NR4A3: A Key Nuclear Receptor in Vascular Biology, Cardiovascular Remodeling, and Beyond

Orphan Nuclear Receptor NR4A3 Promotes Vascular Calcification via Histone Lactylation

BACKGROUND

Medial arterial calcification is a chronic systemic vascular disorder distinct from atherosclerosis and is commonly observed in patients with chronic kidney disease, diabetes, and aging individuals. We previously showed that NR4A3 (nuclear receptor subfamily 4 group A member 3), an orphan nuclear receptor, is a key regulator in apo (apolipoprotein) A-IV-induced atherosclerosis progression; however, its role in vascular calcification is poorly understood.

METHODS

We generated NR4A3-/- mice and 2 different types of medial arterial calcification models to investigate the biological roles of NR4A3 in vascular calcification. RNA-seq was performed to determine the transcriptional profile of NR4A3-/- vascular smooth muscle cells under β-glycerophosphate treatment. We integrated Cleavage Under Targets and Tagmentation analysis and RNA-seq data to further investigate the gene regulatory mechanisms of NR4A3 in arterial calcification and target genes regulated by histone lactylation.

RESULTS

NR4A3 expression was upregulated in calcified aortic tissues from chronic kidney disease mice, 1,25(OH)2VitD3 overload-induced mice, and human calcified aorta. NR4A3 deficiency preserved the vascular smooth muscle cell contractile phenotype, inhibited osteoblast differentiation-related gene expression, and reduced calcium deposition in the vasculature. Further, NR4A3 deficiency lowered the glycolytic rate and lactate production during the calcification process and decreased histone lactylation. Mechanistic studies further showed that NR4A3 enhanced glycolysis activity by directly binding to the promoter regions of the 2 glycolysis genes ALDOA and PFKL and driving their transcriptional initiation. Furthermore, histone lactylation promoted medial calcification both in vivo and in vitro. NR4A3 deficiency inhibited the transcription activation and expression of Phospho1 (phosphatase orphan 1). Consistently, pharmacological inhibition of Phospho1 attenuated calcium deposition in NR4A3-overexpressed vascular smooth muscle cells, whereas overexpression of Phospho1 reversed the anticalcific effect of NR4A3 deficiency in vascular smooth muscle cells.

CONCLUSIONS

Taken together, our findings reveal that NR4A3-mediated histone lactylation is a novel metabolome-epigenome signaling cascade mechanism that participates in the pathogenesis of medial arterial calcification.

Efficacy of Shu-yi-ning-chang decoction on IBS-D: Modulating Nr4a3 pathway to reduce visceral hypersensitivity

AIM OF THE STUDY

To evaluate the therapeutic effect of SYNC in diarrhea irritable bowel syndrome (IBS-D) and explore its underlying mechanism through transcriptomic sequencing (RNA-Seq).

MATERIALS AND METHODS

A rat model of IBS-D was constructed to elucidate the effects of SYNC. Abdominal withdrawal reflex (AWR), fecal water content (FWC), and recording body weight were calculated to assess visceral sensitivity in rats. Histopathological changes in the colon and alterations in mast cell (MC) count were determined. Immunohistochemistry was employed to assess mast cell tryptase (MCT) expression in rat colons. Serum levels of corticotropin-releasing Hormone (CRH), interleukin-6 (IL-6), calcitonin gene-related peptide (CGRP), and 5-hydroxytryptamine (5-HT) were quantified using ELISA. RNA-Seq of colon tissue was performed, followed by Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Western blot analysis was conducted to quantify the expression levels of key proteins in the Nr4a3 pathway in the colon and hypothalamus tissues of rats.

RESULTS

SYNC alleviated visceral hypersensitivity and mood disorders in rats with IBS-D. Moreover, it was positively correlated with its dosage and the observed effects, such as the enhancement of the colon's mucosal lining condition and reduction in the number and activation of MCs within the model group. SYNC reduced the expression levels of factors related to the brain-gut axis and inflammatory markers in the bloodstream. RNA-Seq analysis indicated that SYNC down-regulated the expression of Nr4a3 and PI3K. These SYNC-targeted genes primarily played roles in immune regulation and inflammatory responses, correlating with the modulation of Nr4a3 and the PI3K/AKT pathway. Western blot analysis further confirmed SYNC's influence on inflammation-related MC activation by downregulating key proteins in the Nr4a3/PI3K pathway.

CONCLUSIONS

SYNC inhibited mast cell activation and attenuated visceral hypersensitivity in the colon tissues of IBS-D rats. These effects were mediated by the Nr4a3/PI3K signaling pathway.

Lysyl oxidase expression in smooth muscle cells determines the level of intima calcification in hypercholesterolemia-induced atherosclerosis

INTRODUCTION

Cardiovascular calcification is an important public health issue with an unmeet therapeutic need. We had previously shown that lysyl oxidase (LOX) activity critically influences vascular wall smooth muscle cells (VSMCs) and valvular interstitial cells (VICs) calcification by affecting extracellular matrix remodeling. We have delved into the participation of LOX in atherosclerosis and vascular calcification, as well as in the mineralization of the aortic valve.

METHODS

Immunohistochemical and expression studies were carried out in human atherosclerotic lesions and experimental models, valves from patients with aortic stenosis, VICs, and in a genetically modified mouse model that overexpresses LOX in CMLV (TgLOXCMLV). Hyperlipemia and atherosclerosis was induced in mice through the administration of adeno-associated viruses encoding a PCSK9 mutated form (AAV-PCSK9D374Y) combined with an atherogenic diet.

RESULTS

LOX expression is increased in the neointimal layer of atherosclerotic lesions from human coronary arteries and in VSMC-rich regions of atheromas developed both in the brachiocephalic artery of control (C57BL/6J) animals transduced with PCSK9D374Y and in the aortic root of ApoE-/- mice. In TgLOXCMLV mice, PCSK9D374Y transduction did not significantly alter the enhanced aortic expression of genes involved in matrix remodeling, inflammation, oxidative stress and osteoblastic differentiation. Likewise, LOX transgenesis did not alter the size or lipid content of atherosclerotic lesions in the aortic arch, brachiocephalic artery and aortic root, but exacerbated calcification. Among lysyl oxidase isoenzymes, LOX is the most expressed member of this family in highly calcified human valves, colocalizing with RUNX2 in VICs. The lower calcium deposition and decreased RUNX2 levels triggered by the overexpression of the nuclear receptor NOR-1 in VICs was associated with a reduction in LOX.

CONCLUSIONS

Our results show that LOX expression is increased in atherosclerotic lesions, and that overexpression of this enzyme in VSMC does not affect the size of the atheroma or its lipid content, but it does affect its degree of calcification. Further, these data suggest that the decrease in calcification driven by NOR-1 in VICs would involve a reduction in LOX. These evidences support the interest of LOX as a therapeutic target in cardiovascular calcification.

Upregulation of NOR-1 in calcified human vascular tissues: impact on osteogenic differentiation and calcification

Cardiovascular calcification is a significant public health issue whose pathophysiology is not fully understood. NOR-1 regulates critical processes in cardiovascular remodeling, but its contribution to ectopic calcification is unknown. NOR-1 was overexpressed in human calcific aortic valves and calcified atherosclerotic lesions colocalizing with RUNX2, a factor essential for osteochondrogenic differentiation and calcification. NOR-1 and osteogenic markers were upregulated in calcifying human valvular interstitial cells (VICs) and human vascular smooth muscle cells (VSMCs). Gain- and loss-of-function approaches demonstrated that NOR-1 negatively modulates the expression of osteogenic genes relevant for the osteogenic transdifferentiation (RUNX2, IL-6, BMP2, and ALPL) and calcification of VICs. VSMCs from transgenic mice overexpressing NOR-1 in these cells (TgNOR-1VSMC) expressed lower basal levels of osteogenic genes (IL-6, BMP2, ALPL, OPN) than cells from WT littermates, and their upregulation by a high-phosphate osteogenic medium (OM) was completely prevented by NOR-1 transgenesis. Consistently, this was associated with a dramatic reduction in the calcification of both transgenic VSMCs and aortic rings from TgNOR-1VSMC mice exposed to OM. Atherosclerosis and calcification were induce in mice by the administration of AAV-PCSK9D374Y and a high-fat/high-cholesterol diet. Challenged-TgNOR-1VSMC mice exhibited decreased vascular expression of osteogenic markers, and both less atherosclerotic burden (assessed in whole aorta and lesion size in aortic arch and brachiocephalic artery) and less vascular calcification (assessed either by near-infrared fluorescence imaging or histological analysis) than WT mice. Our data indicate that NOR-1 negatively modulates the expression of genes critically involved in the osteogenic differentiation of VICs and VSMCs, thereby restraining ectopic cardiovascular calcification.

RP11-495P10.1 promotes HCC cell proliferation by regulating reprogramming of glucose metabolism and acetylation of the NR4A3 promoter via the PDK1/PDH axis

The incidence and related death of hepatocellular carcinoma (HCC) have increased over the past decades. However, the molecular mechanisms underlying HCC pathogenesis are not fully understood. Long noncoding RNA (lncRNA) RP11-495P10.1 has been proven to be closely associated with the progression of prostate cancer, but its role and specific mechanism in HCC are still unknown. Here, we identify that RP11-495P10.1 is highly expressed in HCC tissues and cells and contributes to the proliferation of HCC cells. Moreover, this study demonstrates that RP11-495P10.1 affects the proliferation of HCC by negatively regulating the expression of nuclear receptor subfamily 4 group a member 3 (NR4A3). Glycometabolism reprogramming is one of the main characteristics of tumor cells. In this study, we discover that RP11-495P10.1 regulates glycometabolism reprogramming by changing the expression of pyruvate dehydrogenase kinase 1 (PDK1) and pyruvate dehydrogenase (PDH), thus contributing to the proliferation of HCC cells. Furthermore, knockdown of RP11-495P10.1 increases enrichment of H3K27Ac in the promoter of NR4A3 by promoting the activity of PDH and the production of acetyl-CoA, which leads to the increased transcription of NR4A3. Altogether, RP11-495P10.1 promotes HCC cell proliferation by regulating the reprogramming of glucose metabolism and acetylation of the NR4A3 promoter via the PDK1/PDH axis, which provides an lncRNA-oriented therapeutic strategy for the diagnosis and treatment of HCC.

Structural Perspective of NR4A Nuclear Receptor Family and Their Potential Endogenous Ligands

There are 48 nuclear receptors in the human genome, and many members of this superfamily have been implicated in human diseases. The NR4A nuclear receptor family consisting of three members, NR4A1, NR4A2, and NR4A3 (formerly annotated as Nur77, Nurr1, and NOR1, respectively), are still orphan receptors but exert pathological effects on immune-related and neurological diseases. We previously reported that prostaglandin A1 (PGA1) and prostaglandin A2 (PGA2) are potent activators of NR4A3, which bind directly to the ligand-binding domain (LBD) of the receptor. Recently, the co-crystallographic structures of NR4A2-LBD bound to PGA1 and PGA2 were reported, followed by reports of the neuroprotective effects of these possible endogenous ligands in mouse models of Parkinson's disease. Based on these structures, we modeled the binding structures of the other two members (NR4A1 and NR4A3) with these potential endogenous ligands using a template-based modeling method, and reviewed the similarity and diversity of ligand-binding mechanisms in the nuclear receptor family.

Integrated systems biology approach identifies gene targets for endothelial dysfunction

Endothelial dysfunction (ED) is critical in the development and progression of cardiovascular (CV) disorders, yet effective therapeutic targets for ED remain elusive due to limited understanding of its underlying molecular mechanisms. To address this gap, we employed a systems biology approach to identify potential targets for ED. Our study combined multi omics data integration, with siRNA screening, high content imaging and network analysis to prioritise key ED genes and identify a pro- and anti-ED network. We found 26 genes that, upon silencing, exacerbated the ED phenotypes tested, and network propagation identified a pro-ED network enriched in functions associated with inflammatory responses. Conversely, 31 genes ameliorated ED phenotypes, pointing to potential ED targets, and the respective anti-ED network was enriched in hypoxia, angiogenesis and cancer-related processes. An independent screen with 17 drugs found general agreement with the trends from our siRNA screen and further highlighted DUSP1, IL6 and CCL2 as potential candidates for targeting ED. Overall, our results demonstrate the potential of integrated system biology approaches in discovering disease-specific candidate drug targets for endothelial dysfunction.

Novel pharmacological approaches in abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a severe vascular disease and a major public health issue with an unmet medical need for therapy. This disease is featured by a progressive dilation of the abdominal aorta, boosted by atherosclerosis, ageing, and smoking as major risk factors. Aneurysm growth increases the risk of aortic rupture, a life-threatening emergency with high mortality rates. Despite the increasing progress in our knowledge about the etiopathology of AAA, an effective pharmacological treatment against this disorder remains elusive and surgical repair is still the unique available therapeutic approach for high-risk patients. Meanwhile, there is no medical alternative for patients with small aneurysms but close surveillance. Clinical trials assessing the efficacy of antihypertensive agents, statins, doxycycline, or anti-platelet drugs, among others, failed to demonstrate a clear benefit limiting AAA growth, while data from ongoing clinical trials addressing the benefit of metformin on aneurysm progression are eagerly awaited. Recent preclinical studies have postulated new therapeutic targets and pharmacological strategies paving the way for the implementation of future clinical studies exploring these novel therapeutic strategies. This review summarises some of the most relevant clinical and preclinical studies in search of new therapeutic approaches for AAA.

Atherosclerosis and Other Related-Arterial Diseases

Cardiovascular diseases (CVD) are a major cause of morbidity and mortality worldwide, accounting for more than 17 million deaths each year [...].

Identification of immune-related genes in acute myocardial infarction based on integrated bioinformatical methods and experimental verification

Background

Acute myocardial infarction (AMI) is one of the leading causes of death worldwide. The etiology of AMI is complex and has not been fully defined. In recent years, the role of immune response in the development, progression and prognosis of AMI has received increasing attention. The aim of this study was to identify key genes associated with the immune response in AMI and to analyze their immune infiltration.

Methods

The study included a total of two GEO databases, containing 83 patients with AMI and 54 healthy individuals. We used the linear model of microarray data (limma) package to find the differentially expressed genes associated with AMI, performing weighted gene co-expression analysis (WGCNA) to further identify the genes associated with inflammatory response to AMI. We found the final hub genes through the protein-protein interaction (PPI) network and least absolute shrinkage and selection operator (LASSO) regression model. To verify the above conclusions, we constructed mice AMI model, extracting myocardial tissue to perform qRT-PCR. Furthermore, the CIBERSORT tool for immune cells infiltration analysis was also carried out.

Results

A total of 5,425 significant up-regulated and 2,126 down-regulated genes were found in GSE66360 and GSE24519. A total of 116 immune-related genes in close association with AMI were screened by WGCNA analysis. These genes were mostly clustered in the immune response on the basis of GO and KEGG enrichment. With construction of PPI network and LASSO regression analysis, this research found three hub genes (SOCS2, FFAR2, MYO10) among these differentially expressed genes. The immune cell infiltration results revealed that significant differences could be found on T cells CD4 memory activated, Tregs (regulatory T cells), macrophages M2, neutrophils, T cells CD8, T cells CD4 naive, eosinophils between controls and AMI patients.

Translatome analyses by bio-orthogonal non-canonical amino acid labeling reveal that MR1-activated MAIT cells induce an M1 phenotype and antiviral programming in antigen-presenting monocytes

MAIT cells are multifunctional innate-like effector cells recognizing bacterial-derived vitamin B metabolites presented by the non-polymorphic MHC class I related protein 1 (MR1). However, our understanding of MR1-mediated responses of MAIT cells upon their interaction with other immune cells is still incomplete. Here, we performed the first translatome study of primary human MAIT cells interacting with THP-1 monocytes in a bicellular system. We analyzed the interaction between MAIT and THP-1 cells in the presence of the activating 5-OP-RU or the inhibitory Ac-6-FP MR1-ligand. Using bio-orthogonal non-canonical amino acid tagging (BONCAT) we were able to enrich selectively those proteins that were newly translated during MR1-dependent cellular interaction. Subsequently, newly translated proteins were measured cell-type-specifically by ultrasensitive proteomics to decipher the coinciding immune responses in both cell types. This strategy identified over 2,000 MAIT and 3,000 THP-1 active protein translations following MR1 ligand stimulations. Translation in both cell types was found to be increased by 5-OP-RU, which correlated with their conjugation frequency and CD3 polarization at MAIT cell immunological synapses in the presence of 5-OP-RU. In contrast, Ac-6-FP only regulated a few protein translations, including GSK3B, indicating an anergic phenotype. In addition to known effector responses, 5-OP-RU-induced protein translations uncovered type I and type II Interferon-driven protein expression profiles in both MAIT and THP-1 cells. Interestingly, the translatome of THP-1 cells suggested that activated MAIT cells can impact M1/M2 polarization in these cells. Indeed, gene and surface expression of CXCL10, IL-1β, CD80, and CD206 confirmed an M1-like phenotype of macrophages being induced in the presence of 5-OP-RU-activated MAIT cells. Furthermore, we validated that the Interferon-driven translatome was accompanied by the induction of an antiviral phenotype in THP-1 cells, which were found able to suppress viral replication following conjugation with MR1-activated MAIT cells. In conclusion, BONCAT translatomics extended our knowledge of MAIT cell immune responses at the protein level and discovered that MR1-activated MAIT cells are sufficient to induce M1 polarization and an anti-viral program of macrophages.

Comprehensive insights into the function and molecular and pharmacological regulation of neuron-derived orphan receptor 1, an orphan receptor

Neuron-derived orphan receptor 1 (NOR1), also called nuclear receptor subfamily 4 group A member 3 (NR4A3), is a nuclear receptor belonging to the NR4A family. Since no endogenous ligand has been identified to date, NOR1 is also referred to as an orphan receptor. NOR1 is expressed in a variety of cells and tissues, including neurons, vascular smooth muscle cells, T lymphocytes, dendritic cells, tumor cells, heart, liver, and pancreas. Because NOR1 was first identified in apoptotic neurons, it is functionally associated with the regulation of cell migration and the growth of neuronal synapses. In-depth studies have shown that NOR1 can be edited by the immediate early gene and functions as a transcription factor. NOR1 has been shown to be rapidly induced by a number of stimulants including growth factors, fatty acids, and neurotransmitters. Elevated NOR1 levels may be involved in a number of pathophysiological processes. These include regulation of cellular apoptosis and regeneration, neuron formation, contextual fearing memory, inflammation, vascular smooth muscle proliferation, insulin secretion, and tumor development, whereby NOR1 mediates the pathogenesis of numerous diseases such as cerebral ischemia, depression, post-traumatic stress disorder, atherosclerosis, abdominal aortic aneurysm, cardiac hypertrophy, diabetes, osteoarthritis, rheumatoid arthritis, and cancer. However, to date, comprehensive insights into the function of NOR1 are not available in sources published online. In this review, we provide a brief overview of the function and molecular and pharmacological regulation of NOR1 in various pathological or physiological conditions to advance the development of NOR1 as a novel target for disease treatment.

The role of NURR1 in metabolic abnormalities of Parkinson's disease

A constant metabolism and energy supply are crucial to all organs, particularly the brain. Age-dependent neurodegenerative diseases, such as Parkinson’s disease (PD), are associated with alterations in cellular metabolism. These changes have been recognized as a novel hot topic that may provide new insights to help identify risk in the pre-symptomatic phase of the disease, understand disease pathogenesis, track disease progression, and determine critical endpoints. Nuclear receptor-related factor 1 (NURR1), an orphan member of the nuclear receptor superfamily of transcription factors, is a major risk factor in the pathogenesis of PD, and changes in NURR1 expression can have a detrimental effect on cellular metabolism. In this review, we discuss recent evidence that suggests a vital role of NURR1 in dopaminergic (DAergic) neuron development and the pathogenesis of PD. The association between NURR1 and cellular metabolic abnormalities and its implications for PD therapy have been further highlighted.

Vascular Stem/Progenitor Cells in Vessel Injury and Repair

Vascular repair upon vessel injury is essential for the maintenance of arterial homeostasis and function. Stem/progenitor cells were demonstrated to play a crucial role in regeneration and replenishment of damaged vascular cells during vascular repair. Previous studies revealed that myeloid stem/progenitor cells were the main sources of tissue regeneration after vascular injury. However, accumulating evidences from developing lineage tracing studies indicate that various populations of vessel-resident stem/progenitor cells play specific roles in different process of vessel injury and repair. In response to shear stress, inflammation, or other risk factors-induced vascular injury, these vascular stem/progenitor cells can be activated and consequently differentiate into different types of vascular wall cells to participate in vascular repair. In this review, mechanisms that contribute to stem/progenitor cell differentiation and vascular repair are described. Targeting these mechanisms has potential to improve outcome of diseases that are characterized by vascular injury, such as atherosclerosis, hypertension, restenosis, and aortic aneurysm/dissection. Future studies on potential stem cell-based therapy are also highlighted.