Increased levels of soluble endoglin (sEng) are found in serum, plasma, and urine of preeclampsia patients. sEng is released from membrane-bound endoglin through the proteolytic activity of metalloproteases, but its structural heterogeneity suggests the involvement of additional proteases. Considering the roles of thrombin and sEng in preeclampsia pathogenesis, we investigated whether thrombin cleaves endoglin. Sequence analysis revealed a conserved peptide in endoglin similar to the α-thrombin cleavage site of protease-activated receptor-1. Western blot analysis of plasma from preeclamptic women showed endoglin fragments consistent with thrombin-mediated cleavage. Incubation of purified endoglin with thrombin generated specific fragments, whose N- and C-terminal sequencing confirmed the predicted cleavage sites. Furthermore, thrombin treatment of endoglin-expressing cells released sEng and reduced cell surface endoglin. These findings suggest that multiple protease-targeted cleavage sites lead to the generation of sEng fragments, which may reflect endothelial dysfunction and preeclampsia progression. Thrombin cleaves membrane-bound endoglin and soluble endoglin, releasing fragments of varying sizes; these findings emphasize the heterogeneity of sEng in preeclampsia, connecting endothelial dysfunction to the progression of the disease.

Most of the canonical Arg-Gly-Asp (RGD)-containing integrin ligands are extracellular matrix proteins, such as fibronectin, vitronectin and fibrinogen, which regulate cell-ECM adhesion processes. However, during the last years, several reports have demonstrated the existence of non-canonical RGD-containing integrin ligands that are cell surface transmembrane proteins. At variance with the canonical extracellular matrix integrin ligands, the RGD-containing cell surface integrin ligands are involved in cell–cell adhesion processes and function as “integrin counter-receptors”. We propose in this review grouping these transmembrane proteins, which include endoglin, cadherin-5, cadherin-6, cadherin-17, ADAM15, and L1CAM, under the newly coined acronym RGD-ICRs (RGD-containing Integrin Counter-Receptors). We present and discuss the structure of RGD-ICRs, their RGD-based interactions with integrins, the specific signaling pathways triggered in different cell types, as well as their pathophysiological involvement. It can be postulated that RGD-ICRs constitute an emerging group of non-canonical RGD-based integrin counter-receptors. In spite of being encoded by different and independent genes and involved in different pathophysiological processes, all of them appear to have undergone a strong evolutionary convergence in order to acquire the same functional capacity to bind integrins via the RGD motif. Importantly, these RGD-ICRs are also emerging as novel biomarkers and therapeutic targets, with promising clinical potential in a wide array of pathologies.

The 2015 ACMG/AMP standards and guidelines for interpretation of sequence variants are widely used by laboratories, including for variant curation of the hereditary hemorrhagic telangiectasia (HHT) genes. However, the need for gene- and disease-specific modifications and specifications of these general guidelines to optimize and standardize variant classification was recognized at the time of publication. With this goal, the ClinGen HHT variant curation expert panel was formed. Here, we describe our recommended HHT-specific variant classification criteria and the outcomes from pilot testing of 30 variants of the ENG and ACVRL1 genes. Eight of the original ACMG/AMP rules were determined to not be applicable for ENG- or ACVRL1-related HHT or were previously recommended by ClinGen for removal, two rules were unmodified, and the remaining 18 rules were modified according to HHT specifications or previous ClinGen general recommendations. This study demonstrates the importance of HHT-specific criteria in the optimization and standardization of HHT variant classification and conflicting classification resolution.

Supplementary Figure 1 from A Role for Endoglin as a Suppressor of Malignancy during Mouse Skin Carcinogenesis

Supplementary Table 2 from A Role for Endoglin as a Suppressor of Malignancy during Mouse Skin Carcinogenesis

Supplementary Figure 2 from A Role for Endoglin as a Suppressor of Malignancy during Mouse Skin Carcinogenesis

Endoglin (CD105) is an auxiliary receptor of transforming growth factor (TGF)-β family members that is expressed in human melanomas. It is heterogeneously expressed by primary and metastatic melanoma cells, and endoglin targeting as a therapeutic strategy for melanoma tumors is currently been explored. However, its involvement in tumor development and malignancy is not fully understood. Here, we find that endoglin expression correlates with malignancy of primary melanomas and cultured melanoma cell lines. Next, we have analyzed the effect of ectopic endoglin expression on two miRNAs (hsa-mir-214 and hsa-mir-370), both involved in melanoma tumor progression and endoglin regulation. We show that compared with control cells, overexpression of endoglin in the WM-164 melanoma cell line induces; (i) a significant increase of hsa-mir-214 levels in small extracellular vesicles (EVs) as well as an increased trend in cells; and (ii) significantly lower levels of hsa-mir-370 in the EVs fractions, whereas no significant differences were found in cells. As hsa-mir-214 and hsa-mir-370 are not just involved in melanoma tumor progression, but they can also target endoglin-expressing endothelial cells in the tumor vasculature, these results suggest a complex and differential regulatory mechanism involving the intracellular and extracellular signaling of hsa-mir-214 and hsa-mir-370 in melanoma development and progression.

Endoglin, alias CD105, is a human membrane glycoprotein highly expressed in vascular endothelial cells. It is involved in angiogenesis and angiogenesis-related diseases, including the rare vascular pathology known as hereditary hemorrhagic telangiectasia type 1. Although endoglin acts as an accessory receptor for members of the transforming growth factor-β family, in recent years, emerging evidence has shown a novel functional role for this protein beyond the transforming growth factor-β system. In fact, endoglin has been found to be an integrin counterreceptor involved in endothelial cell adhesion processes during pathological inflammatory conditions and primary hemostasis. Furthermore, a circulating form of endoglin, also named as soluble endoglin, whose levels are abnormally increased in different pathological conditions, such as preeclampsia, seems to act as an antagonist of membrane-bound endoglin and as a competitor of the fibrinogen-integrin interaction in platelet-dependent thrombus formation. These studies suggest that membrane-bound endoglin and circulating endoglin are important components involved in vascular homeostasis and hemostasis.

Supplementary Information, Legends 1-3 from A Role for Endoglin as a Suppressor of Malignancy during Mouse Skin Carcinogenesis

Supplementary Figure 3 from A Role for Endoglin as a Suppressor of Malignancy during Mouse Skin Carcinogenesis

Hereditary Hemorrhagic Telangiectasia (HHT) is an autosomal-dominant genetic disorder involving defects in two predominant genes known as endoglin (ENG; HHT-1) and activin receptor-like kinase 1 (ACVRL1/ALK1; HHT-2). It is characterized by mucocutaneous telangiectases that, due to their fragility, frequently break causing recurrent epistaxis and gastrointestinal bleeding. Because of the severity of hemorrhages, the study of the hemostasis involved in these vascular ruptures is critical to find therapies for this disease. Our results demonstrate that HHT patients with high bleeding, as determined by a high Epistaxis Severity Score (ESS), do not have prolonged clotting times or alterations in clotting factors. Considering that coagulation is only one of the processes involved in hemostasis, the main objective of this study was to investigate the overall mechanisms of hemostasis in HHT-1 (Eng+/−) and HHT-2 (Alk1+/−) mouse models, which do not show HHT vascular phenotypes in the meaning of spontaneous bleeding. In Eng+/− mice, the results of in vivo and in vitro assays suggest deficient platelet-endothelium interactions that impair a robust and stable thrombus formation. Consequently, the thrombus could be torn off and dragged by the mechanical force exerted by the bloodstream, leading to the reappearance of hemorrhages. In Alk1+/− mice, an overactivation of the fibrinolysis system was observed. These results support the idea that endoglin and Alk1 haploinsufficiency leads to a common phenotype of impaired hemostasis, but through different mechanisms. This contribution opens new therapeutic approaches to HHT patients' epistaxis.

Supplementary Figure 3 from A Role for Endoglin as a Suppressor of Malignancy during Mouse Skin Carcinogenesis

HomeArteriosclerosis, Thrombosis, and Vascular BiologyVol. 43, No. 8Therapeutic Targeting of the Ang2/Tie Pathway in Endothelial Cells as a Potential Treatment of Hereditary Hemorrhagic Telangiectasia Free AccessEditorialPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessEditorialPDF/EPUBTherapeutic Targeting of the Ang2/Tie Pathway in Endothelial Cells as a Potential Treatment of Hereditary Hemorrhagic Telangiectasia Carmelo Bernabeu Carmelo BernabeuCarmelo Bernabeu Correspondence to: Carmelo Bernabeu, PhD, Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas, 28040 Madrid, Spain. Email E-mail Address: [email protected] https://orcid.org/0000-0002-1563-6162 Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas, Madrid, Spain. Search for more papers by this author Originally published22 Jun 2023https://doi.org/10.1161/ATVBAHA.123.319631Arteriosclerosis, Thrombosis, and Vascular Biology. 2023;43:1404–1408This article is a commentary on the followingANG2 Blockade Diminishes Proangiogenic Cerebrovascular Defects Associated With Models of Hereditary Hemorrhagic TelangiectasiaOther version(s) of this articleYou are viewing the most recent version of this article. Previous versions: June 22, 2023: Ahead of Print See accompanying article on page 1384As many other rare diseases of genetic origin, hereditary hemorrhagic telangiectasia (HHT) is currently in need for a cure. In this issue of Arteriosclerosis, Thrombosis, and Vascular Biology, Zhou et al1 present experimental evidences that pharmacological blockade of Ang2 (angiopoietin-2)—a key regulator of angiogenesis—prevents and improves the vascular lesions in the brain of 3 different genetic mouse models of HHT, suggesting that Ang2-targeted therapies could be used in patients with HHT. This exciting discovery opens up a new research avenue for therapeutic prevention and treatment of vascular malformations in HHT.HHT is an autosomal dominant multisystemic vascular disorder with a prevalence of ≈1:5000 people worldwide. It is characterized by spontaneous and recurrent epistaxis (nose bleeds), mucocutaneous telangiectases, visceral involvement like telangiectases in the gastrointestinal tract, and arteriovenous malformations (AVMs) in the brain, lung, or liver.2–4 Heterozygous mutations in several genes are known to cause HHT. ENG (endoglin) mutations cause HHT1 (OMIM [Online Mendelian Inheritance in Man] No. 187300), ACVRL1 (activin A receptor-like type 1; or ALK1) mutations cause HHT2 (OMIM No. 600376), while MADH4 (mothers against decapentaplegic homolog 4 or SMAD4 [suppressor of mothers against decapentaplegic 4]) mutations cause a syndrome that combines familial juvenile polyposis and HHT (OMIM No. 175050).5 Also, mutations in the GDF2 gene, encoding BMP (bone morphogenetic protein) 9, were described as the cause of an HHT-like syndrome, named as HHT5 (OMIM No. 615506).6,7 Pathogenic mutations in ENG and ACVRL1 genes account for over 95% of all HHT cases, while the remaining cases are caused by SMAD4 or GDF2 variants or by currently undiscovered mutations in coding or noncoding regions.8 All the genes mutated in HHT encode proteins involved in the signaling pathway of the TGF-β (transforming growth factor beta) superfamily, including BMPs (Figure). The signaling pathway affected in HHT encompasses the auxiliary receptor endoglin associated with the signaling serine/threonine kinase receptor ALK1. Both proteins are able to bind the ligands BMP9 and BMP10,9,10 which form a heterodimeric complex that provides most of their BMP biological activity in plasma.11 Upon ligand binding, ALK1 phosphorylates Smad1/5/8 followed by their nuclear translocation in complex with Smad4.8,10 Because endoglin and ALK1 are predominantly expressed in endothelial cells (ECs), which contain the ubiquitous Smad4 and respond to circulating BMP9, they are widely accepted as the main target cells in HHT. In spite of the well-established clinical diagnosis with the so-called Curaçao criteria12 and the deep knowledge about the genetics and the signaling pathway involved, a definite cure for patients with HHT is still needed. Recurrent epistaxis is the hallmark symptom of HHT, often leading to anemia.2–4 During the last decades, epistaxis in patients with HHT is treated with palliative measures, sometimes using drug repurposing strategies, often driven by the pharmaceutical industry. Among the different pharmacological strategies tested are antifibrinolytic agents (tranexamic acid), estrogen receptor modulators (bazedoxifene and raloxifene), antioxidants (N-acetylcysteine and resveratrol), immunosuppressors (tacrolimus), antiangiogenic drugs (bevacizumab, thalidomide, pazopanib, and etamsylate), or β-blockers (propranolol and timolol).13 In addition to the drug repurposing strategy, it is evident that there is an ongoing requirement for new, and hopefully more effective, pharmacological interventions specifically based on HHT pathobiology and multiomic data. Actually, since 2000, many researchers have been using different genetic HHT animal models trying to find the way to prevent and reverse the vascular lesions (telangiectases and AVMs), which are responsible for the clinical symptoms in HHT.14 In this context, Zhou et al1 focus their study on Ang2-based preliminary experimental evidence supporting its involvement in HHT and AVM development. Upon RNA and chromatin immunoprecipitation sequencing experiments on BMP9-stimulated ECs and isolated ECs from a Smad4-inducible EC-specific knockout (Smad4-iECKO) mouse model, the same group identified the EC surface receptor Tek/Tie2 (tyrosine kinase receptor of angiopoietins) and its antagonistic ligand Ang2 as downstream targets of Smad4.15 It was also found that loss of endothelial Smad4 increased Ang2 and decreased Tek levels, resulting in an overall reduction of the angiopoietin-Tek signaling associated with retinal AVM formation and other HHT-associated abnormalities in mice, including enlarged blood vessel diameters. These findings suggested that targeted inhibition of Ang2 holds potential therapeutic value for treating HHT-related AVMs. Indeed, the retinal vascular phenotype (ie, AVM formation and increased vessel calibers) of the Smad4-iEC.KO mouse model of HHT was not only prevented but also reversed by inhibiting Ang2 using an anti-Ang2 antibody.15 More recently, Ang2 regulation was studied in the genetic context of GNAQ mutations, which drive port-wine birthmark-associated Sturge-Weber syndrome (OMIM No. 185300).16 Thus, increased expression of Ang2 induced by the GNAQ variant p.R183Q in human ECs was found to drive the formation of enlarged blood vessels in mice, while knockdown of Ang2 in ECs carrying the GNAQ/R183Q variant normalized the size of the vessels.17,18 As a follow-up to the above findings, now Zhou et al1 have further analyzed and confirmed the regulated expression and function of Ang2 not only in Smad4-iEC.KO but also in Eng-iEC.KO and Alk1-iEC.KO mouse models of HHT (Figure). In this case, the authors centered their studies on brain ECs and brain AVMs, a goal justified by the fact that ≈10% to 20% of patients with HHT present with brain AVMs. These vascular lesions, which are primarily congenital, can lead to seizure, headache, and spontaneous or recurrent intracranial hemorrhage, causing significant morbidity and mortality in HHT.19 Comparative RNA sequencing analyses of isolated brain ECs from Smad4-iEC.KO, Eng-iEC.KO, and Alk1-iEC.KO mice revealed a common proangiogenic transcriptional profile associated with HHT.1 This genetic fingerprint was in agreement with an upregulation of Ang2 in brain vessels and a downregulation of its receptor Tek/Tie2 in HHT mice compared with controls. Accordingly, a reduction of Tek signaling was also observed in vitro using human ECs mimicking the HHT2 condition. Remarkably, in vivo neutralization of Ang2 using a specific monoclonal antibody (LC10) improved, at different degrees, brain vascular lesions in the 3 HHT animal models, a finding consistent with in vitro results showing that inhibition of Ang2 normalizes the gene signature in brain ECs derived from Smad4-iEC.KO mice.1 While providing hope for future pharmacological treatments, additional investigations are needed to better understand the underlying cellular and molecular mechanisms of Ang2 regulation and activity in the HHT setting. For example, although this study has focused on brain AVMs, patients with HHT present with additional vascular lesions like lung and hepatic AVMs or mucosal telangiectases in the nose and gastrointestinal tract. Thus, it will be of interest to assess whether blockade of Ang2 can also improve AVMs/telangiectases from other organs (Figure). Moreover, Ang2 is expressed not only by ECs but also by a wide variety of tissues and cell types including smooth muscle cells, adipocytes, or fibroblasts, raising the question of whether the regulated expression of Ang2 varies with the specific cell lineage. This is a critical point in patients with HHT as the germline mutations driving the vascular phenotype are systemically present in all cell types, at variance with the EC-specific KO of the 3 HHT genes in their respective animal models. Thus, the relative contribution of ECs compared with non-ECs to the overall circulating levels of Ang2 in patients with HHT remains to be determined. So far, contradictory findings regarding circulating tissue or cellular levels of Ang2 in patients or animal models of HHT compared with controls have been reported,15,20–24 while plasma levels of Ang2 appear to skew lower in patients with HHT.20,21,25 More accurate measurements of circulating plasma Ang2 in large cohorts of patients with HHT, including representative HHT subsets, are needed to determine whether the dysregulated levels of Ang2 can be used a biomarker of the disease, in addition to have a potential pathogenic role. Aside from the circulating levels of Ang2, the complex and context-dependent activity of the Ang2/Tek signaling pathway should be taken into account.26,27 Within the vascular microenvironment, Ang2 destabilizes quiescent endothelium acting in an antagonistic manner toward Ang1 (angiopoietin 1)-mediated activation of Tek.28 Ang2 also drives an autocrine regulation of the endothelium through an internal autocrine loop mechanism.29 This would be compatible with an autonomously regulated expression and activity of Ang2 in ECs in a manner independent of the systemic circulating levels of Ang2. Whether the circulating Ang2 can also contribute to this autocrine system by impairing the endothelial Tek signaling, remains to be elucidated (Figure).Download figureDownload PowerPointFigure. Hypothetical model of Ang2 (angiopoietin-2) expression and activity in hereditary hemorrhagic telangiectasia (HHT). In endothelial cells (ECs), heterodimers of BMP (bone morphogenetic protein) 9 and BMP10, members of the TGF-β (transforming growth factor beta) family, bind to an EC surface receptor complex composed by the type I (R-I) receptor named ALK1 and the type II (R-II; BMPR2, ActR2A, ActR2B) receptor, both serine/threonine kinases, as well as the auxiliary receptor endoglin. Upon ligand binding, the R-II phosphorylates ALK1, which in turn phosphorylates the receptor-regulated Smad (R-Smad) family of proteins, Smad1/5/8. Once phosphorylated, R-Smads assemble into heteromeric complexes with Smad4 and translocate into the nucleus to regulate gene expression. BMP9, endoglin, ALK1, and Smad4 proteins are encoded by GDF2, ENG, ACVRL1, and MADH4 genes, whose pathogenic mutations give rise to HHT5, HHT1, HHT2, and juvenile polyposis (JP) and HHT, respectively. Using several mouse models of HHT (Smad4-iEC.KO, Eng-iEC.KO, and Alk1-iEC.KO), Zhou et al1 show that upon silencing HHT genes in ECs, Ang2 expression is increased, likely inducing a vascular remodeling that leads to brain arteriovenous malformations (bAVMs). Remarkably, these bAVMs can be partly prevented and regressed when animals are treated with an antibody anti-Ang2 (LC10). The potential beneficial effect of LC10 on pulmonary arteriovenous malformations (pAVMs) or hepatic arteriovenous malformations (hAVMs) in these animals was not addressed. Upon its overexpression mediated by Weibel-Palade bodies, Ang2 can antagonize Ang1 (angiopoietin 1)-mediated activation of Tek involving PI3K/AKT and drive an autocrine regulation through an internal autocrine loop mechanism (Kim et al28 and Scharpfenecker et al29). Whether the pool of circulating Ang2 derived from non-ECs can also contribute to this autocrine system remains to be determined. The HHT signaling pathway was adapted from Bernabeu et al.8 The figure was partly generated using Servier Medical Art, provided by Servier, licensed under a Creative Commons Attribution 3.0 unported license. ActR2A indicates activin A type 2A receptor; ActR2B, activin A type 2B receptor; Akt, serine/threonine kinase; ALK1, activin receptor-like kinase 1; AVM, arteriovenous malformation; BMPR2, bone morphogenetic protein type 2 receptor; PI3K, phosphatidylinositol 3-kinase; Smad, suppressor of mothers against decapentaplegic; and Tek/Tie2, tyrosine kinase receptor of angiopoietins.Overall, this study provides promising results regarding Ang2-based therapeutics for treating AVMs not only in HHT but also in other vascular diseases. The potential therapeutic treatment of patients with AVM-associated conditions would be benefited by the existence of different drugs targeting the Ang2/Tie signaling pathway. Among the inhibitors of this pathway are antibody-based drugs (nesvacumab, MEDI3617, REGN910-3, LY3127804, and trebananib), a chimeric decoy receptor which can simultaneously bind VEGF-A (vascular endothelial growth factor-A) and angiopoietins (DAAP [double antiangiogenic protein]), and small-molecule inhibitors against Tie2 (ARRY-614, regorafenib, rebastinib, and altiratinib).30 Many of them are currently in clinical development for oncological or ophthalmological applications, like wet age-related macular degeneration, macular edema and retinal vein occlusions. Indeed, some of the ongoing clinical trials targeting the Ang-Tie pathway are already in phase III with encouraging outcomes.30–32ARTICLE INFORMATIONSources of FundingC. Bernabeu acknowledges support from Consejo Superior de Investigaciones Científicas of Spain (201920E022).Disclosures None.FootnotesFor Sources of Funding and Disclosures, see page 1407.The opinions expressed in this article are not necessarily those of the editors or of the American Heart Association.Correspondence to: Carmelo Bernabeu, PhD, Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas, 28040 Madrid, Spain. Email bernabeu.[email protected].csic.esREFERENCES1. Zhou X, Pucel JC, Nomura-Kitabayashi A, Chandakkar P, Guidroz AP, Jhangiani NL, Bao D, Fan J, Arthur HM, Ullmer C, et al. ANG2 blockade diminishes proangiogenic cerebrovascular defects associated with models of hereditary hemorrhagic telangiectasia.Arterioscler Thromb Vasc Biol. 2023; 43:1384–1403. doi: 10.1161/ATVBAHA.123.319385LinkGoogle Scholar2. Shovlin CL. Hereditary haemorrhagic telangiectasia: pathophysiology, diagnosis and treatment.Blood Rev. 2010; 24:203–219. doi: 10.1016/j.blre.2010.07.001CrossrefMedlineGoogle Scholar3. Faughnan ME, Palda VA, Garcia-Tsao G, Geisthoff UW, McDonald J, Proctor DD, Spears J, Brown DH, Buscarini E, Chesnutt MS, et al; HHT Foundation International - Guidelines Working Group. International guidelines for the diagnosis and management of hereditary haemorrhagic telangiectasia.J Med Genet. 2011; 48:73–87. doi: 10.1136/jmg.2009.069013CrossrefMedlineGoogle Scholar4. Faughnan ME, Mager JJ, Hetts SW, Palda VA, Lang-Robertson K, Buscarini E, Deslandres E, Kasthuri RS, Lausman A, Poetker D, et al. Second international guidelines for the diagnosis and management of hereditary hemorrhagic telangiectasia.Ann Intern Med. 2020; 173:989–1001. doi: 10.7326/M20-1443CrossrefMedlineGoogle Scholar5. McDonald J, Wooderchak-Donahue W, VanSant Webb C, Whitehead K, Stevenson DA, Bayrak-Toydemir P. Hereditary hemorrhagic telangiectasia: genetics and molecular diagnostics in a new era.Front Genet. 2015; 6:1. doi: 10.3389/fgene.2015.00001CrossrefMedlineGoogle Scholar6. Wooderchak-Donahue WL, McDonald J, O’Fallon B, Upton PD, Li W, Roman BL, Young S, Plant P, Fülöp GT, Langa C, et al. BMP9 mutations cause a vascular-anomaly syndrome with phenotypic overlap with hereditary hemorrhagic telangiectasia.Am J Hum Genet. 2013; 93:530–537. doi: 10.1016/j.ajhg.2013.07.004CrossrefMedlineGoogle Scholar7. Balachandar S, Graves TJ, Shimonty A, Kerr K, Kilner J, Xiao S, Slade R, Sroya M, Alikian M, Curetean E, et al; Genomics England Research Consortium. Identification and validation of a novel pathogenic variant in GDF2 (BMP9) responsible for hereditary hemorrhagic telangiectasia and pulmonary arteriovenous malformations.Am J Med Genet A. 2022; 188:959–964. doi: 10.1002/ajmg.a.62584CrossrefMedlineGoogle Scholar8. Bernabeu C, Bayrak-Toydemir P, McDonald J, Letarte M. Potential second-hits in hereditary hemorrhagic telangiectasia.J Clin Med. 2020; 9:3571. doi: 10.3390/jcm9113571CrossrefMedlineGoogle Scholar9. Saito T, Bokhove M, Croci R, Zamora-Caballero S, Han L, Letarte M, de Sanctis D, Jovine L. Structural basis of the human endoglin-BMP9 interaction: insights into BMP signaling and HHT1.Cell Rep. 2017; 19:1917–1928. doi: 10.1016/j.celrep.2017.05.011CrossrefMedlineGoogle Scholar10. Roman BL, Hinck AP. ALK1 signaling in development and disease: new paradigms.Cell Mol Life Sci. 2017; 74:4539–4560. doi: 10.1007/s00018-017-2636-4CrossrefMedlineGoogle Scholar11. Tillet E, Ouarné M, Desroches-Castan A, Mallet C, Subileau M, Didier R, Lioutsko A, Belthier G, Feige JJ, Bailly S. A heterodimer formed by bone morphogenetic protein 9 (BMP9) and BMP10 provides most BMP biological activity in plasma.J Biol Chem. 2018; 293:10963–10974. doi: 10.1074/jbc.RA118.002968CrossrefMedlineGoogle Scholar12. Shovlin CL, Guttmacher AE, Buscarini E, Faughnan ME, Hyland RH, Westermann CJ, Kjeldsen AD, Plauchu H. Diagnostic criteria for hereditary hemorrhagic telangiectasia (Rendu-Osler-Weber syndrome).Am J Med Genet. 2000; 91:66–67. doi: 10.1002/(sici)1096-8628(20000306)91:1<66::aid-ajmg12>3.0.co;2-pCrossrefMedlineGoogle Scholar13. Albiñana V, Cuesta AM, Rojas-P I, Gallardo-Vara E, Recio-Poveda L, Bernabéu C, Botella LM. Review of pharmacological strategies with repurposed drugs for hereditary hemorrhagic telangiectasia related bleeding.J Clin Med. 2020; 9:1766. doi: 10.3390/jcm9061766CrossrefMedlineGoogle Scholar14. Arthur HM, Roman BL. An update on preclinical models of hereditary haemorrhagic telangiectasia: insights into disease mechanisms.Front Med (Lausanne). 2022; 9:973964. doi: 10.3389/fmed.2022.973964CrossrefMedlineGoogle Scholar15. Crist AM, Zhou X, Garai J, Lee AR, Thoele J, Ullmer C, Klein C, Zabaleta J, Meadows SM. Angiopoietin-2 inhibition rescues arteriovenous malformation in a Smad4 hereditary hemorrhagic telangiectasia mouse model.Circulation. 2019; 139:2049–2063. doi: 10.1161/CIRCULATIONAHA.118.036952LinkGoogle Scholar16. Van Trigt WK, Kelly KM, Hughes CCW. GNAQ mutations drive port wine birthmark-associated Sturge-Weber syndrome: a review of pathobiology, therapies, and current models.Front Hum Neurosci. 2022; 16:1006027. doi: 10.3389/fnhum.2022.1006027CrossrefMedlineGoogle Scholar17. Huang L, Bichsel C, Norris AL, Thorpe J, Pevsner J, Alexandrescu S, Pinto A, Zurakowski D, Kleiman RJ, Sahin M, et al. Endothelial GNAQ p.R183Q increases ANGPT2 (angiopoietin-2) and drives formation of enlarged blood vessels.Arterioscler Thromb Vasc Biol. 2022; 42:e27–e43. doi: 10.1161/ATVBAHA.121.316651LinkGoogle Scholar18. Khosraviani N, Wu R, Fish JE. Angiopoietin-2: an emerging tie to pathological vessel enlargement.Arterioscler Thromb Vasc Biol. 2022; 42:3–5. doi: 10.1161/ATVBAHA.121.317102LinkGoogle Scholar19. Gamboa NT, Joyce EJ, Eli I, Park MS, Taussky P, Schmidt RH, McDonald J, Whitehead KJ, Kalani MYS. Clinical presentation and treatment paradigms of brain arteriovenous malformations in patients with hereditary hemorrhagic telangiectasia.J Clin Neurosci. 2018; 51:22–28. doi: 10.1016/j.jocn.2018.01.019CrossrefMedlineGoogle Scholar20. Fernandez-L A, Garrido-Martin EM, Sanz-Rodriguez F, Pericacho M, Rodriguez-Barbero A, Eleno N, Lopez-Novoa JM, Düwell A, Vega MA, Bernabeu C, et al. Gene expression fingerprinting for human hereditary hemorrhagic telangiectasia.Hum Mol Genet. 2007; 16:1515–1533. doi: 10.1093/hmg/ddm069CrossrefMedlineGoogle Scholar21. Ojeda-Fernandez L, Barrios L, Rodriguez-Barbero A, Recio-Poveda L, Bernabeu C, Botella LM. Reduced plasma levels of Ang-2 and sEng as novel biomarkers in hereditary hemorrhagic telangiectasia (HHT).Clin Chim Acta. 2010; 411:494–499. doi: 10.1016/j.cca.2009.12.023CrossrefMedlineGoogle Scholar22. Ardelean DS, Jerkic M, Yin M, Peter M, Ngan B, Kerbel RS, Foster FS, Letarte M. Endoglin and activin receptor-like kinase 1 heterozygous mice have a distinct pulmonary and hepatic angiogenic profile and response to anti-VEGF treatment.Angiogenesis. 2014; 17:129–146. doi: 10.1007/s10456-013-9383-4CrossrefMedlineGoogle Scholar23. Ruiz S, Zhao H, Chandakkar P, Chatterjee PK, Papoin J, Blanc L, Metz CN, Campagne F, Marambaud P. A mouse model of hereditary hemorrhagic telangiectasia generated by transmammary-delivered immunoblocking of BMP9 and BMP10.Sci Rep. 2016; 5:37366. doi: 10.1038/srep37366CrossrefMedlineGoogle Scholar24. Ruiz S, Chandakkar P, Zhao H, Papoin J, Chatterjee PK, Christen E, Metz CN, Blanc L, Campagne F, Marambaud P. Tacrolimus rescues the signaling and gene expression signature of endothelial ALK1 loss-of-function and improves HHT vascular pathology.Hum Mol Genet. 2017; 26:4786–4798. doi: 10.1093/hmg/ddx358CrossrefMedlineGoogle Scholar25. Wetzel-Strong SE, Weinsheimer S, Nelson J, Pawlikowska L, Clark D, Starr MD, Liu Y, Kim H, Faughnan ME, Nixon AB, et al. Pilot investigation of circulating angiogenic and inflammatory biomarkers associated with vascular malformations.Orphanet J Rare Dis. 2021; 16:372. doi: 10.1186/s13023-021-02009-7CrossrefMedlineGoogle Scholar26. Eklund L, Kangas J, Saharinen P. Angiopoietin-Tie signalling in the cardiovascular and lymphatic systems.Clin Sci (Lond). 2017; 131:87–103. doi: 10.1042/CS20160129CrossrefMedlineGoogle Scholar27. Akwii RG, Sajib MS, Zahra FT, Mikelis CM. Role of angiopoietin-2 in vascular physiology and pathophysiology.Cells. 2019; 8:471. doi: 10.3390/cells8050471CrossrefMedlineGoogle Scholar28. Kim M, Allen B, Korhonen EA, Nitschké M, Yang HW, Baluk P, Saharinen P, Alitalo K, Daly C, Thurston G, et al. Opposing actions of angiopoietin-2 on Tie2 signaling and FOXO1 activation.J Clin Invest. 2016; 126:3511–3525. doi: 10.1172/JCI84871CrossrefMedlineGoogle Scholar29. Scharpfenecker M, Fiedler U, Reiss Y, Augustin HG. The Tie-2 ligand angiopoietin-2 destabilizes quiescent endothelium through an internal autocrine loop mechanism.J Cell Sci. 2005; 118:771–780. doi: 10.1242/jcs.01653CrossrefMedlineGoogle Scholar30. Saharinen P, Eklund L, Alitalo K. Therapeutic targeting of the angiopoietin-TIE pathway.Nat Rev Drug Discov. 2017; 16:635–661. doi: 10.1038/nrd.2016.278CrossrefMedlineGoogle Scholar31. Parmar D, Apte M. Angiopoietin inhibitors: a review on targeting tumor angiogenesis.Eur J Pharmacol. 2021; 899:174021. doi: 10.1016/j.ejphar.2021.174021CrossrefMedlineGoogle Scholar32. Ferro Desideri L, Traverso CE, Nicolò M. The emerging role of the angiopoietin-Tie pathway as therapeutic target for treating retinal diseases.Expert Opin Ther Targets. 2022; 26:145–154. doi: 10.1080/14728222.2022.2036121CrossrefMedlineGoogle Scholar Previous Back to top Next FiguresReferencesRelatedDetailsRelated articlesANG2 Blockade Diminishes Proangiogenic Cerebrovascular Defects Associated With Models of Hereditary Hemorrhagic TelangiectasiaXingyan Zhou, et al. Arteriosclerosis, Thrombosis, and Vascular Biology. 2023;43:1384-1403 August 2023Vol 43, Issue 8 Advertisement Article InformationMetrics © 2023 American Heart Association, Inc.https://doi.org/10.1161/ATVBAHA.123.319631PMID: 37345521 Originally publishedJune 22, 2023 Keywordsangiopoietinsendothelial cellsEditorialsbrainarteriovenous malformationsPDF download Advertisement

EDITORIAL article Front. Med., 04 September 2023Sec. Pathology Volume 10 - 2023 | https://doi.org/10.3389/fmed.2023.1271756

Supplementary Table 4 from A Role for Endoglin as a Suppressor of Malignancy during Mouse Skin Carcinogenesis

Supplementary Table 3 from A Role for Endoglin as a Suppressor of Malignancy during Mouse Skin Carcinogenesis

Background: The circulating form of human endoglin (sEng) is a cleavage product of membrane-bound endoglin present on endothelial cells. Because sEng encompasses an RGD motif involved in integrin binding, we hypothesized that sEng would be able to bind integrin alpha IIb beta 3, thereby compromising platelet binding to fibrinogen and thrombus stability.Methods: In vitro human platelet aggregation, thrombus retraction, and secretion-competition assays were performed in the presence of sEng. Surface plasmon resonance (SPR) binding and computational (docking) analyses were carried out to evaluate protein-protein interactions. A transgenic mouse overexpressing human sEng (hsEng+) was used to measure bleeding/rebleeding, prothrombin time (PT), blood stream, and embolus formation after FeCl3-induced injury of the carotid artery.Results: Under flow conditions, supplementation of human whole blood with sEng led to a smaller thrombus size. sEng inhibited platelet aggregation and thrombus retraction, interfering with fibrinogen binding, but did not affect platelet activation. SPR binding studies demonstrated that the specific interaction between alpha IIb beta 3 and sEng and molecular modeling showed a good fitting between alpha IIb beta 3 and sEng structures involving the endoglin RGD motif, suggesting the possible formation of a highly stable alpha IIb beta 3/ sEng. hsEng+ mice showed increased bleeding time and number of rebleedings compared to wild-type mice. No differences in PT were denoted between genotypes. After FeCl3 injury, the number of released emboli in hsEng+ mice was higher and the occlusion was slower compared to controls.Conclusions: Our results demonstrate that sEng interferes with thrombus formation and stabilization, likely via its binding to platelet alpha IIb beta 3, suggesting its involvement in primary hemostasis control.