The NRF2 activator DH404 attenuates adverse ventricular remodeling post-myocardial infarction by modifying redox signalling

Bardoxolone methyl attenuates doxorubicin-induced cardiotoxicity by inhibiting the TXNIP-NLRP3 pathway through Nrf2 activation

Bardoxolone methyl, which triggers nuclear factor erythroid 2-related factor (Nrf2), has therapeutic effects against myocardial infarction, heart failure, and other diseases. Nrf2 can inhibit the activation of the thioredoxin-interacting protein (TXNIP)/NLR family pyrin domain-containing protein 3 (NLRP3) pathway. Doxorubicin is an anthracycline chemotherapeutic drug associated with cardiotoxicity, limiting its clinical use. In this study, we explored the specific mechanism of the Nrf2-TXNIP-NLRP3 pathway in doxorubicin-induced cardiotoxicity using bardoxolone methyl in animal and cell models. Using in vivo and in vitro experiments, we show that doxorubicin can induce oxidative stress and pyroptosis in the heart. Western blot and co-immunoprecipitation experimental results found that doxorubicin can reduce the interaction between TXNIP and TRX, increase the interaction between TXNIP and NLRP3, and activate the pyroptosis process. Bardoxolone methyl reduces the accumulation of reactive oxygen species in cardiomyocytes through the Nrf2 pathway, inhibits the interaction between TXNIP and NLRP3, and alleviates the progression of myocardial damage and cardiac fibrosis. Bardoxolone methyl lost its therapeutic effect when the expression of Nrf2 was decreased. Additionally, repressing the expression of TXNIP can inhibit the activation of NLRP3 and alleviate myocardial damage caused by doxorubicin. Collectively, our findings confirm that bardoxolone methyl alleviates doxorubicin-induced cardiotoxicity by activating Nrf2 and inhibiting the TXNIP-NLRP3 pathway.

Ghrelin mediated cardioprotection using in vitro models of oxidative stress

Ghrelin is commonly known as the 'hunger hormone' due to its role in stimulating food intake in humans. However, the roles of ghrelin extend beyond regulating hunger. Our aim was to investigate the ability of ghrelin to protect against hydrogen peroxide (H2O2), a reactive oxygen species commonly associated with cardiac injury. An in vitro model of oxidative stress was developed using H2O2 injured H9c2 cells. Despite lentiviral ghrelin overexpression, H9c2 cell viability and mitochondrial function were not protected following H2O2 injury. We found that H9c2 cells lack expression of the preproghrelin cleavage enzyme prohormone convertase 1 (encoded by PCSK1), required to convert ghrelin to its active form. In contrast, we found that primary rat cardiomyocytes do express PCSK1 and were protected from H2O2 injury by lentiviral ghrelin overexpression. In conclusion, we have shown that ghrelin expression can protect primary rat cardiomyocytes against H2O2, though this effect was not observed in other cell types tested.

Metal profiling in coronary ischemia-reperfusion injury: Implications for KEAP1/NRF2 regulated redox signaling

Coronary ischemia-reperfusion (IR) injury results from a blockage of blood supply to the heart followed by restoration of perfusion, leading to oxidative stress induced pathological processes. Nuclear factor erythroid 2-related factor 2 (NRF2), a master antioxidant transcription factor, plays a key role in regulating redox signaling. Over the past decades, the field of metallomics has provided novel insights into the mechanism of pro-oxidant and antioxidant pathological processes. Both redox-active (e.g. Fe and Cu) and redox-inert (e.g. Zn and Mg) metals play unique roles in establishing redox balance under IR injury. Notably, Zn protects against oxidative stress in coronary IR injury by serving as a cofactor of antioxidant enzymes such as superoxide dismutase [Cu-Zn] (SOD1) and proteins such as metallothionein (MT) and KEAP1/NRF2 mediated antioxidant defenses. An increase in labile Zn2+ inhibits proteasomal degradation and ubiquitination of NRF2 by modifying KEAP1 and glycogen synthase kinase 3β (GSK3β) conformations. Fe and Cu catalyse the formation of reactive oxygen species via the Fenton reaction and also serve as cofactors of antioxidant enzymes and can activate NRF2 antioxidant signaling. We review the evidence that Zn and redox-active metals Fe and Cu affect redox signaling in coronary cells during IR and the mechanisms by which oxidative stress influences cellular metal content. In view of the unique double-edged characteristics of metals, we aim to bridge the role of metals and NRF2 regulated redox signaling to antioxidant defenses in IR injury, with a long-term aim of informing the design and application of novel therapeutics.

Kazinol B protects H9c2 cardiomyocytes from hypoxia/reoxygenation-induced cardiac injury by modulating the AKT/AMPK/Nrf2 signalling pathway

CONTEXT

Kazinol B (KB), an isoprenylated flavan derived from Broussonetia kazinoki Sieb. (Moraceae) root, has long been used in folk medicine.

OBJECTIVE

This study examines the protective effects of KB and its underlying mechanisms in hypoxia and reoxygenation (H/R)-induced cardiac injury in H9c2 rat cardiac myoblasts.

MATERIALS AND METHODS

H9c2 cells were incubated with various concentrations of KB (0, 0.3, 1, 3, 10 and 30 μM) for 2 h and then subjected to H/R insults. The protective effects of KB and its underlying mechanisms were explored.

RESULTS

KB significantly elevated cell viability (1 μM, 1.21-fold; 3 μM, 1.36-fold, and 10 μM, 1.47-fold) and suppressed LDH release (1 μM, 0.77-fold; 3 μM, 0.68-fold, and 10 μM, 0.59-fold) in H/R-induced H9c2 cells. Further, 10 μM KB blocked apoptotic cascades, as shown by the Annexin-V/PI (0.41-fold), DNA fragmentation (0.51-fold), caspase-3 (0.52-fold), PARP activation (0.27-fold) and Bax/Bcl-2 expression (0.28-fold) assays. KB (10 μM) downregulated reactive oxygen species production (0.51-fold) and lipid peroxidation (0.48-fold); it upregulated the activities of GSH-Px (2.08-fold) and SOD (1.72-fold). KB (10 μM) induced Nrf2 nuclear accumulation (1.94-fold) and increased ARE promoter activity (2.15-fold), HO-1 expression (3.07-fold), AKT (3.07-fold) and AMPK (3.07-fold) phosphorylation. Nrf2 knockdown via using Nrf2 siRNA abrogated KB-mediated protective effects against H/R insults. Moreover, pharmacological inhibitors of AKT and AMPK also abrogated KB-induced Nrf2 activation and its protective function.

DISCUSSION AND CONCLUSIONS

KB prevented H/R-induced cardiomyocyte injury via modulating the AKT and AMPK-mediated Nrf2 induction. KB might be a promising drug candidate for managing ischemic cardiac disorders.

Down-Regulation of Long Non-Coding RNA AK139328 Reduces Cell Inflammation and Apoptosis in Cerebral Ischemia Reperfusion Injury

Cerebral ischemia-reperfusion injury (CIRI) refers to the phenomenon that the ischemic injury of brain leads to the injury of brain cells, and ischemic injury is further aggravated after the recovery of blood reperfusion. In this study, we first constructed Oxygen and glucose deprivation/reoxygenation (OGD/R) injury model of PC12 cells, we found that the expression of LncRNA AK139328 in model cells was significantly increased through RT-qPCR. Subsequently, we interfered LncRNA AK139328 in model cells by plasmid transfection and found that interfering LncRNA AK139328 could significantly reduce the expression of inflammatory factors, including TNF a, IL-1β, IL-6, McP-1, and oxidative stress-related factors, including ROS, MDA, LDH, while the expressions of SOD and GSHPx were significantly increased. Flow cytometry was used to detect cell apoptosis, and apoptosisrelated proteins bcl-2, Bax, cleaved-caspase3 and cleaved PARP-1 were detected by western blot. Results show that interfering LncRNA AK139328 could reduce the apoptosis rate of OGD/R cells and the expression of Bax, cleaved caspase3 and cleaved PARP-1, while increasing the expression of bcl-2. Meanwhile, we found that after interfering LncRNA AK139328, the expressions of Nrf2, HO-1, NQO-1 and phosphorylated-P65 increased, while P65 showed no significant changes. This may be related to Nrf2/HO-1 and NF-κB signaling pathways. In a word, our study showed that interfering with LncRNA AK139328 can reduce cell inflammation and apoptosis in CIRI.

Ghrelin ameliorates cardiac fibrosis after myocardial infarction by regulating the Nrf2/NADPH/ROS pathway

To evaluate the role of ghrelin in cardiac fibrosis after myocardial infarction (MI) and to investigate the underlying mechanisms of ghrelin-regulated Nrf2/NADPH/ROS pathway-mediated cardioprotection, the profile of Nrf2, fibrosis markers, and oxidative stress markers were characterized in a rat model of MI and Angiotensin II (Ang II)-stimulated cardiac fibroblasts (CFs). The effects of ghrelin on cardiac function, fibrosis and oxidative stress were investigated after MI in vivo. The role of ghrelin in CF migration and proliferation was evaluated in Ang II-stimulated CFs in vitro. Inhibition of ghrelin receptors using the antagonist, d-Lys3-GHRP-6, in addition to ghrelin was employed in MI and CFs to investigate the direct effect of ghrelin on cardiac fibrosis. Loss function of Nrf2 in CFs was performed to investigate the effect of ghrelin-regulated Nrf2 on oxidative stress and cardiac fibrosis. Ghrelin improved the post-MI cardiac function and reduced cardiac fibrosis. This phenotype is associated with the upregulation of Nrf2 and downregulation of fibrotic proteins, NADPH oxidase and ROS production. In line with in vivo findings, ghrelin attenuated Ang II-stimulated CF migration, proliferation, and oxidative stress in vitro. Inhibition of the ghrelin receptor or knockdown of Nrf2 abolished the beneficial effects of ghrelin on MI or Ang II-stimulated cardiac fibroblasts. In conclusion, ghrelin ameliorates post-MI and Ang II-induced cardiac fibrosis by activating Nrf2, which in turn inhibits the NADPH/ROS pathway.

Pinocembrin ameliorates post-infarct heart failure through activation of Nrf2/HO-1 signaling pathway

Background

Oxidative stress is an important factor involved in the progress of heart failure. The current study was performed to investigate whether pinocembrin was able to ameliorate post-infarct heart failure (PIHF) and the underlying mechanisms.

Methods

Rats were carried out left anterior descending artery ligation to induce myocardial infarction and subsequently raised for 6 weeks to produce chronic heart failure. Then pinocembrin was administrated every other day for 2 weeks. The effects were evaluated by echocardiography, western blot, Masson’s staining, biochemical examinations, immunohistochemistry, and fluorescence. In vitro we also cultured H9c2 cardiomyocytes and cardiac myofibroblasts to further testify the mechanisms.

Results

We found that PIHF-induced deteriorations of cardiac functions were significantly ameliorated by administrating pinocembrin. In addition, the pinocembrin treatment also attenuated collagen deposition and augmented vascular endothelial growth factor receptor 2 in infarct border zone along with an attenuated apoptosis, which were related to an amelioration of oxidative stress evidenced by reduction of reactive oxygen species (ROS) in heart tissue and malondialdehyde (MDA) in serum, and increase of superoxide dismutase (SOD). This were accompanied by upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2)/ heme oxygenase-1 (HO-1) pathway. In vitro experiments we found that specific Nrf2 inhibitor significantly reversed the effects resulted from pinocembrin including antioxidant, anti-apoptosis, anti-fibrosis and neovascularization, which further indicated the amelioration of PIHF by pinocembrin was in a Nrf2/HO-1 pathway-dependent manner.

Conclusion

Pinocembrin ameliorated cardiac functions and remodeling resulted from PIHF by ROS scavenging and Nrf2/HO-1 pathway activation which further attenuated collagen fibers deposition and apoptosis, and facilitated angiogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-021-00363-7.

Nrf2 for cardiac protection: pharmacological options against oxidative stress

Myocardial ischemia or reperfusion increases the generation of reactive oxygen species (ROS) from damaged mitochondria, NADPH oxidases, xanthine oxidase, and inflammation. ROS can be removed by eight endogenous antioxidant and redox systems, many components of which are expressed under the influence of the activated Nrf2 transcription factor. Transcriptomic profiling, sequencing of Nrf2-bound DNA, and Nrf2 gene knockout studies have revealed the power of Nrf2 beyond the antioxidant and detoxification response, from tissue recovery, repair, and remodeling, mitochondrial turnover, and metabolic reprogramming to the suppression of proinflammatory cytokines. Multifaceted regulatory mechanisms for Nrf2 protein levels or activity have been mapped to its functional domains, Nrf2-ECH homology (Neh)1-7. Oxidative stress activates Nrf2 via nuclear translocation, de novo protein translation, and increased protein stability due to removal of the Kelch-like ECH-associated protein 1 (Keap1) checkpoint, or the inactivation of β-transducin repeat-containing protein (β-TrCP), or Hmg-CoA reductase degradation protein 1 (Hrd1). The promise of small-molecule Nrf2 inducers from natural products or derivatives is discussed here. Experimental evidence is presented to support Nrf2 as a lead target for drug development to further improve the treatment outcome for myocardial infarction (MI).

Pharmacological Protection against Ischemia-Reperfusion Injury by Regulating the Nrf2-Keap1-ARE Signaling Pathway

Ischemia/reperfusion (I/R) injury is associated with substantial clinical implications, including a wide range of organs such as the brain, kidneys, lungs, heart, and many others. I/R injury (IRI) occurs due to the tissue injury following the reestablishment of blood supply to ischemic tissues, leading to enhanced aseptic inflammation and stimulation of oxidative stress via reactive oxygen and nitrogen species (ROS/RNS). Since ROS causes membrane lipids’ peroxidation, triggers loss of membrane integrity, denaturation of proteins, DNA damage, and cell death, oxidative stress plays a critical part in I/R pathogenesis. Therefore, ROS regulation could be a promising therapeutic strategy for IRI. In this context, Nrf2 (NF-E2-related factor 2) is a transcription factor that regulates the expression of several factors involved in the cellular defense against oxidative stress and inflammation, including heme oxygenase-1 (HO-1). Numerous studies have shown the potential role of the Nrf2/HO-1 pathway in IRI; thus, we will review the molecular aspects of Nrf2/Kelch-like ECH-associated protein 1 (Keap1)/antioxidant response element (ARE) signaling pathway in I/R, and we will also highlight the recent insights into targeting this pathway as a promising therapeutic strategy for preventing IRI.

Glutaredoxin 1 protects neurons from oxygen-glucose deprivation/reoxygenation (OGD/R)-induced apoptosis and oxidative stress via the modulation of GSK-3β/Nrf2 signaling

Increasing evidence has indicated that glutaredoxin 1 (GRX1) is a potent antioxidant protein that promotes cell survival under conditions of oxidative stress. Oxidative stress-induced neuronal injury contributes to cerebral ischemia/reperfusion injury. However, the role of GRX1-mediated antioxidant defense against neuronal damage during cerebral ischemia/reperfusion injury has not been thoroughly investigated. Thus, the objective of this study was to evaluate whether GRX1 protects neurons against oxygen-glucose deprivation/reoxygenation (OGD/R)-evoked oxidative stress injury in an in vitro model of cerebral ischemia/reperfusion injury. Our data revealed that GRX1 was induced by OGD/R treatment in neurons. Functional assays indicated that loss of GRX1 exacerbated OGD/R-induced apoptosis and the generation of reactive oxygen species (ROS), while GRX1 up-regulation protected against OGD/R-evoked neuronal injury. Further investigation revealed that GRX1 promoted the nuclear expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and enhanced transcription of the Nrf2/antioxidant response element (ARE) in GOD/R-exposed neurons. Furthermore, GRX1 promoted the activation of Nrf2/ARE associated with the modulation of glycogen synthase kinase-3β (GSK-3β). GSK-3β inhibition blocked GRX1 knockdown-mediated suppression of Nrf2 activation. Notably, the suppression of Nrf2 partially reversed GRX1-mediated anti-oxidative stress injury in OGD/R-exposed neurons. In summary, these findings indicate that GRX1 protects neurons against OGD/R-induced oxidative stress injury by enhancing Nrf2 activation via the modulation of GSK-3β. Our study suggests that GRX1 is a potential neuroprotective protein that protects against cerebral ischemia/reperfusion injury.

FXYD1 Is Protective Against Vascular Dysfunction

[Figure: see text].

Nutraceutical, Dietary, and Lifestyle Options for Prevention and Treatment of Ventricular Hypertrophy and Heart Failure

Although well documented drug therapies are available for the management of ventricular hypertrophy (VH) and heart failure (HF), most patients nonetheless experience a downhill course, and further therapeutic measures are needed. Nutraceutical, dietary, and lifestyle measures may have particular merit in this regard, as they are currently available, relatively safe and inexpensive, and can lend themselves to primary prevention as well. A consideration of the pathogenic mechanisms underlying the VH/HF syndrome suggests that measures which control oxidative and endoplasmic reticulum (ER) stress, that support effective nitric oxide and hydrogen sulfide bioactivity, that prevent a reduction in cardiomyocyte pH, and that boost the production of protective hormones, such as fibroblast growth factor 21 (FGF21), while suppressing fibroblast growth factor 23 (FGF23) and marinobufagenin, may have utility for preventing and controlling this syndrome. Agents considered in this essay include phycocyanobilin, N-acetylcysteine, lipoic acid, ferulic acid, zinc, selenium, ubiquinol, astaxanthin, melatonin, tauroursodeoxycholic acid, berberine, citrulline, high-dose folate, cocoa flavanols, hawthorn extract, dietary nitrate, high-dose biotin, soy isoflavones, taurine, carnitine, magnesium orotate, EPA-rich fish oil, glycine, and copper. The potential advantages of whole-food plant-based diets, moderation in salt intake, avoidance of phosphate additives, and regular exercise training and sauna sessions are also discussed. There should be considerable scope for the development of functional foods and supplements which make it more convenient and affordable for patients to consume complementary combinations of the agents discussed here. Research Strategy: Key word searching of PubMed was employed to locate the research papers whose findings are cited in this essay.

The Ubiquitin E3 Ligase TRIM21 Promotes Hepatocarcinogenesis by Suppressing the p62-Keap1-Nrf2 Antioxidant Pathway

BACKGROUND AND AIMS

TRIM21 is a ubiquitin E3 ligase that is implicated in numerous biological processes including immune response, cell metabolism, redox homeostasis, and cancer development. We recently reported that TRIM21 can negatively regulate the p62-Keap1-Nrf2 antioxidant pathway by ubiquitylating p62 and prevents its oligomerization and protein sequestration function. As redox homeostasis plays a pivotal role in many cancers including liver cancer, we sought to determine the role of TRIM21 in hepatocarcinogenesis.

METHODS

We examined the correlation between TRIM21 expression and the disease using publicly available data sets and 49 cases of HCC clinical samples. We used TRIM21 genetic knockout mice to determine how TRIM21 ablation impact HCC induced by the carcinogen DEN plus phenobarbital (PB). We explored the mechanism that loss of TRIM21 protects cells from DEN-induced oxidative damage and cell death.

RESULTS

There is a positive correlation between TRIM21 expression and HCC. Consistently, TRIM21-knockout mice are resistant to DEN-induced hepatocarcinogenesis. This is accompanied by decreased cell death and tissue damage upon DEN treatment, hence reduced hepatic tissue repair response and compensatory proliferation. Cells deficient in TRIM21 display enhanced p62 sequestration of Keap1 and are protected from DEN-induced ROS induction and cell death. Reconstitution of wild-type but not the E3 ligase-dead and the p62 binding-deficient mutant TRIM21 impedes the protection from DEN-induced oxidative damage and cell death in TRIM21-deficient cells.

CONCLUSIONS

Increased TRIM21 expression is associated with human HCC. Genetic ablation of TRIM21 leads to protection against oxidative hepatic damage and decreased hepatocarcinogenesis, suggesting TRIM21 as a preventive and therapeutic target.

NRF2 in Cardiovascular Diseases: a Ray of Hope!

Heart failure is a worldwide pandemic influencing 26 million individuals worldwide and is expanding. Imbalanced redox homeostasis in cardiac cells alters the structure and function of the cells, which leads to contractile dysfunction, myocardial hypertrophy, and fibrosis in chronic heart failure. Various targets and agents acting on these such as siRNA, miRNA, interleukin-1, opioids, vasodilators, and SGLT2 inhibitors are being evaluated for heart failure, and nuclear factor erythroid 2-related factor 2 (NRF2) is one of them. NRF2 is a master transcription factor which is expressed in most of the tissues and exhibits a major role in amplification of the antioxidant pathways associated with the enzymes present in myocardium. Increased ROS generation and PI3K-Akt signaling can activate the receptor NRF2. Various in vitro and in vivo and few clinical studies suggested NRF2 may possess a potential for targeting oxidative stress-induced cardiovascular diseases including heart failures. All these studies collectively propose that upregulation of NRF2 will attenuate the increase in hemodynamic stress and provide beneficial role in cardiovascular diseases. The current review shall familiarize readers about the regulations and functions of NRF2. We have also discussed the current evidences suggesting beneficial role of NRF2 activators in heart failure. Graphical abstract.

BRG1 protects the heart from acute myocardial infarction by reducing oxidative damage through the activation of the NRF2/HO1 signaling pathway

Brahma-related gene 1 (BRG1) regulates the chromatin structure and expression of cardiac genes. Although BRG1 is downregulated in adult cardiomyocytes, it is reactivated during cardiac stress. The role of BRG1 in acute myocardial infarction (AMI) has not been clearly defined. This study assessed the protective role of BRG1 in AMI using cell cultures and an animal model and explored the underlying molecular events. The results showed that in the peri-infarct zone, expression of BRG1 protein was significantly increased relative to the sham group, which was accompanied by NRF2 and HO1 upregulation and KEAP1 downregulation. BRG1 overexpression through adenoviral intramyocardial injection into AMI mice reduced the infarct size and improved cardiac functions with upregulation of NRF2 and its target HO1 and attenuated oxidative damage and cell apoptosis. However, shRNA-mediated Brg1 knockdown had the opposite effects. These results were further confirmed in cultured primary neonatal rat cardiomyocytes (NRCMs) with oxygen-glucose deprivation (OGD). Moreover, the selective NRF2 inhibitor brusatol could partially reverse cardiomyocyte antioxidant ability and BRG1 overexpression-induced cardiac protection in vitro. In addition, co-immunoprecipitation and immunofluorescence data showed that BRG1 overexpression significantly promoted the BRG1/NRF2 co-localization in cardiomyocytes. The chromatin immunoprecipitation-qPCR revealed BRG1 interaction with the Ho1 promoter and BRG1 overexpression could induce BRG1 binding to the Ho1 promoter during the OGD. In conclusion, this study demonstrated that BRG1 upregulation during AMI in vitro and in vivo increased the NRF2 level and NRF2 nuclear accumulation for HO1 expression to alleviate cardiac myocyte oxidative stress and upregulate cardiomyocyte viability. The BRG1-NRF2-HO1 pathway may represent a novel therapeutic target in the prevention of cardiac dysfunction in AMI patients.

MicroRNA-200a represses myocardial infarction-related cell death and inflammation by targeting the Keap1/Nrf2 and β-catenin pathways

BACKGROUND

Acute myocardial infarction (MI) is a main cause of emergency death in the world. MicroRNAs (miRs/miRNAs) are a series of small non-coding RNA molecules, which regulate cardiovascular disorders that involve MI. In this study, we explored the function of miR-200a in MI treatment.

METHODS

We observed down-regulation of miR-200a levels and up-regulation of Keap1 and β-catenin levels in H₂O₂-treated newborn murine ventricular cardiomyocytes (NMVCs) and the infarcted heart tissues of MI mouse models, compared to the non-treated NMVCs and normal heart tissues of healthy mice.

RESULTS

CCK-8 and colony formation assays indicated the reduction in NMVC vitality due to H₂O₂ treatment and the recovery of cell vitality due to miR-200a overexpression, respectively. Flow cytometry with Annexin and PI staining indicated the inhibition of H₂O₂-triggered cell apoptosis through ectopically expressed miR-200a. Western blotting and ELISA analyses that detected pro-inflammatory cell factors [interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α] confirmed that miR-200a prevented H₂O₂-induced NMVC inflammation. Moreover, miR-200a inhibited up-regulation of Keap1 and β-catenin expression in H₂O₂-treated NMVCs by directly binding with the 3'-UTR regions of both Keap1 and β-catenin. Furthermore, overexpression of Keap1 and β-cateninin in H₂O₂-treated NMVCs with recovered miR-200a elevated inflammation and apoptosis, respectively.

CONCLUSION

The results showed that miR-200a expression was inhibited in murine cardiomyocytes due to H₂O₂ stress in MI cardiac tissues and overexpressed miR-200a could protect the cells from death by regulating the Keap1/Nrf2 and β-catenin signal transduction pathways.

The protective effects of memantine against inflammation and impairment of endothelial tube formation induced by oxygen-glucose deprivation/reperfusion

Acute myocardial infarction (AMI) is one of the leading causes of death and disability. The dysregulation of cardiac endothelial cells plays a significant role in the pathogenesis of AMI. In the present study, we investigated the potential of memantine, a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist used in the treatment of Alzheimer's disease, to mitigate the effects of ischemia-reperfusion injury in the peripheral vasculature using human umbilical cord endothelial cells (HUVECs). Previous studies have identified anti-inflammatory and antioxidant effects of memantine, but the effects of memantine on angiogenesis and microtubule formation have not been fully elucidated. Our findings indicate that pretreatment with memantine significantly reduced the expression of interleukin (IL)-6 and IL-8, which are both serum markers if AMI severity. We also demonstrate that memantine could prevent mitochondrial dysfunction and oxidative stress by rescuing mitochondrial membrane potential and reducing the production of reactive oxygen species (ROS) by NADPH oxidase-4 (NOX-4). Importantly, memantine also promoted the expression of the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) antioxidant signaling pathway. Importantly, memantine pretreatment improved cell viability and prevented the decrease in microtubule formation induced by OGD/R. Through a phosphoinositide-3-kinase (PI3K) inhibition experiment, we determined that the PI3K/protein kinase B (Akt) pathway is essential for the effects of memantine on angiogenesis. Together, our findings suggest a potential role for memantine in the prevention and treatment of AMI.

The role of natural products in revealing NRF2 function

Covering: up to 2020The transcription factor NRF2 is one of the body's major defense mechanisms, driving transcription of >300 antioxidant response element (ARE)-regulated genes that are involved in many critical cellular processes including redox regulation, proteostasis, xenobiotic detoxification, and primary metabolism. The transcription factor NRF2 and natural products have an intimately entwined history, as the discovery of NRF2 and much of its rich biology were revealed using natural products both intentionally and unintentionally. In addition, in the last decade a more sinister aspect of NRF2 biology has been revealed. NRF2 is normally present at very low cellular levels and only activated when needed, however, it has been recently revealed that chronic, high levels of NRF2 can lead to diseases such as diabetes and cancer, and may play a role in other diseases. Again, this "dark side" of NRF2 was revealed and studied largely using a natural product, the quassinoid, brusatol. In the present review, we provide an overview of NRF2 structure and function to orient the general reader, we will discuss the history of NRF2 and NRF2-activating compounds and the biology these have revealed, and we will delve into the dark side of NRF2 and contemporary issues related to the dark side biology and the role of natural products in dissecting this biology.

CaMKII/calpain interaction mediates ischemia/reperfusion injury in isolated rat hearts

Previous studies indicated that Ca²⁺/calmodulin-dependent kinase II (CaMKII), a kinase involved in the modulation of ryanodine receptor activity, activates Ca²⁺-regulated protease μ-calpain to promote myocardial ischemia/reperfusion injury. This study was performed to explore the underlying mechanisms in CaMKII-induced calpain activation to better understand heart injury. To examine the Ca²⁺ paradox and ischemia/reperfusion injury, isolated rat hearts were subjected to a Ca²⁺-free solution for 3 min, or left coronary artery occlusion for 40 min, prior to restoration of normal perfusion. Blockade of trans-sarcoplasmic reticulum Ca²⁺ flux using ryanodine and thapsigargin failed to prevent Ca²⁺ paradox-induced heart injury. In contrast, the Ca²⁺ paradox increased CaMKII auto-phosphorylation at Thr²⁸⁷, while the CaMKII inhibitor KN-62 and the Na⁺/Ca²⁺ exchanger inhibitor KB-R7943 alleviated heart injury and calpain activity. Intriguingly, the binding of μ-calpain large subunit calpain-1 (CAPN1) to phospho-CaMKII was blunted by both inhibitors. Thus, a Ca²⁺ leak via the ryanodine receptor is not an essential element in CaMKII-elicited calpain activation. In hearts receiving vector injection, ischemia/reperfusion caused elevated calpain activity and α-fodrin degradation, along with membrane integrity damage, similar to the effects noted in control hearts. Importantly, all these alterations were diminished with delivery of adeno-associated virus expressing mutant CaMKIIδC T287A. Ischemia/reperfusion increased CaMKII auto-phosphorylation and binding of CAPN1 to phospho-CaMKII, and facilitated the translocation of phospho-CaMKII and CAPN1 to the plasma membrane, all of which were reversed by injecting CaMKII mutant. Furthermore, the relocation capacity and the interaction of CaMKII with CAPN1 appeared to be dependent upon CaMKII autophosphorylation, as its mutant delivery increased the level of CaMKII, but did not increase membrane content of CaMKII and CAPN1, or their interactions. Together, CaMKII/calpain interaction represents a new avenue for mediating myocardial ischemia/reperfusion injury, and CaMKII likely serves as both a kinase and a carrier, thereby promoting calpain membrane translocation and activation.

Therapeutic Effects of Nrf2 Activation by Bardoxolone Methyl in Chronic Heart Failure

Oxidative stress plays an important role in the pathogenesis of chronic heart failure (CHF) in many tissues. Increasing evidence suggests that systemic activation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) signaling can protect against postinfarct cardiac remodeling by reducing oxidative stress. However, it remains to be elucidated if Nrf2 activation exerts therapeutic effects in the CHF state. Here, we investigated the beneficial hemodynamic effects of bardoxolone methyl (2-Cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid methyl ester, CDDO-Me), a pharmacological activator of Nrf2, in a rodent model of CHF. Based on echocardiographic analysis, rats at 12 weeks post-myocardial infarction (MI) were randomly split into four groups. CDDO-Me (5 mg/kg, i.p.) was administered daily for another 2 weeks in sham and CHF rats and compared with vehicle treatment. Echocardiographic and hemodynamic analysis suggest that short-term CDDO-Me administration increased stroke volume and cardiac output in CHF rats and decreased left ventricle end-diastolic pressure. Molecular studies revealed that CDDO-Me-induced cardiac functional improvement was attributed to an increase of both Nrf2 transcription and translation, and a decrease of oxidative stress in the noninfarcted areas of the heart. Furthermore, CDDO-Me reduced NF-κB binding and increased Nrf2 binding to the CREB-binding protein, which may contribute to the selective increase of Nrf2 downstream targets, including NADPH Oxidase Quinone 1, Heme Oxygenase 1, Catalase, and Glutamate-Cysteine Ligase Catalytic Subunit, and the attenuation of myocardial inflammation in CHF rats. Our findings suggest that Nrf2 activation may provide beneficial cardiac effects in MI-mediated CHF. SIGNIFICANCE STATEMENT: Chronic heart failure (CHF) is the leading cause of death among the aged worldwide. The imbalance between pro- and antioxidant pathways is a determinant in the pathogenesis of CHF. Systemic activation of Nrf2 and antioxidant protein signaling by bardoxolone methyl may have beneficial effects on cardiac function and result in improvements by enhancing antioxidant enzyme expression and attenuating myocardial inflammation.

Beneficial effects of bardoxolone methyl, an Nrf2 activator, on crush-related acute kidney injury in rats

PURPOSE

The purpose of this study was to investigate the effects of bardoxolone methyl (BM), a nuclear factor erythroid 2-related factor 2 (Nrf2) activator, on acute kidney injury in a rat model of crush syndrome model.

METHODS

Sixty-four rats were separated equally into eight groups, sham (sterile saline ip), crush, crush + vehicle (DMSO ip), and crush + BM (10 mg/kg ip) (n = 8). All groups were also divided as 3 and 24 h after decompression. Crush injury was induced by 6 h of direct compression to both hind limbs of the rats with blocks weighing 3.6 kg on each side, followed by 3 and 24 h of decompression. Kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), tumor necrotizing factor-α (TNF-α), transforming growth factor-β1 (TGF-β1) concentrations, tissue total oxidant status (TOS) and total antioxidant status (TAS) were measured in the kidneys. Serum creatine kinase (CK), blood urea nitrogen (BUN) and creatinine concentrations were also measured. Glomerular and tubular structures were examined histopathologically. Bcl-2 was measured using immunohistochemistry. Apoptosis was assessed using the TUNEL method.

RESULTS

BM treatment reduced KIM-1, NGAL, TNF-α, TGF-β1, TOS concentrations, and increased TAS concentrations in the kidneys 3 and 24 h after decompression. Serum CK, BUN and creatinine concentrations were also reduced with BM. BM treatment decreased apoptosis in crush-related AKI. The Nrf2 activator BM reversed the crush-induced changes in the experimental rats.

CONCLUSION

BM treatment prevented the progression of crush-related AKI in rats possibly through its cytoprotective effects of being an antioxidant, anti-inflammatory and anti-apoptotic agent.

New opportunities for targeting redox dysregulation in cardiovascular disease

Despite substantial promise, the use of antioxidant therapy to improve cardiovascular outcomes has been disappointing. Whilst the fundamental biology supporting their use continues to build, the challenge now is to differentially target dysregulated redox signalling domains and to identify new ways to deliver antioxidant substances. Looking further afield to other disciplines, there is an emerging ‘tool-kit’ containing sophisticated molecular and drug delivery applications. Applying these to the cardiovascular redox field could prove a successful strategy to combat the increasing disease burden. Excessive reactive oxygen species production and protein modifications in the mitochondria has been the target of successful drug development with several positive outcomes emerging in the cardiovascular space, harnessing both improved delivery mechanisms and enhanced understanding of the biological abnormalities. Using this as a blueprint, similar strategies could be applied and expanded upon in other redox-hot-spots, such as the caveolae sub-cellular region, which houses many of the key cardiovascular redox proteins such as NADPH oxidase, endothelial nitric oxide synthase, angiotensin II receptors, and beta adrenoceptors. The expanded tool kit of drug development, including gene and miRNA therapies, nanoparticle technology and micropeptide targeting, can be applied to target dysregulated redox signalling in subcellular compartments of cardiovascular cells. In this review, we consider the opportunities for improving cardiovascular outcomes by utilizing new technology platforms to target subcellular ‘bonfires’ generated by dysregulated redox pathways, to improve clinical outcomes.

Pentamethylquercetin protects against cardiac remodeling via activation of Sestrin2

Oxidative stress is widely involved in pathophysiological processes of cardiac remodeling. Molecules associated with antioxidant functions may be ideal targets for reversing cardiac remodeling. Sestrin2 is the important component of endogenous antioxidant defense, while there is little information on the pathophysiological roles of it in cardiac remodeling. The aim of this study was to investigate whether Sestrin2 is closely involved in cardiac remodeling, and whether the protective effect of pentamethylquercetin (PMQ) on cardiac remodeling is related to upregulation of the Sestrin2 endogenous antioxidant system. We generated a transverse aorta constriction (TAC)-induced pressure-overload cardiac-remodeling model in mice, and also established an isoproterenol (ISO)-induced neonatal rat cardiomyocyte (NRCM) hypertrophy model. The data showed Sestrin2 expression was downregulated significantly, and Nrf2 and HO-1 expression was also reduced in myocardial tissue or NRCM of model group, whereas keap1 expression was upregulated. PMQ significantly ameliorated cardiac remodeling and rectified the abnormal expression of Sestrin2/Nrf2/keap1. Sestrin2 small interfering RNA (SiRNA) reduced the protective effect of PMQ on NRCMs, as well as abolished its regulating effect on the Nrf2/keap1 pathway. In conclusion, Sestrin2 may be an important target in the anti-myocardial remodeling of PMQ.

Nano-oleanolic acid alleviates metabolic dysfunctions in rats with high fat and fructose diet

Obesity, diabetes and related metabolic disorders are among the top prevalent metabolism-related diseases with increasing threat to human health throughout the world. Oleanolic acid (OA) is a natural triterpenoid and an aglycone of many saponins possessing anti-diabetic, antioxidant, hypolipidemic and anti-inflammatory activities. A nano-formulation of OA was recently developed to evaluate the efficiency of nano-OA in the treatment of insulin-resistance and metabolic disorders in high fat and fructose (HFF) diet-fed rats. This study further identified that nano-OA could reduce the increase of body weights, serum insulin, insulin sensitivity index, serum triglycerides, and cholesterol in HFF-fed rats. In consistence, nano-OA was able to attenuate HFF diet-induced lipid accumulation in the liver and improve the structural integrity of mitochondria and endoplasmic reticulum in liver and pancreas in animals fed with HFF diet. In addition, nan-OA can efficaciously mitigate the increase of levels of malondialdehyde (MDA) and nitric oxide (NO), and serum superoxide dismutase (SOD) and catalase (CAT) activities in blood samples. The beneficial effects of nano-OA was further evidenced to be superior to OA formulated in arabic gum and rosiglitazone treatment. Together, this study provides the evidence that nano-OA can effectively improve HFF diet-induced metabolic dysfunctions in rats by improving its bioavailability and pharmacodynamic properties and thus nano-OA may be a potentially efficient agent to treat obesity-related diabetes and metabolic disorders.

Raf kinase inhibitor protein mediates myocardial fibrosis under conditions of enhanced myocardial oxidative stress

Fibrosis is a hallmark of maladaptive cardiac remodelling. Here we report that genome-wide quantitative trait locus (QTL) analyses in recombinant inbred mouse lines of C57BL/6 J and DBA2/J strains identified Raf Kinase Inhibitor Protein (RKIP) as genetic marker of fibrosis progression. C57BL/6 N-RKIP^−/− mice demonstrated diminished fibrosis induced by transverse aortic constriction (TAC) or CCl₄ (carbon tetrachloride) treatment compared with wild-type controls. TAC-induced expression of collagen Iα2 mRNA, Ki67⁺ fibroblasts and marker of oxidative stress 8-hydroxyguanosine (8-dOHG)⁺ fibroblasts as well as the number of fibrocytes in the peripheral blood and bone marrow were markedly reduced in C57BL/6 N-RKIP^−/− mice. RKIP-deficient cardiac fibroblasts demonstrated decreased migration and fibronectin production. This was accompanied by a two-fold increase of the nuclear accumulation of nuclear factor erythroid 2-related factor 2 (Nrf2), the main transcriptional activator of antioxidative proteins, and reduced expression of its inactivators. To test the importance of oxidative stress for this signaling, C57BL/6 J mice were studied. C57BL/6 J, but not the C57BL/6 N-strain, is protected from TAC-induced oxidative stress due to mutation of the nicotinamide nucleotide transhydrogenase gene (Nnt). After TAC surgery, the hearts of Nnt-deficient C57BL/6 J-RKIP^−/− mice revealed diminished oxidative stress, increased left ventricular (LV) fibrosis and collagen Iα2 as well as enhanced basal nuclear expression of Nrf2. In human LV myocardium from both non-failing and failing hearts, RKIP-protein correlated negatively with the nuclear accumulation of Nrf2. In summary, under conditions of Nnt-dependent enhanced myocardial oxidative stress induced by TAC, RKIP plays a maladaptive role for fibrotic myocardial remodeling by suppressing the Nrf2-related beneficial effects.

Recent novel approaches to limit oxidative stress and inflammation in diabetic complications

Diabetes is considered a major burden on the healthcare system of Western and non‐Western societies with the disease reaching epidemic proportions globally. Diabetic patients are highly susceptible to developing micro‐ and macrovascular complications, which contribute significantly to morbidity and mortality rates. Over the past decade, a plethora of research has demonstrated that oxidative stress and inflammation are intricately linked and significant drivers of these diabetic complications. Thus, the focus now has been towards specific mechanism‐based strategies that can target both oxidative stress and inflammatory pathways to improve the outcome of disease burden. This review will focus on the mechanisms that drive these diabetic complications and the feasibility of emerging new therapies to combat oxidative stress and inflammation in the diabetic milieu.

Vascularized Cardiac Spheroids as Novel 3D in vitro Models to Study Cardiac Fibrosis

Spheroid cultures are among the most explored cellular biomaterials used in cardiovascular research, due to their improved integration of biochemical and physiological features of the heart in a defined architectural three-dimensional microenvironment when compared to monolayer cultures. To further explore the potential use of spheroid cultures for research, we engineered a novel in vitro model of the heart with vascularized cardiac spheroids (VCSs), by coculturing cardiac myocytes, endothelial cells, and fibroblasts isolated from dissociated rat neonatal hearts (aged 1-3 days) in hanging drop cultures. To evaluate the validity of VCSs in recapitulating pathophysiological processes typical of the in vivo heart, such as cardiac fibrosis, we then treated VCSs with transforming growth factor beta 1 (TGFβ1), a known profibrotic agent. Our mRNA analysis demonstrated that TGFβ1-treated VCSs present elevated levels of expression of connective tissue growth factor, fibronectin, and TGFβ1 when compared to control cultures. We demonstrated a dramatic increase in collagen deposition following TGFβ1 treatment in VCSs in the PicroSirius Red-stained sections. Doxorubicin, a renowned cardiotoxic and profibrotic agent, triggered apoptosis and disrupted vascular networks in VCSs. Taken together, our findings demonstrate that VCSs are a valid model for the study of the mechanisms involved in cardiac fibrosis, with the potential to be used to investigate novel mechanisms and therapeutics for treating and preventing cardiac fibrosis in vitro.

The role of reactive oxygen species in the pathophysiology of cardiovascular diseases and the clinical significance of myocardial redox

Acute and chronic excessive intracellular increase of reactive oxygen species (ROS) is involved in the development and progression of cardiovascular diseases. ROS are by-products of various oxidative physiological and biochemical processes. Sources of ROS are mitochondrial respiration, NADH/NADPH oxidase, xanthine oxidoreductase or the uncoupling of nitric oxide synthase (NOS) in vascular cells. ROS mediate various signaling pathways that underlie cardiovascular pathophysiology. The delicate equilibrium between free-radical generation and antioxidant defense is altered in favor of the former, thus leading to redox imbalance, oxidative stress, and increased cellular injury. An understanding of the pathophysiological mechanisms mediated by oxidative stress is crucial to the prevention and treatment of cardiovascular diseases.