Tissue factor-containing microparticles released from mesangial cells in response to high glucose and AGE induce tube formation in microvascular cells

Dysregulated coagulation system links to inflammation in diabetic kidney disease

Diabetic kidney disease (DKD) is a significant contributor to end-stage renal disease worldwide. Despite extensive research, the exact mechanisms responsible for its development remain incompletely understood. Notably, patients with diabetes and impaired kidney function exhibit a hypercoagulable state characterized by elevated levels of coagulation molecules in their plasma. Recent studies propose that coagulation molecules such as thrombin, fibrinogen, and platelets are interconnected with the complement system, giving rise to an inflammatory response that potentially accelerates the progression of DKD. Remarkably, investigations have shown that inhibiting the coagulation system may protect the kidneys in various animal models and clinical trials, suggesting that these systems could serve as promising therapeutic targets for DKD. This review aims to shed light on the underlying connections between coagulation and complement systems and their involvement in the advancement of DKD.

Tissue Factor, Thrombosis, and Chronic Kidney Disease

Coagulation abnormalities are common in chronic kidney disease (CKD). Tissue factor (TF, factor III) is a master regulator of the extrinsic coagulation system, activating downstream coagulation proteases, such as factor Xa and thrombin, and promoting fibrin formation. TF and coagulation proteases also activate protease-activated receptors (PARs) and are implicated in various organ injuries. Recent studies have shown the mechanisms by which thrombotic tendency is increased under CKD-specific conditions. Uremic toxins, such as indoxyl sulfate and kynurenine, are accumulated in CKD and activate TF and coagulation; in addition, the TF-coagulation protease-PAR pathway enhances inflammation and fibrosis, thereby exacerbating renal injury. Herein, we review the recent research studies to understand the role of TF in increasing the thrombotic risk and CKD progression.

Melatonin Administration Prevents Placental and Fetal Changes Induced by Gestational Diabetes

Gestational diabetes mellitus (GDM) promotes changes in the placenta and fetuses, due to oxidative stress. Antioxidants can reduce oxidative stress in the placenta. We tested the hypothesis that melatonin (Mel) can prevent these effects in the placenta and fetuses, analyzing their histology, histochemistry, morphometry, and immunohistochemistry. Thirty albino rats were used, divided into groups: CG-pregnant non-diabetic rats; GD-pregnant diabetic rats; GD + Mel-pregnant diabetic rats treated with melatonin. Diabetes was induced by streptozotocin at a dosage of 50 mg/kg i.p. Melatonin was administered in daily injections of 0.8 mg/kg i.p. Melatonin prevented the placental weight and fetal weight and length from increasing, in addition to histomoformetric, histochemical, and immunohistochemical changes in the placentas, compared to the placentas of diabetic females (GD). Thus, we conclude that melatonin has a great potential to prevent placental changes due to GDM.

Dietary modulation of large extracellular vesicles: the good and the bad for human health

Extracellular vesicles (EVs) encompassing nanovesicles derived from the endosome system and generated by plasmatic membrane shedding are of increasing interest in view of their ability to sustain cell-to-cell communication and the possibility that they could be used as surrogate biomarkers of healthy and unhealthy trajectories. Nutritional strategies have been developed to preserve health, and the impact of these strategies on circulating EVs is arousing growing interest. Data available from published studies are now sufficient for a first integration to better understand the role of EVs in the relationship between diet and health. Thus, this review focuses on human intervention studies investigating the impact of diet or its components on circulating EVs. Because of analytical bias, only large EVs have been assessed so far. The analysis highlights that poor-quality diets with elevated fat and sugar content increase levels of circulating large EVs, and these can be partly counteracted by healthy food or some food micronutrients and bioactive compounds. However, knowledge of the content and the biological functions of these diet-induced EVs is still missing. It is important to address these aspects in new research in order to state if EVs are mediators of the effects of diet on health.

Circulating extracellular vesicles during pregnancy in women with type 1 diabetes: a secondary analysis of the CONCEPTT trial

BACKGROUND

Extracellular vesicles are membrane vesicles that are released into the extracellular environment and accumulate in the circulation in vascular disease. We aimed to quantify circulating extracellular vesicles in pregnant women with type 1 diabetes and to examine associations between extracellular vesicle levels, continuous glucose measures, and pregnancy outcomes.

METHODS

We used plasma samples from the Continuous Glucose Monitoring in Women with Type 1 Diabetes in Pregnancy Trial study and quantified circulating extracellular vesicles by flow cytometry (n = 163). Relationships with clinical variables were assessed by repeated measures correlation. Logistic regression was used to assess associations between elevated extracellular vesicle levels and pregnancy outcomes.

RESULTS

Platelet extracellular vesicle levels were inversely associated with glucose time above range and glycaemic variability measures (P < 0.05). A weak positive association was observed between endothelial extracellular vesicles and mean amplitude of glycemic excursion (P < 0.05). In a univariate logistic regression model, high baseline endothelial extracellular vesicles was associated with increased risk of neonatal intensive care unit (NICU) admission (OR: 2.06, 1.03-4.10), and respiratory distress requiring ventilation (OR: 4.98, 1.04-23.92). After adjusting for HbA1c and blood pressure the relationship for NICU admission persisted and an association with hyperbilirubinemia was seen (OR: 2.56, 1.10-5.94). Elevated platelet extracellular vesicles were associated with an increased risk of NICU admission (OR: 2.18, 1.04-4.57), and hyperbilirubinemia (OR: 2.61, 1.11-6.12) after adjusting for HbA1c and blood pressure.

CONCLUSIONS

High levels of extracellular vesicles in early pregnancy were associated with adverse neonatal outcomes. Assessment of extracellular vesicles may represent a novel approach to personalized care in type 1 diabetes pregnancy.

Immunoendocrine Dysregulation during Gestational Diabetes Mellitus: The Central Role of the Placenta

Gestational Diabetes Mellitus (GDM) is a transitory metabolic condition caused by dysregulation triggered by intolerance to carbohydrates, dysfunction of beta-pancreatic and endothelial cells, and insulin resistance during pregnancy. However, this disease includes not only changes related to metabolic distress but also placental immunoendocrine adaptations, resulting in harmful effects to the mother and fetus. In this review, we focus on the placenta as an immuno-endocrine organ that can recognize and respond to the hyperglycemic environment. It synthesizes diverse chemicals that play a role in inflammation, innate defense, endocrine response, oxidative stress, and angiogenesis, all associated with different perinatal outcomes.

Microparticles and cardiovascular diseases

Microparticles are a distinctive group of small vesicles, without nucleus, which are involved as significant modulators in several physiological and pathophysiological mechanisms. Plasma microparticles from various cellular lines have been subject of research. Data suggest that they are key players in development and manifestation of cardiovascular diseases and their presence, in high levels, is associated with chronic inflammation, endothelial damage and thrombosis. The strong correlation of microparticle levels with several outcomes in cardiovascular diseases has led to their utilization as biomarkers. Despite the limited clinical application at present, their significance emerges, mainly because their detection and enumeration methods are improving. This review article summarizes the evidence derived from research, related with the genesis and the function of microparticles in the presence of various cardiovascular risk factors and conditions. The current data provide a substrate for several theories of how microparticles influence various cellular mechanisms by transferring biological information.

Extracellular vesicles and microvascular pathology: Decoding the active dialogue

Extracellular vesicles (EV) are a heterogeneous collection of membrane-surrounded structures released from all studied cells, under both physiological and pathological conditions. These nano-size vesicles carry complex cargoes including different classes of proteins, lipids and nucleic acids and are known to act as a communication and signalling vesicles in various cellular process. In addition to their role in development and progression of pathological disorders which make them potentially great biomarkers, EV have beneficial effects, as they take part in homeostasis. In this review we have analysed the evidence for the role of microvesicles and exosomes secreted from other cells on microvascular endothelium (EV uptake) as well as the role of endothelial-derived vesicles on their neighbouring and distant cells (EV release).

Microvesicles as Emerging Biomarkers and Therapeutic Targets in Cardiometabolic Diseases

Microvesicles (MVs, also known as microparticles) are small vesicles that originate from plasma membrane of almost all eukaryotic cells during apoptosis or activation. MVs can serve as extracellular vehicles to transport bioactive molecules from their parental cells to recipient target cells, thereby serving as novel mediators for intercellular communication. Importantly, more and more evidence indicates that MVs could play important roles in early pathogenesis and subsequent progression of cardiovascular and metabolic diseases. Elevated plasma concentrations of MVs, originating from red blood cells, leukocytes, platelets, or other organs and tissues, have been reported in various cardiometabolic diseases. Circulating MVs could serve as potential biomarkers for disease diagnosis or therapeutic monitoring. In this review, we summarized recently-published studies in the field and discussed the role of MVs in the pathogenesis of cardiometabolic diseases. The emerging values of MVs that serve as biomarker for non-invasive diagnosis and prognosis, as well as their roles as novel therapeutic targets in cardiometabolic diseases, were also described.

High glucose increases the formation and pro-oxidative activity of endothelial microparticles

AIMS/HYPOTHESIS

Individuals with diabetes exhibit increases in circulating endothelial microparticles (eMPs, also referred to as endothelial microvesicles), which are associated with endothelial dysfunction and a heightened risk of cardiovascular complications. We have shown that eMPs are markers and mediators of vascular injury although their role in diabetes is unclear. We hypothesised that the composition and biological activity of eMPs are altered in response to high glucose exposure. We assessed the effects of high glucose on eMP formation, composition and signalling in cultured HUVECs.

METHODS

eMPs were isolated from the media of HUVECs cultured under conditions of normal glucose (eMP^NG), high glucose (eMP^HG) or osmotic control of L-glucose (eMP^LG). eMP size, concentration and surface charge were assessed by nanoparticle tracking analysis and flow cytometry. eMP protein composition was assessed by liquid chromatography-tandem mass spectrometry, and eMP-mediated effects on coagulation, reactive oxygen species (ROS) production and vessel function were assessed.

RESULTS

Exposure of HUVECs to high glucose for 24 h caused a threefold increase in eMP formation, increased mean particle size (269 ± 18 nm vs 226 ± 11 nm) and decreased surface charge. Compared with eMP^NG or eMP^LG, eMP^HG possessed approximately threefold greater pro-coagulant activity, stimulated HUVEC ROS production to a greater extent (~250% of eMP^NG) and were more potent inhibitors of endothelial-dependent relaxation. Proteomic analysis of eMPs identified 1212 independent proteins of which 68 were exclusively found in eMP^HG. Gene ontology analysis revealed that eMP^HG-exclusive proteins were associated with signalling pathways related to blood coagulation, cell signalling and immune cell activation.

CONCLUSIONS/INTERPRETATION

Our results indicate that elevated glucose is a potent stimulus for eMP formation that also alters their molecular composition leading to increased bioactivity. Such effects may contribute to progressive endothelial injury and subsequent cardiovascular complications in diabetes.

The emerging role of coagulation proteases in kidney disease

A role of coagulation proteases in kidney disease beyond their function in normal haemostasis and thrombosis has long been suspected, and studies performed in the past 15 years have provided novel insights into the mechanisms involved. The expression of protease-activated receptors (PARs) in renal cells provides a molecular link between coagulation proteases and renal cell function and revitalizes research evaluating the role of haemostasis regulators in renal disease. Renal cell-specific expression and activity of coagulation proteases, their regulators and their receptors are dynamically altered during disease processes. Furthermore, renal inflammation and tissue remodelling are not only associated, but are causally linked with altered coagulation activation and protease-dependent signalling. Intriguingly, coagulation proteases signal through more than one receptor or induce formation of receptor complexes in a cell-specific manner, emphasizing context specificity. Understanding these cell-specific signalosomes and their regulation in kidney disease is crucial to unravelling the pathophysiological relevance of coagulation regulators in renal disease. In addition, the clinical availability of small molecule targeted anticoagulants as well as the development of PAR antagonists increases the need for in-depth knowledge of the mechanisms through which coagulation proteases might regulate renal physiology.

Ultrastructure of Placenta of Gravidas with Gestational Diabetes Mellitus

Objectives. Gestational diabetes mellitus (GDM) leads to an abnormal placental environment which may cause some structural alterations of placenta and affect placental development and function. In this study, the ultrastructural appearances of term placentas from women with GDM and normal pregnancy were meticulously compared. Materials and Methods. The placenta tissues of term birth from 10 women with GDM and 10 women with normal pregnancy were applied with the signed informed consent. The morphology of fetomaternal interface of placenta was examined using light microscopy (LM) and transmission electron microscopy (TEM). Results. On LM, the following morphological changes in villous tissues were found in the GDM placentas when compared with the control placentas: edematous stroma, apparent increase in the number of syncytial knots, and perivillous fibrin deposition. On TEM, the distinct ultrastructural alterations indicating the degeneration of terminal villi were found in the GDM placentas as follows: thickening of the basal membrane (BM) of vasculosyncytial membrane (VSM) and the VSM itself, significantly fewer or even absent syncytiotrophoblastic microvilli, swollen or completely destroyed mitochondria and endoplasmic reticulum, and syncytiotrophoblasts with multiple vacuoles. Conclusion. Ultrastructural differences exist between GDM and control placentas. The differences of placenta ultrastructure are likely responsible for the impairment of placental barrier and function in GDM.

The impact of insulin treatment on the expression of vascular endothelial cadherin and Beta-catenin in human fetoplacental vessels

Vascular endothelial cadherin and β-catenin play a key role in establishment and maintenance of the endothelial monolayer integrity, regulation of vascular barrier function, and initiation of angiogenesis. The cadherin-catenin complex has been shown to be reduced in type 1 diabetic placenta, but the exact relationship between histopathologic findings and clinical data is not known. Immunohistochemistry of placental tissue from type 1, type 2, and gestational diabetes showed that diabetes per se might be compatible with normal levels of vascular endothelial (VE)-cadherin and β-catenin in fetoplacental vessels as long as the patient has not been treated with insulin. Immunoreactivity of VE-cadherin did correlate poorly with maternal glycemic control, as was investigated in this study, by birth weight, body mass index, and hemoglobin A1c (HbA1c). There was no correlation found between the immunoreactivity of β-catenin and birth weight, body mass index, or HbA1c. However our data did show a strong correlation between immunoreactivity and whether or not the patient had been treated with insulin. Patients diagnosed with gestational diabetes who had not been treated with insulin had similar levels of VE-cadherin and β-catenin to the control group, thus indicating that diabetes per se must not necessarily lead to a reduction. Our study suggests that therapeutic intervention using insulin in pregnancies complicated by diabetes might have potentially harmful effects on placental morphology. Future studies should further investigate these findings.

Angiogenic microvascular endothelial cells release microparticles rich in tissue factor that promotes postischemic collateral vessel formation

OBJECTIVE

Therapeutic angiogenesis is a promising strategy for treating ischemia. Our previous work showed that endogenous endothelial tissue factor (TF) expression induces intracrine signaling and switches-on angiogenesis in microvascular endothelial cells (mECs). We have hypothesized that activated mECs could exert a further paracrine regulation through the release of TF-rich microvascular endothelial microparticles (mEMPs) and induce neovascularization of ischemic tissues.

APPROACH AND RESULTS

Here, we describe for the first time that activated mECs are able to induce reparative neovascularization in ischemic zones by releasing TF-rich microparticles. We show in vitro and in vivo that mEMPs released by both wild-type and TF-upregulated-mECs induce angiogenesis and collateral vessel formation, whereas TF-poor mEMPs derived from TF-silenced mECs are not able to trigger angiogenesis. Isolated TF-bearing mEMPs delivered to nonperfused adductor muscles in a murine hindlimb ischemia model enhance collateral flow and capillary formation evidenced by MRI. TF-bearing mEMPs increase angiogenesis operating via paracrine regulation of neighboring endothelial cells, signaling through the β1-integrin pathway Rac1-ERK1/2-ETS1 and triggering CCL2 (chemokine [C-C motif] ligand 2) production to form new and competent mature neovessels.

CONCLUSIONS

These findings demonstrate that TF-rich mEMPs released by microvascular endothelial cells can overcome the consequences of arterial occlusion and tissue ischemia by promoting postischemic neovascularization and tissue reperfusion.

Characterization of physical properties of tissue factor-containing microvesicles and a comparison of ultracentrifuge-based recovery procedures

Microvesicles were isolated from the conditioned media of 3 cell lines (MDA-MB-231, AsPC-1 and A375) by ultracentrifugation at a range of relative centrifugal forces, and the tissue factor (TF) protein and activity, microvesicle number, size distribution and relative density compared. Also, by expressing TF-tGFP in cells and isolating the microvesicles, the relative density of TF-containing microvesicles was established. Nanoparticle tracking analysis (NTA) indicated that the larger-diameter microvesicles (>200 nm) were primarily sedimented at 100,000g and possessed TF-dependent thrombin and factor Xa generation potential, while in the absence of factor VII, all microvesicles possessed some thrombin generation capacity. Immuno-precipitation of TF-containing microvesicles followed by NTA also indicated the range of these microvesicles to be 200–400 nm. Analysis of the microvesicles by gradient density centrifugation showed that lower-density (<1.1 g/ml) microvesicles were mainly present in the samples recovered at 100,000g and were associated with TF antigen and activity. Analysis of these fractions by NTA confirmed that these fractions were principally composed of the larger-diameter microvesicles. Similar analysis of microvesicles from healthy or patient plasma supported those obtained from conditioned media indicating that TF activity was mainly associated with lower-density microvesicles. Furthermore, centrifugation of healthy plasma, supplemented with TF-tGFP-containing microvesicles, resulted in 67% retrieval of the fluorescent microvesicles at 100,000g, but only 26% could be recovered at 20,000g. Pre-centrifugation of conditioned media or plasma at 10,000g improved the speed and yield of recovered TF-containing microvesicles by subsequent centrifugation at either 20,000g or 100,000g. In conclusion, TF appears to be associated with low-density (1.03–1.08 g/ml), larger-diameter (200–350 nm) microvesicles.

Glycation: the angiogenic paradox in aging and age-related disorders and diseases

Angiogenesis is generally a quiescent process which, however, may be modified by different physiological and pathological conditions. The "angiogenic paradox" has been described in diabetes because this disease impairs the angiogenic response in a manner that differs depending on the organs involved and disease evolution. Aging is also associated with pro- and antiangiogenic processes. Glycation, the post-translational modification of proteins, increases with aging and the progression of diabetes. The effect of glycation on angiogenesis depends on the type of glycated proteins and cells involved. This complex link could be responsible for the "angiogenic paradox" in aging and age-related disorders and diseases. Using diabetes as a model, the present work has attempted to review the age-related angiogenic paradox, in particular the effects of glycation on angiogenesis during aging.

Microvesicles and diabetic complications--novel mediators, potential biomarkers and therapeutic targets

Microvesicles (MVs), also known as microparticles, are small membrane vesicles released from different cell types under different conditions. MVs have been detected in the circulation and in organs/tissues in various diseases, including diabetes. Patients with different types of diabetes and complications have different cellular MV patterns. Studies have shown that MVs may mediate vascular thrombosis, vascular inflammation, angiogenesis, and other pathological processes of the disease through their procoagulant, pro-inflammatory, pro-angiogenic, proteolytic, and other properties. Therefore, MVs contribute to the development of diabetic macrovascular and microvascular complications. In addition, clinical studies have indicated that changes in MV number and composition may reflect the pathophysiological conditions of disease, and therefore, may serve as potential biomarkers for diagnostic and prognostic use. Understanding MVs' involvement in the pathophysiological conditions may provide insight into disease mechanisms and would also be helpful for the development of novel therapeutic strategies in the future. Here, we review the latest publications from our group and other groups and focus on the involvement of MVs in diabetic complications.

Urinary podocyte microparticles identify prealbuminuric diabetic glomerular injury

Microparticles (MPs) are small (0.1-1.0 µm) vesicles shed from the surface of cells in response to stress. Whether podocytes produce MPs and whether this production reflects glomerular injury are unclear. We examined MP formation in cultured human podocytes (hPODs) and diabetic mice. hPODs were exposed to cyclical stretch, high glucose (HG; 25 mM), angiotensin II, or TGF-β. Urinary podocyte MPs were assessed in three mouse models of diabetic nephropathy: streptozotocin (STZ)-treated, OVE26, and Akita mice. Cyclic stretch and HG increased MP release as assessed by flow cytometry (P<0.01 and P<0.05, respectively, versus controls). Inhibition of Rho-kinase (ROCK) with fasudil blocked HG-induced podocyte MP formation. STZ-treated (8 weeks) mice exhibited increased urinary podocyte MPs compared with age-matched nondiabetic mice. Similarly, 16-week-old OVE26 mice had elevated levels of urinary podocyte MPs compared with wild-type littermates (P<0.01). In 1 week post-STZ-treated and 6- and 12-week-old Akita mice, urinary podocyte MPs increased significantly compared with those MPs in nondiabetic mice, despite normal urinary albumin levels. Our results indicate that podocytes produce MPs that are released into urine. Podocyte-derived MPs are generated by exposure to mechanical stretch and high glucose in vitro and could represent early markers of glomerular injury in diabetic nephropathy.

Filamin-A is required for the incorporation of tissue factor into cell-derived microvesicles

We previously reported that the incorporation of tissue factor (TF) into cell-derived microvesicles (MVs) is regulated by the phosphorylation of the cytoplasmic domain of TF. Since the cytoskeletal protein filamin-A is known to bind to the cytoplasmic domain of TF in a phosphorylation-dependent manner, the involvement of filamin-A in the incorporation of TF into MVs was examined. Endothelial cells were transfected to express TF, whereas MDA-MB-231 cells were used to examine endogenously expressed TF. MV release was induced by activating protease-activated receptor-2 (PAR2). Partial suppression of filamin-A expression using two different filamin-A siRNA sequences resulted in significant reductions in the incorporation of TF antigen into MVs as determined by TF-ELISA and western blot analysis, and was reflected in reduced thrombin-generation and FXa-generation capacities of these MVs. Deletion of the cytoplasmic domain of TF also resulted in reduced incorporation of TF into MVs, whereas the suppression of filamin-A expression had no additional effect on the incorporation of truncated TF into MVs. Partial suppression of filamin-A expression had no effect on the number and size distribution of the released MVs. However, >90% suppression of filamin-A expression resulted in increased MV release, possibly as a result of increased instability of the plasma membrane and underlying cytoskeleton. In conclusion, the presence of filamin-A appears to be essential for the incorporation of TF into MVs following PAR2 activation, but is not required for the process of MV formation and release following PAR2 activation.

Microparticle-associated tissue factor is recycled by endothelial cells resulting in enhanced surface tissue factor activity

In this study the uptake of tissue factor (TF)-positive microparticles by endothelial cells and the recycling of the TF component were examined. Human dermal blood endothelial cells (HDBEC) were incubated with microparticles derived from cancer cell lines for up to 6 hours. Measurement of HDBEC cell surface TF antigen revealed two distinct peaks at 30 and 180-240 minutes post-incubation with TF-positive, but not TF-deficient microparticles. However, only the second peak was concurrent with high TF activity as determined by a chromogenic thrombin-generation assay. Annexin V-labelling of HDBEC showed phosphatidylserine exposure following 90 minutes incubation with microparticles, which explains the high TF activity associated with the second antigen peak. Analysis of TF mRNA levels revealed no de novo expression of TF mRNA in response to microparticles, and pre-incubation of cells with cycloheximide did not prevent the appearance of TF. However, blocking endocytosis with a dynamin inhibitor prolonged the disappearance and prevented the reappearance of TF antigen on the cell surface. Incubation of HDBEC with microparticles containing TF-GFP revealed the early co-localisation of TF with Rab4 and Rab5, followed by co-localisation with the late endosomal/trans-Golgi network marker Rab9, and the recycling endosome marker Rab11. siRNA-mediated suppression of Rab11 reduced the reappearance of TF on the cell surface. These data suggest a mechanism by which TF-containing microparticles are internalised by endothelial cells and the TF moiety recycled to the cell surface. Together with the exposure of phosphatidylserine, this is capable of inducing a substantial increase in the procoagulant potential of the surface of endothelial cells.

Microparticles: biomarkers and beyond

Membrane microparticles are submicron fragments of membrane shed into extracellular space from cells under conditions of stress/injury. They may be distinguished from other classes of extracellular vesicles (i.e. exosomes) on the basis of size, content and mechanism of formation. Microparticles are found in plasma and other biological fluids from healthy individuals and their levels are altered in various diseases, including diabetes, chronic kidney disease, pre-eclampsia and hypertension among others. Accordingly, they have been considered biomarkers of vascular injury and pro-thrombotic or pro-inflammatory conditions. In addition to this, emerging evidence suggests that microparticles are not simply a consequence of disease, but that they themselves may contribute to pathological processes. Thus microparticles appear to serve as both markers and mediators of pathology. The present review examines the evidence for microparticles as both biomarkers of, and contributors to, the progression of disease. Approaches for the detection of microparticles are summarized and novel concepts relating to the formation of microparticles and their biological effects are examined.

Enhanced binding of tissue factor-microparticles to collagen-IV and fibronectin leads to increased tissue factor activity in vitro

The role of tissue factor (TF)-containing microparticles in clot propagation has been established, but the ability of circulating microparticles to initiate coagulation has been disputed. However, TF-bearing microparticles, particularly endothelial-microparticles generated during disease, may interact with extracellular matrices which in turn can localise circulating TF to sites of injury. In order to examine this hypothesis in vitro , microparticles were isolated from human coronary artery endothelial cells transfected to overexpress TF, tumour-necrosis factor (TNF) α-treated cells or non-transfected cells lacking TF. The ability of microparticles to bind collagen-IV, fibronectin and fibrin was examined under static conditions and arterial shear rates (650 s⁻¹), and also in the presence of inhibitory antibodies against β1-, β3-, α3- and αv-integrins or an anti-TF antibody. TF-microparticles showed increases of up to 43% and 24% in adherence to collagen-IV and fibronectin, respectively, compared to control microparticles under shear flow. Furthermore, TF-containing microparticles, but not the transfected parent cells had increased levels of β1-integrin compared to TF-deficient microparticles. Pre-incubation of microparticles with a β1-integrin-blocking antibody counteracted the additional adhesion of TF-microparticles compared to control microparticles. Finally, adherence of TF microparticles to collagen-IV or fibronectin resulted in increased TF activity by concentrating TF onto the surface. In conclusion, the presence of TF within microparticles enhances the interactions of endothelial cell-derived microparticles with extracellular matrices in an integrin-dependent manner. Accumulation and localisation of these microparticles in turn results in the enhancement of TF activity. This may be an innate mechanism by which TF-bearing microparticles induce coagulation upon vascular injury.

Purple corn anthocyanins inhibit diabetes-associated glomerular monocyte activation and macrophage infiltration

Diabetic nephropathy (DN) is one of the major diabetic complications and the leading cause of end-stage renal disease. In early DN, renal injury and macrophage accumulation take place in the pathological environment of glomerular vessels adjacent to renal mesangial cells expressing proinflammatory mediators. Purple corn utilized as a daily food is rich in anthocyanins exerting disease-preventive activities as a functional food. This study elucidated whether anthocyanin-rich purple corn extract (PCA) could suppress monocyte activation and macrophage infiltration. In the in vitro study, human endothelial cells and THP-1 monocytes were cultured in conditioned media of human mesangial cells exposed to 33 mM glucose (HG-HRMC). PCA decreased the HG-HRMC-conditioned, media-induced expression of endothelial vascular cell adhesion molecule-1, E-selectin, and monocyte integrins-β1 and -β2 through blocking the mesangial Tyk2 pathway. In the in vivo animal study, db/db mice were treated with 10 mg/kg PCA daily for 8 wk. PCA attenuated CXCR2 induction and the activation of Tyk2 and STAT1/3 in db/db mice. Periodic acid-Schiff staining showed that PCA alleviated mesangial expansion-elicited renal injury in diabetic kidneys. In glomeruli, PCA attenuated the induction of intracellular cell adhesion molecule-1 and CD11b. PCA diminished monocyte chemoattractant protein-1 expression and macrophage inflammatory protein 2 transcription in the diabetic kidney, inhibiting the induction of the macrophage markers CD68 and F4/80. These results demonstrate that PCA antagonized the infiltration and accumulation of macrophages in diabetic kidneys through disturbing the mesangial IL-8-Tyk-STAT signaling pathway. Therefore, PCA may be a potential renoprotective agent treating diabetes-associated glomerulosclerosis.

Tissue factor, blood coagulation, and beyond: an overview

Emerging evidence shows a broad spectrum of biological functions of tissue factor (TF). TF classical role in initiating the extrinsic blood coagulation and its direct thrombotic action in close relation to cardiovascular risks have long been established. TF overexpression/hypercoagulability often observed in many clinical conditions certainly expands its role in proinflammation, diabetes, obesity, cardiovascular diseases, angiogenesis, tumor metastasis, wound repairs, embryonic development, cell adhesion/migration, innate immunity, infection, pregnancy loss, and many others. This paper broadly covers seminal observations to discuss TF pathogenic roles in relation to diverse disease development or manifestation. Biochemically, extracellular TF signaling interfaced through protease-activated receptors (PARs) elicits cellular activation and inflammatory responses. TF diverse biological roles are associated with either coagulation-dependent or noncoagulation-mediated actions. Apparently, TF hypercoagulability refuels a coagulation-inflammation-thrombosis circuit in “autocrine” or “paracrine” fashions, which triggers a wide spectrum of pathophysiology. Accordingly, TF suppression, anticoagulation, PAR blockade, or general anti-inflammation offers an array of therapeutical benefits for easing diverse pathological conditions.

Low molecular weight heparin downregulates tissue factor expression and activity by modulating growth factor receptor-mediated induction of nuclear factor-κB

Treatment of cancer patients with low molecular weight heparin (LMWH) appears to have beneficial effects. In this study, the influence of low molecular weight heparin (LMWH) on tissue factor (TF) expression and activity in five cell lines from various tissues was analysed and explored. Incubation of cells with LMWH (0-2000μg/ml) resulted in the downregulation of TF mRNA expression which was both LMWH concentration-dependent and time-dependent. Downregulation of TF was also measured as decreased cellular TF antigen and activity. Consistently, incubation of cells with LMWH suppressed the nuclear localisation and the transcriptional activity of NFκB. Decreased TF mRNA was largely achievable by incubating the cells with an NFκB inhibitor alone whilst incubation with betulinic acid to activate NFκB reversed the inhibitory influence of LMWH. Cells were also incubated with a range of concentrations of EGF (0-10ng/ml), bFGF (0-20ng/ml) or VEGF (0-4ng/ml) in the presence or absence of LMWH (200μg/ml) for 24h and TF antigen measured. Inclusion of LMWH reduced TF expression in response to EGF, bFGF or VEGF but TF expression was partially restored by increasing concentrations of the growth factors. We conclude that LMWH downregulates TF expression in vitro through a mechanism that involves interference with the function of growth factors which in turn is mediated through the downregulation of the transcriptional activity of NFκB. This mechanism may also explain some of the beneficial influences attributed to LMWH therapy in the treatment of cancer patients.

Glycated albumin modulates endothelial cell thrombogenic and inflammatory responses

BACKGROUND

It has become established that a diabetic vasculature promotes cardiovascular disease progression via changes to endothelial cells, platelets, and the interactions of these cells. It is believed that the majority of these changes are induced by the presence of advanced glycation end products (AGEs), which permanently alter various functions. Studies have shown that platelets perpetuate endothelial cell responses under these conditions. However, the role of changes in endothelial cell thrombogenicity and inflammatory responses, after subjected to AGEs, has not been characterized. Our objective was to evaluate the effects of AGEs on these functions.

METHODS

To accomplish this, albumin was chemically modified by exposure to glucose for up to 8 weeks, and endothelial cells were subjected to glycated albumin for up to 5 days in a cell culture system. A time course for changes in endothelial cell viability, density, morphology, and metabolic activity were investigated, along with the surface expression of intercellular adhesion molecule-1, thrombomodulin, tissue factor, connexin-43, and caveolin-1.

RESULTS

Endothelial cells exposed to irreversibly glycated albumin were less viable, proliferated slower, and had a lower metabolic activity as compared to cells exposed to nonglycated albumin. Endothelial cells that were exposed to any glycated albumin were procoagulant and proinflammatory as compared with all other conditions. There were no overall trends in the expression of connexin-43 or caveolin-1.

CONCLUSIONS

Our data suggest that the presence of irreversible glycated albumin is deleterious to endothelial cells, makes endothelial cells more procoagulant, and promotes inflammatory responses. It is therefore possible that endothelial cell activation may precede and promote platelet activation during diabetic conditions.

Regulation of the incorporation of tissue factor into microparticles by serine phosphorylation of the cytoplasmic domain of tissue factor

The mechanisms that regulate the incorporation and release of tissue factors (TFs) into cell-derived microparticles are as yet unidentified. In this study, we have explored the regulation of TF release into microparticles by the phosphorylation of serine residues within the cytoplasmic domain of TF. Wild-type and mutant forms of TF, containing alanine and aspartate substitutions at Ser253 and Ser258, were overexpressed in coronary artery and dermal microvascular endothelial cells and microparticle release stimulated with PAR2 agonist peptide (PAR2-AP). The release of TF antigen and activity was then monitored. In addition, the phosphorylation state of the two serine residues within the released microparticles and the cells was monitored for 150 min. The release of wild-type TF as procoagulant microparticles peaked at 90 min and declined thereafter in both cell types. The TF within these microparticles was phosphorylated at Ser253 but not at Ser258. Aspartate substitution of Ser253 resulted in rapid release of TF antigen but not activity, whereas TF release was reduced and delayed by alanine substitution of Ser253 or aspartate substitution of Ser258. Alanine substitution of Ser258 prolonged the release of TF following PAR2-AP activation. The release of TF was concurrent with phosphorylation of Ser253 and was followed by dephosphorylation at 120 min and phosphorylation of Ser258. We propose a sequential mechanism in which the phosphorylation of Ser253 through PAR2 activation results in the incorporation of TF into microparticles, simultaneously inducing Ser258 phosphorylation. Phosphorylation of Ser258 in turn promotes the dephosphorylation of Ser253 and suppresses the release of TF.

Low molecular weight heparin suppresses tissue factor-mediated cancer cell invasion and migration in vitro

Elevated expression of tissue factor (TF) has been associated with an increased risk of thrombosis in the majority of cancers. Moreover, treatment of cancer patients with low molecular weight heparin (LMWH) appears to have beneficial effects that reach beyond controlling the immediate hypercoagulable state. In this study, we investigated the influence of the treatment of cancer cells with LMWH (0-2,000 μg/ml) on cell invasiveness and migration in cancer cell lines from five separate tissues; pancreatic, breast, colocarcinoma, ovarian and melanoma. The rate of cell invasion across collagen IV-coated membranes was suppressed in all cell lines tested on incubation with 2,000 μg/ml LMWH, but BxPC-3 and MDA-MB-231 cells also responded to the lowest concentration of 20 μg/ml LMWH. Furthermore, the rate of cell migration was reduced to varying extents in all of the cell lines tested on incubation with 20 μg/ml or higher concentrations of LMWH. The decrease in the rates of invasion and migration also strongly correlated with the reduction in TF protein expression and TF activity in these cells following incubation with LMWH. Moreover, the LMWH-mediated decreases in cellular invasion in the most affected cell lines (BxPC-3 and MDA-MB-231) were restored by transfection of the cells with the mammalian pCMV-XL5-TF expression vector allowing independent overexpression of TF. In conclusion, LMWH appears to suppress the rate of cancer cell invasion and migration in vitro, through a mechanism that is at least in part dependent on the TF protein expression and activity in cancer cells.

Induction of endothelial cell proliferation by recombinant and microparticle-tissue factor involves beta1-integrin and extracellular signal regulated kinase activation

OBJECTIVE

Increased levels of circulating tissue factor (TF) in the form of microparticles increase the risk of thrombosis. However, any direct influence of microparticle-associated TF on vascular endothelial cell proliferation is not known. In this study, the influence of recombinant and microparticle-associated TF on endothelial cell proliferation and mitogen-activated protein kinase signaling mechanisms was examined.

METHODS AND RESULTS

Incubation of human coronary artery endothelial cells with lipidated recombinant full-length TF, or TF-containing microparticles (50 to 200 pmol/L TF), increased the rate of cell proliferation and induced phosphorylation of extracellular signal regulated kinase 1 in a TF-dependent manner. Inhibition of extracellular signal regulated kinase 1/2 using PD98059 or extracellular signal regulated kinase 1/2 antisense oligonucleotides or inhibition of c-Jun N-terminal kinase reduced recombinant TF-mediated cell proliferation. PD98059 also reduced cell proliferation in response to TF-containing microparticles. Inclusion of FVIIa (5 nmol/L) and FXa (10 nmol/L) or preincubation of cells with an inhibitory anti-FVIIa antibody had no additional influence on TF-mediated cell proliferation. However, preincubation of exogenous TF with a beta1-integrin peptide (amino acids 579 to 799) reduced TF-mediated proliferation.

CONCLUSIONS

High concentrations of recombinant or microparticle-associated TF stimulate endothelial cell proliferation through activation of the extracellular signal regulated kinase 1/2 pathway, mediated through a novel mechanism requiring the interaction of exogenous TF with cell surface beta1-integrin and independent of FVIIa.

Vascular dysfunction in the diabetic placenta: causes and consequences

The development and functioning of the human fetoplacental vascular system are vulnerable to the maternal diabetic milieu. These vessels are in direct continuum with the fetal vascular system and are therefore also vulnerable to fetal endocrine derangements. Increased angiogenesis, altered junctional maturity and molecular occupancy, together with increased leakiness, constitute a well-described phenotype of vessels in the Type 1 diabetic human placenta and can be related to increased levels of placental vascular endothelial growth factor. The causes of these observed changes, whether maternal hyperglycaemia or fetal hyperinsulinaemia, still remain to be shown in the human placenta. Mechanistic studies using different vascular systems have shown high glucose and insulin to have profound vascular effects, with elevations in vascular endothelial growth factor, nitric oxide and protein kinase C being behind alterations in junctional adhesion molecules such as occludin and vascular endothelial-cadherin and vascular leakage of albumin. The role of advanced glycation products and oxidative stress in this vascular pathology is also discussed. The altered molecular mechanisms underlying the vascular changes in the diabetic human placenta may reflect similar consequences of high glucose and hyperinsulinaemia.

The role of microparticles in the pathogenesis of rheumatic diseases

Microparticles (MPs) are small membrane-bound vesicles that are emerging as important elements in the pathogenesis of rheumatic diseases owing to their pleiotropic effects on thrombosis, vascular reactivity, angiogenesis and inflammation. Released from cells during activation and apoptosis, MPs carry proteins, lipids and nucleic acids, and serve as platforms for enzymatic processes in thrombosis. Furthermore, MPs can transfer cytokines, receptors, RNA and DNA to modulate the properties of target cells. As MPs appear in the blood in increased numbers during rheumatic disease, they represent novel biomarkers that can be used to assess events in otherwise inaccessible tissues. Future research will define further the pathogenetic role of MPs and explore therapeutic strategies to block their release or signaling properties.

Influence of exogenous tissue factor on estrogen receptor alpha expression in breast cancer cells: involvement of beta1-integrin, PAR2, and mitogen-activated protein kinase activation

Increased expression of tissue factor (TF) has been associated with invasive forms of breast cancer. Conversely, the loss of estrogen receptor alpha (ERalpha) is associated with increased cell invasiveness. We have examined the influence of exogenous truncated recombinant TF (rTF) on ERalpha expression and cell invasiveness and investigated the mechanism of rTF signaling. The influence of rTF on ERalpha expression in MCF-7 and T47D cell lines was investigated using reverse transcription-PCR and ELISA. Cell invasion was measured using Boyden chamber-based invasion assays. Additionally, the interaction of fluorescein-labeled rTF with the surface of MCF-7 cells and particularly with beta(1)-integrin was examined. Treatment of cells with rTF resulted in the down-regulation of ERalpha mRNA and protein over 24 h, which required beta(1)-integrin and involved the mitogen-activated protein kinase pathway but did not require PAR2 activation. The addition of rTF reduced estradiol-mediated cell proliferation as well as increased cell invasiveness requiring both PAR2 and beta(1)-integrin activation. Fluorescein-labeled rTF was shown to bind to the surface of MCF-7 cells within 5 min and peaked at 15 min. The bound rTF colocalized with cellular beta(1)-integrin and was disrupted in the presence of excess unlabeled rTF and an anti-beta(1) polyclonal antibody. Finally, affinity purification of beta(1)-integrin using rTF-conjugated agarose showed a requirement for the presence of divalent cations but not factor VIIa. The results indicate that rTF is capable of down-regulating ERalpha expression in breast cancer cells, resulting in decreases in estrogen-mediated cell proliferation and increased invasiveness. Furthermore, the mechanisms by which rTF induces these changes involve both PAR2 and beta(1)-integrin.