Nrf2 for cardiac protection: pharmacological options against oxidative stress

Catechins: Protective mechanism of antioxidant stress in atherosclerosis

Tea has long been valued for its health benefits, especially its potential to prevent and treat atherosclerosis (AS). Abnormal lipid metabolism and oxidative stress are major factors that contribute to the development of AS. Tea, which originated in China, is believed to help prevent AS. Research has shown that tea is rich in catechins, which is considered a potential source of natural antioxidants. Catechins are the most abundant antioxidants in green tea, and are considered to be the main compound responsible for tea's antioxidant activity. The antioxidant properties of catechins are largely dependent on the structure of molecules, and the number and location of hydroxyl groups or their substituents. As an exogenous antioxidant, catechins can effectively eliminate lipid peroxidation products. They can also play an antioxidant role indirectly by activating the endogenous antioxidant system by regulating enzyme activity and signaling pathways. In this review, we summarized the preventive effect of catechin in AS, and emphasized that improving the antioxidant effect and lipid metabolism disorders of catechins is the key to managing AS.

The role of β-catenin in cardiac diseases

The Wnt/β-catenin signaling pathway is a classical Wnt pathway that regulates the stability and nuclear localization of β-catenin and plays an important role in adult heart development and cardiac tissue homeostasis. In recent years, an increasing number of researchers have implicated the dysregulation of this signaling pathway in a variety of cardiac diseases, such as myocardial infarction, arrhythmias, arrhythmogenic cardiomyopathy, diabetic cardiomyopathies, and myocardial hypertrophy. The morbidity and mortality of cardiac diseases are increasing, which brings great challenges to clinical treatment and seriously affects patient health. Thus, understanding the biological roles of the Wnt/β-catenin pathway in these diseases may be essential for cardiac disease treatment and diagnosis to improve patient quality of life. In this review, we summarize current research on the roles of β-catenin in human cardiac diseases and potential inhibitors of Wnt/β-catenin, which may provide new strategies for cardiac disease therapies.

Ginsenoside F1 attenuates pirarubicin-induced cardiotoxicity by modulating Nrf2 and AKT/Bcl-2 signaling pathways

Background

Pirarubicin (THP) is an anthracycline antibiotic used to treat various malignancies in humans. The clinical usefulness of THP is unfortunately limited by its dose-related cardiotoxicity. Ginsenoside F1 (GF1) is a metabolite formed when the ginsenosides Re and Rg1 are hydrolyzed. However, the protective effects and underlying mechanisms of GF1 on THP-induced cardiotoxicity remain unclear.

Methods

We investigated the anti-apoptotic and anti-oxidative stress effects of GF1 on an in vitro model, using H9c2 cells stimulated by THP, plus trigonelline or AKT inhibitor imidazoquinoxaline (IMQ), as well as an in vivo model using THP-induced cardiotoxicity in rats. Using an enzyme-linked immunosorbent test, the levels of malondialdehyde (MDA), brain natriuretic peptide (BNP), creatine kinase (CK-MB), cardiac troponin (c-TnT), lactate dehydrogenase (LDH), superoxide dismutase (SOD) and glutathione (GSH) were determined. Nuclear factor (erythroid-derived2)-like 2 (Nrf2) and the expression of Nrf2 target genes, including heme oxygenase-1 (HO-1), glutathione-S-transferase (Gst), glutamate-cysteine ligase modifier subunit (GCLM), and expression levels of AKT/Bcl-2 signaling pathway proteins were detected using Western blot analysis.

Results

THP-induced myocardial histopathological damage, electrocardiogram (ECG) abnormalities, and cardiac dysfunction were reduced in vivo by GF1. GF1 also decreased MDA, BNP, CK-MB, c-TnT, and LDH levels in the serum, while raising SOD and GSH levels. GF1 boosted Nrf2 nuclear translocation and Nrf2 target gene expression, including HO-1, Gst, and GCLM. Furthermore, GF1 regulated apoptosis by activating AKT/Bcl-2 signaling pathways. Employing Nrf2 inhibitor trigonelline and AKT inhibitor IMQ revealed that GF1 lacked antioxidant and anti-apoptotic effects.

Conclusion

In conclusion, GF1 was found to alleviate THP-induced cardiotoxicity via modulating Nrf2 and AKT/Bcl-2 signaling pathways, ultimately alleviating myocardial oxidative stress and apoptosis.

Activation of Nrf2 signaling: A key molecular mechanism of protection against cardiovascular diseases by natural products

Cardiovascular diseases (CVD) are a group of cardiac and vascular disorders including myocardial ischemia, congenital heart disease, heart failure, hypertension, atherosclerosis, peripheral artery disease, rheumatic heart disease, and cardiomyopathies. Despite considerable progress in prophylaxis and treatment options, CVDs remain a leading cause of morbidity and mortality and impose an extremely high socioeconomic burden. Oxidative stress (OS) caused by disequilibrium in the generation of reactive oxygen species plays a crucial role in the pathophysiology of CVDs. Nuclear erythroid 2-related factor 2 (Nrf2), a transcription factor of endogenous antioxidant defense systems against OS, is considered an ideal therapeutic target for management of CVDs. Increasingly, natural products have emerged as a potential source of Nrf2 activators with cardioprotective properties and may therefore provide a novel therapeutic tool for CVD. Here, we present an updated comprehensive summary of naturally occurring products with cardioprotective properties that exert their effects by suppression of OS through activation of Nrf2 signaling, with the aim of providing useful insights for the development of therapeutic strategies exploiting natural products.

Does Nrf2 Play a Role of a Master Regulator of Mammalian Aging?

For a long time Nrf2 transcription factor has been attracting attention of researchers investigating phenomenon of aging. Numerous studies have investigated effects of Nrf2 on aging and cell senescence. Nrf2 is often considered as a key player in aging processes, however this needs to be proven. It should be noted that most studies were carried out on invertebrate model organisms, such as nematodes and fruit flies, but not on mammals. This paper briefly presents main mechanisms of mammalian aging and role of inflammation and oxidative stress in this process. The mechanisms of Nrf2 activity regulation, its involvement in aging and development of the senescence-associated secretory phenotype (SASP) are also discussed. Main part of this review is devoted to critical analysis of available experimental data on the role of Nrf2 in mammalian aging.

Ginsenoside Rc attenuates myocardial ischaemic injury through antioxidative and anti-inflammatory effects

CONTEXT

Panax ginseng C. A. Meyer (Araliaceae) is a famous Asian medicine. Ginsenoside Rc is a component isolated from Panax ginseng.

OBJECTIVE

This study evaluates the effect of ginsenoside Rc on myocardial ischaemic injury.

MATERIALS AND METHODS

Male Swiss mice were subcutaneously injected with 50 mg/kg isoproterenol once a day for three days. Ginsenoside Rc (10, 20, or 40 mg/kg) was intragastrically administered 1 h after isoproterenol injection. The mice in the control group were subcutaneously injected with normal saline and intragastrically given 0.5% CMC-Na. CK-MB and troponin T were assayed. Histopathological examination of myocardium was conducted. The expression of Nrf2, GCLC, GCLM and HO-1 in heart tissues was evaluated by Western blot.

RESULTS

In myocardial ischaemic mice, ginsenoside Rc reduced the levels of CK-MB (197.1 ± 15.7, 189.9 ± 19.0, 184.0 ± 14.4 vs. 221.6 ± 27.9) and troponin T (10.3 ± 1.7, 9.5 ± 1.3, 8.7 ± 1.7 vs. 13.4 ± 2.4). Ginsenoside Rc attenuated the necrosis and inflammatory cells infiltration in myocardium. Furthermore, ginsenoside Rc not only decreased the contents of MDA, TNF-α but also increased GSH level in the heart tissues. The expression of Nrf2, GCLC, GCLM and HO-1 was significantly increased in the animals treated with ginsenoside Rc. ML385, an Nrf2 inhibitor, blocked partially the ginsenoside Rc-mediated cardioprotective effect. Ginsenoside Rc attenuated myocardial ischaemic injury in mice, which may be, in part, through its antioxidative and anti-inflammatory effects.

CONCLUSIONS

This study indicated that ginsenoside Rc might be a novel candidate for treatment of myocardial ischaemia.

Adaptive Responses to Hypoxia and/or Hyperoxia in Humans

Significance: Oxygen is indispensable for aerobic life, but its utilization exposes cells and tissues to oxidative stress; thus, tight regulation of cellular, tissue, and systemic oxygen concentrations is crucial. Here, we review the current understanding of how the human organism (mal-)adapts to low (hypoxia) and high (hyperoxia) oxygen levels and how these adaptations may be harnessed as therapeutic or performance enhancing strategies at the systemic level. Recent Advances: Hyperbaric oxygen therapy is already a cornerstone of modern medicine, and the application of mild hypoxia, that is, hypoxia conditioning (HC), to strengthen the resilience of organs or the whole body to severe hypoxic insults is an important preparation for high-altitude sojourns or to protect the cardiovascular system from hypoxic/ischemic damage. Many other applications of adaptations to hypo- and/or hyperoxia are only just emerging. HC-sometimes in combination with hyperoxic interventions-is gaining traction for the treatment of chronic diseases, including numerous neurological disorders, and for performance enhancement. Critical Issues: The dose- and intensity-dependent effects of varying oxygen concentrations render hypoxia- and/or hyperoxia-based interventions potentially highly beneficial, yet hazardous, although the risks versus benefits are as yet ill-defined. Future Directions: The field of low and high oxygen conditioning is expanding rapidly, and novel applications are increasingly recognized, for example, the modulation of aging processes, mood disorders, or metabolic diseases. To advance hypoxia/hyperoxia conditioning to clinical applications, more research on the effects of the intensity, duration, and frequency of altered oxygen concentrations, as well as on individual vulnerabilities to such interventions, is paramount. Antioxid. Redox Signal. 37, 887-912.

Novel Therapeutic Approaches Enhance PGC1-alpha to Reduce Oxidant Stress-Inflammatory Signaling and Improve Functional Recovery in Hibernating Myocardium

Ischemic heart disease affects millions of people around the world. Current treatment options, including coronary artery bypass grafting, do not result in full functional recovery, highlighting the need for novel adjunctive therapeutic approaches. Hibernation describes the myocardial response to prolonged ischemia and involves a set of complex cytoprotective metabolic and functional adaptations. PGC1-alpha, a key regulator of mitochondrial energy metabolism and inhibitor of oxidant-stress-inflammatory signaling, is known to be downregulated in hibernating myocardium. PGC1-alpha is a critical component of cellular stress responses and links cellular metabolism with inflammation in the ischemic heart. While beneficial in the acute setting, a chronic state of hibernation can be associated with self-perpetuating oxidant stress-inflammatory signaling which leads to tissue injury. It is likely that incomplete functional recovery following revascularization of chronically ischemic myocardium is due to persistence of metabolic changes as well as prooxidant and proinflammatory signaling. Enhancement of PGC1-alpha signaling has been proposed as a possible way to improve functional recovery in patients with ischemic heart disease. Adjunctive mesenchymal stem cell therapy has been shown to induce PGC1-alpha signaling in hibernating myocardium and could help improve clinical outcomes for patients undergoing bypass surgery.

Fibroblast growth factor 7 alleviates myocardial infarction by improving oxidative stress via PI3Kα/AKT-mediated regulation of Nrf2 and HXK2

Acute myocardial infarction (MI) triggers oxidative stress, which worsen cardiac function, eventually leads to remodeling and heart failure. Unfortunately, effective therapeutic approaches are lacking. Fibroblast growth factor 7 (FGF7) is proved with respect to its proliferative effects and high expression level during embryonic heart development. However, the regulatory role of FGF7 in cardiovascular disease, especially MI, remains unclear. FGF7 expression was significantly decreased in a mouse model at 7 days after MI. Further experiments suggested that FGF7 alleviated MI-induced cell apoptosis and improved cardiac function. Mechanistic studies revealed that FGF7 attenuated MI by inhibiting oxidative stress. Overexpression of FGF7 actives nuclear factor erythroid 2-related factor 2 (Nrf2) and scavenging of reactive oxygen species (ROS), and thereby improved oxidative stress, mainly controlled by the phosphatidylinositol-3-kinase α (PI3Kα)/AKT signaling pathway. The effects of FGF7 were partly abrogated in Nrf2 deficiency mice. In addition, overexpression of FGF7 promoted hexokinase2 (HXK2) and mitochondrial membrane translocation and suppressed mitochondrial superoxide production to decrease oxidative stress. The role of HXK2 in FGF7-mediated improvement of mitochondrial superoxide production and protection against MI was verified using a HXK2 inhibitor (3-BrPA) and a HXKII VDAC binding domain (HXK2VBD) peptide, which competitively inhibits localization of HXK2 on mitochondria. Furthermore, inhibition of PI3Kα/AKT signaling abolished regulation of Nrf2 and HXK2 by FGF7 upon MI. Together, these results indicate that the cardio protection of FGF7 under MI injury is mostly attributable to its role in maintaining redox homeostasis via Nrf2 and HXK2, which is mediated by PI3Kα/AKT signaling.

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The expression of FGF7 in cardiomyocytes is decreased upon myocardial infarction (MI).

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Overexpression of FGF7 in the heart protects against cardiomyocytes apoptosis in a rodent model of MI.

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FGF7 attenuates MI-induced cardiac apoptosis via maintaining redox homeostasis.

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FGF7 maintains redox homeostasis by promoting mitochondrial HXK2 localization and Nrf2 nuclear translocation.

Chaihujialonggumulitang shows psycho-cardiology therapeutic effect on acute myocardial infarction with comorbid anxiety by the activation of Nrf2/HO-1 pathway and suppression of oxidative stress and apoptosis

BACKGROUND

Anxiety is a common comorbidity of cardiovascular diseases, which deteriorated cardiac function. Chaihujialonggumulitang (BFG) was reported to have antioxidant properties, alleviate myocardial ischemia injury and improve anxiety-like behavior. The Nuclear factor erythroid 2-related factor 2 (Nrf2) /heme oxygenase-1 (HO-1) pathway is the main mechanism to defend against oxidative stress, and improve cardiac function. This study was to investigate the possible mechanism of BFG in the treatment of psycho-cardiology.

METHODS

AMI with comorbid anxiety rat model was established by ligation of the left anterior descending coronary artery combined with uncertain empty bottle stimulation, followed by the administration of BFG (1 mL/100 g/d by gavage) or Dimethyl fumarate (DMF, 10 mg/kg/d by intraperitoneal injection) for 6 days. Echocardiography, myocardial injury markers, H&E, and Masson staining were employed to evaluate cardiac function. Behavioral tests and hippocampus neurotransmitters were applied to record anxiety-like behavior. We employed immunohistochemistry, RT-PCR, western blotting, and biochemical analysis to detect the protein and gene expression of Nrf2/HO-1 pathway-related factors, and oxidative stress and apoptosis parameters.

RESULTS

Rats in the AMI and complex groups showed cardiac function deterioration, as well as anxiety-like behavior. BFG improved echocardiography indicators, reduced myocardial injury markers, and attenuated myocardial pathological changes. BFG also ameliorated anxiety-like behaviors and elevated neurotransmitters levels. BFG promoted the activation of Nrf2/HO-1 pathway, increased antioxidant enzyme activities, reduced lipid peroxidation levels, and alleviated oxidative damage and apoptosis. DMF showed therapeutic effects and molecular mechanisms similar to BFG.

CONCLUSION

BFG may possess a psycho-cardiology therapeutic effect on AMI with comorbid anxiety by the activation of the Nrf2/HO-1 pathway and suppression of oxidative stress and apoptosis.

Butein Ameliorates Oxidative Stress in H9c2 Cardiomyoblasts through Activation of the NRF2 Signaling Pathway

Oxidative stress, defined as an imbalance between reactive oxygen species (ROS) production and the antioxidant defense system, contributes to the pathogenesis of many heart diseases. Therefore, oxidative stress has been highlighted as a therapeutic target for heart disease treatment. Butein, a tetrahydroxychalcone, has potential biological activities, especially antioxidant properties. However, the effect of butein on oxidative-stressed heart cells has been poorly studied. Thus, we sought to identify the antioxidant effects of butein in H9c2 cardiomyoblasts. To elucidate these antioxidant effects, various concentrations of butein were used to pretreat H9c2 cells prior to H₂O₂ treatment. Thereafter, measures of oxidative damages, such as ROS production, antioxidant expression levels, and apoptosis, were evaluated. Butein effectively increased cell viability and rescued the cells from oxidative damage through the inhibition of ROS production, apoptosis, and increased antioxidant expression. Furthermore, butein dramatically inhibited mitochondrial dysfunction and endoplasmic reticulum (ER) stress, which are the main ROS inducers. Nrf2 protein translocated from the cytosol to the nucleus and consequently activated its target genes as oxidative stress suppressors. These findings demonstrate that butein has potential antioxidant effects in H9c2 cardiomyoblasts, suggesting that it could be used as a therapeutic substance for the treatment of cardiac diseases.

Mesenchymal stem cells-derived small extracellular vesicles alleviate diabetic retinopathy by delivering NEDD4

Background

As a leading cause of vision decline and severe blindness in adults, diabetic retinopathy (DR) is characterized by the aggravation of retinal oxidative stress and apoptosis in the early stage. Emerging studies reveal that mesenchymal stem cells-derived small extracellular vesicles (MSC-sEV) treatment represents a promising cell-free approach to alleviate ocular disorders. However, the repairing effects of MSC-sEV in DR remain largely unclear. This study aimed at exploring the role and the underlying mechanism of MSC-sEV in hyperglycemia-induced retinal degeneration.

Methods

In vivo, we used streptozotocin (STZ) to establish diabetic rat model, followed by the intravitreal injection of MSC-sEV to determine the curative effect. The cell viability and antioxidant capacity of retinal pigment epithelium (RPE) cells stimulated with high-glucose (HG) medium after MSC-sEV treatment were analyzed in vitro. By detecting the response of cell signaling pathways in MSC-sEV-treated RPE cells, we explored the functional mechanism of MSC-sEV. Mass spectrometry was performed to reveal the bioactive protein which mediated the role of MSC-sEV.

Results

The intravitreal injection of MSC-sEV elicited antioxidant effects and counteracted retinal apoptosis in STZ-induced DR rat model. MSC-sEV treatment also reduced the oxidative level and enhanced the proliferation ability of RPE cells cultured in HG conditions in vitro. Further studies showed that the increased level of phosphatase and tensin homolog (PTEN) inhibited AKT phosphorylation and nuclear factor erythroid 2-related factor 2 (NRF2) expression in RPE cells stimulated with HG medium, which could be reversed by MSC-sEV intervention. Through mass spectrometry, we illustrated that MSC-sEV-delivered neuronal precursor cell-expressed developmentally downregulated 4 (NEDD4) could cause PTEN ubiquitination and degradation, activate AKT signaling and upregulate NRF2 level to prevent DR progress. Moreover, NEDD4 knockdown impaired MSC-sEV-mediated retinal therapeutic effects.

Conclusions

Our findings indicated that MSC-sEV ameliorated DR through NEDD4-induced regulation on PTEN/AKT/NRF2 signaling pathway, thus revealing the efficiency and mechanism of MSC-sEV-based retinal protection and providing new insights into the treatment of DR.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02983-0.

Metabolic Adaptation-Mediated Cancer Survival and Progression in Oxidative Stress

Undue elevation of ROS levels commonly occurs during cancer evolution as a result of various antitumor therapeutics and/or endogenous immune response. Overwhelming ROS levels induced cancer cell death through the dysregulation of ROS-sensitive glycolytic enzymes, leading to the catastrophic depression of glycolysis and oxidative phosphorylation (OXPHOS), which are critical for cancer survival and progression. However, cancer cells also adapt to such catastrophic oxidative and metabolic stresses by metabolic reprograming, resulting in cancer residuality, progression, and relapse. This adaptation is highly dependent on NADPH and GSH syntheses for ROS scavenging and the upregulation of lipolysis and glutaminolysis, which fuel tricarboxylic acid cycle-coupled OXPHOS and biosynthesis. The underlying mechanism remains poorly understood, thus presenting a promising field with opportunities to manipulate metabolic adaptations for cancer prevention and therapy. In this review, we provide a summary of the mechanisms of metabolic regulation in the adaptation of cancer cells to oxidative stress and the current understanding of its regulatory role in cancer survival and progression.

Beneficial and Detrimental Roles of Heme Oxygenase-1 in the Neurovascular System

Heme oxygenase (HO) has both beneficial and detrimental effects via its metabolites, including carbon monoxide (CO), biliverdin or bilirubin, and ferrous iron. HO-1 is an inducible form of HO that is upregulated by oxidative stress, nitric oxide, CO, and hypoxia, whereas HO-2 is a constitutive form that regulates vascular tone and homeostasis. In brains injured by trauma, ischemia-reperfusion, or Alzheimer’s disease (AD), the long-term expression of HO-1 can be detected, which can lead to cytotoxic ferroptosis via iron accumulation. In contrast, the transient induction of HO-1 in the peri-injured region may have regenerative potential (e.g., angiogenesis, neurogenesis, and mitochondrial biogenesis) and neurovascular protective effects through the CO-mediated signaling pathway, the antioxidant properties of bilirubin, and the iron-mediated ferritin synthesis. In this review, we discuss the dual roles of HO-1 and its metabolites in various neurovascular diseases, including age-related macular degeneration, ischemia-reperfusion injury, traumatic brain injury, Gilbert’s syndrome, and AD.

Redox signaling at the crossroads of human health and disease

Redox biology is at the core of life sciences, accompanied by the close correlation of redox processes with biological activities. Redox homeostasis is a prerequisite for human health, in which the physiological levels of nonradical reactive oxygen species (ROS) function as the primary second messengers to modulate physiological redox signaling by orchestrating multiple redox sensors. However, excessive ROS accumulation, termed oxidative stress (OS), leads to biomolecule damage and subsequent occurrence of various diseases such as type 2 diabetes, atherosclerosis, and cancer. Herein, starting with the evolution of redox biology, we reveal the roles of ROS as multifaceted physiological modulators to mediate redox signaling and sustain redox homeostasis. In addition, we also emphasize the detailed OS mechanisms involved in the initiation and development of several important diseases. ROS as a double-edged sword in disease progression suggest two different therapeutic strategies to treat redox-relevant diseases, in which targeting ROS sources and redox-related effectors to manipulate redox homeostasis will largely promote precision medicine. Therefore, a comprehensive understanding of the redox signaling networks under physiological and pathological conditions will facilitate the development of redox medicine and benefit patients with redox-relevant diseases.

Curcumin Restrains Oxidative Stress of After Intracerebral Hemorrhage in Rat by Activating the Nrf2/HO-1 Pathway

Intracerebral hemorrhage (ICH), a severe hemorrhagic stroke, induces cerebral oxidative stress and severe secondary neurological injury. Curcumin was demonstrated to inhibit oxidative stress in the brain after ICH. However, the pharmacological mechanism needs further research. We used an intrastriatal injection of autologous blood to make the rat ICH model, and then the rat was treated with curcumin (100 mg/kg/day). Modified Neurological Severity Score (mNSS) and corner test results showed that curcumin could significantly promote the neurological recovery of ICH rats. Meanwhile, curcumin could substantially reduce ROS and MDA in the tissues around intracranial hematoma and prevent GSH depletion. To explore the pharmacological molecular mechanism of curcumin, we used HAPI cells and primary rat cortical microglia for in vitro experiments. In vitro, heme-treated cells were used as the cell model of ICH to explore the molecular mechanism of inhibiting oxidative stress by curcumin treatment. The results showed that curcumin significantly inhibited heme-induced oxidative stress, decreased intracellular ROS and MDA, and promoted Nrf2 and its downstream antioxidant gene (HO-1, NQO1, and Gpx4) expression. These results suggest that curcumin inhibits oxidative stress by activating the Nrf2/HO-1 pathway. Here, our results indicate that curcumin can promote the inhibition of oxidative stress in microglia by activating the Nrf2/HO-1 pathway and promoting neurological recovery after ICH, providing a new therapeutic target for clinical treatment of ICH.

Dimethyl Fumarate Ameliorates Doxorubicin-Induced Cardiotoxicity By Activating the Nrf2 Pathway

Doxorubicin (DOX) is limited in clinical application because of its cardiotoxicity. Oxidative stress and apoptosis are crucial in DOX-induced cardiac injury. Dimethyl fumarate (DMF) is an FDA-approved oral drug with powerful effects to reduce oxidative stress and apoptosis through the Nrf2 pathway. This study was aimed to determine whether DMF can protect against DOX-induced cardiac injury. We used both neonatal rat cardiomyocytes (NRCMs) in vitro and DOX-induced cardiac toxicity in vivo to explore the effects of DMF. The results showed that DMF significantly improved cell viability and morphology in NRCMs. In addition, DMF alleviated DOX-induced cardiac injury in rats, as evidenced by decreased CK-MB, LDH levels, improved survival rates, cardiac function, and pathological changes. Moreover, DMF significantly inhibited cardiac oxidative stress by reducing MDA levels and increasing GSH, SOD, and GSH-px levels. And DMF also inhibited DOX-induced cardiac apoptosis by modulating Bax, Bcl-2 and cleaved caspase-3 expression. Moreover, DMF exerted its protective effects against DOX by promoting Nrf2 nuclear translocation, which activated its downstream antioxidant gene Hmox1. Silencing of Nrf2 attenuated the protective effects of DMF in NRCMs as manifested by increased intracellular oxidative stress, elevated apoptosis levels, and decreased cell viability. In addition, DMF showed no protective effects on the viability of DOX-treated tumor cells, which suggested that DMF does not interfere with the antitumor effect of DOX in vitro. In conclusion, our data confirmed that DMF alleviated DOX-induced cardiotoxicity by regulating oxidative stress and apoptosis through the Nrf2 pathway. DMF may serve as a new candidate to alleviate DOX-related cardiotoxicity in the future.

Host/microbiota interactions-derived tryptophan metabolites modulate oxidative stress and inflammation via aryl hydrocarbon receptor signaling

Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that induces the expression of a broad range of downstream genes such as cytochromes P450 enzymes and cyclooxygenase-2. Recent research focuses are shifting from AhR activation induced by xenobiotics to its response patterns to physiological ligands that expand our understanding of how endogenous metabolites as ligands to modulate AhR signaling pathway under homeostasis and pathological conditions. With increasing interest in AhR and its endogenous ligands, it would seem advisable to summarize a variety of endogenous ligands especially host/gut microbiota-derived tryptophan metabolites. Mounting evidence has indicated that AhR play a critical role in the regulation of redox homeostasis and immune responses. In this review, we outline the canonical and non-canonical AhR signalling pathway that is mediated by host/gut microbiota-derived tryptophan metabolites. Through several typical endogenous AhR ligands, we investigated the molecular mechanisms of AhR-induced oxidative stress and inflammation in the pathological milieu, including diabetes, diabetic kidney disease and end-stage renal disease. Finally, we summarize and emphasize the limitations and breakthrough of endogenous AhR ligands from host/microbial tryptophan catabolites. This review might provide novel diagnostic and prognostic approach for refractory human diseases and establish new therapeutic strategies for AhR activation.

Hsa_circ_0007059 promotes apoptosis and inflammation in cardiomyocytes during ischemia by targeting microRNA-378 and microRNA-383

Circular RNAs (circRNAs) are a class of non-coding RNA molecules that are associated with not only normal physiological functions but also various diseases, including cardiac diseases such as myocardial infarction (MI). The present study explored the potential role of circRNA_0007059 (circ_0007059) during MI pathogenesis using in vitro studies. Microarray and quantitative PCR analyses demonstrated elevated circ_0007059 expression and downregulated miR-378 and miR-383 expression in H₂O₂-treated mice cardiomyocytes and infarcted hearts of MI mouse model as compared those in relevant controls. Moreover, circ_0007059 knockdown improved cardiomyocyte viability after H₂O₂ treatment as revealed by the CCK-8 and colony formation assays. Flow cytometry and caspase activity assays demonstrated that circ_0007059 suppressed H₂O₂-induced cardiomyocyte apoptosis. Enzyme-linked immunosorbent assays and Western blotting revealed that inflammatory cytokine (interleukin-1β, interleukin-18 and C-C motif chemokine ligand 5) expression was induced by H₂O₂ treatment and that circ_0007059 repressed H₂O₂-induced inflammation. Bioinformatics analyses and dual-luciferase reporter assays showed that circ_0000759 acts as a miR-378 and miR-383 sponge. Furthermore, the upregulation or suppression of miR-378 and miR-383 expression in H₂O₂-treated cardiomyocytes had similar effects on the apoptosis and inflammation of cardiomyocytes as that of circ_0007059 knockdown or overexpression, respectively. Additionally, lentiviral shRNA-circ_0007059 administration to mice with MI considerably reduced the size of infarcted regions and promoted cardiac activity. Collectively, our findings suggest that circ_0007059 expression is upregulated in mice cardiomyocytes in response to oxidative stress and cardiac tissues of MI mouse model, suggesting its involvement in the pathogenesis of MI by targeting miR-378 and miR-383.

The E3 Ligase TRIM16 Is a Key Suppressor of Pathological Cardiac Hypertrophy

Background: Pathological cardiac hypertrophy is one of the leading causes of heart failure with highly complicated pathogeneses. The E3 ligase TRIM16 (tripartite motif-containing protein 16) has been recognized as a pivotal regulator to control cell survival, immune response, and oxidative stress. However, the role of Trim16 in cardiac hypertrophy is unknown.

METHODS

We generated cardiac-specific knockout mice and adeno-associated virus serotype 9-Trim16 mice to evaluate the function of Trim16 in pathological myocardial hypertrophy. The direct effect of TRIM16 on cardiomyocyte enlargement was examined using an adenovirus system. Furthermore, we combined RNA-sequencing and interactome analysis that was followed by multiple molecular biological methodologies to identify the direct target and corresponding molecular events contributing to TRIM16 function.

RESULTS

We found an intimate correlation of Trim16 expression with hypertrophy-related heart failure in both human and mouse. Our functional investigations and unbiased transcriptomic analyses clearly demonstrated that Trim16 deficiency markedly exacerbated cardiomyocyte enlargement in vitro and in transverse aortic constriction-induced cardiac hypertrophy mouse model, whereas Trim16 overexpression attenuated cardiac hypertrophy and remodeling. Mechanistically, Prdx1 (peroxiredoxin 1) is an essential target of Trim16 in cardiac hypertrophy. We found that Trim16 interacts with Prdx1 and inhibits its phosphorylation, leading to a robust enhancement of its downstream Nrf2 (nuclear factor-erythroid 2-related factor 2) pathway to block cardiac hypertrophy. Trim16-blocked Prdx1 phosphorylation was largely dependent on a direct interaction between Trim16 and Src and the resultant Src ubiquitinational degradation. Notably, Prdx1 knockdown largely abolished the anti-hypertrophic effects of Trim16 overexpression.

CONCLUSIONS

Our findings provide the first evidence supporting Trim16 as a novel suppressor of pathological cardiac hypertrophy and indicate that targeting the Trim16-Prdx1 axis represents a promising therapeutic strategy for hypertrophy-related heart failure.

Nuclear Factor Erythroid 2-Related Factor 2 Activation and Burn-Induced Cardiac Dysfunction

BACKGROUND

Our previous studies have found that burn injury induces cardiac dysfunction through interruption of the antioxidant-response element (ARE) pathway in cardiac mitochondria. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key regulator that activates many antioxidant enzymes. Oltipraz (Olti) is a Nrf2 activator and a well-known inducer of NQO1 along with other enzymes that comprise the Nrf2-associated antioxidants. We propose that Nrf2 activation will induce the ARE pathway, leading to abrogation of burn-induced cardiac dysfunction.

STUDY DESIGN

In this study, we investigated the effect of Nrf2-deficiency in mice on burn-induced cardiac dysfunction. Wild-type (WT) and Nrf2-deficient mice received 30% total body surface area burn injury and were treated with or without Olti and then harvested at 3 hours and 24 hours post burn (3 hpb and 24 hpb).

RESULTS

As expected, Nrf2-deficient mice exhibited exacerbated cardiac dysfunction after burn injury, as measured by Vevo 2100 echocardiography. Electron microscopy showed that Nrf2 depletion worsened burn injury-induced cardiac mitochondrial damage. In addition, Nrf2 depletion increased cardiac mitochondrial dysfunction and myocardial fibrosis after burn injury. Treatment with Olti ameliorated the heart dysfunction in burned Nrf2-/+ mice, improved cardiac mitochondrial structure and oxidative phosphorylation, as well as decreased cardiac fibrosis. These results suggest that Nrf2 and its downstream targets modulate cardiac function after burn injury.

CONCLUSIONS

In summary, Nrf2 depletion worsens cardiac dysfunction after burn injury. Nrf2 activation, with a drug such as Olti, offers a promising therapeutic strategy for abrogating burn-induced cardiac dysfunction.

Nrf2 signaling in heart failure: expression of Nrf2, Keap1, antioxidant, and detoxification genes in dilated or ischemic cardiomyopathy

Increased levels of oxidative stress have been found with heart failure. Whether failing hearts express antioxidant and detoxification enzymes have not been addressed systematically. Nrf2 gene encodes a transcription factor that regulates the expression of antioxidant and detoxification genes. Using RNA-Seq data set from explanted hearts of 37 patients with dilated cardiomyopathy (DCM), 13 patients with ischemic cardiomyopathy (ICM), and 14 nonfailure (NF) donors as a control, we addressed whether failing hearts change the expression of Nrf2, its negative regulator Keap1, and antioxidant or detoxification genes. Significant increases in the ratio of Nrf2 to Keap1 were found to associate with DCM or ICM. Antioxidant genes showed decreased expression in both types of heart failure, including NQO1, SOD1, GPX3, GPX4, GSR, PRDX1, and TXNRD1. Detoxification enzymes, GCLM and EPHX1, also showed decreased expression, whereas the CYP1B1 transcript was elevated in both DCM and ICM. The genes encoding metal-binding protein ferritin were decreased, whereas five out of 12 metallothionein genes showed elevated expression. Our finding on Nrf2 gene expression has been validated by meta-analysis of seven independent data sets of microarray or RNA-Seq for differential gene expression in DCM and ICM from NF controls. In conclusion, minor elevation of Nrf2 gene expression is not coupled to increases in antioxidant and detoxification genes, supporting an impairment of Nrf2 signaling in patients with heart failure. Decreases in multiple antioxidant and detoxification genes are consistent with the observed increases of oxidative stress in failing hearts.

Quercitrin protects human bronchial epithelial cells from oxidative damage

Chronic obstructive pulmonary disease (COPD) is mainly caused by cigarette smoking (CS), with oxidative stress being one key component during its pathogenesis. This study aimed to investigate the effects of quercitrin (QE) on cigarette smoke extract (CSE)-induced cell apoptosis and oxidative stress in human bronchial epithelial cells (HBECs) and its underlying mechanism. HBECs were treated with 2% CSE for 24 h to establish in vitro COPD cellular models. CCK-8 assay and flow cytometry analysis were performed to evaluate cell viability and apoptosis, respectively. Western blotting was applied to examine protein levels and ELISA kits were used to examine contents of the indicated oxidant/antioxidant markers. The results demonstrated that CSE promoted apoptosis and suppressed viability of HBECs and QE reversed these effects. CSE caused increase in T-AOC, superoxide dismutase, and glutathione (GSH) peroxidase contents and decrease in MDA, reactive oxygen species , and GSH contents in HBECs, which were rescued by QE treatment. The CSE-induced Nrf2 nuclear translocation and elevation of NAD(P)H: quinone oxidoreductase 1 (NQO1) and heme oxygenase-1 (HO-1) expression were also reversed by QE in HBECs. The mitogen-activated protein kinase (MAPK) signaling was activated by CSE and further suppressed by QE in HBECs. Collectively, QE exerts a protective role in HBECs against cell apoptosis and oxidative damage via inactivation of the Nrf2/HO-1/NQO1 pathway and the MAPK/ERK pathway.

Metabolomics of oxidative stress: Nrf2 independent depletion of NAD or increases of sugar alcohols

Nrf2 encodes a transcription factor best known for regulating the expression of antioxidant and detoxification genes. Recent evidence suggested that Nrf2 mediates metabolic reprogramming in cancer cells. However, the role of Nrf2 in the biochemical metabolism of cardiac cells has not been studied. Using LC-MS/MS-based metabolomics, we addressed whether knocking out the Nrf2 gene in AC16 human cardiomyocytes affects metabolic reprogramming by oxidative stress. Profiling the basal level metabolites showed an elevated pentose phosphate pathway and increased levels of sugar alcohols, sorbitol, L-arabitol, xylitol and xylonic acid, in Nrf2 KO cells. With sublethal levels of oxidative stress, depletion of NAD, an increase of GDP and elevation of sugar alcohols, sorbitol and dulcitol, were detected in parent wild type (WT) cells. Knocking out Nrf2 did not affect these changes. Biochemical assays confirmed depletion of NAD in WT and Nrf2 KO cells due to H₂O₂ treatment. These data support that although Nrf2 deficiency caused baseline activation of the pentose phosphate pathway and sugar alcohol synthesis, a brief exposure to none-lethal doses of H₂O₂ caused NAD depletion in an Nrf2 independent manner. Loss of NAD may contribute to oxidative stress associated cell degeneration as observed with aging, diabetes and heart failure.

Nrf2 for protection against oxidant generation and mitochondrial damage in cardiac injury

Myocardial infarction is the most common form of acute coronary syndrome. Blockage of a coronary artery due to blood clotting leads to ischemia and subsequent cell death in the form of necrosis, apoptosis, necroptosis and ferroptosis. Revascularization by coronary artery bypass graft surgery or non-surgical percutaneous coronary intervention combined with pharmacotherapy is effective in relieving symptoms and decreasing mortality. However, reactive oxygen species (ROS) are generated from damaged mitochondria, NADPH oxidases, xanthine oxidase, and inflammation. Impairment of mitochondria is shown as decreased metabolic activity, increased ROS production, membrane permeability transition, and release of mitochondrial proteins into the cytoplasm. Oxidative stress activates Nrf2 transcription factor, which in turn mediates the expression of mitofusin 2 (Mfn 2) and proteasomal genes. Increased expression of Mfn2 and inhibition of mitochondrial fission due to decreased Drp1 protein by proteasomal degradation contribute to mitochondrial hyperfusion. Damaged mitochondria can be removed by mitophagy via Parkin or p62 mediated ubiquitination. Mitochondrial biogenesis compensates for the loss of mitochondria, but requires mitochondrial DNA replication and initiation of transcription or translation of mitochondrial genes. Experimental evidence supports a role of Nrf2 in mitophagy, via up-regulation of PINK1 or p62 gene expression; and in mitochondrial biogenesis, by influencing the expression of PGC-1α, NResF1, NResF2, TFAM and mitochondrial genes. Oxidative stress causes Nrf2 activation via Keap1 dissociation, de novo protein translation, and nuclear translocation related to inactivation of GSK3β. The mechanism of Keap 1 mediated Nrf2 activation has been hijacked for Nrf2 activation by small molecules derived from natural products, some of which have been shown capable of mitochondrial protection. Multiple lines of evidence support the importance of Nrf2 in protecting mitochondria and preserving or renewing energy metabolism following tissue injury.

Mitochondrial Quality Control in the Maintenance of Cardiovascular Homeostasis: The Roles and Interregulation of UPS, Mitochondrial Dynamics and Mitophagy

Maintenance of normal function of mitochondria is vital to the fate and health of cardiomyocytes. Mitochondrial quality control (MQC) mechanisms are essential in governing mitochondrial integrity and function. The ubiquitin-proteasome system (UPS), mitochondrial dynamics, and mitophagy are three major components of MQC. With the progress of research, our understanding of MQC mechanisms continues to deepen. Gradually, we realize that the three MQC mechanisms are not independent of each other. To the contrary, there are crosstalk among the mechanisms, which can make them interact with each other and cooperate well, forming a triangle interplay. Briefly, the UPS system can regulate the level of mitochondrial dynamic proteins and mitophagy receptors. In the process of Parkin-dependent mitophagy, the UPS is also widely activated, performing critical roles. Mitochondrial dynamics have a profound influence on mitophagy. In this review, we provide new processes of the three major MQC mechanisms in the background of cardiomyocytes and delve into the relationship between them.