High-phosphate-induced calcification is related to SM22α promoter methylation in vascular smooth muscle cells

METTL3-mediated N6-methyladenosine modification contributes to vascular calcification

AIM

Vascular calcification (VC) is a major adverse cardiovascular event in chronic kidney disease (CKD) patients. N6-methyladenosine (m6A) modification is vital for many biological processes, but its function and possible molecular mechanisms in VC are poorly understood. This study aimed to clarify the function and molecular mechanisms of N6-adenosine-methyltransferase-like 3 (METTL3) in VC.

METHODS AND RESULTS

The results of the bioinformatic analysis showed that METTL3 expression was significantly upregulated in calcified VSMCs. This finding was corroborated by phosphate-induced VSMCs calcification models and 5/6 nephrectomy-induced CKD mouse VC models. Afterward, Alizarin Red S staining and m6A dot blot analysis demonstrated METTL3 overexpression elevated m6A levels and encouraged calcification in VSMCs and mouse aortic rings, while METTL3 knockdown decreased m6A levels and inhibited calcium deposition in these experimental models. Furthermore, METTL3 promoted VC via the PTEN/AKT pathway, and MeRIP verified that METTL3 induced PTEN mRNA degradation by modifying it with m6A. In addition, molecular docking simulations and DARTS assays revealed that quercetin is a natural small-molecule inhibitor of METTL3. The current investigation demonstrated that quercetin mitigated VC by reducing METTL3-dependent m6A levels in vivo and in vitro.

CONCLUSION

In conclusion, this study unraveled the pathogenic mechanism of METTL3-mediated m6A modification in VC and provided new insights to establish METTL3 as a therapeutic target for VC.

The metabolite alpha-ketoglutarate inhibits vascular calcification partially through modulation of TET2/NLRP3 inflammasome signaling pathway

INTRODUCTION

Vascular calcification is prevalent in chronic kidney disease (CKD), but existing medical treatments fail to achieve satisfactory therapeutic effects. Vascular calcification is now recognized as an active multifactorial process involving diverse mechanisms. Alpha-ketoglutarate (AKG), an intermediate in tricarboxylic acid cycle, has been demonstrated to extend lifespan and ameliorate age-related osteoporosis. However, whether AKG inhibits vascular calcification remains unknown.

METHODS

Here, mineral deposition was studied with AKG treatment in rodent and human vascular smooth muscle cells (VSMCs) under osteogenic conditions in vivo and in vitro.

RESULTS

AKG treatment remarkably ameliorated calcification of rat and human arterial rings ex vivo and aortic calcification in CKD rats and mice. Mechanistically, AKG treatment upregulated DNA demethylase ten-eleven translocation 2 (TET2) expression during vascular calcification. Knockdown of TET2 by siRNA and pharmacological inhibition of TET2 by Bobcat339 promoted vascular calcification in rat VSMCs. Bobcat339 also enhanced rat aortic ring calcification. Conversely, TET2 overexpression ameliorated vascular calcification in rat VSMCs, rat aortic rings and CKD rats. Furthermore, VSMC-specific TET2 deficiency promoted aortic calcification in CKD mice. Both TET2 siRNA and Bobcat339 independently counteracted the inhibitory effect of AKG on vascular calcification of rat VSMCs. Inhibitory effect of AKG administration on vascular calcification was reduced in TET2 knockout mice. TET2 overexpression reduced the levels of the NLRP3 inflammasome pathway, cleaved Caspase-1 and IL-1β protein expression in VSMCs and NLRP3 agonist Nigericin-induced cell calcification.

CONCLUSIONS

Our study demonstrate that AKG attenuates vascular calcification partially via upregulation of TET2 and inhibition of NLRP3 inflammasome, indicating the critical role of epigenetic modifier in vascular calcification. Modulation of TET2 may become a promising strategy for the treatment of vascular calcification.

Natural Bioproducts with Epigenetic Properties for Treating Cardiovascular Disorders

Cardiovascular disorders (CVDs) are the leading cause of mortality worldwide, highlighting an urgent need for innovative therapeutic strategies. Recent advancements highlight the potential of naturally derived bioproducts with epigenetic properties to offer protection against CVDs. These compounds act on key epigenetic mechanisms, DNA methylation, histone modifications, and non-coding RNA regulation to modulate gene expression essential for cardiovascular health. This review explores the effects of various bioproducts, such as polyphenols, flavonoids, and other natural extracts, on these epigenetic modifications and their potential benefits in preventing and managing CVDs. We discuss recent discoveries and clinical applications, providing insights into the epigenetic regulatory mechanisms of these compounds as potential epidrugs, naturally derived agents with promising therapeutic prospects in epigenetic therapy for CVDs.

Epigenetic Regulation of Human Vascular Calcification

Vascular diseases present a significant threat to human health worldwide. Atherosclerosis is the most prevalent vascular disease, accounting for the majority of morbidity and mortality globally. Vascular calcification is a dynamic pathological process underlying the development of atherosclerotic plaques and involves the phenotypic transformation of vascular smooth muscle cells (VSMCs) into osteogenic cells. Specifically, the phenotypic switch in VSMCs often involves modifications in gene expression due to epigenetic changes, including DNA methylation, histone modification, and non-coding RNAs. Understanding the role of these epigenetic changes in regulating the pathophysiology of vascular calcification, along with the proteins and pathways that mediate these changes, will aid in identifying new therapeutic candidates to enhance vascular health. This review discusses a comprehensive range of epigenetic modifications and their implications for vascular health and the development of vascular calcification.

Hexasodium Fytate (SNF472 or CSL525) Inhibits Ectopic Calcification in Various Pseudoxanthoma Elasticum and Calcinosis Cutis Animal Models

Background/Objectives: Ectopic calcification is a pathological condition characterized by the mineralization of soft tissues due to the deposition of calcium phosphate crystals. Hexasodium fytate (CSL525, previously known as SNF472) is a crystallization inhibitor being developed for the treatment of ectopic calcification-related disorders. Our aim was to investigate CSL525 for the treatment of soft-tissue calcification disorders in animal models of pseudoxanthoma elasticum and calcinosis cutis. Methods: In a first study, abcc6-/- zebrafish larvae were exposed to 1 mM CSL525 for 7 days or kept under the same conditions without CSL525, and spinal mineralization was quantified. In a second study, abcc6-/- mice were administered subcutaneously with CSL525 at 15 mg/kg thrice weekly for eight weeks. Vehicle-treated WT (C57BL/6J) and abcc6-/- mice served as controls, and muzzle skin calcification was quantified. In a third study, calcinosis cutis was induced in rats through subcutaneous administration of 0.15 mg FeCl3 at two sites in the thorax. Rats were administered either subcutaneous CSL525 (60 mg/kg) or vehicle (0.9% NaCl), and calcium content was measured in the skin. Results: CSL525 significantly reduced the calcified area (~40%) in abcc6a-/- zebrafish larvae. The abcc6-/- mice receiving CSL525 showed a 57% inhibition of muzzle calcification compared to vehicle-treated abcc6-/- mice. CSL525 inhibited skin calcification development by 60% in the calcinosis cutis rat model. Conclusions: CSL525 may prove beneficial not only in preventing the progression of cardiovascular calcification but also in treating other ectopic calcification conditions, including skin calcification associated with genetic disorders such as PXE.

Metabolomics analysis of acute lung injury induced by aortic dissection in mice

Thoracic aortic aneurysm/dissection (TAA/D) is a complicated vascular disorder with galloping development and high mortality. Phenotype switching plays an important role in the pathological process of TAA/D. Previous studies indicated the potential correlation between the expression level of lncRNA RP11-465L10.10 and MMP9 involved in the development of TAA/D. Here, our results showed that RP11-465L10.10 and MMP9 were highly increased in TAD patient tissues, which was consistent in Ang II-induced vascular smooth muscle cell (VSMC) phenotype switching. However, the effects and underlying mechanism of RP11-465L10.10 on VSMC phenotypic switching remain uncertain. Therefore, the expression of SM22α, cell proliferation, and migration were investigated when ectopically expressed RP11-465L10.10 in VSMCs. The results showed that RP11-465L10.10 overexpression decreased SM22α expression and facilitated VSMC proliferation, migration, and MMP9 expression. Furthermore, the NF-κB signaling pathway was enriched in transcriptome data analysis, indicating that NF-κB signaling may be involved in RP11-465L10.10-induced VSMC phenotype switching and MMP9 expression. In conclusion, this study demonstrated that RP11-465L10.10 induces VSMC phenotype switching and MMP9 expression via the NF-κB signaling pathway, suggesting that RP11-465L10.10 might be a potential therapeutic target for TAA/D treatment.

Advanced glycosylation end products promote the progression of CKD-MBD in rats, and its natural inhibitor, quercetin, mitigates disease progression

Chronic kidney disease-mineral and bone metabolism disorder (CKD-MBD) is a common chronic kidney disease (CKD)-associated complication that increases the risk of metabolic bone diseases, fractures, osteoblastic trans-differentiation of vascular smooth muscle cells, and cardiovascular events. SD rats were randomised into five groups with six rats per group: sham, CKD, CKD + advanced glycosylation end products (AGEs), CKD + Quercetin, and CKD + AGEs + Quercetin. The protective effects of AGEs and quercetin on SD rats were assessed by renal function, renal pathology, bone metabolism, osteoblastic trans-differentiation of vascular smooth muscle cells, and the receptor for AGE (RAGE) expression. Compared with the control group, rats in the CKD and CKD + AGEs groups had significantly lower body weight, higher serum AGEs levels, impaired renal function, increased levels of oxidative stress in the kidney and bone marrow tissues, lower femoral bone mineral density (BMD), callus mineralised volume fraction (mineralised bone volume/total volume), abnormal serum bone metabolism levels, and increased renal tissue, bone tissue, and abdominal aorta RAGE expression levels, and the RAGE downstream NF-κB signalling pathway was upregulated. Quercetin significantly improved renal dysfunction, attenuated serum AGE levels, reduced oxidative stress levels in the kidney and bone marrow tissues, and downregulated RAGE expression in the kidney, bone, and abdominal aorta and the RAGE downstream NF-κB signalling pathway in rats with CKD. AGEs are involved in the pathogenesis of CKD-MBD by promoting osteoblastic trans-differentiation of vascular smooth muscle cells and abnormal bone metabolism. Quercetin plays a role in the prevention and treatment of CKD-MBD by reducing the production of AGEs.

Epigenetic DNA Methylation and Protein Homocysteinylation: Key Players in Hypertensive Renovascular Damage

Hypertension has been a threat to the health of people, the mechanism of which, however, remains poorly understood. It is clinically related to loss of nephron function, glomerular sclerosis, or necrosis, resulting in renal functional declines. The mechanisms underlying hypertension's development and progression to organ damage, including hypertensive renal damage, remain to be fully elucidated. As a developing approach, epigenetics has been postulated to elucidate the phenomena that otherwise cannot be explained by genetic studies. The main epigenetic hallmarks, such as DNA methylation, histone acetylation, deacetylation, noncoding RNAs, and protein N-homocysteinylation have been linked with hypertension. In addition to contributing to endothelial dysfunction and oxidative stress, biologically active gases, including NO, CO, and H2S, are crucial regulators contributing to vascular remodeling since their complex interplay conducts homeostatic functions in the renovascular system. Importantly, epigenetic modifications also directly contribute to the pathogenesis of kidney damage via protein N-homocysteinylation. Hence, epigenetic modulation to intervene in renovascular damage is a potential therapeutic approach to treat renal disease and dysfunction. This review illustrates some of the epigenetic hallmarks and their mediators, which have the ability to diminish the injury triggered by hypertension and renal disease. In the end, we provide potential therapeutic possibilities to treat renovascular diseases in hypertension.

Mechanosensory entities and functionality of endothelial cells

The endothelial cells of the blood circulation are exposed to hemodynamic forces, such as cyclic strain, hydrostatic forces, and shear stress caused by the blood fluid's frictional force. Endothelial cells perceive mechanical forces via mechanosensors and thus elicit physiological reactions such as alterations in vessel width. The mechanosensors considered comprise ion channels, structures linked to the plasma membrane, cytoskeletal spectrin scaffold, mechanoreceptors, and junctional proteins. This review focuses on endothelial mechanosensors and how they alter the vascular functions of endothelial cells. The current state of knowledge on the dysregulation of endothelial mechanosensitivity in disease is briefly presented. The interplay in mechanical perception between endothelial cells and vascular smooth muscle cells is briefly outlined. Finally, future research avenues are highlighted, which are necessary to overcome existing limitations.

Therapeutic Potential of Natural Compounds Acting through Epigenetic Mechanisms in Cardiovascular Diseases: Current Findings and Future Directions

Cardiovascular diseases (CVDs) remain a leading global cause of morbidity and mortality. These diseases have a multifaceted nature being influenced by a multitude of biochemical, genetic, environmental, and behavioral factors. Epigenetic modifications have a crucial role in the onset and progression of CVD. Epigenetics, which regulates gene activity without altering the DNA's primary structure, can modulate cardiovascular homeostasis through DNA methylation, histone modification, and non-coding RNA regulation. The effects of environmental stimuli on CVD are mediated by epigenetic changes, which can be reversible and, hence, are susceptible to pharmacological interventions. This represents an opportunity to prevent diseases by targeting harmful epigenetic modifications. Factors such as high-fat diets or nutrient deficiencies can influence epigenetic enzymes, affecting fetal growth, metabolism, oxidative stress, inflammation, and atherosclerosis. Recent studies have shown that plant-derived bioactive compounds can modulate epigenetic regulators and inflammatory responses, contributing to the cardioprotective effects of diets. Understanding these nutriepigenetic effects and their reversibility is crucial for developing effective interventions to combat CVD. This review delves into the general mechanisms of epigenetics, its regulatory roles in CVD, and the potential of epigenetics as a CVD therapeutic strategy. It also examines the role of epigenetic natural compounds (ENCs) in CVD and their potential as intervention tools for prevention and therapy.

Treatment of calcific arterial disease via enhancement of autophagy using GSK343

Vascular calcification is a hallmark of atherosclerotic disease and serves as a strong predictor and risk factor for cardiovascular events. Growing evidence suggests that autophagy may play a protective role in early atherosclerosis. The precise effects of autophagy on VSMC-mediated calcification remain unknown. In this study, we utilized multi-omic profiling to investigate impaired autophagy at the transcriptional level as a key driver of VSMC calcification. Our findings revealed that impaired autophagy is an essential determinant of VSMC calcification. We observed that an osteogenic environment affects the open chromatin status of VSMCs, compromising the transcriptional activation of autophagy initiation genes. In vivo experiments involve pharmacological and genetic activation of autophagy using mouse models of spontaneous large (Mgp-/-) and small (Abcc6-/-) artery calcification. Taken together, these data advance our mechanistic understanding of vascular calcification and provide important insights for a broad range of cardiovascular diseases involving VSMC phenotype switch.

Empagliflozin Attenuates Vascular Calcification in Mice with Chronic Kidney Disease by Regulating the NFR2/HO-1 Anti-Inflammatory Pathway through AMPK Activation

Vascular calcification (VC) is associated with increased cardiovascular risks in patients with chronic kidney disease (CKD). Sodium-glucose cotransporter 2 inhibitors, such as empagliflozin, can improve cardiovascular and renal outcomes. We assessed the expression of Runt-related transcription factor 2 (Runx2), interleukin (IL)-1β, IL-6, AMP-activated protein kinase (AMPK), nuclear factor erythroid-2-related factor (Nrf2), and heme oxygenase 1 (HO-1) in inorganic phosphate-induced VC in mouse vascular smooth muscle cells (VSMCs) to investigate the mechanisms underlying empagliflozin's therapeutic effects. We evaluated biochemical parameters, mean artery pressure (MAP), pulse wave velocity (PWV), transcutaneous glomerular filtration rate (GFR), and histology in an in vivo mouse model with VC induced by an oral high-phosphorus diet following a 5/6 nephrectomy in ApoE^-/- mice. Compared to the control group, empagliflozin-treated mice showed significant reductions in blood glucose, MAP, PWV, and calcification, as well as increased calcium and GFR levels. Empagliflozin inhibited osteogenic trans-differentiation by decreasing inflammatory cytokine expression and increasing AMPK, Nrf2, and HO-1 levels. Empagliflozin mitigates high phosphate-induced calcification in mouse VSMCs through the Nrf2/HO-1 anti-inflammatory pathway by activating AMPK. Animal experiments suggested that empagliflozin reduces VC in CKD ApoE^-/- mice on a high-phosphate diet.

Vascular calcification in CKD: New insights into its mechanisms

Vascular calcification (VC) is a common complication of chronic kidney disease (CKD) and contributes to an increased risk of cardiovascular morbidity and mortality. However, effective therapies are still unavailable at present. It has been well established that VC associated with CKD is not a passive process of calcium phosphate deposition, but an actively regulated and cell-mediated process that shares many similarities with bone formation. Additionally, numerous studies have suggested that CKD patients have specific risk factors and contributors to the development of VC, such as hyperphosphatemia, uremic toxins, oxidative stress and inflammation. Although research efforts in the past decade have greatly improved our knowledge of the multiple factors and mechanisms involved in CKD-related VC, many questions remain unanswered. Moreover, studies from the past decade have demonstrated that epigenetic modifications abnormalities, such as DNA methylation, histone modifications and noncoding RNAs, play an important role in the regulation of VC. This review seeks to provide an overview of the pathophysiological and molecular mechanisms of VC associated with CKD, mainly focusing on the involvement of epigenetic modifications in the initiation and progression of uremic VC, with the aim to develop promising therapies for CKD-related cardiovascular events in the future.

Pathophysiology and Clinical Impacts of Chronic Kidney Disease on Coronary Artery Calcification

The global prevalence of chronic kidney disease (CKD) has increased in recent years. Adverse cardiovascular events have become the main cause of life-threatening events in patients with CKD, and vascular calcification is a risk factor for cardiovascular disease. Vascular calcification, especially coronary artery calcification, is more prevalent, severe, rapidly progressive, and harmful in patients with CKD. Some features and risk factors are unique to vascular calcification in patients with CKD; the formation of vascular calcification is not only influenced by the phenotypic transformation of vascular smooth muscle cells, but also by electrolyte and endocrine dysfunction, uremic toxin accumulation, and other novel factors. The study on the mechanism of vascular calcification in patients with renal insufficiency can provide a basis and new target for the prevention and treatment of this disease. This review aims to illustrate the impact of CKD on vascular calcification and to discuss the recent research data on the pathogenesis and factors involved in vascular calcification, mainly focusing on coronary artery calcification, in patients with CKD.

Silver jubilee: 25 years of the first demonstration of the direct effect of phosphate on the parathyroid cell

Although phosphorus is an essential element for life, it is not found in nature in its native state but rather combined in the form of inorganic phosphates (PO₄^3-), with tightly regulated plasma levels that are associated with deleterious effects and mortality when these are out of bounds. The growing interest in the accumulation of PO₄^3- in human pathophysiology originated in its attributed role in the pathogenesis of secondary hyperparathyroidism (SHPT) in chronic kidney disease. In this article, we review the mechanisms by which this effect was justified and we commemorate the important contribution of a Spanish group led by Dr. M. Rodríguez, just 25 years ago, when they first demonstrated the direct effect of PO₄^3- on the regulation of the synthesis and secretion of parathyroid hormone by maintaining the structural integrity of the parathyroid glands in their original experimental model. In addition to demonstrating the importance of arachidonic acid (AA) and the phospholipase A2-AA pathway as a mediator of parathyroid gland response, these findings were predecessors of the recent description of the important role of PO₄^3- on the activity of the calcium sensor-receptor, and also fueled various lines of research on the importance of PO₄^3- overload not only for the pathophysiology of SHPT but also in its systemic pathogenic role.

Epigenetics: a new warrior against cardiovascular calcification, a forerunner in modern lifestyle diseases

Arterial and aortic valve calcifications are the most prevalent pathophysiological conditions among all the reported cases of cardiovascular calcifications. It increases with several risk factors like age, hypertension, external stimuli, mechanical forces, lipid deposition, malfunction of genes and signaling pathways, enhancement of naturally occurring calcium inhibitors, and many others. Modern-day lifestyle is affected by numerous environmental factors and harmful toxins that impair our health rather than providing benefits. Applying the combinatorial approach or targeting the exact mechanism could be a new strategy for drug designing or attenuating the severity of calcification. Most of the non-communicable diseases are life-threatening; thus, altering the phenotype and not the genotype may reveal the gateway for fighting with upcoming hurdles. Overall, this review summarizes the reason behind the generation of arterial and aortic valve calcification and its related signaling pathways and also the detrimental effects of calcification. In addition, the individual process of epigenetics and how the implementation of this process becomes a novel approach for diminishing the harmful effect of calcification are discussed. Noteworthy, as epigenetics is linked with genetics and environmental factors necessitates further clinical trials for complete and in-depth understanding and application of this strategy in a more specific and prudent manner.

The short-chain fatty acid butyrate accelerates vascular calcification via regulation of histone deacetylases and NF-κB signaling

Recent studies have shown that short-chain fatty acids (SCFAs), primarily acetate, propionate and butyrate, play a crucial role in the pathogenesis of cardiovascular disease. Whether SCFAs regulate vascular calcification, a common pathological change in cardiovascular tissues, remains unclear. This study aimed to investigate the potential role of SCFAs in vascular calcification. Using cellular and animal models of vascular calcification, we showed that butyrate significantly enhanced high phosphate (Pi)-induced calcification and osteogenic transition of vascular smooth muscle cells (VSMC) in vitro, whereas acetate and propionate had no effects. Subsequent studies confirmed that butyrate significantly promoted high Pi-induced aortic ring calcification ex vivo and high dose vitamin D₃ (vD₃)-induced mouse vascular calcification in vivo. Mechanistically, butyrate significantly inhibited histone deacetylase (HDAC) expression in VSMCs, and a pan HDAC inhibitor Trichostatin A showed similar inductive effects on calcification and osteogenic transition of VSMCs to butyrate. In addition, the SCFA sensing receptors Gpr41 and Gpr109a were primarily expressed by VSMCs, and butyrate induced the rapid activation of NF-κB, Wnt and Akt signaling in VSMCs. Intriguingly, the NF-κB inhibitor SC75741 significantly attenuated butyrate-induced calcification and the osteogenic gene Msx2 expression in VSMCs. We showed that knockdown of Gpr41 but not Gpr109a attenuated butyrate-induced VSMC calcification. This study reveals that butyrate accelerates vascular calcification via its dual effects on HDAC inhibition and NF-κB activation. Our data provide novel insights into the role of microbe-host interaction in vascular calcification, and may have implications for the development of potential therapy for vascular calcification.

Epigenetic Control of Vascular Smooth Muscle Cell Function in Atherosclerosis: A Role for DNA Methylation

Atherosclerosis is a complex vascular inflammatory disease in which multiple cell types are involved, including vascular smooth muscle cells (VSMCs). In response to vascular injury and inflammatory stimuli, VSMCs undergo a "phenotypic switching" characterized by extracellular matrix secretion, loss of contractility, and abnormal proliferation and migration, which play a key role in the progression of atherosclerosis. DNA methylation modification is an important epigenetic mechanism that plays an important role in atherosclerosis. Studies investigating abnormal DNA methylation in patients with atherosclerosis have determined a specific DNA methylation profile, and proposed multiple pathways and genes involved in the etiopathogenesis of atherosclerosis. Recent studies have also revealed that DNA methylation modification controls VSMC function by regulating gene expression involved in atherosclerosis. In this review, we summarize the recent advances regarding the epigenetic control of VSMC function by DNA methylation in atherosclerosis and provide insights into the development of VSMC-centered therapeutic strategies.

Microparticles from Hyperphosphatemia-Stimulated Endothelial Cells Promote Vascular Calcification Through Astrocyte-Elevated Gene-1

Endothelial microparticles (EMPs) can be released in chronic kidney disease (CKD). Plasma concentration of high inorganic phosphate (HP) is considered as a decisive determinant of vascular calcification in CKD. We therefore explored the role of HP-induced EMPs (HP-EMPs) in the vascular calcification and its potential mechanism. We observed the shape of HP-EMPs captured by vascular smooth muscle cells (VSMCs) dynamically changed from rare dots, rosettes, to semicircle or circle. Our results demonstrated that HP-EMPs could directly promote VSMC calcification, or accelerate HP-induced calcification through signal transducers and activators of transcription 3 (STAT3)/bone morphogenetic protein-2 (BMP2) signaling pathway. AEG-1 activity was increased through HP-EMPs-induced VSMC calcification, in arteries from uremic rats, or from uremic rats treated with HP-EMPs. AEG-1 deficiency blocked, whereas AEG-1 overexpression exacerbated, the calcium deposition of VSMCs. AEG-1, a target of miR-153-3p, could be suppressed by agomiR-153-3p. Notably, VSMC-specific enhance of miR-153-3p by tail vein injection of aptamer-agomiR-153-3p decreased calcium deposition in both uremia rats treated with HP-EMPs or not. HP-EMPs could directly induce VSMCs calcification and accelerate Pi-induced calcification, and AEG-1 may act as crucial regulator of HP-EMPs-induced vascular calcification. This study sheds light on the therapeutic agents that influence HP-EMPs production or AEG-1 activity, which may be of benefit to treat vascular calcification.

Epigenetic regulation in cardiovascular disease: mechanisms and advances in clinical trials

Epigenetics is closely related to cardiovascular diseases. Genome-wide linkage and association analyses and candidate gene approaches illustrate the multigenic complexity of cardiovascular disease. Several epigenetic mechanisms, such as DNA methylation, histone modification, and noncoding RNA, which are of importance for cardiovascular disease development and regression. Targeting epigenetic key enzymes, especially the DNA methyltransferases, histone methyltransferases, histone acetylases, histone deacetylases and their regulated target genes, could represent an attractive new route for the diagnosis and treatment of cardiovascular diseases. Herein, we summarize the knowledge on epigenetic history and essential regulatory mechanisms in cardiovascular diseases. Furthermore, we discuss the preclinical studies and drugs that are targeted these epigenetic key enzymes for cardiovascular diseases therapy. Finally, we conclude the clinical trials that are going to target some of these processes.

Natural Flavonoids Derived From Fruits Are Potential Agents Against Atherosclerosis

Atherosclerosis, as a chronic inflammatory response, is one of the main causes of cardiovascular diseases. Atherosclerosis is induced by endothelial cell dysfunction, migration and proliferation of smooth muscle cells, accumulation of foam cells and inflammatory response, resulting in plaque accumulation, narrowing and hardening of the artery wall, and ultimately leading to myocardial infarction or sudden death and other serious consequences. Flavonoid is a kind of natural polyphenol compound widely existing in fruits with various structures, mainly including flavonols, flavones, flavanones, flavanols, anthocyanins, isoflavones, and chalcone, etc. Because of its potential health benefits, it is now used in supplements, cosmetics and medicines, and researchers are increasingly paying attention to its role in atherosclerosis. In this paper, we will focus on several important nodes in the development of atherosclerotic disease, including endothelial cell dysfunction, smooth muscle cell migration and proliferation, foam cell accumulation and inflammatory response. At the same time, through the classification of flavonoids from fruits, the role and potential mechanism of flavonoids in atherosclerosis were reviewed, providing a certain direction for the development of fruit flavonoids in the treatment of atherosclerosis drugs.

Long non-coding RNA RP11-465L10.10 promotes vascular smooth muscle cells phenotype switching and MMP9 expression via the NF-κB pathway

Background

Thoracic aortic aneurysm/dissection (TAA/D) are complicated vascular disorders with rapid development and high mortality. Vascular smooth muscle cells (VSMCs) phenotype switching plays an important role in the pathological process of TAA/D. Previous studies have indicated a potential correlation between long non-coding RNA (lncRNA) RP11-465L10.10 and matrix metallopeptidase 9 (MMP9) involved in the development of TAA/D. This study aims to investigate the role of lncRNA RP11-465L10.10 in VSMCs phenotype switching and the molecular mechanism in regulating MMP9 expression.

Methods

The expression of RP11-465L10.10 in vascular tissues and in VMSCs was detected by RT-qPCR. To investigate the role of RP11-465L10.10 on VSMCs phenotype switching, an RP11-465L10.10-overexpressed lentiviral vector was constructed and transfected into VSMCs. Through EdU staining, migration assay, flow cytometry analysis, the roles of RP11-465L10.10 were estimated. Bioinformatics indicated that RP11-465L10.10 upregulating MMP9 expression via NF-κB signaling, and SN50 (a specific inhibitor of NF-κB pathway) was used to inhibit the NF-κB pathway activation, then the expression of MMP9 was detected in RP11-465L10.10 overexpressed VMSCs.

Results

In this study, we found RP11-465L10.10 and MMP9 were highly increased in TAD patient tissues, which was consistent in angiotensin II-induced VSMCs phenotype switching. RP11-465L10.10 overexpression facilitated VSMCs phenotype switching and MMP9 expression. Mechanismly, NF-κB signal pathway was involved in RP11-465L10.10 induced VSMCs phenotype switching and MMP9 expression by transcriptome data analysis and experimental confirm.

Conclusion

This study demonstrated that RP11-465L10.10 induces VSMCs phenotype switching and MMP9 expression via the NF-κB signal pathway, suggesting that RP11-465L10.10 might be a potential therapeutic target for TAA/D treatment.

Epigenetic Regulation of Vascular Smooth Muscle Cell Phenotype Switching in Atherosclerotic Artery Remodeling: A Mini-Review

Atherosclerosis is a chronic inflammatory disease characterized by extensive remodeling of medium and large-sized arteries. Inward remodeling (=lumen shrinkage) of the vascular walls is the underlying cause for ischemia in target organs. Therefore, inward remodeling can be considered the predominant feature of atherosclerotic pathology. Outward remodeling (=lumen enlargement) is a physiological response compensating for lumen shrinkage caused by neointimal hyperplasia, but as a pathological response to changes in blood flow, outward remodeling leads to substantial arterial wall thinning. Thinned vascular walls are prone to rupture, and subsequent thrombus formation accounts for the majority of acute cardiovascular events. Pathological remodeling is driven by inflammatory cells which induce vascular smooth muscle cells to switch from quiescent to a proliferative and migratory phenotype. After decades of intensive research, the molecular mechanisms of arterial remodeling are starting to unfold. In this mini-review, we summarize the current knowledge of the epigenetic and transcriptional regulation of vascular smooth muscle cell phenotype switching from the contractile to the synthetic phenotype involved in arterial remodeling and discuss potential therapeutic options.

ALKBH1 reduces DNA N6-methyladenine to allow for vascular calcification in chronic kidney disease

Vascular calcification is a common complication of chronic kidney disease (CKD), and one of the main risk factors for increased cardiovascular morbidity and mortality in patients with CKD. In this issue of the JCI, Ouyang and Su et al. report that Alkb homolog 1 (ALKBH1), a DNA demethylase, reduced DNA N6-methyladenine (6mA) in vascular smooth muscle cells (VSMCs) and leukocytes, thus leading to aortic arch calcification in the patients with CKD. During the progression of vascular calcification, increased ALKBH1 expression was linked to decreased 6mA levels, findings that the authors noted in both patients with CKD and CKD mouse models. The kidney and vascular disease risk factor soluble urokinase receptor (suPAR) was also elevated in the plasma. Notably, lower 6mA levels induced BMP2-mediated osteogenic reprogramming in the VSMCs. These findings present a function of ALKBH1 in vascular calcification and provide a framework for therapeutic strategies.

ALKBH1-demethylated DNA N6-methyladenine modification triggers vascular calcification via osteogenic reprogramming in chronic kidney disease

Vascular calcification (VC) predicts cardiovascular morbidity and mortality in chronic kidney disease (CKD). To date, the underlying mechanisms remain unclear. We detected leukocyte DNA N6-methyladenine (6mA) levels in patients with CKD with or without aortic arch calcification. We used arteries from CKD mice infected with vascular smooth muscle cell-targeted (VSMC-targeted) adeno-associated virus encoding alkB homolog 1 (Alkbh1) gene or Alkbh1 shRNA to evaluate features of calcification. We identified that leukocyte 6mA levels were significantly reduced as the severity of VC increased in patients with CKD. Decreased 6mA demethylation resulted from the upregulation of ALKBH1. Here, ALKBH1 overexpression aggravated whereas its depletion blunted VC progression and osteogenic reprogramming in vivo and in vitro. Mechanistically, ALKBH1-demethylated DNA 6mA modification could facilitate the binding of octamer-binding transcription factor 4 (Oct4) to bone morphogenetic protein 2 (BMP2) promoter and activate BMP2 transcription. This resulted in osteogenic reprogramming of VSMCs and subsequent VC progression. Either BMP2 or Oct4 depletion alleviated the procalcifying effects of ALKBH1. This suggests that targeting ALKBH1 might be a therapeutic method to reduce the burden of VC in CKD.

Pharmacologic epigenetic modulators of alkaline phosphatase in chronic kidney disease

In chronic kidney disease (CKD), disturbance of several metabolic regulatory mechanisms cause premature ageing, accelerated cardiovascular disease (CVD), and mortality. Single-target interventions have repeatedly failed to improve the prognosis for CKD patients. Epigenetic interventions have the potential to modulate several pathogenetic processes simultaneously. Alkaline phosphatase (ALP) is a robust predictor of CVD and all-cause mortality and implicated in pathogenic processes associated with CVD in CKD.

The Roles of Epigenetics Regulation in Bone Metabolism and Osteoporosis

Osteoporosis is a metabolic disease characterized by decreased bone mineral density and the destruction of bone microstructure, which can lead to increased bone fragility and risk of fracture. In recent years, with the deepening of the research on the pathological mechanism of osteoporosis, the research on epigenetics has made significant progress. Epigenetics refers to changes in gene expression levels that are not caused by changes in gene sequences, mainly including DNA methylation, histone modification, and non-coding RNAs (lncRNA, microRNA, and circRNA). Epigenetics play mainly a post-transcriptional regulatory role and have important functions in the biological signal regulatory network. Studies have shown that epigenetic mechanisms are closely related to osteogenic differentiation, osteogenesis, bone remodeling and other bone metabolism-related processes. Abnormal epigenetic regulation can lead to a series of bone metabolism-related diseases, such as osteoporosis. Considering the important role of epigenetic mechanisms in the regulation of bone metabolism, we mainly review the research progress on epigenetic mechanisms (DNA methylation, histone modification, and non-coding RNAs) in the osteogenic differentiation and the pathogenesis of osteoporosis to provide a new direction for the treatment of bone metabolism-related diseases.

Omics research in vascular calcification

Vascular calcification (VC), the pathological process of hydroxyapatite mineral deposition in the vascular system, is closely associated with aging, atherosclerotic plaque formation, cardiovascular disease (CVD) and diabetes mellitus (DM). Studies have shown that VC is related to cellular phenotypic changes, extracellular vesicles, disordered calcium and phosphate homeostasis, and an imbalance between inducers and inhibitors of VC. Unfortunately, there is currently no effective preventive or targeted treatment for pathologic condition. The rapid evolution of omics technology (genomics, epigenomics, transcriptomics, proteomics and metabolomics) has provided a novel approach for elucidation of pathophysiologic mechanisms in general and those associated with VC specifically. Here, we review articles published over the last twenty years and focus on the current state, challenges, limitations and future of omics in VC research and clinical practice. Highlighting potential targets based on omics technology will improve our understanding of this pathologic condition and assist in the development of potential treatment options for VC related disease.

Omics research in vascular calcification

Vascular calcification (VC), the pathological process of hydroxyapatite mineral deposition in the vascular system, is closely associated with aging, atherosclerotic plaque formation, cardiovascular disease (CVD) and diabetes mellitus (DM). Studies have shown that VC is related to cellular phenotypic changes, extracellular vesicles, disordered calcium phosphate homeostasis and an imbalance between inducers and inhibitors of VC. Unfortunately, there is currently no effective preventive or targeted treatment for this disorder. Recently, the evolution of omics technology (genomics, epigenomics, transcriptomics, proteomics and metabolomics) has paved the way for elucidation of complex biochemical processes and, as such, may provide new insight on VC. Accordingly, we conducted a review of articles published over the last twenty years and herein focus on current and future potential of omics technology in clarifying mechanisms of this disease process. Identification of new biomarkers will provide additional tools in characterizing this pathology and will further assist in the development of potential therapeutic targets.

Uremic serum-induced calcification of human aortic smooth muscle cells is a regulated process involving Klotho and RUNX2

Vascular calcification (VC) is common in subjects with chronic kidney disease (CKD) and is associated with increased cardiovascular risk. It is an active process involving transdifferentiation of arterial smooth muscle cells (SMCs) into osteogenic phenotype. We investigated the ability of serum from CKD subjects to induce calcification in human SMCs in vitro (calcific potential of sera: CP), and associated changes in expression of Runt-related transcription factor 2 (RUNX2), SM22α, and Klotho. Sera from subjects with CKD (18 stage 3, 17 stage 4/5, and 29 stage 5D) and 20 controls were added to human cultured SMCs and CP quantified. The CP of CKD sera was greater (P<0.01) than that of controls, though not influenced by CKD stage. Modification of diet in renal disease estimated glomerular filtration rate (MDRD-4 eGFR) (P<0.001), serum phosphate (P=0.042), receptor activator of nuclear factor κappa-B ligand (RANKL) (P=0.001), parathyroid hormone (PTH) (P=0.014), and high-density lipoprotein (HDL)/cholesterol ratio (P=0.026) were independent predictors of CP accounting for 45% of variation. Adding calcification buffer (CB: calcium chloride [7 mM] and β-glycerophosphate [7 mM]) increased the CP of control sera to approximate that of CKD sera. CP of CKD sera was unchanged. CKD sera increased RUNX2 expression (P<0.01) in human SMCs and decreased SM22α expression (P<0.05). Co-incubating control but not CKD serum with CB further increased RUNX2 expression (P<0.01). Both SM22α and Klotho expression decreased significantly (P<0.01) in the presence of CKD serum, and were virtually abolished with stage 5D sera. These findings support active regulation by CKD serum of in vitro VC by induction of RUNX2 and suppression of SM22α and Klotho.

Epigenetic control of atherosclerosis via DNA methylation: A new therapeutic target?

Atherosclerosis is a disease in which lipid-laden plaques are developed inside the vessel walls of arteries. The immune system is activated, resulting in inflammation and oxidative stress. Endothelial cells (ECs) are activated, arterial smooth muscle cells (SMCs) proliferate, macrophages are activated, and foam cells are developed, leading to dysfunctional ECs. Epigenetic regulatory mechanisms, including DNA methylation, histone modifications, and microRNAs are involved in the modulation of genes that play distinct roles in several aspects of cell biology and physiology, hence linking environmental stimuli to gene regulation. Recent research has investigated the involvement of DNA methylation in the etiopathogenesis of atherosclerosis, and several studies have documented the role of this mechanism in various aspects of the disease. Regulation of DNA methylation plays a critical role in the integrity of ECs, SMC proliferation and formation of atherosclerotic lesions. In this review, we seek to clarify the role of DNA methylation in the development of atherosclerosis through different mechanisms.

Vascular Calcification: An Important Understanding in Nephrology

Vascular calcification (VC) is a life-threatening state in chronic kidney disease (CKD). High cardiovascular mortality and morbidity of CKD cases may root from medial VC promoted by hyperphosphatemia. Vascular calcification is an active, highly regulated, and complex biological process that is mediated by genetics, epigenetics, dysregulated form of matrix mineral metabolism, hormones, and the activation of cellular signaling pathways. Moreover, gut microbiome as a source of uremic toxins (eg, phosphate, advanced glycation end products and indoxyl-sulfate) can be regarded as a potential contributor to VC in CKD. Here, an update on different cellular and molecular processes involved in VC in CKD is discussed to elucidate the probable therapeutic pathways in the future.

Roles of Histone Acetylation Modifiers and Other Epigenetic Regulators in Vascular Calcification

Vascular calcification (VC) is characterized by calcium deposition inside arteries and is closely associated with the morbidity and mortality of atherosclerosis, chronic kidney disease, diabetes, and other cardiovascular diseases (CVDs). VC is now widely known to be an active process occurring in vascular smooth muscle cells (VSMCs) involving multiple mechanisms and factors. These mechanisms share features with the process of bone formation, since the phenotype switching from the contractile to the osteochondrogenic phenotype also occurs in VSMCs during VC. In addition, VC can be regulated by epigenetic factors, including DNA methylation, histone modification, and noncoding RNAs. Although VC is commonly observed in patients with chronic kidney disease and CVD, specific drugs for VC have not been developed. Thus, discovering novel therapeutic targets may be necessary. In this review, we summarize the current experimental evidence regarding the role of epigenetic regulators including histone deacetylases and propose the therapeutic implication of these regulators in the treatment of VC.

Vascular Calcification-New Insights Into Its Mechanism

Vascular calcification (VC), which is categorized by intimal and medial calcification, depending on the site(s) involved within the vessel, is closely related to cardiovascular disease. Specifically, medial calcification is prevalent in certain medical situations, including chronic kidney disease and diabetes. The past few decades have seen extensive research into VC, revealing that the mechanism of VC is not merely a consequence of a high-phosphorous and -calcium milieu, but also occurs via delicate and well-organized biologic processes, including an imbalance between osteochondrogenic signaling and anticalcific events. In addition to traditionally established osteogenic signaling, dysfunctional calcium homeostasis is prerequisite in the development of VC. Moreover, loss of defensive mechanisms, by microorganelle dysfunction, including hyper-fragmented mitochondria, mitochondrial oxidative stress, defective autophagy or mitophagy, and endoplasmic reticulum (ER) stress, may all contribute to VC. To facilitate the understanding of vascular calcification, across any number of bioscientific disciplines, we provide this review of a detailed updated molecular mechanism of VC. This encompasses a vascular smooth muscle phenotypic of osteogenic differentiation, and multiple signaling pathways of VC induction, including the roles of inflammation and cellular microorganelle genesis.

Optimisation of cell and ex vivo culture conditions to study vascular calcification

Medial vascular calcification (MVC) is a highly prevalent disease associated with a high risk of severe, potentially lethal, complications. While animal studies may not systematically be circumvented, in vitro systems have been proven useful to study disease physiopathology. In the context of MVC, the absence of a clinically relevant standardized in vitro method prevents the appropriate comparison and overall interpretation of results originating from different experiments. The aim of our study is to establish in vitro models mimicking in vivo vascular calcification and to select the best methods to unravel the mechanisms involved in MVC. Human aortic smooth muscle cells and rat aortic rings were cultured in different conditions. The influence of fetal calf serum (FCS), alkaline phosphatase, phosphate and calcium concentrations in the medium were evaluated. We identified culture conditions, including the herein reported Aorta Calcifying Medium (ACM), which allowed a reproducible and specific medial calcification of aortic explants. Studying cells and aortic explants cultured, the involvement of bone morphogenetic protein 2 (BMP2) pathway, fibrosis and apoptosis processes in in vitro MVC were demonstrated. Expression of osteoblastic markers was also observed suggesting the occurrence of transdifferentiation of smooth muscle cells to osteoblasts in our models. The use of these models will help researchers in the field of vascular calcification to achieve reproducible results and allow result comparison in a more consistent way.

Osteogenic gene markers are epigenetically reprogrammed during contractile-to-calcifying vascular smooth muscle cell phenotype transition

The understanding of vascular calcification-based mechanism is an urgent pending task in vascular biology and this prompted us to better address this issue by investigating whether DNA methylation mechanism might drive osteogenic marker genes modulation in primary human vascular smooth muscle cells (VSMCs) responding to calcium and phosphate levels overload up to 72 h. Firstly, our data shows this calcifying process recapitulates the molecular repertory of osteogenic biomarkers and specifically requiring RUNX2, Osterix and ALP, BSP genes activations along 72 h in vitro, and this behavior was validated here using other lineages. Conversely, both BMPs 4 and 7 were significantly overexpressed, maybe already as a mechanism in response to RUNX2 and Osterix genes activities identified earlier in response to the calcifying condition, and taken into maintain the calcifying phenotype of VSMCs. Additionally, survival signaling was maintained active and accompanied by a dynamic cytoskeleton rearrangement signaling requiring MAPK and AKT phosphorylations. Moreover, during the contractile-to-calcifying transition phenotype of VSMCs, epigenetic machinery was finely modulated, requiring the translocation of DNMT3B and TET2 into nucleus and this prompted us evaluating whether the profile of osteogenic-related gene promoters' methylation might contribute with this process. By firstly estimating 5meC/5 hmeC ratio changes, we further specifically show the significance of the epigenetic modulation of Osterix and Bone sialoprotein related gene promoters, presenting a positive correlation between the epigenetic signature of their gene promoters and transcriptional patterns. Altogether, our results show for the first time the importance of epigenetic mechanism on modulating osteogenic gene markers reprogramming during calcifying VSMCs phenotype acquisition, which might drive the genesis of vascular ectopic calcification.

The Epigenetic Landscape of Vascular Calcification: An Integrative Perspective

Vascular calcification (VC) is an important complication among patients of advanced age, those with chronic kidney disease, and those with diabetes mellitus. The pathophysiology of VC encompasses passive occurrence of physico-chemical calcium deposition, active cellular secretion of osteoid matrix upon exposure to metabolically noxious stimuli, or a variable combination of both processes. Epigenetic alterations have been shown to participate in this complex environment, through mechanisms including DNA methylation, non-coding RNAs, histone modifications, and chromatin changes. Despite such importance, existing reviews fail to provide a comprehensive view of all relevant reports addressing epigenetic processes in VC, and cross-talk between different epigenetic machineries is rarely examined. We conducted a systematic review based on PUBMED and MEDLINE databases up to 30 September 2019, to identify clinical, translational, and experimental reports addressing epigenetic processes in VC; we retrieved 66 original studies, among which 60.6% looked into the pathogenic role of non-coding RNA, followed by DNA methylation (12.1%), histone modification (9.1%), and chromatin changes (4.5%). Nine (13.6%) reports examined the discrepancy of epigenetic signatures between subjects or tissues with and without VC, supporting their applicability as biomarkers. Assisted by bioinformatic analyses blending in each epigenetic component, we discovered prominent interactions between microRNAs, DNA methylation, and histone modification regarding potential influences on VC risk.

Hypermethylation of mitochondrial DNA in vascular smooth muscle cells impairs cell contractility

Vascular smooth muscle cell (SMC) from arterial stenotic-occlusive diseases is featured with deficiency in mitochondrial respiration and loss of cell contractility. However, the regulatory mechanism of mitochondrial genes and mitochondrial energy metabolism in SMC remains elusive. Here, we described that DNA methyltransferase 1 (DNMT1) translocated to the mitochondria and catalyzed D-loop methylation of mitochondrial DNA in vascular SMCs in response to platelet-derived growth factor-BB (PDGF-BB). Mitochondrial-specific expression of DNMT1 repressed mitochondrial gene expression, caused functional damage, and reduced SMC contractility. Hypermethylation of mitochondrial D-loop regions were detected in the intima-media layer of mouse carotid arteries subjected to either cessation of blood flow or mechanical endothelial injury, and also in vessel specimens from patients with carotid occlusive diseases. Likewise, the ligated mouse arteries exhibited an enhanced mitochondrial binding of DNMT1, repressed mitochondrial gene expression, defects in mitochondrial respiration, and impaired contractility. The impaired contractility of a ligated vessel could be restored by ex vivo transplantation of DNMT1-deleted mitochondria. In summary, we discovered the function of DNMT1-mediated mitochondrial D-loop methylation in the regulation of mitochondrial gene transcription. Methylation of mitochondrial D-loop in vascular SMCs contributes to impaired mitochondrial function and loss of contractile phenotype in vascular occlusive disease.

Atherosclerosis in Chronic Kidney Disease: More, Less, or Just Different?

Patients with chronic kidney disease (CKD) are at an increased risk of premature mortality, mainly from cardiovascular causes. The association between CKD on hemodialysis and accelerated atherosclerosis was described >40 years ago. However, more recently, it has been suggested that the increase in atherosclerosis risk is actually observed in early CKD stages, remaining stable thereafter. In this regard, interventions targeting the pathogenesis of atherosclerosis, such as statins, successful in the general population, have failed to benefit patients with very advanced CKD. This raises the issue of the relative contribution of atherosclerosis versus other forms of cardiovascular injury such as arteriosclerosis or myocardial injury to the increased cardiovascular risk in CKD. In this review, the pathophysiogical contributors to atherosclerosis in CKD that are shared with the general population, or specific to CKD, are discussed. The NEFRONA study (Observatorio Nacional de Atherosclerosis en NEFrologia) prospectively assessed the prevalence and progression of subclinical atherosclerosis (plaque in vascular ultrasound), confirming an increased prevalence of atherosclerosis in patients with moderate CKD. However, the adjusted odds ratio for subclinical atherosclerosis increased with CKD stage, suggesting a contribution of CKD itself to subclinical atherosclerosis. Progression of atherosclerosis was closely related to CKD progression as well as to the baseline presence of atheroma plaque, and to higher phosphate, uric acid, and ferritin and lower 25(OH) vitamin D levels. These insights may help design future clinical trials of stratified personalized medicine targeting atherosclerosis in patients with CKD. Future primary prevention trials should enroll patients with evidence of subclinical atherosclerosis and should provide a comprehensive control of all known risk factors in addition to testing any additional intervention or placebo.

Signaling pathways involved in vascular smooth muscle cell calcification during hyperphosphatemia

Medial vascular calcification has emerged as a putative key factor contributing to the excessive cardiovascular mortality of patients with chronic kidney disease (CKD). Hyperphosphatemia is considered a decisive determinant of vascular calcification in CKD. A critical role in initiation and progression of vascular calcification during elevated phosphate conditions is attributed to vascular smooth muscle cells (VSMCs), which are able to change their phenotype into osteo-/chondroblasts-like cells. These transdifferentiated VSMCs actively promote calcification in the medial layer of the arteries by producing a local pro-calcifying environment as well as nidus sites for precipitation of calcium and phosphate and growth of calcium phosphate crystals. Elevated extracellular phosphate induces osteo-/chondrogenic transdifferentiation of VSMCs through complex intracellular signaling pathways, which are still incompletely understood. The present review addresses critical intracellular pathways controlling osteo-/chondrogenic transdifferentiation of VSMCs and, thus, vascular calcification during hyperphosphatemia. Elucidating these pathways holds a significant promise to open novel therapeutic opportunities counteracting the progression of vascular calcification in CKD.

Autophagy Protects From Uremic Vascular Media Calcification

Chronic kidney disease and diabetes mellitus are associated with extensive media calcification, which leads to increased cardiovascular morbidity and mortality. Here, we investigated the role of autophagy in the pathogenesis of uremic vascular media calcification. DBA/2 mice were fed with high-phosphate diet (HPD) in order to cause vascular calcification. DBA/2 mice on standard chow diet were used as control. In parallel, autophagy and its response to rapamycin, 3-methyladenine (3-MA), and bafilomycin were studied in an in vitro model using mouse vascular smooth muscle cells (MOVAS). DBA/2 mice on HPD developed severe vascular media calcification, which is mirrored in vitro by culturing MOVAS under calcifying conditions. Both, in vitro and in vivo, autophagy significantly increased in MOVAS under calcifying conditions and in aortas of HPD mice, respectively. Histologically, autophagy was located to the aortic Tunica media, but also vascular endothelial cells, and was found to continuously increase during HPD treatment. 3-MA as well as bafilomycin blocked autophagy in MOVAS and increased calcification. Vice versa, rapamycin treatment further increased autophagy and resulted in a significant decrease of vascular calcification in vitro and in vivo. Rapamycin reduced Runx2 transcription levels in aortas and MOVAS to control levels, whereas it increased α-smooth muscle actin and Sm22α transcription in MOVAS to control levels. Furthermore, rapamycin-treated HPD mice survived significantly longer compared to HPD controls. These findings indicate that autophagy is an endogenous response of vascular smooth muscle cells (VSMC) to protect from calcification in uremia. Induction of autophagy by rapamycin protects cells and mice from uremic media calcification possibly by inhibiting osteogenic transdifferentiation of VSMC.

Arterial Calcification Is Regulated Via an miR-204/DNMT3a Regulatory Circuit Both In Vitro and in Female Mice

Arterial calcification is a common cardiovascular disease that initiates from a process of osteoblastic differentiation of vascular smooth muscle cells (VSMCs). Accumulating evidence has demonstrated that microRNAs play an important role in regulating arterial calcification. miR-204 was significantly downregulated in calcified human renal arteries from patients with uremia; calcified arteries of mice, due to 5/6 nephrectomy with a high-phosphate diet (5/6 NTP); and in VSMCs induced by high phosphate concentration. The overexpression of miR-204 alleviated the osteoblastic differentiation of VSMCs. Bisulphite sequencing PCR revealed that CpG sites upstream of miR-204 DNA were hypermethylated in calcified VSMCs; in calcified arteries of mice, due to 5/6 NTP; and in calcified renal artery tissues from patients with uremia. Moreover, increased DNMT3a resulted in the hypermethylation of miR-204 in high phosphate concentration-induced VSMCs, whereas 5-aza-2'-deoxycytidine could restore the expression of miR-204 in high phosphate concentration-induced VSMCs. Moreover, we found that DNMT3a was the target of miR-204, and the methylation ratio of miR-204 was decreased significantly, meaning that the expression of miR-204 was restored when DNMT3a was knocked down by using DNMT3a small interfering RNA, resulting in abrogation of the effect of high phosphate concentration on VSMC calcification. The progress of arterial calcification is regulated by the miR-204/DNMT3a regulatory circuit.

Epigenetic Regulation of Vascular Aging and Age-Related Vascular Diseases

Vascular aging refers to the structural and functional defects that occur in the aorta during the aging process and is characterized by increased vascular cell senescence, vascular dyshomeostasis, and vascular remodeling. Vascular aging is a major risk factor for vascular diseases. However, the current understanding of the biological process of vascular aging and age-related diseases is insufficient. Epigenetic regulation can influence gene expression independently of the gene sequence and mainly includes DNA methylation, histone modifications, and RNA-based gene regulation. Epigenetic regulation plays important roles in many physiological and pathophysiological processes and may explain some gaps in our knowledge regarding the interaction between genes and diseases. In this review, we summarize recent advances in the understanding of the epigenetic regulation of vascular aging and age-related diseases in terms of vascular cell senescence, vascular dyshomeostasis, and vascular remodeling. Moreover, the possibility of targeting epigenetic regulation to delay vascular aging and treat age-related vascular diseases is also discussed.

High phosphate-induced downregulation of PPARγ contributes to CKD-associated vascular calcification

Medial arterial calcification associated with hyperphosphatemia is a main cause of cardiovascular mortality in patients with chronic kidney disease (CKD), but the mechanisms underlying high phosphate-induced vascular calcification remain largely unknown. Here, we observed a significant decrease in the expression of peroxisome proliferator-activated receptor-gamma (PPARγ) in calcified arteries both in CKD patients and in a mouse model of CKD with hyperphosphatemia. In vitro, high phosphate treatment led to a decreased expression of PPARγ in mouse vascular smooth muscle cells (VMSCs), accompanied by apparent osteogenic differentiation and calcification. Pretreatment with PPARγ agonist rosiglitazone significantly reversed high phosphate-induced VSMCs calcification. Further investigation showed that methyl-CpG binding protein 2 (Mecp2)-mediated epigenetic repression was involved in high phosphate-induced PPARγ downregulation. Moreover, the expression of Klotho that has the ability to inhibit vascular calcification by regulating phosphate uptake decreased with the PPARγ reduction in VSMCs after high phosphate treatment, and rosiglitazone failed to inhibit high phosphate-induced calcification in VSMCs with knockdown of Klotho or in aortic rings from Klotho-deficient (kl/kl) mice. Finally, an in vivo study demonstrated that oral administration of rosiglitazone could increase Klotho expression and protect against high phosphate-induced vascular calcification in CKD mice. These findings suggest that the inhibition of PPARγ expression may contribute to the pathogenesis of high phosphate-induced vascular calcification, which may provide a new therapeutic target for vascular calcification in CKD patients.

Peripheral Arterial Disease Genetics: Progress to Date and Challenges Ahead

PURPOSE OF REVIEW

In this paper, we review the progress made thus far in research related to the genetics of peripheral arterial disease (PAD) by detailing efforts to date in heritability, linkage analyses, and candidate gene studies. We further summarize more contemporary genome-wide association studies (GWAS) and epigenetic studies of PAD. Finally, we review current challenges and future avenues of advanced research in PAD genetics including whole genome sequencing studies.

RECENT FINDINGS

Studies have estimated the heritability of PAD to be moderate, though the contribution to this heritability that is independent of traditional cardiovascular risk factors remains unclear. Recent efforts have identified SNPs associated with PAD in GWAS analyses, but these have yet to be replicated in independent studies. Much remains to be discovered in the field of PAD genetics. An improved understanding of the genetic foundation for PAD will allow for earlier diagnosis of disease and a more complete pathophysiological understanding of the mechanisms of the disease leading to novel therapeutic interventions. Future avenues for success will likely arise from very large-scale GWAS, whole genome sequencing, and epigenetic studies involving very well-characterized cohorts.

APE1/Ref-1 Inhibits Phosphate-Induced Calcification and Osteoblastic Phenotype Changes in Vascular Smooth Muscle Cells

Vascular calcification plays a role in the pathogenesis of atherosclerosis, diabetes, and chronic kidney disease; however, the role of apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) in inorganic phosphate (Pi)-induced vascular smooth muscle cell (VSMC) calcification remains unknown. In this study, we investigated the possible role of APE1/Ref-1 in Pi-induced VSMC calcification. We observed that Pi decreased endogenous APE1/Ref-1 expression and promoter activity in VSMCs, and that adenoviral overexpression of APE1/Ref-1 inhibited Pi-induced calcification in VSMCs and in an ex vivo organ culture of a rat aorta. However, a redox mutant of APE1/Ref-1(C65A/C93A) did not reduce Pi-induced calcification in VSMCs, suggesting APE1/Ref-1-mediated redox function against vascular calcification. Additionally, APE1/Ref-1 overexpression inhibited Pi-induced intracellular and mitochondrial reactive oxygen species production, and APE1/Ref-1 overexpression resulted in decreased Pi-induced lactate dehydrogenase activity, pro-apoptotic Bax levels, and increased anti-apoptotic Bcl-2 protein levels. Furthermore, APE1/Ref-1 inhibited Pi-induced osteoblastic differentiation associated with alkaline phosphatase activity and inhibited Pi-exposure-induced loss of the smooth muscle phenotype. Our findings provided valuable insights into the redox function of APE1/Ref-1 in preventing Pi-induced VSMC calcification by inhibiting oxidative stress and osteoblastic differentiation, resulting in prevention of altered osteoblastic phenotypes in VSMCs.