Metallothionein suppresses angiotensin II-induced nicotinamide adenine dinucleotide phosphate oxidase activation, nitrosative stress, apoptosis, and pathological remodeling in the diabetic heart

Ketogenic diet time-dependently prevents NAFLD through upregulating the expression of antioxidant protein metallothionein-2

BACKGROUND & AIMS

The past few decades have witnessed a rapid growth in the prevalence of nonalcoholic fatty liver disease (NAFLD). While the ketogenic diet (KD) is considered for managing NAFLD, the safety and efficacy of the KD on NAFLD has been a controversial topic. Here, we aimed to investigate the effect of KD of different durations on metabolic endpoints in mice with NAFLD and explore the underlying mechanisms.

METHODS

NAFLD mice were fed with KD for 1, 2, 4 and 6 weeks, respectively. The blood biochemical indexes (blood lipids, AST, ALT and etc.) and liver fat were measured. The LC-MS/MS based proteomic analysis was performed on liver tissues. Metallothionein-2 (MT2) was knocked down with adeno-associated virus (AAV) or small interfering RNA (siRNA) in NAFLD mice and AML-12 cells, respectively. H&E, BODIPY and ROS staining were performed to examine lipid deposition and oxidative stress. Furthermore, MT2 protein levels, nucleus/cytoplasm distribution and DNA binding activity of peroxisome proliferators-activated receptors α (PPARα) were evaluated.

RESULTS

KD feeding for 2 weeks showed the best improvement on NAFLD phenotype. Proteomic analysis revealed that MT2 was a key candidate for different metabolic endpoints of NAFLD affected by different durations of KD feeding. MT2 knockdown in NAFLD mice blocked the effects of 2 weeks of KD feeding on HFD-induced steatosis. In mouse primary hepatocytes and AML-12 cells, MT2 protein levels were induced by β-hydroxybutyric acid (β-OHB). MT2 Knockdown blunted the effects of β-OHB on alleviating PA-induced lipid deposition. Mechanistically, 2 weeks of KD or β-OHB treatment reduced oxidative stress and upregulated the protein levels of MT2 in nucleus, which subsequently increased its DNA binding activity and PPARα protein expression.

CONCLUSIONS

Collectively, these findings indicated that KD feeding prevented NAFLD in a time dependent manner and MT2 is a potential target contributing to KD improvement on steatosis.

Withaferin A as a Potential Therapeutic Target for the Treatment of Angiotensin II-Induced Cardiac Cachexia

In our previous studies, we showed that the generation of ovarian tumors in NSG mice (immune-compromised) resulted in the induction of muscle and cardiac cachexia, and treatment with withaferin A (WFA; a steroidal lactone) attenuated both muscle and cardiac cachexia. However, our studies could not address if these restorations by WFA were mediated by its anti-tumorigenic properties that might, in turn, reduce the tumor burden or WFA's direct, inherent anti-cachectic properties. To address this important issue, in our present study, we used a cachectic model induced by the continuous infusion of Ang II by implanting osmotic pumps in immunocompetent C57BL/6 mice. The continuous infusion of Ang II resulted in the loss of the normal functions of the left ventricle (LV) (both systolic and diastolic), including a significant reduction in fractional shortening, an increase in heart weight and LV wall thickness, and the development of cardiac hypertrophy. The infusion of Ang II also resulted in the development of cardiac fibrosis, and significant increases in the expression levels of genes (ANP, BNP, and MHCβ) associated with cardiac hypertrophy and the chemical staining of the collagen abundance as an indication of fibrosis. In addition, Ang II caused a significant increase in expression levels of inflammatory cytokines (IL-6, IL-17, MIP-2, and IFNγ), NLRP3 inflammasomes, AT1 receptor, and a decrease in AT2 receptor. Treatment with WFA rescued the LV functions and heart hypertrophy and fibrosis. Our results demonstrated, for the first time, that, while WFA has anti-tumorigenic properties, it also ameliorates the cardiac dysfunction induced by Ang II, suggesting that it could be an anticachectic agent that induces direct effects on cardiac muscles.

Cellular zinc metabolism and zinc signaling: from biological functions to diseases and therapeutic targets

Zinc metabolism at the cellular level is critical for many biological processes in the body. A key observation is the disruption of cellular homeostasis, often coinciding with disease progression. As an essential factor in maintaining cellular equilibrium, cellular zinc has been increasingly spotlighted in the context of disease development. Extensive research suggests zinc's involvement in promoting malignancy and invasion in cancer cells, despite its low tissue concentration. This has led to a growing body of literature investigating zinc's cellular metabolism, particularly the functions of zinc transporters and storage mechanisms during cancer progression. Zinc transportation is under the control of two major transporter families: SLC30 (ZnT) for the excretion of zinc and SLC39 (ZIP) for the zinc intake. Additionally, the storage of this essential element is predominantly mediated by metallothioneins (MTs). This review consolidates knowledge on the critical functions of cellular zinc signaling and underscores potential molecular pathways linking zinc metabolism to disease progression, with a special focus on cancer. We also compile a summary of clinical trials involving zinc ions. Given the main localization of zinc transporters at the cell membrane, the potential for targeted therapies, including small molecules and monoclonal antibodies, offers promising avenues for future exploration.

Cardiac Metabolism in Heart Failure and Implications for Uremic Cardiomyopathy

Chronic kidney disease is associated with an increased risk for the development and progression of cardiovascular disorders including hypertension, dyslipidemia, and coronary artery disease. Chronic kidney disease may also affect the myocardium through complex systemic changes, resulting in structural remodeling such as hypertrophy and fibrosis, as well as impairments in both diastolic and systolic function. These cardiac changes in the setting of chronic kidney disease define a specific cardiomyopathic phenotype known as uremic cardiomyopathy. Cardiac function is tightly linked to its metabolism, and research over the past 3 decades has revealed significant metabolic remodeling in the myocardium during the development of heart failure. Because the concept of uremic cardiomyopathy has only been recognized in recent years, there are limited data on metabolism in the uremic heart. Nonetheless, recent findings suggest overlapping mechanisms with heart failure. This work reviews key features of metabolic remodeling in the failing heart in the general population and extends this to patients with chronic kidney disease. The knowledge of similarities and differences in cardiac metabolism between heart failure and uremic cardiomyopathy may help identify new targets for mechanistic and therapeutic research on uremic cardiomyopathy.

LncRNA MHRT Prevents Angiotensin II-Induced Myocardial Oxidative Stress and NLRP3 Inflammasome via Nrf2 Activation

The development of angiotensin II (Ang II)-induced cardiomyopathies is reportedly mediated via oxidative stress and inflammation. Nuclear factor erythroid 2-related factor (Nrf2) is an important regulator of cellular antioxidant defense, and reactive oxygen species (ROS) can activate the NLRP3 inflammasome. MHRT is a newly discovered lncRNA exhibiting cardioprotective effects, demonstrated by inhibiting myocardial hypertrophy via Brg1 and myocardial apoptosis via Nrf2 upregulation. However, the underlying mechanism of MHRT remains unclear. We explored the potential protective effects of MHRT against Ang II-induced myocardial oxidative stress and NLRP3-mediated inflammation by targeting Nrf2. Chronic Ang II administration induced NLRP3 inflammasome activation (increased NLRP3, caspase-1 and interleukin-1β expression), oxidative stress (increased 3-nitrotyrosine and 4-hydroxy-2-nonenal), cardiac dysfunction and decreased MHRT and Nrf2 expression. Lentivirus-mediated MHRT overexpression inhibited Ang II (100 nM)-induced oxidative stress and NLRP3 inflammasome activation in AC16 human cardiomyocyte cells. Mechanistically, MHRT overexpression upregulated the expression and function of Nrf2, as determined by the increased transcription of downstream genes HO-1 and CAT, subsequently decreasing intracellular ROS accumulation and inhibiting the expression of thioredoxin-interacting protein (NLRP3 activator) and its direct binding to NLRP3. Accordingly, MHRT could protect against Ang II-induced myocardial injury by decreasing oxidative stress and NLRP3 inflammasome activation via Nrf2 activation.

The Molecular Mechanisms of Defective Copper Metabolism in Diabetic Cardiomyopathy

Copper is an essential trace metal element that significantly affects human physiology and pathology by regulating various important biological processes, including mitochondrial oxidative phosphorylation, connective tissue crosslinking, and antioxidant defense. Copper level has been proved to be closely related to the morbidity and mortality of cardiovascular diseases such as atherosclerosis, heart failure, and diabetic cardiomyopathy (DCM). Copper deficiency can induce cardiac hypertrophy and aggravate cardiomyopathy, while copper excess can mediate various types of cell death, such as autophagy, apoptosis, cuproptosis, pyroptosis, and cardiac hypertrophy and fibrosis. Both copper excess and copper deficiency lead to redox imbalance, activate inflammatory response, and aggravate diabetic cardiomyopathy. This defective copper metabolism suggests a specific metabolic pattern of copper in diabetes and a specific role in the pathogenesis and progression of DCM. This review is aimed at providing a timely summary of the effects of defective copper homeostasis on DCM and discussing potential underlying molecular mechanisms.

Sulforaphane inhibits angiotensin II-induced cardiomyocyte apoptosis by acetylation modification of Nrf2

Oxidative stress is the central cause of angiotensin II (Ang II)-induced myocardial injury, and nuclear factor erythroid 2-related factor (Nrf2) is the core molecule of the anti-oxidant defense system. We have previously demonstrated that sulforaphane (SFN) can prevent Ang II-induced myocardial injury by activating Nrf2; however, the underlying molecular mechanism is still unclear. This study aimed to evaluate whether SFN prevents Ang II-induced cardiomyocyte apoptosis through acetylation modification of <i>Nrf2</i>. Wild-type and <i>Nrf2</i> knockdown embryonic rat cardiomyocytes (H9C2) were exposed to Ang II to induce apoptosis, oxidative stress, and inflammatory responses. SFN treatment significantly reduced Ang II-induced cardiomyocyte apoptosis, inflammation and oxidative stress. Activation of Nrf2 played a critical role in preventing cardiomyocyte apoptosis. After Nrf2 was knockdown, the anti-inflammatory, antioxidant stress of SFN were eliminated. Furthermore, Nrf2 activation by SFN was closely related to the decreased activity of histone deacetylases (HDACs) and increased histone-3 (H3) acetylation levels in <i>Nrf2</i> promoter region. These findings confirm that Nrf2 plays a key role in SFN preventing Ang II-induced cardiomyocyte apoptosis. SFN activates Nrf2 by inhibiting HDACs expression and activation.

EGR1 Is Implicated in Right Ventricular Cardiac Remodeling Associated with Pulmonary Hypertension

Background: Pulmonary hypertension (PH) is a vasoconstrictive disease characterized by elevated mean pulmonary arterial pressure (mPAP) at rest. Idiopathic pulmonary arterial hypertension (iPAH) and chronic thromboembolic pulmonary hypertension (CTEPH) represent two distinct subtypes of PH. Persisting PH leads to right ventricular (RV) hypertrophy, heart failure, and death. RV performance predicts survival and surgical interventions re-establishing physiological mPAP reverse cardiac remodeling. Nonetheless, a considerable number of PH patients are deemed inoperable. The underlying mechanism(s) governing cardiac regeneration, however, remain largely elusive. Methods: In a longitudinal approach, we profiled the transcriptional landscapes of hypertrophic RVs and recovered hearts 3 months after surgery of iPAH and CTEPH patients. Results: Genes associated with cellular responses to inflammatory stimuli and metal ions were downregulated, and cardiac muscle tissue development was induced in iPAH after recovery. In CTEPH patients, genes related to muscle cell development were decreased, and genes governing cardiac conduction were upregulated in RVs following regeneration. Intriguingly, early growth response 1 (EGR1), a profibrotic regulator, was identified as a major transcription factor of hypertrophic RVs in iPAH and CTEPH. A histological assessment confirmed our biocomputational results, and suggested a pivotal role for EGR1 in RV vasculopathy. Conclusion: Our findings improved our understanding of the molecular events driving reverse cardiac remodeling following surgery. EGR1 might represent a promising candidate for targeted therapy of PH patients not eligible for surgical treatment.

Ferroptosis is essential for diabetic cardiomyopathy and is prevented by sulforaphane via AMPK/NRF2 pathways

Herein, we define the role of ferroptosis in the pathogenesis of diabetic cardiomyopathy (DCM) by examining the expression of key regulators of ferroptosis in mice with DCM and a new ex vivo DCM model. Advanced glycation end-products (AGEs), an important pathogenic factor of DCM, were found to induce ferroptosis in engineered cardiac tissues (ECTs), as reflected through increased levels of Ptgs2 and lipid peroxides and decreased ferritin and SLC7A11 levels. Typical morphological changes of ferroptosis in cardiomyocytes were observed using transmission electron microscopy. Inhibition of ferroptosis with ferrostatin-1 and deferoxamine prevented AGE-induced ECT remodeling and dysfunction. Ferroptosis was also evidenced in the heart of type 2 diabetic mice with DCM. Inhibition of ferroptosis by liproxstatin-1 prevented the development of diastolic dysfunction at 3 months after the onset of diabetes. Nuclear factor erythroid 2-related factor 2 (NRF2) activated by sulforaphane inhibited cardiac cell ferroptosis in both AGE-treated ECTs and hearts of DCM mice by upregulating ferritin and SLC7A11 levels. The protective effect of sulforaphane on ferroptosis was AMP-activated protein kinase (AMPK)-dependent. These findings suggest that ferroptosis plays an essential role in the pathogenesis of DCM; sulforaphane prevents ferroptosis and associated pathogenesis via AMPK-mediated NRF2 activation. This suggests a feasible therapeutic approach with sulforaphane to clinically prevent ferroptosis and DCM.

Downregulation of miR-491-5p promotes neovascularization after traumatic brain injury

MicroRNA-491-5p (miR-491-5p) plays an important role in regulating cell proliferation and migration; however, the effect of miR-491-5p on neovascularization after traumatic brain injury remains poorly understood. In this study, a controlled cortical injury model in C57BL/6 mice and an oxygen-glucose deprivation model in microvascular endothelial cells derived from mouse brain were established to simulate traumatic brain injury in vivo and in vitro, respectively. In the in vivo model, quantitative real-time-polymerase chain reaction results showed that the expression of miR-491-5p increased or decreased following the intracerebroventricular injection of an miR-491-5p agomir or antagomir, respectively, and the expression of miR-491-5p decreased slightly after traumatic brain injury. To detect the neuroprotective effects of miR-491-p, neurological severity scores, Morris water maze test, laser speckle techniques, and immunofluorescence staining were assessed, and the results revealed that miR-491-5p downregulation alleviated neurological dysfunction, promoted the recovery of regional cerebral blood flow, increased the number of lectin-stained microvessels, and increased the survival of neurons after traumatic brain injury. During the in vitro experiments, the potential mechanism of miR-491-5p on neovascularization was explored through quantitative real-time-polymerase chain reaction, which showed that miR-491-5p expression increased or decreased in brain microvascular endothelial cells after transfection with an miR-491-5p mimic or inhibitor, respectively. Dual-luciferase reporter and western blot assays verified that metallothionein-2 was a target gene for miR-491-5p. Cell counting kit 8 (CCK-8) assay, flow cytometry, and 2?,7?-dichlorofluorescein diacetate (DCFH-DA) assay results confirmed that the downregulation of miR-491-5p increased brain microvascular endothelial cell viability, reduced cell apoptosis, and alleviated oxidative stress under oxygen-glucose deprivation conditions. Cell scratch assay, Transwell assay, tube formation assay, and western blot assay results demonstrated that miR-491-5p downregulation promoted the migration, proliferation, and tube formation of brain microvascular endothelial cells through a metallothionein-2-dependent hypoxia-inducible factor-1α/vascular endothelial growth factor pathway. These findings confirmed that miR-491-5p downregulation promotes neovascularization, restores cerebral blood flow, and improves the recovery of neurological function after traumatic brain injury. The mechanism may be mediated through a metallothionein-2-dependent hypoxia-inducible factor-1α/vascular endothelial growth factor signaling pathway and the alleviation of oxidative stress. All procedures were approved by Ethics Committee of the First Affiliated Hospital of Chongqing Medical University, China (approval No. 2020-304) on June 22, 2020.

Understanding diabetes-induced cardiomyopathy from the perspective of renin angiotensin aldosterone system

Experimental and clinical evidence suggests that diabetic subjects are predisposed to a distinct cardiovascular dysfunction, known as diabetic cardiomyopathy (DCM), which could be an autonomous disease independent of concomitant micro and macrovascular disorders. DCM is one of the prominent causes of global morbidity and mortality and is on a rising trend with the increase in the prevalence of diabetes mellitus (DM). DCM is characterized by an early left ventricle diastolic dysfunction associated with the slow progression of cardiomyocyte hypertrophy leading to heart failure, which still has no effective therapy. Although the well-known "Renin Angiotensin Aldosterone System (RAAS)" inhibition is considered a gold-standard treatment in heart failure, its role in DCM is still unclear. At the cellular level of DCM, RAAS induces various secondary mechanisms, adding complications to poor prognosis and treatment of DCM. This review highlights the importance of RAAS signaling and its major secondary mechanisms involving inflammation, oxidative stress, mitochondrial dysfunction, and autophagy, their role in establishing DCM. In addition, studies lacking in the specific area of DCM are also highlighted. Therefore, understanding the complex role of RAAS in DCM may lead to the identification of better prognosis and therapeutic strategies in treating DCM.

Correlation between biomarkers of exposure, effect and potential harm in the urine of electronic cigarette users

Objectives

To determine if urinary biomarkers of effect and potential harm are elevated in electronic cigarette users compared with non-smokers and if elevation correlates with increased concentrations of metals in urine.

Study design and setting

This was a cross-sectional study of biomarkers of exposure, effect and potential harm in urine from non-smokers (n=20), electronic cigarette users (n=20) and cigarette smokers (n=13). Participant’s screening and urine collection were performed at the Roswell Park Comprehensive Cancer Center, and biomarker analysis and metal analysis were performed at the University of California, Riverside.

Results

Metallothionein was significantly elevated in the electronic cigarette group (3761±3932 pg/mg) compared with the non-smokers (1129±1294 pg/mg, p=0.05). 8-OHdG (8-hydroxy-2′-deoxyguanosine) was significantly elevated in electronic cigarette users (442.8±300.7 ng/mg) versus non-smokers (221.6±157.8 ng/mg, p=0.01). 8-Isoprostane showed a significant increase in electronic cigarette users (750.8±433 pg/mg) versus non-smokers (411.2±287.4 pg/mg, p=0.03). Linear regression analysis in the electronic cigarette group showed a significant correlation between cotinine and total metal concentration; total metal concentration and metallothionein; cotinine and oxidative DNA damage; and total metal concentration and oxidative DNA damage. Zinc was significantly elevated in the electronic cigarette users (584.5±826.6 µg/g) compared with non-smokers (413.6±233.7 µg/g, p=0.03). Linear regression analysis showed a significant correlation between urinary zinc concentration and 8-OHdG in the electronic cigarette users.

Conclusions

This study is the first to investigate biomarkers of potential harm and effect in electronic cigarette users and to show a linkage to metal exposure. The biomarker levels in electronic cigarette users were similar to (and not lower than) cigarette smokers. In electronic cigarette users, there was a link to elevated total metal exposure and oxidative DNA damage. Specifically, our results demonstrate that zinc concentration was correlated to oxidative DNA damage.

Unfolded protein response during cardiovascular disorders: a tilt towards pro-survival and cellular homeostasis

The endoplasmic reticulum (ER) is an organelle that orchestrates the production and proper assembly of an extensive types of secretory and membrane proteins. Endoplasmic reticulum stress is conventionally related to prolonged disruption in the protein folding machinery resulting in the accumulation of unfolded proteins in the ER. This disruption is often manifested due to oxidative stress, Ca²⁺ leakage, iron imbalance, disease conditions which in turn hampers the cellular homeostasis and induces cellular apoptosis. A mild ER stress is often reverted back to normal. However, cells retaliate to acute ER stress by activating the unfolded protein response (UPR) which comprises three signaling pathways, Activating transcription factor 6 (ATF6), inositol requiring enzyme 1 alpha (IRE1α), and protein kinase RNA-activated-like ER kinase (PERK). The UPR response participates in both protective and pro-apoptotic responses and not much is known about the mechanistic aspects of the switch from pro-survival to pro-apoptosis. When ER stress outpaces UPR response then cell apoptosis prevails which often leads to the development of various diseases including cardiomyopathies. Therefore, it is important to identify molecules that modulate the UPR that may serve as promising tools towards effective treatment of cardiovascular diseases. In this review, we elucidated the latest advances in construing the contribution imparted by the three arms of UPR to combat the adverse environment in the ER to restore cellular homeostasis during cardiomyopathies. We also summarized the various therapeutic agents that plays crucial role in tilting the UPR response towards pro-survival.

Echocardiographic evaluation of the effect of poor blood glucose control on left ventricular function and ascending aorta elasticity

BACKGROUND AND AIMS

Type 2 diabetes mellitus (T2DM) is associated with high cardiovascular risk. Preclinical left ventricular (LV) dysfunction and subclinical arterial stiffness have been documented in patients with T2DM. The aims of this study were to investigate whether there were any differences in LV function and ascending aorta elasticity between T2DM patients with controlled [defined as glycosylated hemoglobin (HbA1c) <6.5%] and uncontrolled (HbA1c ≥6.5%) blood glucose.

METHODS

We studied 86 T2DM patients: 42 T2DM patients with controlled blood glucose (controlled T2DM group) and 44 T2DM patients with uncontrolled blood glucose (uncontrolled T2DM group), and 40 healthy subjects as control. They all underwent transthoracic echocardiography examination, LV systolic function was evaluated by global longitudinal strain (GLS) and LV diastolic function was defined as the ratio of the early diastolic transmitral flow velocity (E) to average mitral annular velocity (e¯). Ascending aorta inner diameters and brachial blood pressure were measured to calculate ascending aorta elastic parameters: compliance (C), distensibility (D), strain (S), stiffness index (SI), Peterson's elastic modulus (EM).

RESULTS

Compared to control, T2DM patients had reduced GLS, increased E/e ̅ and impaired ascending aorta elasticity. Furthermore, LV function and ascending aorta elasticity were more severely damaged in uncontrolled T2DM group compared with controlled T2DM group. By Pearson correlation analysis, the level of HbA_1c was independently associated with the parameters of the LV function and ascending aorta elasticity.

CONCLUSIONS

T2DM can impair the LV myocardial function and ascending aorta elastic properties, which may be further impaired by poor blood glucose control.

Sulforaphane prevents angiotensin II-induced cardiomyopathy by activation of Nrf2 through epigenetic modification

Nuclear factor erythroid 2-related factor (Nrf2) is an important regulator of cellular antioxidant defence. We previously showed that SFN prevented Ang II-induced cardiac damage via activation of Nrf2. However, the underlying mechanism of SFN's persistent cardiac protection remains unclear. This study aimed to explore the potential of SFN in activating cardiac Nrf2 through epigenetic mechanisms. Wild-type mice were injected subcutaneously with Ang II, with or without SFN. Administration of chronic Ang II-induced cardiac inflammatory factor expression, oxidative damage, fibrosis and cardiac remodelling and dysfunction, all of which were effectively improved by SFN treatment, coupled with an up-regulation of Nrf2 and downstream genes. Bisulfite genome sequencing and chromatin immunoprecipitation (ChIP) were performed to detect the methylation level of the first 15 CpGs and histone H3 acetylation (Ac-H3) status in the Nrf2 promoter region, respectively. The results showed that SFN reduced Ang II-induced CpG hypermethylation and promoted Ac-H3 accumulation in the Nrf2 promoter region, accompanied by the inhibition of global DNMT and HDAC activity, and a decreased protein expression of key DNMT and HDAC enzymes. Taken together, SFN exerts its cardioprotective effect through epigenetic modification of Nrf2, which may partially contribute to long-term activation of cardiac Nrf2.

Myeloid differentiation 2 deficiency attenuates AngII-induced arterial vascular oxidative stress, inflammation, and remodeling

Vascular remodeling is a pertinent target for cardiovascular therapy. Vascular smooth muscle cell (VSMC) dysfunction plays a key role in vascular remodeling. Myeloid differentiation 2 (MD2), a cofactor of toll-like receptor 4 (TLR4), is involved in atherosclerotic progress and cardiac remodeling via activation of chronic inflammation. In this study, we explored the role of MD2 in vascular remodeling using an Ang II-induced mouse model and cultured human aortic VSMCs. MD2 deficiency suppressed Ang II-induced vascular fibrosis and phenotypic switching of VSMCs without affecting blood pressure in mice. Mechanistically, MD2 deficiency prevented Ang II-induced expression of inflammatory cytokines and oxidative stress in mice and cultured VSMCs. Furthermore, MD2 deficiency reversed Ang II-activated MAPK signaling and Ang II-downregulated SIRT1 expression. Taken together, MD2 plays a significant role in Ang II-induced vascular oxidative stress, inflammation, and remodeling, indicating that MD2 is a potential therapeutic target for the treatment of vascular remodeling-related cardiovascular diseases.

Mechanisms of diabetic cardiomyopathy and potential therapeutic strategies: preclinical and clinical evidence

The pathogenesis and clinical features of diabetic cardiomyopathy have been well-studied in the past decade, but effective approaches to prevent and treat this disease are limited. Diabetic cardiomyopathy occurs as a result of the dysregulated glucose and lipid metabolism associated with diabetes mellitus, which leads to increased oxidative stress and the activation of multiple inflammatory pathways that mediate cellular and extracellular injury, pathological cardiac remodelling, and diastolic and systolic dysfunction. Preclinical studies in animal models of diabetes have identified multiple intracellular pathways involved in the pathogenesis of diabetic cardiomyopathy and potential cardioprotective strategies to prevent and treat the disease, including antifibrotic agents, anti-inflammatory agents and antioxidants. Some of these interventions have been tested in clinical trials and have shown favourable initial results. In this Review, we discuss the mechanisms underlying the development of diabetic cardiomyopathy and heart failure in type 1 and type 2 diabetes mellitus, and we summarize the evidence from preclinical and clinical studies that might provide guidance for the development of targeted strategies. We also highlight some of the novel pharmacological therapeutic strategies for the treatment and prevention of diabetic cardiomyopathy.

miR-410-5p promotes the development of diabetic cardiomyopathy by suppressing PIM1-induced anti-apoptosis

Diabetic cardiomyopathy (DCM) is a common complication of diabetes mellitus that can cause many severe symptoms, such as heart failure, arrhythmia, and sudden death. However, the molecular mechanisms underlying cardiac dysfunction in DCM remain elusive. In this study, we found that miR-410-5p was increased in the myocardial tissue of a diabetes mellitus (DM) rat model. Further studies confirmed that inhibition of miR-410-5p reduced cell apoptosis by regulating the Bcl-2/Bax axis. Through bioinformatics analysis and luciferase reporter assays, we observed that miR-410-5p directly targets PIM1. Moreover, knockdown of miR-410-5p by antagomir-410-5p improved diabetes-induced cardiac function and myocardial tissue structure. In conclusion, our study demonstrated that miR-410-5p might be involved in the progression of DCM by targeting PIM1 and might be a promising therapeutic target for DCM in the future.

Inhibition of histone demethylase JMJD1C attenuates cardiac hypertrophy and fibrosis induced by angiotensin II

Pathological cardiac hypertrophy is a major risk factor for cardiovascular morbidity and mortality. Histone demethylases (KDMs) are emerging regulators of transcriptional reprograming in cancer, however, their potential role in abnormal heart growth and fibrosis remains largely unknown. The aim of this current study was to examine the role of JMJD1C, an H3K9me2 specific demethylase, in angiotensin II (Ang II) induced cardiac hypertrophy and fibrosis. In this study, we observed that Ang II could increase the expression of JMJD1C detected by Western blot and RT-qPCR in vitro and in vivo. Immunofluorescence staining showed that the treatment of Ang II could increase cardiomyocyte size. RT-qPCR results have shown that Ang II could increase the expression of cell hypertrophic and fibrotic markers in H9c2 cells. Whereas, inhibition of JMJD1C by shRNA and JIB-04, a small molecule histone demethylase inhibitor, significantly reduced Ang II-induced cell hypertrophy, and hypertrophic and fibrotic marker overexpression. Furthermore, cardiomyocyte JMJD1C knockdown decreased Tissue Inhibitor of Metalloproteinases 1 (TIMP1) transcription with pro-fibrotic activity. In conclusion, JMJD1C plays an important role in Ang II-induced cardiac hypertrophy and fibrosis by activating TIMP1 transcription, targeting of JMJD1C may be an effective strategy for the treatment of Ang II-associated cardiac diseases.

Neonatal Murine Engineered Cardiac Tissue Toxicology Model: Impact of Metallothionein Overexpression on Cadmium-Induced Injury

Engineered cardiac tissues (ECTs) serve as robust in vitro models to study human cardiac diseases including cardiac toxicity assays due to rapid structural and functional maturation and the ability to vary ECT composition. Metallothionein (MT) has been shown to be cardioprotective for environmental toxicants including heavy metals. To date, studies on the role of cardiomyocyte (CM)-specific MT expression and function have occurred in dissociated single cell assays or expensive in vivo small animal models. Therefore, we generated 3D ECTs using neonatal mouse ventricular cells from wild-type (WT) and the CM-specific overexpressing MT-transgenic (MT-TG) to determine the effect of MT overexpression on ECT maturation and function. Because Cadmium (Cd) is an environmentally prevalent heavy metal toxicant with direct negative impact on cardiac structure and function, we then determined the effect of MT overexpression to reduce Cd mediated CM toxicity within ECTs. We found: (1) structural and functional maturation was similar in WT and MT-TG ECTs; (2) Cd exposure negatively impacted ECT cell survival, maturation, and function; and (3) MT-ECTs showed reduced Cd toxicity as defined by reduced cleaved caspase 3, reduced Bax/Bcl2 ratio, reduced TdT-mediated dUTP nick-end labeling positive cells, reduced CM loss after Cd treatment, and delayed onset of cardiac dysfunction after Cd treatment. Thus, neonatal murine ECTs can serve as a robust in vitro model for heavy metal toxicity screening and as a platform to evaluate the role cardioprotective mechanisms, such as the MT-TG model, on environmentally relevant toxicants.

Stimulation of Na+/K+-ATPase with an Antibody against Its 4th Extracellular Region Attenuates Angiotensin II-Induced H9c2 Cardiomyocyte Hypertrophy via an AMPK/SIRT3/PPARγ Signaling Pathway

Activation of the renin-angiotensin system (RAS) contributes to the pathogenesis of cardiovascular diseases. Sodium potassium ATPase (NKA) expression and activity are often regulated by angiotensin II (Ang II). This study is aimed at investigating whether DR-Ab, an antibody against 4^th extracellular region of NKA, can protect Ang II-induced cardiomyocyte hypertrophy. Our results showed that Ang II treatment significantly reduced NKA activity and membrane expression. Pretreatment with DR-Ab preserved cell size in Ang II-induced cardiomyopathy by stabilizing the plasma membrane expression of NKA and restoring its activity. DR-Ab reduced intracellular ROS generation through inhibition of NADPH oxidase activity and protection of mitochondrial functions in Ang II-treated H9c2 cardiomyocytes. Pharmacological manipulation and Western blotting analysis demonstrated the cardioprotective effects were mediated by the activation of the AMPK/Sirt-3/PPARγ signaling pathway. Taken together, our results suggest that dysfunction of NKA is an important mechanism for Ang II-induced cardiomyopathy and DR-Ab may be a novel and promising therapeutic approach to treat cardiomyocyte hypertrophy.

Schizandrin B attenuates angiotensin II induced endothelial to mesenchymal transition in vascular endothelium by suppressing NF-κB activation

BACKGROUND

Angiotensin II (Ang II)-induced chronic inflammation and oxidative stress often leads to irreversible vascular injury, in which the endothelial to mesenchymal transition (EndMT) in the endothelial layers are involved. Schisandrin B (Sch B), a natural product isolated from traditional Schisandra chinensis, has been reported to exert vascular protective properties with unclear mechanism.

HYPOTHESIS/PURPOSE

This study investigated the protective effects and mechanism of Sch B against Ang II-induced vascular injury.

METHODS

C57BL/6 mice were subcutaneous injected of Ang II for 4 weeks to induce irreversible vascular injury. In vitro, Ang II-induced HUVECs injury was used to study the underlying mechanism. The markers of EndMT, inflammation and oxidative stress were studied both in vitro and in vivo.

RESULTS

Pre-administration of Sch B effectively attenuated phenotypes of vascular EndMT and fibrosis in Ang II-treated animals, accompanied with decreased inflammatory cytokine and ROS. The in vitro data from HUVECs suggest that Sch B directly targets NF-κB activation to suppress Ang II-induced EndMT and vascular injury. The activation of EndMT in the presence of Ang II is regulated by the NF-κB, a common player in inflammation and oxidative stress. Ang II-induced inflammation and oxidative stress also contributed to vascular EndMT development and Sch B inhibited inflammation/ROS-mediated EndMT by suppressing NF-κB.

CONCLUSION

EndMT contributes to vascular injury in Ang II-treated mice, and it can be prevented via suppressing NF-κB activation by Sch B treatment. These results also imply that NF-κB might be a promising target to attenuate vascular remodeling induced by inflammation and oxidative stress through an EndMT mechanism.

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.

Angiotensin II Causes Biphasic STAT3 Activation Through TLR4 to Initiate Cardiac Remodeling

Evidence indicates that Ang II (angiotensin II) activates STAT3 (signal transducer and activator of transcription 3) in cardiomyocytes. However, the mechanisms underlying STAT3 activation and downstream responses are not fully known. In this study, we show that Ang II caused biphasic STAT3 activation in cardiomyocytes. A rapid and early activation was mediated by direct association between TLR4 (toll-like receptor-4) and STAT3. This early activation increased IL-6 (interleukin-6) production, which in turn, induced the second STAT3 activation through the IL-6/gp130 (glycoprotein 130)/JAK2 (Janus-family tyrosine kinases 2) pathway, resulting in unregulated expression of genes for cardiac remodeling. Moreover, STAT3 inhibition or TLR4 knockout in mice protected against Ang II-induced hypertrophy, fibrosis, and cardiac functional deficits. Thus, Ang II-induced STAT3 activation in cardiomyocytes was biphasic, providing a sequential induction of IL-6 and myocardial remodeling genes, respectively. This work supports a novel mechanism on STAT3 activation in Ang II-induced cardiac dysfunction and remodeling.

Pulmonary arterial hypertension and the potential roles of metallothioneins: A focused review

The pathophysiology of pulmonary arterial hypertension (PAH) is underlined by cell proliferation and vasoconstriction of pulmonary arterioles this involves multiple molecular factors or proteins, but it is not clear what the exact roles of these factors/proteins are. In addition, there may be other factors/proteins that have not been identified that contribute to PAH pathophysiology. Therefore, research has focused on investigating novel role players, in order to facilitate a better understanding of how PAH develop. Evidence suggest that mitochondrial regulators are key role players in PAH pathophysiology, but regulators that have not received sufficient attention in PAH are metallothioneins (MTs). In PAH patients, MT expression is elevated compared to healthy individuals, suggesting that MTs may be possible biomarkers. In other disease-models, MTs have been shown to regulate cell proliferation and vasoconstriction, processes that are instrumental in PAH pathophysiology. Due to the involvement of these processes in PAH pathophysiology and the ability of MTs to modulate them, this paper propose that cellular MTs may also play a role in PAH development. This paper suggests that PAH-research should perhaps begin to investigate the involvement of cellular MTs in the development of PAH.

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.

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Sulforaphane (SFN) protects from intermittent-hypoxia (IH)-induced cardiomyopathy;

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SFN can increase both Nrf2 and metallothionein (MT) but the latter is Nrf2 dependent.

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SFN protects the heart from IH in wild-type and MT-KO mice, but not in Nrf2 mice.

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Nrf2 is indispensable, but not MT, for SFN to protect from IH-induced cardiomyopathy.

Resveratrol Prevents Diabetic Cardiomyopathy by Increasing Nrf2 Expression and Transcriptional Activity

OBJECTIVE

This study investigated if resveratrol ameliorates diabetic cardiomyopathy by targeting associated oxidative stress mechanisms.

METHOD

Type 1 diabetes mellitus (DM) in FVB mice was induced by several intraperitoneal injections of a low dose of streptozotocin. Hyperglycemic and age-matched control mice were given resveratrol (10 mg/kg per day) for 1 month and subsequently monitored for an additional 6 months. Mice were assigned to four groups: control, resveratrol, DM, and DM/resveratrol. Cardiac function and blood pressure were assessed at 1, 3, and 6 months after DM induction. Oxidative damage and cardiac fibrosis were analyzed by histopathology, real-time PCR, and Western blot.

RESULT

Mice in the DM group exhibited increased blood glucose levels, cardiac dysfunction, and high blood pressure at 1, 3, and 6 months after DM induction. Resveratrol did not significantly affect blood glucose levels and blood pressure; however, resveratrol attenuated cardiac dysfunction and hypertrophy in DM mice. Resveratrol also reduced DM-induced fibrosis. In addition, DM mice hearts exhibited increased oxidative damage, as evidenced by elevated accumulation of 3-nitrotyrosine and 4-hydroxynonenal, which were both attenuated by resveratrol. Mechanistically, resveratrol increased NFE2-related factor 2 (Nrf2) expression and transcriptional activity, as well as Nrf2's downstream antioxidative targets.

CONCLUSION

We demonstrated that resveratrol prevents DM-induced cardiomyopathy, in part, by increasing Nrf2 expression and transcriptional activity.

Metallothionein Preserves Akt2 Activity and Cardiac Function via Inhibiting TRB3 in Diabetic Hearts

Cardiac insulin resistance is a key pathogenic factor for diabetic cardiomyopathy (DCM), but the mechanism remains largely unclear. We found that diabetic hearts exhibited decreased phosphorylation of total Akt and isoform Akt2 but not Akt1 in wild-type (WT) male FVB mice, which was accompanied by attenuation of Akt downstream glucose metabolic signal. All of these signal changes were not observed in metallothionein cardiac-specific transgenic (MT-TG) hearts. Furthermore, insulin-induced glucose metabolic signals were attenuated only in WT diabetic hearts. In addition, diabetic hearts exhibited increased Akt-negative regulator tribbles pseudokinase 3 (TRB3) expression only in WT mice, suggesting that MT may preserve Akt2 function via inhibiting TRB3. Moreover, MT prevented tert-butyl hydroperoxide (tBHP)-reduced insulin-stimulated Akt2 phosphorylation in MT-TG cardiomyocytes, which was abolished by specific silencing of Akt2. Specific silencing of TRB3 blocked tBHP inhibition of insulin-stimulated Akt2 phosphorylation in WT cardiomyocytes, whereas overexpression of TRB3 in MT-TG cardiomyocytes and hearts abolished MT preservation of insulin-stimulated Akt2 signals and MT prevention of DCM. Most importantly, supplementation of Zn to induce MT preserved cardiac Akt2 signals and prevented DCM. These results suggest that diabetes-inhibited cardiac Akt2 function via TRB3 upregulation leads to aberrant cardiac glucose metabolism. MT preservation of cardiac Akt2 function by inhibition of TRB3 prevents DCM.

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.

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.

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Sulforaphane (SFN) can prevent angiotensin II (AngII) -induced cardiomyopathy.

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SFN prevents AngII-induced cardiomyopathy via up-regulating and activating Nrf2.

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Cardiac overexpression of Nrf2 prevents Ang II-induced cardiomyopathy.

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Up-regulation and activation of Nrf2 by SFN is achieved through the Akt/GSK-3β/Fyn pathway.

Intermittent hypoxia-induced cardiomyopathy and its prevention by Nrf2 and metallothionein

The mechanism for intermittent hypoxia (IH)-induced cardiomyopathy remains obscure. We reported the prevention of acute and chronic IH-induced cardiac damage by selective cardiac overexpression of metallothionein (MT). Herein we defined that MT-mediated protection from IH-cardiomyopathy is via activation of nuclear factor erythroid 2-related factor 2 (Nrf2), a critical redox-balance controller in the body. For this, mice were exposed to IH for 3 days (acute) or 4 or 8 weeks (chronic). Cardiac Nrf2 and MT expression in response to IH were significantly increased acutely yet decreased chronically. Interestingly, cardiac overexpression (Nrf2-TG) or global deletion of the Nrf2 gene (Nrf2-KO) made mice highly resistant or highly susceptible, respectively, to IH-induced cardiomyopathy and MT expression. Mechanistically, 4-week IH exposure significantly decreased cardiac Nrf2 binding to the MT gene promoter, and thus, depressed both MT transcription and translation in WT mice but not Nrf2-TG mice. Likewise, cardiac MT overexpression prevented chronic IH-induced cardiomyopathy and down-regulation of Nrf2 likely via activation of a PI3K/Akt/GSK-3β/Fyn-dependent signaling pathway. These results reveal an integrated relationship between cardiac Nrf2 and MT expression in response to IH -- acute compensatory up-regulation followed by chronic down-regulation and cardiomyopathy. Cardiac overexpression of either Nrf2 or MT offered cardioprotection from IH via complicated PI3K/Akt/GSK3B/Fyn signaling. Potential therapeutics may target either Nrf2 or MT to prevent chronic IH-induced cardiomyopathy.

Exacerbation of diabetic cardiac hypertrophy in OVE26 mice by angiotensin II is associated with JNK/c-Jun/miR-221-mediated autophagy inhibition

Both diabetes and angiotensin II (Ang II) excess trigger cardiac remodeling and dysfunction, and diabetic cardiomyopathy. We hypothesized that cardiac hypertrophy associated with the development of diabetic cardiomyopathy is worsened by increased Ang II. Male type 1 diabetic OVE26 and wild-type mice were given Ang II (sc., 1.15 mg/kg, twice a day) for 14 days. Diabetes-induced cardiac dysfunction and hypertrophy was exacerbated by Ang II treatment as determined by echocardiography, wheat germ agglutinin staining and atrial natriuretic peptide. Ang II treatment dramatically exacerbated diabetes-caused decreased LC3-II, a marker of autophagy, and increased p62, an indicator of cytosolic protein clearance. Ang II treatment also augmented diabetes-associated increased phosphorylated levels of c-Jun, JNK, mTOR, and miR-221, and decreased of p27 expression, a direct target of miR-221. Chromatin immunoprecipitation assay showed that Ang II elevated c-Jun binding to the promoter of miR-221 in diabetic mice. These results suggest that Ang II accelerates cardiac hypertrophy in the early stage of murine diabetes, probably through activation of the JKN/c-Jun/miR-221 axis and inhibition of downstream autophagy. Therefore, inhibition of Ang II or miR-221 in diabetic individuals may be a potential approach for delaying the onset and/or reducing the severity of diabetic cardiomyopathy.

Pathophysiological Fundamentals of Diabetic Cardiomyopathy

Diabetic cardiomyopathy (DCM) was first recognized more than four decades ago and occurred independent of cardiovascular diseases or hypertension in both type 1 and type 2 diabetic patients. The exact mechanisms underlying this disease remain incompletely understood. Several pathophysiological bases responsible for DCM have been proposed, including the presence of hyperglycemia, nonenzymatic glycosylation of large molecules (e.g., proteins), energy metabolic disturbance, mitochondrial damage and dysfunction, impaired calcium handling, reactive oxygen species formation, inflammation, cardiac cell death, and cardiac hypertrophy and fibrosis, leading to impairment of cardiac contractile functions. Increasing evidence also indicates the phenomenon called "metabolic memory" for diabetes-induced cardiovascular complications, for which epigenetic modulation seemed to play an important role, suggesting that the aforementioned pathogenic bases may be regulated by epigenetic modification. Therefore, this review aims at briefly summarizing the current understanding of the pathophysiological bases for DCM. Although how epigenetic mechanisms play a role remains incompletely understood now, extensive clinical and experimental studies have implicated its importance in regulating the cardiac responses to diabetes, which are believed to shed insight into understanding of the pathophysiological and epigenetic mechanisms for the development of DCM and its possible prevention and/or therapy. © 2017 American Physiological Society. Compr Physiol 7:693-711, 2017.

Leukocyte iNOS is required for inflammation and pathological remodeling in ischemic heart failure

In the failing heart, iNOS is expressed by both macrophages and cardiomyocytes. We hypothesized that inflammatory cell-localized iNOS exacerbates left ventricular (LV) remodeling. Wild-type (WT) C57BL/6 mice underwent total body irradiation and reconstitution with bone marrow from iNOS^-/- mice (iNOS^-/-c) or WT mice (WTc). Chimeric mice underwent coronary ligation to induce large infarction and ischemic heart failure (HF), or sham surgery. After 28 days, as compared with WTc sham mice, WTc HF mice exhibited significant (p < 0.05) mortality, LV dysfunction, hypertrophy, fibrosis, oxidative/nitrative stress, inflammatory activation, and iNOS upregulation. These mice also exhibited a ~twofold increase in circulating Ly6C^hi pro-inflammatory monocytes, and ~sevenfold higher cardiac M1 macrophages, which were primarily CCR2^- cells. In contrast, as compared with WTc HF mice, iNOS^-/-c HF mice exhibited significantly improved survival, LV function, hypertrophy, fibrosis, oxidative/nitrative stress, and inflammatory activation, without differences in overall cardiac iNOS expression. Moreover, iNOS^-/-c HF mice exhibited lower circulating Ly6C^hi monocytes, and augmented cardiac M2 macrophages, but with greater infiltrating monocyte-derived CCR2⁺ macrophages vs. WTc HF mice. Lastly, upon cell-to-cell contact with naïve cardiomyocytes, peritoneal macrophages from WT HF mice depressed contraction, and augmented cardiomyocyte oxygen free radicals and peroxynitrite. These effects were not observed upon contact with macrophages from iNOS^-/- HF mice. We conclude that leukocyte iNOS is obligatory for local and systemic inflammatory activation and cardiac remodeling in ischemic HF. Activated macrophages in HF may directly induce cardiomyocyte contractile dysfunction and oxidant stress upon cell-to-cell contact; this juxtacrine response requires macrophage-localized iNOS.

Sulforaphane Prevents Angiotensin II-Induced Testicular Cell Death via Activation of NRF2

Although angiotensin II (Ang II) was reported to facilitate sperm motility and intratesticular sperm transport, recent findings shed light on the efficacy of Ang II in stimulating inflammatory events in testicular peritubular cells, effect of which may play a role in male infertility. It is still unknown whether Ang II can induce testicular apoptotic cell death, which may be a more direct action of Ang II in male infertility. Therefore, the present study aims to determine whether Ang II can induce testicular apoptotic cell death and whether this action can be prevented by sulforaphane (SFN) via activating nuclear factor (erythroid-derived 2)-like 2 (NRF2), the governor of antioxidant-redox signalling. Eight-week-old male C57BL/6J wild type (WT) and Nrf2 gene knockout mice were treated with Ang II, in the presence or absence of SFN. In WT mice, SFN activated testicular NRF2 expression and function, along with a marked attenuation in Ang II-induced testicular oxidative stress, inflammation, endoplasmic reticulum stress, and apoptotic cell death. Deletion of the Nrf2 gene led to a complete abolishment of these efficacies of SFN. The present study indicated that Ang II may result in testicular apoptotic cell death, which can be prevented by SFN via the activation of NRF2.

Helix B surface peptide attenuates diabetic cardiomyopathy via AMPK-dependent autophagy

BACKGROUND

Erythropoietin (EPO) has been reported to exert protective effects on a host of damaged tissues. However, the erythropoietic effect of this hormone can result in high risks of thrombosis, stroke, and hypertension, remarkably limiting the clinical use of EPO. Helix B surface peptide (HBSP) is a small peptide derived from the helix-B domain of EPO. Surprisingly, HBSP retains the tissue protective properties of EPO without altering the hematocrit. Thus, we evaluated the possible role of HBSP on diabetic cardiomyopathy.

METHODS

Diabetes was induced in mice by intraperitoneal injections of streptozocin (STZ). Mice were randomly treated with normal saline or HBSP. Cardiac function, fibrosis, apoptosis, and myocardial mitochondrial morphology were examined. For in vitro experiments, H9C2 myoblast cells were randomly grouped as normal glucose (NG, 5 mM), NG+HBSP (100 nM), high glucose (HG, 33 mM), HG+HBSP (100 nM), HG+HBSP+3-methyladenine (3-MA, 10 mM), HG+rapamycin (Rapa, 100 nM), and HG+HBSP+Compound C (CC, 10 mM). Autophagosomes, LC3 dots, apoptosis and mitochondria membrane potential (MMP) of H9C2 cells were examined.The expressions of LC3, p62, p-AMPK (Thr172) and p-mTOR (Ser2448) were examined by Western blot.

RESULTS

HBSP markedly improved cardiac function, attenuated cardiac interstitial fibrosis, inhibited myocardial apoptosis, and ameliorated mitochondrial ultrastructure in mice with diabetic cardiomyopathy. HG reduced autophagy in H9C2 cells. HBSP enhanced autophagy in HG-treated H9C2 cells. HBSP reduced the apoptosis index of HG-treated H9C2 cells. HBSP increased the MMP of HG-treated H9C2 cells. HBSP increased the levels of p-AMPK (Thr172), and reduced p-mTOR (Ser2448) in HG-treated H9C2 cells, and the increase of p-AMPK (Thr172) was accompanied by the stimulation of autophagy. Autophagy inhibitor 3-MA and AMPK inhibitor CC mitigated HBSP-induced beneficial effect, whereas autophagy inducer Rapa alleviated the HG-induced cell apoptosis.

CONCLUSIONS

HBSP attenuates diabetic cardiomyopathy via autophagy mediated by AMPK-dependent pathway. HBSP may be a potential therapeutic intervention for diabetic cardiomyopathy.

Transcriptional patterns of reverse remodeling with left ventricular assist devices: a consistent signature

INTRODUCTION

Left ventricular assist device (LVAD) therapy has revolutionized the treatment of patients with advanced heart failure. Although originally intended for bridge-to-transplantation and destination therapy indications, a small subset of patients supported with LVADs exhibit complete myocardial recovery leading to device explanation. However, genetic and molecular determinants of partial and/or complete myocardial recovery remain largely unknown. Areas covered: We summarize current knowledge on alterations in heart failure transcriptome in response to LVAD support, as well as discuss common gene signatures potentially responsible for the reverse remodeling phenotype in the failing human heart. Expert commentary: Reverse remodeling after LVAD is likely a continuum between fully and partially recovered myocardium. Multicenter cardiac tissue repositories linked with detailed phenotype information may facilitate identification of genetic signals responsible for myocardial recovery in LVAD supported patients in the foreseeable future.

Apocynin influence on oxidative stress and cardiac remodeling of spontaneously hypertensive rats with diabetes mellitus

PURPOSE

Although increased oxidative stress is a major component of diabetic hypertensive cardiomyopathy, research into the effects of antioxidants on cardiac remodeling remains scarce. The actions of antioxidant apocynin include inhibiting reactive oxygen species (ROS) generation by nicotinamide adenine dinucleotide phosphate (NADPH) oxidases and ROS scavenging. We evaluated the effects of apocynin on cardiac remodeling in spontaneously hypertensive rats (SHR) with diabetes mellitus (DM).

METHODS

Male SHR were divided into four groups: control (SHR, n = 16); SHR treated with apocynin (SHR-APO; 16 mg/kg/day, added to drinking water; n = 16); diabetic SHR (SHR-DM, n = 13); and SHR-DM treated with apocynin (SHR-DM-APO, n = 14), for eight weeks. DM was induced by streptozotocin (40 mg/kg, single dose). Statistical analyzes: ANOVA and Tukey or Mann-Whitney.

RESULTS

Echocardiogram in diabetic groups showed higher left ventricular and left atrium diameters indexed for body weight, and higher isovolumetric relaxation time than normoglycemic rats; systolic function did not differ between groups. Isolated papillary muscle showed impaired contractile and relaxation function in diabetic groups. Developed tension was lower in SHR-APO than SHR. Myocardial hydroxyproline concentration was higher in SHR-DM than SHR, interstitial collagen fraction was higher in SHR-DM-APO than SHR-APO, and type III collagen protein expression was lower in SHR-DM and SHR-DM-APO than their controls. Type I collagen and lysyl oxidase expression did not differ between groups. Apocynin did not change collagen tissue. Myocardial lipid hydroperoxide concentration was higher in SHR-DM than SHR and SHR-DM-APO. Glutathione peroxidase activity was lower and catalase higher in SHR-DM than SHR. Apocynin attenuated antioxidant enzyme activity changes in SHR-DM-APO. Advanced glycation end-products and NADPH oxidase activity did not differ between groups.

CONCLUSION

Apocynin reduces oxidative stress independently of NADPH oxidase activity and does not change ventricular or myocardial function in spontaneously hypertensive rats with diabetes mellitus. The apocynin-induced myocardial functional impairment in SHR shows that apocynin actions need to be clarified during sustained chronic pressure overload.

Coadjuvants in the Diabetic Complications: Nutraceuticals and Drugs with Pleiotropic Effects

Because diabetes mellitus (DM) is a multifactorial metabolic disease, its prevention and treatment has been a constant challenge for basic and clinical investigators focused on translating their discoveries into clinical treatment of this complex disorder. In this review, we highlight recent experimental and clinical evidences of potential coadjuvants in the management of DM, such as polyphenols (quercetin, resveratrol and silymarin), cultured probiotic microorganisms and drugs acting through direct/indirect or pleiotropic effects on glycemic control in DM. Among several options, we highlight new promising therapeutic coadjuvants, including chemical scavengers, the probiotic kefir and the phosphodiesterase 5 inhibitors, which besides the reduction of hyperglycemia and ameliorate insulin resistance, they reduce oxidative stress and improve endothelial dysfunction in the systemic vascular circulation. In the near future, experimental studies are expected to clear the intracellular pathways involving coadjuvants. The design of clinical trials may also contribute to new strategies with coadjuvants against the harmful effects of diabetic complications.

Zinc deficiency exacerbates while zinc supplement attenuates cardiac hypertrophy in high-fat diet-induced obese mice through modulating p38 MAPK-dependent signaling

Childhood obesity often leads to cardiovascular diseases, such as obesity-related cardiac hypertrophy (ORCH), in adulthood, due to chronic cardiac inflammation. Zinc is structurally and functionally essential for many transcription factors; however, its role in ORCH and underlying mechanism(s) remain unclear and were explored here in mice with obesity induced with high-fat diet (HFD). Four week old mice were fed on either HFD (60%kcal fat) or normal diet (ND, 10% kcal fat) for 3 or 6 months, respectively. Either diet contained one of three different zinc quantities: deficiency (ZD, 10mg zinc per 4057kcal), normal (ZN, 30mg zinc per 4057kcal) or supplement (ZS, 90mg zinc per 4057kcal). HFD induced a time-dependent obesity and ORCH, which was accompanied by increased cardiac inflammation and p38 MAPK activation. These effects were worsened by ZD in HFD/ZD mice and attenuated by ZS in HFD/ZS group, respectively. Also, administration of a p38 MAPK specific inhibitor in HFD mice for 3 months did not affect HFD-induced obesity, but completely abolished HFD-induced, and zinc deficiency-worsened, ORCH and cardiac inflammation. In vitro exposure of adult cardiomyocytes to palmitate induced cell hypertrophy accompanied by increased p38 MAPK activation, which was heightened by zinc depletion with its chelator TPEN. Inhibition of p38 MAPK with its specific siRNA also prevented the effects of palmitate on cardiomyocytes. These findings demonstrate that ZS alleviates but ZD heightens cardiac hypertrophy in HFD-induced obese mice through suppressing p38 MAPK-dependent cardiac inflammatory and hypertrophic pathways.

Role of Mitochondrial Oxidative Stress in Glucose Tolerance, Insulin Resistance, and Cardiac Diastolic Dysfunction

BACKGROUND

Diabetes mellitus (DM) is associated with mitochondrial oxidative stress. We have shown that myocardial oxidative stress leads to diastolic dysfunction in a hypertensive mouse model. Therefore, we hypothesized that diabetes mellitus could cause diastolic dysfunction through mitochondrial oxidative stress and that a mitochondria-targeted antioxidant (MitoTEMPO) could prevent diastolic dysfunction in a diabetic mouse model.

METHODS AND RESULTS

C57BL/6J mice were fed either 60 kcal % fat diet (high-fat diet [HFD]) or normal chow (control) for 8 weeks with or without concurrent MitoTEMPO administration, followed by in vivo assessment of diastolic function and ex vivo studies. HFD mice developed impaired glucose tolerance compared with the control (serum glucose=495±45 mg/dL versus 236±30 mg/dL at 60 minutes after intraperitoneal glucose injection, P<0.05). Myocardial tagged cardiac magnetic resonance imaging showed significantly reduced diastolic circumferential strain (Ecc) rate in the HFD mice compared with controls (5.0±0.3 1/s versus 7.4±0.5 1/s, P<0.05), indicating diastolic dysfunction in the HFD mice. Systolic function was comparable in both groups (left ventricular ejection fraction=66.4±1.4% versus 66.7±1.2%, P>0.05). MitoTEMPO-treated HFD mice showed significant reduction in mitochondria reactive oxygen species, S-glutathionylation of cardiac myosin binding protein C, and diastolic dysfunction, comparable to the control. The fasting insulin levels of MitoTEMPO-treated HFD mice were also comparable to the controls (P>0.05).

CONCLUSIONS

MitoTEMPO treatment prevented insulin resistance and diastolic dysfunction, suggesting that mitochondrial oxidative stress may be involved in the pathophysiology of both conditions.

Fenofibrate increases cardiac autophagy via FGF21/SIRT1 and prevents fibrosis and inflammation in the hearts of Type 1 diabetic mice

Fenofibrate (FF) as a commonly-used lipid-lowering medicine in clinics was examined for its potentially repurposing to prevent the cardiac abnormalities in patients with type 1 diabetes. We demonstrated here that fenofibrate significantly prevented diabetes-induced cardiac dysfunction and remodeling in fibroblast growth factor 21 (FGF21)-dependent manner.

Novel EGFR inhibitors attenuate cardiac hypertrophy induced by angiotensin II

Cardiac hypertrophy is an important risk factor for heart failure. Epidermal growth factor receptor (EGFR) has been found to play a role in the pathogenesis of various cardiovascular diseases. The aim of this current study was to examine the role of EGFR in angiotensin II (Ang II)-induced cardiac hypertrophy and identify the underlying molecular mechanisms. In this study, we observed that both Ang II and EGF could increase the phospohorylation of EGFR and protein kinase B (AKT)/extracellular signal-regulated kinase (ERK), and then induce cell hypertrophy in H9c2 cells. Both pharmacological inhibitors and genetic silencing significantly reduced Ang II-induced EGFR signalling pathway activation, hypertrophic marker overexpression, and cell hypertrophy. In addition, our results showed that Ang II-induced EGFR activation is mediated by c-Src phosphorylation. In vivo, Ang II treatment significantly led to cardiac remodelling including cardiac hypertrophy, disorganization and fibrosis, accompanied by the activation of EGFR signalling pathway in the heart tissues, while all these molecular and pathological alterations were attenuated by the oral administration with EGFR inhibitors. In conclusion, the c-Src-dependent EGFR activation may play an important role in Ang II-induced cardiac hypertrophy, and inhibition of EGFR by specific molecules may be an effective strategy for the treatment of Ang II-associated cardiac diseases.