The circadian clock influences T cell responses to vaccination by regulating dendritic cell antigen processing

Roles of circadian clocks in macrophage metabolism: implications in inflammation and metabolism of lipids, glucose, and amino acids

Macrophages are essential immune cells that play crucial roles in inflammation and tissue homeostasis and are important regulators of metabolic processes, such as the metabolism of glucose, lipids, and amino acids. The regulation of macrophage metabolism by circadian clock genes has been emphasized in many studies. Changes in metabolic profiles occurring after the perturbation of macrophage circadian cycles may underlie the etiology of several diseases. Specifically, chronic inflammatory disorders, such as atherosclerosis, diabetes, cardiovascular diseases, and liver dysfunction, are associated with poor macrophage metabolism. Developing treatment approaches that target metabolic and immunological ailments requires an understanding of the complex relationships among clock genes, disease etiology, and macrophage metabolism. This review explores the molecular mechanisms through which clock genes regulate lipid, amino acid, and glucose metabolism in macrophages and discusses their potential roles in the development and progression of metabolic disorders. The findings underscore the importance of maintaining circadian homeostasis in macrophage function as a promising avenue for therapeutic intervention in diseases involving metabolic dysregulation, given its key roles in inflammation and tissue homeostasis. Moreover, reviewing the therapeutic implications of circadian rhythm in macrophages can help minimize the side effects of treatment. Novel strategies may be beneficial in treating immune-related diseases caused by shifted and blunted circadian rhythms via light exposure, jet lag, seasonal changes, and shift work or disruption to the internal clock (such as stress or disease).

Biorhythm-mimicking growth hormone patch

Timing dosing throughout the day impacts the therapeutic efficacy and side effects of medications. Thus, optimizing release profiles to synchronize drug concentrations with natural rhythms is critical for optimal therapeutic benefits. However, existing delivery systems are still inefficient in delivering drugs in a biorhythm-mimicking fashion. Here we describe a biorhythm-inspired growth hormone transdermal microneedle patch with multistage drug release that mimics the natural rhythm of human growth hormone secretion at night. Programmed drug release is achieved by combining a 'burst-release' module with several 'delayed-release' modules. Compared with the subcutaneous daily injections currently used in clinics, the patch exhibits enhanced efficacy in terms of longitudinal bone growth and bone quality, leading to bone length increases of ~10 mm and ~5 mm in healthy rats and growth hormone gene knockout mice, respectively. Our findings reveal that the biorhythm-mimicking release pattern significantly enhances growth hormone bioavailability and effectively regulates the growth-related biological process, thus boosting the secretion of insulin-like growth factor-1 and ultimately promoting bone growth.

Circadian immunometabolism: A future insight for targeted therapy in cancer

Circadian rhythms send messages to regulate the sleep-wake cycle in living beings, which, regulate various biological activities. It is well known that altered sleep-wake cycles affect host metabolism and significantly deregulate the host immunity. The dysregulation of circadian-related genes is critical for various malignancies. One of the hallmarks of cancer is altered metabolism, the effects of which spill into surrounding microenvironments. Here, we review the emerging literature linking the circadian immunometabolic axis to cancer. Small metabolites are the products of various metabolic pathways, that are usually perturbed in cancer. Genes that regulate circadian rhythms also regulate host metabolism and control metabolite content in the tumor microenvironment. Immune cell infiltration into the tumor site is critical to perform anticancer functions, and altered metabolite content affects their trafficking to the tumor site. A compromised immune response in the tumor microenvironment aids cancer cell proliferation and immune evasion, resulting in metastases. The role of circadian rhythms in these processes is largely overlooked and demands renewed attention in the search for targets against cancer growth and spread. The precision medicine approach requires targeting the circadian immune metabolism in cancer.

Optimizing stem cell infusion timing in the prevention of acute graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a cornerstone treatment for a broad spectrum of malignant and nonmalignant hematological disorders. However, the success of allo-HSCT is often overshadowed by acute graft-versus-host disease (aGVHD), a life-threatening complication. Here, we show in patients and murine models that the circadian timing of stem cell infusion dictates the development of aGVHD. Early-infused patients exhibit a significantly lower incidence and severity of aGVHD, as well as improved survival. We observed time-of-day variations in the levels of cytokines, especially IL-1α, which controls donor T cell responses after transplantation. The levels of IL-1α in patients were strongly associated with the development of aGVHD. Furthermore, preclinical results showed that the administration of IL-1α neutralizing antibodies markedly alleviated aGVHD and increased survival. Our study suggests that scheduling stem cell infusions early in the day could be a simple yet transformative intervention for preventing aGVHD.

Circadian immune system in solid organ transplantation: a review article

The innate and adaptive immune systems are intricately regulated by the circadian clock machinery. Recent clinical investigations have shed light on the influence of timing in organ procurement and transplantation on graft survival. In this review, we explore various mechanisms of immunological functions associated with the steps involved in organ transplantation, spanning from surgical harvesting to reperfusion and linking to the circadian rhythm. A deeper understanding of these processes has the potential to extend the principles of chrono-immunotherapy to the realm of organ transplantation, with the aim of enhancing graft durability and improving patient outcomes. This review concludes with some perspectives on future directions in this exciting and still evolving field of research.

Unveiling the novel role of circadian rhythms in sepsis and septic shock: unexplored implications for chronotherapy

Circadian rhythms are critical to coordinating body processes to external environmental cues, such as light and feeding, to ensure efficiency and maintain optimal health. These rhythms are controlled by 'clock' transcription factors, such as Clock, Bmal1, Per1/2, Cry1/2, and Rev-erbs, which are present in almost every tissue. In modern society, disruptions to normal circadian rhythms are increasingly prevalent due to extended lighting, shift work, and long-distance travel. These disruptions misalign external cues to body processes and contribute to diseases such as obesity and non-alcoholic fatty liver disease. They also exacerbate pre-existing health issues, such as depression and inflammatory bowel disease. The normal inflammatory response to acute infection displays remarkable circadian rhythmicity in humans with increased inflammatory activity during the normal night or rest period. Severe bloodborne infections, exemplified in sepsis and the progression to septic shock, can not only disrupt the circadian rhythmicity of inflammatory processes but can be exacerbated by circadian misalignment. Examples of circadian disruptions during sepsis and septic shock include alteration or loss of hormonal rhythms controlling blood pressure and inflammation, white blood cell counts, and cytokine secretions. These changes to circadian rhythms hinder sepsis and septic shock recovery and also increase mortality. Chronotherapy and chronopharmacotherapy are promising approaches to resynchronise circadian rhythms or leverage circadian rhythms to optimise medication efficacy, respectively, and hold much potential in the treatment of sepsis and septic shock. Despite knowledge of how circadian rhythms change in these grave conditions, very little research has been undertaken on the use of these therapies in support of sepsis management. This review details the circadian disruptions associated with sepsis and septic shock, the influence they have on morbidity and mortality, and the potential clinical benefits of circadian-modulating therapies.

Metabolic reprogramming of macrophages by PKM2 promotes IL-10 production via adenosine

Macrophages play a crucial role in immune responses and undergo metabolic reprogramming to fulfill their functions. The tetramerization of the glycolytic enzyme pyruvate kinase M2 (PKM2) induces the production of the anti-inflammatory cytokine interleukin (IL)-10 in vivo, but the underlying mechanism remains elusive. Here, we report that PKM2 activation with the pharmacological agent TEPP-46 increases IL-10 production in LPS-activated macrophages by metabolic reprogramming, leading to the production and release of ATP from glycolysis. The effect of TEPP-46 is abolished in PKM2-deficient macrophages. Extracellular ATP is converted into adenosine by ectonucleotidases that activate adenosine receptor A2a (A2aR) to enhance IL-10 production. Interestingly, IL-10 production induced by PKM2 activation is associated with improved mitochondrial health. Our results identify adenosine derived from glycolytic ATP as a driver of IL-10 production, highlighting the role of tetrameric PKM2 in regulating glycolysis to promote IL-10 production.

Chronic CRYPTOCHROME deficiency enhances cell-intrinsic antiviral defences

The within-host environment changes over circadian time and influences the replication and severity of viruses. Genetic knockout of the circadian transcription factors CRYPTOCHROME 1 and CRYPTOCHROME 2 (CRY1-/-/CRY2-/-; CKO) leads to altered protein homeostasis and chronic activation of the integrated stress response (ISR). The adaptive ISR signalling pathways help restore cellular homeostasis by downregulating protein synthesis in response to endoplasmic reticulum overloading or viral infections. By quantitative mass spectrometry analysis, we reveal that many viral recognition proteins and type I interferon (IFN) effectors are significantly upregulated in lung fibroblast cells from CKO mice compared with wild-type (WT) mice. This basal 'antiviral state' restricts the growth of influenza A virus and is governed by the interaction between proteotoxic stress response pathways and constitutive type I IFN signalling. CKO proteome composition and type I IFN signature were partially phenocopied upon sustained depletion of CRYPTOCHROME (CRY) proteins using a small-molecule CRY degrader, with modest differential gene expression consistent with differences seen between CKO and WT cells. Our results highlight the crosstalk between circadian rhythms, cell-intrinsic antiviral defences and protein homeostasis, providing a tractable molecular model to investigate the interface of these key contributors to human health and disease.This article is part of the Theo Murphy meeting issue 'Circadian rhythms in infection and immunity'.

Circadian gating: concepts, processes, and opportunities

Circadian clocks provide a biological measure of time that coordinates metabolism, physiology and behaviour with 24 h cycles in the environment. Circadian systems have a variety of characteristic properties, such as entrainment to environmental cues, a self-sustaining rhythm of about 24 h and temperature compensation of the circadian rhythm. In this perspective, we discuss the process of circadian gating, which refers to the restriction of a biological event to particular times of day by the circadian clock. We introduce principles and processes associated with circadian gating in a variety of organisms, including some associated mechanisms. We highlight socioeconomic opportunities presented by the investigation of circadian gating, using selected examples from circadian medicine and agricultural crop production to illustrate its importance.This article is part of the Theo Murphy meeting issue 'Circadian rhythms in infection and immunity'.

Update on the roles of regular daily rhythms in combating brain tumors

An endogenous time-keeping system found in all kingdoms of life, the endogenous circadian clock, is the source of the essential cyclic change mechanism known as the circadian rhythm. The primary circadian clock that synchronizes peripheral circadian clocks to the proper phase is housed in the anterior hypothalamus's suprachiasmatic nuclei (SCN), which functions as a central pacemaker. According to many epidemiological studies, many cancer types, especially brain tumors, have shown evidence of dysregulated clock gene expression, and the connection between clock and brain tumors is highly specific. In some studies, it is reported that the treatment administered in the morning has been linked to prolonged survival for brain cancer patients, and drug sensitivity and gene expression in gliomas follow daily rhythms. These results suggest a relationship between the circadian rhythm and the onset and spread of brain tumors, while further accumulation of research evidence will be needed to establish definitely these positive outcomes as well as to determine the mechanism underlying them. Chronotherapy provides a means of harnessing current medicines to prolong patients' lifespans and improve their quality of life, indicating the significance of circadian rhythm in enhancing the design of future patient care and clinical trials. Moreover, it is implicated that chronobiological therapy target may provide a significant challenge that warrants extensive effort to achieve. This review examines evidence of the relationship of circadian rhythm with glioma molecular pathogenesis and summarizes the mechanisms and drugs implicated in this disease.

Time-of-day control of mitochondria regulates NLRP3 inflammasome activation in macrophages

Macrophages are innate immune cells that orchestrate the process of inflammation, which varies across time of day. This ensures appropriate biological timing of the immune response with the external environment. The NLRP3 inflammasome mediates IL-1-family cytokine release via pyroptosis. Mitochondria play a multifaceted role regulating NLRP3 inflammasome activity. Mitochondria exhibit distinct metabolic changes across time of day, which are influenced by clock genes. However, whether the macrophage clock regulates the NLRP3 inflammasome via mitochondrial control remains unclear. We find heightened mitochondrial membrane potential (Δψm) and enhanced NLRP3 inflammasome activation from peritoneal exudate cells (PECs) isolated at circadian time (CT) 12 compared to CT 0. In vitro time-of-day synchronization of bone-marrow derived macrophages (BMDMs) induced time-dependent differences in NLRP3 inflammasome activation. Myeloid-specific Bmal1-deletion enhanced NLRP3 inflammasome activity in PECs at CT0 and in unsynchronized BMDMs compared to controls. Pharmacologically disrupting Δψm in synchronized cells reduced NLRP3 inflammasome activation to comparable levels, and the same occurred with Bmal1-deletion. These results further demonstrate circadian clock timing of the NLRP3 inflammasome, which is dependent on mitochondrial function and driven through the circadian gene Bmal1.

BMAL1 and CLOCK proteins exhibit differential association with mitochondrial dynamics, protein synthesis pathways and muscle strength in human muscle

Murine models lacking CLOCK/BMAL1 proteins in skeletal muscle (SkM) present muscle deterioration and mitochondria abnormalities. It is unclear whether humans with lower levels of these proteins in the SkM have similar alterations. Here we evaluated the association between BMAL1 and CLOCK protein mass with mitochondrial dynamics parameters and molecular and functional SkM quality markers in males. SkM biopsies were taken from the vastus lateralis of 16 male (non-athletes, non-obese and non-diabetic) subjects (8-9 a.m.). The morphology of mitochondria and their interaction with the sarcoplasmic reticulum (mitochondria-SR) were determined using transmission electron microscopy images. Additionally, protein abundance of the OXPHOS complex, mitochondria fusion/fission regulators, mitophagy and signalling proteins related to muscle protein synthesis were measured. To evaluate the quality of SkM, the cross-sectional area and maximal SkM strength were also measured. The results showed that BMAL1 protein mass was positively associated with mitochondria-SR distance, mitochondria size, mitochondria cristae density and mTOR protein mass. On the other hand, CLOCK protein mass was negatively associated with mitochondria-SR interaction, but positively associated with mitochondria complex III, OPA1 and DRP1 protein mass. Furthermore, CLOCK protein mass was positively associated with the protein synthesis signalling pathway (total mTOR, AKT and P70S6K protein mass) and SkM strength. These findings suggest that the BMAL1 and CLOCK proteins play different roles in regulating mitochondrial dynamics and SkM function in males, and that modulation of these proteins could be a potential therapeutic target for treating muscle diseases. KEY POINTS: In murine models, reductions in BMAL1 and CLOCK proteins lead to changes in mitochondria biology and a decline in muscle function. However, this association has not been explored in humans. We found that in human skeletal muscle, a decrease in BMAL1 protein mass is linked to smaller intermyofibrillar mitochondria, lower mitochondria cristae density, higher interaction between mitochondria and sarcoplasmic reticulum, and reduced mTOR protein mass. Additionally, we found that a decrease in CLOCK protein mass is associated with a higher interaction between mitochondria and sarcoplasmic reticulum, lower protein mass of OPA1 and DRP1, which regulates mitochondria fusion and fission, lower protein synthesis signalling pathway (mTOR, AKT and P70S6K protein mass), and decreased skeletal muscle strength. According to our findings in humans, which are supported by previous studies in animals, the mitochondrial dynamics and skeletal muscle function could be regulated differently by BMAL1 and CLOCK proteins. As a result, targeting the modulation of these proteins could be a potential therapeutic approach for treating muscle diseases and metabolic disorders related to muscle.

Engineered mitochondria exert potent antitumor immunity as a cancer vaccine platform

The preferable antigen delivery profile accompanied by sufficient adjuvants favors vaccine efficiency. Mitochondria, which feature prokaryotic characteristics and contain various damage-associated molecular patterns (DAMPs), are easily taken up by phagocytes and simultaneously activate innate immunity. In the current study, we established a mitochondria engineering platform for generating antigen-enriched mitochondria as cancer vaccine. Ovalbumin (OVA) and tyrosinase-related protein 2 (TRP2) were used as model antigens to synthesize fusion proteins with mitochondria-localized signal peptides. The lentiviral infection system was then employed to produce mitochondrial vaccines containing either OVA or TRP2. Engineered OVA- and TRP2-containing mitochondria (OVA-MITO and TRP2-MITO) were extracted and evaluated as potential cancer vaccines. Impressively, the engineered mitochondria vaccine demonstrated efficient antitumor effects when used as both prophylactic and therapeutic vaccines in murine tumor models. Mechanistically, OVA-MITO and TRP2-MITO potently recruited and activated dendritic cells (DCs) and induced a tumor-specific cell-mediated immunity. Moreover, DC activation by mitochondria vaccine critically involves TLR2 pathway and its lipid agonist, namely, cardiolipin derived from the mitochondrial membrane. The results demonstrated that engineered mitochondria are natively well-orchestrated carriers full of immune stimulants for antigen delivery, which could preferably target local dendritic cells and exert strong adaptive cellular immunity. This proof-of-concept study established a universal platform for vaccine construction with engineered mitochondria bearing alterable antigens for cancers as well as other diseases.

Integration of circadian rhythms and immunotherapy for enhanced precision in brain cancer treatment

Circadian rhythms significantly impact (patho)physiological processes, with disruptions linked to neurodegenerative diseases and heightened cancer vulnerability. While immunotherapy has shown promise in treating various cancers, its efficacy in brain malignancies remains limited. This review explores the nexus of circadian rhythms and immunotherapy in brain cancer treatment, emphasising precision through alignment with the body's internal clock. We evaluate circadian regulation of immune responses, including cell localisation and functional phenotype, and discuss how circadian dysregulation affects anti-cancer immunity. Additionally, we analyse and assess the effectiveness of current immunotherapeutic approaches for brain cancer including immune checkpoint blockades, adoptive cellular therapies, and other novel strategies. Future directions, such as chronotherapy and personalised treatment schedules, are proposed to optimise immunotherapy precision against brain cancers. Overall, this review provides an understanding of the often-overlooked role of circadian rhythms in brain cancer and suggests avenues for improving immunotherapeutic outcomes.

Diurnal rhythms in varicella vaccine effectiveness

BACKGROUNDImmune processes are influenced by circadian rhythms. We evaluate the association between varicella vaccine administration time of day and vaccine effectiveness.METHODSA national cohort, children younger than 6 years, were enrolled between January 2002 and December 2023. We compared children vaccinated during morning (7:00-10:59), late morning to afternoon (11:00-15:59), or evening hours (16:00-19:59). A Cox proportional hazards regression model was used to adjust for ethnicity, sex, and comorbidities. The first varicella infection occurring at least 14 days after vaccination and a second dose administration were treated as terminal events.RESULTSOf 251,141 vaccinated children, 4,501 (1.8%) experienced breakthrough infections. Infection rates differed based on vaccination time, with the lowest rates associated with late morning to afternoon (11:00-15:59), HR 0.88, 95% CI 0.82-0.95, P < 0.001, and the highest rates with evening vaccination (16:00-19:59), HR 1.41, 95% CI 1.32-1.52, P < 0.001. Vaccination timing remained significant after adjustment for ethnicity, sex, and comorbidities. The association between immunization time and infection risk followed a sinusoidal pattern, consistent with a diurnal rhythm in vaccine effectiveness.CONCLUSIONWe report a significant association between the time of varicella vaccination and its clinical effectiveness. Similar association was observed with the COVID-19 vaccine, providing proof of concept consistent with a diurnal rhythm in vaccine effectiveness.

Why does circadian timing of administration matter for immune checkpoint inhibitors' efficacy?

BACKGROUND

Tolerability and antitumour efficacy of chemotherapy and radiation therapy can vary largely according to their time of administration along the 24-h time scale, due to the moderation of their molecular and cellular mechanisms by circadian rhythms. Recent clinical data have highlighted a striking role of dosing time for cancer immunotherapy, thus calling for a critical evaluation.

METHODS

Here, we review the clinical data and we analyse the mechanisms through which circadian rhythms can influence outcomes on ICI therapies. We examine how circadian rhythm disorders can affect tumour immune microenvironment, as a main mechanism linking the circadian clock to the 24-h cycles in ICIs antitumour efficacy.

RESULTS

Real-life data from 18 retrospective studies have revealed that early time-of-day (ToD) infusion of immune checkpoint inhibitors (ICIs) could enhance progression-free and/or overall survival up to fourfold compared to late ToD dosing. The studies involved a total of 3250 patients with metastatic melanoma, lung, kidney, bladder, oesophageal, stomach or liver cancer from 9 countries. Such large and consistent differences in ToD effects on outcomes could only result from a previously ignored robust chronobiological mechanism. The circadian timing system coordinates cellular, tissue and whole-body physiology along the 24-h timescale. Circadian rhythms are generated at the cellular level by a molecular clock system that involves 15 specific clock genes. The disruption of circadian rhythms can trigger or accelerate carcinogenesis, and contribute to cancer treatment failure, possibly through tumour immune evasion resulting from immunosuppressive tumour microenvironment.

CONCLUSIONS AND PERSPECTIVE

Such emerging understanding of circadian rhythms regulation of antitumour immunity now calls for randomised clinical trials of ICIs timing to establish recommendations for personalised chrono-immunotherapies with current and forthcoming drugs.

Watch your clock: it matters for immunotherapy

Does time of day matter for cancer immunotherapy? Whereas the concept of optimizing the time of treatment is well documented for chemotherapy, whether it applies to immunotherapy, a revolutionizing treatment exploiting the power of immune cells to control tumors, has recently been addressed in a study published in Cell.

Chrono-tailored drug delivery systems: recent advances and future directions

Circadian rhythms influence a range of biological processes within the body, with the central clock or suprachiasmatic nucleus (SCN) in the brain synchronising peripheral clocks around the body. These clocks are regulated by external cues, the most influential being the light/dark cycle, in order to synchronise with the external day. Chrono-tailored or circadian drug delivery systems (DDS) aim to optimise drug delivery by releasing drugs at specific times of day to align with circadian rhythms within the body. Although this approach is still relatively new, it has the potential to enhance drug efficacy, minimise side effects, and improve patient compliance. Chrono-tailored DDS have been explored and implemented in various conditions, including asthma, hypertension, and cancer. This review aims to introduce the biology of circadian rhythms and provide an overview of the current research on chrono-tailored DDS, with a particular focus on immunological applications and vaccination. Finally, we draw on some of the key challenges which need to be overcome for chrono-tailored DDS before they can be translated to more widespread use in clinical practice.

Circadian control of tumor immunosuppression affects efficacy of immune checkpoint blockade

The circadian clock is a critical regulator of immunity, and this circadian control of immune modulation has an essential function in host defense and tumor immunosurveillance. Here we use a single-cell RNA sequencing approach and a genetic model of colorectal cancer to identify clock-dependent changes to the immune landscape that control the abundance of immunosuppressive cells and consequent suppression of cytotoxic CD8+ T cells. Of these immunosuppressive cell types, PD-L1-expressing myeloid-derived suppressor cells (MDSCs) peak in abundance in a rhythmic manner. Disruption of the epithelial cell clock regulates the secretion of cytokines that promote heightened inflammation, recruitment of neutrophils and the subsequent development of MDSCs. We also show that time-of-day anti-PD-L1 delivery is most effective when synchronized with the abundance of immunosuppressive MDSCs. Collectively, these data indicate that circadian gating of tumor immunosuppression informs the timing and efficacy of immune checkpoint inhibitors.

Multifaceted mitochondria in innate immunity

The ability of mitochondria to transform the energy we obtain from food into cell phosphorylation potential has long been appreciated. However, recent decades have seen an evolution in our understanding of mitochondria, highlighting their significance as key signal-transducing organelles with essential roles in immunity that extend beyond their bioenergetic function. Importantly, mitochondria retain bacterial motifs as a remnant of their endosymbiotic origin that are recognised by innate immune cells to trigger inflammation and participate in anti-microbial defence. This review aims to explore how mitochondrial physiology, spanning from oxidative phosphorylation (OxPhos) to signalling of mitochondrial nucleic acids, metabolites, and lipids, influences the effector functions of phagocytes. These myriad effector functions include macrophage polarisation, efferocytosis, anti-bactericidal activity, antigen presentation, immune signalling, and cytokine regulation. Strict regulation of these processes is critical for organismal homeostasis that when disrupted may cause injury or contribute to disease. Thus, the expanding body of literature, which continues to highlight the central role of mitochondria in the innate immune system, may provide insights for the development of the next generation of therapies for inflammatory diseases.

Circadian tumor infiltration and function of CD8+ T cells dictate immunotherapy efficacy

The quality and quantity of tumor-infiltrating lymphocytes, particularly CD8+ T cells, are important parameters for the control of tumor growth and response to immunotherapy. Here, we show in murine and human cancers that these parameters exhibit circadian oscillations, driven by both the endogenous circadian clock of leukocytes and rhythmic leukocyte infiltration, which depends on the circadian clock of endothelial cells in the tumor microenvironment. To harness these rhythms therapeutically, we demonstrate that efficacy of chimeric antigen receptor T cell therapy and immune checkpoint blockade can be improved by adjusting the time of treatment during the day. Furthermore, time-of-day-dependent T cell signatures in murine tumor models predict overall survival in patients with melanoma and correlate with response to anti-PD-1 therapy. Our data demonstrate the functional significance of circadian dynamics in the tumor microenvironment and suggest the importance of leveraging these features for improving future clinical trial design and patient care.

Circadian rhythms in solid organ transplantation

Circadian rhythms are daily cycles in physiology that can affect medical interventions. This review considers how these rhythms may relate to solid organ transplantation. It begins by summarizing the mechanism for circadian rhythm generation known as the molecular clock, and basic research connecting the clock to biological activities germane to organ acceptance. Next follows a review of clinical evidence relating time of day to adverse transplantation outcomes. The concluding section discusses knowledge gaps and practical areas where applying circadian biology might improve transplantation success.

Circadian regulation of cancer stem cells and the tumor microenvironment during metastasis

The circadian clock regulates daily rhythms of numerous physiological activities through tightly coordinated modulation of gene expression and biochemical functions. Circadian disruption is associated with enhanced tumor formation and metastasis via dysregulation of key biological processes and modulation of cancer stem cells (CSCs) and their specialized microenvironment. Here, we review how the circadian clock influences CSCs and their local tumor niches in the context of different stages of tumor metastasis. Identifying circadian therapeutic targets could facilitate the development of new treatments that leverage circadian modulation to ablate tumor-resident CSCs, inhibit tumor metastasis and enhance response to current therapies.

Circadian rhythm regulation in the immune system

Circadian rhythms are a ubiquitous feature in nearly all living organisms, representing oscillatory patterns with a 24-h cycle that are widespread across various physiological processes. Circadian rhythms regulate a multitude of physiological systems, including the immune system. At the molecular level, most immune cells autonomously express clock-regulating genes, which play critical roles in regulating immune cell functions. These functions encompass migration, phagocytic activity, immune cell metabolism (such as mitochondrial structural function and metabolism), signalling pathway activation, inflammatory responses, innate immune recognition, and adaptive immune processes (including vaccine responses and pathogen clearance). The endogenous circadian clock orchestrates multifaceted rhythmicity within the immune system, optimizing immune surveillance and responsiveness; this bears significant implications for maintaining immune homeostasis and resilience against diseases. This work provides an overview of circadian rhythm regulation within the immune system.

Immunotherapy time of infusion impacts survival in head and neck cancer: A propensity score matched analysis

The adaptive immune response is physiologically regulated by the circadian rhythm. Data in lung and melanoma malignancies suggests immunotherapy infusions earlier in the day may be associated with improved response; however, the optimal time of administration for patients with head and neck squamous cell carcinoma (HNSCC) is not known. We aimed to evaluate the association of immunotherapy infusion time with overall survival (OS) and progression free survival (PFS) in patients with HNSCC in an Institutional Review Board-approved, retrospective cohort study. 113 patients met study inclusion criteria and 98 patients were included in a propensity score-matched cohort. In the full unmatched cohort (N = 113), each additional 20 % of infusions received after 1500 h conferred an OS hazard ratio (HR) of 1.35 (95 % C.I.1.2-1.6; p-value = 0.0003) and a PFS HR of 1.34 (95 % C.I.1.2-1.6; p-value < 0.0001). A propensity score-matched analysis of patients who did or did not receive ≥20 % of infusions after 1500 h showed that those who were administered ≥20 % of infusions after 1500 h trended towards a shorter OS (HR = 1.35; p-value = 0.26) and a shorter PFS (HR = 1.57, 95 % C.I. 1.02-2.42, p-value = 0.04). Each additional 20 % of infusions received after 1500 h remained robust in the matched cohort multivariable analysis and was associated with shorter OS (adjusted HR = 1.4 (95 % C.I.1.2-1.8), p-value < 0.001). Patients with advanced HNSCC who received more of their infusions in the afternoon were associated with shorter OS and PFS and scheduling immunotherapy infusions earlier in the day may be warranted.

Circadian Effects on Vascular Immunopathologies

Circadian rhythms exert a profound impact on most aspects of mammalian physiology, including the immune and cardiovascular systems. Leukocytes engage in time-of-day-dependent interactions with the vasculature, facilitating the emigration to and the immune surveillance of tissues. This review provides an overview of circadian control of immune-vascular interactions in both the steady state and cardiovascular diseases such as atherosclerosis and infarction. Circadian rhythms impact both the immune and vascular facets of these interactions, primarily through the regulation of chemoattractant and adhesion molecules on immune and endothelial cells. Misaligned light conditions disrupt this rhythm, generally exacerbating atherosclerosis and infarction. In cardiovascular diseases, distinct circadian clock genes, while functioning as part of an integrated circadian system, can have proinflammatory or anti-inflammatory effects on these immune-vascular interactions. Here, we discuss the mechanisms and relevance of circadian rhythms in vascular immunopathologies.

Neutrophil profiling illuminates anti-tumor antigen-presenting potency

Neutrophils, the most abundant and efficient defenders against pathogens, exert opposing functions across cancer types. However, given their short half-life, it remains challenging to explore how neutrophils adopt specific fates in cancer. Here, we generated and integrated single-cell neutrophil transcriptomes from 17 cancer types (225 samples from 143 patients). Neutrophils exhibited extraordinary complexity, with 10 distinct states including inflammation, angiogenesis, and antigen presentation. Notably, the antigen-presenting program was associated with favorable survival in most cancers and could be evoked by leucine metabolism and subsequent histone H3K27ac modification. These neutrophils could further invoke both (neo)antigen-specific and antigen-independent T cell responses. Neutrophil delivery or a leucine diet fine-tuned the immune balance to enhance anti-PD-1 therapy in various murine cancer models. In summary, these data not only indicate the neutrophil divergence across cancers but also suggest therapeutic opportunities such as antigen-presenting neutrophil delivery.

The β2-adrenergic receptor (ADRB2) entrains circadian gene oscillation and diurnal responses to virus infection in CD8 + T cells

Adaptive immune cells are regulated by circadian rhythms (CR) under both steady state conditions and during responses to infection. Cytolytic CD8 + T cells display variable responses to infection depending upon the time of day of exposure. However, the neuronal signals that entrain these cyclic behaviors remain unknown. Immune cells express a variety of neurotransmitter receptors including nicotinic, glucocorticoid, and adrenergic receptors. Here, we demonstrate that the β2-adrenergic receptor (ADRB2) regulates the periodic oscillation of select core clock genes, such as Per2 and Bmal1 , and selective loss of the Adrb2 gene dramatically perturbs the normal diurnal oscillation of clock gene expression in CD8 + T cells. Consequently, their circadian-regulated anti-viral response is dysregulated, and the diurnal development of CD8 + T cells into variegated populations of cytolytic T cell (CTL) effectors is dramatically altered in the absence of ADRB2 signaling. Thus, the Adrb2 directly entrains core clock gene oscillation and regulates CR-dependent T cell responses to virus infection as a function of time-of-day of pathogen exposure.

One Sentence Summary

The β2-adrenergic receptor regulates circadian gene oscillation and downstream daily timing of cytolytic T cell responses to virus infection.

The role of circadian clock in regulating cell functions: implications for diseases

The circadian clock system orchestrates daily behavioral and physiological rhythms, facilitating adaptation to environmental and internal oscillations. Disruptions in circadian rhythms have been linked to increased susceptibility to various diseases and can exacerbate existing conditions. This review delves into the intricate regulation of diurnal gene expression and cell function by circadian clocks across diverse tissues. . Specifically, we explore the rhythmicity of gene expressions, behaviors, and functions in both immune and non-immune cells, elucidating the regulatory effects and mechanisms imposed by circadian clocks. A detailed discussion is centered on elucidating the complex functions of circadian clocks in regulating key cellular signaling pathways. We further review the circadian regulation in diverse diseases, with a focus on inflammatory diseases, cancers, and systemic diseases. By highlighting the intimate interplay between circadian clocks and diseases, especially through clock-controlled cell function, this review contributes to the development of novel disease intervention strategies. This enhanced understanding holds significant promise for the design of targeted therapies that can exploit the circadian regulation mechanisms for improved treatment efficacy.

Objectively measured peri-vaccination sleep does not predict COVID-19 breakthrough infection

Prior studies have shown that sleep duration peri-vaccination influences an individual's antibody response. However, whether peri-vaccination sleep affects real-world vaccine effectiveness is unknown. Here, we tested whether objectively measured sleep around COVID-19 vaccination affected breakthrough infection rates. DETECT is a study of digitally recruited participants who report COVID-19-related information, including vaccination and illness data. Objective sleep data are also recorded through activity trackers. We compared the impact of sleep duration, sleep efficiency, and frequency of awakenings on reported breakthrough infection after the 2nd vaccination and 1st COVID-19 booster. Logistic regression models were created to examine if sleep metrics predicted COVID-19 breakthrough infection independent of age and gender. Self-reported breakthrough COVID-19 infection following 2nd COVID-19 vaccination and 1st booster. 256 out of 5265 individuals reported a breakthrough infection after the 2nd vaccine, and 581 out of 2583 individuals reported a breakthrough after the 1st booster. There was no difference in sleep duration between those with and without breakthrough infection. Increased awakening frequency was associated with breakthrough infection after the 1st booster with 3.01 ± 0.65 awakenings/hour in the breakthrough group compared to 2.82 ± 0.65 awakenings/hour in those without breakthrough (P < 0.001). Cox proportional hazards modeling showed that age < 60 years (hazard ratio 2.15, P < 0.001) and frequency of awakenings (hazard ratio 1.17, P = 0.019) were associated with breakthrough infection after the 1st booster. Sleep duration was not associated with breakthrough infection after COVID vaccination. While increased awakening frequency during sleep was associated with breakthrough infection beyond traditional risk factors, the clinical implications of this finding are unclear.

Analysis of the correlation between immune cell characteristics and insomnia: a Mendelian randomization study

Insomnia, recognized as a prevalent sleep disorder, has garnered extensive attention within the realm of public health. Recent studies indicate a close interaction between the immune system and sleep; however, the specific mechanism remains not yet fully understood. Based on the publicly available Genome-Wide Association Study (GWAS) data, we used two-sample Mendelian randomization (MR) analyses to investigate the associations between 731 immune cell traits and insomnia risk. Five MR analysis methods and a comprehensive sensitivity analysis were used to evaluate the reliability of the results. In this study, we identified that 14 immune characteristics among four immune profiles [median fluorescence intensity (MFI), relative cell count (RC), absolute cell count (AC), and morphological parameters (MP)] demonstrated a significant causal association with insomnia. Specifically, eight immune cell characteristics were associated with an increased risk of insomnia, including CD11c+ monocyte% (P < 0.001), CD11c+ HLA DR++ monocyte% (P = 0.004), CD86+ plasmoid dendritic cell (DC) AC (P < 0.001), CD33br HLA DR+ CD14dim AC (P < 0.001), CD8dim AC (P = 0.002), CCR2 on CD14+ CD16- monocyte (P < 0.001), CD39 on monocyte (P < 0.001), and SSC-A on myeloid DC (P < 0.001). Six immune cell characteristics demonstrated protective effects against insomnia, including PB/PC %B cell (P < 0.001), CM CD4+% CD4+ (P < 0.001), T-cell AC (P < 0.001), BAFF-R on IgD- CD38br (P < 0.001), CD16-CD56 on HLA DR+ NK cells (P < 0.001), and CD14 on CD33br HLA DR+ CD14dim (P < 0.001). Our study established the correlation between immune cell characteristics and insomnia, offering a novel theoretical foundation for the concept of sleep-immune cross talk.NEW & NOTEWORTHY This study investigated the association between 731 immune cell characteristics and insomnia using Mendelian randomization, revealing that 14 immune cell characteristics across four groups of immune traits (MFI, RC, AC, and MP) have a significant and causal association with insomnia risk. Our results contribute to the understanding of the sleep-immune cross talk doctrine and offer a new theoretical basis for immune modulation in treating insomnia.

Circadian immunity from bench to bedside: a practical guide

The immune system is built to counteract unpredictable threats, yet it relies on predictable cycles of activity to function properly. Daily rhythms in immune function are an expanding area of study, and many originate from a genetically based timekeeping mechanism known as the circadian clock. The challenge is how to harness these biological rhythms to improve medical interventions. Here, we review recent literature documenting how circadian clocks organize fundamental innate and adaptive immune activities, the immunologic consequences of circadian rhythm and sleep disruption, and persisting knowledge gaps in the field. We then consider the evidence linking circadian rhythms to vaccination, an important clinical realization of immune function. Finally, we discuss practical steps to translate circadian immunity to the patient's bedside.

Chronic Inflammation Disrupts Circadian Rhythms in Splenic CD4+ and CD8+ T Cells in Mice

Internal circadian clocks coordinate 24 h rhythms in behavior and physiology. Many immune functions show daily oscillations, and cellular circadian clocks can impact immune functions and disease outcome. Inflammation may disrupt circadian clocks in peripheral tissues and innate immune cells. However, it remains elusive if chronic inflammation impacts adaptive immune cell clock, e.g., in CD4+ and CD8+ T lymphocytes. We studied this in the experimental autoimmune encephalomyelitis (EAE), a mouse model for multiple sclerosis, as an established experimental paradigm for chronic inflammation. We analyzed splenic T cell circadian clock and immune gene expression rhythms in mice with late-stage EAE, CFA/PTx-treated, and untreated mice. In both treatment groups, clock gene expression rhythms were altered with differential effects for baseline expression and peak phase compared with control mice. Most immune cell marker genes tested in this study did not show circadian oscillations in either of the three groups, but time-of-day- independent alterations were observed in EAE and CFA/PTx compared to control mice. Notably, T cell effects were likely independent of central clock function as circadian behavioral rhythms in EAE mice remained intact. Together, chronic inflammation induced by CFA/PTx treatment and EAE immunization has lasting effects on circadian rhythms in peripheral immune cells.

The durability of vaccine-induced protection: an overview

INTRODUCTION

Current vaccines vary widely in both their efficacy against infection and disease, and the durability of the efficacy. Some vaccines provide practically lifelong protection with a single dose, while others provide only limited protection following annual boosters. What variables make vaccine-induced immune responses last? Can breakthroughs in these factors and technologies help us produce vaccines with better protection and fewer doses? The durability of vaccine-induced protection is now a hot area in vaccinology research, especially after COVID-19 vaccines lost their luster. It has fueled discussion on the eventual utility of existing vaccines to society and bolstered the anti-vaxxer camp. To sustain public trust in vaccines, lasting vaccines must be developed.

AREAS COVERED

This review summarizes licensed vaccines' protection. It analyses immunological principles and vaccine and vaccinee parameters that determine longevity of antibodies. The review concludes with challenges and the way forward to improve vaccine durability.

EXPERT OPINION

Despite enormous advances, we still lack essential markers and reliable correlates of lasting protection. Most research has focused on humoral immune responses, but we must also focus on innate, mucosal, and cellular responses - their assessment, correlates, determinants, and novel adjuvants. Suitable vaccine designs and platforms for durable immunity must be found.

N-methyl-D-aspartate receptor regulates the circadian clock in megakaryocytic cells and impacts cell proliferation through BMAL1

Peripheral circadian clocks control cell proliferation and survival, but little is known about their role and regulation in megakaryocytic cells. N-methyl-D-aspartate receptor (NMDAR) regulates the central clock in the brain. The purpose of this study was to determine whether NMDAR regulates the megakaryocytic cell clock and whether the megakaryocytic clock regulates cell proliferation and cell death. We found that both the Meg-01 megakaryocytic cell line and native murine megakaryocytes expressed circadian clock genes. Megakaryocyte-directed deletion of Grin1 in mice caused significant disruption of the circadian rhythm pathway at the transcriptional level and increased expression of BMAL1 at the protein level. Similarly, both pharmacological (MK-801) and genetic (GRIN-/-) inhibition of NMDAR in Meg-01 cells in vitro resulted in widespread changes in clock gene expression including increased expression of BMAL1, the core clock transcription factor. BMAL1 overexpression reduced Meg-01 cell proliferation and altered the time-dependent expression of the cell cycle regulators MYC and WEE1, whereas BMAL1 knockdown led to increased cell death in Meg-01-GRIN1-/- cells. Our results demonstrate that NMDAR regulates the circadian clock in megakaryocytic cells and that the circadian clock component BMAL1 contributes to the control of Meg-01 cell proliferation and survival.

The Impact of Vaccination Time on the Antibody Response to an Inactivated Vaccine against SARS-CoV-2 (IMPROVE-2): A Randomized Controlled Trial

There is still controversy about whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination at different times of day will induce a stronger immune response. Therefore, a randomized controlled trial (ChiCTR2100045109) is conducted to investigate the impact of vaccination time on the antibody response to the inactivated vaccine against SARS-CoV-2 from April 15 to 28, 2021. Participants are randomly assigned in a 1:1 ratio to receive inactivated SARS-CoV-2 vaccine in the morning or afternoon. The primary endpoint is the change of neutralizing antibody between baseline and 28 days after the second dose. In total, 503 participants are randomized, and 469 participants (238 in the morning group and 231 in the afternoon group) complete the follow-up. There is no significant difference in the change of neutralizing antibody between baseline and 28 days after the second dose between the morning and afternoon groups (22.2 [13.2, 45.0] AU mL-1  vs 22.0 [14.4, 40.7] AU mL-1 , P = 0.873). In prespecified age and sex subgroup analyses, there is also no significant difference in the morning and afternoon group (all P > 0.05). This study demonstrates that the vaccination time does not affect the antibody response of two doses of inactivated SARS-CoV-2 vaccine.

Circadian clock1a coordinates neutrophil recruitment via nfe212a/duox-reactive oxygen species pathway in zebrafish

Neutrophil recruitment to inflammatory sites appears to be an evolutionarily conserved strategy to fight against exogenous insults. However, the rhythmic characteristics and underlying mechanisms of neutrophil migration on a 24-h timescale are largely unknown. Using the advantage of in vivo imaging of zebrafish, this study explored how the circadian gene clock1a dynamically regulates the rhythmic recruitment of neutrophils to inflammatory challenges. We generated a clock1a mutant and found that neutrophil migration is significantly increased in caudal fin injury and lipopolysaccharide (LPS) injection. Transcriptome sequencing, chromatin immunoprecipitation (ChIP), and dual-luciferase reporting experiments suggest that the clock1a gene regulates neutrophil migration by coordinating the rhythmic expression of nfe212a and duox genes to control the reactive oxygen species (ROS) level. This study ultimately provides a visual model to expand the understanding of the rhythmic mechanisms of neutrophil recruitment on a circadian timescale in a diurnal organism from the perspective of ROS.

Rapid increase in immune surveillance and expression of NKT and γδT cell activation markers after consuming a nutraceutical supplement containing Aloe vera gel, extracts of Poria cocos and rosemary. A randomized placebo-controlled cross-over trial

GOAL

To evaluate the acute impact of a nutraceutical blend on immune surveillance.

STUDY DESIGN

A randomized, double-blind, placebo-controlled, cross-over trial was conducted in 11 healthy subjects. Blood samples were taken immediately before and at 1, 2, and 3 hours after consuming placebo or 500 mg of UP360, which is a blend of botanicals from Aloe vera, Poria cocos, and rosemary (APR extract). Immunophenotyping and flow cytometry quantified numbers of monocytes, NK cells, NKT cells, CD8+ cytotoxic T cells, γδT cells, and total T cells, and expression of CD25 and CD69 activation markers. Plasma was tested for cytokines, chemokines, growth factors, and enzymatic activity of superoxide dismutase and catalase.

RESULTS

Compared to the placebo, consumption of APR extract triggered rapid increases in chemokine levels starting at 1 hour, including IP-10 (P<0.05) and MCP-1 (P<0.1), which peaked at 2 hours (P<0.01) and 3 hours (P<0.05), respectively. The stem cell-mobilizing growth factor G-CSF increased at 2 hours (P<0.05). Increased immune surveillance involved a transient effect for monocytes at 1 hour, followed by NKT cells, CD8+ cytotoxic T cells, and γδT cells at 2-3 hours. Increased immune cell alertness was seen at 1 hour by increased CD25 expression on monocytes (P<0.01), NKT cells (P<0.01), and T cells (P<0.05). NKT cells showed upregulation of CD69 at 2 hours (P<0.01). Increased enzymatic activity was seen at 2 hours for the antioxidant enzymes superoxide dismutase (P<0.05) and catalase (P<0.01).

CONCLUSION

Consumption of APR extract triggered acute changes to chemokine levels. In addition, immune alertness was increased via the expression of activation markers on multiple types of innate immune cells, followed by increased immune surveillance and antioxidant protection. This suggests a beneficial enhancement of natural immune surveillance, likely via a combination of gut-mediated cytokine release and vagus nerve communication, in combination with cellular protection from oxidative stress.

The circadian neutrophil, inside-out

The circadian clock has sway on a myriad of physiological targets, among which the immune and inflammatory systems are particularly prominent. In this review, we discuss how neutrophils, the wildcard of the immune system, are regulated by circadian oscillations. We describe cell-intrinsic and extrinsic diurnal mechanisms governing the general physiology and function of these cells, from purely immune to homeostatic. Repurposing the concepts discovered in other cell types, we then speculate on various uncharted avenues of neutrophil-circadian relationships, such as topology, metabolism, and the regulation of tissue clocks, with the hope of identifying exciting new avenues of work in the context of circadian immunity.

Circadian clocks in health and disease: Dissecting the roles of the biological pacemaker in cancer

In modern society, there is a growing population affected by circadian clock disruption through night shift work, artificial light-at-night exposure, and erratic eating patterns. Concurrently, the rate of cancer incidence in individuals under the age of 50 is increasing at an alarming rate, and though the precise risk factors remain undefined, the potential links between circadian clock deregulation and young-onset cancers is compelling. To explore the complex biological functions of the clock, this review will first provide a framework for the mammalian circadian clock in regulating critical cellular processes including cell cycle control, DNA damage response, DNA repair, and immunity under conditions of physiological homeostasis. Additionally, this review will deconvolute the role of the circadian clock in cancer, citing divergent evidence suggesting tissue-specific roles of the biological pacemaker in cancer types such as breast, lung, colorectal, and hepatocellular carcinoma. Recent evidence has emerged regarding the role of the clock in the intestinal epithelium, as well as new insights into how genetic and environmental disruption of the clock is linked with colorectal cancer, and the molecular underpinnings of these findings will be discussed. To place these findings within a context and framework that can be applied towards human health, a focus on how the circadian clock can be leveraged for cancer prevention and chronomedicine-based therapies will be outlined.