Endothelium is a community of endothelial cells (ECs), which line the blood and lymphatic vessels, thus forming an interface between the tissues and the blood or lympha. This strategic position of endothelium infers its indispensable functional role in controlling vasoregulation, haemostasis, and inflammation. The state of endothelium is simultaneously the cause and effect of many diseases, and this is coupled with modifications of endothelial phenotype represented by markers and with biochemical profile of blood represented by biomarkers. In this paper, we briefly review data on the functional role of endothelium, give definitions of endothelial markers and biomarkers, touch on the methodological approaches for revealing biomarkers, present an implicit role of endothelium in some toxicological mechanistic studies, and survey the role of reactive oxygen species (ROS) in modulation of endothelial status.
The volume of publications on the role of endothelium in health and disease has increased exponentially over the last decades, and it may seem that all problems have been thoroughly considered. There is a plethora of excellent reviews on the subject; newcomers are referred to a few of them as reliable sources of more detailed information than presented in this paper [
Endothelium is the monolayer of endothelial cells (ECs) that lines the interior surface of blood vessels, lymphatic vessels, and heart chambers. It is a natural blood container with a large surface of up to 6000 m2 in humans [
A healthy endothelium is characterized by a vasodilatory phenotype with high levels of nitric oxide (NO) and prostacyclin (PGI2) and low levels of uric acid and reactive oxygen species (ROS). On the other hand, ECs are involved in the aetiology of major human diseases: stroke, diabetes, insulin resistance, heart disease, peripheral vascular disease, tumor growth and metastasis, chronic kidney failure, rheumatoid arthritis, and viral infections [
In spite of extensive studies and impressive results, there is still a need for better understanding of dynamical changes of endothelial markers and biomarkers associated with different disorders. Also, little is known about the role of endothelium in some fields of toxicology: intoxications with organophosphates, hydrocarbons, and so forth. There is a gap between our understanding of immediate and delayed responses of endothelium and the role of ROS in these responses. It would be very interesting to reveal interrelations, feedback, and feed-forward regulatory effects of various sources of ROS in the development of vascular pathologies. Finally, great challenges exist in the methodology of biomarker discovery, which concern instrumental and computational approaches. In this review, we discuss some of these problems, which could help to re-estimate some old data as well as reveal something new in the future.
Cell surface markers are proteins expressed on the surface of cells that often serve as markers of specific cell types. Von Willebrand factor (VWF), together with the Weibel–Palade bodies (WPB), angiotensin-converting enzyme (ACE, CD143), and the cobblestone morphology specific for monolayer cultures, was previously referred to as a few obligate criteria to confirm the authenticity and the purity of endothelial cell culture [
Endothelial cell markers (modified from
Endothelial cell marker | Function |
---|---|
CD13/APN | CD13/aminopeptidase N is a transmembrane peptidase that is induced in the vasculature of solid tumors and is a potent angiogenic regulator. CD13 functions as a novel modulator of signal transduction and cell motility via its influence on specific plasma membrane organization, thus regulating angiogenesis [ |
|
|
CD29/integrin |
Integrin |
|
|
CD31/PECAM-1 | CD31, known as PECAM-1 (platelet/endothelial cell adhesion molecule 1), is a heavily glycosylated transmembrane homophilic adhesion protein that is highly expressed on endothelial cells and is required for migration of leukocytes, playing a key role in removing aged neutrophils from the body. The extracellular domain of CD31 is released during endothelial cell apoptosis. This fragment circulates in the serum of patients suffering from myocardial infarction, acute ischemic stroke, and multiple sclerosis [ |
|
|
CD34 | CD34 is a transmembrane phosphoglycoprotein, first identified on hematopoietic stem and progenitor cells. Cells expressing CD34 are found in the umbilical cord and bone marrow as endothelial progenitor cells, a subset of mesenchymal stem cells, hematopoietic cells, and ECs of blood vessels and pleural lymphatic vessels. The presence of CD34 on nonhematopoietic cells in various tissues has been linked to progenitor and adult stem cell phenotypes [ |
|
|
CD36/SR-B3 | CD36 is known as scavenger receptor class B member 3 (SR-B3), thrombospondin receptor, collagen receptor, platelet membrane glycoprotein IV (GPIV), GPIIIb, and fatty acid translocase (FAT). Upon ligand binding, CD36 transduces signals that mediate a wide range of proinflammatory cellular responses. For example, amyloid- |
|
|
CD39/ENTPD1 | CD39 (ENTPD1) is an ectonucleotidase most abundantly expressed on the surface of ECs and to a lesser degree on the surface of platelets and leukocytes. CD39 catalizes extracellular dephosphorylation of ATP to ADP and AMP. CD39 molecules are liberated from the coronary vascular endothelium by ischemia-reperfusion, and levels of circulating ectonucleotidase may reflect the severity of ischemic vascular injury [ |
|
|
CD44 | CD44 expression in endothelial colony-forming cells (ECFCs) regulates neurovascular trophic effect [ |
|
|
CD47 | Endothelial CD47 molecules participate in intracellular calcium mobilization, increased permeability, and activation of Src and AKT1/PI3K in brain microvascular ECs [ |
|
|
CD54/ICAM-1 | ICAM-1 (intercellular adhesion molecule-1) is a transmembrane protein that is upregulated on endothelial and epithelial cells at sites of inflammation. It mediates the vascular adhesion and paracellular migration of leukocytes with activated LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18). Soluble ICAM-1 participates in angiogenesis being an indicator of EC activation or damage. Elevated levels of soluble ICAM-1 are linked to oxidative stress, hypertension, cardiovascular disease, type 2 diabetes, organ transplant dysfunction, increased abdominal fat mass, liver disease, certain malignancies, and sepsis [ |
|
|
CD61/integrin |
CD61 (integrin |
|
|
CD62E/E-selectin | E-selectin (endothelial leukocyte adhesion molecule-1 (ELAM-1), CD62E) is one of the three members of the selectin family (E-selectin, L-selectin, and P-selectin), which is transiently expressed on ECs in response to IL-1 |
|
|
CD62P/P-selectin | Also known as GMP-140, PADGEM, and LECAM-3; a transmembrane adhesion protein that is upregulated on activated platelets and vascular endothelial cells. P-selectin mediates the initial interaction of circulating leukocytes with activated endothelial cells that produces a characteristic rolling of the leukocytes on the endothelium. It is therefore critical for leukocyte extravasation at sites of inflammation and leukocyte involvement in thrombus formation at sites of vascular injury. |
|
|
CD80/B7-1 | Under certain conditions, ECs can serve as antigen presenting cells by expressing both MHC class I and class II molecules [ |
CD86/B7-2 | |
|
|
CD93/C1qR1 | C1qR1 is also known as C1qRp, collectin receptor, and AA4 antigen. It is a type I transmembrane glycoprotein found not only on ECs, but also on hematopoietic progenitor cells, platelets, and cells of myeloid origin. C1qR1 molecules mediate phagocytosis by monocytes and macrophages upon interaction with soluble defense collagens, such as C1q, MBL, and SP-A. |
|
|
CD102/ICAM-2 | ICAM-2 molecules are abundantly expressed on vascular ECs and lymphohematopoietic cells. They participate in T cell aggregation, NK cytotoxicity, and NK cell migration. |
|
|
CD105/endoglin | Endoglin is a transmembrane type III receptor for TGF- |
|
|
CD106/VCAM-1 | Vascular cell adhesion molecule-1 is a transmembrane molecule that mediates the adhesion of immune cells to the vascular endothelium during inflammation. It binds to several integrins including |
|
|
CD112/nectin-2 | Nectins are type I transmembrane glycoproteins that are calcium-independent Ig-like CAMs. Due to the sequence homology, they were designated as poliovirus receptor-related (PRR) proteins, though do not bind poliovirus. Nectin-1 (CD111, PRR1, herpes virus entry mediator C, or HVEC), nectin-2 (CD112, PRR2, and HVEB), and nectin-3 (PRR3) are found in adherens junctions on neurons, ECs, epithelial cells, and fibroblasts. |
|
|
CD117/c-Kit | CD117/c-Kit is a receptor with tyrosine kinase activity that binds stem cell factor; it is a marker of certain types of hematopoietic progenitors in the bone marrow (hematopoietic stem cells, multipotent progenitors, and common myeloid progenitors). Also, its expression is a distinguishing feature of hemogenic ECs, relative to nonblood-forming ECs [ |
|
|
CD121a/IL-1 RI | IL-1 RI, also known as the type 1 IL-1 receptor and CD121a, is a transmembrane protein in the Toll/IL-1 R (TIR) superfamily. IL-1 RI binds the pleiotropic cytokines IL-1 |
|
|
CD141/thrombomodulin/BDCA-3 | Thrombomodulin (TM), also known as CD141 and BDCA3, is a transmembrane expressed on vascular ECs, arterial smooth muscle cells, monocytes, and macrophages. It binds thrombin and enhances the thrombin-mediated activation of the anticoagulant protein C and the antifibrinolytic TAFI/carboxypeptidase B2. Thrombomodulin also inhibits the ability of thrombin to activate several procoagulant proteins (e.g., fibrinogen, factor V, factor XIII, and PAR-1). Soluble fragments of thrombomodulin are elevated in the serum, urine, and synovial fluid during coagulation disorders, inflammation, and organ failure. |
|
|
CD142/coagulation factor III/tissue factor/thromboplastin | Tissue factor is an integral membrane protein, which has been shown to be produced by several cell types, including ECs. It serves as a cofactor of coagulation factor VII. |
|
|
CD143/ACE | ACE and ACE2 are cell surface proteases, which maintain blood pressure homeostasis and fluid salt balance, mainly due to generation of angiotensin II and inactivation of bradykinin. Also, ACE activities play roles in immunity, reproduction, and neuropeptide regulation. |
|
|
CD144/VE-cadherin | Vascular endothelial (VE)-cadherin is a specific endothelial adhesion molecule located at junctions between ECs. VE-cadherin-mediated adhesion is important for the control of vascular permeability and leukocyte extravasation. Also, VE-cadherin participates in cell proliferation, apoptosis, and modulates vascular endothelial growth factor receptor functions [ |
|
|
CD146/MCAM | CD146 is also known as the melanoma cell adhesion molecule (MCAM) or cell surface glycoprotein MUC18. CD146 is currently used as a marker for ECs. MCAM functions as a receptor for laminin alpha 4, a matrix molecule expressed within the vascular wall by ECs, SMCs, and pericytes. Downregulation of MCAM accelerates cellular senescence in human umbilical cord blood-derived mesenchymal stem cells [ |
|
|
CD147/TRA-1-85 | The TRA-1-85 antigen, or Oka blood group antigen, is a specific epitope of the protein basigin, also known as EMMPRIN and CD147. |
|
|
CD151 | CD151 is a tetraspanin superfamily glycoprotein expressed by ECs, epithelial cells, megakaryocytes, and platelets. It interacts with other tetraspanins and integrins, such as α3/β1, α6/β1, α6/β4, and α7/β1. CD151 plays a role in cellular adhesion, migration, and platelet activation. |
|
|
CD160 | CD160 is a GPI-anchored glycoprotein with one Ig-like V-type domain, found mainly on a subpopulation of cytolytic T cells and NK cells. CD160 serves as a receptor for MHC class I and related molecules. When expressed on ECs, CD160 plays a role in antiangiogenic signaling and apoptotic cell death. |
|
|
CD201/EPCR | EPCR (the endothelial protein C receptor) is a transmembrane glycoprotein expressed on ECs. EPCR inhibits thrombosis through its interactions with protein C, activated protein C (aPC), and coagulation factors VII and VIIa. It enhances the activation of protein C in response to complexes of thrombin-thrombomodulin. A soluble form of EPCR inhibits the anticoagulant activity of APC. EPCR binds to CD11b/CD18 (Mac-1) on monocytes and mediates monocyte adhesion to the vascular endothelium. In addition, it binds to the antigen receptor on gamma/delta T cells, promotes hematopoietic stem cell retention in the bone marrow, and contributes to malaria pathogenicity through binding surface proteins on plasmodium. |
|
|
CD213a/IL-13R alpha 1 | Two members of the type 5 subfamily of type I cytokine receptors also serve as receptors for IL-13, which bind to IL-13 R α1 (CD213a1, also known as NR4) with low affinity, then forming a high affinity receptor together with the IL-4 R alpha chain and causing downstream STAT6 activation. On the other hand, IL-13 can bind IL-13 R alpha 2 (CD213a2) with high affinity and subsequent TGF-β production, though without activation of STAT6. |
|
|
CD248/endosialin | Endosialin, also known as tumor endothelial marker 1 (Tem1), is a 165 kDa transmembrane O-glycosylated protein that contains one C-type lectin, one sushi, one EGF-like domain, and a mucin-like stalk in its extracellular domain (ECD). It is expressed on activated perivascular and stromal cells in embyronic and tumor neovasculature but is downregulated in quiescent vasculature. Endosialin regulates pericyte proliferation, migration, and adhesion to matrix fibronectin and collagens I and IV. |
|
|
CD309/VEGFR2/KDR/Flk-1 | VEGFR2 (vascular endothelial growth factor receptor 2) is a transmembrane receptor tyrosine kinase that mediates the angiogenic effects of VEGF-A and VEGF-C. It is expressed primarily on vascular ECs and endothelial cell progenitors. It is also expressed on endometrial epithelium, hematopoietic stem cells, liver sinusoidal ECs, Sertoli cells and Leydig cells, platelets and megakaryocytes, sensory and autonomic neurons, Schwann cells, Muller glial cells, retinal progenitors, and osteoblasts. An increase in CD309 expression leads to increase of endothelial permeability in microvascular bed [ |
|
|
ADAMs 8, 9, 10, 12, 15, 17, and 33 | The disintegrin and metalloproteinases ADAM10 and ADAM17 serve as principal regulators of cytokines, growth factors, and adhesion molecules, through proteolytic shedding on the cell surface [ |
|
|
ADAMTS-13 | ADAMTS-13 (A disintegrin-like and metalloprotease with thrombospondin type 1 repeats-13) is a zinc-containing metalloprotease enzyme that cleaves von Willebrand factor. It is produced in liver stellate cells and ECs and is present in platelets. It is also produced in kidney podocytes with subsequent deposition in the glomerular basement membrane, thus preventing clot formation. ECs have a major contribution to the bulk production of ADAMTS-13 in the body [ |
|
|
ADAMTS-18 | ADAMTS-18 is a member of a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) family of proteases, participating in angiogenesis and coagulation; dysregulation of these enzymes leads to inflammation, cancer, arthritis, atherosclerosis, and other diseases. Endothelial cell ADAMTS-18 secretion is enhanced by thrombin. Platelet aggregates can be destroyed by the C-terminal ADAMTS-18 fragment [ |
|
|
CXCL16 | Transmembrane CXC chemokine ligand 16. Eryptotic erythrocytes adhere to ECs of the vascular wall in part by interaction of phosphatidylserine exposed at the erythrocyte surface with endothelial CXCL16 [ |
|
|
DCBLD2/ESDN | DCBLD2 (discoidin, CUB, and LCCL domain containing 2), also known as ESDN (endothelial and smooth muscle cell-derived neuropilin-like) and CLCP1, has structural similarities to neuropilins, VEGF receptors, and semaphorins and participates in cell motility and metastasis. |
|
|
Endomucin | Endomucin (endothelial sialomucin; also endomucin-1/2 and mucin-14) is an 80–120 kDa glycoprotein member of the endomucin family of proteins. It is expressed on ECs and function as either a pro- or antiadhesive molecule, depending on its glycosylation pattern. |
|
|
ESAM | ESAM (endothelial cell-selective adhesion molecule) is an EC-associated member of the CTX subgroup of the Ig superfamily. It is associated with tight and adherens junctions and also modulates transendothelial cell migration along with FGF-2. |
|
|
FABP | Fatty acid-binding proteins (FABPs) are small cytoplasmic lipid-binding proteins, which can bind free fatty acids, cholesterol, and retinoids, and are involved in intracellular transport of lipids. Along with other biomarkers, circulating FABPs are used as indicators of tissue damage. Hypoxia affects expression of FABP in ECs [ |
|
|
IgG (immunoglobulin G) | IgGs on HUVECs behave as Ig-producing immune cells. Under the stimulus of external IgGs, some secretory pathways are also activated in HUVECs together with the expression of FcRn, which is associated with newly synthesized IgGs, thus forming complexes to be secreted [ |
|
|
Integrin |
Integrin |
|
|
KLF4 | Krüppel-like factor 4 (KLF4) is a transcription factor, which is a central regulator of sprouting angiogenesis via regulating Notch signaling pathway [ |
|
|
LYVE-1 | Lymphatic vessel endothelial hyaluronan (HA) receptor-1 (LYVE-1) is a 60 kDa type I transmembrane glycoprotein that is a member of the link protein superfamily. It modulates cell behavior and exerts activity during development, tissue remodeling, and disease. It is a marker of lymphatic ECs and is also expressed on hepatic sinusoidal ECs. To a lesser degree, LYVE-1 is found on Kupffer cells, the islets of Langerhans, cortical neurons, and renal epithelium. |
|
|
Notch | Notch signaling is an evolutionary conserved pathway critical for cardiovascular development. The contribution of Notch signaling to the homeostasis of the adult vasculature has emerged as a novel paradigm, which suggests that this pathway is sensitive to environmental factors, including inflammatory mediators and diet-derived by-products, including glucose and lipid metabolites [ |
|
|
Podocalyxin | Podocalyxin (also known as podocalyxin-like protein 1/PODXL or PCLP1) is a sialoglycoprotein that is structurally related to CD34. Podocalyxin is abundantly expressed in embryonic stem cells and also is a marker of hemangioblasts, the common precursors of hematopoietic and ECs. |
|
|
Podoplanin | Podoplanin, also known as T1 alpha and Aggrus, is a mucin-type transmembrane glycoprotein with extensive |
|
|
RLIP76/RALBP1 | RLIP76 (Ral-interacting protein of 76 kDa), also known as RalBP1 (Ral-binding protein 1), is an ATP-dependent transporter of electrophile-glutathione conjugates [ |
|
|
Stabilin-1 and stabilin-2 | Stabilin-1 and stabilin-2 are type I transmembrane members of a family of fasciclin-like hyaluronan (HA) receptor homologs, expressed on sinusoidal ECs and macrophages. |
|
|
TEM8/ANTXR1 | Tumor endothelial marker 8 (TEM8) is one of eight TEM gene products that are associated with tumor angiogenesis. TEM8 and CMG2 (capillary morphogenesis gene 2) are type I transmembrane proteins with an extracellular von Willebrand factor type A domain. They are members of an anthrax toxin receptor family. TEM8 is highly expressed in tumor vasculature and may function as an adhesion molecule during capillary tubulogenesis. |
|
|
THSD1 | THSD1 (thrombospondin type-1 domain-containing protein 1), also known as transmembrane molecule with thrombospondin module (Tmtsp), is a type I transmembrane protein of 95 kDa. It is highly expressed in hematopoietic stem cells and progenitor cells. Also, THSD1 is abundantly expressed on ECs, with the highest expression in the lung. THSD1 is involved in the regulation of vasculogenesis and/or angiogenesis. |
|
|
Tie-1 and Tie-2 | Tie-1/Tie and Tie-2/Tek are receptor tyrosine kinases which have two immunoglobulin-like domains flanking three EGF-like domains, three fibronectin type III-like repeats in the extracellular region, and a split tyrosine kinase domain in the cytoplasmic region. The Tie-2 receptor is an essential regulator of vascular barrier function. Angiopoietins 1 and 2 are the principal ligands of Tie-2, which can exert opposite effects on this receptor [ |
|
|
TNAP | Tissue nonspecific alkaline phosphatase (TNAP) is localized at ECs of brain blood vessels and neuronal membranes, inducing neuronal toxicity via tau dephosphorylation. This function can play a role in the neuronal loss observed in Alzheimer’s disease. TNAP level is increased in blood plasma during cerebrovascular diseases and after brain injury [ |
|
|
TNF RII/TNFRSF1B | TNF RII (tumor necrosis factor receptor II), also known as TNFRSF1B, p75/p80, and CD120b, is a widely expressed receptor for membrane-associated TNF-α and lymphotoxin-α. Its activation initiates proinflammatory and prosurvival responses via NF- |
|
|
VE-cadherin | The cadherin superfamily consists of a large number of cell surface glycoproteins with cadherin repeats, upon which a Ca2+-dependent cell-cell adhesion depends. VE-cadherin is a major endothelial adhesion molecule controlling cellular junctions and blood vessel formation [ |
|
|
VE-statin | VE-statin is a 41 kDa secreted glycoprotein, which is a member of a rather large family of EGF-like domain-containing proteins. VE-statin is a marker of embryonic ECs and is also expressed in ECs of adults. |
|
|
VG5Q | VG5Q, also known as AGGF1, is associated with Klippel-Trenaunay syndrome (KTS), a congenital vascular morphogenesis pathology. VG5Q is expressed by vascular ECs in many tissues. It can be secreted, thus promoting proliferation of the neighboring ECs. |
|
|
VWF | Von Willebrand factor (VWF) is a glycoprotein participating in blood coagulation. It is released from Weibel–Palade bodies (WPB) of ECs and exhibits a binding site for factor VIII (FVIII) and also for heparin. VWF size and function are regulated by protease ADAMTS-13, and disturbance of this function can lead to thrombotic thrombocytopenic purpura. Also, endothelial VWF regulates angiogenesis [ |
The Weibel–Palade bodies are specific endothelial organelles containing VWF, P-selectin (CD62P), and angiopoietin-2 (Angpt2), participating in platelet binding, leukocyte recruitment, and modulation of inflammation, respectively [
Angiotensin-converting enzyme (ACE, EC 3.4.15.1), one of the principal members of renin-angiotensin system (RAS), is a СООН-terminal dipeptidyl carboxypeptidase I, converting angiotensin I to vasoconstrictor angiotensin II, degrading bradykinin [
VEGF receptors 1–3 contain an extracellular segment with seven immunoglobulin-like domains, a transmembrane segment, a juxtamembrane segment, a protein kinase domain with an insert of about 70 amino acid residues, and a C-terminal tail. VEGF-A stimulates the activation of preformed VEGFR2 dimers by the autophosphorylation of activation segment tyrosines followed by the phosphorylation of additional protein-tyrosines that recruit phosphotyrosine-binding proteins thereby leading to signaling by the ERK1/2, AKT, Src, and p38 MAP kinase pathways [
In addition to the VEGF receptor pathway, the angiopoietin (Angpt)-Tie is another EC-specific ligand-receptor signaling pathway necessary for embryonic cardiovascular and lymphatic development. The Angpt-Tie system also controls postnatal angiogenesis, vascular remodelling, and permeability to maintain vascular homeostasis in adults. This pathway is involved in many diseases where the vasculature plays a significant role, such as in cancer, sepsis, diabetes, atherosclerosis, and so forth. Mutations in the TIE2 signaling affect vascular morphogenesis, resulting in venous malformations and primary congenital glaucoma [
Cell adhesion molecules (CAM) make up a significant group (at least a couple of dozen) of endothelial markers, which are involved in homo- or heterophilic binding with other cells or with the extracellular matrix. All representatives of the four principal protein families (immunoglobulins, integrins, cadherins, and selectins) are expressed on the surface of ECs, including IgGs [
Inflammation modulates gene expression through the activation of NF-
Exposure to many agents and factors determines the phenotype and life span of ECs. They respond within minutes to haemodynamic forces, vasoactive, thrombogenic, or inflammatory agents. These acute responses follow a linear receptor-mediated cell signaling pathways with influx of calcium ions, activation of phosphorylations and enzymes that generate auto- or paracrine regulators (PGI2, PGE2, endothelin-1, H2S, NO, CO, etc.), and recruitment and transport of vesicles containing various substances (VWF, t-PA, endothelin-1, etc.) to plasma membrane followed by apical sorting (ADAMTS13) and/or excretion [
РKС occupies one of the central places in the intracellular signaling and reciprocal relations between ROS and classical second messengers. This protein (a family of proteins) has structural features that render it the most important sensor of ROS and redox state of cells [
Besides PKC, p47phox can be phosphorylated by many other kinases: РKА [
Mechanisms of endothelium barrier dysfunction may vary depending on activating agent and prevailing or primary type of ROS. Since H2O2 is the most stable species of ROS, it is used in most experiments for modification of the redox state of the cells and studies of the signaling and toxic effects of ROS. H2O2 is produced from superoxide anion as a result of dismutation reaction, spontaneously or catalyzed by superoxide dismutases (SOD). Moreover, in endothelial and some other cells, H2O2 production is catalyzed by NADPH oxidase 4 [
Early and late events developed in ECs upon the influence of oxidative stress. Explanations and abbreviations are given in the text.
Most mitotically competent mammalian cell types can react to oxidative and other stress factors by undergoing a phenotypically distinctive form of growth arrest called “cellular senescence.” In endothelial cells, these changes result in a phenotype that is proinflammatory, proatherosclerotic, and prothrombotic [
Sequentially or in parallel with senescence, and under chronic oxidative stress, inflammation, influence of insulin-like growth factor II, transforming growth factor-
TGF-
miR-20a has been shown to be reduced during EndoMT, and restoration of its expression by application of FGF-2 correlated with EndoMT regression [
TGF-
To reduce the EndoMT in systemic sclerosis-associated interstitial lung disease, cyclophosphamide is administered by clinicians, whereas mycophenolate or methotrexate has been used for less severe skin progression. Novel agents capable of modulating fibrotic and inflammatory pathways involved in systemic sclerosis pathogenesis include tocilizumab, pirfenidone, tyrosine kinase inhibitors, lipid lysophosphatidic acid 1, and NOX4 inhibitors [
The purpose of diagnostics is to determine the state of a patient, which is characterized by a change in the complex of biochemical, immunological, and other indicators (biomarkers). The term “biomarker” is generally used to define any indicator reflecting the state of an organism as a result of its development and functioning, as well as interaction of the body with an external factor of a chemical, physical, or biological nature [
Transaminases are traditionally considered to be markers of the liver and heart, while the contribution of the endothelium to their blood level is rather obscure. In the ischemia-reperfusion injury, endothelial permeability is increased, together with neutrophil sequestration and a 4-fold rise in blood transaminases [
Much more complex and obscure is a role of endothelium in the development of effects after chronic or acute exposure to some toxic agents, most notably organophosphates (OPs) or nerve agents. Not only neuronal and neuromuscular synapses but also ECs have many signs of autonomic cholinergic regulation. Due to muscarinic receptors, ECs became famous in 1980 as the site for generation of endothelium-dependent relaxing factor (EDRF, later revealed to be nitric oxide) [
(a) Dilated venule (arrow) within the endoneurium of sciatic nerve with aggregated blood cells and their penetration (diapedesis) through the vessel wall (arrowhead). Three weeks after acute exposure to soman (GD). H&E, ×350. (b) Distonic venules (arrows) and congestion of blood cells within (mostly erythrocytes) and around (mostly granulocytes and macrophages, arrowheads) in the mesenterium of small intestine. Two weeks after subacute intoxication with VR (Russian Vx). H&E with additional benzidine staining, ×150.
Norepinephrine- (NA-) induced contraction and carbachol- (CCh-) induced relaxation of rat aorta after subchronic (3 months) exposure to paraoxon (a) and DFP (b) in doses 1/100LD50 (black diamonds) and 2 months of “rehabilitation” period (blue squares).
MS/MS analysis of blood plasma of animals intoxicated with RVX revealed fragments of fibrinopeptide A, signifying that exposure to RVX caused inactivation or reduced expression of exopeptidases (aminopeptidases) [
Biomarkers can be used, and ideally should be used, for quantitative evaluation of the body’s response to external effects [
A biopsy is the gold standard in diagnosing many chronic diseases, though morphological methods are not a common tool in clinical diagnostics. Due to the invasiveness, these techniques are not suitable for continuous monitoring. Moreover, many diseases may not have a morphological analog of the “gold standard,” which necessitates the permanent expansion of functional and point-of-care diagnostics in clinical practice [
Recently, we reported on new screening indicators (biomarkers) for health assessment of the personnel at a chemical weapon destruction facility (CWDF). Blood plasma of healthy donors and of CWDF personnel occupied in different facility workshops or zones was analysed for 27 cytokines. A significant elevation of eotaxin concentration was revealed in blood plasma of the “dirty zone” personnel. For screening assessment of health state of the personnel, a new complex biomarker was suggested: relation of eotaxin × IFN-
A combination of markers defines a combinatorial biomarker, whose identification usually involves multivariable assays [
One of the fields of the search for new biomarkers is metabolomics. The metabolome is the end product of the genome; in fact, it is the totality of all the metabolites, predominantly of low molecular weight. Metabolites are the final or intermediate products of metabolism of living systems (biological matrices) characterizing their functioning mode. In an epistemological classification, the transcriptome (the totality of all mRNAs) and the proteome (the totality of all proteins) should be placed between the genome and the metabolome. The study of the metabolome, however, is sufficiently rewarding, firstly, because the major metabolic pathways are fairly well studied and the existence of the majority of metabolites is well known and, secondly, because the total number of metabolites is relatively small (3 × 103) as compared to the total number of modified proteins (over 107) [
The main methods of metabolomics are nuclear magnetic resonance spectroscopy (NMR) on different nuclei (1H, 13C, 31P, etc.) and gas chromatography-mass spectrometry (GC-MS). NMR spectroscopy is used to detect low molecular weight metabolites in blood, urine, serum, and tissues [
In our recent studies, the influence of chronic exposure to low doses of C6-C10 aliphatic hydrocarbons on metabolic profiles of rats was investigated using GC-MS and high-resolution LC-MS, then a chemometrical algorithm, was applied and combinatorial biomarkers were derived. The ratio of concentrations of pyrophosphate (РРi) and oxalate in the blood plasma was found to be the most sensitive biomarker, called the “
Endothelium is strategically located at the interface between blood and interstitial tissues, and ECs exist in a dynamic equilibrium with their environment constituting simultaneously a source, a barrier, and a target of defensive mediators and therapeutic interventions. As a rule, vascular pathology is caused by multiple factors, involving genetic and environmental ones, whereas the current clinical treatments mostly target individual molecules involved in the pathophysiological pathways; this approach to genotype/phenotype studies is governed by the “one-gene/one-phenotype” hypothesis. At the same time, science is moving ahead and the combination of genomics, proteomics, and metabolomics has described the origin (etiology) and essence (pathophysiology) of vascular-dependent pathologies in a big-data fashion and also revealed new and unrivalled relationships between the omic variability and the restricted definitions of clinical phenotypes of vascular disease [
The endothelial interface in the tissues and the ROS interface in the cells represent the two principal boundaries, cellular and molecular, respectively, that integrate the interior and exterior of the living body. It is now evident that ROS in general and H2O2 in particular serve as the trigger system of ECs and other cells, providing Ca2+-dependent regulation of metabolism with a row of other auxiliary molecules and channels. Not breaking the signaling and metabolic pathways, ROS implement the “orthogonal regulation” of metabolism through modulation of kinetic characteristics of biochemical reactions [
Presently, diet quality indices that embrace overall diet quality in contrast to single nutrients draw increased attention. This is especially relevant to the state of endothelium and vascular diseases. There is a strong association between food patterns (FPs) and endothelial biomarkers. Healthy FPs (higher intakes of fruits and vegetables) have a beneficial effect on endothelial functions, as estimated by the levels of biomarkers such as CRP, sICAM-1, sVCAM-1, and E-selectin molecules. Westernised FPs (abundant in meat, sweets, fried foods, and refined grains) correlated with biomarkers of inflammation and atherogenesis [
Now, we have to finalize and feel obliged to offer some advice, so we will try. In order to prevent or even cure a disease, we need to repair blood vessels in advance or in parallel. For this, we need first to acquire adequate information through adequate diagnostics, which would comprise monitoring the state of endothelium with specific markers/biomarkers. Inter alia, this would help to completely remove the damaging factors. Then, we need to apply natural means (nutraceuticals and physical activity), which would not help to stop flows completely, but to tune their kinetics and harmonize the metabolic and signaling pathways due to soft power, influencing the two principal interfaces: endothelial cells throughout the body and ROS signaling in these and many other cells throughout the body. These advises are not only for “external consumption,” they are the essense of our own perspectives in science.
When something is rotten in a state, one can differently sense it being outside or inside of the state. Supplying adequate information, sometimes simply through mass media, can greatly help people to rationally exploit the natural, material, and financial resources of the state, according to its place on Earth, history, and culture. It is cheap and cheerful. Application of nutraceuticals and physical activities for curing the rotten state of endothelium would greatly help all the tissues and organs, according to their place in the body, ontogenetic features, and functional traits. This is cheap and cheerful, too.
Alpha-smooth muscle actin
Amyloid-
Angiotensin-converting enzyme
Acetylcholinesterase
Alzheimer’s disease
Alanine transaminase
Angiopoietin
Angiotensin
Aspartate transaminase
Blood-brain barrier
Bone morphogenetic protein 7
Cell adhesion molecules
Circulating endothelial cells
Central nervous system
C-reactive protein
Cardiovascular disease
Chemical weapon destruction facility
Diacylglycerol
Diisopropyl fluorophosphate
Diacylglycerol kinase alpha
Endothelial cells
Endothelium-dependent relaxing factor
Epidermal growth factor
Endothelial microparticles
Endothelial-to-mesenchymal transition
Endothelial progenitor cells
Endoplasmic reticulum
Endothelin-1
Fatty acid translocase
Fibroblast growth factor
Food patterns
Glycogen synthase kinase
Hypoxia-inducible factor-1
Human umbilical vein endothelial cells
Intercellular adhesion molecule
Immunoglobulin
Lactate dehydrogenase
Low-density lipoprotein
Lymphocyte function-associated antigen 1
Mitogen-activated protein kinase
Mechanistic target of rapamycin
NO synthase
NADPH oxidase
Osteogenic protein-1
Organophosphates
Organosulfur compounds
Oxidized low-density lipoprotein
Phosphatidic acid
Platelet EC adhesion molecule-1
Peroxisome proliferator-activated receptor
Phosphoinositide 3-kinase
Protein kinase C
Phorbol 12-myristate 13-acetate
Peroxisome proliferator-activated receptor
Peroxiredoxins
Protein tyrosine kinase
Renin-angiotensin system
Riboflavin kinase
Reactive oxygen species
Sirtuins
Superoxide dismutases
Transforming growth factor-
Tissue-nonspecific alkaline phosphatase
Tumor necrosis factor alpha
Tissue plasminogen activator
Transient receptor potential
Vascular endothelial cadherin
Vascular endothelial growth factor
VEGF receptor
Vascular endothelial protein tyrosine phosphatase
Vesiculo-vacuolar organelles
VWF disease
Von Willibrand factor.
The authors confirm that there are no conflicts of interest.
These studies were supported by the Russian Science Foundation (Grant 16-15-00199).