Prevention by sulforaphane of diabetic cardiomyopathy is associated with up-regulation of Nrf2 expression and transcription activation

Protection against diabetic cardiomyopathy is achieved using a combination of sulforaphane and zinc in type 1 diabetic OVE26 mice

Sulforaphane (SFN) can effectively induce nuclear factor E2-related factor 2 (Nrf2), and zinc (Zn) can effectively induce metallothionein (MT), both of which have been shown to protect against diabetic cardiomyopathy (DCM). However, it is unclear whether combined treatment with SFN and Zn offers better cardiac protection than either one alone. Here, we treated 5-week-old OVE mice that spontaneously develop type 1 diabetes with SFN and/or Zn for 18 weeks. Cardiac dysfunction, by echocardiography, and pathological alterations and remodelling, shown by cardiac hypertrophy, fibrosis, inflammation and oxidative damage, examined by histopathology, Western blotting and real-time PCR, were observed in OVE mice. All these dysfunction and pathological abnormalities seen in OVE mice were attenuated in OVE mice with treatment of either SFN, Zn or SFN/Zn, and the combined treatment with SFN/Zn was better than single treatments at ameliorating DCM. In addition, combined SFN and Zn treatment increased Nrf2 function and MT expression in the heart of OVE mice to a greater extent than SFN or Zn alone. This indicates that the dual activation of Nrf2 and MT by combined treatment with SFN and Zn may be more effective than monotherapy at preventing the development of DCM via complementary, additive mechanisms.

4-O-methylhonokiol protects against diabetic cardiomyopathy in type 2 diabetic mice by activation of AMPK-mediated cardiac lipid metabolism improvement

Diabetic cardiomyopathy (DCM) is characterized by increased left ventricular mass and wall thickness, decreased systolic function, reduced ejection fraction (EF) and ultimately heart failure. The 4-O-methylhonokiol (MH) has been isolated mainly from the bark of the root and stem of Magnolia species. In this study, we aimed to elucidate whether MH can effectively prevent DCM in type 2 diabetic (T2D) mice and, if so, whether the protective response of MH is associated with its activation of AMPK-mediated inhibition of lipid accumulation and inflammation. A total number of 40 mice were divided into four groups: Ctrl, Ctrl + MH, T2D, T2D + MH. Five mice from each group were sacrificed after 3-month MH treatment. The remaining animals in each group were kept for additional 3 months without further MH treatment. In T2D mice, the typical DCM symptoms were induced as expected, reflected by decreased ejection fraction and lipotoxic effects inducing lipid accumulation, oxidative stress, inflammatory reactions, and final fibrosis. However, these typical DCM changes were significantly prevented by the MH treatment immediately or 3 months after the 3-month MH treatment, suggesting MH-induced cardiac protection from T2D had a memory effect. Mechanistically, MH cardiac protection from DCM may be associated with its lipid metabolism improvement by the activation of AMPK/CPT1-mediated fatty acid oxidation. In addition, the MH treatment of DCM mice significantly improved their insulin resistance levels by activation of GSK-3β. These results indicate that the treatment of T2D with MH effectively prevents DCM probably via AMPK-dependent improvement of the lipid metabolism.

The impact of exposure of diabetic rats to 900 MHz electromagnetic radiation emitted from mobile phone antenna on hepatic oxidative stress

The excessive exposure of patients with type 2 diabetes mellitus (T2DM) to electromagnetic radiation (EMR) from mobile phones or their base stations antenna may influence oxidative stress and development of diabetic complications. Here, we investigated the effects of exposing type 2 diabetic rats to EMR of 900 MHz emitted from GSM mobile phone antenna for 24 hours/day over a period of 28 days on hyperglycemia and hepatic oxidative stress. Male Sprague-Dawley rats were divided into 4 groups (12 rats/group): control rats, normal rats exposed to EMR, T2DM rats generated by nicotinamide/streptozotocin administration, and T2DM rats exposed to EMR. Our results showed that the exposure of T2DM rats to EMR nonsignificantly reduced the hyperglycemia and hyperinsulinemia compared to unexposed T2DM rats. The exposure of T2DM rats to EMR for 28 days increased the hepatic levels of MDA and Nrf-2 as well as the activities of superoxide dismutase (SOD) and catalase but decreased phosphorylated Akt-2 (pAkt-2) as compared to unexposed T2DM rats. Therefore, the decrease in the hepatic pAkt-2 in T2DM rats after the exposure to EMR may result in elevated level of hepatic MDA, even though the level of Nrf-2 and the activities of SOD and catalase were increased. Abbreviations: BGL: blood glucose level; EMR: electromagnetic radiation; GSM: global system for mobile communication; H2O2: hydrogen peroxide; LSD: least significance difference; MDA:malondialdehyde; Nrf-2: nuclear factor erythroid 2- related factor 2; PI3K: phosphoinositide-3-kinase; pAkt-2: phosphorylated Akt-2; Akt-2: protein kinase; ROS: reactive oxygen species; SEM: standard error of the mean; STZ: streptozotocin; SOD: superoxide dismutase ; O2-: superoxide radical; CT: threshold cycle; T2DM: type 2 diabetes mellitus.

Basic Concepts on the Role of Nuclear Factor Erythroid-Derived 2-Like 2 (Nrf2) in Age-Related Diseases

The transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) is one of the most important oxidative stress regulator in the human body. Once Nrf2 regulates the expression of a large number of cytoprotective genes, it plays a crucial role in the prevention of several diseases, including age-related disorders. However, the involvement of Nrf2 on these conditions is complex and needs to be clarified. Here, a brief compilation of the Nrf2 enrollment in the pathophysiology of the most common age-related diseases and bring insights for future research on the Nrf2 pathway is described. This review shows a controversial response of this transcriptional factor on the presented diseases. This reinforces the necessity of more studies to investigate modulation strategies for Nrf2, making it a possible therapeutic target in the treatment of age-related disorders.

Astragaloside IV Exerts a Myocardial Protective Effect against Cardiac Hypertrophy in Rats, Partially via Activating the Nrf2/HO-1 Signaling Pathway

Previous evidence suggested that astragaloside IV (ASIV) had a cardioprotective effect, but the potential mechanisms were undetermined. This study is aimed at validating the prevention of cardiac hypertrophy in chronic heart failure (CHF) rats and hypertrophy in H9c2 cardiomyocytes by ASIV and at exploring the potential mechanism involved. CHF rat models of abdominal aortic constriction (AAC) were used with the aim of determining the protective effect of ASIV in cardiac hypertrophy in the rats. We proved that ASIV could attenuate cardiac hypertrophy by improving left ventricular function and structure and showed that the expression of nuclear factor-erythroid 2-related factor 2 (Nrf2) and its downstream gene heme oxygenase-1 (HO-1) increased in the high-dose ASIV intervention group. To further investigate the specific mechanism of ASIV, we hypothesized that ASIV might prevent cardiac hypertrophy via activating the Nrf2/HO-1 signaling pathway. We established a cardiomyocyte hypertrophy model induced by angiotensin II (Ang II), which was then transfected with Nrf2 shRNA, to knock down the expression of the Nrf2 gene. We found that the protective effect of ASIV against Ang II-induced cardiomyocyte hypertrophy was abolished in the Nrf2 shRNA transfection group, ultimately aggravating cardiomyocyte hypertrophy induced by Ang II, and it is possible that oxidative stress may be involved in this process. Our results demonstrated that ASIV improved cardiac function and inhibited cardiac hypertrophy by upregulating Nrf2, and this effect was partially achieved by stimulating the Nrf2/HO-1 signaling pathway, suggesting that ASIV could have therapeutic potential for the treatment of cardiac hypertrophy and CHF.

Myricetin Attenuated Diabetes-Associated Kidney Injuries and Dysfunction via Regulating Nuclear Factor (Erythroid Derived 2)-Like 2 and Nuclear Factor-κB Signaling

Background/Aims: Previous studies have suggested that myricetin (Myr) could promote the expression and nuclear translocation of nuclear factor (erythroid-derived 2)-like (Nrf2). This study aimed to investigate whether Myr could attenuate diabetes-associated kidney injuries and dysfunction in wild-type (WT) and Nrf2 knockdown (Nrf2-KD) mice.

Methods: Lentivirus-mediated Nrf2-KD and WT mice were used to establish type 1 diabetes mellitus (DM) by streptozotocin (STZ) injection. WT and Nrf2-KD mice were then randomly allocated into four groups: control (CON), Myr, STZ, and STZ + Myr. Myr (100 mg/kg/day) or vehicle was administered for 6 months. Kidneys were harvested and weighed at the end of the experiment. Hematoxylin and eosin staining and Masson’s trichrome staining were used to assess the morphology and fibrosis of the kidneys, respectively. Urinary albumin-to-creatinine ratio was used to test renal function. Western blotting was performed to determine oxidative-stress- or inflammation-associated signaling pathways. Real-time polymerase chain reaction (RT-PCR) was performed to detect the expression of fibrosis or inflammatory cytokines at the message Ribonucleic Acid (mRNA) level.

Results: In WT mice, Myr alleviated DM-induced renal dysfunction, fibrosis, and oxidative damage and enhanced the expression of Nrf2 and its downstream genes. After knockdown of Nrf2, Myr treatment partially but significantly mitigated DM-induced renal dysfunction and fibrosis, which might be associated with inhibition of the I-kappa-B (IκB)/nuclear factor-κB (NF-κB) (P65) signaling pathway.

Conclusions: This study showed that Myr prevented DM-associated decreased expression of Nrf2 and inhibited IκB/NF-κB (P65) signaling pathway. Moreover, inhibition of IκB/NF-κB (P65) signaling pathway is independent of the regulation of Nrf2. Thus, Myr could be a potential treatment for preventing the development and progression of DM-associated kidney injuries and dysfunction.

HDAC5 catalytic activity suppresses cardiomyocyte oxidative stress and NRF2 target gene expression

Histone deacetylase 5 (HDAC5) and HDAC9 are class IIa HDACs that function as signal-responsive repressors of the epigenetic program for pathological cardiomyocyte hypertrophy. The conserved deacetylase domains of HDAC5 and HDAC9 are not required for inhibition of cardiac hypertrophy. Thus, the biological function of class IIa HDAC catalytic activity in the heart remains unknown. Here we demonstrate that catalytic activity of HDAC5, but not HDAC9, suppresses mitochondrial reactive oxygen species generation and subsequent induction of NF-E2-related factor 2 (NRF2)-dependent antioxidant gene expression in cardiomyocytes. Treatment of cardiomyocytes with TMP195 or TMP269, which are selective class IIa HDAC inhibitors, or shRNA-mediated knockdown of HDAC5 but not HDAC9 leads to stimulation of NRF2-mediated transcription in a reactive oxygen species-dependent manner. Conversely, ectopic expression of catalytically active HDAC5 decreases cardiomyocyte oxidative stress and represses NRF2 activation. These findings establish a role of the catalytic domain of HDAC5 in the control of cardiomyocyte redox homeostasis and define TMP195 and TMP269 as a novel class of NRF2 activators that function by suppressing the enzymatic activity of an epigenetic regulator.

Current Status and Challenges of NRF2 as a Potential Therapeutic Target for Diabetic Cardiomyopathy

Diabetic cardiomyopathy is one of the main causes of heart failure and death in patients with diabetes mellitus. Reactive oxygen species produced excessively in diabetes mellitus cause necrosis, apoptosis, ferroptosis, inflammation, and fibrosis of the myocardium as well as impair the cardiac structure and function. It is increasingly clear that oxidative stress is a principal cause of diabetic cardiomyopathy. The transcription factor nuclear factor-erythroid 2 p45-related factor 2 (NRF2) activates the transcription of more than 200 genes in the human genome. Most of the proteins translated from these genes possess anti-oxidant, anti-inflammatory, anti-apoptotic, anti-ferroptotic, and anti-fibrotic actions. There is a growing body of evidence indicating that NRF2 and its target genes are crucial in preventing high glucose-induced oxidative damage in diabetic cardiomyopathy. Recently, many natural and synthetic activators of NRF2 are shown to possess promising therapeutic effects on diabetic cardiomyopathy in animal models of diabetic cardiomyopathy. Targeting NRF2 signaling by pharmacological entities is a potential approach to ameliorating diabetic cardiomyopathy. However, the persistent high expression of NRF2 in cancer tissues also protects the growth of cancer cells. This "dark side" of NRF2 increases the challenges of using NRF2 activators to treat diabetic cardiomyopathy. In addition, some NRF2 activators were found to have off-target effects. In this review, we summarize the current status and challenges of NRF2 as a potential therapeutic target for diabetic cardiomyopathy.

Luteolin Attenuates Cardiac Ischemia/Reperfusion Injury in Diabetic Rats by Modulating Nrf2 Antioxidative Function

Luteolin has been reported to attenuate ischemia/reperfusion (I/R) injury in the diabetic heart through endothelial nitric oxide synthase- (eNOS-) related antioxidative response. Though the nuclear factor erythroid 2-related factor 2 (Nrf2) is regarded as a key endogenous factor to reduce diabetic oxidative stress, whether luteolin reduces cardiac I/R injury in the diabetic heart via enhancing Nrf2 function needs to be clarified. We hypothesized that pretreatment with luteolin could alleviate cardiac I/R injury in the diabetic heart by affecting the eNOS/Nrf2 signaling pathway. The diabetic rat was produced by a single injection of streptozotocin (65 mg/kg, i.p.) for 6 weeks, and then, luteolin (100 mg/kg/day, i.g.), eNOS inhibitor L-NAME, or Nrf2 inhibitor brusatol was administered for the succedent 2 weeks. After that, the isolated rat heart was exposed to 30 min of global ischemia and 120 min of reperfusion to establish I/R injury. Luteolin markedly ameliorated cardiac function and myocardial viability; upregulated expressions of heme oxygenase-1, superoxide dismutase, glutathione peroxidase, and catalase; and reduced myocardial lactate dehydrogenase release, malondialdehyde, and 8-hydroxydeoxyguanosine in the diabetic I/R heart. All these ameliorating effects of luteolin were significantly reversed by L-NAME or brusatol. Luteolin also markedly reduced S-nitrosylation of Kelch-like ECH-associated protein 1 (Keap1) and upregulated Nrf2 and its transcriptional activity. This effect of luteolin on Keap1/Nrf2 signaling was attenuated by L-NAME. These data reveal that luteolin protects the diabetic heart against I/R injury by enhancing eNOS-mediated S-nitrosylation of Keap1, with subsequent upregulation of Nrf2 and the Nrf2-related antioxidative signaling pathway.

Sulforaphane - role in aging and neurodegeneration

In the last several years, numerous molecules derived from plants and vegetables have been tested for their antioxidant, anti-inflammatory, and anti-aging properties. One of them is sulforaphane (SFN), an isothiocyanate present in cruciferous vegetables. SFN activates the antioxidant and anti-inflammatory responses by inducing Nrf2 pathway and inhibiting NF-κB. It also has an epigenetic effect by inhibiting HDAC and DNA methyltransferases and modifies mitochondrial dynamics. Moreover, SFN preserves proteome homeostasis (proteostasis) by activating the proteasome, which has been shown to lead to increased cellular lifespan and prevent neurodegeneration. In this review, we describe some of the molecular and physical characteristics of SFN, its mechanisms of action, and the effects that SFN treatment induces in order to discuss its relevance as a "miraculous" drug to prevent aging and neurodegeneration.

Proteasome biology and therapeutics in cardiac diseases

The ubiquitin proteasome system (UPS) is the major pathway for intracellular protein degradation in most organs, including the heart. UPS controls many fundamental biological processes such as cell cycle, cell division, immune responses, antigen presentation, apoptosis, and cell signaling. The UPS not only degrades substrates but also regulates activity of gene transcription at the post-transcription level. Emerging evidence suggests that impairment of UPS function is sufficient to cause a number of cardiac diseases, including heart failure, cardiomyopathies, hypertrophy, atrophy, ischemia-reperfusion, and atherosclerosis. Alterations in the expression of UPS components, changes in proteasomal peptidase activities and increased ubiquitinated and oxidized proteins have also been detected in diabetic cardiomyopathy (DCM). However, the pathophysiological role of the UPS in DCM has not been examined. Recently, in vitro and in vivo studies have proven highly valuable in assessing effects of various stressors on the UPS and, in some cases, suggesting a causal link between defective protein clearance and disease phenotypes in different cardiac diseases, including DCM. Translation of these findings to human disease can be greatly strengthened by corroboration of discoveries from experimental model systems using human heart tissue from well-defined patient populations. This review will summarize the general role of the UPS in different cardiac diseases, with major focus on DCM, and on recent advances in therapeutic development.

Rosmarinic acid exerts an antagonistic effect on vascular calcification by regulating the Nrf2 signalling pathway

Vascular calcification (VC) is a process in which calcium phosphate crystals deposit within the intima and middle membrane of the vascular wall. Rosmarinic acid (RA) is a common phenolic compound. It possesses antioxidation, anti-inflammatory, antimicrobial effects. Our experiment aims to investigate the role and molecular mechanism of RA in VC. Rats were fed high-fat feed and injected with vitamin D3 to establish a VC model. β-Glyerophosphate (β GP) was selected to stimulate rat aortic smooth muscle cells (VSMCs) in order to establish the cell calcification model. Kits were used to detect the antioxidant index and calcification index. RA significantly reduced the levels of ALP, MDA, Ca, and P but increased SOD levels. Quantitative real-time polymerase chain reaction (RT-qPCR) and western blot analysis were used to detect various antioxidant-related genes and calcified genes on an mRNA and protein level. The results showed that nuclear factor red cell-2 related factors (Nrf2), haem oxygenase-1 (HO-1), NAD(P)H quinone dehydrogenase (NQO1), and osteoprotegerin (OPG) were up regulated by RA at both the mRNA and protein levels, but kelch-like ECH-associated protein 1 (Keap1), nuclear factor kappa B(NF-κB), cadherin associated protein (β-catenin) and osteogenic transcription factor (Runx2) expression at both the mRNA and protein levels was significantly inhibited. Microscopic examination showed that RA significantly decreased the content of calcified nodules and the production of reactive oxygen species (ROS). When Nrf2 is disturbed, the role of RA is significantly blocked. Our results showed that RA can improve VC by regulating the Nrf2 pathway.

Sulforaphane Protect Against Cadmium-Induced Oxidative Damage in mouse Leydigs Cells by Activating Nrf2/ARE Signaling Pathway

Cadmium (Cd) is harmful for humans and animals, especially for the reproductive system. However, the mechanism of its toxicity has not been elucidated, and how to alleviate its toxicity is very important. This study aimed to explore the role and mechanism of action of sulforaphane (SFN) in protecting mouse Leydigs (TM3) cells from cadmium (Cd)-induced damage. The half-maximal inhibitory concentration (IC₅₀) of Cd and the safe doses of SFN were determined using a methyl thiazolyl tetrazolium (MTT) assay. The testosterone secretion from TM3 cells was measured using the enzyme-linked immunosorbent assay. The intracellular oxidative stress was evaluated using corresponding kits. The cell apoptosis was detected using flow cytometry. The mRNA expression of genes associated with NF-E2-related factor 2 (Nrf2)/antioxidant response element (ARE) signaling was detected using reverse transcription–polymerase chain reaction, including Nrf2, heme oxygenase I (HO-1), glutathione peroxidase (GSH-Px), NAD(P)H:quinone acceptor oxidoreductase 1 (NQO1), and γ-glutamylcysteine synthetase (γ-GCS). The protein expression of Nrf2, GSH-Px, HO-1, γ-GCS, and NQO1 was detected using Western blot analysis. The results showed that the IC₅₀ of Cd to TM3 cells was 51.4 µmol/L. SFN reduced the release of lactate dehydrogenase from Cd-exposed cells. Cd + SFN 2.5 treatment significantly elevated testosterone concentration compared with the Cd group (p < 0.05). SFN significantly increased total superoxide dismutase (T-SOD) and GSH-Px activity and GSH content in Cd-treated cells (p < 0.05; p < 0.01), inhibited the production of malondialdehyde or reactive oxygen species caused by Cd (p < 0.05; p < 0.01), and reduced the apoptotic rate of Cd-induced TM3 cells (p < 0.01). SFN upregulated the mRNA expression of Nrf2, GSH-Px, HO-1, NQO1, and γ-GCS in Cd-treated cells, indicating the protective effect of SFN against Cd-induced oxidative stress or cell apoptosis by activating the Nrf2/ARE signaling pathway.

Lycopene protects against pressure overload-induced cardiac hypertrophy by attenuating oxidative stress

Oxidative stress is considered an important pathogenic process of cardiac hypertrophy. Lycopene is a kind of carotenoid antioxidant that protects the cardiovascular system, so we hypothesized that lycopene might inhibit cardiac hypertrophy by attenuating oxidative stress. Phenylephrine and pressure overload were used to set up the hypertrophic models in vitro and in vivo respectively. Our data revealed that treatment with lycopene can significantly block pressure overload-induced cardiac hypertrophy in in vitro and in vivo studies. Further studies demonstrated that lycopene can reverse the increase in reactive oxygen species (ROS) generation during the process of hypertrophy and can retard the activation of ROS-dependent pro-hypertrophic MAPK and Akt signaling pathways. In addition, protective effects of lycopene on the permeability transition pore opening in neonatal cardiomyocytes were observed. Moreover, we demonstrated that lycopene restored impaired antioxidant response element (ARE) activity and activated ARE-driven expression of antioxidant genes. Consequently, our findings indicated that lycopene inhibited cardiac hypertrophy by suppressing ROS-dependent mechanisms.

Metformin-decavanadate treatment ameliorates hyperglycemia and redox balance of the liver and muscle in a rat model of alloxan-induced diabetes

MetfDeca treatment ameliorate glucose and insulin levels, and reduce the levels of oxidized glutathione, reactive oxygen species, malondialdehyde, and 4-hydroxyalkenal; the superoxide and catalase activities, and glutathione levels were regulated.

Activation of Nrf2 signaling by natural products-can it alleviate diabetes?

Type 2 diabetes mellitus (DM) has reached pandemic proportions and effective prevention strategies are wanted. Its onset is accompanied by cellular distress, the nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor boosting cytoprotective responses, and many phytochemicals activate Nrf2 signaling. Thus, Nrf2 activation by natural products could presumably alleviate DM. We summarize function, regulation and exogenous activation of Nrf2, as well as diabetes-linked and Nrf2-susceptible forms of cellular stress. The reported amelioration of insulin resistance, β-cell dysfunction and diabetic complications by activated Nrf2 as well as the status quo of Nrf2 in precision medicine for DM are reviewed.

Nrf2, a novel molecular target to reduce type 1 diabetes associated secondary complications: The basic considerations

Oxidative stress and inflammation are the mediators of diabetes and related secondary complications. Oxidative stress arises because of the excessive production of reactive oxygen species and diminished antioxidant production due to impaired Nrf2 activation, the master regulator of endogenous antioxidant. It has been established from various animal models that the transcription factor Nrf2 provides cytoprotection, ameliorates oxidative stress, inflammation and delays the progression of diabetes and its associated complications. Whereas, deletion of the transcription factor Nrf2 amplifies tissue level pathogenic alterations. In addition, Nrf2 also regulates the expression of numerous cellular defensive genes and protects against oxidative stress-mediated injuries in diabetes. The present review provides an overview on the role of Nrf2 in type 1 diabetes and explores if it could be a potential target for the treatment of diabetes and related complications. Further, the rationality of different agent's intervention has been discussed to mitigate organ damages induced by diabetes.

New highlights on the health-improving effects of sulforaphane

In this paper, we review recent evidence about the beneficial effects of sulforaphane (SFN), which is the most studied member of isothiocyanates, on both in vivo and in vitro models of different diseases, mainly diabetes and cancer. The role of SFN on oxidative stress, inflammation, and metabolism is discussed, with emphasis on those nuclear factor E2-related factor 2 (Nrf2) pathway-mediated mechanisms. In the case of the anti-inflammatory effects of SFN, the point of convergence seems to be the downregulation of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), with the consequent amelioration of other pathogenic processes such as hypertrophy and fibrosis. We emphasized that SFN shows opposite effects in normal and cancer cells at many levels; for instance, while in normal cells it has protective actions, in cancer cells it blocks the induction of factors related to the malignity of tumors, diminishes their development, and induces cell death. SFN is able to promote apoptosis in cancer cells by many mechanisms, the production of reactive oxygen species being one of the most relevant ones. Given its properties, SFN could be considered as a phytochemical at the forefront of natural medicine.

Nrf2 expression and function, but not MT expression, is indispensable for sulforaphane-mediated protection against intermittent hypoxia-induced cardiomyopathy in mice

We reported previously that nuclear factor erythroid 2-related factor 2 (Nrf2) and metallothionein (MT) play critical roles in preventing intermittent hypoxia (IH)-induced cardiomyopathy. In addition, positive feedback regulation between Nrf2 and MT is required for the efficient compensative responses of the heart to IH. As an activator of Nrf2, sulforaphane (SFN) has attracted attention as a potential protective agent against cardiovascular disease. Here, we investigated whether SFN can up-regulate cardiac Nrf2 expression and function, as well as MT expression, to prevent IH-induced cardiomyopathy, and if so, whether Nrf2 and MT are indispensable for this preventive effect. Nrf2-knock-out (Nrf2-KO) or MT-KO mice and their wild-type (WT) equivalents were exposed to IH for 4 weeks with or without SFN treatment. SFN almost completely prevented IH-induced cardiomyopathy in WT mice, and this preventive effect was abolished in Nrf2-KO mice but retained in MT-KO mice. In IH-exposed WT mice, SFN induced significant increases in the expression levels of Nrf2 and its downstream antioxidant target genes, as well as those of MT, but these effects were not seen in IH-exposed Nrf2-KO mice. By contrast, KO of MT did not affect the ability of SFN to up-regulate the expression of Nrf2 and its downstream antioxidant targets. These results suggest that SFN-induced MT expression is Nrf2-dependent, and SFN prevents IH-induced cardiomyopathy in a Nrf2-dependent manner, for which MT is dispensable. This study provides important information that is relevant to the potential use of SFN to prevent IH-induced cardiomyopathy.

Food Bioactive HDAC Inhibitors in the Epigenetic Regulation of Heart Failure

Approximately 5.7 million U.S. adults have been diagnosed with heart failure (HF). More concerning is that one in nine U.S. deaths included HF as a contributing cause. Current HF drugs (e.g., β-blockers, ACEi) target intracellular signaling cascades downstream of cell surface receptors to prevent cardiac pump dysfunction. However, these drugs fail to target other redundant intracellular signaling pathways and, therefore, limit drug efficacy. As such, it has been postulated that compounds designed to target shared downstream mediators of these signaling pathways would be more efficacious for the treatment of HF. Histone deacetylation has been linked as a key pathogenetic element for the development of HF. Lysine residues undergo diverse and reversible post-translational modifications that include acetylation and have historically been studied as epigenetic modifiers of histone tails within chromatin that provide an important mechanism for regulating gene expression. Of recent, bioactive compounds within our diet have been linked to the regulation of gene expression, in part, through regulation of the epi-genome. It has been reported that food bioactives regulate histone acetylation via direct regulation of writer (histone acetyl transferases, HATs) and eraser (histone deacetylases, HDACs) proteins. Therefore, bioactive food compounds offer unique therapeutic strategies as epigenetic modifiers of heart failure. This review will highlight food bio-actives as modifiers of histone deacetylase activity in the heart.

Exogenous Pancreatic Kallikrein Improves Diabetic Cardiomyopathy in Streptozotocin-Induced Diabetes

Aims: To evaluate the protective effects of exogenous pancreatic kallikrein (PKK) treatment on diabetic cardiomyopathy (DCM) and explore the underlying mechanisms. Methods and Results: Streptozotocin (STZ)-induced diabetic rats, a type 1 diabetic model, were treated with either PKK or saline for 12 weeks. Non-diabetic rats were used as controls. PKK administration attenuated the mitochondria swelling, Z line misalignments, myofibrosis and interstitial collagen accumulation in diabetic myocardial tissue. The oxidative stress imbalance including increased nitrotyrosine, decreased anti-oxidative components such as nuclear receptor nuclear factor like 2 (Nrf2), glutathione peroxidase 1(GPx-1), catalase (CAT) and superoxide dismutase (SOD), were recovered in the heart of PKK-treated diabetic rats. In diabetic rats, protein expression of TGF-β1 and accumulation of collagen I in the heart tissues was decreased after PKK administration. Markers for inflammation were decreased in diabetic rats by PKK treatment. Compared to diabetic rats, PKK reversed the degradation of IκB-α, an inhibitive element of heterotrimer nuclear factor kappa B (NF-κB). The endothelial nitric oxide synthase (eNOS) protein and myocardial nitrate/nitrite were impaired in the heart of diabetic rats, which, however, were restored after PKK treatment. The sarcoplasmic reticulum Ca²⁺-ATPase 2 (SERCA2) and phospholamban (PLN) were mishandled in diabetic rats, while were rectified in PKK-treated diabetic rats. The plasma NT-proBNP level was increased in diabetic rats while was reduced with PKK treatment. Conclusion: PKK protects against DCM via reducing fibrosis, inflammation, and oxidative stress, promoting nitric oxide production, as well as restoring the function of the calcium channel.

A Systematic Review on the Protective Effect of N-Acetyl Cysteine Against Diabetes-Associated Cardiovascular Complications

INTRODUCTION

Heart failure is the leading cause of death in patients with diabetes. No treatment currently exists to specifically protect these patients at risk of developing cardiovascular complications. Accelerated oxidative stress-induced tissue damage due to persistent hyperglycemia is one of the major factors implicated in deteriorated cardiac function within a diabetic state. N-acetyl cysteine (NAC), through its enhanced capacity to endogenously synthesize glutathione, a potent antioxidant, has displayed abundant health-promoting properties and has a favorable safety profile.

OBJECTIVE

An increasing number of experimental studies have reported on the strong ameliorative properties of NAC. We systematically reviewed the data on the cardioprotective potential of this compound to provide an informative summary.

METHODS

Two independent reviewers systematically searched major databases, including PubMed, Cochrane Library, Google scholar, and Embase for available studies reporting on the ameliorative effects of NAC as a monotherapy or in combination with other therapies against diabetes-associated cardiovascular complications. We used the ARRIVE and JBI appraisal guidelines to assess the quality of individual studies included in the review. A meta-analysis could not be performed because the included studies were heterogeneous and data from randomized clinical trials were unavailable.

RESULTS

Most studies support the ameliorative potential of NAC against a number of diabetes-associated complications, including oxidative stress. We discuss future prospects, such as identification of additional molecular mechanisms implicated in diabetes-induced cardiac damage, and highlight limitations, such as insufficient studies reporting on the comparative effect of NAC with common glucose-lowering therapies. Information on the comparative analysis of NAC, in terms of dose selection, administration mode, and its effect on different cardiovascular-related markers is important for translation into clinical studies.

CONCLUSIONS

NAC exhibits strong potential for the protection of the diabetic heart at risk of myocardial infarction through inhibition of oxidative stress. The effect of NAC in preventing both ischemia and non-ischemic-associated cardiac damage is also of interest. Consistency in dose selection in most studies reported remains important in dose translation for clinical relevance.

Knockout of tnni1b in zebrafish causes defects in atrioventricular valve development via the inhibition of the myocardial wnt signaling pathway

The proper development of atrioventricular (AV) valves is critical for heart morphogenesis and for the formation of the cardiac conduction system. Defects in AV valve development are the most common type of congenital heart defect. Cardiac troponin I ( ctnni), a structural and regulatory protein involved in cardiac muscle contraction, is a subunit of the troponin complex, but the functions and molecular mechanisms of ctnni during early heart development remain unclear. We created a knockout zebrafish model in which troponin I type 1b ( tnni1b) ( Tnni-HC, heart and craniofacial) was deleted using the clustered regularly interspaced short palindromic repeat/clustered regularly interspaced short palindromic repeat-associated protein system. In the homozygous mutant, the embryos showed severe pericardial edema, malformation of the heart tube, reduction of heart rate without contraction and with almost no blood flow, heart cavity congestion, and lack of an endocardial ring or valve leaflet, resulting in 88.8 ± 6.0% lethality at 7 d postfertilization. Deletion of tnni1b caused the abnormal expression of several markers involved in AV valve development, including bmp4, cspg2, has2, notch1b, spp1, and Alcam. Myocardial re-expression of tnni1b in mutants partially rescued the pericardial edema phenotype and AV canal (AVC) developmental defects. We further showed that tnni1b knockout in zebrafish and ctnni knockdown in rat h9c2 myocardial cells inhibited cardiac wnt signaling and that myocardial reactivation of wnt signaling partially rescued the abnormal expression of AVC markers caused by the tnni1b deletion. Taken together, our data suggest that tnni1b plays a vital role in zebrafish AV valve development by regulating the myocardial wnt signaling pathway.-Cai, C., Sang, C., Du, J., Jia, H., Tu, J., Wan, Q., Bao, B., Xie, S., Huang, Y., Li, A., Li, J., Yang, K., Wang, S., Lu, Q. Knockout of tnni1b in zebrafish causes defects in atrioventricular valve development via the inhibition of myocardial wnt signaling pathway.

Concerted redox modulation by sulforaphane alleviates diabetes and cardiometabolic syndrome

Diabetes and cardiometabolic disorders such as hypertension and obesity are major risk factors for the development of cardiovascular disease, with a wealth of evidence suggesting that oxidative stress is linked to the initiation and pathogenesis of these disease processes. With yearly increases in the global incidence of cardiovascular diseases (CVD) and diabetes, numerous studies have focused on characterizing whether upregulating antioxidant defenses through exogenous antioxidants (e.g. vitamin E, vitamin C) or activation of endogenous defenses (e.g. the Nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidant defense pathway) may be of benefit. The dietary isothiocyanate sulforaphane (SFN) is currently the subject of several clinical trials for a variety of disease states, including the evaluation of its therapeutic potential to ameliorate diabetic and cardiometabolic complications. SFN is a well characterized and potent Nrf2 inducer, however recent studies suggest its protective actions may be in part mediated by its modulation of various pro-inflammatory (e.g. Nuclear factor-kappa B (NFκB)) and metabolic (e.g. Peroxisome Proliferator-Activator Receptor Gamma (PPARγ)) signaling pathways. The focus of this review is to provide a detailed analysis of the known mechanisms by which SFN modulates Nrf2, NFκB and PPARγ signaling and crosstalk and to provide a critical evaluation of the evidence linking these transcriptional pathways with diabetic and cardiometabolic complications and SFN mediated cytoprotection. To allow comparison between rodent and human studies, we discuss the published bioavailability of SFN metabolites achieved in rodents and man in the context of Nrf2, NFκB and PPARγ signaling. Furthermore, we provide an update on the functional outcomes and implicated signaling pathways reported in recent clinical trials with SFN in Type 2 diabetic patients.

Sulforaphane protection against the development of doxorubicin-induced chronic heart failure is associated with Nrf2 Upregulation

BACKGROUND

Doxorubicin (DOX) is an anthracycline antitumor drug. However, its clinical use is limited by dose-dependent cardiotoxicity and even progresses to chronic heart failure (CHF).

OBJECTIVE

This study aims to investigate whether the Nrf2 activator, sulforaphane (SFN), can prevent DOX-induced CHF.

METHODS

Male Sprague-Dawley rats which received treatment for 6 weeks were divided into four groups (n=30 per group): control, SFN, DOX and DOX plus SFN group.

RESULTS

Results revealed that DOX induced progressive cardiac damage as indicated by increased cardiac injury markers, cardiac inflammation, fibrosis and oxidative stress. SFN significantly prevented DOX-induced progressive cardiac dysfunction between 2-6 weeks and prevented DOX-induced cardiac function deterioration. Furthermore, it significantly decreased ejection fraction and increased the expression of brain natriuretic peptide. SFN also almost completely prevented DOX-induced cardiac oxidative stress, inflammation and fibrosis. SFN upregulated NF-E2-related factor 2 (Nrf2) expression and transcription activity, which was reflected by the increased mRNA expression of Nrf2 and its downstream genes. Furthermore, in cultured H9c2 cardiomyocytes, the protective effect of SFN against DOX-induced fibrotic and inflammatory responses was abolished by Nrf2 silencing.

CONCLUSION

We arrived at the conclusion that DOX-induced CHF can be prevented by SFN through the upregulation of Nrf2 expression and transcriptional function.

Sulforaphane prevents angiotensin II-induced cardiomyopathy by activation of Nrf2 via stimulating the Akt/GSK-3ß/Fyn pathway

AIMS

Activation of nuclear factor erythroid 2-related factor 2 (Nrf2) by sulforaphane (SFN) protects from, and deletion of the Nrf2 gene exaggerates, diabetic cardiomyopathy. Angiotensin II (Ang II) plays a critical role in the development of diabetic cardiomyopathy. Therefore, whether SFN prevents Ang II-induced cardiomyopathy through activation of Nrf2 was examined using wild-type, global deletion of Nrf2 gene (Nrf2-KO) and cardiomyocyte-specific overexpression of Nrf2 gene (Nrf2-TG) mice.

METHODS AND RESULTS

Administration of a subpressor dose of Ang II to wild-type mice induced cardiac oxidative stress, inflammation, remodeling and dysfunction, all of which could be prevented by SFN treatment with Nrf2 up-regulation and activation. Nrf2-KO mice are susceptible, and Nrf2-TG mice are resistant, respectively, to Ang II-induced cardiomyopathy. Meanwhile, the ability of SFN to protect against Ang II-induced cardiac damage was lost in Nrf2-KO mice. Up-regulation and activation of Nrf2 by SFN is accompanied by activation of Akt, inhibition of glycogen synthase kinase (GSK)-3β, and accumulation of Fyn in nuclei. In vitro up-regulation of Nrf2 by SFN was abolished and nuclear Fyn accumulation was increased when cardiac cells were exposed to a PI3K inhibitor or GSK-3β-specific activator.

CONCLUSION

These results suggest that Nrf2 plays a central role in the prevention of Ang II-induced cardiomyopathy, and SFN prevents Ang II-induced cardiomyopathy partially via the Akt/GSK-3β/Fyn-mediated Nrf2 activation.

Protection by dimethyl fumarate against diabetic cardiomyopathy in type 1 diabetic mice likely via activation of nuclear factor erythroid-2 related factor 2

Oxidative stress and inflammation play key roles in the development of diabetic cardiomyopathy (DCM). Dimethyl fumarate (DMF), an FDA approved medicine for relapsing multiple sclerosis, has manifested its antioxidant and anti-inflammatory function mostly in the central nervous system. In this study, we investigated whether DMF could attenuate the development of DCM. Type 1 diabetes mouse model was established using multiple low-dose streptozotocin, and the diabetic mice were treated with DMF (10 mg/kg body weight) for 3 months. Cardiac functions were determined using echocardiography. Oxidative stress, pro-inflammatory cytokines and pro-fibrotic markers were determined with commercially available kits, real-time quantitative PCR or western blot techniques. DCM was characterized by diminished cardiac function, accompanied by oxidative stress and enhanced expression of pro-inflammatory cytokines. Diabetic cardiac tissue exhibited marked fibrosis, revealed by extracellular matrix deposition as determined by Sirius red staining of the myocardial tissues. Furthermore, Nrf2 and its downstream effectors were repressed in diabetic myocardium. On the contrary, diabetic animals treated with DMF exhibited blunted oxidative stress, inflammation, fibrosis and this correlated with Nrf2 activation. Our findings suggest that DMF could potentially thwart diabetes-induced myocardial tissue injury, likely via activation of Nrf2 function, providing firm impetus for future repurposing of DMF in the management of DCM.

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.

Sulforaphane attenuates pulmonary fibrosis by inhibiting the epithelial-mesenchymal transition

Background

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal disease with no effective treatment. The epithelial-mesenchymal transition (EMT) is a critical stage during the development of fibrosis. To assess the effect of sulforaphane (SFN) on the EMT and fibrosis using an in vitro transforming growth factor (TGF)-β1-induced model and an in vivo bleomycin (BLM)-induced model.

Methods

In vitro studies, cell viability, and cytotoxicity were measured using a Cell Counting Kit-8. The functional TGF-β1-induced EMT and fibrosis were assessed using western blotting and a quantitative real-time polymerase chain reaction. The lungs were analyzed histopathologically in vivo using hematoxylin and eosin and Masson’s trichrome staining. The BLM-induced fibrosis was characterized by western blotting and immunohistochemical analyses for fibronectin, TGF-β1, E-cadherin (E-cad), and α-smooth muscle actin (SMA) in lung tissues.

Results

SFN reversed mesenchymal-like changes induced by TGF-β1 and restored cells to their epithelial-like morphology. The results confirmed that the expression of the epithelial marker, E-cadherin, increased after SFN treatment, while expression of the mesenchymal markers, N-cadherin, vimentin, and α-SMA decreased in A549 cells after SFN treatment. In addition, SFN inhibited TGF-β1-induced mRNA expression of the EMT-related transcription factors, Slug, Snail, and Twist. The SFN treatment attenuated TGF-β1-induced expression of fibrosis-related proteins, such as fibronection, collagen I, collagen IV, and α-SMA in MRC-5 cells. Furthermore, SFN reduced the TGF-β1-induced phosphorylation of SMAD2/3 protein in A549 cells and MRC-5 cells. BLM induced fibrosis in mouse lungs that was also attenuated by SFN treatment, and SFN treatment decreased BLM-induced fibronectin expression, TGF-β1 expression, and the levels of collagen I in the lungs of mice.

Conclusions

SFN showed a significant anti-fibrotic effect in TGF-β-treated cell lines and BLM-induced fibrosis in mice. These findings showed that SFN has anti-fibrotic activity that may be considered in the treatment of IPF.

Electronic supplementary material

The online version of this article (10.1186/s40360-018-0204-7) contains supplementary material, which is available to authorized users.

Kaempferol attenuates hyperglycemia-induced cardiac injuries by inhibiting inflammatory responses and oxidative stress

PURPOSE

Suppression of inflammation and oxidative stress is an attractive strategy to against diabetic cardiomyopathy (DCM). Kaempferol (KPF) exerts both anti-inflammatory and antioxidant pharmacological properties. However, little is known about the effect of KPF on protecting myocardial injury in diabetes. The present study aimed to investigate the effect of KPF on DCM and underlying mechanism.

METHODS

Anti-inflammation and anti-oxidative stress activities of KPF were evaluated in H9c2 cells or primary cardiomyocytes by real-time quantitate PCR, immunoblotting, immunofluorescence, ELISA, and FACS. Streptozotocin (STZ)-induced type 1 diabetes mellitus mice were constructed. Corresponding to experiments in vitro, the therapeutic effect of KPF was also assessed using heart tissues from mice.

RESULTS

KPF significantly inhibited high glocose (HG) induced expression of inflammatory cytokines and generation of ROS, leading to reduced fibrotic responses and cell apoptosis in vitro. KPF mediated DCM protective effects through inhibiting nuclear factor-κB (NF-κB) nucleus translocation and activating nuclear factor-erythroid 2 p45-related factor-2 (Nrf-2). In STZ-induced type 1 diabetic mouse model, KPF prevented diabetes-induced cardiac fibrosis and apoptosis. These changes were also accompanied by reducing inflammation and oxidative stress in diabetic mice hearts.

CONCLUSION

KPF is a potential therapeutic agent for the treatment of DCM, mechanically linked to inhibition of NF-κB and Nrf-2 activation.

Sulforaphane, a Natural Isothiocyanate Compound, Improves Cardiac Function and Remodeling by Inhibiting Oxidative Stress and Inflammation in a Rabbit Model of Chronic Heart Failure

Background

The aim of this study was to investigate the effects of sulforaphane (SFN), a natural isothiocyanate compound, in a rabbit ascending aortic cerclage model of chronic heart failure (CHF).

Material/Methods

Thirty New Zealand White rabbits were divided into the sham operation group (n=10), the CHF group (n=10), and the CHF + SFN group (n=10) treated with subcutaneous SFN (0.5 mg/kg) for five days per week for 12 weeks. After 12 weeks, echocardiography and biometric analysis were performed, followed by the examination of the rabbit hearts. Enzyme-linked immunosorbent assay (ELISA) and Western blot were used to detect levels of inflammatory cytokines, superoxide dismutase (SOD), and malondialdehyde (MDA).

Results

In the CHF group, compared with the sham operation group, there was an increase in the heart weight to body weight ratio (HW/BW), the left ventricular weight to body weight ratio (LVW/BW), the left ventricular end diastolic diameter (LVEDD), the left ventricular end systolic diameter (LVESD), plasma brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) levels, the cardiac collagen volume fraction (CVF), apoptotic index, expression levels of collagen I, collagen III, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and malondialdehyde (MDA) in the myocardial tissue, and a decrease in the left ventricular shortening fraction (LVFS) and left ventricular ejection fraction (LVEF), and cardiac superoxide dismutase (SOD) activity. These changes were corrected in the SFN-treated group.

Conclusions

In a rabbit model of CHF, treatment with SFN improved cardiac function and remodeling by inhibiting oxidative stress and inflammation.

Fibroblast growth factor-21 prevents diabetic cardiomyopathy via AMPK-mediated antioxidation and lipid-lowering effects in the heart

Our previous studies showed that both exogenous and endogenous FGF21 inhibited cardiac apoptosis at the early stage of type 1 diabetes. Whether FGF21 induces preventive effect on type 2 diabetes-induced cardiomyopathy was investigated in the present study. High-fat-diet/streptozotocin-induced type 2 diabetes was established in both wild-type (WT) and FGF21-knockout (FGF21-KO) mice followed by treating with FGF21 for 4 months. Diabetic cardiomyopathy (DCM) was diagnosed by significant cardiac dysfunction, remodeling, and cardiac lipid accumulation associated with increased apoptosis, inflammation, and oxidative stress, which was aggravated in FGF21-KO mice. However, the cardiac damage above was prevented by administration of FGF21. Further studies demonstrated that the metabolic regulating effect of FGF21 is not enough, contributing to FGF21-induced significant cardiac protection under diabetic conditions. Therefore, other protective mechanisms must exist. The in vivo cardiac damage was mimicked in primary neonatal or adult mouse cardiomyocytes treated with HG/Pal, which was inhibited by FGF21 treatment. Knockdown of AMPKα1/2, AKT2, or NRF2 with their siRNAs revealed that FGF21 protected cardiomyocytes from HG/Pal partially via upregulating AMPK–AKT2–NRF2-mediated antioxidative pathway. Additionally, knockdown of AMPK suppressed fatty acid β-oxidation via inhibition of ACC–CPT-1 pathway. And, inhibition of fatty acid β-oxidation partially blocked FGF21-induced protection in cardiomyocytes. Further, in vitro and in vivo studies indicated that FGF21-induced cardiac protection against type 2 diabetes was mainly attributed to lipotoxicity rather than glucose toxicity. These results demonstrate that FGF21 functions physiologically and pharmacologically to prevent type 2 diabetic lipotoxicity-induced cardiomyopathy through activation of both AMPK–AKT2–NRF2-mediated antioxidative pathway and AMPK–ACC–CPT-1-mediated lipid-lowering effect in the heart.

SP600125 suppresses Keap1 expression and results in NRF2-mediated prevention of diabetic nephropathy

c-Jun N-terminal kinase (JNK) contributes to the pathogenesis of diabetic nephropathy (DN). The JNK inhibitor SP600125 was reported to ameliorate DN. However, the mechanism remained unclear. We previously reported that SP600125 activated nuclear factor erythroid 2-related factor 2 (NRF2), a governor of the cellular antioxidant defense system, in the aortas of the diabetic mice. Given the critical role of NRF2 in preventing DN, the present study aimed to test whether or not NRF2 is required for SP600125's protection against DN. To test the role of NRF2 in SP600125's effect, streptozotocin-induced C57BL/6 wild-type (WT) and Nrf2-knockout (KO) diabetic mice were treated in the presence or absence of SP600125, for 24 weeks. To explore the mechanism by which SP600125 activates NRF2, mouse mesangial cells (MMCs) were treated with high glucose (HG), in the presence or absence of either SP600125 or JNK siRNA. SP600125 significantly attenuated the diabetes-induced renal oxidative stress, inflammation, fibrosis, pathological change and dysfunction in the WT, but not the Nrf2 KO mice. SP600125 inactivated JNK, inhibited kelch-like ECH-associated protein 1 expression, preserved NRF2 protein and facilitated its nuclear translocation in the kidneys of the WT mice, the effects of which were similarly produced by either SP600125 or JNK siRNA in HG-treated MMCs. Further, both SP600125 and JNK siRNA alleviated HG-induced mesangial oxidative stress and expression of inflammatory and fibrotic genes. The present study demonstrates that NRF2 is required for SP600125's protection against DN. SP600125 activates NRF2 possibly via inhibition of JNK-induced Keap1 expression.

Nrf2 at the heart of oxidative stress and cardiac protection

The NFE2L2 gene encodes the transcription factor Nrf2 best known for regulating the expression of antioxidant and detoxification genes. Gene knockout approaches have demonstrated its universal cytoprotective features. While Nrf2 has been the topic of intensive research in cancer biology since its discovery in 1994, understanding the role of Nrf2 in cardiovascular disease has just begun. The literature concerning Nrf2 in experimental models of atherosclerosis, ischemia, reperfusion, cardiac hypertrophy, heart failure, and diabetes supports its cardiac protective character. In addition to antioxidant and detoxification genes, Nrf2 has been found to regulate genes participating in cell signaling, transcription, anabolic metabolism, autophagy, cell proliferation, extracellular matrix remodeling, and organ development, suggesting that Nrf2 governs damage resistance as well as wound repair and tissue remodeling. A long list of small molecules, most derived from natural products, have been characterized as Nrf2 inducers. These compounds disrupt Keap1-mediated Nrf2 ubquitination, thereby prohibiting proteasomal degradation and allowing Nrf2 protein to accumulate and translocate to the nucleus, where Nrf2 interacts with sMaf to bind to ARE in the promoter of genes. Recently alternative mechanisms driving Nrf2 protein increase have been revealed, including removal of Keap1 by autophagy due to p62/SQSTM1 binding, inhibition of βTrCP or Synoviolin/Hrd1-mediated ubiquitination of Nrf2, and de novo Nrf2 protein translation. We review here a large volume of literature reporting historical and recent discoveries about the function and regulation of Nrf2 gene. Multiple lines of evidence presented here support the potential of dialing up the Nrf2 pathway for cardiac protection in the clinic.

Inhibition of p53 prevents diabetic cardiomyopathy by preventing early-stage apoptosis and cell senescence, reduced glycolysis, and impaired angiogenesis

Elevated tumor suppressor p53 expression has been associated with heart diseases, including the diabetic heart. However, its precise role in the pathogenesis of diabetic cardiomyopathy (DCM) remains unclear. We hypothesized that the development of DCM is attributed to up-regulated p53-mediated both early cardiac cell death and persistent cell senescence, glycolytic and angiogenetic dysfunctions. The present study investigated the effect of p53 inhibition with its specific inhibitor pifithrin-α (PFT-α) on the pathogenesis of DCM and its associated mechanisms. Type 1 diabetes was induced with multiple low doses of streptozotocin. Both hyperglycemic and age-matched control mice were treated with and without PFT-α five times a week for 2 months and then sacrificed at 3 and 6 months post-diabetes. Treatment with PFT-α significantly prevented the progression of diabetes-induced cardiac remodeling and dysfunction (i.e., DCM). Mechanistically, the inhibition of p53 prevented the cardiac apoptosis during early-stage diabetes (0.5 month), attenuated diabetes-induced cell senescence (3 and 6 months), and improved both glycolytic and angiogenic defects by increasing hypoxia-induced factor (HIF)-1α protein stability and upregulating HIF-1α transcription of specific target genes at 3 and 6 months after diabetes. Therefore, the targeted inhibition of p53 in diabetic individuals may provide a novel approach for the prevention of DCM.

Effects of WD‑3 on tumor growth and the expression of integrin αvβ3 and ERK1/2 in mice bearing human gastric cancer using the 18F‑RGD PET/CT imaging system

Activation of the vitronectin receptor αvβ3 and the phosphorylation of extracellular signal‑regulated kinase (ERK)1/2 are critical events during tumor development and progression. The aim of the present study was to investigate the effects of WD‑3, a formula used in traditional Chinese medicine, on integrin αvβ3 and ERK1/2 expression in vivo using a nude mouse‑human gastric cancer xenograft model combined with non‑invasive, real‑time 18F‑Arg‑Gly‑Asp (RGD) positron emission tomography (PET)/computerized tomography (CT) imaging methods. SGC‑7901 human gastric cancer cells were subcutaneously injected into BALB/c nude mice. Following tumor development, animals were randomly assigned into the following 4 groups (n=6 mice/group): Control group (CG), Chinese medicine group (CMG), Western medicine group (WMG) and Chinese and Western medicine combination group (CMG + WMG). Mice in the CG and CMG received daily intragastric injections of 0.5 ml saline and 0.5 ml WD‑3, respectively. Mice in the WMG received an intravenous injection of albumin‑bound paclitaxel (25 mg/kg) on days 0, 2 and 4 Mice in the CMG + WMG received combination therapy of WD‑3 and albumin‑bound paclitaxel. Tumor growth was monitored using standard caliper technique and via PET imaging. 18F‑RGD PET/CT analysis was performed on days 3, 7, 18 and 24 following drug administration. Radioactivity uptake was measured and expressed as the percentage of injected dose (ID) per tissue weight (%ID/g) ​​ and the standardized uptake value (SUV). Animals were sacrificed at 30 days following treatment and tumor weight was measured. Immunohistochemistry was used to detect the expression of phosphorylated (p)‑ERK1/2 protein in tumor tissue samples. No statistically significant differences were observed in %ID/g and SUV among the various groups prior to treatment. At the end of treatment, mice in the CMG, WMG and CMG + WMG exhibited significantly reduced tumor mass when compared with mice in the CG. In addition, mice in the CMG and CMG + WMG demonstrated reduced %ID/g and SUV when compared with mice in the CG. Conversely, mice in the WMG exhibited no significant difference in %ID/g and SUV compared with the CG. Furthermore, p‑ERK1/2 expression was significantly reduced in mice from all treatment groups when compared with those in the CG. The results of the present study suggest that the traditional Chinese formula WD‑3 may inhibit gastric tumor growth, potentially via the downregulation of integrin αvβ3 and the inhibition of ERK1/2 phosphorylation in vivo.

Cardiac and renal upregulation of Nox2 and NF-κB and repression of Nox4 and Nrf2 in season- and diabetes-mediated models of vascular oxidative stress in guinea-pig and rat

The superoxide-forming NADPH oxidase homologues, Nox1, Nox2, and Nox5, seem to mediate the pro-atherosclerotic vascular phenotype. The hydrogen peroxide-forming Nox4 afforded vascular protection, likely via NF-E2-related factor-2 (Nrf2) activation and/or Nox2 downregulation in transgenic mice. We hypothesized that oxidative stress in the intact vasculature involves, aside from the upregulation of the superoxide-forming Noxs, the downregulation of the Nox4/Nrf2 pathway. Guinea-pigs and rats were studied either in winter or in summer, and the streptozotocin diabetic rats in winter. Plasma nitrite, and superoxide production by isolated hearts were measured, while frozen tissues served in biochemical analyses. Summer in both species and diabetes in rats downregulated myocardial Nox4 while reciprocally upregulating Nox2 and Nox5 in guinea-pigs, and Nox2 in rats. Simultaneously, myocardial Nrf2 activity and the expression of the Nrf2-directed heme oxygenase-1 and endothelial NO synthase were reduced while activity of the nuclear factor κB (NF-κB) and the expression of NF-κB-directed inducible NO synthase and the vascular cell adhesion molecule-1 were increased. Cardiac superoxide production was increased while plasma nitrite was decreased reciprocally. Analogous disregulation of Noxs, Nrf2, and NF-κB, occurred in diabetic rat kidneys. Given the diversity of the experimental settings and the uniform pattern of the responses, we speculate that: (1) chronic vascular oxidative stress is a nonspecific (model-, species-, organ-independent) response involving the induction of Nox2 (and Nox5 in guinea-pigs) and the NF-κB pathway, and the repression of Nox4 and the Nrf2 pathway; and (2) the systems Nox2-NF-κB and Nox4-Nrf2 regulate each other negatively.

Diminished stress resistance and defective adaptive homeostasis in age-related diseases

Adaptive homeostasis is defined as the transient expansion or contraction of the homeostatic range following exposure to subtoxic, non-damaging, signaling molecules or events, or the removal or cessation of such molecules or events (Mol. Aspects Med. (2016) 49, 1-7). Adaptive homeostasis allows us to transiently adapt (and then de-adapt) to fluctuating levels of internal and external stressors. The ability to cope with transient changes in internal and external environmental stress, however, diminishes with age. Declining adaptive homeostasis may make older people more susceptible to many diseases. Chronic oxidative stress and defective protein homeostasis (proteostasis) are two major factors associated with the etiology of age-related disorders. In the present paper, we review the contribution of impaired responses to oxidative stress and defective adaptive homeostasis in the development of age-associated diseases.

From the Cover: Alcohol Inhibition of the Enzymatic Activity of Glyceraldehyde 3-Phosphate Dehydrogenase Impairs Cardiac Glucose Utilization, Contributing to Alcoholic Cardiomyopathy

Heavy consumption of alcohol induces cardiomyopathy and is associated with metabolic changes in the heart. The role of altered metabolism in the development of alcoholic cardiomyopathy remains largely unknown but is examined in the present study. The effect of chronic alcohol consumption on cardiac damage was examined in mice fed an alcohol or isocaloric control diet for 2 months. Signaling pathways of alcohol-induced metabolic alteration and pathologic changes were examined in both animal hearts and H9c2 cell cultures. Compared with controls, the hearts from the alcohol-fed mice exhibited cardiac oxidative stress, cell death, a fibrotic response, hypertrophic remodeling, and the eventual development of cardiac dysfunction. All these detrimental effects could be ameliorated by superoxide dismutase mimic Mn (111) tetrakis 1-methyl 4-pyridylporphyrin pentachloride (MnTMPyP) therapy. A mechanistic study showed that chronic alcohol exposure enhanced the expression of proteins regulating fatty acid uptake but impaired the expression of proteins involved in mitochondrial fatty acid oxidation, which compensatively geared the heart to the suboptimal energy source, glucose. However, chronic alcohol exposure also impaired the glycolytic energy production step regulated by glyceraldehyde-3-phosphate dehydrogenase, which further feeds back to enhance glucose uptake signaling and the accumulation of glycolytic intermediate product fructose, resulting in aggravation of alcohol-induced cardiac oxidative stress, cell death, and remodeling. All these dysmetabolic alterations could be normalized by MnTMPyP treatment, along with significant improvement in cardiac cell death and remodeling. These results demonstrate that alcohol-induced oxidative stress and altered glucose metabolism are causal factors for the development of alcoholic cardiomyopathy.

Sulforaphane mitigates cadmium-induced toxicity pattern in human peripheral blood lymphocytes and monocytes

Cadmium (Cd) is a highly toxic and widely distributed heavy metal that induces various diseases in humans through environmental exposure. Therefore, alleviation of Cd-induced toxicity in living organisms is necessary. In this study, we investigated the protective role of sulforaphane on Cd-induced toxicity in human peripheral blood lymphocytes and monocytes. Sulforaphane did not show any major reduction in the viability of lymphocytes and monocytes. However, Cd treatment at a concentration of 50μM induced around 69% cell death. Treatment of IC₁₀-Cd and 100μM sulforaphane combination for 24 and 48h increased viability by 2 and 9% in cells subjected to Cd toxicity, respectively. In addition, IC₂₅ of Cd and 100μM sulforaphane combination recovered 17-20% of cell viability. Cd induced apoptotic and necrotic cell death. Sulforaphane treatment reduced Cd-induced cell death in lymphocytes and monocytes. Our results clearly indicate that when the cells were treated with Cd+sulforaphane combination, sulforaphane decreased the Cd-induced cytotoxic effect in lymphocytes and monocytes. In addition, sulforaphane concentration plays a major role in the alleviation of Cd-induced toxicity.

Myricetin Possesses Potential Protective Effects on Diabetic Cardiomyopathy through Inhibiting IκBα/NFκB and Enhancing Nrf2/HO-1

Diabetic cardiomyopathy (DCM) is associated with a greater risk of mortality in patients with diabetes mellitus. Currently, no specific treatment has been suggested for DCM treatment. This study demonstrated that myricetin (M) attenuated DCM-associated cardiac injury in mice subjected to streptozotocin (SZT) and in neonatal rat cardiomyocytes (NRCM) challenged with high glucose. In vivo investigation demonstrated 6 months of M treatment (200 mg/kg/d) significantly alleviated cardiac hypertrophy, apoptosis, and interstitial fibrosis. Mechanically, M treatment significantly increased the activity of Nrf2/HO-1 pathway, strengthening antioxidative stress capacity evidenced by reversed activities of GPx and SOD, and decreased MDA production. M treatment also inhibited IκBα/NF-κB pathway, resulting in reduced secretion of inflammation cytokines including IL-1β, TNF-α, and IL-6. Besides, the TGFβ/Smad3 signaling was also blunted in DCM mice treated with M. These beneficial effects of M treatment protected cardiomyocytes from apoptosis as shown by decreased TUNEL-positive nucleus, c-caspase 3, and Bax. Similar effects of M treatment could be reproduced in NRCM treated with high glucose. Furthermore, through silencing Nrf2 in NRCM, we found that the regulation of IκBα/NFκB by M was independent on its function on Nrf2. Thus, we concluded that M possesses potential protective effects on DCM through inhibiting IκBα/NFκB and enhancing Nrf2/HO-1.

The Role of Nrf2 in Cardiovascular Function and Disease

Free radicals, reactive oxygen/nitrogen species (ROS/RNS), hydrogen sulphide, and hydrogen peroxide play an important role in both intracellular and intercellular signaling; however, their production and quenching need to be closely regulated to prevent cellular damage. An imbalance, due to exogenous sources of free radicals and chronic upregulation of endogenous production, contributes to many pathological conditions including cardiovascular disease and also more general processes involved in aging. Nuclear factor erythroid 2-like 2 (NFE2L2; commonly known as Nrf2) is a transcription factor that plays a major role in the dynamic regulation of a network of antioxidant and cytoprotective genes, through binding to and activating expression of promoters containing the antioxidant response element (ARE). Nrf2 activity is regulated by many mechanisms, suggesting that tight control is necessary for normal cell function and both hypoactivation and hyperactivation of Nrf2 are indicated in playing a role in different aspects of cardiovascular disease. Targeted activation of Nrf2 or downstream genes may prove to be a useful avenue in developing therapeutics to reduce the impact of cardiovascular disease. We will review the current status of Nrf2 and related signaling in cardiovascular disease and its relevance to current and potential treatment strategies.

Epigallocatechin gallate upregulates NRF2 to prevent diabetic nephropathy via disabling KEAP1

Epigallocatechin gallate (EGCG) is the most abundant and effective green tea catechin and has been reported to attenuate diabetic nephropathy (DN). However, the mechanism by which EGCG ameliorates DN, till now, has remained unclear. EGCG is known as a potent activator of nuclear factor erythroid 2-related factor 2 (NRF2), which plays a key role in cellular defense against diabetes-induced oxidative stress and in the prevention of DN. In the present study, we tested whether NRF2 is required for EGCG protection against DN. Therefore, C57BL/6 wild type (WT) and Nrf2 knockout mice were induced to diabetes by streptozotocin, in the presence or absence of a 24-week treatment with EGCG. In the WT mice, EGCG activated Nrf2 expression and function without altering the expression of Kelch-like ECH-associated protein 1 (Keap1). Diabetes-induced renal oxidative damage, inflammation, fibrosis and albuminuria were significantly prevented by EGCG. Notably, deletion of the Nrf2 gene completely abrogated these actions of EGCG. To further determine the effect of EGCG on KEAP1/NRF2 signaling, mouse mesangial cells were treated with high glucose, in the presence of both Keap1 siRNA and EGCG. Interestingly, EGCG failed to enhance NRF2 signaling and alleviate oxidative, inflammatory and fibrotic indicators, in the presence of Keap1 siRNA. The present study demonstrated, for the first time, that NRF2 plays a critical role in EGCG protection against DN. Other findings indicated that inactivation of KEAP1 protein by EGCG may mediate EGCG function in activating NRF2.

Zinc rescues obesity-induced cardiac hypertrophy via stimulating metallothionein to suppress oxidative stress-activated BCL10/CARD9/p38 MAPK pathway

Obesity often leads to obesity-related cardiac hypertrophy (ORCH), which is suppressed by zinc-induced inactivation of p38 mitogen-activated protein kinase (p38 MAPK). In this study, we investigated the mechanisms by which zinc inactivates p38 MAPK to prevent ORCH. Mice (4-week old) were fed either high fat diet (HFD, 60% kcal fat) or normal diet (ND, 10% kcal fat) containing variable amounts of zinc (deficiency, normal and supplement) for 3 and 6 months. P38 MAPK siRNA and the p38 MAPK inhibitor SB203580 were used to suppress p38 MAPK activity in vitro and in vivo, respectively. HFD activated p38 MAPK and increased expression of B-cell lymphoma/CLL 10 (BCL10) and caspase recruitment domain family member 9 (CARD9). These responses were enhanced by zinc deficiency and attenuated by zinc supplement. Administration of SB203580 to HFD mice or specific siRNA in palmitate-treated cardiomyocytes eliminated the HFD and zinc deficiency activation of p38 MAPK, but did not significantly impact the expression of BCL10 and CARD9. In cultured cardiomyocytes, inhibition of BCL10 expression by siRNA prevented palmitate-induced increased p38 MAPK activation and atrial natriuretic peptide (ANP) expression. In contrast, inhibition of p38 MAPK prevented ANP expression, but did not affect BCL10 expression. Deletion of metallothionein abolished the protective effect of zinc on palmitate-induced up-regulation of BCL10 and phospho-p38 MAPK. HFD and zinc deficiency synergistically induce ORCH by increasing oxidative stress-mediated activation of BCL10/CARD9/p38 MAPK signalling. Zinc supplement ameliorates ORCH through activation of metallothionein to repress oxidative stress-activated BCL10 expression and p38 MAPK activation.