Apoptotic versus autophagic cell death in heart failure

Cardiotoxicity of Selected Vascular Endothelial Growth Factor Receptor Tyrosine Kinase Inhibitors in Patients with Renal Cell Carcinoma

Renal cell carcinoma (RCC) is one of the most frequent malignant neoplasms of the kidney. The therapeutic options available for the treatment of advanced or metastatic RCC include vascular endothelial growth factor receptor (VEGFR)-targeted molecules, for example, tyrosine kinase inhibitors (TKI). Various VEGFR-TKIs proved to be effective in the treatment of patients with solid tumours. The combination of two drugs may prove most beneficial in the treatment of metastatic RCC; however, it also enhances the risk of toxicity compared to monotherapy. Specific VEGFR-TKIs (e.g., sunitinib, sorafenib or pazopanib) may increase the rate of cardiotoxicity in metastatic settings. VEGF inhibitors modulate multiple signalling pathways; thus, the identification of the mechanism underlying cardiotoxicity appears challenging. VEGF signalling is vital for the maintenance of cardiomyocyte homeostasis and cardiac function; therefore, its inhibition can be responsible for the reported adverse effects. Disturbed growth factor signalling pathways may be associated with endothelial dysfunction, impaired revascularization, the development of dilated cardiomyopathy, cardiac hypertrophies and altered peripheral vascular load. Patients at high cardiovascular risk at baseline could benefit from clinical follow-up in the first 2-4 weeks after the introduction of targeted molecular therapy; however, there is no consensus concerning the surveillance strategy.

Roles of autophagy in angiotensin II-induced cardiomyocyte apoptosis

Autophagy is a self-degradation process of cytoplasmic components and occurs in the failing heart. Angiotensin II plays a critical role in the progression of heart failure and induces autophagy. We investigated the mechanism underlying angiotensin II-enhanced autophagy and examined the role of autophagy in angiotensin II-induced cardiomyocyte injury. Neonatal rat cardiomyocytes were treated with angiotensin II (1-100 nmol/L). Angiotensin II dose-dependently increased autophagy indicators of microtubule-associated protein 1 light chain (LC) 3-II and monodansylcadaverine-labelled vesicles. It also enhanced the intracellular production of reactive oxygen species (ROS), assessed by H2DCFDA, an intracellular ROS indicator. NADPH oxidase- and mitochondria-derived ROS production was increased by angiotensin II, while angiotensin II-induced LC3-II expression was suppressed by inhibitors of these sources of ROS. Confocal microscopy revealed that superoxide-producing mitochondria colocalized with lysosomes after the angiotensin II stimulation. Myocyte apoptosis was assessed by nuclear staining with DAPI and caspase-3 activity. A 6-h stimulation with angiotensin II did not affect myocyte apoptosis, while a co-treatment with 3-methyl-adenine (3MA), an autophagy inhibitor, augmented apoptosis. These results indicate that autophagy suppressed apoptosis because it removed damaged mitochondria in the early stages of the angiotensin II stimulation. A longer angiotensin II stimulation for 24 h induced apoptosis and propidium iodide-positive lethal myocytes, while the co-treatment with 3MA did not lead to further increases. In conclusion, angiotensin II-induced autophagy removes ROS-producing mitochondria. Autophagy is a beneficial phenomenon against myocyte apoptosis in the early phase, but its benefit was limited in the late phase of angiotensin II stimulation.

Sphingosylphosphorylcholine ameliorates doxorubicin-induced cardiotoxicity in zebrafish and H9c2 cells by reducing excessive mitophagy and mitochondrial dysfunction

Doxorubicin (DOX, C₂₇H₂₉NO₁₁), is an anthracycline tumor chemotherapy drug, which has significant side effects on many organs including the heart. In recent years, mitochondrial dysfunction caused by DOX was identified as an important reason for cardiotoxic injury. Sphingosylphosphorylcholine (SPC) is essential for mitochondrial homeostasis in our previous report, however, its role in DOX-caused cardiomyopathy has remained elusive. Herein, DOX treated zebrafish embryos (90 μM) and adult fish (2.5 μM/g) were used to simulate DOX-induced cardiotoxic damage. Histopathological and ultrastructural observations showed that SPC (2.5 μM) significantly ameliorated DOX-induced pericardial edema, myocardial vacuolization and apoptosis. Furthermore, SPC (2.5 μM) can significantly inhibit DOX-induced apoptosis and promote cell proliferation in DOX treated H9c2 cells (1 μM), which is dependent on the restoration of mitochondrial homeostasis, including restored mitochondrial membrane potential, mitochondrial superoxide and ATP levels. We finally confirmed that SPC restored mitochondrial homeostasis through ameliorating DOX-induced excessive mitophagy. Mechanistically, SPC reduced calmodulin (CaM) levels and thus inhibiting Parkin activation and Parkin-dependent mitophagy. These results suggest that reducing the cardiotoxicity of chemotherapeutic drugs by targeting SPC may be a new solution to rescue chemotherapy injury.

Understanding the Role of Autophagy in Cancer Formation and Progression Is a Real Opportunity to Treat and Cure Human Cancers

Simple Summary

The modulation of autophagy represents a potential therapeutic strategy for cancer. More than one hundred clinical trials have been conducted or are ongoing to explore the efficacy of autophagy modulators to reduce the tumor growth and potentiate the anti-cancer effects of conventional therapy. Despite this, the effective role of autophagy during tumor initiation, growth, and metastasis remains not well understood. Depending on the cancer type and stage of cancer, autophagy may have tumor suppressor properties as well as help cancer cells to proliferate and evade cancer therapy. The current review aims to summarize the current knowledge about the autophagy implications in cancer and report the therapeutic opportunities based on the modulation of the autophagy process.

Abstract

The malignant transformation of a cell produces the accumulation of several cellular adaptions. These changes determine variations in biological processes that are necessary for a cancerous cell to survive during stressful conditions. Autophagy is the main nutrient recycling and metabolic adaptor mechanism in eukaryotic cells, represents a continuous source of energy and biomolecules, and is fundamental to preserve the correct cellular homeostasis during unfavorable conditions. In recent decades, several findings demonstrate a close relationship between autophagy, malignant transformation, and cancer progression. The evidence suggests that autophagy in the cancer context has a bipolar role (it may act as a tumor suppressor and as a mechanism of cell survival for established tumors) and demonstrates that the targeting of autophagy may represent novel therapeutic opportunities. Accordingly, the modulation of autophagy has important clinical benefits in patients affected by diverse cancer types. Currently, about 30 clinical trials are actively investigating the efficacy of autophagy modulators to enhance the efficacy of cytotoxic chemotherapy treatments. A deeper understanding of the molecular pathways regulating autophagy in the cancer context will provide new ways to target autophagy for improving the therapeutic benefits. Herein, we describe how autophagy participates during malignant transformation and cancer progression, and we report the ultimate efforts to translate this knowledge into specific therapeutic approaches to treat and cure human cancers.

Cardioprotective Effect of Stem-Leaf Saponins From Panax notoginseng on Mice With Sleep Derivation by Inhibiting Abnormal Autophagy Through PI3K/Akt/mTOR Pathway

Sleep deprivation (SD) may lead to serious myocardial injury in cardiovascular diseases. Saponins extracted from the roots of Panax notoginseng, a traditional Chinese medicine beneficial to blood circulation and hemostasis, are the main bioactive components exerting cardiovascular protection in the treatment of heart disorders, such as arrhythmia, ischemia and reperfusion injury, and cardiac hypertrophy. This study aimed to explore the protective effect of stem-leaf saponins from Panax notoginseng (SLSP) on myocardial injury in SD mice. SD was induced by a modified multi-platform method. Cardiac morphological changes were assessed by hematoxylin and eosin (H&E) staining. Heart rate and ejection fraction were detected by specific instruments. Serum levels of atrial natriuretic peptide (ANP) and lactate dehydrogenase (LDH) were measured with biochemical kits. Transmission electron microscopy (TEM), immunofluorescent, and Western blotting analysis were used to observe the process and pathway of autophagy and apoptosis in heart tissue of SD mice. In vitro, rat H9c2 cells pretreated with rapamycin and the effect of SLSP were explored by acridine orange staining, transient transfection, flow cytometry, and Western blotting analysis. SLSP prevented myocardial injury, such as morphological damage, accumulation of autophagosomes in heart tissue, abnormal high heart rate, serum ANP, and serum LDH induced by SD. In addition, it reversed the expressions of proteins involved in the autophagy and apoptosis and activated PI3K/Akt/mTOR signaling pathway that is disturbed by SD. On H9c2 cells induced by rapamycin, SLSP could markedly resume the abnormal autophagy and apoptosis. Collectively, SLSP attenuated excessive autophagy and apoptosis in myocardial cells in heart tissue induced by SD, which might be acted through activating PI3K/Akt/mTOR signaling pathway.

Links between autophagy and tissue mechanics

Physical constraints, such as compression, shear stress, stretching and tension, play major roles during development, tissue homeostasis, immune responses and pathologies. Cells and organelles also face mechanical forces during migration and extravasation, and investigations into how mechanical forces are translated into a wide panel of biological responses, including changes in cell morphology, membrane transport, metabolism, energy production and gene expression, is a flourishing field. Recent studies demonstrate the role of macroautophagy in the integration of physical constraints. The aim of this Review is to summarize and discuss our knowledge of the role of macroautophagy in controlling a large panel of cell responses, from morphological and metabolic changes, to inflammation and senescence, for the integration of mechanical forces. Moreover, wherever possible, we also discuss the cell surface molecules and structures that sense mechanical forces upstream of macroautophagy.

Cardioprotective Effect of Nec-1 in Rats Subjected to MI/R: Downregulation of Autophagy-Like Cell Death

Objective

Necrostatin-1 (Nec-1), an inhibitor of necroptosis, has been reported to protect against myocardial ischemia-reperfusion (MI/R) injury. However, the contribution of the potential antinecroptotic effect of Nec-1 on its infarct limitation and cardiac function improvement effects after MI/R has not been investigated.

Methods

The present study investigated the effect of Nec-1 on myocardial infarct size, necroptosis, and cardiac functional recovery in rats subjected to myocardial ischemia-reperfusion (MI/R 30 min/12, 24, 48, and 72 h).

Results

The study showed that Nec-1 might reduce myocardial cell death and maintain myoarchitectonic integrity, consequently inhibiting the reactive fibrosis process in rats in myocardial ischemia/late reperfusion. Moreover, the administration of Nec-1 (0.6 mg/kg) at the onset of reperfusion significantly reduced the release of creatine kinase and downregulation of autophagy within 24 h after reperfusion, and there was a significantly positive correlation between them.

Conclusion

These results suggest that antinecroptosis treatment may improve the clinical outcomes of patients with ischemic heart disease.

4,6'-Anhydrooxysporidinone from Fusarium lateritium SSF2 Induces Autophagic and Apoptosis Cell Death in MCF-7 Breast Cancer Cells

Previous studies have reported that 4,6′-Anhydrooxysporidinone (SSF2-2), isolated from Fusarium lateritium SSF2, has neuroprotective effects on the HT-22 hippocampal neuronal cell line. However, the anti-cancer effect of SSF2-2 remains unclear. Here, we examined the viability of MCF-7 human breast cancer cells treated with SSF2-2 or left untreated using a cell viability assay kit. The underlying molecular mechanism was further investigated by Western blotting and immunocytochemistry studies. The results demonstrated that SSF2-2 inhibited the viability of MCF-7 cells. Treatment with SSF2-2 increased the levels of cleaved caspase-9, cleaved caspase-7, poly (ADP-ribose) polymerase (PARP), and LC3B. Additionally, SSF2-2 significantly increased the conversion of LC3-I to LC3II and LC3-positive puncta in MCF-7 cells.

CaMKII in Regulation of Cell Death During Myocardial Reperfusion Injury

Cardiovascular disease is the leading cause of death worldwide. In spite of the mature managements of myocardial infarction (MI), post-MI reperfusion (I/R) injury results in high morbidity and mortality. Cardiomyocyte Ca²⁺ overload is a major factor of I/R injury, initiating a cascade of events contributing to cardiomyocyte death and myocardial dysfunction. Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) plays a critical role in cardiomyocyte death response to I/R injury, whose activation is a key feature of myocardial I/R in causing intracellular mitochondrial swelling, endoplasmic reticulum (ER) Ca²⁺ leakage, abnormal myofilament contraction, and other adverse reactions. CaMKII is a multifunctional serine/threonine protein kinase, and CaMKIIδ, the dominant subtype in heart, has been widely studied in the activation, location, and related pathways of cardiomyocytes death, which has been considered as a potential targets for pharmacological inhibition. In this review, we summarize a brief overview of CaMKII with various posttranslational modifications and its properties in myocardial I/R injury. We focus on the molecular mechanism of CaMKII involved in regulation of cell death induced by myocardial I/R including necroptosis and pyroptosis of cardiomyocyte. Finally, we highlight that targeting CaMKII modifications and cell death involved pathways may provide new insights to understand the conversion of cardiomyocyte fate in the setting of myocardial I/R injury.

Induction of autophagy has protective roles in imatinib-induced cardiotoxicity

Cardiotoxicity is one of the severe adverse effects of chemotherapeutic agents. Imatinib was previously reported to induce cardiotoxicity. Autophagy is an intracellular bulk protein and organelle degradation process, but its roles in cardiac diseases are unclear. We examined whether imatinib induces cardiomyocyte autophagy, and the role of autophagy in imatinib-induced cardiotoxicity using in vitro and in vivo experiments. In in vitro experiments, neonatal rat cardiomyocytes were treated with imatinib (1, 5, or 10 μM; 6 h). Myocyte autophagy was assessed by microtubule-associated protein light chain (LC) 3-II, beclin 1, mature cathepsin D, and acridine orange-stained mature autolysosome expression. Imatinib increased their expression, suggesting that it induced autophagy. Consequently, imatinib altered the production of mitochondria-derived reactive oxygen species (ROS) and loss of mitochondrial membrane potential, which were assessed by the fluorescent indicator MitoSOX and JC-1, respectively, leading to cardiomyocyte apoptosis. 3-methyl-adenine (3MA), an autophagic inhibitor, exacerbated imatinib-induced apoptosis by 30 %. In in vivo experiments, C57BL/6 mice were treated with imatinib (50 and 200 mg/kg/day) for 5 weeks in the presence or absence of 3MA. Echocardiographic measurement revealed that imatinib (200 mg) caused dilatation of the left ventricle (LV) and reduced LV fractional shortening. Apoptosis and LC3-II expression in cardiac tissue were increased by imatinib. Co-treatment with 3MA and imatinib further impaired imatinib-induced cardiac apoptosis and LV dysfunction. This study suggests that imatinib induces cardiomyocyte apoptosis, leading to cardiac dysfunction. Imatinib increases cardiomyocyte autophagy as a consequence of apoptosis and autophagy has a pro-survival role in imatinib-induced cardiac impairment.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Identifying Downregulation of Autophagy Markers in Kawasaki Disease

Kawasaki disease (KD) is the most common cause of heart disease acquired in childhood. Even if treated with high-dose intravenous immunoglobulin G (IVIG) at the early stage; children are still at risk of developing coronary artery lesions. Accumulating evidence suggests that autophagy is enhanced in various heart diseases. Evaluating the pathogenic role of autophagy in KD and coronary artery lesions (CAL) may aid in identifying a potential therapeutic target for the treatment or prevention of the disease. Blood samples were obtained from 20 children with KD at the onset of disease and 21 days after IVIG therapy. Twenty children with other causes of febrile disease and 20 healthy children were included as controls. Total RNA was extracted from white blood cells; and autophagy-related gene mRNA expression levels were measured using real-time polymerase chain reaction. The patients with KD had downregulated levels of LC3B mRNA (0.50 ± 0.06 vs. 1.67 ± 0.15; p < 0.001), BECN1 mRNA (0.70 ± 0.08 vs. 1.43 ± 0.23; p < 0.05), and ATG16L1 mRNA (0.28 ± 0.04 vs. 0.96 ± 0.16; p < 0.01) compared to the febrile control group. The values of these parameters all increased significantly 21 days after the IVIG therapy as follows: LC3B mRNA (1.77 ± 0.29 vs. 0.50 ± 0.06; p < 0.001), BECN1 mRNA (1.67 ± 0.36 vs. 0.70 ± 0.08; p < 0.05), and ATG16L1 mRNA (2.96 ± 0.43 vs. 0.28 ± 0.04; p < 0.001), while the level of ATG16L1 mRNA persists low in KD patients with CAL. Our results showed the autophagy-related genes expressions in KD and their change after IVIG administration. This suggests that autophagy may have a protective effect on KD.

p38δ genetic ablation protects female mice from anthracycline cardiotoxicity

The efficacy of an anthracycline antibiotic doxorubicin (DOX) as a chemotherapeutic agent is limited by dose-dependent cardiotoxicity. DOX is associated with activation of intracellular stress signaling pathways including p38 MAPKs. While previous studies have implicated p38 MAPK signaling in DOX-induced cardiac injury, the roles of the individual p38 isoforms, specifically, of the alternative isoforms p38γ and p38δ, remain uncharacterized. We aimed to determine the potential cardioprotective effects of p38γ and p38δ genetic deletion in mice subjected to acute DOX treatment. Male and female wild-type (WT), p38γ-/-, p38δ-/-, and p38γ-/-δ-/- mice were injected with 30 mg/kg DOX and their survival was tracked for 10 days. During this period, cardiac function was assessed by echocardiography and electrocardiography and fibrosis by Picro Sirius Red staining. Immunoblotting was performed to assess the expression of signaling proteins and markers linked to autophagy. Significantly improved survival was observed in p38δ-/- female mice post-DOX relative to WT females, but not in p38γ-/- or p38γ-/-δ-/- male or female mice. The improved survival in DOX-treated p38δ-/- females was associated with decreased fibrosis, increased cardiac output and LV diameter relative to DOX-treated WT females, and similar to saline-treated controls. Structural and echocardiographic parameters were either unchanged or worsened in all other groups. Increased autophagy, as suggested by increased LC3-II level, and decreased mammalian target of rapamycin activation was also observed in DOX-treated p38δ-/- females. p38δ plays a crucial role in promoting DOX-induced cardiotoxicity in female mice by inhibiting autophagy. Therefore, p38δ targeting could be a potential cardioprotective strategy in anthracycline chemotherapy.NEW & NOTEWORTHY This study for the first time identifies the sex-specific roles of the alternative p38γ and p38δ MAPK isoforms in promoting doxorubicin (DOX) cardiotoxicity. We show that p38δ and p38γ/δ systemic deletion was cardioprotective in female but not in male mice. Cardiac structure and function were preserved in DOX-treated p38δ-/- females and autophagy marker was increased.

Mitophagy in Cardiovascular Diseases

Cardiovascular diseases are one of the leading causes of death. Increasing evidence has shown that pharmacological or genetic targeting of mitochondria can ameliorate each stage of these pathologies, which are strongly associated with mitochondrial dysfunction. Removal of inefficient and dysfunctional mitochondria through the process of mitophagy has been reported to be essential for meeting the energetic requirements and maintaining the biochemical homeostasis of cells. This process is useful for counteracting the negative phenotypic changes that occur during cardiovascular diseases, and understanding the molecular players involved might be crucial for the development of potential therapies. Here, we summarize the current knowledge on mitophagy (and autophagy) mechanisms in the context of heart disease with an important focus on atherosclerosis, ischemic heart disease, cardiomyopathies, heart failure, hypertension, arrhythmia, congenital heart disease and peripheral vascular disease. We aim to provide a complete background on the mechanisms of action of this mitochondrial quality control process in cardiology and in cardiac surgery by also reviewing studies on the use of known compounds able to modulate mitophagy for cardioprotective purposes.

Arsenic-induced immunomodulatory effects disorient the survival-death interface by stabilizing the Hsp90/Beclin1 interaction

Ground water arsenic contamination is a global menace. Since arsenic may affect the immune system, leading to immunesuppression, we investigated the effects of acute arsenic exposure on the thymus and spleen using Swiss albino mice, exposed to 5 ppm, 15 ppm and 300 ppm of sodium arsenite for 7 d. Effects on cytokine balance and cell survivability were subsequently analyzed. Our data showed that arsenic treatment induced debilitating alterations in the tissue architecture of thymus and spleen. A dose-dependent decrease in the ratio of CD4⁺-CD8⁺ T-cells was observed along with a pro-inflammatory response and redox imbalance. In addition, pioneering evidences established the ability of arsenic to induce an up regulation of Hsp90, eventually resulting in stabilization of its client protein Beclin-1, an important autophagy-initiating factor. This association initiated the autophagic process, confirmed by co-immunoprecipitation assay, acridine orange staining and Western blot, indicating the effort of cells trying to survive at lower doses. However, increased arsenic assault led to apoptotic cell death in the lymphoid organs, possibly by increased ROS generation. There are several instances of autophagy and apoptosis taking place either simultaneously or sequentially due to oxidative stress. Since arsenic is a potent environmental stress factor, exposure to arsenic led to a dose-dependent increase in both autophagy and apoptosis in the thymus and spleen, and cell death could therefore possibly be induced by autophagy. Therefore, exposure to arsenic leads to serious effects on the immune physiology in mice, which may further have dire consequences on the health of exposed animals.

TBX3 deficiency accelerates apoptosis in cardiomyoblasts through regulation of P21 expression

Congenital heart disease (CHD) is the most common birth defect in newborns. There is increasing evidence that apoptosis and remodeling of the cardiomyoblasts are the major pathology of CHD. Previous research found that T-box transcription factor 3 (TBX3) was compulsory for the regulation of proliferation, cell cycle arrest and apoptosis in various cells. Hence, TBX3 might be involved in the treatment of CHD. The primary aim of this study was to study the effects of TBX3 on apoptosis in aged cardiomyoblasts and investigate the latent mechanism. In the present study, we found TBX3 knockdown induced proliferation inhibition, cell cycle arrest and apoptosis accompanied by mitochondrial dysfunction in cardiomyoblasts at passage 10 to 15. Apoptosis-inducing effects of TBX3 silence could be neutralized by silencing P21 using specific siRNA. In addition, the mRNA and protein expression levels of TBX3 in the heart tissues of sporadic type CHD donors were obviously down-regulated. In conclusion, we demonstrated that TBX3 deficiency accelerated apoptosis via directly regulating P21 expression in senescent cardiomyoblasts.

MicroRNA-183-3p up-regulated by vagus nerve stimulation mitigates chronic systolic heart failure via the reduction of BNIP3L-mediated autophagy

Chronic systolic heart failure (CSHF) was a complex syndrome. Recently, vagus nerve stimulation (VNS), a novel treatment method, has emerged for the treatment of CSHF. therefore the aim of this study was to explore the possible mechanism of VNS treatment alleviating CSHF in rats. Firstly, we found after VNS treatment for 72 h, the level of B-type natriuretic peptide in VNS group was lower than that in CSHF group. In addition, VNS treatment induced the elevated left ventricular ejection fraction level, reduced left ventricular end diastolic volume and left ventricular end systolic volume level in VNS group, suggesting a mitigation of CSHF by VNS. Then we found the level of miR-183-3p in CSHF group was much lower than that in VNS group by High-throughput sequencing. The further results indicated that Bcl-2 interacting protein 3 like (BNIP3L) was identified as the target gene of miR-183-3p, and the expression of BNIP3L was notably reduced in rats of VNS group compared with CSHF group. Moreover, the down-regulated expression of miR-183-3p increased BNIP3L-mediated autophagy in rats of CSHF group compared with VNS group. Further mechanism findings demonstrated that up-regulation of miR-183-3p reduced the expression of BNIP3L, while down-regulation of miR-183-3p facilitated the expression of BNIP3L in H9c2 cells. miR-183-3p could also regulate autophagy by targeting BNIP3L in vitro, which was manifested by overexpression of miR-183-3p to inhibit BNIP3L-mediated autophagy. Our data demonstrated that VNS treatment benefited CSHF via the up-regulation of miRNA-183-3p, which reduced the BNIP3L-mediated autophagy, providing a new therapeutic direction for CSHF.

Cytotoxicity and autophagy induction by graphene quantum dots with different functional groups

Graphene quantum dots (GQDs) possess great potential in various applications due to their superior physicochemical properties and wide array of available surface modifications. However, the toxicity of GQDs has not been systematically assessed, thus hindered their further development; especially, the risk of surface modifications of GQDs is largely unknown. In this study, we employed a lung carcinoma A549 cells as the model to investigate the cytotoxicity and autophagy induction of three types GQDs, including cGQDs (COOH-GQDs), hGQDs (OH-GQDs), and aGQDs (NH₂-GQDs). The results showed hGQDs was the most toxic, as significant cell death was induced at the concentration of 100 μg/mL, determining by WST-1 assay as well as Annexin-V-FITC/PI apoptosis analysis, whereas cGQDs and aGQDs were non-cytotoxic within the measured concentration. Autophagy detection was performed by TEM examination, LC3 fluorescence tracking, and Western-blot. Both aGQDs and hGQDs induced cellular autophagy to various degrees except for cGQDs. Further analysis on autophagy pathways indicated all GQDs significantly activated p-p38MAPK; p-ERK1/2 was inhibited by aGQDs and hGQDs but activated by cGQDs. p-JNK was inhibited by aGQDs and cGQDs, while activated by hGQDs. Simultaneously, Akt was activated by hGQDs but inhibited by aGQDs. Inhibition of autophagy by 3-MA significantly increased the cytotoxicity of GQDs, suggesting that autophagy played a protective role against the toxicity of GQDs. In conclusion, cGQDs showed excellent biocompatibility and may be considered for biological applications. Autophagy induction may be included in the health risk assessment of GQDs as it reflects the stress status which may eventually lead to diseases.

Role of Autophagy in Proteostasis: Friend and Foe in Cardiac Diseases

Due to ageing of the population, the incidence of cardiovascular diseases will increase in the coming years, constituting a substantial burden on health care systems. In particular, atrial fibrillation (AF) is approaching epidemic proportions. It has been identified that the derailment of proteostasis, which is characterized by the loss of homeostasis in protein biosynthesis, folding, trafficking, and clearance by protein degradation systems such as autophagy, underlies the development of common cardiac diseases. Among various safeguards within the proteostasis system, autophagy is a vital cellular process that modulates clearance of misfolded and proteotoxic proteins from cardiomyocytes. On the other hand, excessive autophagy may result in derailment of proteostasis and therefore cardiac dysfunction. Here, we review the interplay between autophagy and proteostasis in the healthy heart, discuss the imbalance between autophagy and proteostasis during cardiac diseases, including AF, and finally explore new druggable targets which may limit cardiac disease initiation and progression.

Hydrogen Sulfide Regulating Myocardial Structure and Function by Targeting Cardiomyocyte Autophagy

Objective:

Hydrogen sulfide (H₂S), a gaseous signal molecule, plays a crucial role in many pathophysiologic processes in the cardiovascular system. Autophagy has been shown to participate in the occurrence of many cardiac diseases. Increasing evidences indicated that H₂S regulates myocardial structure and function in association with the altered autophagy and plays a “switcher” role in the autophagy of myocardial diseases. The aim of this review was to summarize these insights and provide the experimental evidence that H₂S targets cardiomyocyte autophagy to regulate cardiovascular function.

Data Sources:

This review was based on data in articles published in the PubMed databases up to October 30, 2017, with the following keywords: “hydrogen sulfide,” “autophagy,” and “cardiovascular diseases.”

Study Selection:

Original articles and critical reviews on H₂S and autophagy were selected for this review.

Results:

When autophagy plays an adaptive role in the pathogenesis of diseases, H₂S restores autophagy; otherwise, when autophagy plays a detrimental role, H₂S downregulates autophagy to exert a cardioprotective function. For example, H₂S has beneficial effects by regulating autophagy in myocardial ischemia/reperfusion and plays a protective role by inhibiting autophagy during the operation of cardioplegia and cardiopulmonary bypass. H₂S postpones cardiac aging associated with the upregulation of autophagy but improves the left ventricular function of smoking rats by lowering autophagy.

Conclusions:

H₂S exerts cardiovascular protection by regulating autophagy. Cardiovascular autophagy would likely become a potential target of H₂S therapy for cardiovascular diseases.

Internalization of Titanium Dioxide Nanoparticles Is Cytotoxic for H9c2 Rat Cardiomyoblasts

Titanium dioxide nanoparticles (TiO₂ NPs) are widely used in industry and daily life. TiO₂ NPs can penetrate into the body, translocate from the lungs into the circulation and come into contact with cardiac cells. In this work, we evaluated the toxicity of TiO₂ NPs on H9c2 rat cardiomyoblasts. Internalization of TiO₂ NPs and their effect on cell proliferation, viability, oxidative stress and cell death were assessed, as well as cell cycle alterations. Cellular uptake of TiO₂ NPs reduced metabolic activity and cell proliferation and increased oxidative stress by 19-fold measured as H₂DCFDA oxidation. TiO₂ NPs disrupted the plasmatic membrane integrity and decreased the mitochondrial membrane potential. These cytotoxic effects were related with changes in the distribution of cell cycle phases resulting in necrotic death and autophagy. These findings suggest that TiO₂ NPs exposure represents a potential health risk, particularly in the development of cardiovascular diseases via oxidative stress and cell death.

Immunity, Inflammation, and Oxidative Stress in Heart Failure: Emerging Molecular Targets

PURPOSE

Heart failure (HF) remains a major cause of morbidity and mortality worldwide. Although various therapies developed over the last two decades have shown improved long term outcomes in patients with established HF, there has been little progress in preventing the adverse cardiac remodeling that initiates HF. To fill the gap in treatment, current research efforts are focused on understanding novel mechanisms and signaling pathways. Immune activation, inflammation, oxidative stress, alterations in mitochondrial bioenergetics, and autophagy have been postulated as important pathophysiological events in this process. An improved understanding of these complex processes could facilitate a therapeutic shift toward molecular targets that can potentially alter the course of HF.

METHODS

In this review, we address the role of immunity, inflammation, and oxidative stress as well as other novel emerging concepts in the pathophysiology of HF that may have therapeutic implications.

CONCLUSION

Based on the experimental and clinical studies presented here, we anticipate that a better understanding of the pathophysiology of HF will open the door for new therapeutic targets. A one-size-fits-all approach may not be appropriate for all patients with HF, and further clinical trials utilizing molecular targeting in HF may result in improved outcomes.

Systems pharmacological analysis of mitochondrial cardiotoxicity induced by selected tyrosine kinase inhibitors

Tyrosine kinase inhibitors (TKIs) are targeted therapies rapidly becoming favored over conventional cytotoxic chemotherapeutics. Our study investigates two FDA approved TKIs, DASATINIB; indicated for IMATINIB-refractory chronic myeloid leukemia, and SORAFENIB; indicated for hepatocellular carcinoma and advanced renal cell carcinoma. Limited but crucial evidence suggests that these agents can have cardiotoxic side effects ranging from hypertension to heart failure. A greater understanding of the underlying mechanisms of this cardiotoxicity are needed as concerns grow and the capacity to anticipate them is lacking. The objective of this study was to explore the mitochondrial-mediated cardiotoxic mechanisms of the two selected TKIs. This was achieved experimentally using immortalized human cardiomyocytes, AC16 cells, to investigate dose- and time-dependent cell killing, along with measurements of temporal changes in key signaling proteins involved in the intrinsic apoptotic and autophagy pathways upon exposure to these agents. Quantitative systems pharmacology (QSP) models were developed to capture the toxicological response in AC16 cells using protein dynamic data. The developed QSP models captured well all the various trends in protein signaling and cellular responses with good precision on the parameter estimates, and were successfully qualified using external data sets. An interplay between the apoptotic and autophagic pathways was identified to play a major role in determining toxicity associated with the investigated TKIs. The established modeling platform showed utility in elucidating the mechanisms of cardiotoxicity of SORAFENIB and DASATINIB. It may be useful for other small molecule targeted therapies demonstrating cardiac toxicities, and may aid in informing alternate dosing strategies to alleviate cardiotoxicity associated with these therapies.

EZH2 inhibits autophagic cell death of aortic vascular smooth muscle cells to affect aortic dissection

Enhancer of zeste homolog 2 (EZH2), a methyltransferase that di- and tri-methylates lysine-27 of histone H3, largely functions as a transcriptional repressor, and plays a critical role in various kinds of cancers. Here we report a novel function of EZH2 in regulating autophagic cell death (ACD) of vascular smooth muscle cells (VSMCs) that affect aortic dissection (AD). Inhibition of EZH2 activity by UNC1999 or knockdown EZH2 resulted in VSMC loss, while overexpression of EZH2 facilitated VSMC growth, and these effects of EZH2 on VSMCs were independent of proliferation and apoptosis. Interestingly, more autophagic vacuoles and increased LC3II protein levels were identified in VSMCs with EZH2 inhibition or deficiency. Moreover, when compared with counterparts, chloroquine alone, or chloroquine with rapamycin treatment led to more LC3II accumulation in EZH2 inhibited or knockdown VSMCs, which indicated that EZH2 negatively regulated autophagosome formation. In conjunction to this, ATG5 and ATG7 protein levels were remarkably increased in EZH2 inhibited or deficient VSMCs, and ATG5 or ATG7 knockdown virtually rescued VSMC loss induced by EZH2 inhibition or knockdown. In addition, we found that the MEK-ERK1/2 signaling pathway, but not AMPKα, mTOR, or AKT pathway, is responsible for the impact of EZH2 on ACD of VSMCs. Additionally, the adverse effects of EZH2 inhibition or knockdown on VSMCs were largely reversed by PD98059, an inhibitor of MEK1. More importantly, decreased EZH2 expression levels in the aortic wall of patients with AD indicated its contribution to VSMC loss and AD occurrence. Overall, these findings revealed that EZH2 affects ACD of VSMCs and the pathologic process of AD via regulating ATG5 and ATG7 expression and MEK-ERK1/2 signaling. Our hitherto unrecognized findings indicate that EZH2 activation has therapeutic or preventive potential for AD.

Lipotoxic very-long-chain ceramides cause mitochondrial dysfunction, oxidative stress, and cell death in cardiomyocytes

Accumulating data support a role for bioactive lipids as mediators of lipotixicity in cardiomyocytes. One class of these, the ceramides, constitutes a family of molecules that differ in structure and are synthesized by distinct enzymes, ceramide synthase (CerS)1-CerS6. Data support that specific ceramides and the enzymes that catalyze their formation play distinct roles in cell function. In a mouse model of diabetic cardiomyopathy, sphingolipid profiling revealed increases in not only the CerS5-derived ceramides but also in very long chain (VLC) ceramides derived from CerS2. Overexpression of CerS2 elevated VLC ceramides caused insulin resistance, oxidative stress, mitochondrial dysfunction, and mitophagy. Palmitate induced CerS2 and oxidative stress, mitophagy, and apoptosis, which were prevented by depletion of CerS2. Neither overexpression nor knockdown of CerS5 had any function in these processes, suggesting a chain-length dependent impact of ceramides on mitochondrial function. This concept was also supported by the observation that synthetic mitochondria-targeted ceramides led to mitophagy in a manner proportional to N-acyl chain length. Finally, blocking mitophagy exacerbated cell death. Taken together, our results support a model by which CerS2 and VLC ceramides have a distinct role in lipotoxicity, leading to mitochondrial damage, which results in subsequent adaptive mitophagy. Our data reveal a novel lipotoxic pathway through CerS2.-Law, B. A., Liao, X., Moore, K. S., Southard, A., Roddy, P., Ji, R., Szulc, Z., Bielawska, A., Schulze, P. C., Cowart, L. A. Lipotoxic very-long-chain ceramides cause mitochondrial dysfunction, oxidative stress, and cell death in cardiomyocytes.

A polynomial based model for cell fate prediction in human diseases

BACKGROUND

Cell fate regulation directly affects tissue homeostasis and human health. Research on cell fate decision sheds light on key regulators, facilitates understanding the mechanisms, and suggests novel strategies to treat human diseases that are related to abnormal cell development.

RESULTS

In this study, we proposed a polynomial based model to predict cell fate. This model was derived from Taylor series. As a case study, gene expression data of pancreatic cells were adopted to test and verify the model. As numerous features (genes) are available, we employed two kinds of feature selection methods, i.e. correlation based and apoptosis pathway based. Then polynomials of different degrees were used to refine the cell fate prediction function. 10-fold cross-validation was carried out to evaluate the performance of our model. In addition, we analyzed the stability of the resultant cell fate prediction model by evaluating the ranges of the parameters, as well as assessing the variances of the predicted values at randomly selected points. Results show that, within both the two considered gene selection methods, the prediction accuracies of polynomials of different degrees show little differences. Interestingly, the linear polynomial (degree 1 polynomial) is more stable than others. When comparing the linear polynomials based on the two gene selection methods, it shows that although the accuracy of the linear polynomial that uses correlation analysis outcomes is a little higher (achieves 86.62%), the one within genes of the apoptosis pathway is much more stable.

CONCLUSIONS

Considering both the prediction accuracy and the stability of polynomial models of different degrees, the linear model is a preferred choice for cell fate prediction with gene expression data of pancreatic cells. The presented cell fate prediction model can be extended to other cells, which may be important for basic research as well as clinical study of cell development related diseases.

TLR3 contributes to persistent autophagy and heart failure in mice after myocardial infarction

Toll-like receptors (TLRs) are essential immunoreceptors involved in host defence against invading microbes. Recent studies indicate that certain TLRs activate immunological autophagy to eliminate microbes. It remains unknown whether TLRs regulate autophagy to play a role in the heart. This study examined this question. The activation of TLR3 in cultured cardiomyocytes was observed to increase protein levels of autophagic components, including LC3-II, a specific marker for autophagy induction, and p62/SQSTM1, an autophagy receptor normally degraded in the final step of autophagy. The results of transfection with a tandem mRFP-GFP-LC3 adenovirus and use of an autophagic flux inhibitor chloroquine both suggested that TLR3 in cardiomyocytes promotes autophagy induction without affecting autophagic flux. Gene-knockdown experiments showed that the TRIF-dependent pathway mediated the autophagic effect of TLR3. In the mouse model of chronic myocardial infarction, persistent autophagy was observed, concomitant with up-regulated TLR3 expression and increased TLR3-Trif signalling. Germline knockout (KO) of TLR3 inhibited autophagy, reduced infarct size, attenuated heart failure and improved survival. These protective effects were abolished by in vivo administration of an autophagy inducer rapamycin. Similar to the results obtained in cultured cardiomyocytes, TLR3-KO did not prevent autophagic flux in mouse heart. Additionally, this study failed to detect the involvement of inflammation in TLR3-KO-derived protection, as wild-type and TLR3-KO hearts were comparable in inflammatory activity. It is concluded that up-regulated TLR3 expression and signalling contributes to persistent autophagy following MI, which promotes heart failure and lethality.

Autophagy inhibitor 3-methyladenine alleviates overload-exercise-induced cardiac injury in rats

Overload-exercise (OE) causes myocardial injury through inducing autophagy and apoptosis. In this study we examined whether an autophagy inhibitor 3-methyladenine (3-MA) could alleviate OE-induced cardiac injury. Rats were injected with 3-MA (15 mg/kg, iv) or saline before subjected to various intensities of OE, including no swim (control), 2 h swim (mild-intensity exercise, MIE), 2 h swim with 2.5% body weight overload (moderate OE; MOE), 5% overload (intensive OE; IOE) or 2.5% overload until exhausted (exhaustive OE; EOE). After OE, the hearts were harvested for morphological and biochemiacal analysis. The cardiac morphology, autophagosomes and apoptosis were examined with H&E staining, transmission electron microscopy and TUNEL analysis, respectively. Autophagy-related proteins to (LC3-II/I and Beclin-1) and apoptosis-related proteins (Bcl-2/Bax) were assessed using Western blotting. Our results showed that compared with the control, MIE did not change the morphological structures of the heart tissues that exhibited intact myocardial fibers and neatly arranged cardiomyocytes. However, IOE resulted in irregular arrangement of cardiomyocytes and significantly increased width of cardiomyocytes, whereas EOE caused more swollen and even disrupted cardiomyocytes. In parallel with the increased OE intensity (MOE, IOE, EOE), cardiomyocyte autophagy and apoptosis became more and more prominent, evidenced by the increasing number of autophagosomes and expression levels of LC3-II/I and Beclin-1 as well as the increasing apoptotic cells and decreasing Bcl-2/Bax ratio. 3-MA administration significantly attenuated OE-induced morphological changes of cardiomyocytes as well as all the autophagy- and apoptosis-related abnormalities in MOE, IOE and EOE rats. Thus, the autophagy inhibitor 3-MA could alleviate OE-induced heart injury in rats.

Standard Immunohistochemical Assays to Assess Autophagy in Mammalian Tissue

Autophagy is a highly conserved lysosomal degradation pathway with major impact on diverse human pathologies. Despite the development of different methodologies to detect autophagy both in vitro and in vivo, monitoring autophagy in tissue via immunohistochemical techniques is hampered due to the lack of biomarkers. Immunohistochemical detection of a punctate pattern of ATG8/MAP1LC3 proteins is currently the most frequently used approach to detect autophagy in situ, but it depends on a highly sensitive detection method and is prone to misinterpretation. Moreover, reliable MAP1LC3 immunohistochemical staining requires correct tissue processing and high-quality, isoform-specific antibodies. Immunohistochemical analysis of other autophagy-related protein targets such as SQSTM1, ubiquitin, ATG5 or lysosomal proteins is not recommended as marker for autophagic activity in tissue for multiple reasons including aspecific labeling of cellular structures and a lack of differential protein expression during autophagy initiation. To better understand the role of autophagy in human disease, novel biomarkers for visualization of the autophagic process with standard histology techniques are urgently needed.

MicroRNAs and Autophagy: Fine Players in the Control of Chondrocyte Homeostatic Activities in Osteoarthritis

Osteoarthritis (OA) is a debilitating degenerative disease of the articular cartilage with a multifactorial etiology. Aging, the main risk factor for OA development, is associated with a systemic oxidative and inflammatory phenotype. Autophagy is a central housekeeping system that plays an antiaging role by supporting the clearance of senescence-associated alterations of macromolecules and organelles. Autophagy deficiency has been related to OA pathogenesis because of the accumulation of cellular defects in chondrocytes. Microribonucleic acids (microRNAs or miRs) are a well-established class of posttranscriptional modulators belonging to the family of noncoding RNAs that have been identified as key players in the regulation of cellular processes, such as autophagy, by targeting their own cognate mRNAs. Here, we present a state-of-the-art literature review on the role of miRs and autophagy in the scenario of OA pathogenesis. In addition, a comprehensive survey has been performed on the functional connections of the miR network and the autophagy pathway in OA by using "microRNA," "autophagy," and "osteoarthritis" as key words. Discussion of available evidence sheds light on some aspects that need further investigation in order to reach a more comprehensive view of the potential of this topic in OA.

Metabolic Origins of Heart Failure

For more than half a century, metabolic perturbations have been explored in the failing myocardium, highlighting a reversion to a more fetal-like metabolic profile (characterized by depressed fatty acid oxidation and concomitant increased reliance on use of glucose). More recently, alterations in ketone body and amino acid/protein metabolism have been described during heart failure, as well as mitochondrial dysfunction and perturbed metabolic signaling (e.g., acetylation, O-GlcNAcylation). Although numerous mechanisms are likely involved, the current review provides recent advances regarding the metabolic origins of heart failure, and their potential contribution toward contractile dysfunction of the heart.

Cobalt chloride induces RhoA/ROCK activation and remodeling effect in H9c2 cardiomyoblasts: Involvement of PI3K/Akt and MAPK pathways

Chronic heart failure is a serious complication of myocardial infarction, one of the major causes of death worldwide that often leads to adverse cardiac hypertrophy and poor prognosis. Hypoxia-induced cardiac tissue remodeling is considered an important underlying etiology. This study aimed to delineate the signaling profiles of RhoA/ROCK, PI3K/Akt, and MAPK and their involvement in regulation of remodeling events in cultured H9c2 cardiomyoblast cells. In addition to its growth-suppressive effect, the hypoxia-mimetic chemical, cobalt chloride (CoCl₂) significantly induced RhoA kinase activation as revealed by increased MBS phosphorylation and ROCK1/2 expression in H9c2 cells. CoCl₂ treatment up-regulated type I collagen and MMP-9, but did not affect MMP-2, implicating its role in tissue remodeling. Kinetic signal profiling study showed that CoCl₂ also elicited Smad2 hyperphosphorylation and its nuclear translocation in the absence of TGF-β1. In addition, CoCl₂ activated Akt-, ERK1/2-, JNK-, and p38 MAPK-mediated signaling pathways. Kinase inhibition experiments demonstrated that hydroxyfasudil, a RhoA kinase inhibitor, significantly blocked the CoCl₂- and lysophosphatidic acid-evoked Smad2 phosphorylation and overexpression of type I collagen and MMP-9, and that PI3K and ERK interplayed with RhoA and its downstream Smad2 signaling cascade. In conclusion, this study demonstrated that RhoA/ROCK, PI3K/Akt, and MAPK pathways are mechanistically involved in the CoCl₂-stimulated tissue remodeling in H9c2 cardiomyoblast cells. Targeting signaling mediators might be used to mitigate hypoxia-related Smad2 phosphorylation and cardiac remodeling events in ischemic cardiomyopathy.

Autophagy, Metabolic Disease, and Pathogenesis of Heart Dysfunction

In normal physiology, autophagy is recognized as a protective housekeeping mechanism that enables elimination of unhealthy organelles, protein aggregates, and invading pathogens, as well as recycling cell components and producing new building blocks and energy for cellular renovation and homeostasis. However, overactive or depressed autophagy is often associated with the pathogenesis of multiple disorders, including cardiac disease. During metabolic disorders, such as diabetes and obesity, dysregulation of autophagy frequently leads to cell death, cardiomyopathy, and cardiac dysfunction. In this article, we summarize the current understanding of autophagy-its classification, progression, and regulation; its roles in both physiological and pathophysiological conditions; and the balance between autophagy and apoptosis. We also explore how dysregulation of autophagy leads to cell death in models of metabolic disease and its contributing factors-including nutrient state, hyperglycemia, dyslipidemia, insulin inefficiency, and oxidative stress-and outline some recent efforts to restore normal autophagy in pathophysiological states. This information could provide potential targets for the prevention of, or intervention in, cardiac failure in metabolic disorders such as diabetes and obesity.

Necroptotic cell death in failing heart: relevance and proposed mechanisms

As cardiomyocytes have a limited capability for proliferation, renewal, and repair, the loss of heart cells followed by replacement with fibrous tissue is considered to result in the development of ventricular dysfunction and progression to heart failure (HF). The loss of cardiac myocytes in HF has been traditionally believed to occur mainly due to programmed apoptosis or unregulated necrosis. While extensive research work is being carried out to define the exact significance and contribution of both these cell death modalities in the development of HF, recent knowledge has indicated the existence and importance of a different form of cell death called necroptosis in the failing heart. This new cell damaging process, resembling some of the morphological features of passive necrosis as well as maladaptive autophagy, is a programmed process and is orchestrated by a complex set of proteins involving receptor-interacting protein kinase 1 and 3 (RIP1, RIP3) and mixed lineage kinase domain-like protein (MLKL). Activation of the RIP1-RIP3-MLKL signaling pathway leads to disruption of cation homeostasis, plasma membrane rupture, and finally cell death. It seems likely that inhibition of any site in this pathway may prove as an effective pharmacological intervention for preventing the necroptotic cell death in the failing heart. This review is intended to describe general aspects of the signaling pathway associated with necroptosis, to describe its relationship with cardiac dysfunction in some models of cardiac injury and discuss its potential relevance in various types of HF with respect to the underlying pathologic mechanisms.

Mitochondrial involvement in myocyte death and heart failure

As the heart is an energy-demanding organ, impaired cardiac energy metabolism and mitochondrial function have been inexorably linked to cardiac dysfunction. There is a growing recognition that mitochondrial dysfunction contributes to impaired myocardial energetics and increased oxidative stress in cardiomyopathies, cardiac ischemic damage and heart failure (HF), and mitochondrial permeability transition pore opening has been reported a critical trigger of myocyte death and myocardial remodeling. It is well established that mitochondria play pivotal roles in intracellular signaling in both cell death as well as in cardioprotective pathways. Moreover, recent studies have shown that defects in mitochondrial dynamics affecting biogenesis and turnover are linked to cardiac senescence and HF. Accordingly, there has been an increasing interest in targeting mitochondria for HF therapy. This article reviews the background and recent evidence of mitochondrial involvement in several types of cell death (apoptosis, necrosis and autophagy) occurring in HF. In addition, potential strategies for targeting mitochondria are examined, and their utility in HF therapy considered.

Caveolin-3 plays a critical role in autophagy after ischemia-reperfusion

Autophagy is a dynamic recycling process responsible for the breakdown of misfolded proteins and damaged organelles, providing nutrients and energy for cellular renovation and homeostasis. Loss of autophagy is associated with cardiovascular diseases. Caveolin-3 (Cav-3), a muscle-specific isoform, is a structural protein within caveolae and is critical to stress adaptation in the heart. Whether Cav-3 plays a role in regulating autophagy to modulate cardiac stress responses remains unknown. In the present study, we used HL-1 cells, a cardiac muscle cell line, with stable Cav-3 knockdown (Cav-3 KD) and Cav-3 overexpression (Cav-3 OE) to study the impact of Cav-3 in regulation of autophagy. We show that traditional stimulators of autophagy (i.e., rapamycin and starvation) result in upregulation of the process in Cav-3 OE cells while Cav-3 KD cells have a blunted response. Cav-3 coimmunoprecipitated with beclin-1 and Atg12, showing an interaction of caveolin with autophagy-related proteins. In the heart, autophagy may be a major regulator of protection from ischemic stress. We found that Cav-3 KD cells have a decreased expression of autophagy markers [beclin-1, light chain (LC3-II)] after simulated ischemia and ischemia-reperfusion (I/R) compared with WT, whereas OE cells showed increased expression. Moreover, Cav-3 KD cells showed increased cell death and higher level of apoptotic proteins (cleaved caspase-3 and cytochrome c) with suppressed mitochondrial function in response to simulated ischemia and I/R, whereas Cav-3 OE cells were protected and had preserved mitochondrial function. Taken together, these results indicate that autophagy regulates adaptation to cardiac stress in a Cav-3-dependent manner.

Role of proteases in the pathophysiology of cardiac disease

Cardiovascular disease is a major cause of death and thus a great deal of effort has been made in salvaging the diseased myocardium. Although various factors have been identified as possible causes of different cardiac diseases such as heart failure and ischemic heart disease, there is a real need to elucidate their role for the better understanding of the cardiac disease pathology and formulation of strategies for developing newer therapeutic interventions. In view of the intimate involvement of different types of proteases in maintaining cellular structure, the role of proteases in various cardiac diseases has become the focus of recent research. Proteases are present in the cytosol as well as are localized in a number of subcellular organelles in the cell. These are known to use extracellular matrix, cytoskeletal, sarcolemmal, sarcoplasmic reticular, mitochondrial and myofibrillar proteins as substrates. Work from different laboratories using a wide variety of techniques has shown that the activation of proteases causes alterations of a number of specific proteins leading to subcellular remodeling and cardiac dysfunction. Inhibition of protease action by different drugs and agents, therefore, has a clinical relevance and is expected to form a part of new treatment paradigm for improving heart function. This review examines the biochemistry and localization of some of the proteases in the cardiac tissue in addition to identification of the sites of action of some protease inhibitors. (Mol Cell Biochem 263: 241-256, 2004).

Resveratrol Ameliorates Pressure Overload-induced Cardiac Dysfunction and Attenuates Autophagy in Rats

Pressure overload has an important role in heart failure, inducing excessive autophagy in cardiac myocytes that is considered to be pathogenic. Resveratrol has been reported to improve cardiac dysfunction induced by pressure overload, but it has been unclear whether resveratrol ameliorates cardiac dysfunction by regulating autophagy. In this study, heart failure was induced in rats by constriction of the abdominal aorta. Four weeks after surgery, the rats with heart failure were randomized to treatment with resveratrol (8 mg · kg(-1) · d(-1) by intraperitoneal injection) for 28 days or to intraperitoneal injection of the vehicle (propylene glycol) alone. Echocardiography was performed to assess cardiac function. Expression of brain natriuretic peptide messenger RNA in the left ventricle was detected by real-time polymerase chain reaction, whereas expression of proteins associated with autophagy (beclin-1 and lamp-1) was detected by western blotting and immunohistochemistry. Furthermore, autophagic vacuoles were detected in the heart by transmission electron microscopy, and the myocardial ATP content was measured by the bioluminescence method. Treatment with resveratrol significantly improved cardiac dysfunction and reduced brain natriuretic peptide expression in rats with heart failure. Resveratrol down-regulated beclin-1 and lamp-1 expression and also inhibited the formation of autophagic vacuoles in failing hearts. Furthermore, resveratrol restored the myocardial ATP level and reduced phosphorylation of AMP-activated protein kinase at Thr172. These results suggest that resveratrol may inhibit autophagy through inactivation of AMP-activated protein kinase and restoration of ATP in heart failure induced by pressure overload. Accordingly, resveratrol may be beneficial for patients with hypertensive heart disease.

Hypoxia suppresses myocardial survival pathway through HIF-1α-IGFBP-3-dependent signaling and enhances cardiomyocyte autophagic and apoptotic effects mainly via FoxO3a-induced BNIP3 expression

The HIF-1α transcriptional factor and the BH-3 only protein BNIP3 are known to play fundamental roles in response to hypoxia. The objective of this research is to investigate the molecular mechanisms and the correlation of HIF-1α, BNIP3 and IGFBP-3 in hypoxia-induced cardiomyocytes injuries. Heart-derived H9c2 cells and neonatal rat ventricular myocytes (NRVMs) were incubated in normoxic or hypoxic conditions. Hypoxia increased HIF-1α expression and activated the downstream BNIP3 and IGFBP-3 thereby triggered mitochondria-dependent apoptosis. Moreover, IGF1R/PI3K/Akt signaling was attenuated by HIF-1α-dependent IGFBP-3 expression to enhance hypoxia-induced apoptosis. Autophagy suppression with 3-methyladenine or siATG5 or siBeclin-1 significantly decreased myocardial apoptosis under hypoxia. Knockdown of FoxO3a or BNIP3 significantly abrogated hypoxia-induced autophagy and mitochondria-dependent apoptosis. Moreover, prolonged-hypoxia induced HIF-1α stimulated BNIP3 and enhanced IGFBP-3 activation to inhibit IGF1R/PI3K/Akt survival pathway and mediate mitochondria-dependent cardiomyocyte apoptosis. HIF-1α and FoxO3a blockage are sufficient to annul the change of excessive hypoxia of hearts.

BNIP3 promotes calcium and calpain-dependent cell death

AIMS

Loss of cardiac muscle by programmed cell death contributes to the progression of ischemic heart disease. Hypoxia, metabolite waste buildup and energy depletion are components of ischemia which may initiate caspase dependent and independent cell death pathways. Previous work from our laboratory has shown that combined hypoxia with acidosis, a hallmark of ischemia promotes cardiac myocyte injury with increasing severity as the pH declines. Hypoxia-acidosis was demonstrated to activate the pro-apoptotic Bcl-2 protein BNIP3 which initiated opening of the mitochondrial permeability transition pore and cell death in the absence of caspase activation. Because calpains are known to contribute to ischemic myocardial damage in some models, we hypothesized that they are intermediates in the BNIP3-mediated death caused by hypoxia-acidosis.

MAIN METHODS

Neonatal rat cardiac myocytes were subjected to hypoxia with and without acidosis and the contribution of calpains to hypoxia-acidosis cell death determined.

KEY FINDINGS

Here we report that the death pathway activated by hypoxia-acidosis is driven by a combination of calcium-activated calpains and pro-death factors (DNases) secreted by the mitochondria. Cytochrome c accumulated in the cytoplasm during hypoxia-acidosis but caspase activity was repressed through a calpain-dependent process that prevents the cleavage of procaspase 3. Calpain inhibitors provide vigorous protection against hypoxia-acidosis-induced programmed death. Knockdown of BNIP3 with siRNA prevented calpain activation confirming a central role of BNIP3 in this pathway.

SIGNIFICANCE

The results implicate BNIP3 and calpain as dependent components of cardiac myocyte death caused by hypoxia-acidosis.

Shuangshen Ningxin Capsule, a Traditional Chinese Medicinal Preparation, Alleviates Myocardial Ischemia through Autophagy Regulation

Shuangshen Ningxin capsule (SSNX), a modern Chinese formula, has been used to treat cardiovascular diseases in Eastern Asia. Our study focuses on the autophagy regulation of SSNX against coronary artery injuries. Myocardial infarction model was established in Chinese miniswines (CMS) by coronary artery balloon injury. SSNX was administered to the CMS for 8 weeks with 4 mg/kg or 16 mg/kg. Myocardial cells were incubated with 20% SSNX medicated serum for 2 hours. Assays were performed to detect the effects of SSNX on (i) coronary artery diameter by angiography, (ii) hemodynamics by noninvasive hemodynamic monitoring system, (iii) plaque burden and plaque volume by intravenous ultrasound (iv) coronary artery histology by H&E staining, (v) autophagosome by transmission electron microscopy, (vi) lactate dehydrogenase (LDH) leakage, and (vii) Beclin-1 and LC3-I/II expressions by Western blot. The results showed that CMS treated with SSNX exhibited the correction for the disturbed cardiac hemodynamics, increase of coronary artery diameter, reduction of high plaque burden and plaque volume, and decrease of LDH. The inhibitory effect of SSNX on CMS autophagy was demonstrated by the reduction of autophagosome and the downregulation of beclin-1 and LC3-I/II. SSNX may protect coronary artery and increase the stability of plaque through the suppression of myocardial cellular autophagy, which suggests the potentially therapeutic effect of SSNX on ischemic cardiovascular disease.

Methods to assess autophagy in situ--transmission electron microscopy versus immunohistochemistry

Autophagy is a well-conserved lysosomal degradation pathway that plays a major role in both oncogenesis and tumor progression. Transmission electron microscopy (TEM) as well as immunohistochemistry are indispensable tools for the evaluation of autophagy in situ. Here, we describe an optimized protocol for the study of autophagic vacuoles by TEM and elaborate on the immunohistochemical detection of microtubule-associated protein 1 light chain (MAP1LC3, best known as LC3), which is currently considered as one of the most reliable markers of the autophagic process. The advantages, potential pitfalls, and limitations of these methods, as well as their value in the field of autophagy and oncometabolism research are discussed. Overall, we recommend a combined use of different techniques including TEM, immunohistochemistry, and molecular approaches (such as immunoblotting) for the unambiguous detection of autophagy in malignant as well as in normal tissues.

Autophagy in Vascular Disease

Autophagy is a reparative, life-sustaining process by which cytoplasmic components are sequestered in double-membrane vesicles and degraded on fusion with lysosomal compartments. Growing evidence reveals that basal autophagy is an essential in vivo process mediating proper vascular function. Moreover, autophagy is stimulated by many stress-related stimuli in the arterial wall to protect endothelial cells and smooth muscle cells against cell death and the initiation of vascular disease, in particular atherosclerosis. Basal autophagy is atheroprotective during early atherosclerosis but becomes dysfunctional in advanced atherosclerotic plaques. Little is known about autophagy in other vascular disorders, such as aneurysm formation, arterial aging, vascular stiffness, and chronic venous disease, even though autophagy is often impaired. This finding highlights the need for pharmacological interventions with compounds that stimulate the prosurvival effects of autophagy in the vasculature. A large number of animal studies and clinical trials have indicated that oral or stent-based delivery of the autophagy inducer rapamycin or derivatives thereof, collectively known as rapalogs, effectively inhibit the basic mechanisms that control growth and destabilization of atherosclerotic plaques. Other autophagy-inducing drugs, such as spermidine or add-on therapy with widely used antiatherogenic compounds, including statins and metformin, are potentially useful to prevent vascular disease with minimal adverse effects.

Cell competition promotes phenotypically silent cardiomyocyte replacement in the mammalian heart

Heterogeneous anabolic capacity in cell populations can trigger a phenomenon known as cell competition, through which less active cells are eliminated. Cell competition has been induced experimentally in stem/precursor cell populations in insects and mammals and takes place endogenously in early mouse embryonic cells. Here, we show that cell competition can be efficiently induced in mouse cardiomyocytes by mosaic overexpression of Myc during both gestation and adult life. The expansion of the Myc-overexpressing cardiomyocyte population is driven by the elimination of wild-type cardiomyocytes. Importantly, this cardiomyocyte replacement is phenotypically silent and does not affect heart anatomy or function. These results show that the capacity for cell competition in mammals is not restricted to stem cell populations and suggest that stimulated cell competition has potential as a cardiomyocyte-replacement strategy.