MDM2 E3 ligase-mediated ubiquitination and degradation of HDAC1 in vascular calcification

Carbonylation of Runx2 at K176 by 4-Hydroxynonenal Accelerates Vascular Calcification

BACKGROUND

Vascular calcification, which is characterized by calcium deposition in arterial walls and the osteochondrogenic differentiation of vascular smooth muscle cells, is an actively regulated process that involves complex mechanisms. Vascular calcification is associated with increased cardiovascular adverse events. The role of 4-hydroxynonenal (4-HNE), which is the most abundant stable product of lipid peroxidation, in vascular calcification has been poorly investigated.

METHODS

Serum was collected from patients with chronic kidney disease and controls, and the levels of 4-HNE and 8-iso-prostaglandin F2α were measured. Sections of coronary atherosclerotic plaques from donors were immunostained to analyze calcium deposition and 4-HNE. A total of 658 patients with coronary artery disease who received coronary computed tomography angiography were recruited to analyze the relationship between coronary calcification and the rs671 mutation in aldehyde dehydrogenase 2 (ALDH2). ALDH2 knockout (ALDH2-/-) mice, smooth muscle cell-specific ALDH2 knockout mice, ALDH2 transgenic mice, and their controls were used to establish vascular calcification models. Primary mouse aortic smooth muscle cells and human aortic smooth muscle cells were exposed to medium containing β-glycerophosphate and CaCl2 to investigate cell calcification and the underlying molecular mechanisms.

RESULTS

Elevated 4-HNE levels were observed in the serum of patients with chronic kidney disease and model mice and were detected in calcified artery sections by immunostaining. ALDH2 knockout or smooth muscle cell-specific ALDH2 knockout accelerated the development of vascular calcification in model mice, whereas overexpression or activation prevented mouse vascular calcification and the osteochondrogenic differentiation of vascular smooth muscle cells. In patients with coronary artery disease, patients with ALDH2 rs671 gene mutation developed more severe coronary calcification. 4-HNE promoted calcification of both mouse aortic smooth muscle cells and human aortic smooth muscle cells and their osteochondrogenic differentiation in vitro. 4-HNE increased the level of Runx2 (runt-related transcription factor-2), and the effect of 4-HNE on promoting vascular smooth muscle cell calcification was ablated when Runx2 was knocked down. Mutation of Runx2 at lysine 176 reduced its carbonylation and eliminated the 4-HNE-induced upregulation of Runx2.

CONCLUSIONS

Our results suggest that 4-HNE increases Runx2 stabilization by directly carbonylating its K176 site and promotes vascular calcification. ALDH2 might be a potential target for the treatment of vascular calcification.

MDM2 accelerated renal senescence via ubiquitination and degradation of HDAC1

Senescence, an intricate and inevitable biological process, characterized by the gradual loss of homeostasis and declining organ functions. The pathological features of cellular senescence, including cell cycle arrest, metabolic disruptions, and the emergence of senescence-associated secretory phenotypes (SASP), collectively contribute to the intricate and multifaceted nature of senescence. Beyond its classical interaction with p53, murine double minute gene 2 (MDM2), traditionally known as an E3 ubiquitin ligase involved in protein degradation, plays a pivotal role in cellular processes governing senescence. Histone deacetylase (HDAC), a class of histone deacetylases mainly expressed in the nucleus, has emerged as a critical contributor to renal tissues senescence. In this study we investigated the interplay between MDM2 and HDAC1 in renal senescence. We established a natural aging model in mice over a 2-year period that was verified by SA-β-GAL staining and increased expression of senescence-associated markers such as p21, p16, and TNF-α in the kidneys. Furthermore, we showed that the expression of MDM2 was markedly increased, while HDAC1 expression underwent downregulation during renal senescence. This phenomenon was confirmed in H2O2-stimulated HK2 cells in vitro. Knockout of renal tubular MDM2 alleviated renal senescence in aged mice and in H2O2-stimulated HK2 cells. Moreover, we demonstrated that MDM2 promoted renal senescence by orchestrating the ubiquitination and subsequent degradation of HDAC1. These mechanisms synergistically accelerate the aging process in renal tissues, highlighting the intricate interplay between MDM2 and HDAC1, underpinning the age-related organ function decline.

Potential actions of capsaicin for preventing vascular calcification of vascular smooth muscle cells in vitro and in vivo

Vascular calcification (VC) is an accurate risk factor and predictor of adverse cardiovascular events; however, there is currently no effective therapy to specifically prevent VC progression. Capsaicin (Cap) is a bioactive alkaloid isolated from Capsicum annuum L., a traditional medicinal and edible plant that is beneficial for preventing cardiovascular diseases. However, the effect of Cap on VC remains unclear. This study aimed to explore the effects and related mechanisms of Cap on aortic calcification in a mouse and on Pi-induced calcification in vascular smooth muscle cells (VSMCs). First, we established a calcification mouse model with vitamin D3 and evaluated the effects of Cap on calcification mice using von Kossa staining, calcium content, and alkaline phosphatase activity tests. The results showed that Cap significantly improved calcification in mice. VSMCs were then cultured in 2.6 mM Na2HPO4 and 50 μg/mL ascorbic acid for 7 days to obtain a calcification model, and we investigated the effects and mechanisms of Cap on VSMCs calcification by assessing the changes of calcium deposition, calcium content, and subsequent VC biomarkers. These results showed that Cap alleviated VSMCs calcification by upregulating the expressions of TRPV1. Moreover, Cap reduced the expression of Wnt3a and β-catenin, whereas DKK1 antagonised the inhibitory effect of Cap on VSMC calcification. This study is the first to offer direct evidence that Cap inhibits the Wnt/β-catenin signaling pathway by upregulating the expression of the TRPV1 receptor, resulting in the decreased expression of Runx2 and BMP-2, thereby reducing VSMC calcification. Our study may provide novel strategies for preventing the progression of VC. This could serve as a theoretical basis for clinically treating VC with spicy foods.

Epigenetically regulated inflammation in vascular senescence and renal progression of chronic kidney disease

Chronic kidney disease (CKD) and its complications, including vascular senescence and progressive renal fibrosis, are associated with inflammation. Vascular senescence, in particular, has emerged as an instrumental mediator of vascular inflammation that potentially worsens renal function. Epigenetically regulated inflammation involving histone modification, DNA methylation, actions of microRNAs and other non-coding RNAs, and their reciprocal reactions during vascular senescence and inflammaging are underappreciated. Their synergistic effects can contribute to CKD progression. Vascular senotherapeutics or pharmacological anti-senescent therapies based on epigenetic machineries can therefore be plausible options for ameliorating vascular aging and even halting the worsening of renal fibrosis. These include histone deacetylase modulators, histone methyltransferase modulators, other histone modification effectors, DNA methyltransferase inhibitors, telomerase reverse transcriptase enhancers, microRNA mimic delivery, and small molecules with microRNA-regulating potentials. Some of these molecules have already been tested and have shown anecdotal evidence for treating uremic vasculopathy and renal fibrosis, supporting the feasibility of this approach.

Interference of MDM2 attenuates vascular endothelial dysfunction in hypertension partly through blocking Notch1/NLRP3 inflammasome pathway

BACKGROUND

Hypertension is a life-threatening disease mainly featured as vascular endothelial dysfunction. This study aims to explore the regulatory role of murine double minute 2 (MDM2) in hypertension and vascular damage.

METHODS

Mice were infused with angiotensin II (AngII) to establish a hypertension mouse model in vivo and AngII-stimulated HUVECs were constructed to simulate the damage of vascular endothelial cells in hypertension in vitro. The plasmids targeting to MDM2 was injected to mice or transfected to HUVECs. qRT-PCR and western blot were performed to detect corresponding gene expression in mice aorta. Blood pressure was measured. H&E and Masson staining were conducted to evaluate histological changes of aorta. Responses to the acetylcholine (ACh) and sodium nitroprusside (SNP) were assessed in aorta. ZO-1 expression and cell apoptosis were detected by immunofluorescence and TUNEL, respectively. Network formation ability was determined employing a tube formation.

RESULTS

MDM2 was upregulated in hypertensive mice. Knockdown of MDM2 inhibited AngII-induced high BP, histological damage, vascular relaxation to Ach, and promoted the levels of p-eNOS and ZO-1 in the aorta in hypertensive mice. MDM2 knockdown inactivated Notch1 signaling and NLRP3 inflammasome, while the inhibitory effect of MDM2 knockdown on NLRP3 inflammasome activation was partly restored by the activation of Notch1. Furthermore, knockdown of MDM2 relieved AngII-induced endothelial dysfunction in HUVECs, as well as suppressing AngII-promoted cell apoptosis. Whereas, the impacts generated by MDM2 knockdown were partly weakened by the activation of Notch1 signaling or NLRP3 inflammasome.

CONCLUSION

In summary, knockdown of MDM2 can attenuate vascular endothelial dysfunction in hypertension, which may be achieved through inhibiting the activation of Notch1 and NLRP3 inflammasome.

MDM2 provides TOP2 poison resistance by promoting proteolysis of TOP2βcc in a p53-independent manner

DNA topoisomerase II (TOP2) is an enzyme that performs a critical function in manipulating DNA topology during replication, transcription, and chromosomal compaction by forming a vital intermediate known as the TOP2-DNA cleavage complex (TOP2cc). Although the TOP2cc is often transient, stabilization can be achieved by TOP2 poisons, a family of anti-cancer chemotherapeutic agents targeting TOP2, such as etoposide (VP-16), and then induce double-strand breaks (DSBs) in cellular DNA. TOP2cc first needs to be proteolyzed before it can be processed by TDP2 for the removal of these protein adducts and to produce clean DNA ends necessary for proper repair. However, the mechanism by which TOP2βcc is proteolyzed has not been thoroughly studied. In this study, we report that after exposure to VP-16, MDM2, a RING-type E3 ubiquitin ligase, attaches to TOP2β and initiates polyubiquitination and proteasomal degradation. Mechanistically, during exposure to VP-16, TOP2β binds to DNA to form TOP2βcc, which promotes MDM2 binding and subsequent TOP2β ubiquitination and degradation, and results in a decrease in TOP2βcc levels. Biologically, MDM2 inactivation abrogates TOP2β degradation, stabilizes TOP2βcc, and subsequently increases the number of TOP2β-concealed DSBs, resulting in the rapid death of cancer cells via the apoptotic process. Furthermore, we demonstrate the combination activity of VP-16 and RG7112, an MDM2 inhibitor, in the xenograft tumor model and in situ lung cancer mouse model. Taken together, the results of our research reveal an underlying mechanism by which MDM2 promotes cancer cell survival in the presence of TOP2 poisons by activating proteolysis of TOP2βcc in a p53-independent manner, and provides a rationale for the combination of MDM2 inhibitors with TOP2 poisons for cancer therapy.

DNA methylation and histone post-translational modifications in atherosclerosis and a novel perspective for epigenetic therapy

Atherosclerosis, which is a vascular pathology characterized by inflammation and plaque build-up within arterial vessel walls, acts as the important cause of most cardiovascular diseases. Except for a lipid-depository and chronic inflammatory, increasing evidences propose that epigenetic modifications are increasingly associated with atherosclerosis and are of interest from both therapeutic and biomarker perspectives. The chronic progressive nature of atherosclerosis has highlighted atherosclerosis heterogeneity and the fact that specific cell types in the complex milieu of the plaque are, by far, not the only initiators and drivers of atherosclerosis. Instead, the ubiquitous effects of cell type are tightly controlled and directed by the epigenetic signature, which, in turn, is affected by many proatherogenic stimuli, including low-density lipoprotein, proinflammatory, and physical forces of blood circulation. In this review, we summarize the role of DNA methylation and histone post-translational modifications in atherosclerosis. The future research directions and potential therapy for the management of atherosclerosis are also discussed. Video Abstract.

Dopaminergic cell protection and alleviation of neuropsychiatric disease symptoms by VMAT2 expression through the class I HDAC inhibitor TC-H 106

The importance of vesicular monoamine transporter 2 (VMAT2) in dopamine regulation, which is considered crucial for neuropsychiatric disorders, is currently being studied. Moreover, the development of disease treatments using histone deacetylase (HDAC) inhibitors (HDACi) is actively progressing in various fields. Recently, research on the possibility of regulating neuropsychiatric disorders has been conducted. In this study, we evaluated whether VMAT2 expression increased by an HDACi can fine-tune neuropsychotic behavior, such as attention deficit hyperactivity disorder (ADHD) and protect against the cell toxicity through oxidized dopamine. First, approximately 300 candidate HDACi compounds were added to the SH-SY5Y dopaminergic cell line to identify the possible changes in the VMAT2 expression levels, which were measured using quantitative polymerase chain reaction. The results demonstrated, that treatment with pimelic diphenylamide 106 (TC-H 106), a class I HDACi, increased VMAT2 expression in both the SH-SY5Y cells and mouse brain. The increased VMAT2 expression induced by TC-H 106 alleviated the cytotoxicity attributed to 6-hydroxydopamine (6-OHDA) or 1-methyl-4-phenylpyridinium (MPP+ ) and free dopamine treatment. Moreover, dopamine concentrations, both intracellularly and in the synaptosomes, were significantly elevated by increased VMAT2 expression. These results suggest that dopamine concentration regulation by VMAT2 expression induced by TC-H 106 could alter several related behavioral aspects that was confirmed by attenuation of hyperactivity and impulsivity, which were major characteristics of animal model showing ADHD-like behaviors. These results indicate that HDACi-increased VMAT2 expression offers sufficient protections against dopaminergic cell death induced by oxidative stress. Thus, the epigenetic approach could be considered as therapeutic candidate for neuropsychiatric disease regulation.

Discovery of deoxyandrographolide and its novel effect on vascular senescence by targeting HDAC1

Aconitum carmichaelii (Fuzi) is a traditional Chinese medicine that has been widely used in the clinic to save the dying life for over several thousand years. However, the medicinal components of Fuzi in treating vascular senescence (VS) and its potential mechanism remain unclear. In this study, a network pharmacology method was used to explore the possible components and further validated by experiments to get a candidate compound, deoxyandrographolide (DA). DA restrains aging biomarkers, such as p16, p21, γH2A.X, and p53 in vitro and in vivo blood co-culture studies. Histone deacetylase 1 (HDAC1), mouse double minute2 (MDM2), cyclin-dependent kinase 4, and mechanistic target of rapamycin kinase (mTOR) are predicted to be the possible targets of DA based on virtual screening. Subsequent bio-layer interferometry results indicated that DA showed good affinity capability with HDAC1. DA enhances the protein expression of HDAC1 in the angiotensin II-induced senescence process by inhibiting its ubiquitination degradation. Loss of HDAC1 by CRISPR/Cas9 leads to the disappearance of DA's anti-aging property. The enhancement of HDAC1 represses H3K4me3 (a biomarker of chromosomal activity) and improves chromosome stability. RNA sequencing results also confirmed our hypothesis. Our evidence illuminated that DA may achieve as a novel compound in the treatment of VS by improving chromosome stability.

PFKFB3-driven vascular smooth muscle cell glycolysis promotes vascular calcification via the altered FoxO3 and lactate production

A link between increased glycolysis and vascular calcification has recently been reported, but it remains unclear how increased glycolysis contributes to vascular calcification. We therefore investigated the role of PFKFB3, a critical enzyme of glycolysis, in vascular calcification. We found that PFKFB3 expression was upregulated in calcified mouse VSMCs and arteries. We showed that expression of miR-26a-5p and miR-26b-5p in calcified mouse arteries was significantly decreased, and a negative correlation between Pfkfb3 mRNA expression and miR-26a-5p or miR-26b-5p was seen in these samples. Overexpression of miR-26a/b-5p significantly inhibited PFKFB3 expression in VSMCs. Intriguingly, pharmacological inhibition of PFKFB3 using PFK15 or knockdown of PFKFB3 ameliorated vascular calcification in vD3 -overloaded mice in vivo or attenuated high phosphate (Pi)-induced VSMC calcification in vitro. Consistently, knockdown of PFKFB3 significantly reduced glycolysis and osteogenic transdifferentiation of VSMCs, whereas overexpression of PFKFB3 in VSMCs induced the opposite effects. RNA-seq analysis and subsequent experiments revealed that silencing of PFKFB3 inhibited FoxO3 expression in VSMCs. Silencing of FoxO3 phenocopied the effects of PFKFB3 depletion on Ocn and Opg expression but not Alpl in VSMCs. Pyruvate or lactate supplementation, the product of glycolysis, reversed the PFKFB3 depletion-mediated effects on ALP activity and OPG protein expression in VSMCs. Our results reveal that blockade of PFKFB3-mediated glycolysis inhibits vascular calcification in vitro and in vivo. Mechanistically, we show that FoxO3 and lactate production are involved in PFKFB3-driven osteogenic transdifferentiation of VSMCs. PFKFB3 may be a promising therapeutic target for the treatment of vascular calcification.

Lumican silencing ameliorates β-glycerophosphate-mediated vascular smooth muscle cell calcification by attenuating the inhibition of APOB on KIF2C activity

Adverse cardiovascular events are associated with vascular calcification (VC) process, where vascular smooth muscle cells (VSMCs) differentiate into osteoblastic phenotype and deposit hydroxyapatite crystals. Microtubule-associated protein kinesin family member 2C (KIF2C) expression is decreased obviously in VSMC during calcification induction. Accordingly, we investigate the role and potential mechanism of KIF2C on VSMC calcification. The effects of β-glycerophosphate (β-GP)/KIF2C/lumican (LUM) on calcification, calcium content, alkaline phosphatase (ALP) activity, calcification-related markers, Tubulin, the ratio of polymerized (Po) to free (Fr) tubulin, as well as levels of LUM, apolipoprotein B (APOB), and KIF2C were assessed by Alizarin red S staining, calcium assay kit, ALP assay kit, Western blot, immunofluorescence, and quantitative real-time PCR. The interplay between LUM and APOB was estimated using co-immunoprecipitation and immunofluorescence. As a result, β-GP promoted calcification of human VMSCs (HVMSCs) and repressed KIF2C expression. KIF2C overexpression reversed the effect of β-GP on HVSMCs. LUM silencing attenuated β-GP-induced promotion on HVSMC calcification and increased KIF2C expression by interacting with APOB. Collectively, LUM silencing can alleviate β-GP-induced VSMC calcification through mitigating the repression of APOB on KIF2C expression.

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.

Circulating Extracellular Vesicle-Propagated microRNA Signature as a Vascular Calcification Factor in Chronic Kidney Disease

BACKGROUND

Chronic kidney disease (CKD) accelerates vascular calcification via phenotypic switching of vascular smooth muscle cells (VSMCs). We investigated the roles of circulating small extracellular vesicles (sEVs) between the kidneys and VSMCs and uncovered relevant sEV-propagated microRNAs (miRNAs) and their biological signaling pathways.

METHODS AND RESULTS

We established CKD models in rats and mice by adenine-induced tubulointerstitial fibrosis. Cultures of A10 embryonic rat VSMCs showed increased calcification and transcription of osterix (Sp7), osteocalcin (Bglap), and osteopontin (Spp1) when treated with rat CKD serum. sEVs, but not sEV-depleted serum, accelerated calcification in VSMCs. Intraperitoneal administration of a neutral sphingomyelinase and biogenesis/release inhibitor of sEVs, GW4869 (2.5 mg/kg per 2 days), inhibited thoracic aortic calcification in CKD mice under a high-phosphorus diet. GW4869 induced a nearly full recovery of calcification and transcription of osteogenic marker genes. In CKD, the miRNA transcriptome of sEVs revealed a depletion of 4 miRNAs, miR-16-5p, miR-17~92 cluster-originated miR-17-5p/miR-20a-5p, and miR-106b-5p. Their expression decreased in sEVs from CKD patients as kidney function deteriorated. Transfection of VSMCs with each miRNA-mimic mitigated calcification. In silico analyses revealed VEGFA (vascular endothelial growth factor A) as a convergent target of these miRNAs. We found a 16-fold increase in VEGFA transcription in the thoracic aorta of CKD mice under a high-phosphorus diet, which GW4869 reversed. Inhibition of VEGFA-VEGFR2 signaling with sorafenib, fruquintinib, sunitinib, or VEGFR2-targeted siRNA mitigated calcification in VSMCs. Orally administered fruquintinib (2.5 mg/kg per day) for 4 weeks suppressed the transcription of osteogenic marker genes in the mouse aorta. The area under the curve of miR-16-5p, miR-17-5p, 20a-5p, and miR-106b-5p for the prediction of abdominal aortic calcification was 0.7630, 0.7704, 0.7407, and 0.7704, respectively.

CONCLUSIONS

The miRNA transcriptomic signature of circulating sEVs uncovered their pathologic role, devoid of the calcification-protective miRNAs that target VEGFA signaling in CKD-driven vascular calcification. These sEV-propagated miRNAs are potential biomarkers and therapeutic targets for vascular calcification.

Regulation of osteogenesis in bone marrow-derived mesenchymal stem cells via histone deacetylase 1 and 2 co-cultured with human gingival fibroblasts and periodontal ligament cells

OBJECTIVE

This study aimed to determine the regulatory mechanism of bone marrow-derived mesenchymal stem cell (BM-MSC) differentiation mediated by humoral factors derived from human periodontal ligament (HPL) cells and human gingival fibroblasts (HGFs). We analyzed histone deacetylase (HDAC) expression and activity involved in BM-MSC differentiation and determined their regulatory effects in co-cultures of BM-MSCs with HPL cells or HGFs.

BACKGROUND

BM-MSCs can differentiate into various cell types and can, thus, be used in periodontal regenerative therapy. However, the mechanism underlying their differentiation remains unclear. Transplanted BM-MSCs are affected by periodontal cells via direct contact or secretion of humoral factors. Therefore, their activity is regulated by humoral factors derived from HPL cells or HGFs.

METHODS

BM-MSCs were indirectly co-cultured with HPL cells or HGFs under osteogenic or growth conditions and then analyzed for osteogenesis, HDAC1 and HDAC2 expression and activity, and histone H3 acetylation. BM-MSCs were treated with trichostatin A, or their HDAC1 or HDAC2 expression was silenced or overexpressed during osteogenesis. Subsequently, they were evaluated for osteogenesis or the effects of HDAC activity.

RESULTS

BM-MSCs co-cultured with HPL cells or HGFs showed suppressed osteogenesis, HDAC1 and HDAC2 expression, and HDAC phosphorylation; however, histone H3 acetylation was enhanced. Trichostatin A treatment remarkably suppressed osteogenesis, decreasing HDAC expression and enhancing histone H3 acetylation. HDAC1 and HDAC2 silencing negatively regulated osteogenesis in BM-MSCs to the same extent as that achieved by indirect co-culture with HPL cells or HGFs. Conversely, their overexpression positively regulated osteogenesis in BM-MSCs.

CONCLUSION

The suppressive effects of HPL cells and HGFs on BM-MSC osteogenesis were regulated by HDAC expression and histone H3 acetylation to a greater extent than that mediated by HDAC activity. Therefore, regulation of HDAC expression has prospects in clinical applications for effective periodontal regeneration, mainly, bone regeneration.

Cdon suppresses vascular smooth muscle calcification via repression of the Wnt/Runx2 Axis

Osteogenic transdifferentiation of vascular smooth muscle cells (VSMCs) is a risk factor associated with vascular diseases. Wnt signaling is one of the major mechanisms implicated in the osteogenic conversion of VSMCs. Since Cdon has a negative effect on Wnt signaling in distinct cellular processes, we sought to investigate the role of Cdon in vascular calcification. The expression of Cdon was significantly downregulated in VSMCs of the aortas of patients with atherosclerosis and aortic stenosis. Consistently, calcification models, including vitamin D3 (VD3)-injected mice and VSMCs cultured with calcifying media, exhibited reduced Cdon expression. Cdon ablation mice (cKO) exhibited exacerbated aortic stiffness and calcification in response to VD3 compared to the controls. Cdon depletion induced the osteogenic conversion of VSMCs accompanied by cellular senescence. The Cdon-deficient aortas showed a significant alteration in gene expression related to cell proliferation and differentiation together with Wnt signaling regulators. Consistently, Cdon depletion or overexpression in VSMCs elevated or attenuated Wnt-reporter activities, respectively. The deletion mutant of the second immunoglobulin domain (Ig2) in the Cdon ectodomain failed to suppress Wnt signaling and osteogenic conversion of VSMCs. Furthermore, treatment with purified recombinant proteins of the entire ectodomain or Ig2 domain of Cdon displayed suppressive effects on Wnt signaling and VSMC calcification. Our results demonstrate a protective role of Cdon in VSMC calcification by suppressing Wnt signaling. The Ig2 domain of Cdon has the potential as a therapeutic tool to prevent vascular calcification.

Molecular Mechanisms of Vascular Health: Insights From Vascular Aging and Calcification

Cardiovascular disease is the most common cause of death worldwide, especially beyond the age of 65 years, with the vast majority of morbidity and mortality due to myocardial infarction and stroke. Vascular pathology stems from a combination of genetic risk, environmental factors, and the biologic changes associated with aging. The pathogenesis underlying the development of vascular aging, and vascular calcification with aging, in particular, is still not fully understood. Accumulating data suggests that genetic risk, likely compounded by epigenetic modifications, environmental factors, including diabetes and chronic kidney disease, and the plasticity of vascular smooth muscle cells to acquire an osteogenic phenotype are major determinants of age-associated vascular calcification. Understanding the molecular mechanisms underlying genetic and modifiable risk factors in regulating age-associated vascular pathology may inspire strategies to promote healthy vascular aging. This article summarizes current knowledge of concepts and mechanisms of age-associated vascular disease, with an emphasis on vascular calcification.

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.

Roles of Epigenetics in Cardiac Fibroblast Activation and Fibrosis

Cardiac fibrosis is a common pathophysiologic process associated with numerous cardiovascular diseases, resulting in cardiac dysfunction. Cardiac fibroblasts (CFs) play an important role in the production of the extracellular matrix and are the essential cell type in a quiescent state in a healthy heart. In response to diverse pathologic stress and environmental stress, resident CFs convert to activated fibroblasts, referred to as myofibroblasts, which produce more extracellular matrix, contributing to cardiac fibrosis. Although multiple molecular mechanisms are implicated in CFs activation and cardiac fibrosis, there is increasing evidence that epigenetic regulation plays a key role in this process. Epigenetics is a rapidly growing field in biology, and provides a modulated link between pathological stimuli and gene expression profiles, ultimately leading to corresponding pathological changes. Epigenetic modifications are mainly composed of three main categories: DNA methylation, histone modifications, and non-coding RNAs. This review focuses on recent advances regarding epigenetic regulation in cardiac fibrosis and highlights the effects of epigenetic modifications on CFs activation. Finally, we provide some perspectives and prospects for the study of epigenetic modifications and cardiac fibrosis.

Biomechanical regulation of planar cell polarity in endothelial cells

Cell polarity refers to the uneven distribution of certain cytoplasmic components in a cell with a spatial order. The planar cell polarity (PCP), the cell aligns perpendicular to the polar plane, in endothelial cells (ECs) has become a research hot spot. The planar polarity of ECs has a positive significance on the regulation of cardiovascular dysfunction, pathological angiogenesis, and ischemic stroke. The endothelial polarity is stimulated and regulated by biomechanical force. Mechanical stimuli promote endothelial polarization and make ECs produce PCP to maintain the normal physiological and biochemical functions. Here, we overview recent advances in understanding the interplay and mechanism between PCP and ECs function involved in mechanical forces, with a focus on PCP signaling pathways and organelles in regulating the polarity of ECs. And then showed the related diseases caused by ECs polarity dysfunction. This study provides new ideas and therapeutic targets for the treatment of endothelial PCP-related diseases.

MDM2-Mediated Ubiquitination of RXRβ Contributes to Mitochondrial Damage and Related Inflammation in Atherosclerosis

A novel function of retinoid X receptor beta (RXRβ) in endothelial cells has been reported by us during the formation of atherosclerosis. Here, we extended the study to explore the cellular mechanisms of RXRβ protein stability regulation. In this study, we discovered that murine double minute-2 (MDM2) acts as an E3 ubiquitin ligase to target RXRβ for degradation. The result showed that MDM2 directly interacted with and regulated RXRβ protein stability. MDM2 promoted RXRβ poly-ubiquitination and degradation by proteasomes. Moreover, mutated MDM2 RING domain (C464A) or treatment with an MDM2 inhibitor targeting the RING domain of MDM2 lost the ability of MDM2 to regulate RXRβ protein expression and ubiquitination. Furthermore, treatment with MDM2 inhibitor alleviated oxidized low-density lipoprotein-induced mitochondrial damage, activation of TLR9/NF-κB and NLRP3/caspase-1 pathway and production of pro-inflammatory cytokines in endothelial cells. However, all these beneficial effects were reduced by the transfection of RXRβ siRNA. Moreover, pharmacological inhibition of MDM2 attenuated the development of atherosclerosis and reversed mitochondrial damage and related inflammation in the atherosclerotic process in LDLr^-/- mice, along with the increased RXRβ protein expression in the aorta. Therefore, our study uncovers a previously unknown ubiquitination pathway and suggests MDM2-mediated RXRβ ubiquitination as a new therapeutic target in atherosclerosis.

Aged bone matrix-derived extracellular vesicles as a messenger for calcification paradox

Adipocyte differentiation of bone marrow mesenchymal stem/stromal cells (BMSCs) instead of osteoblast formation contributes to age- and menopause-related marrow adiposity and osteoporosis. Vascular calcification often occurs with osteoporosis, a contradictory association called “calcification paradox”. Here we show that extracellular vesicles derived from aged bone matrix (AB-EVs) during bone resorption favor BMSC adipogenesis rather than osteogenesis and augment calcification of vascular smooth muscle cells. Intravenous or intramedullary injection of AB-EVs promotes bone-fat imbalance and exacerbates Vitamin D3 (VD3)-induced vascular calcification in young or old mice. Alendronate (ALE), a bone resorption inhibitor, down-regulates AB-EVs release and attenuates aging- and ovariectomy-induced bone-fat imbalance. In the VD3-treated aged mice, ALE suppresses the ovariectomy-induced aggravation of vascular calcification. MiR-483-5p and miR-2861 are enriched in AB-EVs and essential for the AB-EVs-induced bone-fat imbalance and exacerbation of vascular calcification. Our study uncovers the role of AB-EVs as a messenger for calcification paradox by transferring miR-483-5p and miR-2861.

This study uncovers the role of extracellular vesicles from bone matrix as a messenger in the development of osteoporosis and vascular calcification (calcification paradox) during skeletal aging and menopause by transferring miR-483-5p and miR-2861.

Focusing on Mechanoregulation Axis in Fibrosis: Sensing, Transduction and Effecting

Fibrosis, a pathologic process featured by the excessive deposition of connective tissue components, can affect virtually every organ and has no satisfactory therapy yet. Fibrotic diseases are often associated with organ dysfunction which leads to high morbidity and mortality. Biomechanical stmuli and the corresponding cellular response havebeen identified in fibrogenesis, as the fibrotic remodeling could be seen as the incapacity to reestablish mechanical homeostasis: along with extracellular matrix accumulating, the physical property became more “stiff” and could in turn induce fibrosis. In this review, we provide a comprehensive overview of mechanoregulation in fibrosis, from initialing cellular mechanosensing to intracellular mechanotransduction and processing, and ends up in mechanoeffecting. Our contents are not limited to the cellular mechanism, but further expand to the disorders involved and current clinical trials, providing an insight into the disease and hopefully inspiring new approaches for the treatment of tissue fibrosis.

Activating BK channels ameliorates vascular smooth muscle calcification through Akt signaling

Vascular calcification (VC) is characterized by pathological depositions of calcium and phosphate in the arteries and veins via an active cell-regulated process, in which vascular smooth muscle cells (VSMCs) transform into osteoblast/chondrocyte-like cells as in bone formation. VC is associated with significant morbidity and mortality in chronic kidney disease (CKD) and cardiovascular disease, but the underlying mechanisms remain unclear. In this study we investigated the role of large-conductance calcium-activated potassium (BK) channels in 3 experimental VC models. VC was induced in vascular smooth muscle cells (VSMCs) by β-glycerophosphate (β-GP), or in rats by subtotal nephrectomy, or in mice by high-dosage vitamin D3. We showed that the expression of BK channels in the artery of CKD rats with VC and in β-GP-treated VSMCs was significantly decreased, which was functionally confirmed by patch-clamp recording. In β-GP-treated VSMCs, BK channel opener NS1619 (20 μM) significantly alleviated VC by decreasing calcium content and alkaline phosphatase activity. Furthermore, NS1619 decreased mRNA expression of ostoegenic genes OCN and OPN, as well as Runx2 (a key transcription factor involved in preosteoblast to osteoblast differentiation), and increased the expression of α-SMA protein, whereas BK channel inhibitor paxilline (10 μM) caused the opposite effects. In primary cultured VSMCs from BK^-/- mice, BK deficiency aggravated calcification as did BK channel inhibitor in normal VSMCs. Moreover, calcification was more severe in thoracic aorta rings of BK^-/- mice than in those of wild-type littermates. Administration of BK channel activator BMS191011 (10 mg· kg^-1 ·d^-1) in high-dosage vitamin D3-treated mice significantly ameliorated calcification. Finally, co-treatment with Akt inhibitor MK2206 (1 μM) or FoxO1 inhibitor AS1842856 (3 μM) in calcified VSMCs abrogated the effects of BK channel opener NS1619. Taken together, activation of BK channels ameliorates VC via Akt/FoxO1 signaling pathways. Strategies to activate BK channels and/or enhance BK channel expression may offer therapeutic avenues to control VC.

Hyperphosphatemia-induced degradation of transcription factor EB exacerbates vascular calcification

AIMS

Chronic kidney disease (CKD) and subsequent hyperphosphatemia causes vascular calcification (VC), a strong predictor of mortality. Dysregulation of the autophagy-lysosomal pathway in vascular smooth muscle cells (VSMCs) mediates hyperphosphatemia-dependent VC. However, the process through which lysosomes become dysfunctional remains unknown. Transcription factor EB (TFEB) is a master regulator of lysosome biogenesis. The present study examined the hypothesis that TFEB dysfunction causes VC progression.

METHODS AND RESULTS

Inorganic phosphate (Pi) dose-dependently promoted VC in mouse aorta ex vivo, in rat VSMCs in vitro, and in human aortic smooth muscle cells in vitro, all accompanied by a decrease in TFEB protein. Lysosomal inhibitors or TFEB knockdown using small interfering RNA exacerbated Pi-induced VC in VSMCs. Conversely, TFEB downregulation was not observed in the hypercalcemia-sensitive VC model induced by excessive vitamin D dosages. Feeding rats an adenine-containing diet caused CKD and hyperphosphatemia. VC occurred in the adenine-fed rat aorta and regressed after adenine cessation. In this CKD model, aortic TFEB expression decreased at VC onset but recovered to average levels during recovery from VC after adenine cessation. The calcified area of the CKD rat aorta exhibited lysosomal damage and enhanced TFEB ubiquitination. Hyperphosphatemia in vitro increased insoluble TFEB and decreased soluble TFEB in VSMCs, both of which were abrogated by the proteasome inhibitor, MG-132.

CONCLUSION

Hyperphosphatemia caused VC via TFEB downregulation in VSMCs. Under hyperphosphatemia, TFEB was insolubilized and degraded via the ubiquitin-proteasome system. Our results suggest a new mechanism for the pathogenesis of VC under CKD and hyperphosphatemia.

Regulation of MDM2 E3 ligase-dependent vascular calcification by MSX1/2

Vascular calcification increases morbidity and mortality in patients with cardiovascular and renal diseases. Previously, we reported that histone deacetylase 1 prevents vascular calcification, whereas its E3 ligase, mouse double minute 2 homolog (MDM2), induces vascular calcification. In the present study, we identified the upstream regulator of MDM2. By utilizing cellular models and transgenic mice, we confirmed that E3 ligase activity is required for vascular calcification. By promoter analysis, we found that both msh homeobox 1 (Msx1) and msh homeobox 2 (Msx2) bound to the MDM2 promoter region, which resulted in transcriptional activation of MDM2. The expression levels of both Msx1 and Msx2 were increased in mouse models of vascular calcification and in calcified human coronary arteries. Msx1 and Msx2 potentiated vascular calcification in cellular and mouse models in an MDM2-dependent manner. Our results establish a novel role for MSX1/MSX2 in the transcriptional activation of MDM2 and the resultant increase in MDM2 E3 ligase activity during vascular calcification.

The identification of a signaling pathway involved in triggering vascular calcification, the deposition of calcium phosphate crystals in blood vessels, could inform new therapeutic interventions for related cardiovascular complications. Vascular calcification causes significant complications in patients with metabolic syndrome, renal failure, or cardiovascular disease. In their previous work, Hyun Kook and Duk-Hwa Kwon at Chonnam National University Medical School, Jeollanamdo, Republic of Korea, and coworkers demonstrated that the E3 ligase activity of a protein called MDM2 induces calcification. Now, following further mouse trials, the team have identified an upstream signaling pathway involving several development proteins such as MSX1 and MSX2 which activate MDM2. The activation of this signaling axis leads to the degradation of a key protein that would otherwise prevent calcification. The results may provide a platform for novel therapies targeting the condition.

Proteasomal Degradation of Zn-Dependent Hdacs: The E3-Ligases Implicated and the Designed Protacs That Enable Degradation

Protein degradation by the Ubiquitin-Proteasome System is one of the main mechanisms of the regulation of cellular proteostasis, and the E3 ligases are the key effectors for the protein recognition and degradation. Many E3 ligases have key roles in cell cycle regulation, acting as checkpoints and checkpoint regulators. One of the many important proteins involved in the regulation of the cell cycle are the members of the Histone Deacetylase (HDAC) family. The importance of zinc dependent HDACs in the regulation of chromatin packing and, therefore, gene expression, has made them targets for the design and synthesis of HDAC inhibitors. However, achieving potency and selectivity has proven to be a challenge due to the homology between the zinc dependent HDACs. PROteolysis TArgeting Chimaera (PROTAC) design has been demonstrated to be a useful strategy to inhibit and selectively degrade protein targets. In this review, we attempt to summarize the E3 ligases that naturally ubiquitinate HDACs, analyze their structure, and list the known ligands that can bind to these E3 ligases and be used for PROTAC design, as well as the already described HDAC-targeted PROTACs.

P300/CBP-Associated Factor Activates Cardiac Fibroblasts by SMAD2 Acetylation

Various heart diseases cause cardiac remodeling, which in turn leads to ineffective contraction. Although it is an adaptive response to injury, cardiac fibrosis contributes to this remodeling, for which the reactivation of quiescent myofibroblasts is a key feature. In the present study, we investigated the role of the p300/CBP-associated factor (PCAF), a histone acetyltransferase, in the activation of cardiac fibroblasts. An intraperitoneal (i.p.) injection of a high dose (160 mg/kg) of isoproterenol (ISP) induced cardiac fibrosis and reduced the amount of the PCAF in cardiac fibroblasts in the mouse heart. However, the PCAF activity was significantly increased in cardiac fibroblasts, but not in cardiomyocytes, obtained from ISP-administered mice. An in vitro study using human cardiac fibroblast cells recapitulated the in vivo results; an treatment with transforming growth factor-β1 (TGF-β1) reduced the PCAF, whereas it activated the PCAF in the fibroblasts. PCAF siRNA attenuated the TGF-β1-induced increase in and translocation of fibrosis marker proteins. PCAF siRNA blocked TGF-β1-mediated gel contraction and cell migration. The PCAF directly interacted with and acetylated mothers against decapentaplegic homolog 2 (SMAD2). PCAF siRNA prevented TGF-β1-induced phosphorylation and the nuclear localization of SMAD2. These results suggest that the increase in PCAF activity during cardiac fibrosis may participate in SMAD2 acetylation and thereby in its activation.

Neddylation Regulates Class IIa and III Histone Deacetylases to Mediate Myoblast Differentiation

As the largest tissue in the body, skeletal muscle has multiple functions in movement and energy metabolism. Skeletal myogenesis is controlled by a transcriptional cascade including a set of muscle regulatory factors (MRFs) that includes Myogenic Differentiation 1 (MYOD1), Myocyte Enhancer Factor 2 (MEF2), and Myogenin (MYOG), which direct the fusion of myogenic myoblasts into multinucleated myotubes. Neddylation is a posttranslational modification that covalently conjugates ubiquitin-like NEDD8 (neural precursor cell expressed, developmentally downregulated 8) to protein targets. Inhibition of neddylation impairs muscle differentiation; however, the underlying molecular mechanisms remain less explored. Here, we report that neddylation is temporally regulated during myoblast differentiation. Inhibition of neddylation through pharmacological blockade using MLN4924 (Pevonedistat) or genetic deletion of NEDD8 Activating Enzyme E1 Subunit 1 (NAE1), a subunit of the E1 neddylation-activating enzyme, blocks terminal myoblast differentiation partially through repressing MYOG expression. Mechanistically, we found that neddylation deficiency enhances the mRNA and protein expressions of class IIa histone deacetylases 4 and 5 (HDAC4 and 5) and prevents the downregulation and nuclear export of class III HDAC (NAD-Dependent Protein Deacetylase Sirtuin-1, SIRT1), all of which have been shown to repress MYOD1-mediated MYOG transcriptional activation. Together, our findings for the first time identify the crucial role of neddylation in mediating class IIa and III HDAC co-repressors to control myogenic program and provide new insights into the mechanisms of muscle disease and regeneration.

DUSP26 induces aortic valve calcification by antagonizing MDM2-mediated ubiquitination of DPP4 in human valvular interstitial cells

AIMS

The morbidity and mortality rates of calcific aortic valve disease (CAVD) remain high while treatment options are limited. Here, we evaluated the role and therapeutic value of dual-specificity phosphatase 26 (DUSP26) in CAVD.

METHODS AND RESULTS

Microarray profiling of human calcific aortic valves and normal controls demonstrated that DUSP26 was significantly up-regulated in calcific aortic valves. ApoE-/- mice fed a normal diet or a high cholesterol diet (HCD) were infected with adeno-associated virus serotype 2 carrying DUSP26 short-hairpin RNA to examine the effects of DUSP26 silencing on aortic valve calcification. DUSP26 silencing ameliorated aortic valve calcification in HCD-treated ApoE-/- mice, as evidenced by reduced thickness and calcium deposition in the aortic valve leaflets, improved echocardiographic parameters (decreased peak transvalvular jet velocity and mean transvalvular pressure gradient, as well as increased aortic valve area), and decreased levels of osteogenic markers (Runx2, osterix, and osteocalcin) in the aortic valves. These results were confirmed in osteogenic medium-induced human valvular interstitial cells. Immunoprecipitation, liquid chromatography-tandem mass spectrometry, and functional assays revealed that dipeptidyl peptidase-4 (DPP4) interacted with DUSP26 to mediate the procalcific effects of DUSP26. High N6-methyladenosine levels up-regulated DUSP26 in CAVD; in turn, DUSP26 activated DPP4 by antagonizing mouse double minute 2-mediated ubiquitination and degradation of DPP4, thereby promoting CAVD progression.

CONCLUSION

DUSP26 promotes aortic valve calcification by inhibiting DPP4 degradation. Our findings identify a previously unrecognized mechanism of DPP4 up-regulation in CAVD, suggesting that DUSP26 silencing or inhibition is a viable therapeutic strategy to impede CAVD progression.

Casein Kinase-2 Interacting Protein-1 Regulates Physiological Cardiac Hypertrophy via Inhibition of Histone Deacetylase 4 Phosphorylation

Different kinds of mechanical stimuli acting on the heart lead to different myocardial phenotypes. Physiological stress, such as exercise, leads to adaptive cardiac hypertrophy, which is characterized by a normal cardiac structure and improved cardiac function. Pathological stress, such as sustained cardiac pressure overload, causes maladaptive cardiac remodeling and, eventually, heart failure. Casein kinase-2 interacting protein-1 (CKIP-1) is an important regulator of pathological cardiac remodeling. However, the role of CKIP-1 in physiological cardiac hypertrophy is unknown. We subjected wild-type (WT) mice to a swimming exercise program for 21 days, which caused an increase in myocardial CKIP-1 protein and mRNA expression. We then subjected CKIP-1 knockout (KO) mice and myocardial-specific CKIP-1-overexpressing mice to the 21-day swimming exercise program. Histological and echocardiography analyses revealed that CKIP-1 KO mice underwent pathological cardiac remodeling after swimming, whereas the CKIP-1-overexpressing mice had a similar cardiac phenotype to the WT controls. Histone deacetylase 4 (HDAC4) is a key molecule in the signaling cascade associated with pathological hypertrophy; the phosphorylation levels of HDAC4 were markedly higher in CKIP-1 KO mouse hearts after the swimming exercise program. The phosphorylation levels of HDAC4 did not change after swimming in the hearts of CKIP-1-overexpressing or WT mice. Our results indicate that swimming, a mechanical stress that leads to physiological hypertrophy, triggers pathological cardiac remodeling in CKIP-1 KO mice. CKIP-1 is necessary for physiological cardiac hypertrophy in vivo, and for modulating the phosphorylation level of HDAC4 after physiological stress. Genetically engineering CKIP-1 expression affected heart health in response to exercise.

Ubiquitination-dependent and -independent repression of target genes by SETDB1 reveal a context-dependent role for its methyltransferase activity during adipogenesis

The lysine methyltransferase SETDB1, an enzyme responsible for methylation of histone H3 at lysine 9, plays a key role in H3K9 tri-methylation-dependent silencing of endogenous retroviruses and developmental genes. Recent studies have shown that ubiquitination of human SETDB1 complements its catalytic activity and the silencing of endogenous retroviruses in human embryonic stem cells. However, it is not known whether SETDB1 ubiquitination is essential for its other major role in epigenetic silencing of developmental gene programs. We previously showed that SETDB1 contributes to the formation of H3K4/H3K9me3 bivalent chromatin domains that keep adipogenic Cebpa and Pparg genes in a poised state for activation and restricts the differentiation potential of pre-adipocytes. Here, we show that ubiquitin-resistant K885A mutant of SETDB1 represses adipogenic genes and inhibits pre-adipocyte differentiation similar to wild-type SETDB1. We show this was due to a compensation mechanism for H3K9me3 chromatin modifications on the Cebpa locus by other H3K9 methyltransferases Suv39H1 and Suv39H2. In contrast, the K885A mutant did not repress other SETDB1 target genes such as Tril and Gas6 suggesting SETDB1 represses its target genes by two mechanisms; one that requires its ubiquitination and another that still requires SETDB1 but not its enzyme activity.

EGFR phosphorylates HDAC1 to regulate its expression and anti-apoptotic function

HDAC1 is the prototypical human histone deacetylase (HDAC) enzyme responsible for catalyzing the removal of acetyl group from lysine residues on many substrate proteins. By deacetylating histones and non-histone proteins, HDAC1 has a profound effect on the regulation of gene transcription and many processes related to cell growth and cell death, including cell cycle progression, DNA repair, and apoptosis. Early studies reveal that, like most eukaryotic proteins, the functions and activities of HDAC1 are regulated by post-translational modifications. For example, serine phosphorylation of HDAC1 by protein kinase CK2 promotes HDAC1 deacetylase enzymatic activity and alters its interactions with proteins in corepressor complexes. Here, we describe an alternative signaling pathway by which HDAC1 activities are regulated. Specifically, we discover that EGFR activity promotes the tyrosine phosphorylation of HDAC1, which is necessary for its protein stability. A key EGFR phosphorylation site on HDAC1, Tyr72, mediates HDAC1's anti-apoptotic function. Given that HDAC1 overexpression and EGFR activity are strongly related with tumor progression and cancer cell survival, HDAC1 tyrosine phosphorylation may present a possible target to manipulate HDAC1 protein levels in future potential cancer treatment strategies.

miR-27a-3p Targets ATF3 to Reduce Calcium Deposition in Vascular Smooth Muscle Cells

Vascular calcification, the ectopic deposition of calcium in blood vessels, develops in association with various metabolic diseases and atherosclerosis and is an independent predictor of morbidity and mortality associated with these diseases. Herein, we report that reduction of microRNA-27a-3p (miR-27a-3p) causes an increase in activating transcription factor 3 (ATF3), a novel osteogenic transcription factor, in vascular smooth muscle cells. Both microRNA (miRNA) and mRNA microarrays were performed with rat vascular smooth muscle cells, and reciprocally regulated pairs of miRNA and mRNA were selected after bioinformatics analysis. Inorganic phosphate significantly reduced the expression of miR-27a-3p in A10 cells. The transcript level was also reduced in vitamin D₃-administered mouse aortas. miR-27a-3p mimic reduced calcium deposition, whereas miR-27a-3p inhibitor increased it. The Atf3 mRNA level was upregulated in a cellular vascular calcification model, and miR-27a-3p reduced the Atf3 mRNA and protein levels. Transfection with Atf3 could recover the miR-27a-3p-induced reduction of calcium deposition. Our results suggest that reduction of miR-27a-3p may contribute to the development of vascular calcification by de-repression of ATF3.

A p53/lnc-Ip53 Negative Feedback Loop Regulates Tumor Growth and Chemoresistance

Acetylation is a critical mechanism to modulate tumor-suppressive activity of p53, but the causative roles of long non-coding RNAs (lncRNAs) in p53 acetylation and their biological significance remain unexplored. Here, lncRNA LOC100294145 is discovered to be transactivated by p53 and is thus designated as lnc-Ip53 for lncRNA induced by p53. Furthermore, lnc-Ip53 impedes p53 acetylation by interacting with histone deacetylase 1 (HDAC1) and E1A binding protein p300 (p300) to prevent HDAC1 degradation and attenuate p300 activity, resulting in abrogation of p53 activity and subsequent cell proliferation and apoptosis resistance. Mouse xenograft models reveal that lnc-Ip53 promotes tumor growth and chemoresistance in vivo, which is attenuated by an HDAC inhibitor. Silencing lnc-Ip53 inhibits the growth of xenografts with wild-type p53, but not those expressing acetylation-resistant p53. Consistently, lnc-Ip53 is upregulated in multiple cancer types, including hepatocellular carcinoma (HCC). High levels of lnc-Ip53 is associated with low levels of acetylated p53 in human HCC and mouse xenografts, and is also correlated with poor survival of HCC patients. These findings identify a novel p53/lnc-Ip53 negative feedback loop in cells and indicate that abnormal upregulation of lnc-Ip53 represents an important mechanism to inhibit p53 acetylation/activity and thereby promote tumor growth and chemoresistance, which may be exploited for anticancer therapy.

OGT-Mediated KEAP1 Glycosylation Accelerates NRF2 Degradation Leading to High Phosphate-Induced Vascular Calcification in Chronic Kidney Disease

Unraveling the complex regulatory pathways that mediate the effects of phosphate on vascular smooth muscle cells (VSMCs) may provide novel targets and therapies to limit the destructive effects of vascular calcification (VC) in patients with chronic kidney disease (CKD). Our previous studies have highlighted several signaling networks associated with VSMC autophagy, but the underlying mechanisms remain poorly understood. Thereafter, the current study was performed to characterize the functional relevance of O-linked N-acetylglucosamine (GlcNAc) transferase (OGT) in high phosphate-induced VC in CKD settings. We generated VC models in 5/6 nephrectomized rats in vivo and VSMC calcification models in vitro. Artificial modulation of OGT (knockdown and overexpression) was performed to explore the role of OGT in VSMC autophagy and VC in thoracic aorta, and in vivo experiments were used to substantiate in vitro findings. Mechanistically, co-immunoprecipitation (Co-IP) assay was performed to examine interaction between OGT and kelch like ECH associated protein 1 (KEAP1), and in vivo ubiquitination assay was performed to examine ubiquitination extent of nuclear factor erythroid 2-related factor 2 (NRF2). OGT was highly expressed in high phosphate-induced 5/6 nephrectomized rats and VSMCs. OGT silencing was shown to suppress high phosphate-induced calcification of VSMCs. OGT enhances KEAP1 glycosylation and thereby results in degradation and ubiquitination of NRF2, concurrently inhibiting VSMC autophagy to promote VSMC calcification in 5/6 nephrectomized rats. OGT inhibits VSMC autophagy through the KEAP1/NRF2 axis and thus accelerates high phosphate-induced VC in CKD.

The microRNA miR-134-5p induces calcium deposition by inhibiting histone deacetylase 5 in vascular smooth muscle cells

Calcium deposition in vascular smooth muscle cells (VSMCs) is a form of ectopic ossification in blood vessels. It can result in rigidity of the vasculature and an increase in cardiac events. Here, we report that the microRNA miR‐134‐5p potentiates inorganic phosphate (Pi)‐induced calcium deposition in VSMCs by inhibiting histone deacetylase 5 (HDAC5). Using miRNA microarray analysis of Pi‐treated rat VSMCs, we first selected miR‐134‐5p for further evaluation. Quantitative RT‐PCR confirmed that miR‐134‐5p was increased in Pi‐treated A10 cells, a rat VSMC line. Transfection of miR‐134‐5p mimic potentiated the Pi‐induced increase in calcium contents. miR‐134‐5p increased the amounts of bone runt‐related transcription factor 2 (RUNX2) protein and bone morphogenic protein 2 (BMP2) mRNA in the presence of Pi but decreased the expression of osteoprotegerin (OPG). Bioinformatic analysis showed that the HDAC5 3′untranslated region (3′UTR) was one of the targets of miR‐134‐5p. The luciferase construct containing the 3′UTR of HDAC5 was down‐regulated by miR‐134‐5p mimic in a dose‐dependent manner in VSMCs. Overexpression of HDAC5 mitigated the calcium deposition induced by miR‐134‐5p. Our results suggest that a Pi‐induced increase of miR‐134‐5p may cause vascular calcification through repression of HDAC5.

MDM2-Mediated Ubiquitination of Angiotensin-Converting Enzyme 2 Contributes to the Development of Pulmonary Arterial Hypertension

Supplemental Digital Content is available in the text.

Background:

Angiotensin-converting enzyme 2 (ACE2) converts angiotensin II, a potent vasoconstrictor, to angiotensin-(1–7) and is also a membrane protein that enables coronavirus disease 2019 (COVID-19) infectivity. AMP-activated protein kinase (AMPK) phosphorylation of ACE2 enhances ACE2 stability. This mode of posttranslational modification of ACE2 in vascular endothelial cells is causative of a pulmonary hypertension (PH)–protective phenotype. The oncoprotein MDM2 (murine double minute 2) is an E3 ligase that ubiquitinates its substrates to cause their degradation. In this study, we investigated whether MDM2 is involved in the posttranslational modification of ACE2 through its ubiquitination of ACE2, and whether an AMPK and MDM2 crosstalk regulates the pathogenesis of PH.

Methods:

Bioinformatic analyses were used to explore E3 ligase that ubiquitinates ACE2. Cultured endothelial cells, mouse models, and specimens from patients with idiopathic pulmonary arterial hypertension were used to investigate the crosstalk between AMPK and MDM2 in regulating ACE2 phosphorylation and ubiquitination in the context of PH.

Results:

Levels of MDM2 were increased and those of ACE2 decreased in lung tissues or pulmonary arterial endothelial cells from patients with idiopathic pulmonary arterial hypertension and rodent models of experimental PH. MDM2 inhibition by JNJ-165 reversed the SU5416/hypoxia-induced PH in C57BL/6 mice. ACE2-S680L mice (dephosphorylation at S680) showed PH susceptibility, and ectopic expression of ACE2-S680L/K788R (deubiquitination at K788) reduced experimental PH. Moreover, ACE2-K788R overexpression in mice with endothelial cell–specific AMPKα2 knockout mitigated PH.

Conclusions:

Maladapted posttranslational modification (phosphorylation and ubiquitination) of ACE2 at Ser-680 and Lys-788 is involved in the pathogenesis of pulmonary arterial hypertension and experimental PH. Thus, a combined intervention of AMPK and MDM2 in the pulmonary endothelium might be therapeutically effective in PH treatment.

Hdac9 inhibits medial artery calcification through down-regulation of Osterix

BACKGROUNDS

Medial artery calcification (MAC) significantly contributes to the increased cardiovascular death in patients with chronic kidney disease (CKD). Previous genome-wide association studies have shown that various genetic variants of the histone deacetylase Hdac9 are associated with cardiovascular disease, but the role of Hdac9 in MAC under CKD conditions remains unclear.

METHODS

High phosphate-induced vascular smooth muscle cell (VSMC) calcification and MAC in mice administered with vitamin D3 (vD) were used in the present study. Alizarin red staining, calcium quantitative assay, qPCR, western blotting and histology were performed.

RESULTS

Hdac9 expression was significantly down-regulated during high phosphate-induced vascular smooth muscle cell (VSMC) calcification and MAC in mice administered with vitamin D₃ (vD). Furthermore, high phosphate treatment inhibited phosphorylation of Akt, and pharmacological inhibition of Akt signaling reduced Hdac9 expression in cultured VSMCs. Knockdown of Hdac9 significantly enhanced calcium deposition in VSMCs. Conversely, adenovirus mediated-overexpression of Hdac9 inhibited high phosphate induced VSMC in vitro calcification. Our subsequent mechanistic studies revealed that the anti-calcific effect of Hdac9 was mediated through down-regulation of osteoblast-specific transcription factor Osterix.

CONCLUSION

These data suggest that Hdac9 is a novel inhibitor of MAC and may represent a potential therapeutic target for MAC in CKD patients.

OGT knockdown counteracts high phosphate-induced vascular calcification in chronic kidney disease through autophagy activation by downregulating YAP

AIMS

Pathological vascular calcification (VC), a major risk factor for cardiovascular mortality, is a highly prevalent finding in patients with chronic kidney disease (CKD). We previously analyzed several pathways protecting against high phosphate-induced VC through induction of autophagy. Here, we explored how O-GlcNAc transferase (OGT) affected high phosphate-induced VC of CKD though mediation of autophagy.

MAIN METHODS

In the rats with CKD induced by 5/6 nephrectomy, the VC process was accelerated by a high phosphate diet. The calcification of vascular smooth muscle cells (VSMCs) was induced by high phosphate treatment. We then experimentally tested the effect of OGT on high phosphate-induced VC by conducting loss-of-function experiments. Co-immunoprecipitation and GST pull-down assays were performed to evaluate interaction between OGT and Yes-associated protein (YAP). In mechanistic studies of this pathway, we measured autophagy protein expression and autophagosome formation, as well as calcium deposition and calcium content in VSMCs and in vivo in response to altered expression of OGT and/or YAP.

KEY FINDINGS

OGT was up-regulated in high phosphate-induced VC models in vitro and in vivo. High phosphate-induced calcification in the rat aorta and VSMCs were suppressed by OGT silencing. OGT promoted the glycosylation of YAP to enhance its stability. Importantly, over-expressing YAP reduced autophagy and OGT expedited high phosphate-induced VC by inhibiting autophagy through upregulation of YAP.

SIGNIFICANCE

OGT silencing downregulated YAP to induce autophagy activation, thus suppressing high phosphate-induced VC, which highlighted a promising preventive target against high phosphate-induced VC in CKD.

HDAC1-mediated deacetylation of LSD1 regulates vascular calcification by promoting autophagy in chronic renal failure

Chronic renal failure (CRF) is commonly associated with various adverse consequences including pathological vascular calcification (VC), which represents a significant clinical concern. Existing literature has suggested the involvement of histone deacetylases (HDACs) in the progression of CRF‐induced VC. However, the underlying molecular mechanisms associated with HDACs remain largely unknown. Therefore, we established the adenine‐induced CRF rat model and in vitro VC models based on vascular smooth muscle cells (VSMCs) to examine HDAC1/lysine demethylase 1A (LSD1)/SESN2 as a novel molecular pathway in CRF‐induced VC. Our initial results demonstrated that HDAC1 reduced the formation of VC in vivo and in vitro. HDAC1 was found to deacetylate LSD1, which subsequently led to impaired transcriptional activity in CRF‐induced VC. Moreover, our results illustrated that LSD1 diminished the enrichment of H3K4me2 at the SESN2 promoter. Autophagy was identified as a vasculo‐protective element against calcification in VC. Finally, we found that the inhibitory effects of HDAC1 overexpression on VC were partially abolished via over‐expressed LSD1 in adenine‐induced CRF model rats and in high phosphate‐induced VSMCs. Taken together, these results highlight the crucial role of HDAC1 as an antagonistic factor in the progression of VC in CRF, and also revealed a novel regulatory mechanism by which HDAC1 operates. These findings provide significant insight and a fresh perspective into promising novel treatment strategies by up‐regulating HDAC1 in CRF.

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.

Downregulation of HDAC1 suppresses media degeneration by inhibiting the migration and phenotypic switch of aortic vascular smooth muscle cells in aortic dissection

Although much progress has been made in the diagnosis and treatment of thoracic aortic dissection (TAD), the overall morbidity and mortality rates of TAD are still high. Therefore, the molecular pathogenesis and etiology of TAD need to be elucidated. In this study, we found that histone deacetylase 1 (HDAC1) expression is dramatically higher in the aortic wall of patients with TAD (than that in a normal group) and negatively correlates with the levels of the vascular smooth muscle cell (SMC) contractile-phenotype markers. Knockdown of HDAC1 upregulated both smooth muscle 22 α (SM22α) and α-smooth muscle actin (α-SMA) in platelet-derived growth factor (PDGF)-BB-treated and -untreated SMCs. In addition, the knockdown of HDAC1 markedly decreased SMC viability and migration in contrast to the control group under the conditions of quiescence and PDGF-BB treatment. We also showed that the expression of polycystic kidney disease 1 (PKD1) is decreased in the aortic wall of patients with TAD and negatively correlates with HDAC1 expression. Overexpressed PKD1 obviously increased SM22α and α-SMA expression and reduced the viability and migration of SMCs, but these effects were attenuated by HDAC1. Furthermore, we demonstrated that HDAC1 serves as an important modulator of the migration and phenotypic switch of SMCs by suppressing the PKD1- mammalian target of the rapamycin signaling pathway. HDAC1 downregulation inhibited media degeneration and attenuated the loss of elastic-fiber integrity in a mouse model of TAD. Our results suggest that HDAC1 might be a new target for the treatment of a macrovascular disease such as TAD.

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.

Considering the Role of Murine Double Minute 2 in the Cardiovascular System?

The E3 ubiquitin ligase Murine double minute 2 (MDM2) is the main negative regulator of the tumor protein p53 (TP53). Extensive studies over more than two decades have confirmed MDM2 oncogenic role through mechanisms both TP53-dependent and TP53-independent oncogenic function. These studies have contributed to designate MDM2 as a therapeutic target of choice for cancer treatment and the number of patents for MDM2 antagonists has increased immensely over the last years. However, the question of the physiological functions of MDM2 has not been fully resolved yet, particularly when expressed and regulated physiologically in healthy tissue. Cardiovascular complications are almost an inescapable side-effect of anti-cancer therapies. While several MDM2 antagonists are entering phase I, II and even III of clinical trials, this review proposes to bring awareness on the physiological role of MDM2 in the cardiovascular system.

The Deubiquitinase USP38 Promotes NHEJ Repair through Regulation of HDAC1 Activity and Regulates Cancer Cell Response to Genotoxic Insults

The DNA damage response (DDR) is essential for maintaining genome integrity. Mounting evidence reveals that protein modifications play vital roles in the DDR. Here, we show that USP38 is involved in the DDR by regulating the activity of HDAC1. In response to DNA damage, USP38 interacted with HDAC1 and specifically removed the K63-linked ubiquitin chain promoting the deacetylase activity of HDAC1. As a result, HDAC1 was able to deacetylate H3K56. USP38 deletion resulted in persistent focal accumulation of nonhomologous end joining (NHEJ) factors at DNA damage sites and impaired NHEJ efficiency, causing genome instability and sensitizing cancer cells to genotoxic insults. Knockout of USP38 rendered mice hypersensitive to irradiation and shortened survival. In addition, USP38 was expressed at low levels in certain types of cancers including renal cell carcinoma, indicating dysregulation of USP38 expression contributes to genomic instability and may lead to tumorigenesis. In summary, this study identifies a critical role of USP38 in modulating genome integrity and cancer cell resistance to genotoxic insults by deubiquitinating HDAC1 and regulating its deacetylation activity. SIGNIFICANCE: This study demonstrates that USP38 regulates genome stability and mediates cancer cell resistance to DNA-damaging therapy, providing insight into tumorigenesis and implicating USP38 as a potential target for cancer diagnosis.

Heart failure with preserved ejection fraction: present status and future directions

The clinical importance of heart failure with preserved ejection fraction (HFpEF) has recently become apparent. HFpEF refers to heart failure (HF) symptoms with normal or near-normal cardiac function on echocardiography. Common clinical features of HFpEF include diastolic dysfunction, reduced compliance, and ventricular hypokinesia. HFpEF differs from the better-known HF with reduced ejection fraction (HFrEF). Despite having a "preserved ejection fraction," patients with HFpEF have symptoms such as shortness of breath, excessive tiredness, and limited exercise capability. Furthermore, the mortality rate and cumulative survival rate are as severe in HFpEF as they are in HFrEF. While beta-blockers and renin-angiotensin-aldosterone system modulators can improve the survival rate in HFrEF, no known therapeutic agents show similar effectiveness in HFpEF. Researchers have examined molecular events in the development of HFpEF using small and middle-sized animal models. This review discusses HFpEF with regard to etiology and clinical features and introduces the use of mouse and other animal models of human HFpEF.

Characterization of Circular RNAs in Vascular Smooth Muscle Cells with Vascular Calcification

Circular RNAs (circRNAs) are generally formed by back splicing and are expressed in various cells. Vascular calcification (VC), a common complication of chronic kidney disease (CKD), is often associated with cardiovascular disease. The relationship between circRNAs and VC has not yet been studied. Inorganic phosphate (Pi) was used to treat rat vascular smooth muscle cells to induce VC. circRNAs were identified by analyzing RNA sequencing (RNA-seq) data, and their expression change during VC was validated. The selected circRNAs, including circSamd4a, circSmoc1-1, circMettl9, and circUxs1, were resistant to RNase R digestion and mostly localized in the cytoplasm. While silencing circSamd4a promoted VC, overexpressing it reduced VC in calcium assay and Alizarin red S (ARS) staining. In addition, microRNA (miRNA) microarray, luciferase reporter assay, and calcium assay suggested that circSamd4a could act as a miRNA suppressor. Our data show that circSamd4a has an anti-calcification role by functioning as a miRNA sponge. Moreover, mRNAs that can interact with miRNAs were predicted from RNA-seq and bioinformatics analysis, and the circSamd4a-miRNA-mRNA axis involved in VC was verified by luciferase reporter assay and calcium assay. Since circSamd4a is conserved in humans, it can serve as a novel therapeutic target in resolving VC.