glucocorticoid receptor (GR) signaling depending on time of day and the clock genes, Bmal1 and Cry. Blocking circadian signals, like vasoactive intestinal peptide or glucocorticoids, dramatically slows GBM growth and disease progression. Analysis of human GBM samples from The Cancer Genome Atlas (TCGA) shows that high GR expression significantly increases hazard of mortality. Finally, mouse and human GBM models have intrinsic circadian rhythms in clock gene expression in vitro and in vivo that entrain to the host through glucocorticoid signaling, regardless of tumor type or host immune status. We conclude that GBM entrains to the circadian circuit of the brain, modulating its growth through clock-controlled cues, like glucocorticoids.

Comparative transcriptomic rhythms in the mouse and human prefrontal cortex

Introduction

Alterations in multiple subregions of the human prefrontal cortex (PFC) have been heavily implicated in psychiatric diseases. Moreover, emerging evidence suggests that circadian rhythms in gene expression are present across the brain, including in the PFC, and that these rhythms are altered in disease. However, investigation into the potential circadian mechanisms underlying these diseases in animal models must contend with the fact that the human PFC is highly evolved and specialized relative to that of rodents.

Methods

Here, we use RNA sequencing to lay the groundwork for translational studies of molecular rhythms through a sex-specific, cross species comparison of transcriptomic rhythms between the mouse medial PFC (mPFC) and two subregions of the human PFC, the anterior cingulate cortex (ACC) and the dorsolateral PFC (DLPFC).

Results

We find that while circadian rhythm signaling is conserved across species and subregions, there is a phase shift in the expression of core clock genes between the mouse mPFC and human PFC subregions that differs by sex. Furthermore, we find that the identity of rhythmic transcripts is largely unique between the mouse mPFC and human PFC subregions, with the most overlap (20%, 236 transcripts) between the mouse mPFC and the human ACC in females. Nevertheless, we find that basic biological processes are enriched for rhythmic transcripts across species, with key differences between regions and sexes.

Discussion

Together, this work highlights both the evolutionary conservation of transcriptomic rhythms and the advancement of the human PFC, underscoring the importance of considering cross-species differences when using animal models.

Transcriptomic DN3 clock neuron subtypes regulate Drosophila sleep

Circadian neurons within animal brains orchestrate myriad physiological processes and behaviors, but the contribution of these neurons to the regulation of sleep is not well understood. To address this deficiency, we leveraged single-cell RNA sequencing to generate a comprehensive census of transcriptomic cell types of Drosophila clock neurons. We focused principally on the enigmatic DN3s, which constitute most fly brain clock neurons and were previously almost completely uncharacterized. These DN3s are organized into 12 clusters with unusual gene expression features compared to the more well-studied clock neurons. We further show that previously uncharacterized DN3 subtypes promote sleep through a G protein-coupled receptor, TrissinR. Our findings indicate an intricate regulation of sleep behavior by clock neurons and highlight their remarkable diversity in gene expression and functional properties.

Circadian Rhythms and Lung Cancer in the Context of Aging: A Review of Current Evidence

Circadian rhythm is the internal homeostatic physiological clock that regulates the 24-hour sleep/wake cycle. This biological clock helps to adapt to environmental changes such as light, dark, temperature, and behaviors. Aging, on the other hand, is a process of physiological changes that results in a progressive decline in cells, tissues, and other vital systems of the body. Both aging and the circadian clock are highly interlinked phenomena with a bidirectional relationship. The process of aging leads to circadian disruptions while dysfunctional circadian rhythms promote age-related complications. Both processes involve diverse physiological, molecular, and cellular changes such as modifications in the DNA repair mechanisms, mechanisms, ROS generation, apoptosis, and cell proliferation. This review aims to examine the role of aging and circadian rhythms in the context of lung cancer. This will also review the existing literature on the role of circadian disruptions in the process of aging and vice versa. Various molecular pathways and genes such as BMAL1, SIRT1, HLF, and PER1 and their implications in aging, circadian rhythms, and lung cancer will also be discussed.

Chronic Jet Lag Disrupts Circadian Rhythms and Induces Hyperproliferation in Murine Lacrimal Glands via ROS Accumulation

Purpose

Chronic jet lag (CJL) is known to disrupt circadian rhythms, which regulate various physiological processes, including ocular surface homeostasis. However, the specific effects of CJL on lacrimal gland function and the underlying cellular mechanisms remain poorly understood.

Methods

A CJL model was established using C57BL/6J mice. Extraorbital lacrimal glands (ELGs) were collected at 3-hour intervals for RNA extraction and high-throughput RNA sequencing. Circadian transcriptomic profiles were analyzed, and functional annotations were performed. Hydrogen peroxide levels and total antioxidant capacity in tear fluid were measured using chemometric assays. Immunofluorescence was used to assess cell proliferation, apoptosis, immune cell infiltration in ELGs, and reactive oxygen species (ROS) accumulation. The potential therapeutic effects of alpha-lipoic acid (ALA) on CJL-induced oxidative stress and pathological changes in ELGs were also investigated.

Results

CJL significantly disrupted locomotor activity, altered body temperature rhythms, and modified diurnal oscillations in ELGs. Transcriptomic analysis revealed extensive changes in rhythmic gene expression, phase shifts, and pathway clustering in response to CJL. The disruption of the core circadian clock transcription was associated with ELG hyperproliferation and increased ROS accumulation. tert-Butyl hydroperoxide promoted ELG cell proliferation, and ALA effectively reduced ROS levels and mitigated CJL-induced hyperproliferation.

Conclusions

These findings uncover novel molecular pathways affected by CJL and highlight the potential of antioxidant therapies, such as ALA, in preserving ocular surface health under conditions of circadian rhythm disruption.

Brain Transcriptome Changes Associated With an Acute Increase of Protein O-GlcNAcylation and Implications for Neurodegenerative Disease

Enhancing protein O-GlcNAcylation by pharmacological inhibition of the enzyme O-GlcNAcase (OGA) has been considered as a strategy to decrease tau and amyloid-beta phosphorylation, aggregation, and pathology in Alzheimer's disease (AD). There is still more to be learned about the impact of enhancing global protein O-GlcNAcylation, which is important for understanding the potential of using OGA inhibition to treat neurodegenerative diseases. In this study, we investigated the acute effect of pharmacologically increasing O-GlcNAc levels, using the OGA inhibitor Thiamet G (TG), in normal mouse brains. We hypothesized that the transcriptome signature in response to a 3 h TG treatment (50 mg/kg) provides a comprehensive view of the effect of OGA inhibition. We then performed mRNA sequencing of the brain using NovaSeq PE 150 (n = 5 each group). We identified 1234 significant differentially expressed genes with TG versus saline treatment. Functional enrichment analysis of the upregulated genes identified several upregulated pathways, including genes normally down in AD. Among the downregulated pathways were the cell adhesion pathway as well as genes normally up in AD and aging. When comparing acute to chronic TG treatment, protein autophosphorylation and kinase activity pathways were upregulated, whereas cell adhesion and astrocyte markers were downregulated in both datasets. AMPK subunit Prkab2 was one gene in the kinase activity pathway, and the increase after acute and chronic treatment was confirmed using qPCR. Interestingly, mitochondrial genes and genes normally down in AD were up in acute treatment and down in chronic treatment. Data from this analysis will enable the evaluation of the mechanisms underlying the impact of OGA inhibition in the treatment of AD. In particular, OGA inhibitors appear to have downstream effects related to bioenergetics which may limit their therapeutic benefits.

Intermittent fasting shifts the diurnal transcriptome atlas of transcription factors

Intermittent fasting remains a safe and effective strategy to ameliorate various age-related diseases, but its specific mechanisms are not fully understood. Considering that transcription factors (TFs) determine the response to environmental signals, here, we profiled the diurnal expression of 600 samples across four metabolic tissues sampled every 4 over 24 h from mice placed on five different feeding regimens to provide an atlas of TFs in biological space, time, and feeding regimen. Results showed that 1218 TFs exhibited tissue-specific and temporal expression profiles in ad libitum mice, of which 974 displayed significant oscillations at least in one tissue. Intermittent fasting triggered more than 90% (1161 in 1234) of TFs to oscillate somewhere in the body and repartitioned their tissue-specific expression. A single round of fasting generally promoted TF expression, especially in skeletal muscle and adipose tissues, while intermittent fasting mainly suppressed TF expression. Intermittent fasting down-regulated aging pathway and upregulated the pathway responsible for the inhibition of mammalian target of rapamycin (mTOR). Intermittent fasting shifts the diurnal transcriptome atlas of TFs, and mTOR inhibition may orchestrate intermittent fasting-induced health improvements. This atlas offers a reference and resource to understand how TFs and intermittent fasting may contribute to diurnal rhythm oscillation and bring about specific health benefits.

Optimizing Radiotherapy Timing for Nasopharyngeal Carcinoma: The Impact of Radiation Scheduling on Survival

PURPOSE

Chronoradiobiology has emerged as a potential field of study with therapeutic implications for cancer treatment. We aimed to investigate the association between radiation chronotherapy and the efficacy and toxicity of patients with nasopharyngeal carcinoma (NPC).

PATIENTS AND METHODS

Patients with nonmetastatic NPC treated with intensity-modulated radiotherapy in Fujian Cancer Hospital between January 2017 and December 2019 were included. Propensity score matching (PSM) with 1:1:1 was used to account for selection bias. Cox regression analysis was performed to explore the impact of radiotherapy timing on patient survival. Sensitivity analysis was implemented to determine the size and directional stability.

RESULTS

One thousand forty patients met study inclusion criteria and 332 patients were included in a PSM cohort. In the unmatched cohort analysis, morning radiotherapy exhibited a significantly superior overall survival (OS) outcome (hazard ratio [HR], 0.60 [95% CI, 0.40 to 0.91], adjusted log-rank P = .028) than the afternoon one. After PSM analysis, it was observed that individuals undergoing radiotherapy in the afternoon group (HR, 5.88 [95% CI, 2.55 to 13.58], adjusted log-rank P = .004) and the night group (HR, 4.81 [95% CI, 1.91 to 12.11], adjusted log-rank P = .018) displayed a tendency toward shorter OS compared with the morning group. No significant differences in acute treatment-related adverse effects were observed among the three groups. Morning radiotherapy demonstrated consistent robustness in the multivariable analysis, thereby establishing an association with higher OS. The directionality of the effect size was consistent across sensitivity analysis.

CONCLUSION

These results underscore the potential benefits of scheduling radiotherapy in the morning for NPC management, although prospective studies are needed to confirm these findings.

Circadian rhythms and cancer: implications for timing in therapy

Circadian rhythms, intrinsic cycles spanning approximately 24 h, regulate numerous physiological processes, including sleep-wake cycles, hormone release, and metabolism. These rhythms are orchestrated by the circadian clock, primarily located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Disruptions in circadian rhythms, whether due to genetic mutations, environmental factors, or lifestyle choices, can significantly impact health, contributing to disorders such as sleep disturbances, metabolic syndrome, and cardiovascular diseases. Additionally, there is a profound link between the disruption of circadian rhythms and development of various cancer, the influence on disease incidence and progression. This incurred regulation by circadian clock on pathways has its implication in tumorigenesis, such as cell cycle control, DNA damage response, apoptosis, and metabolism. Furthermore, the circadian timing system modulates the efficacy and toxicity of cancer treatments. In cancer treatment, the use of chronotherapy to optimize the timing of medical treatments, involves administering chemotherapy, radiation, or other therapeutic interventions at specific intervals to enhance efficacy and minimize side effects. This approach capitalizes on the circadian variations in cellular processes, including DNA repair, cell cycle progression, and drug metabolism. Preclinical and clinical studies have demonstrated that chronotherapy can significantly improve the therapeutic index of chemotherapeutic agents like cisplatin and 5-fluorouracil by enhancing anticancer activity and reducing toxicity. Further research is needed to elucidate the mechanisms underlying circadian regulation of cancer and to develop robust chronotherapeutic protocols tailored to individual patients' circadian profiles, potentially transforming cancer care into more effective and personalized treatment strategies.

The neurobiological mechanisms of photoperiod impact on brain functions: a comprehensive review

Variations in day length, or photoperiodism, whether natural or artificial light, significantly impact biological, physiological, and behavioral processes within the brain. Both natural and artificial light sources are environmental factors that significantly influence brain functions and mental well-being. Photoperiodism is a phenomenon, occurring either over a 24 h cycle or seasonally and denotes all biological responses of humans and animals to these fluctuations in day and night length. Conversely, artificial light occurrence refers to the presence of light during nighttime hours and/or its absence during the daytime (unnaturally long and short days, respectively). Light at night, which is a form of light pollution, is prevalent in many societies, especially common in certain emergency occupations. Moreover, individuals with certain mental disorders, such as depression, often exhibit a preference for darkness over daytime light. Nevertheless, disturbances in light patterns can have negative consequences, impacting brain performance through similar mechanisms albeit with varying degrees of severity. Furthermore, changes in day length lead to alterations in the activity of receptors, proteins, ion channels, and molecular signaling pathways, all of which can impact brain health. This review aims to summarize the mechanisms by which day length influences brain functions through neural circuits, hormonal systems, neurochemical processes, cellular activity, and even molecular signaling pathways.

Molecular Rhythmicity in Glia: Importance for Brain Health and Relevance to Psychiatric Disease

Circadian rhythms are approximate 24-hour rhythms present in nearly all aspects of human physiology, including proper brain function. These rhythms are produced at the cellular level through a transcriptional-translational feedback loop known as the molecular clock. Diurnal variation in gene expression has been demonstrated in brain tissue from multiple species, including humans, in both cortical and subcortical regions. Interestingly, these rhythms in gene expression have been shown to be disrupted across psychiatric disorders and may be implicated in their underlying pathophysiology. However, little is known regarding molecular rhythms in specific cell types in the brain and how they might be involved in psychiatric disease. Although glial cells (e.g., astrocytes, microglia, and oligodendrocytes) have been historically understudied compared to neurons, evidence of the molecular clock is found within each of these cell subtypes. Here, we review the current literature, which suggests that molecular rhythmicity is essential to functional physiologic outputs from each glial subtype. Furthermore, disrupted molecular rhythms within these cells and the resultant functional deficits may be relevant to specific phenotypes across psychiatric illnesses. Given that circadian rhythm disruptions have been so integrally tied to psychiatric disease, the molecular mechanisms governing these associations could represent exciting new avenues for future research and potential novel pharmacologic targets for treatment.

Daily rhythm in DNA methylation and the effect of total sleep deprivation

Numerous hormones and genes exhibit diurnal 24-hr rhythms that can also be affected by sleep deprivation. Here we studied diurnal rhythms in DNA methylation under a 24-hr sleep/wake cycle and a subsequent 29 hr of continual wakefulness (1 night of sleep deprivation). Fifteen healthy men (19-35 years) spent 3 days/nights in a sleep laboratory: (1) adaptation; (2) baseline; (3) total sleep deprivation day/night. DNA methylation was analysed from peripheral blood leukocytes, collected every 3 hr for 45 hr (starting at 15:00 hours) during the baseline period and the total sleep deprivation period. Epigenome-wide DNA methylation variation was assessed with the Infinium MethylationEPIC v2.0 Beadchip kit. Rhythm analysis was performed separately for the baseline and the total sleep deprivation time-series data. Pairwise analysis between diurnal samples and sleep deprivation samples at the same timepoint was also carried out to detect differentially methylated positions related to sleep deprivation. Of all DNA methylation sites, 14% exhibited a diurnal rhythm in methylation on the baseline day/night that was altered by sleep deprivation. During sleep deprivation, the number of differentially methylated positions increased towards the end of the sleep deprivation period, with a dominating pattern of hypomethylation. Among differentially methylated positions, an enrichment of genes related to the FAS immune response pathway was detected. In conclusion, DNA methylation exhibits diurnal rhythmicity, and this time-of-day variation needs to be considered when studying DNA methylation as a biomarker in biomedical studies. In addition, the observed DNA methylation changes under wakefulness might serve as a mediator of sleep deprivation-related immune response alterations.

Integrated bioinformatics and interaction analysis to advance chronotherapies for mental disorders

Introduction

Robust connections have been identified between the pathophysiology of mental disorders and the functioning of the circadian system. The overarching objective of this study was to investigate the potential for circadian rhythms to be leveraged for therapeutics in mental disorders.

Methods

We considered two approaches to chronotherapy-optimal timing of existing medications ("clocking the drugs") and redressing circadian abnormalities with small molecules ("drugging the clock"). We assessed whether circadian rhythm-modulating compounds can interact with the prominent drug targets of mental disorders utilizing computational tools like molecular docking and molecular dynamics simulation analysis.

Results

Firstly, an analysis of transcript-level rhythmic patterns in recognized drug targets for mental disorders found that 24-hour rhythmic patterns were measurable in 54.4% of targets in mice and 35.2% in humans. We also identified several drug receptors exhibiting 24-hour rhythmicity involved in critical physiological pathways for neural signaling and communication, such as neuroactive ligand-receptor interaction, calcium signaling pathway, cAMP signaling pathway, and dopaminergic and cholinergic synapses. These findings advocate that further research into the timing of drug administration in mental disorders is urgently required. We observed that many pharmacological modulators of mammalian circadian rhythms, including KL001, SR8278, SR9009, Nobiletin, and MLN4924, exhibit stable binding with psychotropic drug targets.

Discussion

These findings suggest that circadian clock-modulating pharmacologically active small molecules could be investigated further for repurposing in the treatment of mood disorders. In summary, the present analyses indicate the potential of chronotherapeutic approaches to mental disorder pharmacotherapy and specify the need for future circadian rhythm-oriented clinical research.

Behavioural phenotypes of Dicer knockout in the mouse SCN

The suprachiasmatic nucleus (SCN) is the master clock that directly dictates behavioural rhythms to anticipate the earth's light/dark cycles. Although post-transcriptional regulators called microRNAs have been implicated in physiological SCN function, how the absence of the entire mature miRNome impacts SCN output has not yet been explored. To study the behavioural consequences of miRNA depletion in the SCN, we first generated a mouse model in which Dicer is inactivated in the SCN by crossing Syt10Cre mice with Dicerflox mice to study behavioural consequences of miRNA depletion in the SCN. Loss of all mature miRNAs in the SCN shortened the circadian period length by ~37 minutes at the tissue level and by ~45 minutes at the locomotor activity level. Moreover, knockout animals exhibited a reduction in the precision of the circadian rhythm with more variable activity onsets under both LD 12:12 and DD conditions. We also observed that knockouts with higher onset variations were inclined to develop ultradian rhythms under constant light. In a second mouse model, recombination of Dicerflox via Cre delivery specifically in the SCN resulted in loss of behavioural rhythms in some animals depending on the injection efficiency. Together, our observations highlight the importance of microRNAs for a physiological SCN function and their pivotal role in robust circadian oscillations.

Circadian regulation of endoplasmic reticulum calcium response in cultured mouse astrocytes

The circadian clock, an internal time-keeping system orchestrates 24 hr rhythms in physiology and behavior by regulating rhythmic transcription in cells. Astrocytes, the most abundant glial cells, play crucial roles in CNS functions, but the impact of the circadian clock on astrocyte functions remains largely unexplored. In this study, we identified 412 circadian rhythmic transcripts in cultured mouse cortical astrocytes through RNA sequencing. Gene Ontology analysis indicated that genes involved in Ca2+ homeostasis are under circadian control. Notably, Herpud1 (Herp) exhibited robust circadian rhythmicity at both mRNA and protein levels, a rhythm disrupted in astrocytes lacking the circadian transcription factor, BMAL1. HERP regulated endoplasmic reticulum (ER) Ca2+ release by modulating the degradation of inositol 1,4,5-trisphosphate receptors (ITPRs). ATP-stimulated ER Ca2+ release varied with the circadian phase, being more pronounced at subjective night phase, likely due to the rhythmic expression of ITPR2. Correspondingly, ATP-stimulated cytosolic Ca2+ increases were heightened at the subjective night phase. This rhythmic ER Ca2+ response led to circadian phase-dependent variations in the phosphorylation of Connexin 43 (Ser368) and gap junctional communication. Given the role of gap junction channel (GJC) in propagating Ca2+ signals, we suggest that this circadian regulation of ER Ca2+ responses could affect astrocytic modulation of synaptic activity according to the time of day. Overall, our study enhances the understanding of how the circadian clock influences astrocyte function in the CNS, shedding light on their potential role in daily variations of brain activity and health.

Neuronal Progenitors Suffer Genotoxic Stress in the Drosophila Clock Mutant per0

The physiological role and the molecular architecture of the circadian clock in fully developed organisms are well established. Yet, we have a limited understanding of the function of the clock during ontogenesis. We have used a null mutant (per0) of the clock gene period (per) in Drosophila melanogaster to ask whether PER may play a role during normal brain development. In third-instar larvae, we have observed that the absence of functional per results in increased genotoxic stress compared to wild-type controls. We have detected increased double-strand DNA breaks in the central nervous system and chromosome aberrations in dividing neuronal precursor cells. We have demonstrated that reactive oxygen species (ROS) are causal to the genotoxic effect and that expression of PER in glia is necessary and sufficient to suppress such a phenotype. Finally, we have shown that the absence of PER may result in less condensed chromatin, which contributes to DNA damage.

Emerging interactions between circadian rhythms and extracellular vesicles

Circadian rhythms are present across species, tuning internal processes to daily changes in the environment. Driven by genetically encoded circadian clocks present throughout the body, and modulated by external inputs, the circadian system is a key player in metabolic control. However, the molecular mediators underlying coordination between cells and tissues are not well known. Extracellular vesicles (EVs) have emerged over recent years as important players in cell-cell and organ-organ communication, however the influence of circadian rhythms on EVs is not yet understood. Research into this area is still scarce, yet already offers glimpses into the potential impact of circadian rhythms on EV biology. In this review, recent discoveries that reveal, directly or indirectly, a potential role for circadian rhythms in EV abundance, properties, cargo and signalling functions are first discussed. Next, the feedback of EV signalling on circadian clocks is considered. Last, unanswered questions regarding the interaction between circadian rhythms and EVs are examined alongside potential approaches to address them. Overall, the circadian impact on EV signalling is an exciting yet understudied aspect that warrants further investigation.

Circadian Regulation in Diurnal Mammals: Neural Mechanisms and Implications in Translational Research

Diurnal and nocturnal mammals have evolved unique behavioral and physiological adaptations to optimize survival for their day- or night-active lifestyle. The mechanisms underlying the opposite activity patterns are not fully understood but likely involve the interplay between the circadian time-keeping system and various arousal- or sleep-promoting factors, e.g., light or melatonin. Although the circadian systems between the two chronotypes share considerable similarities, the phase relationships between the principal and subordinate oscillators are chronotype-specific. While light promotes arousal and wakefulness in diurnal species like us, it induces sleep in nocturnal ones. Similarly, melatonin, the hormone of darkness, is commonly used as a hypnotic in humans but is secreted in the active phase of nocturnal animals. Thus, the difference between the two chronotypes is more complex than a simple reversal, as the physiological and neurological processes in diurnal mammals during the day are not equivalent to that of nocturnal ones at night. Such chronotype differences could present a significant translational gap when applying research findings obtained from nocturnal rodents to diurnal humans. The potential advantages of diurnal models are being discussed in a few sleep-related conditions including familial natural short sleep (FNSS), obstructive sleep apnea (OSA), and Smith-Magenis syndrome (SMS). Considering the difference in chronotype, a diurnal model will be more adequate for revealing the physiology and physiopathology pertaining to human health and disease, especially in conditions in which circadian rhythm disruption, altered photic response, or melatonin secretion is involved. We hope the recent advances in gene editing in diurnal rodents will promote greater utility of the diurnal models in basic and translational research.

Characterization of clock proteins in the substantia nigra and subthalamic nucleus of the Sapajus apella primate

Clock genes, which are essential for suprachiasmatic nucleus (SCN) function, also play critical roles in other brain regions, and their expression have been the subject of various studies. An increasingly deeper understanding of the expression of these genes in different species contributes to our knowledge of their functions and the factors influencing their expression. Considering that most studies have been conducted in nocturnal rodents, in this study we investigated the presence of Per1, Per2 and Cry1 in neurons of the substantia nigra (SN) and subthalamic nucleus (STN) in a diurnal primate. The immunoreactivity of Per1, Per2, and Cry1 was analyzed using immunohistochemistry, revealing significant Per1-IR, Per2-IR, and Cry1-IR in the SN. While Per1-IR and Per2-IR were also observed in the STN, no Cry1-IR staining was detected in the STN. These results confirm the presence of proteins that regulate circadian rhythms in areas associated with motor behavior.

Circadian rhythms in muscle health and diseases

All major life forms from bacteria to humans have internal clocks that regulate essential biological processes in a roughly 24-h cycle. In mammals, the central clock in the suprachiasmatic nucleus (SCN) is historically considered the top of a hierarchical organisation that dominates subordinate clocks in peripheral tissues and dictates the circadian behaviours of an organism. Recent studies, however, underscore the importance of the local circadian oscillators, such as the skeletal muscle clock, in regulating local metabolism and physiology. Studies in animal models show that the muscle peripheral clock per se is required for the expression of genes involved in glucose, lipid, and amino acid metabolism. Disruption of the muscle clock leads to glucose intolerance, insulin resistance, and alterations in muscle size and force. This highlights the vital role of the muscle clock in controlling muscle physiology and metabolism. In humans, a perturbation in the muscle circadian rhythms is seen in metabolic disorders such as type 2 diabetes, and muscle diseases such as dystrophies. Disruption of muscle metabolism is also seen when the internal rhythms are misaligned with the external rhythms (circadian misalignments) as in shift work. Understanding the mechanisms by which the muscle clock regulates circadian functions may help the development of new strategies, such as chronotherapy, to potentially prevent or treat muscle pathologies and maintain muscle health.

Circadian disruption in cancer hallmarks: Novel insight into the molecular mechanisms of tumorigenesis and cancer treatment

Circadian rhythms are 24-h rhythms governing temporal organization of behavior and physiology generated by molecular clocks composed of autoregulatory transcription-translation feedback loops (TTFLs). Disruption of circadian rhythms leads to a spectrum of pathologies, including cancer by triggering or being involved in different hallmarks. Clock control of phenotypic plasticity involved in tumorigenesis operates in aberrant dedifferentiating to progenitor-like cell states, generation of cancer stem cells (CSCs) and epithelial-to-mesenchymal transition (EMT) events. Circadian rhythms might act as candidates for regulatory mechanisms of cellular senescent and functional determinants of senescence-associated secretory phenotype (SASP). Reciprocal control between clock and epigenetics sheds light on post-transcriptional regulation of circadian rhythms and opens avenues for novel anti-cancer strategies. Additionally, disrupting circadian rhythms influences microbiota communities that could be associated with altered homeostasis contributing to cancer development. Herein, we summarize recent advances in support of the nexus between disruptions of circadian rhythms and cancer hallmarks of new dimensions, thus providing novel perspectives on potentially effective treatment approaches for cancer management.

Circadian rhythms of macrophages are altered by the acidic tumor microenvironment

Tumor-associated macrophages (TAMs) are prime therapeutic targets due to their pro-tumorigenic functions, but varying efficacy of macrophage-targeting therapies highlights our incomplete understanding of how macrophages are regulated within the tumor microenvironment (TME). The circadian clock is a key regulator of macrophage function, but how circadian rhythms of macrophages are influenced by the TME remains unknown. Here, we show that conditions associated with the TME such as polarizing stimuli, acidic pH, and lactate can alter circadian rhythms in macrophages. While cyclic AMP (cAMP) has been reported to play a role in macrophage response to acidic pH, our results indicate pH-driven changes in circadian rhythms are not mediated solely by cAMP signaling. Remarkably, circadian disorder of TAMs was revealed by clock correlation distance analysis. Our data suggest that heterogeneity in circadian rhythms within the TAM population level may underlie this circadian disorder. Finally, we report that circadian regulation of macrophages suppresses tumor growth in a murine model of pancreatic cancer. Our work demonstrates a novel mechanism by which the TME influences macrophage biology through modulation of circadian rhythms.

Resilience to Chronic Stress Is Characterized by Circadian Brain-Liver Coordination

Background

Chronic stress has a profound impact on circadian regulation of physiology. In turn, disruption of circadian rhythms increases the risk of developing both psychiatric and metabolic disorders. To explore the role of chronic stress in modulating the links between neural and metabolic rhythms, we characterized the circadian transcriptional regulation across different brain regions and the liver as well as serum metabolomics in mice exposed to chronic social defeat stress, a validated model for studying depressive-like behaviors.

Methods

Male C57BL/6J mice underwent chronic social defeat stress, and subsequent social interaction screening identified distinct behavioral phenotypes associated with stress resilience and susceptibility. Stressed mice and their control littermates were sacrificed every 4 hours over the circadian cycle for comprehensive analyses of the circadian transcriptome in the hypothalamus, hippocampus, prefrontal cortex, and liver together with assessments of the circadian circulatory metabolome.

Results

Our data demonstrate that stress adaptation was characterized by reprogramming of the brain as well as the hepatic circadian transcriptome. Stress resiliency was associated with an increase in cyclic transcription in the hypothalamus, hippocampus, and liver. Furthermore, cross-tissue analyses revealed that resilient mice had enhanced transcriptional coordination of circadian pathways between the brain and liver. Conversely, susceptibility to social stress resulted in a loss of cross-tissue coordination. Circadian serum metabolomic profiles corroborated the transcriptome data, highlighting that stress-resilient mice gained circadian rhythmicity of circulating metabolites, including bile acids and sphingomyelins.

Conclusions

This study reveals that resilience to stress is characterized by enhanced metabolic rhythms and circadian brain-liver transcriptional coordination.

A Bayesian Framework for Genome-wide Circadian Rhythmicity Biomarker Detection

Circadian rhythms are endogenous ∼24-hour cycles that significantly influence physiological and behavioral processes. These rhythms are governed by a transcriptional-translational feedback loop of core circadian genes and are essential for maintaining overall health. The study of circadian rhythms has expanded into various omics datasets, necessitating accurate analytical methodology for circadian biomarker detection. Here, we introduce a novel Bayesian framework for the genome-wide detection of circadian rhythms that is capable of incorporating prior biological knowledge and adjusting for multiple testing issue via a false discovery rate approach. Our framework leverages a Bayesian hierarchical model and employs a reverse jump Markov chain Monte Carlo (rjMCMC) technique for model selection. Through extensive simulations, our method, BayesCircRhy, demonstrated superior false discovery rate control over competing methods, robustness against heavier-tailed error distributions, and better performance compared to existing approaches. The method's efficacy was further validated in two RNA-Sequencing data, including a human resitrcted feeding data and a mouse aging data, where it successfully identified known and novel circadian genes. R package "BayesianCircadian" for the method is publicly available on GitHub https://github.com/jxncdhc/BayesianCircadian .

Integrative transcriptomic profiling uncovers immune and functional responses to bisphenol a across multiple tissues in male mice

Bisphenol A (BPA), an endocrine-disrupting substance commonly found in plastics and receipts, is associated with adverse effects, including endocrine disorders, reduced fertility, and metabolic issues. To gain insights into its effects on biological systems, we observed the adverse effects of BPA in male Institute of Cancer Research (ICR) mice exposed to BPA at the lowest observed adverse effect level for 6 weeks, in comparison with the control groups. We constructed a comprehensive transcriptome profile using 20 different tissues to analyze the changes in the whole-body systems. This involved employing differential gene expression, tissue-specific gene, and gene co-expression network analyses. The study revealed that BPA exposure led to significant differences in the transcriptome in the thymus, suggesting activation of T-cell differentiation and maturation in response to BPA treatment. Furthermore, various tissues exhibited immune response activation, potentially due to the migration of immune cells from the thymus. BPA exposure also caused immune-related functional changes in the colon, liver, and kidney, as well as abnormal signaling responses in the sperm. The transcriptome analysis serves as a valuable resource for understanding the functional impact of BPA, providing profound insights into the effects of BPA exposure and emphasizing the need for further research on potential associated health risks.

The nuclear transportation of CHRONO regulates the circadian rhythm

The pace of the endogenous circadian clock is important for organisms to maintain homeostasis. CHRONO has been shown to be a core component of the mammalian clock and has recently been implicated to function in several important physiological aspects. To function properly, CHRONO needs to enter the nucleus to repress transcription. We have previously shown that the N terminus of CHRONO is required for its nuclear entry. However, how CHRONO enters the nucleus and regulates the circadian clock remains unknown. Here, we report that a novel nonclassical nuclear localization signal in the N terminus of CHRONO is responsible for its nuclear entry. Multiple nuclear transporters are identified that facilitate the nuclear import of CHRONO. We show that the Arg63 is the critical amino acid of the nuclear localization signal. Using prime editing technology, we precisely edit the Arg63 to Ala at the genomic loci and demonstrate that this mutation prolongs the circadian period, which is similar to knockdown of CHRONO. By using the CHRONO KO and R63A mutant cells, we also investigated the changes in the cytoplasmic/nuclear distribution of BMAL1. We show that BMAL1 localizes more in the cytoplasm in the deficiency of CHRONO nuclear entry. These results provide a model for CHRONO nuclear entry using a network of importins involved in the regulation of the circadian period.

Brighter nights and darker days predict higher mortality risk: A prospective analysis of personal light exposure in >88,000 individuals

Light enhances or disrupts circadian rhythms, depending on the timing of exposure. Circadian disruption contributes to poor health outcomes that increase mortality risk. Whether personal light exposure predicts mortality risk has not been established. We therefore investigated whether personal day and night light, and light patterns that disrupt circadian rhythms, predicted mortality risk. UK Biobank participants (N = 88,905, 62.4 ± 7.8 y, 57% female) wore light sensors for 1 wk. Day and night light exposures were defined by factor analysis of 24-h light profiles. A computational model of the human circadian pacemaker was applied to model circadian amplitude and phase from light data. Cause-specific mortality was recorded in 3,750 participants across a mean (±SD) follow-up period of 8.0 ± 1.0 y. Individuals with brighter day light had incrementally lower all-cause mortality risk (adjusted-HR ranges: 0.84 to 0.90 [50 to 70th light exposure percentiles], 0.74 to 0.84 [70 to 90th], and 0.66 to 0.83 [90 to 100th]), and those with brighter night light had incrementally higher all-cause mortality risk (aHR ranges: 1.15 to 1.18 [70 to 90th], and 1.21 to 1.34 [90 to 100th]), compared to individuals in darker environments (0 to 50th percentiles). Individuals with lower circadian amplitude (aHR range: 0.90 to 0.96 per SD), earlier circadian phase (aHR range: 1.16 to 1.30), or later circadian phase (aHR range: 1.13 to 1.20) had higher all-cause mortality risks. Day light, night light, and circadian amplitude predicted cardiometabolic mortality, with larger hazard ratios than for mortality by other causes. Findings were robust to adjustment for age, sex, ethnicity, photoperiod, and sociodemographic and lifestyle factors. Minimizing night light, maximizing day light, and keeping regular light-dark patterns that enhance circadian rhythms may promote cardiometabolic health and longevity.