AT2 receptor stimulation inhibits phosphate-induced vascular calcification

Construction of a miR-15a-based risk prediction model for vascular calcification detection in patients undergoing hemodialysis

Vascular calcification (VC) is highly prevalent in patients undergoing hemodialysis, and is a significant contributor to the mortality rate. Therefore, biomarkers that can accurately predict the onset of VC are urgently required. Our study aimed to investigate serum miR-15a levels in relation to VC and to develop a predictive model for VC in patients undergoing hemodialysis at the Beijing Friendship Hospital hemodialysis center between 1 January 2019 and 31 December 2020. The patients were categorized into two groups: VC and non-VC. Logistic regression (LR) models were used to examine the risk factors associated with VC. Additionally, we developed an miR-15a-based nomogram based on the results of the multivariate LR analysis. A total of 138 patients under hemodialysis were investigated (age: 58.41 ± 13.22 years; 54 males). VC occurred in 79 (57.2%) patients. Multivariate LR analysis indicated that serum miR-15a, age, and WBC count were independent risk factors for VC. A miR-15a-based nomogram was developed by incorporating the following five predictors: age, dialysis vintage, predialysis nitrogen, WBC count, and miR-15a. The receiver operating characteristic (ROC) curve had an area under the curve of 0.921, diagnostic threshold of 0.396, sensitivity of 0.722, and specificity of 0.932, indicating that this model had good discrimination. This study concluded that serum miR-15a levels, age, and white blood cell (WBC) count are independent risk factors for VC. A nomogram constructed by integrating these risk factors can be used to predict the risk of VC in patients undergoing hemodialysis.

Angiotensin AT2 receptors reduce inflammation and fibrosis in cardiovascular remodeling

The angiotensin AT2 receptor (AT2R), an important member of the "protective arm" of the renin-angiotensin system (RAS), has been recently defined as a therapeutic target in different pathological conditions. The AT2R activates complex signalling pathways linked to cellular proliferation, differentiation, anti-inflammation, antifibrosis, and induction or inhibition of apoptosis. The anti-inflammatory effect of AT2R activation is commonly associated with reduced fibrosis in different models. Current discoveries demonstrated a direct impact of AT2Rs on the regulation of cytokines, transforming growth factor beta1 (TGF-beta1), matrix metalloproteases (MMPs), and synthesis of the extracellular matrix components. This review article summarizes current knowledge on the AT2R in regard to immunity, inflammation and fibrosis in the heart and blood vessels. In particular, the differential influence of the AT2R on cardiovascular remodeling in preclinical models of myocardial infarction, heart failure and aneurysm formation are discussed. Overall, these studies demonstrate that AT2R stimulation represents a promising therapeutic approach to counteract myocardial and aortic damage in cardiovascular diseases.

PPARs in atherosclerosis: The spatial and temporal features from mechanism to druggable targets

BACKGROUND

Atherosclerosis is a chronic and complex disease caused by lipid disorder, inflammation, and other factors. It is closely related to cardiovascular diseases, the chief cause of death globally. Peroxisome proliferator-activated receptors (PPARs) are valuable anti-atherosclerosis targets that showcase multiple roles at different pathological stages of atherosclerosis and for cell types at different tissue sites.

AIM OF REVIEW

Considering the spatial and temporal characteristics of the pathological evolution of atherosclerosis, the roles and pharmacological and clinical studies of PPARs were summarized systematically and updated under different pathological stages and in different vascular cells of atherosclerosis. Moreover, selective PPAR modulators and PPAR-pan agonists can exert their synergistic effects meanwhile reducing the side effects, thereby providing novel insight into future drug development for precise spatial-temporal therapeutic strategy of anti-atherosclerosis targeting PPARs.

KEY SCIENTIFIC

Concepts of Review: Based on the spatial and temporal characteristics of atherosclerosis, we have proposed the importance of stage- and cell type-dependent precision therapy. Initially, PPARs improve endothelial cells' dysfunction by inhibiting inflammation and oxidative stress and then regulate macrophages' lipid metabolism and polarization to improve fatty streak. Finally, PPARs reduce fibrous cap formation by suppressing the proliferation and migration of vascular smooth muscle cells (VSMCs). Therefore, research on the cell type-specific mechanisms of PPARs can provide the foundation for space-time drug treatment. Moreover, pharmacological studies have demonstrated that several drugs or compounds can exert their effects by the activation of PPARs. Selective PPAR modulators (that specifically activate gene subsets of PPARs) can exert tissue and cell-specific effects. Furthermore, the dual- or pan-PPAR agonist could perform a better role in balancing efficacy and side effects. Therefore, research on cells/tissue-specific activation of PPARs and PPAR-pan agonists can provide the basis for precision therapy and drug development of PPARs.

Calcitriol combined with high-calcium and high-phosphorus diet induces vascular calcification model in chronic kidney disease rats

BACKGROUND

Cardiovascular diseases represent a significant complication arising from chronic kidney disease (CKD). Vascular calcification is an important risk factor for cardiovascular diseases. Reducing vascular calcification is therefore critical to reducing mortality in CKD patients.

HYPOTHESIS

This study aims to establish a vascular calcification model in rats with CKD by administering subcutaneous injections of calcitriol in combination with a high-calcium and high-phosphorus diet.

METHODS

The rats were divided into the CKD vascular calcification model group (subtotal nephrectomy+ [SNx+]) and the sham-operated control group (subtotal nephrectomy- [SNx-]). The rats in the SNx(+) group were administered high-calcium and high-phosphorus feeds following a 5/6 nephrectomy. Calcitriol (1 μg/kg, three times a week) was injected subcutaneously at weeks 0, 4, 8, and 12 after the operation. Measurements of body weight, urine, serum biochemical indicators and vascular calcification level were conducted in rats.

RESULTS

(1) Compared with the SNx(-) group, rats in the SNx(+) group experienced an increase in 24-h urine output, urinary phosphorus, and urinary microprotein excretion, along with the development of severe anemia. Additionally, there was a notable elevation in serum phosphorus, blood urea nitrogen, blood creatinine, fibroblast growth factor 23 (FGF-23), and intact parathyroid hormone levels, accompanied by severe hypoproteinemia at week 12. (2) The results of micro-compuyed tomography (μCT) and alizarin S staining of the thoracic aorta demonstrated an increase in vascular calcification in the SNx(+) group. (3) The expression levels of vascular calcification-related proteins were increased.

CONCLUSIONS

The administration of calcitriol combined with a high-calcium and high-phosphorus diet was found to induce vascular calcification in CKD rats, leading to a disturbance in mineral metabolism. Vascular calcification was effectively induced in CKD rats after 12 weeks of modeling, thereby presenting a novel approach for establishing a vascular calcification model in CKD rats, helping to elucidate this clinical condition and its underlying molecular mechanisms.

Shh-Gli2-Runx2 inhibits vascular calcification

BACKGROUND

In patients with chronic kidney disease (CKD), vascular calcification (VC) is common and is associated with a higher risk of all-cause mortality. Shh, one ligand for Hedgehog (Hh) signaling, participates in osteogenesis and several cardiovascular diseases. However, it remains unclear whether Shh is implicated in the development of VC.

METHODS

Inorganic phosphorus 2.6 mM was used to induce vascular smooth muscle cells (VSMCs) calcification. Mice were fed with adenine diet supplement with 1.2% phosphorus to induce VC.

RESULTS

Shh was decreased in VSMCs exposed to inorganic phosphorus, calcified arteries in mice fed with an adenine diet, as well as radial arteries from patients with CKD presenting VC. Overexpression of Shh inhibited VSMCs ostosteoblastic differentiation and calcification, whereas its silencing accelerated these processes. Likewise, mice treated with smoothened agonist (SAG; Hh signaling agonist) showed alleviated VC, and mice treated with cyclopamine (CPN; Hh signaling antagonist) exhibited severe VC. Additionally, overexpression of Gli2 significantly reversed the pro-calcification effect of Shh silencing on VSMCs, suggesting that Shh inhibited VC via Gli2. Mechanistically, Gli2 interacted with Runx2 and promoted its ubiquitin proteasomal degradation, therefore protecting against VC. Of interest, the pro-degradation effect of Gli2 on Runx2 was independent of Smurf1 and Cullin4B.

CONCLUSIONS

Our study provided deeper insight to the pathogenesis of VC, and Shh might be a novel potential target for VC treatment.

Similarities and Differences of Vascular Calcification in Diabetes and Chronic Kidney Disease

Presently, the mechanism of occurrence and development of vascular calcification (VC) is not fully understood; a range of evidence suggests a positive association between diabetes mellitus (DM) and VC. Furthermore, the increasing burden of central vascular disease in patients with chronic kidney disease (CKD) may be due, at least in part, to VC. In this review, we will review recent advances in the mechanisms of VC in the context of CKD and diabetes. The study further unveiled that VC is induced through the stimulation of pro-inflammatory factors, which in turn impairs endothelial function and triggers similar mechanisms in both disease contexts. Notably, hyperglycemia was identified as the distinctive mechanism driving calcification in DM. Conversely, in CKD, calcification is facilitated by mechanisms including mineral metabolism imbalance and the presence of uremic toxins. Additionally, we underscore the significance of investigating vascular alterations and newly identified molecular pathways as potential avenues for therapeutic intervention.

Synthesis of rare-earth metal-organic frameworks to construct high-resolution sensing array for multiplex anions detection, cell imaging and blood phosphorus monitoring

Accurate detection and differentiation of multiple anions is still a difficult problem due to their wide variety, structural similarity, and mutual interference. Hence, four rare-earth metal-organic frameworks (RE-MOFs) including Dy-MOFs, Er-MOFs, Tb-MOFs and Y-MOFs are successfully prepared by using TCPP as the ligand and rare-earth ions as the metal center via coordination chelation. It is found that 7 anions can light up their fluorescence. Thus, a high-resolution sensing array based on RE-MOFs nanoprobes is employed to differentiate these anions from intricate analytes in real-time scenarios. The distinctive host-guest response promotes the RE-MOFs nanoprobes to selectively extract the target anions from the complex samples. By taking advantage of the cross-response between RE-MOFs nanoprobes and anions, it allows to create an array for detecting target analytes using pattern recognition. Additionally, RE-MOFs nanoprobes also facilitate the quantitative analysis of these anions (PO43-, H2PO4-, HPO42-, F-, S2-, CO32- and C2O42-). More importantly, the exceptional effectiveness of this method has been demonstrated through various successful applications, including quality monitoring of 8 toothpaste brands, intracellular phosphate imaging, and blood phosphorus detection in mice with vascular calcification. These findings provide robust evidence for the efficacy and reliability of the RE-MOFs nanoprobes array for anion recognition.

Vascular, valvular and kidney calcification manifested in mouse models of adenine-induced chronic kidney disease

BACKGROUND

Ectopic calcification (EC) involves multiple organ systems in chronic kidney disease (CKD). Previous CKD-animal models primarily focused on a certain histological abnormality but did not show the correlation with calcified development among various tissues. This study compared calcified deposition in various tissues during CKD progression in mice.

METHODS

Male 8-week-old C57BL/6J mice were randomly allocated to the seven groups: a basic, adenine, high-phosphorus, or adenine and high-phosphorus diet for 12-16 weeks (Ctl16, A12, P16, or AP16, respectively); an adenine diet for 4-6 weeks; and a high-phosphorus or adenine and high-phosphorus diet for 10-12 weeks (A6 + P10, A4 + P12, or A4 + AP12, respectively).

RESULTS

Compared to the Ctl16 mice, the P16 mice only displayed a slight abnormality in serum calcium and phosphorus; the A12 mice had the most serious kidney impairment; the A4 + P12 and A6 + P10 mice had similar conditions of CKD, mineral abnormalities, and mild calcification in the kidney and aortic valves; the A4 + AP12 and AP16 groups had severe kidney impairment, mineral abnormalities and calcification in the kidneys, aortic valves and aortas. Furthermore, calcium-phosphate particles were deposited not only in the tubulointerstitial compartment but in the glomerular and tubular basement membrane. The elemental composition of EC in various tissues matched the calcification of human cardiovascular tissue as determined by energy dispersive spectroscopy.

CONCLUSIONS

The severity of CKD was unparalleled with the progression of mineral metabolism disorder and EC. Calcification was closely related in different tissues and observed in the glomerular and tubular basement membranes.

Activation of angiotensin-converting enzyme 2 produces an antidepressant-like effect via MAS receptors in mice

Angiotensin (Ang)-converting-enzyme (ACE) 2 converts Ang II into Ang (1-7), which in turn acts on MAS receptors (ACE2/Ang (1-7)/MAS receptors pathway). This pathway has neuroprotective properties, making it a potential therapeutic target for psychiatric disorders such as depression. Thus, we examined the effects of diminazene aceturate (DIZE), an ACE2 activator, on depressive-like behavior using behavioral, pharmacological, and biochemical assays. To determine whether DIZE or Ang (1-7) produce antidepressant-like effects, we measured the duration of immobility of mice in the tail suspension test following their intracerebroventricular administration. Next, we measured the levels of ACE2 activation in the cerebral cortex, prefrontal cortex, hippocampus, and amygdala after DIZE injection, and examined which cell types, including neurons, microglia, and astrocytes, express ACE2 in the hippocampus using immunofluorescence. Administration of DIZE or Ang (1-7) significantly shortened the duration of immobility time in the tail suspension test, while this effect was inhibited by the co-administration of the MAS receptor antagonist A779. DIZE activated ACE2 in the hippocampus. ACE2 was localized to neurons, astrocytes, and microglia in the hippocampus. In conclusion, these results suggest that DIZE may act on ACE2-positive cells in the hippocampus where it increases the activity of ACE2, thereby enhancing signaling of the ACE2/Ang (1-7)/MAS receptor pathway and resulting in antidepressant-like effects.

Hypertension in chronic kidney disease: What lies behind the scene

Hypertension is a frequent condition encountered during kidney disease development and a leading cause in its progression. Hallmark factors contributing to hypertension constitute a complexity of events that progress chronic kidney disease (CKD) into end-stage renal disease (ESRD). Multiple crosstalk mechanisms are involved in sustaining the inevitable high blood pressure (BP) state in CKD, and these play an important role in the pathogenesis of increased cardiovascular (CV) events associated with CKD. The present review discusses relevant contributory mechanisms underpinning the promotion of hypertension and their consequent eventuation to renal damage and CV disease. In particular, salt and volume expansion, sympathetic nervous system (SNS) hyperactivity, upregulated renin–angiotensin–aldosterone system (RAAS), oxidative stress, vascular remodeling, endothelial dysfunction, and a range of mediators and signaling molecules which are thought to play a role in this concert of events are emphasized. As the control of high BP via therapeutic interventions can represent the key strategy to not only reduce BP but also the CV burden in kidney disease, evidence for major strategic pathways that can alleviate the progression of hypertensive kidney disease are highlighted. This review provides a particular focus on the impact of RAAS antagonists, renal nerve denervation, baroreflex stimulation, and other modalities affecting BP in the context of CKD, to provide interesting perspectives on the management of hypertensive nephropathy and associated CV comorbidities.

The Angiotensin AT2 Receptor: From a Binding Site to a Novel Therapeutic Target

Discovered more than 30 years ago, the angiotensin AT2 receptor (AT2R) has evolved from a binding site with unknown function to a firmly established major effector within the protective arm of the renin-angiotensin system (RAS) and a target for new drugs in development. The AT2R represents an endogenous protective mechanism that can be manipulated in the majority of preclinical models to alleviate lung, renal, cardiovascular, metabolic, cutaneous, and neural diseases as well as cancer. This article is a comprehensive review summarizing our current knowledge of the AT2R, from its discovery to its position within the RAS and its overall functions. This is followed by an in-depth look at the characteristics of the AT2R, including its structure, intracellular signaling, homo- and heterodimerization, and expression. AT2R-selective ligands, from endogenous peptides to synthetic peptides and nonpeptide molecules that are used as research tools, are discussed. Finally, we summarize the known physiological roles of the AT2R and its abundant protective effects in multiple experimental disease models and expound on AT2R ligands that are undergoing development for clinical use. The present review highlights the controversial aspects and gaps in our knowledge of this receptor and illuminates future perspectives for AT2R research. SIGNIFICANCE STATEMENT: The angiotensin AT2 receptor (AT2R) is now regarded as a fully functional and important component of the renin-angiotensin system, with the potential of exerting protective actions in a variety of diseases. This review provides an in-depth view of the AT2R, which has progressed from being an enigma to becoming a therapeutic target.

Calcicoptosis induced by purple sweet potato anthocyanins through the nonosmotic regulation of the NFAT5/S100A4-S100A9 pathway in acute lymphoblastic leukemia

Purple sweet potato is considered an abundant, inexpensive, and ideal source of anthocyanins. Purple sweet potato anthocyanins (PSPAs) have been shown to possess high antimutagenicity and antitumor effects due to the abundance of acylated anthocyanins. However, the effect and underlying mechanism of PSPA effects in acute lymphoblastic leukemia (ALL), especially T-cell acute lymphoblastic leukemia (T-ALL), remain unclear. In this study, the antileukemic effects of PSPAs and the underlying molecular mechanisms were evaluated by in vitro and in silico assays. PSPAs extracted from ten cultivars were analyzed and quantified. Anthocyanins from Nanzi 018, which showed the best antileukemic effect, were selected to analyze the underlying mechanism. First, the PSPAs potently reduced cell viability and induced apoptosis. Additionally, the PSPAs sharply increased intracellular Ca 2+ levels, which resulted in calcium overload in T-ALL cells. Furthermore, on the basis of bioinformatics analyses, we focused on an osmotically regulated transcription factor, NFAT5. Molecular docking preliminarily indicated that PSPA molecules bound and interacted with the NFAT5 protein. Western blot analyses confirmed that PSPAs elicited calcium overload by nonosmotic regulation of NFAT5/S100A4-S100A9 pathway activation. Moreover, pretreatment with a NFAT5 inducer confirmed that PSPAs targeted NFAT5 and affected p38/NF-κB/Bcl-2/Caspase-3 axis activation. This study demonstrates that PSPAs exert their antileukemic effects through calcicoptosis induction by targeting NFAT5.

Vascular Calcification in Chronic Kidney Disease: An Update and Perspective

Chronic kidney disease is a devastating condition resulting from irreversible loss of nephron numbers and function and leading to end-stage renal disease and mineral disorders. Vascular calcification, an ectopic deposition of calcium-phosphate salts in blood vessel walls and heart valves, is an independent risk factor of cardiovascular morbidity and mortality in chronic kidney disease. Moreover, aging and related metabolic disorders are essential risk factors for chronic kidney disease and vascular calcification. Marked progress has been recently made in understanding and treating vascular calcification in chronic kidney disease. However, there is a paucity of systematic reviews summarizing this progress, and investigating unresolved issues is warranted. In this systematic review, we aimed to overview the underlying mechanisms of vascular calcification in chronic kidney diseases and discuss the impact of chronic kidney disease on the pathophysiology of vascular calcification. Additionally, we summarized potential clinical diagnostic biomarkers and therapeutic applications for vascular calcification with chronic kidney disease. This review may offer new insights into the pathogenesis, diagnosis, and therapeutic intervention of vascular calcification.

BRCC36 prevents vascular calcification in chronic kidney disease through the β-catenin signalling pathway

Vascular calcification (VC) is a strong predictor of cardiovascular mortality and overall mortality in patients with chronic kidney disease (CKD); however, the molecular mechanisms underlying VC have yet to be elucidated. Here, we report the role of the deubiquitinating enzyme BRCC36 in the process of VC in CKD. We established an in vitro VC model of vascular smooth muscle cells (VSMCs) and an adenine-induced CKD mouse model. The expression of BRCC36 was significantly decreased in both the in vivo and in vitro VC models. Alizarin red staining and calcium content assays showed that BRCC36 overexpression reduced calcium deposition in the presence of calcifying medium, while the contractile protein α-smooth muscle actin (α-SMA) was upregulated and phosphorylated β-catenin was downregulated. Cell immunofluorescence showed that BRCC36 overexpression also reduced the expression of phosphorylated β-catenin in the nucleus in the presence of calcifying medium. In addition, coimmunoprecipitation showed that BRCC36 can bind to β-catenin. These results suggest that BRCC36 can interact with β-catenin, the main effector protein of the Wnt/β-catenin pathway, inhibiting the phosphorylation of β-catenin and negatively regulating the cell signalling pathway, thereby inhibiting VC. This may provide new insights into the molecular mechanisms of VC in the context of CKD.

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.

Unspliced XBP1 Counteracts β-catenin to Inhibit Vascular Calcification

Background: Vascular calcification is a prevalent complication in chronic kidney disease and contributes to increased cardiovascular morbidity and mortality. XBP1 (X-box binding protein 1), existing as the unspliced (XBP1u) and spliced (XBP1s) forms, is a key component of the endoplasmic reticulum stress involved in vascular diseases. However, whether XBP1u participates in the development of vascular calcification remains unclear. Methods: We aim to investigate the role of XBP1u in vascular calcification.XBP1u protein levels were reduced in high phosphate (Pi)-induced calcified vascular smooth muscle cells (VSMCs), calcified aortas from mice with adenine diet-induced chronic renal failure (CRF) and calcified radial arteries from CRF patients. Results: Inhibition of XBP1u rather than XBP1s upregulated in the expression of the osteogenic markers runt-related transcription factor 2 (Runx2) and msh homeobox2 (Msx2), and exacerbated high Pi-induced VSMC calcification, as verified by calcium deposition and Alizarin red S staining. In contrast, XBP1u overexpression in high Pi-induced VSMCs significantly inhibited osteogenic differentiation and calcification. Consistently, SMC-specific XBP1 deficiency in mice markedly aggravated the adenine diet- and 5/6 nephrectomy-induced vascular calcification compared with that in the control littermates. Further interactome analysis revealed that XBP1u bound directly to β-catenin, a key regulator of vascular calcification, via aa 205-230 in its C-terminal degradation domain. XBP1u interacted with β-catenin to promote its ubiquitin-proteasomal degradation and thus inhibited β-catenin/T-cell factor (TCF)-mediated Runx2 and Msx2 transcription. Knockdown of β-catenin abolished the effect of XBP1u deficiency on VSMC calcification, suggesting a β-catenin-mediated mechanism. Moreover, the degradation of β-catenin promoted by XBP1u was independent of glycogen synthase kinase 3β (GSK-3β)-involved destruction complex. Conclusions: Our study identified XBP1u as a novel endogenous inhibitor of vascular calcification by counteracting β-catenin and promoting its ubiquitin-proteasomal degradation, which represents a new regulatory pathway of β-catenin and a promising target for vascular calcification treatment.

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.

Uraemic Cardiomyopathy in Different Mouse Models

Uraemic cardiomyopathy (UCM) is one of the most common complications in chronic kidney disease (CKD). Our aim was to compare characteristics of various UCM mouse models. Mice were assigned to the following groups: the pole ligation group, 5/6 nephrectomy group (5/6Nx), uninephrectomy plus contralateral ischemia followed by reperfusion group (IR), adenine group, and sham group. Mice were sacrificed at 4, 8, and 16 weeks after surgery in the pole ligation, 5/6Nx, and IR groups, respectively. In the adenine group, mice were sacrificed at 16 weeks after the adenine diet. The structure and function of the heart and the expression of fibroblast growth factor 23 (FGF-23) and growth differentiation factor 15 (GDF-15) in hearts were assessed. The mortality in the 5/6 Nx group was significantly higher than that in the pole ligation, IR, and adenine groups. Echocardiogram and histological examination showed cardiac hypertrophy in the adenine,5/6Nx, ligation group, and IR group. In addition, cardiac fibrosis occurred in all CKD modeling groups. Interestingly, cardiac fibrosis was more serious in the IR and adenine groups. FGF-23 expression in sham mice was similar to that in modeling groups; however, the GDF-15 level was decreased in modeling groups. Our results suggest that the four models of UCM show different phenotypical features, molding time and mortality. GDF-15 expression in the hearts of UCM mice was downregulated compared with sham group mice.

Skeletal endocrinology: where evolutionary advantage meets disease

The regulation of whole-body homeostasis by the skeleton is mediated by its capacity to secrete endocrine signaling molecules. Although bone-derived hormones confer several adaptive benefits, their physiological functions also involve trade-offs, thus eventually contributing to disease. In this manuscript, we discuss the origins and functions of two of the best-studied skeletal mediators, fibroblast growth factor 23 and osteocalcin, in an evolutionary context. Moreover, we provide a theoretical framework seeking to explain the broad involvement of these two hormones in amniote physiology as well as their potential to fuel the development and progression of diseases. Vice versa, we outline which perturbations might be amenable to manipulation of these systems and discuss limitations and ongoing challenges in skeletal endocrine research. Finally, we summarize unresolved questions and potential future studies in this thriving field.

Periostin promotes arterial calcification through PPARγ-related glucose metabolism reprogramming

Extracellular matrix (ECM) exerts a series of biological functions and contributes to almost 30% of the osteogenic process. Periostin is a secreted protein that can alter ECM remodeling in response to vascular injury. However, the role of periostin in vascular calcification has yet to be fully investigated. As found in this study, recombinant periostin accelerated the thoracic aortas calcification, increased the expression of glycolysis key enzymes, and disturbed the normal oxidative phosphorylation (OXPHOS) ex vivo, which could be alleviated by the peroxisome proliferation-activated receptor γ (PPARγ) agonist pioglitazone. In vascular smooth muscle cells (VSMCs), periostin promoted VSMC-osteoblastic phenotype transition and calcium deposition and suppressed PPARγ expression. Mechanistically, periostin caused overactivation of glycolysis and mitochondrial dysfunction in VSMCs as assessed by extracellular acidification rate, oxygen consumption rate, and mitochondrial respiratory chain complex activities. Targeted glycolysis inhibitors reduced mitochondrial calcium overload, apoptosis, and periostin-induced VSMCs calcification. PPARγ agonists preserved glycolysis and OXPHOS in the stimulated microenvironment and reversed periostin-promoted VSMC calcification. Furthermore, plasma periostin, lactate, and matrix Gla protein levels were measured in 274 patients undergoing computed tomography to determine coronary artery calcium score (Agatston score). Plasma periostin and lactate levels were both linked to an Agatston score in patients with coronary artery calcification (CAC). There was also a positive correlation between plasma periostin and lactate levels. This study suggests that downregulation of PPARγ is involved in the mechanism by which periostin accelerates arterial calcification partly through excessive glycolysis activation and unbalanced mitochondrial homeostasis.NEW & NOTEWORTHY Periostin caused arterial calcification, overactivated glycolysis, and damaged OXPHOS. PPARγ agonists alleviated periostin-promoted arterial calcification and corrected abnormal glycolysis and unbalanced mitochondrial homeostasis. There exists a relationship between periostin and lactate in patients with CAC.

User of angiotensin-converting-enzyme inhibitor and/or angiotensin II receptor blocker might be associated with vascular calcification in predialysis chronic kidney disease patients: a retrospective single-center observational study : ACEI/ARB and vascular calcification

Background

Vascular calcification is a prominent feature in chronic kidney disease (CKD) and diabetes mellitus. A recent report suggests that angiotensin II is protective to vascular calcification. Therefore, we investigated the relationship between vascular calcification and use of angiotensin-converting-enzyme inhibitor (ACEI) and/or angiotensin II receptor blocker (ARB) from a cross-sectional view.

Methods

A total of 121 predialysis CKD patients (age 71 ± 12 y; male 72; estimated glomerular filtration rate (eGFR) 20.2 (11.8 - 40.3) mL/min/1.73 m²) who underwent thoracoabdominal plain computed tomography scan were included in this study. The total vascular calcification volume (Calc) was calculated with a three-dimensional imaging software and standardized by body surface area (BSA). The relevance between log [Calc/BSA] and ACEI/ARB use was investigated by multivariate linear regression analyses with or without a time-duration factor of ACEI/ARB use.

Results

The Calc/BSA was 5.62 (2.01 - 12.7) mL/m² in 121 patients. In multivariate analyses adjusted with age, sex, ACEI/ARB and log [eGFR], ACEI/ARB use is significantly and positively associated with log [Calc/BSA] (β = 0.2781, p = 0.0007). Even after the adjustment by age, sex, log [eGFR], phosphate, diabetes mellitus, systolic blood pressure, warfarin, hypertension, dyslipidemia, low-density lipoprotein cholesterol, diuretics and ACEI/ARB, ACEI/ARB use is significantly and positively associated with log [Calc/BSA] (β = 0.1677, p = 0.0487). When 90 patients whose time-duration of ACEI/ARB use was clear in medical records were studied, a multivariate analysis adjusted with age, sex, log [eGFR], and ACEI/ARB duration factors showed that the longer use of ACEI/ARB more than 2 years was significantly, independently and positively associated with log [Calc/BSA] (β = 0.2864, p = 0.0060).

Conclusions

ACEI/ARB user was associated with vascular calcification in predialysis patients with low eGFR. Prospective studies with larger numbers of patients or more in vitro studies are needed to confirm whether this phenomenon is due to the use of ACEI/ARB itself, the underlying disease condition or the prescription bias.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-020-02198-6.

The Interplay of WNT and PPARγ Signaling in Vascular Calcification

Vascular calcification (VC), the ectopic deposition of calcium phosphate crystals in the vessel wall, is one of the primary contributors to cardiovascular death. The pathology of VC is determined by vascular topography, pre-existing diseases, and our genetic heritage. VC evolves from inflammation, mediated by macrophages, and from the osteochondrogenic transition of vascular smooth muscle cells (VSMC) in the atherosclerotic plaque. This pathologic transition partly resembles endochondral ossification, involving the chronologically ordered activation of the β-catenin-independent and -dependent Wingless and Int-1 (WNT) pathways and the termination of peroxisome proliferator-activated receptor γ (PPARγ) signal transduction. Several atherosclerotic plaque studies confirmed the differential activity of PPARγ and the WNT signaling pathways in VC. Notably, the actively regulated β-catenin-dependent and -independent WNT signals increase the osteochondrogenic transformation of VSMC through the up-regulation of the osteochondrogenic transcription factors SRY-box transcription factor 9 (SOX9) and runt-related transcription factor 2 (RUNX2). In addition, we have reported studies showing that WNT signaling pathways may be antagonized by PPARγ activation via the expression of different families of WNT inhibitors and through its direct interaction with β-catenin. In this review, we summarize the existing knowledge on WNT and PPARγ signaling and their interplay during the osteochondrogenic differentiation of VSMC in VC. Finally, we discuss knowledge gaps on this interplay and its possible clinical impact.

The Protective Role of Klotho in CKD-Associated Cardiovascular Disease

Background

Cardiovascular diseases (CVDs) are the leading cause of morbidity and mortality in advanced CKD. The major pathological changes of CKD-associated CVD are severe vascular media calcification, aberrant cardiac remodeling such as hypertrophy and fibrosis, as well as accelerated atherosclerosis. α-Klotho is proposed as an anti-aging gene, which is primarily expressed in the kidney. Recent studies reveal that α-Klotho deficiency is associated with profound cardiovascular dysfunction. Of note, CKD represents extremely declined α-Klotho levels, hinting that α-Klotho deficiency may be implicated in the pathogenesis of CKD-associated CVD.

Summary

Based on the pathogenic mechanism of α-Klotho deficiency and decreased Klotho levels in the circulation even early in stage 1 of CKD, α-Klotho serves as a sensitive biomarker for renal insufficiency and also a novel predictor of risk of overall mortality of CVD events in CKD. Meanwhile, loss of Klotho resulted from kidney dysfunction markedly contributes to the progressive development of CKD and CVD. By contrast, prevention of Klotho decline using exogenous supplementation or genetically activated ways by several mechanisms can dramatically mitigate cardiac dysfunction, prevent vascular calcification, and retard the progression of CKD-accelerated atherosclerosis.

Key Messages

Klotho deficiency is proposed as a novel predictive biomarker as well as a pathogenic contributor to CVD events in CKD. In the future, Klotho may be a crucial potential therapeutic strategy to decrease the burden of CVD comorbidity with CKD in clinics.

X-ray Micro-Computed Tomography: An Emerging Technology to Analyze Vascular Calcification in Animal Models

Vascular calcification describes the formation of mineralized tissue within the blood vessel wall, and it is highly associated with increased cardiovascular morbidity and mortality in patients with chronic kidney disease, diabetes, and atherosclerosis. In this article, we briefly review different rodent models used to study vascular calcification in vivo, and critically assess the strengths and weaknesses of the current techniques used to analyze and quantify calcification in these models, namely 2-D histology and the o-cresolphthalein assay. In light of this, we examine X-ray micro-computed tomography (µCT) as an emerging complementary tool for the analysis of vascular calcification in animal models. We demonstrate that this non-destructive technique allows us to simultaneously quantify and localize calcification in an intact vessel in 3-D, and we consider recent advances in µCT sample preparation techniques. This review also discusses the potential to combine 3-D µCT analyses with subsequent 2-D histological, immunohistochemical, and proteomic approaches in correlative microscopy workflows to obtain rich, multifaceted information on calcification volume, calcification load, and signaling mechanisms from within the same arterial segment. In conclusion we briefly discuss the potential use of µCT to visualize and measure vascular calcification in vivo in real-time.

The protective effects of renin-angiotensin system componts on vascular calcification

Renin-angiotensin system (RAS) has important roles in cardiovascular disease. Angiotensin II (Ang II) and angiotensin-(1-7) (Ang-(1-7)) are major effector peptides of RAS. However, the roles of Ang II type 2 receptor (AT2R) need to be further explored and the roles of Ang-(1-7) are still not very clear on vascular calcification (VC). Therefore, we hypothesized they have effects on preventing VC in vivo and in vitro. VC model is established by inorganic phosphate (IP) cultured with vascular smooth muscle cells (VSMC) for in vitro study and by 5/6 nephrectomy in mice for in vivo study. Increased calcified nodules by Alizarin Red S staining and mRNA expressions of bone morphogenetic protein-2 (BMP-2) and osteocalcin (OCN) by reverse transcription polymerase chain reaction in calcified WT VSMC were significantly inhibited in calcified AT2R overexpression (SmAT2) VSMC or after Ang-(1-7) treatment. After 5/6 nephrectomy, the ratio of positive and total area by Alizarin Red S and von Kossa staining and mRNA expressions of BMP-2 and OCN were significantly increased in ApoE/AT2R knockout mice compared with apolipoprotein E knockout mice, and which were significantly inhibited with Ang-(1-7) administration. Both AT2R and Ang-(1-7) have the effects on preventing VC induced by IP, at least in part through inhibiting BMP-2, OCN expressions, and in which Ang-(1-7) had protective roles mainly through Mas receptor rather than AT2R.

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.

An overview of the mechanisms in vascular calcification during chronic kidney disease

PURPOSE OF REVIEW

Chronic kidney disease (CKD) facilitates a unique environment to strongly accelerate vascular calcification - the pathological deposition of calcium-phosphate in the vasculature. These calcifications are associated with the excessive cardiovascular mortality of CKD patients.

RECENT FINDINGS

Vascular calcification is a multifaceted active process, mediated, at least partly, by vascular smooth muscle cells. These cells are able to transdifferentiate into cells with osteo/chondrogenic properties, which exert multiple effects to facilitate vascular tissue mineralization. As the understanding of the underlying pathophysiology increases, first therapeutic concepts begin to emerge.

SUMMARY

This brief review provides an overview on the so far known mechanisms involved in the initiation and progression of vascular calcification in CKD.

Inhibition of Gastrin-Releasing Peptide Attenuates Phosphate-Induced Vascular Calcification

Vascular calcification is the pathological deposition of calcium/phosphate in the vascular system and is closely associated with cardiovascular morbidity and mortality. Here, we investigated the role of gastrin-releasing peptide (GRP) in phosphate-induced vascular calcification and its potential regulatory mechanism. We found that the silencing of GRP gene and treatment with the GRP receptor antagonist, RC-3095, attenuated the inorganic phosphate-induced calcification of vascular smooth muscle cells (VSMCs). This attenuation was caused by inhibiting phenotype change, apoptosis and matrix vesicle release in VSMCs. Moreover, the treatment with RC-3095 effectively ameliorated phosphate-induced calcium deposition in rat aortas ex vivo and aortas of chronic kidney disease in mice in vivo. Therefore, the regulation of the GRP-GRP receptor axis may be a potential strategy for treatment of diseases associated with excessive vascular calcification.

Trimethylamine-N-Oxide Promotes Vascular Calcification Through Activation of NLRP3 (Nucleotide-Binding Domain, Leucine-Rich-Containing Family, Pyrin Domain-Containing-3) Inflammasome and NF-κB (Nuclear Factor κB) Signals

Objectives:

Vascular calcification is highly prevalent in patients with chronic kidney disease. Increased plasma trimethylamine N-oxide (TMAO), a gut microbiota-dependent product, concentrations are found in patients undergoing hemodialysis. However, a clear mechanistic link between TMAO and vascular calcification is not yet established. In this study, we investigate whether TMAO participates in the progression of vascular calcification using in vitro, ex vivo, and in vivo models.

Approach and Results:

Alizarin red staining revealed that TMAO promoted calcium/phosphate-induced calcification of rat and human vascular smooth muscle cells in a dose-dependent manner, and this was confirmed by calcium content assay. Similarly, TMAO upregulated the expression of bone-related molecules including Runx2 (Runt-related transcription factor 2) and BMP2 (bone morphogenetic protein-2), suggesting that TMAO promoted osteogenic differentiation of vascular smooth muscle cells. In addition, ex vivo study also showed the positive regulatory effect of TMAO on vascular calcification. Furthermore, we found that TMAO accelerated vascular calcification in rats with chronic kidney disease, as indicated by Mico-computed tomography analysis, alizarin red staining and calcium content assay. By contrast, reducing TMAO levels by antibiotics attenuated vascular calcification in chronic kidney disease rats. Interestingly, TMAO activated NLRP3 (nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3) inflammasome and NF-κB (nuclear factor κB) signals during vascular calcification. Inhibition of NLRP3 inflammasome and NF-κB signals attenuated TMAO-induced vascular smooth muscle cell calcification.

Conclusions:

This study for the first time demonstrates that TMAO promotes vascular calcification through activation of NLRP3 inflammasome and NF-κB signals, suggesting the potential link between gut microbial metabolism and vascular calcification. Reducing the levels of TMAO could become a potential treatment strategy for vascular calcification in chronic kidney disease.

PPAR-γ Ligand Inhibits Nasopharyngeal Carcinoma Cell Proliferation and Metastasis by Regulating E2F2

Purpose

Peroxisome proliferator-activated receptor-γ (PPAR-γ) is a nuclear hormone receptor with a key role in lipid metabolism. Previous studies have identified various roles of PPAR-γ in cell cycle progression, cellular proliferation, and tumor progression. However, no report has described a role for PPAR-γ in human nasopharyngeal carcinoma (NPC). Notably, some studies have reported a relationship between PPAR-γ and E2F transcription factor 2 (E2F2), which has been identified as a regulator of cell cycle, apoptosis, and the DNA damage response. Notably, E2F2 has also been reported to correlate with a poor prognosis in patients with various malignancies.

Methods

We used immunohistochemical (IHC) and western blot methods to evaluate PPAR-γ and E2F2 expression and function in nonkeratinizing NPC and nasopharyngitis (NPG) tissue samples, as well as western blotting and CCK8 analyses in the NPC cell lines, CNE1 and CNE2.

Results

We observed lower levels of PPAR-γ expression in nonkeratinizing NPC tissues compared with NPG tissues and determined an association between a low level of PPAR-γ expression with a more advanced tumor stage. Furthermore, strong E2F2 expression was detected in nonkeratinizing NPC tissues. We further demonstrated that rosiglitazone, a PPAR-γ agonist, reduced E2F2 expression and proliferation in NPC cell lines.

Conclusions

Our study results revealed a novel role for the PPAR-γ–E2F2 pathway in controlling NPC cell proliferation and metastasis.