Elevated serum soluble endoglin (sCD105) decreased during extracorporeal elimination therapy for familial hypercholesterolemia

Overview of multifunctional Tregs in cardiovascular disease: From insights into cellular functions to clinical implications

Regulatory T cells (Tregs) are crucial in regulating T-cell-mediated immune responses. Numerous studies have shown that dysfunction or decreased numbers of Tregs may be involved in inflammatory cardiovascular diseases (CVDs) such as atherosclerosis, hypertension, myocardial infarction, myocarditis, cardiomyopathy, valvular heart diseases, heart failure, and abdominal aortic aneurysm. Tregs can help to ameliorate CVDs by suppressing excessive inflammation through various mechanisms, including inhibition of T cells and B cells, inhibition of macrophage-induced inflammation, inhibition of dendritic cells and foam cell formation, and induction of anti-inflammatory macrophages. Enhancing or restoring the immunosuppressive activity of Tregs may thus serve as a fundamental immunotherapy to treat hypertension and CVDs. However, the precise molecular mechanisms underlying the Tregs-induced protection against hypertension and CVDs remain to be investigated. This review focuses on recent advances in our understanding of Tregs subsets and function in CVDs. In addition, we discuss promising strategies for using Tregs through various pharmacological approaches to treat hypertension and CVDs.

Long-term observational study of renal outcome after preeclampsia: Role of soluble fms-like tyrosine kinase-1(sFlt-1)/ placental growth factor (PlGF) and endoglin

Introduction

Preeclampsia (PE) is an important complication of pregnancy that can lead to chronic kidney disease. Soluble fms-like tyrosine kinase-1 (sFlt-1), placental growth factor (PlGF), the sFlt-1/PlGF ratio and endoglin are biomarkers for the differential diagnosis of PE and other diseases. We aimed to explore the correlation of these biomarkers with long-term renal function, blood pressure and the urine albumin/creatinine ratio (UACR) in PE patients.

Methods

34 patients with PE were enrolled. Blood samples for sFlt-1, PlGF, endoglin and the urine albumin/creatinine ratio (UACR) were collected at the time of PE diagnosis (at 35–40 weeks’ gestational age (GA) (87.50% of cases). After delivery, the patients were followed up at three months and one year to assess blood pressure, renal function and the UACR.

Results

Thirty-four PE patients were included, and 17 completed the study. The estimated glomerular filtration rate (eGFR) decreased significantly at three months and one year after follow-up (128.20 ± 10.34 to 120.75 ± 10.166 ml/min/1.73 m² (p = 0.001) at three months and 126.71 ± 9.948 to 114.29 ± 11.274 ml/min/1.73 m² (p < 0.001) at one year). The endoglin level correlated significantly with the eGFR level during PE, but there was no correlation of any biomarker with eGFR, blood pressure, or the UACR at one year.

Conclusion

Women with PE have a reduction of eGFR at three months and one year after the diagnosis of PE. Only endoglin is correlated with eGFR antepartum; however, it is not correlated with long-term renal function, blood pressure or the UACR.

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Preeclampsia has been suggested to increase the risk of kidney problems.

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The soluble endoglin level and sFlt-1:PlGF ratio can predict early and late-onset preeclampsia.

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Analysis of angiogenic factors may be associated with long term renal function.

Targeting the cytoskeleton and extracellular matrix in cardiovascular disease drug discovery

INTRODUCTION

Currently, cardiovascular disease (CVD) drug discovery has focused primarily on addressing the inflammation and immunopathology aspects inherent to various CVD phenotypes such as cardiac fibrosis and coronary artery disease. However, recent findings suggest new biological pathways for cytoskeletal and extracellular matrix (ECM) regulation across diverse CVDs, such as the roles of matricellular proteins (e.g. tenascin-C) in regulating the cellular microenvironment. The success of anti-inflammatory drugs like colchicine, which targets microtubule polymerization, further suggests that the cardiac cytoskeleton and ECM provide prospective therapeutic opportunities.

AREAS COVERED

Potential therapeutic targets include proteins such as gelsolin and calponin 2, which play pivotal roles in plaque development. This review focuses on the dynamic role that the cytoskeleton and ECM play in CVD pathophysiology, highlighting how novel target discovery in cytoskeletal and ECM-related genes may enable therapeutics development to alter the regulation of cellular architecture in plaque formation and rupture, cardiac contractility, and other molecular mechanisms.

EXPERT OPINION

Further research into the cardiac cytoskeleton and its associated ECM proteins is an area ripe for novel target discovery. Furthermore, the structural connection between the cytoskeleton and the ECM provides an opportunity to evaluate both entities as sources of potential therapeutic targets for CVDs.

The role of endoglin and its soluble form in pathogenesis of preeclampsia

Preeclampsia remains till today a leading cause of maternal and fetal morbidity and mortality. Pathophysiology of the disease is not yet fully elucidated, though it is evident that it revolves around placenta. Cellular ischemia in the preeclamptic placenta creates an imbalance between angiogenic and anti-angiogenic factors in maternal circulation. Endoglin, a transmembrane co-receptor of transforming growth factor β (TGF-β) demonstrating angiogenic effects, is involved in a variety of angiogenesis-dependent diseases with endothelial dysfunction, including preeclampsia. Endoglin expression is up-regulated in preeclamptic placentas, through mechanisms mainly induced by hypoxia, oxidative stress and oxysterol-mediated activation of liver X receptors. Overexpression of endoglin results in an increase of its soluble form in maternal circulation. Soluble endoglin represents the extracellular domain of membrane endoglin, cleaved by the action of metalloproteinases, predominantly matrix metalloproteinase-14. Released in circulation, soluble endoglin interferes in TGF-β1 and activin receptor-like kinase 1 signaling pathways and inhibits endothelial nitric oxide synthase activation, consequently deranging angiogenesis and promoting vasoconstriction. Due to these properties, soluble endoglin actively contributes to the impaired placentation observed in preeclampsia, as well as to the pathogenesis and manifestation of its clinical signs and symptoms, especially hypertension and proteinuria. The significant role of endoglin and soluble endoglin in pathophysiology of preeclampsia could have prognostic, diagnostic and therapeutic perspectives. Further research is essential to extensively explore the potential use of these molecules in the management of preeclampsia in clinical settings.

High Soluble Endoglin Levels Affect Aortic Vascular Function during Mice Aging

Endoglin is a 180 kDa transmembrane glycoprotein that was demonstrated to be present in two different endoglin forms, namely membrane endoglin (Eng) and soluble endoglin (sEng). Increased sEng levels in the circulation have been detected in atherosclerosis, arterial hypertension, and type II diabetes mellitus. Moreover, sEng was shown to aggravate endothelial dysfunction when combined with a high-fat diet, suggesting it might be a risk factor for the development of endothelial dysfunction in combination with other risk factors. Therefore, this study hypothesized that high sEng levels exposure for 12 months combined with aging (an essential risk factor of atherosclerosis development) would aggravate vascular function in mouse aorta. Male transgenic mice with high levels of human sEng in plasma (Sol-Eng⁺) and their age-matched male transgenic littermates that do not develop high soluble endoglin (Control) on a chow diet were used. The aging process was initiated to contribute to endothelial dysfunction/atherosclerosis development, and it lasted 12 months. Wire myograph analysis showed impairment contractility in the Sol-Eng⁺ group when compared to the control group after KCl and PGF_2α administration. Endothelium-dependent responsiveness to Ach was not significantly different between these groups. Western blot analysis revealed significantly decreased protein expression of Eng, p-eNOS, and ID1 expression in the Sol-Eng⁺ group compared to the control group suggesting reduced Eng signaling. In conclusion, we demonstrated for the first time that long-term exposure to high levels of sEng during aging results in alteration of vasoconstriction properties of the aorta, reduced eNOS phosphorylation, decreased Eng expression, and altered Eng signaling. These findings suggest that sEng can be considered a risk factor for the development of vascular dysfunction during aging and a potential therapeutical target for pharmacological intervention.

Endoglin/CD105-Based Imaging of Cancer and Cardiovascular Diseases: A Systematic Review

Molecular imaging of pathologic lesions can improve efficient detection of cancer and cardiovascular diseases. A shared pathophysiological feature is angiogenesis, the formation of new blood vessels. Endoglin (CD105) is a coreceptor for ligands of the Transforming Growth Factor-β (TGF-β) family and is highly expressed on angiogenic endothelial cells. Therefore, endoglin-based imaging has been explored to visualize lesions of the aforementioned diseases. This systematic review highlights the progress in endoglin-based imaging of cancer, atherosclerosis, myocardial infarction, and aortic aneurysm, focusing on positron emission tomography (PET), single-photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), near-infrared fluorescence (NIRF) imaging, and ultrasound imaging. PubMed was searched combining the following subjects and their respective synonyms or relevant subterms: "Endoglin", "Imaging/Image-guided surgery". In total, 59 papers were found eligible to be included: 58 reporting about preclinical animal or in vitro models and one ex vivo study in human organs. In addition to exact data extraction of imaging modality type, tumor or cardiovascular disease model, and tracer (class), outcomes were described via a narrative synthesis. Collectively, the data identify endoglin as a suitable target for intraoperative and diagnostic imaging of the neovasculature in tumors, whereas for cardiovascular diseases, the evidence remains scarce but promising.

Membrane and soluble endoglin role in cardiovascular and metabolic disorders related to metabolic syndrome

Membrane endoglin (Eng, CD105) is a transmembrane glycoprotein essential for the proper function of vascular endothelium. It might be cleaved by matrix metalloproteinases to form soluble endoglin (sEng), which is released into the circulation. Metabolic syndrome comprises conditions/symptoms that usually coincide (endothelial dysfunction, arterial hypertension, hyperglycemia, obesity-related insulin resistance, and hypercholesterolemia), and are considered risk factors for cardiometabolic disorders such as atherosclerosis, type II diabetes mellitus, and liver disorders. The purpose of this review is to highlight current knowledge about the role of Eng and sEng in the disorders mentioned above, in vivo and in vitro extent, where we can find a wide range of contradictory results. We propose that reduced Eng expression is a hallmark of endothelial dysfunction development in chronic pathologies related to metabolic syndrome. Eng expression is also essential for leukocyte transmigration and acute inflammation, suggesting that Eng is crucial for the regulation of endothelial function during the acute phase of vascular defense reaction to harmful conditions. sEng was shown to be a circulating biomarker of preeclampsia, and we propose that it might be a biomarker of metabolic syndrome-related symptoms and pathologies, including hypercholesterolemia, hyperglycemia, arterial hypertension, and diabetes mellitus as well, despite the fact that some contradictory findings have been reported. Besides, sEng can participate in the development of endothelial dysfunction and promote the development of arterial hypertension, suggesting that high levels of sEng promote metabolic syndrome symptoms and complications. Therefore, we suggest that the treatment of metabolic syndrome should take into account the importance of Eng in the endothelial function and levels of sEng as a biomarker and risk factor of related pathologies.

Association of Alk1 and Endoglin Polymorphisms with Cardiovascular Damage

Cardiovascular diseases are associated to risk factors as obesity, hypertension and diabetes. The transforming growth factor-β1 receptors ALK1 and endoglin regulate blood pressure and vascular homeostasis. However, no studies relate the association of ALK1 and endoglin polymorphisms with cardiovascular risk factors. We analysed the predictive value of the ALK1 and endoglin polymorphisms on cardiovascular target organ damage in hypertensive and diabetic patients in 379 subjects with or without hypertension and diabetes in a Primary Care setting. The ALK1 rs2071219 polymorphism (AA genotype) is associated with a lower presence of diabetic retinopathy and with the absence of altered basal glycaemia. Being carrier of the ALK1 rs3847859 polymorphism (G allele) is associated with lower basal heart rate and with higher LDL-cholesterol levels. The endoglin rs3739817 polymorphism (AA genotype) is associated with higher levels of LDL-cholesterol, and being carrier of the endoglin rs10987759 polymorphism (C allele) is associated with higher haemoglobin levels and with an increased heart rate. Summarizing, several ALK1 and endoglin gene polymorphisms increase the risk of cardiovascular events. The analysis of these polymorphisms in populations at risk, in combination with the determination of other parameters and biomarkers, could implement the diagnosis and prognosis of susceptibility to cardiovascular damage.

Long term effects of soluble endoglin and mild hypercholesterolemia in mice hearts

Soluble endoglin (sEng) released into the circulation was suggested to be related to cardiovascular based pathologies. It was demonstrated that a combination of high sEng levels and long-term exposure (six months) to high fat diet (HFD) resulted in aggravation of endothelial dysfunction in the aorta. Thus, in this study, we hypothesized that a similar experimental design would affect the heart morphology, TGFβ signaling, inflammation, fibrosis, oxidative stress and eNOS signaling in myocardium in transgenic mice overexpressing human sEng. Three-month-old female transgenic mice overexpressing human sEng in plasma (Sol-Eng+ high) and their age-matched littermates with low levels of human sEng (Sol-Eng+ low) were fed a high-fat diet containing 1.25% of cholesterol and 40% of fat for six months. A blood analysis was performed, and the heart samples were analyzed by qRT-PCR and Western blot. The results of this study showed no effects of sEng and HFD on myocardial morphology/hypertrophy/fibrosis. However, the expression of pSmad2/3 and p-eNOS was reduced in Sol-Eng+ high mice. On the other hand, sEng and HFD did not significantly affect the expression of selected members of TGFβ signaling (membrane endoglin, TGFβRII, ALK-5, ALK-1, Id-1, PAI-1), inflammation (VCAM-1, ICAM-1), oxidative stress (NQO1, HO-1) and heart remodeling (PDGFβ, COL1A1, β-MHC). In conclusion, the results of this study confirmed that sEng, even combined with a high-fat diet inducing hypercholesterolemia administered for six months, does not affect the structure of the heart with respect to hypertrophy, fibrosis, inflammation and oxidative stress. Interestingly, pSmad2/3/p-eNOS signaling was reduced in both the heart in this study and the aorta in the previous study, suggesting a possible alteration of NO metabolism caused by six months exposure to high sEng levels and HFD. Thus, we might conclude that sEng combined with a high-fat diet might be related to the alteration of NO production due to altered pSmad2/3/p-eNOS signaling in the heart and aorta.

High-fat diet-induced GAIT element-mediated translational silencing of mRNAs encoding inflammatory proteins in macrophage protects against atherosclerosis

Previously, we identified a mechanism of inflammation control directed by ribosomal protein L13a and "GAIT" (Gamma Activated Inhibitor of Translation) elements in target mRNAs and showed that its elimination in myeloid cell-specific L13a knockout mice (L13a KO) increased atherosclerosis susceptibility and severity. Here, we investigated the mechanistic basis of this endogenous defense against atherosclerosis. We compared molecular and cellular aspects of atherosclerosis in high-fat diet (HFD)-fed L13a KO and intact (control) mice. HFD treatment of control mice induced release of L13a from 60S ribosome, formation of RNA-binding complex, and subsequent GAIT element-mediated translational silencing. Atherosclerotic plaques from HFD-treated KO mice showed increased infiltration of M1 type inflammatory macrophages. Macrophages from KO mice showed increased phagocytic activity and elevated expression of LDL receptor and pro-inflammatory mediators. NanoString analysis of the plaques from KO mice showed upregulation of a number of mRNAs encoding inflammatory proteins. Bioinformatics analysis suggests the presence of the potential GAIT elements in the 3'UTRs of several of these mRNAs. Macrophage induces L13a/GAIT-dependent translational silencing of inflammatory genes in response to HFD as an endogenous defense against atherosclerosis in ApoE^-/- model.

Novel Biomarkers for Evaluation of Endothelial Dysfunction

Endothelial dysfunction is one of the earliest indicators of cardiovascular (CV) dysfunction, and its evaluation would be of considerable importance to stratify CV risk of many diseases and to assess the efficacy of atheroprotective treatments. Flow-mediated dilation is the most widely used method to study endothelial function. However, it is operator-dependent and can be influenced by physiological variations. Circulating biomarkers are a promising alternative. Due to the complexity of endothelial function, many of the biomarkers studied do not provide consistent information about the endothelium when measured alone. New circulating markers are being explored and some of them are thought to be suitable for the clinical setting. In this review, we focus on novel biomarkers of endothelial dysfunction, particularly endothelial microparticles, endocan, and endoglin, and discuss whether they fulfill the criteria to be applied in clinical practice.

Isolation, culturing and gene expression profiling of inner mass cells from stable and vulnerable carotid atherosclerotic plaques

The connective tissue components that form the atherosclerotic plaque body are produced by the plaque inner mass cells (PIMC), located inside the plaque. We report an approach to isolate and culture cells from the connective tissue of stable and vulnerable human atherosclerotic plaques based on elimination of non-connective tissue cells such as blood and non-plaque intima cells with a lysis buffer. The resulting plaque cells were characterized by growth capacity, morphology, transcriptome profiling and specific protein expression. Plaque cells slowly proliferated for up to three passages unaffected by the use of proliferation stimulants or changes of culture media composition. Stable plaques yielded more cells than vulnerable ones. Plaque cell cultures also contained several morphological cellular types. RNA-seq profiles of plaque cells were different from any of the cell types known to be involved in atherogenesis. The expression of the following proteins was observed in cultured plaque cells: smooth muscle cells marker α-SMA, macrophage marker CD14, extracellular matrix proteins aggrecan, fibronectin, neovascularisation markers VEGF-A, CD105, cellular adhesion receptor CD31 and progenitor/dedifferentiation receptor CD34. Differential expression of several notable transcripts in cells from stable and vulnerable plaques suggests the value of plaque cell culture studies for the search of plaque vulnerability markers.

Effects of acute insulin-induced hypoglycaemia on endothelial microparticles in adults with and without type 2 diabetes

AIMS

To assess whether endothelial microparticles (EMPs), novel surrogate markers of endothelial injury and dysfunction, are differentially produced in response to acute insulin-induced hypoglycaemia in adults with and without type 2 diabetes.

MATERIALS AND METHODS

A prospective, parallel study was conducted in individuals with type 2 diabetes (n = 23) and controls (n = 22). Hypoglycaemia (<2.2 mmoL/L: <40 mg/dL) was achieved by intravenous infusion of soluble insulin. Blood samples were collected at baseline and at 0, 30, 60, 120, 240 minutes and 24 hours after hypoglycaemia and analysed for CD31⁺ (platelet endothelial cell adhesion molecule-1), CD54⁺ (intercellular adhesion molecule 1), CD62-E⁺ (E-selectin), CD105⁺ (endoglin), CD106⁺ (vascular cell adhesion molecule 1) and CD142⁺ (tissue factor) EMPs by flow cytometry. The peak elevations (% rise from 0 minutes after hypoglycaemia) in EMP within 240 minutes after insulin-induced hypoglycaemia were modelled using a regression model, with adjustment for relevant covariates. All EMPs were expressed as percentage from 0 minutes hypoglycaemia for each time point and total areas under the curve (AUC_0min-24h ) were calculated.

RESULTS

Following insulin-induced hypoglycaemia, levels of circulating EMPs were maximal at 240 minutes (P < 0.001) and returned to baseline values within 24 hours for both groups. The peak elevations (% rise from 0 minutes following hypoglycaemia) seen in CD31⁺ , CD54⁺ , CD62-E⁺ , CD105⁺ and CD142⁺ EMPs within 240 minutes were associated with diabetes status after adjustments for all relevant covariates. Individuals with type 2 diabetes showed increased CD31⁺ EMPs AUC_0min-24h (P = 0.014) and CD105⁺ EMPs AUC_0min-24h (P = 0.006) compared with controls, but there were no differences for CD54⁺ (P = 0.91), CD62-E⁺ (P = 0.14), CD106⁺ (P = 0.36) or CD142⁺ (P = 0.77) EMPs AUC_0min-24h .

CONCLUSIONS

The associations between peak elevations within 240 minutes after insulin-induced hypoglycaemia for CD31⁺ , CD54⁺ , CD62-E⁺ , CD105⁺ and CD142⁺ and diabetes status indicate that the assessment of a panel of EMPs within this timeframe would identify a hypoglycaemic event in this population. The greater overall responses over time (AUCs) for apoptosis-induced CD31⁺ and CD105⁺ EMPs suggest that hypoglycaemia exerts greater endothelial stress in type 2 diabetes.

Regulation and role of endoglin in cholesterol-induced endothelial and vascular dysfunction in vivo and in vitro

Our objective was to investigate the effect of cholesterol [hypercholesterolemia and 7-ketocholesterol (7K)] on endoglin (Eng) expression and regulation with respect to endothelial or vascular dysfunction in vivo and in vitro. In vivo experiments were performed in 2-mo-old atherosclerosis-prone apolipoprotein E-deficient/LDL receptor-deficient (ApoE^-/-/LDLR^-/-) female mice and their wild-type C57BL/6J littermates. In in vitro experiments, human aortic endothelial cells (HAECs) were treated with 7K. ApoE^-/-/LDLR^-/- mice developed hypercholesterolemia accompanied by increased circulating levels of P-selectin and Eng and a disruption of NO metabolism. Functional analysis of the aorta demonstrated impaired vascular reactivity, and Western blot analysis revealed down-regulation of membrane Eng/Smad2/3/eNOS signaling in ApoE^-/-/LDLR^-/- mice. 7K increased Eng expression via Krüppel-like factor 6 (KLF6), liver X nuclear receptor, and NF-κB in HAECs. 7K-induced Eng expression was prevented by the treatment with 2-hydroxypropyl-β-cyclodextrin; 8-{[5-chloro-2-(4-methylpiperazin-1-yl) pyridine-4-carbonyl] amino}-1-(4-fluorophenyl)-4, 5-dihydrobenzo[g]indazole-3-carboxamide; or by KLF6 silencing. 7K induced increased adhesion and transmigration of monocytic human leukemia promonocytic cell line cells and was prevented by Eng silencing. We concluded that hypercholesterolemia altered Eng expression and signaling, followed by endothelial or vascular dysfunction before formation of atherosclerotic lesions in ApoE^-/-/LDLR^-/- mice. By contrast, 7K increased Eng expression and induced inflammation in HAECs, which was followed by an increased adhesion and transmigration of monocytes via endothelium, which was prevented by Eng inhibition. Thus, we propose a relevant role for Eng in endothelial or vascular dysfunction or inflammation when exposed to cholesterol.-Vicen, M., Vitverova, B., Havelek, R., Blazickova, K., Machacek, M., Rathouska, J., Najmanová, I., Dolezelova, E., Prasnicka, A., Sternak, M., Bernabeu, C., Nachtigal, P. Regulation and role of endoglin in cholesterol-induced endothelial and vascular dysfunction in vivo and in vitro.

Plasma endoglin in Type2 diabetic patients with nephropathy

BACKGROUND

Diabetic nephropathy may be a common complication of diabetes mellitus. Endoglin is glycoprotein located on cell surfaces of endothelial cells and is part of the transforming growth factor beta (TGF- β) receptor. Endoglin expression is enhanced in endothelial cells during injury and inflammation. The aim of this study was to estimate the plasma level of soluble endoglin (sEng) in type 2 diabetic patients (with and without nephropathy). Also to explore its availability as marker for disease progression.

METHODS

In this study, sixty eight patients with type 2 diabetes mellitus (T2DM) were included; the patients were sub-grouped to normoalbuminuria without nephropathy and moderately increased albuminuria (microalbuminuria) with nephropathy groups with 13 individuals as control group. Plasma soluble endoglin level was determined using ELISA technique. Fasting plasma glucose (FPG), glycated haemoglobin (HbA1c), lipid profile, and creatinine were determined using colorimetric assay, whereas glomerular filtration rate (GFR) was calculated.

RESULTS

The plasma level of sEng of both normoalbuminuria group 1 and microalbuminuria group 2 were significantly higher when compared to control group. While, the plasma level of sEng in microalbuminuria group 2 was nonsignificant lower when compared to normoalbuminuria group 1. Also, there was a significant positive association between plasma level of sEng and HbA1c, HDL-C and urinary albumin concentration in normoalbuminuria group.

CONCLUSION

Plasma level of soluble Endoglin is markedly increase prior to alteration in endothelial function, and increases to lesser extent with the developing of diabetic nephropathy which indicated disease progression and development of vascular abnormalities.

Circulating soluble endoglin modifies the inflammatory response in mice

Inflammation is associated with every health condition, and is an important component of many pathologies such as cardiovascular diseases. Circulating levels of soluble endoglin have been shown to be higher in the serum of patients with cardiovascular diseases with a significant inflammatory component. The aim of this study was to evaluate the implication of circulating soluble endoglin in the inflammatory response. For this purpose, a transgenic mouse expressing human soluble endoglin (sEng+) was employed, and three different inflammatory approaches were used to mimic inflammatory conditions in different tissues. This study shows that control sEng+ mice have a normal inflammatory state. The lung and kidney injury induced by the inflammatory agents was reduced in sEng+ mice, especially the intra-alveolar and kidney infiltrates, suggesting a possible reduction in inflammation induced by soluble endoglin. To deepen into this possible effect, the leukocyte number in the bronchoalveolar lavage and air pouch lavage was evaluated and a significant reduction of neutrophil infiltration in LPS-treated lungs and ischemic kidneys from sEng+ with respect to WT mice was observed. Additionally, the mechanisms through which soluble endoglin prevents inflammation were studied. We found that in sEng+ animals the increment of proinflammatory cytokines, TNFα, IL1β and IL6, induced by the inflammatory stimulus was reduced. Soluble endoglin also prevents the augmented adhesion molecules, ICAM, VCAM and E-selectin induced by the inflammatory stimulus. In addition, vascular permeability increased by inflammatory agents was also reduced by soluble endoglin. These results suggest that soluble endoglin modulates inflammatory-related diseases and open new perspectives leading to the development of novel and targeted approaches for the prevention and treatment of cardiovascular diseases.

Preeclampsia and coronary plaque erosion: Manifestations of endothelial dysfunction resulting in cardiovascular events in women

Atherosclerosis is the major underlying pathology of cardiovascular disease (CVD). The risk for CVD is increased in women with a history of preeclampsia. Multiple studies have indicated that accelerated atherosclerosis underlies this increased CVD risk. Furthermore, it has been suggested that endothelial dysfunction and inflammation play an important role in the increased CVD risk of women with preeclampsia. Rupture or erosion of atherosclerotic plaques can induce the formation of thrombi that underlie the onset of acute clinical CVD such as myocardial infarction and stroke. In relatively young women, cardiovascular events are mainly due to plaque erosions. Eroded plaques have a distinct morphology compared to ruptured plaques, but have been understudied as a substrate for CVD. The currently available evidence points towards lesions with features of stability such as high collagen content and smooth muscle cells and with distinct mechanisms that further promote the pro-thrombotic environment such as Toll Like Receptor (TLR) signaling and endothelial apoptosis. These suggested mechanisms, that point to endothelial dysfunction and intimal thickening, may also play a role in preeclampsia. Pregnancy is considered a stress test for the cardiovascular system with preeclampsia as an additional pathological substrate for earlier manifestation of vascular disease. This review provides a summary of the possible common mechanisms involved in preeclampsia and accelerated atherosclerosis in young females and highlights plaque erosion as a likely substrate for CVD events in women with a history of preeclampsia.

Soluble Endoglin Level Increase Occurs Prior to Development of Subclinical Structural Vascular Alterations in Diabetic Adolescents

OBJECTIVE

Soluble endoglin (S-endoglin) has been implicated as a potential marker of endothelial dysfunction (ED) and was reported to be elevated in diabetic adults, correlating with the severity of diabetic vasculopathy. However, circulating S-endoglin and its association with other markers of ED have not been formerly analyzed in the first decade of diabetes onset in adolescents with type 1 diabetes mellitus (T1DM).

METHODS

Fifty-eight adolescents with moderately/poorly controlled T1DM were included in this study and twenty-nine healthy adolescents served as controls. The diabetic group was divided into two groups based on the presence of microalbuminuria, as the microalbuminuria group (n=15) and the normoalbuminuria group (n=43). Functional vascular alterations were evaluated by measuring serum S-endoglin and plasma nitric oxide (NO) concentrations, the flow-mediated dilatation (FMD) of the brachial artery. Carotid intima media thickness (CIMT) was measured for evaluation of structural vascular alterations.

RESULTS

The S-endoglin and NO levels of both microalbuminuria and normoalbuminuria groups were higher than those of the control group (for S-endoglin, p=0.047 and p<0.001; for NO, p=0.004 and p=0.006, respectively). The FMD percent was lower in the microalbuminuria group compared to the normoalbuminuria and control groups (p=0.036 and p=0.020, respectively). There were negative correlations between S-endoglin concentration and FMD percent (r=-0.213, p=0.051) and between serum S-endoglin concentration and albumin excretion rate (r=-0.361, p=0.005). No significant differences were found in CIMT among any of the groups (p=0.443).

CONCLUSION

In adolescents with T1DM, S-endoglin concentrations might increase in parallel to the deterioration in endothelial function before subclinical structural vascular alterations become evident.

Mice Lacking Endoglin in Macrophages Show an Impaired Immune Response

Endoglin is an auxiliary receptor for members of the TGF-β superfamily and plays an important role in the homeostasis of the vessel wall. Mutations in endoglin gene (ENG) or in the closely related TGF-β receptor type I ACVRL1/ALK1 are responsible for a rare dominant vascular dysplasia, the Hereditary Hemorrhagic Telangiectasia (HHT), or Rendu-Osler-Weber syndrome. Endoglin is also expressed in human macrophages, but its role in macrophage function remains unknown. In this work, we show that endoglin expression is triggered during the monocyte-macrophage differentiation process, both in vitro and during the in vivo differentiation of blood monocytes recruited to foci of inflammation in wild-type C57BL/6 mice. To analyze the role of endoglin in macrophages in vivo, an endoglin myeloid lineage specific knock-out mouse line (Eng^fl/flLysMCre) was generated. These mice show a predisposition to develop spontaneous infections by opportunistic bacteria. Eng^fl/flLysMCre mice also display increased survival following LPS-induced peritonitis, suggesting a delayed immune response. Phagocytic activity is impaired in peritoneal macrophages, altering one of the main functions of macrophages which contributes to the initiation of the immune response. We also observed altered expression of TGF-β1 target genes in endoglin deficient peritoneal macrophages. Overall, the altered immune activity of endoglin deficient macrophages could help to explain the higher rate of infectious diseases seen in HHT1 patients.

Endoglin is a transmembrane protein and an auxiliary receptor for TGF-β with an important role in the homeostasis of the vessel wall. However, endoglin was originally identified as a human cell surface antigen expressed in a pre-B leukemic cell line. Mutations in ENG are responsible for the Hereditary Hemorrhagic Telangiectasia type 1 (HHT1) or Rendu-Osler-Weber syndrome. HHT is a rare disease, with a prevalence of 1/5,000 to 1/8,000. It is an autosomal dominant disorder characterized by a multisystemic vascular dysplasia, recurrent hemorrhages and arteriovenous malformations in internal organs. Interestingly, endoglin expression is also triggered during the monocyte-macrophage differentiation process. In our laboratory, we described that up-regulation of endoglin during in vitro differentiation of blood monocytes is age-dependent and impaired in monocytes from HHT patients, suggesting a role of endoglin in macrophages. In the present work, we first analyzed endoglin expression during differentiation of peripheral blood monocytes to macrophages under in vitro and in vivo conditions. Next, to investigate endoglin’s role in macrophage function in vivo, a myeloid-lineage specific endoglin knock-out mouse line was generated (Eng^fl/flLysMCre). Endoglin deficiency in macrophages predisposed animals to spontaneous infections and led to delayed endotoxin-induced mortality. Phagocytic activity by peritoneal macrophages was reduced in the absence of endoglin and altered expression of TGF-β target genes was consistent with an altered balance of TGF-β signaling. The results show a novel role for endoglin in mouse macrophages, which if analogous in human macrophages, may explain, at least in part, the increased infection rates seen in HHT patients.

Experimental procedures to identify and validate specific mRNA targets of miRNAs

Functionally matured microRNAs (miRNAs) are small single-stranded non-coding RNA molecules which are emerging as important post-transcriptional regulators of gene expression and consequently are central players in many physiological and pathological processes. Since the biological roles of individual miRNAs will be dictated by the mRNAs that they regulate, the identification and validation of miRNA/mRNA target interactions is critical for our understanding of the regulatory networks governing biological processes. We promulgate the combined use of prediction algorithms, the examination of curated databases of experimentally supported miRNA/mRNA interactions, manual sequence inspection of cataloged miRNA binding sites in specific target mRNAs, and review of the published literature as a reliable practice for identifying and prioritizing biologically important miRNA/mRNA target pairs. Once a preferred miRNA/mRNA target pair has been selected, we propose that the authenticity of a functional miRNA/mRNA target pair be validated by fulfilling four well-defined experimental criteria. This review summarizes our current knowledge of miRNA biology, miRNA/mRNA target prediction algorithms, validated miRNA/mRNA target data bases, and outlines several experimental methods by which miRNA/mRNA targets can be authenticated. In addition, a case study of human endoglin is presented as an example of the utilization of these methodologies.

Structural and ultrastructural evaluation of the aortic wall after transplantation of bone marrow-derived cells (BMCs) in a model for atherosclerosis

Stem cells are characterized by their ability to differentiate into multiple cell lineages and display the paracrine effect. The aim of this work was to evaluate the effect of therapy with bone marrow-derived cells (BMCs) on glucose, lipid metabolism, and aortic wall remodeling in mice through the administration of a high-fat diet and subsequent BMCs transplantation. C57BL/6 mice were fed a control diet (CO group) or an atherogenic diet (AT group). After 16 weeks, the AT group was divided into 4 subgroups: an AT 14 days group and AT 21 days group that were given an injection of vehicle and sacrificed after 14 and 21 days, respectively, and an AT-BMC 14 days group and AT-BMC 21 days group that were given an injection of BMCs and sacrificed after 14 and 21 days, respectively. The BMCs transplant had reduced blood glucose, triglycerides, and total cholesterol. There was no significant difference in relation to body mass between the transplanted groups and non-transplanted groups, and all were different than CO. There was no significant difference in the glycemic curve among AT 14 days, AT-BMC 14 days, and AT 21 days, and these were different than the CO and the AT-BMC 21 days groups. The increased thickness of the aortic wall was observed in all atherogenic groups, but was significantly smaller in group AT-BMC 21 days compared to AT 14 days and AT 21 days. Vacuoles in the media tunic, delamination and the thinning of the elastic lamellae were observed in AT 14 days and AT 21 days. The smallest number of these was displayed on the AT-BMC 14 days and AT-BMC 21 days. Marking to CD105, CD133, and CD68 were observed in AT 14 days and AT 21 days. These markings were not observed in AT-BMC 14 days or in AT-BMC 21 days. Electron micrographs show the beneficial remodeling in AT-BMC 14 days and AT-BMC 21 days, and the structural organization was similar to the CO group. Vesicles of pinocytosis, projection of smooth muscle cells, and delamination of the internal elastic lamina are seen in groups AT 14 days and AT 21 days. Endothelial cells were preserved, and regular and continuous contour in internal elastic lamelae were observed in the CO, the AT-BMC 14 days, and AT-BMC 21 days groups. In conclusion, in an atherosclerotic model using mice and atherogenic diet, the injection of BMCs improves glucose, lipid metabolism, and causes a beneficial remodeling of the aortic wall.

High soluble endoglin levels do not induce endothelial dysfunction in mouse aorta

Increased levels of a soluble form of endoglin (sEng) circulating in plasma have been detected in various pathological conditions related to cardiovascular system. High concentration of sEng was also proposed to contribute to the development of endothelial dysfunction, but there is no direct evidence to support this hypothesis. Therefore, in the present work we analyzed whether high sEng levels induce endothelial dysfunction in aorta by using transgenic mice with high expression of human sEng. Transgenic mice with high expression of human sEng on CBAxC57Bl/6J background (Sol-Eng⁺) and age-matched transgenic littermates that do not develop high levels of human soluble endoglin (control animals in this study) on chow diet were used. As expected, male and female Sol-Eng⁺ transgenic mice showed higher levels of plasma concentrations of human sEng as well as increased blood arterial pressure, as compared to control animals. Functional analysis either in vivo or ex vivo in isolated aorta demonstrated that the endothelium-dependent vascular function was similar in Sol-Eng⁺ and control mice. In addition, Western blot analysis showed no differences between Sol-Eng⁺ and control mice in the protein expression levels of endoglin, endothelial NO-synthase (eNOS) and pro-inflammatory ICAM-1 and VCAM-1 from aorta. Our results demonstrate that high levels of soluble endoglin alone do not induce endothelial dysfunction in Sol-Eng⁺ mice. However, these data do not rule out the possibility that soluble endoglin might contribute to alteration of endothelial function in combination with other risk factors related to cardiovascular disorders.

Mating decreases plasma levels of TGFβ1 and regulates myosalpinx expression of TGFβ1/TGFBR3 in the rat

Mating shuts down a 2-methoxyestradiol (2ME)-dependent, non-genomic activity that is responsible for accelerating egg transport in the rat oviduct. The aims of this work were to investigate the role of TGFβ1 in this 2ME-reduced activity and to determine the effect of mating on the expression and distribution of TGFβ1 and its receptor TGFBR3 in the rat oviduct. We determined the level of TGFβ1 in the plasma and oviductal fluid at 1, 3, or 6 hr during Day 1 of the oestrous cycle in unmated or mated animals. We then examined if 2ME accelerates oviductal egg transport in unmated rats that were previously treated with a neutralizing TGFβ1 antibody. The expression of Tgfb1 and Tgfbr3 mRNA and the level and distribution of TGFBR3 protein in the oviduct were also determined at these time points. Mating decreased TGFβ1 in the plasma, but not in the oviductal fluid, whereas antibody neutralization of circulating TGFβ1 did not prevent the effect of 2ME on egg transport. Mating decreased Tgfb1 and hastened the increase in TGFBR3 abundance in the myosalpinx. These results indicate that mating decreased circulating levels of TGFβ1 without shutting down the non-genomic 2ME response that normally accelerates egg transport. Levels of Tgfb1 transcript and TGFBR3 protein, however, changed in the myosalpinx of mated rats, suggesting a role for mating-associated factors in the autocrine and paracrine effects of TGFβ in the oviduct.

Endoglin in liver fibrogenesis: Bridging basic science and clinical practice

Endoglin, also known as cluster of differentiation CD105, was originally identified 25 years ago as a novel marker of endothelial cells. Later it was shown that endoglin is also expressed in pro-fibrogenic cells including mesangial cells, cardiac and scleroderma fibroblasts, and hepatic stellate cells. It is an integral membrane-bound disulfide-linked 180 kDa homodimeric receptor that acts as a transforming growth factor-β (TGF-β) auxiliary co-receptor. In humans, several hundreds of mutations of the endoglin gene are known that give rise to an autosomal dominant bleeding disorder that is characterized by localized angiodysplasia and arteriovenous malformation. This disease is termed hereditary hemorrhagic telangiectasia type I and induces various vascular lesions, mainly on the face, lips, hands and gastrointestinal mucosa. Two variants of endoglin (i.e., S- and L-endoglin) are formed by alternative splicing that distinguishes from each other in the length of their cytoplasmic tails. Moreover, a soluble form of endoglin, i.e., sol-Eng, is shedded by the matrix metalloprotease-14 that cleaves within the extracellular juxtamembrane region. Endoglin interacts with the TGF-β signaling receptors and influences Smad-dependent and -independent effects. Recent work has demonstrated that endoglin is a crucial mediator during liver fibrogenesis that critically controls the activity of the different Smad branches. In the present review, we summarize the present knowledge of endoglin expression and function, its involvement in fibrogenic Smad signaling, current models to investigate endoglin function, and the diagnostic value of endoglin in liver disease.

Therapeutic approaches to drug targets in atherosclerosis

Non-communicable diseases such as cancer, atherosclerosis and diabetes are responsible for major social and health burden as millions of people are dying every year. Out of which, atherosclerosis is the leading cause of deaths worldwide. The lipid abnormality is one of the major modifiable risk factors for atherosclerosis. Both genetic and environmental components are associated with the development of atherosclerotic plaques. Immune and inflammatory mediators have a complex role in the initiation and progression of atherosclerosis. Understanding of all these processes will help to invent a range of new biomarkers and novel treatment modalities targeting various cellular events in acute and chronic inflammation that are accountable for atherosclerosis. Several biochemical pathways, receptors and enzymes are involved in the development of atherosclerosis that would be possible targets for improving strategies for disease diagnosis and management. Earlier anti-inflammatory or lipid-lowering treatments could be useful for alleviating morbidity and mortality of atherosclerotic cardiovascular diseases. However, novel drug targets like endoglin receptor, PPARα, squalene synthase, thyroid hormone analogues, scavenger receptor and thyroid hormone analogues are more powerful to control the process of atherosclerosis. Therefore, the review briefly focuses on different novel targets that act at the starting stage of the plaque form to the thrombus formation in the atherosclerosis.

The EGFR-mTOR pathway and laryngeal cancer angiogenesis

Epidermal growth factor receptor (EGFR) is a trans-membrane tyrosine kinase taking part in cell transformation and tumor progression. One of the downstream pathways controlled by EGFR involves the mammalian target of rapamycin (mTOR), a proto-oncogene activated in several cell functions. Recent evidence seems to confirm that both EGFR and mTOR regulate angiogenesis. The aim of this study was to investigate the expression of EGFR and mTOR in laryngeal squamous cell carcinoma (LSCC) cells in a retrospective clinical setting and their correlation with tumor neo-angiogenesis, judged on the grounds of CD105-assessed microvascular density (MVD), and prognosis. We considered 76 consecutive patients with LSCC treated with surgery alone. Immunohistochemical expressions of EGFR, mTOR, and CD105 were measured using image analysis and findings underwent statistical analysis using univariate and multivariate models. We found that nodal status correlated significantly with patient prognosis in terms of disease-free survival (DFS) (p = 0.01). There was a strong direct correlation between mTOR and EGFR expression (p = 0.0003), and between mTOR and CD105-assessed MVD (p = 0.0025). Patients with a CD105-assessed MVD >5.28 % had a significantly higher recurrence rate (RR) (p = 0.026), and a significantly shorter DFS (p = 0.025). On multivariate analysis, only N stage [hazard ratio (HR) 3.54, p = 0.009] and CD105-assessed MVD (HR 2.87, p = 0.027) maintained their independent prognostic significance in terms of DFS. Judging from our promising findings, the EGFR-mTOR pathway should be investigated further to understand its role in LSCC neo-angiogenesis.

The ALK-1/Smad1 pathway in cardiovascular physiopathology. A new target for therapy?

Activin receptor-like kinase-1 or ALK-1 is a type I cell surface receptor for the transforming growth factor-β (TGF-β) family of proteins. The role of ALK-1 in endothelial cells biology and in angiogenesis has been thoroughly studied by many authors. However, it has been recently suggested a possible role of ALK-1 in cardiovascular homeostasis. ALK-1 is not only expressed in endothelial cells but also in smooth muscle cells, myofibroblast, hepatic stellate cells, chondrocytes, monocytes, myoblasts, macrophages or fibroblasts, but its role in these cells have not been deeply analyzed. Due to the function of ALK-1 in these cells, this receptor plays a role in several cardiovascular diseases. Animals with ALK-1 haploinsufficiency and patients with mutations in Acvrl1 (the gene that codifies for ALK-1) develop type-2 Hereditary Hemorrhagic Telangiectasia. Moreover, ALK-1 heterozygous mice develop pulmonary hypertension. Higher levels of ALK-1 have been observed in atherosclerotic plaques, suggesting a possible protector role of this receptor. ALK-1 deficiency is also related to the development of arteriovenous malformations (AVMs). Besides, due to the ability of ALK-1 to regulate cell proliferation and migration, and to modulate extracellular matrix (ECM) protein expression in several cell types, ALK-1 has been now demonstrated to play an important role in cardiovascular remodeling. In this review, we would like to offer a complete vision of the role of ALK-1 in many process related to cardiovascular homeostasis, and the involvement of this protein in the development of cardiovascular diseases, suggesting the possibility of using the ALK-1/smad-1 pathway as a powerful therapeutic target.

Endoglin: a critical mediator of cardiovascular health

Endoglin (CD105) is a type III auxiliary receptor for the transforming growth factor beta (TGFβ) superfamily. Several lines of evidence suggest that endoglin plays a critical role in maintaining cardiovascular homeostasis. Seemingly disparate disease conditions, including hereditary hemorrhagic telangiectasia, pre-eclampsia, and cardiac fibrosis, have now been associated with endoglin. Given the central role of the TGFβ superfamily in multiple disease conditions, this review provides a detailed update on endoglin as an evolving therapeutic target in the management of cardiovascular disease.