Oxidized antithrombin is a dual inhibitor of coagulation and angiogenesis: Importance of low heparin affinity

Antioxidant role of methionine-containing intra- and extracellular proteins

Significant evidence suggests that reversible oxidation of methionine residues provides a mechanism capable of scavenging reactive species, thus creating a cycle with catalytic efficiency to counteract or mitigate deleterious effects of ROS on other functionally important amino acid residues. Because of the absence of MSRs in the blood plasma, oxidation of methionines in extracellular proteins is effectively irreversible and, therefore, the ability of methionines to serve as interceptors of oxidant molecules without impairment of the structure and function of plasma proteins is still debatable. This review presents data on the oxidative modification of both intracellular and extracellular proteins that differ drastically in their spatial structures and functions indicating that the proteins contain antioxidant methionines/the oxidation of which does not affect (or has a minor effect) on their functional properties. The functional consequences of methionine oxidation in proteins have been mainly identified from studies in vitro and, to a very limited extent, in vivo. Hence, much of the functioning of plasma proteins constantly subjected to oxidative stress remains unclear and requires further research to understand the evolutionary role of methionine oxidation in proteins for the maintenance of homeostasis and risk factors affecting the development of ROS-related pathologies. Data presented in this review contribute to increased evidence of antioxidant role of surface-exposed methionines and can be useful for understanding a possible mechanism that supports or impairs structure-function relationships of proteins subjected to oxidative stress.

Microvascular Experimentation in the Chick Chorioallantoic Membrane as a Model for Screening Angiogenic Agents including from Gene-Modified Cells

The chick chorioallantoic membrane (CAM) assay model of angiogenesis has been highlighted as a relatively quick, low cost and effective model for the study of pro-angiogenic and anti-angiogenic factors. The chick CAM is a highly vascularised extraembryonic membrane which functions for gas exchange, nutrient exchange and waste removal for the growing chick embryo. It is beneficial as it can function as a treatment screening tool, which bridges the gap between cell based in vitro studies and in vivo animal experimentation. In this review, we explore the benefits and drawbacks of the CAM assay to study microcirculation, by the investigation of each distinct stage of the CAM assay procedure, including cultivation techniques, treatment applications and methods of determining an angiogenic response using this assay. We detail the angiogenic effect of treatments, including drugs, metabolites, genes and cells used in conjunction with the CAM assay, while also highlighting the testing of genetically modified cells. We also present a detailed exploration of the advantages and limitations of different CAM analysis techniques, including visual assessment, histological and molecular analysis along with vascular casting methods and live blood flow observations.

Structural alteration in hypochlorous acid modified antithrombin indicates generation of neo-epitopes

Increased tendency of cancer patients to develop venous thromboembolism (VTE) is associated with high rates of mortality. Elevation of procoagulant proteins and down regulation of naturally occurring coagulation inhibitors appears to form the basis of high risk of VTE in malignancy. A reduced level of anticoagulant protein like antithrombin (AT) will influence both coagulation and angiogenesis, as its cleaved and latent conformations show potent antiangiogenic activity. We show a concentration dependent perturbation in the secondary and tertiary structures of AT conformers exposed to hypochlorous acid (HOCl). Modulated under a very narrow concentration range of HOCl, native AT undergoes oligomerization, aggregation and fragmentation based on spectroscopic, SDS and native-PAGE studies. Factor Xa inhibition assay demonstrated a progressive decrease in inhibition activity of AT on modification by HOCl. Bis-ANS result showed that hydrophobic patches were more exposed in the case of HOCl-modified AT when assessed fluorometrically. Dosage of HOCl-modified AT in experimental animals induced high titer antibodies showing more specificity towards modified forms in comparison to unmodified forms. Auto-antibodies isolated from cancer patients also showed enhanced binding with HOCl-modified AT in comparison to native counterpart. Compared to normal AT, structurally and functionally altered conformation of HOCl-modified AT showed increased immunogenic sensitivity. HOCl modified AT can contribute to prothrombotic and angiogenic environment during cancer progression/development.

Dexamethasone Preconditioning in Cardiac Procedures Reduces Decreased Antithrombin Activity and Is Associated to Beneficial Outcomes: Role of Endothelium

Introduction: Decreased antithrombin (AT) activity in patients scheduled for cardiovascular surgery under cardiopulmonary bypass (CPB) is related to increased postoperative complications and hospitalization time. Indirect evidence suggests that glucocorticoids mitigate this decreased AT activity. To better understand the beneficial effects of AT we have analyzed: (i) the clinical relevance of acute dexamethasone (DX) administration before cardiac surgery on AT activity, (ii) the modulation by DX of AT expression in human endothelial cells (hECs), (iii) the activity of AT on migration and angiogenesis of hECs, or on angiogenesis of rat aorta. Methods: A retrospective cohort study in patients undergoing aortic valve replacement surgery was designed to evaluate the effect of DX administration on AT activity at five separate time points: preoperatively, during CPB, at intensive care unit admission and at 12 and 24 h post-intervention. We have analyzed also clinical differences in postoperative outcomes as safety and the length of stay in hospitalization. Changes in mRNA levels of AT induced by DX were determined by qRT-PCR in human coronary (hCEC), aorta (hAEC) and cardiac microvasculature (hCMEC) endothelial cells. AT activity on migration and angiogenesis were also assayed. Angiogenic growth of rat aortic rings incubated in Matrigel® was determined in presence and absence of AT. Results: The cohort comprised 51 patients in the control group and 29 patients in the group receiving dexamethasone. Preoperative DX supplementation reduced intraoperative decrease of AT activity (67.71 ± 10.49% DX treated vs. 58.12 ± 9.11% untreated, p < 0.001) that could be related to a decrease in the hospitalization time (7.59 ± 4.08 days DX treated vs. 13.59 ± 16.00 days untreated, p = 0.014). Treatment of hECs with 500 nM DX slightly increased AT expression. Incubation with 0.5 and 1 IU/mL of AT increased migration and angiogenesis in hCAECs and hAECs, but not in hCMECs. The same concentrations of AT potentiated angiogenic sprouting of new vessels from rat aorta. Conclusion: Preoperative DX supplementation could be an interesting procedure to avoid excessive decrease in AT levels during cardiac surgery. Positive outcomes associated with maintaining adequate AT levels could be related to its potential beneficial effect on endothelial function (migration and angiogenesis).

Antithrombotic potential of esculin 7, 3', 4', 5', 6'-O-pentasulfate (EPS) for its role in thrombus reduction using rat thrombosis model

Currently available anticoagulants for prevention and treatment of thrombosis have several limitations, thus, small organic scaffolds that can dissolve clots in vivo in a dose dependent manner with lesser side effects are highly desirable. Here we report the synthesis of esculin pentasulfate (EPS) and assessment of its in vitro, in vivo and ex vivo anticoagulant and antithrombotic potential. Assessment of in vitro clotting times showed prolonged activated partial thromboplastin time (APTT), prothrombin time (PT) and thrombin time (TT) in the presence of EPS. EPS also showed remarkable reduction in thrombus formation when administered in occlusion induced thrombotic rats at a low dose (2.5 mg/kg). Further, assessment of clot rate with plasma isolated from EPS treated rats confirmed its anticoagulation potential. EPS at varying concentrations showed no significant cytotoxic effect on HEK293 cell line. Further, molecular docking analysis of EPS with known anticoagulant proteins [(antithrombin (ATIII) and heparin cofactor II (HCF II)] that require heparin revealed good binding affinity (-7.9 kcal/mol) with ATIII but not with HCF II. ATIII when incubated with EPS showed increased fluorescence intensity, with no change in secondary structure. Overall, our results clearly show the in vivo modulation of thrombus formation using a modified natural scaffold EPS.

Contributions of 3D Cell Cultures for Cancer Research

Cancer cell lines have contributed immensely in understanding the complex physiology of cancers. They are excellent material for studies as they offer homogenous samples without individual variations and can be utilised with ease and flexibility. Also, the number of assays and end-points one can study is almost limitless; with the advantage of improvising, modifying or altering several variables and methods. Literally, a new dimension to cancer research has been achieved by the advent of 3Dimensional (3D) cell culture techniques. This approach increased many folds the ways in which cancer cell lines can be utilised for understanding complex cancer biology. 3D cell culture techniques are now the preferred way of using cancer cell lines to bridge the gap between the 'absolute in vitro' and 'true in vivo'. The aspects of cancer biology that 3D cell culture systems have contributed include morphology, microenvironment, gene and protein expression, invasion/migration/metastasis, angiogenesis, tumour metabolism and drug discovery, testing chemotherapeutic agents, adaptive responses and cancer stem cells. We present here, a comprehensive review on the applications of 3D cell culture systems for these aspects of cancers. J. Cell. Physiol. 232: 2679-2697, 2017. © 2016 Wiley Periodicals, Inc.

Role of heparin and non heparin binding serpins in coagulation and angiogenesis: A complex interplay

Pro-coagulant, anti-coagulant and fibrinolytic pathways are responsible for maintaining hemostatic balance under physiological conditions. Any deviation from these pathways would result in hypercoagulability leading to life threatening diseases like myocardial infarction, stroke, portal vein thrombosis, deep vein thrombosis (DVT) and pulmonary embolism (PE). Angiogenesis is the process of sprouting of new blood vessels from pre-existing ones and plays a critical role in vascular repair, diabetic retinopathy, chronic inflammation and cancer progression. Serpins; a superfamily of protease inhibitors, play a key role in regulating both angiogenesis and coagulation. They are characterized by the presence of highly conserved secondary structure comprising of 3 β-sheets and 7-9 α-helices. Inhibitory role of serpins is modulated by binding to cofactors, specially heparin and heparan sulfate proteoglycans (HSPGs) present on cell surfaces and extracellular matrix. Heparin and HSPGs are the mainstay of anti-coagulant therapy and also have therapeutic potential as anti-angiogenic inhibitors. Many of the heparin binding serpins that regulate coagulation cascade are also potent inhibitors of angiogenesis. Understanding the molecular mechanism of the switch between their specific anti-coagulant and anti-angiogenic role during inflammation, stress and regular hemostasis is important. In this review, we have tried to integrate the role of different serpins, their interaction with cofactors and their interplay in regulating coagulation and angiogenesis.