Targeting REV-ERBα for therapeutic purposes: promises and challenges

Sleep deprivation alters hepatic UGT1A9 and propofol metabolism in mice

Sleep deprivation (SD) causes circadian misalignment, and circadian clock disruption is associated with metabolic diseases such as obesity, insulin resistance, and diabetes. However, the underlying mechanism for SD-induced circadian clock disruption as well as metabolic enzyme changes is still lacking. Here, we developed SD sensitizes mice with disrupted circadian rhythms to demonstrate the regulation role and mechanism of SD in UDP-glucuronosyltransferases (UGTs) expression and the metabolism of corresponding substrates. We found that UGT Family 1 Member A9 (UGT1A9) expression was significantly decreased in the liver of SD mice, which led to an elevation exposure and prolonged anesthesia effect of propofol, which was attributed to the decreased metabolism. Meanwhile, SD down-regulated basic helix-loop-helix ARNT like 1 (BMAL1) and its target clock genes period circadian clock (Per), cryptochrome circadian regulator (Cry), and nuclear receptor subfamily 1 group D member 1 (Rev-erb) expression in mice. Furthermore, the positive regulation of UGTIA9 mRNA and protein levels by Bmal1 was confirmed in hepatocyte-specific Bmal1-knockout mice (Bmal1-hkO) and Bmal1-overexpressed AML-12 cells. At last, through a combination of promoter analysis, luciferase reporter assay, and chromatin immunoprecipitation (ChIP) assay, it was conducted that Bmal1 regulates Ugtla9 expression by directly binding the -864 bp E-box in Ugtla9 promotor or indirectly acting on the Rev-erbα- differentiated embryo chondrocyte 2 (Dec2) axis. In conclusion, our findings suggested that SD can lead to altered drug disposition and effects in vivo, and Bmal1 plays a crucial role in the crosstalk between SD-induced circadian clock disruption and drug metabolism. It initiates a new direction for the understanding of drug efficacy and toxicity changes in SD conditions and provides a scientific basis for improving the rationality of drug use.

Chronobiotics: classifications of existing circadian clock modulators, future perspectives

The review summarizes recent achievements and future prospects in the use of chronobiotics for regulating circadian rhythms regulation. Special attention is paid to the mechanisms' action, their classification, and the impact of chemical interventions on the biological clock. Chronobiotics defined as a diverse group of compounds capable of restoring disrupted circadian functions, addressing challenges such as irregular work schedules, artificial light exposure or ageing. The review categorizes these compounds by their pharmacological effects, molecular targets, and chemical structures, underlining their ability to enhance or inhibit key circadian components like CLOCK, BMAL1, PER, and CRY. A particular focus is placed on the therapeutic applications of chronobiotics, including their potential for treating sleep disorders, metabolic issues, and age-related rhythm disturbances, underscoring their wide-ranging applicability in health care. Chronobiotic compounds have promising roles in maintaining physiological rhythms, supporting healthy aging, and enhancing personalised health care. Given their diverse therapeutic potential, chronobiotics are positioned as a significant avenue for further clinical application, marking them as a crucial area of ongoing research and innovation.

Nuclear receptor Rev-erbα alleviates intervertebral disc degeneration by recruiting NCoR-HDAC3 co-repressor and inhibiting NLRP3 inflammasome

Intervertebral discs (IVDs) are rhythmic tissues that experience daily low-load recovery. Notably, aging and abnormal mechanical stress predispose IVDs to degeneration due to dysrhythmia-induced disordered metabolism. Meanwhile, Rev-erbα acts as a transcriptional repressor in maintaining biorhythms and homeostasis; however, its function in IVD homeostasis and degeneration remains unclear. This study assessed the relationship between low Rev-erbα expression levels and IVD degeneration. Rev-erbα deficiency accelerated needle puncture or aging-induced IVD degeneration, characterized by increased extracellular matrix (ECM) catabolism and nucleus pulposus (NP) cell apoptosis. Mechanistically, Rev-erbα knockdown in NP cells aggravated rhIL1β-induced NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome activation, exacerbating the imbalanced ECM and NP cell apoptosis. Meanwhile, blocking NLRP3 inflammasome activation mitigated Rev-erbα deficiency and needle puncture-induced IVD degeneration. Particularly, Rev-erbα mediated the transcriptional repression of the NLRP3 inflammasome via the ligand heme-binding of nuclear receptor co-repressor (NCoR) and histone deacetylase 3 (HDAC3) complex. Thus, the increased expression of Rev-erbα in NP cells following short-term rhIL1β treatment failed to inhibit NLRP3 transcription in vitro owing to heme depletion. Pharmacological activation of Rev-erbα in vivo and in vitro alleviated IVD degeneration by altering the NLRP3 inflammasome. Taken together, targeting Rev-erbα may be a potential therapeutic strategy for alleviating IVD degeneration and its related diseases.

NR1D1 activation alleviates inflammatory response through inhibition of IL-6 expression in bovine endometrial epithelial cells

Endometritis, an inflammatory disease affecting dairy cattle, causes substantial economic losses in the dairy industry. Conventional treatment using uterine infusion of antibiotics often results in bacterial resistance and antibiotic residues in milk. Thus, identifying novel, effective therapeutic targets for endometritis in dairy cows is necessary. Nuclear receptor subfamily 1 group D member 1 (NR1D1) activation attenuates inflammatory responses in various diseases through transcriptional repression; however, its role in treating bovine endometritis remains unclear. This study investigated the role and underlying mechanisms of NR1D1 in endometritis using a bovine endometrial epithelial cell line (BENDs) and primary bovine endometrial epithelial cells, both induced with Escherichia coli lipopolysaccharide (LPS). Immunofluorescence staining revealed the predominant nuclear localization of NR1D1 in endometrial epithelial cells. LPS treatment (1 μg/mL for 12 h) significantly increased the expression levels of NR1D1 and proinflammatory cytokines (IL-6, IL-1β, IL-8, and CCL5) in BENDs. Immunohistochemical staining showed elevated NR1D1 expression in uterine tissues of cows with endometritis. Deletion of NR1D1 significantly increased IL-6 mRNA expression; NR1D1 overexpression substantially repressed IL-6 expression in BENDs. NR1D1 agonist SR9009 attenuated LPS-induced mRNA expression of proinflammatory cytokines (IL-6, IL-1β, CCL5) in both BENDs and primary endometrial epithelial cells. Additionally, SR9009 treatment attenuated LPS-induced inflammatory responses in the endometrium of mice. Dual-luciferase reporter assays and real-time monitoring via luminescence assays showed that NR1D1 overexpression significantly repressed luciferase activity driven by the IL-6 promoter region, which was abolished by deletion of the retinoic acid receptor-related orphan receptor-responsive element (-473 to -479) within the IL-6 promoter fragment. In summary, NR1D1 activation alleviates the inflammatory response of BENDs by repressing the expression of proinflammatory cytokines, at least partly via IL-6, suggesting NR1D1 is a promising therapeutic target for endometritis prevention and treatment.

Nr1d1 inhibition mitigates intermittent hypoxia-induced pulmonary hypertension via Dusp1-mediated Erk1/2 deactivation and mitochondrial fission attenuation

Intermittent hypoxia (IH) precipitates pulmonary vasoconstriction, culminating in the onset of pulmonary hypertension (PH) among individuals afflicted with sleep apnea. While Nuclear receptor subfamily 1 group D member 1 (Nr1d1) is progressively recognized as pivotal regulator of cellular physiology, the role in the pathogenesis of IH-induced PH remains largely uncharted. The expression of Nr1d1 was examined in IH-induced rodent PH and in IH-treated PASMCs. To elucidate the contribution of Nr1d1 to the development of IH-induced PH, we employed siRNA to modulate Nr1d1 expression in vitro and employed serotype 1 adeno-associated virus (AAV1) in vivo. Nr1d1 levels were elevated in IH-induced rodents PH lung tissues and IH-treated PASMCs. Knocking down Nr1d1 by AAV1 effectively inhibited PH progression in chronic IH-induced PH models. Mechanistic investigations identified dual specificity phosphatase 1 (Dusp1), as a direct target that Nr1d1 trans-repressed, mediating Nr1d1's regulatory influence on Erk1/2/Drp1 signaling. Nr1d1 deficiency ameliorates mitochondrial dysfunction and fission by restoring Dusp1 dysregulation and Drp1 phosphorylation. Activation of Erk1/2 with PMA reversed the Dusp1-mediated regulation of Drp1 phosphorylation, indicating the involvement of the Erk1/2 pathway in Drp1 phosphorylation controlled by Dusp1. Meanwhile, intermittent hypoxia induced more severe PH in Dusp1 knockout mice compared with wild-type mice. Our data unveil a novel role for Nr1d1 in IH-induced PH pathogenesis and an undisclosed Nr1d1-Dusp1 axis in PASMCs mitochondrial fission regulation.

A New Frontier in Cystic Fibrosis Pathophysiology: How and When Clock Genes Can Affect the Inflammatory/Immune Response in a Genetic Disease Model

Cystic fibrosis (CF) is a monogenic syndrome caused by variants in the CF Transmembrane Conductance Regulator (CFTR) gene, affecting various organ and systems, in particular the lung, pancreas, sweat glands, liver, gastrointestinal tract, vas deferens, and vascular system. While for some organs, e.g., the pancreas, a strict genotype-phenotype occurs, others, such as the lung, display a different pathophysiologic outcome in the presence of the same mutational asset, arguing for genetic and environmental modifiers influencing severity and clinical trajectory. CFTR variants trigger a pathophysiological cascade of events responsible for chronic inflammatory responses, many aspects of which, especially related to immunity, are not ascertained yet. Although clock genes expression and function are known modulators of the innate and adaptive immunity, their involvement in CF has been only observed in relation to sleep abnormalities. The aim of this review is to present current evidence on the clock genes role in immune-inflammatory responses at the lung level. While information on this topic is known in other chronic airway diseases (chronic obstructive pulmonary disease and asthma), CF lung disease (CFLD) is lacking in this knowledge. We will present the bidirectional effect between clock genes and inflammatory factors that could possibly be implicated in the CFLD. It must be stressed that besides sleep disturbance and its mechanisms, there are not studies directly addressing the exact nature of clock genes' involvement in inflammation and immunity in CF, pointing out the directions of new and deepened studies in this monogenic affection. Importantly, clock genes have been found to be druggable by means of genetic tools or pharmacological agents, and this could have therapeutic implications in CFLD.

Comprehensive analysis of distinct circadian clock subtypes of adult diffuse glioma and their associations with clinicopathological, genetic, and epigenetic profiles

The circadian clock (CC) has biological and clinical implications in gliomas. Most studies focused on CC effects on the tumor microenvironment and the application of chronotherapy. The present study focused on CC gene expression patterns and intracellular oncogenic activities. Glioma gene expression data were collected from The Human Cancer Genome Atlas (TCGA) project. After applying inclusion and exclusion criteria, we selected 666 patients from TCGA-GBM and TCGA-LGG projects and included important clinicopathological variables. The entire cohort was subjected to clustering analysis and divided into CC1 and CC2 subtypes based on statistical, biological, and clinical criteria. CC2 gliomas showed higher expression of BMAL1 and CRY1 and lower expression of CRY2 and PER2 (adjusted P < .001). CC2 gliomas had q higher activity of cell proliferation, metabolic reprogramming, angiogenesis, hypoxia, and many oncogenic signals (P < .001). The CC2 subtype contained a higher proportion of glioblastomas (P < .001) and had a worse prognosis (P < .001). Stratified Kaplan-Meier and multivariable Cox analyses illustrated that the CC subtype is an independent prognostic factor to clinicopathological characteristics (P < .001), genetic aberrations (P = .006), and biological processes (P < .001). Thus, this study shows statistical evidence of CC subtypes and their biological, and clinicopathological significance in adult gliomas.

Nuclear receptor Rev-erbα role in fine-tuning erythropoietin gene expression

ABSTRACT

The regulation of red blood cell (RBC) homeostasis by erythropoietin (EPO) is critical for O2 transport and maintaining the adequate number of RBCs in vertebrates. Therefore, dysregulation in EPO synthesis results in disease conditions such as polycythemia in the case of excessive EPO production and anemia, which occurs when EPO is inadequately produced. EPO plays a crucial role in treating anemic patients; however, its overproduction can increase blood viscosity, potentially leading to fatal heart failure. Consequently, the identification of druggable transcription factors and their associated ligands capable of regulating EPO offers a promising therapeutic approach to address EPO-related disorders. This study unveils a novel regulatory mechanism involving 2 pivotal nuclear receptors (NRs), Rev-ERBA (Rev-erbα, is a truncation of reverse c-erbAa) and RAR-related orphan receptor A (RORα), in the control of EPO gene expression. Rev-erbα acts as a cell-intrinsic negative regulator, playing a vital role in maintaining erythropoiesis at the correct level. It accomplishes this by directly binding to newly identified response elements within the human and mouse EPO gene promoter, thereby repressing EPO production. These findings are further supported by the discovery that a Rev-erbα agonist (SR9011) effectively suppresses hypoxia-induced EPO expression in mice. In contrast, RORα functions as a positive regulator of EPO gene expression, also binding to the same response elements in the promoter to induce EPO production. Finally, the results of this study revealed that the 2 NRs, Rev-erbα and RORα, influence EPO synthesis in a negative and positive manner, respectively, suggesting that the modulating activity of these 2 NRs could provide a method to target disorders linked with EPO dysregulation.

BMAL1 sex-specific effects in the neonatal mouse airway exposed to moderate hyperoxia

Supplemental O2 (hyperoxia) is a critical intervention for premature infants (<34 weeks) but consequently is associated with development of bronchial airway hyperreactivity (AHR) and asthma. Clinical practice shifted toward the use of moderate hyperoxia (<60% O2), but risk for subsequent airway disease remains. In mouse models of moderate hyperoxia, neonatal mice have increased AHR with effects on airway smooth muscle (ASM), a cell type involved in airway tone, bronchodilation, and remodeling. Understanding mechanisms by which moderate O2 during the perinatal period initiates sustained airway changes is critical to drive therapeutic advancements toward treating airway diseases. We propose that cellular clock factor BMAL1 is functionally important in developing mouse airways. In adult mice, cellular clocks target pathways highly relevant to asthma pathophysiology and Bmal1 deletion increases inflammatory response, worsens lung function, and impacts survival outcomes. Our understanding of BMAL1 in the developing lung is limited, but our previous findings show functional relevance of clocks in human fetal ASM exposed to O2. Here, we characterize Bmal1 in our established mouse neonatal hyperoxia model. Our data show that Bmal1 KO deleteriously impacts the developing lung in the context of O2 and these data highlight the importance of neonatal sex in understanding airway disease.

The role of ferroptosis in acute kidney injury: mechanisms and potential therapeutic targets

Acute kidney injury (AKI) is one of the most common and severe clinical renal syndromes with high morbidity and mortality. Ferroptosis is a form of programmed cell death (PCD), is characterized by iron overload, reactive oxygen species accumulation, and lipid peroxidation. As ferroptosis has been increasingly studied in recent years, it is closely associated with the pathophysiological process of AKI and provides a target for the treatment of AKI. This review offers a comprehensive overview of the regulatory mechanisms of ferroptosis, summarizes its role in various AKI models, and explores its interaction with other forms of cell death, it also presents research on ferroptosis in AKI progression to other diseases. Additionally, the review highlights methods for detecting and assessing AKI through the lens of ferroptosis and describes potential inhibitors of ferroptosis for AKI treatment. Finally, the review presents a perspective on the future of clinical AKI treatment, aiming to stimulate further research on ferroptosis in AKI.

REV-ERBα negatively regulates NLRP6 transcription and reduces the severity of Salmonella infection in mice

Non-typhoidal Salmonella infection is among the most frequent foodborne diseases threatening human health worldwide. The host circadian clock orchestrates daily rhythms to adapt to environmental changes, including coordinating immune function in response to potential infections. However, the molecular mechanisms underlying the interplay between the circadian clock and the immune system in modulating infection processes are incompletely understood. Here, we demonstrate that NLRP6, a novel nucleotide-oligomerization domain (NOD)-like receptor (NLR) family member highly expressed in the intestine, is closely associated with the differential day-night response to Salmonella infection. The core clock component REV-ERBα negatively regulates NLRP6 transcription, leading to the rhythmic expression of NLRP6 and the secretion of IL-18 in intestinal epithelial cells, playing a crucial role in mediating the differential day-night response to Salmonella infection. Activating REV-ERBα with agonist SR9009 in wild-type mice attenuated the severity of infection by decreasing the NLRP6 level in intestinal epithelial cells. Our findings provide new insights into the association between the host circadian clock and the immune response to enteric infections by revealing the regulation of Salmonella infection via the inhibitory effect of REV-ERBα on NLRP6 transcription. Targeting REV-ERBα to modulate NLRP6 activation may be a potential therapeutic strategy for bacterial infections.

Mitophagy Regulates the Circadian Rhythms by Degrading NR1D1 in Simulated Microgravity and Isolation Environments

Long-term spaceflight is known to induce disruptions in circadian rhythms, which are driven by a central pacemaker located in the suprachiasmatic nucleus (SCN) of the hypothalamus, but the underlying molecular mechanisms remain unclear. Here, we developed a rat model that simulated microgravity and isolation environments through tail suspension and isolation (TSI). We found that the TSI environment imposed circadian disruptions to the core body temperature, heart rate, and locomotor-activity rhythms of rats, especially in the amplitude of these rhythms. In TSI model rats' SCNs, the core circadian gene NR1D1 showed higher protein but not mRNA levels along with decreased BMAL1 levels, which indicated that NR1D1 could be regulated through post-translational regulation. The autophagosome marker LC3 could directly bind to NR1D1 via the LC3-interacting region (LIR) motifs and induce the degradation of NR1D1 in a mitophagy-dependent manner. Defects in mitophagy led to the reversal of NR1D1 degradation, thereby suppressing the expression of BMAL1. Mitophagy deficiency and subsequent mitochondrial dysfunction were observed in the SCN of TSI models. Urolithin A (UA), a mitophagy activator, demonstrated an ability to enhance the amplitude of core body temperature, heart rate, and locomotor-activity rhythms by prompting mitophagy induction to degrade NR1D1. Cumulatively, our results demonstrate that mitophagy exerts circadian control by regulating NR1D1 degradation, revealing mitophagy as a potential target for long-term spaceflight as well as diseases with SCN circadian disruption.

Deciphering the diurnal rhythm regulating mechanism of flavin-containing monooxygenase 3 in mouse liver

Circadian genes play an important role in the field of drug metabolism. Flavin-containing monooxygenase 3 is a well-known phase I enzyme which participates in metabolism of many exogenous and endogenous substances, especially production of trimethylamine N-oxide. Here, we aimed to decipher diurnal rhythms of flavin-containing monooxygenase 3 expression and activity, and explore the regulation mechanism by clock genes. Our results showed that its mRNA and protein exhibited robust diurnal rhythms in mouse liver and cell lines. Consistently, significant alterations were observed for in vitro microsomal N-oxidation rates of procainamide, which kept in line with its protein expression at different time in wild-type and reverse erythroblastosis virus α knockout mice. Further, flavin-containing monooxygenase 3 was negatively regulated by E4 promoter-binding protein 4 in AML12 and Hepa1-6 cells, while it was positively influenced by reverse erythroblastosis virus α and brain and muscle ARNT-like protein-1. Moreover, luciferase reporter assays and electrophoretic mobility shift assays showed E4 promoter-binding protein 4 inhibited the transcription of flavin-containing monooxygenase 3 by binding to a D-box1 element (-1606/-1594 bp), while brain and muscle ARNT-like protein-1 positively activated the transcription via direct binding to three E-boxes (-863/-858 bp, -507/-498 bp, and -115/-104 bp) in this enzyme promoter. Taken together, this study would be helpful to reveal the mechanism of clock-controlled drug metabolism and facilitate the practice of chrono-therapeutics.

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.

Pterostilbene targets the molecular oscillator RORγ to restore circadian rhythm oscillation and protect against sleep restriction induced metabolic disorders

BACKGROUND

Considerable researches have directed toward metabolic disorders caused by sleep restriction (SR). SR-induced disruption of circadian metabolic rhythmicity is identified as an important pathophysiological mechanism. The flavonoid pterostilbene (PTE) is abundant in the traditional Chinese medicine dragon's blood with protective efficacy against obesity-related metabolic dysfunctions. Our previous study found that PTE ameliorates exercise intolerance and clock gene oscillation in the skeletal muscles subjected to SR.

PURPOSE

This study aimed to explore whether PTE improves SR-induced metabolic disorders and delineate the relationship between PTE and the circadian clock.

STUDY DESIGN AND METHODS

Two hundred male C57/B6J mice were kept awake for 20 h/d over five consecutive days and concurrently gavaged with 50, 100, or 200 mg/kg·bw/d PTE. Food consumption and body weight were monitored, and the metabolic status of the mice was evaluated by performing OGTT and ITT, measuring the serum lipid profiles and liver histopathology in response to SR. Daily behavior was analyzed by Clocklab™. The circadian rhythms of the liver clock genes and metabolic output genes were evaluated by cosine analysis. Binding between PTE and RORα/γ or NR1D1/2 was investigated by molecular docking. A luciferase reporter assay was used to determine the impact of PTE on Bmal1 transcription in SR-exposed mice co-transfected with Ad-BMAL1-LUC plus Ad-RORγ-mCherry or Ad-NR1D1-EGFP.

RESULTS

PTE significantly ameliorated abnormal glucose and lipid metabolism (p < 0.05) in SR-exposed mice. PTE improved circadian behavior (p < 0.05) and rescued the circadian rhythm oscillation of the liver clock (p < 0.05) and metabolic output genes (p < 0.05) under SR condition. Molecular docking disclosed that PTE might interact with RORs, and PTE was found to increase Bmal1 promoter luciferase activity with RORE elements in the presence of Ad-RORγ-mCherry (p < 0.05).

CONCLUSIONS

PTE may protect against SR-induced metabolic disorders by directly modulating RORγ to maintain circadian metabolic rhythm. The findings provide valuable insights into the potential use of PTE in the treatment of metabolic disorders associated with disruptions in the circadian rhythm.

Depletion of ApoA5 aggravates spontaneous and diet-induced nonalcoholic fatty liver disease by reducing hepatic NR1D1 in hamsters

Background: ApoA5 mainly synthesized and secreted by liver is a key modulator of lipoprotein lipase (LPL) activity and triglyceride-rich lipoproteins (TRLs). Although the role of ApoA5 in extrahepatic triglyceride (TG) metabolism in circulation has been well documented, the relationship between ApoA5 and nonalcoholic fatty liver disease (NAFLD) remains incompletely understood and the underlying molecular mechanism still needs to be elucidated. Methods: We used CRISPR/Cas9 gene editing to delete Apoa5 gene from Syrian golden hamster, a small rodent model replicating human metabolic features. Then, the ApoA5-deficient (ApoA5-/-) hamsters were used to investigate NAFLD with or without challenging a high fat diet (HFD). Results: ApoA5-/- hamsters exhibited hypertriglyceridemia (HTG) with markedly elevated TG levels at 2300 mg/dL and hepatic steatosis on a regular chow diet, accompanied with an increase in the expression levels of genes regulating lipolysis and small adipocytes in the adipose tissue. An HFD challenge predisposed ApoA5-/- hamsters to severe HTG (sHTG) and nonalcoholic steatohepatitis (NASH). Mechanistic studies in vitro and in vivo revealed that targeting ApoA5 disrupted NR1D1 mRNA stability in the HepG2 cells and the liver to reduce both mRNA and protein levels of NR1D1, respectively. Overexpression of human NR1D1 by adeno-associated virus 8 (AAV8) in the livers of ApoA5-/- hamsters significantly ameliorated fatty liver without affecting plasma lipid levels. Moreover, restoration of hepatic ApoA5 or activation of UCP1 in brown adipose tissue (BAT) by cold exposure or CL316243 administration could significantly correct sHTG and hepatic steatosis in ApoA5-/- hamsters. Conclusions: Our data demonstrate that HTG caused by ApoA5 deficiency in hamsters is sufficient to elicit hepatic steatosis and HFD aggravates NAFLD by reducing hepatic NR1D1 mRNA and protein levels, which provides a mechanistic link between ApoA5 and NAFLD and suggests the new insights into the potential therapeutic approaches for the treatment of HTG and the related disorders due to ApoA5 deficiency in the clinical trials in future.

Functional Characterization of Circadian Nuclear Receptors REV-ERBα and REV-ERBβ in Human Osteosarcoma Cell Cultures

REV-ERBα and its paralog, REV-ERBβ, encoded by NR1D1 and NR1D2 genes, are key nuclear receptors that link the circadian timing system and metabolic homeostasis. Since heme is an endogenous ligand, REV-ERBs have been considered key components of the circadian molecular clock and can be pharmacologically targeted to treat various circadian rhythm-related diseases, such as cardiometabolic, inflammatory, and neuropsychiatric diseases, as well as cancer. REV-ERBs are believed to be functionally redundant and compensatory, although they often affect the expression of gene subsets in an isoform-specific manner. Therefore, this study aimed to identify the redundant and distinct roles of each isoform in controlling its target genes by comparing the transcriptome profiles of a panel of mutant U2OS human osteosarcoma cells in which either NR1D1 or NR1D2 was ablated. Indeed, our transcriptomic analyses revealed that most REV-ERB-regulated genes are controlled by redundant or even additive actions. However, the RNA expression profiles of each single mutant cell line also provide strong evidence for isoform-dependent actions. For example, REV-ERBα is more responsible for regulating the NF-κΒ signaling pathway, whereas a group of extracellular matrix components requires REV-ERBβ to maintain their expression. We found that REV-ERBs have isoform-selective functions in the regulation of certain circadian output pathways despite their overlapping roles in the circadian molecular clock. Thus, the development of isoform-selective REV-ERB modulators can help treat metabolic disturbances and certain types of cancer.

Recent Advances in Hepatic Metabolic Regulation by the Nuclear Factor Rev-erbɑ

Rev-erbɑ (NR1D1) is a nuclear receptor superfamily member that plays a vital role in mammalian molecular clocks and metabolism. Rev-erbɑ can regulate the metabolism of drugs and the body's glucose metabolism, lipid metabolism, and adipogenesis. It is even one of the important regulatory factors regulating the occurrence of metabolic diseases (e.g., diabetes, fatty liver). Metabolic enzymes mediate most drug metabolic reactions in the body. Rev-erbɑ has been recognized to regulate drug metabolic enzymes (such as Cyp2b10 and Ugt1a9). Therefore, this paper mainly reviewed that Rev-erbɑ regulates I and II metabolic enzymes in the liver to affect drug pharmacokinetics. The expression of these drug metabolic enzymes (up-regulated or down-regulated) is related to drug exposure and effects/ toxicity. In addition, our discussion extends to Rev-erbɑ regulating some transporters (such as P-gp, Mrp2, and Bcrp), as they also play an essential role in drug metabolism. Finally, we briefly describe the role and mechanism of nuclear receptor Rev-erbɑ in lipid and glucose homeostasis, obesity, and metabolic disorders syndrome. In conclusion, this paper aims to understand better the role and mechanism of Rev-erbɑ in regulating drug metabolism, lipid, glucose homeostasis, obesity, and metabolic disorders syndrome, which explores how to target Rev-erbɑ to guide the design and development of new drugs and provide scientific reference for the molecular mechanism of new drug development, rational drug use, and drug interaction.

Targeting NR1D1 in organ injury: challenges and prospects

Nuclear receptor subfamily 1, group D, member 1 (NR1D1, also known as REV-ERBα) belongs to the nuclear receptor (NR) family, and is a heme-binding component of the circadian clock that consolidates circadian oscillators. In addition to repressing the transcription of multiple clock genes associated with circadian rhythms, NR1D1 has a wide range of downstream target genes that are intimately involved in many physiopathological processes, including autophagy, immunity, inflammation, metabolism and aging in multiple organs. This review focuses on the pivotal role of NR1D1 as a key transcription factor in the gene regulatory network, with particular emphasis on the milestones of the latest discoveries of NR1D1 ligands. NR1D1 is considered as a promising drug target for treating diverse diseases and may contribute to research on innovative biomarkers and therapeutic targets for organ injury-related diseases. Further research on NR1D1 ligands in prospective human trials may pave the way for their clinical application in many organ injury-related disorders.

Si-Ni-San reverses dietary fat absorption defects in a murine model of depression

Depression is often associated with fatigue/energy loss. However, we lack a detailed understanding of the factors explaining this association. In this study, we uncovered that depressed mice have a defect in fat absorption, resulting in weight loss and reduced circulating lipid levels. Si-Ni-San (SNS), a basic formula of traditional Chinese medicine (TCM) for the treatment of depression, was found to not only alleviate depression-like behaviors, but also reverse the weight loss and dietary fat absorption of depressed mice. We found that SNS improved body weight and circulating lipid levels of depressed mice by up-regulating proteins [such as FFA uptake protein (CD36), TAG synthesis proteins (GPAT3, MOGAT2, DGAT1 and DGAT2) and chylomicron packaging proteins (MTP and APOB)] in the fat absorption pathway. Furthermore, cell-based results conducted with LPS-stimulated mouse MODE-K and human Caco-2 cells support that SNS, as well as Sinensetin (SIN) and Nobiletin (NOB), the two active components of the formula, have a role in regulating lipid absorption. Mechanistic studies revealed that SNS reverses body weight and fat absorption defects of depressed mice in part through the NR1D1/BMAL1/DGAT2 axis. These findings advance our understanding of the crosstalk between depression and energy loss, highlight the importance of gut function in disease management, and provide a basis for the application of SNS in the clinical treatment of depression and related disorders.

International Union of Basic and Clinical Pharmacology CXIII: Nuclear Receptor Superfamily-Update 2023

The NR superfamily comprises 48 transcription factors in humans that control a plethora of gene network programs involved in a wide range of physiologic processes. This review will summarize and discuss recent progress in NR biology and drug development derived from integrating various approaches, including biophysical techniques, structural studies, and translational investigation. We also highlight how defective NR signaling results in various diseases and disorders and how NRs can be targeted for therapeutic intervention via modulation via binding to synthetic lipophilic ligands. Furthermore, we also review recent studies that improved our understanding of NR structure and signaling. SIGNIFICANCE STATEMENT: Nuclear receptors (NRs) are ligand-regulated transcription factors that are critical regulators of myriad physiological processes. NRs serve as receptors for an array of drugs, and in this review, we provide an update on recent research into the roles of these drug targets.

Effect of miR-34a on the expression of clock and clock-controlled genes in DLD1 and Lovo human cancer cells with different backgrounds with respect to p53 functionality and 17β-estradiol-mediated regulation

The small non-coding RNA miR-34a is a p53-regulated miRNA that acts as a tumour suppressor of colorectal cancer (CRC). Oncogenesis is also negatively influenced by deregulation of the circadian system in many types of tumours with various genetic backgrounds. As the clock gene per2 was recently recognized as one of the target genes of miR-34a, we focused on the miR-34a-mediated influence on the circadian oscillator in CRC cell lines DLD1 and LoVo, which differ in their p53 status. Previously, a sex-dependent association between the expression of per2 and that of miR-34a was demonstrated in CRC patients. Therefore, we also investigated the effect of 17β-estradiol (E2) on miR-34a oncostatic functions. miR-34a mimic caused a pronounced inhibition of per2 expression in both cell lines. Moreover, miR-34a mimic significantly inhibited bmal1 expression in LoVo and rev-erbα expression in DLD1 cells and induced clock gene expression in both cell lines. miR-34a mimic caused a pronounced decrease in sirt1 and cyclin D1 expression, which may be related to the inhibition of proliferation observed after mir-34a administration in DLD1 cells. E2 administration inhibited the migration and proliferation of DLD1 cells. E2 and miR-34a, when administered simultaneously, did not potentiate each other's effects. To conclude, miR-34a strongly influences the expression of components of the circadian oscillator without respect to p53 status and exerts its oncostatic effects via inhibition of sirt1 and cyclin D1 mRNA expression. E2 administration inhibits the growth of DLD1 cells; however, this effect seems to be independent of miR-34a-mediated action. With respect to the possible use of miR-34a in cancer treatment, clock genes can be considered as off-target genes, as changes in their expression induced by miR-34a treatment do not contribute to the oncostatic functions of miR-34a. Possible ambiguous oncogenic characteristics should be taken into consideration in future clinical studies focused on miR-34a.

Targeting Rev-Erbα to protect against ischemia-reperfusion-induced acute lung injury in rats

BACKGROUND

The dysregulation of local circadian clock has been implicated in the pathogenesis of a broad spectrum of diseases. However, the pathophysiological role of intrinsic circadian clocks Rev-Erbα in ischemia-reperfusion (IR)-induced acute lung injury (ALI) remains unclear.

METHODS

The IR-ALI model was established by subjecting isolated perfused rat lungs to 40 min of ischemia followed by 60 min of reperfusion. Rats were randomly assigned to one of six groups: control, control + SR9009 (Rev-Erbα agonist, 50 mg/kg), IR, and IR + SR9009 at one of three dosages (12.5, 25, 50 mg/kg). Bronchoalveolar lavage fluids (BALF) and lung tissues were obtained and analyzed. In vitro experiments utilized mouse lung epithelial cells (MLE-12) exposed to hypoxia-reoxygenation (HR) and pretreated with SR9009 (10 µM/L) and Rev-Erbα siRNA.

RESULTS

SR9009 exhibited a dose-dependent reduction in lung edema in IR-ALI. It significantly inhibited the production of TNF-α, IL-6, and CINC-1 in BALF. Moreover, SR9009 treatment restored suppressed IκB-α levels and reduced nuclear NF-κB p65 levels in lung tissues. In addition, a SR9009 mitigated IR-induced apoptosis and mitogen-activated protein kinase (MAPK) activation in injured lung tissue. Finally, treatment with Rev-Erbα antagonist SR8278 abolished the protective action of SR9009. In vitro analyses showed that SR9009 attenuated NF-κB activation and KC/CXCL-1 levels in MLE-12 cells exposed to HR, and these effects were significantly abrogated by Rev-Erbα siRNA.

CONCLUSIONS

The findings suggest that SR9009 exerts protective effects against IR-ALI in a Rev-Erbα-dependent manner. SR9009 may provide a novel adjuvant therapeutic approach for IR-ALI.

NR1D1 Stimulates Antitumor Immune Responses in Breast Cancer by Activating cGAS-STING Signaling

Potentiating antitumor immunity is a promising therapeutic approach for treating a variety of cancers, including breast cancer. One potential strategy to promote antitumor immunity is targeting DNA damage response. Given that the nuclear receptor NR1D1 (also known as REV-ERBα) inhibits DNA repair in breast cancer cells, we explored the role of NR1D1 in antitumor CD8+ T-cell responses. First, deletion of Nr1d1 in MMTV-PyMT transgenic mice resulted in increased tumor growth and lung metastasis. Orthotopic allograft experiments suggested that loss of Nr1d1 in tumor cells rather than in stromal cells played a prominent role in increasing tumor progression. Comprehensive transcriptome analyses revealed that biological processes including type I IFN signaling and T cell-mediated immune responses were associated with NR1D1. Indeed, the expression of type I IFNs and infiltration of CD8+ T cells and natural killer cells in tumors were suppressed in Nr1d1-/-;MMTV-PyMT mice. Mechanistically, NR1D1 promoted DNA damage-induced accumulation of cytosolic DNA fragments and activated cGAS-STING signaling, which increased the production of type I IFNs and downstream chemokines CCL5 and CXCL10. Pharmacologic activation of NR1D1 by its ligand, SR9009, enhanced type I IFN-mediated antitumor immunity accompanied by the suppression of tumor progression and lung metastasis. Taken together, these findings reveal the critical role of NR1D1 in enhancing antitumor CD8+ T-cell responses, suggesting that NR1D1 may be a good therapeutic target for breast cancer.

SIGNIFICANCE

NR1D1 suppresses breast cancer progression and lung metastasis by enhancing antitumor immunity via cGAS-STING pathway activation, which provides potential immunotherapeutic strategies for breast cancer.

Daily rhythms of REV-ERBα and its role as transcriptional repressor of clock genes in fish hepatic oscillator

The REV-ERBα nuclear receptor is a key component of the molecular machinery of circadian oscillators in mammals. While the rhythmic expression of this receptor has been described in teleosts, several critical aspects of its regulation remain unknown, such as which synchronizers entrain its rhythm, and whether it can modulate the expression of other clock genes. The objective of this study was to gain deeper understanding of the role of REV-ERBα in the fish circadian system. To this end, we first investigated the cues that entrain the rhythm of rev-erbα expression in the goldfish (Carassius auratus) liver and hypothalamus. A 12-h shift in feeding time induced a parallel shift in the hepatic rhythm of rev-erbα expression, confirming that this gene is food-entrainable in the goldfish liver. In contrast, light seems the main driver of rev-erbα rhythmic expression in the hypothalamus. Next, we examined the effects of REV-ERBα activation on locomotor activity and hepatic expression of clock genes. Subchronic treatment with the REV-ERBα agonist SR9009 slightly decreased locomotor activity anticipating light onset and food arrival, and downregulated hepatic bmal1a, clock1a, cry1a, per1a and pparα expression. This generalized repressing action of REV-ERBα on the expression of hepatic clock genes was confirmed in vitro by using agonists (SR9009 and GSK4112) and antagonist (SR8278) of this receptor. Overall, the present work reveals that REV-ERBα modulates the daily expression of the main genes of the teleostean liver clock, reinforcing its role in the liver temporal homeostasis, which seems highly conserved in both fish and mammals.

Microglial REV-ERBα regulates inflammation and lipid droplet formation to drive tauopathy in male mice

Alzheimer's disease, the most common age-related neurodegenerative disease, is characterized by tau aggregation and associated with disrupted circadian rhythms and dampened clock gene expression. REV-ERBα is a core circadian clock protein which also serves as a nuclear receptor and transcriptional repressor involved in lipid metabolism and macrophage function. Global REV-ERBα deletion has been shown to promote microglial activation and mitigate amyloid plaque formation. However, the cell-autonomous effects of microglial REV-ERBα in healthy brain and in tauopathy are unexplored. Here, we show that microglial REV-ERBα deletion enhances inflammatory signaling, disrupts lipid metabolism, and causes lipid droplet (LD) accumulation specifically in male microglia. These events impair microglial tau phagocytosis, which can be partially rescued by blockage of LD formation. In vivo, microglial REV-ERBα deletion exacerbates tau aggregation and neuroinflammation in two mouse tauopathy models, specifically in male mice. These data demonstrate the importance of microglial lipid droplets in tau accumulation and reveal REV-ERBα as a therapeutically accessible, sex-dependent regulator of microglial inflammatory signaling, lipid metabolism, and tauopathy.

Polycyclic aromatic hydrocarbons (PAHs) in ambient air of Guangzhou city: Exposure levels, health effects and cytotoxicity

Polycyclic aromatic hydrocarbons (PAHs) in PM2.5 pose potentially serious threats to human health. In this study, the distribution characteristics of 16 priority controlled, fine PM (PM2.5)-bound PAHs in the ambient air of Guangzhou city were analysed from 2016 to 2019. Four high-molecular-weight PAHs with the highest annual average concentrations were benzo[ghi]perylene (BghiP; 0.757 ng/m3), indeno(1,2,3-cd)pyrene (IcdP; 0.627 ng/m3), benzo[b]fluoranthene (BbF, 0.519 ng/m3) and 3,4-benzopyrene (BaP; 0.426 ng/m3). Increasing concentrations of BghiP, IcdP, BbF and BaP were associated with increasing numbers of outpatient visits for respiratory diseases, indicating that exposure to these PAHs potentially causes acute respiratory injury in residents. Acute exposure of the human bronchial epithelial cell line BEAS-2B cells to BghiP, IcdP, BbF and BaP in vitro resulted in acute inflammation, DNA damage and apoptosis. Further bioinformatic analysis indicated that nuclear receptor subfamily 1 group D member 1 (NR1D1) may be a key target gene involved in mediating the toxic effects of BghiP. Collectively, our results suggest that BghiP and the other PAHs represented by it can damage the respiratory system and induce lung cancer. This study provides valuable evidence regarding the potential health risks posed by local ambient PAHs pollution.

Impact of the circadian nuclear receptor REV-ERBα in dorsal raphe 5-HT neurons on social interaction behavior, especially social preference

Social interaction among conspecifics is essential for maintaining adaptive, cooperative, and social behaviors, along with survival among mammals. The 5-hydroxytryptamine (5-HT) neuronal system is an important neurotransmitter system for regulating social behaviors; however, the circadian role of 5-HT in social interaction behaviors is unclear. To investigate whether the circadian nuclear receptor REV-ERBα, a transcriptional repressor of the rate-limiting enzyme tryptophan hydroxylase 2 (Tph2) gene in 5-HT biosynthesis, may affect social interaction behaviors, we generated a conditional knockout (cKO) mouse by targeting Rev-Erbα in dorsal raphe (DR) 5-HT neurons (5-HTDR-specific REV-ERBα cKO) using the CRISPR/Cas9 gene editing system and assayed social behaviors, including social preference and social recognition, with a three-chamber social interaction test at two circadian time (CT) points, i.e., at dawn (CT00) and dusk (CT12). The genetic ablation of Rev-Erbα in DR 5-HTergic neurons caused impaired social interaction behaviors, particularly social preference but not social recognition, with no difference between the two CT points. This deficit of social preference induced by Rev-Erbα in 5-HTDR-specific mice is functionally associated with real-time elevated neuron activity and 5-HT levels at dusk, as determined by fiber-photometry imaging sensors. Moreover, optogenetic inhibition of DR to nucleus accumbens (NAc) 5-HTergic circuit restored the impairment of social preference in 5-HTDR-specific REV-ERBα cKO mice. These results suggest the significance of the circadian regulation of 5-HT levels by REV-ERBα in regulating social interaction behaviors.

Inhibition of mPGES-2 ameliorates NASH by activating NR1D1 via heme

BACKGROUND AND AIMS

Nonalcoholic fatty liver disease (NAFLD), a complex metabolic syndrome, has limited therapeutic options. Microsomal prostaglandin E synthase-2 (mPGES-2) was originally discovered as a prostaglandin E 2 (PGE 2 ) synthase; however, it does not produce PGE 2 in the liver. Moreover, the role of mPGES-2 in NAFLD remains undefined. Herein, we aimed to determine the function and mechanism of mPGES-2 in liver steatosis and steatohepatitis.

APPROACH AND RESULTS

To evaluate the role of mPGES-2 in NAFLD, whole-body or hepatocyte-specific mPGES-2-deficient mice fed a high-fat or methionine-choline-deficient diet were used. Compared with control mice, mPGES-2-deficient mice showed reduced hepatic lipid accumulation, along with ameliorated liver injury, inflammation, and fibrosis. Furthermore, the protective effect of mPGES-2 deficiency against NAFLD was dependent on decreased cytochrome P450 4A14 and increased acyl-CoA thioesterase 4 levels regulated by the heme receptor nuclear receptor subfamily 1 group D member 1 (NR1D1), but not PGE 2 . Heme regulated the increased NR1D1 activity mediated by mPGES-2 deficiency. Further, we confirmed the protective role of the mPGES-2 inhibitor SZ0232 in NAFLD therapy.

CONCLUSION

Our study indicates the pathogenic role of mPGES-2 and outlines the mechanism in mediating NAFLD, thereby highlighting the therapeutic potential of mPGES-2 inhibition in liver steatosis and steatohepatitis.

Clock gene NR1D1 might be a novel target for the treatment of bladder cancer

PURPOSE

To explore the role of circadian clock gene NR1D1 (REV-erbα) in bladder cancer (BC).

METHODS

Firstly, the association of NR1D1 level with clinical characteristics and prognosis was investigated among patients diagnosed with BC. Secondly, CCK-8, transwell, and colony formation experiments were performed among BC cells treated with Rev-erbα agonist (SR9009), as well as lentivirus and siRNA, for which NR1D1 were overexpressed (OE) and knocked down (KD), respectively. Thirdly, cell cycle and apoptosis were tested by flowcytometry. PI3K/AKT/mTOR pathway proteins were determined in OE-NR1D1 cells. Finally, OE-NR1D1 and OE-Control BC cells were subcutaneously implanted in BALB/c nude mice. The tumor size and protein levels were compared between groups. A P < 0.05 was considered as statistically significant.

RESULTS

Patients with NR1D1 positive status had a longer disease-free survival than those with negative expression. The cell viability, migration, and colony formation of BC cells after treated with SR9009 were significantly suppressed. OE-NR1D1 cells had obviously inhibited cell viability, migration, and colony formation, while those were found strengthened in KD-NR1D1 cells. Besides, KD-NR1D1 cells were observed with a lower proportion of dead cells and G0/G1 cells, but a higher ratio of G2/M. The changes of p-AKT, p-S6, p-4EBP1, and FASN involved in PI3K/AKT/mTOR pathway were detected in OE- and KD-NR1D1 BC cells. Finally, in vivo data demonstrated that overexpression of NR1D1 suppressed the tumorigenicity of BC cells.

CONCLUSION

NR1D1 played a role of tumor suppressor and it might become a novel target for the treatment of BC.

Gegen Qinlian Decoction treatment of asymptomatic hyperuricemia by targeting circadian immune function

BACKGROUND

The Gegen Qinlian Decoction (GGQLD) is a renowned traditional Chinese medicinal formula that has been used for centuries to effectively treat asymptomatic Hyperuricemia (HUA). This study aims to investigate the underlying mechanism of GGQLD's therapeutic effects on HUA.

METHODS

The study enrolled a total of 25 healthy participants and 32 middle-aged and elderly individuals with asymptomatic HUA. All asymptomatic HUA participants were treated with GGQLD. Venous blood samples were collected from all participants to isolate peripheral blood mononuclear cells (PBMCs), which were then analyzed for biological profiles using flow cytometry. Network pharmacology analysis was utilized to identify the potential pathways involved in the therapeutic effects of GGQLD. Transcriptomic patterns of cultured proximal tubule epithelial cells (PTECs) were evaluated via bulk RNA-seq, and critical differentially expressed genes (DEGs) were identified and verified through ELISA. Molecular docking and molecular dynamics (MD) simulation were employed to investigate the potential compounds in GGQLD that may be involved in treating HUA.

RESULTS

Network pharmacology analysis revealed that immune-related pathways might be involved in the therapeutic mechanism of GGQLD. RNA-seq analysis confirmed the involvement of innate lymphoid cell (ILC) development-related genes and clock genes. Polychromatic flow cytometric analysis demonstrated that GGQLD treatment reduced the proportion of ILC3s in total ILCs in asymptomatic HUA patients. ELISA results showed that GGQLD treatment reduced the levels of activating factors, such as ILC3-IL-18 and IL-1β, in the plasma of HUA patients. GGQLD was also found to regulate circadian clock gene expression in PBMCs to treat asymptomatic HUA. Furthermore, the interaction between 40 compounds in GGQLD and HDAC3 (Histone Deacetylase 3), NLRP3 (NOD-like receptor protein 3), RORA (RAR-related orphan receptor A), and REV-ERBα (nuclear receptor subfamily 1) revealed that GGQLD may regulate ILCs and clock genes to treat asymptomatic HUA.

CONCLUSIONS

The regulation of circadian clock gene expression and the proportion of ILC cells may be involved in the therapeutic effects of GGQLD on asymptomatic HUA patients.

The circadian rhythm: an influential soundtrack in the diabetes story

Type 2 Diabetes Mellitus (T2DM) has been the main category of metabolic diseases in recent years due to changes in lifestyle and environmental conditions such as diet and physical activity. On the other hand, the circadian rhythm is one of the most significant biological pathways in humans and other mammals, which is affected by light, sleep, and human activity. However, this cycle is controlled via complicated cellular pathways with feedback loops. It is widely known that changes in the circadian rhythm can alter some metabolic pathways of body cells and could affect the treatment process, particularly for metabolic diseases like T2DM. The aim of this study is to explore the importance of the circadian rhythm in the occurrence of T2DM via reviewing the metabolic pathways involved, their relationship with the circadian rhythm from two perspectives, lifestyle and molecular pathways, and their effect on T2DM pathophysiology. These impacts have been demonstrated in a variety of studies and led to the development of approaches such as time-restricted feeding, chronotherapy (time-specific therapies), and circadian molecule stabilizers.

The Role of REV-ERB Receptors in Cancer Pathogenesis

REV-ERB receptors are members of the nuclear receptor superfamily of proteins, which act as both intracellular receptors and transcription factors, therefore modulating the expression of target genes. REV-ERBs act as transcription repressors because of their unique structure. Their predominant role involves the control of peripheral circadian rhythmicity by participating in a transcription-translation feedback loop with other major clock genes. Regarding their role in cancer pathogenesis, recent studies in various cancerous tissues have revealed that their expression was downregulated in the majority of the cases. Dysregulation of their expression was also implicated in cancer-associated cachexia. The pharmacological restoration of their effects is feasible with synthetic agonists, which have been explored in preclinical studies but with scarce data. There is a need for further investigation, primarily with mechanistic studies, on the effect of the REV-ERB-induced circadian rhythm deregulation in carcinogenesis and cancer-related systemic effects, such as cachexia, in order to address the potential of relevant therapeutic implications.

CRS: a circadian rhythm score model for predicting prognosis and treatment response in cancer patients

BACKGROUND

Circadian rhythm regulates complex physiological activities in organisms. A strong link between circadian dysfunction and cancer has been identified. However, the factors of dysregulation and functional significance of circadian rhythm genes in cancer have received little attention.

METHODS

In 18 cancer types from The Cancer Genome Atlas (TCGA), the differential expression and genetic variation of 48 circadian rhythm genes (CRGs) were examined. The circadian rhythm score (CRS) model was created using the ssGSEA method, and patients were divided into high and low groups based on the CRS. The Kaplan-Meier curve was created to assess the patient survival rate. Cibersort and estimate methods were used to identify the infiltration characteristics of immune cells between different CRS subgroups. Gene Expression Omnibus (GEO) dataset is used as verification queue and model stability evaluation queue. The CRS model's ability to predict chemotherapy and immunotherapy was assessed. Wilcoxon rank-sum test was used to compare the differences of CRS among different patients. We use CRS to identify potential "clock-drugs" by the connective map method.

RESULTS

Transcriptomic and genomic analyses of 48 CRGs revealed that most core clock genes are up-regulated, while clock control genes are down-regulated. Furthermore, we show that copy number variation may affect CRGs aberrations. Based on CRS, patients can be classified into two groups with significant differences in survival and immune cell infiltration. Further studies showed that patients with low CRS were more sensitive to chemotherapy and immunotherapy. Additionally, we identified 10 compounds (e.g. flubendazole, MLN-4924, ingenol) that are positively associated with CRS, and have the potential to modulate circadian rhythms.

CONCLUSIONS

CRS can be utilized as a clinical indicator to predict patient prognosis and responsiveness to therapy, and identify potential "clock-drugs".

Circadian clock molecule REV-ERBα regulates lung fibrotic progression through collagen stabilization

Molecular clock REV-ERBα is central to regulating lung injuries, and decreased REV-ERBα abundance mediates sensitivity to pro-fibrotic insults and exacerbates fibrotic progression. In this study, we determine the role of REV-ERBα in fibrogenesis induced by bleomycin and Influenza A virus (IAV). Bleomycin exposure decreases the abundance of REV-ERBα, and mice dosed with bleomycin at night display exacerbated lung fibrogenesis. Rev-erbα agonist (SR9009) treatment prevents bleomycin induced collagen overexpression in mice. Rev-erbα global heterozygous (Rev-erbα Het) mice infected with IAV showed augmented levels of collagens and lysyl oxidases compared with WT-infected mice. Furthermore, Rev-erbα agonist (GSK4112) prevents collagen and lysyl oxidase overexpression induced by TGFβ in human lung fibroblasts, whereas the Rev-erbα antagonist exacerbates it. Overall, these results indicate that loss of REV-ERBα exacerbates the fibrotic responses by promoting collagen and lysyl oxidase expression, whereas Rev-erbα agonist prevents it. This study provides the potential of Rev-erbα agonists in the treatment of pulmonary fibrosis.

Circadian Rhythm Regulator REV-ERBα Attenuates Neuroapoptosis in Early Brain Injury After Experimental Subarachnoid Hemorrhage in Rats

Subarachnoid hemorrhage (SAH) is associated with circadian rhythm abnormalities, in which REV-ERBα plays a major regulatory role. Our ambition was to investigate the capacity of REV-ERBα to inhibit neuronal neuroapoptosis induced by early brain injury (EBI) after SAH. The endovascular perforation model was used to produce experimental SAH in Sprague-Dawley rats. Specific small-interfering RNA was used to downregulate the expression REV-ERBα while SR9009 was used to upregulate the expression before assessments. Short- and long-term neurobehavior assessments, immunofluorescence staining, TUNEL staining, Nissl staining, brain water content, and Western blot were performed. The expression level of endogenous REVERBα tended to increase and then decrease after SAH and peaked at 48 h. REV-ERBα upregulation diminished neuronal apoptosis and enhanced neurological function deficits. Meanwhile, REV-ERBα downregulation aggravated the damage. Furthermore, the levels of downstream proteins of REV-ERBα (i.e., brain and muscle ARNT-like 1 (BMAL1) and circadian locomotor output cycles kaput (CLOCK)) changed accordingly with REV-ERBα regulation. REV-ERBα may attenuate neuronal apoptosis in EBI after SAH through the BMAL1/CLOCK pathway.

Proximal tubular Bmal1 protects against chronic kidney injury and renal fibrosis by maintaining of cellular metabolic homeostasis

Recent studies suggest that deletion of the core clock gene Bmal1 in the kidney has a significant influence on renal physiological functions. However, the role of renal Bmal1 in chronic kidney disease (CKD) remains poorly understood. Here by generating mice lacking Bmal1 in proximal tubule (Bmal1^flox/flox-KAP-Cre⁺, ptKO) and inducing CKD with the adenine diet model, we found that lack of Bmal1 in proximal tubule did not alter renal water and electrolyte homeostasis. However, adenine-induced renal injury indexes, including blood urea nitrogen, serum creatinine, and proteinuria, were markedly augmented in the ptKO mice. The ptKO kidneys also developed aggravated tubulointerstitial fibrosis and epithelial-mesenchymal transformation. Mechanistically, RNAseq analysis revealed significant downregulation of the expression of genes related to energy and substance metabolism, in particular fatty acid oxidation and glutathione/homocysteine metabolism, in the ptKO kidneys. Consistently, the renal contents of ATP and glutathione were markedly reduced in the ptKO mice, suggesting the disruption of cellular metabolic homeostasis. Moreover, we demonstrated that Bmal1 can activate the transcription of cystathionine β-synthase (CBS), a key enzyme for homocysteine metabolism and glutathione biosynthesis, through direct recruitment to the E-box motifs of its promoter. Supporting the in vivo findings, knockdown of Bmal1 in cultured proximal tubular cells inhibited CBS expression and amplified albumin-induced cell injury and fibrogenesis, while glutathione supplementation remarkably reversed these changes. Taken together, we concluded that deletion of Bmal1 in proximal tubule may aggravate chronic kidney injury and exacerbate renal fibrosis, the mechanism is related to suppressing CBS transcription and disturbing glutathione related metabolic homeostasis. These findings suggest a protective role of Bmal1 in chronic tubular injury and offer a novel target for treating CKD.

Circadian stabilization loop: the regulatory hub and therapeutic target promoting circadian resilience and physiological health

The circadian clock is a fundamental biological mechanism that orchestrates essential cellular and physiological processes to optimize fitness and health. The basic functional unit is the cell-autonomous oscillator, consisting of intersecting negative feedback loops. Whereas the core loop is primarily responsible for rhythm generation, auxiliary loops, most notably the secondary or stabilization loop, play pivotal roles to confer temporal precision and molecular robustness. The stabilization loop contains opposing nuclear receptor subfamilies REV-ERBs and retinoic acid receptor-related orphan receptors (RORs), competing to modulate rhythmic expression of the basic helix-loop-helix ARNT like 1 ( Bmal1) genes in the core loop as well as other clock-controlled genes. Therefore, REV-ERBs and RORs are strategically located to interface the oscillator and the global transcriptomic network, promoting cellular homeostasis and physiological fitness throughout lifespan. Disruption of REV-ERB and ROR functions has been linked with diseases and aging, and pharmacological manipulation of these factors has shown promise in various mouse disease models. Nobiletin is a natural compound that directly binds to and activates RORα/γ, modulating circadian rhythms, and shows robust in vivo efficacies to combat clock-associated pathophysiologies and age-related decline. Results from several studies demonstrate an inverse relation between nobiletin efficacy and clock functional state, where nobiletin elicits little effect in young and healthy mice with growing efficacy as the clock is perturbed by environmental and genetic challenges. This mode of action is consistent with the function of the stabilization loop to promote circadian and physiological resilience. Future studies should further investigate the function and mechanism of REV-ERBs and RORs, and test strategies targeting these factors against disease and aging.

Circadian stabilization loop: the regulatory hub and therapeutic target promoting circadian resilience and physiological health

The circadian clock is a fundamental biological mechanism that orchestrates essential cellular and physiological processes to optimize fitness and health. The basic functional unit is the cell-autonomous oscillator, consisting of intersecting negative feedback loops. Whereas the core loop is primarily responsible for rhythm generation, auxiliary loops, most notably the secondary or stabilization loop, play pivotal roles to confer temporal precision and molecular robustness. The stabilization loop contains opposing nuclear receptor subfamilies REV-ERBs and retinoic acid receptor-related orphan receptors (RORs), competing to modulate rhythmic expression of the basic helix-loop-helix ARNT like 1 ( Bmal1) genes in the core loop as well as other clock-controlled genes. Therefore, REV-ERBs and RORs are strategically located to interface the oscillator and the global transcriptomic network, promoting cellular homeostasis and physiological fitness throughout lifespan. Disruption of REV-ERB and ROR functions has been linked with diseases and aging, and pharmacological manipulation of these factors has shown promise in various mouse disease models. Nobiletin is a natural compound that directly binds to and activates RORα/γ, modulating circadian rhythms, and shows robust in vivo efficacies to combat clock-associated pathophysiologies and age-related decline. Results from several studies demonstrate an inverse relation between nobiletin efficacy and clock functional state, where nobiletin elicits little effect in young and healthy mice with growing efficacy as the clock is perturbed by environmental and genetic challenges. This mode of action is consistent with the function of the stabilization loop to promote circadian and physiological resilience. Future studies should further investigate the function and mechanism of REV-ERBs and RORs, and test strategies targeting these factors against disease and aging.

Circadian clock-based therapeutics in chronic pulmonary diseases

The circadian clock is the biochemical oscillator that orchestrates the observable circadian rhythms in physiology and behavior. Disruption of the circadian clock in the lungs during chronic pulmonary diseases is considered one of the key etiological risk factors that drive pathobiology. Preclinical studies support that pharmacological manipulation of the circadian clock is a conceivable approach for the development of novel clock-based therapeutics. Despite recent advances, no effort has been undertaken to integrate novel findings for the treatment and management of chronic lung diseases. We, therefore, recognize the need to discuss the candidate clock genes that can be potentially targeted for therapeutic intervention. Here, we aim to create the first roadmap that will advance the development of circadian- clock-based therapeutics that may provide better outcomes in treating chronic pulmonary diseases.

The combination of nuclear receptor NR1D1 and ULK1 promotes mitophagy in adipocytes to ameliorate obesity

Obesity is a severe disease worldwide. Mitochondrial autophagy (mitophagy) may be related to metabolic abnormalities in obese individuals, but the mechanism is still unclear. We aimed to investigate whether nuclear receptors NR1D1 and ULK1 influence obesity by affecting mitophagy. In vitro model was established by inducing 3T3-L1 cells differentiation. MTT was detected cell viability. ELISA was tested triglyceride (TG). Oil red O staining was performed to detect lipid droplets. Flow cytometry was measured mtROS. ChIP and Dual-luciferase reporter assay were verified NR1D1 bind to ULK1. LC3 level was detected by IF. After differentiation medium treatment, cell viability was decreased, TG content and lipid droplets were increased Moreover, NR1D1 expression was reduced in Model group. NR1D1 overexpression was increased cell viability, reduced TG content and lipid droplets. Subsequently, NR1D1 inhibited TOM20 and mtROS, whereas, Parkin and PINK1 were accelerated. NR1D1 overexpression facilitated LC3 expression, whereas ULK1 knockdown was reversed the effect of NR1D1 overexpression. Liensinine also reversed the effect of NR1D1 overexpression, that is, cell viability was reduced, mtROS, TG content and lipid droplets were increased. The combination of nuclear receptor NR1D1 and ULK1 promoted mitophagy in adipocytes to alleviate obesity, which provided new target and strategy for obesity treatment.Abbreviations: Mitochondrial autophagy (mitophagy), triglyceride (TG), Uncoordinated-51 like autophagy activating kinase 1 (ULK1), Nuclear receptor subfamily 1 group D member 1 (NR1D1), American Type Culture Collection (ATCC), fetal bovine serum (FBS), 3-isobutyl-1-methylxanthine (IBMX), dexamethasone (DEX), short hairpin RNA ULK1 (sh-ULK1), wild-type (WT), mutant (MUT), Enzyme-linked immunosorbent assay (ELISA), mitochondrial reactive oxygen species (mtROS), Chromatin immunoprecipitation (ChIP), Quantitative real-time PCR (qRT-PCR), Immunofluorescence (IF), standard deviation (SD).

Structural basis of synthetic agonist activation of the nuclear receptor REV-ERB

The nuclear receptor REV-ERB plays an important role in a range of physiological processes. REV-ERB behaves as a ligand-dependent transcriptional repressor and heme has been identified as a physiological agonist. Our current understanding of how ligands bind to and regulate transcriptional repression by REV-ERB is based on the structure of heme bound to REV-ERB. However, porphyrin (heme) analogues have been avoided as a source of synthetic agonists due to the wide range of heme binding proteins and potential pleotropic effects. How non-porphyrin synthetic agonists bind to and regulate REV-ERB has not yet been defined. Here, we characterize a high affinity synthetic REV-ERB agonist, STL1267, and describe its mechanism of binding to REV-ERB as well as the method by which it recruits transcriptional corepressor both of which are unique and distinct from that of heme-bound REV-ERB.

Infection by a helminth parasite is associated with changes in DNA methylation in the house sparrow

Parasites can exert strong selective pressures on their hosts and influence the evolution of host immunity. While several studies have examined the genetic basis for parasite resistance, the role of epigenetics in the immune response to parasites is less understood. Yet, epigenetic modifications, such as changes in DNA methylation, may allow species to respond rapidly to parasite prevalence or virulence. To test the role of DNA methylation in relation to parasite infection, we examined genome-wide DNA methylation before and during infection by a parasitic nematode, Syngamus trachea, in a natural population of house sparrows (Passer domesticus) using reduced representation bisulfite sequencing (RRBS). We found that DNA methylation levels were slightly lower in infected house sparrows, and we identified candidate genes relating to the initial immune response, activation of innate and adaptive immunity, and mucus membrane functional integrity that were differentially methylated between infected and control birds. Subsequently, we used methylation-sensitive high-resolution melting (MS-HRM) analyses to verify the relationship between methylation proportion and S. trachea infection status at two candidate genes in a larger sample dataset. We found that methylation level at NR1D1, but not CLDN22, remained related to infection status and that juvenile recruitment probability was positively related to methylation level at NR1D1. This underscores the importance of performing follow-up studies on candidate genes. Our findings demonstrate that plasticity in the immune response to parasites can be epigenetically mediated and highlight the potential for epigenetic studies in natural populations to provide further mechanistic insight into host-parasite interactions.

Scutellaria baicalensis Georgi regulates REV-ERBα/BMAL1 to protect against skin aging in mice

Scutellaria baicalensis Georgi (SBG) is a traditional Chinese medicine widely used to treat disorders such as hypertension, dysentery and hemorrhaging. Here, we aimed to assess the pharmacological effects of SBG on skin aging and to investigate the underlying mechanisms. Mice with skin aging were established by treatment with D-galactose and ultraviolet-B. SBG (topical application) showed a protective effect on skin aging in mice, as evidenced by less formation of skin wrinkles, higher levels of SOD (superoxide dismutase) and HYP (hydroxyproline) as well as a lower level of MDA (malondialdehyde). In the meantime, skin MMP-1 and p53 expression were lower, epidermis was thinner and collagen amount was higher in SBG-treated mice. Anti-skin aging effects of SBG were also confirmed in NIH3T3 and HaCaT cells, as well as in mouse primary dermal fibroblasts and human primary epidermal keratinocytes. Furthermore, we found that loss of Rev-erbα (a known repressor of Bmal1) up-regulated skin BMAL1 (a clock component and a known anti-aging factor) and ameliorated skin aging in mice. Moreover, SBG dose-dependently increased the expression of BMAL1 in the skin of aged mice and in senescent NIT3H3 cells. In addition, based on a combination of Gal4 chimeric, luciferase reporter and expression assays, SBG was identified as an antagonist of REV-ERBα and thus an inducer of BMAL1 expression. In conclusion, SBG antagonizes REV-ERBα to up-regulate BMAL1 and to protect against skin aging in mice.

The nuclear receptor REV-ERBα regulates CYP2E1 expression and acetaminophen hepatotoxicity

CYP2E1 plays an important role in drug metabolism and drug-induced hepatotoxicity. Here, we aimed to investigate a potential role for the nuclear receptor REV-ERBα in regulation of CYP2E1 expression and acetaminophen (APAP)-induced hepatotoxicity, and to determine the underlying mechanisms.Regulatory effects of REV-ERBα on CYP2E1 expression were assessed in vivo (using Rev-erbα^-/- mice) and in vitro (using AML12 and HepG2 cells). In vitro microsomal CYP2E1 activity was probed using its specific substrate p-nitrophenol. Pharmacokinetic and acute toxicities studies were performed with Rev-erbα^-/- and wild-type mice after APAP administration.We found that Rev-erbα ablation led to decreases in hepatic CYP2E1 expression and activity in mice. In line with this, APAP-induced hepatotoxicity was attenuated in Rev-erbα-deficient mice. The attenuated toxicity was due to down-regulation of APAP metabolism mediated by CYP2E1, which was evidenced by a decrease in formation of the toxic intermediate metabolite NAPQI (i.e., reduced APAP-Cysteine and APAP-N-acetylcysteine levels). Furthermore, positive regulation of CYP2E1 expression by REV-ERBα was confirmed in both AML12 and HepG2 cells. Based on luciferase reporter assays, it was found that REV-ERBα regulated Cyp2e1 transcription and expression through repression of DEC2.In conclusion, REV-ERBα positively regulates CYP2E1 expression in mice, thereby affecting APAP metabolism and hepatotoxicity.

Circadian rhythms and pancreas physiology: A review

Type 2 diabetes mellitus, obesity and metabolic syndrome are becoming more prevalent worldwide and will present an increasingly challenging burden on healthcare systems. These interlinked metabolic abnormalities predispose affected individuals to a plethora of complications and comorbidities. Furthermore, diabetes is estimated by the World Health Organization to have caused 1.5 million deaths in 2019, with this figure projected to rise in coming years. This highlights the need for further research into the management of metabolic diseases and their complications. Studies on circadian rhythms, referring to physiological and behavioral changes which repeat approximately every 24 hours, may provide important insight into managing metabolic disease. Epidemiological studies show that populations who are at risk of circadian disruption such as night shift workers and regular long-haul flyers are also at an elevated risk of metabolic abnormalities such as insulin resistance and obesity. Aberrant expression of circadian genes appears to contribute to the dysregulation of metabolic functions such as insulin secretion, glucose homeostasis and energy expenditure. The potential clinical implications of these findings have been highlighted in animal studies and pilot studies in humans giving rise to the development of circadian interventions strategies including chronotherapy (time-specific therapy), time-restricted feeding, and circadian molecule stabilizers/analogues. Research into these areas will provide insights into the future of circadian medicine in metabolic diseases. In this review, we discuss the physiology of metabolism and the role of circadian timing in regulating these metabolic functions. Also, we review the clinical aspects of circadian physiology and the impact that ongoing and future research may have on the management of metabolic disease.

New insight into ischemic stroke: Circadian rhythm in post-stroke angiogenesis

The circadian rhythm is an endogenous clock system that coordinates and optimizes various physiological and pathophysiological processes, which accord with the master and the peripheral clock. Increasing evidence indicates that endogenous circadian rhythm disruption is involved in the lesion volume and recovery of ischemic stroke. As a critical recovery mechanism in post-stroke, angiogenesis reestablishes the regional blood supply and enhances cognitive and behavioral abilities, which is mainly composed of the following processes: endothelial cell proliferation, migration, and pericyte recruitment. The available evidence revealed that the circadian governs many aspects of angiogenesis. This study reviews the mechanism by which circadian rhythms regulate the process of angiogenesis and its contribution to functional recovery in post-stroke at the aspects of the molecular level. A comprehensive understanding of the circadian clock regulating angiogenesis in post-stroke is expected to develop new strategies for the treatment of cerebral infarction.

A Review on the Molecular Mechanisms of Action of Natural Products in Preventing Bone Diseases

The drugs used for treating bone diseases (BDs), at present, elicit hazardous side effects that include certain types of cancers and strokes, hence the ongoing quest for the discovery of alternatives with little or no side effects. Natural products (NPs), mainly of plant origin, have shown compelling promise in the treatments of BDs, with little or no side effects. However, the paucity in knowledge of the mechanisms behind their activities on bone remodeling has remained a hindrance to NPs’ adoption. This review discusses the pathological development of some BDs, the NP-targeted components, and the actions exerted on bone remodeling signaling pathways (e.g., Receptor Activator of Nuclear Factor κ B-ligand (RANKL)/monocyte/macrophage colony-stimulating factor (M-CSF)/osteoprotegerin (OPG), mitogen-activated protein kinase (MAPK)s/c-Jun N-terminal kinase (JNK)/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), Kelch-like ECH-associated protein 1 (Keap-1)/nuclear factor erythroid 2–related factor 2 (Nrf2)/Heme Oxygenase-1 (HO-1), Bone Morphogenetic Protein 2 (BMP2)-Wnt/β-catenin, PhosphatidylInositol 3-Kinase (PI3K)/protein kinase B (Akt)/Glycogen Synthase Kinase 3 Beta (GSK3β), and other signaling pathways). Although majority of the studies on the osteoprotective properties of NPs against BDs were conducted ex vivo and mostly on animals, the use of NPs for treating human BDs and the prospects for future development remain promising.

Hepatitis B and circadian rhythm of the liver

The circadian rhythm in humans is determined by the central clock located in the hypothalamus’s suprachiasmatic nucleus, and it synchronizes the peripheral clocks in other tissues. Circadian clock genes and clock-controlled genes exist in almost all cell types. They have an essential role in many physiological processes, including lipid metabolism in the liver, regulation of the immune system, and the severity of infections. In addition, circadian rhythm genes can stimulate the immune response of host cells to virus infection. Hepatitis B virus (HBV) infection is the leading cause of liver disease and liver cancer globally. HBV infection depends on the host cell, and hepatocyte circadian rhythm genes are associated with HBV replication, survival, and spread. The core circadian rhythm proteins, REV-ERB and brain and muscle ARNTL-like protein 1, have a crucial role in HBV replication in hepatocytes. In addition to influencing the virus’s life cycle, the circadian rhythm also affects the pharmacokinetics and efficacy of antiviral vaccines. Therefore, it is vital to apply antiviral therapy at the appropriate time of day to reduce toxicity and improve the effectiveness of antiviral treatment. For these reasons, understanding the role of the circadian rhythm in the regulation of HBV infection and host responses to the virus provides us with a new perspective of the interplay of the circadian rhythm and anti-HBV therapy. Therefore, this review emphasizes the importance of the circadian rhythm in HBV infection and the optimization of antiviral treatment based on the circadian rhythm-dependent immune response.

Co-regulation of circadian clock genes and microRNAs in bone metabolism

Mammalian bone is constantly metabolized from the embryonic stage, and the maintenance of bone health depends on the dynamic balance between bone resorption and bone formation, mediated by osteoclasts and osteoblasts. It is widely recognized that circadian clock genes can regulate bone metabolism. In recent years, the regulation of bone metabolism by non-coding RNAs has become a hotspot of research. MicroRNAs can participate in bone catabolism and anabolism by targeting key factors related to bone metabolism, including circadian clock genes. However, research in this field has been conducted only in recent years and the mechanisms involved are not yet well established. Recent studies have focused on how to target circadian clock genes to treat some diseases, such as autoimmune diseases, but few have focused on the co-regulation of circadian clock genes and microRNAs in bone metabolic diseases. Therefore, in this paper we review the progress of research on the co-regulation of bone metabolism by circadian clock genes and microRNAs, aiming to provide new ideas for the prevention and treatment of bone metabolic diseases such as osteoporosis.