Unrestrained p38 MAPK activation in Dusp1/4 double-null mice induces cardiomyopathy

Baicalin ameliorates angiotensin II-induced cardiac hypertrophy and mitogen-activated protein kinase signaling pathway activation: A target-based network pharmacology approach

Baicalin, a flavonoid glycoside from Scutellaria baicalensis Georgi., exerts anti-hypertensive effects. The present study aimed to assess the cardioprotective role of baicalin and explore its potential mechanisms. Network pharmacology analysis pointed out a total of 477 potential targets of baicalin were obtained from the PharmMapper and SwissTargetPrediction databases, while 11,280 targets were identified associating with hypertensive heart disease from GeneCards database. Based on the above 382 common targets, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses revealed enrichment in the regulation of cardiac hypertrophy, cardiac contraction, cardiac relaxation, as well as the mitogen-activated protein kinase (MAPK) and other signaling pathways. Moreover, baicalin treatment exhibited the amelioration of increased cardiac index and pathological alterations in angiotensin II (Ang II)-infused C57BL/6 mice. Furthermore, baicalin treatment demonstrated a reduction in cell surface area and a down-regulation of hypertrophy markers (including atrial natriuretic peptide and brain natriuretic peptide) in vivo and in vitro. In addition, baicalin treatment led to a decrease in the expression of phosphorylated c-Jun N-terminal kinase (p-JNK)/JNK, phosphorylated p38 (p-p38)/p38, and phosphorylated extracellular signal-regulated kinase (p-ERK)/ERK in the cardiac tissues of Ang II-infused mice and Ang II-stimulated H9c2 cells. These findings highlight the cardioprotective effects of baicalin, as it alleviates hypertensive cardiac injury, cardiac hypertrophy, and the activation of the MAPK pathway.

Regulatory network analysis based on integrated miRNA-TF reveals key genes in heart failure

The etiology and pathophysiology of heart failure are still unknown. Increasing evidence suggests that abnormal microRNAs (miRNAs) and transcription factors (TFs) expression may be associated with the development of heart failure. Therefore, this study aims to explore key miRNAs, TFs, and related genes in heart failure to gain a greater understanding of the pathogenesis of heart failure. To search and download the dataset of mRNA chips related to heart failure from the GEO database (GSE59867, GSE9128, and GSE134766), we analyzed differential genes and screened the common differentially expressed genes on two chips using R language software. The binary interactions and circuits among miRNAs, TFs, and corresponding genes were determined by Pearson correlation coefficient. A regulatory network of miRNAs, TFs, and target genes was constructed based on bioinformatics. By comparing the sequences of patients with and without heart failure, five downregulated genes with hypermethylated mRNA and three upregulated genes with hypomethylated mRNA were identified. The miRNA-TF gene regulatory network consisted of 26 miRNAs, 22 TFs and six genes. GO and KEGG analysis results revealed that BP terms like cellular response to organic substance, cellular response to cytokine stimulus, and KEGG pathways like osteoclast differentiation, MAPK signaling pathway, and legionellosis were enriched of the DEGs. TMEM87A, PPP2R2A, DUSP1, and miR-92a have great potential as biomarkers for heart failure. The integrated analysis of the mRNA expression spectrum and microRNA-transcription factor-gene revealed the regulatory network of heart failure, which may provide clues to its alternative treatment.

Temporal gene signature of myofibroblast transformation in Peyronie's disease: first insights into the molecular mechanisms of irreversibility

BACKGROUND

Transformation of resident fibroblasts to profibrotic myofibroblasts in the tunica albuginea is a critical step in the pathophysiology of Peyronie's disease (PD). We have previously shown that myofibroblasts do not revert to the fibroblast phenotype and we suggested that there is a point of no return at 36 hours after induction of the transformation. However, the molecular mechanisms that drive this proposed irreversibility are not known.

AIM

Identify molecular pathways that drive the irreversibility of myofibroblast transformation by analyzing the expression of the genes involved in the process in a temporal fashion.

METHODS

Human primary fibroblasts obtained from tunica albuginea of patients with Peyronie's disease were transformed to myofibroblasts using transforming growth factor beta 1 (TGF-β1). The mRNA of the cells was collected at 0, 24, 36, 48, and 72 hours after stimulation with TGF-β1 and then analyzed using a Nanostring nCounter Fibrosis panel. The gene expression results were analyzed using Reactome pathway analysis database and ANNi, a deep learning-based inference algorithm based on a swarm approach.

OUTCOMES

The study outcome was the time course of changes in gene expression during transformation of PD-derived fibroblasts to myofibroblasts.

RESULTS

The temporal analysis of the gene expression revealed that the majority of the changes at the gene expression level happened within the first 24 hours and remained so throughout the 72-hour period. At 36 hours, significant changes were observed in genes involved in MAPK-Hedgehog signaling pathways.

CLINICAL TRANSLATION

This study highlights the importance of early intervention in clinical management of PD and the future potential of new drugs targeting the point of no return.

STRENGTHS AND LIMITATIONS

The use of human primary cells and confirmation of results with further RNA analysis are the strengths of this study. The study was limited to 760 genes rather than the whole transcriptome.

CONCLUSION

This study is to our knowledge the first analysis of temporal gene expression associated with the regulation of the transformation of resident fibroblasts to profibrotic myofibroblasts in PD. Further research is warranted to investigate the role of the MAPK-Hedgehog signaling pathways in reversibility of PD.

The Senescent Heart-"Age Doth Wither Its Infinite Variety"

Cardiovascular diseases are a leading cause of morbidity and mortality world-wide. While many factors like smoking, hypertension, diabetes, dyslipidaemia, a sedentary lifestyle, and genetic factors can predispose to cardiovascular diseases, the natural process of aging is by itself a major determinant of the risk. Cardiac aging is marked by a conglomerate of cellular and molecular changes, exacerbated by age-driven decline in cardiac regeneration capacity. Although the phenotypes of cardiac aging are well characterised, the underlying molecular mechanisms are far less explored. Recent advances unequivocally link cardiovascular aging to the dysregulation of critical signalling pathways in cardiac fibroblasts, which compromises the critical role of these cells in maintaining the structural and functional integrity of the myocardium. Clearly, the identification of cardiac fibroblast-specific factors and mechanisms that regulate cardiac fibroblast function in the senescent myocardium is of immense importance. In this regard, recent studies show that Discoidin domain receptor 2 (DDR2), a collagen-activated receptor tyrosine kinase predominantly located in cardiac fibroblasts, has an obligate role in cardiac fibroblast function and cardiovascular fibrosis. Incisive studies on the molecular basis of cardiovascular aging and dysregulated fibroblast function in the senescent heart would pave the way for effective strategies to mitigate cardiovascular diseases in a rapidly growing elderly population.

The Role of Fibroblast Growth Factor Signaling in Somitogenesis

Fibroblast growth factor (FGF) signaling is conserved from cnidaria to mammals (Ornitz and Itoh, 2022) and it regulates several critical processes such as differentiation, proliferation, apoptosis, cell migration, and embryonic development. One pivotal process FGF signaling controls is the division of vertebrate paraxial mesoderm into repeated segmented units called somites (i.e., somitogenesis). Somite segmentation occurs periodically and sequentially in a head-to-tail manner, and lays down the plan for compartmentalized development of the vertebrate body axis (Gomez et al., 2008). These somites later give rise to vertebrae, tendons, and skeletal muscle. Somite segments form sequentially from the anterior end of the presomitic mesoderm (PSM). The periodicity of somite segmentation is conferred by the segmentation clock, comprising oscillatory expression of Hairy and enhancer-of-split (Her/Hes) genes in the PSM. The positional information for somite boundaries is instructed by the double phosphorylated extracellular signal-regulated kinase (ppERK) gradient, which is the relevant readout of FGF signaling during somitogenesis (Sawada et al., 2001; Delfini et al., 2005; Simsek and Ozbudak, 2018; Simsek et al., 2023). In this review, we summarize the crosstalk between the segmentation clock and FGF/ppERK gradient and discuss how that leads to periodic somite boundary formation. We also draw attention to outstanding questions regarding the interconnected roles of the segmentation clock and ppERK gradient, and close with suggested future directions of study.

Identification of biomarkers and immune infiltration in acute myocardial infarction and heart failure by integrated analysis

The mortality of heart failure after acute myocardial infarction (AMI) remains high. The aim of the present study was to analyze hub genes and immune infiltration in patients with AMI and heart failure (HF). The study utilized five publicly available gene expression datasets from peripheral blood in patients with AMI who either developed or did not develop HF. The unbiased patterns of 24 immune cell were estimated by xCell algorithm. Single-cell RNA sequencing data were used to examine the immune cell infiltration in heart failure patients. Hub genes were validated by quantitative reverse transcription-PCR (RT-qPCR). In comparison with the coronary heart disease (CHD) group, immune infiltration analysis of AMI patients showed that macrophages M1, macrophages, monocytes, natural killer (NK) cells, and NKT cells were the five most highly activated cell types. Five common immune-related genes (S100A12, AQP9, CSF3R, S100A9, and CD14) were identified as hub genes associated with AMI. Using RT-qPCR, we confirmed FOS, DUSP1, CXCL8, and NFKBIA as the potential biomarkers to identify AMI patients at risk of HF. The study identified several transcripts that differentiate between AMI and CHD, and between HF and non-HF patients. These findings could improve our understanding of the immune response in AMI and HF, and allow for early identification of AMI patients at risk of HF.

Inhibition of microRNA-122 alleviates pyroptosis by targeting dual-specificity phosphatase 4 in myocardial ischemia/reperfusion injury

Pyroptosis is a type of programmed cell death that induces myocardial ischemia-reperfusion injury (I/RI), which leads to cardiac dysfunction and even lethal reperfusion injury. MiR-122 is a liver-specific miRNA associated with coronary heart disease, but its role in pyroptosis activation in myocardial I/RI remains unclear. Thus, this study aimed to determine whether miR-122 inhibition exerts myocardial I/RI protection in in vivo and in vitro models. An I/RI model was established in vivo using C57BL/J6 male mice. MiR-122 expression was upregulated in the heart tissues from the I/RI group. Quantitative results of echocardiography parameters showed that miR-122 inhibition improved cardiac function and downregulated interleukin (IL)-1β, IL-18, caspase 1, and caspase 11. However, pretransfection with recombinant adeno-associated virus type 9 encoding a DUSP4-specific siRNA (AAV9-siDUSP4) blocked the protective effects of miR-122 inhibition. A hypoxia/reoxygenation (H/R) model was established to mimic the I/R condition in vitro using H9C2 cells. Results showed that miR-122 inhibition increased superoxide dismutase activity (SOD) and cell viability and decreased malondialdehyde (MDA) level, IL-1β, IL-18, caspase 1, caspase 11, and cell death. These protective effects were abolished by transfection with DUSP4-specific siRNA. In summary, miR-122 expression is upregulated in I/RI, and miR-122 inhibition alleviates I/RI by suppressing pyroptosis through targeting DUSP4. Thus, miR-122 may be a novel therapeutic target for treating myocardial I/RI.

TRPA1 promotes the maturation of embryonic stem cell-derived cardiomyocytes by regulating mitochondrial biogenesis and dynamics

BACKGROUND

Cardiomyocytes derived from pluripotent stem cells (PSC-CMs) have been widely accepted as a promising cell source for cardiac drug screening and heart regeneration therapies. However, unlike adult cardiomyocytes, the underdeveloped structure, the immature electrophysiological properties and metabolic phenotype of PSC-CMs limit their application. This project aimed to study the role of the transient receptor potential ankyrin 1 (TRPA1) channel in regulating the maturation of embryonic stem cell-derived cardiomyocytes (ESC-CMs).

METHODS

The activity and expression of TRPA1 in ESC-CMs were modulated by pharmacological or molecular approaches. Knockdown or overexpression of genes was done by infection of cells with adenoviral vectors carrying the gene of interest as a gene delivery tool. Immunostaining followed by confocal microscopy was used to reveal cellular structure such as sarcomere. Staining of mitochondria was performed by MitoTracker staining followed by confocal microscopy. Calcium imaging was performed by fluo-4 staining followed by confocal microscopy. Electrophysiological measurement was performed by whole-cell patch clamping. Gene expression was measured at mRNA level by qPCR and at protein level by Western blot. Oxygen consumption rates were measured by a Seahorse Analyzer.

RESULTS

TRPA1 was found to positively regulate the maturation of CMs. TRPA1 knockdown caused nascent cell structure, impaired Ca²⁺ handling and electrophysiological properties, and reduced metabolic capacity in ESC-CMs. The immaturity of ESC-CMs induced by TRPA1 knockdown was accompanied by reduced mitochondrial biogenesis and fusion. Mechanistically, we found that peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), the key transcriptional coactivator related to mitochondrial biogenesis and metabolism, was downregulated by TRPA1 knockdown. Interestingly, overexpression of PGC-1α ameliorated the halted maturation induced by TRPA1 knockdown. Notably, phosphorylated p38 MAPK was upregulated, while MAPK phosphatase-1 (MKP-1), a calcium-sensitive MAPK inhibitor, was downregulated in TRPA1 knockdown cells, suggesting that TRPA1 may regulate the maturation of ESC-CMs through MKP-1-p38 MAPK-PGC-1α pathway.

CONCLUSIONS

Taken together, our study reveals the novel function of TRPA1 in promoting the maturation of CMs. As multiple stimuli have been known to activate TRPA1, and TRPA1-specific activators are also available, this study provides a novel and straightforward strategy for improving the maturation of PSC-CMs by activating TRPA1. Since a major limitation for the successful application of PSC-CMs for research and medicine lies in their immature phenotypes, the present study takes a big step closer to the practical use of PSC-CMs.

Inhibiting O-GlcNAcylation impacts p38 and Erk1/2 signaling and perturbs cardiomyocyte hypertrophy

The dynamic cycling of O-linked GlcNAc (O-GlcNAc) on and off Ser/Thr residues of intracellular proteins, termed O-GlcNAcylation, is mediated by the conserved enzymes O-GlcNAc transferase (OGT) and O-GlcNAcase. O-GlcNAc cycling is important in homeostatic and stress responses, and its perturbation sensitizes the heart to ischemic and other injuries. Despite considerable progress, many molecular pathways impacted by O-GlcNAcylation in the heart remain unclear. The mitogen-activated protein kinase (MAPK) pathway is a central signaling cascade that coordinates developmental, physiological, and pathological responses in the heart. The developmental or adaptive arm of MAPK signaling is primarily mediated by Erk kinases, while the pathophysiologic arm is mediated by p38 and Jnk kinases. Here, we examine whether O-GlcNAcylation affects MAPK signaling in cardiac myocytes, focusing on Erk1/2 and p38 in basal and hypertrophic conditions induced by phenylephrine. Using metabolic labeling of glycans coupled with alkyne-azide "click" chemistry, we found that Erk1/2 and p38 are O-GlcNAcylated. Supporting the regulation of p38 by O-GlcNAcylation, the OGT inhibitor, OSMI-1, triggers the phosphorylation of p38, an event that involves the NOX2-Ask1-MKK3/6 signaling axis and also the noncanonical activator Tab1. Additionally, OGT inhibition blocks the phenylephrine-induced phosphorylation of Erk1/2. Consistent with perturbed MAPK signaling, OSMI-1-treated cardiomyocytes have a blunted hypertrophic response to phenylephrine, decreased expression of cTnT (key component of the contractile apparatus), and increased expression of maladaptive natriuretic factors Anp and Bnp. Collectively, these studies highlight new roles for O-GlcNAcylation in maintaining a balanced activity of Erk1/2 and p38 MAPKs during hypertrophic growth responses in cardiomyocytes.

Dual Specific Phosphatase 7 Exacerbates Dilated Cardiomyopathy, Heart Failure, and Cardiac Death by Inactivating the ERK1/2 Signaling Pathway

Heart failure is one of the most common but complicated end-stage syndromes in clinical practice. Dilated cardiomyopathy is a myocardial structural abnormality that is associated with heart failure. Dual-specificity phosphatases (DUSPs) are a group of protein phosphatases that regulate signaling pathways in numerous diseases; however, their physiological and pathological impact on cardiovascular disease remains unknown. In the present study, we generated two transgenic mouse models, a DUSP7 knockout and a cardiac-specific DUSP7 overexpressor. Mice overexpressing DUSP7 showed an exacerbated disease phenotype, including severe dilated cardiomyopathy, heart failure, and cardiac death. We further demonstrated that high levels of DUSP7 inhibited ERK1/2 phosphorylation and influenced downstream c-MYC, c-FOS, and c-JUN gene expression but did not affect upstream activators. Taken together, our study reveals a novel molecular mechanism for DUSP7 and provides a new therapeutic target and clinical path to alleviate dilated cardiomyopathy and improve cardiac function.

Dual specificity phosphatase 7 drives the formation of cardiac mesoderm in mouse embryonic stem cells

Dual specificity phosphatase 7 (DUSP7) is a protein belonging to a broad group of phosphatases that can dephosphorylate phosphoserine/phosphothreonine as well as phosphotyrosine residues within the same substrate. DUSP7 has been linked to the negative regulation of mitogen activated protein kinases (MAPK), and in particular to the regulation of extracellular signal-regulated kinases 1 and 2 (ERK1/2). MAPKs play an important role in embryonic development, where their duration, magnitude, and spatiotemporal activity must be strictly controlled by other proteins, among others by DUSPs. In this study, we focused on the effect of DUSP7 depletion on the in vitro differentiation of mouse embryonic stem (ES) cells. We showed that even though DUSP7 knock-out ES cells do retain some of their basic characteristics, when it comes to differentiation, they preferentially differentiate towards neural cells, while the formation of early cardiac mesoderm is repressed. Therefore, our data indicate that DUSP7 is necessary for the correct formation of neuroectoderm and cardiac mesoderm during the in vitro differentiation of ES cells.

Transcriptomic analysis reveals crucial regulatory roles of immediate-early response genes and related signaling pathways in coronavirus infectious bronchitis virus infection

Coronavirus infection of cells differentially regulates the expression of host genes and their related pathways. In this study, we present the transcriptomic profile of cells infected with gammacoronavirus infectious bronchitis virus (IBV). In IBV-infected human non-small cell lung carcinoma cells (H1299 cells), a total of 1162 differentially expressed genes (DEGs), including 984 upregulated and 178 downregulated genes, was identified. These DEGs were mainly enriched in MAPK and Wnt signaling pathways, and 5 out of the 10 top upregulated genes in all transcripts were immediate-early response genes (IEGs). In addition, the induction of 11 transcripts was validated in IBV-infected H1299 and Vero cells by RT-qPCR. The accuracy, reliability and genericity of the transcriptomic data were demonstrated by functional characterization of these IEGs in cells infected with different coronaviruses in our previous publications. This study provides a reliable transcriptomic profile of host genes and pathways regulated by coronavirus infection.

Febuxostat increases ventricular arrhythmogenesis through calcium handling dysregulation in human induced pluripotent stem cell-derived cardiomyocytes

Febuxostat is a xanthine oxidase inhibitor used to reduce the formation of uric acid and prevent gout attacks. Previous studies have suggested that febuxostat was associated with a higher risk of cardiovascular events, including atrial fibrillation, compared with allopurinol, another anti-hyperuricemia drug. Whereas in our clinical practice, we identified two cases of febuxostat-associated ventricular tachycardia events. The proarrhythmogenic effects of febuxostat on human cardiomyocytes and underlined mechanisms remain poorly understood. In this study, we employed real time cell analysis (RTCA) and calcium transient to investigate the effects of febuxostat on the cytotoxicity and electrophysiology properties of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Up to 10 μM febuxostat treatment did not show toxicity to cell viability. However, 48-hour febuxostat exposure generated dose-dependent increased irregular calcium transients and decreased calcium transient amplitude. Furthermore, RNA-seq analysis indicated that the MAPK signaling pathway was enriched in the febuxostat-treated group, especially the protein kinases JNK. Western blotting of three main protein kinases demonstrated that JNK activation is related to febuxostat-induced arrythmia rather than ERK or p38. The dysfunctional calcium dynamics of febuxostat-treated hiPSC-CMs could be ameliorated by SP600125, the inhibitor of JNK. In conclusion, our study demonstrated that febuxostat increases the predisposition to ventricular arrythmia by dysregulating calcium dynamics.

Combined Dusp4 and p53 loss with Dbf4 amplification drives tumorigenesis via cell cycle restriction and replication stress escape in breast cancer

AIM

Deregulated signaling pathways are a hallmark feature of oncogenesis and driver of tumor progression. Dual specificity protein phosphatase 4 (DUSP4) is a critical negative regulator of the mitogen-activated protein kinase (MAPK) pathway and is often deleted or epigenetically silenced in tumors. DUSP4 alterations lead to hyperactivation of MAPK signaling in many cancers, including breast cancer, which often harbor mutations in cell cycle checkpoint genes, particularly in TP53.

METHODS

Using a genetically engineered mouse model, we generated mammary-specific Dusp4-deleted primary epithelial cells to investigate the necessary conditions in which DUSP4 loss may drive breast cancer oncogenesis.

RESULTS

We found that Dusp4 loss alone is insufficient in mediating tumorigenesis, but alternatively converges with loss in Trp53 and MYC amplification to induce tumorigenesis primarily through chromosome 5 amplification, which specifically upregulates Dbf4, a cell cycle gene that promotes cellular replication by mediating cell cycle checkpoint escape.

CONCLUSIONS

This study identifies a novel mechanism for breast tumorigenesis implicating Dusp4 loss and p53 mutations in cellular acquisition of Dbf4 upregulation as a driver of cellular replication and cell cycle checkpoint escape.

Transcriptomal Insights of Heart Failure from Normality to Recovery

Current management of heart failure (HF) is centred on modulating the progression of symptoms and severity of left ventricular dysfunction. However, specific understandings of genetic and molecular targets are needed for more precise treatments. To attain a clearer picture of this, we studied transcriptome changes in a chronic progressive HF model. Fifteen sheep (Ovis aries) underwent supracoronary aortic banding using an inflatable cuff. Controlled and progressive induction of pressure overload in the LV was monitored by echocardiography. Endomyocardial biopsies were collected throughout the development of LV failure (LVF) and during the stage of recovery. RNA-seq data were analysed using the PANTHER database, Metascape, and DisGeNET to annotate the gene expression for functional ontologies. Echocardiography revealed distinct clinical differences between the progressive stages of hypertrophy, dilatation, and failure. A unique set of transcript expressions in each stage was identified, despite an overlap of gene expression. The removal of pressure overload allowed the LV to recover functionally. Compared to the control stage, there were a total of 256 genes significantly changed in their expression in failure, 210 genes in hypertrophy, and 73 genes in dilatation. Gene expression in the recovery stage was comparable with the control stage with a well-noted improvement in LV function. RNA-seq revealed the expression of genes in each stage that are not reported in cardiovascular pathology. We identified genes that may be potentially involved in the aetiology of progressive stages of HF, and that may provide future targets for its management.

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.

UBR3 promotes inflammation and apoptosis via DUSP1/p38 pathway in the nucleus pulposus cells of patients with intervertebral disc degeneration

Intervertebral disc disease (IDD) is a primary cause of low back pain, affecting 5% of individuals. Previous study have shown that dual-specificity (Thr/Tyr) phosphatase 1 (DUSP1) regulates p38 MAPK activity and DUSP1 level is regulated by ubiquitination. As an E3 ubiquitin-protein ligase, UBR3 has been shown to regulate a variety of biological processes through ubiquitination. However, the role of UBR3/DUSP1/p38 in IDD remains to be elucidated. In the current study, we found that UBR3 was significantly increased in the nucleus pulposus tissues of IDD patients and was correlated with IDD severity. Silencing UBR3 promoted the growth, inhibited apoptosis, and inhibited inflammation in primary NPCs. Mechanism study suggested that UBR3 exerted its effects through p38. Co-immunoprecipitation assay indicated that UBR3 promoted DUSP1 ubiquitination. Overexpression of DUSP1 reversed the effect of UBR3 overexpression. Our data also supported that UBR3 was positively correlated with p-p38, but negatively correlated with DUSP1 in IDD. In summary, UBR3 promotes inflammation and apoptosis via inhibiting the p38 signaling pathway by DUSP1 ubiquitination in the NPCs of IDD patients. These findings highlight the importance of UBR3/DUSP1/p38 signaling pathway in IDD and provide new insights for the prevention and treatment of IDD.

Sleeve Gastrectomy Ameliorates Diabetes-Induced Cardiac Hypertrophy Correlates With the MAPK Signaling Pathway

Background: Cardiac hypertrophy as a main pathological manifestation of diabetic cardiomyopathy (DCM), is a significant complication of diabetes. Bariatric surgery has been proven to relieve DCM; however, whether it can alleviate diabetes-induced cardiac hypertrophy is undefined.

Methods: Diabetic and obese rats were performed sleeve gastrectomy (SG) after having diabetes for 16weeks. The rats were euthanized 8weeks after SG. Metabolic parameters, heart function parameters, myocardial glucose uptake, morphometric and histological changes, and the expression level of mitogen-activated protein kinases (MAPKs) were determined and compared among the control group (CON group), diabetes mellitus group (DM group), sham operation group (SHAM group), and SG group.

Results: Compared with the SHAM group, the blood glucose, body weight, insulin resistance, and other metabolic parameters were significantly improved in the SG group. There was also a marked improvement in myocardial morphometric and histological parameters after SG. Furthermore, the myocardial glucose uptake and heart function were reversed after SG. Additionally, the phosphorylation of MAPKs was inhibited after SG, including p38 MAPKs, c-Jun N-terminal kinases (JNKs), and extracellular signal-regulated kinases 1/2 (ERK1/2). The expression of DUSP6, which dephosphorylates ERK1/2, was upregulated after SG. These findings suggest that SG ameliorated diabetes-induced cardiac hypertrophy correlates with the MAPK signaling pathway.

Conclusion: These results showed that diabetes-induced cardiac hypertrophy was ameliorated after SG was closely related to the inhibition of the MAPK signaling pathway and upregulation of DUSP6. Therefore, this study provides a novel strategy for treating diabetes-induced cardiac hypertrophy.

Methylation of dual-specificity phosphatase 4 controls cell differentiation

Mitogen-activated protein kinases (MAPKs) are inactivated by dual-specificity phosphatases (DUSPs), the activities of which are tightly regulated during cell differentiation. Using knockdown screening and single-cell transcriptional analysis, we demonstrate that DUSP4 is the phosphatase that specifically inactivates p38 kinase to promote megakaryocyte (Mk) differentiation. Mechanistically, PRMT1-mediated methylation of DUSP4 triggers its ubiquitinylation by an E3 ligase HUWE1. Interestingly, the mechanistic axis of the DUSP4 degradation and p38 activation is also associated with a transcriptional signature of immune activation in Mk cells. In the context of thrombocytopenia observed in myelodysplastic syndrome (MDS), we demonstrate that high levels of p38 MAPK and PRMT1 are associated with low platelet counts and adverse prognosis, while pharmacological inhibition of p38 MAPK or PRMT1 stimulates megakaryopoiesis. These findings provide mechanistic insights into the role of the PRMT1-DUSP4-p38 axis on Mk differentiation and present a strategy for treatment of thrombocytopenia associated with MDS.

SAHA could inhibit TGF-β1/p38 pathway in MI-induced cardiac fibrosis through DUSP4 overexpression

Growing evidences have revealed that a histone deacetylase inhibitor (HDACi), suberoylanilide hydroxamic acid (SAHA) has anti-fibrotic effect in different diseases. In this study, we first evaluated whether SAHA could suppress cardiac fibrosis. Mice with MI-induced cardiac fibrosis were treated with SAHA by intraperitoneal injection and their cardiac function was improved after SAHA treatment. Results of western blotting and qRT-PCR in heart tissues suggested that TGFβ1/P38 pathway was activated in MI mice, and this effect was reversed by SAHA. Cell proliferation assay suggested that SAHA could suppress TGF-β1-induced cardiac fibroblasts proliferation. Furthermore, results of western blotting and qRT-PCR in cardiac fibroblasts depicted that SAHA may exert its anti-fibrotic effect through inhibiting TGF-β1-induced P38 phosphorylation by promoting DUSP4 expression. Our findings may substantiate SAHA as a promising treatment for MI-induced cardiac fibrosis.

Dual specific phosphatases (DUSPs) in cardiac hypertrophy and failure

Pressure overload and other stress stimuli elicit a host of adaptive and maladaptive signaling cascades that eventually lead to cardiac hypertrophy and heart failure. Among those, the mitogen-activated protein kinase (MAPK) signaling pathway has been shown to play a prominent role. The dual specificity phosphatases (DUSPs), also known as MAPK specific phosphatases (MKPs), that can dephosphorylate the MAPKs and inactivate them are gaining increasing attention as potential drug targets. Here we try to review recent advancements in understanding the roles of the different DUSPs, and the pathways that they regulate in cardiac remodeling. We focus on the regulation of three main MAPK branches - the p38 kinases, the c-Jun-N-terminal kinases (JNKs) and the extracellular signal-regulated kinases (ERK) by various DUSPs and try to examine their roles.

Global gene expression analysis using RNA-seq reveals the new roles of Panax notoginseng Saponins in ischemic cardiomyocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Panax notoginseng saponins (PNS), the main active ingredients of Panax notoginseng (Burkill) F.H.Chen, have been clinically used for cardiovascular diseases treatment in China as the Traditional Chinese Medicine (TCM) (Duan et al., 2017). Evidence demonstrated that PNS protected cardiomyocytes from myocardial ischemia, but the more underlying molecular mechanisms of the protective effect are still unclear. The aims of this study are to systematically know the function of PNS and discover new roles of PNS in ischemic cardiomyocytes.

MATERIALS AND METHODS

To confirm PNS function on ischemic cardiomyopathy, we established in vitro myocardial ischemia model on H9C2 cardiomyocyte line, which was induced by oxygen-glucose depletion (OGD). Then RNA-seq was carried out to systematically analyze global gene expression. This study was aimed to systematically investigate the protective effect and more potential molecular mechanisms of PNS on H9C2 cardiomyocytes in vitro through whole-transcriptome analysis with total RNA sequencing (RNA-Seq).

RESULTS

PNS exhibited anti-apoptotic effect in H9C2 cardiomyocytes in OGD-induced myocardial ischemia model. Through RNA-seq, we found that OGD affected expression profiling of many genes, including upregulated and downregulated genes. PNS inhibited cardiomyocyte apoptosis and death through rescuing cell cycle arrest, the DNA double-strand breakage repair process and chromosome segregation. Interestingly, for the canonical signaling pathways regulation, RNA-seq showed PNS could inhibit cardiac hypertrophy, MAPK signaling pathway, and re-activate PI3K/AKT and AMPK signaling pathways. Experimental data also confirmed the PNS could protect cardiomyocytes from OGD-induced apoptosis through activating PI3K/AKT and AMPK signaling pathways. Moreover, RNA-seq demonstrated that the expression levels of many non-coding RNAs, such as miRNAs and lncRNAs, were significantly affected after PNS treatment, suggesting that PNS could protect cardiomyocytes through regulating non-coding RNAs.

CONCLUSION

RNA-seq systematically revealed different novel roles of Panax Notoginseng Saponins (PNS) in protecting cardiomyocytes from apoptosis, induced by myocardial ischemia, through rescuing cell cycle arrest and cardiac hypertrophy, re-activating the DNA double-strand breakage repair process, chromosome segregation, PI3K/Akt and AMPK signaling pathways and regulating non-coding RNAs.

Risk Prediction in Patients With Heart Failure With Preserved Ejection Fraction Using Gene Expression Data and Machine Learning

Heart failure with preserved ejection fraction (HFpEF) has become a major health issue because of its high mortality, high heterogeneity, and poor prognosis. Using genomic data to classify patients into different risk groups is a promising method to facilitate the identification of high-risk groups for further precision treatment. Here, we applied six machine learning models, namely kernel partial least squares with the genetic algorithm (GA-KPLS), the least absolute shrinkage and selection operator (LASSO), random forest, ridge regression, support vector machine, and the conventional logistic regression model, to predict HFpEF risk and to identify subgroups at high risk of death based on gene expression data. The model performance was evaluated using various criteria. Our analysis was focused on 149 HFpEF patients from the Framingham Heart Study cohort who were classified into good-outcome and poor-outcome groups based on their 3-year survival outcome. The results showed that the GA-KPLS model exhibited the best performance in predicting patient risk. We further identified 116 differentially expressed genes (DEGs) between the two groups, thus providing novel therapeutic targets for HFpEF. Additionally, the DEGs were enriched in Gene Ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways related to HFpEF. The GA-KPLS-based HFpEF model is a powerful method for risk stratification of 3-year mortality in HFpEF patients.

Dual-Specificity Phosphatase 26 Protects Against Cardiac Hypertrophy Through TAK1

Background Heart pathological hypertrophy has been recognized as a predisposing risk factor for heart failure and arrhythmia. DUSP (dual-specificity phosphatase) 26 is a member of the DUSP family of proteins, which has a significant effect on nonalcoholic fatty liver disease, neuroblastoma, glioma, and so on. However, the involvement of DUSP26 in cardiac hypertrophy remains unclear. Methods and Results Our study showed that DUSP26 expression was significantly increased in mouse hearts in response to pressure overload as well as in angiotensin II-treated cardiomyocytes. Cardiac-specific overexpression of DUSP26 mice showed attenuated cardiac hypertrophy and fibrosis, while deficiency of DUSP26 in mouse hearts resulted in increased cardiac hypertrophy and deteriorated cardiac function. Similar effects were also observed in cellular hypertrophy induced by angiotensin II. Importantly, we showed that DUSP26 bound to transforming growth factor-β activated kinase 1 and inhibited transforming growth factor-β activated kinase 1 phosphorylation, which led to suppression of the mitogen-activated protein kinase signaling pathway. In addition, transforming growth factor-β activated kinase 1-specific inhibitor inhibited cardiomyocyte hypertrophy induced by angiotensin II and attenuated the exaggerated hypertrophic response in DUSP26 conditional knockout mice. Conclusions Taken together, DUSP26 was induced in cardiac hypertrophy and protected against pressure overload induced cardiac hypertrophy by modulating transforming growth factor-β activated kinase 1-p38/ c-Jun N-terminal kinase-signaling axis. Therefore, DUSP26 may provide a therapeutic target for treatment of cardiac hypertrophy and heart failure.

MBNL1 regulates isoproterenol-induced myocardial remodelling in vitro and in vivo

Myocardial remodelling is a common phenomenon in cardiovascular diseases, which threaten human health and the quality of life. Due to the lack of effective early diagnosis and treatment methods, the molecular mechanism of myocardial remodelling should be explored in depth. In this study, we observed the high expression of MBNL1 in cardiac tissue and peripheral blood of an isoproterenol (ISO)-induced cardiac hypertrophy mouse model. MBNL1 promoted ISO-induced cardiac hypertrophy and fibrosis by stabilizing Myocardin mRNA in vivo and in vitro. Meanwhile, an increase in MBNL1 may induce the apoptosis of cardiomyocytes treated with ISO via TNF-α signalling. Interestingly, MBNL1 can be activated by p300 in cardiomyocytes treated with ISO. At last, Myocardin can reverse activate the expression of MBNL1. These results suggest that MBNL1 may be a potential target for the early diagnosis and clinical treatment of myocardial remodelling.

Intra-Cellular Calcium Signaling Pathways (PKC, RAS/RAF/MAPK, PI3K) in Lamina Cribrosa Cells in Glaucoma

The lamina cribrosa (LC) is a key site of fibrotic damage in glaucomatous optic neuropathy and the precise mechanisms of LC change remain unclear. Elevated Ca²⁺ is a major driver of fibrosis, and therefore intracellular Ca²⁺ signaling pathways are relevant glaucoma-related mechanisms that need to be studied. Protein kinase C (PKC), mitogen-activated MAPK kinases (p38 and p42/44-MAPK), and the PI3K/mTOR axis are key Ca²⁺ signal transducers in fibrosis and we therefore investigated their expression and activity in normal and glaucoma cultured LC cells. We show, using Western immune-blotting, that hyposmotic-induced cellular swelling activates PKCα, p42/p44, and p38 MAPKs, the activity is transient and biphasic as it peaks between 2 min and 10 min. The expression and activity of PKCα, p38 and p42/p44-MAPKs are significantly (p < 0.05) increased in glaucoma LC cells at basal level, and at different time-points after hyposmotic stretch. We also found elevated mRNA expression of mRNA expression of PI3K, IP3R, mTOR, and CaMKII in glaucoma LC cells. This study has identified abnormalities in multiple calcium signaling pathways (PKCα, MAPK, PI3K) in glaucoma LC cells, which might have significant functional and therapeutic implications in optic nerve head (ONH) fibrosis and cupping in glaucoma.

Regulators of cardiac fibroblast cell state

Fibroblasts are the primary regulator of cardiac extracellular matrix (ECM). In response to disease stimuli cardiac fibroblasts undergo cell state transitions to a myofibroblast phenotype, which underlies the fibrotic response in the heart and other organs. Identifying regulators of fibroblast state transitions would inform which pathways could be therapeutically modulated to tactically control maladaptive extracellular matrix remodeling. Indeed, a deeper understanding of fibroblast cell state and plasticity is necessary for controlling its fate for therapeutic benefit. p38 mitogen activated protein kinase (MAPK), which is part of the noncanonical transforming growth factor β (TGFβ) pathway, is a central regulator of fibroblast to myofibroblast cell state transitions that is activated by chemical and mechanical stress signals. Fibroblast intrinsic signaling, local and global cardiac mechanics, and multicellular interactions individually and synergistically impact these state transitions and hence the ECM, which will be reviewed here in the context of cardiac fibrosis.

Rho kinase cascade activation in circulating leukocytes in patients with diabetes mellitus type 2

Background

The intracellular ROCK signaling pathway is an important modulator of blood pressure and of cardiovascular and renal remodeling when Rho-kinase activity is increased. Besides, in preclinical models of diabetes, ROCK activation has also a role in abnormal glucose metabolism as well as in subsequent vascular and myocardial dysfunction. In humans, there are a few data assessing ROCK activation in patients with type 2 diabetes mellitus (T2D) and no studies assessing upstream/downstream components of the ROCK pathway. We assessed here levels of ROCK activation and some of the RhoA/ROCK cascade molecules in peripheral blood mononuclear cells (PBMCs) in T2D patients under current treatment.

Methods

Cross-sectional observational study comparing 28 T2D patients under current antidiabetic treatment with 31 consecutive healthy subjects, matched by age and gender. Circulating levels of malondialdehyde, angiotensin II and inflammatory cytokines IL-6 and IL-8 were determined in all subjects. ROCK activation in PMBCs, upstream and downstream cascade proteins, and levels of the proinflammatory molecules VCAM, ICAM-1 and IL-8 were determined in their PMBCs by Western blot.

Results

Compared to healthy controls, ROCK activation in T2D patients measured by 2 direct ROCK targets in PBMCs was increased by 420 and 570% (p < 0001) and it correlated significantly with serum glucose levels. p38 MAPK phosphorylation (downstream from ROCK) and JAK-2 (upstream from ROCK) were significantly higher in the T2D patients by 580% and 220%, respectively. In T2D patients, significantly increased PBMC levels of the proinflammatory molecules VCAM-1, ICAM-1 and IL-8 were observed compared to control subjects (by 180%, 360% and 260%, respectively). Circulating levels of Ang II and MDA were significantly higher in T2D patients by 29 and 63%, respectively.

Conclusions

T2D patients under treatment with glucose-lowering drugs, antihypertensive treatment as well as with statins have significantly increased ROCK activation in their circulating leukocytes along with higher phosphorylation of downstream cascade proteins despite pharmacologic treatment, along with increased plasma angiotensin II and MDA levels. ROCK inhibition might have an additional role in the prevention and treatment of T2D.

miR-1468-3p Promotes Aging-Related Cardiac Fibrosis

Non-coding microRNAs (miRNAs) are powerful regulators of gene expression and critically involved in cardiovascular pathophysiology. The aim of the current study was to identify miRNAs regulating cardiac fibrosis. Cardiac samples of age-matched control subjects and sudden cardiac death (SCD) victims with primary myocardial fibrosis (PMF) were subjected to miRNA profiling. Old SCD victims with PMF and healthy aged human hearts showed increased expression of miR-1468-3p. In vitro studies in human cardiac fibroblasts showed that augmenting miR-1468-3p levels induces collagen deposition and cell metabolic activity and enhances collagen 1, connective tissue growth factor, and periostin expression. In addition, miR-1468-3p promotes cellular senescence with increased senescence-associated β-galactosidase activity and increased expression of p53 and p16. AntimiR-1468-3p antagonized transforming growth factor β1 (TGF-β1)-induced collagen deposition and metabolic activity. Mechanistically, mimic-1468-3p enhanced p38 phosphorylation, while antimiR-1468-3p decreased TGF-β1-induced p38 activation and abolished p38-induced collagen deposition. RNA sequencing analysis, a computational prediction model, and qPCR analysis identified dual-specificity phosphatases (DUSPs) as miR-1468-3p target genes, and regulation of DUSP1 by miR-1468-3p was confirmed with a dual-luciferase reporter assay. In conclusion, miR-1468-3p promotes cardiac fibrosis by enhancing TGF-β1-p38 signaling. Targeting miR-1468-3p in the older population may be of therapeutic interest to reduce cardiac fibrosis.

High-Density Lipoprotein (HDL) Inhibits Serum Amyloid A (SAA)-Induced Vascular and Renal Dysfunctions in Apolipoprotein E-Deficient Mice

Serum amyloid A (SAA) promotes endothelial inflammation and dysfunction that is associated with cardiovascular disease and renal pathologies. SAA is an apoprotein for high-density lipoprotein (HDL) and its sequestration to HDL diminishes SAA bioactivity. Herein we investigated the effect of co-supplementing HDL on SAA-mediated changes to vascular and renal function in apolipoprotein E-deficient (ApoE^-/^-) mice in the absence of a high-fat diet. Male ApoE^-/- mice received recombinant human SAA or vehicle (control) by intraperitoneal (i.p.) injection every three days for two weeks with or without freshly isolated human HDL supplemented by intravenous (i.v.) injection in the two weeks preceding SAA stimulation. Aorta and kidney were harvested 4 or 18 weeks after commencement of treatment. At 4 weeks after commencement of treatment, SAA increased aortic vascular cell adhesion molecule (VCAM)-1 expression and F₂-isoprostane level and decreased cyclic guanosine monophosphate (cGMP), consistent with SAA stimulating endothelial dysfunction and promoting atherosclerosis. SAA also stimulated renal injury and inflammation that manifested as increased urinary protein, kidney injury molecule (KIM)-1, and renal tissue cytokine/chemokine levels as well as increased protein tyrosine chlorination and P38 MAPkinase activation and decreased in Bowman's space, confirming that SAA elicited a pro-inflammatory phenotype in the kidney. At 18 weeks, vascular lesions increased significantly in the cohort of ApoE^-/- mice treated with SAA alone. By contrast, pretreatment of mice with HDL decreased SAA pro-inflammatory activity, inhibited SAA enhancement of aortic lesion size and renal function, and prevented changes to glomerular Bowman's space. Taken together, these data indicate that supplemented HDL reduces SAA-mediated endothelial and renal dysfunction in an atherosclerosis-prone mouse model.

Rho-kinase pathway activation and apoptosis in circulating leucocytes in patients with heart failure with reduced ejection fraction

Background

Increased Rho‐kinase activity in circulating leucocytes is observed in heart failure with reduced ejection fraction (HFrEF). However, there is little information in HFrEF regarding other Rho‐kinase pathway components an on the relationship between Rho‐kinase and apoptosis. Here, Rho‐kinase activation levels and phosphorylation of major downstream molecules and apoptosis levels were measured for the first time both in HFrEF patients and healthy individuals.

Methods

Cross‐sectional study comparing HFrEF patients (n = 20) and healthy controls (n = 19). Rho‐kinase activity in circulating leucocytes (peripheral blood mononuclear cells, PBMCs) was determined by myosin light chain phosphatase 1 (MYPT1) and ezrin‐radixin‐moesin (ERM) phosphorylation. Rho‐kinase cascade proteins phosphorylation p38‐MAPK, myosin light chain‐2, JAK and JNK were also analysed along with apoptosis.

Results

MYPT1 and ERM phosphorylation were significantly elevated in HFrEF patients, (3.9‐ and 4.8‐fold higher than in controls, respectively). JAK phosphorylation was significantly increased by 300% over controls. Phosphorylation of downstream molecules p38‐MAPK and myosin light chain‐2 was significantly higher by 360% and 490%, respectively, while JNK phosphorylation was reduced by 60%. Catecholamine and angiotensin II levels were significantly higher in HFrEF patients, while angiotensin‐(1‐9) levels were lower. Apoptosis in circulating leucocytes was significantly increased in HFrEF patients by 2.8‐fold compared with controls and significantly correlated with Rho‐kinase activation.

Conclusion

Rho‐kinase pathway is activated in PMBCs from HFrEF patients despite optimal treatment, and it is closely associated with neurohormonal activation and with apoptosis. ROCK cascade inhibition might induce clinical benefits in HFrEF patients, and its assessment in PMBCs could be useful to evaluate reverse remodelling and disease regression.

p38α MAPK proximity assay reveals a regulatory mechanism of alternative splicing in cardiomyocytes

The p38 mitogen-activated protein kinase (MAPK) signaling pathway is essential for normal heart function. However, p38 also contributes to heart failure pathogenesis by affecting cardiomyocytes contractility and survival. To unravel part of the complex role of p38 in cardiac function, we performed an APEX2-based proximity assay in cultured neonatal rat ventricular myocytes and identified the protein interaction networks (interactomes) of two highly expressed p38 isoforms in the heart. We found that p38α and p38γ have distinct interactomes in cardiomyocytes under both basal and osmotic stress-activated states. Interestingly, the activated p38α interactome contains many RNA-binding proteins implicated in splicing, including the serine/arginine-rich splicing factor 3 (SRSF3). Its interaction with the activated p38α was validated by co-immunoprecipitation. The cytoplasmic abundance and alternative splicing function of SRSF3 are also both modulated by the p38 signaling pathway. Our findings reveal a new function for p38 as a specific regulator of SRSF3 in cardiomyocytes.

Cardiac Fibroblast p38 MAPK: A Critical Regulator of Myocardial Remodeling

The cardiac fibroblast is a remarkably versatile cell type that coordinates inflammatory, fibrotic and hypertrophic responses in the heart through a complex array of intracellular and intercellular signaling mechanisms. One important signaling node that has been identified involves p38 MAPK; a family of kinases activated in response to stress and inflammatory stimuli that modulates multiple aspects of cardiac fibroblast function, including inflammatory responses, myofibroblast differentiation, extracellular matrix turnover and the paracrine induction of cardiomyocyte hypertrophy. This review explores the emerging importance of the p38 MAPK pathway in cardiac fibroblasts, describes the molecular mechanisms by which it regulates the expression of key genes, and highlights its potential as a therapeutic target for reducing adverse myocardial remodeling.

Diabetes-Induced DUSP4 Reduction Promotes Podocyte Dysfunction and Progression of Diabetic Nephropathy

Diabetic nephropathy (DN) remains the leading cause of end-stage renal disease. Hyperglycemia-induced podocyte dysfunction is a major contributor of renal function impairment in DN. Previous studies showed that activation of mitogen-activated protein kinase (MAPK) in diabetes promotes podocyte dysfunction and cell death. Dual specificity phosphatases (DUSPs) are a family of phosphatases mainly responsible for MAPK inhibition. In this study, we demonstrated that diabetes and high glucose exposure decreased DUSP4 expression in cultured podocytes and glomeruli. Diabetes-induced DUSP4 reduction enhanced p38 and c-Jun N-terminal kinase (JNK) activity and podocyte dysfunction. The overexpression of DUSP4 prevented the activation of p38, JNK, caspase 3/7 activity, and NADPH oxidase 4 expression induced by high glucose level exposure. Deletion of DUSP4 exacerbated albuminuria and increased mesangial expansion and glomerular fibrosis in diabetic mice. These morphological changes were associated with profound podocyte foot process effacement, cell death, and sustained p38 and JNK activation. Moreover, inhibition of protein kinase C-δ prevented DUSP4 expression decline and p38/JNK activation in the podocytes and renal cortex of diabetic mice. Analysis of DUSP4 expression in the renal cortex of patients with diabetes revealed that decreased DUSP4 mRNA expression correlated with reduced estimated glomerular filtration rate (<60 mL/min/1.73 m²). Thus, this study demonstrates that preserving DUSP4 expression could protect against podocyte dysfunction and preserve glomerular function in DN.

Inactivation of Cyclic AMP Response Element Transcription Caused by Constitutive p38 Activation Is Mediated by Hyperphosphorylation-Dependent CRTC2 Nucleocytoplasmic Transport

The p38 signal transduction pathway can be activated transiently or constitutively, depending on the contexts in which the activation occurs. However, the biological consequence of constitutive activation of p38 is largely unknown. After screening 300 transcriptional cofactors, we identified CRTC2 as a downstream substrate of constitutively activated p38. Constitutive, rather than transient, activation of p38 led to hyperphosphorylation of CRTC2, resulting in CRTC2 cytosolic relocation and subsequent inactivation of cyclic AMP response element (CRE)-mediated transcription. Interestingly, the cytosolic translocation of CRTC2 depended on phosphorylation accumulation at multiple sites (≥11 phosphoserine/phosphothreonine residues) but not on specific sites. The hyperphosphorylation-driven nucleocytoplasmic transport of CRTC2 may not be a rare case of nuclear export of proteins, as we also observed that constitutively activated p38 promoted FOS nuclear export in a hyperphosphorylation-dependent manner. Collectively, our study uncovered a previously unknown mechanism of inactivation of selected transcription, which results from hyperphosphorylation-driven nucleocytoplasmic transport of cofactors or transcription factors mediated by constitutively active kinase.

Dual-specificity phosphatase 4 is upregulated during skeletal muscle atrophy and modulates extracellular signal-regulated kinase activity

Skeletal muscle atrophy results from disparate physiological conditions, including denervation, corticosteroid treatment, and aging. The purpose of this study was to describe and characterize the function of dual-specificity phosphatase 4 (Dusp4) in skeletal muscle after it was found to be induced in response to neurogenic atrophy. Quantitative PCR and Western blot analysis revealed that Dusp4 is expressed during myoblast proliferation but rapidly disappears as muscle cells differentiate. The Dusp4 regulatory region was cloned and found to contain a conserved E-box element that negatively regulates Dusp4 reporter gene activity in response to myogenic regulatory factor expression. In addition, the proximal 3′-untranslated region of Dusp4 acts in an inhibitory manner to repress reporter gene activity as muscle cells progress through the differentiation process. To determine potential function, Dusp4 was fused with green fluorescent protein, expressed in C2C12 cells, and found to localize to the nucleus of proliferating myoblasts. Furthermore, Dusp4 overexpression delayed C2C12 muscle cell differentiation and resulted in repression of a MAP kinase signaling pathway reporter gene. Ectopic expression of a Dusp4 dominant negative mutant blocked muscle cell differentiation and attenuated MAP kinase signaling by preferentially targeting the ERK1/2 branch, but not the p38 branch, of the MAP kinase signaling cascade in skeletal muscle cells. The findings presented in this study provide the first description of Dusp4 in skeletal muscle and suggest that Dusp4 may play an important role in the regulation of muscle cell differentiation by regulating MAP kinase signaling.

p38 MAPK activity is associated with the histological degree of interstitial fibrosis in IgA nephropathy patients

Activation of p38 mitogen-activated protein kinase (MAPK) is associated with tissue fibrosis, and inhibition of p38 MAPK can attenuate the progression of fibrosis. We aimed to investigate whether p38 MAPK activity in kidney tissue confirmed by immunohistochemical staining is associated with renal tubulointerstitial fibrosis in chronic kidney disease patients with IgA nephropathy. We collected kidney biopsy specimens from 341 IgA nephropathy patients and 15 control patients to identify the clinical and histopathological factors associated with kidney tubulointerstitial fibrosis and to find an association between kidney phosphorylated p38 immunoactivity and pathological grading. In addition, we aimed to investigate whether the anti-fibrotic effect of p38 MAPK inhibition can be identified by assessing the immunostaining intensity of phosphorylated p38 in kidney tissue. A renal tubulointerstitial fibrosis model was introduced using 7-week-old C57BL/6 mice subjected to unilateral ureteral obstruction (UUO). The p38 MAPK inhibitor SB-731445 was injected intraperitoneally every day for 7 days, and changes in renal fibrosis-associated markers were investigated. Assessment of kidney biopsy specimens from IgA nephropathy patients revealed that the degree of interstitial fibrosis was significantly associated with the tissue immunoactivity of phosphorylated p38. High-grade interstitial fibrosis was associated with a low glomerular filtration rate, high proteinuria, and high-grade histopathological changes, including tubular atrophy, interstitial inflammation, and glomerular sclerosis. In a mouse UUO model, renal protein expression of COL1 and phosphorylated p38 were significantly increased, and the protein expression of COL1 and phosphorylated p38 decreased in mice administered 10 mg/kg/day p38 MAPK inhibitor. We found that kidney interstitial fibrosis is associated with increased immunoactivity of phosphorylated p38 in a UUO mouse model and in human IgA nephropathy patients and that the anti-fibrotic effect of p38 MAPK inhibition can be confirmed using immunohistochemical staining for phosphorylated p38 in kidney tissue.

Elevated dual specificity protein phosphatase 4 in cardiomyopathy caused by lamin A/C gene mutation is primarily ERK1/2-dependent and its depletion improves cardiac function and survival

Mutations in the lamin A/C gene (LMNA) encoding the nuclear intermediate filament proteins lamins A and C cause a group of tissue-selective diseases, the most common of which is dilated cardiomyopathy (herein referred to as LMNA cardiomyopathy) with variable skeletal muscle involvement. We previously showed that cardiomyocyte-specific overexpression of dual specificity protein phosphatase 4 (DUSP4) is involved in the pathogenesis of LMNA cardiomyopathy. However, how mutations in LMNA activate Dusp4 expression and whether it is necessary for the development of LMNA cardiomyopathy are currently unknown. We now show that female LmnaH222P/H222P mice, a model for LMNA cardiomyopathy, have increased Dusp4 expression and hyperactivation of extracellular signal-regulated kinase (ERK) 1/2 with delayed kinetics relative to male mice, consistent with the sex-dependent delay in the onset and progression of disease. Mechanistically, we show that the H222P amino acid substitution in lamin A enhances its binding to ERK1/2 and increases sequestration at the nuclear envelope. Finally, we show that genetic deletion of Dusp4 has beneficial effects on heart function and prolongs survival in LmnaH222P/H222P mice. These results further establish Dusp4 as a key contributor to the pathogenesis of LMNA cardiomyopathy and a potential target for drug therapy.

Novel protective role for MAP kinase phosphatase 2 in inflammatory arthritis

Objectives

We have previously shown mitogen-activated protein kinase phosphatase 2 (MKP-2) to be a key regulator of proinflammatory cytokines in macrophages. In the study presented here, we investigated the role of MKP-2 in inflammatory arthritis with a particular focus on neutrophils.

Methods

To achieve this, we subjected MKP-2 deficient and wild type mice to collagen antibody induced arthritis, an innate model of arthritis, and determined disease pathology. To further our investigation, we depleted neutrophils in a prophylactic and therapeutic fashion. Last, we used chemotaxis assays to analyse the impact of MKP-2 deletion on neutrophil migration.

Results

MKP-2^-/- mice showed a significant increase in disease pathology linked to elevated levels of proarthritic cytokines and chemokines TNF-α, IL-6 and MCP-1 in comparison to wild type controls. This phenotype is prevented or abolished after administration of neutrophil depleting antibody prior or after onset of disease, respectively. While MCP-1 levels were not affected, neutrophil depletion diminished TNF-α and reduced IL-6, thus linking these cytokines to neutrophils. In vivo imaging showed that MKP-2^-/- mice had an increased influx of neutrophils into affected joints, which was higher and potentially prolonged than in wild type animals. Furthermore, using chemotaxis assays we revealed that MKP-2 deficient neutrophils migrate faster towards a Leukotriene B4 gradient. This process correlated with a reduced phosphorylation of ERK in MKP-2^-/- neutrophils.

Conclusions

This is the first study to show a protective role for MKP-2 in inflammatory arthritis.

Modelling cadmium-induced cardiotoxicity using human pluripotent stem cell-derived cardiomyocytes

Cadmium, a highly ubiquitous toxic heavy metal, has been widely recognized as an environmental and industrial pollutant, which confers serious threats to human health. The molecular mechanisms of the cadmium-induced cardiotoxicity (CIC) have not been studied in human cardiomyocytes at the cellular level. Here we showed that human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) can recapitulate the CIC at the cellular level. The cadmium-treated hPSC-CMs exhibited cellular phenotype including reduced cell viability, increased apoptosis, cardiac sarcomeric disorganization, elevated reactive oxygen species, altered action potential profile and cardiac arrhythmias. RNA-sequencing analysis revealed a differential transcriptome profile and activated MAPK signalling pathway in cadmium-treated hPSC-CMs, and suppression of P38 MAPK but not ERK MAPK or JNK MAPK rescued CIC phenotype. We further identified that suppression of PI3K/Akt signalling pathway is sufficient to reverse the CIC phenotype, which may play an important role in CIC. Taken together, our data indicate that hPSC-CMs can serve as a suitable model for the exploration of molecular mechanisms underlying CIC and for the discovery of CIC cardioprotective drugs.

Changes in cardiac resident fibroblast physiology and phenotype in aging

The cardiac fibroblast plays a central role in tissue homeostasis and in repair after injury. With aging, dysregulated cardiac fibroblasts have a reduced capacity to activate a canonical transforming growth factor-β-Smad pathway and differentiate poorly into contractile myofibroblasts. That results in the formation of an insufficient scar after myocardial infarction. In contrast, in the uninjured aged heart, fibroblasts are activated and acquire a profibrotic phenotype that leads to interstitial fibrosis, ventricular stiffness, and diastolic dysfunction, all conditions that may lead to heart failure. There is an apparent paradox in aging, wherein reparative fibrosis is impaired but interstitial, adverse fibrosis is augmented. This could be explained by analyzing the effectiveness of signaling pathways in resident fibroblasts from young versus aged hearts. Whereas defective signaling by transforming growth factor-β leads to insufficient scar formation by myofibroblasts, enhanced activation of the ERK1/2 pathway may be responsible for interstitial fibrosis mediated by activated fibroblasts. Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/fibroblast-phenotypic-changes-in-the-aging-heart/ .

Mechanism underlying the contractile activity of UTP in the mammalian heart

We previously reported that uridine 5'-triphosphate (UTP), a pyrimidine nucleoside triphosphate produced a concentration- and time-dependent increase in the contraction force in isolated right atrial preparations from patients undergoing cardiac bypass surgery due to angina pectoris. The stimulation of the force of contraction was sustained rather than transient. In the present study, we tried to elucidate the underlying receptor and signal transduction for this effect of UTP. Therefore, we measured the effect of UTP on force of contraction, phosphorylation of p38 and ERK1/2, in human atrial preparations, atrial preparations from genetically modified mice, cardiomyocytes from adult mice and cardiomyocytes from neonatal rats. UTP exerted a positive inotropic effect in isolated electrically driven left atrial preparations from wild-type (WT) mice and P2Y₂-, P2Y₄- and P2Y₆-receptor knockout mice. Therefore, we concluded that these P2Y receptors did not mediate the inotropic effects of UTP in atrial preparations from mice. However, UTP (like ATP) increased the phosphorylation states of p38 and ERK1/2 in neonatal rat cardiomyocytes, adult mouse cardiomyocytes and human atrial tissue in vitro. U0126, a MEK 1/2- signal cascade inhibitor, attenuated this phosphorylation and the positive inotropic effects of UTP in murine and human atrial preparations. We suggest that presently unknown receptors mediate the positive inotropic effect of UTP in murine and human atria. We hypothesize that UTP stimulates inotropy via p38 or ERK1/2 phosphorylation. We speculate that UTP may be a valuable target in the development of new drugs aimed at treating human systolic heart failure.

Protecting the heart through MK2 modulation, toward a role in diabetic cardiomyopathy and lipid metabolism

Various signaling pathways have been identified in the heart as important players during development, physiological adaptation or pathological processes. This includes the MAPK families, particularly p38MAPK, which is involved in several key cellular processes, including differentiation, proliferation, apoptosis, inflammation, metabolism and survival. Disrupted p38MAPK signaling has been associated with several diseases, including cardiovascular diseases (CVD) as well as diabetes and its related complications. Despite efforts to translate this knowledge into therapeutic avenues, p38 inhibitors have failed in clinical trials due to adverse effects. Inhibition of MK2, a downstream target of p38, appears to be a promising alternative strategy. Targeting MK2 activity may avoid the adverse effects linked to p38 inhibition, while maintaining its beneficial effects. MK2 was first considered as a therapeutic target in inflammatory diseases such as rheumatoid polyarthritis. A growing body of evidence now supports a key role of MK2 signaling in the pathogenesis of CVD, particularly ischemia/reperfusion injury, hypertrophy, and hypertension and that its inhibition or inactivation is associated with improved heart and vascular functions. More recently, MK2 was shown to be a potential player in diabetes and related complications, particularly in liver and heart, and perturbations in calcium handling and lipid metabolism. In this review, we will discuss recent advances in our knowledge of the role of MK2 in p38MAPK-mediated signaling and the benefits of its loss of function in CVD and diabetes, with an emphasis on the roles of MK2 in calcium handling and lipid metabolism. This article is part of a Special issue entitled Cardiac adaptations to obesity, diabetes and insulin resistance, edited by Professors Jan F.C. Glatz, Jason R.B. Dyck and Christine Des Rosiers.

Dual-Specificity Phosphatase 4 Overexpression in Cells Prevents Hypoxia/Reoxygenation-Induced Apoptosis via the Upregulation of eNOS

Mitogen-activated protein kinases (MAPKs) signaling cascades regulate several cellular functions, including differentiation, proliferation, survival, and apoptosis. The duration and magnitude of phosphorylation of these MAPKs are decisive determinants of their physiological functions. Dual-specificity phosphatases exert kinetic control over these signaling cascades. Previously, we demonstrated that DUSP4^−/− hearts sustain a larger infarct and have poor functional recovery, when isolated hearts were subjected to ischemia/reperfusion. Uncontrolled p38 activation and upregulation of Nox4 expression are the main effectors for this functional alteration. Here, dual-specificity phosphatase 4 (DUSP4) overexpression in endothelial cells was used to investigate the role of DUSP4 on the modulation of reactive oxygen species (ROS) generation and vascular function, when cells were subjected to hypoxia/reoxygenation (H/R) insult. Immunostaining with cleaved caspase-3 revealed that DUSP4 overexpression prevents caspase-3 activation and apoptosis after H/R. The beneficial effects occur via modulating p38 activity, increased NO bioavailability, and reduced oxidative stress. More importantly, DUSP4 overexpression upregulates eNOS protein expression (1.62 ± 0.33 versus 0.65 ± 0.16) during H/R-induced stress. NO is a critical small molecule involved in regulating vascular tone, vascular growth, platelet aggregation, and modulation of inflammation. The level of NO generation determined using DAF-2 fluorescence demonstrated that DUSP4 overexpression augments NO production and thus improves vascular function. The level of superoxide generated from cells after being subjected to H/R was determined using dihydroethidium-HPLC method. The results suggested that DUSP4 overexpression in cells decreases H/R-induced superoxide generation (1.56 ± 0.14 versus 1.19 ± 0.05) and thus reduces oxidant stress. This also correlates with the reduction in the total protein S-glutathionylation, an indicator of protein oxidation. These results further support our hypothesis that DUSP4 is an antioxidant gene and a key phosphatase in modulating MAPKs, especially p38, during oxidative stress, which regulates ROS generation and eNOS expression and thus protects against oxidant-induced injury or apoptosis. Overall, DUSP4 may serve as an excellent molecular target for the treatment of ischemic heart disease.

DUSP-1 gene expression is not regulated by promoter methylation in diabetes-associated cardiac hypertrophy

BACKGROUND

The exact mechanism causing decreased expression of the dual specific phosphatase-1 ( DUSP-1) gene in diabetes-associated cardiac hypertrophy is not known. DNA promoter methylation is often associated with decreased gene expression in many diseases including cardiovascular diseases. So, we investigated whether epigenetic silencing via promoter methylation is involved in the decreased expression of DUSP-1 in diabetes-associated cardiac hypertrophy.

METHODS

Real-time polymerase chain reaction (PCR) and Western blotting confirmed the down regulation of the DUSP-1 gene at transcriptional and translational levels. Bisulfite-converted DNA samples from myocardium of rat model of diabetic cardiomyopathy (DCM), high glucose (HG)-treated neonatal rat cardiomyocytes (NRCMs) and cardiac tissues from archived human myocardial DCM autopsies along with their respective controls were analyzed for methylation in the promoter region of the DUSP-1 gene.

RESULTS

We observed no methylation in the promoter regions of the DUSP-1 gene in DCM rat hearts, in HG-treated NRCMs (between -355 bp and -174 bp) and in cardiac tissues from archived human myocardial DCM autopsies (between -274 bp and -73 bp).

CONCLUSION

Methylation-mediated silencing of the DUSP-1 promoter does not appear to be associated with reduced expression, indicating the involvement of other factors in specific suppression of DUSP-1 in diabetes-associated cardiac hypertrophy.

Profiling Subcellular Protein Phosphatase Responses to Coxsackievirus B3 Infection of Cardiomyocytes

Cellular responses to stimuli involve dynamic and localized changes in protein kinases and phosphatases. Here, we report a generalized functional assay for high-throughput profiling of multiple protein phosphatases with subcellular resolution and apply it to analyze coxsackievirus B3 (CVB3) infection counteracted by interferon signaling. Using on-plate cell fractionation optimized for adherent cells, we isolate protein extracts containing active endogenous phosphatases from cell membranes, the cytoplasm, and the nucleus. The extracts contain all major classes of protein phosphatases and catalyze dephosphorylation of plate-bound phosphosubstrates in a microtiter format, with cellular activity quantified at the end point by phosphospecific ELISA. The platform is optimized for six phosphosubstrates (ERK2, JNK1, p38α, MK2, CREB, and STAT1) and measures specific activities from extracts of fewer than 50,000 cells. The assay was exploited to examine viral and antiviral signaling in AC16 cardiomyocytes, which we show can be engineered to serve as susceptible and permissive hosts for CVB3. Phosphatase responses were profiled in these cells by completing a full-factorial experiment for CVB3 infection and type I/II interferon signaling. Over 850 functional measurements revealed several independent, subcellular changes in specific phosphatase activities. During CVB3 infection, we found that type I interferon signaling increases subcellular JNK1 phosphatase activity, inhibiting nuclear JNK1 activity that otherwise promotes viral protein synthesis in the infected host cell. Our assay provides a high-throughput way to capture perturbations in important negative regulators of intracellular signal-transduction networks.

Regulation of cardiac hypertrophy and remodeling through the dual-specificity MAPK phosphatases (DUSPs)

Mitogen-activated protein kinases (MAPKs) play a critical role in regulating cardiac hypertrophy and remodeling in response to increased workload or pathological insults. The spatiotemporal activities and inactivation of MAPKs are tightly controlled by a family of dual-specificity MAPK phosphatases (DUSPs). Over the past 2 decades, we and others have determined the critical role for selected DUSP family members in controlling MAPK activity in the heart and the ensuing effects on ventricular growth and remodeling. More specifically, studies from mice deficient for individual Dusp genes as well as heart-specific inducible transgene-mediated overexpression have implicated select DUSPs as essential signaling effectors in the heart that function by dynamically regulating the level, subcellular and temporal activities of the extracellular signal-regulated kinases (ERKs), c-Jun N-terminal kinases (JNKs) and p38 MAPKs. This review summarizes recent literature on the physiological and pathological roles of MAPK-specific DUSPs in regulating MAPK signaling in the heart and the effect on cardiac growth and remodeling.

Dual specific phosphatase 12 ameliorates cardiac hypertrophy in response to pressure overload

Pathological cardiac hypertrophy is an independent risk factor of heart failure. However, we still lack effective methods to reverse cardiac hypertrophy. DUSP12 is a member of the dual specific phosphatase (DUSP) family, which is characterized by its DUSP activity to dephosphorylate both tyrosine and serine/threonine residues on one substrate. Some DUSPs have been identified as being involved in the regulation of cardiac hypertrophy. However, the role of DUSP12 during pathological cardiac hypertrophy is still unclear. In the present study, we observed a significant decrease in DUSP12 expression in hypertrophic hearts and cardiomyocytes. Using a genetic loss-of-function murine model, we demonstrated that DUSP12 deficiency apparently aggravated pressure overload-induced cardiac hypertrophy and fibrosis as well as impaired cardiac function, whereas cardiac-specific overexpression of DUPS12 was capable of reversing this hypertrophic and fibrotic phenotype and improving contractile function. Furthermore, we demonstrated that JNK1/2 activity but neither ERK1/2 nor p38 activity was increased in the DUSP12 deficient group and decreased in the DUSP12 overexpression group both in vitro and in vivo under hypertrophic stress conditions. Pharmacological inhibition of JNK1/2 activity (SP600125) is capable of reversing the hypertrophic phenotype in DUSP12 knockout (KO) mice. DUSP12 protects against pathological cardiac hypertrophy and related pathologies. This regulatory role of DUSP12 is primarily through c-Jun N-terminal kinase (JNK) inhibition. DUSP12 could be a promising therapeutic target of pathological cardiac hypertrophy. DUSP12 is down-regulated in hypertrophic hearts. An absence of DUSP12 aggravated cardiac hypertrophy, whereas cardiomyocyte-specific DUSP12 overexpression can alleviate this hypertrophic phenotype with improved cardiac function. Further study demonstrated that DUSP12 inhibited JNK activity to attenuate pathological cardiac hypertrophy.