Circadian Clocks in the Immune System

Potential effects of shift work on skin autoimmune diseases

Shift work is associated with systemic chronic inflammation, impaired host and tumor defense and dysregulated immune responses to harmless antigens such as allergens or auto-antigens. Thus, shift workers are at higher risk to develop a systemic autoimmune disease and circadian disruption with sleep impairment seem to be the key underlying mechanisms. Presumably, disturbances of the sleep-wake cycle also drive skin-specific autoimmune diseases, but epidemiological and experimental evidence so far is scarce. This review summarizes the effects of shift work, circadian misalignment, poor sleep, and the effect of potential hormonal mediators such as stress mediators or melatonin on skin barrier functions and on innate and adaptive skin immunity. Human studies as well as animal models were considered. We will also address advantages and potential pitfalls in animal models of shift work, and possible confounders that could drive skin autoimmune diseases in shift workers such as adverse lifestyle habits and psychosocial influences. Finally, we will outline feasible countermeasures that may reduce the risk of systemic and skin autoimmunity in shift workers, as well as treatment options and highlight outstanding questions that should be addressed in future studies.

Dual-Targeted Nanodiscs Revealing the Cross-Talk between Osteogenic Differentiation of Mesenchymal Stem Cells and Macrophages

Ongoing research has highlighted the significance of the cross-play of macrophages and mesenchymal stem cells (MSCs). Lysine-specific demethylase 6B (KDM6B) has been shown to control osteogenic differentiation of MSCs by depleting trimethylated histone 3 lysine 27 (H3K27me3). However, to date, the role of KDM6B in bone marrow-derived macrophages (BMDMs) remains controversial. Here, a chromatin immunoprecipitation assay (ChIP) proved that KDM6B derived from osteogenic-induced BMSCs could bind to the promoter region of BMDMs' brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein-1 (BMAL1) gene in a coculture system and activate BMAL1. Transcriptome sequencing and experiments in vitro showed that the overexpression of BMAL1 in BMDM could inhibit the TLR2/NF-κB signaling pathway, reduce pyroptosis, and decrease the M1/M2 ratio, thereby promoting osteogenic differentiation of BMSCs. Furthermore, bone and macrophage dual-targeted GSK-J4 (KDM6B inhibitor)-loaded nanodiscs were synthesized via binding SDSSD-apoA-1 peptide analogs (APA) peptide, which indirectly proved the critical role of KDM6B in osteogenesis in vivo. Overall, we demonstrated that KDM6B serves as a positive circulation trigger during osteogenic differentiation by decreasing the ratio of M1/M2 both in vitro and in vivo. Collectively, these results provide insight into basic research in the field of osteoporosis and bone repair.

NOX2 inhibition enables retention of the circadian clock in BV2 microglia and primary macrophages

Introduction

Sustained neuroinflammation is a major contributor to the progression of neurodegenerative diseases such as Alzheimer's (AD) and Parkinson's (PD) diseases. Neuroinflammation, like other cellular processes, is affected by the circadian clock. Microglia, the resident immune cells in the brain, act as major contributors to neuroinflammation and are under the influence of the circadian clock. Microglial responses such as activation, recruitment, and cytokine expression are rhythmic in their response to various stimuli. While the link between circadian rhythms and neuroinflammation is clear, significant gaps remain in our understanding of this complex relationship. To gain a greater understanding of this relationship, the interaction between the microglial circadian clock and the enzyme NADPH Oxidase Isoform 2 (NOX2) was studied; NOX2 is essential for the production of reactive oxygen species (ROS) in oxidative stress, an integral characteristic of neuroinflammation.

Methods

BV2 microglia were examined over circadian time, demonstrating oscillations of the clock genes Per2 and Bmal1 and the NOX2 subunits gp91phox and p47phox.

Results

The BV2 microglial clock exerted significant control over NOX2 expression and inhibition of NOX2 enabled the microglia to retain a functional circadian clock while reducing levels of ROS and inflammatory cytokines. These trends were mirrored in mouse bone marrow-derived primary macrophages.

Conclusions

NOX2 plays a crucial role in the interaction between the circadian clock and the activation of microglia/macrophages into their pro-inflammatory state, which has important implications in the control of neuroinflammation.

Temporal transcriptome reveals that circadian clock is involved in the dynamic regulation of immune response to bacterial infection in Bombyx mori

The circadian clock plays a critical role in the regulation of host immune defense. However, the mechanistic basis for this regulation is largely unknown. Herein, the core clock gene cryptochrome1 (cry1) knockout line in Bombyx mori, an invertebrate animal model, was constructed to obtain the silkworm with dysfunctional molecular clock, and the dynamic regulation of the circadian clock on the immune responsiveness within 24 h of Staphylococcus aureus infection was analyzed. We found that deletion of cry1 decreased viability of silkworms and significantly reduced resistance of larvae to S. aureus. Time series RNA-seq analysis identified thousands of rhythmically expressed genes, including immune response genes, in the larval immune tissue, fat bodies. Uninfected cry1 knockout silkworms exhibited expression patterns of rhythmically expressed genes similar to wild-type (WT) silkworms infected with S. aureus. However, cry1 knockout silkworms exhibited a seriously weakened response to S. aureus infection. The immune response peaked at 6 and 24 h after infection, during which "transcription storms" occurred, and the expression levels of the immune response genes, PGRP and antimicrobial peptides (AMPs), were significantly upregulated in WT. In contrast, cry1 knockout did not effectively activate Toll, Imd, or NF-κB signaling pathways during the immune adjustment period from 12 to 18 h after infection, resulting in failure to initiate the immune responsiveness peak at 24 h after infection. This may be related to inhibited silkworm fat body energy metabolism. These results demonstrated the dynamic regulation of circadian clock on silkworm immune response to bacterial infection and provided important insights into host antimicrobial defense mechanisms.

Dendritic cells direct circadian anti-tumour immune responses

The process of cancer immunosurveillance is a mechanism of tumour suppression that can protect the host from cancer development throughout its lifetime^1,2. However, it is unknown whether the effectiveness of cancer immunosurveillance fluctuates over a single day. Here we demonstrate that the initial time of day of tumour engraftment dictates the ensuing tumour size across mouse cancer models. Using immunodeficient mice as well as mice lacking lineage-specific circadian functions, we show that dendritic cells (DCs) and CD8⁺ T cells exert circadian anti-tumour functions that control melanoma volume. Specifically, we find that rhythmic trafficking of DCs to the tumour draining lymph node governs a circadian response of tumour-antigen-specific CD8⁺ T cells that is dependent on the circadian expression of the co-stimulatory molecule CD80. As a consequence, cancer immunotherapy is more effective when synchronized with DC functions, shows circadian outcomes in mice and suggests similar effects in humans. These data demonstrate that the circadian rhythms of anti-tumour immune components are not only critical for controlling tumour size but can also be of therapeutic relevance.

Positive Interaction Between CG, CC Genotypes of Cryptochrome Circadian Clocks 1, and Energy-Adjusted Dietary Inflammatory Index on High Sensitivity C-Reactive Protein Level in Women With Central Obesity

Creating a complex balance between dietary composition, circadian rhythm, and the hemostasis control of energy is important for managing diseases. Therefore, we aimed to determine the interaction between cryptochrome circadian clocks 1 polymorphism and energy-adjusted dietary inflammatory index (E-DII) on high-sensitivity C-reactive protein in women with central obesity. This cross-sectional study recruited 220 Iranian women aged 18-45 with central obesity. The 147-item semi-quantitative food frequency questionnaire was used to assess the dietary intakes, and the E-DII score was calculated. Anthropometric and biochemical measurements were determined. By polymerase chain response-restricted length polymorphism method, cryptochrome circadian clocks 1 polymorphism was assigned. Participants were categorized into three groups based on the E-DII score, then categorized according to cryptochrome circadian clocks 1 genotypes. The mean and standard deviation of age, BMI, and high-sensitivity C-reactive protein (hs-CRP) were 35.61 ± 9.57 years, 30.97 ± 4.16 kg/m², and 4.82 ± 5.16 mg/dL, respectively. The interaction of the CG genotype and E-DII score had a significant association with higher hs-CRP level compared to GG genotype as the reference group (β, 1.19; 95% CI, 0.11-2.27; p value, 0.03). There was a marginally significant association between the interaction of the CC genotype and the E-DII score with higher hs-CRP level compared to the GG genotype as the reference group (β, 0.85; 95% CI, -0.15 to 1.86; p value, 0.05). There is probably positive interaction between CG, CC genotypes of cryptochrome circadian clocks 1, and E-DII score on the high-sensitivity C-reactive protein level in women with central obesity.

Glucocorticoids coordinate the bladder peripheral clock and diurnal micturition pattern in mice

Peripheral clocks function to regulate each organ and are synchronized though various molecular and behavioral signals. However, signals that entrain the bladder clock remain elusive. Here, we show that glucocorticoids are a key cue for the bladder clock in vitro and in vivo. A pBmal1-dLuc human urothelial cell-line showed significant shifts in gene expression after cortisol treatment. In vivo, rhythmic bladder clock gene expression was unchanged by bilateral adrenalectomy but shifted 4 h forward by corticosterone administration at the inactive phase. Moreover, the bladder clock shifted 8-12 h in mice that underwent both bilateral adrenalectomy and corticosterone administration at the inactive phase. These mice showed decreases in the diurnal rhythm of volume voided per micturition, while maintaining diurnal activity rhythms. These results indicate that the diurnal rhythm of glucocorticoid signaling is a zeitgeber that overcomes other bladder clock entrainment factors and coordinates the diurnal rhythm of volume voided per micturition.

Association between night shift work and methylation of a subset of immune-related genes

Introduction

Night shift (NS) work has been associated with an increased risk of different conditions characterized by altered inflammatory and immune responses, such as cardio-metabolic and infectious diseases, cancer, and obesity. Epigenetic modifications, such as DNA methylation, might mirror alterations in biological processes that are influenced by NS work.

Methods

The present study was conducted on 94 healthy female workers with different working schedules and aimed at identifying whether NS was associated with plasmatic concentrations of the inflammatory proteins NLRP3 and TNF-alpha, as well as with DNA methylation levels of ten human endogenous retroviral (HERV) sequences, and nine genes selected for their role in immune and inflammatory processes. We also explored the possible role of the body mass index (BMI) as an additional susceptibility factor that might influence the effects of NS work on the tested epigenetic modifications.

Results and discussion

We observed a positive association between NS and NLRP3 levels (p-value 0.0379). Moreover, NS workers retained different methylation levels for ERVFRD-1 (p-value = 0.0274), HERV-L (p-value = 0.0377), and HERV-P (p-value = 0.0140) elements, and for BIRC2 (p-value = 0.0460), FLRT3 (p-value = 0.0422), MIG6 (p-value = 0.0085), and SIRT1 (p-value = 0.0497) genes. We also observed that the BMI modified the relationship between NS and the methylation of ERVE, HERV-L, and ERVW-1 elements. Overall, our results suggest that HERV methylation could pose as a promising biomolecular sensor to monitor not only the effect of NS work but also the cumulative effect of multiple stressors.

The time dimension to stroke: Circadian effects on stroke outcomes and mechanisms

The circadian system is widely involved in the various pathological outcomes affected by time dimension changes. In the brain, the master circadian clock, also known as the "pacemaker," is present in the hypothalamus's suprachiasmatic nucleus (SCN). The SCN consists of molecular circadian clocks that operate in each neuron and other brain cells. These circadian mechanisms are controlled by the transcription and translation of specific genes such as the clock circadian regulator (Clock) and brain and muscle ARNT-Like 1 (Bmal1). Period (Per1-3) and cryptochrome (Cry1 and 2) negatively feedback and regulate the clock genes. Variations in the circadian cycle and these clock genes can affect stroke outcomes. Studies suggest that the peak stroke occurs in the morning after patients awaken from sleep, while stroke severity and poor outcomes worsen at midnight. The main risk factor associated with stroke is high blood pressure (hypertension). Blood pressure usually dips by 15-20% during sleep, but many hypertensives do not display this normal dipping pattern and are non-dippers. A sleep blood pressure is the primary determinant of stroke risk. This article discusses the possible mechanism associated with circadian rhythm and stroke outcomes.

Regulation of Cytotoxic CD8+ T Cells by the Circadian Clock

Most aspects of physiology, including immunity, present 24-h variations called circadian rhythms. In this review, we examine the literature on the circadian regulation of CD8+ T cells, which are important to fight intracellular infections and tumors. CD8+ T cells express circadian clock genes, and ∼6% of their transcriptome presents circadian oscillations. CD8+ T cell counts present 24-h rhythms in the blood and in secondary lymphoid organs, which depend on the clock in these cells as well as on hormonal rhythms. Moreover, the strength of the response of these cells to Ag presentation varies according to time of day, a rhythm dependent on the CD8+ T cell clock. The relevance of CD8+ T cell circadian rhythms is shown by the daily variations in the fight of intracellular infections. Such a circadian regulation also has implications for cancer, as well as the optimization of vaccination and immunotherapy.

NSAID chronotherapy after impacted third molar extraction: a randomized controlled trial

OBJECTIVES

Postoperative pain management impacts patients' quality of life and morbidity. Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen are widely used for this following a 3-doses-per-day regime. However, pain and inflammation follow a circadian rhythm, and animal models assessing the scheduling of NSAID administration (e.g., chronotherapy) have shown that while their use during the active phase of the day enhances postoperative recovery, their administration during the resting phase could have detrimental effects. This observation has led us to hypothesize that night administration of NSAID might be unnecessary in post-surgical scenarios. Therefore, a randomized clinical trial was conducted to test this hypothesis in surgical third molar extractions.

MATERIALS AND METHODS

Seventy (18-35 years) healthy participants requiring surgical removal of impacted lower third molars were recruited and randomized into a double-blind placebo-controlled study. For three days postoperatively, the treatment group (n = 33) received ibuprofen (400 mg) at 8 AM, 1 PM, and a placebo at 8 PM, while the control group (n = 37) received ibuprofen (400 mg) at 8 AM, 1 PM, and 8 PM. Pain severity was assessed by visual analog scale (VAS) and healing indicators including facial swelling, mouth opening, and C-reactive protein blood levels were also measured.

RESULTS

Pain VAS measures showed a circadian variation peaking at night. Also, no significant differences were observed between the two groups of the study in terms of postoperative pain scores (estimate: 0.50, 95% CI = [- 0.38, 1.39]) or any other healing indicator.

CONCLUSIONS

Postoperative pain follows a circadian rhythm. Moreover, night administration of ibuprofen might not provide any significant benefits in terms of pain management and control of inflammation, and two doses during the day only could be sufficient for pain management after surgical interventions.

KNOWLEDGE TRANSFER STATEMENT

Even though this study cannot rule out the possibility that a reduced regime is different than a standard regime, nocturnal doses of ibuprofen seem to have no clinical significance in the short term, and the results of this study provide evidence in favor of reducing ibuprofen administration from three doses to two doses only after third molar surgery.

Preliminary evidence that daily light exposure enhances the antibody response to influenza vaccination in patients with dementia

Enhancing lighting conditions in institutions for individuals with dementia improves their sleep, circadian rhythms and well-being. Here, we report first findings that exposure to brighter light during daytime may support the immune response to the annual influenza vaccination. Eighty older institutionalised patients suffering from dementia (54 women and 26 men) continuously wore an activity tracker for 8 weeks to assess individual light exposure and rest-activity cycles. We analysed the patients’ immune response from two blood samples taken before and 4 weeks after the annual influenza vaccination. Individual antibody concentrations to three influenza virus strains (H3N2, H1N1, IB) were quantified via hemagglutination inhibition assays. By quantifying individual light exposure profiles (including daylight), we classified the patients into a low and a high light exposure group based on a median illuminance of 392.6 lux. The two light exposure groups did not differ in cognitive impairment severity, age or gender distribution. However, patients in the high light exposure group showed a significantly greater circadian rest-activity amplitude (i.e., more daytime activity and less nighttime activity) along with a significantly greater antibody titer increase to the H3N2 vaccine than patients in the low light exposure group, despite similar pre-vaccination concentrations. Sufficient seroprotective responses to all three influenza virus strains were attained for ≥75% of participants. These data provide preliminary evidence for a potentially enhanced immune response in patients with dementia when they received more daily light. Future studies are needed to determine whether regular daily light exposure may have beneficial effects on the human immune system, either directly or via a stabilising circadian sleep-wake rhythms.

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Data from individual light exposures and circadian rest-activity cycles in 80 institutionalised patients with dementia.

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Blood samples were taken before and 4 weeks after the annual influenza vaccination.

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Patients with on average higher light exposure had higher specific antibody titer ratios after the influenza strain H3N2 vaccine.

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Circadian rest-activity amplitude and inter-daily stability were also higher in the group with higher daily light exposures.

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The results provide preliminary evidencefor beneficial effects of light on the immune system in patients with dementia.

When the clock ticks wrong with COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a member of the coronavirus family that causes the novel coronavirus disease first diagnosed in 2019 (COVID-19). Although many studies have been carried out in recent months to determine why the disease clinical presentations and outcomes can vary significantly from asymptomatic to severe or lethal, the underlying mechanisms are not fully understood. It is likely that unique individual characteristics can strongly influence the broad disease variability; thus, tailored diagnostic and therapeutic approaches are needed to improve clinical outcomes. The circadian clock is a critical regulatory mechanism orchestrating major physiological and pathological processes. It is generally accepted that more than half of the cell-specific genes in any given organ are under circadian control. Although it is known that a specific role of the circadian clock is to coordinate the immune system's steady-state function and response to infectious threats, the links between the circadian clock and SARS-CoV-2 infection are only now emerging. How inter-individual variability of the circadian profile and its dysregulation may play a role in the differences noted in the COVID-19-related disease presentations, and outcome remains largely underinvestigated. This review summarizes the current evidence on the potential links between circadian clock dysregulation and SARS-CoV-2 infection susceptibility, disease presentation and progression, and clinical outcomes. Further research in this area may contribute towards novel circadian-centred prognostic, diagnostic and therapeutic approaches for COVID-19 in the era of precision health.

Circadian rhythm-related factors of PER and CRY family genes function as novel therapeutic targets and prognostic biomarkers in lung adenocarcinoma

The period (PER) and cryptochrome (CRY) families play critical roles in circadian rhythms. The imbalance of circadian factors may lead to the occurrence of cancer. Expressions of PER and CRY family members decrease in various cancers. Nevertheless, expression levels, genetic variations, and molecular mechanisms of PER and CRY family members in lung adenocarcinoma (LUAD) and their correlations with prognoses and immune infiltration in LUAD patients are still unclear. In this study, to identify their biological functions in LUAD development, comprehensive high-throughput techniques were applied to analyze the relationships of expressions of PER and CRY family members with genetic variations, molecular mechanisms, and immune infiltration. The present results showed that transcription levels of PER1 and CRY2 in LUAD were significantly downregulated. High expression levels of PER2, PER3, CRY1, and CRY2 indicated longer overall survival. Some cancer signaling pathways were related to PER and CRY family members, such as cell-cycle, histidine metabolism, and progesterone-mediated oocyte maturation pathways. Expressions of PER and CRY family members significantly affected the infiltration of different immune cells. In conclusion, our findings may help better understand the molecular basis of LUAD, and provide new perspectives of PER and CRY family members as novel biomarkers for LUAD.

Ecoimmunology in the field: Measuring multiple dimensions of immune function with minimally invasive, field-adapted techniques

OBJECTIVE

Immune function is multifaceted and characterizations based on single biomarkers may be uninformative or misleading, particularly when considered across ecological contexts. However, measuring the many facets of immunity in the field can be challenging, since many measures cannot be obtained on-site, necessitating sample preservation and transport. Here we assess state-of-the-art methods for measuring immunity, focusing on measures that require a minimal blood sample obtained from a finger prick, which can be: (1) dried on filter paper, (2) frozen in liquid nitrogen, or (3) stabilized with chemical reagents.

RESULTS

We review immune measures that can be obtained from point-of-care devices or from immunoassays of dried blood spots (DBSs), field methods for flow cytometry, the use of RNA or DNA sequencing and quantification, and the application of immune activation assays under field conditions.

CONCLUSIONS

Stable protein products, such as immunoglobulins and C-reactive protein are reliably measured in DBSs. Because less stable proteins, such as cytokines, may be problematic to measure even in fresh blood, mRNA from stabilized blood may provide a cleaner measure of cytokine and broader immune-related gene expression. Gene methylation assays or mRNA sequencing also allow for the quantification of many other parameters, including the inference of leukocyte subsets, though with less accuracy than with flow cytometry. Combining these techniques provides an improvement over single-marker studies, allowing for a more nuanced understanding of how social and ecological variables are linked to immune measures and disease risk in diverse populations and settings.

Melatonin inhibits muscular-mucosal stretch-sensitive bladder afferents via the MT2 receptors

Melatonin is a circadian rhythm regulator capable of controlling a variety of physiological processes in the body. It predominantly acts via the melatonin 1 (MT1) and MT2 receptors expressed in the CNS neurons and peripheral organs and tissues. Melatonin can modulate urinary bladder function, however, to date it is not known if melatonin can regulate activity of sensory neurons innervating the bladder. Bladder afferents play an important role in urine storage and voiding. Therefore, this study aims to determine if melatonin can regulate mechanosensitivity of 2 major classes of sensory neurons in the guinea pig bladder: stretch-insensitive mucosal and low threshold stretch-sensitive muscular-mucosal afferents. The effects of melatonin on the mechanosensitivity of mucosal and muscular-mucosal afferents were measured ex vivo using single unit extracellular recording. Melatonin did not affect the responses of mucosal afferents to stroking of their receptive fields but did concentration-dependently, significantly inhibit 69% of muscular-mucosal afferents responses to stroking and bladder stretch. This inhibitory effect was not affected by the MT1 receptor antagonist, S26131 but was blocked by the selective MT2 receptor antagonists, K-185 and 4-P-PDOT. Forskolin significantly potentiated the responses of muscular-mucosal afferents to stroking and stretch, which were prevented by melatonin. These findings demonstrate a direct inhibitory effect of melatonin on the mechanosensitivity of low threshold stretch-sensitive muscular-mucosal bladder afferents acting via MT2 receptors, which is independent from its action on detrusor muscle. This may have important clinical implications for the treatment of many common bladder disorders including nocturia.

Redox Biology of Melatonin: Discriminating Between Circadian and Noncircadian Functions

Melatonin has not only to be seen as a regulator of circadian clocks. In addition to its chronobiotic functions, it displays other actions, especially in cell protection. This includes antioxidant, anti-inflammatory, and mitochondria-protecting effects. Although protection is also modulated by the circadian system, the respective actions of melatonin can be distinguished and differ with regard to dose requirements in therapeutic settings. It is the aim of this article to outline these differences in terms of function, signaling, and dosage. Focus has been placed on both the nexus and the dissecting properties between circadian and noncircadian mechanisms. This has to consider details beyond the classic view of melatonin's role, such as widespread synthesis in extrapineal tissues, formation in mitochondria, effects on the mitochondrial permeability transition pore, and secondary signaling, for example, via upregulation of sirtuins and by regulating noncoding RNAs, especially microRNAs. The relevance of these findings, the differences and connections between circadian and noncircadian functions of melatonin shed light on the regulation of inflammation, including macrophage/microglia polarization, damage-associated molecular patterns, avoidance of cytokine storms, and mitochondrial functions, with numerous consequences to antioxidative protection, that is, aspects of high actuality with regard to deadly viral and bacterial diseases. Antioxid. Redox Signal. 37, 704-725.

Identifying hub circadian rhythm biomarkers and immune cell infiltration in rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease with symptoms characterized by typical circadian rhythmic changes. This study aimed to identify the hub circadian rhythm genes (CRGs) in RA and explore their association with immune cell infiltration and pathogenesis of RA.

Methods

The differentially expressed CRGs (DECRGs) between RA and normal control samples were screened from Datasets GSE12021 and GSE55235. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and Gene Set Enrichment Analysis were used to explore the potential functional mechanisms of DECRGs in RA. Weighted Gene Co-expression Network Analysis and Least Absolute Shrinkage and Selection Operator regression analysis were performed to identify hub CRGs of RA. CIBERSORT was conducted to compare the infiltration level of immune cells in RA and control synovial tissue and their relationship with hub genes. In addition, the diagnostic value of hub biomarkers was evaluated by the area under the receiver operator characteristic curve. Further, a nomogram prediction model was constructed and its significance for clinical decision-making was evaluated.

Results

The green module was identified as the hub module associated with RA. Four hub CRGs (EGR1, FOSL2, GADD45B, and NFIL3) were identified and showed that they had the highest specificity and sensitivity for RA diagnosis, respectively. The expression levels and diagnostic values of these genes were externally validated in the dataset GSE55457. A nomogram prediction model based on the four hub CRGs was constructed and proved to have a certain clinical decision value. Additionally, the correlation analysis of immune cells with hub genes showed that all hub genes were significantly positively correlated with activated mast cells, resting memory CD4+ T cells, and monocytes. Whereas, all hub genes were negatively correlated with plasma cells, CD8+ T cells, and activated memory CD4+ T cells. Meanwhile, FOSL2 and GADD45B were negatively correlated with Tfh cells.

Conclusion

Four hub CRGs were identified and showed excellent diagnostic value for RA. These genes may be involved in the pathological process of RA by disrupting the rhythmic oscillations of cytokines through immune-related pathways and could be considered molecular targets for future chronotherapy against RA.

Disruption of cellular immune response among male rotating night shift workers in Spain– The HORMONIT study

Introduction

Preliminary studies suggest that night shift work is associated with a desynchronization of rhythmic immune markers, possibly explaining the increased risk of infection, cardiometabolic disorders, and cancer in shift workers.

Methods

This study included 51 male rotating shift workers from a car industry in Barcelona, Spain, sampled twice toward the end of a 3-week night shift (22:00-06:00 h) and a 3-week day shift (06:00-14:00 h) rotation. We collected four blood samples per worker, at the start and end of each shift. We measured 27 cytokines, chemokines and growth factors in plasma samples by luminex using the Cytokine Human Magnetic 30-Plex Panel LHC6003M and applied linear mixed models to examine within-person associations between shift work and analytes’ concentrations, comparing samples taken at 06:00 h on a day and night shift. We also conducted a factor analysis using analyte concentrations from all 4 time points for each individual to identify common factors and determine if these factors were altered by shift work.

Results

We observed lower levels of 15 analytes in the night shift compared to the day shift including cytokines (pro-inflammatory TNF-α, IL-2R; anti-inflammatory IL1-RA; Th1 IL-2, Th2 IL-4 and Th17 Il-17), chemokines (IP-10, MIP-1α, MIP-1β, RANTES) and growth factors (EGF, G-CSF, HGF, VEGF, FGF). In a factor analysis, three factors were identified. The main factor (Factor 1), explaining 57% of the variance and including IL-1β, IL-12, IL-15, MIP-1α, MIP-1β, EGF and FGF; and another factor (Factor 3) explaining 10% of the variance and including the Th1 cytokine IL-12, were inversely associated with the night shift (coefficient: -0.17, 95%CI -0.32 to -0.01 and coefficient: -0.22, 95%CI -0.38, -0.06, for Factors 1 and 3, respectively). Our results indicate that night shift disrupts the levels of several immune markers, which could contribute to the increased risk of infections and cancer reported in night shift workers.

Conclusion

Night shift is associated with disruption of multiple immune response pathways.

Topographical Distribution and Phenotype of Resident Meibomian Gland Orifice Immune Cells (MOICs) in Mice and the Effects of Topical Benzalkonium Chloride (BAK)

Meibomian gland orifices (MGOs) are located along the eyelid margin and secrete meibum into the tear film. The profile of resident innate immune cells (ICs) at this site is not well understood. The distribution and phenotype of resident ICs around MGOs in mice was investigated and herein defined as MGO-associated immune cells (MOICs). The effect of topical 0.1% benzalkonium chloride (BAK) on MOICs was also assessed. Eyelids from healthy CD11ceYFP and Cx3cr1gfp/gfp mice aged three or seven months were compared. ICs were identified as CD11c+, Cx3cr1+, and MHC-II+ using four-colour immunostaining and confocal microscopy. MOIC density was variable but clustered around MGOs. There were more CD11c+ MOICs in three-month-old compared with seven-month-old mice (three-month-old: 893 ± 449 cells/mm2 vs. seven-month-old: 593 ± 493 cells/mm2, p = 0.004). Along the eyelid margin, there was a decreasing gradient of CD11c+ MOIC density in three-month-old mice (nasal: 1003 ± 369 cells/mm2, vs. central: 946 ± 574 cells/mm2, vs. temporal: 731 ± 353 cells/mm2, p = 0.044). Cx3cr1-deficient mice had two-fold fewer MHC-II+ MOICs, suggesting a role for Cx3cr1 receptor signaling in meibomian gland surveillance. CD11c+ MOIC density was lower in BAK-exposed eyes compared to saline-treated controls, suggesting a change in homeostasis. This study provides novel insight into resident ICs located at MGOs, and their contribution to MG homeostasis.

Diel rhythm of the inflammatory cytokine il1b in the Japanese medaka (Oryzias latipes) regulated by core components of the circadian clock

In recent years, studies on circadian control in immunity have been actively conducted in mammals, but little is known about circadian rhythms in the field of fish immunology. In this study, we aimed to analyse the regulation of the diel oscillation of inflammatory cytokine interleukin-1β (il1b) gene expression by core components of the circadian clock in Japanese medaka (Oryzias latipes). The expression of il1b and clock genes (bmal1 and clock1) in medaka acclimated to a 12:12 light (L): dark (D) cycle showed diel rhythm. Additionally, higher expression of il1b was detected in medaka embryo cells (OLHdrR-e3) overexpressing bmal1 and clock1. A significant decrease in il1b expression was observed in OLHdrR-e3 cells after bmal1 knockdown using morpholino oligos. These changes may be mediated by transcriptional regulation via clock proteins, which target the E-box sequence in the cis-element of il1b as identified using luciferase reporter assays. Moreover, LPS stimulation and pathogenic bacterial infection at different zeitgeber time (ZT) under LD12:12 conditions affected the degree of il1b expression, which showed high and low responsiveness to both immuno-stimulations at ZT2 and ZT14, respectively. These results suggested that fish IL-1β exhibited diel oscillation regulated by clock proteins, and its responsiveness to immune-stimulation depends on the time of day.

Human Variation in DNA Repair, Immune Function, and Cancer Risk

DNA damage constantly threatens genome integrity, and DNA repair deficiency is associated with increased cancer risk. An intuitive and widely accepted explanation for this relationship is that unrepaired DNA damage leads to carcinogenesis due to the accumulation of mutations in somatic cells. But DNA repair also plays key roles in the function of immune cells, and immunodeficiency is an important risk factor for many cancers. Thus, it is possible that emerging links between inter-individual variation in DNA repair capacity and cancer risk are driven, at least in part, by variation in immune function, but this idea is underexplored. In this review we present an overview of the current understanding of the links between cancer risk and both inter-individual variation in DNA repair capacity and inter-individual variation in immune function. We discuss factors that play a role in both types of variability, including age, lifestyle, and environmental exposures. In conclusion, we propose a research paradigm that incorporates functional studies of both genome integrity and the immune system to predict cancer risk and lay the groundwork for personalized prevention.

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.

The circadian immune system

The immune system is highly time-of-day dependent. Pioneering studies in the 1960s were the first to identify immune responses to be under a circadian control. Only in the last decade, however, have the molecular factors governing circadian immune rhythms been identified. These studies have revealed a highly complex picture of the interconnectivity of rhythmicity within immune cells with that of their environment. Here, we provide a global overview of the circadian immune system, focusing on recent advances in the rapidly expanding field of circadian immunology.

Linking circadian rhythms to microbiome-gut-brain axis in aging-associated neurodegenerative diseases

Emerging evidence suggests that both disruption of circadian rhythms and gut dysbiosis are closely related to aging-associated neurodegenerative diseases. Over the last decade, the microbiota-gut-brain axis has been an emerging field and revolutionized studies in pathology, diagnosis, and treatment of neurological disorders. Crosstalk between the brain and gut microbiota can be accomplished via the endocrine, immune, and nervous system. Recent studies have shown that the composition and diurnal oscillation of gut microbiota are influenced by host circadian rhythms. This provides a new perspective for investigating the microbiome-gut-brain axis. We aim to review current understanding and research on the dynamic interaction between circadian rhythms and the microbiome-gut-brain axis. Furthermore, we will address the possible neurodegenerative disease contribution through circadian rhythms and microbiome-gut-brain axis crosstalk.

Circadian Dependence of the Acute Immune Response to Myocardial Infarction

Circadian rhythms influence the recruitment of immune cells and the onset of inflammation, which is pivotal in the response to ischemic cardiac injury after a myocardial infarction (MI). The hyperacute immune response that occurs within the first few hours after a MI has not yet been elucidated. Therefore, we characterized the immune response and myocardial damage 3 hours after a MI occurs over a full twenty-four-hour period to investigate the role of the circadian rhythms in this response. MI was induced at Zeitgeber Time (ZT) 2, 8, 14, and 20 by permanent ligation of the left anterior descending coronary artery. Three hours after surgery, animals were terminated and blood and hearts collected to assess the immunological status and cardiac damage. Blood leukocyte numbers varied throughout the day, peaking during the rest-phase (ZT2 and 8). Extravasation of leukocytes was more pronounced during the active-phase (ZT14 and 20) and was associated with greater chemokine release to the blood and expression of adhesion molecules in the heart. Damage to the heart, measured by Troponin-I plasma levels, was elevated during this time frame. Clock gene oscillations remained intact in both MI-induced and sham-operated mice hearts, which could explain the circadian influence of the hyperacute inflammatory response after a MI. These findings are in line with the clinical observation that patients who experience a MI early in the morning (i.e., early active phase) have worse clinical outcomes. This study provides further insight on the immune response occurring shortly after an MI, which may contribute to the development of novel and optimization of current therapeutic approaches.

The journey of neutropoiesis: how complex landscapes in bone marrow guide continuous neutrophil lineage determination

Neutrophils are the most abundant white blood cell, and they differentiate in homeostasis in the bone marrow from hematopoietic stem cells (HSCs) via multiple intermediate progenitor cells into mature cells that enter the circulation. Recent findings support a continuous model of differentiation in the bone marrow of heterogeneous HSCs and progenitor populations. Cell fate decisions at the levels of proliferation and differentiation are enforced through expression of lineage-determining transcription factors and their interactions, which are influenced by intrinsic (intracellular) and extrinsic (extracellular) mechanisms. Neutrophil homeostasis is subjected to positive-feedback loops, stemming from the gut microbiome, as well as negative-feedback loops resulting from the clearance of apoptotic neutrophils by mature macrophages. Finally, the cellular kinetics regarding the replenishing of the mature neutrophil pool is discussed in light of recent contradictory data.

Relationship between circadian genes and memory impairment caused by sleep deprivation

Background

Sleep deprivation (SD)-induced cognitive impairment is highly prevalent worldwide and has attracted widespread attention. The temporal and spatial oscillations of circadian genes are severely disturbed after SD, leading to a progressive loss of their physiological rhythms, which in turn affects memory function. However, there is a lack of research on the role of circadian genes and memory function after SD. Therefore, the present study aims to investigate the relationship between circadian genes and memory function and provide potential therapeutic insights into the mechanism of SD-induced memory impairment.

Methods

Gene expression profiles of GSE33302 and GSE9442 from the Gene Expression Omnibus (GEO) were applied to identify differentially expressed genes (DEGs). Subsequently, both datasets were subjected to Gene Set Enrichment Analysis (GSEA) to determine the overall gene changes in the hippocampus and brain after SD. A Gene Oncology (GO) analysis and Protein-Protein Interaction (PPI) analysis were employed to explore the genes related to circadian rhythm, with their relationship and importance determined through a correlation analysis and a receiver operating characteristic curve (ROC), respectively. The water maze experiments detected behavioral changes related to memory function in SD rats. The expression of circadian genes in several critical organs such as the brain, heart, liver, and lungs and their correlation with memory function was investigated using several microarrays. Finally, changes in the hippocampal immune environment after SD were analyzed using the CIBERSORT in R software.

Results

The quality of the two datasets was very good. After SD, changes were seen primarily in genes related to memory impairment and immune function. Genes related to circadian rhythm were highly correlated with engagement in muscle structure development and circadian rhythm. Seven circadian genes showed their potential therapeutic value in SD. Water maze experiments confirmed that SD exacerbates memory impairment-related behaviors, including prolonged escape latencies and reduced numbers of rats crossing the platform. The expression of circadian genes was verified, while some genes were also significant in the heart, liver, and lungs. All seven circadian genes were also associated with memory markers in SD. The contents of four immune cells in the hippocampal immune environment changed after SD. Seven circadian genes were related to multiple immune cells.

Conclusions

In the present study, we found that SD leads to memory impairment accompanied by changes in circadian rhythm-related genes. Seven circadian genes play crucial roles in memory impairment after SD. Naïve B cells and follicular helper T cells are closely related to SD. These findings provide new insights into the treatment of memory impairment caused by SD.

Psychosomatic syndromes are associated with IL-6 pro-inflammatory cytokine in heart failure patients

Psychosomatic syndromes have emerged as an important source of comorbidity in cardiac patients and have been associated with increased risk for adverse outcomes in patients with heart failure (HF). Understanding of the mechanisms underlying this connection is limited, however immune activity represents a possible pathway. While there have been numerous studies connecting immune activity to psychosomatic psychopathology, there is a lack of research on patients with HF. We examined forty-one consecutive outpatients affected by HF. We assessed psychosomatic psychopathology using the Diagnostic Criteria for Psychosomatic Research (DCPR) and the Patient Health Questionnaire-15 (PHQ-15). The Psychosocial Index (PSI) was used for assessing stress and psychosocial dimensions. Depression was evaluated with Beck Depression Inventory-II (BDI-II). Circulating levels of proinflammatory cytokines IL-6 and TNF-alpha were ascertained. Univariate and multivariable regression models were used to test for associations between inflammatory cytokines and psychosomatic psychopathology (i.e., DCPR syndromes, PHQ-15) and psychological dimensions (i.e., BDI-II, PSI). A significant positive correlation was found between IL-6 levels and psychosomatic psychopathology even when controlling for any confounding variables (i.e., Body-mass index (BMI), New York Heart Association (NYHA) class, smoking habits, alcohol consumption, statin use, aspirin use, beta blockers use, age, and gender). In contrast, the associations between TNF-alpha levels were non-significant. These findings can contribute to research in support of a psychoneuroimmune connection between psychosomatic psychopathology and HF. Findings also suggest the possibility that elevated IL-6 levels are more relevant for the pathogenesis of psychosomatic syndromes than for depression in patients with HF.

The role of melatonin in the molecular mechanisms underlying metaflammation and infections in obesity: A narrative review

Obesity is a chronic condition whose management is a critical challenge for physicians. The scientific community has increased its focus on the molecular mechanisms involved in obesity etiopathogenesis to better manage patients with obesity and its associated complications. The tight connection between adipose tissue and the immune system has been demonstrated to play a crucial role in inflammation, and melatonin is important for circadian rhythm regulation and metabolic homeostasis, in which it orchestrates several molecular mechanisms involved in obesity and associated inflammation. Melatonin also regulates innate and adaptive immunity; its antioxidant properties are linked to reduced predisposition to infection and weight gain in patients with obesity through the modulation of the immune response, which has a significant beneficial effect on inflammation and, consequently, on the metabolic state. Low melatonin levels have been linked to obesity, and melatonin supplementation can reduce body weight, improve metabolic profile, and ameliorate immune responses and pro-inflammatory stimuli. The role of melatonin in obesity is mainly related to improved oxidative stress signaling, modulation of adipokine secretion, and a switching from white-to-brown adipose tissue phenotype and activity. Moreover, the role of melatonin in obesity modulation by controlling circadian rhythm has recently emerged as a pivotal mechanism for lipid and glucose metabolism dysfunction in adipose, muscle, and liver tissues. Melatonin may also regulate the immune system by acting directly on thymus morphology and activity as well as by modulating oxidative stress and inflammatory states during infections. The tight association between melatonin and immune response regulation is coordinated by Toll-like receptors, which are rhythmically expressed during the day. Their expression may be strongly modulated by melatonin as their signaling is highly inhibited by melatonin. The current review summarizes studies of melatonin-induced mechanisms involved in infection regulation, particularly the modulation of obesity-associated inflammation and systemic complications.

The Role of Tumor Necrosis Factor Alpha Antagonists (Anti TNF-α) in Personalized Treatment of Patients with Isolated Polymyalgia Rheumatica (PMR): Past and Possible Future Scenarios

Background: Glucocorticoids (GCs) are the cornerstone of polymyalgia rheumatica (PMR) therapy, but their long-term use (as is usually necessary in PMR patients) can induce many adverse events. Alternatives have long been sought. The primary aim of our narrative review is to provide an overview about the use of anti-tumor necrosis factor alpha (TNF-α) drugs in patients with PMR, and discuss advantages and disadvantages. Materials and methods: we performed a non-systematic literature search (PRISMA protocol not followed) on PubMed and Medline (OVID interface). Results and Conclusions: only two anti TNF-α drugs have been prescribed to PMR patients: infliximab in 62 patients and etanercept in 28 patients. These drugs were normally used in addition to GCs when significant comorbidities and/or relapsing PMR were present; less commonly, they were used as first-line therapy. In general, they have been scarcely successful in patients with PMR. Indeed, randomized controlled trials did not confirm the positive results reported in case reports and/or case series. However, an administration schedule and study design different from those proposed in the past could favour new scenarios in the interest of PMR patients.

Circadian control of heparan sulfate levels times phagocytosis of amyloid beta aggregates

Alzheimer's Disease (AD) is a neuroinflammatory disease characterized partly by the inability to clear, and subsequent build-up, of amyloid-beta (Aβ). AD has a bi-directional relationship with circadian disruption (CD) with sleep disturbances starting years before disease onset. However, the molecular mechanism underlying the relationship of CD and AD has not been elucidated. Myeloid-based phagocytosis, a key component in the metabolism of Aβ, is circadianly-regulated, presenting a potential link between CD and AD. In this work, we revealed that the phagocytosis of Aβ42 undergoes a daily circadian oscillation. We found the circadian timing of global heparan sulfate proteoglycan (HSPG) biosynthesis was the molecular timer for the clock-controlled phagocytosis of Aβ and that both HSPG binding and aggregation may play a role in this oscillation. These data highlight that circadian regulation in immune cells may play a role in the intricate relationship between the circadian clock and AD.

Gut microbiota dysbiosis of type 2 diabetic mice impairs the intestinal daily rhythms of GLP-1 sensitivity

The gut-brain-beta cell glucagon-like peptide-1 (GLP-1)-dependent axis and the clock genes both control insulin secretion. Evidence shows that a keystone of this molecular interaction could be the gut microbiota. We analyzed in mice the circadian profile of GLP-1 sensitivity on insulin secretion and the impact of the autonomic neuropathy, antibiotic treated in different diabetic mouse models and in germ-free colonized mice. We show that GLP-1sensitivity is maximal during the dark feeding period, i.e., the postprandial state. Coincidently, the ileum expression of GLP-1 receptor and peripherin is increased and tightly correlated with a subset of clock gene. Since both are markers of enteric neurons, it suggests a role in the gut-brain-beta cell GLP-1-dependent axis. We evaluated the importance of gut microbiota dysbiosis and found that the abundance of ileum bacteria, particularly Ruminococcaceae and Lachnospiraceae, oscillated diurnally, with a maximum during the dark period, along with expression patterns of a subset of clock genes. This diurnal pattern of circadian gene expression and Lachnospiraceae abundance was also observed in two separate mouse models of gut microbiota dysbiosis and of autonomic neuropathy with impaired GLP-1 sensitivity (1.high-fat diet-fed type 2 diabetic, 2.antibiotic-treated/germ-free mice). Our data show that GLP-1 sensitivity relies on specific pattern of intestinal clock gene expression and specific gut bacteria. This new statement opens opportunities to treat diabetic patient with GLP-1-based therapies by using on a possible pre/probiotic co-treatment to improve the time-dependent efficiency of these therapies.

Microglia and monocytes in inflammatory CNS disease: integrating phenotype and function

In neurological diseases, the actions of microglia, the resident myeloid cells of the CNS parenchyma, may diverge from, or intersect with, those of recruited monocytes to drive immune-mediated pathology. However, defining the precise roles of each cell type has historically been impeded by the lack of discriminating markers and experimental systems capable of accurately identifying them. Our ability to distinguish microglia from monocytes in neuroinflammation has advanced with single-cell technologies, new markers and drugs that identify and deplete them, respectively. Nevertheless, the focus of individual studies on particular cell types, diseases or experimental approaches has limited our ability to connect phenotype and function more widely and across diverse CNS pathologies. Here, we critically review, tabulate and integrate the disease-specific functions and immune profiles of microglia and monocytes to provide a comprehensive atlas of myeloid responses in viral encephalitis, demyelination, neurodegeneration and ischemic injury. In emphasizing the differential roles of microglia and monocytes in the severe neuroinflammatory disease of viral encephalitis, we connect inflammatory pathways common to equally incapacitating diseases with less severe inflammation. We examine these findings in the context of human studies and highlight the benefits and inherent limitations of animal models that may impede or facilitate clinical translation. This enables us to highlight common and contrasting, non-redundant and often opposing roles of microglia and monocytes in disease that could be targeted therapeutically.

Editorial: Parasites- the importance of time

The special edition of Parasite Immunology ‘Parasites—The importance of time’ embraces the intersection between three established research disciplines—parasitology, immunology, and circadian biology. Each of these research areas has a longstanding history littered with landmark discoveries with the intersect between the three bringing exciting findings and new questions and perhaps even a greater sense of awe in terms of how parasites have evolved to interact and live with their hosts.

Chronoradiobiology of Breast Cancer: The Time Is Now to Link Circadian Rhythm and Radiation Biology

Circadian disruption has been linked to cancer development, progression, and radiation response. Clinical evidence to date shows that circadian genetic variation and time of treatment affect radiation response and toxicity for women with breast cancer. At the molecular level, there is interplay between circadian clock regulators such as PER1, which mediates ATM and p53-mediated cell cycle gating and apoptosis. These molecular alterations may govern aggressive cancer phenotypes, outcomes, and radiation response. Exploiting the various circadian clock mechanisms may enhance the therapeutic index of radiation by decreasing toxicity, increasing disease control, and improving outcomes. We will review the body’s natural circadian rhythms and clock gene-regulation while exploring preclinical and clinical evidence that implicates chronobiological disruptions in the etiology of breast cancer. We will discuss radiobiological principles and the circadian regulation of DNA damage responses. Lastly, we will present potential rational therapeutic approaches that target circadian pathways to improve outcomes in breast cancer. Understanding the implications of optimal timing in cancer treatment and exploring ways to entrain circadian biology with light, diet, and chronobiological agents like melatonin may provide an avenue for enhancing the therapeutic index of radiotherapy.

Melatonin as an immunomodulator in children with Down syndrome

BACKGROUND

Down syndrome (DS) is a disorder characterised by marked immune dysfunction, increased mortality from sepsis, chronic inflammation, increased oxidative stress, sleep disturbance and possibly abnormal endogenous melatonin levels. Melatonin has a myriad of immune functions, and we hypothesised that this therapeutic agent could modulate the innate immune system in this cohort.

METHODS

We investigated neutrophil and monocyte function (CD11b, TLR4 expression by flow cytometry), genes involved in TLR signalling (MyD88, IRAK4, TRIF), the inflammasome (NLRP3, IL-1β), and circadian rhythm (BMAL, CLOCK, CRY) by qPCR, and inflammatory cytokines (IL-2, IL-6, IL-8, IL-18, IL-1β, TNF-α, IFN-γ, IL-10, IL-1ra, VEGF, Epo, GM-CSF) by enzyme-linked immunosorbent assay (ELISA) following immunomodulation with LPS endotoxin and melatonin. 47 children with DS and 23 age- and sex-matched controls were recruited.

RESULTS

We demonstrated that melatonin has several significant effects by reducing CD11b and TLR4 expression, attenuating TLR signalling, genes involved in the inflammasome and has the potential to reduce LPS-induced inflammatory responses.

CONCLUSIONS

Immunomodulatory effects of melatonin were found in both paediatric cohorts with more marked effects in the children with DS. Melatonin mediates immune response through a wide array of mechanisms and this immunomodulator may buffer the inflammatory response by regulating pro and anti-inflammatory signalling.

IMPACT

We highlight that melatonin mediates its immune response through a wide array of mechanisms, its effects appear to be dose dependant and children with Down syndrome may be more receptive to treatment with it. Immunomodulatory effects of melatonin were demonstrated with marked effects in the children with Down syndrome with a reduction of MyD88, IL-1ß and NLRP3 expression in whole-blood samples. Melatonin is a proposed anti-inflammatory agent with a well-established safety profile, that has the potential for mitigation of pro- and anti-inflammatory cytokines in paediatric Down syndrome cohorts, though further clinical trials are warranted.

Circadian effects on UV-induced damage and mutations

Skin cancer is the most diagnosed type of cancer in the United States, and while most of these malignancies are highly treatable, treatment costs still exceed $8 billion annually. Over the last 50 years, the annual incidence of skin cancer has steadily grown; therefore, understanding the environmental factors driving these types of cancer is a prominent research-focus. A causality between ultraviolet radiation (UVR) exposure and skin cancer is well-established, but exposure to UVR alone is not necessarily sufficient to induce carcinogenesis. The emerging field of circadian biology intersects strongly with the physiological systems of the mammalian body and introduces a unique opportunity for analyzing mechanisms of homeostatic disruption. The circadian clock refers to the approximate 24-hour cycle, in which protein levels of specific clock-controlled genes (CCGs) fluctuate based on the time of day. Though these CCGs are tissue specific, the skin has been observed to have a robust circadian clock that plays a role in its response to UVR exposure. This in-depth review will detail the mechanisms of the circadian clock and its role in cellular homeostasis. Next, the skin's response to UVR exposure and its induction of DNA damage and mutations will be covered - with an additional focus placed on how the circadian clock influences this response through nucleotide excision repair. Lastly, this review will discuss current models for studying UVR-induced skin lesions and perturbations of the circadian clock, as well as the impact of these factors on human health.

The involvement of host circadian clocks in the regulation of the immune response to parasitic infections in mammals

Circadian rhythms are recurring variations of physiology with a period of ~24 hours, generated by circadian clocks located throughout the body. Studies have shown a circadian regulation of many aspects of immunity. Immune cells have intrinsic clock mechanisms, and innate and adaptive immune responses - such as leukocyte migration, magnitude of inflammation, cytokine production and cell differentiation - are under circadian control. This circadian regulation has consequences for infections including parasitic infections. In the context of Leishmania infection, the circadian clock within host immune cells modulates the magnitude of the infection and the inflammatory response triggered by the parasite. As for malaria, rhythms within the immune system were shown to impact the developmental cycles of Plasmodium parasites within red blood cells. Further, host circadian rhythms impact infections by multicellular parasites; for example, infection with helminth Trichuris muris shows different kinetics of worm expulsion depending on time of day of infection, a variation that depends on the dendritic cell clock. Although the research on the circadian control of immunity in the context of parasitic infections is in its infancy, the research reviewed here suggests a crucial involvement of host circadian rhythms in immunity on the development and progression of parasitic infections.

Shift Work Predicts Increases in Lipopolysaccharide-Binding Protein, Interleukin-10, and Leukocyte Counts in a Cross-Sectional Study of Healthy Volunteers Carrying Low-Grade Systemic Inflammation

The disruption of inflammatory responses is a potential mechanism behind the harmful effects of shift work and is associated with increased risk of hypertension, stroke, obesity, diabetes, and cancer. These responses are linked to the proliferation of leukocytes in shift workers, suggesting a systemic signal as a potential mediator. The purpose of this study was to assess the relationship between systemic inflammation, leukocyte counts, and systemic endotoxemia in samples from a diverse cohort of day workers and shift workers. Participants (normothermic and normotensive) were healthy volunteers, non-smoking, and drug- and medication-free. The following outcomes were measured: C-reactive protein, TNF-α, IL-6, IL-1β, IL-10, leukocyte counts (monocytes, lymphocytes, and neutrophils), and lipopolysaccharide-binding protein (LBP). Risk factors that increase systemic inflammation, such as blood pressure, sleep loss, and cortisol, were also assessed. The results indicated that shift workers slept significantly less than day workers and had significantly increased concentrations of all of the cytokines measured as well as plasma cortisol. Regression models found that after controlling for covariates, shift-work exposure predicted the significant increase observed in IL-10, leukocyte counts, and LBP. Our results suggest that acute increases in low-grade systemic endotoxemia are unresolved during chronic shift-work exposure. This ongoing immune challenge may underlie the disrupted inflammatory responses characteristic of shift-work-related pathologies. Systemic endotoxemia may represent a novel target to investigate the early effects of exposure to shift-work schedules.

The Circadian Clock Protein BMAL1 Acts as a Metabolic Sensor In Macrophages to Control the Production of Pro IL-1β

The transcription factor BMAL1 is a clock protein that generates daily or circadian rhythms in physiological functions including the inflammatory response of macrophages. Intracellular metabolic pathways direct the macrophage inflammatory response, however whether the clock is impacting intracellular metabolism to direct this response is unclear. Specific metabolic reprogramming of macrophages controls the production of the potent pro-inflammatory cytokine IL-1β. We now describe that the macrophage molecular clock, through Bmal1, regulates the uptake of glucose, its flux through glycolysis and the Krebs cycle, including the production of the metabolite succinate to drive Il-1β production. We further demonstrate that BMAL1 modulates the level and localisation of the glycolytic enzyme PKM2, which in turn activates STAT3 to further drive Il-1β mRNA expression. Overall, this work demonstrates that BMAL1 is a key metabolic sensor in macrophages, and its deficiency leads to a metabolic shift of enhanced glycolysis and mitochondrial respiration, leading to a heightened pro-inflammatory state. These data provide insight into the control of macrophage driven inflammation by the molecular clock, and the potential for time-based therapeutics against a range of chronic inflammatory diseases.

Is There a Link between Circadian Clock Protein PERIOD 3 (PER3) (rs57875989) Variant and the Severity of COVID-19 Infection?

OBJECTIVE

Corona Virus Disease-2019 (COVID-19) has been among the major infectious events of the century. In today's literature where COVID-19 and host factor effects are frequently examined, we aimed to examine another factor: Circadian Clock Protein PERIOD 3 (PER3). There is a significant correlation between PER3 gene polymorphism and circadian rhythm disturbances and immune system dysregulation.

METHODS

In our study, we recruited 200 patients diagnosed with COVID-19 in our hospital between April-June 2020, and 100 volunteers without known comorbidities to create a healthy control group. After comparing the initial gene polymorphisms of the patients with healthy controls, three separate clinical subgroups were formed. Gene polymorphism distribution and statistical significance were examined in the formed patient groups.

RESULTS

No significant difference was found between the patient group and the healthy controls (P>0.05, for all). When patients were divided into two separate clinical subgroups as exitus/alive according to their last condition during their 28-day follow-up, the 4R/5R genotype was significantly more common in patients with a mortal course (P=0.007). The PER3 4R/5R genotype was found at a significantly higher rate in the group of patients with the need for intensive care (P=0.034).

CONCLUSION

The 4R/5R genotype may be associated with the need for intensive care and mortality in COVID-19 patients. These important results will be a guide for future studies.

NF-κB modifies the mammalian circadian clock through interaction with the core clock protein BMAL1

In mammals, the circadian clock coordinates cell physiological processes including inflammation. Recent studies suggested a crosstalk between these two pathways. However, the mechanism of how inflammation affects the clock is not well understood. Here, we investigated the role of the proinflammatory transcription factor NF-κB in regulating clock function. Using a combination of genetic and pharmacological approaches, we show that perturbation of the canonical NF-κB subunit RELA in the human U2OS cellular model altered core clock gene expression. While RELA activation shortened period length and dampened amplitude, its inhibition lengthened period length and caused amplitude phenotypes. NF-κB perturbation also altered circadian rhythms in the master suprachiasmatic nucleus (SCN) clock and locomotor activity behavior under different light/dark conditions. We show that RELA, like the clock repressor CRY1, repressed the transcriptional activity of BMAL1/CLOCK at the circadian E-box cis-element. Biochemical and biophysical analysis showed that RELA binds to the transactivation domain of BMAL1. These data support a model in which NF-kB competes with CRY1 and coactivator CBP/p300 for BMAL1 binding to affect circadian transcription. This is further supported by chromatin immunoprecipitation analysis showing that binding of RELA, BMAL1 and CLOCK converges on the E-boxes of clock genes. Taken together, these data support a significant role for NF-κB in directly regulating the circadian clock and highlight mutual regulation between the circadian and inflammatory pathways.

Chronobiology and Chronotherapy in Inflammatory Joint Diseases

Circadian rhythm perturbations can impact the evolution of different conditions, including autoimmune diseases. This narrative review summarizes the current understanding of circadian biology in inflammatory joint diseases and discusses the potential application of chronotherapy. Proinflammatory cytokines are key players in the development and progression of rheumatoid arthritis (RA), regulating cell survival/apoptosis, differentiation, and proliferation. The production and secretion of inflammatory cytokines show a dependence on the human day–night cycle, resulting in changing cytokine plasma levels over 24 h. Moreover, beyond the circadian rhythm of cytokine secretion, disturbances in timekeeping mechanisms have been proposed in RA. Taking into consideration chronotherapy concepts, modified-release (MR) prednisone tablets have been introduced to counteract the negative effects of night-time peaks of proinflammatory cytokines. Low-dose MR prednisone seems to be able to improve the course of RA, reduce morning stiffness and morning serum levels of IL-6, and induce significant clinical benefits. Additionally, methotrexate (MTX) chronotherapy has been reported to be associated with a significant improvement in RA activity score. Similar effects have been described for polymyalgia rheumatica and gout, although the available literature is still limited. Growing knowledge of chronobiology applied to inflammatory joint diseases could stimulate the development of new drug strategies to treat patients in accordance with biological rhythms and minimize side effects.

The circadian clock and diseases of the skin

Organisms have an evolutionarily conserved internal rhythm that helps them anticipate and adapt to daily changes in the environment. Synchronized to the light-dark cycle with a period of around 24 hours, the timing of the circadian clock is set by light-triggering signals sent from the retina to the suprachiasmatic nucleus. Other inputs, including food intake, exercise, and temperature, also affect clocks in peripheral tissues, including skin. Here, we review the intricate interplay between the core clock network and fundamental physiological processes in skin such as homeostasis, regeneration, and immune- and stress responses. We illustrate the effect of feeding time on the skin circadian clock and skin functions, a previously overlooked area of research. We then discuss works that relate the circadian clock and its disruption to skin diseases, including skin cancer, sunburn, hair loss, aging, infections, inflammatory skin diseases, and wound healing. Finally, we highlight the promise of circadian medicine for skin disease prevention and management.

Circadian disruption and human health

Circadian disruption is pervasive and can occur at multiple organizational levels, contributing to poor health outcomes at individual and population levels. Evidence points to a bidirectional relationship, in that circadian disruption increases disease severity and many diseases can disrupt circadian rhythms. Importantly, circadian disruption can increase the risk for the expression and development of neurologic, psychiatric, cardiometabolic, and immune disorders. Thus, harnessing the rich findings from preclinical and translational research in circadian biology to enhance health via circadian-based approaches represents a unique opportunity for personalized/precision medicine and overall societal well-being. In this Review, we discuss the implications of circadian disruption for human health using a bench-to-bedside approach. Evidence from preclinical and translational science is applied to a clinical and population-based approach. Given the broad implications of circadian regulation for human health, this Review focuses its discussion on selected examples in neurologic, psychiatric, metabolic, cardiovascular, allergic, and immunologic disorders that highlight the interrelatedness between circadian disruption and human disease and the potential of circadian-based interventions, such as bright light therapy and exogenous melatonin, as well as chronotherapy to improve and/or modify disease outcomes.

APOE4 is associated with elevated blood lipids and lower levels of innate immune biomarkers in a tropical Amerindian subsistence population

In post-industrial settings, apolipoprotein E4 (APOE4) is associated with increased cardiovascular and neurological disease risk. However, the majority of human evolutionary history occurred in environments with higher pathogenic diversity and low cardiovascular risk. We hypothesize that in high-pathogen and energy-limited contexts, the APOE4 allele confers benefits by reducing innate inflammation when uninfected, while maintaining higher lipid levels that buffer costs of immune activation during infection. Among Tsimane forager-farmers of Bolivia (N = 1266, 50% female), APOE4 is associated with 30% lower C-reactive protein, and higher total cholesterol and oxidized LDL. Blood lipids were either not associated, or negatively associated with inflammatory biomarkers, except for associations of oxidized LDL and inflammation which were limited to obese adults. Further, APOE4 carriers maintain higher levels of total and LDL cholesterol at low body mass indices (BMIs). These results suggest that the relationship between APOE4 and lipids may be beneficial for pathogen-driven immune responses and unlikely to increase cardiovascular risk in an active subsistence population.

Nuclear Receptors and Clock Components in Cardiovascular Diseases

Cardiovascular diseases (CVD) are still the first cause of death worldwide. Their main origin is the development of atherosclerotic plaque, which consists in the accumulation of lipids and inflammatory leucocytes within the vascular wall of large vessels. Beyond dyslipidemia, diabetes, obesity, hypertension and smoking, the alteration of circadian rhythms, in shift workers for instance, has recently been recognized as an additional risk factor. Accordingly, targeting a pro-atherogenic pathway at the right time window, namely chronotherapy, has proven its efficiency in reducing plaque progression without affecting healthy tissues in mice, thus providing the rationale of such an approach to treat CVD and to reduce drug side effects. Nuclear receptors are transcriptional factors involved in the control of many physiological processes. Among them, Rev-erbs and RORs control metabolic homeostasis, inflammatory processes and the biological clock. In this review, we discuss the opportunity to dampen atherosclerosis progression by targeting such ligand-activated core clock components in a (chrono-)therapeutic approach in order to treat CVD.

Association between serum markers of the humoral immune system and inflammation in the Swedish AMORIS study

BACKGROUND

Although the onset of inflammatory cascades may profoundly influence the nature of antibody responses, the interplay between inflammatory and humoral (antibody) immune markers remains unclear. Thus, we explored the reciprocity between the humoral immune system and inflammation and assessed how external socio-demographic factors may influence these interactions. From the AMORIS cohort, 5513 individuals were identified with baseline measurements of serum humoral immune [immunoglobulin G, A & M (IgG, IgA, IgM)] and inflammation (C-reactive protein (CRP), albumin, haptoglobin, white blood cells (WBC), iron and total iron-binding capacity) markers measured on the same day. Correlation analysis, principal component analysis and hierarchical clustering were used to evaluate biomarkers correlation, variation and associations. Multivariate analysis of variance was used to assess associations between biomarkers and educational level, socio-economic status, sex and age.

RESULTS

Frequently used serum markers for inflammation, CRP, haptoglobin and white blood cells, correlated together. Hierarchical clustering and principal component analysis confirmed the interaction between these main biological responses, showing an acute response component (CRP, Haptoglobin, WBC, IgM) and adaptive response component (Albumin, Iron, TIBC, IgA, IgG). A socioeconomic gradient associated with worse health outcomes was observed, specifically low educational level, older age and male sex were associated with serum levels that indicated infection and inflammation.

CONCLUSIONS

These findings indicate that serum markers of the humoral immune system and inflammation closely interact in response to infection or inflammation. Clustering analysis presented two main immune response components: an acute and an adaptive response, comprising markers of both biological pathways. Future studies should shift from single internal marker assessment to multiple humoral and inflammation serum markers combined, when assessing risk of clinical outcomes such as cancer.