ERK: A Key Player in the Pathophysiology of Cardiac Hypertrophy

Inorganic arsenic induces sex-dependent pathological hypertrophy in the heart

Arsenic exposure though drinking water is widespread and well associated with adverse cardiovascular outcomes, yet the pathophysiological mechanisms by which iAS induces these effects are largely unknown. Recently, an epidemiological study in an American population with a low burden of cardiovascular risk factors found that iAS exposure was associated with altered left ventricular geometry. Considering the possibility that iAS directly induces cardiac remodeling independently of hypertension, we investigated the impact of an environmentally relevant iAS exposure on the structure and function of male and female hearts. Adult male and female C56BL/6J mice were exposed to 615 μg/L iAS for 8 wk. Males exhibited increased systolic blood pressure via tail cuff photoplethysmography, left ventricular wall thickening via transthoracic echocardiography, and increased plasma atrial natriuretic peptide via enzyme immunoassay. RT-qPCR revealed increased myocardial RNA transcripts of Acta1, Myh7, and Nppa and decreased Myh6, providing evidence of pathological hypertrophy in the male heart. Similar changes were not detected in females, and nitric oxide-dependent mechanisms of cardioprotection in the heart appeared to remain intact. Further investigation found that Rcan1 was upregulated in male hearts and that iAS activated NFAT in HEK-293 cells via luciferase assay. Interestingly, iAS induced similar hypertrophic gene expression changes in neonatal rat ventricular myocytes, which were blocked by calcineurin inhibition, suggesting that iAS may induce pathological cardiac hypertrophy in part by targeting the calcineurin-NFAT pathway. As such, these results highlight iAS exposure as an independent cardiovascular risk factor and provide biological impetus for its removal from human consumption.NEW & NOTEWORTHY This investigation provides the first mechanistic link between an environmentally relevant dose of inorganic arsenic (iAS) and pathological hypertrophy in the heart. By demonstrating that iAS exposure may cause pathological cardiac hypertrophy not only by increasing systolic blood pressure but also by potentially activating calcineurin-nuclear factor of activated T cells and inducing fetal gene expression, these results provide novel mechanistic insight into the theat of iAS exposure to the heart, which is necessary to identify targets for medical and public health intervention.

Silencing of Sphingosine kinase 1 Affects Maturation Pathways in Mouse Neonatal Cardiomyocytes

Sphingosine kinase-1 (Sphk1) and its product, sphingosine-1-phosphate (S1P) are important regulators of cardiac growth and function. Numerous studies have reported that Sphk1/S1P signaling is essential for embryonic cardiac development and promotes pathological cardiac hypertrophy in adulthood. However, no studies have addressed the role of Sphk1 in postnatal cardiomyocyte (CM) development so far. The present study aimed to assess the molecular mechanism(s) by which Sphk1 silencing might influence CMs development and hypertrophy in vitro. Neonatal mouse CMs were transfected with siRNA against Sphk1 or negative control, and subsequently treated with 1 µM angiotensin II (AngII) or a control buffer for 24 h. The results of RNASeq analysis revealed that diminished expression of Sphk1 significantly accelerated neonatal CM maturation by inhibiting cell proliferation and inducing developmental pathways in the stress (AngII-induced) conditions. Importantly, similar effects were observed in the control conditions. Enhanced maturation of Sphk1-lacking CMs was further confirmed by the upregulation of the physiological hypertrophy-related signaling pathway involving Akt and downstream glycogen synthase kinase 3 beta (Gsk3β) downregulation. In summary, we demonstrated that the Sphk1 silencing in neonatal mouse CMs facilitated their postnatal maturation in both physiological and stress conditions.

Late Health Effects of Partial Body Irradiation Injury in a Minipig Model Are Associated with Changes in Systemic and Cardiac IGF-1 Signaling

Clinical, epidemiological, and experimental evidence demonstrate non-cancer, cardiovascular, and endocrine effects of ionizing radiation exposure including growth hormone deficiency, obesity, metabolic syndrome, diabetes, and hyperinsulinemia. Insulin-like growth factor-1 (IGF-1) signaling perturbations are implicated in development of cardiovascular disease and metabolic syndrome. The minipig is an emerging model for studying radiation effects given its high analogy to human anatomy and physiology. Here we use a minipig model to study late health effects of radiation by exposing male Göttingen minipigs to 1.9–2.0 Gy X-rays (lower limb tibias spared). Animals were monitored for 120 days following irradiation and blood counts, body weight, heart rate, clinical chemistry parameters, and circulating biomarkers were assessed longitudinally. Collagen deposition, histolopathology, IGF-1 signaling, and mRNA sequencing were evaluated in tissues. Our findings indicate a single exposure induced histopathological changes, attenuated circulating IGF-1, and disrupted cardiac IGF-1 signaling. Electrolytes, lipid profiles, liver and kidney markers, and heart rate and rhythm were also affected. In the heart, collagen deposition was significantly increased and transforming growth factor beta-1 (TGF-beta-1) was induced following irradiation; collagen deposition and fibrosis were also observed in the kidney of irradiated animals. Our findings show Göttingen minipigs are a suitable large animal model to study long-term effects of radiation exposure and radiation-induced inhibition of IGF-1 signaling may play a role in development of late organ injuries.

Water-soluble alkaloids extracted from Aconiti Radix lateralis praeparata protect against chronic heart failure in rats via a calcium signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Many studies have shown the beneficial effects of aconite water-soluble alkaloid extract (AWA) in experimental models of heart disease, which have been ascribed to the presence of aconine, hypaconine, talatisamine, fuziline, neoline, and songorine. This study evaluated the effects of a chemically characterized AWA by chemical content, evaluated its effects in suprarenal abdominal aortic coarctation surgery (AAC)-induced chronic heart failure (CHF) in rats, and revealed the underlying mechanisms of action by proteomics.

METHODS

Rats were distributed into different groups: sham, model, and AWA-treated groups (10, 20, and 40 mg/kg/day). Sham rats received surgery without AAC, whereas model rats an AWA-treated groups underwent AAC surgery. after 8 weeks, the treatment group was fed AWA for 4 weeks, and body weight was assessed weekly. At the end of the treatment, heart function was tested by echocardiography. AAC-induced chronic heart failure, including myocardial fibrosis, cardiomyocyte hypertrophy, and apoptosis, was evaluated in heart tissue and plasma by RT-qPCR, ELISA, hematoxylin and eosin (H&E) staining, Masson's trichrome staining, TUNEL staining, and immunofluorescence staining of α-SMA, Col Ⅰ, and Col Ⅲ. Then, a proteomics approach was used to explore the underlying mechanisms of action of AWA in chronic heart failure.

RESULTS

AWA administration reduced body weight gain, myocardial fibrosis, cardiomyocyte hypertrophy, and apoptosis, and rats showed improvement in cardiac function compared to model group. The extract significantly ameliorated the AAC-induced altered expression of heart failure markers such as ANP, NT-proBNP, and β-MHC, as well as fibrosis, hypertrophy markers MMP-2 and MMP-9, and other heart failure-related factors including plasma levels of TNF-α and IL-6. Furthermore, the extract reduced the protein expression of α-SMA, Col Ⅰ, and Col Ⅲ in the left ventricular (LV), thus inhibiting the LV remodeling associated with CHF. In addition, proteomics characterization of differentially expressed proteins showed that AWA administration inhibited left ventricular remodeling in CHF rats via a calcium signaling pathway, and reversed the expression of RyR2 and SERCA2a.

CONCLUSIONS

AWA extract exerts beneficial effects in an AAC-induced CHF model in rats, which was associated with an improvement in LV function, hypertrophy, fibrosis, and apoptotic status. These effects may be related to the regulation of calcium signaling by the altered expression of RyR2 and SERCA2a.

Myocardial Impact of NHE1 Regulation by Sildenafil

The cardiac Na⁺/H⁺ exchanger (NHE1) is a membrane glycoprotein fundamental for proper cell functioning due its multiple housekeeping tasks, including regulation of intracellular pH, Na⁺ concentration, and cell volume. In the heart, hyperactivation of NHE1 has been linked to the development of different pathologies. Several studies in animal models that reproduce the deleterious effects of ischemia/reperfusion injury or cardiac hypertrophy have conclusively demonstrated that NHE1 inhibition provides cardioprotection. Unfortunately, NHE1 inhibitors failed to reproduce these effects in the clinical arena. The reasons for those discrepancies are not apparent yet. However, a reasonable clue to consider would be that drugs that completely abolish the exchanger activity, including that its essential housekeeping function may not be the best therapeutic approach. Therefore, interventions tending to specifically reduce its hyperactive state without affecting its basal activity emerge as a novel potential gold standard. In this regard, a promising goal seems to be the modulation of the phosphorylation state of the cytosolic tail of the exchanger. Recent own experiments demonstrated that Sildenafil, a phosphodiesterase 5A inhibitor drug that has been widely used for the treatment of erectile dysfunction is able to decrease NHE1 phosphorylation, and hence reduce its hyperactivity. In connection, growing evidence demonstrates cardioprotective properties of Sildenafil against different cardiac pathologies, with the distinctive characteristic of directly affecting cardiac tissue without altering blood pressure. This mini-review was aimed to focus on the regulation of NHE1 activity by Sildenafil. For this purpose, experimental data reporting Sildenafil effects in different animal models of heart disease will be discussed.

Isosteviol Protects H9c2 Cells Against Hypoxia-reoxygenation by Activating ERK1/2

AIMS

In the present study, we have investigated the cardioprotective properties of Isosteviol (STV) under conditions of hypoxia-reoxygenation and elucidated the underlying mechanism.

BACKGROUND

In our previous studies, we have determined that STV exhibits neuro- and cardio-protective properties. However, the mechanism underlying STV-induced cardioprotection has not yet been fully understood.

METHODS

All experiments were performed on rat heart embryonic H9c2 cell line. To induce hypoxia- reoxygenation, cells were exposed to 1% oxygen (in no glucose and no sodium pyruvate DMEM) following by reoxygenation (using fully supplemented MEM). Cells viability was tested by MTT assay, and protein levels were compared by Western blotting.

RESULTS

Treatment of heart embryonic H9c2 cells with STV (10 μM) significantly increased the survival of cells exposed to hypoxia-reoxygenation. STV (10 μM) activated ERK1/2 and DRP1 in hypoxia-reoxygenation, but did not have any effects on ERK1/2 or DRP1 in normoxia. STV (10 μM) did not regulate CAMKII, AKT or AMPK signaling pathways.

CONCLUSION

Taken all together, our findings demonstrate that 1) STV protects H9c2 cells against hypoxia-reoxygenation and that 2) this effect is mediated via ERK1/2. The property of STV that selectively activates ERK1/2 in cells exposed to stress, but not in cells under non-stress conditions, makes this compound a promising candidate-drug for therapy against myocardial ischemia-reperfusion in clinical practice.

Circulating microRNAs May Serve as Biomarkers for Hypertensive Emergency End-Organ Injuries and Address Underlying Pathways in an Animal Model

There is an incomplete understanding of the underlying pathophysiology in hypertensive emergencies, where severely elevated blood pressure causes acute end-organ injuries, as opposed to the long-term manifestations of chronic hypertension. Furthermore, current biomarkers are unable to detect early end-organ injuries like hypertensive encephalopathy and renal thrombotic microangiopathy. We hypothesized that circulating microRNAs (c-miRs) could identify acute and chronic complications of severe hypertension, and that combinations of c-miRs could elucidate important pathways involved. We studied the diagnostic accuracy of 145 c-miRs in Dahl salt-sensitive rats fed either a low-salt (N = 20: 0.3% NaCl) or a high-salt (N = 60: 8% NaCl) diet. Subclinical hypertensive encephalopathy and thrombotic microangiopathy were diagnosed by histopathology. In addition, heart failure with preserved ejection fraction was evaluated with echocardiography and N-terminal pro-brain natriuretic peptide; and endothelial dysfunction was studied using acetylcholine-induced aorta ring relaxation. Systolic blood pressure increased severely in animals on a high-salt diet (high-salt 205 ± 20 mm Hg vs. low-salt 152 ± 18 mm Hg, p < 0.001). Partial least squares discriminant analysis revealed 68 c-miRs discriminating between animals with and without hypertensive emergency complications. Twenty-nine c-miRs were strongly associated with hypertensive encephalopathy, 24 c-miRs with thrombotic microangiopathy, 30 c-miRs with heart failure with preserved ejection fraction, and 28 c-miRs with endothelial dysfunction. Hypertensive encephalopathy, thrombotic microangiopathy and heart failure with preserved ejection fraction were associated with deviations in many of the same c-miRs, whereas endothelial dysfunction was associated with a different set of c-miRs. Several of these c-miRs demonstrated fair to good diagnostic accuracy for a composite outcome of hypertensive encephalopathy, thrombotic microangiopathy and heart failure with preserved ejection fraction in receiver-operating-curve analyses (area-under-curve 0.75–0.88). Target prediction revealed an enrichment of genes related to several pathways relevant for cardiovascular disease (e.g., mucin type O-glycan biosynthesis, MAPK, Wnt, Hippo, and TGF-beta signaling). C-miRs could potentially serve as biomarkers of severe hypertensive end-organ injuries and elucidate important pathways involved.

Sunitinib-induced cardiac hypertrophy and the endothelin axis

Anti-angiogenics drugs in clinical use for cancer treatment induce cardiotoxic side effects. The endothelin axis is involved in hypertension and cardiac remodelling, and addition of an endothelin receptor antagonist to the anti-angiogenic sunitinib was shown to reduce cardiotoxicity of sunitinib in mice. Here, we explored further the antidote effect of the endothelin receptor antagonist macitentan in sunitinib-treated animals on cardiac remodeling.

Methods: Tumor-bearing mice treated per os daily by sunitinib or vehicle were imaged before and after 1, 3 and 6 weeks of treatment by positron emission tomography using [¹⁸F]fluorodeoxyglucose and by echocardiography. Non-tumor-bearing animals were randomly assigned to be treated per os daily by vehicle or sunitinib or macitentan or sunitinib+macitentan, and imaged by echocardiography after 5 weeks. Hearts were harvested for histology and molecular analysis at the end of in vivo exploration.

Results: Sunitinib treatment increases left ventricular mass and ejection fraction and induces cardiac fibrosis. Sunitinib also induces an early increase in cardiac uptake of [¹⁸F]fluorodeoxyglucose, which is significantly correlated with increased left ventricular mass at the end of treatment. Co-administration of macitentan prevents sunitinib-induced hypertension, increase in ejection fraction and cardiac fibrosis, but fails to prevent increase of the left ventricular mass.

Conclusion: Early metabolic changes predict sunitinib-induced cardiac remodeling. Endothelin blockade can prevent some but not all cardiotoxic side-effects of sunitinib, in particular left ventricle hypertrophy that appears to be induced by sunitinib through an endothelin-independent mechanism.

How progressive cancer endangers the heart: an intriguing and underestimated problem

Since it came into being as a discipline, cardio-oncology has focused on the prevention and treatment of cardiotoxicity induced by antitumor chemotherapy and radiotherapy. Over time, it has been proved that even more detrimental is the direct effect generated by cancer cells that release pro-cachectic factors in the bloodstream. Secreted molecules target different organs at a distance, including the heart. Inflammatory and neuronal modulators released by the tumor bulk, either as free molecules or through exosomes, contribute to the pathogenesis of cardiac disease. Progressive cancer causes cachexia and severe cardiac muscle wasting accompanied by cardiomyocyte atrophy, tissue fibrosis, and several functional impairments up to heart failure. The molecular mechanisms responsible for such a cardiac muscle wasting have been partially elucidated in animal models, but minimally investigated in humans, although severe cardiac dysfunction exacerbates global cachexia and hampers efficient anti-cancer treatments. This review provides an overview of cancer-induced structural cardiac and functional damage, drawing on both clinical and scientific research. We start by looking at the pathophysiological mechanisms and evolving epidemiology and go on to discuss prevention, diagnosis, and a multimodal policy of intervention aimed at providing overall prognosis and global care for patients. Despite much interest in the cardiotoxicity of cancer therapies, the direct tumor effect on the heart remains poorly explored. There is still a lack of diagnostic criteria for the identification of the early stages of cardiac disease in cancer patients, while the possibilities that there are for effective prevention are largely underestimated. Research on innovative therapies has claimed considerable advances in preclinical studies, but none of the molecular targets suitable for clinical application has been approved for therapy. These issues are critically discussed here.

Recent advances in the design and development of formyl peptide receptor 2 (FPR2/ALX) agonists as pro-resolving agents with diverse therapeutic potential

Under physiological conditions the initiation, duration and amplitude of inflammatory responses are tightly regulated to ensure the restoration of homeostasis. The resolution of inflammation in these circumstances is dictated by responses to endogenously generated mediators. Mimicry of such mediators underpins the principle of promoting the resolution of inflammation in treating inflammatory pathologies. The formyl peptide receptor 2 (FPR2/ALX) is a G-protein coupled receptor known to play a crucial role in maintaining host defence and orchestrating the inflammatory process. FPR2/ALX can be activated by a wide range of distinct agonists, including lipids, proteins, peptides, and an array of synthetic small molecule agonists. The focus of this review is to provide a comprehensive overview of recent progress made in the development of FPR2/ALX agonists which promote resolution and tissue regeneration.

Liver Kinase B1 (LKB1) Regulates Proliferation and Apoptosis of Non-Small Cell Lung Cancer A549 Cells via Targeting ERK Signaling Pathway

Objective

To study the effect and potential mechanism of LKB1 on non-small cell lung cancer (NSCLC) A549 cells.

Material and Methods

A549 cells were divided into control group, LKB1 negative control (NC) group, LKB1 group, ERK inhibitor group and LKB1 + ERK activator group. Cell proliferation and apoptosis were detected by cell counting kit (CCK-8) assay and flow cytometry, respectively. Transwell assay was used to analyze the invasion ability of A549 cells. The expression of apoptosis and ERK signaling pathway-related proteins were studied by Western blot. Furthermore, a nude mouse xenograft model was constructed and treated with LKB1, ERK inhibitor and activator, respectively. The tumor volume and tumor weight were measured. Immunohistochemistry was used to test the expression of Ki-67 protein in tumor tissues, and TUNEL staining was used to test the apoptosis. Moreover, Western blot was used to detect ERK signaling pathway-related proteins in tumor tissues.

Results

Compared with control and NC groups, cell proliferation and invasion were inhibited in ERK inhibitor and LKB1 groups, while apoptosis and apoptosis-related proteins were increased (p < 0.05). Further study showed that ERK activator can reverse the effect of LKB1 in A549 cells. In nude mice, ERK inhibitor and LKB1 can reduce cell tumorigenicity and inhibit proliferation. Apoptosis was increased by ERK inhibitor and LKB1 treatment. Western blot showed that LKB1 and ERK inhibitor could reduce the protein expression of p-ERK1/2. However, the indicators above were the opposite in the ERK activator group.

Conclusion

LKB1 overexpression can inhibit proliferation and promote apoptosis of NSCLC A549 cells, and its mechanism may be related to inhibition of the ERK signaling pathway.

ICS II protects against cardiac hypertrophy by regulating metabolic remodelling, not by inhibiting autophagy

Cardiac hypertrophy is characterized by a shift in metabolic substrate utilization. Therefore, the regulation of ketone body uptake and metabolism may have beneficial effects on heart injuries that induce cardiac remodelling. In this study, we investigated whether icariside II (ICS II) protects against cardiac hypertrophy in mice and cardiomyocytes. To create cardiac hypertrophy animal and cell models, mice were subjected to transverse aortic constriction (TAC), and embryonic rat cardiomyocytes (H9C2) were stimulated with angiotensin II, a neurohumoral stressor. Both the in vivo and in vitro results suggest that ICS II treatment ameliorated pressure overload–induced cardiac hypertrophy and preserved heart function. In addition, apoptosis and oxidative stress were reduced in the presence of ICS II. Moreover, ICS II inhibited excess autophagy in TAC‐induced hearts and angiotensin II–stimulated cardiomyocytes. Mechanistically, we found that ICS II administration regulated SIRT3 expression in cardiac remodelling. SIRT3 activation increased ketone body transportation and utilization. Collectively, our data show that ICS II attenuated cardiac hypertrophy by modulating ketone body and fatty acid metabolism, and that this was likely due to the activation of the SIRT3‐AMPK pathway. ICS II treatment may provide a new therapeutic strategy for improving myocardial metabolism in cardiac hypertrophy and heart failure.

Eccrine Sweat Gland and Its Regeneration: Current Status and Future Directions

Eccrine sweat glands (ESGs) play an important role in temperature regulation by secreting sweat. Insufficiency or dysfunction of ESGs in a hot environment or during exercise can lead to hyperthermia, heat exhaustion, heatstroke, and even death, but the ability of ESGs to repair and regenerate themselves is very weak and limited. Repairing the damaged ESGs and regenerating the lost or dysfunctional ESGs poses a challenge for dermatologists and bum surgeons. To promote and accelerate research on the repair and regeneration of ESGs, we summarized the development, structure and function of ESGs, and current strategies to repair and regenerate ESGs based on stem cells, scaffolds, and possible signaling pathways involved.

Aerobic exercise training attenuates doxorubicin-induced ultrastructural changes in rat ventricular myocytes

AIMS

To investigate the effects of aerobic exercise training on cardiomyocyte ultrastructure, oxidative stress, and activation of protein synthesis pathways in a model of cardiomyopathy induced by doxorubicin (Dox).

MAIN METHODS

Male Sprague Dawley rats were randomly assigned to Control (saline, sedentary), Dox/sedentary (DoxSed), or Dox/exercise (DoxEx) groups. Saline or Dox were injected i.p. for 10 days (1 mg/kg/d). Aerobic exercise training was performed for 9 wks (starting with drug administration) on a treadmill, 5 d/wk, 30 min/d at 60% of maximum velocity. After euthanasia, the left ventricle (LV) was dissected, and processed for microscopy or frozen for Western blot and kinetic measurement of antioxidant enzymes activity.

KEY FINDINGS

Dox resulted in a mortality of 31.2% of sedentary animals, whilst all animals from both Control and DoxEx groups survived. DoxSed animals presented increased LV connective tissue deposition alongside with massive sarcomeric disorganization with dissolution of myofibrils and wavy Z-lines. There was an increase in oxidative damage and a reduction in the activation of both Akt and ERK pathways in LV from DoxSed compared to Control group. Aerobic training caused notable changes in myocardial structure with reduced fibrosis and preservation of myofibrils integrity and sarcomere organization. This was associated with reduced LV oxidative damage and increased activity of antioxidant enzymes, and an increase in the activation of PI3K-Akt pathway.

SIGNIFICANCE

Aerobic exercise training was effective in preventing mortality caused by Dox and in preserving LV ultrastructure, partially via activation of the physiological protein synthesis pathway, PI3K-Akt, and reducing oxidative stress.

Context-specific network modeling identifies new crosstalk in β-adrenergic cardiac hypertrophy

Cardiac hypertrophy is a context-dependent phenomenon wherein a myriad of biochemical and biomechanical factors regulate myocardial growth through a complex large-scale signaling network. Although numerous studies have investigated hypertrophic signaling pathways, less is known about hypertrophy signaling as a whole network and how this network acts in a context-dependent manner. Here, we developed a systematic approach, CLASSED (Context-specific Logic-bASed Signaling nEtwork Development), to revise a large-scale signaling model based on context-specific data and identify main reactions and new crosstalks regulating context-specific response. CLASSED involves four sequential stages with an automated validation module as a core which builds a logic-based ODE model from the interaction graph and outputs the model validation percent. The context-specific model is developed by estimation of default parameters, classified qualitative validation, hybrid Morris-Sobol global sensitivity analysis, and discovery of missing context-dependent crosstalks. Applying this pipeline to our prior-knowledge hypertrophy network with context-specific data revealed key signaling reactions which distinctly regulate cell response to isoproterenol, phenylephrine, angiotensin II and stretch. Furthermore, with CLASSED we developed a context-specific model of β-adrenergic cardiac hypertrophy. The model predicted new crosstalks between calcium/calmodulin-dependent pathways and upstream signaling of Ras in the ISO-specific context. Experiments in cardiomyocytes validated the model’s predictions on the role of CaMKII-Gβγ and CaN-Gβγ interactions in mediating hypertrophic signals in ISO-specific context and revealed a difference in the phosphorylation magnitude and translocation of ERK1/2 between cardiac myocytes and fibroblasts. CLASSED is a systematic approach for developing context-specific large-scale signaling networks, yielding insights into new-found crosstalks in β-adrenergic cardiac hypertrophy.

Pathological cardiac hypertrophy is a disease in which the heart grows abnormally in response to different motivators such as high blood pressure or variations in hormones and growth factors. The shape of the heart after its growth depends on the context in which it grows. Since cell signaling in the cardiac cells plays a key role in the determination of heart shape, a thorough understanding of cardiac cells signaling in each context enlightens the mechanisms which control response of cardiac cells. However, cell signaling in cardiac hypertrophy comprises a complex web of pathways with numerous interactions, and predicting how these interactions control the hypertrophic signal in each context is not achievable by only experiments or general computational models. To address this need, we developed an approach to bring together the experimental data of each context with a signaling network curated from literature to identify the main players of cardiac cells response in each context and attain the context-specific models of cardiac hypertrophy. By utilizing our approach, we identified the main regulators of cardiac hypertrophy in four important contexts. We developed a network model of β-adrenergic cardiac hypertrophy, and predicted and validated new interactions that regulate cardiac cells response in this context.

Protein kinase D participates in cardiomyocyte hypertrophy by regulating extracellular signal-regulated and myocyte enhancer factor 2D

OBJECTIVE

Cardiomyocyte hypertrophy is an important feature of hypertension. However, its molecular underpinnings, especially the signaling cascades, remain unclear. Here we hypothesized that a protein kinase D (PKD)-dependent extracellular signal-regulated kinase 5 (ERK5) pathway was able to regulate downstream myocyte enhancer factor 2D (MEF2D), affecting prohypertrophic responses to angiotensin II (Ang II).

METHODS

Neonatal rat cardiomyocytes from 2- to 3-day-old Sprague-Dawley rats were prepared and Western blot, real-time quantitative PCR and immunofluorescence staining were used to assess the activation and translocation of pathway signaling molecules. Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) expression and [3H]-leucine (Leu) incorporation were measured to determine cell hypertrophy.

RESULTS

Elevated levels of phosphorylated PKD (p-PKD) and ERK5 (p-ERK5) were observed in cardiomyocytes stimulated with Ang II, while silencing protein kinase C epsilon (PKCɛ) resulted in significantly lower levels of p-PKD. Furthermore, Ang II-induced ERK5 activated translocation was mediated by the PKD pathway. Consequently, inhibiting PKCɛ, PKD and ERK5 by siRNA significantly attenuated Ang II-induced MEF2D activation, ANP and BNP mRNA expression, and [3H]-Leu incorporation.

CONCLUSIONS

Our studies are the first to show that the PKCɛ/PKD/ERK5/MEF2D pathway plays an important role in the cardiomyocyte hypertrophy response to Ang II.

Mep1a contributes to Ang II-induced cardiac remodeling by promoting cardiac hypertrophy, fibrosis and inflammation

Pathological cardiac remodeling, characterized by excessive deposition of extracellular matrix proteins and cardiac hypertrophy, leads to the development of heart failure. Meprin α (Mep1a), a zinc metalloprotease, previously reported to participate in the regulation of inflammatory response and fibrosis, may also contribute to cardiac remodeling, although whether and how it participates in this process remains unknown. Here, in this work, we investigated the role of Mep1a in pathological cardiac remodeling, as well as the effects of the Mep1a inhibitor actinonin on cardiac remodeling-associated phenotypes. We found that Mep1a deficiency or chemical inhibition both significantly alleviated TAC- and Ang II-induced cardiac remodeling and dysfunction. Mep1a deletion and blocking both attenuated TAC- and Ang II-induced heart enlargement and increases in the thickness of the left ventricle anterior and posterior walls, and reduced expression of pro-hypertrophic markers, including atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and myosin heavy chain beta (β-MHC). In addition, Mep1a deletion and blocking significantly inhibited TAC- and Ang II-induced cardiac fibroblast activation and production of extracellular matrix (ECM). Moreover, in Mep1a^-/- mice and treatment with actinonin significantly reduced Ang II-induced infiltration of macrophages and proinflammatory cytokines. Notably, we found that in vitro, Mep1a is expressed in cardiac myocytes and fibroblasts and that Mep1a deletion or chemical inhibition both markedly suppressed Ang II-induced hypertrophy of rat or mouse cardiac myocytes and activation of rat or mouse cardiac fibroblasts. In addition, blocking Mep1a in macrophages reduced Ang II-induced expression of interleukin (IL)-6 and IL-1β, strongly suggesting that Mep1a participates in cardiac remodeling processes through regulation of inflammatory cytokine expression. Mechanism studies revealed that Mep1a mediated ERK1/2 activation in cardiac myocytes, fibroblasts and macrophages and contributed to cardiac remodeling. In light of our findings that blocking Mep1a can ameliorate cardiac remodeling via inhibition of cardiac hypertrophy, fibrosis, and inflammation, Mep1a may therefore serve as a strong potential candidate for therapeutic targeting to prevent cardiac remodeling.

Targeting Orai1-Mediated Store-Operated Ca2+ Entry in Heart Failure

The archetypal store-operated Ca²⁺ channels (SOCs), Orai1, which are stimulated by the endo/sarcoplasmic reticulum (ER/SR) Ca²⁺ sensor stromal interaction molecule 1 (STIM1) upon Ca²⁺ store depletion is traditionally viewed as instrumental for the function of non-excitable cells. In the recent years, expression and function of Orai1 have gained recognition in excitable cardiomyocytes, albeit controversial. Even if its cardiac physiological role in adult is still elusive and needs to be clarified, Orai1 contribution in cardiac diseases such as cardiac hypertrophy and heart failure (HF) is increasingly recognized. The present review surveys our current arising knowledge on the new role of Orai1 channels in the heart and debates on its participation to cardiac hypertrophy and HF.

Redox Regulation by Protein S-Glutathionylation: From Molecular Mechanisms to Implications in Health and Disease

S-glutathionylation, the post-translational modification forming mixed disulfides between protein reactive thiols and glutathione, regulates redox-based signaling events in the cell and serves as a protective mechanism against oxidative damage. S-glutathionylation alters protein function, interactions, and localization across physiological processes, and its aberrant function is implicated in various human diseases. In this review, we discuss the current understanding of the molecular mechanisms of S-glutathionylation and describe the changing levels of expression of S-glutathionylation in the context of aging, cancer, cardiovascular, and liver diseases.

New role of TRPM4 channel in the cardiac excitation-contraction coupling in response to physiological and pathological hypertrophy in mouse

The transient receptor potential Melastatin 4 (TRPM4) channel is a calcium-activated non-selective cation channel expressed widely. In the heart, using a knock-out mouse model, the TRPM4 channel has been shown to be involved in multiple processes, including β-adrenergic regulation, cardiac conduction, action potential duration and hypertrophic adaptations. This channel was recently shown to be involved in stress-induced cardiac arrhythmias in a mouse model overexpressing TRPM4 in ventricular cardiomyocytes. However, the link between TRPM4 channel expression in ventricular cardiomyocytes, the hypertrophic response to stress and/or cellular arrhythmias has yet to be elucidated. In this present study, we induced pathological hypertrophy in response to myocardial infarction using a mouse model of Trpm4 gene invalidation, and demonstrate that TRPM4 is essential for survival. We also demonstrate that the TRPM4 is required to activate both the Akt and Calcineurin pathways. Finally, using two hypertrophy models, either a physiological response to endurance training or a pathological response to myocardial infarction, we show that TRPM4 plays a role in regulating transient calcium amplitudes and leads to the development of cellular arrhythmias potentially in cooperation with the Sodium-calcium exchange (NCX). Here, we report two functions of the TRPM4 channel: first its role in adaptive hypertrophy, and second its association with NCX could mediate transient calcium amplitudes which trigger cellular arrhythmias.

Drug Development and the Use of Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Disease Modeling and Drug Toxicity Screening

: Over the years, numerous groups have employed human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) as a superb human-compatible model for investigating the function and dysfunction of cardiomyocytes, drug screening and toxicity, disease modeling and for the development of novel drugs for heart diseases. In this review, we discuss the broad use of iPSC-CMs for drug development and disease modeling, in two related themes. In the first theme-drug development, adverse drug reactions, mechanisms of cardiotoxicity and the need for efficient drug screening protocols-we discuss the critical need to screen old and new drugs, the process of drug development, marketing and Adverse Drug reactions (ADRs), drug-induced cardiotoxicity, safety screening during drug development, drug development and patient-specific effect and different mechanisms of ADRs. In the second theme-using iPSC-CMs for disease modeling and developing novel drugs for heart diseases-we discuss the rationale for using iPSC-CMs and modeling acquired and inherited heart diseases with iPSC-CMs.

MEK1/2 Inhibition in Murine Heart and Aorta After Oral Administration of Refametinib Supplemented Drinking Water

Upregulation of the RAS-RAF-MEK-ERK-MAPK pathway is involved in the development of several human tumors, aortic aneurysms, atherosclerosis, and cardiomyopathy. Refametinib, a highly selective MEK-inhibitor, has already shown antineoplastic activity in phase II trials. Furthermore, it showed potency to attenuate aortic root growth in murine models. Current formulations of this drug however necessitate oral gavage as a delivery method for long-term studies, which is labor-intensive and induces stress and occasional injury, potentially confounding results. Therefore, we developed a novel oral administration method for refametinib. A 2-hydroxypropyl-beta-cyclodextrin (HPBCD) based drinking water preparation of refametinib was formulated, for which a selective, analytical UHPLC-UV method was developed to assess the in-use stability. Next, 16 week old male wild-type C57Bl/6J mice received either a daily dose of 50 or 75 mg/kg/day refametinib or were given regular drinking water during 7 days. In both dosage groups the refametinib plasma levels were measured (n = 10 or 7, respectively). Furthermore, pERK/total ERK protein levels were calculated in the myocardial and aortic tissue of mice receiving a daily dose of 50 mg/kg/day refametinib and untreated mice (n = 4/group). After 7 days no significant degradation of refametinib was observed when dissolved in drinking water provided that drinking bottles were protected from UV/visible light. Furthermore, a dose-dependent increase in refametinib plasma levels was found whereby active plasma levels (> 1.2 µg/mL) were obtained even in the lowest dose-group of 50 mg/kg/day. A significant reduction of pERK/total ERK protein levels compared to untreated mice was observed in aortic and myocardial tissue of mice receiving a daily dose of 50 mg/kg/day refametinib. Importantly, a relatively high mortality rate was noted in the highest dose group (n = 5). This approach provides a valid alternative oral administration method for refametinib with a reduced risk of complications due to animal manipulation and without loss of functionality, which can be implemented in future research regarding the malignant upregulation of the RAS-RAF-MEK-ERK-MAPK pathway. However, care must be taken not to exceed the toxic dose.

Dihydrotanshinone I Ameliorates Cardiac Hypertrophy in Diabetic Mice Induced by Chronic High-Fat Feeding

Salvia miltiorrhiza Bge. (Danshen) is widely used to improve blood circulation and the dredge meridian in traditional Chinese medicine. In the present study, we evaluated the effects of dihydrotanshinone I (DHTS), a natural product from Danshen, on chronic high-fat feeding-induced cardiac remodeling and dysfunction. DHTS (25 mg/kg, intraperitoneal) did not affect blood glucose, insulin levels, and glucose intolerance. However, it alleviated diastolic dysfunction induced by the high-fat diet, as indicated by the increase in the ratio of peak early filling velocity to peak late filling velocity of the mitral and suppression of the extension of the isovolumic relaxation phase of the left ventricle. Further investigations revealed that DHTS ameliorated high-fat induced cardiac hypertrophy in mice and suppressed insulin-induced enlargement of cardiomyocytes in vitro. In neonatal cardiomyocytes, DHTS restored insulin-induced suppression of CCAAT/enhancer-binding protein beta-2 isoform (CEBPβ) and the phosphorylation of glycogen synthase kinase-3β (GSK3β) and extracellular signal-regulated kinase (ERK). Taken together, our results indicated that DHTS ameliorated cardiac hypertrophy and diastolic dysfunction in high-fat-fed mice, probably through the inhibition of insulin-induced suppression of CEBPβ and phosphorylation of GSK3β and ERK in cardiomyocytes.

Cardioprotection by isosteviol derivate JC105: A unique drug property to activate ERK1/2 only when cells are exposed to hypoxia-reoxygenation

In the present study, we have investigated potential cardioprotective properties of Isosteviol analogue we recently synthesized and named JC105. Treatment of heart embryonic H9c2 cells with JC105 (10 μM) significantly increased survival of cells exposed to hypoxia‐reoxygenation. JC105 (10 μM) activated ERK1/2, DRP1 and increased levels of cardioprotective SUR2A in hypoxia‐reoxygenation, but did not have any effects on ERK1/2, DRP1 and/or SUR2A in normoxia. U0126 (10 μM) inhibited JC105‐mediated phosphorylation of ERK1/2 and DRP1 without affecting AKT or AMPK, which were also not regulated by JC105. Seahorse bioenergetic analysis demonstrated that JC105 (10 μM) did not affect mitochondria at rest, but it counteracted all mitochondrial effects of hypoxia‐reoxygenation. Cytoprotection afforded by JC105 was inhibited by U0126 (10 μM). Taken all together, these demonstrate that (a) JC105 protects H9c2 cells against hypoxia‐reoxygenation and that (b) this effect is mediated via ERK1/2. The unique property of JC105 is that selectively activates ERK1/2 in cells exposed to stress, but not in cells under non‐stress conditions.

Systems Toxicology Approach for Testing Chemical Cardiotoxicity in Larval Zebrafish

Transcriptomic approaches can give insight into molecular mechanisms underlying chemical toxicity and are increasingly being used as part of toxicological assessments. To aid the interpretation of transcriptomic data, we have developed a systems toxicology method that relies on a computable biological network model. We created the first network model describing cardiotoxicity in zebrafish larvae-a valuable emerging model species in testing cardiotoxicity associated with drugs and chemicals. The network is based on scientific literature and represents hierarchical molecular pathways that lead from receptor activation to cardiac pathologies. To test the ability of our approach to detect cardiotoxic outcomes from transcriptomic data, we have selected three publicly available data sets that reported chemically induced heart pathologies in zebrafish larvae for five different chemicals. Network-based analysis detected cardiac perturbations for four out of five chemicals tested, for two of them using transcriptomic data collected up to 3 days before the onset of a visible phenotype. Additionally, we identified distinct molecular pathways that were activated by the different chemicals. The results demonstrate that the proposed integrational method can be used for evaluating the effects of chemicals on the zebrafish cardiac function and, together with observed cardiac apical end points, can provide a comprehensive method for connecting molecular events to organ toxicity. The computable network model is freely available and may be used to generate mechanistic hypotheses and quantifiable perturbation values from any zebrafish transcriptomic data.

Dietary Fat and Sugar Differentially Affect β-Adrenergic Stimulation of Cardiac ERK and AKT Pathways in C57BL/6 Male Mice Subjected to High-Calorie Feeding

BACKGROUND

High dietary fat and sugar promote cardiac hypertrophy independently from an increase in blood pressure. The respective contribution that each macronutrient exerts on cardiac growth signaling pathways remains unclear.

OBJECTIVE

The goal of this study was to investigate the mechanisms by which high amounts of dietary fat and sugar affect cardiac growth regulatory pathways.

METHODS

Male C57BL/6 mice (9 wk old; n = 20/group) were fed a standard rodent diet (STD; kcal% protein-fat-carbohydrate, 29-17-54), a high-fat diet (HFD; 20-60-20), a high-fat and high-sugar Western diet (WD; 20-45-35), a high-sugar diet with mixed carbohydrates (HCD; 20-10-70), or a high-sucrose diet (HSD; 20-10-70). Body composition was assessed weekly by EchoMRI. Whole-body glucose utilization was assessed with an intraperitoneal glucose tolerance test. After 6 wk on diets, mice were treated with saline or 20 mg/kg isoproterenol (ISO), and the activity of cardiac growth regulatory pathways was analyzed by immunoblotting. Data were analyzed by ANOVA with data from the STD group included for references only.

RESULTS

Compared with HCD and HSD, WD and HFD increased body fat mass 2.7- to 3.8-fold (P < 0.001), induced glucose intolerance (P < 0.001), and increased insulin concentrations >1.5-fold (P < 0.05), thereby enhancing basal and ISO-stimulated AKT phosphorylation at both threonine 308 and serine 473 residues (+25-63%; P < 0.05). Compared with HFD, the high-sugar diets potentiated ISO-mediated stimulation of the glucose-sensitive kinases PYK2 (>47%; P < 0.05 for HCD and HSD) and ERK (>34%; P < 0.05 for WD, HCD, and HSD), thereby leading to increased phosphorylation of protein synthesis regulator S6K1 at threonine 389 residue (>64%; P < 0.05 for WD, HCD, and HSD).

CONCLUSIONS

Dietary fat and sugar affect cardiac growth signaling pathways in C57BL/6 mice through distinct and additive mechanisms. The findings may provide new insights into the role of overnutrition in pathological cardiac remodeling.

Interference with ERK-dimerization at the nucleocytosolic interface targets pathological ERK1/2 signaling without cardiotoxic side-effects

Dysregulation of extracellular signal-regulated kinases (ERK1/2) is linked to several diseases including heart failure, genetic syndromes and cancer. Inhibition of ERK1/2, however, can cause severe cardiac side-effects, precluding its wide therapeutic application. ERK^T188-autophosphorylation was identified to cause pathological cardiac hypertrophy. Here we report that interference with ERK-dimerization, a prerequisite for ERK^T188-phosphorylation, minimizes cardiac hypertrophy without inducing cardiac adverse effects: an ERK-dimerization inhibitory peptide (EDI) prevents ERK^T188-phosphorylation, nuclear ERK1/2-signaling and cardiomyocyte hypertrophy, protecting from pressure-overload-induced heart failure in mice whilst preserving ERK1/2-activity and cytosolic survival signaling. We also examine this alternative ERK1/2-targeting strategy in cancer: indeed, ERK^T188-phosphorylation is strongly upregulated in cancer and EDI efficiently suppresses cancer cell proliferation without causing cardiotoxicity. This powerful cardio-safe strategy of interfering with ERK-dimerization thus combats pathological ERK1/2-signaling in heart and cancer, and may potentially expand therapeutic options for ERK1/2-related diseases, such as heart failure and genetic syndromes.

Drugs targeting dysregulated ERK1/2 signaling can cause severe cardiac side effects, precluding their wide therapeutic application. Here, a new and cardio-safe targeting strategy is presented that interferes with ERK dimerization to prevent pathological ERK1/2 signaling in the heart and cancer.

Polyphyllin I attenuates pressure over-load induced cardiac hypertrophy via inhibition of Wnt/β-catenin signaling pathway

AIMS

Cardiac hypertrophy is one of most important risk factors for cardiovascular mortality. Activation of Wnt/β-catenin signaling pathway is acknowledged to be an important mechanism for pathogenesis of cardiac hypertrophy. Polyphyllin I (PPI), a component in the traditional Chinese medicinal herb, has shown anticancer effect partially via interruption of Wnt/β-catenin signaling pathway. Our aim was to test whether PPI attenuates cardiac hypertrophy.

MATERIALS AND METHODS

Adult male C57BL/6J mice were subjected to either pressure overload generated by transverse aortic constriction (TAC) or sham surgery (control group). Angiotensin-II (Ang-II) was used to induce cardiomyocyte hypertrophy in vitro. PPI was intraperitoneally administrated daily for 4 weeks after TAC surgery and then cardiac function was determined by echocardiography and histological analysis was performed.

KEY FINDINGS

PPI significantly ameliorated cardiac dysfunction of mice subjected to TAC. Meanwhile, PPI attenuated TAC induced cardiac hypertrophy indicated by blunted increase in heart mass, cross section area of cardiomyocyte, cardiac fibrosis and expression of hypertrophic biomarkers ANP, BNP and β-MHC. In addition, PPI also ameliorated Ang-II induced cardiomyocyte hypertrophy in vitro. Importantly, PPI decreased protein expression of active β-catenin/total β-catenin, phosphorylation of GSK3β and Wnt target genes c-myc, c-jun, c-fos and cyclin D1 and its anti-hypertrophic effect was blunted by supplementation of Wnt 3a.

SIGNIFICANCE

Our results suggest that PPI attenuates cardiac dysfunction and attenuate development of pressure over-load induced cardiac hypertrophic via suppressing Wnt/β-catenin signaling pathway. PPI might be a candidate drug for treatment of cardiac hypertrophy.

Exploratory Analysis of Circulating miRNA Signatures in Atrial Fibrillation Patients Determining Potential Biomarkers to Support Decision-Making in Anticoagulation and Catheter Ablation

Novel biomarkers are desired to improve risk management for patients with atrial fibrillation (AF). We measured 179 plasma miRNAs in 83 AF patients using multiplex qRT-PCR. Plasma levels of eight (i.e., hsa-miR-22-3p, hsa-miR-128-3p, hsa-miR-130a-3p, hsa-miR-140-5p, hsa-miR-143-3p, hsa-miR-148b-3p, hsa-miR-497-5p, hsa-miR-652-3p) and three (i.e., hsa-miR-144-5p, hsa-miR-192-5p, hsa-miR-194-5p) miRNAs showed positive and negative correlations with CHA₂DS₂-VASc scores, respectively, which also showed negative and positive correlations with catheter ablation (CA) procedure, respectively, within the follow-up observation period up to 6-month after enrollment. These 11 miRNAs were functionally associated with TGF-β signaling and androgen signaling based on pathway enrichment analysis. Seven of possible target genes of these miRNAs, namely TGFBR1, PDGFRA, ZEB1, IGFR1, BCL2, MAPK1 and DICER1 were found to be modulated by more than four miRNAs of the eleven. Of them, TGFBR1, PDGFRA, ZEB1 and BCL2 are reported to exert pro-fibrotic functions, suggesting that dysregulations of these eleven miRNAs may reflect pro-fibrotic condition in the high-risk patients. Although highly speculative, these miRNAs may potentially serve as potential biomarkers, providing mechanistic and quantitative information for pathophysiology in daily clinical practice with AF such as possible pro-fibrotic state in left atrium, which would enhance the risk of stroke and reduce the preference for performing CA.

A cathelicidin-related antimicrobial peptide suppresses cardiac hypertrophy induced by pressure overload by regulating IGFR1/PI3K/AKT and TLR9/AMPKα

Cathelicidin-related antimicrobial peptide (CRAMP), an antimicrobial peptide, was reported to protect against myocardial ischemia/reperfusion injury. However, the effect of CRAMP on pressure overload-induced cardiac hypertrophy was unknown. This study explored the role of CRAMP on cardiac hypertrophy. A cardiac hypertrophy mouse model was induced by aortic banding surgery. Seven days after surgery, mice were given mCRAMP by intraperitoneal injection (8 mg/kg/d) for 7 weeks. Cardiac hypertrophy was evaluated by the hypertrophic response and fibrosis level as well as cardiac function. Mice were also injected with AAV9-shCRAMP to knockdown CRAMP in the mouse heart. CRAMP levels first increased and then reduced in the remodeling heart, as well as in angiotensin II-stimulated endothelial cells but not in cardiomyocytes and fibroblasts. mCRAMP protected against the pressure overload-induced cardiac remodeling process, while CRAMP knockdown accelerated this process. mCRAMP reduced the inflammatory response and oxidative stress in the hypertrophic heart, while mCRAMP deficiency deteriorated the pressure overload-induced inflammatory response and oxidative stress. mCRAMP inhibited the angiotensin II-stimulated hypertrophic response and oxidative stress in neonatal rat cardiomyocytes, but mCRAMP did not help the angiotensin II-induced inflammatory response and oxidative stress in endothelial cells. Mechanistically, we found that mCRAMP suppressed the cardiac hypertrophic response by activating the IGFR1/PI3K/AKT pathway via directly binding to IGFR1. AKT knockout mice completely reversed the anti-hypertrophic effect of mCRAMP but not its anti-oxidative effect. We also found that mCRAMP ameliorated cardiac oxidative stress by activating the TLR9/AMPKa pathway. This was confirmed by a TLR9 knockout mouse experiment, in which a TLR9 knockout partly reversed the anti-hypertrophic effect of mCRAMP and completely counteracted the anti-oxidative effect of mCRAMP. In summary, mCRAMP protected against pressure overload-induced cardiac hypertrophy by activating both the IGFR1/PI3K/AKT and TLR9/AMPKa pathways in cardiomyocytes.

Macrophage migration inhibitory factor increases atrial arrhythmogenesis through CD74 signaling

Macrophage migration inhibitory factor (MIF), a pleiotropic inflammatory cytokine, is highly expressed in patients with atrial fibrillation (AF). CD74 (major histocompatibility complex, class II invariant chain) is the main receptor for MIF. However, the role of the MIF/CD74 axis in atrial arrhythmogenesis is unclear. In this study, we investigated the effects of MIF/CD74 signaling on atrial electrophysiological characteristics and determined its underlying mechanisms. Confocal fluorescence microscopy, patch clamp, and western blot analysis were used to study calcium homeostasis, ionic currents, and calcium-related signaling in MIF-treated HL-1 atrial cardiomyocytes with or without anti-CD74 neutralized antibodies treatment. Furthermore, electrocardiographic telemetry recording and echocardiography were obtained from mice treated with MIF. Compared with controls, MIF-treated HL-1 myocytes had increased calcium transients, sarcoplasmic reticulum (SR) calcium content, Na⁺/Ca²⁺ exchanger (NCX) efflux rate, calcium leak, transient outward potassium current, and ultra-rapid delayed rectifier potassium current. Furthermore, MIF could induce expression of SR Ca²⁺ATPase, NCX, phosphorylation of ryanodine receptor 2 (RyR2), and activation of calcium/calmodulin kinase II (CaMKII) when compared with control cells. MIF-mediated electrical dysregulation and CaMKII-RyR2 signaling activation were attenuated through blocking of CD74. Moreover, MIF-injected mice had lesser left atrium fractional shortening, greater atrial fibrosis, and atrial ectopic beats than control (nonspecific immunoglobulin treated) or MIF combined with anti-CD74 neutralized antibody-treated mice. Consequently, our study on MIF/CD74 signaling has pointed out a new potential therapeutic intervention of AF patients with MIF elevation.

Association of thoracic spine deformity and cardiovascular disease in a mouse model for Marfan syndrome

Aims

Cardiovascular manifestations are a major cause of mortality in Marfan syndrome (MFS). Animal models that mimic the syndrome and its clinical variability are instrumental for understanding the genesis and risk factors for cardiovascular disease in MFS. This study used morphological and ultrastructural analysis to the understanding of the development of cardiovascular phenotypes of the the mgΔ^loxPneo model for MFS.

Methods and results

We studied 6-month-old female mice of the 129/Sv background, 6 wild type (WT) and 24 heterozygous animals from the mgΔ^loxPneo model. Descending thoracic aortic aneurysm and/or dissection (dTAAD) were identified in 75% of the MFS animals, defining two subgroups: MFS with (MFS⁺) and without (MFS^-) dTAAD. Both subgroups showed increased fragmentation of elastic fibers, predominance of type I collagen surrounding the elastic fiber and fragmentation of interlaminar fibers when compared to WT. However, only MFS animals with spine tortuosity developed aortic aneurysm/dissection. The aorta of MFS⁺ animals were more tortuous compared to those of MFS^- and WT mice, possibly causing perturbations of the luminal blood flow. This was evidenced by the detection of diminished aorta-blood flow in MFS⁺. Accordingly, only MFS⁺ animals presented a process of concentric cardiac hypertrophy and a significantly decreased ratio of left and right ventricle lumen area.

Conclusions

We show that mgΔ^loxPneo model mimics the vascular disease observed in MFS patients. Furthermore, the study indicates role of thoracic spine deformity in the development of aorta diseases. We suggest that degradation of support structures of the aortic wall; deficiency in the sustenance of the thoracic vertebrae; and their compression over the adjacent aorta resulting in disturbed blood flow is a triad of factors involved in the genesis of dissection/aneurysm of thoracic aorta.

Left Ventricular Hypertrophy: Roles of Mitochondria CYP1B1 and Melatonergic Pathways in Co-Ordinating Wider Pathophysiology

Left ventricular hypertrophy (LVH) can be adaptive, as arising from exercise, or pathological, most commonly when driven by hypertension. The pathophysiology of LVH is consistently associated with an increase in cytochrome P450 (CYP)1B1 and mitogen-activated protein kinases (MAPKs) and a decrease in sirtuins and mitochondria functioning. Treatment is usually targeted to hypertension management, although it is widely accepted that treatment outcomes could be improved with cardiomyocyte hypertrophy targeted interventions. The current article reviews the wide, but disparate, bodies of data pertaining to LVH pathoetiology and pathophysiology, proposing a significant role for variations in the N-acetylserotonin (NAS)/melatonin ratio within mitochondria in driving the biological underpinnings of LVH. Heightened levels of mitochondria CYP1B1 drive the ‘backward’ conversion of melatonin to NAS, resulting in a loss of the co-operative interactions of melatonin and sirtuin-3 within mitochondria. NAS activates the brain-derived neurotrophic factor receptor, TrkB, leading to raised trophic signalling via cyclic adenosine 3′,5′-monophosphate (cAMP)-response element binding protein (CREB) and the MAPKs, which are significantly increased in LVH. The gut microbiome may be intimately linked to how stress and depression associate with LVH and hypertension, with gut microbiome derived butyrate, and other histone deacetylase inhibitors, significant modulators of the melatonergic pathways and LVH more generally. This provides a model of LVH that has significant treatment and research implications.