ASK1 regulates cardiomyocyte death but not hypertrophy in transgenic mice

Guhong injection mitigates myocardial ischemia/reperfusion injury by activating GST P to inhibit ASK1-JNK/p38 pathway

BACKGROUND

Guhong injection (GHI), a novel compound preparation that is composed of a chemical drug, namely aceglutamide, and the aqueous extract of safflower (Carthamus tinctorius L.), exhibits extreme antioxidative, antiapoptotic, anti-inflammatory, and neuroprotective effects. Since oxidative stress, apoptosis, and inflammatory response are all the dominant mechanisms of myocardial ischemia/reperfusion (MI/R) injury, we probe into the protective mechanism of GHI on MI/R injury for the first time.

METHODS

In this research, we first employed molecular docking to determine whether three active ingredients in GHI, acetylglutamine (NAG), hydroxysafflor yellow A (HSYA), and syringin, possessed the potential activity to modulate the protein, glutathione S-transferase P (GST P). We further identified the protective effect of GHI on myocardial tissue with TTC staining, HE staining, TUNEL staining, and ELISA, and on H9c2 with flow cytometry and ELISA. We next explored whether the cardioprotective effect of GHI on left anterior descending ligation-reperfusion in rats and hypoxia/reoxygenation (H/R) in H9c2 cells was related to activate GST P to inhibit ASK1-JNK/p38 pathway via approaches of qRT-PCR and Western blot.

RESULTS

Results of molecular docking indicated that all three compounds spontaneously docked to GST P, among them the binding affinities of both HSYA and syringin to GST P were higher than NAG. In vivo, GHI reduced myocardial infarction size and mitigated myocardial pathological injury. In vitro, GHI enhanced cell viability and extenuated depolarization of mitochondrial membrane potential. In addition, the results of in vivo and in vitro studies demonstrated that the cardioprotection of GHI was associated with improving the mRNA and protein expression levels of GST P to modulate oxidative stress, and inhibiting the levels of mRNA expression and protein phosphorylation of ASK1, JNK, and p38. However, the suppressed effect of GHI on ASK1-JNK/p38 pathway was reversed by ethacrynic acid (EA, a GST inhibitor), indicating that the regulation of GHI on ASK1-JNK/p38 was related to the activity of GST P. Besides, the in vitro results of qRT-PCR and western-blot also certified that the inhibited JNK and p38 further reduced Bax expression and elevated Bcl-2 expression to reduce the expression of caspase-3 to exert anti-apoptosis effects.

CONCLUSION

Taken together, the cardioprotection of GHI mainly incarnated in activating GST P to relieve oxidation properties, thereby inhibiting ASK1-JNK/p38 pathway to suppress apoptosis.

The Impact of Exercise on Redox Equilibrium in Cardiovascular Diseases

Cardiovascular diseases constitute the most important public health problem in the world. They are characterized by inflammation and oxidative stress in the heart and blood. Physical activity is recognized as one of the best ways to prevent these diseases, and it has already been applied in treatment. Physical exercise, both aerobic and anaerobic and single and multiple, is linked to the oxidant–antioxidant imbalance; however, this leads to positive adaptive changes in, among others, the increase in antioxidant capacity. The goal of the paper was to discuss the issue of redox equilibrium in the human organism in the course of cardiovascular diseases to systemize updated knowledge in the context of exercise impacts on the organism. Antioxidant supplementation is also an important issue since antioxidant supplements still have great potential regarding their use as drugs in these diseases.

Oxidative stress - Complex pathological issues concerning the hallmark of cardiovascular and metabolic disorders

Oxidative stress is a complex biological process characterized by the excessive production of reactive oxygen species (ROS) that act as destroyers of the REDOX balance in the body and, implicitly, inducing oxidative damage. All the metabolisms are impaired in oxidative stress and even nucleic acid balance is influenced. ROS will promote structural changes of the tissues and organs due to interaction with proteins and phospholipids. The constellation of the cardiovascular risk factors (CVRFs) will usually develop in subjects with predisposition to cardiac disorders. Oxidative stress is usually related with hypertension (HTN), diabetes mellitus (DM), obesity and cardiovascular diseases (CVDs) like coronary artery disease (CAD), cardiomyopathy or heart failure (HF), that can develop in subjects with the above-mentioned diseases. Elements describing the complex relationship between CVD and oxidative stress should be properly explored and described because prevention may be the optimal approach. Our paper aims to expose in detail the complex physiopathology of oxidative stress in CVD occurrence and novelties regarding the phenomenon. Biomarkers assessing oxidative stress or therapy targeting specific pathways represent a major progress that actually change the outcome of subjects with CVD. New antioxidants therapy specific for each CVD represents a captivating and interesting future perspective with tremendous benefits on subject's outcome.

Oxidative Stress in Human Pathology and Aging: Molecular Mechanisms and Perspectives

Reactive oxygen and nitrogen species (RONS) are generated through various endogenous and exogenous processes; however, they are neutralized by enzymatic and non-enzymatic antioxidants. An imbalance between the generation and neutralization of oxidants results in the progression to oxidative stress (OS), which in turn gives rise to various diseases, disorders and aging. The characteristics of aging include the progressive loss of function in tissues and organs. The theory of aging explains that age-related functional losses are due to accumulation of reactive oxygen species (ROS), their subsequent damages and tissue deformities. Moreover, the diseases and disorders caused by OS include cardiovascular diseases [CVDs], chronic obstructive pulmonary disease, chronic kidney disease, neurodegenerative diseases and cancer. OS, induced by ROS, is neutralized by different enzymatic and non-enzymatic antioxidants and prevents cells, tissues and organs from damage. However, prolonged OS decreases the content of antioxidant status of cells by reducing the activities of reductants and antioxidative enzymes and gives rise to different pathological conditions. Therefore, the aim of the present review is to discuss the mechanism of ROS-induced OS signaling and their age-associated complications mediated through their toxic manifestations in order to devise effective preventive and curative natural therapeutic remedies.

Cellular Stress and Molecular Responses in Bladder Ischemia

The concept of bladder ischemia as a contributing factor to detrusor overactivity and lower urinary tract symptoms (LUTS) is evolving. Bladder ischemia as a consequence of pelvic arterial atherosclerosis was first documented in experimental models and later in elderly patients with LUTS. It was shown that early-stage moderate ischemia produces detrusor overactivity, while prolonged severe ischemia provokes changes consistent with detrusor underactivity. Recent studies imply a central role of cellular energy sensors, cellular stress sensors, and stress response molecules in bladder responses to ischemia. The cellular energy sensor adenosine monophosphate-activated protein kinase was shown to play a role in detrusor overactivity and neurodegeneration in bladder ischemia. The cellular stress sensors apoptosis signal-regulating kinase 1 and caspase-3 along with heat shock proteins were characterized as important contributing factors to smooth muscle structural modifications and apoptotic responses in bladder ischemia. Downstream pathways seem to involve hypoxia-inducible factor, transforming growth factor beta, vascular endothelial growth factor, and nerve growth factor. Molecular responses to bladder ischemia were associated with differential protein expression, the accumulation of non-coded amino acids, and post-translational modifications of contractile proteins and stress response molecules. Further insight into cellular stress responses in bladder ischemia may provide novel diagnostic and therapeutic targets against LUTS.

NAFLD as a continuous driver in the whole spectrum of vascular disease

Vascular disease is the prime determinant to cardiovascular morbidities and mortalities, which comprises the early vascular damage and subsequent cardiovascular events. Non-alcohol Fatty Liver Disease (NAFLD) is a systemic metabolic disorder that drives the progression of vascular disease through complex interactions. Although a causal relationship between NAFLD and cardiovascular disease (CVD) has not been established, a growing number of epidemiological studies have demonstrated an independent association between NAFLD and early vascular disease and subsequent cardiovascular events. In addition, mechanistic studies suggest that NAFLD initiates and accelerates vascular injury by increasing systemic inflammation and oxidative stress, impairing insulin sensitivity and lipid metabolism, and modulating epigenetics, the intestinal flora and hepatic autonomic nervous system; thus, NAFLD is a putative driving force for CVD progression. In this review, we summarize the clinical evidence supporting the association of NAFLD with subclinical vascular disease and cardiovascular events and discuss the potential mechanisms by which NAFLD promotes the progression of vascular disease.

Role of GALNT4 in protecting against cardiac hypertrophy through ASK1 signaling pathway

Pathological myocardial hypertrophy is regulated by multiple pathways. However, its underlying pathogenesis has not been fully explored. The goal of this work was to elucidate the function of polypeptide N-acetylgalactosaminyltransferase 4 (GALNT4) in myocardial hypertrophy and its underlying mechanism of action. We illustrated that GALNT4 was upregulated in the models of hypertrophy. Two cardiac hypertrophy models were established through partial transection of the aorta in GALNT4-knockout (GALNT4-KO) mice and adeno-associated virus 9-GALNT4 (AAV9-GALNT4) mice. The GALNT4-KO mice demonstrated accelerated cardiac hypertrophy, dysfunction, and fibrosis, whereas the opposite phenotype was observed in AAV9-GALNT4 mice. Similarly, GALNT4 overexpression mitigated the degree of phenylephrine-induced cardiomyocyte hypertrophy in vitro whereas GALNT4 knockdown aggravated the hypertrophy. In terms of mechanism, GALNT4 deficiency increased the phosphorylation and activation of ASK1 and its downstream targets (JNK and p38), whereas GALNT4 overexpression inhibited activation of the ASK1 pathway. Furthermore, we demonstrated that GALNT4 can directly bind to ASK1 inhibiting its N-terminally mediated dimerization and the subsequent phosphorylation of ASK1. Finally, an ASK1 inhibitor (iASK1) was able to reverse the effects of GALNT4 in vitro. In summary, GALNT4 may serve as a new regulatory factor and therapeutic target by blocking the activation of the ASK1 signaling cascade.

Apocynin attenuates diabetic cardiomyopathy by suppressing ASK1-p38/JNK signaling

Diabetic cardiomyopathy (DCM) significantly increased the morbidity of heart failure in diabetic patients. Long-time oxidative stress is an indisputable contributor for DCM development. Apocynin (APO) has been suggested to be a potential drug against oxidative stress. The study aims to find out the effects of APO on DCM and the related mechanisms. Mice were randomly divided into four groups: control (CON), APO, DCM and DCM + APO. Echocardiography analyses, histological analyses, Western blot and RT-PCR were used to explore the roles and mechanisms of APO in DCM. Isolated neonatal rat cardiomyocytes (NRCMs) and cardiac fibroblasts (CFs) were used for further confirming the APO treatment effects in vitro. Deteriorated cardiac function, enlarged cardiomyocytes, excess cardiac fibrosis and significant cardiac oxidative stress were observed in DCM group. However, APO treatment successfully improved cardiac function, decreased cardiac hypertrophy and fibrosis, and depressed oxidative stress. Mechanistically, APO treatment markedly suppressed apoptosis signal regulating kinase 1(ASK1)-p38/c-jun N-terminal kinase (JNK) signaling and reduced apoptosis. It also inhibited NRCM apoptosis and CF activation via depressing ASK1-p38/JNK signaling in vitro. Moreover, adenovirus-mediated ASK1 overexpression completely removed the protection of APO in vitro. In conclusion, APO treatment could effectively attenuate DCM-associated injuries in vivo and protect against high glucose-induced NRCM and CF injuries in vitro via suppressing ASK1-p38/JNK signaling. APO might be a potential ASK1 inhibitor for treating DCM.

LITAF acts as a novel regulator for pathological cardiac hypertrophy

Pathological hypertrophy generally progresses to heart failure. Exploring effective and promising therapeutic targets might lead to progress in preventing its detrimental outcomes. Our current knowledge about lipopolysaccharide-induced tumor necrosis factor-α factor (LITAF) is mainly limited to regulate inflammation. However, the role of LITAF in other settings that are not that relevant to inflammation, such as cardiac remodeling and heart failure, remains largely unknown. In the present study, we found that the expression of LITAF decreased in hypertrophic hearts and cardiomyocytes. Meanwhile, LITAF protected cultured neonatal rat cardiomyocytes against phenylephrine-induced hypertrophy. Moreover, using LITAF knockout mice, we demonstrated that LITAF deficiency exacerbated cardiac hypertrophy and fibrosis compared with wild-type mice. Mechanistically, LITAF directly binds to the N-terminal of ASK1, thus disrupting the dimerization of ASK1 and blocking ASK1 activation, ultimately inhibiting ASK1-JNK/p38 signaling over-activation and protecting against cardiac hypertrophy. Furthermore, AAV9-mediated LITAF overexpression attenuated cardiac hypertrophy in vivo. Conclusions: Our findings uncover the novel role of LITAF as a negative regulator of cardiac remodeling. Targeting the interaction between LITAF and ASK1 could be a promising therapeutic strategy for pathological cardiac remodeling.

The Heart of the Alzheimer's: A Mindful View of Heart Disease

Purpose of Review: This review summarizes the current evidence for the involvement of proteotoxicity and protein quality control systems defects in diseases of the central nervous and cardiovascular systems. Specifically, it presents the commonalities between the pathophysiology of protein misfolding diseases in the heart and the brain. Recent Findings: The involvement of protein homeostasis dysfunction has been for long time investigated and accepted as one of the leading pathophysiological causes of neurodegenerative diseases. In cardiovascular diseases instead the mechanistic focus had been on the primary role of Ca2+ dishomeostasis, myofilament dysfunction as well as extracellular fibrosis, whereas no attention was given to misfolding of proteins as a pathogenetic mechanism. Instead, in the recent years, several contributions have shown protein aggregates in failing hearts similar to the ones found in the brain and increasing evidence have highlighted the crucial importance that proteotoxicity exerts via pre-amyloidogenic species in cardiovascular diseases as well as the prominent role of the cellular response to misfolded protein accumulation. As a result, proteotoxicity, unfolding protein response (UPR), and ubiquitin-proteasome system (UPS) have recently been investigated as potential key pathogenic pathways and therapeutic targets for heart disease. Summary: Overall, the current knowledge summarized in this review describes how the misfolding process in the brain parallels in the heart. Understanding the folding and unfolding mechanisms involved early through studies in the heart will provide new knowledge for neurodegenerative proteinopathies and may prepare the stage for targeted and personalized interventions.

NFκB promotes oxidative stress-induced necrosis and ischemia/reperfusion injury by inhibiting Nrf2-ARE pathway

In this study, we identified an unexpected pro-cell death role for NFκB in mediating oxidative stress-induced necrosis, and provide new mechanistic evidence that NFκB, in cooperation with HDAC3, negatively regulates Nrf2-ARE anti-oxidative signaling through transcriptional silencing. We showed that genetic inactivation of NFκB-p65 inhibited, whereas activation of NFκB promoted, oxidative stress-induced cell death and HMGB1 release, a biomarker of necrosis. Moreover, NFκB-luciferase activity was elevated in cardiomyocytes after simulated ischemia/reperfusion (sI/R) or doxorubicin (DOX) treatment, and inhibition of NFκB with Ad-p65-shRNA or Ad-IκBαM diminished sI/R- and DOX-induced cell death and HMGB1 release. Importantly, NFκB negatively regulated Nrf2-ARE activity and the expression of antioxidant proteins. Mechanistically, co-immunoprecipitation revealed that p65 was required for Nrf2-HDAC3 interaction and transcriptional silencing of Nrf2-ARE activity. Further, the ability of HDAC3 to repress Nrf2-ARE activity was lost in p65 deficient cells. Pharmacologic inhibition of HADCs or NFκB with trichostatin A (TSA) or BMS-345541, respectively, increased Nrf2-ARE activity and promoted cell survival after sI/R. In vivo, NFκB transcriptional activity in the mouse heart was significantly elevated after ischemia/reperfusion (I/R) injury, which was abolished by cardiomyocyte-specific deletion of p65 using p65fl/flNkx2.5-Cre mice. Moreover, genetic ablation of p65 in the mouse heart attenuated myocardial infarct size after acute I/R injury and improved cardiac remodeling and functional recovery after chronic myocardial infarction. Thus, our results identified NFκB as a key regulator of oxidative stress-induced necrosis by suppressing the Nrf2-ARE antioxidant pathway through an HDAC3-dependent mechanism. This study also revealed a new pathogenic role of NFκB in cardiac ischemic injury and pathological remodeling.

Zinc Finger Protein ZBTB20 protects against cardiac remodelling post-myocardial infarction via ROS-TNFα/ASK1/JNK pathway regulation

This study aims to determine the efficacy of Zinc finger protein ZBTB20 in treatment of post‐infarction cardiac remodelling. For this purpose, left anterior descending (LAD) ligation was operated on mice to induce myocardial infarction (MI) with sham control group as contrast and adeno‐associated virus (AAV9) system was used to deliver ZBTB20 to mouse heart by myocardial injection with vehicle‐injected control group as contrast two weeks before MI surgery. Then four weeks after MI, vehicle‐treated mice with left ventricular (LV) remodelling underwent deterioration of cardiac function, with symptoms of hypertrophy, interstitial fibrosis, inflammation and apoptosis. The vehicle‐injected mice also showed increase of infarct size and decrease of survival rate. Meanwhile, the ZBTB20‐overexpressed mice displayed improvement after MI. Moreover, the anti‐apoptosis effect of ZBTB20 was further confirmed in H9c2 cells subjected to hypoxia in vitro. Further study suggested that ZBTB20 exerts cardioprotection by inhibiting tumour necrosis factor α/apoptosis signal‐regulating kinase 1 (ASK1)/c‐Jun N‐terminal kinase 1/2 (JNK1/2) signalling, which was confirmed by shRNA‐JNK adenoviruses transfection or a JNK activator in vitro as well as ASK1 overexpression in vivo. In summary, our data suggest that ZBTB20 could alleviate cardiac remodelling post‐MI. Thus, administration of ZBTB20 can be considered as a promising treatment strategy for heart failure post‐MI.

Significance Statement: ZBTB20 could alleviate cardiac remodelling post‐MI via inhibition of ASK1/JNK1/2 signalling.

Galectin-3 knock down inhibits cardiac ischemia-reperfusion injury through interacting with bcl-2 and modulating cell apoptosis

Acute myocardial infarction (AMI) is a fetal cardiovascular disease with high morbidity and mortality worldwide. In the present study, we elucidated the role of galectin-3 in preventing myocardial ischemic reperfusion injury. We found that galactin-3 was significantly up-regulated in the myocardium and cardiomyocyte subjected to ischemia/reperfusion (I/R) and hypoxia/reoxygenation (H/R) treatment, respectively. Galectin-3 knockdown significantly decreased the ischemic size of the left ventricular and the apoptosis of cardiomyocytes. Moreover, galectin-3 knockdown reversed the decrease of mitochondrial membrane potential and inhibited the inflammation response in myocardium and cultured cardiomyocyte induced by I/R and H/R, respectively. Further, this study revealed that galectin-3 interacted with bcl-2, instead of bax, in the cardiomyocyte, and regulated the phosphorylation of AKT, p70s6k, JNK, IκB and p65. Our findings demonstrated that galectin-3 could prevent myocardial I/R injury through interacting with bcl-2.

Regulation of Cellular Stress Signaling in Bladder Ischemia

Introduction

The etiology of lower urinary tract symptoms in patients with non-obstructed non-neurogenic bladder remains largely unknown. Clinical studies divulged a significant correlation between reduced bladder blood flow and low bladder compliance. Animal models of bladder ischemia displayed structural modifications, characterized by loss of smooth muscle cells and accumulation of connective tissue in the bladder wall. The underlying mechanisms contributing to structural damage in bladder ischemia remain largely elusive. We previously reported that structural modifications in bladder ischemia correlate with upregulated stress proteins and cell survival signaling, suggesting the potential role of cellular stress in ischemic damage. However, stress response molecules and downstream pathways eliciting bladder damage in ischemia remain largely undetermined.

Methods

Using a rat model of bladder ischemia along with a cell culture hypoxia model, we investigated stress signaling molecules in the ischemic bladder tissues and hypoxic bladder smooth muscle cells.

Results

Our data suggest simultaneous upregulation of two major cellular stress-sensing molecules, namely apoptosis signal-regulating kinase 1 (ASK1) and caspase-3, implying degenerative insult via stress signaling pathway in bladder ischemia. Consistent with bladder ischemia, incubation of cultured human bladder smooth muscle cells at low oxygen tension increased both ASK1 and caspase-3 expression, insinuating hypoxia as an essential factor in ASK1 and caspase-3 upregulation. Gene deletion of ASK1 by ASK1 siRNA in cultured smooth muscle cells prevented caspase-3 upregulation by hypoxia, suggesting caspase-3 regulation by ASK1 under the ischemic/hypoxic conditions. Upregulation of ASK1 and caspase-3 in rat bladder ischemia and human bladder smooth muscle cell hypoxia was associated with subcellular structural modifications consistent with the initial stages of apoptotic insult.

Conclusion

Our data suggest that stress sensing by ASK1 and caspase-3 may contribute to subcellular structural damage and low bladder compliance. The ASK1/caspase-3 pathway may provide therapeutic targets against cellular stress and degenerative responses in bladder ischemia.

Redox Regulation of Cardiac ASK1 (Apoptosis Signal-Regulating Kinase 1) Controls p38-MAPK (Mitogen-Activated Protein Kinase) and Orchestrates Cardiac Remodeling to Hypertension

Supplemental Digital Content is available in the text.

Systemic hypertension increases cardiac workload causing cardiomyocyte hypertrophy and increased cardiac fibrosis. An underlying feature is increased production of reactive oxygen species. Redox-sensitive ASK1 (apoptosis signal-regulating kinase 1) activates stress-regulated protein kinases (p38-MAPK [mitogen-activated protein kinases] and JNKs [c-Jun N-terminal kinases]) and promotes fibrosis in various tissues. Here, we determined the specificity of ASK1 signaling in the heart, with the hypothesis that ASK1 inhibitors may be used to manage fibrosis in hypertensive heart disease. Using immunoblotting, we established that moderate levels of H₂O₂ activate ASK1 in neonatal rat cardiomyocytes and perfused rat hearts. ASK1 was activated during ischemia in adult rat hearts, but not on reperfusion, consistent with activation by moderate (not high) reactive oxygen species levels. In contrast, IL (interleukin)-1β activated an alternative kinase, TAK1 (transforming growth factor–activated kinase 1). ASK1 was not activated by IL1β in cardiomyocytes and activation in perfused hearts was due to increased reactive oxygen species. Selonsertib (ASK1 inhibitor) prevented activation of p38-MAPKs (but not JNKs) by oxidative stresses in cultured cardiomyocytes and perfused hearts. In vivo (C57Bl/6J mice with osmotic minipumps for drug delivery), selonsertib (4 mg/[kg·d]) alone did not affect cardiac function/dimensions (assessed by echocardiography). However, it suppressed hypertension-induced cardiac hypertrophy resulting from angiotensin II (0.8 mg/[kg·d], 7d), with inhibition of Nppa/Nppb mRNA upregulation, reduced cardiomyocyte hypertrophy and, notably, significant reductions in interstitial and perivascular fibrosis. Our data identify a specific reactive oxygen species→ASK1→p38-MAPK pathway in the heart and establish that ASK1 inhibitors protect the heart from hypertension-induced cardiac remodeling. Thus, targeting the ASK1→p38-MAPK nexus has potential therapeutic viability as a treatment for hypertensive heart disease.

Regulation of Long Non-coding RNAs and MicroRNAs in Heart Disease: Insight Into Mechanisms and Therapeutic Approaches

Cardiovascular disease is the leading cause of mortality worldwide and there is an increasing need to identify new therapeutic targets that could be used to prevent or treat these diseases. Due to recent scientific advances, non-coding RNAs are widely accepted as important regulators of cellular processes, and the identification of an axis of interaction between long non-coding RNAs (lncRNAs) and micro RNAs (miRNAs) has provided another platform through which cardiovascular disease could be targeted therapeutically. Increasing evidence has detailed the importance of these non-coding RNAs, both individually and in an axis of regulation, in the processes and diseases involving the heart. However, further investigation into the consequences of targeting this mechanism, as well as refinement of how the system is targeted, are required before a treatment can be provided in clinic. This level of genomic regulation provides an exciting potential novel therapeutic strategy for the treatment of cardiovascular disease.

Unfolded protein response in cardiovascular disease

The unfolded protein response (UPR) is a highly conserved molecular machinery, which protects the cells against a diverse variety of stimuli. Activation of this element has been associated with both human health and disease. The purpose of the current manuscript is to provide the most updated information on the involvement of UPR towards the improvement; or deterioration of cardiovascular functions. Since UPR is consisted of three distinct elements, namely the activating transcription factor 6, the protein kinase RNA-like endoplasmic reticulum kinase; and the inositol-requiring enzyme-1α, a highly orchestrated manipulation of those molecular branches may provide new therapeutic possibilities against the severe outcomes of cardiovascular disease.

TBC1D25 Regulates Cardiac Remodeling Through TAK1 Signaling Pathway

Cardiac remodeling is a major early event of heart failure, which is regulated by multiple signaling pathways. Here, we demonstrate that TBC1D25 is upregulated during pathological cardiac remodeling. The aim of this study is to determine the role of TBC1D25 in cardiac remodeling and to illustrate the underlying molecular mechanism. Specifically, cardiac remodeling was induced in TBC1D25-KO mice and their wild-type control mice through partial transverse aortic constriction (TAC) of aortic arch. Knockout TBC1D25 exacerbated cardiac hypertrophy, fibrosis and dysfunction. Meanwhile, TBC1D25 overexpression in both H9C2 cells and NRCMs alleviate Angiotensin II-induced cardiomyocyte hypertrophy in vitro. Moreover, TBC1D25 deficiency increases the phosphorylation levels of TAK1 and its downstream molecular (JNK and p38), whereas overexpressed TBC1D25 inhibits phosphorylation of TAK1, JNK and p38. And TAK1 is the key molecule in this process. Furthermore, we demonstrated that TBC1D25 could directly interacts with TAK1 by immunoprecipitation assay and GST pull-down assay, and the interaction needs the amino acids from at least 138 to 226 in the C-terminal region of TBC1D25 and from 1 to 300 in the C-terminal region of TAK1. We conclude that TBC1D25 suppresses pathological cardiac remodeling via regulating TAK1-JNK/p38 signaling pathway, which suggests that TBC1D25 will likely become a promising therapeutic target for heart failure.

H2S attenuates injury after ischemic stroke by diminishing the assembly of CaMKII with ASK1-MKK3-p38 signaling module

Cerebral ischemia/reperfusion (I/R) injury is a leading cause of learning and memory dysfunction. Hydrogen sulfide (H₂S) has been shown to confer neuroprotection in various neurodegenerative diseases, including cerebral I/R-induced hippocampal CA1 injury. However, the underlying mechanisms have not been completely understood. In the present study, rats were pretreated with SAM/NaHS (SAM, an H₂S agonist, and NaHS, an H₂S donor) only or SAM/NaHS combined with CaM (an activator of CaMKII) prior to cerebral ischemia. The Morris water maze test demonstrated that SAM/NaHS could alleviate learning and memory impairment induced by cerebral I/R injury. Cresyl violet staining was used to show the survival of hippocampal CA1 pyramidal neurons. SAM/NaHS significantly increased the number of surviving cells, whereas CaM weakened the protection induced by SAM/NaHS. The immunohistochemistry results indicated that the number of Iba1-positive microglia significantly increased after cerebral I/R. Compared with the I/R group, the number of Iba1-positive microglia in the SAM/NaHS groups significantly decreased. Co-Immunoprecipitation and immunoblotting were conducted to demonstrate that SAM/NaHS suppressed the assembly of CaMKII with the ASK1-MKK3-p38 signal module after cerebral I/R, which decreased the phosphorylation of p38. In contrast, CaM significantly inhibited the effects of SAM/NaHS. Taken together, the results suggested that SAM/NaHS could suppress cerebral I/R injury by downregulating p38 phosphorylation via decreasing the assembly of CaMKII with the ASK1-MKK3-p38 signal module.

Regulator of G Protein Signaling 6 Facilities Cardiac Hypertrophy by Activating Apoptosis Signal-Regulating Kinase 1-P38/c-JUN N-Terminal Kinase 1/2 Signaling

Background

Regulator of G protein signaling 6 (RGS6) is an important member of the RGS family and produces pleiotropic regulatory effects on cardiac pathophysiology. However, the role of RGS6 protein in cardiomyocytes during angiotensin II– and pressure overload–induced cardiac hypertrophy remain unknown.

Methods and Results

Here, we used a genetic approach to study the regulatory role of RGS6 in cardiomyocytes during pathological cardiac hypertrophy. RGS6 expression was significantly increased in failing human hearts and in hypertrophic murine hearts. The extent of aortic banding–induced cardiac hypertrophy, dysfunction, and fibrosis in cardiac‐specific RGS6 knockout mice was alleviated, whereas the hearts of transgenic mice with cardiac‐specific RGS6 overexpression exhibited exacerbated responses to pressure overload. Consistent with these findings, RGS6 also facilitated an angiotensin II–induced hypertrophic response in isolated cardiomyocytes. According to the mechanistic studies, RGS6 mediated cardiac hypertrophy by directly interacting with apoptosis signal–regulating kinase 1, which further activates the P38‐c‐JUN N‐terminal kinase 1/2 signaling pathway.

Conclusions

Based on our findings, RGS6 aggravates cardiac hypertrophy, and the RGS6‐apoptosis signal–regulating kinase 1 pathway represents a potential therapeutic target to attenuate pressure overload–driven cardiac remodeling.

MicroRNA-145 Protects against Myocardial Ischemia Reperfusion Injury via CaMKII-Mediated Antiapoptotic and Anti-Inflammatory Pathways

MicroRNA-145 (miR-145) has been shown to play an important role in cardiovascular system disorders; however, the underlying mechanism is not completely understood. The purpose of this study was aimed at elucidating the cardioprotective effects of miR-145 against myocardial ischemia/reperfusion (I/R) injury. We established a rat myocardial I/R model with 45 min left anterior descending coronary artery (LAD) occlusion and 2 h reperfusion. The levels of myocardial enzymes, apoptotic, inflammatory, and oxidative indices were determined. The arrhythmia score was assessed by programmed electrical stimulation (PES). Quantitative real-time PCR and western blot were applied to evaluate the expression levels of miR-145 and related target proteins, respectively. I/R injury decreased the expression of miR-145; however, upregulated miR-145 markedly reduced the elevation of ST segment, decreased corrected QT (QTc) intervals, and attenuated I/R-induced electrophysiological instability. Furthermore, miR-145 suppressed myocardium apoptotic, inflammatory, and oxidative response as well as the phosphorylation of Ca²⁺/calmodulin-dependent protein kinase II (CaMKII), ryanodine receptor2 (RyR2 Ser2814), apoptosis signal-regulating kinase 1 (ASK1), c-Jun NH2-terminal kinases (JNK), and nuclear translocation of nuclear factor kappa-B (NF-κB) p65. In summary, overexpression of miR-145 alleviates I/R-induced myocardial electrophysiological instability and apoptotic and inflammatory response via inhibition of the CaMKII-mediated ASK1 antiapoptotic pathway and NF-κB p65 anti-inflammatory pathways.

ASK1 Inhibition Halts Disease Progression in Preclinical Models of Pulmonary Arterial Hypertension

RATIONALE

Progression of pulmonary arterial hypertension (PAH) is associated with pathological remodeling of the pulmonary vasculature and the right ventricle (RV). Oxidative stress drives the remodeling process through activation of MAPKs (mitogen-activated protein kinases), which stimulate apoptosis, inflammation, and fibrosis.

OBJECTIVES

We investigated whether pharmacological inhibition of the redox-sensitive apical MAPK, ASK1 (apoptosis signal-regulating kinase 1), can halt the progression of pulmonary vascular and RV remodeling.

METHODS

A selective, orally available ASK1 inhibitor, GS-444217, was administered to two preclinical rat models of PAH (monocrotaline and Sugen/hypoxia), a murine model of RV pressure overload induced by pulmonary artery banding, and cellular models.

MEASUREMENTS AND MAIN RESULTS

Oral administration of GS-444217 dose dependently reduced pulmonary arterial pressure and reduced RV hypertrophy in PAH models. The therapeutic efficacy of GS-444217 was associated with reduced ASK1 phosphorylation, reduced muscularization of the pulmonary arteries, and reduced fibrotic gene expression in the RV. Importantly, efficacy was observed when GS-444217 was administered to animals with established disease and also directly reduced cardiac fibrosis and improved cardiac function in a model of isolated RV pressure overload. In cellular models, GS-444217 reduced phosphorylation of p38 and JNK (c-Jun N-terminal kinase) induced by adenoviral overexpression of ASK1 in rat cardiomyocytes and reduced activation/migration of primary mouse cardiac fibroblasts and human pulmonary adventitial fibroblasts derived from patients with PAH.

CONCLUSIONS

ASK1 inhibition reduced pathological remodeling of the pulmonary vasculature and the right ventricle and halted progression of pulmonary hypertension in rodent models. These preclinical data inform the first description of a causal role of ASK1 in PAH disease pathogenesis.

Loss of thioredoxin 2 alters mitochondrial respiratory function and induces cardiomyocyte hypertrophy

Thioredoxin 2 (Trx2), as a member of the thioredoxin system in mitochondria, is involved in controlling mitochondrial redox state. However, the role of Trx2 in cardiac biology is not fully understood. In the present study, the expression of Trx2 is silenced in quiescent neonatal rat ventricular cardiomyocytes (NRVCs) and mitochondrial respiratory function and cardiomyocyte hypertrophy are assessed. The results show that Trx2 depletion does not induce significant cytotoxicity in quiescent NRVCs. Remarkably, Trx2 depletion results in cardiomyocyte hypertrophy as determined by increased cell size and protein synthesis. Furthermore, Trx2 depletion inhibits AMPK activity and AMPK activator reversed cellular hypertrophy. Trx2 depletion enhances mitochondrial ROS generation without impact on cellular ROS level. Trx2 depletion has no effect on mitochondrial biogenesis. Specifically, Trx2 depletion increases mitochondrial respiration flux and total ATP concentration under quiescent conditions. To decipher the relationship between ROS generation, mitochondrial respiration flux, and AMPK signaling, mitochondrial metabolism and ROS was specifically inhibited, and the results show that AMPK inactivation and hypertrophic response in Trx2-silenced cells is reversed by respiration blockers but not ROS scavenger. In conclusion, these results show that beyond mitochondrial ROS scavenging, Trx2 controls mitochondrial respiratory function in quiescent cardiomyocytes and is implicated in cardiomyocyte hypertrophy via AMPK signaling.

Mitochondrial ROS Drive Sudden Cardiac Death and Chronic Proteome Remodeling in Heart Failure

RATIONALE

Despite increasing prevalence and incidence of heart failure (HF), therapeutic options remain limited. In early stages of HF, sudden cardiac death (SCD) from ventricular arrhythmias claims many lives. Reactive oxygen species (ROS) have been implicated in both arrhythmias and contractile dysfunction. However, little is known about how ROS in specific subcellular compartments contribute to HF or SCD pathophysiology. The role of ROS in chronic proteome remodeling has not been explored.

OBJECTIVE

We will test the hypothesis that elevated mitochondrial ROS (mROS) is a principal source of oxidative stress in HF and in vivo reduction of mROS mitigates SCD.

METHODS AND RESULTS

Using a unique guinea pig model of nonischemic HF that recapitulates important features of human HF, including prolonged QT interval and high incidence of spontaneous arrhythmic SCD, compartment-specific ROS sensors revealed increased mROS in resting and contracting left ventricular myocytes in failing hearts. Importantly, the mitochondrially targeted antioxidant (MitoTEMPO) normalized global cellular ROS. Further, in vivo MitoTEMPO treatment of HF animals prevented and reversed HF, eliminated SCD by decreasing dispersion of repolarization and ventricular arrhythmias, suppressed chronic HF-induced remodeling of the expression proteome, and prevented specific phosphoproteome alterations. Pathway analysis of mROS-sensitive networks indicated that increased mROS in HF disrupts the normal coupling between cytosolic signals and nuclear gene programs driving mitochondrial function, antioxidant enzymes, Ca²⁺ handling, and action potential repolarization, suggesting new targets for therapeutic intervention.

CONCLUSIONS

mROS drive both acute emergent events, such as electrical instability responsible for SCD, and those that mediate chronic HF remodeling, characterized by suppression or altered phosphorylation of metabolic, antioxidant, and ion transport protein networks. In vivo reduction of mROS prevents and reverses electrical instability, SCD, and HF. Our findings support the feasibility of targeting the mitochondria as a potential new therapy for HF and SCD while identifying new mROS-sensitive protein modifications.

Endoplasmic reticulum stress in the heart: insights into mechanisms and drug targets

The endoplasmic reticulum (ER) serves several essential cellular functions including protein synthesis, protein folding, protein translocation, calcium homoeostasis and lipid biosynthesis. Physiological or pathological stimuli, which disrupt ER homoeostasis and disturb its functions, lead to an accumulation of misfolded and unfolded proteins, a condition referred to as ER stress. ER stress triggers the unfolded protein response to restore the homoeostasis of ER, through activating transcriptional and translational pathways. However, prolonged ER stress will lead to cell dysfunction and apoptosis. Recent evidence revealed that ER stress is involved in the development and progression of various heart diseases, such as cardiac hypertrophy, ischaemic heart diseases and heart failure. Therefore, improved understanding of the molecular mechanisms of ER stress in heart disease will help to investigate more potential targets for new therapeutic interventions and drug discovery.

LINKED ARTICLES

This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.

Right ventricular fibrosis and dysfunction: Actual concepts and common misconceptions

Fibrosis and remodeling of the right ventricle (RV) are associated with RV dysfunction and mortality of patients with pulmonary hypertension (PH) but it is unknown how much RV fibrosis contributes to RV dysfunction and mortality. RV fibrosis manifests as fibroblast accumulation and collagen deposition which may be excessive. Although extracellular matrix deposition leads to elevated ventricular stiffness, it is not known to which extent it affects RV function. Various animal models of pulmonary hypertension have been established to investigate the role of fibrosis in RV dysfunction and failure. However, they do not perfectly resemble the human disease. In the current review we describe the major characteristics of RV fibrosis, molecular mechanisms regulating the fibrotic process, and discuss how therapeutic targeting of fibrosis might affect RV function.

ASK family in cardiovascular biology and medicine

Cardiovascular disease is a major cause of death worldwide. Mitogen-activated protein kinase (MAPK) signal cascades signaling pathways play crucial roles in cardiovascular pathophysiology. Apoptosis signal-regulating kinase (ASK) family members ASK1, ASK2 and ASK3 are the key molecules in MAPK signal cascades and are activated by various stresses. ASK1 is the most extensively studied MAPKKK and is involved in regulation of the cellular functions such as cell survival, proliferation, inflammation and apoptosis. The current review focuses on the relationship between ASK1 and cardiovascular disease, while exploring the novel therapeutic strategies for cardiovascular disease involved in the ASK1 signal pathway.

The role of reactive oxygen species in the pathophysiology of cardiovascular diseases and the clinical significance of myocardial redox

Acute and chronic excessive intracellular increase of reactive oxygen species (ROS) is involved in the development and progression of cardiovascular diseases. ROS are by-products of various oxidative physiological and biochemical processes. Sources of ROS are mitochondrial respiration, NADH/NADPH oxidase, xanthine oxidoreductase or the uncoupling of nitric oxide synthase (NOS) in vascular cells. ROS mediate various signaling pathways that underlie cardiovascular pathophysiology. The delicate equilibrium between free-radical generation and antioxidant defense is altered in favor of the former, thus leading to redox imbalance, oxidative stress, and increased cellular injury. An understanding of the pathophysiological mechanisms mediated by oxidative stress is crucial to the prevention and treatment of cardiovascular diseases.

Mitochondrial Metabolism in Aging Heart

Altered mitochondrial metabolism is the underlying basis for the increased sensitivity in the aged heart to stress. The aged heart exhibits impaired metabolic flexibility, with a decreased capacity to oxidize fatty acids and enhanced dependence on glucose metabolism. Aging impairs mitochondrial oxidative phosphorylation, with a greater role played by the mitochondria located between the myofibrils, the interfibrillar mitochondria. With aging, there is a decrease in activity of complexes III and IV, which account for the decrease in respiration. Furthermore, aging decreases mitochondrial content among the myofibrils. The end result is that in the interfibrillar area, there is ≈50% decrease in mitochondrial function, affecting all substrates. The defective mitochondria persist in the aged heart, leading to enhanced oxidant production and oxidative injury and the activation of oxidant signaling for cell death. Aging defects in mitochondria represent new therapeutic targets, whether by manipulation of the mitochondrial proteome, modulation of electron transport, activation of biogenesis or mitophagy, or the regulation of mitochondrial fission and fusion. These mechanisms provide new ways to attenuate cardiac disease in elders by preemptive treatment of age-related defects, in contrast to the treatment of disease-induced dysfunction.

Translocase of Inner Membrane 50 Functions as a Novel Protective Regulator of Pathological Cardiac Hypertrophy

BACKGROUND

Translocase of inner membrane 50 (TIM50) is a member of the translocase of inner membrane (TIM) complex in the mitochondria. Previous research has demonstrated the role of TIM50 in the regulation of oxidative stress and cardiac morphology. However, the role of TIM50 in pathological cardiac hypertrophy remains unknown.

METHODS AND RESULTS

In the present study we found that the expression of TIM50 was downregulated in hypertrophic hearts. Using genetic loss-of-function animal models, we demonstrated that TIM50 deficiency increased heart and cardiomyocyte size with more severe cardiac fibrosis compared with wild-type littermates. Moreover, we generated cardiomyocyte-specific TIM50 transgenic mice in which the hypertrophic and fibrotic phenotypes were all alleviated. Next, we tested reactive oxygen species generation and the activities of the antioxidant enzymes superoxide dismutase and catalase, and also respiratory chain complexes I, II, and IV, finding that all the activities were regulated by TIM50. Meanwhile, expression of the ASK1-JNK/P38 axis was increased in TIM50-deficient mice, and TIM50 overexpression decreased the activity of the ASK1-JNK/P38 axis. Finally, we treated mice with the antioxidant N-acetyl cysteine to reduce oxidative stress. After N-acetyl cysteine treatment, the deteriorative hypertrophic and fibrotic phenotypes caused by TIM50 deficiency were all remarkably reversed.

CONCLUSIONS

These data indicated that TIM50 could attenuate pathological cardiac hypertrophy primarily by reducing oxidative stress. TIM50 could be a promising target for the prevention and therapy of cardiac hypertrophy and heart failure.

The fibrosis-cell death axis in heart failure

Cardiac stress can induce morphological, structural and functional changes of the heart, referred to as cardiac remodeling. Myocardial infarction or sustained overload as a result of pathological causes such as hypertension or valve insufficiency may result in progressive remodeling and finally lead to heart failure (HF). Whereas pathological and physiological (exercise, pregnancy) overload both stimulate cardiomyocyte growth (hypertrophy), only pathological remodeling is characterized by increased deposition of extracellular matrix proteins, termed fibrosis, and loss of cardiomyocytes by necrosis, apoptosis and/or phagocytosis. HF is strongly associated with age, and cardiomyocyte loss and fibrosis are typical signs of the aging heart. Fibrosis results in stiffening of the heart, conductivity problems and reduced oxygen diffusion, and is associated with diminished ventricular function and arrhythmias. As a consequence, the workload of cardiomyocytes in the fibrotic heart is further augmented, whereas the physiological environment is becoming less favorable. This causes additional cardiomyocyte death and replacement of lost cardiomyocytes by fibrotic material, generating a vicious cycle of further decline of cardiac function. Breaking this fibrosis-cell death axis could halt further pathological and age-related cardiac regression and potentially reverse remodeling. In this review, we will describe the interaction between cardiac fibrosis, cardiomyocyte hypertrophy and cell death, and discuss potential strategies for tackling progressive cardiac remodeling and HF.

Loss of AKAP150 promotes pathological remodelling and heart failure propensity by disrupting calcium cycling and contractile reserve

AIMS

Impaired Ca^2 +cycling and myocyte contractility are a hallmark of heart failure triggered by pathological stress such as hemodynamic overload. The A-Kinase anchoring protein AKAP150 has been shown to coordinate key aspects of adrenergic regulation of Ca²⁺cycling and excitation-contraction in cardiomyocytes. However, the role of the AKAP150 signalling complexes in the pathogenesis of heart failure has not been investigated.

METHODS AND RESULTS

Here we examined how AKAP150 signalling complexes impact Ca²⁺cycling, myocyte contractility, and heart failure susceptibility following pathological stress. We detected a significant reduction of AKAP150 expression in the failing mouse heart induced by pressure overload. Importantly, cardiac-specific AKAP150 knockout mice were predisposed to develop dilated cardiomyopathy with severe cardiac dysfunction and fibrosis after pressure overload. Loss of AKAP150 also promoted pathological remodelling and heart failure progression following myocardial infarction. However, ablation of AKAP150 did not affect calcineurin-nuclear factor of activated T cells signalling in cardiomyocytes or pressure overload- or agonist-induced cardiac hypertrophy. Immunoprecipitation studies showed that AKAP150 was associated with SERCA2, phospholamban, and ryanodine receptor-2, providing a targeted control of sarcoplasmic reticulum Ca²⁺regulatory proteins. Mechanistically, loss of AKAP150 led to impaired Ca²⁺cycling and reduced myocyte contractility reserve following adrenergic stimulation or pressure overload.

CONCLUSIONS

These findings define a critical role for AKAP150 in regulating Ca²⁺cycling and myocardial ionotropy following pathological stress, suggesting the AKAP150 signalling pathway may serve as a novel therapeutic target for heart failure.

MicroRNA-Mediated Down-Regulation of Apoptosis Signal-Regulating Kinase 1 (ASK1) Attenuates the Apoptosis of Human Mesenchymal Stem Cells (MSCs) Transplanted into Infarcted Heart

Stem cell therapy using adult stem cells, such as mesenchymal stem cells (MSCs) has produced some promising results in treating the damaged heart. However, the low survival rate of MSCs after transplantation is still one of the crucial factors that limit the therapeutic effect of stem cells. In the damaged heart, oxidative stress due to reactive oxygen species (ROS) production can cause the death of transplanted MSCs. Apoptosis signal-regulating kinase 1 (ASK1) has been implicated in the development of oxidative stress-related pathologic conditions. Thus, we hypothesized that down-regulation of ASK1 in human MSCs (hMSCs) might attenuate the post-transplantation death of MSCs. To test this hypothesis, we screened microRNAs (miRNAs) based on a miRNA-target prediction database and empirical data and investigated the anti-apoptotic effect of selected miRNAs on human adipose-derived stem cells (hASCs) and on rat myocardial infarction (MI) models. Our data indicated that miRNA-301a most significantly suppressed ASK1 expression in hASCs. Apoptosis-related genes were significantly down-regulated in miRNA-301a-enriched hASCs exposed to hypoxic conditions. Taken together, these data show that miRNA-mediated down-regulation of ASK1 protects MSCs during post-transplantation, leading to an increase in the efficacy of MSC-based cell therapy.

Pleiotropic properties of ASK1

BACKGROUND

Apoptosis signal-regulating kinase 1 (ASK1), also known as mitogen-activated protein kinase kinase kinase 5 (MAP3K5), has the potential to induce cellular apoptosis under various physiological conditions. It has long been suggested that ASK1 is highly sensitive to oxidative stress and contributes substantially to apoptosis. However, recent studies have indicated that ASK1 has pleiotropic roles in living organisms through other mechanisms in addition to apoptosis.

SCOPE OF THE REVIEW

This review describes the physiological functions of ASK1 in living organisms, focusing on the regulatory mechanisms of ASK1 activity and its importance in the pathogenesis of various diseases. We also highlight recent works published within the past few years.

MAJOR CONCLUSIONS

ASK1 forms a high-molecular-mass complex within the cell, designated as the ASK1 signalosome. Soon after the discovery of ASK1, several regulatory components of the ASK1 signalosome have been revealed, including thioredoxin (Trx), tumor-necrosis factor α receptor-associated factors (TRAFs) and 14-3-3s. In parallel with the precise analyses unveiling the molecular basis of ASK1 regulation, the physiological or pathophysiological significance of ASK1 in diverse organs has been elucidated. In addition to the generation of global knockout mice or tissue-specific knockout mice, ASK1-specific inhibitors have illuminated the biological roles of ASK1.

GENERAL SIGNIFICANCE

The multi-faceted features of the function of ASK1 have been discovered over the past two decades, revealing that ASK1 is a crucial molecule for maintaining cellular homeostasis, especially under conditions of stress. Based on the results that ASK1 deficiency provides beneficial effects for several diseases, modulating ASK1 activity is a promising method to ameliorate a subset of diseases.

CUEDC2 modulates cardiomyocyte oxidative capacity by regulating GPX1 stability

The irreversible loss of cardiomyocytes due to oxidative stress is the main cause of heart dysfunction following ischemia/reperfusion (I/R) injury and ageing-induced cardiomyopathy. Here, we report that CUEDC2, a CUE domain-containing protein, plays a critical role in oxidative stress-induced cardiac injury. Cuedc2(-/-) cardiomyocytes exhibited a greater resistance to oxidative stress-induced cell death. Loss of CUEDC2 enhanced the antioxidant capacity of cardiomyocytes, promoted reactive oxygen species (ROS) scavenging, and subsequently inhibited the redox-dependent activation of signaling pathways. Notably, CUEDC2 promoted E3 ubiquitin ligases tripartite motif-containing 33 (TRIM33)-mediated the antioxidant enzyme, glutathione peroxidase 1 (GPX1) ubiquitination, and proteasome-dependent degradation. Ablation of CUEDC2 upregulated the protein level of GPX1 in the heart significantly. Strikingly, in vivo, the infarct size of Cuedc2(-/-) heart was significantly decreased after I/R injury, and aged Cuedc2(-/-) mice preserved better heart function as the overall ROS levels in their hearts were significantly lower. Our results demonstrated a novel role of CUEDC2 in cardiomyocyte death regulation. Manipulating CUEDC2 level might be an attractive therapeutic strategy for promoting cardiomyocyte survival following oxidative stress-induced cardiac injury.

Thioredoxin superfamily and its effects on cardiac physiology and pathology

A precise control of oxidation/reduction of protein thiols is essential for intact cardiac physiology. Irreversible oxidative modifications have been proposed to play a role in the pathogenesis of cardiovascular diseases. An imbalance of redox homeostasis with diminution of antioxidant capacities predisposes the heart to oxidant injury. There is growing interest in endoplasmic reticulum (ER) stress in the cardiovascular field, since perturbation of redox homeostasis in the ER is sufficient to cause ER stress. Because a number of human diseases are related to altered redox homeostasis and defects in protein folding, many research efforts have been devoted in recent years to understanding the structure and enzymatic properties of the thioredoxin superfamily. The thioredoxin superfamily has been well documented as thiol oxidoreductases to exert a role in various cell signaling pathways. The redox properties of the thioredoxin motif account for the different functions of several members of the thioredoxin superfamily. While thioredoxin and glutaredoxin primarily act as antioxidants by reducing protein disulfides and mixed disulfide, another member of the superfamily, protein disulfide isomerase (PDI), can act as an oxidant by forming intrachain disulfide bonds that contribute to proper protein folding. Increasing evidence suggests a pivotal role of PDI in the survival pathway that promotes cardiomyocyte survival and leads to more favorable cardiac remodeling. Thus, the thiol redox state is important for cellular redox signaling and survival pathway in the heart. This review summarizes the key features of major members of the thioredoxin superfamily directly involved in cardiac physiology and pathology.

TAK1 Regulates Myocardial Response to Pathological Stress via NFAT, NFκB, and Bnip3 Pathways

TAK1 (TGFβ-activated kinase-1) signaling is essential in regulating a number of important biological functions, including innate immunity, inflammatory response, cell growth and differentiation, and myocardial homeostasis. The precise role of TAK1 in the adult heart under pathological conditions remains largely unknown. Importantly, we observed that TAK1 is upregulated during compensatory hypertrophy but downregulated in end-stage heart failure. Here we generated transgenic mice with inducible expression of an active TAK1 mutant (TAK1ΔN) in the adult heart. TAK1ΔN transgenic mice developed greater cardiac hypertrophy compared with control mice after transverse aortic constriction (TAC), which was largely blocked by ablation of calcineurin Aβ. Expression of TAK1ΔN also promoted NFAT (nuclear factor of activated T-cells) transcriptional activity in luciferase reporter mice at baseline, which was further enhanced after TAC. Our results revealed that activation of TAK1 promoted adaptive cardiac hypertrophy through a cross-talk between calcineurin-NFAT and IKK-NFκB pathways. More significantly, adult-onset inducible expression of TAK1ΔN protected the myocardium from adverse remodeling and heart failure after myocardial infarction or long-term pressure overload, by preventing cardiac cell death and fibrosis. Mechanistically, TAK1 exerts its cardioprotective effect through activation of NFAT/NFκB, downregulation of Bnip3, and inhibition of cardiac cell death.

ASK1 mediates the teratogenicity of diabetes in the developing heart by inducing ER stress and inhibiting critical factors essential for cardiac development

Maternal diabetes in mice induces heart defects similar to those observed in human diabetic pregnancies. Diabetes enhances apoptosis and suppresses cell proliferation in the developing heart, yet the underlying mechanism remains elusive. Apoptosis signal-regulating kinase 1 (ASK1) activates the proapoptotic c-Jun NH2-terminal kinase 1/2 (JNK1/2) leading to apoptosis, suggesting a possible role of ASK1 in diabetes-induced heart defects. We aimed to investigate whether ASK1 is activated in the heart and whether deleting the Ask1 gene blocks diabetes-induced adverse events and heart defect formation. The ASK1-JNK1/2 pathway was activated by diabetes. Deleting Ask1 gene significantly reduced the rate of heart defects, including ventricular septal defects (VSDs) and persistent truncus arteriosus (PTA). Additionally, Ask1 deletion diminished diabetes-induced JNK1/2 phosphorylation and its downstream transcription factors and endoplasmic reticulum (ER) stress markers. Consistent with this, caspase activation and apoptosis were blunted. Ask1 deletion blocked the increase in cell cycle inhibitors (p21 and p27) and the decrease in cyclin D1 and D3 and reversed diabetes-repressed cell proliferation. Ask1 deletion also restored the expression of BMP4, NKX2.5, and GATA5, Smad1/5/8 phosphorylation, whose mutations or deletion result in reduced cell proliferation, VSD, and PTA formation. We conclude that ASK1 may mediate the teratogenicity of diabetes through activating the JNK1/2-ER stress pathway and inhibiting cell cycle progression, thereby impeding the cardiogenesis pathways essential for ventricular septation and outflow tract development.

Dickkopf-3 protects against cardiac dysfunction and ventricular remodelling following myocardial infarction

Dickkopf-3 (DKK3) is a secreted glycoprotein of the Dickkopf family (DKK1-4) that modulates Wnt signalling. DKK3 has been reported to regulate cell development, proliferation, apoptosis, and immune response. However, the functional role of DKK3 in cardiac remodelling after myocardial infarction (MI) has not yet been elucidated. This study aimed to explore the functional significance of DKK3 in the regulation of post-MI remodelling and its underlying mechanisms. MI was induced by surgical left anterior descending coronary artery ligation in transgenic mice expressing cardiac-specific DKK3 and DKK3 knockout (KO) mice as well as their non-transgenic and DKK3(+/+) littermates. Our results demonstrated that after MI, mice with DKK3 deficiency had increased mortality, greater infarct size, and exacerbated left ventricular (LV) dysfunction. Significantly, at 1 week post-MI, the hearts of DKK3-KO mice exhibited increased apoptosis, inflammation, and LV remodelling compared with the hearts of their DKK3(+/+) littermates. Conversely, DKK3 overexpression led to the opposite phenotype after infarction. Similar results were observed in cultured neonatal rat cardiomyocytes exposed to hypoxia in vitro. Mechanistically, DKK3 promotes cardioprotection by interrupting the ASK1-JNK/p38 signalling cascades. In conclusion, our results indicate that DKK3 protects against the development of MI-induced cardiac remodelling via negative regulation of the ASK1-JNK/p38 signalling pathway. Thus, our study suggests that DKK3 may represent a potential therapeutic target for the treatment of heart failure after MI.

c-kit+ cells minimally contribute cardiomyocytes to the heart

If and how the heart regenerates after an injury event is highly debated. c-kit-expressing cardiac progenitor cells have been reported as the primary source for generation of new myocardium after injury. Here we generated two genetic approaches in mice to examine if endogenous c-kit⁺ cells contribute differentiated cardiomyocytes to the heart during development, with aging or after injury in adulthood. A cDNA encoding either Cre recombinase or a tamoxifen inducible MerCreMer chimeric protein was targeted to the Kit locus in mice and then bred with reporter lines to permanently mark cell lineage. Endogenous c-kit⁺ cells did produce new cardiomyocytes within the heart, although at a percentage of ≈0.03% or less, and if a preponderance towards cellular fusion is considered, the percentage falls below ≈0.008%. In contrast, c-kit⁺ cells amply generated cardiac endothelial cells. Thus, endogenous c-kit⁺ cells can generate cardiomyocytes within the heart, although likely at a functionally insignificant level.

Depletion of apoptosis signal-regulating kinase 1 prevents bile duct ligation-induced necroinflammation and subsequent peribiliary fibrosis

Apoptosis signal-regulating kinase 1 (ASK1), also known as mitogen-activated protein kinase kinase kinase (MAP3K), is ubiquitously expressed and situated in an important upstream position of many signal transduction pathways. ASK1 plays a pivotal role in stressor-induced cell survival and inflammatory reactions. To ascertain the regulatory functions of ASK1 in bile duct ligation (BDL)-induced liver injury, we examined the net effects of ASK1 depletion on hepatic necroinflammation and/or fibrosis. We subjected C57BL/6 wild-type (WT) or ASK1-deficient (ASK1(-/-)) mice to sham or BDL surgery for 14 days. In day 3 BDL animals, ASK1(-/-) mice had significantly fewer bile infarcts along with more reduced interlobular or portal inflammatory infiltrate of various immune cells, including neutrophils, compared with WT mice in which ASK1 expression was markedly activated. Morphologically apoptotic hepatocytes or cholangiocytes were negligible in both the sham and BDL animals. In contrast, ASK1(-/-) mice had significantly less proliferating activity of not only hepatocytes but also large cholangiocytes than WT mice. Day 14 BDL ASK1(-/-) mice manifested potential antifibrogenic aspects of ASK1 deficiency, characterized by significantly fewer activated peribiliary fibrogenic cells and peribiliary fibrosis. These observations indicate that ASK1-mediated hepatic necroinflammation and proliferation, but not apoptosis, are closely linked to liver fibrosis and fibrogenesis. A specific ASK1 pathway blocker or inhibitor might offer a therapeutic strategy against human cholestatic diseases.

Cardioprotective 3',4'-dihydroxyflavonol attenuation of JNK and p38(MAPK) signalling involves CaMKII inhibition

DiOHF (3',4'-dihydroxyflavonol) is cardioprotective against I/R (ischaemia/reperfusion) injury. The biological activities of flavonols are associated with kinase modulation to alter cell signalling. We thus investigated the effects of DiOHF on the activation of MAPKs (mitogen-activated protein kinases) that regulate the cardiac stress response. In an ovine model of I/R, JNK (c-Jun N-terminal kinase), p38(MAPK), ERK (extracellular-signal-regulated kinase) and Akt were activated, and NP202, a pro-drug of DiOHF, reduced infarct size and inhibited JNK and p38(MAPK) activation, whereas ERK and Akt phosphorylation were unaltered. Similarly, in cultured myoblasts, DiOHF pre-treatment preserved viability and inhibited activation of JNK and p38(MAPK), but not ERK in response to acute oxidative and chemotoxic stress. Furthermore, DiOHF prevented stress-activation of the direct upstream regulators MKK4/7 (MAPK kinase 4/7) and MKK3/6 respectively. We utilized small-molecule affinity purification and identified CaMKII (Ca(2+)/calmodulin-dependent protein kinase II) as a kinase targeted by DiOHF and demonstrated potent CaMKII inhibition by DiOHF in vitro. Moreover, the specific inhibition of CaMKII with KN-93, but not KN-92, prevented oxidative stress-induced activation of JNK and p38(MAPK). The present study indicates DiOHF inhibition of CaMKII and attenuation of MKK3/6→p38(MAPK) and MKK4/7→JNK signalling as a requirement for the protective effects of DiOHF against stress stimuli and myocardial I/R injury.

Mouse models of heart failure: cell signaling and cell survival

Heart failure is one of the paramount global causes of morbidity and mortality. Despite this pandemic need, the available clinical counter-measures have not altered substantially in recent decades, most notably in the context of pharmacological interventions. Cell death plays a causal role in heart failure, and its inhibition poses a promising approach that has not been thoroughly explored. In previous approaches to target discovery, clinical failures have reflected a deficiency in mechanistic understanding, and in some instances, failure to systematically translate laboratory findings toward the clinic. Here, we review diverse mouse models of heart failure, with an emphasis on those that identify potential targets for pharmacological inhibition of cell death, and on how their translation into effective therapies might be improved in the future.

An apoptosis signal-regulating kinase 1 inhibitor reduces cardiomyocyte apoptosis and infarct size in a rat ischemia-reperfusion model

PURPOSES

We determined whether a small molecule inhibitor of apoptosis signal-regulating kinase 1 (ASK1-i) could reduce myocardial infarct size in a rat ischemia/reperfusion model.

METHODS AND RESULTS

Sprague-Dawley rats were randomized to 3 groups: ASK1-i infusion (n = 16), vehicle infusion (n = 16), or ischemic preconditioning (IPC; n = 15). Infusion of ASK1-i (10 mg/kg, iv) or vehicle commenced 45 minutes before myocardial ischemia. IPC consisted of 3 cycles of 3 minutes of coronary occlusion followed by 5 minutes of reperfusion immediately before index myocardial ischemia, which consisted of 30-minute left coronary occlusion followed by 180 minutes of reperfusion. Pathologic analysis revealed no significant difference in the ischemic risk size among the 3 groups. ASK1-I and IPC significantly reduced myocardial infarct size (27.7% ± 3.3%, 16.5% ± 3.4%, and 41.5% ± 4.8% in the ASK1-i group, the IPC group, and the vehicle group, respectively; P = 0.0002) and apoptosis (the percentage of apoptotic nuclei averaged 11.6% ± 1.0%, 10.2% ± 1.7%, and 17.7% ± 2.0% in the ASK1-i group, IPC group, and vehicle group, respectively, P = 0.0055).

CONCLUSIONS

A small molecule inhibitor of ASK1 was shown for the first time to reduce apoptosis and myocardial infarct size in a rat model of ischemia/reperfusion.

Thioredoxin 1 is essential for sodium sulfide-mediated cardioprotection in the setting of heart failure

OBJECTIVE

The aim of this study was to determine whether thioredoxin 1 (Trx1) mediates the cardioprotective effects of hydrogen sulfide (H2S) in a model of ischemic-induced heart failure (HF).

APPROACH AND RESULTS

Mice with a cardiac-specific overexpression of a dominant negative mutant of Trx1 and wild-type littermates were subjected to ischemic-induced HF. Treatment with H2S as sodium sulfide (Na2S) not only increased the gene and protein expression of Trx1 in the absence of ischemia but also augmented the HF-induced increase in both. Wild-type mice treated with Na2S experienced less left-ventricular dilatation, improved left-ventricular function, and less cardiac hypertrophy after the induction of HF. In contrast, Na2S therapy failed to improve any of these parameters in the dominant negative mutant of Trx1 mice. Studies aimed at evaluating the underlying cardioprotective mechanisms found that Na2S therapy inhibited HF-induced apoptosis signaling kinase-1 signaling and nuclear export of histone deacetylase 4 in a Trx1-dependent manner.

CONCLUSIONS

These findings provide novel information that the upregulation of Trx1 by Na2S therapy in the setting of HF sets into motion events, such as the inhibition of apoptosis signaling kinase-1 signaling and histone deacetylase 4 nuclear export, which ultimately leads to the attenuationof left-ventricular remodeling.