Mediating Cardiomyocyte Apoptosis Research Articles

Complement factor D derived from epicardial adipose tissue participates in cardiomyocyte apoptosis after myocardial infarction by mediating PARP-1 activity

BackgroundAcute myocardial infarction (MI) is considered to be the main cause of congestive heart failure. The aim of this study was to provide an in-depth analysis of athophysiological processes and provide key targets for intervention in the occurrence of acute MI. MethodsA rat model of MI was established by ligation of left anterior descending branch. Heart tissue, epicardial adipose tissue (EAT) and subcutaneous adipose tissue (SAT) were collected. H9c2 cells were used to explore the mechanism of complement factor D (CFD) regulating cardiomyocyte apoptosis. ResultsMyocardial apoptosis were observed in MI rat, and more EAT was found in the MI group in vivo. The conditioned medium prepared by EAT (EAT-CM) significantly reduced the activity of H9c2 cells. The content of CFD in EAT was significantly increased, and CFD promoted cardiomyocyte apoptosis in vitro and CFD-IN1 (a selective inhibitor of CFD) could revised this effect. CFD induced poly ADP-ribosepolymerase-1 (PARP-1) overactivation. Furthermore, the addition of pan-caspase inhibitor Z-VAD in the SAT-CM + CFD group couldn't affect H9c2 cell apoptosis. CFD induced cell apoptosis via PARP-1 activation and PARP-1 inhibitor 3-Aminobenzamide could revise this effect. The injection of CFD-IN1 in MI rat model confirmed that inhibition of CFD activity alleviated cardiomyocytes apoptosis. ConclusionOur findings indicate that EAT mediating cardiomyocyte apoptosis after MI through secretion of CFD and activation of PARP-1 activity.

Tax1 banding protein 1 exacerbates heart failure in mice by activating ITCH-P73-BNIP3-mediated cardiomyocyte apoptosis.

Tax1 banding protein 1 (Tax1bp1) was originally identified as an NF-κB regulatory protein that participated in inflammatory, antiviral and innate immune processes. Tax1bp1 also functions as an autophagy receptor that plays a role in autophagy. Our previous study shows that Tax1bp1 protects against cardiomyopathy in STZ-induced diabetic mice. In this study we investigated the role of Tax1bp1 in heart failure. Pressure overload-induced heart failure model was established in mice by aortic banding (AB) surgery, and angiotensin II (Ang II)-induced heart failure model was established by infusion of Ang II through osmotic minipump for 4 weeks. We showed that the expression levels of Tax1bp1 in the heart were markedly increased 2 and 4 weeks after AB surgery. Knockdown of Tax1bp1 in mouse hearts significantly ameliorated both AB- and Ang II infusion-induced heart failure parameters. On the contrary, AB-induced heart failure was aggravated in cardiac-specific Tax1bp1 transgenic mice. Similar results were observed in neonatal rat cardiomyocytes (NRCMs) under Ang II insult. We demonstrated that the pro-heart failure effect of Tax1bp1 resulted from its interaction with the E3 ligase ITCH to promote the transcription factor P73 ubiquitination and degradation, causing enhanced BCL2 interacting protein 3 (BNIP3)-mediated cardiomyocyte apoptosis. Knockdown ITCH or BNIP3 in NRCMs significantly reduced Ang II-induced apoptosis in vitro. Similarly, BNIP3 knockdown attenuated heart failure in cardiac-specific Tax1bp1 transgenic mice. In the left ventricles of heart failure patients, Tax1bp1 expression level was significantly increased; Tax1bp1 gene expression was negatively correlated with left ventricular ejection fraction in heart failure patients. Collectively, the Tax1bp1 increase in heart failure enhances ITCH-P73-BNIP3-mediated cardiomyocyte apoptosis and induced cardiac injury. Tax1bp1 may serve as a potent therapeutic target for the treatment of heart failure.• Cardiac Tax1bp1 transgene mice were more vulnerable to cardiac dysfunction under stress.• Cardiac Tax1bp1 transgene mice were more vulnerable to cardiac dysfunction under stress.• Knockout of Tax1bp1 in mouse hearts ameliorated heart failure induced by pressure overload.• Tax1bp1 interacts with the E3 ligase Itch to promote P73 ubiquitination and degradation, causing enhanced BNIP3-mediated apoptosis.• Tax1bp1 may become a target of new therapeutic methods for treating heart failure.

MiR-1/133 attenuates cardiomyocyte apoptosis and electrical remodeling in mice with viral myocarditis.

The role of miR-1 and miR-133 in regulating the expression of potassium and calcium ion channels, and mediating cardiomyocyte apoptosis in mice with viral myocarditis (VMC) is investigated herein. Male Balb/c mice were randomly divided into groups: control group, VMC group, VMC + miR-1/133 mimics group, or VMC + miR-1/133 negative control (NC) group. VMC was induced with coxsackievirus B3 (CVB3). MiR-1/133 mimics ameliorated cardiac dysfunction in VMC mice and was compared to the VMC+NC group. Hematoxylin and eosin staining showed a well-arranged myocardium without inflammatory cell infiltration in the myocardial matrix of the control group. However, in the VMC and VMC+NC groups, the myocardium was disorganized and swollen with necrosis, and the myocardial matrix was infiltrated with inflammatory cells. These changes were alleviated by miR-1/133 mimics. TUNEL staining revealed decreased cardiomyocyte apoptosis in the VMC + miR-1/133 mimics group compared with the VMC group. In addition, miR-1/133 mimics up-regulated the expression of miR-1 and miR-133, the potassium channel genes Kcnd2 and Kcnj2, as well as Bcl-2, and down-regulated the expression of the potassium channel suppressor gene Irx5, L-type calcium channel subunit gene a1c (Cacna1c), Bax, and caspase-9 in the myocardium of VMC mice. MiR-1/133 also up-regulated the protein levels of Kv4.2 and Kir2.1, and down-regulated the expression of CaV1.2 in the myocardium of VMC mice. MiR-1 and miR-133 decreased cardiomyocyte apoptosis by mediating the expression of apoptosis-related genes in the hearts of VMC mice.

Critical roles of microRNA-141-3p and CHD8 in hypoxia/reoxygenation-induced cardiomyocyte apoptosis

BackgroundCardiovascular diseases are currently the leading cause of death in humans. The high mortality of cardiac diseases is associated with myocardial ischemia and reperfusion (I/R). Recent studies have reported that microRNAs (miRNAs) play important roles in cell apoptosis. However, it is not known yet whether miR-141-3p contributes to the regulation of cardiomyocyte apoptosis. It has been well established that in vitro hypoxia/reoxygenation (H/R) model can follow in vivo myocardial I/R injury. This study aimed to investigate the effects of miR-141-3p and CHD8 on cardiomyocyte apoptosis following H/R.ResultsWe found that H/R remarkably reduces the expression of miR-141-3p but enhances CHD8 expression both in mRNA and protein in H9c2 cardiomyocytes. We also found either overexpression of miR-141-3p by transfection of miR-141-3p mimics or inhibition of CHD8 by transfection of small interfering RNA (siRNA) significantly decrease cardiomyocyte apoptosis induced by H/R. Moreover, miR-141-3p interacts with CHD8. Furthermore, miR-141-3p and CHD8 reduce the expression of p21.ConclusionMiR-141-3p and CHD8 play critical roles in cardiomyocyte apoptosis induced by H/R. These studies suggest that miR-141-3p and CHD8 mediated cardiomyocyte apoptosis may offer a novel therapeutic strategy against myocardial I/R injury-induced cardiovascular diseases.

SurR9C84A protects and recovers human cardiomyocytes from hypoxia induced apoptosis

Survivin, as an anti-apoptotic protein and a cell cycle regulator, is recently gaining importance for its regenerative potential in salvaging injured hypoxic cells of vital organs such as heart. Different strategies are being employed to upregulate survivin expression in dying hypoxic cardiomyocytes. We investigated the cardioprotective potential of a cell permeable survivin mutant protein SurR9C84A, for the management of hypoxia mediated cardiomyocyte apoptosis, in a novel and clinically relevant model employing primary human cardiomyocytes (HCM). The aim of this research work was to study the efficacy and mechanism of SurR9C84A facilitated cardioprotection and regeneration in hypoxic HCM. To mimic hypoxic microenvironment in vitro, well characterized HCM were treated with 100µm (48h) cobalt chloride to induce hypoxia. Hypoxia induced (HI) HCM were further treated with SurR9C84A (1µg/mL) in order to analyse its cardioprotective efficacy. Confocal microscopy showed rapid internalization of SurR9C84A and scanning electron microscopy revealed the reinstatement of cytoskeleton projections in HI HCM. SurR9C84A treatment increased cell viability, reduced cell death via, apoptosis (Annexin-V assay), and downregulated free cardiac troponin T and MMP-9 expression. SurR9C84A also upregulated the expression of proliferation markers (PCNA and Ki-67) and downregulated mitochondrial depolarization and ROS levels thereby, impeding cell death. Human Apoptosis Array further revealed that SurR9C84A downregulated expression of pro-apoptotic markers and augmented expression of HSPs and HTRA2/Omi. SurR9C84A treatment led to enhanced levels of survivin, VEGF, PI3K and pAkt. SurR9C84A proved non-toxic to normoxic HCM, as validated through unaltered cell proliferation and other marker levels. Its pre-treatment exhibited lesser susceptibility to hypoxia/damage. SurR9C84A holds a promising clinical potential for human cardiomyocyte survival and proliferation following hypoxic injury.

MicroRNA-93 inhibits ischemia-reperfusion induced cardiomyocyte apoptosis by targeting PTEN.

MicroRNAs have been implicated in some biological and pathological processes, including the myocardial ischemia/reperfusion (I/R) injury. Recent findings demonstrated that miR-93 might provide a potential cardioprotective effect on ischemic heart disease. This study was to investigate the role of miR-93 in I/R-induced cardiomyocyte injury and the potential mechanism. In this study, we found that hypoxia/reoxygenation (H/R) dramatically increased LDH release, MDA contents, ROS generation, and endoplasmic reticulum stress (ERS)-mediated cardiomyocyte apoptosis, which were attenuated by co-transfection with miR-93 mimic. Phosphatase and tensin homolog (PTEN) was identified as the target gene of miR-93. Furthermore, miR-93 mimic significantly increased p-Akt levels under H/R, which was partially released by LY294002. In addtion, Ad-miR-93 also attenuated myocardial I/R injury in vivo, manifested by reduced LDH and CK levels, infarct area and cell apoptosis. Taken together, our findings indicates that miR-93 could protect against I/R-induced cardiomyocyte apoptosis by inhibiting PI3K/AKT/PTEN signaling.

Salvianolic acid B protects against doxorubicin induced cardiac dysfunction via inhibition of ER stress mediated cardiomyocyte apoptosis.

Salvia miltiorrhiza Bunge is a well-known medicinal plant in China. Salvianolic acid B (Sal B) is the most abundant bioactive compound extracted from the root of S. miltiorrhiza. The present study investigates the effect of Sal B on cardiac function and cardiomyocyte apoptosis in doxorubicin (DOX)-treated mice. After pretreatment with Sal B (2 mg kg-1 iv) for 7 d, male BALB/c mice were injected with a single dose of DOX (20 mg kg-1 ip). The cardioprotective effect of Sal B was observed on the 7th day after DOX treatment. DOX caused retarded body growth, apoptotic damage, and Bcl-2 expression disturbance. In contrast, Sal B pretreatment (2 mg kg-1 iv before DOX administration) attenuated the DOX induced apoptotic damage in heart tissues. Further study indicated that Sal B protected against DOX induced cardiotoxicity, at least, partially, by inhibiting endoplasmic reticulum stress, and by being involved in the PI3K/Akt pathway. These findings clarified the potential of Sal B as a promising reagent for treating DOX induced cardiotoxicity.

MicroRNA-377 Mediates Cardiomyocyte Apoptosis Induced by Cyclosporin A

Cyclosporin A (CsA) is a potent immunosuppressant that has wide clinical applications for autoimmune disorders and prevention of rejection in organ transplantation. However, its liver, kidney, and heart toxicity has limited its use. In this study, we investigated the mechanism by which CsA induced cardiomyocyte apoptosis. Through microarray analysis, we found that the expression of microRNA (miR)-377 was regulated by CsA. Ectopic overexpression of miR-377 led to increased apoptosis in cardiomyocytes, as evidenced by an increased number of apoptotic cells, increased levels of proapoptotic proteins, decreased levels of antiapoptotic proteins, and elevated caspase pathway activity. We also found that miR-377 was required for CsA-induced apoptosis, because inhibition of miR-377 expression markedly reduced the ability of CsA to induce cardiomyocyte apoptosis. In addition, we identified XIAP and NRP2 as direct targets for miR-377. The expression levels of these 2 antiapoptotic proteins were negatively regulated by miR-377, as well as by CsA both in vitro and in vivo. Our data suggested that CsA induced cardiomyocyte apoptosis through the miR-377–XIAP/NRP2 axis.

Calpain-1 induces endoplasmic reticulum stress in promoting cardiomyocyte apoptosis following hypoxia/reoxygenation

Both calpain activation and endoplasmic reticulum (ER) stress are implicated in ischemic heart injury. However, the role of calpain in ER stress remains largely elusive. This study investigated whether calpain activation causes ER stress, thereby mediating cardiomyocyte apoptosis in an in vitro model of hypoxia/re-oxygenation (H/R). In neonatal mouse cardiomyocytes and rat cardiomyocyte-like H9c2 cells, up-regulation of calpain-1 sufficiently induced ER stress, c-Jun N-terminal protein kinase1/2 (JNK1/2) activation and apoptosis. Inhibition of ER stress or JNK1/2 prevented apoptosis induced by calpain-1. In an in vitro model of H/R-induced injury in cardiomyocytes, H/R was induced by a 24-hour hypoxia followed by a 24-hour re-oxygenation. H/R activated calpain-1, induced ER stress and JNK1/2 activation, and triggered apoptosis. Inhibition of calpain and ER stress blocked JNK1/2 activation and prevented H/R-induced apoptosis. Furthermore, blockade of JNK1/2 signaling inhibited apoptosis following H/R. The role of calpain in ER stress was also demonstrated in an in vivo model of ischemia/reperfusion using transgenic mice over-expressing calpastatin. In summary, calpain-1 induces ER stress and JNK1/2 activation, thereby mediating apoptosis in cardiomyocytes. Accordingly, inhibition of calpain prevents ER stress, JNK1/2 activation and apoptosis in H/R-induced cardiomyocytes. Thus, ER stress/JNK1/2 activation may represent an important mechanism linking calpain-1 to ischemic injury.

Myocardial 14-3-3η protein protects against mitochondria mediated apoptosis

There is a definite cardioprotective role for 14-3-3η protein against pressure overload induced cardiac hypertrophy and streptozotocin induced cardiac dysfunction in type 1 diabetes mellitus (DM). But it is not conclusive whether it has any influence on mitochondrial mediated cardiomyocyte apoptosis in type 2 DM. In order to test this hypothesis, we have used C57BL6/J (WT) mice with cardiac specific dominant negative mutation of 14-3-3η protein (DN 14-3-3η). Both WT and DN 14-3-3η mice were fed with high fat diet (HFD) for 12weeks. Their body weight and blood glucose levels were measured weekly and compared with standard diet (SD) fed mice. By the end of 12weeks, echocardiography was performed. Frozen myocardial sections were prepared to stain the apoptotic cardiomyocytes using TUNEL staining. DN 14-3-3η mice fed with HFD showed cardiac dysfunction as identified by the decreased fractional shortening and ejection fraction and increased cardiomyocyte apoptosis in TUNEL staining. Western blotting analysis using mitochondrial fraction of the ventricular tissue homogenates showed a significant reduction in the level of cytochrome c suggesting its translocation into cytoplasm, which may be crucial in inducing cardiomyocyte apoptosis. In addition, DN 14-3-3η mice depicted significantly increased levels of NADPH oxidase subunits suggesting oxidative stress, a significant reduction in phospho apoptosis signal-regulating kinase-1 (p-Ask-1) and increase in Ask-1 and phospho c-Jun N-terminal kinase (p-JNK) levels suggesting activation of Ask-1/JNK signaling. These results suggest that 14-3-3η has a protective role against mitochondria mediated cardiomyocyte apoptosis with the involvement of Ask-1/JNK signaling during HFD induced type 2 DM.

The stress-related hormone norepinephrine induced upregulation of Nix, contributing to ECM protein expression.

Organ fibrosis has been viewed as a major medical problem that leads to progressive dysfunction of the organ and eventually the death of patients. Stress-related hormone norepinephrine (NE) has been reported to exert fibrogenic actions in the injured organ. Nix plays a critical role in pressure overload-induced cardiac remodeling and heart failure through mediating cardiomyocyte apoptosis. However, cardiac remodeling also includes fibrosis. Whether Nix is involved in stress-induced fibrosis remains unclear. The present study was designed to determine the role of Nix in NE-induced NIH/3T3 fibroblasts. The results showed that Nix was upregulated and closely associated with cell proliferation, collagen and fibronectin expression in NIH/3T3 fibroblasts following NE treatment. Overexpression of Nix promoted collagen and fibronectin expression, whereas the suppression of Nix resulted in a strong reduction in collagen and fibronectin expression. Moreover, the increases in collagen and fibronectin expression induced by NE were successively increased when Nix was overexpressed and reduced when Nix was inhibited. Furthermore, we demonstrated that the PKC activation is responsible for the upregulation of Nix induced by NE. Inhibition of Nix expression with α-adrenoceptor antagonist, β-adrenoceptor antagonist or PKC inhibitor attenuated NE-induced collagen and fibronectin expression. Our data revealed that Nix is a novel mediator of NE-induced fibrosis. Thus, it would provide a new insight into the development of effective preventative measures and therapies of tissue fibrosis.

Pigment epithelium-derived factor promotes Fas-induced cardiomyocyte apoptosis via its receptor phospholipase A2

AimsCardiovascular diseases cause significant morbidity and mortality worldwide. Recently, our research team demonstrated that a multifunctional cytokine, pigment epithelium-derived factor (PEDF), plays a critical role in regulating myocardial infarction. However, few researchers have studied the molecular mechanisms by which PEDF and its receptors influence the pathophysiology of cardiovascular disease. We tested the hypothesis that PEDF affects cardiomyocyte apoptosis under hypoxic conditions and determined the role that its receptors phospholipase A2 (PLA2) and laminin receptor play in this process. Main methodsCardiomyocytes were isolated from neonatal mice and treated with PEDF under normoxic and hypoxic conditions; then, apoptosis was assessed using Annexin V/PI staining and flow cytometry. Western blotting and immunofluorescence staining were used to detect PEDF receptor expression, and siRNA knockdown of PEDF receptors was performed to determine which receptor was involved in mediating cardiomyocyte apoptosis. Key findingsOur results demonstrated that PEDF increased cardiomyocyte apoptosis during hypoxia via Fas and that PEDF receptors were expressed on cardiomyocyte cell membranes. Furthermore, siRNA experiments indicated that the PEDF receptor PLA2 was responsible for inducing cardiomyocyte apoptosis via the Fas pathway. SignificancePEDF promoted Fas-induced cardiomyocyte apoptosis via its receptor PLA2.

Hypoxic Postconditioning Inhibits Endoplasmic Reticulum Stress–Mediated Cardiomyocyte Apoptosis by Targeting PUMA

Postconditioning prevents cardiomyocytes from ischemia/reperfusion-induced apoptosis. However, little is known about the molecular mechanisms that mediate the cardioprotective effect of postconditioning. Here, we hypothesized that postconditioning targeted p53 upregulated modulator of apoptosis (PUMA) to protect cardiomyocytes against endoplasmic reticulum stress-mediated apoptosis. Our results demonstrated that postconditioning could inhibit GRP78 (78-kDa glucose-regulated protein) expression, caspase-12 activation, and cardiomyocyte apoptosis by regulating PUMA expression. In addition, p53 is involved in the regulatory role of postconditioning in PUMA expression. Our data reveal a cardioprotective pathway of postconditioning in which it represses PUMA.

Extracellular matrix protein CCN1 regulates cardiomyocyte apoptosis in mice with stress-induced cardiac injury

Expression of extracellular matrix protein CCN1 is induced in end-stage ischaemic cardiomyopathy in humans, and after cardiac ischaemia and reperfusion in experimental animal models. Despite its well-documented angiogenic activities, CCN1 increases the cytotoxicities of the tumour necrosis factor family cytokines, which promotes apoptosis in fibroblasts. We aimed to determine the physiological function of CCN1 in an injured heart. To assess the function of CCN1 in vivo, knock-in mice carrying the apoptosis-defective mutant allele Ccn1-dm were tested in an isoproterenol (ISO)-induced myocardial injury model (100 mg/kg/day of sc injected ISO for 5 days). Compared with wild-type mice, Ccn1(dm/dm) mice were remarkably resistant to ISO-induced cardiac injury; they showed no post-treatment cardiomyocyte apoptosis or myocardial tissue damage. ISO cardiotoxicity was dependent on Fas ligand (FasL) and its downstream signalling. Using primary cultures of cardiomyocytes isolated from rats, we demonstrated that CCN1 sensitized FasL-mediated apoptosis by engaging its cell-surface receptor integrin α6β1 and up-regulating intracellular reactive oxygen species (ROS), which activated mitogen-activated protein kinase p38, and increased cell-surface Fas expression. CCN1 is a critical pathophysiological regulator that mediates cardiomyocyte apoptosis during work-overload-induced cardiac injury. CCN1 increases cellular susceptibility to Fas-induced apoptosis by increasing ROS and cell-surface Fas expression.

Journal-related Activities and Other Special Activities at the 2012 American Society of Anesthesiologists Annual Meeting

Journal-related Activities and Other Special Activities at the 2012 American Society of Anesthesiologists Annual Meeting

Interleukin-17A Contributes to Myocardial Ischemia/Reperfusion Injury by Regulating Cardiomyocyte Apoptosis and Neutrophil Infiltration

This study tested whether interleukin (IL)-17A is involved in the pathogenesis of mouse myocardial ischemia/reperfusion (I/R) injury and investigated the mechanisms. Inflammatory processes play a major role in myocardial I/R injury. We recently identified IL-17A as an important cytokine in inflammatory cardiovascular diseases such as atherosclerosis and viral myocarditis. However, its role in myocardial I/R injury remains unknown. The involvement of IL-17A was assessed in functional assays in mouse myocardial I/R injury by neutralization/repletion or genetic deficiency of IL-17A, and its mechanism on cardiomyocyte apoptosis and neutrophil infiltration were further studied in vivo and in vitro. Interleukin-17A was elevated after murine left coronary artery ligation and reperfusion. Intracellular cytokine staining revealed that γδT lymphocytes but not CD4(+) helper T cells were a major source of IL-17A. Anti-IL-17A monoclonal antibody treatment or IL-17A knockout markedly ameliorated I/R injury, as demonstrated by reduced infarct size, reduced cardiac troponin T levels, and improved cardiac function. This improvement was associated with a reduction in cardiomyocyte apoptosis and neutrophil infiltration. In contrast, repletion of exogenous IL-17A induced the opposite effect. In vitro study showed that IL-17A mediated cardiomyocyte apoptosis through regulating the Bax/Bcl-2 ratio, induced CXC chemokine-mediated neutrophil migration and promoted neutrophil-endothelial cell adherence through induction of endothelial cell E-selectin and inter-cellular adhesion molecule-1 expression. IL-17A mainly produced by γδT cells plays a pathogenic role in myocardial I/R injury by inducing cardiomyocyte apoptosis and neutrophil infiltration.

Epigallocatechin gallate, the major component of polyphenols in green tea, inhibits telomere attrition mediated cardiomyocyte apoptosis in cardiac hypertrophy

BackgroundTelomere signaling plays a role in regulating cardiomyocyte apoptosis during cardiac dysfunction. In this study, we investigated the effects of epigallocatechin gallate (EGCG), the major component of polyphenols in green tea, on telomere dependent apoptotic signal in pressure overload cardiac hypertrophy. Methods and resultsCardiac hypertrophy in rats was established by abdominal aortic constriction (AC). EGCG 50, 100mg/kg, quercetin (Que) 100mg/kg, captopril (Cap) 50mg/kg, losartan (Los) 30mg/kg and carvedilol (Carv) 30mg/kg was intragastrically administered for 6weeks. Three, five and 7weeks after aortic constriction, the heart weight indices increased progressively. Malondialdehyde (MDA) contents progressively increased, while superoxide dismutase (SOD) activities decreased. Progressive cardiomyocyte apoptosis and telomere attrition were also found. Although no significant alteration of telomerase reverse transcriptase (TERT) mRNA was found till 7weeks after aortic constriction, progressive upregulation of p53, c-myc and downregulation of bcl-2, telomere repeat-binding factor 2(TRF2) were seen. EGCG, quercetin, captopril, losartan and carvedilol markedly reduced heart weight indices and apoptotic cardiomyocyte in hypertrophic myocardium, but they had different effects on apoptotic related proteins bcl-2, p53 and c-myc. EGCG, quercetin and carvedilol, have potent antioxidant effects as evidenced by reduction of MDA contents and resumption of SOD activities. EGCG, quercetin and carvedilol could prevent telomere attrition and telomere repeat-binding factor 2 (TRF2) loss remarkably, whereas captopril and losartan had no effect on oxidative stress and telomere signal. ConclusionsPressure overload induced cardiac hypertrophy initiates oxidative stress, induces telomere repeat-binding factor 2 loss and accelerates telomere shortening in hypertrophic myocardium. EGCG, quercetin and carvedilol with potent antioxidant effect, may inhibit cardiac myocyte apoptosis by preventing telomere shortening and telomere repeat-binding factor 2 (TRF2) loss.

Calcium-sensing receptor activation contributed to apoptosis stimulates TRPC6 channel in rat neonatal ventricular myocytes

Capacitative calcium entry (CCE) refers to the influx of calcium through plasma membrane channels activated on depletion of endoplasmic sarcoplasmic/reticulum (ER/SR) Ca 2+ stores, which is performed mainly by the transient receptor potential (TRP) channels. TRP channels are expressed in cardiomyocytes. Calcium-sensing receptor (CaR) is also expressed in rat cardiac tissue and plays an important role in mediating cardiomyocyte apoptosis. However, there are no data regarding the link between CaR and TRP channels in rat heart. In this study, in rat neonatal myocytes, by Ca 2+ imaging, we found that the depletion of ER/SR Ca 2+ stores by thapsigargin (TG) elicited a transient rise in cytoplasmic Ca 2+ ([Ca 2+] i), followed by sustained increase depending on extracellular Ca 2+. But, TRP channels inhibitor (SKF96365), not L-type channels or the Na +/Ca 2+ exchanger inhibitors, inhibited [Ca 2+] i relatively high. Then, we found that the stimulation of CaR with its activator gadolinium chloride (GdCl 3) or by an increased extracellular Ca 2+([Ca 2+] o) increased the concentration of intracelluar Ca 2+, whereas, the sustained elevation of [Ca 2+] i was reduced in the presence of SKF96365. Similarly, the duration of [Ca 2+] i increase was also shortened in the absence of extracellular Ca 2+. Western blot analysis showed that GdCl 3 increased the expression of TRPC6, which was reversed by SKF96365. Additionally, SKF96365 reduced cardiomyocyte apoptosis induced by GdCl 3. Our results suggested that CCE exhibited in rat neonatal myocytes and CaR activation induced Ca 2+-permeable cationic channels TRPCs to gate the CCE, for which TRPC6 was one of the most likely candidates. TRPC6 channel was functionally coupled with CaR to enhance the cardiomyocyte apoptosis.

Inhibition of the activity of Rho-kinase reduces cardiomyocyte apoptosis in heart ischemia/reperfusion via suppressing JNK-mediated AIF translocation

Background Recent studies have demonstrated that Rho-kinase has been proposed to play an important role in the pathogenesis of heart ischemia/reperfusion (I/R) injury. However, the mechanism of Rho-kinase mediated cardiomyocyte apoptosis in I/R is still not thoroughly understood. Method Studies were performed with female Wistar rats. Results Ischemia followed by reperfusion caused a significant increase in Rho-kinase, c-Jun NH2-terminal kinase (JNK) and apoptosis-inducing factor (AIF) activity. Administration of fasudil, an inhibitor of Rho-kinase, decreased myocardial infarction size from 59.89 ± 3.83% to 38.62 ± 2.66% ( P < 0.05) and cell apoptosis from 32.78 ± 5.1% to 17.05 ± 4.2% ( P < 0.05). Western blot analysis showed that administration of fasudil reduced the activation of JNK and attenuated mitochondrial-nuclear translocation of AIF. Additionally, administration of SP600125, an inhibitor of JNK, attenuated mitochondrial-nuclear translocation of AIF. Conclusion The inhibition of Rho-kinase reduced cell apoptosis in I/R in vivo via suppression of JNK-mediated AIF translocation.

Abstract 1949: The Protein Kinase MAP4K4 Is Activated in Failing Human Hearts and Mediates Cardiomyocyte Apoptosis in Experimental Models, in vitro and in vivo

Mitogen-activated protein kinases (MAPKs) have been implicated in cardiac muscle hypertrophy, apoptosis, and heart failure, but relatively little is known of the proximal MAP4Ks that might couple cardiac stress signals to downstream effector kinases. Previously we have shown that epitope-tagged MAP4K4 (hematopoietic progenitor kinase/germinal center kinase-like kinase, HGK) was activated by diverse apoptotic signals in cultured cardiomyocytes and transgenic mouse hearts. Here, we report results for the activation of MAP4K4 in the hearts of patients undergoing therapeutic transplantation, and for the functional consequences of disrupting endogenous MAP4K4 by RNA interference. Compared with 10 control donor hearts obtained at overlapping ages, MAP4K4 activity increased in all subjects with dilated (4.5-fold; N = 13), hypertrophic (4-fold; N = 5), ischemic (2.5-fold; N = 6) and adriamycin-induced cardiomyopathy (3-fold, N = 2; p &lt; 0.001 for all four groups). Activity of the MAP4K4 target, TGFbeta-activated kinase-1 (TAK1/MAP3K7), and the executioner caspase, caspase-3, increased concordantly in all subjects. In mouse myocardium, each of four biological signals for cardiomyocyte apoptosis induced the kinase activity of MAP4K4: biomechanical stress, ischemia/reperfusion injury, and gain-of-function mutations for TNFalpha and Gq. Analogous results were seen in cultured cardiomyocytes, using oxidative stress, ceramide and the cardiotoxic anti-cancer drug doxorubicin. Transgenic expression of MAP4K4 in myocardium produced little or no baseline phenotype, but markedly sensitized the myocardium to apoptosis caused by Gq. In culture, we proved that MAP4K4 induces apoptosis via TAK1, JNK, and the mitochondrial death pathway. As predicted, ceramide-induced and hydrogen peroxide-induced apoptosis was suppressed using RNA interference to silence expression of MAP4K4. Thus, MAP4K4 is activated in response to many specific cardiac death signals, and mediates cardiac apoptosis in vitro and in vivo. The prevalent activation of MAP4K4 in failing human hearts and the pro-death actions of the kinase suggest that MAP4K4 is a possible therapeutic target in the treatment of apoptotic cardiomyopathies.