Genetic or pharmacologic blockade of mPGES-2 attenuates renal lipotoxicity and diabetic kidney disease by targeting Rev-Erbα/FABP5 signaling.

Diabetic kidney disease (DKD) is one of the most common complications of diabetes, and no specific drugs are clinically available. We have previously demonstrated that inhibiting microsomal prostaglandin E synthase-2 (mPGES-2) alleviated type 2 diabetes by enhancing ß cell function and promoting insulin production. However, the involvement of mPGES-2 in DKD remains unclear. Here, we aimed to analyze the association of enhanced mPGES-2 expression with impaired metabolic homeostasis of renal lipids and subsequent renal damage. Notably, global knockout or pharmacological blockage of mPGES-2 attenuated diabetic podocyte injury and tubulointerstitial fibrosis, thereby ameliorating lipid accumulation and lipotoxicity. These findings were further confirmed in podocyte- or tubule-specific mPGES-2-deficient mice. Mechanistically, mPGES-2 and Rev-Erbα competed for heme binding to regulate fatty acid binding protein 5 expression and lipid metabolism in the diabetic kidney. Our findings suggest a potential strategy for treating DKD via mPGES-2 inhibition.

PTZ-kindled rat model; evaluation of seizure, hippocampal EGR-1, and Rev-erbα gene regulation, behavioral analysis, and antioxidant capacity of Gum Arabic.

BACKGROUND: Epilepsy is a neurological disease characterized by recurrent seizures, hyperexcitable neurons and various behavioral comorbidities. The electrical charge during seizures depletes the antioxidant defense mechanism in the epileptic brain and increases the oxidative burden. Natural antioxidant compounds are potential therapeutics in the treatment of two major pathologies of epilepsy with their anticonvulsant and anxiolytic effects and can modulate these targets. Gum Arabic is one of the natural plant polysaccharides that is non-toxic and biodegradable. METHODS AND RESULTS: A total of 30 Wistar albino male rats (8-12 weeks, 350-500 g), were randomly divided into 5 groups with 6 animals in each group: 1-Control, 2-Sham (Phosphate buffer saline (PBS)), 3-PTZ, 4-Gum Arabic, 5-PTZ + Gum Arabic. PTZ was administered i.p at 35 mg/kg/day for 11 days. After 48 h, the injection was completed with 75 mg/kg PTZ. Locomotor activity, immobilization, rearing, grooming, eating, and drinking behaviors were recorded with the LABORAS behavior system for 30 min after kindling. Animals were treated with Gum Arabic (2 mg/kg/day, oral gavage) for 10 days. At the end of the period, animal behavior was recorded again. Then the hippocampus tissues were removed. Oxidative parameters (TAS and TOS), early growth response 1 (EGR1) and nuclear receptor subfamily 1 group D member 1 (Rev-erbα) gene expressions and behaviors were analyzed. CONCLUSION: Gum Arabic increased TAS levels (P = 0.000), decreased TOS levels (P = 0.000), and thus exhibited antioxidant properties by reducing oxidative stress burden. EGR1, which was upregulated in the seizure group, was downregulated after treatment (P = 0.000), and Rev-erbα was downregulated in seizure and upregulated after treatment (P = 0.000). Gum arabic may be an antiepileptic and anxiolytic therapeutic in improving epileptic seizures by reducing oxidative stress burden through EGR1 and Rev-erbα.0.

NR1D1-rearranged soft tissue tumour: A clinicopathological and molecular analysis of four additional cases.

AIMS: Nuclear receptor subfamily 1 group D member 1 (NR1D1)-rearranged soft tissue tumour is a newly described entity with an epithelioid morphology and a potential for aggressive behaviour. Largely due to under-recognition, this tumour type has not yet been widely acknowledged. Herein, we report four additional cases to further expand its clinicopathological and molecular spectrum. METHODS AND RESULTS: Four mesenchymal tumours with NR1D1 rearrangement were identified from our consultation files. There were one male and three females with ages ranging from 19 to 47 years (median = 28.5 years). Tumour occurred in the tongue, neck, hip and index finger, respectively. Histologically, two tumours were composed predominantly of epithelioid cells; one tumour had admixed epithelioid-spindle cells and one tumour consisted of monomorphic small round to ovoid cells. By immunohistochemistry, none of the tumours expressed lineage-specific markers. Targeted RNA-sequencing identified NR1D1 fusions in all four tumours, the partner genes being MAML2, MAML3, KMT2A and NCOA2, respectively. The novel MAML3 and NCOA2 rearrangements were confirmed by fluorescence in-situ hybridisation analysis. On follow-up (2-23 months), one patient experienced local recurrence due to incomplete resection and one patient developed lung metastasis. The other two patients were alive without disease. CONCLUSIONS: This study adds more support for NR1D1-rearranged soft tissue tumour as an emerging entity. The occurrence of two additional tumours in the head and neck region, description of a small round cell variant and identification of novel MAML3, KMT2A and NCOA2 partners further expand its clinicopathological and molecular spectrum. More studies on larger series are necessary to validate the fully malignant potential of NR1D1-rearranged soft tissue tumour.

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.

Sex-dependent relationship of polymorphisms in CLOCK and REV-ERBα genes with body mass index and lipid levels in children.

Circadian rhythms, which are governed by a circadian clock, regulate important biological processes associated with obesity. SNPs in circadian clock genes have been linked to energy and lipid homeostasis. The aim of our study was to evaluate the associations of CLOCK and REV-ERBα SNPs with BMI and plasma lipid levels in pre-pubertal boys and girls. The study sample population comprised 1268 children aged 6-8 years. Information regarding anthropometric parameters and plasma lipid concentrations was available. Genotyping of CLOCK SNPs rs1801260, rs4580704, rs3749474, rs3736544 and rs4864548 and REV-ERBα SNPs rs2017427, rs20711570 and rs2314339 was performed by RT-PCR. The CLOCK SNPs rs3749474 and rs4864548 were significantly associated with BMI in girls but no in boys. Female carriers of the minor alleles for these SNPs presented lower BMI compared to non-carriers. A significant association of the REV-ERBα SNP rs2071570 with plasma total cholesterol, LDL-cholesterol and Apo B in males was also observed. Male AA carriers showed lower plasma levels of total cholesterol, LDL-cholesterol and Apo B levels as compared with carriers of the C allele. No significant associations between any of the studied REV-ERBα SNPs and plasma lipid levels were observed in females. In summary, CLOCK and REV-ERBα SNPs were associated with BMI and plasma lipid levels respectively in a sex-dependent manner. Our findings suggest that sex-related factors may interact with Clock genes SNPs conditioning the effects of these polymorphisms on circadian alterations.

Overlaps Between CDS Regions of Protein-Coding Genes in the Human Genome: A Case Study on the NR1D1-THRA Gene Pair.

For several decades, it has been known that a substantial number of genes within human DNA exhibit overlap; however, the biological and evolutionary significance of these overlaps remain poorly understood. This study focused on investigating specific instances of overlap where the overlapping DNA region encompasses the coding DNA sequences (CDSs) of protein-coding genes. The results revealed that proteins encoded by overlapping CDSs exhibit greater disorder than those from nonoverlapping CDSs. Additionally, these DNA regions were identified as GC-rich. This could be partially attributed to the absence of stop codons from two distinct reading frames rather than one. Furthermore, these regions were found to harbour fewer single-nucleotide polymorphism (SNP) sites, possibly due to constraints arising from the overlapping state where mutations could affect two genes simultaneously.While elucidating these properties, the NR1D1-THRA gene pair emerged as an exceptional case with highly structured proteins and a distinctly conserved sequence across eutherian mammals. Both NR1D1 and THRA are nuclear receptors lacking a ligand-binding domain at their C-terminus, which is the region where these gene pairs overlap. The NR1D1 gene is involved in the regulation of circadian rhythm, while the THRA gene encodes a thyroid hormone receptor, and both play crucial roles in various physiological processes. This study suggests that, in addition to their well-established functions, the specifically overlapping CDS regions of these genes may encode protein segments with additional, yet undiscovered, biological roles.

Structure-Activity Relationship and Biological Investigation of a REV-ERBα-Selective Agonist SR-29065 (34) for Autoimmune Disorders.

Autoimmune diseases affect 50 million Americans, predominantly women, and are thought to be one of the top 10 leading causes of death among women in age groups up to 65 years. A central role for TH17 cells has been highlighted by genome-wide association studies (GWAS) linking genes preferentially expressed in TH17 cells to several human autoimmune diseases. We and others have reported that the nuclear receptors REV-ERBα and ß are cell-intrinsic repressors of TH17 cell development and pathogenicity and might therefore be therapeutic targets for intervention. Herein, we describe detailed SAR studies of a novel REV-ERBα-selective scaffold. Metabolic stability of the ligands was optimized allowing for in vivo interrogation of the receptor in a mouse model of multiple sclerosis (EAE) with a ligand (34). Reduction in frequency and number of T-cells in the CNS as well as key REV-ERB target genes is a measure of target engagement in vivo.

The cross-talk between leptin and circadian rhythm signaling proteins in physiological processes: a systematic review.

BACKGROUND: Today, modern lifestyles and disrupted sleep patterns cause circadian clock rhythm impairments that are associated with altered leptin levels, which subsequently affect a wide range of physiological processes and have significant health burdens on societies. Nevertheless, there has been no systematic review of circadian clock genes and proteins, leptin, and related signaling pathways. METHODS: Accordingly, we systematically reviewed circadian clock proteins, leptin, and molecular mechanisms between them by searching Pubmed, Scopus, ProQuest, Web of Sciences, and Google Scholar until September 2022. After considering the inclusion and exclusion criteria, 20 animal studies were selected. The risk of bias was assessed in each study. RESULTS: The results clarified the reciprocal interconnected relationship between circadian clock genes and leptin. Circadian clock genes regulate leptin expression and signaling via different mechanisms, such as CLOCK-BMAL1 heterodimers, which increase the expression of PPARs. PPARs induce the expression of C/EBPα, a key factor in upregulating leptin expression. CLOCK-BMAL1 also induces the expression of Per1 and Rev-erb genes. PER1 activates mTORC1 and mTORC1 enhances the expression of C/EBPα. In addition, REV-ERBs activate the leptin signaling pathway. Also, leptin controls the expression of circadian clock genes by triggering the AMPK and ERK/MAPK signaling pathways, which regulate the activity of PPARs. Moreover, the roles of these molecular mechanisms are elucidated in different physiological processes and organs. CONCLUSIONS: Crosstalk between circadian clock genes and leptin and their affecting elements should be considered in the selection of new therapeutic targets for related disorders, especially obesity and metabolic impairments.

An in silico investigation: Can melatonin serve as an adjuvant in NR1D1-linked chronotherapy for amyotrophic lateral sclerosis?

Chronobiology, which studies biological rhythms and their impacts on health, presents a potential avenue for treating amyotrophic lateral sclerosis. Clock gene-related therapies, focusing on genes responsible for regulating biological rhythms, may hold promise in the treatment. Among these clock genes, nuclear receptor subfamily 1 Group D member 1 (NR1D1) plays a vital role in neurodegenerative diseases. In this particular study, it was aimed to investigate the potential of FDA-approved drugs commonly used in amyotrophic lateral sclerosis treatment and melatonin, a hormone known for its role in regulating sleep-wake cycles, as ligands for clock gene-related therapy. The ligands were subjected to molecular docking and molecular dynamics simulation methods against the NR1D1 clock gene. These results suggested that combining melatonin with FDA-approved medications commonly used in the treatment might yield positive outcomes. This study provides preliminary data and lays the groundwork for future investigations involving in vitro (laboratory-based) and in vivo (animal or human-based) research on chronotherapy. In summary, this research highlights the potential of clock gene-related therapy utilizing melatonin in conjunction with FDA-approved drugs for amyotrophic lateral sclerosis treatment, offering insights into novel treatment strategies. The findings underscore the need for further studies to explore the effectiveness of this hypothetical approach in experimental and clinical settings.

How the circadian nuclear orphan receptor REV-ERBα represses transcription: Temporal and spatial phase separation combined.

In this issue of Molecular Cell, Zhu et al.1 demonstrate that REV-ERBα and its co-repressor NCOR1 are assembled into daytime-dependent liquid droplets that constitute hubs in which the transcription of multiple REV-ERBα target genes is simultaneously repressed.

An intrinsically disordered region controlling condensation of a circadian clock component and rhythmic transcription in the liver.

Circadian gene transcription is fundamental to metabolic physiology. Here we report that the nuclear receptor REV-ERBα, a repressive component of the molecular clock, forms circadian condensates in the nuclei of mouse liver. These condensates are dictated by an intrinsically disordered region (IDR) located in the protein's hinge region which specifically concentrates nuclear receptor corepressor 1 (NCOR1) at the genome. IDR deletion diminishes the recruitment of NCOR1 and disrupts rhythmic gene transcription in vivo. REV-ERBα condensates are located at high-order transcriptional repressive hubs in the liver genome that are highly correlated with circadian gene repression. Deletion of the IDR disrupts transcriptional repressive hubs and diminishes silencing of target genes by REV-ERBα. This work demonstrates physiological circadian protein condensates containing REV-ERBα whose IDR is required for hub formation and the control of rhythmic gene expression.

Uncovering the Novel Role of NR1D1 in Regulating BNIP3-Mediated Mitophagy in Ulcerative Colitis.

BACKGROUND: Ulcerative colitis (UC) is a chronic, incurable condition characterized by mucosal inflammation and intestinal epithelial cell (IEC) damage. The circadian clock gene NR1D1, implicated in UC and the critical mitophagy process for epithelial repair, needs further exploration regarding its role in mitophagy regulation in UC. METHODS: We created a jet lag mouse model and induced colitis with dextran sulfate sodium (DSS), investigating NR1D1's role. Intestinal-specific Nr1d1 knockout mice were also generated. RNA sequencing, chromatin immunoprecipitation (ChIP), and dual-luciferase reporter assays helped ascertain NR1D1's regulatory effect on BNIP3 expression. The mitochondrial state in IECs was assessed through transmission electron microscopy, while confocal microscopy evaluated mitophagy-associated protein expression in colon tissue and CCD841 cells. Cell apoptosis and reactive oxygen species (ROS) were measured via flow cytometry. RESULTS: We observed reduced NR1D1 expression in the IECs of UC patients, accentuated under jet lag and DSS exposure in mice. NR1D1 ablation led to disrupted immune homeostasis and declined mitophagy in IECs. NR1D1, usually a transcriptional repressor, was a positive regulator of BNIP3 expression, leading to impaired mitophagy, cellular inflammation, and apoptosis. Administering the NR1D1 agonist SR9009 ameliorated colitis symptoms, primarily by rectifying defective mitophagy. CONCLUSIONS: Our results suggest that NR1D1 bridges the circadian clock and UC, controlling BNIP3-mediated mitophagy and representing a potential therapeutic target. Its agonist, SR9009, shows promise in UC symptom alleviation.

Hypoxia activation attenuates progesterone synthesis in goat trophoblast cells via NR1D1 inhibition of StAR expression†.

Trophoblast plays a crucial role in gestation maintenance and embryo implantation, partly due to the synthesis of progesterone. It has been demonstrated that hypoxia regulates invasion, proliferation, and differentiation of trophoblast cells. Additionally, human trophoblasts display rhythmic expression of circadian clock genes. However, it remains unclear if the circadian clock system is present in goat trophoblast cells (GTCs), and its involvement in hypoxia regulation of steroid hormone synthesis remains elusive. In this study, immunofluorescence staining revealed that both BMAL1 and NR1D1 (two circadian clock components) were highly expressed in GTCs. Quantitative real-time PCR analysis showed that several circadian clock genes were rhythmically expressed in forskolin-synchronized GTCs. To mimic hypoxia, GTCs were treated with hypoxia-inducing reagents (CoCl2 or DMOG). Quantitative real-time PCR results demonstrated that hypoxia perturbed the mRNA expression of circadian clock genes and StAR. Notably, the increased expression of NR1D1 and the reduction of StAR expression in hypoxic GTCs were also detected by western blotting. In addition, progesterone secretion exhibited a notable decline in hypoxic GTCs. SR9009, an NR1D1 agonist, significantly decreased StAR expression at both the mRNA and protein levels and markedly inhibited progesterone secretion in GTCs. Moreover, SR8278, an NR1D1 antagonist, partially reversed the inhibitory effect of CoCl2 on mRNA and protein expression levels of StAR and progesterone synthesis in GTCs. Our results demonstrate that hypoxia reduces StAR expression via the activation of NR1D1 signaling in GTCs, thus inhibiting progesterone synthesis. These findings provide new insights into the NR1D1 regulation of progesterone synthesis in GTCs under hypoxic conditions.

Microglia depletion ameliorates neuroinflammation, anxiety-like behavior, and cognitive deficits in a sex-specific manner in Rev-erbα knockout mice.

The circadian system is an evolutionarily adaptive system that synchronizes biological and physiological activities within the body to the 24 h oscillations on Earth. At the molecular level, circadian clock proteins are transcriptional factors that regulate the rhythmic expression of genes involved in numerous physiological processes such as sleep, cognition, mood, and immune function. Environmental and genetic disruption of the circadian clock can lead to pathology. For example, global deletion of the circadian clock gene Rev-erbα (RKO) leads to hyperlocomotion, increased anxiety-like behaviors, and cognitive impairments in male mice; however, the mechanisms underlying behavioral changes remain unclear. Here we hypothesized that RKO alters microglia function leading to neuroinflammation and altered mood and cognition, and that microglia depletion can resolve neuroinflammation and restore behavior. We show that microglia depletion (CSF1R inhibitor, PLX5622) in 8-month-old RKO mice ameliorated hyperactivity, memory impairments, and anxiety/risky-like behaviors. RKO mice exhibited striking increases in expression of pro-inflammatory cytokines (e.g., IL-1ß and IL-6). Surprisingly, these increases were only fully reversed by microglia depletion in the male but not female RKO hippocampus. In contrast, male RKO mice showed greater alterations in microglial morphology and phagocytic activity than females. In both sexes, microglia depletion reduced microglial branching and decreased CD68 production without altering astrogliosis. Taken together, we show that male and female RKO mice exhibit unique perturbations to the neuroimmune system, but microglia depletion is effective at rescuing aspects of behavioral changes in both sexes. These results demonstrate that microglia are involved in Rev-erbα-mediated changes in behavior and neuroinflammation.

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.

Rev-erbα agonists suppresses TGFß1-induced fibroblast-to-myofibroblast transition and pro-fibrotic phenotype in human lung fibroblasts.

Idiopathic pulmonary fibrosis (IPF) is an interstitial lung disease characterized by excessive scarring of the lungs that can lead to respiratory failure and death. Lungs of patients with IPF demonstrate excessive deposition of extracellular matrix (ECM) and an increased presence of pro-fibrotic mediators such as transforming growth factor-beta 1 (TGFß1), which is a major driver of fibroblast-to-myofibroblast transition (FMT). Current literature supports that circadian clock dysfunction plays an essential role in the pathophysiology of various chronic inflammatory lung diseases such as asthma, chronic obstructive pulmonary disease, and IPF. The circadian clock transcription factor Rev-erbα is encoded by Nr1d1 that regulates daily rhythms of gene expression linked to immunity, inflammation, and metabolism. However, investigations into the potential roles of Rev-erbα in TGFß-induced FMT and ECM accumulation are limited. In this study, we utilized several novel small molecule Rev-erbα agonists (GSK41122, SR9009, and SR9011) and a Rev-erbα antagonist (SR8278) to determine the roles of Rev-erbα in regulating TGFß1-induced FMT and pro-fibrotic phenotypes in human lung fibroblasts. WI-38 cells were either pre-treated/co-treated with or without Rev-erbα agonist/antagonist along with TGFß1. After 48 h, the following parameters were evaluated: secretion of COL1A1 (Slot-Blot analysis) and IL-6 (ELISA) into condition media, expressions of α-smooth muscle actin (αSMA: immunostaining and confocal microscopy), and pro-fibrotic proteins (αSMA and COL1A1 by immunoblotting), as well as gene expression of pro-fibrotic targets (qRT-PCR: Acta2, Fn1, and Col1a1). Results revealed that Rev-erbα agonists inhibited TGFß1-induced FMT (αSMA and COL1A1), and ECM production (reduced gene expression of Acta2, Fn1, and Col1a1), and decreased pro-inflammatory cytokine IL-6 release. The Rev-erbα antagonist promoted TGFß1-induced pro-fibrotic phenotypes. These findings support the potential of novel circadian clock-based therapeutics, such as Rev-erbα agonist, for the treatment and management of fibrotic lung diseases and disorders.

The REV-ERB Nuclear Receptors: Timekeepers for the Core Clock Period and Metabolism.

REV-ERB nuclear receptors are potent transcriptional repressors that play an important role in the core mammalian molecular clock and metabolism. Deletion of both REV-ERBα and its largely redundant isoform REV-ERBß in a murine tissue-specific manner have shed light on their specific functions in clock mechanisms and circadian metabolism. This review highlights recent findings that establish REV-ERBs as crucial circadian timekeepers in a variety of tissues, regulating overlapping and distinct processes that maintain normal physiology and protect from metabolic dysfunction.

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.

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.

Hepatocyte SREBP signaling mediates clock communication within the liver.

Rhythmic intraorgan communication coordinates environmental signals and the cell-intrinsic clock to maintain organ homeostasis. Hepatocyte-specific KO of core components of the molecular clock Rev-erbα and -ß (Reverb-hDKO) alters cholesterol and lipid metabolism in hepatocytes as well as rhythmic gene expression in nonparenchymal cells (NPCs) of the liver. Here, we report that in fatty liver caused by diet-induced obesity (DIO), hepatocyte SREBP cleavage-activating protein (SCAP) was required for Reverb-hDKO-induced diurnal rhythmic remodeling and epigenomic reprogramming in liver macrophages (LMs). Integrative analyses of isolated hepatocytes and LMs revealed that SCAP-dependent lipidomic changes in REV-ERB-depleted hepatocytes led to the enhancement of LM metabolic rhythms. Hepatocytic loss of REV-ERBα and ß (REV-ERBs) also attenuated LM rhythms via SCAP-independent polypeptide secretion. These results shed light on the signaling mechanisms by which hepatocytes regulate diurnal rhythms in NPCs in fatty liver disease caused by DIO.