Proteomic remodeling of mitochondria in heart failure

Myocardial proteome changes in aortic stenosis rats subjected to long-term aerobic exercise

The effects of exercise training (ET) on the heart of aortic stenosis (AS) rats are controversial and the mechanisms involved in alterations induced by ET have been poorly clarified. In this study, we analyzed the myocardial proteome to identify proteins modulated by moderate-intensity aerobic ET in rats with chronic supravalvular AS. Wistar rats were divided into four groups: sedentary control (C-Sed), exercised control (C-Ex), sedentary aortic stenosis (AS-Sed), and exercised AS (AS-Ex). ET consisted of five treadmill running sessions per week for 16 weeks. Statistical analysis was performed by ANOVA or Kruskal-Wallis and Goodman tests. Results were discussed at a significance level of 5%. At the end of the experiment, AS-Ex rats had higher functional capacity, lower blood lactate concentration, and better cardiac structural and left ventricular (LV) functional parameters than the AS-Sed. Myocardial proteome analysis showed that AS-Sed had higher relative protein abundance related to the glycolytic pathway, oxidative stress, and inflammation, and lower relative protein abundance related to beta-oxidation than C-Sed. AS-Ex had higher abundance of one protein related to mitochondrial biogenesis and lower relative protein abundance associated with oxidative stress and inflammation than AS-Sed. Proteomic data were validated for proteins related to lipid and glycolytic metabolism. Chronic pressure overload changes the abundance of myocardial proteins that are mainly involved in lipid and glycolytic energy metabolism in rats. Moderate-intensity aerobic training attenuates changes in proteins related to oxidative stress and inflammation and increases the COX4I1 protein, related to mitochondrial biogenesis. Protein changes are combined with improved functional capacity, cardiac remodeling, and LV function in AS rats.

Heart Metabolism in Sepsis-Induced Cardiomyopathy-Unusual Metabolic Dysfunction of the Heart

Due to the need for continuous work, the heart uses up to 8% of the total energy expenditure. Due to the relatively low adenosine triphosphate (ATP) storage capacity, the heart's work is dependent on its production. This is possible due to the metabolic flexibility of the heart, which allows it to use numerous substrates as a source of energy. Under normal conditions, a healthy heart obtains approximately 95% of its ATP by oxidative phosphorylation in the mitochondria. The primary source of energy is fatty acid oxidation, the rest of the energy comes from the oxidation of pyruvate. A failed heart is characterised by a disturbance in these proportions, with the contribution of individual components as a source of energy depending on the aetiology and stage of heart failure. A unique form of cardiac dysfunction is sepsis-induced cardiomyopathy, characterised by a significant reduction in energy production and impairment of cardiac oxidation of both fatty acids and glucose. Metabolic disorders appear to contribute to the pathogenesis of cardiac dysfunction and therefore are a promising target for future therapies. However, as many aspects of the metabolism of the failing heart remain unexplained, this issue requires further research.

Desmin Correlated with Cx43 May Facilitate Intercellular Electrical Coupling during Chronic Heart Failure

Desmin is one of five major intermediate filament proteins in cardiomyocytes. Desmin contributes to the maintenance of healthy muscle. The desmin content in cardiomyocytes directly affects the long-term prognosis of patients with heart failure, and lack of desmin leads to myocyte contractile dysfunction. However, the mechanism is elusive. In this study, we measured desmin expression using western blotting and qPCR in the failed hearts of human patients and rats. Our results showed that desmin content was reduced at the protein level in failed hearts and isolated cardiomyocytes. The association of desmin and the gap junction proteins connexin 43 (Cx43) and zonula occludens-1 (ZO-1) was also investigated. Immunoprecipitation assay showed that desmin was associated with Cx43 in cardiomyocytes. To compare the electrical integration of skeletal myoblasts in cocultures with cardiac myocytes, familial amyloid polyneuropathy (FAP) activation rate was found in 33% desmin overexpressing skeletal myoblasts. Desmin not only affected Cx43 and ZO-1 expression but also facilitated the complex of Cx43 and ZO-1 in skeletal myoblasts, which enhanced cell-to-cell electrical coupling of skeletal myoblasts with cardiac myocytes. Desmin has potential as a novel therapeutic target for heart failure. Preservation of desmin may attenuate heart failure.

Cardiovascular Risk Factors and Markers

Cardiovascular risk is assessed for the prediction and appropriate management of patients using collections of identified risk markers obtained from clinical questionnaire information, concentrations of certain blood molecules (e.g., N-terminal proB-type natriuretic peptide fragment and soluble receptors of tumor-necrosis factor-α and interleukin-2), imaging data using various modalities, and electrocardiographic variables, in addition to traditional risk factors.

Melatonin Efficacy in Obese Leptin-Deficient Mice Heart

Cardiomyocytes are particularly sensitive to oxidative damage due to the link between mitochondria and sarcoplasmic reticulum necessary for calcium flux and contraction. Melatonin, important indoleamine secreted by the pineal gland during darkness, also has important cardioprotective properties. We designed the present study to define morphological and ultrastructural changes in cardiomyocytes and mainly in mitochondria of an animal model of obesity (ob/ob mice), when treated orally or not with melatonin at 100 mg/kg/day for 8 weeks (from 5 up to 13 week of life). We observed that ob/ob mice mitochondria in sub-sarcolemmal and inter-myofibrillar compartments are often devoid of cristae with an abnormally large size, which are called mega-mitochondria. Moreover, in ob/ob mice the hypertrophic cardiomyocytes expressed high level of 4hydroxy-2-nonenal (4HNE), a marker of lipid peroxidation but scarce degree of mitofusin2, indicative of mitochondrial sufferance. Melatonin oral supplementation in ob/ob mice restores mitochondrial cristae, enhances mitofusin2 expression and minimizes 4HNE and p62/SQSTM1, an index of aberrant autophagic flux. At pericardial fat level, adipose tissue depot strictly associated with myocardium infarction, melatonin reduces adipocyte hypertrophy and inversely regulates 4HNE and adiponectin expressions. In summary, melatonin might represent a safe dietary adjuvant to hamper cardiac mitochondria remodeling and the hypoxic status that occur in pre-diabetic obese mice at 13 weeks of life.

Evidence of Altered Mitochondrial Protein Expression After Chronic Ethanol Consumption in the Aged Estrogen-Deficient Female Rat Heart

BACKGROUND

Estrogen loss has been implicated to increase the risk of alcoholic cardiomyopathy in postmenopausal women. The purpose of this study was to identify novel mitochondrial protein targets for the treatment of alcoholic cardiomyopathy in aged women using a state-of-the-art proteomic approach. We hypothesized that chronic ethanol (EtOH) ingestion exacerbates maladaptive mitochondrial protein expression in the aged female heart.

METHODS

Adult (3 months) and aged (18 months) F344 ovary-intact or ovariectomized (OVX) rats were randomly assigned an EtOH or control Lieber-DeCarli "all-liquid" diet for 20 weeks. Proteomic analyses were conducted in mitochondria isolated from left ventricles using isobaric tags for relative and absolute quantification (iTRAQ) 8plex labeling and mass spectrometry (n = 3 to 5/group).

RESULTS

After EtOH, significant differences (false discovery rate <5%) were observed in electron transport chain components (NADH dehydrogenase [ubiquinone] flavoprotein 2) as well as proteins involved in lipid metabolism (2,4 dienoyl-CoA reductase) and cellular defense (catalase), suggesting a possible link to congestive heart failure. Directional changes in protein levels were confirmed by Western blotting. Additionally, EtOH significantly reduced state 3 mitochondrial respiration in all groups, yet only reduced respiratory control index in the aged OVX rat heart (p < 0.05).

CONCLUSIONS

Collectively, the data reveal that EtOH-induced changes in the mitochondrial proteome exacerbate cardiac dysfunction in aged and estrogen-deficient hearts, but not in adult. In conclusion, iTRAQ is a powerful tool for investigating new mitochondrial targets of alcoholic cardiomyopathy.

Calcineurin signaling in the heart: The importance of time and place

The calcium-activated protein phosphatase, calcineurin, lies at the intersection of protein phosphorylation and calcium signaling cascades, where it provides an essential nodal point for coordination between these two fundamental modes of intracellular communication. In excitatory cells, such as neurons and cardiomyocytes, that experience rapid and frequent changes in cytoplasmic calcium, calcineurin protein levels are exceptionally high, suggesting that these cells require high levels of calcineurin activity. Yet, it is widely recognized that excessive activation of calcineurin in the heart contributes to pathological hypertrophic remodeling and the progression to failure. How does a calcium activated enzyme function in the calcium-rich environment of the continuously contracting heart without pathological consequences? This review will discuss the wide range of calcineurin substrates relevant to cardiovascular health and the mechanisms calcineurin uses to find and act on appropriate substrates in the appropriate location while potentially avoiding others. Fundamental differences in calcineurin signaling in neonatal verses adult cardiomyocytes will be addressed as well as the importance of maintaining heterogeneity in calcineurin activity across the myocardium. Finally, we will discuss how circadian oscillations in calcineurin activity may facilitate integration with other essential but conflicting processes, allowing a healthy heart to reap the benefits of calcineurin signaling while avoiding the detrimental consequences of sustained calcineurin activity that can culminate in heart failure.

Traditional and novel tools to probe the mitochondrial metabolism in health and disease

Mitochondrial metabolism links energy production to other essential cellular processes such as signaling, cellular differentiation, and apoptosis. In addition to producing adenosine triphosphate (ATP) as an energy source, mitochondria are responsible for the synthesis of a myriad of important metabolites and cofactors such as tetrahydrofolate, α-ketoacids, steroids, aminolevulinic acid, biotin, lipoic acid, acetyl-CoA, iron-sulfur clusters, heme, and ubiquinone. Furthermore, mitochondria and their metabolism have been implicated in aging and several human diseases, including inherited mitochondrial disorders, cardiac dysfunction, heart failure, neurodegenerative diseases, diabetes, and cancer. Therefore, there is great interest in understanding mitochondrial metabolism and the complex relationship it has with other cellular processes. A large number of studies on mitochondrial metabolism have been conducted in the last 50 years, taking a broad range of approaches. In this review, we summarize and discuss the most commonly used tools that have been used to study different aspects of the metabolism of mitochondria: ranging from dyes that monitor changes in the mitochondrial membrane potential and pharmacological tools to study respiration or ATP synthesis, to more modern tools such as genetically encoded biosensors and trans-omic approaches enabled by recent advances in mass spectrometry, computation, and other technologies. These tools have allowed the large number of studies that have shaped our current understanding of mitochondrial metabolism. WIREs Syst Biol Med 2017, 9:e1373. doi: 10.1002/wsbm.1373 For further resources related to this article, please visit the WIREs website.

Role of microRNA in metabolic shift during heart failure

Heart failure (HF) is an end point resulting from a number of disease states. The prognosis for HF patients is poor with survival rates precipitously low. Energy metabolism is centrally linked to the development of HF, and it involves the proteomic remodeling of numerous pathways, many of which are targeted to the mitochondrion. microRNAs (miRNA) are noncoding RNAs that influence posttranscriptional gene regulation. miRNA have garnered considerable attention for their ability to orchestrate changes to the transcriptome, and ultimately the proteome, during HF. Recently, interest in the role played by miRNA in the regulation of energy metabolism at the mitochondrion has emerged. Cardiac proteome remodeling during HF includes axes impacting hypertrophy, oxidative stress, calcium homeostasis, and metabolic fuel transition. Although it is established that the pathological environment of hypoxia and hemodynamic stress significantly contribute to the HF phenotype, it remains unclear as to the mechanistic underpinnings driving proteome remodeling. The aim of this review is to present evidence highlighting the role played by miRNA in these processes as a means for linking pathological stimuli with proteomic alteration. The differential expression of proteins of substrate transport, glycolysis, β-oxidation, ketone metabolism, the citric acid cycle (CAC), and the electron transport chain (ETC) are paralleled by the differential expression of miRNA species that modulate these processes. Identification of miRNAs that translocate to cardiomyocyte mitochondria (miR-181c, miR-378) influencing the expression of the mitochondrial genome-encoded transcripts as well as suggested import modulators are discussed. Current insights, applications, and challenges of miRNA-based therapeutics are also described.

Post-Translational Modifications of Cardiac Mitochondrial Proteins in Cardiovascular Disease: Not Lost in Translation

Protein post-translational modifications (PTMs) are crucial in regulating cellular biology by playing key roles in processes such as the rapid on and off switching of signaling network and the regulation of enzymatic activities without affecting gene expressions. PTMs lead to conformational changes in the tertiary structure of protein and resultant regulation of protein function such as activation, inhibition, or signaling roles. PTMs such as phosphorylation, acetylation, and S-nitrosylation of specific sites in proteins have key roles in regulation of mitochondrial functions, thereby contributing to the progression to heart failure. Despite the extensive study of PTMs in mitochondrial proteins much remains unclear. Further research is yet to be undertaken to elucidate how changes in the proteins may lead to cardiovascular and metabolic disease progression in particular. We aimed to summarize the various types of PTMs that occur in mitochondrial proteins, which might be associated with heart failure. This study will increase the understanding of cardiovascular diseases through PTM.

Mitochondrial oxidative metabolism and uncoupling proteins in the failing heart

Despite significant progress in cardiovascular medicine, myocardial ischemia and infarction, progressing eventually to the final end point heart failure (HF), remain the leading cause of morbidity and mortality in the USA. HF is a complex syndrome that results from any structural or functional impairment in ventricular filling or blood ejection. Ultimately, the heart's inability to supply the body's tissues with enough blood may lead to death. Mechanistically, the hallmarks of the failing heart include abnormal energy metabolism, increased production of reactive oxygen species (ROS) and defects in excitation-contraction coupling. HF is a highly dynamic pathological process, and observed alterations in cardiac metabolism and function depend on the disease progression. In the early stages, cardiac remodeling characterized by normal or slightly increased fatty acid (FA) oxidation plays a compensatory, cardioprotective role. However, upon progression of HF, FA oxidation and mitochondrial oxidative activity are decreased, resulting in a significant drop in cardiac ATP levels. In HF, as a compensatory response to decreased oxidative metabolism, glucose uptake and glycolysis are upregulated, but this upregulation is not sufficient to compensate for a drop in ATP production. Elevated mitochondrial ROS generation and ROS-mediated damage, when they overwhelm the cellular antioxidant defense system, induce heart injury and contribute to the progression of HF. Mitochondrial uncoupling proteins (UCPs), which promote proton leak across the inner mitochondrial membrane, have emerged as essential regulators of mitochondrial membrane potential, respiratory activity and ROS generation. Although the physiological role of UCP2 and UCP3, expressed in the heart, has not been clearly established, increasing evidence suggests that these proteins by promoting mild uncoupling could reduce mitochondrial ROS generation and cardiomyocyte apoptosis and ameliorate thereby myocardial function. Further investigation on the alterations in cardiac UCP activity and regulation will advance our understanding of their physiological roles in the healthy and diseased heart and also may facilitate the development of novel and more efficient therapies.

Physiological and structural differences in spatially distinct subpopulations of cardiac mitochondria: influence of cardiac pathologies

Cardiac tissue contains discrete pools of mitochondria that are characterized by their subcellular spatial arrangement. Subsarcolemmal mitochondria (SSM) exist below the cell membrane, interfibrillar mitochondria (IFM) reside in rows between the myofibrils, and perinuclear mitochondria are situated at the nuclear poles. Microstructural imaging of heart tissue coupled with the development of differential isolation techniques designed to sequentially separate spatially distinct mitochondrial subpopulations have revealed differences in morphological features including shape, absolute size, and internal cristae arrangement. These findings have been complemented by functional studies indicating differences in biochemical parameters and, potentially, functional roles for the ATP generated, based upon subcellular location. Consequently, mitochondrial subpopulations appear to be influenced differently during cardiac pathologies including ischemia/reperfusion, heart failure, aging, exercise, and diabetes mellitus. These influences may be the result of specific structural and functional disparities between mitochondrial subpopulations such that the stress elicited by a given cardiac insult differentially impacts subcellular locales and the mitochondria contained within. The goal of this review is to highlight some of the inherent structural and functional differences that exist between spatially distinct cardiac mitochondrial subpopulations as well as provide an overview of the differential impact of various cardiac pathologies on spatially distinct mitochondrial subpopulations. As an outcome, we will instill a basis for incorporating subcellular spatial location when evaluating the impact of cardiac pathologies on the mitochondrion. Incorporation of subcellular spatial location may offer the greatest potential for delineating the influence of cardiac pathology on this critical organelle.

Protection from oxidative and electrophilic stress in the Gsta4-null mouse heart

4-Hydroxynonenal (4-HNE) mediates many pathological effects of oxidative and electrophilic stress and signals to activate cytoprotective gene expression regulated by NF-E2-related factor 2 (Nrf2). By exhibiting very high levels of 4-HNE-conjugating activity, the murine glutathione transferase alpha 4 (GSTA4-4) helps regulate cellular 4-HNE levels. To examine the role of 4-HNE in vivo, we disrupted the murine Gsta4 gene. Gsta4-null mice exhibited no cardiac phenotype under normal conditions and no difference in cardiac 4-HNE level as compared to wild-type mice. We hypothesized that the Nrf2 pathway might contribute an important compensatory mechanism to remove excess cardiac 4-HNE in Gsta4-null mice. Cardiac nuclear extracts from Gsta4-null mice exhibited significantly higher Nrf2 binding to antioxidant response elements. We also observed responses in critical Nrf2 target gene products: elevated Sod2, Cat, and Akr1b7 mRNA levels and significant increases in both cardiac antioxidant and anti-electrophile enzyme activities. Gsta4-null mice were less sensitive and maintained normal cardiac function following chronic doxorubicin treatment, known to increase cardiac 4-HNE levels. Hence, in the absence of GSTA4-4 to modulate both physiological and pathological 4-HNE levels, the adaptive Nrf2 pathway may be primed to contribute to a preconditioned cardiac phenotype in the Gsta4-null mouse.

Oxidative post-translational modifications develop LONP1 dysfunction in pressure overload heart failure

BACKGROUND

Mitochondrial compromise is a fundamental contributor to heart failure. Recent studies have revealed that several surveillance systems maintain mitochondrial integrity. The present study evaluated the role of mitochondrial AAA+ protease in a mouse model of pressure overload heart failure.

METHODS AND RESULTS

The fluorescein isothiocyanate casein assay and immunoblotting for endogenous mitochondrial proteins revealed a marked reduction in ATP-dependent proteolytic activity in failing heart mitochondria. The level of reduced cysteine was decreased, and tyrosine nitration and protein carbonylation were promoted in Lon protease homolog (LONP1), the most abundant mitochondrial AAA+ protease, in heart failure. Comprehensive analysis revealed that electron transport chain protein levels were increased even with a reduction in the expression of their corresponding mRNAs in heart failure, which indicated decreased protein turnover and resulted in the accumulation of oxidative damage in the electron transport chain. The induction of mitochondria-targeted human catalase ameliorated proteolytic activity and protein homeostasis in the electron transport chain, leading to improvements in mitochondrial energetics and cardiac contractility even during the late stage of pressure overload. Moreover, the infusion of mitoTEMPO, a mitochondria-targeted superoxide dismutase mimetic, recovered oxidative modifications of LONP1 and improved mitochondrial respiration capacity and cardiac function. The in vivo small interfering RNA repression of LONP1 partially canceled the protective effects of mitochondria-targeted human catalase induction and mitoTEMPO infusion.

CONCLUSIONS

Oxidative post-translational modifications attenuate mitochondrial AAA+ protease activity, which is involved in impaired electron transport chain protein homeostasis, mitochondrial respiration deficiency, and left ventricular contractile dysfunction. Oxidatively inactivated proteases may be an endogenous target for mitoTEMPO treatment in pressure overload heart failure.

Mitochondrial proteome remodeling in ischemic heart failure

AIMS

Mitochondrial dysfunction is an important part of the decline in cardiac function in heart failure. We hypothesized for hypothesized that there would be specific abnormalities in mitochondrial function and proteome with the progression of ischemic heart failure (HF).

MAIN METHODS

We used a high left anterior descending artery (LAD) ligation in 3-4month old male rats to generate HF. Rats were studied 9weeks post-ligation.

KEY FINDINGS

Electron microscopy of left ventricle samples showed mitochondrial changes including decreased size, increased number, abnormal distribution, and cristae loss. Mitochondria in ischemic HF exhibited decreased total ATP, impaired mitochondrial respiration, as well as reduced complex I activity. Analysis of LV mitochondrial proteins by mass spectrometry was performed, and 31 differentially expressed proteins (p<0.05) of more than 500 total proteins were identified. Of these proteins, 15 were up-regulated and 16 were down-regulated in the failing heart. A set of complex I proteins was significantly decreased, consistent with the impairment of complex I activity. There were distinct changes in mitochondrial function and proteome in ischemic HF. Although there were similarities, the distinction between the reported proteomic changed with TAC pressure overload induced HF and ischemic HF in the current study suggested different pathological mechanisms.

SIGNIFICANCE

Specific changes in mitochondrial protein expression, which correlate with changes in mitochondrial function, have been identified in ischemic HF for the first time.

Characterization, design, and function of the mitochondrial proteome: from organs to organisms

Mitochondria are a common energy source for organs and organisms; their diverse functions are specialized according to the unique phenotypes of their hosting environment. Perturbation of mitochondrial homeostasis accompanies significant pathological phenotypes. However, the connections between mitochondrial proteome properties and function remain to be experimentally established on a systematic level. This uncertainty impedes the contextualization and translation of proteomic data to the molecular derivations of mitochondrial diseases. We present a collection of mitochondrial features and functions from four model systems, including two cardiac mitochondrial proteomes from distinct genomes (human and mouse), two unique organ mitochondrial proteomes from identical genetic codons (mouse heart and mouse liver), as well as a relevant metazoan out-group (drosophila). The data, composed of mitochondrial protein abundance and their biochemical activities, capture the core functionalities of these mitochondria. This investigation allowed us to redefine the core mitochondrial proteome from organs and organisms, as well as the relevant contributions from genetic information and hosting milieu. Our study has identified significant enrichment of disease-associated genes and their products. Furthermore, correlational analyses suggest that mitochondrial proteome design is primarily driven by cellular environment. Taken together, these results connect proteome feature with mitochondrial function, providing a prospective resource for mitochondrial pathophysiology and developing novel therapeutic targets in medicine.

Comparative differential proteomic profiles of nonfailing and failing hearts after in vivo thoracic aortic constriction in mice overexpressing FKBP12.6

Chronic pressure overload (PO) induces pathological left ventricular hypertrophy (LVH) leading to congestive heart failure (HF). Overexpression of FKBP12.6 (FK506-binding protein [K]) in mice should prevent Ca2+-leak during diastole and may improve overall cardiac function. In order to decipher molecular mechanisms involved in thoracic aortic constriction (TAC)-induced cardiac remodeling and the influence of gender and genotype, we performed a proteomic analysis using two-dimensional differential in-gel electrophoresis (2D-DIGE), mass spectrometry, and bioinformatics techniques to identify alterations in characteristic biological networks. Wild-type (W) and K mice of both genders underwent TAC. Thirty days post-TAC, the altered cardiac remodeling was accompanied with systolic and diastolic dysfunction in all experimental groups. A gender difference in inflammatory protein expression (fibrinogen, α-1-antitrypsin isoforms) and in calreticulin occurred (males > females). Detoxification enzymes and cytoskeletal proteins were noticeably increased in K mice. Both non- and congestive failing mouse heart exhibited down- and upregulation of proteins related to mitochondrial function and purine metabolism, respectively. HF was characterized by a decrease in enzymes related to iron homeostasis, and altered mitochondrial protein expression related to fatty acid metabolism, glycolysis, and redox balance. Moreover, two distinct differential protein profiles characterized TAC-induced pathological LVH and congestive HF in all TAC mice. FKBP12.6 overexpression did not influence TAC-induced deleterious effects. Huntingtin was revealed as a potential mediator for HF. A broad dysregulation of signaling proteins associated with congestive HF suggested that different sets of proteins could be selected as useful biomarkers for HF progression and might predict outcome in PO-induced pathological LVH.

αB-crystallin regulates oxidative stress-induced apoptosis in cardiac H9c2 cells via the PI3K/AKT pathway

The present study was carried out to observe the protective effects of αB-crystallin protein on hydrogen peroxide (H2O2)-induced injury in rat myocardial cells (H9c2) and to investigate the mechanisms of these protective effects at the cellular level, which could provide the experimental basis for future applications of αB-crystallin in the treatment of cardiovascular disease. Western blotting was used to measure the expression of αB-crystallin in cultured H9c2 cells in vitro. A αB-crystallin recombinant expression vector, pcDNA3.1-Cryab, was constructed to transfect H9c2 cells for the establishment of cells that stably expressed αB-crystallin. A tetrazolium-based colorimetric assay (MTT test) was used to measure changes in the viability of the H9c2 cells at 1, 2, 3 and 4 h after induced by 150 μM H2O2 to establish a model of H2O2 injury to cells. H2O2 was applied to H9c2 cells that were stably transfected with αB-crystallin, and the effect of αB-crystallin overexpression on the viability of myocardial cells subjected to H2O2-induced injury was measured by the MTT assay. The effect of αB-crystallin overexpression on the H2O2-induced injury of H9c2 cells was also analyzed by flow cytometry. The mitochondrial components and cytoplasmic components of H9c2 cells were separated, and western blotting was used to measure the effect of αB-crystallin overexpression on the release of cytochrome c from the mitochondria. Western blotting was also used to measure the effect of αB-crystallin overexpression on the expression of the anti-apoptosis protein Bcl-2 and components of the phosphatidylinositol 3-OH kinase (PI3K)/AKT pathway. The αB-crystallin recombinant expression vector pcDNA3.1-Cryab successfully transfected H9c2 cells, and H9c2 cells that were stably transfected with αB-crystallin were established after G418 selection. The measurements carried out by western blotting showed that αB-crystallin proteins are expressed in normal H9c2 cells, but the proteins' expression was much higher in pcDNA3.1-Cryab transfected cells (P < 0.01). The MTT assays showed that 4 h of H2O2 treatment induced significant injury in H9c2 cells (P < 0.01), but αB-crystallin overexpression can effectively antagonize the H2O2-induced injury to H9c2 cells (P < 0.05). The results of flow cytometry analysis showed that αB-crystallin overexpression can significantly reduce apoptosis in H2O2-injured H9c2 cells (P < 0.05). The results of western blotting showed that αB-crystallin overexpression in myocardial cells can reduce the H2O2-induced release of cytochrome c from the mitochondria (P < 0.05), antagonize the H2O2-induced downregulation of Bcl-2 (P < 0.05) and magnify the decrease in phosphorylated AKT levels induced by H2O2 injury (P < 0.05). The overexpression of αB-crystallin has a protective effect on H2O2-injured H9c2 cells, and αB-crystallin can play a protective role by reducing apoptosis, reducing the release of cytochrome c from the mitochondria and antagonizing the downregulation of Bcl-2 expression. The protective effects of αB-crystallin may be related to the PI3K/AKT pathway.

Differential regulation of EHD3 in human and mammalian heart failure

Electrical and structural remodeling during the progression of cardiovascular disease is associated with adverse outcomes subjecting affected patients to overt heart failure (HF) and/or sudden death. Dysfunction in integral membrane protein trafficking has long been linked with maladaptive electrical remodeling. However, little is known regarding the molecular identity or function of these intracellular targeting pathways in the heart. Eps15 homology domain-containing (EHD) gene products (EHD1-4) are polypeptides linked with endosomal trafficking, membrane protein recycling, and lipid homeostasis in a wide variety of cell types. EHD3 was recently established as a critical mediator of membrane protein trafficking in the heart. Here, we investigate the potential link between EHD3 function and heart disease. Using four different HF models including ischemic rat heart, pressure overloaded mouse heart, chronic pacing-induced canine heart, and non-ischemic failing human myocardium we provide the first evidence that EHD3 levels are consistently increased in HF. Notably, the expression of the Na/Ca exchanger (NCX1), targeted by EHD3 in heart is similarly elevated in HF. Finally, we identify a molecular pathway for EHD3 regulation in heart failure downstream of reactive oxygen species and angiotensin II signaling. Together, our new data identify EHD3 as a previously unrecognized component of the cardiac remodeling pathway.