Cell Autonomous Circadian Systems and Their Relation to Inflammation

Research progress of circadian rhythm in cardiovascular disease: A bibliometric study from 2002 to 2022

Background

Given that the circadian rhythm is intricately linked to cardiovascular physiological functions, the objective of this investigation was to employ bibliometric visualization analysis in order to scrutinize the trends, hotspots, and prospects of the circadian rhythm and cardiovascular disease (CVD) over the past two decades.

Methods

A thorough exploration of the literature related to the circadian rhythm and CVD was conducted via the Web of Science Core Collection database spanning the years 2002-2022. Advanced software tools, including citespace and VOSviewer, were employed to carry out a comprehensive analysis of the co-occurrence and collaborative relationships among countries, institutions, journals, references, and keywords found in this literature. Furthermore, correlation mapping was executed to provide a visual representation of the data.

Results

The present study encompassed a total of 3399 published works, comprising of 2691 articles and 708 reviews. The publications under scrutiny were primarily derived from countries such as the United States, Japan, and China. The most prominent research institutions were found to be the University of Vigo, University of Minnesota, and Harvard University. Notably, the journal Chronobiology International, alongside its co-cited publications, had the most substantial contribution to the research in this field. Following an exhaustive analysis, the most frequently observed keywords were identified as circadian rhythm, blood pressure, hypertension, heart rate, heart rate variability, and melatonin. Furthermore, a nascent analysis indicated that future research might gravitate towards topics such as inflammation, metabolism, oxidative stress, and autophagy, thereby indicating new directions for investigation.

Conclusion

This analysis represents the first instance of bibliometric scrutiny pertaining to circadian rhythm and its correlation with cardiovascular disease (CVD) through the use of visualization software. Notably, this study has succeeded in highlighting the recent research frontiers and prominent trajectories in this field, thereby providing a valuable contribution to the literature.

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.

Interactions of circadian clock genes with the hallmarks of cancer

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

The role of PGE2 and EP receptors on lung's immune and structural cells; possibilities for future asthma therapy

Asthma is the most common airway chronic disease with treatments aimed mainly to control the symptoms. Adrenergic receptor agonists, corticosteroids and anti-leukotrienes have been used for decades, and the development of more targeted asthma treatments, known as biological therapies, were only recently established. However, due to the complexity of asthma and the limited efficacy as well as the side effects of available treatments, there is an urgent need for a new generation of asthma therapies. The anti-inflammatory and bronchodilatory effects of prostaglandin E2 in asthma are promising, yet complicated by undesirable side effects, such as cough and airway irritation. In this review, we summarize the most important literature on the role of all four E prostanoid (EP) receptors on the lung's immune and structural cells to further dissect the relevance of EP2/EP4 receptors as potential targets for future asthma therapy.

BMAL1/FOXA2-induced rhythmic fluctuations in IL-6 contribute to nocturnal asthma attacks

The circadian clock is closely associated with inflammatory reactions. Increased inflammatory cytokine levels have been detected in the airways of nocturnal asthma. However, the mechanisms that contribute to the nocturnal increase in inflammatory responses and the relationship with circadian clock remain unknown.

Methods

Inflammatory cytokine levels were measured in asthma patients with and without nocturnal symptoms. Allergic airway disease was induced in mice by ovalbumin (OVA), and different periods of light/dark cycles were used to induce circadian rhythm disorders. Serum shock was used to stimulate the rhythmic expression in human bronchial epidermal cells (16HBE). The expression and oscillation of circadian clock genes and inflammatory cytokines in 16HBE cells subjected to brain and muscle ARNT-like protein-1 (BMAL1) and Forkhead Box A2 (FOXA2) knockdown and treatment with a FOXA2 overexpression plasmid were assessed.

Results

Serum IL-6 was found to be significantly higher in asthmatic patients with nocturnal symptoms than those without nocturnal symptoms. The OVA-induced asthma model with a circadian rhythm disorder and 16HBE cells treated with serum shock showed an increase in IL-6 levels and a negative correlation with BMAL1 and FOXA2. The knockdown of BMAL1 resulted in a lower correlation between IL-6 and other rhythm clock genes. Furthermore, knockdown of the BMAL1 and FOXA2 in 16HBE cells reduced the expression and rhythmic fluctuations of IL-6.

Conclusions

Our findings suggest that there are increased IL-6 levels in nocturnal asthma resulting from inhibition of the BMAL1/FOXA2 signalling pathway in airway epithelial cells.

Melatonin signalling in Schwann cells during neuroregeneration

It has widely been thought that in the process of nerve regeneration Schwann cells populate the injury site with myelinating, non–myelinating, phagocytic, repair, and mesenchyme–like phenotypes. It is now clear that the Schwann cells modify their shape and basal lamina as to accommodate re–growing axons, at the same time clear myelin debris generated upon injury, and regulate expression of extracellular matrix proteins at and around the lesion site. Such a remarkable plasticity may follow an intrinsic functional rhythm or a systemic circadian clock matching the demands of accurate timing and precision of signalling cascades in the regenerating nervous system. Schwann cells react to changes in the external circadian clock clues and to the Zeitgeber hormone melatonin by altering their plasticity. This raises the question of whether melatonin regulates Schwann cell activity during neurorepair and if circadian control and rhythmicity of Schwann cell functions are vital aspects of neuroregeneration. Here, we have focused on different schools of thought and emerging concepts of melatonin–mediated signalling in Schwann cells underlying peripheral nerve regeneration and discuss circadian rhythmicity as a possible component of neurorepair.

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.

Disrupted Expression of Circadian Clock Genes in Patients with Bronchial Asthma

Purpose

Circadian clock is synchronized to the 24-hour day by the daily light–dark cycle and proper function of circadian rhythm is essential for many physiological processes. Disruption of circadian rhythm can affect disease processes and influence disease severity, treatment responses, and even survivorship. In this retrospective case-controlled study, we tried to explore whether expression of circadian clock genes was disturbed in patients with bronchial asthma.

Patients and Methods

We performed real-time quantitative reverse transcriptase-polymerase chain reactions to examine the expression of the nine core circadian clock genes (BMAL1, CK1ε, CLOCK, CRY1, CRY2, PER1, PER2, PER3, and TIM) in total leukocytes of peripheral blood collected at chest clinics from 120 patients with asthma and 60 health individuals.

Results

Expression levels of the nine circadian clock genes were significantly different between patients and healthy individuals, but not associated with the asthma control status. We also noted the difference of PER3 expression in asthmatic patients with and without nocturnal symptoms. In well-controlled asthmatics, expression of BMAL1, CK1ε, CLOCK, CRY1, CRY2, and PER1 was significantly lower in patients with nocturnal symptoms than those without nocturnal symptoms. However, in not well-controlled asthmatics, expression of only BMAL1, CK1ε, PER1, and PER2 was significantly different between patients with and without nocturnal symptoms. Binary logistic regression analysis selected BMAL1, CKIε, PER3, and TIM as independent factors for bronchial asthma and ROC curves showed the combined expression of these four genes enhanced the capability of predicting asthma (AUC=0.924; 95% CI=0.875–0.958; P<0.001).

Conclusion

Our results showed altered expression of circadian clock genes in patients with bronchial asthma and down-regulated PER3 in patients with nocturnal symptoms. Altered expression of circadian clock genes was also observed in asthmatics with or without nocturnal symptoms in well- or not well-controlled subgroups. Combined expression of BMAL1, CKIε, PER3, and TIM could be a potential predictor for bronchial asthma.