Lipocalin-2 (NGAL) Attenuates Autophagy to Exacerbate Cardiac Apoptosis Induced by Myocardial Ischemia

Evaluation of neutrophil gelatinase-associated lipocalin (NGAL), hypoxia-induced factor-1 alpha (HIF-1α) and apelin 13 levels as new potential biomarkers for pulmonary thromboembolism: A prospective clinical study

AIM

The objective was to evaluate the serum levels of neutrophil gelatinase-associated lipocalin (NGAL), hypoxia-induced factor-1 alpha (HIF-1α), and apelin 13 in patients with acute pulmonary thromboembolism (PE) and to investigate their diagnostic and prognostic role in PE patients with different mortality risk groups.

MATERIAL AND METHODS

This study was conducted in a tertiary referral center and included 124 subjects with 94 cases of PE and 30 cases of healthy control group. All subjects were 18 years of age or older. The diagnosis of PE was done with computed tomography angiography of the thorax. After the diagnosis of acute PE, the serum levels of neutrophil gelatinase-associated lipocalin (NGAL), hypoxia-induced factor-1 alpha (HIF-1α), and apelin 13 levels were measured with a commercial enzyme-linked immunosorbent assay (ELISA) kit.

RESULTS

The median and IQR (interquartile range) age of patients and control groups were 68 (56-76) and 61.5 (56-67) years, respectively. The majority of patients with PE had risk factors (97.88 %), and only two (2.12 %) had no known risk factors. HIF-1 alpha level was found to be higher in the patient group than in the control group (p = 0.03). At the same time, the HIF-1 alpha level was found to be higher in the high mortality risk group than in the control group, low mortality risk group and intermediate-low mortality risk group (p = 0.000, 0.011, 0.002, respectively). While there was no significant difference in NGAL level between the patient group and the control group, a significant difference was observed between the mortality groups. NGAL level was found to be higher in the high mortality risk group than the control group, low mortality risk group, and medium-low mortality risk group (p = 0.001, 0.000, 0.010, respectively). Apelin 13 levels did not differ significantly in all groups.

CONCLUSION

HIF-1 alpha is a promising biomarker in distinguishing between patients and control groups and in identifying those with high mortality risk in the patient group. At the same time, NGAL can be used as a successful biomarker in determining the group with high mortality risk in cases of PE.

Using Omics to Identify Novel Therapeutic Targets in Heart Failure

Omics refers to the measurement and analysis of the totality of molecules or biological processes involved within an organism. Examples of omics data include genomics, transcriptomics, epigenomics, proteomics, metabolomics, and more. In this review, we present the available literature reporting omics data on heart failure that can inform the development of novel treatments or innovative treatment strategies for this disease. This includes polygenic risk scores to improve prediction of genomic data and the potential of multiomics to more efficiently identify potential treatment targets for further study. We also discuss the limitations of omic analyses and the barriers that must be overcome to maximize the utility of these types of studies. Finally, we address the current state of the field and future opportunities for using multiomics to better personalize heart failure treatment strategies.

Study on therapeutic mechanism of total salvianolic acids against myocardial ischemia-reperfusion injury based on network pharmacology, molecular docking, and experimental study

ETHNOPHARMACOLOGICAL RELEVANCE

Radix Salviae miltiorrhizae, also known as Danshen in Chinese, effectively activates the blood and resolves stasis. Total salvianolic acids (SA) is the main active ingredient of Danshen, and related preparations, such as salvianolate injection are commonly used clinically to treat myocardial ischemia-reperfusion injury (MIRI). However, the potential targets and key active ingredients of SA have not been sufficiently investigated.

AIM OF THE STUDY

This study aimed to investigate the mechanism of action of SA in treating MIRI.

MATERIALS AND METHODS

Network pharmacology and molecular docking techniques were used to predict SA targets against MIRI. The key acting pathway of SA were validated by performing experiments in a rat MIRI model.

RESULTS

Twenty potential ingredients and 54 targets of SA in treating MIRI were identified. Ingredient-target-pathway network analysis revealed that salvianolic acid B and rosmarinic acid had the highest degree value. Pathway enrichment analysis showed that SA may regulate MIRI through the IL-17 signaling pathway, and this result was confirmed in the rat MIRI experiment.

CONCLUSION

The results of this study indicate that SA may protect MIRI by regulating the IL-17 pathway.

Ischemia-induced cardiac dysfunction is exacerbated in adiponectin-knockout mice due to impaired autophagy flux

Strategies to enhance autophagy flux have been suggested to improve outcomes in cardiac ischemic models. We explored the role of adiponectin in mediating cardiac autophagy under ischemic conditions induced by permanent coronary artery ligation. We studied the molecular mechanisms underlying adiponectin's cardio-protective effects in adiponectin knockout (Ad-KO) compared with wild-type (WT) mice subjected to ischemia by coronary artery ligation and H9c2 cardiomyocyte cell line exposed to hypoxia. Systemic infusion of a cathepsin-B activatable near-infrared probe as a biomarker for autophagy and detection via noninvasive three-dimensional fluorescence molecular tomography combined with computerized tomography to quantitate temporal changes, indicated increased activity in the myocardium of WT mice after myocardial infarction which was attenuated in Ad-KO. Seven days of ischemia increased myocardial adiponectin accumulation and elevated ULK1/AMPK phosphorylation and autophagy assessed by Western blotting for LC3 and p62, an outcome not observed in Ad-KO mice. Cell death, assessed by TUNEL analysis and the ratio of Bcl-2:Bax, plus cardiac dysfunction, measured using echocardiography with strain analysis, were exacerbated in Ad-KO mice. Using cellular models, we observed that adiponectin stimulated autophagy flux in isolated primary adult cardiomyocytes and increased basal and hypoxia-induced autophagy in H9c2 cells. Real-time temporal analysis of caspase-3/7 activation and caspase-3 Western blot indicated that adiponectin suppressed activation by hypoxia. Hypoxia-induced mitochondrial reactive oxygen species production and cell death were also attenuated by adiponectin. Importantly, the ability of adiponectin to reduce caspase-3/7 activation and cell death was not observed in autophagy-deficient cells generated by CRISPR-mediated deletion of Atg7. Collectively, our data indicate that adiponectin acts in an autophagy-dependent manner to attenuate cardiomyocyte caspase-3/7 activation and cell death in response to hypoxia in vitro and ischemia in mice.

Lipocalin-2 induces mitochondrial dysfunction in renal tubular cells via mTOR pathway activation

Mitochondrial dysfunction is a critical process in renal epithelial cells upon kidney injury. While its implication in kidney disease progression is established, the mechanisms modulating it remain unclear. Here, we describe the role of Lipocalin-2 (LCN2), a protein expressed in injured tubular cells, in mitochondrial dysfunction. We show that LCN2 expression decreases mitochondrial mass and function and induces mitochondrial fragmentation. Importantly, while LCN2 expression favors DRP1 mitochondrial recruitment, DRP1 inhibition antagonizes LCN2's effect on mitochondrial shape. Remarkably, LCN2 promotes mitochondrial fragmentation independently of its secretion or transport iron activity. Mechanistically, intracellular LCN2 expression increases mTOR activity, and rapamycin inhibits LCN2's effect on mitochondrial shape. In vivo, Lcn2 gene inactivation prevents mTOR activation and mitochondrial length decrease observed upon ischemia-reperfusion-induced kidney injury (IRI) in Lcn2+/+ mice. Our data identify LCN2 as a key regulator of mitochondrial dynamics and further elucidate the mechanisms leading to mitochondrial dysfunction.

Lipocalin-2-mediated astrocyte pyroptosis promotes neuroinflammatory injury via NLRP3 inflammasome activation in cerebral ischemia/reperfusion injury

BACKGROUND

Neuroinflammation is a vital pathophysiological process during ischemic stroke. Activated astrocytes play a major role in inflammation. Lipocalin-2 (LCN2), secreted by activated astrocytes, promotes neuroinflammation. Pyroptosis is a pro-inflammatory form of programmed cell death that has emerged as a new area of research in stroke. Nevertheless, the potential role of LCN2 in astrocyte pyroptosis remains unclear.

METHODS

An ischemic stroke model was established by middle cerebral artery occlusion (MCAO) in vivo. In this study, in vitro, oxygen-glucose deprivation and reoxygenation (O/R) were applied to cultured astrocytes. 24p3R (the LCN2 receptor) was inhibited by astrocyte-specific adeno-associated virus (AAV-GFAP-24p3Ri). MCC950 and Nigericin sodium salt (Nig) were used to inhibit or promote the activation of NLRP3 inflammasome pharmacologically, respectively. Histological and biochemical analyses were performed to assess astrocyte and neuron death. Additionally, the neurological deficits of mice were evaluated.

RESULTS

LCN2 expression was significantly induced in astrocytes 24 h after stroke onset in the mouse MCAO model. Lcn2 knockout (Lcn2^-/-) mice exhibited reduced infarct volume and improved neurological and cognitive functions after MCAO. LCN2 and its receptor 24p3R were colocalized in astrocytes. Mechanistically, suppression of 24p3R by AAV-GFAP-24p3Ri alleviated pyroptosis-related pore formation and the secretion of pro-inflammatory cytokines via LCN2, which was then reversed by Nig-induced NLRP3 inflammasome activation. Astrocyte pyroptosis was exacerbated in Lcn2^-/- mice by intracerebroventricular administration of recombinant LCN2 (rLCN2), while this aggravation was restricted by blocking 24p3R or inhibiting NLRP3 inflammasome activation with MCC950.

CONCLUSION

LCN2/24p3R mediates astrocyte pyroptosis via NLRP3 inflammasome activation following cerebral ischemia/reperfusion injury.

Protective Role for Smooth Muscle Cell Hepcidin in Abdominal Aortic Aneurysm

BACKGROUND

Hepcidin is a liver-derived hormone that controls systemic iron homeostasis, by inhibiting the iron exporter ferroportin in the gut and spleen, respective sites of iron absorption and recycling. Hepcidin is also expressed ectopically in the context of cardiovascular disease. However, the precise role of ectopic hepcidin in underlying pathophysiology is unknown. In patients with abdominal aortic aneurysm (AAA), hepcidin is markedly induced in smooth muscle cells (SMCs) of the aneurysm wall and inversely correlated with the expression of LCN2 (lipocalin-2), a protein implicated in AAA pathology. In addition, plasma hepcidin levels were inversely correlated with aneurysm growth, suggesting hepcidin has a potential disease-modifying role.

METHODS

To probe the role of SMC-derived hepcidin in the setting of AAA, we applied AngII (Angiotensin-II)-induced AAA model to mice harbouring an inducible, SMC-specific deletion of hepcidin. To determine whether SMC-derived hepcidin acted cell-autonomously, we also used mice harboring an inducible SMC-specific knock-in of hepcidin-resistant ferroportinC326Y. The involvement of LCN2 was established using a LCN2-neutralizing antibody.

RESULTS

Mice with SMC-specific deletion of hepcidin or knock-in of hepcidin-resistant ferroportinC326Y had a heightened AAA phenotype compared with controls. In both models, SMCs exhibited raised ferroportin expression and reduced iron retention, accompanied by failure to suppress LCN2, impaired autophagy in SMCs, and greater aortic neutrophil infiltration. Pretreatment with LCN2-neutralizing antibody restored autophagy, reduced neutrophil infiltration, and prevented the heightened AAA phenotype. Finally, plasma hepcidin levels were consistently lower in mice with SMC-specific deletion of hepcidin than in controls, indicating that SMC-derived hepcidin contributes to the circulating pool in AAA.

CONCLUSIONS

Hepcidin elevation in SMCs plays a protective role in the setting of AAA. These findings are the first demonstration of a protective rather than deleterious role for hepcidin in cardiovascular disease. They highlight the need to further explore the prognostic and therapeutic value of hepcidin outside disorders of iron homeostasis.

Lipocalin family proteins and their diverse roles in cardiovascular disease

The lipocalin (LCN) family members, a group of small extracellular proteins with 160-180 amino acids in length, can be detected in all kingdoms of life from bacteria to human beings. They are characterized by low similarity of amino acid sequence but highly conserved tertiary structures with an eight-stranded antiparallel β-barrel which forms a cup-shaped ligand binding pocket. In addition to bind small hydrophobic ligands (i.e., fatty acids, odorants, retinoids, and steroids) and transport them to specific cells, lipocalins (LCNs) can interact with specific cell membrane receptors to activate their downstream signaling pathways, and with soluble macromolecules to form the complex. Consequently, LCNs exhibit great functional diversity. Accumulating evidence has demonstrated that LCN family proteins exert multiple layers of function in the regulation of many physiological processes and human diseases (i.e., cancers, immune disorders, metabolic disease, neurological/psychiatric disorders, and cardiovascular disease). In this review, we firstly introduce the structural and sequence properties of LCNs. Next, six LCNs including apolipoprotein D (ApoD), ApoM, lipocalin 2 (LCN2), LCN10, retinol-binding protein 4 (RBP4), and Lipocalin-type prostaglandin D synthase (L-PGDS) which have been characterized so far are highlighted for their diagnostic/prognostic values and their potential effects on coronary artery disease and myocardial infarction injury. The roles of these 6 LCNs in cardiac hypertrophy, heart failure, diabetes-induced cardiac disorder, and septic cardiomyopathy are also summarized. Finally, their therapeutic potential for cardiovascular disease is discussed in each section.

Catalpol Inhibits Autophagy to Ameliorate Doxorubicin-Induced Cardiotoxicity via the AKT-mTOR Pathway

As a kind of anthracycline, doxorubicin (DOX) is commonly used as an antitumor drug, but its clinical application has been greatly hindered due to its severe cardiotoxicity. Hence, in this study, we investigated the role of catalpol (CTP) and its effect on DOX-induced cardiotoxicity.The cardiac function of mice was evaluated by assessing lactate dehydrogenase, creatine kinase isoenzyme, heart weight to body weight, and heart weight/tibia length levels. Histopathological changes were observed using hematoxylin and eosin staining, and the terminal deoxynucleotidyl transferase dUTP nick end labeling assay was used to examine myocardial apoptosis. Superoxide dismutase (SOD) activity, glutathione (GSH), and malondialdehyde (MDA) levels were measured to confirm the changes in oxidative stress. Western blotting showed the levels of autophagy- and pathway-related proteins. Expression of autophagy marker LC3 was examined using immunofluorescence staining.CTP alleviated DOX-induced cardiac damage in mice. We further observed upregulated SOD and GSH levels, and downregulated MDA level after the CTP treatment in DOX-treated mice, indicating the protective role of CTP against oxidative injury. DOX-induced myocardial apoptosis was also inhibited by CTP treatment in mice. In addition, CTP decreased the levels of Beclin1 and LC3II/LC3I, increased the levels of P62, and activated the protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway in DOX-treated mice.CTP ameliorated DOX-induced cardiotoxicity by inhibiting oxidative stress, myocardial apoptosis, and autophagy via the AKT-mTOR pathway.

Increased LCN2 (lipocalin 2) in the RPE decreases autophagy and activates inflammasome-ferroptosis processes in a mouse model of dry AMD

In dry age-related macular degeneration (AMD), LCN2 (lipocalin 2) is upregulated. Whereas LCN2 has been implicated in AMD pathogenesis, the mechanism remains unknown. Here, we report that in retinal pigmented epithelial (RPE) cells, LCN2 regulates macroautophagy/autophagy, in addition to maintaining iron homeostasis. LCN2 binds to ATG4B to form an LCN2-ATG4B-LC3-II complex, thereby regulating ATG4B activity and LC3-II lipidation. Thus, increased LCN2 reduced autophagy flux. Moreover, RPE cells from cryba1 KO, as well as sting1 KO and Sting1Gt mutant mice (models with abnormal iron chelation), showed decreased autophagy flux and increased LCN2, indicative of CGAS- and STING1-mediated inflammasome activation. Live cell imaging of RPE cells with elevated LCN2 also showed a correlation between inflammasome activation and increased fluorescence intensity of the Liperfluo dye, indicative of oxidative stress-induced ferroptosis. Interestingly, both in human AMD patients and in mouse models with a dry AMD-like phenotype (cryba1 cKO and KO), the LCN2 homodimer variant is increased significantly compared to the monomer. Sub-retinal injection of the LCN2 homodimer secreted by RPE cells into NOD-SCID mice leads to retinal degeneration. In addition, we generated an LCN2 monoclonal antibody that neutralizes both the monomer and homodimer variants and rescued autophagy and ferroptosis activities in cryba1 cKO mice. Furthermore, the antibody rescued retinal function in cryba1 cKO mice as assessed by electroretinography. Here, we identify a molecular pathway whereby increased LCN2 elicits pathophysiology in the RPE, cells known to drive dry AMD pathology, thus providing a possible therapeutic strategy for a disease with no current treatment options.Abbreviations: ACTB: actin, beta; Ad-GFP: adenovirus-green fluorescent protein; Ad-LCN2: adenovirus-lipocalin 2; Ad-LCN2-GFP: adenovirus-LCN2-green fluorescent protein; LCN2AKT2: AKT serine/threonine kinase 2; AMBRA1: autophagy and beclin 1 regulator 1; AMD: age-related macular degeneration; ARPE19: adult retinal pigment epithelial cell line-19; Asp278: aspartate 278; ATG4B: autophagy related 4B cysteine peptidase; ATG4C: autophagy related 4C cysteine peptidase; ATG7: autophagy related 7; ATG9B: autophagy related 9B; BLOC-1: biogenesis of lysosomal organelles complex 1; BLOC1S1: biogenesis of lysosomal organelles complex 1 subunit 1; C57BL/6J: C57 black 6J; CGAS: cyclic GMP-AMP synthase; ChQ: chloroquine; cKO: conditional knockout; Cys74: cysteine 74; Dab2: DAB adaptor protein 2; Def: deferoxamine; DHE: dihydroethidium; DMSO: dimethyl sulfoxide; ERG: electroretinography; FAC: ferric ammonium citrate; Fe2+: ferrous; FTH1: ferritin heavy chain 1; GPX: glutathione peroxidase; GST: glutathione S-transferase; H2O2: hydrogen peroxide; His280: histidine 280; IFNL/IFNλ: interferon lambda; IL1B/IL-1β: interleukin 1 beta; IS: Inner segment; ITGB1/integrin β1: integrin subunit beta 1; KO: knockout; LC3-GST: microtubule associated protein 1 light chain 3-GST; C-terminal fusion; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; LCN2: lipocalin 2; mAb: monoclonal antibody; MDA: malondialdehyde; MMP9: matrix metallopeptidase 9; NLRP3: NLR family pyrin domain containing 3; NOD-SCID: nonobese diabetic-severe combined immunodeficiency; OS: outer segment; PBS: phosphate-buffered saline; PMEL/PMEL17: premelanosome protein; RFP: red fluorescent protein; rLCN2: recombinant LCN2; ROS: reactive oxygen species; RPE SM: retinal pigmented epithelium spent medium; RPE: retinal pigment epithelium; RSL3: RAS-selective lethal; scRNAseq: single-cell ribonucleic acid sequencing; SD-OCT: spectral domain optical coherence tomography; shRNA: small hairpin ribonucleic acid; SM: spent medium; SOD1: superoxide dismutase 1; SQSTM1/p62: sequestosome 1; STAT1: signal transducer and activator of transcription 1; STING1: stimulator of interferon response cGAMP interactor 1; TYR: tyrosinase; VCL: vinculin; WT: wild type.

Sex-dependent expression of neutrophil gelatinase-associated lipocalin in aortic stenosis

BACKGROUND

Accumulating evidence suggest the existence of sex-related differences in the pathogenesis of aortic stenosis (AS) with inflammation, oxidative stress, fibrosis and calcification being over-represented in men. Neutrophil gelatinase-associated lipocalin (NGAL) is expressed in a myriad of tissues and cell types, and it is associated with acute and chronic pathological processes comprising inflammation, fibrosis or calcification. Sex-dependent signatures have been evidenced for NGAL which expression has been associated predominantly in males to metabolic and cardiovascular disorders. We aimed to analyse sex-related differences of NGAL in AS and its role in the inflammatory and fibrocalcific progression of AS.

METHODS AND RESULTS

220 (60.45% men) patients with severe AS elective for surgical aortic valve (AV) replacement were recruited. Immunohistochemistry revealed higher expression of NGAL in calcific areas of AVs and that was validated by qPCR in in 65 (60% men) donors. Valve interstitial cells (VICs) were a source of NGAL in these samples. Proteome profiler analyses evidenced higher expression of NGAL in men compared to women, and that was further validated by ELISA. NGAL expression in the AV was correlated with inflammation, oxidative stress, and osteogenic markers, as well as calcium score. The expression of NGAL, both intracellular and secreted (sNGAL), was significantly deregulated only in calcifying male-derived VICs. Depletion of intracellular NGAL in calcifying male-derived VICs was associated with pro-inflammatory profiles, dysbalanced matrix remodelling and pro-osteogenic profiles. Conversely, exogenous NGAL mediated inflammatory and dysbalanced matrix remodelling in calcifying VICs, and all that was prevented by the pharmacological blockade of NGAL.

CONCLUSIONS

Owing to the over-expression of NGAL, the AV from men may be endowed with higher expression of inflammatory, oxidative stress, matrix remodelling and osteogenic markers supporting the progression of calcific AS phenotypes. The expression of NGAL in the VIC emerges as a potential therapeutic checkpoint, with its effects being potentially reverted by the pharmacological blockade of extracellular NGAL.

Lipocalin-2 participates in sepsis-induced myocardial injury by mediating lipid accumulation and mitochondrial dysfunction

BACKGROUND

Sepsis-induced cardiomyopathy (SIC) is one major cause of death for sepsis but lacks timely diagnosis and specific treatment due to unclear mechanisms. Lipocalin-2 (LCN-2) is a key regulator of lipid metabolism which has been recently proved closely related to sepsis, however, the relationship between LCN-2 and septic myocardial injury remains unknown. We aim to explore the role of LCN-2 in the pathological progress of SIC based on clinical and laboratory evidence.

METHODS

Consecutive patients admitted to the intensive care unit (ICU) from August 2021 to April 2022 fulfilling the criteria of severe sepsis were included. The level of LCN-2 in plasma was assayed and analyzed with clinical characteristics. Biostatistical analysis was performed for further identification and pathway enrichment. Mouse model for SIC was thereafter established, in which plasma and tissue LCN-2 levels were tested. RNA sequencing was used for verification and to reveal the possible mechanism. Mitochondrial function and intracellular lipid levels were assayed to further assess the biological effects of targeting LCN-2 in cardiomyocytes with small interference RNAs (siRNAs).

RESULTS

The level of LCN-2 in plasma was markedly higher in patients with severe sepsis and was associated with higher cardiac biomarkers and lower LVEF. In the in vivo experiment, circulating LCN-2 from plasma was found to increase in SIC mice. A higher level of LCN-2 transcription in myocardial tissue was also found in SIC and showed a clear time relationship. RNA sequencing analysis showed the level of LCN-2 was associated with several gene-sets relevant to mitochondrial function and lipid metabolism-associated pathways. The suppression of LCN-2 protected mitochondrial morphology and limited the production of ROS, as well as restored the mitochondrial membrane potential damaged by LPS. Neutral lipid staining showed prominent lipid accumulation in LPS group, which was alleviated by the treatment of siLCN2.

CONCLUSION

The level of LCN-2 is significantly increased in SIC at both circulating and tissue levels, which is correlated with the severity of myocardial injury indicators, and may work as an early and great predictor of SIC. LCN-2 probably participates in the process of septic myocardial injury through mediating lipid accumulation and affecting mitochondrial function.

Exploring the Role of Lipid-Binding Proteins and Oxidative Stress in Neurodegenerative Disorders: A Focus on the Neuroprotective Effects of Nutraceutical Supplementation and Physical Exercise

The human brain is primarily composed of lipids, and their homeostasis is crucial to carry on normal neuronal functions. In order to provide an adequate amount of lipid transport in and out of the central nervous system, organisms need a set of proteins able to bind them. Therefore, alterations in the structure or function of lipid-binding proteins negatively affect brain homeostasis, as well as increase inflammation and oxidative stress with the consequent risk of neurodegeneration. In this regard, lifestyle changes seem to be protective against neurodegenerative processes. Nutraceutical supplementation with antioxidant molecules has proven to be useful in proving cognitive functions. Additionally, regular physical activity seems to protect neuronal vitality and increases antioxidant defenses. The aim of the present review was to investigate mechanisms that link lipid-binding protein dysfunction and oxidative stress to cognitive decline, also underlining the neuroprotective effects of diet and exercise.

Anti-tumor effects of dual PI3K-HDAC inhibitor CUDC-907 on activation of ROS-IRE1α-JNK-mediated cytotoxic autophagy in esophageal cancer

Background

PI3K-Akt pathway activation and the expression of histone deacetylases (HDACs) are highly increased in esophageal cancer, suggesting that inhibition of such targets may be a viable therapeutic strategy. Herein, we aimed to evaluate the anti-tumor effect of CUDC-907, a dual PI3K-HDAC inhibitor, in esophageal squamous cell carcinoma (ESCC).

Methods

The anti-tumor effects of CUDC-907 in ESCC were evaluated using cell counting kit-8, flow cytometry, and western blot. mRNA-sequencing was used to explore the mechanism underlying CUDC-907 anti-tumor effects. The relations of reactive oxygen species (ROS), lipocalin 2 (LCN2), and CUDC-907 were determined by flow cytometry, rescue experiments, and western blot. The activation of the IRE1α-JNK-CHOP signal cascade was confirmed by western blot. The in vivo inhibitory effects of CUDC-907 were examined by a subcutaneous xenograft model in nude mice.

Results

CUDC-907 displayed effective inhibition in the proliferation, migration, and invasion of ESCC cells. Through an mRNA-sequencing and functional enrichment analysis, autophagy was found to be associated with cancer cells death. CUDC-907 not only inhibited the PI3K-Akt-mTOR pathways to result in autophagy, but also induced ROS accumulation to activate IRE1α-JNK-CHOP-mediated cytotoxic autophagy by downregulating LCN2 expression. Consistently, the in vivo anti-tumor effects of CUDC-907 accompanied by the downregulated expression of p-mTOR and LCN2 and upregulated expression of p-IRE1α and LC3B-II were evaluated in a xenograft mouse model.

Conclusion

Our findings suggested the clinical development and administration of CUDC-907 might act as a novel treatment strategy for ESCC. A more in-depth understanding of the anti-tumor effect of CUDC-907 in ESCC will benefit the clinically targeted treatment of ESCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00855-x.

Lipocalin-2 in neutrophils induces ferroptosis in septic cardiac dysfunction via increasing labile iron pool of cardiomyocytes

Cardiac dysfunction is a common complication of sepsis with high mortality. The present study was designed to identify the effect of neutrophil-derived lipocalin-2 (LCN2) in septic cardiac dysfunction (SCD) and its potential mechanism. Wild-type (WT) and LCN2-knockout (LCN2 KO) mice were peritoneally injected with lipopolysaccharide (LPS) to induce SCD. The cardiac function was assessed 12 h after LPS injection by echocardiography. Cardiac tissue was harvested for the evaluation of malonaldehyde (MDA) and prostaglandin E synthase 2 (PTGS2) mRNA levels. LPS induced ferroptosis and SCD in mice. LCN2 deficiency attenuated cardiac injury post-LPS administration. In vitro, LCN2 expression in neutrophils increased in response to LPS. Ferroptosis of cardiomyocytes induced by conditioned medium (CM) from LPS-induced neutrophils of WT mice could be attenuated in CM from LPS-induced neutrophils of LCN2 KO mice. Exogenous LCN2 induced H9C2 cell ferroptosis via increasing labile iron pool (LIP). In conclusion, our results showed that LCN2 deficiency prevented heart dysfunction and ferroptosis in SCD mice and suggested that neutrophil-derived LCN2 might be a promising therapeutic target for SCD.

Autophagy and beyond: Unraveling the complexity of UNC-51-like kinase 1 (ULK1) from biological functions to therapeutic implications

UNC-51-like kinase 1 (ULK1), as a serine/threonine kinase, is an autophagic initiator in mammals and a homologous protein of autophagy related protein (Atg) 1 in yeast and of UNC-51 in Caenorhabditis elegans. ULK1 is well-known for autophagy activation, which is evolutionarily conserved in protein transport and indispensable to maintain cell homeostasis. As the direct target of energy and nutrition-sensing kinase, ULK1 may contribute to the distribution and utilization of cellular resources in response to metabolism and is closely associated with multiple pathophysiological processes. Moreover, ULK1 has been widely reported to play a crucial role in human diseases, including cancer, neurodegenerative diseases, cardiovascular disease, and infections, and subsequently targeted small-molecule inhibitors or activators are also demonstrated. Interestingly, the non-autophagy function of ULK1 has been emerging, indicating that non-autophagy-relevant ULK1 signaling network is also linked with diseases under some specific contexts. Therefore, in this review, we summarized the structure and functions of ULK1 as an autophagic initiator, with a focus on some new approaches, and further elucidated the key roles of ULK1 in autophagy and non-autophagy. Additionally, we also discussed the relationships between ULK1 and human diseases, as well as illustrated a rapid progress for better understanding of the discovery of more candidate small-molecule drugs targeting ULK1, which will provide a clue on novel ULK1-targeted therapeutics in the future.

Integrated Serum Pharmacochemistry and Network Pharmacology Approach to Explore the Effective Components and Potential Mechanisms of Menispermi Rhizoma Against Myocardial Ischemia

Background: Myocardial ischemia (MI) is a leading cause of death worldwide. Menispermi Rhizoma is a traditional Chinese medicine that exerts a variety of beneficial pharmacological activities in many diseases, including MI.

Purpose: Serum pharmacochemistry and network pharmacology were used to explore the material basis and mechanism of action of Menispermi Rhizoma against MI.

Methods: The absorbed components of Menispermi Rhizoma in rat plasma were analyzed by ultra-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry (UPLC-Q-TOF/MS). The key components, targets, pathways, and interrelated information were obtained by network pharmacology. The potential effective components of Menispermi Rhizoma against MI were screened by methyl-thiazolyl-tetrazolium (MTT) assay, and the cardioprotective effect and mechanism of active components were verified by Western blotting and molecular docking.

Results: In total, 25 absorbed components of Menispermi Rhizoma in plasma were identified. Network pharmacology revealed 81 major targets of Menispermi Rhizoma against MI, mainly involving the regulation of the PI3K/AKT and MAPK pathways. In vitro validation of H9c2 cells revealed that acutumine, daurisoline, dauricoside, and 6-O-demethylmenisporphine are the main bioactive components of Menispermi Rhizoma. The levels of lactate dehydrogenase, creatine kinase, and malondialdehyde (MDA) were significantly decreased by four alkaloids, whereas the activities of superoxide dismutase (SOD) and glutathione (GSH) were significantly increased. Four alkaloids effectively protected H9c2 cells against OGD-induced apoptosis by Hoechst/PI staining and flow cytometry assay. Western blotting results showed that the four alkaloids upregulated the expression ratio of Bcl-2/Bax and downregulated the expression levels of Cyt-C and cleaved caspase 3, which further supported the anti-cardiomyocyte apoptosis and antioxidative stress effect of Menispermi Rhizoma. Molecular docking confirmed that the four compounds were capable of binding to AKT1, MAPK1, EGFR, CASP3, and MAPK8 proteins, suggesting the protective effect of Menispermi Rhizoma on MI via PI3K/AKT, MAPK, and apoptosis pathways.

Conclusion: Menispermi Rhizoma exerted cardioprotective effects through the effect characteristics: multiple-ingredient, multi-target, and multi-pathway. This research provided a reference for further mechanistic research on wider applications of Menispermi Rhizoma for MI treatment.

Neutrophil degranulation and myocardial infarction

Myocardial infarction (MI) is one of the most common cardiac emergencies with high morbidity and is a leading cause of death worldwide. Since MI could develop into a life-threatening emergency and could also seriously affect the life quality of patients, continuous efforts have been made to create an effective strategy to prevent the occurrence of MI and reduce MI-related mortality. Numerous studies have confirmed that neutrophils play important roles in inflammation and innate immunity, which provide the first line of defense against microorganisms by producing inflammatory cytokines and chemokines, releasing reactive oxygen species, and degranulating components of neutrophil cytoplasmic granules to kill pathogens. Recently, researchers reported that neutrophils are closely related to the severity and prognosis of patients with MI, and neutrophil to lymphocyte ratio in post-MI patients had predictive value for major adverse cardiac events. Neutrophils have been increasingly recognized to exert important functions in MI. Especially, granule proteins released by neutrophil degranulation after neutrophil activation have been suggested to involve in the process of MI. This article reviewed the current research progress of neutrophil granules in MI and discusses neutrophil degranulation associated diagnosis and treatment strategies.

The impact of autophagy modulation on phenotype and survival of cardiac stromal cells under metabolic stress

Cardiac stromal cells (CSCs) embrace multiple phenotypes and are a contributory factor in tissue homeostasis and repair. They can be exploited as therapeutic mediators against cardiac fibrosis and remodeling, but their survival and cardioprotective properties can be decreased by microenvironmental cues. We evaluated the impact of autophagy modulation by different pharmacological/genetic approaches on the viability and phenotype of murine CSCs, which had been subjected to nutrient deprivation or hyperglycemia, in order to mimic relevant stress conditions and risk factors of cardiovascular diseases. Our results show that autophagy is activated in CSCs by nutrient deprivation, and that autophagy induction by trehalose or autophagy-related protein 7 (ATG7)-overexpression can significantly preserve CSC viability. Furthermore, autophagy induction is associated with a higher proportion of primitive, non-activated stem cell antigen 1 (Sca1)-positive cells, and with a reduced fibrotic fraction (positive for the discoidin domain-containing receptor 2, DDR2) in the CSC pool after nutrient deprivation. Hyperglycemia, on the other hand, is associated with reduced autophagic flux in CSCs, and with a significant reduction in primitive Sca1+ cells. Autophagy induction by adenoviral-mediated ATG7-overexpression maintains a cardioprotective, anti-inflammatory and pro-angiogenic paracrine profile of CSCs exposed to hyperglycemia for 1 week. Finally, autophagy induction by ATG7-overexpression during hyperglycemia can significantly preserve cell viability in CSCs, which were subsequently exposed to nutrient deprivation, reducing hyperglycemia-induced impairment of cell resistance to stress. In conclusion, our results show that autophagy stimulation preserves CSC viability and function in response to metabolic stressors, suggesting that it may boost the beneficial functions of CSCs in cardiac repair mechanisms.

Lipocalin 2 Influences Bone and Muscle Phenotype in the MDX Mouse Model of Duchenne Muscular Dystrophy

Lipocalin 2 (Lcn2) is an adipokine involved in bone and energy metabolism. Its serum levels correlate with bone mechanical unloading and inflammation, two conditions representing hallmarks of Duchenne Muscular Dystrophy (DMD). Therefore, we investigated the role of Lcn2 in bone loss induced by muscle failure in the MDX mouse model of DMD. We found increased Lcn2 serum levels in MDX mice at 1, 3, 6, and 12 months of age. Consistently, Lcn2 mRNA was higher in MDX versus WT muscles. Immunohistochemistry showed Lcn2 expression in mononuclear cells between muscle fibres and in muscle fibres, thus confirming the gene expression results. We then ablated Lcn2 in MDX mice, breeding them with Lcn2^−/− mice (MDXxLcn2^−/−), resulting in a higher percentage of trabecular volume/total tissue volume compared to MDX mice, likely due to reduced bone resorption. Moreover, MDXxLcn2^−/− mice presented with higher grip strength, increased intact muscle fibres, and reduced serum creatine kinase levels compared to MDX. Consistently, blocking Lcn2 by treating 2-month-old MDX mice with an anti-Lcn2 monoclonal antibody (Lcn2Ab) increased trabecular volume, while reducing osteoclast surface/bone surface compared to MDX mice treated with irrelevant IgG. Grip force was also increased, and diaphragm fibrosis was reduced by the Lcn2Ab. These results suggest that Lcn2 could be a possible therapeutic target to treat DMD-induced bone loss.

LCN2 deficiency ameliorates doxorubicin-induced cardiomyopathy in mice

Doxorubicin (DOX) is an effective anticancer drug with the side effect of irreparable cardiomyopathy. Lipocalin-2 (LCN2) has been identified as an important regulator of oxidative stress and inflammation in cardiovascular disease pathophysiology. Here, we demonstrate that LCN2 deletion increases autophagic flux in the DOX-treated hearts. Mice were injected intraperitoneally six times with 30 mg/kg DOX. Echocardiography showed that DOX-treated wild-type (WT) mice had markedly weaker cardiac function compared to saline-treated WT mice. In DOX-treated LCN2 knockout (KO) mice, cardiac function was partially restored. Histological analysis showed a reduction in cardiomyocyte diameter in DOX-treated WT mice that was ameliorated in DOX-treated LCN2KO mice. Cardiac levels of phosphorylated signal transducer and activator of transcription 3, LCN2, heme oxygenase-1, and NAD (P) H dehydrogenase were markedly greater in DOX-treated WT mice than in DOX-treated LCN2KO mice. Light chain 3B (LC3B)II expression was higher in DOX-treated WT mice, but lower in DOX-treated LCN2KO mice when compared to saline-treated WT mice. Less co-localization of LC3B and lysosomal-associated membrane protein 1 was observed in DOX-treated WT mice than in DOX-treated LCN2KO mice. LCN2 co-localized with LC3B-stained cells in the DOX-treated WT mouse heart, but not in the DOX-treated LCN2KO mouse heart. These findings indicate that the cardiotoxic effect of DOX is due to autophagosome accumulation mediated by LCN2 upregulation and that LCN2 may inhibit autophagic flux, leading to DOX-induced cardiomyopathy.

Neutrophil Gelatinase-Associated Lipocalin From Macrophages Plays a Critical Role in Renal Fibrosis Via the CCL5 (Chemokine Ligand 5)-Th2 Cells-IL4 (Interleukin 4) Pathway

NGAL (neutrophil gelatinase-associated lipocalin; or lipocalin 2, Lcn2) is a novel mineralocorticoid target in the cardiovascular system. We showed that Lcn2 gene invalidation protects against proteinuria and renal injury upon mineralocorticoid excess and we hypothesized that NGAL produced from macrophages promotes the expression of chemoattractant molecules involved these renal lesions. The role of NGAL was analyzed using myeloid-specific (MΦ KO NGAL) Lcn2 knockout mice challenged with uni-nephrectomy, aldosterone, and salt (NAS) for 6 weeks. The role of the CCL5 (chemokine ligand 5) and IL4 (interleukin 4) in kidney fibrosis was studied by administration of the CCL5 receptor antagonist maraviroc or by injections of an anti-IL4 neutralizing antibody. In CTL mice, NAS increased the renal expression of extracellular matrix proteins, such as collagen I, αSMA, and fibronectin associated with interstitial fibrosis which were blunted in MΦ KO NGAL mice. The expression of CCL5 was blunted in sorted macrophages from MΦ KO NGAL mice challenged by NAS and in macrophages obtained from KO NGAL mice and challenged ex vivo with aldosterone and salt. The pharmacological blockade of the CCL5 receptor reduced renal fibrosis and the CD4⁺ Th cell infiltration induced by NAS. Neutralization of IL4 in NAS mice blunted kidney fibrosis and the overexpression of profibrotic proteins, such as collagen I, αSMA, and fibronectin. In conclusion, NGAL produced by macrophages plays a critical role in renal fibrosis and modulates the CCL5/IL4 pathway in mice exposed to mineralocorticoid excess.

Lipocalin 2 as a link between ageing, risk factor conditions and age-related brain diseases

Chronic (neuro)inflammation plays an important role in many age-related central nervous system (CNS) diseases, including Alzheimer's disease, Parkinson's disease and vascular dementia. Inflammation also characterizes many conditions that form a risk factor for these CNS disorders, such as physical inactivity, obesity and cardiovascular disease. Lipocalin 2 (Lcn2) is an inflammatory protein shown to be involved in different age-related CNS diseases, as well as risk factor conditions thereof. Lcn2 expression is increased in the periphery and the brain in different age-related CNS diseases and also their risk factor conditions. Experimental studies indicate that Lcn2 contributes to various neuropathophysiological processes of age-related CNS diseases, including exacerbated neuroinflammation, cell death and iron dysregulation, which may negatively impact cognitive function. We hypothesize that increased Lcn2 levels as a result of age-related risk factor conditions may sensitize the brain and increase the risk to develop age-related CNS diseases. In this review we first provide a comprehensive overview of the known functions of Lcn2, and its effects in the CNS. Subsequently, this review explores Lcn2 as a potential (neuro)inflammatory link between different risk factor conditions and the development of age-related CNS disorders. Altogether, evidence convincingly indicates Lcn2 as a key constituent in ageing and age-related brain diseases.

Neutrophil Gelatinase-Associated Lipocalin 2 Accelerates Hypoxia-Induced Endothelial Cell Injury via eNOS/NRF2 Signalling

Objective

Neutrophil gelatinase-associated lipocalin (NGAL), a lipocalin, is implicated in many cardiovascular diseases (CVD). The effect of NGAL on endothelial cells (ECs), particularly on ECs injured because of hypoxia, is unclear. In this study, we aim to explore the effect of NGAL in an EC injury in response to hypoxia.

Materials and Methods

In this experimental study, we isolated and cultured mouse heart ECs (MHECs). The EC injury model was established by exposure of the ECs to hypoxia for 24 hours. The ECs were treated with NGAL (30, 60, 120, 250 and 500 ng/ml). Cell inflammation and oxidative stress were detected by corresponding assays. Apoptotic cells were stained by the terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay.

Results

NGAL increased the inflammatory response at the baseline level and further augmented the hypoxia-induced inflammation response. Reactive oxygen species (ROS) levels increased upon NGAL treatment, which caused antioxidase/oxidase imbalance. NGAL also exaggerated hypoxia-induced oxidative stress. The cell apoptosis rate also increased in both the NGAL-treated normoxic and hypoxic conditions. NGAL also reduced endothelial nitric oxide synthase (eNOS)-nitric oxide (NO) signalling, thus decreasing the expression and nuclear translocation of nuclear factor erythroid-2-related factor 2 (NRF2), which was confirmed by overexpression of NRF2.

Conclusion

NGAL exaggerates EC injury in both normoxic and hypoxic conditions by inhibiting the eNOS-NRF2 pathway.

Self-eating and Heart: The Emerging Roles of Autophagy in Calcific Aortic Valve Disease

Autophagy is a self-degradative pathway by which subcellular elements are broken down intracellularly to maintain cellular homeostasis. Cardiac autophagy commonly decreases with aging and is accompanied by the accumulation of misfolded proteins and dysfunctional organelles, which are undesirable to the cell. Reduction of autophagy over time leads to aging-related cardiac dysfunction and is inversely related to longevity. However, despite the increasing interest in autophagy in cardiac diseases and aging, the process remains an undervalued and disregarded object in calcific valvular disease. Neither the nature through which autophagy is triggered nor the interplay between autophagic machinery and targeted molecules during aortic valve calcification are fully understood. Recently, the upregulation of autophagy has been shown to result in cardioprotective effects against cell death as well as its origin. Here, we review the evidence that shows how autophagy can be both beneficial and detrimental as it pertains to aortic valve calcification in the heart.

Lipocalin 2 increases after high-intensity exercise in humans and influences muscle gene expression and differentiation in mice

Lipocalin 2 (LCN2) is an adipokine that accomplishes several functions in diverse organs. However, its importance in muscle and physical exercise is currently unknown. We observed that following acute high‐intensity exercise (“Gran Sasso d'Italia” vertical run), LCN2 serum levels were increased. The Wnt pathway antagonist, DKK1, was also increased after the run, positively correlating with LCN2, and the same was found for the cytokine Interleukin 6. We, therefore, investigated the involvement of LCN2 in muscle physiology employing an Lcn2 global knockout (Lcn2^−/−) mouse model. Lcn2^−/− mice presented with smaller muscle fibres but normal muscle performance (grip strength metre) and muscle weight. At variance with wild type (WT) mice, the inflammatory cytokine Interleukin 6 was undetectable in Lcn2^−/− mice at all ages. Intriguingly, Lcn2^−/− mice did not lose gastrocnemius and quadriceps muscle mass and muscle performance following hindlimb suspension, while at variance with WT, they lose soleus muscle mass. In vitro, LCN2 treatment reduced the myogenic differentiation of C2C12 and primary mouse myoblasts and influenced their gene expression. Treating myoblasts with LCN2 reduced myogenesis, suggesting that LCN2 may negatively affect muscle physiology when upregulated following high‐intensity exercise.

Iron Reshapes the Gut Microbiome and Host Metabolism

Compelling studies have established that the gut microbiome is a modifier of metabolic health. Changes in the composition of the gut microbiome are influenced by genetics and the environment, including diet. Iron is a potential node of crosstalk between the host-microbe relationship and metabolic disease. Although iron is well characterized as a frequent traveling companion of metabolic disease, the role of iron is underappreciated because the mechanisms of iron's influence on host metabolism are poorly characterized. Both iron deficiency and excessive amounts leading to iron overload can have detrimental effects on cardiometabolic health. Optimal iron homeostasis is critical for regulation of host immunity and metabolism in addition to regulation of commensal and pathogenic enteric bacteria. In this article we review evidence to support the notion that altering composition of the gut microbiome may be an important route via which iron impacts cardiometabolic health. We discuss reshaping of the microbiome by iron, the physiological significance and the potential for therapeutic interventions.

Regulation of the Nfkbiz Gene and Its Protein Product IkBζ in Animal Models of Sepsis and Endotoxic Shock

Sepsis is a life-threatening condition that arises from a poorly regulated inflammatory response to pathogenic organisms. Current treatments are limited to antibiotics, fluid resuscitation, and other supportive therapies. New targets for monitoring disease progression and therapeutic interventions are therefore critically needed. We previously reported that lipocalin-2 (Lcn2), a bacteriostatic mediator with potent proapoptotic activities, was robustly induced in sepsis. Other studies showed that Lcn2 was a predictor of mortality in septic patients. However, how Lcn2 is regulated during sepsis is poorly understood. We evaluated how IkBζ, an inducer of Lcn2, was regulated in sepsis using both the cecal ligation and puncture (CLP) and endotoxemia (lipopolysaccharide [LPS]) animal models. We show that Nfkbiz, the gene encoding IkBζ, was rapidly stimulated but, unlike Lcn2, whose expression persists during sepsis, mRNA levels of Nfkbiz decline to near basal levels several hours after its induction. In contrast, we observed that IkBζ expression remained highly elevated in septic animals following CLP but not LPS, indicating the occurrence of a CLP-specific mechanism that extends IkBζ half-life. By using an inhibitor of IkBζ, we determined that the expression of Lcn2 was largely controlled by IkBζ. Altogether, these data indicate that the high IkBζ expression in tissues likely contributes to the elevated expression of Lcn2 in sepsis. Since IkBζ is also capable of promoting or repressing other inflammatory genes, it might exert a central role in sepsis.

Antifibrotic effect of novel neutrophil gelatinase-associated lipocalin inhibitors in cardiac and renal disease models

Neutrophil gelatinase-associated lipocalin (NGAL) is involved in cardiovascular and renal diseases. Gene inactivation of NGAL blunts the pathophysiological consequences of cardiovascular and renal damage. We aimed to design chemical NGAL inhibitors and investigate its effects in experimental models of myocardial infarction (MI) and chronic kidney disease induced by 5/6 nephrectomy (CKD) on respectively 8–12 weeks old C57Bl6/j and FVB/N male mice. Among the 32 NGAL inhibitors tested, GPZ614741 and GPZ058225 fully blocked NGAL-induced inflammatory and profibrotic markers in human cardiac fibroblasts and primary mouse kidney fibroblasts. The administration of GPZ614741 (100 mg/kg/day) for three months, was able to improve cardiac function in MI mice and reduced myocardial fibrosis and inflammation. The administration of GPZ614741 (100 mg/kg/day) for two months resulting to no renal function improvement but prevented the increase in blood pressure, renal tubulointerstitial fibrosis and profibrotic marker expression in CKD mice. In conclusion, we have identified new compounds with potent inhibitory activity on NGAL-profibrotic and pro-inflammatory effects. GPZ614741 prevented interstitial fibrosis and dysfunction associated with MI, as well as tubulointerstitial fibrosis in a CKD model. These inhibitors could be used for other diseases that involve NGAL, such as cancer or metabolic diseases, creating new therapeutic options.

Systematic Analysis of tRNA-Derived Small RNAs Discloses New Therapeutic Targets of Caloric Restriction in Myocardial Ischemic Rats

Caloric restriction (CR) is a novel dietary therapy that has a protective effect on myocardial ischemia. However, the mechanisms underlying the therapeutic effect of CR remain unclear. Transfer RNA-derived small RNAs (tsRNAs) are a novel type of short non-coding RNAs that have potential regulatory functions in various physiological and pathological processes. In this study, we explored new therapeutic targets of CR through tsRNA sequencing. Rats were randomly divided into three groups: a normal control group (norm group), isoproterenol (ISO)-induced myocardial ischemic group (MI group), and CR pretreatment plus ISO-induced myocardial ischemic group (CR + MI group). Triphenyl tetrazolium chloride staining, terminal deoxynucleotidyl transferase dUTP nick-end labeling staining, serum creatine kinase (CK) and lactic acid dehydrogenase activity detection kits, and creatine kinase isoenzyme 1 levels were used to measure the degree of myocardial ischemic injury. These indicators of myocardial ischemia were significantly improved in the CR + MI group compared with those in the MI group. In the ischemic myocardial tissue of the MI group, a total of 708 precisely matched tsRNAs were identified, and 302 tsRNAs (fold change >1.5, P < 0.05) were significantly changed when compared with those in the norm group. Furthermore, 55 tsRNAs were significantly regulated by CR pretreatment, among which five tsRNAs (tiRNA-His-GTG-004, tRF-Gly-TCC-018, tRF-Cys-GCA-022, tRF-Lys-CTT-026, tRF-Met-CAT-008) were randomly selected and verified by quantitative real-time polymerase chain reaction. In addition, predictions of target genes and bioinformatics analysis indicated that these tsRNAs may play a therapeutic role through the regulation of macromolecular metabolism. In conclusion, our findings reveal that tsRNAs are potential therapeutic targets for CR pre-pretreatment to improve myocardial ischemic injury. This study provides new ideas for future research on elucidating the mechanisms of CR pretreatment in ameliorating myocardial ischemic injury.

Diosmetin alleviates hypoxia‑induced myocardial apoptosis by inducing autophagy through AMPK activation

Diosmetin has shown great potential in the control of several diseases. The aim of the present study was to evaluate the role of diosmetin as a candidate agent for the treatment of myocardial infarction which was mainly caused by hypoxia. The model of hypoxia‑injured myocardial cells was established using the H9c2 cell line. Cell viability was determined using Cell Counting Kit‑8, cell apoptosis was determined by Annexin V‑FITC Apoptosis Detection Kit and cleaved caspase‑3 level was assessed by western blot analysis. Autophagy was monitored using a commercial kit, and a well‑established reporter system was used to confirm the role of diosmetin in autophagy. The activity of adenosine 5'‑monophosphate‑activated protein kinase (AMPK) signaling was detected by western blot analysis. Cell viability assay indicated that diosmetin alleviated hypoxia‑induced cell death of H9c2 cells in a dose‑dependent manner. Data of the apoptosis assay revealed that diosmetin reduced the proportion of apoptotic cells in the hypoxia‑injured H9c2 cells. It was also found that the occurrence of autophagy was promoted when hypoxia‑injured cells were treated with diosmetin alone, and results of the western blot analysis revealed that AMPK signaling was activated by diosmetin. Administration of diosmetin together with an inhibitor of autophagy (3‑methyladenine, 3‑MA) or AMPK (Compound C) was able to decrease the diosmetin‑induced autophagy as well as the cytoprotective effects in the hypoxia‑injured cells. Our study concluded that diosmetin exhibits a cytoprotective effect on hypoxia‑injured myocardial cells by inducing autophagy and alleviating apoptosis. AMPK was demonstrated to regulate the observed effects caused by diosmetin. This investigation confirmed diosmetin as a promising drug candidate for myocardial infarction treatment. The present findings regarding the inherent molecular mechanisms involved in the protective effects of diosmetin promote the clinical application of diosmetin.

Sevoflurane Preconditioning Confers Delayed Cardioprotection by Upregulating AMP-Activated Protein Kinase Levels to Restore Autophagic Flux in Ischemia-Reperfusion Rat Hearts

Background

Volatile anesthetic preconditioning confers delayed cardioprotection against ischemia/reperfusion injury (I/R). AMP-activated protein kinase (AMPK) takes part in autophagy activation. Furthermore, autophagic flux is thought to be impaired after I/R. We hypothesized that delayed cardioprotection can restore autophagic flux by activating AMPK.

Material/Methods

All male rat hearts underwent 30-min ischemia and 120-min reperfusion with or without sevoflurane exposure. AMPK inhibitor compound C (250 μg/kg, iv) was given at the reperfusion period. Autophagic flux blocker chloroquine (10 mg/kg, ip) was administrated 1 h before the experiment. Myocardial infarction, nicotinamide adenine dinucleotide (NAD⁺) content, and cytochrome c were measured. To evaluate autophagic flux, the markers of microtubule-associated protein 1 light chain 3 (LC3) I and II, P62 and Beclin 1, and lysosome-associated membrane protein-2 (LAMP 2) were analyzed.

Results

The delayed cardioprotection enhanced post-ischemic AMPK activation, reduced infarction, CK-MB level, NAD⁺ content loss and cytochrome c release, and compound C blocked these effects. Sevoflurane restored impaired autophagic flux through a lower ratio of LC3II/LC3I, downregulation of P62 and Beclin 1, and higher expression in LAMP 2. Consistently, compound C inhibited these changes of autophagy flux. Moreover, chloroquine pretreatment abolished sevoflurane-induced infarct size reduction, CK-MB level, NAD⁺ content loss, and cytochrome c release, with concomitant increase the ratios of LC3II/LC3I and levels of P62 and Beclin 1, but p-AMPK expression was not downregulated by chloroquine.

Conclusions

Sevoflurane exerts a delayed cardioprotective effects against myocardial injury in rats by activation of AMPK and restoration of I/R-impaired autophagic flux.

Autophagy inhibition in 3T3-L1 adipocytes breaks the crosstalk with tumor cells by suppression of adipokine production

Several studies have revealed the functional importance of autophagy in both adipogenesis and carcinogenesis. Here, we investigated autophagy as a link between tumorigenesis and adipogenesis using 3T3-L1 cells, which have been shown to closely mimic the in vivo differentiation process. The relative levels of LC3-II/I showed that autophagy was the highest after 4–6 days of initiation of differentiation and it diminished thereafter. Furthermore, chloroquine (CQ), a late autophagy inhibitor, effectively inhibited adipogenic differentiation of 3T3-L1 cells, suggesting that autophagy may have a positive impact on adipogenic differentiation. Notably, real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis showed that CQ completely blocked the mRNA expression of three adipokines (adiponectin, leptin, and peroxisome proliferator-activated receptor-γ (PPARγ)), which increased proportionally to adipocyte differentiation. Using adipokine antibody arrays, we also found that among 38 adipokines examined, 6 adipokines were significantly differentially regulated in mature adipocytes compared to those in preadipocytes. A comparative analysis of adipokine production revealed that CQ-treated adipocytes displayed a profile similar to that of preadipocytes. Subsequently, CQ treatment significantly inhibited the migration capacity of v-Ha-ras-transformed cells in both 3T3-L1 adipocyte-conditioned medium and co-culture with 3T3-L1 using a transwell plate. Taken together, our results suggest that autophagy inhibition blocks the production of mediators relevant to the adipogenic process and may significantly contribute to reducing obesity-related cancer risk.

Lipid-Binding Proteins in Brain Health and Disease

A proper lipid management is paramount for a healthy brain. Lipid homeostasis alterations are known to be causative or risk factors for many neurodegenerative diseases, or key elements in the recovery from nervous system injuries of different etiology. In addition to lipid biogenesis and catabolism, non-enzymatic lipid-binding proteins play an important role in brain function and maintenance through aging. Among these types of lipoproteins, apolipoprotein E has received much attention due to the relationship of particular alleles of its gene with the risk and progression of Alzheimer's disease. However, other lipid-binding proteins whose role in lipid homeostasis and control are less known need to be brought to the attention of both researchers and clinicians. The aim of this review is to cover the knowledge of lipid-managing proteins in the brain, with particular attention to new candidates to be relevant for brain function and health.

Lipocalin-2 Predicts Long-Term Outcome of Normotensive Patients with Acute Pulmonary Embolism

Normotensive patients with acute pulmonary embolism (APE) are accompanied by heterogeneously adverse events. Responding to tissue injury, lipocalin-2 (LCN-2) is elevated in experimental APE model and associated with short-term prognosis. However, the prognostic value of LCN-2 in normotensive patients with APE for long-term major adverse events (MAEs) remains unknown. We evaluated the association of plasma LCN-2 levels with the median 467-day outcome in 170 normotensive patients with APE. We also assessed whether LCN-2 could improve risk stratification. MAEs consisted of mortality or recurrence of venous thromboembolism. During follow-up, 17 (10%) patients suffered from MAEs. These patients had higher LCN-2 levels compared with patients without MAEs (median: 13.97 vs. 8.55 ng/ml, P = 0.01). The proportion of MAEs in the intermediate-low-risk group (14.0%) was higher than that in the intermediate-high-risk group (5.3%). LCN-2 levels independently had prognostic value for MAEs in overall (HR = 3.40, 95% CI 1.46-7.90) and intermediate-risk group (HR = 3.88, 95% CI 1.63-9.23). LCN-2 also showed incremental value in overall (ΔC-index: 0.13, 95% CI 0.02-0.24; category-based NRI = 0.25, 95% CI 0.07-0.42) and intermediate-risk patients (ΔC-index: 0.13, 95% CI 0.05-0.31; category-based NRI = 0.44, 95% CI 0.24-0.65). Adding LCN-2 (cut-off value = 11 ng/ml) to the current risk algorithm improved MAEs of intermediate-risk reclassification (intermediate-high vs. intermediate-low = 25.6% vs. 6.0%, P = 0.002). Elevated plasma LCN-2 levels predict long-term MAEs among normotensive patients with APE. LCN-2 might be a useful biomarker for risk stratification in the intermediate-risk group.

Neutrophil Gelatinase-Associated Lipocalin2 Exaggerates Cardiomyocyte Hypoxia Injury by Inhibiting Integrin β3 Signaling

Background

The neutrophil inflammatory protein, lipocalin-2 (NGAL), is elevated in certain forms of cardiac hypertrophy and acute heart failure. However, the specific role of NGAL in cardiac hypoxia injury is unclear. This study aimed to elucidate the functional role of NGAL in cardiomyocyte hypoxia injury.

Material/Methods

Neonatal rat cardiomyocytes were transfected with adenovirus [(Ad-NGAL] to overexpress human-NGAL and then were exposed to hypoxia for 24 h to establish a hypoxia model. Cell inflammation was detected by RT-PCT and ELISA assay. Cell apoptosis was detected by TUNEL assay. Oxidative stress was also detected by commercial kits.

Results

An increased inflammatory response, apoptosis, and augmented oxidative stress were observed after exposure to hypoxia, while NGAL overexpression in cells increased the expression and release of inflammatory cytokines. NGAL overexpression also increased the number of apoptotic cells and the imbalance of Bax/Bcl-2 protein expression. Moreover, NGAL overexpression increased the levels of reactive oxygen species and oxidase activity, but reduced anti-oxidase activity. Mechanistically, we found that NGAL decreased the expression of integrin β3, but not the expression of integrin avβ3 and avβ5, thus inhibiting the downstream protein AKT. When we used the constitutively activated AKT overexpression adenovirus to activate AKT, the deteriorated phenotype by NGAL was counteracted.

Conclusions

NGAL can directly affect cardiomyocytes and cause cardiomyocyte deteriorated hypoxia injury through inhibiting integrin β3 signaling.

MiR-138-5p exacerbates hypoxia/reperfusion-induced heart injury through the inactivation of SIRT1-PGC-1α

OBJECTIVES

A drastic reduction in myocardial cell apoptosis plays a crucial role in the treatment/management of myocardial infarction, a major cardiovascular health challenge confronting the world, especially the Western world. Accumulating evidence indicates that the cardiotoxicity caused by the apoptotic machinery is partly regulated by miRNAs. The aim of this research is to investigate the role of miR-138-5p on hypoxia/reperfusion-induced heart injury.

METHODS

The expression of miR-138-5p was determined in heart tissue from myocardial infarction patients and rats. Rats were transfection with a miR-138-5p inhibitor to silence miR-138-5p. The cardiac function of rats was detected via echocardiography. SIRT1 and PGC-1α expression in cardiac infarction was detected via quantitative Real-time PCR (qPCR) and Western blot analysis, while the TUNEL assay was used to determine myocardial apoptosis.

RESULTS

Our observations showed that miR-138-5p expression was upregulated after the induction of myocardial infarction. The miR-138-5p inhibitor significantly improved cardiac function, increased the expression of SIRT1 and PGC-1α, and decreased the rate of myocardial apoptosis, whereas siRNA-SIRT1 reversed these protective effects.

CONCLUSIONS

In conclusion, our study demonstrated that miR-138-5p could promote cardiac ischemia injury via inhibition of the silent information regulator 1 and peroxisome proliferator-initiated receptor gamma and coactivator 1 alpha (SIRT1-PGC-1α) axis.

Protective effect of gastrodin on myocardial ischemia-reperfusion injury and the expression of Bax and Bcl-2

The protective effects of gastrodin on myocardial ischemia-reperfusion injury in rats and the underlying mechanism were investigated. Sprague Dawley (SD) rats were randomly divided into three groups, of which the gastrodin group was treated with gastrodin, and the other two groups were treated with normal saline. In the myocardial ischemia-reperfusion model group, myocardial ischemia was induced by ligation of the left anterior descending coronary artery, and myocardial reperfusion was performed by ligature removal. Only thread without ligation for the sham operation group was conducted. The rats were euthanized 8 days after surgery. Heart tissues were harvested and used for measurement of apoptotic rate and expression levels of apoptosis-related proteins. Serum levels of cytokines were measured also using blood samples. Compared with the myocardial ischemia-reperfusion model group, significant reduction of cardiomyocyte apoptosis was observed in the gastrodin group (P<0.05). In the gastrodin group, the protein and mRNA expression levels for Bax and activated caspase-3 decreased, while for Bcl-2 increased (P<0.05). Gastrodin can downregulate inflammatory cytokines (P<0.05) and upregulate anti-inflammatory cytokines such as IL-10 (P<0.05) in serum of SD rats. Therefore, gastrodin played a protective role in myocardial ischemia-reperfusion injury by regulating the expression levels of apoptosis-related signaling proteins and inflammatory cytokines.

Bone marrow mesenchymal stem cells-derived conditioned medium protects cardiomyocytes from hypoxia/reoxygenation-induced injury through Notch2/mTOR/autophagy signaling

Bone marrow mesenchymal stem cells (BMSC) can ameliorate ischemic injury of various tissues. However, the molecular mechanisms involved remain to be clarified. In this study, we intend to investigate the effects of BMSC-derived conditioned medium (BMSC-CM) on hypoxia/reoxygenation (H/R)-induced injury of H9c2 myocardial cells, and the potential mechanisms. Cell injury was determined through level of cell viability, lactate dehydrogenase (LDH) release, total intracellular reactive oxygen species (ROS), mitochondrial membrane potential (Δψm), and cell apoptosis. Autophagic activity of cells was detected through levels of the autophagy-associated proteins and autophagic flux. Results showed that BMSC-CM alleviated H/R-induced injury in H9c2 cells, as demonstrated by increased cell viability and Δψm, decreased ROS production, LDH release, and cell apoptosis. Furthermore, the H/R treatment induced a decrease in autophagic activity and an increase in Notch2 signaling activation in H9c2 cells. In the presence of BMSC-CM, the autophagic activity impaired by the H/R treatment was upregulated with decreased phosphorylation of mTOR, and the activation of Notch2 signaling was downregulated. These effects of BMSC-CM could be replicated by Notch signaling inhibitor. In contrast, inhibitors of cell autophagy including chloroquine (CQ) and 3-methyladenine, diminished the protective effects of BMSC-CM. Taken together results, our study showed that BMSC-CM could protect H9c2 cells from H/R-induced injury potentially through regulating Notch2/mTOR/autophagy signaling. These findings may provide a novel insight into the mechanisms of BMSC-CM in therapy of myocardial ischemia/reperfusion injury as well as other ischemic diseases.

Iron induces insulin resistance in cardiomyocytes via regulation of oxidative stress

Iron overload is associated with various pathological changes which contribute to heart failure. Here, we examined mechanisms via which iron alters cardiomyocyte insulin sensitivity. Treatment of primary adult and neonatal cardiomyocytes as well as H9c2 cells with iron decreased insulin sensitivity determined via Western blotting or immunofluorescent detection of Akt and p70S6K phosphorylation and glucose uptake. Using CellROX deep red or DCF-DA probes we also observed that iron increased generation of reactive oxygen species (ROS), and that pretreatment with the superoxide dismutase mimetic MnTBAP reduced ROS production and attenuated iron-induced insulin resistance. SKQ1 and allopurinol but not apocynin reduced iron-induced ROS suggesting mitochondria and xanthine oxidase contribute to cellular ROS in response to iron. Western blotting for LC3-I, LC3-II and P62 levels as well as immunofluorescent co-detection of autophagosomes with Cyto-ID and lysosomal cathepsin activity indicated that iron attenuated autophagic flux without altering total expression of Atg7 or beclin-1 and phosphorylation of mTORC1 and ULK1. This conclusion was reinforced via protein accumulation detected using Click-iT HPG labelling after iron treatment. The adiponectin receptor agonist AdipoRon increased autophagic flux and improved insulin sensitivity both alone and in the presence of iron. We created an autophagy-deficient cell model by overexpressing a dominant-negative Atg5 mutant in H9c2 cells and this confirmed that reduced autophagy flux correlated with less insulin sensitivity. In conclusion, our study showed that iron promoted a cascade of ROS production, reduced autophagy and insulin resistance in cardiomyocytes.

H2O2 Signaling-Triggered PI3K Mediates Mitochondrial Protection to Participate in Early Cardioprotection by Exercise Preconditioning

Previous studies have shown that early exercise preconditioning (EEP) imparts a protective effect on acute cardiovascular stress. However, how mitophagy participates in exercise preconditioning- (EP-) induced cardioprotection remains unclear. EEP may involve mitochondrial protection, which presumably crosstalks with predominant H₂O₂ oxidative stress. Our EEP protocol involves four periods of 10 min running with 10 min recovery intervals. We added a period of exhaustive running and a pretreatment using phosphoinositide 3-kinase (PI3K)/autophagy inhibitor wortmannin to test this protective effect. By using transmission electron microscopy (TEM), laser scanning confocal microscopy, and other molecular biotechnology methods, we detected related markers and specifically analyzed the relationship between mitophagic proteins and mitochondrial translocation. We determined that exhaustive exercise associated with various elevated injuries targeted the myocardium, oxidative stress, hypoxia-ischemia, and mitochondrial ultrastructure. However, exhaustion induced limited mitochondrial protection through a H₂O₂-independent manner to inhibit voltage-dependent anion channel isoform 1 (VDAC1) instead of mitophagy. EEP was apparently safe to the heart. In EEP-induced cardioprotection, EEP provided suppression to exhaustive exercise (EE) injuries by translocating Bnip3 to the mitochondria by recruiting the autophagosome protein LC3 to induce mitophagy, which is potentially triggered by H₂O₂ and influenced by Beclin1-dependent autophagy. Pretreatment with the wortmannin further attenuated these effects induced by EEP and resulted in the expression of proapoptotic phenotypes such as oxidative injury, elevated Beclin1/Bcl-2 ratio, cytochrome c leakage, mitochondrial dynamin-1-like protein (Drp-1) expression, and VDAC1 dephosphorylation. These observations suggest that H₂O₂ generation regulates mitochondrial protection in EEP-induced cardioprotection.

Serum levels of melatonin may contribute to the pathogenesis of heart failure in children with median age of 1 year

OBJECTIVE

Melatonin has a protective role in adults with cardiovascular disease, but the effects of melatonin in children with cardiac dysfunction are not well understood. This study was designed to explore the variations in melatonin, myeloperoxidase, and caspase-3 levels in children suffering from heart failure.

METHODS

Seventy-two pediatric patients with heart failure and twelve healthy children were enrolled in this study. A modified Ross scoring system was used to evaluate clinical cardiac function. Patients with a score of >2 points were included in the study and were divided into three groups according to severity of heart failure: mild (score: 3-6), moderate (score: 7-9), and severe (score: 10-12). Echocardiographic parameters, laboratory data, and serum levels of melatonin, myeloperoxidase, and caspase-3 were measured and analyzed in all patients.

RESULTS

Compared with patients with mild and moderate heart failure, patients in the severe heart failure group had significantly decreased left ventricular ejection fraction (p<0.001), and significantly increased serum melatonin levels (p=0.013) and myeloperoxidase levels (p<0.001). Serum melatonin levels were positively correlated with serum caspase-3 levels (p<0.001). The optimal cutoff values of serum melatonin levels for the diagnosis of severe heart failure and primary cardiomyopathy in pediatric patients with heart failure were 54.14pg/mL and 32.88pg/mL, respectively.

CONCLUSIONS

Serum melatonin and myeloperoxidase levels were increased in children with severe heart failure. It is likely that increasing melatonin levels may act as a compensatory mechanism in pediatric children with heart failure.

More than a simple biomarker: the role of NGAL in cardiovascular and renal diseases

Neutrophil gelatinase-associated lipocalin (NGAL) is a small circulating protein that is highly modulated in a wide variety of pathological situations, making it a useful biomarker of various disease states. It is one of the best markers of acute kidney injury, as it is rapidly released after tubular damage. However, a growing body of evidence highlights an important role for NGAL beyond that of a biomarker of renal dysfunction. Indeed, numerous studies have demonstrated a role for NGAL in both cardiovascular and renal diseases. In the present review, we summarize current knowledge concerning the involvement of NGAL in cardiovascular and renal diseases and discuss the various mechanisms underlying its pathological implications.

(‑)‑Epicatechin protects against myocardial ischemia‑induced cardiac injury via activation of the PTEN/PI3K/AKT pathway

Flavonol (−)-epicatechin (EPI) is primarily contained in green tea (Camellia sinensis) and cocoa beans (Theobroma cacao), and has been demonstrated to be beneficial for the health of the cardiovascular system. However, the effect and the underlying mechanism of EPI on myocardial ischemia induced cardiac injury has not yet been determined. Therefore, the present study aimed to detect whether EPI inhibited myocardial ischemia injury. An in vivo mouse myocardial ischemia model was induced by the ligation of left descending coronary artery for 7 days. EPI (1 mg/kg/day) was administrated 10 days prior to myocardial ischemia operation. The in vitro mouse myocardial ischemia model was induced by cultivating neonatal mouse cardiomyocytes under anoxia condition for 12 h. Cardiomyocytes were treated with EPI (5 µM) for 1 h and then incubated under anoxia conditions. Mouse hearts and cultured cardiomyocytes were used for hematoxylin-eosin, masson, ultrasonography, terminal dUTP nick end-labeling, immunofluorescence, western blotting and MTT assays. Results revealed that myocardial ischemia-induced mouse cardiac injury was significantly inhibited by EPI, as evidenced by decreased myocardial apoptosis, cardiac fibrosis and myocardial hypertrophy and improved cardiac function. In addition, it was confirmed that EPI serves a protective effect against myocardial ischemia via the phosphatase and tensin homolog (PTEN)/phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway, which was reversed by the PI3K inhibitor, LY294002. The protective role of EPI in myocardial apoptosis was further confirmed on mouse cardiomyocytes following anoxia treatment in vitro. In conclusion, the data suggested that EPI protects against myocardial ischemia induced cardiac injury through the PTEN/PI3K/AKT signaling pathway in vivo and in vitro, which may provide clinical therapeutic approaches and targets for cardiac ischemia injury.

NR4A2 protects cardiomyocytes against myocardial infarction injury by promoting autophagy

Myocardial infarction (MI), characterized by ischemia-induced cardiomyocyte apoptosis, is the leading cause of mortality worldwide. NR4A2, a member of the NR4A orphan nucleus receptor family, is upregulated in mouse hearts with MI injury. Furthermore, NR4A2 knockdown aggravates heart injury as evidenced by enlarged hearts and increased apoptosis. To elucidate the underlying mechanisms of NR4A2-regulated apoptosis, we used H9c2 cardiomyocytes deprived of serum and neonatal rat cardiomyocytes (NRCMs) exposed to hypoxia to mimic ischemic conditions in vivo. As NR4A2 knockdown aggravates cardiomyocyte apoptosis, while NR4A2 overexpression ameliorates it, NR4A2 upregulation was considered an adaptive response to ischemia-induced cardiomyocyte apoptosis. By detecting changes in LC3 and using autophagy detection tools including Bafilomycin A1, 3MA and rapamycin, we found that NR4A2 knockdown promoted apoptosis through blocking autophagic flux. This apoptotic response was phenocopied by downregulation of NR4A2 after autophagic flux was impaired by Bafilomycin A1. Further study showed that NR4A2 binds to p53 directly and decreases its levels when it inhibits apoptosis; thus, p53/Bax is the downstream effector of NR4A2-mediated apoptosis, as previously reported. Changes in p53/Bax that were regulated by NR4A2 were also detected in injured hearts with NR4A2 knockdown. In addition, miR-212-3p is the upstream regulator of NR4A2, and it could downregulate the expression of NR4A2, as well as p53/Bax. The mechanism underlying the role of NR4A2 in apoptosis and autophagy was elucidated, and NR4A2 may be a therapeutic drug target for heart failure.