Cardiomyocyte-GSK-3α promotes mPTP opening and heart failure in mice with chronic pressure overload

GSK-3α-BNIP3 axis promotes mitophagy in human cardiomyocytes under hypoxia

Dysregulated autophagy/mitophagy is one of the major causes of cardiac injury in ischemic conditions. Glycogen synthase kinase-3alpha (GSK-3α) has been shown to play a crucial role in the pathophysiology of cardiac diseases. However, the precise role of GSK-3α in cardiac mitophagy remains unknown. Herein, we investigated the role of GSK-3α in cardiac mitophagy by employing AC16 human cardiomyocytes under the condition of acute hypoxia. We observed that the gain-of-GSK-3α function profoundly induced mitophagy in the AC16 cardiomyocytes post-hypoxia. Moreover, GSK-3α overexpression led to increased ROS generation and mitochondrial dysfunction in cardiomyocytes, accompanied by enhanced mitophagy displayed by increased mt-mKeima intensity under hypoxia. Mechanistically, we identified that GSK-3α promotes mitophagy through upregulation of BNIP3, caused by GSK-3α-mediated increase in expression of HIF-1α and FOXO3a in cardiomyocytes post-hypoxia. Moreover, GSK-3α displayed a physical interaction with BNIP3 and, inhibited PINK1 and Parkin recruitment to mitochondria was observed specifically under hypoxia. Taken together, we identified a novel mechanism of mitophagy in human cardiomyocytes. GSK-3α promotes mitochondrial dysfunction and regulates FOXO3a -mediated BNIP3 overexpression in cardiomyocytes to facilitate mitophagy following hypoxia. An interaction between GSK-3α and BNIP3 suggests a role of GSK-3α in BNIP3 recruitment to the mitochondrial membrane where it enhances mitophagy in stressed cardiomyocytes independent of the PINK1/Parkin.

The role of serine/threonine protein kinases in cardiovascular disease and potential therapeutic methods

Protein phosphorylation is an important link in a variety of signaling pathways, and most of the important life processes in cells involve protein phosphorylation. Based on the amino acid residues of phosphorylated proteins, protein kinases can be categorized into the following families: serine/threonine protein kinases, tyrosine-specific protein kinases, histidine-specific protein kinases, tryptophan kinases, and aspartate/glutamyl protein kinases. Of all the protein kinases, most are serine/threonine kinases, where serine/threonine protein kinases are protein kinases that catalyze the phosphorylation of serine or threonine residues on target proteins using ATP as a phosphate donor. The current socially accepted classification of serine/threonine kinases is to divide them into seven major groups: protein kinase A, G, C (AGC), CMGC, Calmodulin-dependent protein kinase (CAMK), Casein kinase (CK1), STE, Tyrosine kinase (TKL) and others. After decades of research, a preliminary understanding of the specific classification and respective functions of serine/threonine kinases has entered a new period of exploration. In this paper, we review the literature of the previous years and introduce the specific signaling pathways and related therapeutic modalities played by each of the small protein kinases in the serine/threonine protein kinase family, respectively, in some common cardiovascular system diseases such as heart failure, myocardial infarction, ischemia-reperfusion injury, and diabetic cardiomyopathy. To a certain extent, the current research results, including molecular mechanisms and therapeutic methods, are fully summarized and a systematic report is made for the prevention and treatment of cardiovascular diseases in the future.

Natural compound screening predicts novel GSK-3 isoform-specific inhibitors

Glycogen synthase kinase-3 (GSK-3) plays important roles in the pathogenesis of cardiovascular, metabolic, neurological disorders and cancer. Isoform-specific loss of either GSK-3α or GSK-3β often provides cytoprotective effects under such clinical conditions. However, available synthetic small molecule inhibitors are relatively non-specific, and their chronic use may lead to adverse effects. Therefore, screening for natural compound inhibitors to identify the isoform-specific inhibitors may provide improved clinical utility. Here, we screened 70 natural compounds to identify novel natural GSK-3 inhibitors employing comprehensive in silico and biochemical approaches. Molecular docking and pharmacokinetics analysis identified two natural compounds Psoralidin and Rosmarinic acid as potential GSK-3 inhibitors. Specifically, Psoralidin and Rosmarinic acid exhibited the highest binding affinities for GSK-3α and GSK-3β, respectively. Consistent with in silico findings, the kinase assay-driven IC50 revealed superior inhibitory effects of Psoralidin against GSK-3α (IC50 = 2.26 μM) vs. GSK-3β (IC50 = 4.23 μM) while Rosmarinic acid was found to be more potent against GSK-3β (IC50 = 2.24 μM) than GSK-3α (IC50 = 5.14 μM). Taken together, these studies show that the identified natural compounds may serve as GSK-3 inhibitors with Psoralidin serving as a better inhibitor for GSK-3α and Rosmarinic for GSK-3β isoform, respectively. Further characterization employing in vitro and preclinical models will be required to test the utility of these compounds as GSK-3 inhibitors for cardiometabolic and neurological disorders and cancers.

Potential regulatory role of epigenetic modifications in aging-related heart failure

Heart failure (HF) is a serious clinical syndrome and a serious development or advanced stage of various heart diseases. Aging is an independent factor that causes pathological damage in cardiomyopathy and participates in the occurrence of HF at the molecular level by affecting mechanisms such as telomere shortening and mitochondrial dysfunction. Epigenetic changes have a significant impact on the aging process, and there is increasing evidence that genetic and epigenetic changes are key features of aging and aging-related diseases. Epigenetic modifications can affect genetic information by changing the chromatin state without changing the DNA sequence. Most of the genetic loci that are highly associated with cardiovascular diseases (CVD) are located in non-coding regions of the genome; therefore, the epigenetic mechanism of CVD has attracted much attention. In this review, we focus on the molecular mechanisms of HF during aging and epigenetic modifications mediating aging-related HF, emphasizing that epigenetic mechanisms play an important role in the pathogenesis of aging-related CVD and can be used as potential diagnostic and prognostic biomarkers, as well as therapeutic targets.

GSK-3α aggravates inflammation, metabolic derangement, and cardiac injury post-ischemia/reperfusion

Reperfusion after acute myocardial infarction further exaggerates cardiac injury and adverse remodeling. Irrespective of cardiac cell types, loss of specifically the α isoform of the protein kinase GSK-3 is protective in chronic cardiac diseases. However, the role of GSK-3α in clinically relevant ischemia/reperfusion (I/R)-induced cardiac injury is unknown. Here, we challenged cardiomyocyte-specific conditional GSK-3α knockout (cKO) and littermate control mice with I/R injury and investigated the underlying molecular mechanism using an in vitro GSK-3α gain-of-function model in AC16 cardiomyocytes post-hypoxia/reoxygenation (H/R). Analysis revealed a significantly lower percentage of infarct area in the cKO vs. control hearts post-I/R. Consistent with in vivo findings, GSK-3α overexpression promoted AC16 cardiomyocyte death post-H/R which was accompanied by an induction of reactive oxygen species (ROS) generation. Consistently, GSK-3α gain-of-function caused mitochondrial dysfunction by significantly suppressing mitochondrial membrane potential. Transcriptomic analysis of GSK-3α overexpressing cardiomyocytes challenged with hypoxia or H/R revealed that NOD-like receptor (NLR), TNF, NF-κB, IL-17, and mitogen-activated protein kinase (MAPK) signaling pathways were among the most upregulated pathways. Glutathione and fatty acid metabolism were among the top downregulated pathways post-H/R. Together, these observations suggest that loss of cardiomyocyte-GSK-3α attenuates cardiac injury post-I/R potentially through limiting the myocardial inflammation, mitochondrial dysfunction, and metabolic derangement. Therefore, selective inhibition of GSK-3α may provide beneficial effects in I/R-induced cardiac injury and remodeling. KEY MESSAGES: GSK-3α promotes cardiac injury post-ischemia/reperfusion (I/R). GSK-3α regulates inflammatory and metabolic pathways post-hypoxia/reoxygenation (H/R). GSK-3α overexpression upregulates NOD-like receptor (NLR), TNF, NF-kB, IL-17, and MAPK signaling pathways in cardiomyocytes post-H/R. GSK-3α downregulates glutathione and fatty acid metabolic pathways in cardiomyocytes post-H/R.

Cardiac fibroblast GSK-3α aggravates ischemic cardiac injury by promoting fibrosis, inflammation, and impairing angiogenesis

Myocardial infarction (MI) is the leading cause of death worldwide. Glycogen synthase kinase-3 (GSK-3) has been considered to be a promising therapeutic target for cardiovascular diseases. GSK-3 is a family of ubiquitously expressed serine/threonine kinases. GSK-3 isoforms appear to play overlapping, unique, and even opposing functions in the heart. Previously, our group identified that cardiac fibroblast (FB) GSK-3β acts as a negative regulator of fibrotic remodeling in the ischemic heart. However, the role of FB-GSK-3α in MI pathology is not defined. To determine the role of FB-GSK-3α in MI-induced adverse cardiac remodeling, GSK-3α was deleted specifically in the residential fibroblast or myofibroblast (MyoFB) using tamoxifen (TAM) inducible Tcf21 or Periostin (Postn) promoter-driven Cre recombinase, respectively. Echocardiographic analysis revealed that FB- or MyoFB-specific GSK-3α deletion prevented the development of dilative remodeling and cardiac dysfunction. Morphometrics and histology studies confirmed improvement in capillary density and a remarkable reduction in hypertrophy and fibrosis in the KO group. We harvested the hearts at 4 weeks post-MI and analyzed signature genes of adverse remodeling. Specifically, qPCR analysis was performed to examine the gene panels of inflammation (TNFα, IL-6, IL-1β), fibrosis (COL1A1, COL3A1, COMP, Fibronectin-1, Latent TGF-β binding protein 2), and hypertrophy (ANP, BNP, MYH7). These molecular markers were essentially normalized due to FB-specific GSK-3α deletion. Further molecular studies confirmed that FB-GSK-3α could regulate NF-kB activation and expression of angiogenesis-related proteins. Our findings suggest that FB-GSK-3α plays a critical role in the pathological cardiac remodeling of ischemic hearts, therefore, it could be therapeutically targeted.

Statin Therapy Induces Gut Leakage and Neuromuscular Disjunction in Patients With Chronic Heart Failure

ABSTRACT

Statins are commonly used to limit the risk of cardiovascular diseases, including ischemic heart attack and stroke. However, treatment often leads to myopathy and muscle weakness. Therefore, a better understanding of underlying pathomechanism is needed to improve the clinical outcomes. Here, we assessed the physical performance, including handgrip strength (HGS), gait speed (GS), and short physical performance battery, in 172 patients diagnosed with chronic heart failure (CHF) treated with (n = 50) or without (n = 122) statin and 59 controls. The plasma biomarkers, including sarcopenia marker C-terminal agrin fragment-22 (CAF22), intestinal barrier integrity marker zonulin, and C-reactive protein (CRP), were measured and correlated with the physical performance of patients. The HGS, short physical performance battery scores, and GS were significantly compromised in patients with CHF versus controls. Irrespective of etiology, significant elevation of plasma CAF22, zonulin, and CRP was observed in patients with CHF. There were strong inverse correlations of CAF22 with HGS (r 2 = 0.34, P < 0.0001), short physical performance battery scores (r 2 = 0.08, P = 0.0001), and GS (r 2 = 0.143, P < 0.0001). Strikingly, CAF22 and zonulin were positively correlated with each other (r 2 = 0.10, P = 0.0002) and with the level of CRP in patients with CHF. Further investigations revealed a significant induction of CAF22, zonulin, and CRP in patients with CHF taking statin versus nonstatin group. Consistently, HGS and GS were significantly lower in the statin versus nonstatin CHF patients' group. Collectively, statin therapy adversely affects the neuromuscular junction and intestinal barrier, which potentially induces systemic inflammation and physical disability in patients with CHF. Further prospective confirmation of the findings is required in a well-controlled study.

PM2.5-Induced Cardiac Structural Modifications and Declined Pro-Survival Signalling Pathways Are Responsible for the Inefficiency of GSK-3β Inhibitor in Attenuating Myocardial Ischemia-Reperfusion Injury in Rats

Circulatory GSK3β is recognized as a biomarker and therapeutic target for diseases, including myocardial diseases. However, its potential as a target for myocardial ischemia-reperfusion injury (IR) in the presence of PM2.5 exposure is unclear. Wistar rats underwent IR following either a 21-day or single exposure to PM2.5 at a concentration of 250 µg/m3. The effects of GSK3β inhibitor on cardiac physiology, tissue injury, mitochondrial function, and the PI3K/AKT/GSK3β signalling axis were examined. The inhibitor was not effective in improving hemodynamics or reducing IR-induced infarction in the myocardium exposed to PM2.5 for 21 days. However, for a single-day exposure, the inhibitor showed potential in mitigating cardiac injury. In normal hearts undergoing IR, the inhibitor activated the PI3K/AKT signalling pathway, improved mitochondrial function, and reduced oxidative stress. These positive effects were not observed in PM2.5-exposed rats. Furthermore, the inhibitor stimulated autophagy in hearts exposed to PM2.5 for 21 days and subjected to IR, resulting in increased mTOR expression and decreased AMPK expression. In normal hearts and those exposed to a single dose of PM2.5, the inhibitor effectively activated the PI3K/Akt/AMPK axis. These findings suggest that GSK3β may not be a reliable therapeutic target for IR in the presence of chronic PM2.5 exposure.

Circulating H-FABP as a biomarker of frailty in patients with chronic heart failure

Increased vulnerability to physiologic stressors, termed frailty, is a common occurrence in patients with chronic heart failure (CHF). However, the definite biomarkers to assess frailty in CHF patients are not known. Here, we assessed the frailty phenotype and its potential association with heart failure (HF) markers in CHF patients. We categorized controls (n = 59) and CHF patients (n = 80), the participants, into robust, pre-frail, and frail based on the cardiovascular health study (CHS) frailty index. The plasma levels of HF markers, including tumorigenicity 2 (s-ST2), galectin-3, and heart-type fatty acid binding protein (H-FABP), were measured and correlated with frailty phenotype and cardiac function. The levels of plasma s-ST2, galectin-3, and H-FABP were profoundly elevated in CHF patients. Conversely, the frailty index scores were significantly lower in ischemic and non-ischemic CHF patients versus controls. Of the assessed HF markers, only H-FABP was positively correlated (r2 = 0.07, P = 0.02) with the frailty score in CHF patients. Collectively, these observations suggest that circulating H-FABP may serve as a biomarker of frailty in CHF patients.

GSK-3 at the heart of cardiometabolic diseases: Isoform-specific targeting is critical to therapeutic benefit

Glycogen synthase kinase-3 (GSK-3) is a family of serine/threonine kinases. The GSK-3 family has 2 isoforms, GSK-3α and GSK-3β. The GSK-3 isoforms have been shown to play overlapping as well as isoform-specific-unique roles in both, organ homeostasis and the pathogenesis of multiple diseases. In the present review, we will particularly focus on expanding the isoform-specific role of GSK-3 in the pathophysiology of cardiometabolic disorders. We will highlight recent data from our lab that demonstrated the critical role of cardiac fibroblast (CF) GSK-3α in promoting injury-induced myofibroblast transformation, adverse fibrotic remodeling, and deterioration of cardiac function. We will also discuss studies that found the exact opposite role of CF-GSK-3β in cardiac fibrosis. We will review emerging studies with inducible cardiomyocyte (CM)-specific as well as global isoform-specific GSK-3 KOs that demonstrated inhibition of both GSK-3 isoforms provides benefits against obesity-associated cardiometabolic pathologies. The underlying molecular interactions and crosstalk among GSK-3 and other signaling pathways will be discussed. We will briefly review the specificity and limitations of the available small molecule inhibitors targeting GSK-3 and their potential applications to treat metabolic disorders. Finally, we will summarize these findings and offer our perspective on envisioning GSK-3 as a therapeutic target for the management of cardiometabolic diseases.

Matrine-induced nephrotoxicity via GSK-3β/nrf2-mediated mitochondria-dependent apoptosis

INTRODUCTION

Matrine (MT), an ingredient extracted from the Chinese herb Sophora flavescens, can result in nephrotoxicity because of long-term exposure. However, the underlying mechanism by which MT leads to kidney injury remains unclear. This study aimed to investigate the roles of oxidative stress and mitochondria in MT-induced kidney toxicity both in vitro and in vivo.

METHODS

Mice were exposed to MT for 20 days, and NRK-52E cells were exposed to MT with or without LiCl (a GSK-3β inhibitor), tert-Butylhydroquinone (t-BHQ, an Nrf2 activator), or small interfering RNA.

RESULTS

The results showed that MT caused nephrotoxicity accompanied by an increase in reactive oxygen species (ROS) accumulation and mitochondrial dysfunction. Meanwhile, MT significantly upregulated glycogen synthase kinase-3β (GSK-3β) activity, released cytochrome c (Cyt C) and cleaved caspase-3, decreased the activity of nuclear factor-erythroid 2-related Factor 2 (Nrf2), and reduced the expression of heme oxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase 1 (NQO-1), which led to the inactivation of antioxidant enzymes and the activation of apoptosis. In addition, GSK-3β inhibition by LiCl or small interfering RNA pretreatment or Nrf2 activation by t-BHQ pretreatment attenuated the toxic effects of MT in NRK-52E cells.

CONCLUSIONS

Taken together, these results revealed that MT-induced apoptosis triggered kidney toxicity and that GSK-3β or Nrf2 might serve as a promising nephroprotective target for MT-induced kidney injury.

Nicotinamide riboside kinase-2 regulates metabolic adaptation in the ischemic heart

Ischemia-induced metabolic remodeling plays a critical role in the pathogenesis of adverse cardiac remodeling and heart failure however, the underlying molecular mechanism is largely unknown. Here, we assess the potential roles of nicotinamide riboside kinase-2 (NRK-2), a muscle-specific protein, in ischemia-induced metabolic switch and heart failure through employing transcriptomic and metabolomic approaches in ischemic NRK-2 knockout mice. The investigations revealed NRK-2 as a novel regulator of several metabolic processes in the ischemic heart. Cardiac metabolism and mitochondrial function and fibrosis were identified as top dysregulated cellular processes in the KO hearts post-MI. Several genes linked to mitochondrial function, metabolism, and cardiomyocyte structural proteins were severely downregulated in the ischemic NRK-2 KO hearts. Analysis revealed significantly upregulated ECM-related pathways which was accompanied by the upregulation of several key cell signaling pathways including SMAD, MAPK, cGMP, integrin, and Akt in the KO heart post-MI. Metabolomic studies identified profound upregulation of metabolites mevalonic acid, 3,4-dihydroxyphenylglycol, 2-penylbutyric acid, and uridine. However, other metabolites stearic acid, 8,11,14-eicosatrienoic acid, and 2-pyrrolidinone were significantly downregulated in the ischemic KO hearts. Taken together, these findings suggest that NRK-2 promotes metabolic adaptation in the ischemic heart. The aberrant metabolism in the ischemic NRK-2 KO heart is largely driven by dysregulated cGMP and Akt and mitochondrial pathways. KEY MESSAGES: Post-myocardial infarction metabolic switch critically regulates the pathogenesis of adverse cardiac remodeling and heart failure. Here, we report NRK-2 as a novel regulator of several cellular processes including metabolism and mitochondrial function post-MI. NRK-2 deficiency leads to downregulation of genes important for mitochondrial pathway, metabolism, and cardiomyocyte structural proteins in the ischemic heart. It was accompanied by upregulation of several key cell signaling pathways including SMAD, MAPK, cGMP, integrin, and Akt and dysregulation of numerous metabolites essential for cardiac bioenergetics. Taken together, these findings suggest that NRK-2 is critical for metabolic adaptation of the ischemic heart.

Active Ingredient Paeonol of Jijiu Huiyang Decoction Alleviates Isoproterenol-Induced Chronic Heart Failure via the GSK3A/PPARα Pathway

Background

The pharmacological mechanism of the traditional Chinese medicine formula-Jijiu Huiyang decoction (JJHYD), which contains several herbal medicines for the treatment of chronic heart failure (CHF), is yet unknown. Method and Materials. The main active components of JJHYD were analyzed by ultrahigh-performance liquid chromatography-mass spectrometry (UHPLC-MS/MS). The target genes of JJHYD and CHF were retrieved through multiple databases, a drug-ingredient-target-disease network was created, and KEGG enrichment and GO analyses were carried out. The binding ability of paeonol and Glycogen Synthase Kinase-3 alpha (GSK3A) was confirmed by molecular docking. CHF animal model and cell model were constructed. The effects of paeonol on cardiac dysfunction, myocardial hypertrophy, cardiac lipid accumulation, and myocardial apoptosis were detected by echocardiography, histopathology, and flow cytometry, respectively. The effects of paeonol on the expression of myocardial hypertrophy index, GSK3A, and genes or proteins related to the PPARα pathway were determined by qRT-PCR or western blot.

Result

UHPLC-MS/MS analysis combined with database verification showed a total of 227 chemical components in JJHYD, among which paeonol was the one with heart-protective roles and had the highest content. Paeonol alleviated isoproterenol-induced cardiac lipid accumulation, cardiac hypertrophy, and myocardial dysfunction and inhibited the activation of the PPARα pathway, while overexpression of GSK3A reversed these effects of paeonol. However, the reversal effects of GSK3A overexpression could be offset by siPPARα.

Conclusion

As the main active substance of JJHYD, paeonol participates in the protection of CHF by targeting the GSK3A/PPARα signaling pathway to reduce lipid toxicity.

Ponatinib Drives Cardiotoxicity by S100A8/A9-NLRP3-IL-1β Mediated Inflammation

BACKGROUND

The tyrosine kinase inhibitor ponatinib is the only treatment option for chronic myelogenous leukemia patients with T315I (gatekeeper) mutation. Pharmacovigilance analysis of Food and Drug Administration and World Health Organization datasets has revealed that ponatinib is the most cardiotoxic agent among all Food and Drug Administration-approved tyrosine kinase inhibitors in a real-world scenario. However, the mechanism of ponatinib-induced cardiotoxicity is unknown.

METHODS

The lack of well-optimized mouse models has hampered the in vivo cardio-oncology studies. Here, we show that cardiovascular comorbidity mouse models evidence a robust cardiac pathological phenotype upon ponatinib treatment. A combination of multiple in vitro and in vivo models was employed to delineate the underlying molecular mechanisms.

RESULTS

An unbiased RNA sequencing analysis identified the enrichment of dysregulated inflammatory genes, including a multifold upregulation of alarmins S100A8/A9, as a top hit in ponatinib-treated hearts. Mechanistically, we demonstrate that ponatinib activates the S100A8/A9-TLR4 (Toll-like receptor 4)-NLRP3 (NLR family pyrin domain-containing 3)-IL (interleukin)-1β signaling pathway in cardiac and systemic myeloid cells, in vitro and in vivo, thereby leading to excessive myocardial and systemic inflammation. Excessive inflammation was central to the cardiac pathology because interventions with broad-spectrum immunosuppressive glucocorticoid dexamethasone or specific inhibitors of NLRP3 (CY-09) or S100A9 (paquinimod) nearly abolished the ponatinib-induced cardiac dysfunction.

CONCLUSIONS

Taken together, these findings uncover a novel mechanism of ponatinib-induced cardiac inflammation leading to cardiac dysfunction. From a translational perspective, our results provide critical preclinical data and rationale for a clinical investigation into immunosuppressive interventions for managing ponatinib-induced cardiotoxicity.

Novel GSK-3β Inhibitor Neopetroside A Protects Against Murine Myocardial Ischemia/Reperfusion Injury

Recent trends suggest novel natural compounds as promising treatments for cardiovascular disease. The authors examined how neopetroside A, a natural pyridine nucleoside containing an α-glycoside bond, regulates mitochondrial metabolism and heart function and investigated its cardioprotective role against ischemia/reperfusion injury. Neopetroside A treatment maintained cardiac hemodynamic status and mitochondrial respiration capacity and significantly prevented cardiac fibrosis in murine models. These effects can be attributed to preserved cellular and mitochondrial function caused by the inhibition of glycogen synthase kinase-3 beta, which regulates the ratio of nicotinamide adenine dinucleotide to nicotinamide adenine dinucleotide, reduced, through activation of the nuclear factor erythroid 2-related factor 2/NAD(P)H quinone oxidoreductase 1 axis in a phosphorylation-independent manner.

Fibroblast GSK-3α Promotes Fibrosis via RAF-MEK-ERK Pathway in the Injured Heart

BACKGROUND

Heart failure is the leading cause of mortality, morbidity, and health care expenditures worldwide. Numerous studies have implicated GSK-3 (glycogen synthase kinase-3) as a promising therapeutic target for cardiovascular diseases. GSK-3 isoforms seem to play overlapping, unique and even opposing functions in the heart. Previously, we have shown that of the 2 isoforms of GSK-3, cardiac fibroblast GSK-3β acts as a negative regulator of myocardial fibrosis in the ischemic heart. However, the role of cardiac fibroblast-GSK-3α in the pathogenesis of cardiac diseases is completely unknown.

METHODS

To define the role of cardiac fibroblast-GSK-3α in myocardial fibrosis and heart failure, GSK-3α was deleted from fibroblasts or myofibroblasts with tamoxifen-inducible Tcf21- or Postn-promoter-driven Cre recombinase. Control and GSK-3α KO mice were subjected to cardiac injury and heart parameters were evaluated. The fibroblast kinome mapping was carried out to delineate molecular mechanism followed by in vivo and in vitro analysis.

RESULTS

Fibroblast-specific GSK-3α deletion restricted fibrotic remodeling and preserved function of the injured heart. We observed reductions in cell migration, collagen gel contraction, α-SMA protein levels, and expression of ECM genes in TGFβ1-treated KO fibroblasts, indicating that GSK-3α is required for myofibroblast transformation. Surprisingly, GSK-3α deletion did not affect SMAD3 activation, suggesting the profibrotic role of GSK-3α is SMAD3 independent. The molecular studies confirmed decreased ERK signaling in GSK-3α-KO CFs. Conversely, adenovirus-mediated expression of a constitutively active form of GSK-3α (Ad-GSK-3αS21A) in fibroblasts increased ERK activation and expression of fibrogenic proteins. Importantly, this effect was abolished by ERK inhibition.

CONCLUSIONS

GSK-3α-mediated MEK-ERK activation is a critical profibrotic signaling circuit in the injured heart, which operates independently of the canonical TGF-β1-SMAD3 pathway. Therefore, strategies to inhibit the GSK-3α-MEK-ERK signaling circuit could prevent adverse fibrosis in diseased hearts.

ELA-11 protects the heart against oxidative stress injury induced apoptosis through ERK/MAPK and PI3K/AKT signaling pathways

Increasing evidence revealed that apoptosis and oxidative stress injury were associated with the pathophysiology of doxorubicin (DOX)-induced myocardial injury. ELABELA (ELA) is a newly identified peptide with 32 amino acids, can reduce hypertension with exogenous infusion. However, the effect of 11-residue furn-cleaved fragment (ELA-11) is still unclear. We first administrated ELA-11 in DOX-injured mice and measured the cardiac function and investigated the effect of ELA-11 in vivo. We found that ELA-11 alleviated heart injury induced by DOX and inhibited cardiac tissues from apoptosis. In vitro, ELA-11 regulated the sensitivity towards apoptosis induced by oxidative stress with DOX treatment through PI3K/AKT and ERK/MAPK signaling pathway. Similarly, ELA-11 inhibited oxidative stress-induced apoptosis in cobalt chloride (CoCl₂)-injured cardiomyocytes. Moreover, ELA-11 protected cardiomyocyte by interacting with Apelin receptor (APJ) by using 4-oxo-6-((pyrimidin-2-ylthio) methyl)-4H-pyran-3-yl 4-nitrobenzoate (ML221). Hence, our results indicated a protective role of ELA-11 in oxidative stress-induced apoptosis in DOX-induced myocardial injury.

Identification of metabolic pathways underlying FGF1 and CHIR99021-mediated cardioprotection

Acute myocardial infarction is a leading cause of death worldwide. We have previously identified two cardioprotective molecules — FGF1 and CHIR99021— that confer cardioprotection in mouse and pig models of acute myocardial infarction. Here, we aimed to determine if improved myocardial metabolism contributes to this cardioprotection. Nanofibers loaded with FGF1 and CHIR99021 were intramyocardially injected to ischemic myocardium of adult mice immediately following surgically induced myocardial infarction. Animals were euthanized 3 and 7 days later. Our data suggested that FGF1/CHIR99021 nanofibers enhanced the heart’s capacity to utilize glycolysis as an energy source and reduced the accumulation of branched-chain amino acids in ischemic myocardium. The impact of FGF1/CHIR99021 on metabolism was more obvious in the first three days post myocardial infarction. Taken together, these findings suggest that FGF1/CHIR99021 protects the heart against ischemic injury via improving myocardial metabolism which may be exploited for treatment of acute myocardial infarction in humans.

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FGF1/CHIR confer cardioprotection in myocardial infarction animals

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FGF1/CHIR enhance the capability of ischemic hearts to produce energy via glycolysis

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FGF1/CHIR reduce the abundance of branched chain amino acids in ischemic hearts

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This study reveals a novel approach to correct metabolic disorders in ischemic hearts

DYRK1B-STAT3 Drives Cardiac Hypertrophy and Heart Failure by Impairing Mitochondrial Bioenergetics

BACKGROUND

Heart failure is a global public health issue that is associated with increasing morbidity and mortality. Previous studies have suggested that mitochondrial dysfunction plays critical roles in the progression of heart failure; however, the underlying mechanisms remain unclear. Because kinases have been reported to modulate mitochondrial function, we investigated the effects of DYRK1B (dual-specificity tyrosine-regulated kinase 1B) on mitochondrial bioenergetics, cardiac hypertrophy, and heart failure.

METHODS

We engineered DYRK1B transgenic and knockout mice and used transverse aortic constriction to produce an in vivo model of cardiac hypertrophy. The effects of DYRK1B and its downstream mediators were subsequently elucidated using RNA-sequencing analysis and mitochondrial functional analysis.

RESULTS

We found that DYRK1B expression was clearly upregulated in failing human myocardium and in hypertrophic murine hearts, as well. Cardiac-specific DYRK1B overexpression resulted in cardiac dysfunction accompanied by a decline in the left ventricular ejection fraction, fraction shortening, and increased cardiac fibrosis. In striking contrast to DYRK1B overexpression, the deletion of DYRK1B mitigated transverse aortic constriction-induced cardiac hypertrophy and heart failure. Mechanistically, DYRK1B was positively associated with impaired mitochondrial bioenergetics by directly binding with STAT3 to increase its phosphorylation and nuclear accumulation, ultimately contributing toward the downregulation of PGC-1α (peroxisome proliferator-activated receptor gamma coactivator-1α). Furthermore, the inhibition of DYRK1B or STAT3 activity using specific inhibitors was able to restore cardiac performance by rejuvenating mitochondrial bioenergetics.

CONCLUSIONS

Taken together, the findings of this study provide new insights into the previously unrecognized role of DYRK1B in mitochondrial bioenergetics and the progression of cardiac hypertrophy and heart failure. Consequently, these findings may provide new therapeutic options for patients with heart failure.

Nicotinamide riboside kinase-2 inhibits JNK pathway and limits dilated cardiomyopathy in mice with chronic pressure overload

Nicotinamide riboside kinase-2 (NRK-2) has recently emerged as a critical regulator of cardiac remodeling however, underlying molecular mechanisms is largely unknown. To explore the same, NRK2 knockout (KO) and littermate control mice were subjected to trans-aortic constriction (TAC) or sham surgeries and cardiac function was assessed by serial M-mode echocardiography. A mild cardiac contractile dysfunction was observed in the KOs at the early adaptive phase of remodeling followed by a significant deterioration during the maladaptive cardiac remodeling phase. Consistently, NRK2 KO hearts displayed increased cardiac hypertrophy and heart failure reflected by morphometric parameters as well as increased fetal genes ANP and BNP expressions. Histological assessment revealed an extensive left ventricular (LV) chamber dilatation accompanied by elevated cardiomyopathy and fibrosis in the KO hearts post-TAC. In a gain-of-function model, NRK-2 overexpressing in AC16 cardiomyocytes displayed significantly attenuated fetal genes ANP and BNP expression. Consistently, NRK-2 overexpression attenuated angiotensin II- induced cardiomyocyte death. Mechanistically, we identified NRK-2 as a regulator of JNK MAP kinase and mitochondrial function where NRK-2 overexpression in human cardiomyocytes markedly suppressed the angiotensin II- induced JNK activation and mitochondrial depolarization. Thus, our results demonstrate that NRK-2 plays protective roles in pressure overload- induced dilatative cardiac remodeling and, genetic ablation exacerbates dilated cardiomyopathy, interstitial collagen deposition, and cardiac dysfunction post-TAC due, in part, to increased JNK activation and mitochondrial dysfunction.

Sulphenylation of CypD at Cysteine 104: A Novel Mechanism by Which SO2 Inhibits Cardiomyocyte Apoptosis

Objectives: The study was designed to explore the role of endogenous gaseous signaling molecule sulfur dioxide (SO2) in the control of cardiomyocyte apoptosis and its molecular mechanisms.

Methods: Neonatal mouse cardiac myocytes (NMCMs) and H9c2 cells were used in the cell experiments. The endogenous SO2 pathway including SO2 level and the expression of SO2-generating enzyme aspartate aminotransferase 1/2 (AAT1/2) were detected in NMCMs. The apoptosis of cardiomyocytes was examined by a TUNEL assay. The cleavage and the activity of apoptotic proteins caspase9 and caspase3 were measured. The content of ATP, the opening of mitochondrial permeability transition pore (mPTP), and the cytochrome c (cytc) leakage were detected by immunofluorescence. The sulphenylation of cyclophilin-D (CypD) was detected by biotin switch analysis. The four CypD mutant plasmids in which cysteine sites were mutated to serine were constructed to identify the SO2-affected site in vitro.

Results: ISO down-regulated the endogenous SO2/AAT pathway of cardiomyocytes in association with a significant increase in cardiomyocyte apoptosis, demonstrated by the increases in apoptosis, cleaved-caspase3/caspase3 ratio, and caspase3 activity. Furthermore, ISO significantly reduced ATP production in H9c2 cells, but the supplement of SO2 significantly restored the content of ATP. ISO stimulated mPTP opening, resulting in an increase in the release of cytc, which further increased the ratio of cleaved caspase9/caspase9 and enhanced the protein activity of caspase9. While, the supplementation of SO2 reversed the above effects. Mechanistically, SO2 did not affect CypD protein expression, but sulphenylated CypD and inhibited mPTP opening, resulting in an inhibition of cardiomyocyte apoptosis. The C104S mutation in CypD abolished SO2-induced sulphenylation of CypD, and thereby blocked the inhibitory effect of SO2 on the mPTP opening and cardiomyocyte apoptosis.

Conclusion: Endogenous SO2 sulphenylated CypD at Cys104 to inhibit mPTP opening, and thus protected against cardiomyocyte apoptosis.

Knockdown of forkhead box protein P1 alleviates hypoxia reoxygenation injury in H9c2 cells through regulating Pik3ip1/Akt/eNOS and ROS/mPTP pathway

Forkhead box protein P1 (Foxp1) exerts an extensive array of physiological and pathophysiological impacts on the cardiovascular system. However, the exact function of myocardial Foxp1 in myocardial ischemic reperfusion injury (MIRI) stays largely vague. The hypoxia reoxygenation model of H9c2 cells (the rat ventricular myoblasts) closely mimics myocardial ischemia-reperfusion injury. This report intends to research the effects and mechanisms underlying Foxp1 on H9c2 cells in response to hypoxia (12 h)/reoxygenation (4 h) (HR) stimulation. Expressions of Foxp1 and Phosphatidylinositol 3-kinase interacting protein 1 (Pik3ip1) were both upregulated in ischemia/reperfusion (IR)/HR-induced injury. Stimulation through HR led to marked increases in cellular apoptosis, mitochondrial dysfunction, and superoxide generation in H9c2 cells, which were rescued with knockdown of Foxp1 by siRNA. Silence of Foxp1 depressed expression of Pik3ip1 directly activated the PI3K/Akt/eNOS pathway and promoted nitric oxide (NO) release. Moreover, the knockdown of Foxp1 blunted HR-induced enhancement of reactive oxygen species (ROS) generation, thus alleviating excessive persistence of mitochondrial permeability transition pore (mPTP) opening and decreased mitochondrial apoptosis-associated protein expressions in H9c2 cells. Meanwhile, these cardioprotective effects can be abolished by LY294002, NG-nitro-L-arginine methyl ester (L-NAME), and Atractyloside (ATR), respectively. In summary, our findings indicated that knockdown of Foxp1 prevented HR-induced encouragement of apoptosis and oxidative stress via PI3K/Akt/eNOS signaling activation by targeting Pik3ip1 and improved mitochondrial function by inhibiting ROS-mediated mPTP opening. Inhibition of Foxp1 may be a promising therapeutic avenue for MIRI.

Cardiomyocyte-GSK-3β deficiency induces cardiac progenitor cell proliferation in the ischemic heart through paracrine mechanisms

Cardiomyopathy is an irreparable loss and novel strategies are needed to induce resident cardiac progenitor cell (CPC) proliferation in situ to enhance the possibility of cardiac regeneration. Here, we sought to identify the potential roles of glycogen synthase kinase-3β (GSK-3β), a critical regulator of cell proliferation and differentiation, in CPC proliferation post-myocardial infarction (MI). Cardiomyocyte-specific conditional GSK-3β knockout (cKO) and littermate control mice were employed and challenged with MI. Though cardiac left ventricular chamber dimension and contractile functions were comparable at 2 weeks post-MI, cKO mice displayed significantly preserved LV chamber and contractile function versus control mice at 4 weeks post-MI. Consistent with protective phenotypes, an increased percentage of c-kit-positive cells (KPCs) were observed in the cKO hearts at 4 and 6 weeks post-MI which was accompanied by increased levels of cardiomyocyte proliferation. Further analysis revealed that the observed increased number of KPCs in the ischemic cKO hearts was mainly from a cardiac lineage, as the majority of identified KPCs were negative for the hematopoietic lineage marker, CD45. Mechanistically, cardiomyocyte-GSK-3β profoundly suppresses the expression and secretion of growth factors, including basic-fibroblast growth factor, angiopoietin-2, erythropoietin, stem cell factor, platelet-derived growth factor-BB, granulocyte colony-stimulating factor, and vascular endothelial growth factor, post-hypoxia. In conclusion, our findings strongly suggest that loss of cardiomyocyte-GSK-3β promotes cardiomyocyte and resident CPC proliferation post-MI. The induction of cardiomyocyte and CPC proliferation in the ischemic cKO hearts is potentially regulated by autocrine and paracrine signaling governed by dysregulated growth factors post-MI. A strategy to inhibit cardiomyocyte-GSK-3β could be helpful for the promotion of in situ cardiac regeneration post-ischemic injury.

Resveratrol Prevents Right Ventricle Dysfunction, Calcium Mishandling, and Energetic Failure via SIRT3 Stimulation in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is characterized by pulmonary vessel remodeling; however, its severity and impact on survival depend on right ventricular (RV) failure. Resveratrol (RES), a polyphenol found in red wine, exhibits cardioprotective effects on RV dysfunction in PAH. However, most literature has focused on RES protective effect on lung vasculature; recent finding indicates that RES has a cardioprotective effect independent of pulmonary arterial pressure on RV dysfunction, although the underlying mechanism in RV has not been determined. Therefore, this study is aimed at evaluating sirtuin-3 (SIRT3) modulation by RES in RV using a monocrotaline- (MC-) induced PAH rat model. Myocyte function was evaluated by confocal microscopy as cell contractility, calcium signaling, and mitochondrial membrane potential (ΔΨm); cell energetics was assessed by high-resolution respirometry, and western blot and immunoprecipitation evaluated posttranslational modifications. PAH significantly affects mitochondrial function in RV; PAH is prone to mitochondrial permeability transition pore (mPTP) opening, thus decreasing the mitochondrial membrane potential. The compromised cellular energetics affects cardiomyocyte function by decreasing sarco-endoplasmic reticulum Ca²⁺-ATPase (SERCA) activity and delaying myofilament unbinding, disrupting cell relaxation. RES partially protects mitochondrial integrity by deacetylating cyclophilin-D, a critical component of the mPTP, increasing SIRT3 expression and activity and preventing mPTP opening. The preserved energetic capability rescues cell relaxation by maintaining SERCA activity. Avoiding Ca²⁺ transient and cell contractility mismatch by preserving mitochondrial function describes, for the first time, impairment in excitation-contraction-energetics coupling in RV failure. These results highlight the importance of mitochondrial energetics and mPTP in PAH.

Repurposing Nintedanib for pathological cardiac remodeling and dysfunction

Heart Failure (HF) is the leading cause of death worldwide. Myocardial fibrosis, one of the clinical manifestations implicated in almost every form of heart disease, contributes significantly to HF development. However, there is no approved drug specifically designed to target cardiac fibrosis. Nintedanib (NTB) is an FDA approved tyrosine kinase inhibitor for idiopathic pulmonary fibrosis (IPF) and chronic fibrosing interstitial lung diseases (ILD). The favorable clinical outcome of NTB in IPF patients is well established. Furthermore, NTB is well tolerated in IPF patients irrespective of cardiovascular comorbidities. However, there is a lack of direct evidence to support the therapeutic efficacy and safety of NTB in cardiac diseases. In this study we examined the effects of NTB treatment on cardiac fibrosis and dysfunction using a murine model of HF. Specifically, 10 weeks old C57BL/6J male mice were subjected to Transverse Aortic Constriction (TAC) surgery. NTB was administered once daily by oral gavage (50 mg/kg) till 16 weeks post-TAC. Cardiac function was monitored by serial echocardiography. Histological analysis and morphometric studies were performed at 16 weeks post-TAC. In the control group, systolic dysfunction started developing from 4 weeks post-surgery and progressed till 16 weeks. However, NTB treatment prevented TAC-induced cardiac functional decline. In another experiment, NTB treatment was stopped at 8 weeks, and animals were followed till 16 weeks post-TAC. Surprisingly, NTB's beneficial effect on cardiac function was maintained even after treatment interruption. NTB treatment remarkably reduced cardiac fibrosis as confirmed by Masson's trichrome staining and decreased expression of collagen genes (COL1A1, COL3A1). Compared to the TAC group, NTB treated mice showed a lower HW/TL ratio and cardiomyocyte cross-sectional area. NTB treatment reduced myocardial and systemic inflammation by inhibiting pro-inflammatory subsets and promoting regulatory T cells (Tregs). Our in vitro studies demonstrated that NTB prevents myofibroblast transformation, TGFβ1-induced SMAD3 phosphorylation, and the production of fibrogenic proteins (Fibronectin-1, α-SMA). However, NTB promoted immunosuppressive phenotype in Tregs, and altered vital signaling pathways in isolated cardiac fibroblast and cardiomyocytes, suggesting that its biological effect and underlying cardiac protection mechanisms are not limited to fibroblast and fibrosis alone. Our findings provide a proof of concept for repurposing NTB to combat adverse myocardial fibrosis and encourage the need for further validation in large animal models and subsequent clinical development for HF patients.

Regulation of Mitochondrial Quality Control by Natural Drugs in the Treatment of Cardiovascular Diseases: Potential and Advantages

Mitochondria are double-membraned cellular organelles that provide the required energy and metabolic intermediates to cardiomyocytes. Mitochondrial respiratory chain defects, structure abnormalities, and DNA mutations can affect the normal function of cardiomyocytes, causing an imbalance in intracellular calcium ion homeostasis, production of reactive oxygen species, and apoptosis. Mitochondrial quality control (MQC) is an important process that maintains mitochondrial homeostasis in cardiomyocytes and involves multi-level regulatory mechanisms, such as mitophagy, mitochondrial fission and fusion, mitochondrial energy metabolism, mitochondrial antioxidant system, and mitochondrial respiratory chain. Furthermore, MQC plays a role in the pathological mechanisms of various cardiovascular diseases (CVDs). In recent years, the regulatory effects of natural plants, drugs, and active ingredients on MQC in the context of CVDs have received significant attention. Effective active ingredients in natural drugs can influence the production of energy-supplying substances in the mitochondria, interfere with the expression of genes associated with mitochondrial energy requirements, and regulate various mechanisms of MQC modulation. Thus, these ingredients have therapeutic effects against CVDs. This review provides useful information about novel treatment options for CVDs and development of novel drugs targeting MQC.

Cardiovascular Changes Associated with Hypertensive Heart Disease and Aging

Cardiovascular diseases are the leading cause of mortality and morbidity worldwide and account for more than 17.9 million deaths (World Health Organization report). Hypertension and aging are two major risk factors for the development of cardiac structural and functional abnormalities. Hypertension, or elevated blood pressure, if left untreated can result in myocardial hypertrophy leading to heart failure (HF). Left ventricular hypertrophy consequent to pressure overload is recognized as the most important predictor of congestive HF and sudden death. The pathological changes occurring during hypertensive heart disease are very complex and involve many cellular and molecular alterations. In contrast, the cardiac changes that occur with aging are a slow but life-long process and involve all of the structural components in the heart and vasculature. However, these structural changes in the cardiovascular system lead to alterations in overall cardiac physiology and function. The pace at which these pathophysiological changes occur varies between individuals owing to many genetic and environmental risk factors. This review highlights the molecular mechanisms of cardiac structural and functional alterations associated with hypertension and aging.

The Functions of Mitochondrial 2',3'-Cyclic Nucleotide-3'-Phosphodiesterase and Prospects for Its Future

2′,3′-cyclic nucleotide-3′-phosphodiesterase (CNPase) is a myelin-associated enzyme that catalyzes the phosphodiester hydrolysis of 2’,3’-cyclic nucleotides to 2’-nucleotides. However, its presence is also found in unmyelinated cells and other cellular structures. Understanding of its specific physiological functions, particularly in unmyelinated cells, is still incomplete. This review concentrates on the role of mitochondrial CNPase (mtCNPase), independent of myelin. mtCNPase is able to regulate the functioning of the mitochondrial permeability transition pore (mPTP), and thus is involved in the mechanisms of cell death, both apoptosis and necrosis. Its participation in the development of various diseases and pathological conditions, such as aging, heart disease and alcohol dependence, is also reviewed. As such, mtCNPase can be considered as a potential target for the development of therapeutic strategies in the treatment of mitochondria-related diseases.

Crosstalk between GSK-3β-actuated molecular cascades and myocardial physiology

The finding of "glycogen synthase kinase-3" (GSK-3) was initially identified as a protein kinase that phosphorylate and inhibited glycogen synthase. However, it was soon discovered that GSK-3 also has significant impact in regulation of truly astonishing number of critical intracellular signaling pathways ranging from regulation of cell growth, neurology, heart failure, diabetes, aging, inflammation, and cancer. Recent studies have validated the feasibility of targeting GSK-3 for its vital therapeutic potential to maintain normal myocardial homeostasis, conversely, its loss is incompatible with life as it can abrupt cell cycle and endorse fatal cardiomyopathy. The current study focuses on its expanding therapeutic action in myocardial tissue, concentrating primarily on its role in diabetes-associated cardiac complication, apoptosis and metabolism, heart failure, cardiac hypertrophy, and myocardial infarction. The current report also includes the finding of our previous investigation that has shown the impact of GSK-3β inhibitor against diabetes-associated myocardial injury and experimentally induced myocardial infarction. We have also discussed some recent identified GSK-3β inhibitors for their cardio-protective potential. The crosstalk of various underlying mechanisms that highlight the significant role of GSK-3β in myocardial pathophysiology have been discussed in the present report. For these literatures, we will rely profoundly on our previous studies and those of others to reconcile some of the deceptive contradictions in the literature.

Emerging roles of GSK-3α in pathophysiology: Emphasis on cardio-metabolic disorders

Glycogen synthase kinase-3 (GSK-3) is a widely expressed serine/threonine kinase regulates a variety of cellular processes including proliferation, differentiation and death. Mammals harbor two structurally similar isoforms GSK-3α and β that have overlapping as well as unique functions. Of the two, GSK-3β has been studied (and reviewed) in far greater detail with analysis of GSK-3α often as an afterthought. It is now evident that systemic, chronic inhibition of either GSK-3β or both GSK-3α/β is not clinically feasible and if achieved would likely lead to adverse clinical conditions. Emerging evidence suggests important and specific roles for GSK-3α in fatty acid accumulation, insulin resistance, amyloid-β-protein precursor metabolism, atherosclerosis, cardiomyopathy, fibrosis, aging, fertility, and in a variety of cancers. Selective targeting of GSK-3α may present a novel therapeutic opportunity to alleviate a number of pathological conditions. In this review, we assess the evidence for roles of GSK-3α in a variety of pathophysiological settings.

Nicotinamide riboside kinase-2 alleviates ischemia-induced heart failure through P38 signaling

Nicotinamide riboside kinase-2 (NRK-2), a muscle-specific β1 integrin binding protein, predominantly expresses in skeletal muscle with a trace amount expressed in healthy cardiac tissue. NRK-2 expression dramatically increases in mouse and human ischemic heart however, the specific role of NRK-2 in the pathophysiology of ischemic cardiac diseases is unknown. We employed NRK2 knockout (KO) mice to identify the role of NRK-2 in ischemia-induced cardiac remodeling and dysfunction. Following myocardial infarction (MI), or sham surgeries, serial echocardiography was performed in the KO and littermate control mice. Cardiac contractile function rapidly declined and left ventricular interior dimension (LVID) was significantly increased in the ischemic KO vs. control mice at 2 weeks post-MI. An increase in mortality was observed in the KO vs. control group. The KO hearts displayed increased cardiac hypertrophy and heart failure reflected by morphometric analysis. Consistently, histological assessment revealed an extensive and thin scar and dilated LV chamber accompanied with elevated fibrosis in the KOs post-MI. Mechanistically, we observed that loss of NRK-2 enhanced p38α activation following ischemic injury. Consistently, ex vivo studies demonstrated that the gain of NRK-2 function suppresses the p38α as well as fibroblast activation (α-SMA expression) upon TGF-β stimulation, and limits cardiomyocytes death upon hypoxia/re‑oxygenation. Collectively our findings show, for the first time, that NRK-2 plays a critical role in heart failure progression following ischemic injury. NRK-2 deficiency promotes post-MI scar expansion, rapid LV chamber dilatation, cardiac dysfunction and fibrosis possibly due to increased p38α activation.