A matter of time: study of circadian clocks and their role in inflammation

Diet/photoperiod mediated changes in cerebellar clock genes causes locomotor shifts and imperative changes in BDNF-TrkB pathway

Neuropsychological studies report anxiety and depression like symptoms in patients suffering from lifestyle disorder but its impact on locomotor function lacks clarity. Our study investigates locomotor deficits resulting due to perturbations in cerebellum of high fat diet (HFD), chronodisruption (CD) or a combination (HCD) model of lifestyle disorder. Significant downregulation in levels of cerebellar clock genes (Bmal-1, Clock, Per 1 and Per 2) and Bdnf-Trkb pathway genes (Bdnf, TrkB and Syn1 levels) were recorded. Further, locomotor deficits were observed in all the three experimental groups as evidenced by actimeter test, pole test and wire hanging test. Nuclear pyknosis of Purkinje cells, their derangement and inflammation were the hallmark of cerebellar tissue of all the three experimental groups. Taken together, this study generates important links between cerebellar clock oscillations, locomotor function and Bdnf-TrkB signaling.

Circadian Control of the Response of Macrophages to Plasmodium Spp.-Infected Red Blood Cells

Malaria is a serious vector-borne disease characterized by periodic episodes of high fever and strong immune responses that are coordinated with the daily synchronized parasite replication cycle inside RBCs. As immune cells harbor an autonomous circadian clock that controls various aspects of the immune response, we sought to determine whether the intensity of the immune response to Plasmodium spp., the parasite causing malaria, depends on time of infection. To do this, we developed a culture model in which mouse bone marrow-derived macrophages are stimulated with RBCs infected with Plasmodium berghei ANKA (iRBCs). Lysed iRBCs, but not intact iRBCs or uninfected RBCs, triggered an inflammatory immune response in bone marrow-derived macrophages. By stimulating at four different circadian time points (16, 22, 28, or 34 h postsynchronization of the cells' clock), 24-h rhythms in reactive oxygen species and cytokines/chemokines were found. Furthermore, the analysis of the macrophage proteome and phosphoproteome revealed global changes in response to iRBCs that varied according to circadian time. This included many proteins and signaling pathways known to be involved in the response to Plasmodium infection. In summary, our findings show that the circadian clock within macrophages determines the magnitude of the inflammatory response upon stimulation with ruptured iRBCs, along with changes of the cell proteome and phosphoproteome.

Advancements in research on the association between the biological CLOCK and type 2 diabetes

Due to the Earth's rotation, the natural environment exhibits a light-dark diurnal cycle close to 24 hours. To adapt to this energy intake pattern, organisms have developed a 24-hour rhythmic diurnal cycle over long periods, known as the circadian rhythm, or biological clock. With the gradual advancement of research on the biological clock, it has become increasingly evident that disruptions in the circadian rhythm are closely associated with the occurrence of type 2 diabetes (T2D). To further understand the progress of research on T2D and the biological clock, this paper reviews the correlation between the biological clock and glucose metabolism and analyzes its potential mechanisms. Based on this, we discuss the potential factors contributing to circadian rhythm disruption and their impact on the risk of developing T2D, aiming to explore new possible intervention measures for the prevention and treatment of T2D in the future. Under the light-dark circadian rhythm, in order to adapt to this change, the human body forms an internal biological clock involving a variety of genes, proteins and other molecules. The main mechanism is the transcription-translation feedback loop centered on the CLOCK/BMAL1 heterodimer. The expression of important circadian clock genes that constitute this loop can regulate T2DM-related blood glucose traits such as glucose uptake, fat metabolism, insulin secretion/glucagon secretion and sensitivity in various peripheral tissues and organs. In addition, sleep, light, and dietary factors under circadian rhythms also affect the occurrence of T2DM.

The disrupted molecular circadian clock of monocytes and macrophages in allergic inflammation

Introduction

Macrophage dysfunction is a common feature of inflammatory disorders such as asthma, which is characterized by a strong circadian rhythm.

Methods and results

We monitored the protein expression pattern of the molecular circadian clock in human peripheral blood monocytes from healthy, allergic, and asthmatic donors during a whole day. Monocytes cultured of these donors allowed us to examine circadian protein expression in human monocyte-derived macrophages, M1- and M2- polarized macrophages. In monocytes, particularly from allergic asthmatics, the oscillating expression of circadian proteins CLOCK, BMAL, REV ERBs, and RORs was significantly altered. Similar changes in BMAL1 were observed in polarized macrophages from allergic donors and in tissue-resident macrophages from activated precision cut lung slices. We confirmed clock modulating, anti-inflammatory, and lung-protective properties of the inverse ROR agonist SR1001 by reduced secretion of macrophage inflammatory protein and increase in phagocytosis. Using a house dust mite model, we verified the therapeutic effect of SR1001 in vivo.

Discussion

Overall, our data suggest an interaction between the molecular circadian clock and monocytes/macrophages effector function in inflammatory lung diseases. The use of SR1001 leads to inflammatory resolution in vitro and in vivo and represents a promising clock-based therapeutic approach for chronic pulmonary diseases such as asthma.

Chikungunya Virus, Metabolism, and Circadian Rhythmicity Interplay in Phagocytic Cells

Chikungunya virus (CHIKV) is transmitted to humans by mosquitoes of the genus Aedes, causing the chikungunya fever disease, associated with inflammation and severe articular incapacitating pain. There has been a worldwide reemergence of chikungunya and the number of cases increased to 271,006 in 2022 in the Americas alone. The replication of CHIKV takes place in several cell types, including phagocytic cells. Monocytes and macrophages are susceptible to infection by CHIKV; at the same time, they provide protection as components of the innate immune system. However, in host-pathogen interactions, CHIKV might have the ability to alter the function of immune cells, partly by rewiring the tricarboxylic acid cycle. Some viral evasion mechanisms depend on the metabolic reprogramming of immune cells, and the cell metabolism is intertwined with circadian rhythmicity; thus, a circadian immunovirometabolism axis may influence viral pathogenicity. Therefore, analyzing the interplay between viral infection, circadian rhythmicity, and cellular metabolic reprogramming in human macrophages could shed some light on the new field of immunovirometabolism and eventually contribute to the development of novel drugs and therapeutic approaches based on circadian rhythmicity and metabolic reprogramming.

Acute Circadian Disruption Due to Constant Light Promotes Caspase 1 Activation in the Mouse Hippocampus

In mammals, the circadian system controls various physiological processes to maintain metabolism, behavior, and immune function during a daily 24 h cycle. Although driven by a cell-autonomous core clock in the hypothalamus, rhythmic activities are entrained to external cues, such as environmental lighting conditions. Exposure to artificial light at night (ALAN) can cause circadian disruption and thus is linked to an increased occurrence of civilization diseases in modern society. Moreover, alterations of circadian rhythms and dysregulation of immune responses, including inflammasome activation, are common attributes of neurodegenerative diseases, including Alzheimer', Parkinson's, and Huntington's disease. Although there is evidence that the inflammasome in the hippocampus is activated by stress, the direct effect of circadian disruption on inflammasome activation remains poorly understood. In the present study, we aimed to analyze whether exposure to constant light (LL) affects inflammasome activation in the mouse hippocampus. In addition to decreased circadian power and reduced locomotor activity, we found cleaved caspase 1 significantly elevated in the hippocampus of mice exposed to LL. However, we did not find hallmarks of inflammasome priming or cleavage of pro-interleukins. These findings suggest that acute circadian disruption leads to an assembled "ready to start" inflammasome, which may turn the brain more vulnerable to additional aversive stimuli.

Interactions of circadian clock genes with the hallmarks of cancer

The molecular machinery of the circadian clock regulates the expression of many genes and processes in the organism, allowing the adaptation of cellular activities to the daily light-dark cycles. Disruption of the circadian rhythm can lead to various pathologies, including cancer. Thus, disturbance of the normal circadian clock at both genetic and environmental levels has been described as an independent risk factor for cancer. In addition, researchers have proposed that circadian genes may have a tissue-dependent and/or context-dependent role in tumorigenesis and may function both as tumor suppressors and oncogenes. Finally, circadian clock core genes may trigger or at least be involved in different hallmarks of cancer. Hence, expanding the knowledge of the molecular basis of the circadian clock would be helpful to identify new prognostic markers of tumorigenesis and potential therapeutic targets.

Evaluating Pain Behaviours: Widely Used Mechanical and Thermal Methods in Rodents

Globally, over 300 million surgical procedures are performed annually, with pain being one of the most common post-operative side effects. During the onset of injury, acute pain plays a protective role in alerting the individual to remove noxious stimuli, while long-lasting chronic pain without any physiological reason is detrimental to the recovery process. Hence, it created an urgent need to better understand the pain mechanism and explore therapeutic targets. Despite the hardship in performing human pain studies due to ethical considerations, clinically relevant rodent pain models provide an excellent opportunity to perform pain studies. Several neurobehavioural tests are used to assess the drug efficacy in rodents to determine avoidance behaviour latency and threshold. This review article provides a methodological overview of mechanical (i.e. von Frey, Mechanical Conflict System) and thermal (i.e. Hargreaves Assay, Hot and Cold Plate, Temperature Place Preference) tests to assess pain in clinically relevant pain rodent models. We further discussed the current modifications of those tests along with their use in literature, the impact of confounding variables, advantages and disadvantages.

Influence of electromagnetic fields on the circadian rhythm: Implications for human health and disease

Living organisms have evolved within the natural electromagnetic fields (EMFs) of the earth which comprise the global atmospheric electrical circuit, Schumann resonances (SRs) and the geomagnetic field. Research suggests that the circadian rhythm, which controls several physiological functions in the human body, can be influenced by light but also by the earth's EMFs. Cyclic solar disturbances, including sunspots and seasonal weakening of the geomagnetic field, can affect human health, possibly by disrupting the circadian rhythm and downstream physiological functions. Severe disruption of the circadian rhythm increases inflammation which can induce fatigue, fever and flu-like symptoms in a fraction of the population and worsen existing symptoms in old and diseased individuals, leading to periodic spikes of infectious and chronic diseases. Possible mechanisms underlying sensing of the earth's EMFs involve entrainment via electrons and electromagnetic waves, light-dependent radical pair formation in retina cryptochromes, and paramagnetic magnetite nanoparticles. Factors such as electromagnetic pollution from wireless devices, base antennas and low orbit internet satellites, shielding by non-conductive materials used in shoes and buildings, and local geomagnetic anomalies may also affect sensing of the earth's EMFs by the human body and contribute to circadian rhythm disruption and disease development.

The association between sedentary behavior, exercise, and sleep disturbance: A mediation analysis of inflammatory biomarkers

Background

Two related lifestyle behaviors associated with sleep disturbance are sedentary behavior and physical exercise participation. We aimed to use a population-based study to disentangle the relationships between sedentary behavior, exercise, and sleep disturbance based on blood-cell-based inflammatory biomarkers.

Methods

A total of 22,599 participants from the National Health and Nutrition Examination Survey (NHANES) were included in the analyses. Sleep disturbance was assessed according to the NHANES questionnaire. Exercise participation ansd sedentary behavior were evaluated by the global physical activity questionnaire. The inflammatory biomarkers in the examination were white blood cell (WBC) count, neutrophil count (NEU), neutrophil-to-lymphocyte ratio (NLR), and systemic immune inflammation index (SII). A complex multistage sampling design and weighted multivariable logistic regression were applied for further analysis. Mediation models were constructed to figure out the mediating role of inflammatory biomarkers.

Results

The weighted prevalence of sleep disturbance was 24.17%. Sedentary behavior and exercise were associated with sleep disturbance after full adjustment [for sedentary behavior, OR (95% CI): 1.261 (1.154, 1.377); for exercise, OR (95% CI): 0.849 (0.757, 0.953)]. In severe sedentary behavior groups, the mitigation effect of exercise on sleep disturbance was observed [OR (95% CI): 0.687 (0.551, 0.857)]. For the mechanism, strong associations were detected between inflammatory biomarkers and sleep disturbance. Mediation analysis showed that WBC, NEU, NLR, and SII mediated the statistical association between sedentary behavior and sleep disturbance with proportions (%) of 2.09, 2.27, 1.76, and 0.82, respectively.

Conclusions

Our data suggested that sedentary behavior was a risk factor for sleep disturbance. Blood-cell-based inflammatory biomarkers were an easily accessible and cost-effective strategy for identifying sleep disturbance and also significantly mediated the association between sedentary behavior and sleep disturbance. Exercise was proved to be effective in severe sedentary behavior groups to improve sleep disturbance symptoms, while the internal mechanism needed further exploration.

Diclofenac Disrupts the Circadian Clock and through Complex Cross-Talks Aggravates Immune-Mediated Liver Injury-A Repeated Dose Study in Minipigs for 28 Days

Diclofenac effectively reduces pain and inflammation; however, its use is associated with hepato- and nephrotoxicity. To delineate mechanisms of injury, we investigated a clinically relevant (3 mg/kg) and high-dose (15 mg/kg) in minipigs for 4 weeks. Initially, serum biochemistries and blood-smears indicated an inflammatory response but returned to normal after 4 weeks of treatment. Notwithstanding, histopathology revealed drug-induced hepatitis, marked glycogen depletion, necrosis and steatosis. Strikingly, the genomic study revealed diclofenac to desynchronize the liver clock with manifest inductions of its components CLOCK, NPAS2 and BMAL1. The > 4-fold induced CRY1 expression underscored an activated core-loop, and the dose dependent > 60% reduction in PER2mRNA repressed the negative feedback loop; however, it exacerbated hepatotoxicity. Bioinformatics enabled the construction of gene-regulatory networks, and we linked the disruption of the liver-clock to impaired glycogenesis, lipid metabolism and the control of immune responses, as shown by the 3-, 6- and 8-fold induced expression of pro-inflammatory CXCL2, lysozyme and ß-defensin. Additionally, diclofenac treatment caused adrenocortical hypertrophy and thymic atrophy, and we evidenced induced glucocorticoid receptor (GR) activity by immunohistochemistry. Given that REV-ERB connects the circadian clock with hepatic GR, its > 80% repression alleviated immune responses as manifested by repressed expressions of CXCL9(90%), CCL8(60%) and RSAD2(70%). Together, we propose a circuitry, whereby diclofenac desynchronizes the liver clock in the control of the hepatic metabolism and immune response.

IL-6 deletion decreased REV-ERBα protein and influenced autophagy and mitochondrial markers in the skeletal muscle after acute exercise

Interleukin 6 (IL-6) acts as a pro and anti-inflammatory cytokine, has an intense correlation with exercise intensity, and activates various pathways such as autophagy and mitochondrial unfolded protein response. Also, IL-6 is interconnected to circadian clock-related inflammation and can be suppressed by the nuclear receptor subfamily 1, group D, member 1 (Nr1d1, protein product REV-ERBα). Since IL-6 is linked to physical exercise-modulated metabolic pathways such as autophagy and mitochondrial metabolism, we investigated the relationship of IL-6 with REV-ERBα in the adaptations of these molecular pathways in response to acute intense physical exercise in skeletal muscle. The present study was divided into three experiments. In the first one, wild-type (WT) and IL-6 knockout (IL-6 KO) mice were divided into three groups: Basal time (Basal; sacrificed before the acute exercise), 1 hour (1hr post-Ex; sacrificed 1 hour after the acute exercise), and 3 hours (3hr post-Ex; sacrificed 3 hours after the acute exercise). In the second experiment, C2C12 cells received IL-6 physiological concentrations or REV-ERBα agonist, SR9009. In the last experiment, WT mice received SR9009 injections. After the protocols, the gastrocnemius muscle or the cells were collected for reverse transcription-quantitative polymerase chain reaction (RTq-PCR) and immunoblotting techniques. In summary, the downregulation of REV-ERBα, autophagic flux, and most mitochondrial genes was verified in the IL-6 KO mice independent of exercise. The WT and IL-6 KO treated with SR9009 showed an upregulation of autophagic genes. C2C12 cells receiving IL-6 did not modulate the Nr1d1 mRNA levels but upregulated the expression of some mitochondrial genes. However, when treated with SR9009, IL-6 and mitochondrial gene expression were upregulated in C2C12 cells. The autophagic flux in C2C12 suggest the participation of REV-ERBα protein in the IL-6-induced autophagy. In conclusion, the present study verified that the adaptations required through physical exercise (increases in mitochondrial content and improvement of autophagy machinery) might be intermediated by an interaction between IL-6 and REVERBα.

Identification of circadian clock genes as regulators of immune infiltration in Hepatocellular Carcinoma

Background: Multiple studies have reported that the immune system is under the control of a circadian clock, especially in cancers, but how circadian clock genes shape tumor immune cell infiltration in hepatocellular carcinoma (HCC) remains unclear.

Methods: The rhythmicity of circadian clock genes was investigated using the GETx database. The expression and methylation level of circadian clock genes in HCC and paracancerous was evaluated using the GETx and TCGA databases. The differential expression of circadian clock genes in HCC was analyzed using the “limma” package of the R 4.0.4 software. The prognosis of each circadian clock gene was accessed by Kaplan-Meier survival analysis and Cox proportional hazards regression analysis. Quantitative real-time PCR and immunohistochemistry (IHC) was carried out to confirm the results. The relationship between circadian rhythm and immune infiltration in HCC was evaluated using the TIMER database and the CIBERSORT algorithm.

Results: In addition to RORA, RORB, and ARNTL2, there was a rhythmic expression of other circadian clock genes in liver tissue. The correlation between the expression of circadian clock genes differed when comparing HCC and liver tissue. HCC patients who express low levels of PER-1and CRY2 had a poor overall survival (OS). In contrast, patients with higher expression of NPAS2 had a poor prognosis. In HCC, the expression of the PER-1, CRY2, and NPAS2 genes was closely related to immune infiltration.

Conclusion: Our study indicated the disruption of the expression of circadian clock-regulated genes in HCC and identified PER-1, CRY2, and NPAS2 as independent predictors of survival. These genes may be applied as candidate molecular targets for diagnosis and therapy of HCC.

Administration time-dependent effects of poly (I:C) on antioxidant and immune responses along the diurnal time scale in zebrafish

The circadian clock of vertebrates regulates many biological processes, including the immune system. This paper investigated whether responsiveness to poly (I:C), a synthetic analog of double-stranded RNA used as an immunostimulant, exhibits day/night differences in zebrafish. Fish were intraperitoneally (IP) injected with either phosphate-buffered saline (PBS) or poly (I:C) at two different time points: "Zeitgeber Time" (ZT) 4 (day) and ZT16 (night). Then, 6 h later, fish were euthanized, and tissue samples (skin, liver and kidney) were collected. A control group (intact fish) was also sampled at the same time points. The effect of poly (I:C) on the expression of antioxidant and immune genes was time-of-day-dependent, and the response was stronger following poly (I:C) administration in the day than at night. Time-dependent differences were observed for some genes in the PBS and control groups. However, these differences were tissue-specific. In liver, almost all the genes were affected by time of day. In kidney, poly (I:C) affected the expression of all the gene markers regardless of administration time. These findings highlight the importance of considering the time to administer poly (I:C) when evaluating the fish immune response.

The Natural Janus Kinase Inhibitor Agerarin Downregulates Interleukin-4-Induced PER2 Expression in HaCaT Keratinocytes

The circadian clock system is closely associated with inflammatory responses. Dysregulation of the circadian clock genes in the skin impairs the skin barrier function and affects the pathophysiology of atopic dermatitis. Interleukin 4 (IL-4) is a proinflammatory cytokine derived from T-helper type 2 cells; it plays a critical role in the pathogenesis of atopic dermatitis. Agerarin (6,7-dimethoxy-2,2-dimethyl-2H-chromene) is a natural JAK1/2/3 inhibitor isolated from Ageratum houstonianum that has a protective effect on the epidermal skin barrier. However, it remains unclear whether agerarin affects the circadian clock system. The aim of this study is to investigate the effect of agerarin on IL-4-induced PER2 gene expression in human keratinocytes through reverse transcription (RT)-PCR, quantitative real-time PCR (qPCR), immunoblotting, immunofluorescence microscopic analysis, and real-time bioluminescence analysis. We found that agerarin reduced IL-4-induced PER2 mRNA expression by suppressing the JAK-STAT3 pathway. In addition, real-time bioluminescence analysis in PER2:luc2p promoter-reporter cells revealed that agerarin restored the oscillatory rhythmicity of PER2 promoter activity altered by IL-4. These findings suggest that agerarin may be useful as a cosmeceutical agent against inflammatory skin conditions associated with disrupted circadian rhythms, such as atopic dermatitis.

Fish female-biased gene cyp19a1a leads to female antiviral response attenuation between sexes by autophagic degradation of MITA

From insects to mammals, both innate and adaptive immune response are usually higher in females than in males, with the sex chromosome and hormonal differences considered the main reasons. Here, we report that zebrafish cyp19a1a (cytochrome P450, family 19, subfamily A, polypeptide 1a), an autosomal gene with female-biased expression, causes female fish to exhibit a lower antiviral response. First, we successfully constructed an infection model by intraperitoneal injection of spring viremia of carp virus (SVCV) into zebrafish (Danio rerio) and Carassius auratus herpesvirus (CaHV) in gibel carp (Carassius gibelio). Specifically, female fish were more vulnerable to viral infection than males, accompanied by a significantly weaker interferon (IFN) expression. After screening several candidates, cyp19a1a, which was highly expressed in female fish tissues, was selected for further analysis. The IFN expression and antiviral response were significantly higher in cyp19a1a-/- than in cyp19a1a+/+. Further investigation of the molecular mechanism revealed that Cyp19a1a targets mediator of IRF3 activation (MITA) for autophagic degradation. Interestingly, in the absence of MITA, Cyp19a1a alone could not elicit an autophagic response. Furthermore, the autophagy factor ATG14 (autophagy-related 14) was found interacted with Cyp19a1a to either promote or attenuate Cyp19a1a-mediated MITA degradation by either being overexpressed or knocked down, respectively. At the cellular level, both the normal and MITA-enhanced cellular antiviral responses were diminished by Cyp19a1a. These findings demonstrated a sex difference in the antiviral response based on a regulation mechanism controlled by a female-biased gene besides sex chromosome and hormonal differences, supplying the current understanding of sex differences in fish.

Sinapic Acid Ameliorates REV-ERB α Modulated Mitochondrial Fission against MPTP-Induced Parkinson's Disease Model

Parkinson’s disease (PD) is the second most common neurodegenerative disease worldwide, and accumulating evidence indicates that mitochondrial dysfunction is associated with progressive deterioration in PD patients. Previous studies have shown that sinapic acid has a neuroprotective effect, but its mechanisms of action remain unclear. The neuroprotective effect of sinapic acid was assayed in a PD mouse model generated by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) as well as in SH-SY5Y cells. Target protein expression was detected by western blotting. Sinapic acid treatment attenuated the behavioral defects and loss of dopaminergic neurons in the PD models. Sinapic acid also improved mitochondrial function in the PD models. MPTP treatment increased the abundance of mitochondrial fission proteins such as dynamin-related protein 1 (Drp1) and phospho-Drp1 Ser616. In addition, MPTP decreased the expression of the REV-ERB α protein. These changes were attenuated by sinapic acid treatment. We used the pharmacological REV-ERB α inhibitor SR8278 to confirmation of protective effect of sinapic acid. Treatment of SR8278 with sinapic acid reversed the protein expression of phospho-Drp1 Ser616 and REV-ERB α on MPTP-treated mice. Our findings demonstrated that sinapic acid protects against MPTP-induced PD and these effects might be related to the inhibiting abnormal mitochondrial fission through REV-ERB α.

Is it time for chronopharmacology in NASH?

Liver homeostasis is strongly influenced by the circadian clock, an evolutionarily conserved mechanism synchronising physiology and behaviour across a 24-hour cycle. Disruption of the clock has been heavily implicated in the pathogenesis of metabolic dysfunction including non-alcoholic fatty liver (NAFL) and non-alcoholic steatohepatitis (NASH). Furthermore, many of the current NASH drug candidates specifically target pathways known to be under circadian control including fatty acid synthesis and signalling via the farnesoid X receptor, fibroblast growth factor 19 and 21, peroxisome proliferator-activated receptor α and γ, glucagon-like peptide 1, and the thyroid hormone receptor. Despite this, there has been little consideration of the application of chronopharmacology in NASH, a strategy whereby the timing of drug delivery is informed by biological rhythms in order to maximise efficacy and tolerability. Chronopharmacology has been shown to have significant clinical benefits in a variety of settings including cardiovascular disease and cancer therapy. The rationale for its application in NASH is therefore compelling. However, no clinical trials in NASH have specifically explored the impact of drug timing on disease progression and patient outcomes. This may contribute to the wide variability in reported outcomes of NASH trials and partly explain why even late-phase trials have stalled because of a lack of efficacy or safety concerns. In this opinion piece, we describe the potential for chronopharmacology in NASH, discuss how the major NASH drug candidates are influenced by circadian biology, and encourage greater consideration of the timing of drug administration in the design of future clinical trials.

How exposure to chronic stress contributes to the development of type 2 diabetes: A complexity science approach

Chronic stress contributes to the onset of type 2 diabetes (T2D), yet the underlying etiological mechanisms are not fully understood. Responses to stress are influenced by earlier experiences, sex, emotions and cognition, and involve a complex network of neurotransmitters and hormones, that affect multiple biological systems. In addition, the systems activated by stress can be altered by behavioral, metabolic and environmental factors. The impact of stress on metabolic health can thus be considered an emergent process, involving different types of interactions between multiple variables, that are driven by non-linear dynamics at different spatiotemporal scales. To obtain a more comprehensive picture of the links between chronic stress and T2D, we followed a complexity science approach to build a causal loop diagram (CLD) connecting the various mediators and processes involved in stress responses relevant for T2D pathogenesis. This CLD could help develop novel computational models and formulate new hypotheses regarding disease etiology.

Blunted rest-activity rhythm is associated with increased white blood-cell-based inflammatory markers in adults: an analysis from NHANES 2011-2014

Circadian rhythm disruption is associated with immune system disturbance and has been observed in many health problems where chronic-inflammation acts as a major contributor. We aim to examine whether rest-activity circadian rhythm is associated with chronic inflammation using white blood-cell-based inflammatory indices including white blood cell (WBC) count, neutrophil count, neutrophil-to-lymphocyte ratio (NLR) and systemic immune-inflammation index (SII). We analyzed the data from 8089 adults (age≥20) with at least 4 days of validated accelerometer recordings and a valid WBC count from the National Health and Nutrition Examination Survey (NHANES) 2011-2014. Non-parametric rest-activity circadian rhythm parameters were derived from the accelerometer recordings. In the models adjusting multiple covariates, a one-quantile increase in relative amplitude (i.e. more robust circadian rhythm) was associated with 1 × 10⁸ cells/L decrease in WBC number (95% CI: 5 × 10⁷ to 1.5 × 10⁸, P < .001), 7 × 10⁷ cells/L decrease in neutrophils (95% CI: 3 × 10⁷ to 1.1 × 10⁸, P = .003) and 15.2 × 10⁹ /L decrease in SII (95% CI: 6 × 10⁹ /L to 20 × 10⁹/L, P = .019). Consistent results were also observed for the association of M10 value and L5 value with these inflammatory indices. Our results indicated that blunted rest-activity circadian rhythm is associated with increased white blood-cell-based inflammatory indices in adults, suggesting interventions aiming at enhancing circadian rhythm by lifestyle programs may be a novel approach to improve the general health.

Circadian Rhythm and Nuclear Receptors

All life of Earth has evolved mechanisms to track time. This permits anticipation of predictable changes in light/dark, and in most cases also directs fed/fasted cycles, and sleep/wake. The nuclear receptors enjoy a close relationship with the molecular machinery of the clock. Some play a core role within the circadian machinery, other respond to ligands which oscillate in concentration, and physical cross-talk between clock transcription factors, eg cryptochromes, and multiple nuclear receptors also enable coupling of nuclear receptor function to time of day. Essential processes including inflammation, and energy metabolism are strongly regulated by both the circadian machinery, and rhythmic behaviour, and also by multiple members of the nuclear receptor family. An emerging theme is reciprocal regulation of key processes by different members of the nuclear receptor family, for example NR1D1/2, and NR1F1, in regulation of the core circadian clock transcription factor BMAL1.

Mucosal circadian rhythm pathway genes altered by aging and periodontitis

As circadian processes can impact the immune system and are affected by infections and inflammation, this study examined the expression of circadian rhythm genes in periodontitis.

METHODS

Macaca mulatta were used with naturally-occurring and ligature-induced periodontitis. Gingival tissue samples were obtained from healthy, diseased, and resolved sites in four groups: young (≤3 years), adolescent (3-7 years), adult (12-26) and aged (18-23 years). Microarrays targeted circadian rhythm (n = 42), inflammation/tissue destruction (n = 11), bone biology (n = 8) and hypoxia pathway (n = 7) genes.

RESULTS

The expression of many circadian rhythm genes, across functional components of the pathway, was decreased in healthy tissues from younger and aged animals, as well as showing significant decreases with periodontitis. Negative correlations of the circadian rhythm gene levels with inflammatory mediators and tissue destructive/remodeling genes were particularly accentuated in disease. A dominance of positive correlations with hypoxia genes was observed, except HIF1A, that was uniformly negatively correlated in health, disease and resolution.

CONCLUSIONS

The chronic inflammation of periodontitis exhibits an alteration of the circadian rhythm pathway, predominantly via decreased gene expression. Thus, variation in disease expression and the underlying molecular mechanisms of disease may be altered due to changes in regulation of the circadian rhythm pathway functions.

Reduced neuroinflammation and enhanced neurogenesis following chronic agomelatine treatment in rats undergoing chronic constant light

Experimental studies have revealed the involvement of neuroinflammation mediated by activated microglia in the pathophysiology of depression, suggesting a novel target for treatment. The atypical antidepressant Agomelatine (Ago) has an advantage compared to the classical antidepressants due to its chronobiotic activity and unique pharmacological profile as a selective agonist at the melatonin receptors and an antagonist at the 5HT_2C receptors. We have recently revealed that Ago can exert a potent antidepressant effect in rats exposed to a chronic constant light (CCL). In the present study, we hypothesized that the anti-inflammatory activity of this melatonin analog on activated neuroglia in specific brain structures might contribute to its antidepressant effect in this model. Chronic Ago treatment (40 mg/kg, i.p. for 21 days) was executed during the last 3 weeks of a 6-week period of CCL exposure in rats. The CCL-vehicle-treated rats showed a profound neuroinflammation characterized by microgliosis and astrogliosis in the hippocampus, basolateral amygdala (BL) and partly in the piriform cortex (Pir) confirmed by immunohistochemistry. With the exception of the Pir, the CCL regime was accompanied by neuronal damage, identified by Nissl staining, in the hippocampus and basolateral amygdala and impaired neurogenesis with reduced dendritic complexity of hippocampal neuroprogenitor cells detected by doublecortin-positive cells in the dentate gyrus (DG) subgranular zone compared to the control group. Ago reversed the gliosis in a region-specific manner and partially restored the suppressed DG neurogenesis. Ago failed to produce neuroprotection in CCL exposed rats. The present results suggest that the beneficial effects of Ago represent an important mechanism underlying its antidepressant effect in models characterized by impaired circadian rhythms.

Melatonin in Early Nutrition: Long-Term Effects on Cardiovascular System

Breastfeeding protects against adverse cardiovascular outcomes in the long term. Melatonin is an active molecule that is present in the breast milk produced at night beginning in the first stages of lactation. This indoleamine appears to be a relevant contributor to the benefits of breast milk because it can affect infant health in several ways. The melatonin concentration in breast milk varies in a circadian pattern, making breast milk a chrononutrient. The consumption of melatonin can induce the first circadian stimulation in the infant's body at an age when his/her own circadian machinery is not functioning yet. This molecule is also a powerful antioxidant with the ability to act on infant cells directly as a scavenger and indirectly by lowering oxidant molecule production and enhancing the antioxidant capacity of the body. Melatonin also participates in regulating inflammation. Furthermore, melatonin can participate in shaping the gut microbiota composition, richness, and variation over time, also modulating which molecules are absorbed by the host. In all these ways, melatonin from breast milk influences weight gain in infants, limiting the development of obesity and comorbidities in the long term, and it can help shape the ideal cellular environment for the development of the infant's cardiovascular system.

The circadian timing of noise exposure influences noise-induced inflammatory responses in the mouse cochlea

INTRODUCTION

Noise-induced hearing loss is one of the most common forms of sensorineural hearing loss. Nevertheless, the mechanisms of noise-induced hearing loss are still not fully understood.

OBJECTIVE

To investigate the dynamics of inflammatory responses in the mammalian cochlea following noise trauma at two different times, once during the light cycle and once during the dark.

METHODS

We challenged C57BL/6J mice with moderate, continuous noise trauma at either 9 a.m. or 9 p.m. Auditory function, histological changes in hair cells, and modifications in gene expression levels of inflammatory mediators were assessed at specific time points. Shifts in auditory brainstem response thresholds were measured at 1, 3, 7 and 14 days after noise exposure to measure potential noise-induced hearing loss. Cochlear basilar-membrane immunofluorescent staining was performed at 3 and 14 days after noise exposure. The mRNA levels of several inflammatory mediators were measured via quantitative real-time polymerase chain reaction before (pre) and after (0, 3, 12, 24 and 72 h) noise exposure.

RESULTS

We found that all noise-exposed mice developed a temporary threshold shift and that there were no significant differences between daytime and nighttime noise exposures in terms of inducing hearing-threshold shifts. Similarly, we did not detect significant histological changes in hair cells between these two groups. However, we discovered an interesting phenomenon in that the peak mRNA levels of IL-1β, IL-6, CCL2 and TNF-α were higher in day noise-exposed mice compared to those in night noise-exposed mice, and these mRNA levels subsided more slowly in day noise-exposed mice.

CONCLUSION

Overall, these observations suggest that the circadian timing of noise exposure has a significant effect on noise-induced inflammatory responses in the mouse cochlea and that a greater inflammatory response might occur after daytime exposure.

The transcriptional repressor Rev-erbα regulates circadian expression of the astrocyte Fabp7 mRNA

The astrocyte brain-type fatty-acid binding protein (Fabp7) circadian gene expression is synchronized in the same temporal phase throughout mammalian brain. Cellular and molecular mechanisms that contribute to this coordinated expression are not completely understood, but likely involve the nuclear receptor Rev-erbα (NR1D1), a transcriptional repressor. We performed ChIP-seq on ventral tegmental area (VTA) and identified gene targets of Rev-erbα, including Fabp7. We confirmed that Rev-erbα binds to the Fabp7 promoter in multiple brain areas, including hippocampus, hypothalamus, and VTA, and showed that Fabp7 gene expression is upregulated in Rev-erbα knock-out mice. Compared to Fabp7 mRNA levels, Fabp3 and Fabp5 mRNA were unaffected by Rev-erbα depletion in hippocampus, suggesting that these effects are specific to Fabp7. To determine whether these effects of Rev-erbα depletion occur broadly throughout the brain, we also evaluated Fabp mRNA expression levels in multiple brain areas, including cerebellum, cortex, hypothalamus, striatum, and VTA in Rev-erbα knock-out mice. While small but significant changes in Fabp5 mRNA expression exist in some of these areas, the magnitude of these effects are minimal to that of Fabp7 mRNA expression, which was over 6-fold across all brain regions. These studies suggest that Rev-erbα is a transcriptional repressor of Fabp7 gene expression throughout mammalian brain.

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The transcriptional repressor Rev-erbα binds to the Fabp7 promoter across brain areas.

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Multiple Rev-erbα response element binding sites exist on the Fabp7 promoter.

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Rev-erbα is required for Fabp7 transcriptional repression and circadian expression.

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Rev-erbα depletion does not affect other Fabp-type gene expression in brain.

Circadian Biology and Stroke

Circadian biology modulates almost all aspects of mammalian physiology, disease, and response to therapies. Emerging data suggest that circadian biology may significantly affect the mechanisms of susceptibility, injury, recovery, and the response to therapy in stroke. In this review/perspective, we survey the accumulating literature and attempt to connect molecular, cellular, and physiological pathways in circadian biology to clinical consequences in stroke. Accounting for the complex and multifactorial effects of circadian rhythm may improve translational opportunities for stroke diagnostics and therapeutics.

Circadian clock: a regulator of the immunity in cancer

The circadian clock is an endogenous timekeeper system that controls and optimizes biological processes, which are consistent with a master circadian clock and peripheral clocks and are controlled by various genes. Notably, the disruption of circadian clock genes has been identified to affect a wide range of ailments, including cancers. The cancer-immunity cycle is composed of seven major steps, namely cancer cell antigen release and presentation, priming and activation of effector immunity cells, trafficking, and infiltration of immunity to tumors, and elimination of cancer cells. Existing evidence indicates that the circadian clock functions as a gate that govern many aspects of the cancer-immunity cycle. In this review, we highlight the importance of the circadian clock during tumorigenesis, and discuss the potential role of the circadian clock in the cancer-immunity cycle. A comprehensive understanding of the regulatory function of the circadian clock in the cancer-immunity cycle holds promise in developing new strategies for the treatment of cancer.

Nuclear Receptors as Multiple Regulators of NLRP3 Inflammasome Function

Nuclear receptors are important bridges between lipid signaling molecules and transcription responses. Beside their role in several developmental and physiological processes, many of these receptors have been shown to regulate and determine the fate of immune cells, and the outcome of immune responses under physiological and pathological conditions. While NLRP3 inflammasome is assumed as key regulator for innate and adaptive immune responses, and has been associated with various pathological events, the precise impact of the nuclear receptors on the function of inflammasome is hardly investigated. A wide variety of factors and conditions have been identified as modulators of NLRP3 inflammasome activation, and at the same time, many of the nuclear receptors are known to regulate, and interact with these factors, including cellular metabolism and various signaling pathways. Nuclear receptors are in the focus of many researches, as these receptors are easy to manipulate by lipid soluble molecules. Importantly, nuclear receptors mediate regulatory mechanisms at multiple levels: not only at transcription level, but also in the cytosol via non-genomic effects. Their importance is also reflected by the numerous approved drugs that have been developed in the past decade to specifically target nuclear receptors subtypes. Researches aiming to delineate mechanisms that regulate NLRP3 inflammasome activation draw a wide range of attention due to their unquestionable importance in infectious and sterile inflammatory conditions. In this review, we provide an overview of current reports and knowledge about NLRP3 inflammasome regulation from the perspective of nuclear receptors, in order to bring new insight to the potentially therapeutic aspect in targeting NLRP3 inflammasome and NLRP3 inflammasome-associated diseases.

Chronic circadian shift leads to adipose tissue inflammation and fibrosis

The circadian clock exerts temporal coordination of metabolic pathways. Clock disruption is intimately linked with the development of obesity and insulin resistance, and our previous studies found that the essential clock transcription activator, Brain and Muscle Arnt-like 1 (Bmal1), is a key regulator of adipogenesis. However, the metabolic consequences of chronic shiftwork on adipose tissues have not been clearly defined. Here, using an environmental lighting-induced clock disruption that mimics rotating shiftwork schedule, we show that chronic clock dysregulation for 6 months in mice resulted in striking adipocyte hypertrophy with adipose tissue inflammation and fibrosis. Both visceral and subcutaneous depots display enlarged adipocyte with prominent crown-like structures indicative of macrophage infiltration together with evidence of extracellular matrix remodeling. Global transcriptomic analyses of these fat depots revealed that shiftwork resulted in up-regulations of inflammatory, adipogenic and angiogenic pathways with disruption of normal time-of-the-day-dependent regulation. These changes in adipose tissues are associated with impaired insulin signaling in mice subjected to shiftwork, together with suppression of the mTOR signaling pathway. Taken together, our study identified the significant adipose depot dysfunctions induced by chronic shiftwork regimen that may underlie the link between circadian misalignment and insulin resistance.

Identifying new cellular mechanisms of mineralocorticoid receptor activation in the heart

Recent studies have expanded our understanding of the actions of the mineralocorticoid receptor (MR) to a diverse array of tissue types that differ substantially from the epithelial cells of the renal nephron. In these cell types the role of the MR has been largely, but not exclusively, defined in terms of pathogenic signalling pathways leading to tissue injury and remodelling. Macrophages and cardiomyocytes are two cell types in which the MR plays a central role in the cardiac tissue response to injury, renovascular hypertension and oxidative stress for example. Macrophages are critical for resolution of tissue injury and wound healing and their pleiotropic actions are central to the development of many forms of heart, renal and vascular disease. The MR in cardiomyocytes is not only essential for the chronotropic and ionotropic actions of mineralocorticoids in the short and longer term, but also for induction of hypertrophic and proinflammatory signalling programs. The present review discusses recent studies, presented at the Aldosterone and Hypertension Satellite of the 15th Asian-Pacific Congress of Hypertension, investigating new mechanisms for MR signalling in these cells and how their dysfunction contributes to the onset and progression of cardiovascular disease and heart failure.

Circadian Rhythm: Potential Therapeutic Target for Atherosclerosis and Thrombosis

Every organism has an intrinsic biological rhythm that orchestrates biological processes in adjusting to daily environmental changes. Circadian rhythms are maintained by networks of molecular clocks throughout the core and peripheral tissues, including immune cells, blood vessels, and perivascular adipose tissues. Recent findings have suggested strong correlations between the circadian clock and cardiovascular diseases. Desynchronization between the circadian rhythm and body metabolism contributes to the development of cardiovascular diseases including arteriosclerosis and thrombosis. Circadian rhythms are involved in controlling inflammatory processes and metabolisms, which can influence the pathology of arteriosclerosis and thrombosis. Circadian clock genes are critical in maintaining the robust relationship between diurnal variation and the cardiovascular system. The circadian machinery in the vascular system may be a novel therapeutic target for the prevention and treatment of cardiovascular diseases. The research on circadian rhythms in cardiovascular diseases is still progressing. In this review, we briefly summarize recent studies on circadian rhythms and cardiovascular homeostasis, focusing on the circadian control of inflammatory processes and metabolisms. Based on the recent findings, we discuss the potential target molecules for future therapeutic strategies against cardiovascular diseases by targeting the circadian clock.

Proinflammatory Cytokines Perturb Mouse and Human Pancreatic Islet Circadian Rhythmicity and Induce Uncoordinated β-Cell Clock Gene Expression via Nitric Oxide, Lysine Deacetylases, and Immunoproteasomal Activity

Pancreatic β-cell-specific clock knockout mice develop β-cell oxidative-stress and failure, as well as glucose-intolerance. How inflammatory stress affects the cellular clock is under-investigated. Real-time recording of Per2:luciferase reporter activity in murine and human pancreatic islets demonstrated that the proinflammatory cytokine interleukin-1β (IL-1β) lengthened the circadian period. qPCR-profiling of core clock gene expression in insulin-producing cells suggested that the combination of the proinflammatory cytokines IL-1β and interferon-γ (IFN-γ) caused pronounced but uncoordinated increases in mRNA levels of multiple core clock genes, in particular of reverse-erythroblastosis virus α (Rev-erbα), in a dose- and time-dependent manner. The REV-ERBα/β agonist SR9009, used to mimic cytokine-mediated Rev-erbα induction, reduced constitutive and cytokine-induced brain and muscle arnt-like 1 (Bmal1) mRNA levels in INS-1 cells as expected. SR9009 induced reactive oxygen species (ROS), reduced insulin-1/2 (Ins-1/2) mRNA and accumulated- and glucose-stimulated insulin secretion, reduced cell viability, and increased apoptosis levels, reminiscent of cytokine toxicity. In contrast, low (<5,0 μM) concentrations of SR9009 increased Ins-1 mRNA and accumulated insulin-secretion without affecting INS-1 cell viability, mirroring low-concentration IL-1β mediated β-cell stimulation. Inhibiting nitric oxide (NO) synthesis, the lysine deacetylase HDAC3 and the immunoproteasome reduced cytokine-mediated increases in clock gene expression. In conclusion, the cytokine-combination perturbed the intrinsic clocks operative in mouse and human pancreatic islets and induced uncoordinated clock gene expression in INS-1 cells, the latter effect associated with NO, HDAC3, and immunoproteasome activity.

The clock regulator Bmal1 protects against muscular dystrophy

The muscle-intrinsic clock machinery is required for the maintenance of muscle growth, remodeling and function. Our previous studies demonstrated that the essential transcription activator of the molecular clock feed-back loop, Brain and Muscle Arnt-Like 1(Bmal1), plays a critical role in myogenic progenitor behavior to promote and regenerative myogenesis. Using genetic approaches targeting Bmal1 in the DMDmdx (mdx) dystrophic mouse model, here we report that the loss of Bmal1 function significantly accelerated dystrophic disease progression. In contrast to the mild dystrophic changes in mdx mice, the genetic loss-of-function of Bmal1 aggravated muscle damage in this dystrophic disease background, as indicated by persistently elevated creatine kinase levels, increased injury area and reduced muscle grip strength. Mechanistic studies revealed that markedly impaired myogenic progenitor proliferation and myogenic response underlie the defective new myofiber formation in the chronic dystrophic milieu. Taken together, our study identified the function of pro-myogenic clock gene Bmal1 in protecting against dystrophic damage, suggesting the potential for augmenting Bmal1 function to ameliorate dystrophic or degenerative muscle diseases.

Innate Rhythms: Clocks at the Center of Monocyte and Macrophage Function

The circadian cycle allows organisms to track external time of day and predict/respond to changes in the external environment. In higher order organisms, circadian rhythmicity is a central feature of innate and adaptive immunity. We focus on the role of the molecular clock and circadian rhythmicity specifically in monocytes and macrophages of the innate immune system. These cells display rhythmicity in their internal functions, such as metabolism and inflammatory mediator production as well as their external functions in pathogen sensing, phagocytosis, and migration. These inflammatory mediators are of clinical interest as many are therapeutic targets in inflammatory disease such as cardiovascular disease, diabetes, and rheumatoid arthritis. Moreover, circadian rhythm disruption is closely linked with increased prevalence of these conditions. Therefore, understanding the mechanisms by which circadian disruption affects monocyte/macrophage function will provide insights into novel therapeutic opportunities for these chronic inflammatory diseases.

Chronic circadian disruption modulates breast cancer stemness and immune microenvironment to drive metastasis in mice

Breast cancer is the most common type of cancer worldwide and one of the major causes of cancer death in women. Epidemiological studies have established a link between night-shift work and increased cancer risk, suggesting that circadian disruption may play a role in carcinogenesis. Here, we aim to shed light on the effect of chronic jetlag (JL) on mammary tumour development. To do this, we use a mouse model of spontaneous mammary tumourigenesis and subject it to chronic circadian disruption. We observe that circadian disruption significantly increases cancer-cell dissemination and lung metastasis. It also enhances the stemness and tumour-initiating potential of tumour cells and creates an immunosuppressive shift in the tumour microenvironment. Finally, our results suggest that the use of a CXCR2 inhibitor could correct the effect of JL on cancer-cell dissemination and metastasis. Altogether, our data provide a conceptual framework to better understand and manage the effects of chronic circadian disruption on breast cancer progression.

Circadian disruption is implicated in the development of different human cancers. Here the authors show that chronic circadian disruption, through continuous jet lag, only moderately affects primary tumour growth but promotes cancer-cell dissemination and metastasis in a mouse model of spontaneous mammary tumorigenesis.

A Pro- and Anti-inflammatory Axis Modulates the Macrophage Circadian Clock

The circadian clock broadly governs immune cell function, leading to time-of-day differences in inflammatory responses and subsequently, pathogen clearance. However, the effect of inflammatory signals on circadian machinery is poorly understood. We found that in bone marrow-derived macrophages, some host-derived pro-inflammatory cytokines, e.g., IFN-γ or TNF-α, and pathogen-associated molecular patterns, e.g., LPS or Pam3Csk4, suppress the amplitude in oscillations of circadian negative feedback arm clock components such as PER2, and when examined, specific combinations of these immune-related signals suppressed the amplitude of these oscillations to a greater degree in both bone marrow-derived and peritoneal macrophages. At the transcript level, multiple components of the circadian clock were affected in different ways by pro-inflammatory stimulus, including Per2 and Nr1d1. This suppressive effect on PER2 did not arise from nor correlate with cell death or clock resetting. Suppression of the clock by IFN-γ was dependent on its cognate receptor; however, pharmacological inhibition of the canonical JAK/STAT and MEK pathways did not hinder suppression, suggesting a mechanism involving a non-canonical pathway. In contrast, anti-inflammatory signals such as IL-4 and dexamethasone enhanced the expression of PER2 protein and Per2 mRNA. Our results suggest that the circadian system in macrophages can differentially respond to pro- and anti-inflammatory signals in their microenvironments.

Nuclear Receptors as Regulators of Pituitary Corticotroph Pro-Opiomelanocortin Transcription

The hypothalamic–pituitary–adrenal (HPA) axis plays a critical role in adaptive stress responses and maintaining organism homeostasis. The pituitary corticotroph is the central player in the HPA axis and is regulated by a plethora of hormonal and stress related factors that synergistically interact to activate and temper pro-opiomelanocortin (POMC) transcription, to either increase or decrease adrenocorticotropic hormone (ACTH) production and secretion as needed. Nuclear receptors are a family of highly conserved transcription factors that can also be induced by various physiologic signals, and they mediate their responses via multiple targets to regulate metabolism and homeostasis. In this review, we summarize the modulatory roles of nuclear receptors on pituitary corticotroph cell POMC transcription, describe the unique and complex role these factors play in hypothalamic–pituitary–adrenal axis (HPA) regulation and discuss potential therapeutic targets in disease states.

Chronobiological Influence Over Cardiovascular Function: The Good, the Bad, and the Ugly

Essentially all biological processes fluctuate over the course of the day, observed at cellular (eg, transcription, translation, and signaling), organ (eg, contractility and metabolism), and whole-body (eg, physical activity and appetite) levels. It is, therefore, not surprising that both cardiovascular physiology (eg, heart rate and blood pressure) and pathophysiology (eg, onset of adverse cardiovascular events) oscillate during the 24-hour day. Chronobiological influence over biological processes involves a complex interaction of factors that are extrinsic (eg, neurohumoral factors) and intrinsic (eg, circadian clocks) to cells. Here, we focus on circadian governance of 6 fundamentally important processes: metabolism, signaling, electrophysiology, extracellular matrix, clotting, and inflammation. In each case, we discuss (1) the physiological significance for circadian regulation of these processes (ie, the good); (2) the pathological consequence of circadian governance impairment (ie, the bad); and (3) whether persistence/augmentation of circadian influences contribute to pathogenesis during distinct disease states (ie, the ugly). Finally, the translational impact of chronobiology on cardiovascular disease is highlighted.

Circadian Host-Microbiome Interactions in Immunity

The gut microbiome plays a critical role in regulating host immunity and can no longer be regarded as a bystander in human health and disease. In recent years, circadian (24 h) oscillations have been identified in the composition of the microbiota, its biophysical localization within the intestinal tract and its metabolic outputs. The gut microbiome and its key metabolic outputs, such as short chain fatty acids and tryptophan metabolites contribute to maintenance of intestinal immunity by promoting barrier function, regulating the host mucosal immune system and maintaining the function of gut-associated immune cell populations. Loss of rhythmic host-microbiome interactions disrupts host immunity and increases risk of inflammation and metabolic complications. Here we review factors that drive circadian variation in the microbiome, including meal timing, dietary composition and host circadian clocks. We also consider how host-microbiome interactions impact the core molecular clock and its rhythmic outputs in addition to the potential impact of this relationship on circadian control of immunity.

A Review of Pain Assessment Methods in Laboratory Rodents

Ensuring that laboratory rodent pain is well managed underpins the ethical acceptability of working with these animals in research. Appropriate treatment of pain in laboratory rodents requires accurate assessments of the presence or absence of pain to the extent possible. This can be challenging some situations because laboratory rodents are prey species that may show subtle signs of pain. Although a number of standard algesiometry assays have been used to assess evoked pain responses in rodents for many decades, these methods likely represent an oversimplification of pain assessment and many require animal handling during testing, which can result in stress-induced analgesia. More recent pain assessment methods, such as the use of ethograms, facial grimace scoring, burrowing, and nest-building, focus on evaluating changes in spontaneous behaviors or activities of rodents in their home environments. Many of these assessment methods are time-consuming to conduct. While many of these newer tests show promise for providing a more accurate assessment of pain, most require more study to determine their reliability and sensitivity across a broad range of experimental conditions, as well as between species and strains of animals. Regular observation of laboratory rodents before and after painful procedures with consistent use of 2 or more assessment methods is likely to improve pain detection and lead to improved treatment and care-a primary goal for improving overall animal welfare.

The Tilapia collagen peptide mixture TY001 protects against LPS-induced inflammation, disruption of glucose metabolism, and aberrant expression of circadian clock genes in mice

The Tilapia collagen peptide mixture TY001 has been shown to accelerate wound healing in streptozotocin-induced diabetic mice and to protect against streptozotocin-induced inflammation and elevation in blood glucose. The goals of the present study are to further study TY001 effects on lipopolysaccharide (LPS)-induced inflammation and metabolic syndrome. LPS is known to disrupt circadian clock to produce toxic effects, the effects of TY001 on rhythmic alterations of serum cytokines and hepatic clock gene expressions were examined. Mice were given TY001 (30 g/L, ≈ 40 g/kg) through the drinking water for 30 days, and on the 21st day of TY001 supplementation, LPS (0.25 mg/kg, ip, daily) was given for 9 days to establish the inflammation model. Repeated LPS injections produced inflammation, impaired glucose metabolism, and suppressed the expression of circadian clock core genes Bmal1 and Clock; clock feedback gene Cry1, Cry2, Per1, and Per2; clock target gene Rev-erbα and RORα. TY001 prevented LPS-induced elevations of TNFα, IL-1β, IL-6, and IL-10 in the liver, along with improved histopathology. TY001 reduced LPS-elevated fasting blood glucose and increased LPS-reduced serum insulin levels, probably via increased glucose transporter GLUT2, enhanced insulin signaling p-Akt and p-IRS-1Try612. Importantly, LPS-induced circadian elevations of serum TNFα and IL-1β and aberrant expression of circadian clock genes in the liver were ameliorated by TY001. Immunohistochemistry revealed that the LPS decreased Bmal1 and Clock protein in the liver, which was recovered by TY001. Taken together, TY001 is effective against LPS-induced inflammation, disruption of glucose metabolism and disruption of circadian clock gene expressions. Abbreviations: TY001: Tilapia collagen peptide mixture; LPS: Lipopolysaccharide; TNFα: Tumor necrosis factor-α; IL-1β: Interleukin-1β; GLUT2: Glucose transporter 2.

Circadian regulation of neutrophils: Control by a cell-autonomous clock or systemic factors?

BACKGROUND

The circadian time-measuring system enables the organism to anticipate and effectively respond to regular daily changes in the environment and is therefore a crucial factor of adaptation. A large body of epidemiological data underlines the circadian characteristics of human immune functions. Circadian control of neutrophil responsiveness contributes to daily changes in the pathology of both acute and chronic inflammation and may therefore time-dependently influence the outcome of therapeutic approaches.

AIM

This review summarizes recent data on the role of the circadian clock in the control of immune responses, particularly of those linked to neutrophil activity, and possible mechanisms of the regulation.

DISCUSSION

In the first section of this review we present the recent model of the mammalian molecular clock by introducing the main transcription-translation feedback loops and discussing the pace-setting role of post-translational modifications. The next sections summarize clinical, epidemiological and experimental data regarding the daily control of immune responses and studies analysing expression of clock components in various leukocytes and particularly, in human peripheral neutrophils. As the latter data indicate that expression of components of the cell-autonomous clock is relatively low in neutrophils, in the last section we review recent findings suggesting a role for systemic and local factors in the regulation of rhythmic neutrophil responses.

The Clinical Biology of Cystic Fibrosis Transmembrane Regulator Protein: Its Role and Function in Extrapulmonary Disease

Normal cystic fibrosis (CF) transmembrane regulator (CFTR) protein has multiple functions in health and disease. Many mutations in the CFTR gene produce abnormal or absent protein. CFTR protein dysfunction underlies the classic CF phenotype of progressive pulmonary and GI pathology but may underlie diseases not usually associated with CF. This review highlights selected extrapulmonary disease that may be associated with abnormal CFTR. Increasing survival in CF is associated with increasing incidence of diseases associated with aging. CFTR dysfunction in older individuals may have novel effects on glucose metabolism, control of insulin release, regulation of circadian rhythm, and cancer cell pathophysiology. In individuals who have cancers with acquired CFTR suppression, their tumors may more likely exhibit rapid expansion, epithelial-to-mesenchymal transformation, abnormally reduced apoptosis, and increased metastatic potential. The new modulators of CFTR protein synthesis could facilitate the additional exploration needed to better understand the unfolding clinical biology of CFTR in human disease, even as they revolutionize treatment of patients with CF.

Diurnal rhythms in peripheral blood immune cell numbers of domestic pigs

Diurnal rhythms within the immune system are considered important for immune competence. Until now, they were mostly studied in humans and rodents. However, as the domestic pig is regarded as suitable animal model and due to its importance in agriculture, this study aimed to characterize diurnal rhythmicity in porcine circulating leukocyte numbers. Eighteen pigs were studied over periods of up to 50 h. Cosinor analyses revealed diurnal rhythms in cell numbers of most investigated immune cell populations in blood. Whereas T cell, dendritic cell, and eosinophil counts peaked during nighttime, NK cell and neutrophil counts peaked during daytime. Relative amplitudes of cell numbers in blood differed in T helper cell subtypes with distinctive differentiation states. Mixed model analyses revealed that plasma cortisol concentration was negatively associated with cell numbers of most leukocyte types, except for NK cells and neutrophils. The observed rhythms mainly resemble those found in humans and rodents.

Medical hypothesis: Light at night is a factor worth considering in critical care units

Exposure to light at night is not an innocuous consequence of modernization. There are compelling data linking long-term exposure to occupational and environmental light at night with serious health conditions, including heart disease, obesity, diabetes, and cancer. However, far less is known about the physiological and behavioral effects of acute exposure to light at night. Among healthy volunteers, acute night-time light exposure increases systolic blood pressure and inflammatory markers in the blood, and impairs glucose regulation. Whether critically ill patients in a hospital setting experience the same physiological shifts in response to evening light exposure is not known. This paper reviews the available data on light at night effects on health and wellbeing, and argues that the data are sufficiently compelling to warrant studies of how lighting in intensive care units may be influencing patient recovery.

Circadian clock cryptochrome proteins regulate autoimmunity

The circadian system regulates numerous physiological processes including immune responses. Here, we show that mice deficient of the circadian clock genes Cry1 and Cry2 [Cry double knockout (DKO)] develop an autoimmune phenotype including high serum IgG concentrations, serum antinuclear antibodies, and precipitation of IgG, IgM, and complement 3 in glomeruli and massive infiltration of leukocytes into the lungs and kidneys. Flow cytometry of lymphoid organs revealed decreased pre-B cell numbers and a higher percentage of mature recirculating B cells in the bone marrow, as well as increased numbers of B2 B cells in the peritoneal cavity of Cry DKO mice. The B cell receptor (BCR) proximal signaling pathway plays a critical role in autoimmunity regulation. Activation of Cry DKO splenic B cells elicited markedly enhanced tyrosine phosphorylation of cellular proteins compared with cells from control mice, suggesting that overactivation of the BCR-signaling pathway may contribute to the autoimmunity phenotype in the Cry DKO mice. In addition, the expression of C1q, the deficiency of which contributes to the pathogenesis of systemic lupus erythematosus, was significantly down-regulated in Cry DKO B cells. Our results suggest that B cell development, the BCR-signaling pathway, and C1q expression are regulated by circadian clock CRY proteins and that their dysregulation through loss of CRY contributes to autoimmunity.

Bidirectional Regulation of Circadian Disturbance and Inflammation in Inflammatory Bowel Disease

BACKGROUND

Tight crosstalk between the circadian and immune systems has been reported in several inflammatory diseases. We hypothesized that circadian timekeeping was perturbed in inflammatory bowel disease (IBD), and that the bidirectional regulation of circadian disturbance and inflammation may be involved in the pathogenesis of IBD.

METHODS

Patients with ulcerative colitis (51) and Crohn's disease (39) and 42 healthy controls were recruited and their circadian gene expression levels evaluated. Dextran sodium sulfate/2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis mouse models, and lipopolysaccharide-stimulated macrophages, were examined to detect the influence of inflammation on circadian gene expression, both in vivo and in vitro. Light/dark shift and time-restricted feeding models were also used to evaluate the influence of circadian disturbance on a mouse colitis model.

RESULTS

We found that (1) almost all circadian genes were reduced in both intestinal biopsies and the peripheral blood mononuclear cells of patients with IBD, especially in patients with ulcerative colitis. Nearly all circadian genes of biopsy tissues showed negative correlations with a Mayo score or a simplified endoscopic activity score for Crohn's disease. Circadian genes of peripheral blood mononuclear cells correlated well with erythrocyte sedimentation rate and C-reactive protein levels in IBD. (2) Exposure to dextran sodium sulfate/2,4,6-trinitrobenzene sulfonic acid and lipopolysaccharide-induced marked changes in circadian gene expression profiles. (3) A phase shift exacerbated colitis in mice, with the increased secretion of proinflammatory cytokines and activation of inflammatory-related signaling pathways.

CONCLUSIONS

Our results suggested that inflammation and circadian genes showed complex bidirectional regulations that were relevant to IBD. Consequently, the circadian clock seems to be a potential target for IBD therapy.

Misalignment with the external light environment drives metabolic and cardiac dysfunction

Most organisms use internal biological clocks to match behavioural and physiological processes to specific phases of the day-night cycle. Central to this is the synchronisation of internal processes across multiple organ systems. Environmental desynchrony (e.g. shift work) profoundly impacts human health, increasing cardiovascular disease and diabetes risk, yet the underlying mechanisms remain unclear. Here, we characterise the impact of desynchrony between the internal clock and the external light-dark (LD) cycle on mammalian physiology. We reveal that even under stable LD environments, phase misalignment has a profound effect, with decreased metabolic efficiency and disrupted cardiac function including prolonged QT interval duration. Importantly, physiological dysfunction is not driven by disrupted core clock function, nor by an internal desynchrony between organs, but rather the altered phase relationship between the internal clockwork and the external environment. We suggest phase misalignment as a major driver of pathologies associated with shift work, chronotype and social jetlag.The misalignment between internal circadian rhythm and the day-night cycle can be caused by genetic, behavioural and environmental factors, and may have a profound impact on human physiology. Here West et al. show that desynchrony between the internal clock and the external environment alter metabolic parameters and cardiac function in mice.