The mammalian suprachiasmatic nucleus (SCN) orchestrates daily (circadian) rhythms of physiology and behavior by broadcasting timing cues generated autonomously by its mutually reinforcing network of ~10,000 neurons and ~3000 astrocytes. Although astrocytic control of extracellular glutamate and GABA has been implicated in driving circadian oscillations in SCN gene expression and neuronal activity, the full scale of the network-level signaling mechanisms is unknown. To understand better how this astrocyte-neuron network operates, we adopted a multi-omics approach, first using SILAC-based mass spectrometry to generate an SCN proteome where ~7% of identified proteins were circadian. This circadian proteome was analyzed bioinformatically alongside existing single-cell RNAseq transcriptomic data to identify the cell-types and processes to which they contribute. This highlighted "S100 protein binding," tracked to astrocytes, and revealed annexin-A2 (Anxa2) as an astrocyte-enriched circadian protein for further investigation. We show that Anxa2 and its partner S100a10 are co-expressed and enriched in SCN astrocytes. We also show that pharmacological disruption of their association acutely and reversibly dysregulated the circadian cycle of astrocytic calcium levels and progressively compromised SCN neuronal oscillations. Anxa2 and S100a10 interaction therefore constitutes an astrocytic cellular signaling axis that regulates circadian neuronal excitability and ultimately SCN network coherence necessary for circadian timekeeping.

Cells of the body rely on the circadian clock to orchestrate daily changes in physiology that impact both homeostatic and pathological conditions, such as the inflammatory autoimmune disease rheumatoid arthritis (RA). In RA, high levels of proinflammatory cytokines peak early in the morning hours, reflected by daily changes in joint stiffness. Chronotherapy (or circadian medicine) seeks to delivery drugs at optimal times to maximize their efficacy. However, chronotherapy remains a largely unexplored approach for disease modifying, antirheumatic treatment, particularly for cell-based therapies. In this study, we developed autonomous chronogenetic gene circuits that produce the biologic drug interleukin-1 receptor antagonist (IL-1Ra) with desired phase and amplitude. We compared expression of IL-1Ra from circuits that contained different circadian promoter elements (E'-boxes, D-boxes, or RREs) and their ability to respond to inflammatory challenges in murine pre-differentiated induced pluripotent stem cells (PDiPSC) or engineered cartilage pellets. We confirmed that each circuit reliably peaked at a distinct circadian time over multiple days. Engineered cells generated significant amounts of IL-1Ra on a circadian basis, which protected them from circadian dysregulation and inflammatory damage. These programmable chronogenetic circuits have the potential to align with an individual's circadian rhythm for optimized, self-regulated daily drug delivery.

The suprachiasmatic nucleus (SCN) serves as the central circadian clock in mammals, coordinating daily rhythms in both behavior and physiology. In the SCN, gastrin-releasing peptide (GRP)-producing neurons (GRPNs) are predominantly located in the core region, suggesting their possible involvement in photic entrainment. However, the specific contribution of GRPNs to the regulation of circadian rhythms remains poorly understood. This study utilized a Cre-driver mouse line, Grp-iCre knock-in (KI) mice, in which Cre recombinase is exclusively expressed in GRPNs, allowing the selective manipulation of SCN GRPNs to investigate their characteristics and functional roles in circadian regulation. All experiments were conducted in adult male mice. Anatomical tracing revealed that SCN GRPNs primarily project to the thalamus and hypothalamus, whereas input mapping demonstrated that SCN GRPNs receive most synaptic inputs from within the SCN. Behavioral analyses revealed that neither GRP deficiency nor ablation of SCN GRPNs significantly affected circadian locomotor activity rhythms or photic entrainment. However, chemogenetic stimulation of the SCN GRPNs is sufficient to induce phase shifts in behavioral rhythms. Additionally, calcium imaging with fiber photometry indicated that SCN GRPNs quickly responded to photic stimulation, with increased neural activity following retinal exposure to white light. These findings suggest that SCN GRPNs play a role in photic entrainment, albeit potentially redundant with other neuronal populations such as vasoactive intestinal peptide-producing neurons.

To better understand the potential health threats and underlying visual pathways of long-term light at night (LAN) exposure, we adopted a widely accepted diurnal animal model tree shrew (Tupaia belangeri chinensis), which is a close relative to primates, and evaluated the deleterious effects of long-term LAN exposure. We used an early-night LAN paradigm that was established in mice to examine behavioral and physiological consequences in adult male tree shrews. We found that 3-wk LAN exposure significantly impaired the mood and long-term memory of tree shrews without affecting the general activity pattern. We identified retinal projections to the perihabenular nucleus (pHb), a crucial area in LAN-induced negative mood, and demonstrated that the pHb continues to innervate the nucleus accumbens (NAc) in tree shrews. Moreover, the pHb was required for the LAN effect on mood but not long-term memory. Transcriptomic profiling of brain tissues containing the NAc area revealed drastic changes of several depression-related genes in NAc neurons post-LAN treatment, suggesting that long-term exposure to nighttime light could result in lasting changes in tree shrews. Collectively, we present behavioral and neural structural evidence that LAN exerts depression-inducing effects in diurnal animals via a pHb-related visual pathway, which may facilitate the translation from laboratory findings of excessive LAN exposure to clinical applications in humans.

While there is extensive literature on both the neuronal circuitry of rhythms and the intracellular molecular clock, there is a large component of signaling that has been understudied: interstitial fluid (ISF)-fluid that surrounds the cells in the extracellular space of tissue. In this review, we highlight evidence in the circadian literature supporting ISF signaling as key to circadian synchronization and entrainment and propose new mechanisms of how fluid movement between the brain and periphery may act as zeitgebers by examining the main ISF pathways of the body, focusing on circadian regulation of the glymphatic and lymphatic systems. We identify key pieces of circadian research that point to ISF as an important timing medium, expand on the basics of cerebrospinal fluid (CSF) and ISF production, and outline the basic structure and function of the glymphatic and lymphatic systems.

The regulation of the cyclic oscillation of the components of the circadian clock is complex in itself. Numerous clock interactions with processes and molecules present in cells further complicate this mechanism. Recently, the anti-aging protein Silencing Information Regulator Two family member, SIRT1, has been linked with the molecular circadian clock. In this study, we investigated the in vitro effect of aminooxyacetic acid on SIRT1 expression in relation to circadian dynamics of Cry1 and Bma11 expressions in serum shocked NIH-3 T3 and HaCaT cells. The study was carried out in the context of the inhibitory activity of aminooxyacetic acid against cystathionine-β-synthase and cystathionine-γ-lyase. We have shown that aminooxyacetic acid effectively inhibits SIRT1 transcription and synthesis, which, given the pleiotropic effects of sirtuin 1 on numerous metabolic pathways, may have other implications. We also found that AOAA contributes to up-regulation of the expression of the Cry1 and Bmal1 genes in cells. This effect does not appear to be related to inhibition of the activity of cystathionine-β-synthase and cystathionine-γ-lyase. At the same time, this does not deny the role of hydrogen sulphide, a product of the activity of these enzymes, in the regulation of the circadian clock.

Nursing shift work disrupts circadian rhythms, negatively impacting physical and mental health. Night shift workers face the added challenge of shift work disorder. Resilience training may help mitigate these effects and improve perceived organizational support.

We aimed to examine the effect of the Community Resilience Model® training on outcomes (ie, perception of organizational support, resilience, burnout, distress, and intention to leave) among shift workers at an academic medical center while exploring differences in demographics, work characteristics, and outcomes by shift type (day vs night).

Training was offered to all nursing roles. Work characteristics, demographics, and nurse outcomes were collected via an online survey. Binomial logistic regressions were conducted for all outcomes.

Of our sampling (N = 878), 52.6% were nurse staff, 23% usually worked night shifts, and 28% attended training. Night shift workers reported significantly lower perceptions of organizational support (P = .03) and resilience (P = .005). Over 55% of night shift workers reported burnout compared to 45% of day shift workers. Sixty-three percent of night and 51% of day shift workers were distressed (P = .002). Training attendees reported significantly higher perceptions of organizational support. Participants reporting higher perceived organizational support also reported less burnout, distress, and intention to leave.

Participants in resilience training rated higher perceptions of organizational support, particularly among night shift workers, who reported lower support, resilience, and higher burnout and distress. These results suggest that resilience training may benefit night shift workers by enhancing support and reducing negative outcomes.

Circadian clocks temporally orchestrate the behavioural and physiological rhythms. The core molecules establishing the circadian clock are clear; however, the critical signalling pathways that cause or favour the homeostasis are poorly understood. Here, we report that anti-Müllerian hormone (Amh)-mediated signalling plays an important role in sustaining circadian homeostasis in zebrafish. Notably, amh knockout dampens molecular clock oscillations and disrupts both behavioural and hormonal circadian rhythms, which are recapitulated in bmpr2a null mutants. Somatotropes and gonadotropes are identified as Amh-targeted pituitary cell populations. Single-cell transcriptome analysis further reveals a lineage-specific regulation of pituitary clock by Amh. Moreover, Amh-induced effect on clock gene expression can be abolished by blocking Smad1/5/9 phosphorylation and bmpr2a knockout. Mechanistically, Amh binds to its receptors, Bmpr2a/Bmpr1bb, which in turn activate Smad1/5/9 by phosphorylation and promote circadian gene expression. Our findings reveal a key hormone signalling pathway for circadian homeostasis in zebrafish with implications for rhythmic organ functions and circadian health.

The circadian clock has evolved to synchronize animal behaviour and physiology with the external environment. Present in almost all cells, the clock is made up of a transcription-translation feedback loop that is responsive to cues such as light/dark cycles (photoperiod) and the time of feeding. Chinook salmon (Oncorhynchus tshawytscha) is a fish species whose clock is thought to be adapted in natural populations according to their latitude, where photoperiod variation can be extreme in northern spring/summer conditions. Here, we probed for the expression of circadian clock genes in four tissues of juvenile Chinook salmon under different environmental conditions. We find that the circadian clock is optimal when photoperiod is coupled with regular feeding during daylight hours. We further tested the effects of constant light and time-restricted feeding, environmental factors that are known to affect daily gene expression rhythms, on the expression of clock genes, appetite-regulating hormones, and metabolic regulators in the intestine of juvenile Chinook. We find that overall constant light is chrono-disruptive irrespective of the timing of food. The resulting disruption in gene expression produces aberrant rhythms, and affects glucose homeostasis, despite an increase in growth. Our data suggests photoperiod and time-restricted feeding could be optimized in Chinook aquaculture and raise the question of whether and how photoperiod changes are compensated in northern-adapted populations.

The hypothalamic suprachiasmatic nucleus (SCN) hosts the central circadian pacemaker and regulates daily rhythms in physiology and behavior. The SCN is composed of peptidergic neuron populations expressing arginine vasopressin (AVP) and vasoactive intestinal polypeptide (VIP), as well as glial cells. Patients with Prader-Willi Syndrome (PWS) commonly experience circadian disturbances, which are particularly evident in their sleep/wake patterns. Using publicly available single-cell RNA sequencing data, we assessed the cell-type specificity of PWS-causative genes in murine SCN, which revealed the differential presence of PWS-related genes in glial and neural subpopulations. We then investigated neurons and glial cells in the SCN using immunohistochemistry in the postmortem hypothalami of PWS subjects and matched controls. We profiled neural populations characterized by AVP and VIP, astroglia characterized by glial fibrillary acid protein (GFAP), and microglia marked by ionized calcium-binding adapter molecule 1 (Iba1) and NADPH oxidase 2 (NOX2). Our analysis revealed an increased total number, neuronal density, and relative staining intensity of AVP-containing neurons in the PWS compared to controls while VIP-containing cells were unaltered. In contrast, GFAP-expressing astroglial cells were significantly lower in PWS subjects. Moreover, we did not detect any differences in microglia between PWS subjects and controls. Collectively, our findings show that PWS selectively affects AVP-containing neurons and GFAP-expressing astrocytes in the SCN. As each of these cell populations can affect the daily rhythmicity of the SCN biological clock machinery, the disruption of these cells may contribute to the circadian disturbances in patients with PWS.

Attention-deficit/hyperactivity disorder (ADHD) is a frequently observed condition, with about 70% of individuals diagnosed with ADHD experiencing irregular sleep-wake patterns. Beyond the primary symptoms of ADHD, there is a significant overlap with sleep-related issues, indicating that disrupted sleep patterns may exacerbate ADHD symptoms. ADHD-related sleep problems can be traced to a delayed circadian rhythm and a later onset of melatonin production. Therefore, normalizing circadian rhythms has been proposed as a potential therapeutic target for psychiatric disorders. Recent animal studies have provided compelling evidence linking peroxisome proliferator-activated receptor gamma (PPARγ), a key regulator of energy metabolism, to the regulation of physiological and behavioral rhythms. In this study, we hypothesized that treating fibroblasts from ADHD patients, which exhibit disturbances in circadian rhythmicity that are replicated in peripheral fibroblasts, with rosiglitazone may restore their circadian rhythmicity to that of the controls. To this end, we used cultures of fibroblasts obtained from skin biopsy explants of ADHD patients and controls and investigated the temporal patterns of clock gene expression over a period of 24 h. We report that the administration of the PPARγ agonist, rosiglitazone significantly realigns the chronobiological patterns of ADHD patient samples and control groups by inducing phase shifts in the expression of the BMAL1, PER3, and CRY1 clock genes. Nevertheless, rosiglitazone showed limited impact on the amplitude and phase of CLOCK1, NPAS2, and PER1. No notable changes were observed in PER2 and PER3 gene expression. The data from cultured human dermal fibroblasts indicate that PPARγ-agonists may help regulate circadian molecular mechanisms. Given the shared genetic pathways between ADHD and obesity, future studies could investigate the potential of RSG as a treatment for circadian rhythm disorders, particularly in obese patients with ADHD.

To date, several biological alterations associated with the refugee status have been investigated. However, none of them has focused on the allostatic load (AL) index that is a collective measure of biological responses to stress. Therefore, the present study aimed to assess the AL index and its correlates in 60 Ukrainian refugees who migrated to Poland after the Russian invasion. The AL index was measured in 60 Ukrainian refugees and 50 controls matched for age and sex. It was based on sex-specific distributions of 15 biomarkers (cardiovascular markers, anthropometric measures, inflammatory markers, glucose homeostasis parameters, lipids, and steroids). Psychopathological symptoms and behavioral characteristics were assessed using self-reports. Refugees had significantly higher AL index together with higher scores of insomnia, negative affect, depressive and anxiety symptoms, avoidance and hyperarousal symptoms of post-traumatic stress disorder as well as lower levels of positive affect. Similarly, a lifetime exposure to traumatic stressors was significantly higher among Ukrainian refugees. Linear regression analyses demonstrated that lower levels of positive affect (interactive effects with the refugee status but not main associations) and higher levels of insomnia (interactive effects with the refugee status and main associations) were associated with elevated AL index after adjustment for age, education, cigarette smoking status, somatic disease, medication use, and head trauma history. In summary, the findings indicate systemic dysregulations of biological stress responses in Ukrainian refugees that are attributable to higher levels of insomnia and lower levels of positive affect in this population.

The basic helix-loop-helix PER-ARNT-SIM (bHLH-PAS) proteins BMAL1 and CLOCK heterodimerize to form the master transcription factor governing rhythmic gene expression. Owing to connections between circadian regulation and numerous physiological pathways, targeting the BMAL1-CLOCK complex pharmacologically is an attractive entry point for intervening in circadian-related processes. In this study, we developed a small molecule, Core Circadian Modulator (CCM), that targets the cavity in the PASB domain of BMAL1, causing it to expand, leading to conformational changes in the PASB domain and altering the functions of BMAL1 as a transcription factor. Biochemical, structural and cellular investigations validate the high level of selectivity of CCM in engaging BMAL1, enabling direct access to BMAL1-CLOCK cellular activities. CCM induces dose-dependent alterations in PER2-Luc oscillations and orchestrates the downregulation of inflammatory and phagocytic pathways in macrophages. These findings collectively reveal that the BMAL1 protein architecture is inherently configured to enable the binding of chemical ligands for functional modulation.

Disruption of the circadian clock is associated with the development of inflammatory bowel disease (IBD), but the underlying mechanisms remain unclear. Here, we observe that mice in the early active phase (Zeitgeber time 12, ZT12) of the circadian clock are more tolerant to dextran sodium sulfate (DSS)-induced colitis, compared to those in the early resting phase (ZT0). The expression of the circadian gene Bmal1 peaks in the early resting phase and declines in the early active phase. Bmal1 knockout in the intestinal epithelium reduces DSS-induced inflammatory symptoms. Mechanistically, BMAL1 promotes apoptosis by binding to apoptosis-related genes, including Bax, p53, and Bak1, and promotes their expression. Intriguingly, we observe circadian apoptotic rhythms in the homeostatic intestinal epithelium, while Bmal1 deletion reduces cell apoptosis. Consistently, reducing Bmal1 expression by the REV-ERBα agonist SR9009 has the best therapeutic efficacy against DSS-induced colitis at ZT0. Collectively, our data demonstrate that the Bmal1-centered circadian clock is involved in intestinal injury repair.

The suprachiasmatic nucleus (SCN) synchronises circadian rhythmicity (~24 h) across the body. The SCN cell-autonomous clock is modelled qualitatively as a transcriptional-translational feedback loop (TTFL), with heteromeric complexes of transcriptional activator and repressor proteins driving cyclical gene expression. How these proteins really behave within the SCN, individually and in relation to each other, is poorly understood. Imaging SCN slices from a novel array of knock-in reporter mice, we quantify the dynamic behaviours of combined repressors PERIOD2 (PER2) and CRYPTOCHROME1 (CRY1), and activator BMAL1. We reveal a spectrum of protein-specific intracellular and spatiotemporal behaviours that run counter to the qualitative TTFL model. We also show that PER and CRY1 exert independent actions on TTFL oscillations, and that their individual stabilities play a critical role in SCN circadian dynamics. These results reveal a rich and unanticipated complexity in the dynamic behaviours and functions of endogenous circadian proteins, prompting re-appraisal of current transcriptional-translational feedback loop models of the suprachiasmatic nucleus.

Inflammatory bowel disease (IBD), comprising ulcerative colitis (UC) and Crohn's disease (CD), is characterized by chronic intestinal inflammation. Recent research has highlighted the significant interplay between IBD pathogenesis and circadian rhythms. This review synthesizes current evidence regarding circadian regulation in IBD, covering three main areas: (1) circadian rhythms in intestinal physiology, (2) circadian disruption patterns in IBD patients, and (3) the role of clock genes in IBD pathogenesis. We discuss how these findings may inform novel chronotherapeutic approaches for IBD treatment. Future research directions that could facilitate translation of chronobiological insights into clinical applications are also explored.

Sleep problems are common in the general population, with evidence suggesting a link between circadian rhythm disruptions and various health outcomes. However, the role of chronotype in influencing colorectal cancer (CRC) risk, particularly in conjunction with genetic predisposition, remains unclear and warrants further investigation.

We analyzed data from 295,729 UK Biobank participants, among whom 4305 developed colorectal cancer. Chronotype was self-reported as morning or evening type, and a polygenic risk score for chronotype was generated from 316 genome-wide significant SNPs using 23andMe effect sizes to reduce overlap bias. Colorectal cancer risk was estimated using Cox proportional hazards models adjusted for age, sex, smoking, alcohol consumption, and the Townsend index.

Late chronotype and high polygenic risk were independently associated with an increased risk of CRC. Compared to participants with an early chronotype, those with a late chronotype exhibited a 6.5% increased risk of CRC [HR 1.065, P = 0.046]. Similarly, individuals in the high genetic risk group had a 11.0% increased risk compared with those in the low genetic risk group [HR, 1.110, P = 0.032]. Stratified analyses revealed that individuals with an intermediate genetic risk who had a late chronotype showed a 17.6% higher risk of CRC [OR, 1.176, P = 0.004], whereas those with a high genetic risk had a 25.3% increase [OR, 1.253, P = 0.001]. Through analyzing the combined effects of chronotype and PRS, we found that among individuals with an early chronotype, those with intermediate PRS had a 15.4% increased risk of CRC [HR, 1.154, P = 0.005], and those with high PRS had a 14.7% increased risk [HR, 1.147, P = 0.027].

Our findings highlight the importance of considering circadian rhythm patterns and genetic predispositions when assessing CRC risk, suggesting that chronotype may be associated with CRC risk, but further studies are needed to integrate objective circadian measurements.

Amelogenesis is a highly regulated process involving multiple signaling pathways, among which the transforming growth factor-β1 (TGF-β1) signaling pathway plays a pivotal role in enamel formation. This review firstly elucidates the critical functions of TGF-β1 in regulating ameloblast behavior and enamel development, encompassing ameloblast proliferation, differentiation, apoptosis, enamel matrix protein synthesis, and mineralization. Secondly, based on emerging evidence, we further discuss potential interactions between TGF-β signaling and circadian regulation in enamel formation, although this relationship requires further experimental validation. Finally, future research directions are proposed to further investigate the relationship between TGF-β1 and the circadian clock in the context of amelogenesis.

Oscillatory p53 expression occurs in individual cells responding to DNA breaks. While the majority of cells exhibit the same qualitative response, quantitative features of the oscillations (e.g., amplitude or period) can be highly variable between cells, generating heterogeneity in downstream cell fate responses. Since heterogeneity can be detrimental to therapies based on DNA damage, methods to induce synchronization of p53 oscillations across cells in a population have the potential to generate more predictable responses to DNA-damaging treatments. Using mathematical modeling and time-lapse microscopy, we demonstrated that p53 oscillations can be synchronized through the phenomenon of phase resetting. Surprisingly, p53 oscillations were synchronized over a wider range of damage-induction frequencies than predicted computationally. Recapitulating the range of synchronizing frequencies required, non-intuitively, a less robust oscillator. We showed that p53 phase resetting altered the expression of downstream targets responsible for cell fate depending on target mRNA stability. This study demonstrates that p53 oscillations can be phase reset and highlights the potential of driving p53 dynamics to reduce cellular variability and synchronize cell fate responses to DNA damage.

This paper presents a comprehensive framework that traces the evolution of consciousness through a continuum of recursive processes spanning reaction, temporogenesis, symbiogenesis, and cognogenesis. By integrating biological cooperation, temporal structuring, and self-referential processing, our model provides a novel perspective on how complexity emerges and scales across evolutionary time. Reaction is established as the foundational mechanism that enables adaptive responses to environmental stimuli, which, through recursive refinement, transitions into temporogenesis-the synchronization of internal processes with external temporal rhythms. Symbiogenesis further enhances this process by fostering cooperative interactions at multiple biological levels, facilitating the emergence of higher-order cognitive functions. Cognogenesis represents the culmination of these recursive processes, where self-awareness and intentionality arise through iterative feedback loops. Our framework offers a biologically grounded pathway to addressing the "hard problem" of consciousness by proposing that subjective experience emerges as a result of progressively complex recursive interactions rather than as a static or isolated phenomenon. In comparing our approach with established theories such as Integrated Information Theory, Global Workspace Theory, and enactive cognition, we highlight its unique contributions in situating consciousness within a broader evolutionary and biological context. This work aims to provide a foundational model that bridges the gap between reaction and reflection, offering empirical avenues for further exploration in neuroscience, evolutionary biology, and artificial intelligence.

Utilizing a randomized control design, 42 healthy adults (22.5 ± 2.8 years) participated in alternate-day modified fasting over a 12-day treatment period. Assessments of sleep included sleep time, efficiency, latency and wake after sleep onset, and assessments of physical activity included steps, energy expenditure, sedentary time, time spent in light physical activity and time spent in moderate-to-vigorous activity. Additional measurements included body composition and mood. The alternate-day modified fasting group consumed 25.8% ± 0.3% fewer calories compared with the control group (p = 0.03). There were no differences between groups for change in body mass index (p = 0.87), total fat mass (p = 0.91) or total lean mass (p = 0.88). Daily energy expenditure did not differ between groups (p = 0.11). On fast days, participants spent 34.5 ± 12.7 more minutes sedentary (p = 0.01), took 1100 ± 362 fewer steps (p < 0.01), and engaged in 27.2 ± 8.4 fewer minutes of moderate-to-vigorous physical activity (p = 0.00) compared with non-fasting days. Sleep duration, efficiency, latency or wake after sleep onset were not different between conditions (p = 0.92, p = 0.10, p = 0.09 and p = 0.66, respectively). We conclude that alternate-day modified fasting does not alter sleep time, efficiency, latency or wake after sleep onset in people reporting poor sleep quality, and does not alter overall physical activity. Although average daily physical activity is not altered, fasting in this manner does tend to result in more sedentary time and less physical activity with compensation on non-fasting days.

To investigate the impact of corneal sensory nerve injury on lacrimal gland function, focusing on mechanisms involving the superior salivatory nucleus (SSN), circadian rhythm disruption, immune microenvironment alterations, and the potential for neural regeneration.

A murine model of corneal sensory nerve injury was used to assess lacrimal gland function, with tear secretion measured using the phenol red thread test. Transcriptomic analysis of lacrimal glands examined circadian rhythm and immune-related gene expression. Basic fibroblast growth factor (bFGF) was used to promote corneal nerve regeneration, and its effects on tear secretion and nerve repair were evaluated.

Corneal nerve injury resulted in a 35% reduction in tear secretion and significantly impaired SSN activity, as evidenced by a 31% decrease in c-FOS-positive neurons in choline acetyltransferase (ChAT)-expressing neurons. Transcriptomic analysis revealed significant downregulation of immune-related pathways, including Toll-like receptor (TLR), NOD-like receptor (NLR), and T-cell receptor signaling. Circadian rhythm gene expression exhibited phase shifts, with a 2.13-hour delay in peak expression and a substantial change in the number and types of rhythmic genes, which were enriched in different signaling pathways. The bFGF treatment restored tear secretion by 22% and promoted nerve regeneration, although nerve fiber density remained 74% lower than that of controls.

Corneal sensory nerve injury disrupts both central and peripheral circadian clock functions in the lacrimal gland, leading to reduced tear secretion and immune dysregulation. These findings highlight the novel role of circadian rhythms and neural-immune interactions in lacrimal gland dysfunction. Neural regeneration strategies, such as bFGF, offer therapeutic potential for dry eye syndrome, providing new directions for clinical intervention.

Cells of the body rely on the circadian clock to orchestrate daily changes in physiology that impact both homeostatic and pathological conditions, such as the inflammatory autoimmune disease rheumatoid arthritis (RA). In RA, high levels of proinflammatory cytokines peak early in the morning hours, reflected by daily changes in joint stiffness. Chronotherapy (or circadian medicine) seeks to delivery drugs at optimal times to maximize their efficacy. However, chronotherapy remains a largely unexplored approach for disease modifying, antirheumatic treatment, particularly for cell-based therapies. In this study, we developed autonomous chronogenetic gene circuits that produce the biologic drug interleukin-1 receptor antagonist (IL-1Ra) with desired phase and amplitude. We compared expression of IL-1Ra from circuits that contained different circadian promoter elements (E'-boxes, D-boxes, or RREs) and their ability to respond to inflammatory challenges in murine pre-differentiated induced pluripotent stem cells (PDiPSC) or engineered cartilage pellets. We confirmed that each circuit reliably peaked at a distinct circadian time over multiple days. Engineered cells generated significant amounts of IL-1Ra on a circadian basis, which protected them from circadian dysregulation and inflammatory damage. These programmable chronogenetic circuits have the potential to align with an individual's circadian rhythm for optimized, self-regulated daily drug delivery.

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.

We examine the relationship between sleep, glymphatics and Alzheimer's disease (AD), and recent work questioning glymphatic clearance during sleep. We highlight a need for understanding glymphatic and/or other mechanism of clearance during sleep, and review glymphatic flow measurement methods. Further, we explore dual orexin receptor antagonists (DORAs) potential to mitigate AD sleep disturbances and enhance clearance. Further research could elucidate a linkage between DORAs, improved sleep and reducing AD pathophysiology.

Circadian rhythm plays a critical role in the progression of autoimmune diseases. While our previous study demonstrated the therapeutic effects of melatonin in experimental autoimmune uveitis, the involvement of circadian rhythm remained unclear. Using a light-induced circadian rhythm disruption model, we showed that disrupted circadian rhythms exacerbate autoimmune uveitis by impairing the stability and function of Treg cells. Mechanistically, we identified the core clock gene Per1, which is significantly reduced under circadian disruption, is essential for Treg cell metabolism and immunoregulatory function. This study underscores the pivotal role of circadian rhythm-related Treg cells in autoimmune disease progression.

This review explores the complex interplay between genetic predispositions to obesity, circadian rhythms, metabolic regulation, and sleep. It highlights how genetic factors underlying obesity exacerbate metabolic dysfunction through circadian misalignment and examines promising interventions to mitigate these effects.

Genome-wide association Studies (GWAS) have identified numerous Single Nucleotide Polymorphisms (SNPs) associated with obesity traits, attributing 40-75% heritability to body mass index (BMI). These findings illuminate critical links between genetic obesity, circadian clocks, and metabolic processes. SNPs in clock-related genes influence metabolic pathways, with disruptions in circadian rhythms-driven by poor sleep hygiene or erratic eating patterns-amplifying metabolic dysfunction. Circadian clocks, synchronized with the 24-h light-dark cycle, regulate key metabolic activities, including glucose metabolism, lipid storage, and energy utilization. Genetic mutations or external disruptions, such as irregular sleep or eating habits, can destabilize circadian rhythms, promoting weight gain and metabolic disorders. Circadian misalignment in individuals with genetic predispositions to obesity disrupts the release of key metabolic hormones, such as leptin and insulin, impairing hunger regulation and fat storage. Interventions like time-restricted feeding (TRF) and structured physical activity offer promising strategies to restore circadian harmony, improve metabolic health, and mitigate obesity-related risks.

Obesity is associated with metabolic and immune perturbations (ie, insulin resistance, increased inflammation, and oxidative stress), circadian rhythm dysregulation, and gut microbial changes that can promote colorectal tumorigenesis. Colorectal cancer (CRC) is the third most incident cancer in the United States. This narrative review examines the effects of intermittend fasting on factors influencing colon tumorigenesis, such as body weight, metabolic and immune markers, circadian rythm, and the gut microbiota in humans. Findings suggest that intermittent fasting regimens can lead to weight loss and shifts in metabolic markers, which could be preventive for CRC but effects on the gut microbiota composition and functions still remains elusive.

Glutamate represents the dominant neurotransmitter that conveys the light information to the brain, including the suprachiasmatic nucleus (SCN), the central pacemaker for the circadian system. The neuronal and astrocytic glutamate transporters are crucial for maintaining efficient glutamatergic signaling. In the SCN, glutamatergic nerve terminals from the retina terminate on vasoactive intestinal polypeptide (VIP) neurons, which are essential for circadian functions. To date, little is known about the role of the core circadian clock gene, Bmal1, in glutamatergic neurotransmission of light signal to various brain regions.

The aim of this study was to further elucidate the role of Bmal1 in glutamatergic neurotransmission from the retina to the SCN. We therefore examined the spontaneous rhythmic locomotor activity, neuronal and glial glutamate transporters, as well as the ultrastructure of the synapse between the retinal ganglion cells (RGCs) and the SCN in adult male Bmal1-/- mice.

We found that the deletion of Bmal1 affects the light-mediated behavior in mice, decreases the retinal thickness and affects the vesicular glutamate transporters (vGLUT1, 2) in the retina. Within the SCN, the immunoreaction of vGLUT1, 2, glial glutamate transporters (GLAST) and VIP was decreased while the glutamate concentration was elevated. At the ultrastructure level, the presynaptic terminals were enlarged and the distance between the synaptic vesicles and the synaptic cleft was increased, indicative of a decrease in the readily releasable pool at the excitatory synapses in Bmal1-/-.

Our data suggests that Bmal1 deletion affects the glutamate transmission in the retina and the SCN and affects the behavioral responses to light.

The circadian rhythm of cortisol, a key hormone essential for maintaining metabolic balance and stress homeostasis, is profoundly disrupted by night-shift work. This narrative review examines the physiological mechanisms underlying cortisol regulation, the effects of shift work on its circadian rhythm, the associated health risks, and potential mitigation strategies. Night-shift work alters the natural secretion pattern of cortisol, leading to dysregulation of the hypothalamic-pituitary-adrenal axis, which in turn can contribute to metabolic disorders, cardiovascular diseases, and impaired cognitive function. Understanding the physiological pathways mediating these changes is crucial for developing targeted interventions to mitigate the adverse effects of circadian misalignment. Potential strategies, such as controlled light exposure, strategic napping, and personalized scheduling, may help to stabilize cortisol rhythms and improve health outcomes. This review aims to provide insights that can guide future research and inform occupational health policies for night-shift workers by addressing these challenges.

Circadian rhythms are biological systems that provide approximately 24-h cycles for the behavior and physiological functions of organisms. As diverse modern lifestyles often cause disturbances in circadian rhythms, new approaches to their regulation are required. Therefore, new compounds that affect circadian rhythms have been explored in edible mushrooms. The extract from the culture filtrate of Cyclocybe cf. erebia showed activity that advanced the circadian rhythm in a bioassay with mouse fibroblasts expressing the LUCIFERASE protein under the control of the Period2 promoter. Bioassay-guided fractionation of the extract resulted in the isolation of the compound. Spectroscopic analyses identified the compound as a phthalide derivative, and the compound was named cyclocybelide. Treatment of mouse fibroblasts with the compound shifted the circadian rhythm forward, irrespective of the timing of treatment. In addition, some phthalide derivatives with hydroxy and methoxy groups showed similar effects on circadian rhythms.

Despite the pivotal role of the hypothalamus in regulating various physiological processes, our understanding of its developmental trajectory and subregional organization during childhood and adolescence remains limited, as well as how emotional and behavioral problems can impact hypothalamic development, potentially leading to neurodevelopmental disorders.

This population-based longitudinal cohort study utilized data from a representative sample of 702 children, who were followed two to five times. Emotional and behavioral problems were assessed using the Strengths and Difficulties Questionnaire (SDQ). Linear mixed models were employed to delineate developmental trajectories and behavioral regulation.

Using an automated segmentation technique, we quantified the volumes and asymmetries of the hypothalamus and its subregions in a large longitudinal sample of 702 subjects aged 6-15 years with 1371 MRI scans, and mapped their developmental trajectories. Our findings indicate that while the anterior and posterior regions of the hypothalamus exhibit a tendency toward decline, the tubular region demonstrates a linear increase which is influenced by lateralization, sex, and intracranial volume. Furthermore, emotional and behavioral problems - particularly emotional symptoms and peer relationship problems - accelerate development in superior tubular and anterior-superior regions.

In this study, we initially delineated the developmental trajectories of the hypothalamus and its subregions from childhood to adolescence based on a longitudinal cohort study. Our findings revealed that the development of hypothalamus followed the pattern of "lateral early to medial late, and dorsomedial early to ventromedial late", and the emotional and behavioral problems accelerate hypothalamic development. This study provides preliminary evidence regarding the impact of emotional and behavioral problems on the dynamic development of the hypothalamus, offering a crucial foundation for future prevention and intervention strategies targeting cognitive and emotional behavioral problems.

Sleep is an essential health requirement; human body needs sufficient amount and quality of sleep to ensure its health. Sleep disturbance led to deterioration in renal functions. This study aimed to asses effect of sleep disturbance on nephrin protein in renal corpuscle. A sample of thirty adult male albino rats, subjected to sleep disturbance by light, divided into three groups; control group with normal sleep rhythm of 12-12 h dark- light phases, group A: subjected to interruption of sleep by light at three intervals, group B: rats were exposed to a reduction in sleep time by continuous light stimulation for 7 h. Animals were sacrificed by euthanasia, their kidneys were dissected and prepared for paraffin, sections stained for Nephrin protein, and the immunohistochemical intensity was quantified by Aperio Image Scope analysis software. This study showed variations in the effect of sleep disturbance patterns by light exposure on nephrin protein expression in renal corpuscles; in the control group a strong patchy distribution of Nephrine in the peripheral region of the glomerulus, group A showed a significant reduction compared to the control group, and group B a weak expression of nephrin protein in the glomerulus, with significant changes between group B and group A, but no significant changes between group B and control. These changes reflect that sleep disturbance affects the structural integrity of the slit diaphragm and nephrin protein expression, which is considered a novel protein for the slit diaphragm structural integrity, and a sign of podocyte injury.

In recent years, the increase in extreme climates, such as persistent high temperatures and drought, has adversely affected the growth and development of fast-growing trees. Melatonin (MT) plays an important role in plant responses to biotic and abiotic stresses, yet there is a lack of research on the specific role of limiting enzyme genes for MT biosynthesis in fast-growing woody plants. In this study, we investigated the function of PtoASMT, a key rate-limiting enzyme encoding gene for MT biosynthesis, which can be induced by drought, salt, and the phytohormones ABA, SA and JA. Our results show that: (1) PtoASMT was widely expressed in all tissues of poplar, but was highly expressed in petioles, moderately expressed in roots, stems, shoots and young leaves, exhibiting a typical diurnal expression rhythm in leaves, with the encoded protein localized on chloroplasts; (2) the content of MT was significantly promoted in overexpressing PtoASMT transgenic poplar plants, but there were no obvious differences in their growth and development; (3) overexpressing PtoASMT plants exhibited stronger drought tolerance, accumulating less reactive oxygen species (ROS) under drought stress relative to wild-type plants, whereas knockout PtoASMT plants were more sensitive and accumulated more ROS; (4) overexpressing PtoASMT plants were more resistant to fungi Dothiorella gregaria than WT plants, while knockout plants showed higher sensitivity; meanwhile, the expression of disease resistance-related genes (PRs and JAZ10) was significantly altered. We conclude that PtoASMT enhances the resistance of poplar to drought and Dothiorella gregaria by mediating MT biosynthesis in poplar. These findings contribute to a better understanding the role of ASMT gene in MT accumulation and stress resistance in poplar.

We investigated the transcription of circadian clock genes in publicly available datasets of gene expression in medulloblastoma (MB) tissues using the R2 Genomics Analysis and Visualization Platform. Differential expression of the core clock genes among the four consensus subgroups of MB (defined in 2012 as Group 3, Group 4, the SHH group, and the WNT group) included the core clock genes (CLOCK, NPAS2, PER1, PER2, CRY1, CRY2, BMAL1, BMAL2, NR1D1, and TIMELESS) and genes which encode proteins that regulate the transcription of clock genes (CIPC, FBXL21, and USP2). The over-expression of several clock genes, including CIPC, was found in individuals with the isochromosome 17q chromosomal aberration in MB Group 3 and Group 4. The most significant biological pathways associated with clock gene expression were ribosome subunits, phototransduction, GABAergic synapse, WNT signaling pathway, and the Fanconi anemia pathway. Survival analysis of clock genes was examined using the Kaplan-Meier method and the Cox proportional hazards regression model through the R2 Genomics Platform. Two clock genes most significantly related to survival were CRY1 and USP2. The data suggest that several clock proteins, including CRY1 and USP2, be investigated as potential therapeutic targets in MB.

Neurogenesis is an active process of creating new neurons in the neurogenic zone. It is influenced by many factors, including the circadian system, which is synchronized by light. Neurogenesis in laboratory rodents peaks at night, and the rodents are nocturnal, contrary to humans that are active during the day. Here, we studied whether proliferation and apoptosis exhibit a daily rhythm in the brain of the diurnal songbird zebra finch (Taeniopygia guttata) and whether the cell proliferation peaks during the dark phase of the day, as in rodents. We injected the birds with the cell proliferation marker 5-ethynyl-2´-deoxyuridine (EdU; thymidine analog), quantified the number of dividing cells in the neurogenic ventricular zone (VZ), and measured mRNA expression of clock genes as well as genes indicating cell proliferation or apoptosis. First, we confirmed the daily rhythms of the clock genes. Next we found that proliferation along the whole VZ did not exhibit a daily rhythm. However, proliferation in the central ventral part of the VZ, i.e. "the hot-spot" area, showed a daily rhythm of proliferation. The highest number of newborn cells was detected in the dark phase of the day. The relative expression of the apoptotic genes caspase 3, Bcl-2, and Bax as well as the proliferating cell nuclear antigen (PCNA) did not show any rhythm. In summary, our results show that cell proliferation in the "hot-spot" region of the VZ in diurnal songbirds shows rhythmic activity over a period of 24 h and that the maximum cell proliferation occurs in the passive phase. This study may have implications for understanding the mechanisms underlying the daily regulation of brain cell proliferation in different species.

Bulky DNA adducts are mostly formed by external factors such as UV irradiation, smoking or treatment with DNA crosslinking agents. If such DNA adducts are not removed by nucleotide excision repair, they can lead to formation of driver mutations that contribute to cancer formation. Transcription factors (TFs) may critically affect both DNA adduct formation and repair efficiency at the binding site to DNA. For example, "hotspot" mutations in melanoma coincide with UV-induced accumulated cyclobutane pyrimidine dimer (CPD) adducts and/or inhibited repair at the binding sites of some TFs. Similarly, anticancer treatment with DNA cross-linkers may additionally generate DNA adducts leading to secondary mutations and the formation of malignant subclones. In addition, some TFs are overexpressed in response to UV irradiation or chemotherapeutic treatment, activating oncogenic and anti-oncogenic pathways independently of nucleotide excision repair itself. This review focuses on the interplay between TFs and nucleotide excision repair during cancer development and progression.