Inflammation-induced Thrombosis Research Articles

ROS-Driven Structural and Functional Fibrinogen Modifications Are Reverted By JAK Inhibition in Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPNs) are bone marrow diseases characterized by excess clonal hematopoiesis resulting in elevated peripheral blood counts. Subtypes include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). They share clinical features (e.g., splenomegaly, thrombotic complications, risk of leukemic transformation), and a common molecular basis: the dysregulation of the JAK-STAT pathway, which confers a hypersensitivity of hematopoietic stem cells (HSC) to the action of growth factors and cytokines, and, as a result, an overproduction of blood cells. Genetic analysis of patients with MPNs revealed that >95% of patients with PV and about 50% of patients with ET or PMF carry an activating point mutation in the JAK2 gene (JAK2-V617F). Despite clinical evidence indicating a higher susceptibility of MPN patients to develop thrombotic disease, the underlying pathogenetic mechanisms are not fully understood. It appears that thrombosis is the result of a severe inflammatory response associated to remarkable oxidative stress in the presence of endothelial dysfunction and a procoagulant environment. Hypercoagulability is a consequence of disrupted hemostasis and fibrinolysis due to damage of the endothelium and defective fibrinolysis. Evidence suggests that overproduction of ROS and a deprived antioxidant system play a major role in the pathogenesis of MPN, as well as in the resistance to tyrosine-kinase inhibitor therapy. Moreover, systemic inflammation is thought to be the main trigger of thrombosis and seems to be mainly mediated by pro-inflammatory cytokines along with endothelial cell dysfunction. Recent studies have provided evidence that fibrinogen plays a multifaceted role in inflammatory responses and autoimmunity. The ability of fibrinogen to participate in the inflammatory response depends on its specific interaction with integrins, the leukocyte cell surface adhesion receptors expressed on neutrophils, monocytes, macrophages, and several subsets of lymphocytes. In MPN patients, endothelial cell dysfunction, increased reactive oxygen species (ROS) production, and proinflammatory cytokines have been reported, together with impaired fibrinolysis. We also investigated the potential role of oxidative stress and inflammation in the promotion of thrombosis. In order to study the mechanisms of inflammation-induced thrombosis in MPN patients, the aim of the present study was to investigate the role of oxidation-induced structural and functional fibrinogen modifications in MPN patients. The eventual counteracting effects of ruxolitinib, a first-in-class JAK inhibitor, were also assessed. 40 MPN patients and 40 age- and sex-matched healthy control subjects were included in the study. We measured specific oxidative stress markers andtheir modifications in plasma, and functional and structural parameters in purified fibrinogen fractions. Marked signs of oxidative stress in plasma (P<0.01 versus controls) and, correspondingly, an increased extent of fibrinogen oxidation (P<0.01 versus controls) were observed in patients. Furthermore, fibrinogen fractions purified from MPN patients exhibited significantly reduced clotting ability and decreased susceptibility to plasmin-induced lysis (P<0.01 versus controls). Alterations in fibrinogen secondary structure, as suggested by circular dichroism spectroscopy, and in fibrin clot architecture were also identified. Importantly, clot structure obtained by stimulated emission depletion (STED) super-resolution microscopy indicated modifications in fiber diameter and clot porosity in MPN patients (P<0.01 versus controls). In patient samples, fibrinogen clot analysis and oxidative-dependent changes reveal novel structural and functional fibrinogen modifications which may favor thrombotic complications in MPNs. In patients receiving ruxolitinib, a significant improvement in redox status was observed, accompanied by a significant improvement in fibrinogen structural and functional features, suggesting a potential impactof ruxolitinib on cardiovascular prevention in MPNs.

МЕХАНИЗМЫ ТРОМБО-ВОСПАЛЕНИЯ У ПАЦИЕНТОВ С СИСТЕМНОЙ КРАСНОЙ ВОЛЧАНКОЙ

Introduction. Systemic lupus erythematosus (SLE) is a systemic autoimmune inflammatory disease. According to different authors, the incidence of thrombotic complications in this disease is higher than the average in the population and can be up to 40%. Aim. The aim of the present review is to provide an overview of mechanisms of thrombosis in patients with systemic lupus erythematosus. Material and methods. Analytical review of foreign and native publications in PubMed and eLibrary.ru between 1985-2020. Results and discussion. SLE represents a model of inflammation-induced thrombosis. The hypercoagulability state which characterizes SLE seems to be associated with inflammation-driven alterations of the thrombotic balance. Tissue-nonspecific autoantibodies, as well as cytokines and acute phase proteins induce a proinflammatory endothelial cell phenotype. Platelets are activated following endothelial dysfunction; they participate in inflammatory and thrombotic events occurring in an injured area. One of the possible initiators of the thrombosis process is considered to be an interaction of antiphospholipid antibodies with phospholipids of platelet membranes, endothelium and phospholipid-linked plasma proteins. Local unbalanced thrombin generation leading to hypercoagulability is another source central for thrombosis. Patients with systemic lupus erythematosus show multidirectional disorders of the coagulation system, with predominance of hypercoagulation especially in patients with II-III degree of disease activity. Conclusion. The mechanism of thrombo-inflammation in systemic lupus erythematosus is multifactorial, involving all components of the hemostatic system. Chronic endothelial dysfunction, platelet activation, hypercoagulation, suppression of fibrinolysis reflects an interplay between thrombosis and inflammation. Persisting autoimmune inflammation plays a key role in these abnormalities.

Dissecting Platelet's Role in Viral Infection: A Double-Edged Effector of the Immune System.

Platelets play a major role in the processes of primary hemostasis and pathological inflammation-induced thrombosis. In the mid-2000s, several studies expanded the role of these particular cells, placing them in the "immune continuum" and thus changing the understanding of their function in both innate and adaptive immune responses. Among the many receptors they express on their surface, platelets express Toll-Like Receptors (TLRs), key receptors in the inflammatory cell-cell reaction and in the interaction between innate and adaptive immunity. In response to an infectious stimulus, platelets will become differentially activated. Platelet activation is variable depending on whether platelets are activated by a hemostatic or pathogen stimulus. This review highlights the role that platelets play in platelet modulation count and adaptative immune response during viral infection.

Vascular Behçet syndrome: from pathogenesis to treatment.

Behçet syndrome is a rare, chronic inflammatory disease of unknown aetiopathogenesis, most commonly presenting with mucocutaneous and ocular manifestations. Vascular involvement, most frequently superficialvein and deepvein thrombosis, can occur in up to 50% of patients with Behçet syndrome. Venous thrombosis at atypical sites (inferior and superior vena cava, suprahepatic veins with Budd-Chiari syndrome, portal vein, cerebral sinuses and right atrium and/or ventricle) and arterial involvement (mostly in situ thrombosis and aneurysms of the pulmonary arteries, as well as aneurysms of the abdominal aorta, and peripheral and visceral arteries) are also unique features of Behçet syndrome. Behçet syndrome is considered a natural model of inflammation-induced thrombosis in humans, with an impaired immune-inflammatory response rather than traditional cardiovascular risk factors contributing to thrombogenesis. Specifically, neutrophil hyperactivation and neutrophil-mediated mechanisms of damage directly promote endothelial dysfunction, platelet activation and thrombogenesis in Behçet syndrome. This unusual pathogenesis directly determines the treatment approach, which relies mostly on immunosuppressants rather than anticoagulants for treatment of thrombosis and for secondary prevention. This Review discusses the main histopathological, pathogenetic and clinical aspects of vascular Behçet syndrome, addressing their implications for therapeutic management. Future perspectives in terms of pathogenetic studies, disease monitoring and treatment strategies are also discussed.

Gegen Qinlian pills alleviate carrageenan-induced thrombosis in mice model by regulating the HMGB1/NF-κB/NLRP3 signaling

The high incidence of thrombotic events is one of the clinical characteristics of coronavirus disease of 2019 (COVID-19), due to a hyperinflammatory response caused by the virus. Gegen Qinlian Pills (GQP) is a Traditional Chinese Medicine that is included in the Chinese Pharmacopoeia and played an important role in the clinical fight against COVID-19. Although GQP has shown the potential to treat thrombosis, there is no relevant research on its treatment of thrombosis so far. We hypothesized that GQP may be capable inhibit inflammation-induced thrombosis. We tested our hypothesis in a carrageenan-induced thrombosis mouse model in vivo and lipopolysaccharide (LPS)-induced human endothelial cells (HUVECs) in vitro. We used a carrageenan-induced mouse thrombus model to confirm the inhibitory effect of GQP on inflammation-induced thrombus. In vitro, studies in human umbilical vein endothelial cells (HUVECs) and in silico network pharmacology analyses were performed to reveal the underlying mechanisms of GQP and determine the main components, targets, and pathways of GQP, respectively. Oral administration of 227.5 mg/kg, 445 mg/kg and 910 mg/kg of GQP significantly inhibited thrombi in the lung, liver, and tail and augmented tail blood flow of carrageenan-induced mice with reduced plasma tumor necrosis factor α (TNF-α) and diminished expression of high mobility group box 1 (HMGB1) in lung tissues. GQP ethanol extract (1, 2, or 5 μg/ml) also reduced the adhesion of platelets to LPS stimulated HUVECs. The TNF-α and the expression of HMGB1, nuclear factor kappa B (NF-κB), and NLR family pyrin domain containing 3 (NLRP3) in LPS stimulated HUVECs were also attenuated. Moreover, we analyzed the components of GQP and inferred the main targets, biological processes, and pathways of GQP in the treatment of inflammation-induced thrombosis through network pharmacology. Overall, we demonstrated that GQP could reduce inflammation-induced thrombosis by inhibiting HMGB1/NFκB/NLRP3 signaling and provided an accurate explanation for the multi-target, multi-function mechanism of GQP in the treatment of thromboinflammation, and provides a reference for the clinical usage of GQP.

Arterial and venous involvement in Behçet's syndrome: a narrative review.

Behçet syndrome (BS) is a unique type of vasculitis that affects veins and arteries of all sizes, leading to recurrent vascular events, mostly venous thrombosis. The prevalence of venous thromboembolism in BS patients ranges between 15 and 40%. Thrombosis is usually an early manifestation leading to diagnosis of BS in up to 40% of patients. BS is per se a model of inflammation-induced thrombosis. The primary autoimmune response activates lymphocytes that in turn produce a cytokine cascade that activates neutrophils, which modify the secondary structure of fibrinogen making it less susceptible to plasmin-induced lysis. This leads to endothelial dysfunction, platelet activation and overexpression of tissue factor leading to inflammatory thrombi, usually attached to the wall. The pathogenesis of thrombosis is especially relevant to direct the specific treatment, that is based on immunosuppression rather than anticoagulation. Superficial vein thrombosis (SVT) and deep vein thrombosis (DVT) are the most common form of thrombosis in BS, but thrombosis in atypical sites (cava vein, suprahepatic veins, intracardiac thrombus) and arterial involvement can also occur. We assessed the latest update of the European League Against Rheumatism recommendations for the management of BS. Vascular Behçet treatment is usually based of immunosuppressants, and the role of anticoagulation remains controversial. The use of interventional and surgical procedures should be carefully evaluated, due to the risk of triggering a vascular pathergy phenomenon.

Kidney Dysfunction Is Associated with Thrombosis and Disease Severity in Myeloproliferative Neoplasms: Implications from the German Study Group for MPN Bioregistry.

Simple SummaryIn patients with myeloproliferative neoplasms (MPN) and in patients with kidney dysfunction, a higher rate of thrombosis has been reported compared with the general population. Furthermore, MPN patients are more prone to develop kidney dysfunction. In our study, we assessed the importance of specific risk factors for kidney dysfunction and thrombosis in MPN patients. We found that the rate of thrombosis is correlated with the degree of kidney dysfunction, especially in myelofibrosis. Significant associations for kidney dysfunction included arterial hypertension, MPN treatment, and increased inflammation, and those for thrombosis comprised arterial hypertension, non-excessive platelet counts, and antithrombotic therapy. The identified risk factor associations varied between MPN subtypes. Our data suggest that kidney dysfunction in MPN patients is associated with an increased risk of thrombosis, mandating closer monitoring, and, possibly, early thromboprophylaxis.Inflammation-induced thrombosis represents a severe complication in patients with myeloproliferative neoplasms (MPN) and in those with kidney dysfunction. Overlapping disease-specific attributes suggest common mechanisms involved in MPN pathogenesis, kidney dysfunction, and thrombosis. Data from 1420 patients with essential thrombocythemia (ET, 33.7%), polycythemia vera (PV, 38.5%), and myelofibrosis (MF, 27.9%) were extracted from the bioregistry of the German Study Group for MPN. The total cohort was subdivided according to the calculated estimated glomerular filtration rate (eGFR, (mL/min/1.73 m2)) into eGFR1 (≥90, 21%), eGFR2 (60–89, 56%), and eGFR3 (<60, 22%). A total of 29% of the patients had a history of thrombosis. A higher rate of thrombosis and longer MPN duration was observed in eGFR3 than in eGFR2 and eGFR1. Kidney dysfunction occurred earlier in ET than in PV or MF. Multiple logistic regression analysis identified arterial hypertension, MPN treatment, increased uric acid, and lactate dehydrogenase levels as risk factors for kidney dysfunction in MPN patients. Risk factors for thrombosis included arterial hypertension, non-excessive platelet counts, and antithrombotic therapy. The risk factors for kidney dysfunction and thrombosis varied between MPN subtypes. Physicians should be aware of the increased risk for kidney disease in MPN patients, which warrants closer monitoring and, possibly, early thromboprophylaxis.

Differential procoagulatory response of microvascular, arterial and venous endothelial cells upon inflammation in vitro

IntroductionInflammation induces a procoagulant phenotype of endothelial cells (EC) with the exposure of tissue factor (TF), a potent initiator of the extrinsic coagulation cascade. Although systemic inflammation affects the whole vascular system, thrombotic lesions occur particularly in microcirculation. This raises the question of whether TF-procoagulant activity (TF-PCA) differs between EC from arterial, venous, and microvascular beds. Materials and methodsFunctional coagulation tests, including TF-PCA, and inflammatory responses were investigated on arterial, venous and microvascular endothelial cells. Interleukin-6 (IL-6) and TF-levels were determined in cohort of 59 septic patients. ResultsWe found that tumor necrosis factor alpha (TNFα), lipopolysaccharide, and interleukin-1β induce a solid, dose-dependent increase in TF-PCA, which is highest in microvascular EC. A positive correlation of interleukin-6 (IL-6) with TF levels was observed in a cohort of 59 septic patients. In contrast, TF-PCA was independent of IL-6 concentrations in vitro. Re-analysis of publicly available gene expression data revealed that among the top 50 genes annotated to coagulation, TF is one of three regulated genes common to the three investigated EC subtypes. The response to inflammatory stimuli in terms of exposure of leukocyte-endothelial- and platelet-endothelial adhesion molecules (E-selectin and PECAM-1), remodeling of adherens junctions, co-exposure of negatively charged surfaces nor breakdown of the glycocalyx was comparable between the EC subtypes and did not explain the higher TF-PCA on microvascular cells. We found that the ratio of TF and TFPI exposure on the endothelial membrane significantly differs between the EC subtypes. ConclusionsThese findings indicate that the ratio of TF to its inhibitor TFPI is a determinant of endothelial TF-PCA, which is most pronounced on microvascular endothelial cells and might explain why the microvascular system is particularly susceptible to inflammation-induced thrombosis.

Targeting AnxA1/Formyl Peptide Receptor 2 Pathway Affords Protection against Pathological Thrombo-Inflammation.

Stroke is a leading cause of death and disability globally and is associated with a number of co-morbidities including sepsis and sickle cell disease (SCD). Despite thrombo-inflammation underlying these co-morbidities, its pathogenesis remains complicated and drug discovery programs aimed at reducing and resolving the detrimental effects remain a major therapeutic challenge. The objective of this study was to assess whether the anti-inflammatory pro-resolving protein Annexin A1 (AnxA1) was able to reduce inflammation-induced thrombosis and suppress platelet activation and thrombus formation in the cerebral microvasculature. Using two distinct models of pathological thrombo-inflammation (lipopolysaccharide (LPS) and sickle transgenic mice (STM)), thrombosis was induced in the murine brain using photoactivation (light/dye) coupled with intravital microscopy. The heightened inflammation-induced microvascular thrombosis present in these two distinct thrombo-inflammatory models was inhibited significantly by the administration of AnxA1 mimetic peptide AnxA1Ac2-26 (an effect more pronounced in the SCD model vs. the endotoxin model) and mediated by the key resolution receptor, Fpr2/ALX. Furthermore, AnxA1Ac2-26 treatment was able to hamper platelet aggregation by reducing platelet stimulation and aggregation (by moderating αIIbβ3 and P-selectin). These findings suggest that targeting the AnxA1/Fpr2/ALX pathway represents an attractive novel treatment strategy for resolving thrombo-inflammation, counteracting e.g., stroke in high-risk patient cohorts.

COVID-19, septic shock and syndrome of disseminated intravascular coagulation syndrome. Part 1

The pandemic of a new coronavirus infection (Coronavirus Disease 2019, COVID-19) caused by SARS-CoV-2 became a real challenge to humanity and the medical community in 2020 and raised a number of medical, social and even philosophical questions. An almost avalanche-like increase in the number of infected people in a short time, due to the high contagiousness of viral infection, allowed us to identify groups of patients with mild, moderate and severe forms of the disease. Doctors around the world are faced with an acute problem of treating a large number of patients in critical conditions caused by COVID-19.&#x0D; From the currently available information on clinical cases of COVID-19, it follows that COVID-19 patients in critical condition have a clinical picture of disseminated intravascular coagulation (DIC), septic shock with the development of multiple organ failure.&#x0D; The first part of the article discusses the pathogenesis of non-specific universal biological responses of the body in critical condition - from the Sanarelli-Schwartzman phenomenon to the DIC, septic shock, systemic inflammatory response syndrome and the so-called neutrophil extracellular traps (NETs). The questions of cytokine storm in severe forms of systemic inflammatory response syndrome (SIRS), the role of inflammation in the activation of coagulation, and the relationship between inflammation and thrombosis are discussed. Modern ideas about the mechanisms of so-called NETosis, their role in the occurrence of immunothrombosis and inflammation-induced thrombosis in autoimmune diseases - vasculitis, antiphospholipid syndrome, and systemic lupus erythematosus is highlighted. The article discusses the possibility of participation of ADAMTS-13 metalloproteinase in the pathogenesis of multiple organ failure in severe endotheliopathy in patients with viral septic shock.

Venous involvement in inflammatory disorders.

To review the association of venous thrombosis and inflammatory disorders. Various systemic inflammatory diseases of which Behçet's syndrome is the prototype are associated with an increased risk of venous thrombosis. Recent data indicate that venous wall thickness is increased among Behçet's syndrome patients with no history of venous thrombosis and thrombosis in Behçet's syndrome could be a unique model of inflammation-induced thrombosis. Patients with inflammatory bowel disease (IBD) have a two to three time-fold increased risk of developing thromboembolic complications compared with general population. The risk of venous thrombosis is increased after surgical interventions and is higher in ulcerative colitis compared with Crohn's disease. Despite similarities with Behçet's syndrome, anticoagulation is advised as the main treatment in IBD, while there is uncertainty about the duration of antithrombotic prophylaxis. Antineutrophil cytoplasmic antibody-associated vasculitides and ankylosing spondylitis are also other inflammatory disorders associated with a thrombotic risk. Underlying mechanisms of venous thrombosis in inflammatory disorders are not clearly understood. How we might prevent thrombosis, should we screen asymptomatic patients, what should we use for the treatment (immunosuppression or anticoagulation or both) and what should be the duration of this treatment also need to be addressed. Finally, the link between inflammation and thrombosis should be more intensively studied.

Behçet's Syndrome as a Model of Thrombo-Inflammation: The Role of Neutrophils.

Behçet's syndrome (BS) is a systemic vasculitis, clinically characterized by different organ involvement and often complicated by thrombosis which occurs in vessels of all sizes. Thrombosis is more frequent in male patients with active disease and represents an important cause of morbidity and mortality. Neutrophil involvement in BS has been repeatedly suggested in the last few years. Indeed, neutrophils have been shown to be hyperactivated in BS patients, probably with a HLAB51 related contribution, and represent the main cells infiltrating not only oral and genital ulcers or erythema nodosum, but also other sites. Besides being deputed to host defense against micro-organisms, neutrophils display fundamental roles both in inflammation and tissue damage becoming inappropriately activated by cytokines, chemokines and autoantibodies and subsequently producing large amounts of superoxide anion () via NADPH oxidase (NOX2). The strict relationship between inflammation and hemostasis has been already demonstrated. Indeed, inflammation and immune-mediated disorders increase the risk of thrombosis, but the pathways that link these processes have not been completely elucidated. In this regard, we recently demonstrated, in a large population of BS patients, a new neutrophil-dependent pathogenetic mechanism of thrombosis. In particular, it was shown that neutrophils, mainly through NADPH oxidase, produce excessive amounts of reactive oxygen species (ROS), which are able to markedly modify the secondary structure of fibrinogen and hence the overall architecture of the fibrin clot that becomes less susceptible to plasmin-induced lysis. These data point out that BS represents “per se” a model of inflammation-induced thrombosis and suggest that neutrophils specifically contribute to thrombo-inflammation in this rare disease. In particular, it is suggested that an alteration in fibrinogen structure and function are associated with enhanced ROS production via neutrophil NADPH oxidase. Altogether, these findings improve our understanding of the intricate pathogenetic mechanisms of thrombo-inflammation and may indicate potential new therapeutic targets.

Behçet's syndrome as a tool to dissect the mechanisms of thrombo-inflammation: clinical and pathogenetic aspects.

Behçet's syndrome (BS) is a complex disease with different organ involvement. The vascular one is the most intriguing, considering the existence of a specific group of patients suffering from recurrent vascular events involving the venous and, more rarely, the arterial vessels. Several clinical clues suggest the inflammatory nature of thrombosis in BS, especially of the venous involvement, thus BS is considered a model of inflammation-induced thrombosis. Unique among other inflammatory conditions, venous involvement (together with the arterial one) is currently treated with immunosuppressants, rather than with anti-coagulants. Although many in-vitro studies have suggested the different roles of the multiple players involved in clot formation, in-vivo models are crucial to study this process in a physiological context. At present, no clear mechanisms describing the pathophysiology of thrombo-inflammation in BS exist. Recently, we focused our attention on BS patients as a human in-vivo model of inflammation-induced thrombosis to investigate a new mechanism of clot formation. Indeed, fibrinogen displays a critical role not only in inflammatory processes, but also in clot formation, both in the fibrin network and in platelet aggregation. Reactive oxygen species (ROS)-derived modifications represent the main post-translational fibrinogen alterations responsible for structural and functional changes. Recent data have revealed that neutrophils (pivotal in the pathogenetic mechanisms leading to BS damage) promote fibrinogen oxidation and thrombus formation in BS. Altogether, these new findings may help understand the pathogenetic bases of inflammation-induced thrombosis and, more importantly, may suggest potential targets for innovative therapeutic approaches.

Primary Human Lung Alveolus-on-a-chip Model of Intravascular Thrombosis for Assessment of Therapeutics.

Pulmonary thrombosis is a significant cause of patient mortality; however, there are no effective in vitro models of thrombi formation in human lung microvessels that could also assess therapeutics and toxicology of antithrombotic drugs. Here, we show that a microfluidic lung alveolus-on-a-chip lined by human primary alveolar epithelium interfaced with endothelium and cultured under flowing whole blood can be used to perform quantitative analysis of organ-level contributions to inflammation-induced thrombosis. This microfluidic chip recapitulates in vivo responses, including platelet-endothelial dynamics and revealed that lipopolysaccharide (LPS) endotoxin indirectly stimulates intravascular thrombosis by activating the alveolar epithelium, rather than acting directly on endothelium. This model is also used to analyze inhibition of endothelial activation and thrombosis due to a protease activated receptor-1 (PAR-1) antagonist, demonstrating its ability to dissect complex responses and identify antithrombotic therapeutics. Thus, this methodology offers a new approach to study human pathophysiology of pulmonary thrombosis and advance drug development.

THU0029 Inflammation is Strongly Associated with Lupus Anticoagulant Positivity, Independent of Known Autoimmune Disease and Recent Venous or Arterial Thrombosis

BackgroundThe antiphospholipid syndrome (APS) is an auto-immune disorder defined by presence of antiphospholipid antibodies and either thrombosis or obstetric complications (1). Laboratory part of the diagnosis of APS comprise of...

Inflammation-Induced Thrombosis: Mechanisms, Disease Associations and Management

Although inflammation-induced thrombosis is a well-known entity, its pathogenesis remains complicated. There are complex interactions between inflammation and hemostasis, involving proinflammatory cytokines, chemokines, adhesion molecules, tissue factor expression, platelet and endothelial activation, and microparticles. Inflammation increases procoagulant factors, and also inhibits natural anticoagulant pathways and fibrinolytic activity, causing a thrombotic tendency. Besides, chronic inflammation may cause endothelial damage, resulting in the loss of physiologic anticoagulant, antiaggregant and vasodilatory properties of endothelium. However, inflammation- induced venous thrombosis may develop even in the absence of vessel wall damage. On the other hand, coagulation also augments inflammation, causing a vicious cycle. This is mainly achieved by means of thrombin-induced secretion of proinflammatory cytokines and growth factors. Platelets may also trigger inflammation by activating the dendritic cells. There are many systemic inflammatory diseases characterized by thrombotic tendency, including Behçet disease (BD), antineutrophilic cytoplasmic antibody-associated vasculitides, Takayasu arteritis, rheumatoid arthritis, systemic lupus erythematosus, antiphosholipid syndrome, familial Mediterranean fever, thromboangiitis obliterans (TAO) and inflammatory bowel diseases. Inflammation-induced thrombosis may respond to immunosuppressive (IS) treatment, as in the case of BD. However effectiveness of this treatment can not be generalized to all other inflammatory diseases. For instance, IS agents do not have any beneficial role in the management of TAO. Heparin, antiplatelet agents such as aspirin and clopidogrel, colchicine and statins also have some antiinflammatory activity. However, decreased responsiveness to aspirin and clopidogrel treatments may be observed in inflammatory diseases, due to antiplatelet resistance caused by systemic inflammation. In the present review, we aimed to discuss the details of the complex crosstalk between inflammation and hemostasis in the context of available data. We also intended to overview the major inflammatory diseases with thrombotic tendency, as well as to discuss the general principles of the management of inflammation-induced thrombosis.

Mac-1 (CD11b/CD18) links inflammation and thrombosis after glomerular injury.

Inflammation and thrombosis coexist in several disorders. Although it is recognized that leukocytes may induce a procoagulant state at sites of inflammation, the critical molecular determinants of this process remain largely unknown. To examine mechanisms of inflammation-induced thrombosis, we developed a murine model of thrombotic glomerulonephritis (TGN), a known cause of acute renal failure in patients. This model, induced by lipopolysaccharide and antibody to the glomerular basement membrane, led to rapid glomerular neutrophil recruitment, thrombotic glomerular lesions with endothelial cell injury, and renal dysfunction. In mice immunodepleted of neutrophils or lacking the leukocyte-specific integrin Mac-1, neutrophil recruitment, endothelial injury, glomerular thrombosis, and acute renal failure were markedly attenuated despite the robust generation of renal cytokines. Neutrophil elastase is a likely effector of Mac-1 because its activity was reduced in Mac-1-deficient mice and the phenotype in mice deficient in Mac-1 or neutrophil elastase was similar. Platelets accumulated in glomerular capillaries within 4 hours of TGN before evidence of thrombosis. Platelet immunodepletion before TGN markedly exacerbated hematuria (hemorrhage), inflammation, and injury, whereas thrombocytopenic Mac-1-deficient mice remained resistant to disease, indicating that initial glomerular platelet deposition protects the vessel wall from neutrophil-mediated sequelae. The subsequent thrombosis relied on the interaction of Mac-1 on recruited neutrophils with glycoprotein Ibalpha on platelets as antibody-mediated disruption of this interaction attenuated TGN without affecting renal neutrophil accumulation. These observations establish Mac-1 on neutrophils as a critical molecular link between inflammation and thrombosis and suggest it as an attractive target for antithrombotic therapy.

Effects of TNF-α and curcumin on the expression of thrombomodulin and endothelial protein C receptor in human endothelial cells

The objective of this study was to elucidate the effects of tumor necrosis factor-alpha (TNF-α) on the expression of thrombomodulin (TM) and endothelial protein C receptor (EPCR) in human endothelial cells as well as the effect of curcumin, a spice and coloring food compound, as a potential therapeutic agent. Human umbilical vein endothelial cells (HUVECs) treated with TNF-α (2.0 ng/ml) showed reduced TM mRNA levels by 80%, 97%, 94%, and 97% at 3, 6, 12, and 24 h, respectively ( P<0.05), by real-time PCR analysis. Dose-dependent study showed that TM mRNA levels of HUVECs were decreased by 86%, 89%, 91%, and 94% after treatment of TNF-α (0, 0.25, 0.5, 1, and 2 ng/ml) for 6 h, respectively ( P<0.05). TM protein levels in HUVECs were significantly reduced by 69% in TNF-α-treated cells as compared to controls ( P<0.05) by Western blot analysis. Secreted protein and activity of TM of HUVEC cultures were also significantly reduced in TNF-α-treated cells. In addition, EPCR mRNA levels of HUVECs were significantly reduced in TNF-α-treated group as compared to controls ( P<0.05). Furthermore, these effects were observed in other types of endothelial cells from human coronary arteries, lung, and skin. Curcumin effectively blocked these effects of TNF-α on downregulation of TM and EPCR. These data demonstrate that TNF-α significantly decreases expression of TM and EPCR at both mRNA and protein levels in several human endothelial cells. Curcumin can effectively block TNF-α-induced endothelial dysfunction. This study suggests a new molecular mechanism of inflammation-induced thrombosis and a new therapeutic strategy to prevent this clinical problem.