The regulation of protein acetylation influences the redox homeostasis to protect the heart

Ornithine carbamoyltransferase (OTC) is a key enzyme in the urea cycle to detoxify ammonium produced from amino acid catabolism. OTC deficiency is an X-linked genetic disorder ranging from fatal in newborns to hyperammonemia and anorexia in adults. Through affinity purification of acetylated peptides and mass spectrometry, we identified that OTC is acetylated on lysine residues, including Lys88, which is also mutated in OTC-deficient patients. OTC acetylation was confirmed to occur under physiological conditions. Biochemical characterizations revealed that OTC Lys88 acetylation decreases the affinity for carbamoyl phosphate, one of the two OTC substrates, and the maximum velocity, whereas the K(m) for ornithine, the other OTC substrate, is not affected. Furthermore, Lys88 acetylation is regulated by both extracellular glucose and amino acid availability, indicating that OTC activity may be regulated by cellular metabolic status. Our results provide an example of the novel mechanism of regulating metabolic enzyme activity through protein acetylation.

Loss of reduction-oxidation (redox) homeostasis and generation of excess free oxygen radicals play an important role in the pathogenesis of diabetes, hypertension, and consequent cardiovascular disease. Reactive oxygen species are integral in routine in physiologic mechanisms. However, loss of redox homeostasis contributes to proinflammatory and profibrotic pathways that promote impairments in insulin metabolic signaling, reduced endothelial-mediated vasorelaxation, and associated cardiovascular and renal structural and functional abnormalities. Redox control of metabolic function is a dynamic process with reversible pro- and anti-free radical processes. Labile iron is necessary for the catalysis of superoxide anion, hydrogen peroxide, and the generation of the damaging hydroxyl radical. Acute hypoxia and cellular damage in cardiovascular tissue liberate larger amounts of cytosolic and extracellular iron that is poorly liganded; thus, large increases in the generation of oxygen free radicals are possible, causing tissue damage. The understanding of iron and the imbalance of redox homeostasis within the vasculature is integral in hypertension and progression of metabolic dysregulation that contributes to insulin resistance, endothelial dysfunction, and cardiovascular and kidney disease.

Redox homeostasis, the delicate balance between oxidative and reductive processes, is crucial for cellular function and overall organismal health. At the molecular level, cells need to maintain a fine balance between the levels of reactive oxygen species (ROS) and reducing equivalents such as glutathione and nicotinamide adenine dinucleotide phosphate. The perturbation of redox homeostasis due to excessive ROS production leads to oxidative stress that can damage lipids, proteins, and nucleic acids. Conversely, an overly reduced cellular environment due to overabundant reducing equivalents results in reductive stress, which also interferes with important cellular signaling and physiological processes. Disrupted redox homeostasis is linked to various pathological conditions, including neurodegenerative diseases, inflammatory diseases, cancer, and cardiovascular diseases. Cells employ diverse mechanisms to manage redox imbalance. The hypoxia response pathway, mediated by hypoxia-inducible factors and responsible for sensing and defending against low oxygen levels, plays a vital role in maintaining redox homeostasis. In this review, we highlight the complex and multifaceted crosstalk between hypoxia-inducible factors and redox homeostasis and discuss avenues for future research. Understanding the molecular mechanisms that link hypoxia-inducible factors to oxidative and reductive stresses is essential for comprehending several pathological conditions associated with hypoxia and redox imbalance.

Acetylation of proteins with the addition of an acetyl group on the lysine residue is one of the vital posttranslational modifications that regulate protein stability, function and intracellular compartmentalization. Like other posttranslational modifications, protein acetylation influences many if not all vital functions of the cell. Protein acetylation has been originally associated with histone acetylation regulated by Histone Acetyl Transferase (HAT) and Histone Deacetylase (HDAC) and was mainly considered to be involved in epigenetic regulation through chromatin remodelling. It is now widely referred to as lysine acetylation orchestrated by lysine acetyl transferase (KAT) and lysine deacetylase (KDAC) and influences many cellular functions. Protein acetylation fine tunes the redox balance and cell signalling in the context of cancer by exerting its control on expression of two very important redox sensors viz. Nrf2 and NF-κB. Accumulating evidences show that inhibitors of deacetylase (KDACi), responsible for cytotoxic effects in cancer cells, mediate their actions by inhibiting the deacetylases, thereby simulating an hyperacetylation state of histone as well as non-histone proteins, similar to the one created by KATs. Emergence of calreticulin (CRT) mediated protein acetylation system using polyphenolic acetates as donors coupled with over expression of CRT has opened new avenues for targeting protein acetylation for improving cancer therapy. Modifiers of protein acetylation are therefore, emerging as a class of anticancer therapeutics and adjuvant as they inhibit growth, induce differentiation and death (apoptosis) differentially in cancer cells and also exhibit chemo-radiation sensitizing potential. Although pre-clinical investigations with many natural and synthetic KDAC inhibitors have been very promising, their clinical utility has so far been limited to certain types of cancers of the hematopoietic system. The future of protein acetylation modifiers appears to depend on the development of newer engineered molecules and their rational combinations that can exploit the differences in the regulation of protein acetylation between tumor and normal cells/tissues.

Thoughts on Future Trends in Cardiology

Ferroptosis, distinct from apoptosis, necrosis, autophagy, and other types of cell death, is a novel iron-dependent regulated cell death characterized by the accumulation of lipid peroxides and redox imbalance with distinct morphological, biochemical, and genetic features. Dysregulation of iron homeostasis, the disruption of antioxidative stress pathways and lipid peroxidation are crucial in ferroptosis. Ferroptosis is involved in the pathogenesis of several cardiovascular diseases, including atherosclerosis, cardiomyopathy, myocardial infarction, ischemia-reperfusion injury, abdominal aortic aneurysm, aortic dissection, and heart failure. Therefore, a comprehensive understanding of the mechanisms that regulate ferroptosis in cardiovascular diseases will enhance the prevention and treatment of these diseases. This review discusses the latest findings on the molecular mechanisms of ferroptosis and its regulation in cardiovascular diseases, the application of ferroptosis modulators in cardiovascular diseases, and the role of traditional Chinese medicines in ferroptosis regulation to provide a comprehensive understanding of the pathogenesis of cardiovascular diseases and identify new prevention and treatment options.

Reactive species, such as those of oxygen, nitrogen, and sulfur, are considered part of normal cellular metabolism and play significant roles that can impact several signaling processes in ways that lead to either cellular sustenance, protection, or damage. Cellular redox processes involve a balance in the production of reactive species (RS) and their removal because redox imbalance may facilitate oxidative damage. Physiologically, redox homeostasis is essential for the maintenance of many cellular processes. RS may serve as signaling molecules or cause oxidative cellular damage depending on the delicate equilibrium between RS production and their efficient removal through the use of enzymatic or nonenzymatic cellular mechanisms. Moreover, accumulating evidence suggests that redox imbalance plays a significant role in the progression of several neurodegenerative diseases. For example, studies have shown that redox imbalance in the brain mediates neurodegeneration and alters normal cytoprotective responses to stress. Therefore, this review describes redox homeostasis in neurodegenerative diseases with a focus on Alzheimer's and Parkinson's disease. A clearer understanding of the redox-regulated processes in neurodegenerative disorders may afford opportunities for newer therapeutic strategies.

Mitochondrial proton leak is the principal mechanism that incompletely couples substrate oxygen to ATP generation. This chapter briefly addresses the recent progress made in understanding the role of proton leak in the pathogenesis of cardiovascular diseases. Majority of the proton conductance is mediated by uncoupling proteins (UCPs) located in the mitochondrial inner membrane. It is evident that the proton leak and reactive oxygen species (ROS) generated from electron transport chain (ETC) in mitochondria are linked to each other. Increased ROS production has been shown to induce proton conductance, and in return, increased proton conductance suppresses ROS production, suggesting the existence of a positive feedback loop that protects the biological systems from detrimental effects of augmented oxidative stress. There is mounting evidence attributing to proton leak and uncoupling proteins a crucial role in the pathogenesis of cardiovascular disease. We can surmise the role of "uncoupling" in cardiovascular disorders as follows; First, the magnitude of the proton leak and the mechanism involved in mediating the proton leak determine whether there is a protective effect against ischemia-reperfusion (IR) injury. Second, uncoupling by UCP2 preserves vascular function in diet-induced obese mice as well as in diabetes. Third, etiology determines whether the proton conductance is altered or not during hypertension. And fourth, proton leak regulates ATP synthesis-uncoupled mitochondrial ROS generation, which determines pathological activation of endothelial cells for recruitment of inflammatory cells. Continue effort in improving our understanding in the role of proton leak in the pathogenesis of cardiovascular and metabolic diseases would lead to identification of novel therapeutic targets for treatment.

Hypertension is one of the major risk factor able to promote development and progression of several cardiovascular diseases, including left ventricular hypertrophy and dysfunction, myocardial infarction, stroke, and congestive heart failure. Also, it is one of the major driven of high cardiovascular risk profile in patients with metabolic complications, including obesity, metabolic syndrome and diabetes, as well as in those with renal disease. Thus, effective control of hypertension is a key factor for any preventing strategy aimed at reducing the burden of hypertension-related cardiovascular diseases in the clinical practice. Among various regulatory and contra-regulatory systems involved in the pathogenesis of cardiovascular and renal diseases, renin-angiotensin system (RAS) plays a major role. However, despite the identification of renin and the availability of various assays for measuring its plasma activity, the specific pathophysiological role of RAS has not yet fully characterized. In the last years, however, several notions on the RAS have been improved by the results of large, randomized clinical trials, performed in different clinical settings and in different populations treated with RAS inhibiting drugs, including angiotensin converting enzyme (ACE) inhibitors and antagonists of the AT1 receptor for angiotensin II (ARBs). These findings suggest that the RAS should be considered to have a central role in the pathogenesis of different cardiovascular diseases, for both therapeutic and preventive purposes, without having to measure its level of activation in each patient. The present document will discuss the most critical issues of the pathogenesis of different cardiovascular diseases with a specific focus on RAS blocking agents, including ACE inhibitors and ARBs, in the light of the most recent evidence supporting the use of these drugs in the clinical management of hypertension and hypertension-related cardiovascular diseases.

Inflammation is an important process involved in several cardiovascular diseases (CVDs), and nod‐like receptor family pyrin domain containing 3 (NLRP3) inflammasome is a vital player in innate immunity and inflammation. In this review, we aim to provide a comprehensive summary of the current knowledge on the role and involvement of NLRP3 inflammasome in the pathogenesis and treatment of CVDs. NLRP3 inflammasome functions as a molecular platform, and triggers the activation of caspase‐1 and cleavage of pro‐IL‐1β, pro‐IL‐18, and gasdermin D (GSDMD). Cleaved NT‐GSDMD forms pores in the cell membrane and initiates pyroptosis, inducing cell death and release of many intracellular pro‐inflammatory molecules. NLRP3 inflammasome activation is triggered via inter‐related pathways downstream of K+ efflux, lysosomal disruption, and mitochondrial dysfunction. In addition, the Golgi apparatus and noncoding RNAs are gradually being recognized to play important roles in NLRP3 inflammasome activation. Many investigations have revealed the association between NLRP3 inflammasome and CVDs, including atherosclerosis, ischemia/reperfusion (I/R) injury and heart failure induced by pressure overload or cardiomyopathy. Some existing medications, including orthodox and natural medicines, used for CVD treatment have been newly discovered to act via NLRP3 inflammasome. In addition, NLRP3 inflammasome pathway components such as NLRP3, caspase‐1, and IL‐1β may be considered as novel therapeutic targets for CVDs. Thus, NLRP3 inflammasome is a key molecule involved in the pathogenesis of CVDs, and further research focused on development of NLRP3 inflammasome‐based targeted therapies for CVDs and the clinical evaluation of these therapies is essential.

Mitochondrial dysfunction is increasingly recognized as a critical driver in the pathogenesis of cardiovascular diseases. Mitochondrial quality control (MQC) is an ensemble of adaptive mechanisms aimed at maintaining mitochondrial integrity and functionality and is essential for cardiomyocyte viability and optimal cardiac performance under the stress of cardiovascular pathology. The key MQC components include mitochondrial fission, fusion, mitophagy, and mitochondria-dependent cell death, each contributing uniquely to cellular homeostasis. The dynamic interplay among these processes is intricately linked to pathological phenomena, such as redox imbalance, calcium overload, dysregulated energy metabolism, impaired signal transduction, mitochondrial unfolded protein response, and endoplasmic reticulum stress. Aberrant mitochondrial fission is an early marker of mitochondrial injury and cardiomyocyte apoptosis, whereas reduced mitochondrial fusion is frequently observed in stressed cardiomyocytes and is associated with mitochondrial dysfunction and cardiac impairment. Mitophagy is a protective, selective autophagic degradation process that eliminates structurally compromised mitochondria, preserving mitochondrial network integrity. However, dysregulated mitophagy can exacerbate cellular injury, promoting cell death. Beyond their role as the primary energy source of the cell, mitochondria are also central regulators of cardiomyocyte survival, mediating apoptosis and necroptosis in reperfused myocardium. Consequently, MQC impairment may be a determining factor in cardiomyocyte fate. This review consolidates current insights into the regulatory mechanisms and pathological significance of MQC across diverse cardiovascular conditions, highlighting potential therapeutic avenues for the clinical management of heart diseases.

Endothelial cell (EC), consisting of the innermost cellular layer of all types of vessels, is not only a barrier composer but also performing multiple functions in physiological processes. It actively controls the vascular tone and the extravasation of water, solutes, and macromolecules; modulates circulating immune cells as well as platelet and leukocyte recruitment/adhesion and activation. In addition, EC also tightly keeps coagulation/fibrinolysis balance and plays a major role in angiogenesis. Therefore, endothelial dysfunction contributes to the pathogenesis of many diseases. Growing pieces of evidence suggest that histone protein acetylation, an epigenetic mark, is altered in ECs under different conditions, and the acetylation status change at different lysine sites on histone protein plays a key role in endothelial dysfunction and involved in hyperglycemia, hypertension, inflammatory disease, cancer and so on. In this review, we highlight the importance of histone acetylation in regulating endothelial functions and discuss the roles of histone acetylation across the transcriptional unit of protein-coding genes in ECs under different disease-related pathophysiological processes. Since histone acetylation changes are conserved and reversible, the knowledge of histone acetylation in endothelial function regulation could provide insights to develop epigenetic interventions in preventing or treating endothelial dysfunction-related diseases.

Heart disease is the number one cause of death in developed countries. Metabolic diseases influence the severity of heart disease linked to risk factors which are thought to alter epigenetic mechanisms. Pyruvate dehydrogenase (PDH) kinases (PDK), which phosphorylate and reduce the activity of PDH the nexus of glucose oxidation and fatty acid oxidation are sensitive to metabolic status. Four isozymes of PDK (PDK1-4) exist with PDK2 and PDK4 as the major regulators in cardiac tissue. Owing to the role of PDH in regulating pyruvate to acetyl-CoA, we hypothesized that PDK inhibition may regulate protein acetylation through increasing acetyl-CoA because of PDH activation leading to post-translational modifications both directly to proteins in metabolic pathways as well as to histones associated with the genes encoding them. To test this, we utilized PDK2 germline knockout mice (P2KO), PDK4 germline knockout mice (P4KO), and PDK2 and PDK4 double knockout (DKO) mice for molecular analysis. Our results identify a novel increase in whole-cell protein acetylation in P2KO left ventricle tissue (LV). However, protein acetylation in P4KO LV was not changed compared to WT mice. The most robust protein acetylation was observed in the DKO LV. Furthermore, when we explored sub-cellular distribution of protein acetylation, the greatest increases were found on cytoplasmic proteins, with moderate changes in mitochondrial proteins. We also found PDK2 ablation induces histone H3 acetylation, which may also lead to changes in gene expression. Moreover, this protein acetylation in P2KO and DKO was not seen in other tissues examined (e.g., liver, skeletal muscle). The hyperacetylation is robust in male LV compared to female LV. In conclusion, our study supports a novel protein acetylation mechanism that is both tissue and PDK isozyme specific highlighting the role of PDK2, which is relatively understudied compared to PDK4 in heart disease. Further study will evaluate if the hyperacetylation has a beneficial effect in various heart disease settings as well as identify the impact on changes in gene expression. This study supports PDK isozyme-specific inhibition strategies will be required to develop therapeutic targets of cardiovascular disease with metabolic inflexibility.

HomeCirculation ResearchVol. 126, No. 11Introduction to the Obesity, Metabolic Syndrome, and CVD Compendium Free AccessReview ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyRedditDiggEmail Jump toFree AccessReview ArticlePDF/EPUBIntroduction to the Obesity, Metabolic Syndrome, and CVD Compendium Kathryn J. Moore and Ravi Shah Kathryn J. MooreKathryn J. Moore From the Department of Medicine, Leon H. Charney Division of Cardiology, New York University Grossman School of Medicine, NY (K.J.M.) Search for more papers by this author and Ravi ShahRavi Shah Cardiology Division, Department of Medicine, Massachusetts General Hospital, Boston (R.S.). Search for more papers by this author Originally published21 May 2020https://doi.org/10.1161/CIRCRESAHA.120.317240Circulation Research. 2020;126:1475–1476Other version(s) of this articleYou are viewing the most recent version of this article. Previous versions: May 21, 2020: Previous Version of Record Obesity is a major threat to cardiovascular health worldwide. Although early studies focused on body mass index as a generalized measure of obesity and its relation to cardiovascular disease (CVD), studies within the last decade have turned to identify select markers of adipose tissue physiology and metabolic dysfunction to clarify the impact of obesity on CVD. In this Circulation Research compendium, we feature contributions from leading scientists in the fields of diabetes and obesity to update investigators and clinicians on how our understanding of the connection between obesity and CVD has evolved and the current state of the field.The articles in this Compendium Series cover the spectrum of research, from epidemiology of populations and clinical trials in patients to molecular mechanisms in animal model systems.Després et al1 open the series with an overview of the clinical epidemiology of obesity, focusing specifically on the role of regional fat (eg, visceral and hepatic fat) in the pathogenesis of CVD in obese individuals. Next, in their contribution to basic mechanisms of diabetic heart disease, Ritchie and Abel2 review the current understanding of underlying factors and pathways contributing to the pathogenesis of diabetic cardiovascular disease. This is complemented by Goodarzi’s and Rotter’s3 review of the growing insights from genetic epidemiological studies of obesity and diabetes mellitus and, particularly, the role of human genetic variation in type 2 diabetes risk and CVD.The link between metabolic inflammation and CVD pathogenesis has received much attention in the last decade. In a series of reviews, this Compendium highlights the present paradigms and emerging hypotheses of the roles that immune cells play in metabolic homeostasis and the pathogenesis of cardiometabolic diseases. Wu and Ballantyne4 detail the intricate interplay of metabolic Inflammation and insulin resistance in obesity, whereas Schmidt et al5 provide a comprehensive overview of the eclectic cast of immune cells that orchestrates innate immune activation in obesity and metabolic perturbations. Complementing these contributions, Weinstock et al6 review how insights from single cell RNA-sequencing are expanding our understanding of the heterogeneity and complex interactions of immune cells in adipose tissue in health and disease.New insights into human adipose and heart physiology continue to emerge from the integration of omics and imaging technologies in translational and clinical research. Chen and Gerszten7 address how metabolomics and proteomics are being harnessed to define the landscape of molecular alterations in diabetes and to improve diagnostic and therapeutic strategies. Peterson and Gropler8 review the state-of-the-art in metabolic and molecular imaging of diabetic cardiomyopathy. Finally, Heffron et al9 detail how treatment approaches in obesity, such as bariatric surgery, impact metabolic risk factors and cardiovascular disease.The compilation of reviews in this Compendium reflects the collective work of leading investigators in the areas of diabetes and cardiometabolic diseases. Together, they build a comprehensive overview of how obesity and metabolic physiology contribute to CVD and the emerging opportunities for improved detection, intervention, and potentially, prevention of cardiometabolic diseases. Although it is not possible to cover every aspect of a field as large and complex as Obesity, Metabolic Syndrome, and CVD, we hope that this compendium will help the readers to keep abreast of recent developments and future directions in this rapidly evolving field.Sources of FundingWork in the Moore lab is supported by grants from the NIH (R35HL135799 and P01HL131481).DisclosuresNone.FootnotesThe opinions expressed in this article are not necessarily those of the editors or of the American Heart Association.For Sources of Funding and Disclosures, see page 1476.

Robust experimental and observational data implicate inflammation as a fundamental driver in the pathogenesis of atherosclerotic cardiovascular disease (CVD).1 Chronic inflammatory diseases provide unique opportunities to gain insight into mechanisms of accelerated atherogenesis in broader populations. Patients with diseases such as psoriasis and rheumatoid arthritis that are characterized by chronically higher levels of systemic inflammation also have substantially elevated risk of CVD, and this risk is lower when these patients are treated with anti-inflammatory medications. For example, studies of patients with psoriasis, a chronic inflammatory skin disorder, have suggested ≈25% reduction in CVD risk with the use of disease modifying agents that suppress systemic inflammation.2 In these populations, traditional risk assessment tools often underestimate the true burden of cardiovascular risk, at least in part because of inadequately capturing the magnitude of inflammatory risk. Hence, there is a need for more reliable inflammatory risk assessment tools. Article, see p 1242 An important avenue of research that addresses this gap comes from recent technical advances in high-performance metabolomics profiling, both nuclear magnetic resonance spectroscopy and mass spectrometry technologies that now allow the identification and quantification of systemic inflammation through protein glycosylation signatures. Regulated enzymatic glycosylation involves the post-translational modification of proteins by attaching oligosaccharide (sugar) moieties and is an important step in regulating protein folding, localization, function, and stability. The significance of these glycosylated attachments is exemplified by their role in modulating numerous biological processes, including cell trafficking, signal transduction, regulation of metabolism, and host–pathogen recognition. As they reflect more downstream protein phenotypes, characterizing the human glycome has received increasing interest …