Evidence for a hyper-reductive redox in a sub-set of heart failure patients

Integrative transcriptomics and proteomics analysis reveal the protection of Astragaloside IV against myocardial fibrosis by regulating senescence

Myocardial fibrosis (MF) is a pivotal pathological process implicated in various cardiovascular diseases, particularly heart failure. Astragaloside IV (AS-IV), a natural compound derived from Astragalus membranaceus, possesses potent cardioprotective properties. However, the precise molecular mechanisms underlying its anti-MF effects, particularly in relation to senescence, remain elusive. Thus, this study aimed to investigate the therapeutic potential and underlying molecular mechanisms of AS-IV in treating ISO-induced MF in mice, employing transcriptomics, proteomics, in vitro, and in vivo experiments. We assessed the positive effects of AS-IV on ISO-induced MF using HE staining, Masson staining, ELISA, immunohistochemical staining, transthoracic echocardiography, transmission electron microscopy, and DHE fluorescence staining. Additionally, we elucidated the regulatory role of AS-IV in MF through comprehensive transcriptomics and proteomics analyses, complemented by Western blotting and RT-qPCR validation of pertinent molecular pathways. Our findings demonstrated that AS-IV treatment markedly attenuated ISO-induced myocardial injury and oxidative stress, concomitantly inhibiting the release of SASPs. Furthermore, integrated transcriptomics and proteomics analyses revealed that the anti-MF mechanism of AS-IV was associated with regulating cellular senescence and the p53 signaling pathway. These results highlight AS-IV exerts its anti-MF effects not only by inhibiting oxidative stress but also by modulating senescence through the p53 signaling pathway.

Novel Oxidative Stress Biomarkers with Risk Prognosis Values in Heart Failure

Oxidative stress (OS) is mediated by reactive oxygen species (ROS), which in cardiovascular and other disease states, damage DNA, lipids, proteins, other cellular and extra-cellular components. OS is both initiated by, and triggers inflammation, cardiomyocyte apoptosis, matrix remodeling, myocardial fibrosis, and neurohumoral activation. These have been linked to the development of heart failure (HF). Circulating biomarkers generated by OS offer potential utility in patient management and therapeutic targeting. Novel OS-related biomarkers such as NADPH oxidases (sNox2-dp, Nrf2), advanced glycation end-products (AGE), and myeloperoxidase (MPO), are signaling molecules reflecting pathobiological changes in HF. This review aims to evaluate current OS-related biomarkers and their associations with clinical outcomes and to highlight those with greatest promise in diagnosis, risk stratification and therapeutic targeting in HF.

Succinate level is increased and succinate dehydrogenase exerts forward and reverse catalytic activities in lipopolysaccharides-stimulated cardiac tissue: The protective role of dimethyl malonate

This study aimed to investigate the alterations of myocardial succinate and fumarate levels with or without succinate dehydrogenase (SDH) inhibitor dimethyl malonate during 24 h of lipopolysaccharides (LPS) challenge, as well as the effects of dimethyl malonate on the impaired cardiac tissue. Myocardial succinate and fumarate levels were increased in the initial 9 h of LPS challenge. During this time, dimethyl malonate increased the succinate level, decreased the fumarate level, aggravated the cardiac dysfunction, reduced the oxidative stress, had little effect on interleukin-1β production, promoted interleukin-10 production and bothered the ATP production. Co-treatment with exogenous succinate significantly increased interleukin-1β production in this period. After 12 h of LPS challenge, myocardial the succinate level increased sharply, while the fumarate level gradually decreased. During 12-24 h of LPS challenge, dimethyl malonate effectively reduced the succinate level, increased the fumarate level, improved cardiac dysfunction, inhibited interleukin-1β production, and had little effect on oxidative stress, interleukin-10 production, and ATP production. LPS challenge also significantly increased the myocardial succinate receptor 1 expression and circulating succinate level. Inhibition of succinate receptor 1 significantly reduced the mRNA expression of interleukin-1β. In conclusion, the current study suggests that myocardial succinate accumulates during LPS challenge, and that SDH activity may be transformed (from forward to reversed) and involved in a line of stress response. Dimethyl malonate inhibits SDH and, depending on the time of treatment, reduces LPS-induced cardiac impairment. Furthermore, accumulated succinate exerts pro-inflammatory effects partly via succinate receptor 1 signaling.

Redox signaling in heart failure and therapeutic implications

Heart failure is a growing health burden worldwide characterized by alterations in excitation-contraction coupling, cardiac energetic deficit and oxidative stress. While current treatments are mostly limited to antagonization of neuroendocrine activation, more recent data suggest that also targeting metabolism may provide substantial prognostic benefit. However, although in a broad spectrum of preclinical models, oxidative stress plays a causal role for the development and progression of heart failure, no treatment that targets reactive oxygen species (ROS) directly has entered the clinical arena yet. In the heart, ROS derive from various sources, such as NADPH oxidases, xanthine oxidase, uncoupled nitric oxide synthase and mitochondria. While mitochondria are the primary source of ROS in the heart, communication between different ROS sources may be relevant for physiological signalling events as well as pathologically elevated ROS that deteriorate excitation-contraction coupling, induce hypertrophy and/or trigger cell death. Here, we review the sources of ROS in the heart, the modes of pathological activation of ROS formation as well as therapeutic approaches that may target ROS specifically in mitochondria.

Identification of Nrf2-responsive microRNA networks as putative mediators of myocardial reductive stress

Although recent advances in the treatment of acute coronary heart disease have reduced mortality rates, few therapeutic strategies exist to mitigate the progressive loss of cardiac function that manifests as heart failure. Nuclear factor, erythroid 2 like 2 (Nfe2l2, Nrf2) is a transcriptional regulator that is known to confer transient myocardial cytoprotection following acute ischemic insult; however, its sustained activation paradoxically causes a reductive environment characterized by excessive antioxidant activity. We previously identified a subset of 16 microRNAs (miRNA) significantly diminished in Nrf2-ablated (Nrf2-/-) mouse hearts, leading to the hypothesis that increasing levels of Nrf2 activation augments miRNA induction and post-transcriptional dysregulation. Here, we report the identification of distinct miRNA signatures (i.e. "reductomiRs") associated with Nrf2 overexpression in a cardiac-specific and constitutively active Nrf2 transgenic (caNrf2-Tg) mice expressing low (TgL) and high (TgH) levels. We also found several Nrf2 dose-responsive miRNAs harboring proximal antioxidant response elements (AREs), implicating these "reductomiRs" as putative meditators of Nrf2-dependent post-transcriptional regulation. Analysis of mRNA-sequencing identified a complex network of miRNAs and effector mRNAs encoding known pathological hallmarks of cardiac stress-response. Altogether, these data support Nrf2 as a putative regulator of cardiac miRNA expression and provide novel candidates for future mechanistic investigation to understand the relationship between myocardial reductive stress and cardiac pathophysiology.

Reductive stress in cancer

Reductive stress is defined as a condition characterized by excess accumulation of reducing equivalents (e.g., NADH, NADPH, GSH), surpassing the activity of endogenous oxidoreductases. Excessive reducing equivalents can perturb cell signaling pathways, change the formation of disulfide bonding in proteins, disturb mitochondrial homeostasis or decrease metabolism. Reductive stress is influenced by cellular antioxidant load, its flux and a subverted homeostasis that paradoxically can result in excess ROS induction. Balanced reducing equivalents and antioxidant enzymes that contribute to reductive stress can be regulated by Nrf2, typically considered as an oxidative stress induced transcription factor. Cancer cells may coordinate distinct pools of redox couples under reductive stress and these may link to biological consequences from both molecular and translational standpoints. In cancer, there is recent interest in understanding how selective induction of reductive stress may influence therapeutic management and disease progression.

Concurrent diabetes and heart failure: interplay and novel therapeutic approaches

Diabetes mellitus increases the risk of developing heart failure, and the co-existence of both diseases worsens cardiovascular outcomes, hospitalization and the progression of heart failure. Despite current advancements on therapeutic strategies to manage hyperglycemia, the likelihood of developing diabetes-induced heart failure is still significant, especially with the accelerating global prevalence of diabetes and an ageing population. This raises the likelihood of other contributing mechanisms beyond hyperglycemia in predisposing diabetic patients to cardiovascular disease risk. There has been considerable interest in understanding the alterations in cardiac structure and function in the diabetic patients, collectively termed as "diabetic cardiomyopathy". However, the factors that contribute to the development of diabetic cardiomyopathies is not fully understood. This review summarizes the main characteristics of diabetic cardiomyopathies, and the basic mechanisms that contribute to its occurrence. This includes perturbations in insulin resistance, fuel preference, reactive oxygen species generation, inflammation, cell death pathways, neurohormonal mechanisms, advanced glycated end-products accumulation, lipotoxicity, glucotoxicity, and posttranslational modifications in the heart of the diabetic. This review also discusses the impact of antihyperglycemic therapies on the development of heart failure, as well as how current heart failure therapies influence glycemic control in diabetic patients. We also highlight the current knowledge gaps in understanding how diabetes induces heart failure.

The vasculature: a therapeutic target in heart failure?

It is well established that the vasculature plays a crucial role in maintaining oxygen and nutrients supply to the heart. Increasing evidence further suggest that the microcirculation has additional roles in supporting a healthy microenvironment. Heart failure is well known to be associated with changes and functional impairment of the microvasculature. The specific ablation of protective signals in endothelial cells in experimental models is sufficient to induce heart failure. Therefore, restoring a healthy endothelium and microcirculation may be a valuable therapeutic strategy to treat heart failure. The present review article will summarize the current understanding of the vascular contribution to heart failure with reduced or preserved ejection fraction. Novel therapeutic approaches including next generation pro-angiogenic therapies and non-coding RNA therapeutics, as well as the targeting of metabolites or metabolic signaling, vascular inflammation and senescence will be discussed.

Reductive stress in striated muscle cells

Reductive stress is defined as a condition of sustained increase in cellular glutathione/glutathione disulfide and NADH/NAD+ ratios. Reductive stress is emerging as an important pathophysiological event in several diseased states, being as detrimental as is oxidative stress. Occurrence of reductive stress has been documented in several cardiomyopathies and is an important pathophysiological factor particularly in coronary artery disease and myocardial infarction. Excess activation of the transcription factor, Nrf2-the master regulator of the antioxidant response-, consequent in most cases to defective autophagy, can lead to reductive stress. In addition, hyperglycemia-induced activation of the polyol pathway can lead to increased NADH/NAD+ ratio, which might translate into increased levels of hydrogen sulfide-via enhanced activity of cystathionine β-synthase-that would fuel reductive stress through inhibition of mitochondrial complex I. Reductive stress may be either a potential weapon against cancer priming tumor cells to apoptosis or a cancer's ally promoting tumor cell proliferation and making tumor cells resistant to reactive oxygen species-inducing drugs. In non-cancer pathological states reductive stress is definitely harmful paradoxically leading to reactive oxygen species overproduction via excess NADPH oxidase 4 activity. In face of the documented occurrence of reductive stress in several heart diseases, there is much less information about the occurrence and effects of reductive stress in skeletal muscle tissue. In the present review we describe relevant results emerged from studies of reductive stress in the heart and review skeletal muscle conditions in which reductive stress has been experimentally documented and those in which reductive stress might have an as yet unrecognized pathophysiological role. Establishing whether reductive stress has a (patho)physiological role in skeletal muscle will hopefully contribute to answer the question whether antioxidant supplementation to the general population, athletes, and a large cohort of patients (e.g. heart, sarcopenic, dystrophic, myopathic, cancer, and bronco-pulmonary patients) is harmless or detrimental.

Forced expression of miR-143 and -145 in cardiomyocytes induces cardiomyopathy with a reductive redox shift

BACKGROUND

Animal model studies show that reductive stress is involved in cardiomyopathy and myopathy, but the exact physiological relevance remains unknown. In addition, the microRNAs miR-143 and miR-145 have been shown to be upregulated in cardiac diseases, but the underlying mechanisms associated with these regulators have yet to be explored.

METHODS

We developed transgenic mouse lines expressing exogenous miR-143 and miR-145 under the control of the alpha-myosin heavy chain (αMHC) promoter/enhancer.

RESULTS

The two transgenic lines showed dilated cardiomyopathy-like characteristics and early lethality with markedly increased expression of miR-143. The expression of hexokinase 2 (HK2), a cardioprotective gene that is a target of miR-143, was strongly suppressed in the transgenic hearts, but the in vitro HK activity and adenosine triphosphate (ATP) content were comparable to those observed in wild-type mice. In addition, transgenic complementation of HK2 expression did not reduce mortality rates. Although HK2 is crucial for the pentose phosphate pathway (PPP) and glycolysis, the ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG) was unexpectedly higher in the hearts of transgenic mice. The expression of gamma-glutamylcysteine synthetase heavy subunit (γ-GCSc) and the in vitro activity of glutathione reductase (GR) were also higher, suggesting that the recycling of GSH and its de novo biosynthesis were augmented in transgenic hearts. Furthermore, the expression levels of glucose-6-phosphate dehydrogenase (G6PD, a rate-limiting enzyme for the PPP) and p62/SQSTM1 (a potent inducer of glycolysis and glutathione production) were elevated, while p62/SQSTM1 was upregulated at the mRNA level rather than as a result of autophagy inhibition. Consistent with this observation, nuclear factor erythroid-2 related factor 2 (Nrf2), Jun N-terminal kinase (JNK) and inositol-requiring enzyme 1 alpha (IRE1α) were activated, all of which are known to induce p62/SQSTM1 expression.

CONCLUSIONS

Overexpression of miR-143 and miR-145 leads to a unique dilated cardiomyopathy phenotype with a reductive redox shift despite marked downregulation of HK2 expression. Reductive stress may be involved in a wider range of cardiomyopathies than previously thought.

Reductive Stress: Neglected Science

Over the past six decades, the concept of "redox" was focused on one arm of the redox spectrum: oxidative stress. In fact, a vast majority of experimental and clinical studies addressing redox mechanisms claimed "oxidative stress" as the culprit for acute or chronic disease conditions. Recent studies have documented that reactive oxygen species (ROS) are crucial signaling molecules facilitating various cellular processes. Thus, abrogation of these key ROS signaling through abundant antioxidant systems will result in detrimental effects. This Forum highlights the emerging concepts and related mechanisms of the other extreme of the redox spectrum, known as "reductive stress (RS)." The Forum including original research and review articles discusses the causes and consequences of RS in various biological and pathological conditions such as metabolism, cancer, drug resistance, cardiac hypertrophy, and microbial adaptations.

Convergences of Life Sciences and Engineering in Understanding and Treating Heart Failure

On March 1 and 2, 2018, the National Institutes of Health 2018 Progenitor Cell Translational Consortium, Cardiovascular Bioengineering Symposium, was held at the University of Alabama at Birmingham. Convergence of life sciences and engineering to advance the understanding and treatment of heart failure was the theme of the meeting. Over 150 attendees were present, and >40 scientists presented their latest work on engineering human functional myocardium for disease modeling, drug development, and heart failure research. The scientists, engineers, and physicians in the field of cardiovascular sciences met and discussed the most recent advances in their work and proposed future strategies for overcoming the major roadblocks of cardiovascular bioengineering and therapy. Particular emphasis was given for manipulation and using of stem/progenitor cells, biomaterials, and methods to provide molecular, chemical, and mechanical cues to cells to influence their identity and fate in vitro and in vivo. Collectively, these works are profoundly impacting and progressing toward deciphering the mechanisms and developing novel treatments for left ventricular dysfunction of failing hearts. Here, we present some important perspectives that emerged from this meeting.

Heart Failure in Type 2 Diabetes Mellitus

Patients with diabetes mellitus have >2× the risk for developing heart failure (HF; HF with reduced ejection fraction and HF with preserved ejection fraction). Cardiovascular outcomes, hospitalization, and prognosis are worse for patients with diabetes mellitus relative to those without. Beyond the structural and functional changes that characterize diabetic cardiomyopathy, a complex underlying, and interrelated pathophysiology exists. Despite the success of many commonly used antihyperglycemic therapies to lower hyperglycemia in type 2 diabetes mellitus the high prevalence of HF persists. This, therefore, raises the possibility that additional factors beyond glycemia might contribute to the increased HF risk in diabetes mellitus. This review summarizes the state of knowledge about the impact of existing antihyperglycemic therapies on HF and discusses potential mechanisms for beneficial or deleterious effects. Second, we review currently approved pharmacological therapies for HF and review evidence that addresses their efficacy in the context of diabetes mellitus. Dysregulation of many cellular mechanisms in multiple models of diabetic cardiomyopathy and in human hearts have been described. These include oxidative stress, inflammation, endoplasmic reticulum stress, aberrant insulin signaling, accumulation of advanced glycated end-products, altered autophagy, changes in myocardial substrate metabolism and mitochondrial bioenergetics, lipotoxicity, and altered signal transduction such as GRK (g-protein receptor kinase) signaling, renin angiotensin aldosterone signaling and β-2 adrenergic receptor signaling. These pathophysiological pathways might be amenable to pharmacological therapy to reduce the risk of HF in the context of type 2 diabetes mellitus. Successful targeting of these pathways could alter the prognosis and risk of HF beyond what is currently achieved using existing antihyperglycemic and HF therapeutics.

Analysis of levels of oxidative stress markers depending on the left ventricular ejection fraction in patients with chronic heart failure

Aim.To study and analyze the levels of oxidative stress (OS) markers (malondialdehyde (MDA), superoxide dismutase (SOD), advanced oxidation protein products (AOPPs)) depending on the left ventricular ejection fraction (LVEF) and functional class (FC) in patients with chronic heart failure (CHF).

Material and methods.We examined 60 somatically healthy individuals and 345 patients with CHF, which were divided into three main groups depending on the LVEF and subgroups depending on FC. The levels of OS markers were determined in blood serum — MDA, SOD and AOPPs.

Results.In the group of patients with preserved LVEF and FC II-IV CHF, levels of MDA and AOPPs were statistically significantly higher, and the SOD level was lower compared to the control group. In the group of patients with moderately reduced and reduced LVEF, the levels of MDA and AOPPs were statistically significantly higher, and SOD activity was lower compared with the control group and the group of patients with CHF and preserved LVEF. In patients with CHF with higher FC, there was a statistically significant increase of MDA and AOPPs levels and decrease of SOD activity. The most pronounced changes in the levels of above-mentioned markers were recorded in patients with reduced LVEF. According to the correlation analysis a direct relationship between the levels of markers of the OS and clinical manifestations of the disease was found.

Conclusion.Changes in levels of MDA, SOD and AOPPs in patients with CHF were detected already in the early stages of the disease compared with the control group. In patients with higher FC CHF and preserved, moderately reduced and reduced LVEF, a statistically significant increase in the levels of MDA and AOPPs and a decrease of SOD activity were observed. The most pronounced changes in the levels of the markers were indicated in patients with reduced LVEF.

Cardiac-specific overexpression of aldehyde dehydrogenase 2 exacerbates cardiac remodeling in response to pressure overload

Pathological cardiac remodeling during heart failure is associated with higher levels of lipid peroxidation products and lower abundance of several aldehyde detoxification enzymes, including aldehyde dehydrogenase 2 (ALDH2). An emerging idea that could explain these findings concerns the role of electrophilic species in redox signaling, which may be important for adaptive responses to stress or injury. The purpose of this study was to determine whether genetically increasing ALDH2 activity affects pressure overload-induced cardiac dysfunction. Mice subjected to transverse aortic constriction (TAC) for 12 weeks developed myocardial hypertrophy and cardiac dysfunction, which were associated with diminished ALDH2 expression and activity. Cardiac-specific expression of the human ALDH2 gene in mice augmented myocardial ALDH2 activity but did not improve cardiac function in response to pressure overload. After 12 weeks of TAC, ALDH2 transgenic mice had larger hearts than their wild-type littermates and lower capillary density. These findings show that overexpression of ALDH2 augments the hypertrophic response to pressure overload and imply that downregulation of ALDH2 may be an adaptive response to certain forms of cardiac pathology.