WWP2 regulates pathological cardiac fibrosis by modulating SMAD2 signaling

WWP2 Regulates Renal Fibrosis and the Metabolic Reprogramming of Profibrotic Myofibroblasts

Key Points

WWP2 expression is elevated in the tubulointerstitium of fibrotic kidneys and contributes to CKD pathogenesis and progression. WWP2 uncouples the profibrotic activation and cell proliferation in renal myofibroblasts. WWP2 controls mitochondrial respiration in renal myofibroblasts through the metabolic regulator peroxisome proliferator-activated receptor gamma coactivator 1-alpha.

Background

Renal fibrosis is a common pathologic end point in CKD that is challenging to reverse, and myofibroblasts are responsible for the accumulation of a fibrillar collagen–rich extracellular matrix. Recent studies have unveiled myofibroblasts' diversity in proliferative and fibrotic characteristics, which are linked to different metabolic states. We previously demonstrated the regulation of extracellular matrix genes and tissue fibrosis by WWP2, a multifunctional E3 ubiquitin–protein ligase. Here, we investigate WWP2 in renal fibrosis and in the metabolic reprograming of myofibroblasts in CKD.

Methods

We used kidney samples from patients with CKD and WWP2 -null kidney disease mice models and leveraged single-cell RNA sequencing analysis to detail the cell-specific regulation of WWP2 in fibrotic kidneys. Experiments in primary cultured myofibroblasts by bulk-RNA sequencing, chromatin immunoprecipitation sequencing, metabolomics, and cellular metabolism assays were used to study the metabolic regulation of WWP2 and its downstream signaling.

Results

The tubulointerstitial expression of WWP2 was associated with fibrotic progression in patients with CKD and in murine kidney disease models. WWP2 deficiency promoted myofibroblast proliferation and halted profibrotic activation, reducing the severity of renal fibrosis in vivo . In renal myofibroblasts, WWP2 deficiency increased fatty acid oxidation and activated the pentose phosphate pathway, boosting mitochondrial respiration at the expense of glycolysis. WWP2 suppressed the transcription of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), a metabolic mediator of fibrotic response, and pharmacologic inhibition of PGC-1α partially abrogated the protective effects of WWP2 deficiency on myofibroblasts.

Conclusions

WWP2 regulates the metabolic reprogramming of profibrotic myofibroblasts by a WWP2-PGC-1α axis, and WWP2 deficiency protects against renal fibrosis in CKD.

Specific isoforms of the ubiquitin ligase gene WWP2 are targets of osteoarthritis genetic risk via a differentially methylated DNA sequence

BACKGROUND

Transitioning from a genetic association signal to an effector gene and a targetable molecular mechanism requires the application of functional fine-mapping tools such as reporter assays and genome editing. In this report, we undertook such studies on the osteoarthritis (OA) risk that is marked by single nucleotide polymorphism (SNP) rs34195470 (A > G). The OA risk-conferring G allele of this SNP associates with increased DNA methylation (DNAm) at two CpG dinucleotides within WWP2. This gene encodes a ubiquitin ligase and is the host gene of microRNA-140 (miR-140). WWP2 and miR-140 are both regulators of TGFβ signaling.

METHODS

Nucleic acids were extracted from adult OA (arthroplasty) and foetal cartilage. Samples were genotyped and DNAm quantified by pyrosequencing at the two CpGs plus 14 flanking CpGs. CpGs were tested for transcriptional regulatory effects using a chondrocyte cell line and reporter gene assay. DNAm was altered using epigenetic editing, with the impact on gene expression determined using RT-qPCR. In silico analysis complemented laboratory experiments.

RESULTS

rs34195470 genotype associates with differential methylation at 14 of the 16 CpGs in OA cartilage, forming a methylation quantitative trait locus (mQTL). The mQTL is less pronounced in foetal cartilage (5/16 CpGs). The reporter assay revealed that the CpGs reside within a transcriptional regulator. Epigenetic editing to increase their DNAm resulted in altered expression of the full-length and N-terminal transcript isoforms of WWP2. No changes in expression were observed for the C-terminal isoform of WWP2 or for miR-140.

CONCLUSIONS

As far as we are aware, this is the first experimental demonstration of an OA association signal targeting specific transcript isoforms of a gene. The WWP2 isoforms encode proteins with varying substrate specificities for the components of the TGFβ signaling pathway. Future analysis should focus on the substrates regulated by the two WWP2 isoforms that are the targets of this genetic risk.

Post-translational modifications in diabetic cardiomyopathy

The increasing attention towards diabetic cardiomyopathy as a distinctive complication of diabetes mellitus has highlighted the need for standardized diagnostic criteria and targeted treatment approaches in clinical practice. Ongoing research is gradually unravelling the pathogenesis of diabetic cardiomyopathy, with a particular emphasis on investigating various post-translational modifications. These modifications dynamically regulate protein function in response to changes in the internal and external environment, and their disturbance of homeostasis holds significant relevance for the development of chronic ailments. This review provides a comprehensive overview of the common post-translational modifications involved in the initiation and progression of diabetic cardiomyopathy, including O-GlcNAcylation, phosphorylation, methylation, acetylation and ubiquitination. Additionally, the review discusses drug development strategies for targeting key post-translational modification targets, such as agonists, inhibitors and PROTAC (proteolysis targeting chimaera) technology that targets E3 ubiquitin ligases.

HBI-8000 improves heart failure with preserved ejection fraction via the TGF-β1/MAPK signalling pathway

Heart failure with preserved ejection fraction (HFpEF) accounts for approximately 50% of total heart failure patients and is characterized by peripheral circulation, cardiac remodelling and comorbidities (such as advanced age, obesity, hypertension and diabetes) with limited treatment options. Chidamide (HBI-8000) is a domestically produced benzamide-based histone deacetylase isoform-selective inhibitor used for the treatment of relapsed refractory peripheral T-cell lymphomas. Based on our in vivo studies, we propose that HBI-8000 exerts its therapeutic effects by inhibiting myocardial fibrosis and myocardial hypertrophy in HFpEF patients. At the cellular level, we found that HBI-8000 inhibits AngII-induced proliferation and activation of CFs and downregulates the expression of fibrosis-related factors. In addition, we observed that the HFpEF group and AngII stimulation significantly increased the expression of TGF-β1 as well as phosphorylated p38MAPK, JNK and ERK, whereas the expression of the above factors was significantly reduced after HBI-8000 treatment. Activation of the TGF-β1/MAPK pathway promotes the development of fibrotic remodelling, and pretreatment with SB203580 (p38MAPK inhibitor) reverses this pathological change. In conclusion, our data suggest that HBI-8000 inhibits fibrosis by modulating the TGF-β1/MAPK pathway thereby improving HFpEF. Therefore, HBI-8000 may become a new hope for the treatment of HFpEF patients.

E3 ubiquitin ligase WWP2 as a promising therapeutic target for diverse human diseases

Mammalian E3 ubiquitin ligases have emerged in recent years as critical regulators of cellular homeostasis due to their roles in targeting substrate proteins for ubiquitination and triggering subsequent downstream signals. In this review, we describe the multiple roles of WWP2, an E3 ubiquitin ligase with unique and important functions in regulating a wide range of biological processes, including DNA repair, gene expression, signal transduction, and cell-fate decisions. As such, WWP2 has evolved to play a key role in normal physiology and diseases, such as tumorigenesis, skeletal development and diseases, immune regulation, cardiovascular disease, and others. We attempt to provide an overview of the biochemical, physiological, and pathophysiological roles of WWP2, as well as open questions for future research, particularly in the context of putative therapeutic opportunities.

The E3 ubiquitin ligases regulate inflammation in cardiovascular diseases

Accumulating evidence has illustrated that the E3 ubiquitin ligases critically participate in the development and progression of cardiovascular diseases. Dysregulation of E3 ubiquitin ligases exacerbates cardiovascular diseases. Blockade or activation of E3 ubiquitin ligases mitigates cardiovascular performance. Therefore, in this review, we mainly introduced the critical role and underlying molecular mechanisms of E3 ubiquitin ligase NEDD4 family in governing the initiation and progression of cardiovascular diseases, including ITCH, WWP1, WWP2, Smurf1, Smurf2, Nedd4-1 and Nedd4-2. Moreover, the functions and molecular insights of other E3 ubiquitin ligases, such as F-box proteins, in cardiovascular disease development and malignant progression are described. Furthermore, we illustrate several compounds that alter the expression of E3 ubiquitin ligases to alleviate cardiovascular diseases. Therefore, modulation of E3 ubiquitin ligases could be a novel and promising strategy for improvement of therapeutic efficacy of deteriorative cardiovascular diseases.

Identification of diagnostic model in heart failure with myocardial fibrosis and conduction block by integrated gene co-expression network analysis

BACKGROUND

Despite the advancements in heart failure(HF) research, the early diagnosis of HF continues to be a challenging issue in clinical practice. This study aims to investigate the genes related to myocardial fibrosis and conduction block, with the goal of developing a diagnostic model for early treatment of HF in patients.

METHOD

The gene expression profiles of GSE57345, GSE16499, and GSE9128 were obtained from the Gene Expression Omnibus (GEO) database. After merging the expression profile data and adjusting for batch effects, differentially expressed genes (DEGs) associated with conduction block and myocardial fibrosis were identified. Gene Ontology (GO) resources, Kyoto Encyclopedia of Genes and Genomes (KEGG) resources, and gene set enrichment analysis (GSEA) were utilized for functional enrichment analysis. A protein-protein interaction network (PPI) was constructed using a string database. Potential key genes were selected based on the bioinformatics information mentioned above. SVM and LASSO were employed to identify hub genes and construct the module associated with HF. The mRNA levels of TAC mice and external datasets (GSE141910 and GSE59867) are utilized for validating the diagnostic model. Additionally, the study explores the relationship between the diagnostic model and immune cell infiltration.

RESULTS

A total of 395 genes exhibiting differential expression were identified. Functional enrichment analysis revealed that these specific genes primarily participate in biological processes and pathways associated with the constituents of the extracellular matrix (ECM), immune system processes, and inflammatory responses. We identified a diagnostic model consisting of 16 hub genes, and its predictive performance was validated using external data sets and a transverse aortic coarctation (TAC) mouse model. In addition, we observed significant differences in mRNA expression of 7 genes in the TAC mouse model. Interestingly, our study also unveiled a correlation between these model genes and immune cell infiltration.

CONCLUSIONS

We identified sixteen key genes associated with myocardial fibrosis and conduction block, as well as diagnostic models for heart failure. Our findings have significant implications for the intensive management of individuals with potential genetic variants associated with heart failure, especially in the context of advancing cell-targeted therapy for myocardial fibrosis.

Spatial Mechano-Signaling Regulation of GTPases through Non-Degradative Ubiquitination

Blood flow produces shear stress exerted on the endothelial layer of the vessels. Spatial characterization of the endothelial proteome is required to uncover the mechanisms of endothelial activation by shear stress, as blood flow varies in the vasculature. An integrative ubiquitinome and proteome analysis of shear-stressed endothelial cells demonstrated that the non-degradative ubiquitination of several GTPases is regulated by mechano-signaling. Spatial analysis reveals increased ubiquitination of the small GTPase RAP1 in the descending aorta, a region exposed to laminar shear stress. The ubiquitin ligase WWP2 is identified as a novel regulator of RAP1 ubiquitination during shear stress response. Non-degradative ubiquitination fine-tunes the function of GTPases by modifying their interacting network. Specifically, WWP2-mediated RAP1 ubiquitination at lysine 31 switches the balance from the RAP1/ Talin 1 (TLN1) toward RAP1/ Afadin (AFDN) or RAP1/ RAS Interacting Protein 1 (RASIP1) complex formation, which is essential to suppress shear stress-induced reactive oxygen species (ROS) production and maintain endothelial barrier integrity. Increased ROS production in endothelial cells in the descending aorta of endothelial-specific Wwp2-knockout mice leads to increased levels of oxidized lipids and inflammation. These results highlight the importance of the spatially regulated non-degradative ubiquitination of GTPases in endothelial mechano-activation.

Substrate-dependent interaction of SPOP and RACK1 aggravates cardiac fibrosis following myocardial infarction

Speckle-type pox virus and zinc finger (POZ) protein (SPOP), a substrate recognition adaptor of cullin-3 (CUL3)/RING-type E3 ligase complex, is investigated for its role in cardiac fibrosis in our study. Cardiac fibroblasts (CFs) activation was achieved with TGF-β1 (20 ng/mL) and MI mouse model was established by ligation of the left anterior descending coronary, and lentivirus was employed to mediate interference of SPOP expression. SPOP was increased both in fibrotic post-MI mouse hearts and TGF-β1-treated CFs. The gain-of-function of SPOP promoted myofibroblast transformation in CFs, and exacerbated cardiac fibrosis and cardiac dysfunction in MI mice, while the loss-of-function of SPOP exhibited the opposite effects. Mechanistically, SPOP bound to the receptor of activated protein C kinase 1 (RACK1) and induced its ubiquitination and degradation by recognizing Ser/Thr-rich motifs on RACK1, leading to Smad3-mediated activation of CFs. Forced RACK1 expression canceled the effects of SPOP on cardiac fibrosis. The study reveals therapeutic targets for fibrosis-related cardiac diseases.

Aloe-emodin ameliorated MI-induced cardiac remodeling in mice via inhibiting TGF-β/SMAD signaling via up-regulating SMAD7

BACKGROUND

Aloe-emodin (AE), a natural anthraquinone extract from traditional Chinese medicinal plants, has been certified to protect against acute myocardial ischemia. However, its effect on cardiac remodeling after chronic myocardial infarction (MI) and the possible mechanism remain unclear.

PURPOSE

This study investigated the effect of AE on cardiac remodeling and oxidative damage induced by myocardial infarction (MI) in vitro and explored the underlying mechanisms.

METHODS

Echocardiography and Masson staining were used to demonstrate myocardial dysfunction and fibrosis. Cell apoptosis was detected by TUNEL staining. The expressions of fibrosis-related factors such as type I collagen, α-smooth muscle actin (α-SMA) and connective tissue growth factor (CTGF) were detected by Western blot.

RESULTS

Our data demonstrated that AE treatment significantly improved cardiac function, reduced structural remodeling, and reduced cardiac apoptosis and oxidative stress in mice with myocardial infarction. In vitro, AE could protect neonatal mouse cardiomyocytes (NMCM) from angiotensin II (Ang II)-induced cardiomyocyte hypertrophy and apoptosis, and significantly inhibited (p < 0.05) Ang II-induced reactive oxygen species (ROS) increase. Furthermore, AE treatment significantly reversed the Ang ii-induced upregulation.

CONCLUSION

In summary, our work reveals for the first time that AE activates the TGF-β signaling pathway by up-regulating Smad7 expression, which in turn regulates the expression of fibrosis-related genes, ultimately improving cardiac function, inhibiting the development of cardiac fibrosis and hypertrophy in rats with chronic MI.

Down-regulation of WWP2 aggravates Type 2 diabetes mellitus-induced vascular endothelial injury through modulating ubiquitination and degradation of DDX3X

BACKGROUND

Endothelial injury caused by Type 2 diabetes mellitus (T2DM) is considered as a mainstay in the pathophysiology of diabetic vascular complications (DVCs). However, the molecular mechanism of T2DM-induced endothelial injury remains largely unknown. Here, we found that endothelial WW domain-containing E3 ubiquitin protein ligase 2 (WWP2) act as a novel regulator for T2DM-induced vascular endothelial injury through modulating ubiquitination and degradation of DEAD-box helicase 3 X-linked (DDX3X).

METHODS

Single-cell transcriptome analysis was used to evaluate WWP2 expression in vascular endothelial cells of T2DM patients and healthy controls. Endothelial-specific Wwp2 knockout mice were used to investigate the effect of WWP2 on T2DM-induced vascular endothelial injury. In vitro loss- and gain-of-function studies were performed to assess the function of WWP2 on cell proliferation and apoptosis of human umbilical vein endothelial cells. The substrate protein of WWP2 was verified using mass spectrometry, coimmunoprecipitation assays and immunofluorescence assays. The mechanism of WWP2 regulation on substrate protein was investigated by pulse-chase assay and ubiquitination assay.

RESULTS

The expression of WWP2 was significantly down-regulated in vascular endothelial cells during T2DM. Endothelial-specific Wwp2 knockout in mice significantly aggravated T2DM-induced vascular endothelial injury and vascular remodeling after endothelial injury. Our in vitro experiments showed that WWP2 protected against endothelial injury by promoting cell proliferation and inhibiting apoptosis in ECs. Mechanically, we found that WWP2 is down-regulated in high glucose and palmitic acid (HG/PA)-induced ECs due to c-Jun N-terminal kinase (JNK) activation, and uncovered that WWP2 suppresses HG/PA-induced endothelial injury by catalyzing K63-linked polyubiquitination of DDX3X and targeting it for proteasomal degradation.

CONCLUSION

Our studies revealed the key role of endothelial WWP2 and the fundamental importance of the JNK-WWP2-DDX3X regulatory axis in T2DM-induced vascular endothelial injury, suggesting that WWP2 may serve as a new therapeutic target for DVCs.

Trypanosoma cruzi dysregulates expression profile of piRNAs in primary human cardiac fibroblasts during early infection phase

Trypanosoma cruzi, the etiological agent of Chagas Disease, causes severe morbidity, mortality, and economic burden worldwide. Though originally endemic to Central and South America, globalization has led to increased parasite presence in most industrialized countries. About 40% of infected individuals will develop cardiovascular, neurological, and/or gastrointestinal pathologies. Accumulating evidence suggests that the parasite induces alterations in host gene expression profiles in order to facilitate infection and pathogenesis. The role of regulatory gene expression machinery during T. cruzi infection, particularly small noncoding RNAs, has yet to be elucidated. In this study, we aim to evaluate dysregulation of a class of sncRNAs called piRNAs during early phase of T. cruzi infection in primary human cardiac fibroblasts by RNA-Seq. We subsequently performed in silico analysis to predict piRNA-mRNA interactions. We validated the expression of these selected piRNAs and their targets during early parasite infection phase by stem loop qPCR and qPCR, respectively. We found about 26,496,863 clean reads (92.72%) which mapped to the human reference genome. During parasite challenge, 441 unique piRNAs were differentially expressed. Of these differentially expressed piRNAs, 29 were known and 412 were novel. In silico analysis showed several of these piRNAs were computationally predicted to target and potentially regulate expression of genes including SMAD2, EGR1, ICAM1, CX3CL1, and CXCR2, which have been implicated in parasite infection, pathogenesis, and various cardiomyopathies. Further evaluation of the function of these individual piRNAs in gene regulation and expression will enhance our understanding of early molecular mechanisms contributing to infection and pathogenesis. Our findings here suggest that piRNAs play important roles in infectious disease pathogenesis and can serve as potential biomarkers and therapeutic targets.

The E3 ubiquitin ligase WWP2 regulates pro-fibrogenic monocyte infiltration and activity in heart fibrosis

Non-ischemic cardiomyopathy (NICM) can cause left ventricular dysfunction through interstitial fibrosis, which corresponds to the failure of cardiac tissue remodeling. Recent evidence implicates monocytes/macrophages in the etiopathology of cardiac fibrosis, but giving their heterogeneity and the antagonizing roles of macrophage subtypes in fibrosis, targeting these cells has been challenging. Here we focus on WWP2, an E3 ubiquitin ligase that acts as a positive genetic regulator of human and murine cardiac fibrosis, and show that myeloid specific deletion of WWP2 reduces cardiac fibrosis in hypertension-induced NICM. By using single cell RNA sequencing analysis of immune cells in the same model, we establish the functional heterogeneity of macrophages and define an early pro-fibrogenic phase of NICM that is driven by Ccl5-expressing Ly6c^high monocytes. Among cardiac macrophage subtypes, WWP2 dysfunction primarily affects Ly6c^high monocytes via modulating Ccl5, and consequentially macrophage infiltration and activation, which contributes to reduced myofibroblast trans-differentiation. WWP2 interacts with transcription factor IRF7, promoting its non-degradative mono-ubiquitination, nuclear translocation and transcriptional activity, leading to upregulation of Ccl5 at transcriptional level. We identify a pro-fibrogenic macrophage subtype in non-ischemic cardiomyopathy, and demonstrate that WWP2 is a key regulator of IRF7-mediated Ccl5/Ly6c^high monocyte axis in heart fibrosis.

Genome-wide associations of aortic distensibility suggest causality for aortic aneurysms and brain white matter hyperintensities

Aortic dimensions and distensibility are key risk factors for aortic aneurysms and dissections, as well as for other cardiovascular and cerebrovascular diseases. We present genome-wide associations of ascending and descending aortic distensibility and area derived from cardiac magnetic resonance imaging (MRI) data of up to 32,590 Caucasian individuals in UK Biobank. We identify 102 loci (including 27 novel associations) tagging genes related to cardiovascular development, extracellular matrix production, smooth muscle cell contraction and heritable aortic diseases. Functional analyses highlight four signalling pathways associated with aortic distensibility (TGF-β, IGF, VEGF and PDGF). We identify distinct sex-specific associations with aortic traits. We develop co-expression networks associated with aortic traits and apply phenome-wide Mendelian randomization (MR-PheWAS), generating evidence for a causal role for aortic distensibility in development of aortic aneurysms. Multivariable MR suggests a causal relationship between aortic distensibility and cerebral white matter hyperintensities, mechanistically linking aortic traits and brain small vessel disease.

WWP2 overexpression inhibits the antitumor effects of doxorubicin in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common liver cancer that accounts for 90% of cases. Doxorubicin exhibits a broad spectrum of antitumor activity and is one of the most active agents in HCC. WW domain-containing protein 2 (WWP2) is highly expressed in HCC tissues and activates protein kinase B (AKT) signaling pathway to enhance tumor metastasis. However, the role of WWP2 in the glycolysis and antitumor effects of doxorubicin and the epigenetic alterations of WWP2 in HCC remain to be elucidated. The levels of WWP2 and N6-methyladenosine methyltransferase-like 3 (METTL3) in clinical samples and cells were investigated. WWP2 were silenced or overexpressed to study the role of WWP2 in regulating cell proliferation, colony formation, and glycolysis. RNA immunoprecipitation was performed to test m⁶ A levels. Quantitative reverse-transcription polymerase chain reaction (RT-PCR) and Western blot were used to measure mRNA and protein, respectively. WWP2 silencing inhibits cell proliferation, colony formation, and glycolysis, while WWP2 overexpression has the inverse effects via the AKT signaling pathway. Silencing WWP2 enhances doxorubicin's antitumor effect, while WWP2 overexpression suppresses doxorubicin's antitumor effect. Data also support that METTL3 mediates WWP2 m6A modification, and m6A reader, IGF2BP2, binds to the methylated WWP2 to promote the stability of WWP2, leading to upregulation of WWP2. METTL3 mediates WWP2 m6A modification, which can be recognized and bound by IGF2BP2 to increase the stability of WWP2, leading to WWP2 overexpression which inhibits the antitumor effects of doxorubicin through METTL3/WWP2/AKT/glycolysis axis.

Signaling cascades in the failing heart and emerging therapeutic strategies

Chronic heart failure is the end stage of cardiac diseases. With a high prevalence and a high mortality rate worldwide, chronic heart failure is one of the heaviest health-related burdens. In addition to the standard neurohormonal blockade therapy, several medications have been developed for chronic heart failure treatment, but the population-wide improvement in chronic heart failure prognosis over time has been modest, and novel therapies are still needed. Mechanistic discovery and technical innovation are powerful driving forces for therapeutic development. On the one hand, the past decades have witnessed great progress in understanding the mechanism of chronic heart failure. It is now known that chronic heart failure is not only a matter involving cardiomyocytes. Instead, chronic heart failure involves numerous signaling pathways in noncardiomyocytes, including fibroblasts, immune cells, vascular cells, and lymphatic endothelial cells, and crosstalk among these cells. The complex regulatory network includes protein-protein, protein-RNA, and RNA-RNA interactions. These achievements in mechanistic studies provide novel insights for future therapeutic targets. On the other hand, with the development of modern biological techniques, targeting a protein pharmacologically is no longer the sole option for treating chronic heart failure. Gene therapy can directly manipulate the expression level of genes; gene editing techniques provide hope for curing hereditary cardiomyopathy; cell therapy aims to replace dysfunctional cardiomyocytes; and xenotransplantation may solve the problem of donor heart shortages. In this paper, we reviewed these two aspects in the field of failing heart signaling cascades and emerging therapeutic strategies based on modern biological techniques.

An unexpected role for BAG3 in regulating PARP1 ubiquitination in oxidative stress-related endothelial damage

Oxidative stress-associated endothelial damage is the initiation factor of cardiovascular disease, and protein posttranslational modifications play critical roles in this process. Bcl-2-associated athanogene 3 (BAG3) is a molecular chaperone regulator of the BAG family, which interacts with various proteins and influences cell survival by activating multiple pathways. BAG3 undergoes posttranslational modifications; however, research evaluating BAG3 acetylation and its regulatory mechanism is lacking. In addition, the interacting protein and regulatory mechanism of BAG3 in oxidative stress-associated endothelial damage remain unclear. Here, key molecular interactions and protein modifications of BAG3 were identified in oxidative stress-associated endothelial damage. Endothelial-specific BAG3 knockout in the mouse model starkly enhances oxidative stress-associated endothelial damage and vascular remodeling, while BAG3 overexpression in mice significantly relieves this process. Mechanistically, poly(ADP-ribose) polymerase 1 (PARP1), causing oxidative stress, was identified as a novel physiological substrate of BAG3. Indeed, BAG3 binds to PARP1's BRCT domain to promote its ubiquitination (K249 residue) by enhancing the E3 ubiquitin ligase WWP2, which leads to proteasome-induced PARP1 degradation. Furthermore, we surprisingly found that BAG3 represents a new substrate of the acetyltransferase CREB-binding protein (CBP) and the deacetylase Sirtuin 2 (SIRT2) under physiological conditions. CBP/SIRT2 interacted with BAG3 and acetylated/deacetylated BAG3's K431 residue. Finally, deacetylated BAG3 promoted the ubiquitination of PARP1. This work reveals a novel regulatory system, with deacetylation-dependent regulation of BAG3 promoting PARP1 ubiquitination and degradation via enhancing WWP2, which is one possible mechanism to decrease vulnerability of oxidative stress in endothelial cells.

•

Endothelial-specific BAG3 knockout in mice aggravates oxidative stress endothelial injury.

•

BAG3 transgenic mice relieves oxidative stress endothelial injury.

•

BAG3 promotes ubiquitination at the K249 residue of PARP1 via mobilization of the E3 ubiquitin ligase WWP2.

•

CBP/SIRT2 interacted with BAG3 and acetylated/deacetylated BAG3's K431 residue.

•

Deacetylated BAG3 promoted the ubiquitination of PARP1.

Deletion of BACH1 Attenuates Atherosclerosis by Reducing Endothelial Inflammation

BACKGROUND

The transcription factor BACH1 (BTB and CNC homology 1) suppressed endothelial cells (ECs) proliferation and migration and impaired angiogenesis in the ischemic hindlimbs of adult mice. However, the role and underlying mechanisms of BACH1 in atherosclerosis remain unclear.

METHODS

Mouse models of atherosclerosis in endothelial cell (EC)-specific-Bach1 knockout mice were used to study the role of BACH1 in the regulation of atherogenesis and the underlying mechanisms.

RESULTS

Genetic analyses revealed that coronary artery disease-associated risk variant rs2832227 was associated with BACH1 gene expression in carotid plaques from patients. BACH1 was upregulated in ECs of human and mouse atherosclerotic plaques. Endothelial Bach1 deficiency decreased turbulent blood flow- or western diet-induced atherosclerotic lesions, macrophage content in plaques, expression of endothelial adhesion molecules (ICAM1 [intercellular cell adhesion molecule-1] and VCAM1 [vascular cell adhesion molecule-1]), and reduced plasma TNF-α (tumor necrosis factor-α) and IL-1β levels in atherosclerotic mice. BACH1 deletion or knockdown inhibited monocyte-endothelial adhesion and reduced oscillatory shear stress or TNF-α-mediated induction of endothelial adhesion molecules and/or proinflammatory cytokines in mouse ECs, human umbilical vein ECs, and human aortic ECs. Mechanistic studies showed that upon oscillatory shear stress or TNF-α stimulation, BACH1 and YAP (yes-associated protein) were induced and translocated into the nucleus in ECs. BACH1 upregulated YAP expression by binding to the YAP promoter. BACH1 formed a complex with YAP inducing the transcription of adhesion molecules. YAP overexpression in ECs counteracted the antiatherosclerotic effect mediated by Bach1-deletion in mice. Rosuvastatin inhibited BACH1 expression by upregulating microRNA let-7a in ECs, and decreased Bach1 expression in the vascular endothelium of hyperlipidemic mice. BACH1 was colocalized with YAP, and the expression of BACH1 was positively correlated with YAP and proinflammatory genes, as well as adhesion molecules in human atherosclerotic plaques.

CONCLUSIONS

These data identify BACH1 as a mechanosensor of hemodynamic stress and reveal that the BACH1-YAP transcriptional network is essential to vascular inflammation and atherogenesis. BACH1 shows potential as a novel therapeutic target in atherosclerosis.

Fibroblast mechanotransduction network predicts targets for mechano-adaptive infarct therapies

Regional control of fibrosis after myocardial infarction is critical for maintaining structural integrity in the infarct while preventing collagen accumulation in non-infarcted areas. Cardiac fibroblasts modulate matrix turnover in response to biochemical and biomechanical cues, but the complex interactions between signaling pathways confound efforts to develop therapies for regional scar formation. We employed a logic-based ordinary differential equation model of fibroblast mechano-chemo signal transduction to predict matrix protein expression in response to canonical biochemical stimuli and mechanical tension. Functional analysis of mechano-chemo interactions showed extensive pathway crosstalk with tension amplifying, dampening, or reversing responses to biochemical stimuli. Comprehensive drug target screens identified 13 mechano-adaptive therapies that promote matrix accumulation in regions where it is needed and reduce matrix levels in regions where it is not needed. Our predictions suggest that mechano-chemo interactions likely mediate cell behavior across many tissues and demonstrate the utility of multi-pathway signaling networks in discovering therapies for context-specific disease states.

miR-30a-5p inhibits the proliferation and collagen formation of cardiac fibroblasts in diabetic cardiomyopathy

Cardiac fibrosis is one of the major pathological characteristics of diabetic cardiomyopathy (DCM). MicroRNAs (miRNAs, miRs) have been identified as key regulators in the progression of cardiac fibrosis. This study aimed to investigate the role of miR-30a-5p in DCM and the underlying mechanism. The rat model of diabetes mellitus (DM) was established by streptozotocin injection, and the rat primary cardiac fibroblasts (CFs) were isolated from cardiac tissue and then treated with high glucose (HG). MTT assay was performed to assess the viability of CFs. Dual-luciferase reporter gene assay was conducted to verify the interaction between miR-30a-5p and Smad2. The expression of miR-30a-5p was downregulated in the myocardial tissues of DM rats and HG-stimulated CFs. Overexpression of miR-30a-5p reduced Smad2 levels and inhibited collagen formation in HG-stimulated CFs and DM rats, as well as decreased the proliferation of CFs induced by HG. Smad2 was a target of miR-30a-5p and its expression was inhibited by miR-30a-5p. Furthermore, the simultaneous overexpression of Smad2 and miR-30a-5p reversed the effect of miR-30a-5p overexpression alone in CFs. Our results indicated that miR-30a-5p reduced Smad2 expression and also induced a decrease in proliferation and collagen formation in DCM.

Long noncoding RNA NEAT1 promotes cardiac fibrosis in heart failure through increased recruitment of EZH2 to the Smad7 promoter region

Cardiac fibrosis, a well-known major pathological process that ultimately leads to heart failure, has attracted increasing attention and focus in recent years. A large amount of research indicates that long noncoding RNAs (lncRNAs) play an important role in cardiac fibrosis, but little is known about the specific function and mechanism of the lncRNA NEAT1 in the progression of cardiac fibrosis to heart failure. In the present study, we have demonstrated that the lncRNA NEAT1 is upregulated in patients with heart failure. Similarly, the expression of Neat1 was also increased in the left ventricular tissue of transverse aortic constriction (TAC) surgery mice and cardiac fibroblasts treated with TGF-β1. Further, gain-of-function and loss-of-function experiments showed that silencing of Neat1 attenuated cardiac fibrosis, while overexpression of Neat1 with adenovirus significantly aggravated the in vitro progression of fibrosis. With regard to the underlying mechanism, our experiments showed that Neat1 recruited EZH2 to the promoter region of Smad7 through physical binding of EZH2 to the promoter region, as a result of which Smad7 expression was inhibited and the progression of cardiac fibrosis was ultimately exacerbated. We found that the introduction of shNeat1 carried by adeno-associated virus-9 significantly ameliorated cardiac fibrosis and dysfunction caused by TAC surgery in mice. Overall, our study findings demonstrate that the lncRNA Neat1 accelerates the progression of cardiac fibrosis and dysfunction by recruiting EZH2 to suppress Smad7 expression. Thus, NEAT1 may serve as a target for the treatment of cardiac fibrosis.

Deep learning enables genetic analysis of the human thoracic aorta

Enlargement or aneurysm of the aorta predisposes to dissection, an important cause of sudden death. We trained a deep learning model to evaluate the dimensions of the ascending and descending thoracic aorta in 4.6 million cardiac magnetic resonance images from the UK Biobank. We then conducted genome-wide association studies in 39,688 individuals, identifying 82 loci associated with ascending and 47 with descending thoracic aortic diameter, of which 14 loci overlapped. Transcriptome-wide analyses, rare-variant burden tests and human aortic single nucleus RNA sequencing prioritized genes including SVIL, which was strongly associated with descending aortic diameter. A polygenic score for ascending aortic diameter was associated with thoracic aortic aneurysm in 385,621 UK Biobank participants (hazard ratio = 1.43 per s.d., confidence interval 1.32-1.54, P = 3.3 × 10-20). Our results illustrate the potential for rapidly defining quantitative traits with deep learning, an approach that can be broadly applied to biomedical images.

Ubiquitin ligase Wwp1 gene deletion attenuates diastolic dysfunction in pressure-overload hypertrophy

Heart failure with a preserved left ventricular (LV) ejection fraction (HFpEF) often arises from a prolonged LV pressure overload (LVPO) and accompanied by abnormal extracellular matrix (ECM) accumulation. The E3 ubiquitin ligase WWP1 is a fundamental determinant ECM turnover. We tested the hypothesis that genetic ablation of Wwp1 would alter the progression of LVPO-induced HFpEF. LV echocardiography in mice with global Wwp1 deletion (n = 23; Wwp1-/-) was performed at 12 wk of age (baseline) and then at 2 and 4 wk following LVPO (transverse aortic banding) or surgery without LVPO induction. Age-matched wild-type mice (Wwp1+/+; n = 23) underwent identical protocols. LV EF remained constant and unchanged with LVPO and LV mass increased in both groups but was lower in the Wwp1-/- mice. With LVPO, the E/A ratio, an index of LV filling, was 3.97 ± 0.46 in Wwp1+/+ but was 1.73 ± 0.19 in the Wwp1-/- group (P < 0.05). At the transcriptional level, mRNA for fibrillar collagens (types I and III) decreased by approximately 50% in Wwp1-/- compared with the Wwp1+/+ group at 4 wk post-LVPO (P < 0.05) and was paralleled by a similar difference in LV fibrillar collagen content as measured by histochemistry. Moreover, mRNA levels for determinants favoring ECM accumulation, such as transforming growth factor (TGF), increased with LVPO, but were lower in the Wwp1-/- group. The absence of Wwp1 reduced the development of left ventricular hypertrophy and subsequent progression to HFpEF. Modulating the WWP1 pathway could be a therapeutic target to alter the natural history of HFpEF.NEW & NOTEWORTHY Heart failure with a preserved left ventricular (LV) ejection fraction (HFpEF) often arises from a prolonged LV pressure overload (LVPO) and is accompanied by abnormal extracellular matrix (ECM) accumulation. It is now recognized that the ECM is a dynamic entity that is regulated at multiple post-transcriptional levels, including the E3 ubiquitin ligases, such as WWP1. In the present study, WWP1 deletion in the context of an LVPO stimulus reduced functional indices of HFpEF progression and determinants of ECM remodeling.

DUSP26 induces aortic valve calcification by antagonizing MDM2-mediated ubiquitination of DPP4 in human valvular interstitial cells

AIMS

The morbidity and mortality rates of calcific aortic valve disease (CAVD) remain high while treatment options are limited. Here, we evaluated the role and therapeutic value of dual-specificity phosphatase 26 (DUSP26) in CAVD.

METHODS AND RESULTS

Microarray profiling of human calcific aortic valves and normal controls demonstrated that DUSP26 was significantly up-regulated in calcific aortic valves. ApoE-/- mice fed a normal diet or a high cholesterol diet (HCD) were infected with adeno-associated virus serotype 2 carrying DUSP26 short-hairpin RNA to examine the effects of DUSP26 silencing on aortic valve calcification. DUSP26 silencing ameliorated aortic valve calcification in HCD-treated ApoE-/- mice, as evidenced by reduced thickness and calcium deposition in the aortic valve leaflets, improved echocardiographic parameters (decreased peak transvalvular jet velocity and mean transvalvular pressure gradient, as well as increased aortic valve area), and decreased levels of osteogenic markers (Runx2, osterix, and osteocalcin) in the aortic valves. These results were confirmed in osteogenic medium-induced human valvular interstitial cells. Immunoprecipitation, liquid chromatography-tandem mass spectrometry, and functional assays revealed that dipeptidyl peptidase-4 (DPP4) interacted with DUSP26 to mediate the procalcific effects of DUSP26. High N6-methyladenosine levels up-regulated DUSP26 in CAVD; in turn, DUSP26 activated DPP4 by antagonizing mouse double minute 2-mediated ubiquitination and degradation of DPP4, thereby promoting CAVD progression.

CONCLUSION

DUSP26 promotes aortic valve calcification by inhibiting DPP4 degradation. Our findings identify a previously unrecognized mechanism of DPP4 up-regulation in CAVD, suggesting that DUSP26 silencing or inhibition is a viable therapeutic strategy to impede CAVD progression.

Elevated IgE promotes cardiac fibrosis by suppressing miR-486a-5p

Rationale: Cardiac fibrosis is an important feature of cardiac remodeling and is a hallmark of heart failure. Recent studies indicate that elevated IgE plays a causal role in pathological cardiac remodeling. However, the underlying mechanism of how IgE promotes cardiac fibrosis has not been fully elucidated. Methods and Results: To explore the function of IgE in cardiac fibrosis, we stimulated mouse primary cardiac fibroblasts (CFs) with IgE and found that both IgE receptor (FcεR1) and fibrosis related proteins were increased after IgE stimulation. Specific deletion of FcεR1 in CFs alleviated angiotensin II (Ang II)-induced cardiac fibrosis in mice. To investigate the mechanisms underlying the IgE-mediated cardiac fibrosis, deep miRNA-seq was performed. Bioinformatics and signaling pathway analysis revealed that IgE upregulated Col1a1 and Col3a1 expression in CFs by repressing miR-486a-5p, with Smad1 participating downstream of miR-486a-5p in this process. Lentivirus-mediated overexpression of miR-486a-5p was found to alleviate Ang II-induced myocardial interstitial fibrosis in mice. Moreover, miR-486-5p serum levels were lower in patients with heart failure than in healthy controls, and were negatively correlated with NT-proBNP levels. Conclusions: Our study demonstrates that elevated IgE promotes pathological cardiac fibrosis by modulating miR-486a-5p and downstream factors, such as Smad1. These findings suggest new targets for pathological cardiac fibrosis intervention.

The Role of HECT-Type E3 Ligase in the Development of Cardiac Disease

Despite advances in medicine, cardiac disease remains an increasing health problem associated with a high mortality rate. Maladaptive cardiac remodeling, such as cardiac hypertrophy and fibrosis, is a risk factor for heart failure; therefore, it is critical to identify new therapeutic targets. Failing heart is reported to be associated with hyper-ubiquitylation and impairment of the ubiquitin–proteasome system, indicating an importance of ubiquitylation in the development of cardiac disease. Ubiquitylation is a post-translational modification that plays a pivotal role in protein function and degradation. In 1995, homologous to E6AP C-terminus (HECT) type E3 ligases were discovered. E3 ligases are key enzymes in ubiquitylation and are classified into three families: really interesting new genes (RING), HECT, and RING-between-RINGs (RBRs). Moreover, 28 HECT-type E3 ligases have been identified in human beings. It is well conserved in evolution and is characterized by the direct attachment of ubiquitin to substrates. HECT-type E3 ligase is reported to be involved in a wide range of human diseases and health. The role of HECT-type E3 ligases in the development of cardiac diseases has been uncovered in the last decade. There are only a few review articles summarizing recent advancements regarding HECT-type E3 ligase in the field of cardiac disease. This study focused on cardiac remodeling and described the role of HECT-type E3 ligases in the development of cardiac disease. Moreover, this study revealed that the current knowledge could be exploited for the development of new clinical therapies.

WWP2 and PPP1R3A are abnormally regulated in arrhythmia-induced cardiac damage

The present work aimed to identify the roles of WWP2 (an E3 ubiquitin-protein ligase) and protein phosphatase 1 regulatory subunit 3A (PPP1R3A) in different pathological stages of cardiac arrhythmia development. Leptin-deficient mice (C57BLKS-Lepr^db/Lepr^db) were used for the development of initial and severe stages of cardiac arrhythmia. Histology, ECG, immunohistochemistry and Western blotting were used to analyse cardiac arrhythmia, WWP2 and PPP1R3A expression. Histopathological studies of 4-month-old mice showed cardiac degeneration, cellular lesions, and swollen tissue structure with loss of tissue elasticity, indicative of the initial condition of cardiac arrhythmia. The leptin-deficient 7-month-old mice showed cardiac tissue hardening with increased secretion of extracellular matrix. The development of initial- and severe-cardiac arrhythmia was further evident with electrocardiogram studies, which showed more PP interval variations as the disease progressed. At the molecular level, WWP2 showed marginal upregulation in the initial stages of arrhythmia and was predominantly expressed within nuclei. WWP2 was overexpressed 6.6-fold in the severe stage of cardiac arrhythmia and was spread throughout the tissue layer. Interestingly, PPP1R3A was significantly overexpressed in initial cardiac arrhythmia conditions, but was downregulated and restricted to more nuclear expression in advanced cardiac arrhythmia. Silencing of PPP1R3A, enhances the expression of WWP2 to 5.3-fold in initial stages, but remarkable variation not observed in advanced cardiac arrhythmia conditions. Our results suggest that PPP1R3A had a control over WWP2 in the initial stages of cardiac arrhythmia. In particular, PPP1R3A overexpression implies its potential protective effect in initial cardiac arrhythmia stages.

Multiomics Analysis of Transcriptome, Epigenome, and Genome Uncovers Putative Mechanisms for Dilated Cardiomyopathy

Objective

Multiple genes have been identified to cause dilated cardiomyopathy (DCM). Nevertheless, there is still a lack of comprehensive elucidation of the molecular characteristics for DCM. Herein, we aimed to uncover putative molecular features for DCM by multiomics analysis.

Methods

Differentially expressed genes (DEGs) were obtained from different RNA sequencing (RNA-seq) datasets of left ventricle samples from healthy donors and DCM patients. Furthermore, protein-protein interaction (PPI) analysis was then presented. Differentially methylated genes (DMGs) were identified between DCM and control samples. Following integration of DEGs and DMGs, differentially expressed and methylated genes were acquired and their biological functions were analyzed by the clusterProfiler package. Whole exome sequencing of blood samples from 69 DCM patients was constructed in our cohort, which was analyzed the maftools package. The expression of key mutated genes was verified by three independent datasets.

Results

1407 common DEGs were identified for DCM after integration of the two RNA-seq datasets. A PPI network was constructed, composed of 171 up- and 136 downregulated genes. Four hub genes were identified for DCM, including C3 (degree = 24), GNB3 (degree = 23), QSOX1 (degree = 21), and APOB (degree = 17). Moreover, 285 hyper- and 321 hypomethylated genes were screened for DCM. After integration, 20 differentially expressed and methylated genes were identified, which were associated with cell differentiation and protein digestion and absorption. Among single-nucleotide variant (SNV), C>T was the most frequent mutation classification for DCM. MUC4 was the most frequent mutation gene which occupied 71% across 69 samples, followed by PHLDA1, AHNAK2, and MAML3. These mutated genes were confirmed to be differentially expressed between DCM and control samples.

Conclusion

Our findings comprehensively analyzed molecular characteristics from the transcriptome, epigenome, and genome perspectives for DCM, which could provide practical implications for DCM.

Asenapine maleate inhibits angiotensin II-induced proliferation and activation of cardiac fibroblasts via the ROS/TGFβ1/MAPK signaling pathway

BACKGROUND

Cardiac fibrosis will increase wall stiffness and diastolic dysfunction, which will eventually lead to heart failure. Asenapine maleate (AM) is widely used in the treatment of schizophrenia. In the current study, we explored the potential mechanism underlying the role of AM in angiotensin II (Ang II)-induced cardiac fibrosis.

METHODS

Cardiac fibroblasts (CFs) were stimulated using Ang II with or without AM. Cell proliferation was measured using the cell counting kit-8 assay and the Cell-Light EdU Apollo567 In Vitro Kit. The expression levels of proliferating cell nuclear antigen (PCNA) and α-smooth muscle actin (α-SMA) were detected using immunofluorescence or western blotting. At the protein level, the expression levels of the components of the transforming growth factor beta 1 (TGFβ1)/mitogen-activated protein kinase (MAPK) signaling pathway were also detected.

RESULTS

After Ang II stimulation, TGFβ1, TGFβ1 receptor, α-SMA, fibronectin (Fn), collagen type I (Col1), and collagen type III (Col3) mRNA levels increased; the TGFβ1/MAPK signaling pathway was activated in CFs. After AM pretreatment, cell proliferation was inhibited, the numbers of PCNA -positive cells and the levels of cardiac fibrosis markers decreased. The activity of the TGFβ1/MAPK signaling pathway was also inhibited. Therefore, AM can inhibit cardiac fibrosis by blocking the Ang II-induced activation through TGFβ1/MAPK signaling pathway.

CONCLUSIONS

This is the first report to demonstrate that AM can inhibit Ang II-induced cardiac fibrosis by down-regulating the TGFβ1/MAPK signaling pathway. In this process, AM inhibited the proliferation and activation of CFs and reduced the levels of cardiac fibrosis markers. Thus, AM represents a potential treatment strategy for cardiac fibrosis.

Individualized interactomes for network-based precision medicine in hypertrophic cardiomyopathy with implications for other clinical pathophenotypes

Progress in precision medicine is limited by insufficient knowledge of transcriptomic or proteomic features in involved tissues that define pathobiological differences between patients. Here, myectomy tissue from patients with obstructive hypertrophic cardiomyopathy and heart failure is analyzed using RNA-Seq, and the results are used to develop individualized protein-protein interaction networks. From this approach, hypertrophic cardiomyopathy is distinguished from dilated cardiomyopathy based on the protein-protein interaction network pattern. Within the hypertrophic cardiomyopathy cohort, the patient-specific networks are variable in complexity, and enriched for 30 endophenotypes. The cardiac Janus kinase 2-Signal Transducer and Activator of Transcription 3-collagen 4A2 (JAK2-STAT3-COL4A2) expression profile informed by the networks was able to discriminate two hypertrophic cardiomyopathy patients with extreme fibrosis phenotypes. Patient-specific network features also associate with other important hypertrophic cardiomyopathy clinical phenotypes. These proof-of-concept findings introduce personalized protein-protein interaction networks (reticulotypes) for characterizing patient-specific pathobiology, thereby offering a direct strategy for advancing precision medicine.

Handling High-Throughput Omics Data for Systems Genetics Analysis

Omics data are being generated and collected at unprecedented scale. During the last decade, single omics, such as genomics, transcriptomics, proteomics, and metabolomics, have already highlighted pathophysiological pathways underpinning a variety of conditions across all the fields of medicine.In fact, high-throughput data generated by the comprehensive and unbiased analysis of an entire segment of the flow of genetic information (i.e., genetic variants in the case of genomics, or gene expression in transcriptomics) certainly provide a plethora of information and a precious support to dissect the mechanisms involved in complex diseases.Yet the most effective approach, set to fully exploit the potential of such big data, lies in the possibility to integrate various omics to unveil previously unappreciated pathways. This approach is the foundation of Systems Biology and allows to overcome the limitations inherent to single omics and traditional biology analyses.A robust and powerful strategy has been developed to integrate genetics and gene expression data in the framework of Systems Genetics. With this technique the first two layers of the flow of genetic information are integrated and specifically it is possible to pinpoint which genetic variants are associated with gene co-expression networks.Here we present a versatile bioinformatic protocol that can be used to study the Systems Genetics of CTLs, in order to identify genes (also known as master regulators) that influence the activation of biological pathways in these cells in a particular state or condition.

Genomics of Human Fibrotic Diseases: Disordered Wound Healing Response

Fibrotic disease, which is implicated in almost half of all deaths worldwide, is the result of an uncontrolled wound healing response to injury in which tissue is replaced by deposition of excess extracellular matrix, leading to fibrosis and loss of organ function. A plethora of genome-wide association studies, microarrays, exome sequencing studies, DNA methylation arrays, next-generation sequencing, and profiling of noncoding RNAs have been performed in patient-derived fibrotic tissue, with the shared goal of utilizing genomics to identify the transcriptional networks and biological pathways underlying the development of fibrotic diseases. In this review, we discuss fibrosing disorders of the skin, liver, kidney, lung, and heart, systematically (1) characterizing the initial acute injury that drives unresolved inflammation, (2) identifying genomic studies that have defined the pathologic gene changes leading to excess matrix deposition and fibrogenesis, and (3) summarizing therapies targeting pro-fibrotic genes and networks identified in the genomic studies. Ultimately, successful bench-to-bedside translation of observations from genomic studies will result in the development of novel anti-fibrotic therapeutics that improve functional quality of life for patients and decrease mortality from fibrotic diseases.

Mechanical circulatory support does not reduce advanced myocardial fibrosis in patients with end-stage heart failure

AIMS

Mechanical unloading by ventricular assist devices (VADs) has become increasingly important for the therapy of end-stage heart failure during the last decade. However, VAD support was claimed to be associated with partial reverse remodelling. Unfortunately, the literature describes the contradictory effects of VAD systems on cardiac fibrosis, a hallmark of cardiac remodelling. To clarify these inconsistent results, the effects on cardiac fibrosis before and after mechanical unloading in 125 patients were examined.

METHODS AND RESULTS

Left ventricular myocardial tissue from ischaemic or non-ischaemic cardiomyopathy patients undergoing VAD implantation and subsequent cardiac transplantation and non-failing hearts of the control group were analysed for 4-hydroxyproline (4OH-P) content as a marker for collagen protein. In addition, collagen cross-linking and mRNAs of collagens I and III and transforming growth factor beta-1 were measured. 4OH-P content was significantly increased in failing hearts compared with the control group and increased (P < 0.05) after mechanical unloading (nmol/mg tissue, mean ± standard deviation: 16.74 ± 9.68 vs. 7.75 ± 2.39 and 18.57 ± 9.19). However, plotting of the 4OH-P ratios (post/pre-VAD) against the collagen content pre-VAD could be fitted by non-linear regression. Collagen cross-linking correlated strongly with the total collagen content in pre- and post-VAD myocardium (r²  = 0.73 and 0.71, respectively). In contrast to the total collagen content, all three mRNAs of fibrotic genes were significantly down-regulated during VAD support when compared to pre-VAD.

CONCLUSIONS

This investigation of a comparably large patient cohort revealed that cardiac fibrosis was strongly increased in heart failure and increased even after mechanical unloading. The mRNAs of collagens I and III are independently regulated from the collagen protein.

ABRO1 stabilizes the deubiquitinase BRCC3 through inhibiting its degradation mediated by the E3 ubiquitin ligase WWP2

BRCA1/BRCA2-containing complex subunit 3 (BRCC3) is a lysine 63-specific deubiquitinase involved in multiple biological processes, such as DNA repair and immune responses. However, the regulation mechanism for BRCC3 protein stability is still unknown. Here, we demonstrate that BRCC3 is mainly degraded through the ubiquitin-proteasome pathway. The HECT-type E3 ubiquitin ligase WWP2 modulates BRCC3 ubiquitination and degradation. ABRO1, a subunit of the BRCC36 isopeptidase complex (BRISC), competes with WWP2 to bind to BRCC3, thereby preventing WWP2-mediated BRCC3 ubiquitination and enhancing BRCC3 stability. Functionally, we show that lentivirus-mediated overexpression of WWP2 in murine macrophages inhibits NLRP3 inflammasome activation by decreasing BRCC3 protein level. This study provides the first insights into the regulation of BRCC3 stability and expands our knowledge about the physiological function of WWP2.

Altered Enhancer and Promoter Usage Leads to Differential Gene Expression in the Normal and Failed Human Heart

BACKGROUND

The failing heart is characterized by changes in gene expression. However, the regulatory regions of the genome that drive these gene expression changes have not been well defined in human hearts.

METHODS

To define genome-wide enhancer and promoter use in heart failure, cap analysis of gene expression sequencing was applied to 3 healthy and 4 failed human hearts to identify promoter and enhancer regions used in left ventricles. Healthy hearts were derived from donors unused for transplantation and failed hearts were obtained as discarded tissue after transplantation.

RESULTS

Cap analysis of gene expression sequencing identified a combined potential for ≈23 000 promoters and ≈5000 enhancers active in human left ventricles. Of these, 17 000 promoters and 1800 enhancers had additional support for their regulatory function. Comparing promoter usage between healthy and failed hearts highlighted promoter shifts which altered aminoterminal protein sequences. Enhancer usage between healthy and failed hearts identified a majority of differentially used heart failure enhancers were intronic and primarily localized within the first intron, revealing this position as a common feature associated with tissue-specific gene expression changes in the heart.

CONCLUSIONS

This data set defines the dynamic genomic regulatory landscape underlying heart failure and serves as an important resource for understanding genetic contributions to cardiac dysfunction. Additionally, regulatory changes contributing to heart failure are attractive therapeutic targets for controlling ventricular remodeling and clinical progression.

E3 Ubiquitin ligase NEDD4 family‑regulatory network in cardiovascular disease

Protein ubiquitination represents a critical modification occurring after translation. E3 ligase catalyzes the covalent binding of ubiquitin to the protein substrate, which could be degraded. Ubiquitination as an important protein post-translational modification is closely related to cardiovascular disease. The NEDD4 family, belonging to HECT class of E3 ubiquitin ligases can recognize different substrate proteins, including PTEN, ENaC, Nav1.5, SMAD2, PARP1, Septin4, ALK1, SERCA2a, TGFβR3 and so on, via the WW domain to catalyze ubiquitination, thus participating in multiple cardiovascular-related disease such as hypertension, arrhythmia, myocardial infarction, heart failure, cardiotoxicity, cardiac hypertrophy, myocardial fibrosis, cardiac remodeling, atherosclerosis, pulmonary hypertension and heart valve disease. However, there is currently no review comprehensively clarifying the important role of NEDD4 family proteins in the cardiovascular system. Therefore, the present review summarized recent studies about NEDD4 family members in cardiovascular disease, providing novel insights into the prevention and treatment of cardiovascular disease. In addition, assessing transgenic animals and performing gene silencing would further identify the ubiquitination targets of NEDD4. NEDD4 quantification in clinical samples would also constitute an important method for determining NEDD4 significance in cardiovascular disease.

WWP2 regulates SIRT1-STAT3 acetylation and phosphorylation involved in hypertensive angiopathy

WWP2 is a HECT‐type E3 ubiquitin ligase that regulates various physiological and pathological activities by binding to different substrates, but its function and regulatory mechanism in vascular smooth muscle cells (VSMCs) are still unknown. Here, we clarified the role of WWP2 in the regulation of SIRT1‐STAT3 and the impact of this regulatory process in VSMCs. We demonstrated that WWP2 expression was significantly increased in angiotensin II‐induced VSMCs model. Knockdown of WWP2 significantly inhibited angiotensin II‐induced VSMCs proliferation, migration and phenotypic transformation, whereas overexpression of WWP2 had opposite effects. In vivo experiments showed that vascular smooth muscle‐specific WWP2 knockout mice significantly relieved angiotensin II‐induced hypertensive angiopathy. Mechanistically, mass spectrometry and co‐immunoprecipitation assays identified that WWP2 is a novel interacting protein of SIRT1 and STAT3. Moreover, WWP2 formed a complex with SIRT1‐STAT3, inhibiting the interaction between SIRT1 and STAT3, then reducing the inhibitory effect of SIRT1 on STAT3, ensuing promoting STAT3‐K685 acetylation and STAT3‐Y705 phosphorylation in angiotensin II‐induced VSMCs and mice. In conclusion, WWP2 modulates hypertensive angiopathy by regulating SIRT1‐STAT3 and WWP2 suppression in VSMCs can alleviate hypertensive angiopathy vitro and vivo. These findings provide new insights into the treatment of hypertensive vascular diseases.

Smad7 Binds Differently to Individual and Tandem WW3 and WW4 Domains of WWP2 Ubiquitin Ligase Isoforms

WWP2 is an E3 ubiquitin ligase that differentially regulates the contextual tumour suppressor/progressor TGFβ signalling pathway by alternate isoform expression. WWP2 isoforms select signal transducer Smad2/3 or inhibitor Smad7 substrates for degradation through different compositions of protein–protein interaction WW domains. The WW4 domain-containing WWP2-C induces Smad7 turnover in vivo and positively regulates the metastatic epithelial–mesenchymal transition programme. This activity and the overexpression of these isoforms in human cancers make them candidates for therapeutic intervention. Here, we use NMR spectroscopy to solve the solution structure of the WWP2 WW4 domain and observe the binding characteristics of Smad7 substrate peptide. We also reveal that WW4 has an enhanced affinity for a Smad7 peptide phosphorylated at serine 206 adjacent to the PPxY motif. Using the same approach, we show that the WW3 domain also binds Smad7 and has significantly enhanced Smad7 binding affinity when expressed in tandem with the WW4 domain. Furthermore, and relevant to these biophysical findings, we present evidence for a novel WWP2 isoform (WWP2C-ΔHECT) comprising WW3–WW4 tandem domains and a truncated HECT domain that can inhibit TGFβ signalling pathway activity, providing a further layer of complexity and feedback to the WWP2 regulatory apparatus. Collectively, our data reveal a structural platform for Smad substrate selection by WWP2 isoform WW domains that may be significant in the context of WWP2 isoform switching linked to tumorigenesis.