Maf links Neuregulin1 signaling to cholesterol synthesis in myelinating Schwann cells.

Cholesterol is a major constituent of myelin membranes, which insulate axons and allow saltatory conduction. Therefore, Schwann cells, the myelinating glia of the peripheral nervous system, need to produce large amounts of cholesterol. Here, we define a crucial role of the transcription factor Maf in myelination and cholesterol biosynthesis and show that Maf acts downstream from Neuregulin1 (Nrg1). Maf expression is induced when Schwann cells begin myelination. Genetic ablation of Maf resulted in hypomyelination that resembled mice with defective Nrg1 signaling. Importantly, loss of Maf or Nrg1 signaling resulted in a down-regulation of the cholesterol synthesis program, and Maf directly binds to enhancers of cholesterol synthesis genes. Furthermore, we identified the molecular mechanisms by which Nrg1 signaling regulates Maf levels. Transcription of Maf depends on calmodulin-dependent kinases downstream from Nrg1, whereas Nrg1-MAPK signaling stabilizes Maf protein. Our results delineate a novel signaling cascade regulating cholesterol synthesis in myelinating Schwann cells.

Neuregulin1 Nuclear Signaling Influences Adult Neurogenesis and Regulates a Schizophrenia Susceptibility Gene Network within the Mouse Dentate Gyrus.

Neuregulin1 (Nrg1) signaling is critical for neuronal development and function from fate specification to synaptic plasticity. Type III Nrg1 is a synaptic protein which engages in bidirectional signaling with its receptor ErbB4. Forward signaling engages ErbB4 phosphorylation, whereas back signaling engages two known mechanisms: (1) local axonal PI3K-AKT signaling and (2) cleavage by γ-secretase resulting in cytosolic release of the intracellular domain (ICD), which can traffic to the nucleus (Bao et al., 2003; Hancock et al., 2008). To dissect the contribution of these alternate signaling strategies to neuronal development, we generated a transgenic mouse with a missense mutation (V321L) in the Nrg1 transmembrane domain that disrupts nuclear back signaling with minimal effects on forward signaling or local back signaling and was previously found to be associated with psychosis (Walss-Bass et al., 2006). We combined RNA sequencing, retroviral fate mapping of neural stem cells, behavioral analyses, and various network analyses of transcriptomic data to investigate the effect of disrupting Nrg1 nuclear back signaling in the dentate gyrus (DG) of male and female mice. The V321L mutation impairs nuclear translocation of the Nrg1 ICD and alters gene expression in the DG. V321L mice show reduced stem cell proliferation, altered cell cycle dynamics, fate specification defects, and dendritic dysmorphogenesis. Orthologs of known schizophrenia (SCZ)-susceptibility genes were dysregulated in the V321L DG. These genes coordinated a larger network with other dysregulated genes. Weighted gene correlation network analysis and protein interaction network analyses revealed striking similarity between DG transcriptomes of V321L mouse and humans with SCZ.

Neuregulin 4 Attenuates Podocyte Injury and Proteinuria in Part by Activating AMPK/mTOR-Mediated Autophagy in Mice.

In this study, we investigate the effect of neuregulin 4 (NRG4) on podocyte damage in a mouse model of diabetic nephropathy (DN) and we elucidate the underlying molecular mechanisms. In vivo experiments were conducted using a C57BL/6 mouse model of DN to determine the effect of NRG4 on proteinuria and podocyte injury, and in vitro experiments were performed with conditionally immortalized mouse podocytes treated with high glucose and NRG4 to assess the protective effects of NRG4 on podocyte injury. Autophagy-related protein levels and related signaling pathways were evaluated both in vivo and in vitro. The involvement of the adenosine monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway was detected using chloroquine or AMPK inhibitors. The results showed that the AMPK/mTOR pathway was involved in the protective roles of NRG4 against high glucose-mediated podocyte injury. Also, NRG4 significantly decreased albuminuria in DN mice. PAS staining indicated that NRG4 mitigated glomerular volume and mesangium expansion in DN mice. Consistently, western blot and RT-PCR analyses confirmed that NRG4 decreased the expression of pro-fibrotic molecules in the glomeruli of DN mice. The immunofluorescence results showed that NRG4 retained expression of podocin and nephrin, whereas transmission electron microscopy revealed that NRG4 alleviated podocyte injury. In DN mice, NRG4 decreased podocyte apoptosis and increased expression of nephrin and podocin, while decreasing the expression of desmin and HIF1α. Overall, NRG4 improved albuminuria, glomerulosclerosis, glomerulomegaly, and hypoxia in DN mice. The in vitro experiments showed that NRG4 inhibited HG-induced podocyte injury and apoptosis. Furthermore, autophagy of the glomeruli decreased in DN mice, but reactivated following NRG4 intervention. NRG4 intervention was found to partially activate autophagy via the AMPK/mTOR signaling pathway. Consequently, when the AMPK/mTOR pathway was suppressed or autophagy was inhibited, the beneficial effects of NRG4 intervention on podocyte injury were diminished. These results indicate that NRG4 intervention attenuates podocyte injury and apoptosis by promoting autophagy in the kidneys of DN mice, in part, by activating the AMPK/mTOR signaling pathway.

Circular RNA RRM2 alleviates metabolic dysfunction-associated steatotic liver disease by targeting miR-142-5p to increase NRG1 expression.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a prevalent chronic liver condition worldwide, demanding further investigation into its pathogenesis. Circular RNAs (circRNAs) are emerging as pivotal regulators in MASLD processes, yet their pathological implications in MASLD remain poorly understood. This study focused on elucidating the role of circular RNA ribonucleotide reductase subunit M2 (circRRM2) in MASLD progression. In this study, we used both in vitro and in vivo MASLD models using long-chain-free fatty acid (FFA)-treated hepatocytes and high-fat diet (HFD)-induced MASLD in mice, respectively. We determined the expression patterns of circRRM2, microRNA-142-5p (miR-142-5p), and neuregulin 1 (NRG1) in livers of MASLD-afflicted mice and MASLD hepatocytes by RT-qPCR. Dual-luciferase reporter assays verified the binding relationships among circRRM2, miR-142-5p, and NRG1. We conducted further analyses of their roles in MASLD hepatocytes and modulated circRRM2, miR-142-5p, and NRG1 expression in vitro by transfection. Our findings were validated in vivo. The results demonstrated reduced levels of circRRM2 and NRG1, along with elevated miR-142-5p expression in MASLD livers and hepatocytes. Overexpression of circRRM2 downregulated lipogenesis-related genes and decreased triglycerides accumulation in livers of MASLD mice. MiR-142-5p, which interacts with circRRM2, effectively counteracted the effects of circRRM2 in MASLD hepatocytes. Furthermore, NRG1 was identified as a miR-142-5p target, and its overexpression mitigated the regulatory impact of miR-142-5p on MASLD hepatocytes. In conclusion, circRRM2, via its role as a miR-142-5p sponge, upregulating NRG1, possibly influenced triglycerides accumulation in both in vitro and in vivo MASLD models.NEW & NOTEWORTHY CircRRM2 expression was downregulated in free fatty acid (FFA)-challenged hepatocytes and high-fat diet (HFD) fed mice. Overexpressed circular RNA ribonucleotide reductase subunit M2 (circRRM2) attenuated metabolic dysfunction-associated steatotic liver disease (MASLD) development by suppressing FFA-induced triglycerides accumulation. CircRRM2 targeted microRNA-142-5p (miR-142-5p), which served as an upstream inhibitor of neuregulin 1 (NRG1) and collaboratively regulated MASLD progression.

Prrx1b restricts fibrosis and promotes Nrg1-dependent cardiomyocyte proliferation during zebrafish heart regeneration.

Fibroblasts are activated to repair the heart following injury. Fibroblast activation in the mammalian heart leads to a permanent fibrotic scar that impairs cardiac function. In other organisms, such as zebrafish, cardiac injury is followed by transient fibrosis and scar-free regeneration. The mechanisms that drive scarring versus scar-free regeneration are not well understood. Here, we show that the homeobox-containing transcription factor Prrx1b is required for scar-free regeneration of the zebrafish heart as the loss of Prrx1b results in excessive fibrosis and impaired cardiomyocyte proliferation. Through lineage tracing and single-cell RNA sequencing, we find that Prrx1b is activated in epicardial-derived cells where it restricts TGFß ligand expression and collagen production. Furthermore, through combined in vitro experiments in human fetal epicardial-derived cells and in vivo rescue experiments in zebrafish, we conclude that Prrx1 stimulates Nrg1 expression and promotes cardiomyocyte proliferation. Collectively, these results indicate that Prrx1 is a key transcription factor that balances fibrosis and regeneration in the injured zebrafish heart. This article has an associated 'The people behind the papers' interview.

Lipid metabolic reprogramming mediated by circulating Nrg4 alleviates metabolic dysfunction-associated steatotic liver disease during the early recovery phase after sleeve gastrectomy.

BACKGROUND: The metabolic benefits of bariatric surgery that contribute to the alleviation of metabolic dysfunction-associated steatotic liver disease (MASLD) have been reported. However, the processes and mechanisms underlying the contribution of lipid metabolic reprogramming after bariatric surgery to attenuating MASLD remain elusive. METHODS: A case-control study was designed to evaluate the impact of three of the most common adipokines (Nrg4, leptin, and adiponectin) on hepatic steatosis in the early recovery phase following sleeve gastrectomy (SG). A series of rodent and cell line experiments were subsequently used to determine the role and mechanism of secreted adipokines following SG in the alleviation of MASLD. RESULTS: In morbidly obese patients, an increase in circulating Nrg4 levels is associated with the alleviation of hepatic steatosis in the early recovery phase following SG before remarkable weight loss. The temporal parameters of the mice confirmed that an increase in circulating Nrg4 levels was initially stimulated by SG and contributed to the beneficial effect of SG on hepatic lipid deposition. Moreover, this occurred early following bariatric surgery. Mechanistically, gain- and loss-of-function studies in mice or cell lines revealed that circulating Nrg4 activates ErbB4, which could positively regulate fatty acid oxidation in hepatocytes to reduce intracellular lipid deposition. CONCLUSIONS: This study demonstrated that the rapid effect of SG on hepatic lipid metabolic reprogramming mediated by circulating Nrg4 alleviates MASLD.

SIBP-03, a novel anti-HER3 antibody, exerts antitumor effects and synergizes with EGFR- and HER2-targeted drugs.

HER3 (human epidermal growth factor receptor 3) acts through heterodimerization with EGFR (epidermal growth factor receptor) or HER2 to play an essential role in activating phosphoinositide 3-kinase (PI3K) and AKT signaling-a crucial pathway that promotes tumor cell survival. HER3 is a promising target for cancer therapy, and several HER3-directed antibodies have already entered into clinical trials. In this study we characterized a novel anti-HER3 monoclonal antibody, SIBP-03. SIBP-03 (0.01-10 µg/mL) specifically and concentration-dependently blocked both neuregulin (NRG)-dependent and -independent HER3 activation, attenuated HER3-mediated downstream signaling and inhibited cell proliferation. This antitumor activity was dependent, at least in part, on SIBP-03-induced, cell-mediated cytotoxicity and cellular phagocytosis. Importantly, SIBP-03 enhanced the antitumor activity of EGFR- or HER2-targeted drugs (cetuximab or trastuzumab) in vitro and in vivo. The mechanisms underlying this synergy involve increased inhibition of HER3-mediated downstream signaling. Collectively, these results demonstrated that SIBP-03, which is currently undergoing a Phase I clinical trial in China, may offer a new treatment option for patients with cancers harboring activated HER3, particularly as part of a combinational therapeutic strategy.

Neuregulin 1 as a potential biomarker for disease progression in moyamoya disease: A case-control study in Chinese population.

OBJECTIVE: Moyamoya disease (MMD) is a rare and progressive stenosis of cerebral arteries characterized by abnormally proliferative vasculopathy. Current studies have demonstrated that Neuregulin 1 (NRG1) plays a key role in angiogenesis-related disorders. Thus, the aim of our study is to investigate the serum NRG1 levels and their clinical correlations in MMD patients. METHODS: In this study, thirty adult patients with MMD and age-gender matched healthy controls were enrolled from our hospital between July 2020 and April 2022. Peripheral blood samples were collected at baseline, and clinical data were obtained from the electronic medical record system. Serum NRG1 concentrations were measured by enzyme-linked immunosorbent assay. Sanger sequencing was applied to detect the RNF213 p.R4810K mutation. RESULTS: The serum NRG1 levels were significantly higher in MMD patients compared to controls (14.48 ± 10.81 vs.7.54 ± 6.35mmol/L, p < 0.001). No statistical difference in baseline clinical characteristics was found between both groups. Correlation analyses showed that NRG1 levels were positively associated with Suzuki staging (r = 0.4137, p = 0.023) while not related to other clinical features (reduced cerebral blood flow, posterior cerebral artery involvement, bilateral or unilateral steno-occlusive changes). Furthermore, subgroup analysis revealed that MMD patients with the RNF213 p.R4810K mutation presented with significantly higher NRG1 levels than those without the mutation (9.60 ± 0.929 vs. 25.89 ± 4.338 mmol/L, p = 0.001). CONCLUSIONS: Our study suggests that increased serum NRG1 levels may constitute a characteristic feature of MMD, indicating a potential positive correlation with disease progression and the presence of the RNF213 mutation. This positions NRG1 as a potentially crucial target for further studies aimed at comprehending the pathogenesis of MMD.

Myeloid Cell-Derived IL-1 Signaling Damps Neuregulin-1 from Fibroblasts to Suppress Colitis-Induced Early Repair of the Intestinal Epithelium.

Neuregulin-1 (Nrg1, gene symbol: Nrg1), a ligand of the ErbB receptor family, promotes intestinal epithelial cell proliferation and repair. However, the dynamics and accurate derivation of Nrg1 expression during colitis remain unclear. By analyzing the public single-cell RNA-sequencing datasets and employing a dextran sulfate sodium (DSS)-induced colitis model, we investigated the cell source of Nrg1 expression and its potential regulator in the process of epithelial healing. Nrg1 was majorly expressed in stem-like fibroblasts arising early in mouse colon after DSS administration, and Nrg1-Erbb3 signaling was identified as a potential mediator of interaction between stem-like fibroblasts and colonic epithelial cells. During the ongoing colitis phase, a significant infiltration of macrophages and neutrophils secreting IL-1ß emerged, accompanied by the rise in stem-like fibroblasts that co-expressed Nrg1 and IL-1 receptor 1. By stimulating intestinal or lung fibroblasts with IL-1ß in the context of inflammation, we observed a downregulation of Nrg1 expression. Patients with inflammatory bowel disease also exhibited an increase in NRG1+IL1R1+ fibroblasts and an interaction of NRG1-ERBB between IL1R1+ fibroblasts and colonic epithelial cells. This study reveals a novel potential mechanism for mucosal healing after inflammation-induced epithelial injury, in which inflammatory myeloid cell-derived IL-1ß suppresses the early regeneration of intestinal tissue by interfering with the secretion of reparative neuregulin-1 by stem-like fibroblasts.

Neuregulin 2 Is a Candidate Gene for Autism Spectrum Disorder.

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder with heterogeneous and complex genetic underpinnings. Our previous microarray gene expression profiling identified significantly different neuregulin-2 gene (NRG2) expression between ASD patients and controls. Thus, we aimed to clarify whether NRG2 is a candidate gene associated with ASD. The study consisted of two stages. First, we used real-time quantitative PCR in 20 ASDs and 20 controls to confirm the microarray gene expression profiling results. The average NRG2 gene expression level in patients with ASD (3.23 ± 2.80) was significantly lower than that in the controls (9.27 ± 4.78, p < 0.001). Next, we conducted resequencing of all the exons of NRG2 in a sample of 349 individuals with ASD, aiming to identify variants of the NRG2 associated with ASD. We identified three variants, including two single nucleotide variants (SNVs), IVS3 + 13A > G (rs889022) and IVS10 + 32T > A (rs182642591), and one small deletion at exon 11 of NRG2 (delGCCCGG, rs933769137). Using data from the Taiwan Biobank as the controls, we found no significant differences in allele frequencies of rs889022 and rs182642591 between two groups. However, there is a significant difference in the genotype and allele frequency distribution of rs933769137 between ASDs and controls (p < 0.0001). The small deletion is located in the EGF-like domain at the C-terminal of the NRG2 precursor protein. Our findings suggest that NRG2 might be a susceptibility gene for ASD.

The involvement of Neuregulin-1 in the process of facial nerve injury repair through the utilization of dental pulp stem cells.

BACKGROUND: Facial nerve injury often results in poor prognosis due to the challenging process of nerve regeneration. Neuregulin-1, a human calmodulin, is under investigation in this study for its impact on the reparative capabilities of Dental Pulp Stem Cells (DPSCs) in facial nerve injury. METHODS: Lentivirus was used to transfect and construct Neuregulin-1 overexpressed DPSCs. Various techniques assessed the effects of Neuregulin-1: osteogenic induction, lipid induction, Reverse Transcription Polymerase Chain Reaction, Western Blot, Cell Counting Kit-8 assay, wound healing, immunofluorescence, Phalloidin staining, nerve stem action potential, Hematoxylin-eosin staining, transmission electron microscopy, and immunohistochemistry. RESULTS: Neuregulin-1 effectively enhanced the proliferation, migration, and cytoskeletal rearrangement of DPSCs, while simultaneously suppressing the expression of Ras homolog gene family member A (RhoA) and Microfilament actin (F-actin). These changes facilitated the neural differentiation of DPSCs. Additionally, in vivo experiments showed that Neuregulin-1 expedited the restoration of action potential in the facial nerve trunk, increased the thickness of the myelin sheath, and stimulated axon regeneration. CONCLUSION: Neuregulin-1 has the capability to facilitate the repair of facial nerve injuries by promoting the regenerative capacity of DPSCs. Thus, Neuregulin-1 is a significant potential gene in the reparative processes of nerve damage.

Study on the relationship between Methylation of Neuregulin (NRG) Gene and Cervical Carcinoma.

Objective: To investigate the relationship between the DNA methylation state of NRG1 promoter and its expression changes, and to analyze the clinical significance of its regulatory mechanism of DNA methylation in cervical carcinoma. Methods: This was a retrospective study. One-hundred and twenty patients from the Department of Gynecology of Cangzhou People's Hospital from September 2017 to September 2019 were selected, including 40 cases of cervical SCC, 40 cases of high grade squamous intraepithelial lesions(HSIL) and 40 cases of control cervical tissues. RT-qPCR, immunohistochemistry and DNA methylation-specific PCR(MSP) were used to detect the mRNA and protein expression of NRG1 and DNA methylation status in different tissue types. Results: Immunohistochemical results showed that the positive protein expression rate of NRG1 gene in the SCC group was lower than that in both HSIL and Control groups. RT-qPCR results showed that the mRNA gene of NRG1 gradually decreased in expression with the increase of cervical tissue lesions, with a statistically significant difference. Similarly, it also found that the mRNA expression level of NRG1 in the SCC group was independent of patients' age (p>0.05), but significantly correlated with tumor pathological staging, surgical pathology staging and lymphatic metastasis (p<0.05). Furthermore, methylation-specific PCR results revealed a significantly higher DNA methylation rate of NRG1 gene in the SCC group than in both HSIL and Control groups, with a statistically significant difference. Moreover, the methylation degree of NRG1 gene in SCC tissues was negatively correlated with its mRNA expression (p<0.05). Conclusions: Abnormal DNA hypermethylation of NRG1 gene inhibits the expression of mRNA and protein in the progression of cervical tissue from normal to cancerous state, which is involved in the occurrence and development of cervical carcinoma.

Neuregulin 1 and ErbB4 Kinase Actively Regulate Sharp Wave Ripples in the Hippocampus.

Sharp wave ripples (SW-Rs) in the hippocampus are synchronized bursts of hippocampal pyramidal neurons (PyNs), critical for spatial working memory. However, the molecular underpinnings of SW-Rs remain poorly understood. We show that SW-Rs in hippocampal slices from both male and female mice were suppressed by neuregulin 1 (NRG1), an epidermal growth factor whose expression is enhanced by neuronal activity. Pharmacological inhibition of ErbB4, a receptor tyrosine kinase for NRG1, increases SW-R occurrence rate in hippocampal slices. These results suggest an important role of NRG1-ErbB4 signaling in regulating SW-Rs. To further test this notion, we characterized SW-Rs in freely moving male mice, chemical genetic mutant mice, where ErbB4 can be specifically inhibited by the bulky inhibitor 1NMPP1. Remarkably, SW-R occurrence was increased by 1NMPP1. We found that 1NMPP1 increased the firing rate of PyN neurons, yet disrupted PyN neuron dynamics during SW-R events. Furthermore, 1NMPP1 increased SW-R occurrence during both nonrapid eye movement (NREM) sleep states and wake states with a greater impact on SW-Rs during wake states. In accord, spatial working memory was attenuated in male mice. Together these results indicate that dynamic activity of ErbB4 kinase is critical to SW-Rs and spatial working memory. This study reveals a novel regulatory mechanism of SW-Rs and a novel function of the NRG1-ErbB4 signaling.SIGNIFICANCE STATEMENT Sharp wave ripples (SW-Rs) are a hippocampal event, important for memory functioning. Yet the molecular pathways that regulate SW-Rs remain unclear. Neuregulin 1 (NRG1), previously known to be increased in pyramidal neuron's (PyNs) in an activity dependent manner, signals to its receptor, ErbB4 kinase, that is in important regulator of GABAergic transmission and long-term potentiation in the hippocampus. Our findings demonstrate that SW-Rs are regulated by this signaling pathway in a dynamic manner. Not only so, we show that this signaling pathway is dynamically needed for spatial working memory. These data suggest a molecular signaling pathway, NRG1-ErbB4, that regulates an important network event of the hippocampus, SW-Rs, that underlies memory functioning.

A prognostic biomarker NRG1 promotes U-87 MG glioblastoma cell malignancy by inhibiting autophagy via ERBB2/AKT/mTOR pathway.

Glioblastoma (GBM) is the most common and aggressive primary brain malignancy. Studies have shown that autophagy-related (ATG) genes play important roles in regulating GBM malignancy. However, the mechanism still needs to be fully elucidated. Based on clinical and gene expression information of GBM patients downloaded from The The Cancer Genome Atlas database, Kaplan-Meier, univariate Cox regression, least absolute shrinkage and selection operator regression and multivariate Cox regression were applied to construct a risk signature for GBM prognosis, followed by validation using receiver operating characteristic analysis. Next, Cell Counting Kit-8, wound healing assay, flow cytometry, monodansyl cadaverine autophagy staining assay, immunofluorescence staining and western blot, either in the absence or presence of ERBB2/AKT/mTOR inhibitors, were carried out in GBM U87 cell line to explore molecular pathway underlying GBM malignancy. A three-ATG-gene signature (HIF1A, ITGA3, and NGR1) was constructed for GBM prognosis with the greatest contribution from NRG1. In vitro experiments showed that NRG1 promoted U87 cell migration and proliferation by inhibiting autophagy, and ERBB2/AKT/mTOR is a downstream pathway that mediates the autophagy-inhibitory effects of NRG1. We constructed an ATG gene prognostic model for GBM and demonstrated that NRG1 inhibited autophagy by activating ERBB2/AKT/mTOR, promoting GBM malignancy, thus providing new insights into the molecular contribution of autophagy in GBM malignancy.

Neuregulin-1 reverses anxiety-like behavior and social behavior deficits induced by unilateral micro-injection of CoCl2 into the ventral hippocampus (vHPC).

Neuregulin-1 (NRG1) is an epidermal growth factor family member with essential roles in the developing and adult nervous systems. In recent years, establishing evidence has collectively suggested that NRG1 is a new modulator of central nervous system (CNS) injury and disease, with multifaceted roles in neuroprotection, remyelination, neuroinflammation, and other repair mechanisms. NRG1 signaling exerts its effects via the tyrosine kinase receptors ErbB2-ErbB4. The NRG1/ErbB network in CNS pathology and repair has evolved, primarily in recent years. In the present study, we demonstrated that a unilateral microinjection of CoCl2 into the ventral hippocampus (vHPC) induced hypoxic insult and led to anxiety-related behaviors and deficit sociability in mice. NRG1 treatment significantly alleviated the CoCl2-induced increase of hypoxic-related molecules and behavioral abnormalities. Furthermore, NRG1 reduced the CoCl2-induced neuroinflammation and neuronal deficits in the vHPC or primary hippocampal neurons in mice. Collectively, these results suggest that NRG1 ameliorates hypoxia by alleviating synaptic deficits and behavioral abnormalities of the CoCl2-induced vHPC hypoxic model.

Notch1 signaling activation alleviates coronary microvascular dysfunction through histone modification of Nrg-1 via the interaction between NICD and GCN5.

The Notch signaling pathway is related to endothelial dysfunction in coronary atherosclerosis. Our objective was to explore the role of Notch signaling in coronary microvascular dysfunction (CMD). CMD models were constructed by sodium laurate injection in vivo and homocysteine (Hcy) stimulation in vitro. The binding ability of Notch Intracellular Domain (NICD)/H3K9Ac/GCN5 (General Control Non-derepressible 5) to Neuregulin-1 (Nrg-1) promoter was examined by chromatin immunoprecipitation. Immunofluorescence staining was conducted to detect CD31 positive cells, NICD localization, and co-localization of NICD and GCN5. Flow cytometry and Tunel staining were conducted to identify the apoptosis. Hematoxylin and eosin staining, quantitative real-time PCR, western blot, immunohistochemical staining, co-immunoprecipitation, and double luciferase report analysis were also conducted. Notch signaling pathway-related protein levels were decreased, levels of Nrg-1 and the phosphorylation of ErbB2 and ErbB4 were enhanced in CMD models. Interference with Nrg-1 further increased the apoptosis in Hcy-induced cardiac microvascular endothelial cells (CMECs). Meanwhile, the activation of the Notch signaling pathway increased the levels of Nrg-1 and the phosphorylation of ErbB2 and ErbB4, as well as inhibited the apoptosis induced by Hcy. Furthermore, NICD and histone acetyltransferase enzyme GCN5 could regulate Nrg-1 promoter activity by affecting the expression of acetylation-modified protein H3K9Ac. In addition, NICD also interacted with GCN5. In vivo results also confirmed that the activation of the Notch signal alleviated CMD. Notch signaling pathway regulates Nrg-1 level through synergistic interaction with GCN5, thereby mitigating CMD.

The relationship of circulating neuregulin 4 and irisin, and traditional and novel cardiometabolic risk factors with the risk and severity of coronary artery disease.

BACKGROUND AND AIMS: Neuregulin 4 (NRG4) and irisin are adipokines that have been suggested to be associated with cardiometabolic risk factors and coronary artery disease (CAD), but the data are inconclusive. This study aimed to investigate the relationship between circulating NRG4 and irisin and cardiometabolic risk factors with CAD risk and severity. METHODS AND RESULTS: In this cross-sectional study, the presence of CAD and the severity of stenosis (gensini score) were documented based on coronary angiography in 166 adults. Circulating NRG4 and irisin, glucose homeostasis markers, hs-CRP, lipid profiles, blood pressure, and anthropometric measurements were assessed as well. Age (p = 0.005), sex (p = 0.008), SBP (p = 0.033), DBP (p = 0.04), MAP (p = 0.018), FBG (p = 0.012), insulin (p = 0.039) and HOMA-IR (p = 0.01) were significantly associated with odds of having CAD. The final logistic regression model showed that age, sex, HOMA-IR, and MAP were the most important determinants of having CAD. There were no significant associations between circulating irisin and NRG4 with odds of having CAD. The final general linear model showed that being men (ß = 17.303, 95% CI: 7.086-27.52, P = 0.001), age (Aß = 0.712, 95% CI: 0.21-1.214, P = 0.006), HOMA-IR (Aß = 2.168, 95% CI: 0.256 to 4.079, P = 0.027), and NRG4 level (ß = 1.836, 95% CI: 0.119-3.553, P = 0.036) were directly associated with higher gensini score. Participants with the three-vessel disease had a mean increase of about 5 units in circulating irisin compared to those with no clinical CAD (ß = 5.221, 95% CI: 0.454-9.987, p = 0.032). CONCLUSIONS: This study showed that the adipokines NRG4 and Irisin might be associated with the severity of coronary stenosis.

Recombinant human neuregulin-1 alleviates immobilization-induced neuromuscular dysfunction via neuregulin-1/ErbB signaling pathway in rat.

Immobilization-induced Neuromuscular Dysfunction (NMD) increases morbidity and mortality of patients in Intensive Care Units. However, the underlying mechanism of NMD remain poorly elucidated which limited the development of therapeutic method for NMD. Here we developed an immobilization rat model and tested the hypothesis that decreased expression of NRG-1, abnormal expression and distribution of nicotinic acetylcholine receptors (nAChRs) in skeletal muscle caused by immobilization can lead to NMD. To investigate the role of NRG-1/ErbB pathway on immobilization-induced NMD, exogenous recombinant human neuregulin-1 (rhNRG-1) was used to increase the expression of NRG-1 in skeletal muscle during immobilization. It was observed rhNRG-1 significantly alleviated the muscle loss and enhanced the expression of ε-nAChR, while diminished the expression of γ- and α7-nAChR and NMD. Interestingly, ErbB inhibitor PD158780 blocked the protective effects of rhNRG-1. Collectively, the results of present study suggested that rhNRG-1 attenuated immobilization-induced muscle loss and NMD, suppressed γ- and α7-nAChR production, enhanced ε-nAChR synthesis via activating NRG-1/ErbB pathway. Taken together, our findings provide novel insights into NMD contribution, suggesting that the rhNRG-1 is a promising therapy to protect against immobilization-induced myopathy.

Neuregulin modulates hormone receptor levels in breast cancer through concerted action on multiple signaling pathways.

The Neuregulins (NRGs) are growth factors that bind and activate ErbB/HER receptor tyrosine kinases. Some reports have described an interplay between this ligand-receptor system and hormonal receptors in breast cancer. However, the mechanisms by which NRGs regulate hormonal receptor signaling have not been sufficiently described. Here, we show that in breast cancer cells the activation of NRG receptors down-regulated ERα through a double mechanism that included post-transcriptional and transcriptional effects. This regulation required the concerted participation of three signaling routes: the PI3K/AKT/mTOR, ERK1/2, and ERK5 pathways. Moreover, these three routes were also involved in the phosphorylation of ERα at serines 118 and 167, two residues implicated in resistance to endocrine therapies. On the other hand, NRGs conferred resistance to fulvestrant in breast cancer cells and this resistance could be reversed when the three pathways activated by NRGs were simultaneously inhibited. Our results indicate that estrogen receptor-positive (ER+) breast tumors that can have access to NRGs may be resistant to fulvestrant. This resistance could be overcome if strategies to target the three main pathways involved in the interplay between NRG receptors and ERα could be developed.

Prenatal dexamethasone exposure induces anxiety- and depressive-like behavior of male offspring rats through intrauterine programming of the activation of NRG1-ErbB4 signaling in hippocampal PV interneurons.

Dexamethasone is a commonly used synthetic glucocorticoid in the clinic. As a compound that can cross the placental barrier to promote fetal lung maturation, dexamethasone is extensively used in pregnant women at risk of premature delivery. However, the use of glucocorticoids during pregnancy increases the risk of neurodevelopmental disorders. In the present study, we observed anxiety- and depressive-like behavior changes and hyperexcitability of hippocampal neurons in adult rat offspring with previous prenatal dexamethasone exposure (PDE); the observed changes were related to in utero damage of parvalbumin interneurons. A programmed change in neuregulin 1 (NRG1)-Erb-b2 receptor tyrosine kinase 4 (ErbB4) signaling was the key to the damage of parvalbumin interneurons in the hippocampus of PDE offspring. Anxiety- and depressive-like behavior, NRG1-ErbB4 signaling activation, and damage of parvalbumin interneurons in PDE offspring were aggravated after chronic stress. The intervention of NRG1-ErbB4 signaling contributed to the improvement in dexamethasone-mediated injury to parvalbumin interneurons. These results suggested that PDE might cause anxiety- and depressive-like behavior changes in male rat offspring through the programmed activation of NRG1-ErbB4 signaling, resulting in damage to parvalbumin interneurons and hyperactivity of the hippocampus. Intrauterine programming of neuregulin 1 (NRG1)-Erb-b2 receptor tyrosine kinase 4 (ERBB4) overactivation by dexamethasone mediates anxiety- and depressive-like behavior in male rat offspring.