Tumour necrosis factor-alpha in uraemic serum promotes osteoblastic transition and calcification of vascular smooth muscle cells via extracellular signal-regulated kinases and activator protein 1/c-FOS-mediated induction of interleukin 6 expression

Stimulation of endothelin-1 production by autoantibodies present in patients with scleroderma renal crisis

Here, we investigate how autoantibodies against G protein-coupled receptors (GPCRs) on endothelial cells, which are present in patients with scleroderma renal crisis (SRC) impact on endothelin-1 (ET-1) production in human microvascular endothelial cells (HMECs). To this end, serum IgG fraction was isolated from SRC patients and applied to HMECs in culture. Compared to cells treated with either plain control medium or serum IgG from healthy individuals, exposure of HMECs to SRC-IgG resulted in a time- and concentration-dependent increase in ET-1 expression and release. This effect could be blocked by the protease activated receptor 1 (PAR1) inhibitor and mimicked by thrombin, the PAR1 activator. Transcription factor C-FOS/AP-1 and tissue factor (TF) were identified as mediators of these responses. Thus, it can be concluded that serum IgG fraction from SRC patients stimulates endothelial cells to produce ET-1, acting through PAR1 in cooperation with TF.

Advances in the mechanisms of vascular calcification in chronic kidney disease

Vascular calcification (VC) is common in patients with advanced chronic kidney disease (CKD).A series of factors, such as calcium and phosphorus metabolism disorders, uremic toxin accumulation, inflammation and oxidative stress and cellular senescence, cause osteoblast-like differentiation of vascular smooth muscle cells, secretion of extracellular vesicles, and imbalance of calcium regulatory factors, which together promote the development of VC in CKD. Recent advances in epigenetics have provided better tools for the investigation of VC etiology and new approaches for finding more accurate biomarkers. These advances have not only deepened our understanding of the pathophysiological mechanisms of VC in CKD, but also provided valuable clues for the optimization of clinical predictors and the exploration of potential therapeutic targets. The aim of this article is to provide a comprehensive overview of the pathogenesis of CKD VC, especially the new advances made in recent years, including the various key factors mentioned above. Through the comprehensive analysis, we expect to provide a solid theoretical foundation and research direction for future studies targeting the specific mechanisms of CKD VC, the establishment of clinical predictive indicators and the development of potential therapeutic strategies.

Roles of Lysyl oxidases (LOX(L)) in pathologic calcification

Calcification of tissues involves the formation and deposition of calcium-containing crystals in the extracellular matrix (ECM). While this process is normal in bones, it becomes pathological when it occurs in cardiovascular and musculoskeletal soft tissues. Pathological calcification (PC) triggers detrimental pathways such as inflammation and oxidative stress, contributing to tissue damage and dysregulated tissue biomechanics, ultimately leading to severe complications and even death. The underlying mechanisms of PC remain elusive. Emerging evidence suggests a significant role of lysyl oxidases (LOX(L)) in PC. LOX(L) are a group of five enzymes involved in collagen cross-linking and ECM maturation. Beyond their classical role in bone mineralization, recent investigations propose new non-classical roles for LOX(L) that could be relevant in PC. In this review, we analyzed and summarized the functions of LOX(L) in cardiovascular and musculoskeletal PC, highlighting their deleterious roles in most studies. To date, specific inhibitors targeting LOX(L) isoforms are under development. New therapeutic tools targeting LOX(L) are warranted in PC and must avoid adverse effects on physiological bone mineralization.

Role of Uremic Toxins in Vascular Inflammation Associated with Chronic Kidney Disease

Cardiovascular disease (CVD) is a major complication of chronic kidney disease (CKD), despite improvements in patient care. Vascular inflammation is a crucial process in the pathogenesis of CVD and a critical factor in the cardiovascular complications in CKD patients. CKD promotes a pro-inflammatory environment that impacts the vascular wall, leading to endothelial dysfunction, increased oxidative stress, and vascular remodeling. The uremic toxins that accumulate as kidney function declines are key contributors to vascular inflammatory processes. Our review will examine how CKD leads to vascular inflammation, paving the way to CVD. We will provide an overview of the mechanisms of vascular inflammation induced by uremic toxins, with a particular focus on those derived from tryptophan metabolism. These toxins, along with their receptor, the aryl hydrocarbon receptor (AHR), have emerged as key players linking inflammation and thrombosis. A deeper understanding of the mechanisms underlying inflammation in CKD, particularly those driven by uremic toxins, could reveal valuable therapeutic targets to alleviate the burden of CVD in CKD patients.

Contribution of FOS in neutrophils to venous thromboembolism via miR-144 based on bioinformatic prediction and validation

The Finkel-Biskis-Jinkins Osteosarcoma (c-Fos; encoded by FOS) plays an important role in several cardiovascular diseases, including atherosclerosis and stroke. However, the relationship between FOS and venous thromboembolism (VTE) remains unknown. We identified differentially expressed genes in Gene Expression Omnibus dataset, GSE48000, comprising VTE patients and healthy individuals, and analysed them using CIBERSORT and weighted co-expression network analysis (WGCNA). FOS and CD46 expressions were significantly downregulated (FOS p = 2.26E-05, CD64 p = 8.83E-05) and strongly linked to neutrophil activity in VTE. We used GSE19151 and performed PCR to confirm that FOS and CD46 had diagnostic potential for VTE; however, only FOS showed differential expression by PCR and ELISA in whole blood samples. Moreover, we found that hsa-miR-144 which regulates FOS expression was significantly upregulated in VTE. Furthermore, FOS expression was significantly downregulated in neutrophils of VTE patients (p = 0.03). RNA sequencing performed on whole blood samples of VTE patients showed that FOS exerted its effects in VTE via the leptin-mediated adipokine signalling pathway. Our results suggest that FOS and related genes or proteins can outperform traditional clinical markers and may be used as diagnostic biomarkers for VTE.

Caspase-3/gasdermin-E axis facilitates the progression of coronary artery calcification by inducing the release of high mobility group box protein 1

Coronary artery calcification (CAC) is commonly observed in atherosclerotic plaques, which is a pathogenic factor for severe coronary artery disease (CAD). The phenotype changes of vascular smooth muscle cells (VSMCs) are found to participate in CAC progression, which is mainly induced by vascular inflammation and oxidative stress (OS). HMGB1, a critical inflammatory cytokine, is recently reported to induce arterial calcification, which is regulated by the Caspase-3/gasdermin-E (GSDME) axis. However, the function of the Caspase-3/GSDME axis in CAC is unknown. Herein, the involvement of the Caspase-3/GSDME axis in CAC was studied to explore the possible targets for CAC. CAC model was constructed in mice, which was verified by red cytoplasm in coronary artery tissues, increased macrophage infiltration, aggravated inflammation, and enhanced RAGE signaling, accompanied by an increased release of HMGB1 and an activated Caspase-3/ GSDME axis. In β-GP-treated MOVAS-1 cells, calcification, the ROS accumulation, enhanced LDH and HMGB1 release, enlarged macrophage production, aggravated inflammation, and activated RAGE signaling were observed, which were markedly abolished by the transfection of si-HMGB1 and si-GSDME. Moreover, the calcification deposition, the activity of Caspase-3/ GSDME axis, release of HMGB1, macrophage infiltration, cytokine production, and RAGE signaling in CAC mice were notably alleviated by VSMCs-specific GSDME knockdown, not by hematopoietic stem cells (HSCs)-specific GSDME knockdown. Collectively, Caspase-3/GSDME axis facilitated the progression of CAC by inducing the release of HMGB1.

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.

Vascular calcification and cellular signaling pathways as potential therapeutic targets

Increased vascular calcification (VC) is observed in patients with cardiovascular diseases such as atherosclerosis, diabetes, and chronic kidney disease. VC is divided into three types according to its location: intimal, medial, and valvular. Various cellular signaling pathways are associated with VC, including the Wnt, mitogen-activated protein kinase, phosphatidylinositol-3 kinase/Akt, cyclic nucleotide-dependent protein kinase, protein kinase C, calcium/calmodulin-dependent kinase II, adenosine monophosphate-activated protein kinase/mammalian target of rapamycin, Ras homologous GTPase, apoptosis, Notch, and cytokine signaling pathways. In this review, we discuss the literature concerning the key cellular signaling pathways associated with VC and their role as potential therapeutic targets. Inhibitors to these pathways represent good candidates for use as potential therapeutic agents for the prevention and treatment of VC.

Autoantibodies from patients with kidney allograft vasculopathy stimulate a proinflammatory switch in endothelial cells and monocytes mediated via GPCR-directed PAR1-TNF-α signaling

Non-HLA-directed regulatory autoantibodies (RABs) are known to target G-protein coupled receptors (GPCRs) and thereby contribute to kidney transplant vasculopathy and failure. However, the detailed underlying signaling mechanisms in human microvascular endothelial cells (HMECs) and immune cells need to be clarified in more detail. In this study, we compared the immune stimulatory effects and concomitant intracellular and extracellular signaling mechanisms of immunoglobulin G (IgG)-fractions from kidney transplant patients with allograft vasculopathy (KTx-IgG), to that from patients without vasculopathy, or matched healthy controls (Con-IgG). We found that KTx-IgG from patients with vasculopathy, but not KTx-IgG from patients without vasculopathy or Con-IgG, elicits HMEC activation and subsequent upregulation and secretion of tumor necrosis factor alpha (TNF-α) from HMECs, which was amplified in the presence of the protease-activated thrombin receptor 1 (PAR1) activator thrombin, but could be omitted by selectively blocking the PAR1 receptor. The amount and activity of the TNF-α secreted by HMECs stimulated with KTx-IgG from patients with vasculopathy was sufficient to induce subsequent THP-1 monocytic cell activation. Furthermore, AP-1/c-FOS, was identified as crucial transcription factor complex controlling the KTx-IgG-induced endothelial TNF-α synthesis, and mircoRNA-let-7f-5p as a regulatory element in modulating the underlying signaling cascade. In conclusion, exposure of HMECs to KTx-IgG from patients with allograft vasculopathy, but not KTx-IgG from patients without vasculopathy or healthy Con-IgG, triggers signaling through the PAR1-AP-1/c-FOS-miRNA-let7-axis, to control TNF-α gene transcription and TNF-α-induced monocyte activation. These observations offer a greater mechanistic understanding of endothelial cells and subsequent immune cell activation in the clinical setting of transplant vasculopathy that can eventually lead to transplant failure, irrespective of alloantigen-directed responses.

Expanded Hemodialysis ameliorates uremia-induced impairment of vasculoprotective KLF2 and concomitant proinflammatory priming of endothelial cells through an ERK/AP1/cFOS-dependent mechanism

Aims

Expanded hemodialysis (HDx) therapy with improved molecular cut-off dialyzers exerts beneficial effects on lowering uremia-associated chronic systemic microinflammation, a driver of endothelial dysfunction and cardiovascular disease (CVD) in hemodialysis (HD) patients with end-stage renal disease (ESRD). However, studies on the underlying molecular mechanisms are still at an early stage. Here, we identify the (endothelial) transcription factor Krüppel-like factor 2 (KLF2) and its associated molecular signalling pathways as key targets and regulators of uremia-induced endothelial micro-inflammation in the HD/ESRD setting, which is crucial for vascular homeostasis and controlling detrimental vascular inflammation.

Methods and results

First, we found that human microvascular endothelial cells (HMECs) and other typical endothelial and kidney model cell lines (e.g. HUVECs, HREC, and HEK) exposed to uremic serum from patients treated with two different hemodialysis regimens in the Permeability Enhancement to Reduce Chronic Inflammation II (PERCI-II) crossover clinical trial - comparing High-Flux (HF) and Medium Cut-Off (MCO) membranes - exhibited strongly reduced expression of vasculoprotective KLF2 with HF dialyzers, while dialysis with MCO dialyzers led to the maintenance and restoration of physiological KLF2 levels in HMECs. Mechanistic follow-up revealed that the strong downmodulation of KLF2 in HMECs exposed to uremic serum was mediated by a dominant engagement of detrimental ERK instead of beneficial AKT signalling, with subsequent AP1-/c-FOS binding in the KLF2 promoter region, followed by the detrimental triggering of pleiotropic inflammatory mediators, while the introduction of a KLF2 overexpression plasmid could restore physiological KLF2 levels and downmodulate the detrimental vascular inflammation in a mechanistic rescue approach.

Conclusion

Uremia downmodulates vasculoprotective KLF2 in endothelium, leading to detrimental vascular inflammation, while MCO dialysis with the novel improved HDx therapy approach can maintain physiological levels of vasculoprotective KLF2.

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.

VX-765 ameliorates CKD VSMC calcification by regulating STAT3 activation

BACKGROUND

Recent clinical evidences show that caspase-1 inhibitor-VX-765 attenuates atherosclerosis in ApoE deficient mice. However, there is rarely information about the effect of VX-765 on hyperphosphatemia-induced vascular smooth muscle cells (VSMCs) calcification or vascular calcification in chronic kidney disease (CKD) rats. Here we investigate the effect of VX-765 on vascular calcification in uremia circumstances.

METHODS

Hyperphosphatemia-induced VSMC calcification were evaluated by Alizarin Red S. Aortas from CKD rats which were gavaged with VX-765 were examined for calcification signal using micro-CT. Levels of NLRP3, caspase-1, and GSDMD were measured by quantitative real-time PCR, western blotting, immunofluorescence assay, and immunohistochemistry.

RESULTS

We demonstrated for the first time that the levels of NLRP3, caspase-1, GSDMD, IL-1β, and IL-18 were up-regulated in hyperphosphatemia-induced calcifying VSMCs. Blockade of caspase-1 activation by VX-765 inhibited pyroptosis-related molecules and VSMC calcification in a concentration-dependent manner in vitro. Further analysis of aortas from calcified CKD rats showed an up-regulation of caspase-1 and GSDMD expression compared with those non-calcified vascular tissue from control rats or with those decreased-calcified vascular tissue from CKD rats treated with 50 mg/kg/d, which indicated that pyroptotic indicators were tightly correlated with CKD arterial calcification. In vitro studies further demonstrated that VX-765 ameliorated hyperphosphatemia-induced VSMCs calcification through inhibiting the STAT3 activation.

CONCLUSIONS

Our findings indicated that VX-765 could inhibit hyperphosphatemia-induced calcifying VSMCs and ameliorate vascular calcification in CKD rats. VX-765 might be a potential treatment strategy for CKD vascular calcification.

The crosstalk between endothelial cells and vascular smooth muscle cells aggravates high phosphorus-induced arterial calcification

Arterial calcification is highly prevalent, particularly in patients with end-stage renal disease (ESRD). The osteogenic differentiation of vascular smooth muscle cells (VSMCs) is the critical process for the development of arterial calcification. However, the detailed mechanism of VSMCs calcification remains to be elucidated. Here, we investigated the role of exosomes (Exos) derived from endothelial cells (ECs) in arterial calcification and its potential mechanisms in ESRD. Accelerated VSMCs calcification was observed when VSMCs were exposed to ECs culture media stimulated by uremic serum or high concentration of inorganic phosphate (3.5 mM Pi). and the pro-calcification effect of the ECs culture media was attenuated by exosome depletion. Exosomes derived from high concentrations of inorganic phosphate-induced ECs (ECs^HPi-Exos) could be uptaken by VSMCs and promoted VSMCs calcification. Microarray analysis showed that miR-670-3p was dramatically increased in ECs^HPi-Exos compared with exosomes derived from normal concentrations of inorganic phosphate (0.9 mM Pi) induced ECs (ECs^NPi-Exos). Mechanistically, insulin-like growth factor 1 (IGF-1) was identified as the downstream target of miR-670-3p in regulating VSMCs calcification. Notably, ECs-specific knock-in of miR-670-3p of the 5/6 nephrectomy with a high-phosphate diet (miR-670-3p^EC-KI + NTP) mice that upregulated the level of miR-670-3p in artery tissues and significantly increased artery calcification. Finally, we validated that the level of circulation of plasma exosomal miR-670-3p was much higher in patients with ESRD compared with healthy controls. Elevated levels of plasma exosomal miR-670-3p were associated with a decline in IGF-1 and more severe artery calcification in patients with ESRD. Collectively, these findings suggested that ECs-derived exosomal miR-670-3p could promote arterial calcification by targeting IGF-1, which may serve as a potential therapeutic target for arterial calcification in ESRD patients.

Interleukin 2 receptor subunit beta as a novel hub gene plays a potential role in the immune microenvironment of abdominal aortic aneurysms

BACKGROUND

Abdominal aortic aneurysm (AAA) is potentially life threatening and characterized by immune-inflammatory cell infiltration and extracellular matrix degradation. Currently, pharmacotherapy mainly aims to control risk factors without reversion of the dilated aorta. This study analyzed the immune-inflammatory response and identified the immune-related hub genes of AAA.

METHOD

Gene Expression Omnibus datasets (GSE57691, GSE47472 and GSE7084) were downloaded. After identification of GSE57691 differentially expressed genes (DEGs), weighted gene co-expression network analysis of the DEGs was performed. Through enrichment analysis of each module and screening in Immunology Database and Analysis Portal, immune-related hub genes were identified via protein-protein interaction (PPI) network construction and lasso regression. CIBERSORT was utilized to analyze AAA immune infiltration. The correlations between the immune-related hub genes and infiltrating immune cells were investigated. Receiver operating characteristic (ROC) curve analysis was performed to determine immune-related hub gene cutoff values, which were validated in GSE47472 and GSE7084.

RESULT

In GSE57691, 1,018 DEGs were identified. Five modules were identified in the co-expression network. The blue and green modules were found to be related to immune-inflammatory responses, and 61 immune-related genes were identified. PPI and lasso regression analyses identified FOS, IL-6 and IL2RB as AAA immune-related hub genes. CIBERSORT analysis indicated significantly increased infiltration of naive B cells, memory activated CD4 T cells, follicular helper T cells, monocytes and M1 macrophages and significantly decreased infiltration of M2 macrophages in AAA compared with normal samples. IL2RB was more strongly associated with immune infiltration in AAA than were FOS and IL6. The IL2RB area under the ROC curve (AUC) value was > 0.9 in both the training and validation set, demonstrating its strong, stable diagnostic value in AAA.

CONCLUSION

AAA and normal samples had different immune infiltration statuses. IL2RB was identified as an immune-related hub gene and a potential hub gene with significant diagnostic value in AAA.

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.

Inflammation promotes erythropoietin induced vascular calcification by activating p38 pathway

The current research aimed to verify the effects of erythropoietin (EPO) on vascular calcification under inflammatory conditions and the molecular regulator of vascular calcification induced by EPO. To induce vascular calcification and systemic chronic inflammation in SD rats, EPO was administered intraperitoneally, and 10% casein was injected subcutaneously. The administration period lasted for 20 consecutive weeks. Blood samples were subsequently collected to detect inflammatory factors and vascular calcification. Additionally, high-dose EPOs were applied to stimulate primary vascular smooth muscle cells (VSMCs), and vascular calcification was measured using alizarin red staining, alkaline phosphatase (ALP) activity, and calcium salt quantification. The probe 2',7'-dichlorofluorescein diacetate (DCFH-DA) was employed to detect cellular reactive oxygen species (ROS) levels. The expressions of bone formation-related protein and anti-calcification protein matrix gla protein (MGP) were determined via Western blot. Compared with the control group, calcium deposits and vascular calcification were increased in the EPO group, tumor necrosis factor-alpha (TNF-α) group and TNF-α+ EPO group, whereas MGP was significantly reduced. Moreover, under the stimulation of TNF-α and EPO+TNF-α, pp38/p38 was increased substantially, the addition of p38 inhibitor SB203580 could significantly reduce calcium deposits and vascular calcification. In vivo experiment, compared with the EPO group, calcium salt deposition and vascular calcification were elevated in the EPO+casein group. The present results revealed that high-dose EPO could cause calcification of the abdominal aorta in rats. The inflammatory response aggravated the vascular calcification induced by EPO via activating p38 and ROS levels.

Angiogenic Role of Mesothelium-Derived Chemokine CXCL1 During Unfavorable Peritoneal Tissue Remodeling in Patients Receiving Peritoneal Dialysis as Renal Replacement Therapy

Peritoneal dialysis (PD) is a valuable ‘home treatment’ option, even more so during the ongoing Coronavirus pandemic. However, the long-term use of PD is limited by unfavourable tissue remodelling in the peritoneal membrane, which is associated with inflammation-induced angiogenesis. This appears to be driven primarily through vascular endothelial growth factor (VEGF), while the involvement of other angiogenic signaling pathways is still poorly understood. Here, we have identified the crucial contribution of mesothelial cell-derived angiogenic CXC chemokine ligand 1 (CXCL1) to peritoneal angiogenesis in PD. CXCL1 expression and peritoneal microvessel density were analysed in biopsies obtained by the International Peritoneal Biobank (NCT01893710 at www.clinicaltrials.gov), comparing 13 children with end-stage kidney disease before initiating PD to 43 children on chronic PD. The angiogenic potential of mesothelial cell-derived CXCL1 was assessed in vitro by measuring endothelial tube formation of human microvascular endothelial cells (HMECs) treated with conditioned medium from human peritoneal mesothelial cells (HPMCs) stimulated to release CXCL1 by treatment with either recombinant IL-17 or PD effluent. We found that the capillary density in the human peritoneum correlated with local CXCL1 expression. Both CXCL1 expression and microvessel density were higher in PD patients than in the age-matched patients prior to initiation of PD. Exposure of HMECs to recombinant CXCL1 or conditioned medium from IL-17-stimulated HPMCs resulted in increased endothelial tube formation, while selective inhibition of mesothelial CXCL1 production by specific antibodies or through silencing of relevant transcription factors abolished the proangiogenic effect of HPMC-conditioned medium. In conclusion, peritoneal mesothelium-derived CXCL1 promotes endothelial tube formation in vitro and associates with peritoneal microvessel density in uremic patients undergoing PD, thus providing novel targets for therapeutic intervention to prolong PD therapy.

Expanded Hemodialysis Therapy Ameliorates Uremia-Induced Systemic Microinflammation and Endothelial Dysfunction by Modulating VEGF, TNF-α and AP-1 Signaling

Abstract

Systemic chronic microinflammation and altered cytokine signaling, with adjunct cardiovascular disease (CVD), endothelial maladaptation and dysfunction is common in dialysis patients suffering from end-stage renal disease and associated with increased morbidity and mortality. New hemodialysis filters might offer improvements. We here studied the impact of novel improved molecular cut-off hemodialysis filters on systemic microinflammation, uremia and endothelial dysfunction. Human endothelial cells (ECs) were incubated with uremic serum obtained from patients treated with two different hemodialysis regimens in the Permeability Enhancement to Reduce Chronic Inflammation (PERCI-II) crossover clinical trial, comparing High-Flux (HF) and Medium Cut-Off (MCO) membranes, and then assessed for their vascular endothelial growth factor (VEGF) production and angiogenesis. Compared to HF membranes, dialysis with MCO membranes lead to a reduction in proinflammatory mediators and reduced endothelial VEGF production and angiogenesis. Cytokine multiplex screening identified tumor necrosis factor (TNF) superfamily members as promising targets. The influence of TNF-α and its soluble receptors (sTNF-R1 and sTNF-R2) on endothelial VEGF promoter activation, protein release, and the involved signaling pathways was analyzed, revealing that this detrimental signaling was indeed induced by TNF-α and mediated by AP-1/c-FOS signaling. In conclusion, uremic toxins, in particular TNF-signaling, promote endothelial maladaptation, VEGF expression and aberrant angiogenesis, which can be positively modulated by dialysis with novel MCO membranes.

Translational Perspective and Graphical Abstract

Systemic microinflammation, altered cytokine signaling, cardiovascular disease, and endothelial maladaptation/dysfunction are common clinical complications in dialysis patients suffering from end-stage renal disease. We studied the impact of novel improved medium-cut-off hemodialysis filters on uremia and endothelial dysfunction. We can show that uremic toxins, especially TNF-signaling, promote endothelial maladaptation, VEGF expression and aberrant angiogenesis, which can be positively modulated by dialysis with novel improved medium-cut-off membranes.

Autoantibodies from Patients with Scleroderma Renal Crisis Promote PAR-1 Receptor Activation and IL-6 Production in Endothelial Cells

BACKGROUND

Scleroderma renal crisis (SRC) is a life-threatening complication of systemic sclerosis (SSc). Autoantibodies (Abs) against endothelial cell antigens have been implicated in SSc and SRC. However, their detailed roles remain poorly defined. Pro-inflammatory cytokine interleukin-6 (IL-6) has been found to be increased in SSc, but its role in SRC is unclear. Here, we aimed to determine how the autoantibodies from patients with SSc and SRC affect IL-6 secretion by micro-vascular endothelial cells (HMECs).

METHODS

Serum IgG fractions were isolated from either SSc patients with SRC (n = 4) or healthy individuals (n = 4) and then each experiment with HMECs was performed with SSc-IgG from a separate patient or separate healthy control. IL-6 expression and release by HMECs was assessed by quantitative reverse transcription and quantitative PCR (RT-qPCR) and immunoassays, respectively. The mechanisms underlying the production of IL-6 were analyzed by transient HMEC transfections with IL-6 promoter constructs, electrophoretic mobility shift assays, Western blots and flow cytometry.

RESULTS

Exposure of HMECs to IgG from SSc patients, but not from healthy controls, resulted in a time- and dose-dependent increase in IL-6 secretion, which was associated with increased AKT, p70S6K, and ERK1/2 signalling, as well as increased c-FOS/AP-1 transcriptional activity. All these effects could be reduced by the blockade of the endothelial PAR-1 receptor and/or c-FOS/AP-1silencing.

CONCLUSIONS

Autoantibodies against PAR-1 found in patients with SSc and SRC induce IL-6 production by endothelial cells through signalling pathways controlled by the AP-1 transcription factor. These observations offer a greater understanding of adverse endothelial cell responses to autoantibodies present in patients with SRC.

Atorvastatin Promotes Macrocalcification, But Not Microcalcification in Atherosclerotic Rabbits: An 18F-NaF PET/CT Study

INTRODUCTION

Our study aimed to investigate the effect of atorvastatin on plaque calcification by matching the results obtained by 18F-sodium fluoride (18F-NaF) positron emission tomography (PET)/computed tomography (CT) with data from histologic sections.

METHODS AND RESULTS

The rabbits were divided into 2 groups as follows: an atherosclerosis group (n = 10) and an atorvastatin group (n = 10). All rabbits underwent an abdominal aortic operation and were fed a high-fat diet to induce atherosclerosis. Plasma samples were used to analyze serum inflammation markers and blood lipid levels. 18F-NaF PET/CT scans were performed twice. The plaque area, macrophage number and calcification were measured, and the data from the pathological sections were matched with the 18F-NaF PET/CT scan results. The mean standardized uptake value (0.725 ± 0.126 vs. 0.603 ± 0.071, P < 0.001) and maximum standardized uptake value (1.024 ± 0.116 vs. 0.854 ± 0.091, P < 0.001) significantly increased in the atherosclerosis group, but only slightly increased in the atorvastatin group (0.616 ± 0.103 vs. 0.613 ± 0.094, P = 0.384; 0.853 ± 0.099 vs.0.837 ± 0.089, P < 0.001, respectively). The total calcium density was significantly increased in rabbits treated with atorvastatin compared with rabbits not treated with atorvastatin (1.64 ± 0.90 vs. 0.49 ± 0.35, P < 0.001), but the microcalcification level was significantly lower. There were more microcalcification deposits in the areas with increased radioactive uptake of 18F-NaF.

CONCLUSIONS

Our study suggests that the anti-inflammatory activity of atorvastatin may promote macrocalcification but not microcalcification within atherosclerotic plaques. 18F-NaF PET/CT can detect plaque microcalcifications.

Inflammation: a putative link between phosphate metabolism and cardiovascular disease

Dietary habits in the western world lead to increasing phosphate intake. Under physiological conditions, extraosseous precipitation of phosphate with calcium is prevented by a mineral buffering system composed of calcification inhibitors and tight control of serum phosphate levels. The coordinated hormonal regulation of serum phosphate involves fibroblast growth factor 23 (FGF23), αKlotho, parathyroid hormone (PTH) and calcitriol. A severe derangement of phosphate homeostasis is observed in patients with chronic kidney disease (CKD), a patient collective with extremely high risk of cardiovascular morbidity and mortality. Higher phosphate levels in serum have been associated with increased risk for cardiovascular disease (CVD) in CKD patients, but also in the general population. The causal connections between phosphate and CVD are currently incompletely understood. An assumed link between phosphate and cardiovascular risk is the development of medial vascular calcification, a process actively promoted and regulated by a complex mechanistic interplay involving activation of pro-inflammatory signalling. Emerging evidence indicates a link between disturbances in phosphate homeostasis and inflammation. The present review focuses on critical interactions of phosphate homeostasis, inflammation, vascular calcification and CVD. Especially, pro-inflammatory responses mediating hyperphosphatemia-related development of vascular calcification as well as FGF23 as a critical factor in the interplay between inflammation and cardiovascular alterations, beyond its phosphaturic effects, are addressed.

Uremic Toxins and Frailty in Patients with Chronic Kidney Disease: A Molecular Insight

The accumulation of uremic toxins (UTs) is a prototypical manifestation of uremic milieu that follows renal function decline (chronic kidney disease, CKD). Frailty as a potential outcome-relevant indicator is also prevalent in CKD. The intertwined relationship between uremic toxins, including small/large solutes (phosphate, asymmetric dimethylarginine) and protein-bound ones like indoxyl sulfate (IS) and p-cresyl sulfate (pCS), and frailty pathogenesis has been documented recently. Uremic toxins were shown in vitro and in vivo to induce noxious effects on many organ systems and likely influenced frailty development through their effects on multiple preceding events and companions of frailty, such as sarcopenia/muscle wasting, cognitive impairment/cognitive frailty, osteoporosis/osteodystrophy, vascular calcification, and cardiopulmonary deconditioning. These organ-specific effects may be mediated through different molecular mechanisms or signal pathways such as peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α), mitogen-activated protein kinase (MAPK) signaling, aryl hydrocarbon receptor (AhR)/nuclear factor-κB (NF-κB), nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), Runt-related transcription factor 2 (RUNX2), bone morphogenic protein 2 (BMP2), osterix, Notch signaling, autophagy effectors, microRNAs, and reactive oxygen species induction. Anecdotal clinical studies also suggest that frailty may further accelerate renal function decline, thereby augmenting the accumulation of UTs in affected individuals. Judging from these threads of evidence, management strategies aiming for uremic toxin reduction may be a promising approach for frailty amelioration in patients with CKD. Uremic toxin lowering strategies may bear the potential of improving patients’ outcomes and restoring their quality of life, through frailty attenuation. Pathogenic molecule-targeted therapeutics potentially disconnect the association between uremic toxins and frailty, additionally serving as an outcome-modifying approach in the future.

Calciprotein Particles: Balancing Mineral Homeostasis and Vascular Pathology

[Figure: see text].

Transcriptional Regulation of Thrombin-Induced Endothelial VEGF Induction and Proangiogenic Response

Thrombin, the ligand of the protease-activated receptor 1 (PAR1), is a well-known stimulator of proangiogenic responses in vascular endothelial cells (ECs), which are mediated through the induction of vascular endothelial growth factor (VEGF). However, the transcriptional events underlying this thrombin-induced VEGF induction and angiogenic response are less well understood at present. As reported here, we conducted detailed promotor activation and signal transduction pathway studies in human microvascular ECs, to decipher the transcription factors and the intracellular signaling events underlying the thrombin and PAR-1-induced endothelial VEGF induction. We found that c-FOS is a key transcription factor controlling thrombin-induced EC VEGF synthesis and angiogenesis. Upon the binding and internalization of its G-protein-coupled PAR-1 receptor, thrombin triggers ERK1/2 signaling and activation of the nuclear AP-1/c-FOS transcription factor complex, which then leads to VEGF transcription, extracellular secretion, and concomitant proangiogenic responses of ECs. In conclusion, exposure of human microvascular ECs to thrombin triggers signaling through the PAR-1–ERK1/2–AP-1/c-FOS axis to control VEGF gene transcription and VEGF-induced angiogenesis. These observations offer a greater understanding of endothelial responses to thromboinflammation, which may help to interpret the results of clinical trials tackling the conditions associated with endothelial injury and thrombosis.

Uremic Toxins in the Progression of Chronic Kidney Disease and Cardiovascular Disease: Mechanisms and Therapeutic Targets

Chronic kidney disease (CKD) is a progressive loss of renal function. The gradual decline in kidney function leads to an accumulation of toxins normally cleared by the kidneys, resulting in uremia. Uremic toxins are classified into three categories: free water-soluble low-molecular-weight solutes, protein-bound solutes, and middle molecules. CKD patients have increased risk of developing cardiovascular disease (CVD), due to an assortment of CKD-specific risk factors. The accumulation of uremic toxins in the circulation and in tissues is associated with the progression of CKD and its co-morbidities, including CVD. Although numerous uremic toxins have been identified to date and many of them are believed to play a role in the progression of CKD and CVD, very few toxins have been extensively studied. The pathophysiological mechanisms of uremic toxins must be investigated further for a better understanding of their roles in disease progression and to develop therapeutic interventions against uremic toxicity. This review discusses the renal and cardiovascular toxicity of uremic toxins indoxyl sulfate, p-cresyl sulfate, hippuric acid, TMAO, ADMA, TNF-α, and IL-6. A focus is also placed on potential therapeutic targets against uremic toxicity.

Role of Uremic Toxins in Early Vascular Ageing and Calcification

In patients with advanced chronic kidney disease (CKD), the accumulation of uremic toxins, caused by a combination of decreased excretion secondary to reduced kidney function and increased generation secondary to aberrant expression of metabolite genes, interferes with different biological functions of cells and organs, contributing to a state of chronic inflammation and other adverse biologic effects that may cause tissue damage. Several uremic toxins have been implicated in severe vascular smooth muscle cells (VSMCs) changes and other alterations leading to vascular calcification (VC) and early vascular ageing (EVA). The above mentioned are predominant clinical features of patients with CKD, contributing to their exceptionally high cardiovascular mortality. Herein, we present an update on pathophysiological processes and mediators underlying VC and EVA induced by uremic toxins. Moreover, we discuss their clinical impact, and possible therapeutic targets aiming at preventing or ameliorating the harmful effects of uremic toxins on the vasculature.

Vascular dysfunction as a potential culprit of sarcopenia

Aging-related changes to biological structures such as cardiovascular and musculoskeletal systems contribute to the development of comorbid conditions including cardiovascular disease and frailty, and ultimately lead to premature death. Although, frail older adults often demonstrate both cardiovascular and musculoskeletal comorbidities, the etiology of sarcopenia, and especially the contribution of cardiovascular aging is unclear. Aging-related vascular calcification is prevalent in older adults and is a known risk factor for cardiovascular disease and death. The effect vascular calcification has on function during aging is not well understood. Emerging findings suggest vascular calcification can impact skeletal muscle perfusion, negatively affecting nutrient and oxygen delivery to skeletal muscle, ultimately accelerating muscle loss and functional decline. The present review summarizes existing evidence on the biological mechanisms linking vascular calcification with sarcopenia during aging.

Empagliflozin restores chronic kidney disease-induced impairment of endothelial regulation of cardiomyocyte relaxation and contraction

Chronic kidney disease (CKD) promotes development of cardiac abnormalities and is highly prevalent in patients with heart failure, particularly in those with preserved ejection fraction. CKD is associated with endothelial dysfunction, however, whether CKD can induce impairment of endothelium-to-cardiomyocyte crosstalk leading to impairment of cardiomyocyte function is not known. The sodium-glucose co-transporter 2 inhibitor, empagliflozin, reduced cardiovascular events in diabetic patients with or without CKD, suggesting its potential as a new treatment for heart failure with preserved ejection fraction. We hypothesized that uremic serum from patients with CKD would impair endothelial control of cardiomyocyte relaxation and contraction, and that empagliflozin would protect against this effect. Using a co-culture system of human cardiac microvascular endothelial cells with adult rat ventricular cardiomyocytes to measure cardiomyocyte relaxation and contraction, we showed that serum from patients with CKD impaired endothelial enhancement of cardiomyocyte function which was rescued by empagliflozin. Exposure to uremic serum reduced human cardiac microvascular endothelial cell nitric oxide bioavailability, and increased mitochondrial reactive oxygen species and 3-nitrotyrosine levels, indicating nitric oxide scavenging by reactive oxygen species. Empagliflozin attenuated uremic serum-induced generation of endothelial mitochondrial reactive oxygen species, leading to restoration of nitric oxide production and endothelium-mediated enhancement of nitric oxide levels in cardiomyocytes, an effect largely independent of sodium-hydrogen exchanger-1. Thus, empagliflozin restores the beneficial effect of cardiac microvascular endothelial cells on cardiomyocyte function by reducing mitochondrial oxidative damage, leading to reduced reactive oxygen species accumulation and increased endothelial nitric oxide bioavailability.

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 Crossroads between Infection and Bone Loss

Bone homeostasis, based on a tight balance between bone formation and bone degradation, is affected by infection. On one hand, some invading pathogens are capable of directly colonizing the bone, leading to its destruction. On the other hand, immune mediators produced in response to infection may dysregulate the deposition of mineral matrix by osteoblasts and/or the resorption of bone by osteoclasts. Therefore, bone loss pathologies may develop in response to infection, and their detection and treatment are challenging. Possible biomarkers of impaired bone metabolism during chronic infection need to be identified to improve the diagnosis and management of infection-associated osteopenia. Further understanding of the impact of infections on bone metabolism is imperative for the early detection, prevention, and/or reversion of bone loss. Here, we review the mechanisms responsible for bone loss as a direct and/or indirect consequence of infection.

Uremic Toxins Affecting Cardiovascular Calcification: A Systematic Review

Cardiovascular calcification is highly prevalent and associated with increased morbidity in chronic kidney disease (CKD). This review examines the impact of uremic toxins, which accumulate in CKD due to a failing kidney function, on cardiovascular calcification. A systematic literature search identified 41 uremic toxins that have been studied in relation to cardiovascular calcification. For 29 substances, a potentially causal role in cardiovascular calcification was addressed in in vitro or animal studies. A calcification-inducing effect was revealed for 16 substances, whereas for three uremic toxins, namely the guanidino compounds asymmetric and symmetric dimethylarginine, as well as guanidinosuccinic acid, a calcification inhibitory effect was identified in vitro. At a mechanistic level, effects of uremic toxins on calcification could be linked to the induction of inflammation or oxidative stress, smooth muscle cell osteogenic transdifferentiation and/or apoptosis, or alkaline phosphatase activity. For all middle molecular weight and protein-bound uremic toxins that were found to affect cardiovascular calcification, an increasing effect on calcification was revealed, supporting the need to focus on an increased removal efficiency of these uremic toxin classes in dialysis. In conclusion, of all uremic toxins studied with respect to calcification regulatory effects to date, more uremic toxins promote rather than reduce cardiovascular calcification processes. Additionally, it highlights that only a relatively small part of uremic toxins has been screened for effects on calcification, supporting further investigation of uremic toxins, as well as of associated post-translational modifications, on cardiovascular calcification processes.

Regulation of Vascular Calcification by Reactive Oxygen Species

Vascular calcification is the deposition of hydroxyapatite crystals in the medial or intimal layers of arteries that is usually associated with other pathological conditions including but not limited to chronic kidney disease, atherosclerosis and diabetes. Calcification is an active, cell-regulated process involving the phenotype transition of vascular smooth muscle cells (VSMCs) from contractile to osteoblast/chondrocyte-like cells. Diverse triggers and signal transduction pathways have been identified behind vascular calcification. In this review, we focus on the role of reactive oxygen species (ROS) in the osteochondrogenic phenotype switch of VSMCs and subsequent calcification. Vascular calcification is associated with elevated ROS production. Excessive ROS contribute to the activation of certain osteochondrogenic signal transduction pathways, thereby accelerating osteochondrogenic transdifferentiation of VSMCs. Inhibition of ROS production and ROS scavengers and activation of endogenous protective mechanisms are promising therapeutic approaches in the prevention of osteochondrogenic transdifferentiation of VSMCs and subsequent vascular calcification. The present review discusses the formation and actions of excess ROS in different experimental models of calcification, and the potential of ROS-lowering strategies in the prevention of this deleterious condition.

Uremic Toxins and Vascular Calcification-Missing the Forest for All the Trees

The cardiorenal syndrome relates to the detrimental interplay between the vascular system and the kidney. The uremic milieu induced by reduced kidney function alters the phenotype of vascular smooth muscle cells (VSMC) and promotes vascular calcification, a condition which is strongly linked to cardiovascular morbidity and mortality. Biological mechanisms involved include generation of reactive oxygen species, inflammation and accelerated senescence. A better understanding of the vasotoxic effects of uremic retention molecules may reveal novel avenues to reduce vascular calcification in CKD. The present review aims to present a state of the art on the role of uremic toxins in pathogenesis of vascular calcification. Evidence, so far, is fragmentary and limited with only a few uremic toxins being investigated, often by a single group of investigators. Experimental heterogeneity furthermore hampers comparison. There is a clear need for a concerted action harmonizing and standardizing experimental protocols and combining efforts of basic and clinical researchers to solve the complex puzzle of uremic vascular calcification.

Attenuating Effects of Pyrogallol-Phloroglucinol-6,6-Bieckol on Vascular Smooth Muscle Cell Phenotype Changes to Osteoblastic Cells and Vascular Calcification Induced by High Fat Diet

Advanced glycation end products/receptor for AGEs (AGEs/RAGEs) or Toll like receptor 4 (TLR4) induce vascular smooth muscle cell (VSMC) phenotype changes in osteoblast-like cells and vascular calcification. We analyzed the effect of Ecklonia cava extract (ECE) or pyrogallol-phloroglucinol-6,6-bieckol (PPB) on VSMC phenotype changes and vascular calcification prompted by a high-fat diet (HFD). HFD unregulated RAGE, TLR4, transforming growth factor beta (TGFβ), bone morphogenetic protein 2 (BMP2), protein kinase C (PKC), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signals in the aorta of mice. ECE and PPB restored the increase of those signal pathways. AGE- or palmitate-treated VSMC indicated similar changes with the animal. HFD increased osteoblast-like VSMC, which was evaluated by measuring core-binding factor alpha-1 (CBFα-1) and osteocalcin expression and alkaline phosphatase (ALP) activity in the aorta. ECE and PPB reduced vascular calcification, which was analyzed by the calcium deposition ratio, and Alizarin red S stain was increased by HFD. PPB and ECE reduced systolic, diastolic, and mean blood pressure, which increased by HFD. PPB and ECE reduced the phenotype changes of VSMC to osteoblast-like cells and vascular calcification and therefore lowered the blood pressure.

Network determinants of cardiovascular calcification and repositioned drug treatments

Ectopic cardiovascular calcification is a highly prevalent pathology for which there are no effective novel or repurposed pharmacotherapeutics to prevent disease progression. We created a human calcification endophenotype module (ie, the "calcificasome") by mapping vascular calcification genes (proteins) to the human vascular smooth muscle-specific protein-protein interactome (218 nodes and 632 edges, P < 10^-5 ). Network proximity analysis was used to demonstrate that the calcificasome overlapped significantly with endophenotype modules governing inflammation, thrombosis, and fibrosis in the human interactome (P < 0.001). A network-based drug repurposing analysis further revealed that everolimus, temsirolimus, and pomalidomide are predicted to target the calcificasome. The efficacy of these agents in limiting calcification was confirmed experimentally by treating human coronary artery smooth muscle cells in an in vitro calcification assay. Each of the drugs affected expression or activity of their predicted target in the network, and decreased calcification significantly (P < 0.009). An integrated network analytical approach identified novel mediators of ectopic cardiovascular calcification and biologically plausible candidate drugs that could be repurposed to target calcification. This methodological framework for drug repurposing has broad applicability to other diseases.

Zinc ameliorates human aortic valve calcification through GPR39 mediated ERK1/2 signalling pathway

AIMS

Calcific aortic valve disease (CAVD) is the most common heart valve disease in the Western world. It has been reported that zinc is accumulated in calcified human aortic valves. However, whether zinc directly regulates CAVD is yet to be elucidated. The present study sought to determine the potential role of zinc in the pathogenesis of CAVD.

METHODS AND RESULTS

Using a combination of a human valve interstitial cell (hVIC) calcification model, human aortic valve tissues, and blood samples, we report that 20 μM zinc supplementation attenuates hVIC in vitro calcification, and that this is mediated through inhibition of apoptosis and osteogenic differentiation via the zinc-sensing receptor GPR39-dependent ERK1/2 signalling pathway. Furthermore, we report that GPR39 protein expression is dramatically reduced in calcified human aortic valves, and there is a significant reduction in zinc serum levels in patients with CAVD. Moreover, we reveal that 20 μM zinc treatment prevents the reduction of GPR39 observed in calcified hVICs. We also show that the zinc transporter ZIP13 and ZIP14 are significantly increased in hVICs in response to zinc treatment. Knockdown of ZIP13 or ZIP14 significantly inhibited hVIC in vitro calcification and osteogenic differentiation.

CONCLUSIONS

Together, these findings suggest that zinc is a novel inhibitor of CAVD, and report that zinc transporter ZIP13 and ZIP14 are important regulators of hVIC in vitro calcification and osteogenic differentiation. Zinc supplementation may offer a potential therapeutic strategy for CAVD.

Induced osteogenic differentiation of human smooth muscle cells as a model of vascular calcification

Vascular calcification is a severe pathological event in the manifestation of atherosclerosis. Pathogenic triggers mediating osteogenic differentiation of arterial smooth muscle cells (SMC) in humans remain insufficiently understood and are to a large extent investigated in animal models or cells derived thereof. Here, we describe an in vitro model based on SMC derived from healthy and diseased humans that allows to comprehensively investigate vascular calcification mechanisms. Comparing the impact of the commonly used SMC culture media VascuLife, DMEM, and M199, cells were characterised by immunofluorescence, flow cytometry, qPCR, and regarding their contractility and proliferative capacity. Irrespective of the arterial origin, the clinical background and the expansion medium used, all cells expressed typical molecular SMC marker while contractility varied between donors. Interestingly, the ability to induce an osteogenic differentiation strongly depended on the culture medium, with only SMC cultured in DMEM depositing calcified matrix upon osteogenic stimulation, which correlated with increased alkaline phosphatase activity, increased inorganic phosphate level and upregulation of osteogenic gene markers. Our optimized model is suitable for donor-oriented as well as broader screening of potential pathogenic mediators triggering vascular calcification. Translational studies aiming to identify and to evaluate therapeutic targets in a personalized fashion would be feasible.

Geniposide alleviates atherosclerosis by regulating macrophage polarization via the FOS/MAPK signaling pathway

OBJECTIVE

To assess geniposide's effects in New Zealand rabbits with high-fat diet induced atherosclerosis and to explore the underpinning mechanisms.

MATERIALS AND METHODS

Aorta histological changes were evaluated by intravenous ultrasound (IVUS) and H&E staining. Lipid accumulation in the aortic was quantified by Oil Red O staining. Then, RNA sequencing (RNA-seq) was carried out for detecting differentially expressed genes in rabbit high-fat diet induced atherosclerosis. The levels of the cytokines CRP, IL-1β and IL-10 were determined by ELISA. Protein levels of iNOS and Arg-1 were assessed by Western blot and immunohistochemical staining. The mRNA expression levels of NR4A1, CD14, FOS, IL1A, iNOS and Arg-1 were detected by quantitative real-time PCR (qPCR).

RESULTS

Geniposide markedly reduced the degree of atherosclerotic lesions in aorta tissues. RNA-seq and qPCR demonstrated that NR4A1, CD14, FOS and IL1A mRNA amounts were overtly increased in New Zealand rabbits with high-fat diet induced atherosclerosis. Moreover, geniposide reduced iNOS (M1 phenotype) mRNA and protein amounts as well as IL-1β secretion, which were enhanced in New Zealand rabbits with high-fat diet induced atherosclerosis. Besides, Arg-1 (M2 phenotype) mRNA and protein amounts were significantly increased after geniposide treatment, as well as IL-10 secretion.

CONCLUSION

These findings suggest that geniposide could inhibit the progression of and stabilize atherosclerotic plaques in rabbits by suppressing M1 macrophage polarization and promoting M2 polarization through the FOS/MAPK signaling pathway.

Calcium Phosphate Bions Cause Intimal Hyperplasia in Intact Aortas of Normolipidemic Rats through Endothelial Injury

Calcium phosphate bions (CPBs) are formed under blood supersaturation with calcium and phosphate owing to the mineral chaperone fetuin-A and representing mineralo-organic particles consisting of bioapatite and multiple serum proteins. While protecting the arteries from a rapid medial calcification, CPBs cause endothelial injury and aggravate intimal hyperplasia in balloon-injured rat aortas. Here, we asked whether CPBs induce intimal hyperplasia in intact rat arteries in the absence of cardiovascular risk factors. Normolipidemic Wistar rats were subjected to regular (once/thrice per week over 5 weeks) tail vein injections of either spherical (CPB-S) or needle-shaped CPBs (CPB-N), magnesium phosphate bions (MPBs), or physiological saline (n = 5 per group). Neointima was revealed in 3/10 and 4/10 rats which received CPB-S or CPB-N, respectively, regardless of the injection regimen or blood flow pattern in the aortic segments. In contrast, none of the rats treated with MPBs or physiological saline had intimal hyperplasia. The animals also did not display signs of liver or spleen injury as well as extraskeletal calcium deposits. Serum alanine/aspartate transaminases, interleukin-1β, MCP-1/CCL2, C-reactive protein, and ceruloplasmin levels did not differ among the groups. Hence, CPBs may provoke intimal hyperplasia via direct endothelial injury regardless of their shape or type of blood flow.

Multi-Parameter Analysis of Biobanked Human Bone Marrow Stromal Cells Shows Little Influence for Donor Age and Mild Comorbidities on Phenotypic and Functional Properties

Heterogeneous populations of human bone marrow-derived stromal cells (BMSC) are among the most frequently tested cellular therapeutics for treating degenerative and immune disorders, which occur predominantly in the aging population. Currently, it is unclear whether advanced donor age and commonly associated comorbidities affect the properties of ex vivo-expanded BMSCs. Thus, we stratified cells from adult and elderly donors from our biobank (n = 10 and n = 13, mean age 38 and 72 years, respectively) and compared their phenotypic and functional performance, using multiple assays typically employed as minimal criteria for defining multipotent mesenchymal stromal cells (MSCs). We found that BMSCs from both cohorts meet the standard criteria for MSC, exhibiting similar morphology, growth kinetics, gene expression profiles, and pro-angiogenic and immunosuppressive potential and the capacity to differentiate toward adipogenic, chondrogenic, and osteogenic lineages. We found no substantial differences between cells from the adult and elderly cohorts. As positive controls, we studied the impact of in vitro aging and inflammatory cytokine stimulation. Both conditions clearly affected the cellular properties, independent of donor age. We conclude that in vitro aging rather than in vivo donor aging influences BMSC characteristics.

FGF23 and Phosphate-Cardiovascular Toxins in CKD

Elevated levels of fibroblast growth factor 23 (FGF23) and phosphate are highly associated with increased cardiovascular disease and mortality in patients suffering from chronic kidney disease (CKD). As the kidney function declines, serum phosphate levels rise and subsequently induce the secretion of the phosphaturic hormone FGF23. In early stages of CKD, FGF23 prevents the increase of serum phosphate levels and thereby attenuates phosphate-induced vascular calcification, whereas in end-stage kidney disease, FGF23 fails to maintain phosphate homeostasis. Both hyperphosphatemia and elevated FGF23 levels promote the development of hypertension, vascular calcification, and left ventricular hypertrophy by distinct mechanisms. Therefore, FGF23 and phosphate are considered promising therapeutic targets to improve the cardiovascular outcome in CKD patients. Previous therapeutic strategies are based on dietary and pharmacological reduction of serum phosphate, and consequently FGF23 levels. However, clinical trials proving the effects on the cardiovascular outcome are lacking. Recent publications provide evidence for new promising therapeutic interventions, such as magnesium supplementation and direct targeting of phosphate and FGF receptors to prevent toxicity of FGF23 and hyperphosphatemia in CKD patients.

Plaque Calcification

Vascular calcification (VC) is strongly associated with all-cause mortality and is an independent predictor of cardiovascular events. Resulting from its complex, multifaceted nature, targeted treatments for VC have not yet been developed. Lipoproteins are well characterized in the pathogenesis of atherosclerotic plaques, leading to the development of plaque regressing therapeutics. Although their roles in plaque progression are well documented, their roles in VC, and calcification of a plaque, are not well understood. In this review, early in vitro data and clinical correlations suggest an inhibitory role for HDL (high-density lipoproteins) in VC, a stimulatory role for LDL (low-density lipoprotein) and VLDL (very low-density lipoprotein) and a potentially causal role for Lp(a) (lipoprotein [a]). Additionally, after treatment with a statin or PCSK9 (proprotein convertase subtilisin/kexin type 9) inhibitor, plaque calcification is observed to increase. With the notion that differing morphologies of plaque calcification associate with either a more stable or unstable plaque phenotype, uncovering the mechanisms of lipoprotein-artery wall interactions could produce targeted therapeutic options for VC.

New Insights into the Roles of Monocytes/Macrophages in Cardiovascular Calcification Associated with Chronic Kidney Disease

Cardiovascular disease (CVD) is an important cause of death in patients with chronic kidney disease (CKD), and cardiovascular calcification (CVC) is one of the strongest predictors of CVD in this population. Cardiovascular calcification results from complex cellular interactions involving the endothelium, vascular/valvular cells (i.e., vascular smooth muscle cells, valvular interstitial cells and resident fibroblasts), and monocyte-derived macrophages. Indeed, the production of pro-inflammatory cytokines and oxidative stress by monocyte-derived macrophages is responsible for the osteogenic transformation and mineralization of vascular/valvular cells. However, monocytes/macrophages show the ability to modify their phenotype, and consequently their functions, when facing environmental modifications. This plasticity complicates efforts to understand the pathogenesis of CVC-particularly in a CKD setting, where both uraemic toxins and CKD treatment may affect monocyte/macrophage functions and thereby influence CVC. Here, we review (i) the mechanisms by which each monocyte/macrophage subset either promotes or prevents CVC, and (ii) how both uraemic toxins and CKD therapies might affect these monocyte/macrophage functions.

Chlamydia pneumoniae infection promotes vascular smooth muscle cell migration via c-Fos/interleukin-17C signaling

Chlamydia pneumoniae (C. pneumoniae) infection is associated with the initiation and progression of atherosclerosis. The migration of vascular smooth muscle cell (VSMC) from the media to the intima is a key event in the development of atherosclerosis. Interleukin-17C (IL-17C) could enhance cell migration ability. The aim of our study is to investigate the role of IL-17C in C. pneumoniae infection-promoted VSMC migration, thereby possibly accelerating atherosclerosis. We firstly demonstrated that C. pneumoniae infection significantly increased IL-17C expression in VSMCs in the atherosclerotic lesion area from ApoE deficient mice. Our in vitro study further showed that IL-17C is required for C. pneumoniae infection-promoted VSMC migration, and its expression could be regulated by c-Fos through phosphorylating extracellular signal-regulated kinase (ERK). Unexpectedly, in the present study, we also found that IL-17C is critical for C. pneumoniae infection-induced c-Fos activation. c-Fos expression and activation induced by the exposure to recombinant IL-17C were markedly suppressed in the presence of the ERK inhibitor PD98059. These results suggest a possible positive feedback between c-Fos and IL-17C after C. pneumoniae infection. Taken together, our results indicate that C. pneumoniae infection promotes VSMC migration via c-Fos/IL-17C signaling.

IL-6 and sIL-6R induces STAT3-dependent differentiation of human VSMCs into osteoblast-like cells through JMJD2B-mediated histone demethylation of RUNX2

Inflammation and vascular calcification are independent risk factors of cardiovascular events. Vascular smooth muscle cells (VSMCs) exhibit osteoblast-like characteristics in response to various stimuli such as oxidized cholesterol and inflammation. However the precise mechanism of transcriptional regulation of VSMCs by inflammatory stimuli remains unclear. We investigated the process and mechanisms of inflammatory cytokine-induced transformation of human VSMCs (hVSMCs) into osteoblast-like cells, with a special focus on epigenetic changes. Our results demonstrated: (1) interleukin-6 (IL-6)/soluble interleukin-6 receptor (sIL-6R) induced transformation of hVSMCs into an osteoblast phenotype, with subsequent vascular calcification, based on the results of Alizarin Red S staining and O-Cresolphthalein complexone method; (2) IL-6/sIL-6R accelerated the expression of runt-related transcription factor 2 (RUNX2) based on the results of quantitative real-time polymerase chain reaction; (3) Knockdown of signal transducer and activator of transcription (STAT) 3 reduced IL-6/sIL-6R-induced RUNX2 mRNA expression and osteoblast transdifferentiation of hVSMCs; (4) Chromatin immunoprecipitation (ChIP) coupled with PCR (ChIP-PCR) identified a STAT-binding site in RUNX2 promoter region containing trimethylated histone 3 lysine 9 (H3K9me3), a transcriptional repressor, and H3K4me3, a transcriptional enhancer. Stimulation with IL-6/sIL-6R suppressed H3K9me3 but not H3K4me3 through the recruitment of jumonji domain-containing protein (JMJD) 2B, a histone lysine demethylase, at the STAT-binding site in RUNX2 promoter region; (5) IL-6/sIL-6R-induced RUNX2 gene expression was inhibited in hVSMCs pretreated with JIB04, JMJD2 inhibitor, and the inhibitory effect was JIB04 dose-dependent. Our results indicate that the IL-6/STAT3/JMJD2B pathway regulates hVSMCs differentiation into osteoblast-like cells, which suggest its pathogenic role in vascular calcification associated with chronic inflammation.

Apabetalone downregulates factors and pathways associated with vascular calcification

BACKGROUND AND AIMS

Apabetalone is an inhibitor of bromodomain and extraterminal (BET) proteins. In clinical trials, apabetalone reduced the incidence of major adverse cardiac events (MACE) in patients with cardiovascular disease and reduced circulating factors that promote vascular calcification (VC). Because VC contributes to MACE, effects of apabetalone on pro-calcific processes were examined.

METHODS AND RESULTS

Apabetalone inhibited extracellular calcium deposition and opposed induction of transdifferentiation markers in human coronary artery vascular smooth muscle cells (VSMCs) under osteogenic culture conditions. Tissue-nonspecific alkaline phosphatase (TNAP) is a key contributor to VC, and apabetalone suppressed osteogenic induction of the mRNA, protein and enzyme activity. The liver is a major source of circulating TNAP, and apabetalone also downregulated TNAP expression in primary human hepatocytes. BRD4, a transcriptional regulator and target of apabetalone, has been linked to calcification. Osteogenic transdifferentiation of VSMCs resulted in disassembly of 100 BRD4-rich enhancers, with concomitant enlargement of remaining enhancers. Apabetalone reduced the size of BRD4-rich enhancers, consistent with disrupting BRD4 association with chromatin. 38 genes were uniquely associated with BRD4-rich enhancers in osteogenic conditions; 11 were previously associated with calcification. Apabetalone reduced levels of BRD4 on many of these enhancers, which correlated with decreased expression of the associated gene. Bioinformatics revealed BRD4 may cooperate with 7 specific transcription factors to promote transdifferentiation and calcification.

CONCLUSIONS

Apabetalone counters transdifferentiation and calcification of VSMCs via an epigenetic mechanism involving specific transcription factors. The mechanistic findings, combined with evidence from clinical trials, support further development of apabetalone as a therapeutic for VC.

The Impact of Uremic Toxins on Vascular Smooth Muscle Cell Function

Chronic kidney disease (CKD) is associated with profound vascular remodeling, which accelerates the progression of cardiovascular disease. This remodeling is characterized by intimal hyperplasia, accelerated atherosclerosis, excessive vascular calcification, and vascular stiffness. Vascular smooth muscle cell (VSMC) dysfunction has a key role in the remodeling process. Under uremic conditions, VSMCs can switch from a contractile phenotype to a synthetic phenotype, and undergo abnormal proliferation, migration, senescence, apoptosis, and calcification. A growing body of data from experiments in vitro and animal models suggests that uremic toxins (such as inorganic phosphate, indoxyl sulfate and advanced-glycation end products) may directly impact the VSMCs’ physiological functions. Chronic, low-grade inflammation and oxidative stress—hallmarks of CKD—are also strong inducers of VSMC dysfunction. Here, we review current knowledge about the impact of uremic toxins on VSMC function in CKD, and the consequences for pathological vascular remodeling.