Calcification Of VSMCs Research Articles

#289 Lipocalin-2 promotes cardiovascular calcification in chronic kidney disease by upregulating STAT3/NCOA4-mediated ferritinophagy and ferroptosis

Abstract Background and Aims Cardiovascular calcification (CVC) is a common complication of chronic kidney disease (CKD) and contributes to cardiovascular morbidity and mortality without any effective therapies. To date, the underlying mechanism of CKD-CVC has not been elucidated. Recent studies suggest that ferroptosis is a novel programmed cell death that may play a role in the process of CKD-CVC, but the mechanism is largely unclear. Ferritinophagy is an important inducer of ferroptosis that is regulated by nuclear receptor coactivator 4 (NCOA4). However, the relationship between ferritinophagy and CKD-CVC has not been explored. Lipocalin-2 (LCN2) is an iron-trafficking protein that has been associated with both osteogenesis and ferroptosis, but the exact role and molecular mechanism of LCN2 in CKD-CVC needs to be explored. Method A cross-sectional clinical study was utilized to examine the association between LCN2 expression and CKD-CVC in serum and calcified radial arteries of CKD patients. LCN2 knockout mice, their wild type littermates and mice infected with VSMCs-targeted adeno-associated virus encoding LCN2 gene or negative control gene were all fed by the high adenine and phosphate diet to induce CKD-CVC.VSMCs transfected with LCN2-overexpressing lentivirus, LCN2-shRNA lentivirus or LCN2 siRNA and recombinant LCN2 stimulated VSMCs were treated under the condition of calcifying medium to investigate the role of LCN2 in CKD-CVC in vitro. Cardiovascular calcification was evaluated by Von-kossa staining and tissue calcium content assay. VSMCs calcification were checked by the Alizarin Red Staining and cellular calcium content assay. Cellular reactive oxygen species (ROS) were measured by the DCFDA assay. Lipid peroxidation was measured by the fluorescence of the fatty acid analog C11-BODIPY581/591 probe. Intracellular labile ferrous iron levels were measured by fluorescence of Phen Green SK probe and ferro-orange probe. Transmission electron microscopy was also used to examine mitochondrial change of ferroptosis. Results The cross-sectional study identified that LCN2 levels in serum and radial arteries were significantly increased as the severity of CKD-CVC increased. High adenine and phosphate diet intake provokes renal fibrosis and cardiovascular calcification in vivo. In vitro, five-days high phosphate sodium stimulation induced calcium deposition and osteoblastic trans differentiation of VSMCs. Meanwhile, high phosphate also increased the levels of ferroptosis in VSMCs as evidenced by decreased cell viability, iron and ROS accumulation, upregulated PTGS2 and MDA levels, reduced glutathione peroxidase 4 (GPX4) levels and significantly mitochondrial damage in VSMCs. Intriguingly, calcium deposition in VSMCs could be reversed by the ferroptosis inhibitor ferrostatin-1. LCN2 expression was significantly upregulated both in the aorta of mice and calcified VSMCs. Compared with WT mice, deletion of LCN2 inhibited cardiovascular calcification whereas VSMC-targeted LCN2 overexpression aggravated CKD-CVC. Consistently, LCN2 knockdown also alleviated calcium deposition of VSMCs. Meanwhile, inhibition of ferroptosis were observed after LCN2 silencing as evidenced by decreased ferrous and lipid oxidation while increased levels of GPX4. Mechanically, we demonstrated high phosphate increased the protein level of NCOA4 and downregulated FTH1, which was reversed by depletion of LCN2. Knockdown of NCOA4 partly alleviated the ferritin reduction, ferroptosis, and calcification in VSMCs, indicating that NCOA4-mediated ferritinophagy was required for VSMCs calcification. Furthermore, we found that the recombinant LCN2 treatment significantly upregulated phosphorylated STAT3. STAT3 signaling inhibitor abolished the recombinant LCN2 induced NCOA4 upregulation and calcification in VSMCs. Conclusion Our findings indicate that the pro-calcific effect of high phosphate is due to VSMCs ferroptosis mediated by LCN2 upregulation. LCN2 silencing alleviates CKD-CVC by suppressing the STAT3/ NCOA4/FTH1 signaling mediated ferritinophagy. LCN2 could serve as a candidate therapeutic strategy for CKD-CVC.

#3986 THE ROLE AND MECHANISM OF EZH2 IN VASCULAR CALCIFICATION ASSOCIATED WITH CHRONIC KIDNEY DISEASE

Abstract Background and Aims Vascular calcification (VC) is a prevalent complication in chronic kidney disease and contributes to increased cardiovascular morbidity and mortality. EZH2 (Enhancer of zeste 2 homolog-2) is reported as a key epigenetic regulator involved in various kidney diseases such as acute kidney injury, renal fibrosis, diabetic nephropathy, and lupus nephritis. In this study, we aimed to investigated the role of EZH2 in chronic kidney disease associated vascular calcification. Method 1. Patients and Radial Artery Analysis Radial arteries with or without calcification from patients with end-stage renal disease that underwent arterial venous fistular surgery were collected for Von Kossa staining and immunohistochemical (IHC) staining. 2. Animal model of Chronic renal failure-Vascular Calcification (CRF-VC) (in vivo) An adenine and phosphate (1.2%) diet-induced CRF mouse model was designed following an 8-week program. The thoracoabdominal arteries of mice and rats were dissected to assay Ca deposition and histological analysis. Plasma levels of Alkaline phosphate (ALP), and phosphate (Pi) were measured. The transcription level of EZH2 and Runt-related transcription factor 2 (Runx2) were measured by real-time PCR and IHC staining. 3. Aortic ring calcification (ex vivo) Thoracic aortas were dissected from SD rat. To induce calcification, Pi (NaH2PO4/Na2HPO4 [pH = 7.4]) was added to HG-DMEM at a final concentration of 2.6 mmol/l. After the indicated incubation periods (3, 5, 7 days), samples were taken for Calcium deposition assay, Western blotting and histological analysis. 4. Cell culture and treatment (in vitro) Calcification of rat smooth muscle embryonic thoracic aorta cell line A7r5 (VSMC) was induced by incubation in calcifying media. 3-deazaneplanocin A (3-DZNeP), a carbocyclic analog of adenosine was added right after Pi to block EZH2 activation. After the indicated incubation periods, samples were collected for Calcium deposition assay and Western blotting analysis. Results 1. In vivo, EZH2 protein level was increased in calcified radial arteries from patients with end-stage renal disease that underwent arterial venous fistular operation. In CRF-VC mice model, the aortic calcium deposition markedly aggravated in the group induced by adenine diet. Severe vascular calcification was also induced as shown by increased intensity of von Kossa. Moreover, IHC and q-PCR results showed that the protein and transcriptional levels of EZH2 expression were upregulated in calcified aortas of CRF mice, in paralleled with the increased expression Runx2 in protein and transcriptional levels. 2. Ex vivo, histological analysis revealed significant medial vascular calcification in the aortic ring culture with this calcifying medium for 7 days. Similarly, WB results showed that the expression of EZH2 and its downstream, methylation of Histone H3 at lysine 27 (H3K27me3), were significantly enhanced after high Pi medium stimulation while the osteogenic markers Runx2, Osteopontin (OPN) and Msh homeobox 2 (Msx2) protein levels were upregulated and the expression of VSMC differentiation markers α-Smooth muscle actin (α-SMA), Calponin (CNN) and Smooth muscle protein 22 (SM22) were downregulated. 3. In vitro, the osteogenic markers Runx2, OPN and Msx2 were significantly upregulated in high Pi treated VSMCs compared to control VSMCs. Moreover, the epigenetic markers EZH2 and H3K27me3a were markedly repressed in calcifying VSMCs by time. 4. 3-DZNep treatment reduced the calcium deposition in a concentration dependent manner. Western blotting showed that 3-DZNep treatment blocked the increased expression of osteogenic markers Runx2, Bone morphogenetic protein 2 (BMP2) as well as epigenetic markers EZH2 and H3K27me3a by high Pi treatment, indicating that inhibition of EZH2 attenuates VSMCs Calcification. Conclusion Our study revealed that EZH2 is highly expressed in calcified vascular tissues of CRF patients and CRF mice, rat aorta culture and VSMCs calcification models, and EZH2 inhibitor 3-DZNep attenuated calcification of VSMCs. EZH2 could be a promising target for treatment of vascular calcification in CRF patients.

A novel protective role of lipoxin in inhibiting diabetic vascular calcification via YAP signalling: Health prevention and regulation

Vascular calcification is highly prevalent in diabetes patients, with detrimental consequences and no effective prevention and treatment strategies are currently available. Though the protective effect of lipoxin (LX) against vascular diseases has been demonstrated, its effect on diabetic vascular calcification remains unknown. AGEs dose-dependently induced calcification and the expression of osteogenesis-related markers, coupled with the activation of yes-associated protein (YAP). Mechanistically, YAP activation enhanced the AGE-induced osteogenic phenotype and calcification, but inhibition of YAP signalling alleviated this response. Further, an in vivo diabetic mouse model was established using a combination of a high-fat diet and multiple formulations of low-dose streptozotocin. Consistent with the in vitro results, diabetes promoted YAP expression and its subcellular localization in the nucleus in the arterial tunica media. The results demonstrate that LX attenuates the trans-differentiation and calcification of VSMCs in diabetes mellitus via YAP signalling, suggesting LX to be a potent therapeutic for preventing diabetic vascular calcification.

TNFα activation and TGFβ blockage act synergistically for smooth muscle cell calcification in patients with venous thrombosis via TGFβ/ERK pathway.

Venous calcification has been observed in post‐thrombotic syndrome (PTS) patients; yet, the cell types and possible mechanisms regulating this process are still unclear. We evaluated the calcium deposition within the venous wall, the cell type involved in the calcified remodelling of the venous wall after thrombosis and explored possible mechanisms in vitro. Calcium deposition was found in human specimens of superficial thrombotic veins and was co‐localized with VSMCs markers αSMA and TAGLN (also known as SM22α). Besides, the expression of osteogenesis‐related genes was dramatically changed in superficial thrombotic veins. Moreover, the inhibition of the TGFβ signalling pathway after TNFα treatment effectively induced the expression of osteogenic phenotype markers, the calcium salt deposits and the obvious phosphorylation of ERK1/2 and JNK2 in the VSMCs calcification model. Supplementing TGFβ2 or blocking the activation of the ERK/MAPK signalling pathway prevented the transformation of VSMCs into osteoblast‐like cells in vitro. Taken together, VSMCs have an important role in venous calcification after thrombosis. Supplementing TGFβ2 or inhibiting the ERK/MAPK signalling pathway can reduce the appearance of VSMCs osteogenic phenotype. Our findings may present a novel therapeutic approach to prevent of vascular calcification after venous thrombosis.

Galectin-3 induces vascular smooth muscle cells calcification via AMPK/TXNIP pathway.

Galectin-3 plays an important role in atherosclerosis. Upregulation of VSMCs calcification is involved in the progression and development of vulnerable plaques. Thioredoxin-interacting protein (TXNIP) has been regarded as an important determinant in regulating inflammation and oxidative stress. In this study, we evaluated the role of TXNIP in galectin-3-induced vascular calcification. A primary culture of mouse VSMCs was established by enzymatic digestion of aorta. Small interfering (si) RNA was used to knock down the expression of target gene. VSMCs were treated with 3-methyladenine (3-MA) or compound C respectively. Western blot was performed to detect the protein level in VSMCs, Alkaline phosphatase (ALP) and Alizarin red staining was used to observe calcium deposition. Dihydroethidium (DHE) staining was used to observe the reactive oxygen species (ROS) production. Here we showed that galectin-3 increased aorta and VSMCs calcification, which was associated with AMPK/TXNIP upregulation and autophagy activation. TXNIP inhibition decreased galectin-3-induced aorta and VSMCs calcification and autophagy activation. 3-MA or Atg5 siRNA decreased galectin-3-induced upregulation of Runx2, BMP2 and OPN. AMPK mediated galectin-3-induced VSMCs osteogenic differentiation. These findings illustrated that TXNIP mediated galectin-3-induced vascular calcification, AMPK and autophagy activation were also associated with this process.

ILF3 is responsible for hyperlipidemia-induced arteriosclerotic calcification by mediating BMP2 and STAT1 transcription

Calcification is common in atherosclerotic plaque and can induce vulnerability, which further leads to myocardial infarction, plaque rupture and stroke. The mechanisms of atherosclerotic calcification are poorly characterized. Interleukin enhancer binding factor 3 (ILF3) has been identified as a novel factor affecting dyslipidemia and stroke subtypes. However, the precise role of ILF3 in atherosclerotic calcification remains unclear. In this study, we used smooth muscle-conditional ILF3 knockout (ILF3SM-KO) and transgenic mice (ILF3SM-Tg) and macrophage-conditional ILF3 knockout (ILF3M-KO) and transgenic (ILF3M-Tg) mice respectively. Here we showed that ILF3 expression is increased in calcified human aortic vascular smooth muscle cells (HAVSMCs) and calcified atherosclerotic plaque in humans and mice. We then found that hyperlipidemia increases ILF3 expression and exacerbates calcification of VSMCs and macrophages by regulating bone morphogenetic protein 2 (BMP2) and signal transducer and activator of transcription 1 (STAT1) transcription. We further explored the molecular mechanisms of ILF3 in atherosclerotic calcification and revealed that ILF3 acts on the promoter regions of BMP2 and STAT1 and mediates BMP2 upregulation and STAT1 downregulation, which promotes atherosclerotic calcification. Our results demonstrate the effect of ILF3 in atherosclerotic calcification. Inhibition of ILF3 may be a useful therapy for preventing and even reversing atherosclerotic calcification.

The intermediate-conductance calcium-activated potassium channel KCa3.1 contributes to alkalinization-induced vascular calcification in vitro.

ObjectiveIn order to find new strategies for the prevention of vascular calcification in uremic individuals especially treated by dialysis and develop novel therapeutic targets in vascular calcification, we explore the role of KCa3.1 in alkalinization‐induced VSMCs calcification in vitro.MethodRat VSMCs calcification model was established by beta‐glycerophosphate (β‐GP, 10 mM) induction. The pH of Dulbecco's modified Eagle's medium (DMEM) was adjusted every 24 h with 10 mM HCl or 10 mM NaHCO3. The mineralization was measured by Alizarin Red staining and O‐cresolphthalein complex one method. mRNA and protein expression were detected by RT‐PCR and Western blot or immunofluorescence. Ca2+ influx was measured by Elisa.ResultThe results indicated that alkalization induced an increase in Ca2+ influx to enhance VSMCs calcification. Furthermore, the increase of calcification was associated with the expression of KCa3.1 via advanced expression of osteoblastic differentiation markers alkaline phosphatase (ALP) and Runt‐related transcription factor 2 (Runx2). Blocking KCa3.1 with TRAM‐34 or shRNA vector can significantly lowered the effects of calcification in the activity of ALP and Runx2 expression.ConclusionTogether all, our studies suggested that alkalinization can promote vascular calcification by upregulating KCa3.1 channel and enhancing osteogenic/chondrogenic differentiation by upregulating Runx2. The specific inhibitor TRAM‐34 and KCa3.1‐shRNA ameliorated VSMCs calcification by downregulating KCa3.1.

MO565M2 MACROPHAGES REGULATE MOUSE AORTIC SMOOTH MUSCLE CELL CALCIFICATION BY TRANSMITTING SENESCENCE INFORMATION

Abstract Background and Aims Vascular calcification is highly prevalent in chronic kidney disease (CKD)with high morbidity and mortality. Complex pathological mechanisms are involved in the development of vascular calcification, including aging. Previous work have indicated that M2-macrophage promote mouse aortic smooth muscle cells (MAoSMCs) calcification. The present study aimed to understand the contribution of M2-macrophage to MAoSMCs calcification by focusing on the mechanisms underlying the transmitting senescence information Method The expression of IFITM3 and P16, marker of aging, in aging macrophages were confimed by RT-qPCR, western blotting and immunofluorescence staining. Then, the MAoSMCs were co-cultured with the supernatant of M2 macrophages. The expression of IFITM3 and P16 in MAoSMCs also were detected. Alizarin red staining and calcium content assay were used to analyse MAoSMCs calcification. We modulated the expression of IFITM3 using siRNAs to study M2-macrophages function in regulating MAoSMCs calcification.We detected the expression of IFITM3 and P16 in co-cultivate MAoSMCs and validate intracellular calcium contents by calcium test kit. Results In the present study, we observed a significant increase in the expression of IFITM3 and P16 expression in M2 macrophages.Compared with M0 and M1 macrophages, the expression of IFITM3 and P16 at lowlevel. Alizarin red staining and calcium content assay revealed that M2 macrophage-mediated IFITM3 and P16 overexpression led to an apparent VSMC calcification in the presence of M2 macrophages medium.By contrast, inhibition of IFITM3 by siRNAs significantly blocked calcification of VSMCs in vitro. Moreover, we found that aging macrophages that overexpressed of IFITM3 and P16 increased in rats with CKD. Furthermore, pharmacological inhibition of aging signal was shown to block IFITM3-induced VSMC calcification. These findings demonstrate for the first time that M2 macrophage-mediated IFITM3 contributes to vascular calcification through a mechanism involving transmitting Senescence signalling. Conclusion Collectively, our present study demonstrated that the functional importance of M2 macrophage-IFITM3 dependent vascular calcification and provided a novel mechanistic insight to the macrophage senescence in CKD.

Effect of Erythropoietin on Calcification of Vascular Smooth Muscle Cells and Its Molecular Regulatory Mechanism.

To investigate its effect and molecular regulatory mechanism on vascular calcification, EPO was added to vascular smooth muscle cells cultured in vitro and injected intraperitoneally into SD rats. The effect of EPO on VSMC calcification was determined by alizarin red staining and ALP activity. Differentially expressed genes were screened by transcriptome sequencing and the relationship and function were verified. We found EPO promotes VSMC calcification in vitro and blood calcification in vivo in a dose-dependent manner. A total of 88 upregulated genes and 59 downregulated genes were detected in transcriptome sequencing, among which the expression of genes associated with bone formation exhibited a marked increase, namely the GATA6 transcription factor, BMP2, RUNX2, OPN, and OCN. Dual luciferase assay has indicated that the binding of GATA6 to BMP2 promoter facilitates the transcription of BMP2. Taken together, findings indicate that EPO can enhance the calcification of VSMCs by activating the GATA6/BMP2 signal axis.

Microvesicles from indoxyl sulfate-treated endothelial cells induce vascular calcification in vitro

Vascular calcification (VC), an unpredictable pathophysiological process and critical event in patients with cardiovascular diseases (CVDs), is the leading cause of morbi-mortality and disability in chronic kidney disease (CKD) patients worldwide. Currently, no diagnostic method is available for identifying patients at risk of VC development; the pathology is detected when the process is irreversible. Extracellular vesicles (EVs) from endothelial cells might promote VC. Therefore, their evaluation and characterization could be useful for designing new diagnostic tools. The aim of the present study is to investigate whether microvesicles (MVs) from endothelial cells damaged by uremic toxin and indoxyl sulfate (IS) could induce calcification in human vascular smooth muscle cells (VMSCs). Besides, we have also analyzed the molecular mechanisms by which these endothelial MVs can promote VC development. Endothelial damage has been evaluated according to the percentage of senescence in endothelial cells, differential microRNAs in endothelial cells, and the amount of MVs released per cell. To identify the role of MVs in VC, VSMCs were treated with MVs from IS-treated endothelial cells. Calcium, inflammatory gene expression, and procalcification mediator levels in VSMCs were determined. IS-treated endothelial cells underwent senescence and exhibited modulated microRNA expression and an increase in the release of MVs. VSMCs exposed to these MVs modulated the expression of pro-inflammatory genes and some mediators involved in calcification progression. MVs produced by IS-treated endothelial cells promoted calcification in VSMCs.

Calciprotein particle inhibition explains magnesium-mediated protection against vascular calcification.

BackgroundPhosphate (Pi) toxicity is a strong determinant of vascular calcification development in chronic kidney disease (CKD). Magnesium (Mg2+) may improve cardiovascular risk via vascular calcification. The mechanism by which Mg2+ counteracts vascular calcification remains incompletely described. Here we investigated the effects of Mg2+ on Pi and secondary crystalline calciprotein particles (CPP2)-induced calcification and crystal maturation.MethodsVascular smooth muscle cells (VSMCs) were treated with high Pi or CPP2 and supplemented with Mg2+ to study cellular calcification. The effect of Mg2+ on CPP maturation, morphology and composition was studied by medium absorbance, electron microscopy and energy dispersive spectroscopy. To translate our findings to CKD patients, the effects of Mg2+ on calcification propensity (T50) were measured in sera from CKD patients and healthy controls.ResultsMg2+ supplementation prevented Pi-induced calcification in VSMCs. Mg2+ dose-dependently delayed the maturation of primary CPP1 to CPP2 in vitro. Mg2+ did not prevent calcification and associated gene and protein expression when added to already formed CPP2. Confirmatory experiments in human serum demonstrated that the addition of 0.2 mmol/L Mg2+ increased T50 from healthy controls by 51 ± 15 min (P < 0.05) and CKD patients by 44 ± 13 min (P < 0.05). Each further 0.2 mmol/L addition of Mg2+ led to further increases in both groups.ConclusionsOur results demonstrate that crystalline CPP2 mediates Pi-induced calcification in VSMCs. In vitro, Mg2+ delays crystalline CPP2 formation and thereby prevents Pi-induced calcification.

Vitamin K Ameliorates Nicotine-Induced Calcification Of Vsmcs By Inhibiting Oxidative Stress And Extracellular Vesicle Secretion

Vitamin K Ameliorates Nicotine-Induced Calcification Of Vsmcs By Inhibiting Oxidative Stress And Extracellular Vesicle Secretion

HIF-1α/PDK4/autophagy pathway protects against advanced glycation end-products induced vascular smooth muscle cell calcification

Osteogenic differentiation of VSMC is one of the main causes of diabetic vascular calcification, and AGEs accumulation accelerates the calcification of VSMCs in diabetic patients. Autophagy has also been found to play an important role in the process of vascular calcification. However, the potential link between AGEs, autophagy and vascular calcification is still unclear and was investigated in this study. Primary VSMCs were isolated from the thoracic aorta of Sprague Dawley rats and cultured with AGEs-BSA to induce osteogenic differentiation. VSMCs calcification was evaluated by measuring the calcium content, RUNX2 protein levels, and by Alizarin red S staining. We demonstrated that treatment of VSMCs with AGE-BSA increased the expression of HIF-1α and PDK4. AGE-BSA treatment increased LC3-II and decreased p62 protein levels. AGE-BSA exposure enhanced autophagic flux determined by mRFP-GFP-LC3 adenovirus, induced co-localization of LC3-II and LAMP-1, and increased the number of autophagasome under TEM. HIF-1α/PDK4 pathway was activated during AGEs-induced autophagy of VSMCs. In addition, autophagy played a protective role during AGE-induced calcification of VSMCs. In conclusion, AGEs enhance autophagy via the HIF-1α/PDK4 signaling pathway, and autophagy helps attenuate AGE-induced calcification of VSMCs.

Lactate accelerates calcification in VSMCs through suppression of BNIP3-mediated mitophagy

Arterial media calcification is one of the major complications of diabetes mellitus, which is related to oxidative stress and apoptosis. Mitophagy is a special regulation of mitochondrial homeostasis and takes control of intracellular ROS generation and apoptotic pathways. High circulating levels of lactate usually accompanies diabetes. The potential link between lactate, mitophagy and vascular calcification is investigated in this study. Lactate treatment accelerated VSMC calcification, evaluated by measuring the calcium content, ALP activity, RUNX2, BMP-2 protein levels, and Alizarin red S staining. Lactate exposure caused excessive intracellular ROS generation and VSMC apoptosis. Lactate also impaired mitochondrial function, determined by mPTP opening rate, mitochondrial membrane potential and mitochondrial biogenesis markers. Western blot analysis of LC3-II and p62 and mRFP-GFP-LC3 adenovirus detection for autophagy flux revealed that lactate blocked autophagy flux. LC3-II co-staining with LAMP-1 and autophagosome quantification revealed lactate inhibited autophagy. Furthermore, lactate inhibited mitophagy, which was confirmed by TOMM20 and BNIP3 protein levels, LC3-II colocalization with BNIP3 and TEM assays. In addition, BNIP3-mediated mitophagy played a protective role against VSMC calcification in the presence of lactate. This study suggests that lactate accelerates osteoblastic phenotype transition of VSMC and calcium deposition partly through the BNIP3-mediated mitophagy deficiency induced oxidative stress and apoptosis.

GW29-e0328 Lactate promotes VSMCs calcification via MCT1-induced apoptosis

GW29-e0328 Lactate promotes VSMCs calcification via MCT1-induced apoptosis

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

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

MiR-26a regulates vascular smooth muscle cell calcification in vitro through targeting CTGF.

Vascular calcification is one of the most important factors for high morbidity and mortality from cardiovascular and cerebrovascular diseases. The aim of this study is to investigate the effect and mechanism of miR-26a on vascular smooth muscle cell calcification. First, the VSMCs were induced by β-glycerol phosphate (β-GP) for 7d and 14d, and Alizarin Red S staining was performed to examine the mineralized nodule change; then real time RT-PCR and western blotting were performed to explore the expression of miR-26a, CTGF, OPG, RANKL and ALP in un-induced and β-GP-induced VSMCs; next, the VSMCs were transfected with miR-26a mimics, and Alizarin Red S staining was performed to examine the mineralized nodule change; finally, real time RT-PCR and western blotting were performed to explore the expression of miR-26a, CTGF, OPG, RANKL and ALP in un-transfected and miR-26a mimics transfected VSMCs. After β-GP treatment, β-GP promoted clear mineralized nodule changes, and miR-26a and OPG expression were significantly decreased and CTGF, RANKL and ALP expression were increased in VSMCs. Overexpression of miR-26a inhibited VSMCs calcification induced by β-GP, and regulated the expression of CTGF, OPG, RANKL and ALP. Our findings suggested that up-regulation of miR-26a before β-GP treatment inhibits VSMCs calcification through targeting CTGF (Fig. 4, Ref. 18).

Nedd4 Deficiency in Vascular Smooth Muscle Promotes Vascular Calcification by Stabilizing pSmad1

The nonosseous calcification process such as atherosclerosis is one of the major complications in several types of metabolic diseases. In a previous study, we uncovered that aberrant activity of transforming growth factor β (TGF-β) signaling pathway could contribute to the vascular smooth muscle cells' (VSMCs) calcification process. Also, we identified NEDD4 E3 ligase as a key suppressor of bone morphogenetic protein (BMP)/Smad pathway via a polyubiquitination-dependent selective degradation of C-terminal phosphorylated Smad1 (pSmad1) activated by TGF-β. Here, we further validated and confirmed the role of Nedd4 in in vivo vascular calcification progression. First, Nedd4 deletion in SM22α-positive mouse tissues (Nedd4fl/fl ;SM22α-Cre) showed deformed aortic structures with disarranged elastin fibers at 24 weeks after birth. Second, vitamin D-induced aorta vascular calcification rate in Nedd4fl/fl ;SM22α-Cre mice was significantly higher than their wild-type littermates. Nedd4fl/fl ;SM22α-Cre mice showed a development of vascular calcification even at very low-level injection of vitamin D, but this was not exhibited in wild-type littermates. Third, we confirmed that TGF-β1-induced pSmad1 levels were elevated in Nedd4-deficient primary VSMCs isolated from Nedd4fl/fl ;SM22α-Cre mice. Fourth, we further found that Nedd4fl/fl ;SM22α-Cre mVSMCs gained mesenchymal cell properties toward osteoblast-like differentiation by a stable isotope labeling in cell culture (SILAC)-based proteomics analysis. Finally, epigenetic analysis revealed that methylation levels of human NEDD4 gene promoter were significantly increased in atherosclerosis patients. Collectively, abnormal expression or dysfunction of Nedd4 E3 ligase could be involved in vascular calcification of VSMCs by activating bone-forming signals during atherosclerosis progression. © 2016 American Society for Bone and Mineral Research.

Estrogen Inhibits Calcification of VSMCs via Promotion of Autophagy

Estrogen Inhibits Calcification of VSMCs via Promotion of Autophagy

Intra-Section Analysis of Human Coronary Arteries Reveals a Potential Role for Micro-Calcifications in Macrophage Recruitment in the Early Stage of Atherosclerosis.

BackgroundVascular calcification is associated with poor cardiovascular outcome. Histochemical analysis of calcification and the expression of proteins involved in mineralization are usually based on whole section analysis, thereby often ignoring regional differences in atherosclerotic lesions. At present, limited information is available about factors involved in the initiation and progression of atherosclerosis.Aim of This StudyThis study investigates the intra-section association of micro-calcifications with markers for atherosclerosis in randomly chosen section areas of human coronary arteries. Moreover, the possible causal relationship between calcifying vascular smooth muscle cells and inflammation was explored in vitro.Technical ApproachTo gain insights into the pathogenesis of atherosclerosis, we performed analysis of the distribution of micro-calcifications using a 3-MeV proton microbeam. Additionally, we performed systematic analyses of 30 to 40 regions of 12 coronary sections obtained from 6 patients including histology and immuno-histochemistry. Section areas were classified according to CD68 positivity. In vitro experiments using human vascular smooth muscle cells (hVSMCs) were performed to evaluate causal relationships between calcification and inflammation.ResultsFrom each section multiple areas were randomly chosen and subsequently analyzed. Depositions of calcium crystals at the micrometer scale were already observed in areas with early pre-atheroma type I lesions. Micro-calcifications were initiated at the elastica interna concomitantly with upregulation of the uncarboxylated form of matrix Gla-protein (ucMGP). Both the amount of calcium crystals and ucMGP staining increased from type I to IV atherosclerotic lesions. Osteochondrogenic markers BMP-2 and osteocalcin were only significantly increased in type IV atheroma lesions, and at this stage correlated with the degree of calcification. From atheroma area type III onwards a considerable number of CD68 positive cells were observed in combination with calcification, suggesting a pro-inflammatory effect of micro-calcifications. In vitro, invasion assays revealed chemoattractant properties of cell-culture medium of calcifying vascular smooth muscle cells towards THP-1 cells, which implies pro-inflammatory effect of calcium deposits. Additionally, calcifying hVSMCs revealed a pro-inflammatory profile as compared to non-calcifying hVSMCs.ConclusionOur data indicate that calcification of VSMCs is one of the earliest events in the genesis of atherosclerosis, which strongly correlates with ucMGP staining. Our findings suggest that loss of calcification inhibitors and/or failure of inhibitory capacity is causative for the early precipitation of calcium, with concomitant increased inflammation followed by osteochondrogenic transdifferentiation of VSMCs.