Necroptotic cell death in failing heart: relevance and proposed mechanisms

Necroptosis: a significant and promising target for intervention of cardiovascular disease

Due to changes in dietary structures, population aging, and the exacerbation of metabolic risk factors, the incidence of cardiovascular disease continues to rise annually, posing a significant health burden worldwide. Cell death plays a crucial role in the onset and progression of cardiovascular diseases. As a regulated endpoint encountered by cells under adverse stress conditions, the execution of necroptosis is regulated by classicalpathways, the calmodulin-dependent protein kinases (CaMK) pathway, and mitochondria-dependent pathways, and implicated in various cardiovascular diseases, including atherosclerosis, myocardial infarction, myocardial ischemia-reperfusion injury (IRI), heart failure, diabetic cardiomyopathy, dilated cardiomyopathy, hypertrophic cardiomyopathy, chemotherapy drug-induced cardiomyopathy, and abdominal aortic aneurysm (AAA). To further investigate potential therapeutic targets for cardiovascular diseases, we also analyzed the main molecules and their inhibitors involved in necroptosis in an effort to uncover insights for treatment.

Necrosis-like cell death modes in heart failure: the influence of aetiology and the effects of RIP3 inhibition

Since cell dying in heart failure (HF) may vary based on the aetiology, we examined the main forms of regulated necrosis, such as necroptosis and pyroptosis, in the hearts damaged due to myocardial infarction (MI) or pressure overload. We also investigated the effects of a drug inhibiting RIP3, a proposed convergent point for both these necrosis-like cell death modes. In rat hearts, left ventricular function, remodelling, pro-cell death, and pro-inflammatory events were investigated, and the pharmacodynamic action of RIP3 inhibitor (GSK'872) was assessed. Regardless of the HF aetiology, the heart cells were dying due to necroptosis, albeit the upstream signals may be different. Pyroptosis was observed only in post-MI HF. The dysregulated miRNAs in post-MI hearts were accompanied by higher levels of a predicted target, HMGB1, its receptors (TLRs), as well as the exacerbation of inflammation likely originating from macrophages. The RIP3 inhibitor suppressed necroptosis, unlike pyroptosis, normalised the dysregulated miRNAs and tended to decrease collagen content and affect macrophage infiltration without affecting cardiac function or structure. The drug also mitigated the local heart inflammation and normalised the higher circulating HMGB1 in rats with post-MI HF. Elevated serum levels of HMGB1 were also detected in HF patients and positively correlated with C-reactive protein, highlighting pro-inflammatory axis. In conclusion, in MI-, but not pressure overload-induced HF, both necroptosis and pyroptosis operate and might underlie HF pathogenesis. The RIP3-targeting pharmacological intervention might protect the heart by preventing pro-death and pro-inflammatory mechanisms, however, additional strategies targeting multiple pro-death pathways may exhibit greater cardioprotection.

Novel therapeutic targets for cardiorenal syndrome

Cardiorenal syndrome (CRS) is an interdependent dysfunction of the heart and kidneys, where failure in one organ precipitates failure in the other. The pathophysiology involves sustained renin-angiotensin-aldosterone-system (RAAS) activation, mitochondrial dysfunction, inflammation, fibrosis, oxidative stress and tissue remodeling, culminating in organ dysfunction. Existing therapies targeting the RAAS, diuretics and other agents have limitations, including diuretic resistance and compensatory sodium reabsorption. Therefore, there is a pressing need for novel druggable targets involved in CRS pathogenesis. This review addresses the challenges of existing treatments and emphasizes the importance of discovering new therapeutic targets. It highlights emerging targets such as Klotho, sex-determining region Y box 9 (SOX9), receptor-interacting protein kinase 3 (RIPK3), β-amino-isobutyric acid (BAIBA), thrombospondin-1 (TSP-1), among others, with their potential roles in CRS.

Novel, non-conventional pathways of necroptosis in the heart and other organs: Molecular mechanisms, regulation and inter-organelle interplay

Necroptosis, a cell death modality that is defined as a necrosis-like cell death depending on the receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like pseudokinase (MLKL), has been found to underlie the injury of various organs. Nevertheless, the molecular background of this cell loss seems to also involve, at least under certain circumstances, some novel axes, such as RIPK3-PGAM5-Drp1 (mitochondrial protein phosphatase 5-dynamin-related protein 1), RIPK3-CaMKII (Ca2+/calmodulin-dependent protein kinase II) and RIPK3-JNK-BNIP3 (c-Jun N-terminal kinase-BCL2 Interacting Protein 3). In addition, endoplasmic reticulum stress and oxidative stress via the higher production of reactive oxygen species produced by the mitochondrial enzymes and the enzymes of the plasma membrane have been implicated in necroptosis, thereby depicting an inter-organelle interplay in the mechanisms of this cell death. However, the role and relationship between these novel non-conventional signalling and the well-accepted canonical pathway in terms of tissue- and/or disease-specific prioritisation is completely unknown. In this review, we provide current knowledge on some necroptotic pathways being not directly associated with RIPK3-MLKL execution and report studies showing the role of respective microRNAs in the regulation of necroptotic injury in the heart and in some other tissues having a high expression of the pro-necroptotic proteins.

The pathophysiological role of receptor-interacting protein kinase 3 in cardiovascular disease

Recent studies have found that receptor interacting protein kinase 3 (RIPK3) can mediate CaMK Ⅱ phosphorylation and oxidation, open mitochondrial permeability transition pore (mPTP), and induce myocardial necroptosis. The increased expression or phosphorylation of RIPK3 is one of the important markers of necroptosis; Inhibition of CaMK Ⅱ phosphorylation or oxidation significantly reduces RIPK3 mediated myocardial necroptosis; Studies have shown that necroptosis plays an important role in the occurrence and development of cardiovascular diseases; Using the selective inhibitor GSK '872 of RIPK3 can effectively inhibit the occurrence and development of cardiovascular diseases, and can reverse cardiovascular and cardiac dysfunction caused by overexpression of RIPK3. In this review, we provide a brief overview of the current knowledge on RIPK3 in mediating necroptosis, inflammatory response, and oxidative stress, and discussed the role of RIPK3 in cardiovascular diseases such as atherosclerosis, myocardial ischaemia, myocardial infarction, and heart failure.

Pharmaceutical Therapies for Necroptosis in Myocardial Ischemia-Reperfusion Injury

Cardiovascular disease morbidity/mortality are increasing due to an aging population and the rising prevalence of diabetes and obesity. Therefore, innovative cardioprotective measures are required to reduce cardiovascular disease morbidity/mortality. The role of necroptosis in myocardial ischemia-reperfusion injury (MI-RI) is beyond doubt, but the molecular mechanisms of necroptosis remain incompletely elucidated. Growing evidence suggests that MI-RI frequently results from the superposition of multiple pathways, with autophagy, ferroptosis, and CypD-mediated mitochondrial damage, and necroptosis all contributing to MI-RI. Receptor-interacting protein kinases (RIPK1 and RIPK3) as well as mixed lineage kinase domain-like pseudokinase (MLKL) activation is accompanied by the activation of other signaling pathways, such as Ca²⁺/calmodulin-dependent protein kinase II (CaMKII), NF-κB, and JNK-Bnip3. These pathways participate in the pathological process of MI-RI. Recent studies have shown that inhibitors of necroptosis can reduce myocardial inflammation, infarct size, and restore cardiac function. In this review, we will summarize the molecular mechanisms of necroptosis, the links between necroptosis and other pathways, and current breakthroughs in pharmaceutical therapies for necroptosis.

Essential Amino Acids-Rich Diet Increases Cardiomyocytes Protection in Doxorubicin-Treated Mice

BACKGROUND

Doxorubicin (Doxo) is a widely prescribed drug against many malignant cancers. Unfortunately, its utility is limited by its toxicity, in particular a progressive induction of congestive heart failure. Doxo acts primarily as a mitochondrial toxin, with consequent increased production of reactive oxygen species (ROS) and attendant oxidative stress, which drives cardiac dysfunction and cell death. A diet containing a special mixture of all essential amino acids (EAAs) has been shown to increase mitochondriogenesis, and reduce oxidative stress both in skeletal muscle and heart. So, we hypothesized that such a diet could play a favorable role in preventing Doxo-induced cardiomyocyte damage.

METHODS

Using transmission electron microscopy, we evaluated cells' morphology and mitochondria parameters in adult mice. In addition, by immunohistochemistry, we evaluated the expression of pro-survival marker Klotho, as well as markers of necroptosis (RIP1/3), inflammation (TNFα, IL1, NFkB), and defense against oxidative stress (SOD1, glutathione peroxidase, citrate synthase).

RESULTS

Diets with excess essential amino acids (EAAs) increased the expression of Klotho and enhanced anti-oxidative and anti-inflammatory responses, thereby promoting cell survival.

CONCLUSION

Our results further extend the current knowledge about the cardioprotective role of EAAs and provide a novel theoretical basis for their preemptive administration to cancer patients undergoing chemotherapy to alleviate the development and severity of Doxo-induced cardiomyopathy.

The MEF2A transcription factor interactome in cardiomyocytes

Transcriptional regulators encoded by the Myocyte Enhancer Factor 2 (MEF2) gene family play a fundamental role in cardiac development, homeostasis and pathology. Previous studies indicate that MEF2A protein-protein interactions serve as a network hub in several cardiomyocyte cellular processes. Based on the idea that interactions with regulatory protein partners underly the diverse roles of MEF2A in cardiomyocyte gene expression, we undertook a systematic unbiased screen of the MEF2A protein interactome in primary cardiomyocytes using an affinity purification-based quantitative mass spectrometry approach. Bioinformatic processing of the MEF2A interactome revealed protein networks involved in the regulation of programmed cell death, inflammatory responses, actin dynamics and stress signaling in primary cardiomyocytes. Further biochemical and functional confirmation of specific protein-protein interactions documented a dynamic interaction between MEF2A and STAT3 proteins. Integration of transcriptome level data from MEF2A and STAT3-depleted cardiomyocytes reveals that the balance between MEF2A and STAT3 activity exerts a level of executive control over the inflammatory response and cardiomyocyte cell survival and experimentally ameliorates Phenylephrine induced cardiomyocyte hypertrophy. Lastly, we identified several MEF2A/STAT3 co-regulated genes, including the MMP9 gene. Herein, we document the cardiomyocyte MEF2A interactome, which furthers our understanding of protein networks involved in the hierarchical control of normal and pathophysiological cardiomyocyte gene expression in the mammalian heart.

GSK2795039 prevents RIP1-RIP3-MLKL-mediated cardiomyocyte necroptosis in doxorubicin-induced heart failure through inhibition of NADPH oxidase-derived oxidative stress

Doxorubicin (DOX), which is widely used for the treatment of cancer, induces cardiomyopathy associated with NADPH oxidase-derived reactive oxygen species. GSK2795039 is a novel small molecular NADPH oxidase 2 (Nox2) inhibitor. In this study, we investigated whether GSK2795039 prevents receptor-interacting protein kinase 1 (RIP1)-RIP3-mixed lineage kinase domain-like protein (MLKL)-mediated cardiomyocyte necroptosis in DOX-induced heart failure through NADPH oxidase inhibition. Eight-week old mice were randomly divided into 4 groups: control, GSK2795039, DOX and DOX plus GSK2795039. H9C2 cardiomyocytes were treated with DOX and GSK2795039. In DOX-treated mice, the survival rate was reduced, left ventricular (LV) end-systolic dimension was increased and LV fractional shortening was decreased, and these alterations were attenuated by the GSK2795039 treatment. GSK2795039 inhibited not only myocardial NADPH oxidase subunit gp91phox (Nox2) protein, but also p22phox, p47phox and p67phox proteins and prevented oxidative stress 8-hydroxy-2'-deoxyguanosine levels in DOX-treated mice. RIP3 protein and phosphorylated RIP1 (p-RIP1), p-RIP3 and p-MLKL proteins, reflective of their respective kinase activities, markers of necroptosis, were markedly increased in DOX-treated mice, and the increases were prevented by GSK2795039. GSK2795039 prevented the increases in serum lactate dehydrogenase and myocardial fibrosis in DOX-treated mice. Similarly, in DOX-treated cardiomyocytes, GSK2795039 improved cell viability, attenuated apoptosis and necrosis and prevented the increases in p-RIP1, p-RIP3 and p-MLKL expression. In conclusion, GSK2795039 prevents RIP1-RIP3-MLKL-mediated cardiomyocyte necroptosis through inhibition of NADPH oxidase-derived oxidative stress, leading to the improvement of myocardial remodeling and function in DOX-induced heart failure. These findings suggest that GSK2795039 may have implications for the treatment of DOX-induced cardiomyopathy.

Perfluorooctane Sulfonate Induces Dysfunction of Human Umbilical Vein Endothelial Cells via Ferroptosis Pathway

(1) Background: Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant, and it is receiving increasing attention regarding its human health risks due to its extensive use. Endothelial dysfunction is a mark of cardiovascular disease, but the basic mechanism of PFOS-induced endothelial dysfunction is still not fully understood. Ferroptosis is a newly defined regulatory cell death driven by cellular metabolism and iron-dependent lipid peroxidation. Although ferroptosis has been shown to be involved in the pathogenesis of cardiovascular diseases, the involvement of ferroptosis in the pathogenesis of endothelial dysfunction caused by PFOS remains unclear. (2) Purpose: To explore the role of ferroptosis in the dysfunction of endothelial cells and underlying mechanisms. (3) Methods: Human umbilical vein endothelial cells (HUVECs) were exposed to PFOS or PFOS and Fer-1. The viability, morphology change under electronic microscope, lipid-reactive oxygen species (lipid-ROS), and production of nitric oxide (NO) were determined. The expression of glutathione peroxidase 4(GPX4), ferritin heavy chain protein 1 (FTH1), heme oxygenase 1 (HO-1) and Acyl-CoA synthetase long-chain family member 4 (ACSL4) were analyzed via Western blot analysis. (4) Results: PFOS was shown to cause a decrease in viability and morphological changes of mitochondria, and well as an increase in lipid droplets. The expression of GPX4, FTH1 and HO-1 was decreased, and that of ACSL4 was increased after exposure to PFOS. In addition to the above-mentioned ferroptosis-related manifestations, there was also a reduction in NO content. (5) Conclusions: PFOS induces ferroptosis by regulating the GPX4 and ACSL4 pathways, which leads to HUVEC dysfunction.

Necroptosis in heart disease: Molecular mechanisms and therapeutic implications

Cell death is a crucial event underlying cardiac ischemic injury, pathological remodeling, and heart failure. Unlike apoptosis, necrosis had long been regarded as a passive and unregulated process. However, recent studies demonstrate that a significant subset of necrotic cell death is actively mediated through regulated pathways - a process known as "regulated necrosis". As a form of regulated necrosis, necroptosis is mediated by death receptors and executed through the activation of receptor interacting protein kinase 3 (RIPK3) and its downstream substrate mixed lineage kinase-like domain (MLKL). Recent studies have provided compelling evidence that necroptosis plays an important role in myocardial homeostasis, ischemic injury, pathological remodeling, and heart failure. Moreover, it has been shown that genetic and pharmacological manipulations of the necroptosis signaling pathway elicit cardioprotective effects. Important progress has also been made regarding the molecular mechanisms that regulate necroptotic cell death in vitro and in vivo. In this review, we discuss molecular and cellular mechanisms of necroptosis, potential crosstalk between necroptosis and other cell death pathways, functional implications of necroptosis in heart disease, and new therapeutic strategies that target necroptosis signaling.

Therapeutic Peptides to Treat Myocardial Ischemia-Reperfusion Injury

Cardiovascular diseases (CVD) including acute myocardial infarction (AMI) rank first in worldwide mortality and according to the World Health Organization (WHO), they will stay at this rank until 2030. Prompt revascularization of the occluded artery to reperfuse the myocardium is the only recommended treatment (by angioplasty or thrombolysis) to decrease infarct size (IS). However, despite beneficial effects on ischemic lesions, reperfusion leads to ischemia-reperfusion (IR) injury related mainly to apoptosis. Improvement of revascularization techniques and patient care has decreased myocardial infarction (MI) mortality however heart failure (HF) morbidity is increasing, contributing to the cost-intense worldwide HF epidemic. Currently, there is no treatment for reperfusion injury despite promising results in animal models. There is now an obvious need to develop new cardioprotective strategies to decrease morbidity/mortality of CVD, which is increasing due to the aging of the population and the rising prevalence rates of diabetes and obesity. In this review, we will summarize the different therapeutic peptides developed or used focused on the treatment of myocardial IR injury (MIRI). Therapeutic peptides will be presented depending on their interacting mechanisms (apoptosis, necroptosis, and inflammation) reported as playing an important role in reperfusion injury following myocardial ischemia. The search and development of therapeutic peptides have become very active, with increasing numbers of candidates entering clinical trials. Their optimization and their potential application in the treatment of patients with AMI will be discussed.

Interplay of Oxidative Stress and Necrosis-like Cell Death in Cardiac Ischemia/Reperfusion Injury: A Focus on Necroptosis

Extensive research work has been carried out to define the exact significance and contribution of regulated necrosis-like cell death program, such as necroptosis to cardiac ischemic injury. This cell damaging process plays a critical role in the pathomechanisms of myocardial infarction (MI) and post-infarction heart failure (HF). Accordingly, it has been documented that the modulation of key molecules of the canonical signaling pathway of necroptosis, involving receptor-interacting protein kinases (RIP1 and RIP3) as well as mixed lineage kinase domain-like pseudokinase (MLKL), elicit cardioprotective effects. This is evidenced by the reduction of the MI-induced infarct size, alleviation of myocardial dysfunction, and adverse cardiac remodeling. In addition to this molecular signaling of necroptosis, the non-canonical pathway, involving Ca2+/calmodulin-dependent protein kinase II (CaMKII)-mediated regulation of mitochondrial permeability transition pore (mPTP) opening, and phosphoglycerate mutase 5 (PGAM5)–dynamin-related protein 1 (Drp-1)-induced mitochondrial fission, has recently been linked to ischemic heart injury. Since MI and HF are characterized by an imbalance between reactive oxygen species production and degradation as well as the occurrence of necroptosis in the heart, it is likely that oxidative stress (OS) may be involved in the mechanisms of this cell death program for inducing cardiac damage. In this review, therefore, several observations from different studies are presented to support this paradigm linking cardiac OS, the canonical and non-canonical pathways of necroptosis, and ischemia-induced injury. It is concluded that a multiple therapeutic approach targeting some specific changes in OS and necroptosis may be beneficial in improving the treatment of ischemic heart disease.

Preliminary evidence for the presence of multiple forms of cell death in diabetes cardiomyopathy

Diabetic mellitus (DM) is a common degenerative chronic metabolic disease often accompanied by severe cardiovascular complications (DCCs) as major causes of death in diabetic patients with diabetic cardiomyopathy (DCM) as the most common DCC. The metabolic disturbance in DCM generates the conditions/substrates and inducers/triggers and activates the signaling molecules and death executioners leading to cardiomyocyte death which accelerates the development of DCM and the degeneration of DCM to heart failure. Various forms of programmed active cell death including apoptosis, pyroptosis, autophagic cell death, autosis, necroptosis, ferroptosis and entosis have been identified and characterized in many types of cardiac disease. Evidence has also been obtained for the presence of multiple forms of cell death in DCM. Most importantly, published animal experiments have demonstrated that suppression of cardiomyocyte death of any forms yields tremendous protective effects on DCM. Herein, we provide the most updated data on the subject of cell death in DCM, critical analysis of published results focusing on the pathophysiological roles of cell death, and pertinent perspectives of future studies.

Enhanced oxidative stress mediates pathological autophagy and necroptosis in cardiac myocytes in pressure overload induced heart failure in rats

In cardiac myocytes in vitro, hydrogen peroxide induces autophagic cell death and necroptosis. Oxidative stress, myocyte autophagy and necroptosis coexist in heart failure (HF). In this study, we tested the hypothesis that excessive oxidative stress mediates pathological autophagy and necroptosis in myocytes in pressure overload-induced HF. HF was produced by chronic pressure overload induced by abdominal aortic constriction (AAC) in rats. Rats with AAC or sham operation were randomised to orally receive an antioxidant N-acetylcysteine (NAC) or placebo for 4 weeks. Echocardiography was performed for the assessments of left ventricular (LV) structure and function. AAC rats exhibited decreased LV fractional shortening (FS) at 4 weeks after surgery. NAC treatment attenuated decreased LV FS in AAC rats. In AAC rats, myocardial level of 8-hydroxydeoxyguanosine assessed by immunohistochemical staining, indicative of oxidative stress, was increased, LC3 II protein, a marker of autophagy, Beclin1 protein and Atg4b, Atg5, Atg7 and Atg12 mRNA expression were markedly increased, RIP1, RIP3 and MLKL expression, indicative of necroptosis, was increased, and all of the alterations in AAC rats were prevented by the NAC treatment. NAC treatment also attenuated myocyte cross-sectional area and myocardial fibrosis in AAC rats. In conclusion, NAC treatment prevented the increases in oxidative stress, myocyte autophagy and necroptosis and the decrease in LV systolic function in pressure overload-induced HF. These findings suggest that enhanced oxidative stress mediates pathological autophagy and necroptosis in myocytes, leading to LV systolic dysfunction, and antioxidants may be of value to prevent HF through the inhibition of excessive autophagy and necroptosis.

Polypeptide Globular Adiponectin Ameliorates Hypoxia/Reoxygenation-Induced Cardiomyocyte Injury by Inhibiting Both Apoptosis and Necroptosis

Adiponectin is a small peptide secreted and a key component of the endocrine system and immune system. Although globular adiponectin protects myocardial ischemia/reperfusion-induced cardiomyocyte injury, the protective mechanisms remain largely unresolved. Using a neonatal rat ventricular myocyte hypoxia/reoxygenation model, we investigated the role of its potential mechanisms of necroptosis in globular adiponectin-mediated protection in hypoxia/reoxygenation-induced cardiomyocyte injury as compared to apoptosis. We found that globular adiponectin treatment attenuated cardiomyocyte injury as indicated by increased cell viability and reduced lactate dehydrogenase release following hypoxia/reoxygenation. Immunofluorescence staining and Western blotting demonstrated that both necroptosis and apoptosis were triggered by hypoxia/reoxygenation and diminished by globular adiponectin. Necrostatin-1 (RIP1-specific inhibitor) and Z-VAD-FMK (pan-caspase inhibitor) only mimicked the inhibition of necroptosis and apoptosis, respectively, by globular adiponectin in hypoxia/reoxygenation-treated cardiomyocytes. Globular adiponectin attenuated reactive oxygen species production, oxidative damage, and p38MAPK and NF-κB signaling, all important for necroptosis and apoptosis. Collectively, our study suggests that globular adiponectin inhibits hypoxia/reoxygenation-induced necroptosis and apoptosis in cardiomyocytes probably by reducing oxidative stress and interrupting p38MAPK signaling.

TEAD1 protects against necroptosis in postmitotic cardiomyocytes through regulation of nuclear DNA-encoded mitochondrial genes

The Hippo signaling effector, TEAD1 plays an essential role in cardiovascular development. However, a role for TEAD1 in postmitotic cardiomyocytes (CMs) remains incompletely understood. Herein we reported that TEAD1 is required for postmitotic CM survival. We found that adult mice with ubiquitous or CM-specific loss of Tead1 present with a rapid lethality due to an acute-onset dilated cardiomyopathy. Surprisingly, deletion of Tead1 activated the necroptotic pathway and induced massive cardiomyocyte necroptosis, but not apoptosis. In contrast to apoptosis, necroptosis is a pro-inflammatory form of cell death and consistent with this, dramatically higher levels of markers of activated macrophages and pro-inflammatory cytokines were observed in the hearts of Tead1 knockout mice. Blocking necroptosis by administration of necrostatin-1 rescued Tead1 deletion-induced heart failure. Mechanistically, genome-wide transcriptome and ChIP-seq analysis revealed that in adult hearts, Tead1 directly activates a large set of nuclear DNA-encoded mitochondrial genes required for assembly of the electron transfer complex and the production of ATP. Loss of Tead1 expression in adult CMs increased mitochondrial reactive oxygen species, disrupted the structure of mitochondria, reduced complex I-IV driven oxygen consumption and ATP levels, resulting in the activation of necroptosis. This study identifies an unexpected paradigm in which TEAD1 is essential for postmitotic CM survival by maintaining the expression of nuclear DNA-encoded mitochondrial genes required for ATP synthesis.

Targeting necroptosis as therapeutic potential in chronic myocardial infarction

Cardiovascular diseases (CVDs) are considered the predominant cause of morbidity and mortality globally. Of these, myocardial infarction (MI) is the most common cause of CVD mortality. MI is a life-threatening condition which occurs when coronary perfusion is interrupted leading to cardiomyocyte death. Subsequent to MI, consequences include adverse cardiac remodeling and cardiac dysfunction mainly contribute to the development of heart failure (HF). It has been shown that loss of functional cardiomyocytes in MI-induced HF are associated with several cell death pathways, in particular necroptosis. Although the entire mechanism underlying necroptosis in MI progression is still not widely recognized, some recent studies have reported beneficial effects of necroptosis inhibitors on cell viability and cardiac function in chronic MI models. Therefore, extensive investigation into the necroptosis signaling pathway is indicated for further study. This article comprehensively reviews the context of the underlying mechanisms of necroptosis in chronic MI-induced HF in in vitro, in vivo and clinical studies. These findings could inform ways of developing novel therapeutic strategies to improve the clinical outcomes in MI patients from this point forward.

Ferroptosis Is a Potential Novel Diagnostic and Therapeutic Target for Patients With Cardiomyopathy

Cardiomyocyte death is a fundamental progress in cardiomyopathy. However, the mechanism of triggering the death of myocardial cells remains unclear. Ferroptosis, which is the nonapoptotic, iron-dependent, and peroxidation-driven programmed cell death pathway, that is abundant and readily accessible, was not discovered until recently with a pharmacological approach. New researches have demonstrated the close relationship between ferroptosis and the development of many cardiovascular diseases, and several ferroptosis inhibitors, iron chelators, and small antioxidant molecules can relieve myocardial injury by blocking the ferroptosis pathways. Notably, ferroptosis is gradually being considered as an important cell death mechanism in the animal models with multiple cardiomyopathies. In this review, we will discuss the mechanism of ferroptosis and the important role of ferroptosis in cardiomyopathy with a special emphasis on the value of ferroptosis as a potential novel diagnostic and therapeutic target for patients suffering from cardiomyopathy in the future.

RIPK3 Induces Cardiomyocyte Necroptosis via Inhibition of AMPK-Parkin-Mitophagy in Cardiac Remodelling after Myocardial Infarction

Receptor-interacting protein 3- (RIPK3-) modulated necroptosis plays a critical role in cardiac remodelling after myocardial infarction (MI). However, the precise regulatory mechanism is not fully elucidated yet. In the present study, we showed that RIPK3 expression was upregulated in myocardial tissue after MI in a mouse model by coronary artery ligation, as well as in the cardiomyocytes following hypoxic injury in vitro. The increase of RIPK3 expression was found to be accompanied by severe cardiac remodelling, cardiac dysfunction, and higher mortality. Elevated RIPK3 expression subsequently abrogated the AMPK pathway that was accompanied by inhibition of Parkin-mediated mitophagy. Loss of mitophagy increased the opening of mitochondrial permeability transition pore (mPTP), which ultimately induced the cardiomyocyte necroptosis. In contrast, genetic ablation of Ripk3 induced the AMPK/Parkin-mitophagy pathway, favouring a prosurvival state that eventually inhibited mPTP opening and induced the necroptosis of cardiomyocytes in the post-MI cardiac remodelling. In conclusion, our results revealed a key mechanism by which necroptosis could be mediated by RIPK3 via the AMPK/Parkin-mitophagy/mPTP opening axis, which provides a potential therapeutic target in the management of heart failure after MI.

Klotho attenuates angiotensin II‑induced cardiotoxicity through suppression of necroptosis and oxidative stress

Hyperglycemia is known to lead to cardiac injury and inflammation through the reactive oxygen species (ROS)‑Toll‑like receptor 4 (TLR4)‑necroptosis pathway. Similarly, angiotensin II (Ang II) activates the TLR4‑nuclear factor κB (NF‑κB) p65 pathway, while the protein Klotho is known to inhibit this pathway, protecting cardiac cells from Ang II‑induced injury. However, there is currently a lack of data on whether necroptosis participates in Ang II‑induced cardiac injury and whether the Klotho protein has an effect on this process. The present study aimed to explore whether inhibition of the TLR4/NF‑κB p65 necroptosis pathway is involved in the Klotho protein‑mediated protection against the Ang II‑induced cardiac injury and inflammation. H9c2 cardiac cells were incubated with 0.01 mM Ang II. Western blotting was used to assess the expression of receptor‑interacting protein kinase 3 (RIP3), mixed‑lineage kinase domain‑like protein (MLKL), TLR4 and NF‑κB p65. The present study also assessed injury indexes: Inflammatory cytokine expression, mitochondrial membrane potential (ΔΨm), apoptosis, ROS production and cell viability. The expression of TLR4, phosphorylated (p)‑NF‑κB p65, RIP3 and MLKL were increased by incubation with Ang II in H9c2 cells. The pretreatment of H9c2 cells with necrostatin‑1 (Nec‑1, an inhibitor of necroptosis) or TAK‑242 (a small molecule inhibitor of TLR4) attenuated the upregulation of RIP3 and MLKL caused by Ang II. Klotho protein cotreatment also reversed the Ang II‑induced upregulation of TLR4, p‑NF‑κB p65, RIP3 and MLKL. Furthermore, Ang II decreased cell viability and upregulated the secretion of inflammatory cytokines, ΔΨm loss and ROS generation blocked by pretreatment with Nec‑1 or Klotho protein. Thus, it was determined that Klotho can attenuate the Ang II‑induced necroptosis of cardiomyocytes through the TLR4/NF‑κB p65 pathway, which suggests that Klotho could be a potential therapeutic drug against Ang II‑induced cardiotoxicity.

Docosahexaenoic acid alleviates cell injury and improves barrier function by suppressing necroptosis signalling in TNF-α-challenged porcine intestinal epithelial cells

Long-chain n-3 polyunsaturated fatty acids are known to have beneficial effects on intestinal health. However, the underling mechanisms are largely unknown. The present study was conducted to investigate whether docosahexaenoic acid (DHA) attenuates TNF-α-induced intestinal cell injury and barrier dysfunction by modulating necroptosis signalling. Intestinal porcine epithelial cell line 1 was cultured with or without 12.5 µg/ml DHA, followed by exposure to 50 ng/ml TNF-α for indicated time periods. DHA restored cell viability and cell number triggered by TNF-α. DHA also improved barrier function, which was indicated by increased trans-epithelial electrical resistance, decreased FD4 flux and increased membrane localisation of zonula occludins (ZO-1) and claudin-1. Moreover, DHA suppressed cell necrosis in TNF-α-challenged cells, as shown in the IncuCyte ZOOM™ live cell imaging system and transmission electron microscopy. In addition, DHA decreased protein expression of TNF receptor, receptor interacting protein kinase 1, RIP3 and phosphorylation of mixed lineage kinase-like protein, phosphoglycerate mutase family 5, dynamin-related protein 1 and high mobility group box-1 protein. Furthermore, DHA suppressed protein expression of caspase-3 and caspase-8. Collectively, these results indicate that DHA is capable of alleviating TNF-α-induced cell injury and barrier dysfunction by suppressing the necroptosis signalling pathway.

Long noncoding RNAs: Important participants and potential therapeutic targets for myocardial ischaemia reperfusion injury

Myocardial ischaemia reperfusion (I/R) injury is one of the leading causes of coronary artery disease-associated morbidity and mortality. While different strategies have been used to limit I/R injuries, cardiac functions often do not recover to the normal level as anticipated. Recent studies have pointed to important roles of long noncoding RNAs (lncRNAs) in the development of myocardial I/R injury. LncRNA is a class of RNA molecules of more than 200 nucleotides in length which are not translated into proteins. I/R causes dysregulation of lncRNA expression in cardiomyocytes, thereby affecting multiple cellular functions including mitochondrial homeostasis, apoptosis, necrosis and autophagy, suggesting that manipulating lncRNAs may be of great potential in counteracting I/R injury-induced myocardial dysfunctions. In this review, we provide an updated summary on our knowledge about contributions of lncRNAs to the development of I/R injury, with an emphasis on the functional links between several well established cardiac lncRNAs and regulation of cellular outcomes post I/R.

The Molecular Mechanisms of Iron Metabolism and Its Role in Cardiac Dysfunction and Cardioprotection

Iron is an essential mineral participating in different functions of the organism under physiological conditions. Numerous biological processes, such as oxygen and lipid metabolism, protein production, cellular respiration, and DNA synthesis, require the presence of iron, and mitochondria play an important role in the processes of iron metabolism. In addition to its physiological role, iron may be also involved in the adaptive processes of myocardial "conditioning". On the other hand, disorders of iron metabolism are involved in the pathological mechanisms of the most common human diseases and include a wide range of them, such as type 2 diabetes, obesity, and non-alcoholic fatty liver disease, and accelerate the development of atherosclerosis. Furthermore, iron also exerts potentially deleterious effects that may be manifested under conditions of ischemia/reperfusion (I/R) injury, myocardial infarction, heart failure, coronary artery angioplasty, or heart transplantation, due to its involvement in reactive oxygen species (ROS) production. Moreover, iron has been recently described to participate in the mechanisms of iron-dependent cell death defined as "ferroptosis". Ferroptosis is a form of regulated cell death that is distinct from apoptosis, necroptosis, and other types of cell death. Ferroptosis has been shown to be associated with I/R injury and several other cardiac diseases as a significant form of cell death in cardiomyocytes. In this review, we will discuss the role of iron in cardiovascular diseases, especially in myocardial I/R injury, and protective mechanisms stimulated by different forms of "conditioning" with a special emphasis on the novel targets for cardioprotection.

Programmed Cell Death in the Left and Right Ventricle of the Late Phase of Post-Infarction Heart Failure

While necroptosis has been shown to contribute to the pathogenesis of post-infarction heart failure (HF), the role of autophagy remains unclear. Likewise, linkage between these two cell death modalities has not been sufficiently investigated. HF was induced by 60-min left coronary occlusion in adult Wistar rats and heart function was assessed 6 weeks later followed by immunoblotting analysis of necroptotic and autophagic proteins in both the left (LV) and right ventricle (RV). HF had no effect on RIP1 and RIP3 expression. PhosphoSer229-RIP3, acting as a pro-necroptotic signal, was increased in LV while deceased in RV of failing hearts. Total MLKL was elevated in RV only. Decrease in pSer555-ULK1, increase in pSer473-Akt and no significant elevation in beclin-1 and LC3-II/I ratio indicated rather a lowered rate of autophagy in LV. No beclin-1 upregulation and decreased LC3 processing also suggested the inhibition of both autophagosome formation and maturation in RV of failing hearts. In contrast, p89 PARP1 fragment, a marker of executed apoptosis, was increased in RV only. This is the first study showing a different signaling in ventricles of the late phase of post-infarction HF, highlighting necroptosis itself rather than its linkage with autophagy in LV, and apoptosis in RV.

Bufalin engages in RIP1-dependent and ROS-dependent programmed necroptosis in breast cancer cells by targeting the RIP1/RIP3/PGAM5 pathway

Breast cancer causes high mortality among females worldwide. Bufalin has recently been shown to trigger tumor cell death, although the mechanism of cytotoxicity remains unclear. The cytotoxicity of bufalin in breast cancer cells was examined using an MTT assay. The modes of death and intracellular reactive oxygen species production were measured by flow cytometry. We also observed cellular morphologic changes by Hoechst 33342 and propidium iodide staining and transmission electron microscopy. Western blotting was performed to determine the expression levels of related proteins. Our results showed that bufalin reduced cellular viability and promoted reactive oxygen species production, which could be inhibited by Nec-1 and N-acetylcysteine. Necroptosis was detected by Hoechst 33342 and propidium iodide staining and transmission electron microscopy. Western blot analysis showed that bufalin induced necroptosis by upregulating the necroptosis mediator RIP1 and the RIP1/RIP3/PGAM5 pathway. Taken together, these findings indicated that bufalin induces breast cancer cell necroptosis by targeting the RIP1/RIP3/PGAM5 pathway.

Plasma concentration of receptor-interacting protein kinase-3 as a potential biomarker for diagnosis and prognosis in heart failure

BACKGROUND

Receptor-interacting serine-threonine kinase 3 (RIP3) is a key mediator of programmed necrosis (necroptosis), and is implicated in cardiac remodeling and heart failure (HF) triggered by ischemia-reperfusion or oxidative stress in animal study. However, its value in the diagnosis and prognosis of human HF remains unclear.

METHODS

Plasma RIP3 concentrations in 91 HF patients and 95 healthy volunteers were detected by enzyme-linked immunosorbent assay (ELISA). A receiver operating characteristic (ROC) curve was generated to evaluate the diagnostic value of RIP3. Follow-up was conducted, and the composite endpoint was defined as all-cause mortality/readmission due to decompensated HF/worse New York Heart Association (NYHA) functional class. The relationship between RIP3 and patient outcome was examined.

RESULTS

Plasma concentrations of RIP3 were significantly increased in patients with HF compared to controls (P < 0.001). ROC analysis supported plasma RIP3 as a good diagnostic marker for HF, with an optimal cutoff value of 357 pg/ml (AUC = 0.934, sensitivity = 0.846, specificity = 0.905). Kaplan-Meier survival analysis also supported increased plasma RIP3 as a predictor for a poor prognosis in HF (cutoff value = 622.2 pg/ml, P < 0.05). Additionally, binary logistic regression analysis revealed RIP3 to be an independent risk factor for all-cause mortality (OR = 11.844, P = 0.02), worse NYHA (OR = 9.013, P = 0.009) and a composite endpoint (OR = 5.065, P = 0.013).

CONCLUSIONS

Plasma concentration of RIP3 is significantly elevated in HF and associated with the prognosis. Plasma RIP3 possibly constitutes a valuable diagnostic and prognostic biomarker for HF.

Exercise-mediated regulation of autophagy in the cardiovascular system

Cardiovascular disease is the leading cause of human death worldwide. Autophagy is an evolutionarily conserved degradation pathway, which is a highly conserved cellular degradation process in which lysosomes decompose their own organelles and recycle the resulting macromolecules. Autophagy is critical in maintaining cardiovascular homeostasis and function, and excessive or insufficient autophagy or autophagic flux can lead to cardiovascular disease. Enormous evidence indicates that exercise training plays a beneficial role in the prevention and treatment of cardiovascular diseases. The regulation of autophagy during exercise is a bidirectional process. For cardiovascular disease caused by either insufficient or excessive autophagy, exercise training restores normal autophagy function and delays the progression of cardiovascular disease. An in-depth exploration and discussion of exercise-mediated regulation of autophagy in the cardiovascular system can broaden our view about the prevention of various autophagy-related diseases through exercise training. In this article, we review autophagy and its related signaling pathways, as well as autophagy-dependent beneficial effects of exercise in cardiovascular system.

Cardioprotective Role of Melatonin in Acute Myocardial Infarction

Melatonin is a pleiotropic, indole secreted, and synthesized by the human pineal gland. Melatonin has biological effects including anti-apoptosis, protecting mitochondria, anti-oxidation, anti-inflammation, and stimulating target cells to secrete cytokines. Its protective effect on cardiomyocytes in acute myocardial infarction (AMI) has caused widespread interest in the actions of this molecule. The effects of melatonin against oxidative stress, promoting autophagic repair of cells, regulating immune and inflammatory responses, enhancing mitochondrial function, and relieving endoplasmic reticulum stress, play crucial roles in protecting cardiomyocytes from infarction. Mitochondrial apoptosis and dysfunction are common occurrence in cardiomyocyte injury after myocardial infarction. This review focuses on the targets of melatonin in protecting cardiomyocytes in AMI, the main molecular signaling pathways that melatonin influences in its endogenous protective role in myocardial infarction, and the developmental prospect of melatonin in myocardial infarction treatment.

Mitochondrial and mitochondrial-independent pathways of myocardial cell death during ischaemia and reperfusion injury

Acute myocardial infarction causes lethal injury to cardiomyocytes during both ischaemia and reperfusion (IR). It is important to define the precise mechanisms by which they die in order to develop strategies to protect the heart from IR injury. Necrosis is known to play a major role in myocardial IR injury. There is also evidence for significant myocardial death by other pathways such as apoptosis, although this has been challenged. Mitochondria play a central role in both of these pathways of cell death, as either a causal mechanism is the case of mitochondrial permeability transition leading to necrosis, or as part of the signalling pathway in mitochondrial cytochrome c release and apoptosis. Autophagy may impact this process by removing dysfunctional proteins or even entire mitochondria through a process called mitophagy. More recently, roles for other programmed mechanisms of cell death such as necroptosis and pyroptosis have been described, and inhibitors of these pathways have been shown to be cardioprotective. In this review, we discuss both mitochondrial and mitochondrial‐independent pathways of the major modes of cell death, their role in IR injury and their potential to be targeted as part of a cardioprotective strategy. This article is part of a special Issue entitled ‘Mitochondria as targets of acute cardioprotection’ and emerged as part of the discussions of the European Union (EU)‐CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

Metformin mediates cardioprotection against aging-induced ischemic necroptosis

Necroptosis is crucially involved in severe cardiac pathological conditions. However, whether necroptosis contributes to age‐related intolerance to ischemia/reperfusion (I/R) injury remains elusive. In addition, metformin as a potential anti‐aging related injury drug, how it interacts with myocardial necroptosis is not yet clear. Male C57BL/6 mice at 3–4‐ (young) and 22–24 months of age (aged) and RIPK3‐deficient (Ripk3^−/−) mice were used to investigate aging‐related I/R injury in vivo. Metformin (125 μg/kg, i.p.), necrostatin‐1 (3.5 mg/kg), and adenovirus vector encoding p62‐shRNAs (Ad‐sh‐p62) were used to treat aging mice. I/R‐induced myocardial necroptosis was exaggerated in aged mice, which correlated with autophagy defects characterized by p62 accumulation in aged hearts or aged human myocardium. Functionally, blocking autophagic flux promoted H/R‐evoked cardiomyocyte necroptosis in vitro. We further revealed that p62 forms a complex with RIP1‐RIP3 (necrosome) and promotes the binding of RIP1 and RIP3. In mice, necrostatin‐1 treatment (a RIP1 inhibitor), RIP3 deficiency, and cardiac p62 knockdown in vivo demonstrated that p62‐RIP1‐RIP3‐dependent myocardial necroptosis contributes to aging‐related myocardial vulnerability to I/R injury. Notably, metformin treatment disrupted p62‐RIP1‐RIP3 complexes and effectively repressed I/R‐induced necroptosis in aged hearts, ultimately reducing mortality in this model. These findings highlight previously unknown mechanisms of aging‐related myocardial ischemic vulnerability: p62‐necrosome‐dependent necroptosis. Metformin acts as a cardioprotective agent that inhibits this unfavorable chain mechanism of aging‐related I/R susceptibility.

The Nrf-2/HO-1 Signaling Axis: A Ray of Hope in Cardiovascular Diseases

Cardiovascular disease, which can lead to angina and shortness of breath, remains one of the most serious threats to human health. Owing to its imperceptible symptoms, it is difficult to determine the pathogenesis and treatment methods for cardiovascular disease. Nuclear factor erythropoietin-2-related factor 2/heme oxygenase 1 (Nrf2/HO-1) is a protein found in all cells of the human body. It is activated, transferred to the nucleus, and bound to DNA by antioxidant response elements (AREs). As a regulator of the antioxidant system, it upregulates the expression of HO-1 to reduce oxidative stress. Nrf2/HO-1 also has the ability to modulate calcium levels to prevent ferroptosis, pyroptosis, autophagy, programmed cell necrosis, alkaliptosis, and clockophagy. In view of the importance of Nrf2/HO-1 in the regulation of homeostasis, this review summarizes current research on the relationship between cardiovascular disease and Nrf2/HO-1. Normal cardiovascular diseases, such as viral myocarditis and myocardial ischemia-reperfusion injury, have been treated with Nrf2/HO-1. Rheumatic heart disease, cardiac tumors, arteriosclerosis, arrhythmia, hypertensive heart disease, and myocardial infarction have also been treated during experiments. Research has demonstrated the clinical application of Nrf2/HO-1 in pediatric cardiovascular disease; further clinical trials will help elucidate the potential of the Nrf2/HO-1 signaling axis.

Small Molecules with Big Impacts on Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading cause of morbidity and mortality worldwide. Although in recent years there has been a significant progress in the diagnosis, treatment, and prognosis of CVD, but due to their complex pathobiology, developing novel biomarkers and therapeutic interventions are still in need. MicroRNAs (miRNAs) are a fraction of non-coding RNAs that act as micro-regulators of gene expression. Mounting evidences over the last decade confirmed that microRNAs were deregulated in several CVDs and manipulating their expression could affect homeostasis, differentiation, and function of cardiovascular system. Here, we review the current knowledge concerning the roles of miRNAs in cardiovascular diseases with more details on cardiac remodeling, arrhythmias, and atherosclerosis. In addition, we discuss the latest findings on the potential therapeutic applications of miRNAs in cardiovascular diseases.

Treatment of hypoxia-dependent cardiovascular diseases by myo-inositol trispyrophosphate (ITPP)-enhancement of oxygen delivery by red blood cells

Heart failure is a consequence of progression hypoxia-dependent tissue damages. Therapeutic approaches to restore and/or protect the healthy cardiac tissue have largely failed and remain a major challenge of regenerative medicine. The myo-inositol trispyrophosphate (ITPP) is a modifier of haemoglobin which enters the red blood cells and modifies the haemoglobin properties, allowing for easier and better delivery of oxygen by the blood. Here, we show that this treatment approach in an in vivo model of myocardial infarction (MI) results in an efficient protection from heart failure, and we demonstrate the recovery effect on post-MI left ventricular remodelling in the rat model. Cultured cardiomyocytes used to study the molecular mechanism of action of ITPP in vitro displayed the fast stimulation of HIF-1 upon hypoxic conditions. HIF-1 overexpression was prevented by ITPP when incorporated into red blood cells applied in a model of blood-perfused cardiomyocytes coupling the dynamic shear stress effect to the enhanced O₂ supply by modification of haemoglobin ability to release O₂ in hypoxia. ITPP treatment appears a breakthrough strategy for the efficient and safe treatment of hypoxia- or ischaemia-induced injury of cardiac tissue.

Activation of ALDH2 attenuates high glucose induced rat cardiomyocyte fibrosis and necroptosis

Necroptosis is one of a regulated programmed death mode, fibrosis is closely related with cell death. It has been reported that inhibition of necroptosis can play the protective role in cardiac ischemia and reperfusion injury, stroke and other diseases, but the mechanisms of aldehyde dehydrogenases 2 (ALDH2) against high glucose induced neonatal rat ventricular primary cardiomyocytes fibrosis and necroptosis had not been elucidated clearly. This study was to observe the effect of ALDH2 on high glucose (HG) induced myocardial fibrosis and necroptosis in primary rat cardiomyocytes model. In contrast to normal glucose group, in HG group, with the decreases of ALDH2 activity, mRNA and protein levels, the cardiomyocytes viability was decreased, reactive oxygen species (ROS), the inflammation factors - tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β) levels, collagen I (col I) and col III mRNA expressions and tissue inhibitors of matrix metalloproteinase 4 (TIMP4) protein expression were increased, while matrix metalloproteinase 14 (MMP14) protein level, the ratio of MMP14/TIMP4 were decreased, and the necroptosis key factors - the receptor interacting protein 1 (RIP1), RIP3 and mixed lineage kinase domain-like protein (MLKL) at mRNA and protein expressions were increased, the inflammasome core proteins - NLRP3 and ASC protein expressions were also increased, the apoptosis rate and necrosis rate were also increased. When the cardiomyocytes were treated with Alda-1 (the ALDH2 agonist) in HG intervention, the cell viability, ALDH2 activity, mRNA and protein levels, MMP14 protein level, the ratio of MMP14/TIMP4 were higher, ROS and TNF-α, IL-6, IL-1β levels, RIP1, RIP3, MLKL, NLRP3 and ASC expressions, col I and col III, TIMP4 expressions, the apoptosis rate and necrosis rate were lower than in HG group. Daidzin, the antagonist of ALDH2 abolished the role of Alda-1. In summary, ALDH2 maybe is a key regulator in high glucose induced cardiomyocytes injury. Activation of ALDH2 prevented the happening of fibrosis, apoptosis and necroptosis in high glucose induced primary cardiomyocytes injury model, the protective effects were related to the inhibiting of oxidative stress and inflammation, changing of MMP14 and TIMP4, then inhibiting the happening of fibrosis, apoptosis and necroptosis. These findings advance our understanding of the intensive mechanisms of ALDH2's cardioprotection, and provide the targeted basis for clinical diabetes treatment.

EPA and DHA attenuate deoxynivalenol-induced intestinal porcine epithelial cell injury and protect barrier function integrity by inhibiting necroptosis signaling pathway

Deoxynivalenol (DON) is one of the most common mycotoxins that contaminates food or feed and cause intestinal damage. Long-chain n-3 polyunsaturated fatty acids (PUFA) such as EPA and DHA exert beneficial effects on intestinal integrity in animal models and clinical trials. Necroptosis signaling pathway plays a critical role in intestinal cell injury. This study tested the hypothesis that EPA and DHA could alleviate DON-induced injury to intestinal porcine epithelial cells through modulation of the necroptosis signaling pathway. Intestinal porcine epithelial cell 1 (IPEC-1) cells were cultured with or without EPA or DHA (6.25-25 μg/mL) in the presence or absence of 0.5 μg/mL DON for indicated time points. Cell viability, cell number, lactate dehydrogenase (LDH) activity, cell necrosis, transepithelial electrical resistance (TEER), fluorescein isothiocyanate-labeled dextran 4kDa (FD4) flux, tight junction protein distribution, and protein abundance of necroptosis related signals were determined. EPA and DHA promoted cell growth indicated by higher cell viability and cell number, and inhibited cell injury indicated by lower LDH activity in the media. EPA and DHA also improved intestinal barrier function, indicated by higher TEER and lower permeability of FD4 flux as well as increased proportions of tight junction proteins located in the plasma membrane. Moreover, EPA and DHA decreased cell necrosis demonstrated by live cell imaging and transmission electron microscopy. Finally, EPA and DHA downregulated protein expressions of necroptosis related signals including tumor necrosis factor receptor (TNFR1), receptor interacting protein kinase 1 (RIP1), RIP3, phosphorylated mixed lineage kinase-like protein (MLKL), phosphoglycerate mutase family 5 (PGAM5), dynamin-related protein 1 (Drp1), and high mobility group box-1 protein (HMGB1). EPA and DHA also inhibited protein expression of caspase-3 and caspase-8. These results suggest that EPA and DHA prevent DON-induced intestinal cell injury and enhance barrier function, which is associated with inhibition of the necroptosis signaling pathway.

Parkin Regulates Programmed Necrosis and Myocardial Ischemia/Reperfusion Injury by Targeting Cyclophilin-D

Aims: Cardiomyocyte death critically contributes to the pathogenesis of cardiac disorders, such as myocardial infarction, heart failure, and cardiac ischemia/reperfusion (I/R) injury. As one of the main forms of cardiac cell death, necrosis plays a critical role in heart diseases. Multiple signaling pathways of necrosis have been demonstrated, in which death receptors, receptor-interacting serine/threonine-protein 1 and 3 kinases, and cyclophilin-D (CypD) have been deeply implicated. However, the fundamental mechanism underlying myocardial necroptosis, especially the mitochondrial permeability transition pore (mPTP)-CypD-dependent death pathway, is poorly understood. Parkin functions as an E3 ubiquitin protein ligase that mainly mediates mitophagy cascades. As yet, it is not clear whether Parkin participates in regulating necrosis and myocardial I/R injury. Results: Here, our results showed that Parkin mediated mitophagy and inhibited necrosis under oxidative stress. In further exploring the underlying mechanisms, we found that Parkin suppressed mPTP opening by catalyzing the ubiquitination of CypD in necrotic cascades, which were not involved in Parkin-regulated mitophagy. Parkin inhibited necrosis, reduced myocardial I/R injury, and improved cardiac function. Innovation: Our present work reveals a highlighted connection between the mitochondrial matrix-localized Parkin and the mPTP-CypD-dependent necrotic signaling pathway in cardiac injury. Conclusion: Our results revealed a novel myocardial necrotic regulating model composed of Parkin, CypD, and mPTP, which may provide potential therapeutic targets and strategies to modulate the levels of these molecules.

Oxidative Stress in Cell Death and Cardiovascular Diseases

ROS functions as a second messenger and modulates multiple signaling pathways under the physiological conditions. However, excessive intracellular ROS causes damage to the molecular components of the cell, which promotes the pathogenesis of various human diseases. Cardiovascular diseases are serious threats to human health with extremely high rates of morbidity and mortality. Dysregulation of cell death promotes the pathogenesis of cardiovascular diseases and is the clinical target during the disease treatment. Numerous studies show that ROS production is closely linked to the cell death process and promotes the occurrence and development of the cardiovascular diseases. In this review, we summarize the regulation of intracellular ROS, the roles of ROS played in the development of cardiovascular diseases, and the programmed cell death induced by intracellular ROS. We also focus on anti-ROS system and the potential application of anti-ROS strategy in the treatment of cardiovascular diseases.

Aldehyde Dehydrogenase 2 and Heart Failure

Heart failure (HF) is a structural or functional cardiac abnormal syndrome characterized with series of symptoms and signs such as breathlessness, fatigue, pulmonary crackles, and peripheral edema. Being a terminal phase of most myocardial lesions, HF has become a leading cause of mobility and mortality worldwide, associated with heavy clinical burden and economic costs affecting over 23 million people [14]. There is an increase to 5.5% with systolic dysfunction and an increase to 36.0% with diastolic dysfunction in people 60 years or older [85]. The costs accompanied with heart failure stand 2-3% of the total healthcare system expenditure in high-income countries and are expected to increase >2-fold in the next 2 decades [34].

Guidelines for evaluating myocardial cell death

Cell death is a fundamental process in cardiac pathologies. Recent studies have revealed multiple forms of cell death, and several of them have been demonstrated to underlie adverse cardiac remodeling and heart failure. With the expansion in the area of myocardial cell death and increasing concerns over rigor and reproducibility, it is important and timely to set a guideline for the best practices of evaluating myocardial cell death. There are six major forms of regulated cell death observed in cardiac pathologies, namely apoptosis, necroptosis, mitochondrial-mediated necrosis, pyroptosis, ferroptosis, and autophagic cell death. In this article, we describe the best methods to identify, measure, and evaluate these modes of myocardial cell death. In addition, we discuss the limitations of currently practiced myocardial cell death mechanisms.

Inhibition of Phosphoglycerate Mutase 5 Reduces Necroptosis in Rat Hearts Following Ischemia/Reperfusion Through Suppression of Dynamin-Related Protein 1

PURPOSE

Necroptosis is an important form of cell death following myocardial ischemia/reperfusion (I/R) and phosphoglycerate mutase 5 (PGAM5) functions as the convergent point for multiple necrosis pathways. This study aims to investigate whether inhibition of PGAM5 could reduce I/R-induced myocardial necroptosis and the underlying mechanisms.

METHODS

The SD rat hearts (or H9c2 cells) were subjected to 1-h ischemia (or 10-h hypoxia) plus 3-h reperfusion (or 4-h reoxygenation) to establish the I/R (or H/R) injury model. The myocardial injury was assessed by the methods of biochemistry, H&E (hematoxylin and eosin), and PI/DAPI (propidium iodide/4',6-diamidino-2-phenylindole) staining, respectively. Drug interventions or gene knockdown was used to verify the role of PGAM5 in I/R (or H/R)-induced myocardial necroptosis and possible mechanisms.

RESULTS

The I/R-treated heart showed the injuries (increase in infarct size and creatine kinase release), upregulation of PGAM5, dynamin-related protein 1 (Drp1), p-Drp1-S616, and necroptosis-relevant proteins (RIPK1/RIPK3, receptor-interacting protein kinase 1/3; MLKL, mixed lineage kinase domain-like); these phenomena were attenuated by inhibition of PGAM5 or RIPK1. In H9c2 cells, H/R treatment elevated the levels of PGAM5, RIPK1, RIPK3, MLKL, Drp1, and p-Drp1-S616 and induced mitochondrial dysfunctions (elevation in mitochondrial membrane potential and ROS level) and cellular necrosis (increase in LDH release and the ratio of PI⁺/DAPI⁺ cells); these effects were blocked by inhibition or knockdown of PGAM5.

CONCLUSIONS

Inhibition of PGAM5 can reduce necroptosis in I/R-treated rat hearts through suppression of Drp1; there is a positive feedback between RIPK1 and PGAM5, and PGAM5 might serve as a novel therapeutic target for prevention of myocardial I/R injury.

Different signalling in infarcted and non-infarcted areas of rat failing hearts: A role of necroptosis and inflammation

Necroptosis has been recognized in heart failure (HF). In this study, we investigated detailed necroptotic signalling in infarcted and non‐infarcted areas separately and its mechanistic link with main features of HF. Post‐infarction HF in rats was induced by left coronary occlusion (60 minutes) followed by 42‐day reperfusion. Heart function was assessed echocardiographically. Molecular signalling and proposed mechanisms (oxidative stress, collagen deposition and inflammation) were investigated in whole hearts and in subcellular fractions when appropriate. In post‐infarction failing hearts, TNF and pSer229‐RIP3 levels were comparably increased in both infarcted and non‐infarcted areas. Its cytotoxic downstream molecule p‐MLKL, indicating necroptosis execution, was detected in infarcted area. In non‐infarcted area, despite increased pSer229‐RIP3, p‐MLKL was present in neither whole cells nor the cell membrane known to be associated with necroptosis execution. Likewise, increased membrane lipoperoxidation and NOX2 levels unlikely promoted pro‐necroptotic environment in non‐infarcted area. Collagen deposition and the inflammatory csp‐1‐IL‐1β axis were active in both areas of failing hearts, while being more pronounced in infarcted tissue. Although apoptotic proteins were differently expressed in infarcted and non‐infarcted tissue, apoptosis was found to play an insignificant role. p‐MLKL‐driven necroptosis and inflammation while inflammation only (without necroptotic cell death) seem to underlie fibrotic healing and progressive injury in infarcted and non‐infarcted areas of failing hearts, respectively. Upregulation of pSer229‐RIP3 in both HF areas suggests that this kinase, associated with both necroptosis and inflammation, is likely to play a dual role in HF progression.

Definition of hidden drug cardiotoxicity: paradigm change in cardiac safety testing and its clinical implications

Unexpected cardiac adverse effects are the leading causes of discontinuation of clinical trials and withdrawal of drugs from the market. Since the original observations in the mid-90s, it has been well established that cardiovascular risk factors and comorbidities (such as ageing, hyperlipidaemia, and diabetes) and their medications (e.g. nitrate tolerance, adenosine triphosphate-dependent potassium inhibitor antidiabetic drugs, statins, etc.) may interfere with cardiac ischaemic tolerance and endogenous cardioprotective signalling pathways. Indeed drugs may exert unwanted effects on the diseased and treated heart that is hidden in the healthy myocardium. Hidden cardiotoxic effects may be due to (i) drug-induced enhancement of deleterious signalling due to ischaemia/reperfusion injury and/or the presence of risk factors and/or (ii) inhibition of cardioprotective survival signalling pathways, both of which may lead to ischaemia-related cell death and/or pro-arrhythmic effects. This led to a novel concept of 'hidden cardiotoxicity', defined as cardiotoxity of a drug that manifests only in the diseased heart with e.g. ischaemia/reperfusion injury and/or in the presence of its major comorbidities. Little is known on the mechanism of hidden cardiotoxocity, moreover, hidden cardiotoxicity cannot be revealed by the routinely used non-clinical cardiac safety testing methods on healthy animals or tissues. Therefore, here, we emphasize the need for development of novel cardiac safety testing platform involving combined experimental models of cardiac diseases (especially myocardial ischaemia/reperfusion and ischaemic conditioning) in the presence and absence of major cardiovascular comorbidities and/or cotreatments.

Autophagy and Oncosis/Necroptosis Are Enhanced in Cardiomyocytes from Heart Failure Patients

Background

Although originally described as a survival mechanism, it is unknown whether and to what extent autophagy is implicated in the terminal stages of heart failure. Here, we studied magnitude and evolution of autophagy in patients with intractable heart failure.

Material/Methods

Myocardial samples were obtained from 22 patients with ischemic cardiomyopathy and idiopathic dilated cardiomyopathy who were undergoing cardiac transplantation. Hearts from 11 patients who died from non-cardiac causes were used as control samples. Autophagy was evaluated by immunostaining with a monoclonal microtubule associated protein light chain 3 (LC3)-II antibody, while the relationship of autophagy with apoptosis and oncosis was assessed by double staining with TUNEL (terminal deoxynucleotidyl transferase – mediated deoxyuridine triphosphate nick end labeling) assay and complement 9 (C9) immunological staining, respectively. In addition, several necroptotic markers, including RIP1 and RIP3 (receptor interacting protein kinase 1 and 3), anti-C3 (cleaved-caspase-3), and anti-NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) were assessed by immunohistochemistry.

Results

Anti-LC3-II staining was detected in 8.7±1.6% of the heart failure patient heart samples and in 1.2±0.3% of control patient heart samples. Vacuole formation started at one nuclear pole, before becoming bipolar and involving the cytosol. Subsequently, the autophagic process extended also to the nuclei, which underwent a progressive vacuolization and disintegration, assuming a peculiar “strawberry like appearance”. Myocytes with extensive vacuole formation exhibited nuclear degeneration, which was associated with TUNEL, C3, C9, RIP1, and RIP3 positive staining. Conversely, myocytes with less extensive vacuole formation showed RIP1 and NF-κB positive staining, though not positivity for other cell death markers.

Conclusions

Autophagy was extensively detected in end-stage heart failure and its progression, resulted in secondary cell death, with occurrence of oncosis and necroptosis exceeding that of apoptosis. Conversely, activation of the RIP1/NF-κB pathway was associated with cell survival.

Determination of Novel Highly Effective Necrostatin Nec-1s in Rat Plasma by High Performance Liquid Chromatography Hyphenated with Quadrupole-Time-of-Flight Mass Spectrometry

Necrostatins have been shown to retard necroptosis, a programmed necrotic-like cell death, which has been shown to underlie pathophysiology of various diseases. Nec-1s, a novel highly effective necrostatin, overcomes some drawbacks of former necrostatin analogues. The determination of Nec-1s in biological system, however, has not been carried out so far. Therefore, this study was undertaken to optimize and validate the HPLC-DAD-Q-TOF method for the assessment of Nec-1s levels in the plasma what is the necessity for designing its proper dosing regimen for in vivo studies. Benefits of the proposed analytical protocol include: (i) simple sample preparation (precipitation of plasma proteins, evaporation of acetonitrile, reconstitution in mobile phase), (ii) fast, selective and sensitive analysis due to a highly orthogonal LC-MS system providing less than 8 min analysis time, (iii) detection of Nec-1s without any matrix interferences, and quantitation of very low concentration levels of Nec-1s (LLOQ ~ 20 ng/mL), (iv) high reliability of Nec-1s determination with precision and accuracy values meeting the FDA criteria for biomedical analysis. The proposed analytical protocol is suitable for routine use in relevant biological studies, and, in this work, it was successfully applied for monitoring of Nec-1s plasma levels in rats providing reproducible and consistent results. Based on pharmacokinetic features, which can also be assessed due to the results of this study, there will be efforts to perform both acute and chronic in vivo studies and potential clinical safety studies first.

Protective role of melatonin in cardiac ischemia-reperfusion injury: From pathogenesis to targeted therapy

Acute myocardial infarction (MI) is a major cause of mortality and disability worldwide. In patients with MI, the treatment option for reducing acute myocardial ischemic injury and limiting MI size is timely and effective myocardial reperfusion using either thombolytic therapy or primary percutaneous coronary intervention (PCI). However, the procedure of reperfusion itself induces cardiomyocyte death, known as myocardial reperfusion injury, for which there is still no effective therapy. Recent evidence has depicted a promising role of melatonin, which possesses powerful antioxidative and anti-inflammatory properties, in the prevention of ischemia-reperfusion (IR) injury and the protection against cardiomyocyte death. A number of reports explored the mechanism of action behind melatonin-induced beneficial effects against myocardial IR injury. In this review, we summarize the research progress related to IR injury and discuss the unique actions of melatonin as a protective agent. Furthermore, the possible mechanisms responsible for the myocardial benefits of melatonin against reperfusion injury are listed with the prospect of the use of melatonin in clinical application.