Cardiac ankyrin repeat protein attenuates cardiomyocyte apoptosis by upregulation of Bcl-2 expression

Research progress of ankyrin repeat domain 1 protein: an updated review

Ankyrin repeat domain 1 (Ankrd1) is an acute response protein that belongs to the muscle ankyrin repeat protein (MARP) family. Accumulating evidence has revealed that Ankrd1 plays a crucial role in a wide range of biological processes and diseases. This review consolidates current knowledge on Ankrd1's functions in myocardium and skeletal muscle development, neurogenesis, cancer, bone formation, angiogenesis, wound healing, fibrosis, apoptosis, inflammation, and infection. The comprehensive profile of Ankrd1 in cardiovascular diseases, myopathy, and its potential as a candidate prognostic and diagnostic biomarker are also discussed. In the future, more studies of Ankrd1 are warranted to clarify its role in diseases and assess its potential as a therapeutic target.

ANKRD1 Promotes Breast Cancer Metastasis by Activating NF-κB-MAGE-A6 Pathway

Early detection and surgical excision of tumors have helped improve the survival rate of patients with breast cancer. However, patients with metastatic cancer typically have a poor prognosis. In this study, we propose that ANKRD1 promotes metastasis of breast cancer. ANKRD1 was found to be highly expressed in the MDA-MB-231 and MDA-LM-2 highly metastatic breast cancer cell lines compared to the non-metastatic breast cancer cell lines (MCF-7, ZR-75-30, T47D) and normal breast cancer cells (MCF-10A). Furthermore, high-grade tumors showed increased levels of ANKRD1 compared to low-grade tumors. Both in vitro and in vivo functional studies demonstrated the essential role of ANKRD1 in cancer cell migration and invasion. The previous studies have suggested a significant role of NF-κB and MAGE-A6 in breast cancer metastasis, but the upstream regulators of this axis are not well characterized. Our study suggests that ANKRD1 promotes metastasis of breast cancer by activating NF-κB as well as MAGE-A6 signaling. Our findings show that ANKRD1 is a potential therapeutic target and a diagnostic marker for breast cancer metastasis.

Is the Hippo Pathway Effector Yes-Associated Protein a Potential Key Player of Dairy Cattle Cystic Ovarian Disease Pathogenesis?

Cystic ovarian disease (COD) in dairy cattle is characterized by preovulatory follicles that become cysts, fail to ovulate and persist in the ovary; consequently, interfering with normal ovarian cyclicity. The intraovarian key players that orchestrate the alterations occurring in the preovulatory follicle and that culminate with cyst formation and persistence, however, remain uncertain. Interestingly, the Hippo pathway effector yes-associated protein (YAP) has been described in humans and mice as a key player of anovulatory cystic disorders. To start elucidating if YAP deregulation in ovarian follicle cells can be also involved in the pathogenesis of COD, we have generated a series of novel results using spontaneously occurring cystic follicles in cattle. We found that mRNA and protein levels of YAP are significantly higher in granulosa (GCs) and theca cells (TCs) isolated from cystic follicles (follicular structures of at least 20 mm in diameter) in comparison to respective cell types isolated from non-cystic large follicles (≥12 mm). In addition, immunohistochemistry and Western blot analyses used to determine YAP phosphorylation pattern suggest that YAP transcriptional activity is augmented is cystic GCs. These results were confirmed by a significant increase in the mRNA levels encoding for the classic YAP-TEAD transcriptional target genes CTGF, BIRC5 and ANKRD1 in GCs from follicle cysts in comparison to non-cystic large follicles. Taken together, these results provide considerable insight of a completely novel signaling pathway that seems to play an important role in ovarian cystic disease pathogenesis in dairy cattle.

Transcription Factors Involved in the Development and Prognosis of Cardiac Remodeling

To compensate increasing workload, heart must work harder with structural changes, indicated by increasing size and changing shape, causing cardiac remodeling. However, pathological and unlimited compensated cardiac remodeling will ultimately lead to decompensation and heart failure. In the past decade, numerous studies have explored many signaling pathways involved in cardiac remodeling, but the complete mechanism of cardiac remodeling is still unrecognized, which hinders effective treatment and drug development. As gene transcriptional regulators, transcription factors control multiple cellular activities and play a critical role in cardiac remodeling. This review summarizes the regulation of fetal gene reprogramming, energy metabolism, apoptosis, autophagy in cardiomyocytes and myofibroblast activation of cardiac fibroblasts by transcription factors, with an emphasis on their potential roles in the development and prognosis of cardiac remodeling.

Understanding the molecular basis of cardiomyopathy

Inherited cardiomyopathies are a major cause of mortality and morbidity worldwide and can be caused by mutations in a wide range of proteins located in different cellular compartments. The present review is based on Dr. Ju Chen's 2021 Robert M. Berne Distinguished Lectureship of the American Physiological Society Cardiovascular Section, in which he provided an overview of the current knowledge on the cardiomyopathy-associated proteins that have been studied in his laboratory. The review provides a general summary of the proteins in different compartments of cardiomyocytes associated with cardiomyopathies, with specific focus on the proteins that have been studied in Dr. Chen's laboratory.

Irisin Enhances Angiogenesis of Mesenchymal Stem Cells to Promote Cardiac Function in Myocardial Infarction via PI3k/Akt Activation

Background and Objectives

With the growing incidence of acute myocardial infarction (MI), angiogenesis is vital for cardiac function post-MI. The role of bone marrow mesenchymal stem cells (BMSCs) in angiogenesis has been previously confirmed. Irisin is considered a potential vector for angiogenesis. The objective of the present study was to investigate the potential role of irisin in the angiogenesis of BMSCs.

Methods and Results

In vivo, irisin-treated BMSCs (BMSCs＋irisin) were transplanted into an MI mouse model. On day 28 post-MI, blood vessel markers were detected, and cardiac function and infarct areas of mice were evaluated. In vitro, paracrine effects were assessed by examining tube formation in human umbilical vein endothelial cells (HUVECs) co-cultured with the BMSCs＋irisin supernatant. The scratch wound-healing assay was performed to evaluate HUVEC migration. Western blotting was performed to determine PI3k/Akt pathway activation in the BMSCs＋irisin group. Transplantation of BMSCs＋irisin promoted greater angiogenesis, resulting in better cardiac function in the MI mouse model than in controls. In the BMSC＋irisin group, HUVECs demonstrated enhanced tube formation and migration. Activation of the PI3k/Akt pathway was found to be involved in mediating the role of irisin in the angiogenesis of BMSCs.

Conclusions

In cardiovascular diseases such as MI, irisin administration can enhance angiogenesis of BMSCs and promote cardiac function via the PI3k/Akt pathway, optimizing the therapeutic effect based on BMSCs transplantation.

Cardiac ankyrin repeat protein contributes to dilated cardiomyopathy and heart failure

Cardiac ankyrin repeat protein (CARP) is a cardiac-specific stress-response protein which exerts diverse effects to modulate cardiac remodeling in response to pathological stimuli. We examined the role of CARP in postnatal cardiac development and function under basal conditions in mice. Transgenic mice that selectively overexpressed CARP in heart (CARP Tg) exhibited dilated cardiac chambers, impaired heart function, and cardiac fibrosis as assessed by echocardiography and histological staining. Furthermore, the mice had a shorter lifespan and reduced survival rate in response to ischemic acute myocardial infarction. Immunofluorescence demonstrated the overexpressed CARP protein was predominantly accumulated in the nuclei of cardiomyocytes. Microarray analysis revealed that the nuclear localization of CARP was associated with the suppression of calcium-handling proteins. In vitro experiments revealed that CARP overexpression resulted in decreased cell contraction and calcium transient. In post-mortem cardiac specimens from patients with dilated cardiomyopathy and end-stage heart failure, CARP was significantly increased. Taken together, our data identified CARP as a crucial contributor in dilated cardiomyopathy and heart failure which was associated with its regulation of calcium-handling proteins.

SRT1720 Pretreatment Promotes Mitochondrial Biogenesis of Aged Human Mesenchymal Stem Cells and Improves Their Engraftment in Postinfarct Nonhuman Primate Hearts

Declined function of aged mesenchymal stem cells (MSCs) diminishes the benefits of cell therapy for myocardial infarction (MI). Our previous study has demonstrated that SRT1720, a specific SIRT1 activator, could protect aged human MSCs (hMSCs) against apoptosis. The purpose of the present study was to investigate the role of mitochondria in the antiapoptotic effects of SRT1720. In addition, we established a nonhuman primate MI model to evaluate cell engraftment of SRT1720-pretreated aged hMSCs (SRT1720-OMSCs). A hydrogen peroxide (H₂O₂)-induced apoptosis model was established in vitro to mimic MI microenvironment. Compared with vehicle-treated aged hMSCs (Vehicle-OMSCs), SRT1720-OMSCs showed alleviated apoptosis level, significantly decreased caspase-3 and caspase-9 activation, and reduced release of cytochrome c when subjected to H₂O₂ treatment. Mitochondrial contents were compared between young and aged hMSCs and our data showed that aged hMSCs had lower mitochondrial DNA (mtDNA) copy numbers and protein expression levels of components of the mitochondrial electron transport chain (ETC) than young hMSCs. Also, treatment with SRT1720 resulted in enhanced MitoTracker staining, increased mtDNA levels and expression of mitochondrial ETC components in aged hMSCs. Furthermore, SRT1720-OMSCs exhibited elevated mitochondrial respiratory capacity and higher mitochondrial membrane potential. In vivo study demonstrated that SRT1720-OMSCs had higher engraftment rates than Vehicle-OMSCs at 3 days after transplantation into the infarcted nonhuman primate hearts. Taken together, these results suggest that SRT1720 promotes mitochondrial biogenesis and function of aged hMSCs, which is involved in its protective effects against H₂O₂-induced apoptosis. These findings encourage further exploration of the optimization of aged stem cells function via regulating mitochondrial function.

Overexpression of Activating Transcription Factor 3 Alleviates Cardiac Microvascular Ischemia/Reperfusion Injury in Rats

Activating transcription factor 3 (ATF3) has been confirmed to be responsive to oxidative stress and to negatively regulate the activity of Toll-like receptor 4 (TLR4). However, the effect of ATF3 on cardiac microvascular ischemia/reperfusion (I/R) injury remains unknown. The GEO2R online tool was employed to obtain differentially expressed genes GSE4105 and GSE122020, in two rat I/R injury microarray datasets. We established a rat myocardial I/R model in vivo, and also generated an in vitro hypoxia/reoxygenation (H/R) model of cardiomyoblast H9c2 cells. Overexpression of ATF3 was achieved by adenoviral-mediated gene transfer (Ad-ATF3). Rats were randomly divided into four groups: sham, I/R, I/R + Ad-Lacz (as a control), and I/R + Ad-ATF3. ELISA, CCK-8, DCFH-DA probe, qRT-PCR and Western blotting were used to determine the expression of ATF3, oxidative indices, cellular injury and TLR4/NF-κB pathway-associated proteins. Transmission electron microscopy, immunohistochemistry and immunofluorescence were used to detect the leukocyte infiltration and the alteration of microvascular morphology and function in vivo. Echocardiographic and hemodynamic data were also obtained. Bioinformatics analysis revealed that ATF3 was upregulated in I/R myocardia in two independent rat myocardial I/R models. Cardiac microvascular I/R injury included leukocyte infiltration, microvascular integrity disruption, and microvascular perfusion defect, which eventually resulted in the deterioration of hemodynamic parameters and heart function. Ad-ATF3 significantly restored microvascular function, increased cardiac microvascular perfusion, and improved hemodynamic parameters and heart function. Mechanistically, Ad-ATF3 ameliorated oxidative stress, inhibited TLR4/NF-κB pathway activation and down-regulated the expression of downstream proinflammatory cytokines in I/R myocardium in vivo and in H/R H9c2 cells in vitro. ATF3 overexpression protects against cardiac microvascular I/R injury in part by inhibiting the TLR4/NF-κB pathway and oxidative stress.

Extracellular vesicles from anoxia preconditioned mesenchymal stem cells alleviate myocardial ischemia/reperfusion injury

Extracellular vesicles (EVs) produced by anoxia-preconditioned mesenchymal stem cells (MSCs) may afford greater cardioprotection against myocardial ischemia-reperfusion injury (MIRI) than EVs derived from normoxic MSCs. Here, we isolated EVs from mouse adipose-derived MSCs (ADSCs) subjected to anoxia preconditioning or normoxia and evaluated their ability to promote survival of mouse cardiomyocytes following MIRI in vivo and anoxia/reoxygenation (AR) in vitro. Injection of anoxia-preconditioned ADSC EVs (Int-EVs) reduced both infarct size and cardiomyocyte apoptosis to a greater extent than normoxic ADSC EVs (NC-EVs) in mice subjected to MIRI. Sequencing EV-associated miRNAs revealed differential upregulation of ten miRNAs predicted to bind thioredoxin-interacting protein (TXNIP), an inflammasome- and pyroptosis-related protein. We confirmed direct binding of miRNA224-5p, the most upregulated miRNA in Int-EVs, to TXNIP and asserted through western blotting and apoptosis assays a critical protective role for this miRNA against AR-induced cardiomyocyte death. Our results suggest that ischemia-reperfusion triggers TXNIP-induced inflammasome activation in cardiomyocytes, which leads to apoptosis rather than pyroptosis due to low basal levels of the pyroptosis executioner protein gasdermin D in these cells. The antiapoptotic effect of EV-associated miRNA224-5p would in turn result from TXNIP downregulation, which prevents caspase-1-mediated degradation of GATA4 and sustains the expression of Bcl-2.

Leptin enhances glycolysis via OPA1-mediated mitochondrial fusion to promote mesenchymal stem cell survival

Transplantation of mesenchymal stem cells (MSCs) is emerging as a potential therapy for cardiovascular diseases. However, the poor survival of transplanted MSCs is a major obstacle to improving their clinical efficacy. Accumulating evidence indicates that hypoxic preconditioning (HPC) can improve the survival of MSCs. It has been previously reported that leptin plays a critical role in HPC‑enhanced MSC survival through increasing optic atrophy 1 (OPA1)‑dependent mitochondrial fusion. Survival of MSCs mainly relies on glycolysis as an energy source. The close relationship between leptin and glucose homeostasis has attracted intense scientific interest. Furthermore, emerging evidence indicates that mitochondrial dynamics (fusion and fission) are associated with alterations in glycolysis. The aim of the present study was to investigate whether leptin increases MSC survival through metabolic regulation. Leptin‑modulated increased OPA1 expression was found to be associated with increased glycolysis. However, the glycolytic efficacy of leptin was abrogated after silencing OPA1 using a selective siRNA, suggesting that OPA1 directly regulates glycolysis. Furthermore, the activation of sodium‑glucose symporter 1 (SGLT1) was markedly induced by leptin. However, leptin‑induced glycolysis was primarily blocked by SGLT1 inhibitor treatment. Thus, leptin regulates OPA1‑dependent glycolysis to improve MSC survival primarily through SGLT1 activation. We therefore identified a pivotal leptin/OPA1/SGLT1 signaling pathway for mitochondrial dynamic‑mediated glycolysis, which may optimize the therapeutic efficiency of MSCs.

Ankyrin repeat domain 1: A novel gene for cardiac septal defects

INTRODUCTION

Cardiac septal defects account for more than 50% of congenital heart defects. Ankyrin repeat domain 1 (ANKRD1) is an important transcription factor that is mutated in multiple cardiac diseases; however, a relationship between the ANKRD1 mutation and cardiac septal defects has not been described.

METHODS

We examined genetic mutations in a large family with three cardiac septal defect patients. Whole exome sequencing, bioinformatics and conservation analysis were utilized to predict the pathogenicity of candidate mutations. Dual luciferase reporter assay and nuclear localization experiments were performed to evaluate the influence of target mutation.

RESULTS

A heterozygous, missense variant of ANKRD1 (MIM* 609599): NM_014391: exon6: c.C560T:p.S187F was identified at a highly conserved region. Sanger sequencing in extended family members demonstrated an incomplete inheritance model. When co-activated with NKX2.5, ANKRD1 repressed ANF expression as assessed by a dual-luciferase reporter assay, and p.S187F mutation enhanced the repressive effect (0.318 ± 0.018 versus 0.564 ± 0.048, p < 0.01). A real-time polymerase chain reaction confirmed that p.S187F mutation of ANKRD1 decreased the expression of endogenous ANF (0.85 ± 0.05 versus 0.61 ± 0.04, p < 0.01). Furthermore, nuclear localization experiments demonstrated that the mutation significantly decreased the nuclear distribution of ANKRD1.

CONCLUSIONS

The present study is the first to identify the p.S187F mutant of ANKRD1, which is associated with cardiac septal defects.

Protective effects of saffron and its active components against oxidative stress and apoptosis in endothelial cells

In this study, we investigated the role of mitogen-activated protein kinase (MAPK) signaling pathways in mediation of the protective effects of saffron extract, saffron essential oil, safranal and crocin on bovine aortic endothelial cells against oxidative injury. The viability of cells in response to H₂O₂-induced toxicity (0.4, 2 and 10 mM) was measured using resazurin assay in the presence or absence of saffron extract (2-40 μg/ml), saffron oil (2-40 μg/ml), safranal (2-40 μM) and crocin (2-40 μM). Dichlorodihydrofluorescin diacetate was used as an indicator for the amount of reactive oxygen species (ROS) in cells at the same concentrations of samples as the former test. In addition, propidium iodide staining of the fragmented DNA was performed to measure the level of apoptotic cells by the application of 2-10 μM of crocin and safranal. Finally, the proteins involved in apoptosis were detected using western blotting at the concentration of 0, 2, 10 μM for crocin and safranal. The results indicated that all tested moieties improved viability and reduced ROS production in H₂O₂-treated cells (p < 0.001 compared to H₂O₂). In addition, a significant decrease in apoptosis (3-35%) was observed in the cells that were treated with crocin and safranal. The observed protective effects of crocin and safranal were associated with the activation of SAPK/JNK and inhibition of ERK ½ that are related to MAPK pathways. The antioxidant and anti-apoptotic activities of saffron and its ingredients in endothelial cells are mediated via MAPK signaling pathways and might be of therapeutic potential for endothelial dysfunctionalities.

Myocardial reparative functions of exosomes from mesenchymal stem cells are enhanced by hypoxia treatment of the cells via transferring microRNA-210 in an nSMase2-dependent way

Hypoxia treatment enhances paracrine effect of mesenchymal stem cells (MSCs). The aim of this study was to investigate whether exosomes from hypoxia-treated MSCs (Exo^H) are superior to those from normoxia-treated MSCs (Exo^N) for myocardial repair. Mouse bone marrow-derived MSCs were cultured under hypoxia or normoxia for 24 h, and exosomes from conditioned media were intramyocardially injected into infarcted heart of C57BL/6 mouse. Exo^H resulted in significantly higher survival, smaller scar size and better cardiac functions recovery. Exo^H conferred increased vascular density, lower cardiomyocytes (CMs) apoptosis, reduced fibrosis and increased recruitment of cardiac progenitor cells in the infarcted heart relative to Exo^N. MicroRNA analysis revealed significantly higher levels of microRNA-210 (miR-210) in Exo^H compared with Exo^N. Transfection of a miR-210 mimic into endothelial cells (ECs) and CMs conferred similar biological effects as Exo^H. Hypoxia treatment of MSCs increased the expression of neutral sphingomyelinase 2 (nSMase2) which is crucial for exosome secretion. Blocking the activity of nSMase2 resulted in reduced miR-210 secretion and abrogated the beneficial effects of Exo^H. In conclusion, hypoxic culture augments miR-210 and nSMase2 activities in MSCs and their secreted exosomes, and this is responsible at least in part for the enhanced cardioprotective actions of exosomes derived from hypoxia-treated cells.

Electron leak from NDUFA13 within mitochondrial complex I attenuates ischemia-reperfusion injury via dimerized STAT3

Reactive oxygen species (ROS) generation due to electron leak from the mitochondria may be involved in physiological or pathological processes. NDUFA13 is an accessory subunit of mitochondria complex I with a unique molecular structure and is located close to FeS clusters with low electrochemical potentials. Here, we generated cardiac-specific conditional NDUFA13 heterozygous knockout mice. At the basal state, a moderate down-regulation of NDUFA13 created a leak within complex I, resulting in a mild increase in cytoplasm localized H₂O₂, but not superoxide. The resultant ROS served as a second messenger and was responsible for the STAT3 dimerization and, hence, the activation of antiapoptotic signaling, which eventually significantly suppressed the superoxide burst and decreased the infarct size during the ischemia-reperfusion process.

The causative relationship between specific mitochondrial molecular structure and reactive oxygen species (ROS) generation has attracted much attention. NDUFA13 is a newly identified accessory subunit of mitochondria complex I with a unique molecular structure and a location that is very close to the subunits of complex I of low electrochemical potentials. It has been reported that down-regulated NDUFA13 rendered tumor cells more resistant to apoptosis. Thus, this molecule might provide an ideal opportunity for us to investigate the profile of ROS generation and its role in cell protection against apoptosis. In the present study, we generated cardiac-specific tamoxifen-inducible NDUFA13 knockout mice and demonstrated that cardiac-specific heterozygous knockout (cHet) mice exhibited normal cardiac morphology and function in the basal state but were more resistant to apoptosis when exposed to ischemia-reperfusion (I/R) injury. cHet mice showed a preserved capacity of oxygen consumption rate by complex I and II, which can match the oxygen consumption driven by electron donors of N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD)+ascorbate. Interestingly, at basal state, cHet mice exhibited a higher H₂O₂ level in the cytosol, but not in the mitochondria. Importantly, increased H₂O₂ served as a second messenger and led to the STAT3 dimerization and, hence, activation of antiapoptotic signaling, which eventually significantly suppressed the superoxide burst and decreased the infarct size during the I/R process in cHet mice.

EphrinB2 Regulates Cardiac Fibrosis Through Modulating the Interaction of Stat3 and TGF-β/Smad3 Signaling

RATIONALE

Cardiac fibrosis is a common feature in left ventricular remodeling that leads to heart failure, regardless of the cause. EphrinB2 (erythropoietin-producing hepatoma interactor B2), a pivotal bidirectional signaling molecule ubiquitously expressed in mammals, is crucial in angiogenesis during development and disease progression. Recently, EphrinB2 was reported to protect kidneys from injury-induced fibrogenesis. However, its role in cardiac fibrosis remains to be clarified.

OBJECTIVE

We sought to determine the role of EphrinB2 in cardiac fibrosis and the underlying mechanisms during the pathological remodeling process.

METHODS AND RESULTS

EphrinB2 was highly expressed in the myocardium of patients with advanced heart failure, as well as in mouse models of myocardial infarction and cardiac hypertrophy induced by angiotensin II infusion, which was accompanied by myofibroblast activation and collagen fiber deposition. In contrast, intramyocardial injection of lentiviruses carrying EphrinB2-shRNA ameliorated cardiac fibrosis and improved cardiac function in mouse model of myocardial infarction. Furthermore, in vitro studies in cultured cardiac fibroblasts demonstrated that EphrinB2 promoted the differentiation of cardiac fibroblasts into myofibroblasts in normoxic and hypoxic conditions. Mechanistically, the profibrotic effect of EphrinB2 on cardiac fibroblast was determined via activating the Stat3 (signal transducer and activator of transcription 3) and TGF-β (transforming growth factor-β)/Smad3 (mothers against decapentaplegic homolog 3) signaling. We further determined that EphrinB2 modulated the interaction between Stat3 and Smad3 and identified that the MAD homology 2 domain of Smad3 and the coil-coil domain and DNA-binding domain of Stat3 mediated the interaction.

CONCLUSIONS

This study uncovered a previously unrecognized profibrotic role of EphrinB2 in cardiac fibrosis, which is achieved through the interaction of Stat3 with TGF-β/Smad3 signaling, implying a promising therapeutic target in fibrotic diseases and heart failure.

Iodine-131 induces apoptosis in human cardiac muscle cells through the p53/Bax/caspase-3 and PIDD/caspase-2/ t‑BID/cytochrome c/caspase-3 signaling pathway

The aim of this study was to elucidate the effects of iodine-131 on the induction of apoptosis in human cardiac muscle cells and the underlying molecular mechanisms. We found that iodine-131 reduced cell proliferation, induced apoptosis, induced p53, PIDD, t-BID (mitochondria) protein expression, suppressed cytochrome c (mitochondria) protein expression, and increased Bax protein expression, and promoted caspase-2, -3 and -9 expression levels in human cardiac muscle cells. Meanwhile, si-p53 inhibited the effects of iodine-131 on the reduction in cell proliferation and induction of apoptosis in human cardiac muscle cells through regulation of Bax/cytochrome c/caspase-3 and PIDD/caspase‑2/t-BID/cytochrome c/caspase-3 signaling pathway. After si-Bax reduced the effects of iodine-131, it reduced cell proliferation and induced apoptosis in human cardiac muscle cells through the cytochrome c/caspase-3 signaling pathway. However, si-caspase-2 also reduced the effects of iodine-131 on the reduction of cell proliferation and induction of apoptosis in human cardiac muscle cells through the t-BID/cytochrome c/caspase-3 signaling pathway. These findings demonstrated that iodine-131 induces apoptosis in human cardiac muscle cells through the p53/Bax/caspase-3 and PIDD/caspase-2/t-BID/cytochrome c/caspase-3 signaling pathway.

Ankyrin Repeat Domain 1 Protein: A Functionally Pleiotropic Protein with Cardiac Biomarker Potential

The ankyrin repeat domain 1 (ANKRD1) protein is a cardiac-specific stress-response protein that is part of the muscle ankyrin repeat protein family. ANKRD1 is functionally pleiotropic, playing pivotal roles in transcriptional regulation, sarcomere assembly and mechano-sensing in the heart. Importantly, cardiac ANKRD1 has been shown to be highly induced in various cardiomyopathies and in heart failure, although it is still unclear what impact this may have on the pathophysiology of heart failure. This review aims at highlighting the known properties, functions and regulation of ANKRD1, with focus on the underlying mechanisms that may be involved. The current views on the actions of ANKRD1 in cardiovascular disease and its utility as a candidate cardiac biomarker with diagnostic and/or prognostic potential are also discussed. More studies of ANKRD1 are warranted to obtain deeper functional insights into this molecule to allow assessment of its potential clinical applications as a diagnostic or prognostic marker and/or as a possible therapeutic target.

Downregulation of miR-200c protects cardiomyocytes from hypoxia-induced apoptosis by targeting GATA-4

Hypoxia-induced cardiomyocyte apoptosis plays an important role in the development of ischemic heart disease. MicroRNAs (miRNAs or miRs) are emerging as critical regulators of hypoxia-induced cardiomyocyte apoptosis. miR-200c is an miRNA that has been reported to be related to apoptosis in various pathological processes; however, its role in hypoxia‑induced cardiomyocyte apoptosis remains unclear. In the present study, we aimed to investigate the potential role and underlying mechanism of miR-200c in regulating hypoxia‑induced cardiomyocyte apoptosis. We found that miR-200c was significantly upregulated by hypoxia in cardiomyocytes, as detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The lactate dehydrogenase, MTT, Annexin V/propidium iodide apoptosis and caspase-3 activity assays showed that downregulation of miR-200c markedly improved cell survival and suppressed the apoptosis of cardiomyocytes in response to hypoxia. Bioinformatics analysis and the dual-luciferase reporter assay demonstrated that miR-200c directly targeted the 3'-untranslated region of GATA-4, an important transcription factor for cardiomyocyte survival. RT-qPCR and western blot analysis showed that suppression of miR-200c significantly increased GATA-4 expression. Furthermore, downregulation of miR-200c upregulated the expression of the anti-apoptotic gene Bcl-2. However, the protective effects against hypoxia induced by the downregulation of miR‑200c were significantly abolished by GATA-4 knockdown. Taken together, our results suggest that downregulation of miR-200c protects cardiomyocytes from hypoxia-induced apoptosis by targeting GATA-4, providing a potential therapeutic molecular target for the treatment of ischemic heart disease.

Differential Impacts of Alternative Splicing Networks on Apoptosis

Apoptosis functions as a common mechanism to eliminate unnecessary or damaged cells during cell renewal and tissue development in multicellular organisms. More than 200 proteins constitute complex networks involved in apoptotic regulation. Imbalanced expressions of apoptosis-related factors frequently lead to malignant diseases. The biological functions of several apoptotic factors are manipulated through alternative splicing mechanisms which expand gene diversity by generating discrete variants from one messenger RNA precursor. It is widely observed that alternatively-spliced variants encoded from apoptosis-related genes exhibit differential effects on apoptotic regulation. Alternative splicing events are meticulously regulated by the interplay between trans-splicing factors and cis-responsive elements surrounding the regulated exons. The major focus of this review is to highlight recent studies that illustrate the influences of alternative splicing networks on apoptotic regulation which participates in diverse cellular processes and diseases.