Thrombin regulates the expression of proangiogenic cytokines via proteolytic activation of protease-activated receptor-1

Microvascular Contributions to Alzheimer Disease Pathogenesis: Is Alzheimer Disease Primarily an Endotheliopathy?

Alzheimer disease (AD) models are based on the notion that abnormal protein aggregation is the primary event in AD, which begins a decade or longer prior to symptom onset, and culminates in neurodegeneration; however, emerging evidence from animal and clinical studies suggests that reduced blood flow due to capillary loss and endothelial dysfunction are early and primary events in AD pathogenesis, which may precede amyloid and tau aggregation, and contribute to neuronal and synaptic injury via direct and indirect mechanisms. Recent data from clinical studies suggests that endothelial dysfunction is closely associated with cognitive outcomes in AD and that therapeutic strategies which promote endothelial repair in early AD may offer a potential opportunity to prevent or slow disease progression. This review examines evidence from clinical, imaging, neuropathological, and animal studies supporting vascular contributions to the onset and progression of AD pathology. Together, these observations support the notion that the onset of AD may be primarily influenced by vascular, rather than neurodegenerative, mechanisms and emphasize the importance of further investigations into the vascular hypothesis of AD.

Role of Thrombin in Central Nervous System Injury and Disease

Thrombin is a Na+-activated allosteric serine protease of the chymotrypsin family involved in coagulation, inflammation, cell protection, and apoptosis. Increasingly, the role of thrombin in the brain has been explored. Low concentrations of thrombin are neuroprotective, while high concentrations exert pathological effects. However, greater attention regarding the involvement of thrombin in normal and pathological processes in the central nervous system is warranted. In this review, we explore the mechanisms of thrombin action, localization, and functions in the central nervous system and describe the involvement of thrombin in stroke and intracerebral hemorrhage, neurodegenerative diseases, epilepsy, traumatic brain injury, and primary central nervous system tumors. We aim to comprehensively characterize the role of thrombin in neurological disease and injury.

Targeting coagulation activation in severe COVID-19 pneumonia: lessons from bacterial pneumonia and sepsis

Novel coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), has rapidly spread throughout the world, resulting in a pandemic with high mortality. There are no effective treatments for the management of severe COVID-19 and current therapeutic trials are focused on antiviral therapy and attenuation of hyper-inflammation with anti-cytokine therapy. Severe COVID-19 pneumonia shares some pathological similarities with severe bacterial pneumonia and sepsis. In particular, it disrupts the haemostatic balance, which results in a procoagulant state locally in the lungs and systemically. This culminates in the formation of microthrombi, disseminated intravascular coagulation and multi-organ failure. The deleterious effects of exaggerated inflammatory responses and activation of coagulation have been investigated in bacterial pneumonia and sepsis and there is recognition that although these pathways are important for the host immune response to pathogens, they can lead to bystander tissue injury and are negatively associated with survival. In the past two decades, evidence from preclinical studies has led to the emergence of potential anticoagulant therapeutic strategies for the treatment of patients with pneumonia, sepsis and acute respiratory distress syndrome, and some of these anticoagulant approaches have been trialled in humans. Here, we review the evidence from preclinical studies and clinical trials of anticoagulant treatment strategies in bacterial pneumonia and sepsis, and discuss the importance of these findings in the context of COVID-19.

Thrombin Inhibition by Argatroban: Potential Therapeutic Benefits in COVID-19

Thrombin is a trypsin-like serine protease with multiple physiological functions. Its role in coagulation and thrombosis is well-established. Nevertheless, thrombin also plays a major role in inflammation by activating protease-activated receptors. In addition, thrombin is also involved in angiogenesis, fibrosis, and viral infections. Considering the pathogenesis of COVID-19 pandemic, thrombin inhibitors may exert multiple potential therapeutic benefits including antithrombotic, anti-inflammatory, and antiviral activities. In this review, we describe the clinical features of COVID-19, the thrombin’s roles in various pathologies, and the potential of argatroban in COVID-19 patients. Argatroban is a synthetic, small molecule, direct, competitive, and selective inhibitor of thrombin. It is approved to parenterally prevent and/or treat heparin-induced thrombocytopenia in addition to other thrombotic conditions. Argatroban also possesses anti-inflammatory and antiviral activities and has a well-established pharmacokinetics profile. It also appears to lack a significant risk of drug–drug interactions with therapeutics currently being evaluated for COVID-19. Thus, argatroban presents a substantial promise in treating severe cases of COVID-19; however, this promise is yet to be established in randomized, controlled clinical trials.

P2Y12 Inhibition beyond Thrombosis: Effects on Inflammation

The P2Y₁₂ receptor is a key player in platelet activation and a major target for antithrombotic drugs. The beneficial effects of P2Y₁₂ receptor antagonists might, however, not be restricted to the primary and secondary prevention of arterial thrombosis. Indeed, it has been established that platelet activation also has an essential role in inflammation. Additionally, nonplatelet P2Y₁₂ receptors present in immune cells and vascular smooth muscle cells might be effective players in the inflammatory response. This review will investigate the biological and clinical impact of P2Y₁₂ receptor inhibition beyond its platelet-driven antithrombotic effects, focusing on its anti-inflammatory role. We will discuss the potential molecular and cellular mechanisms of P2Y₁₂-mediated inflammation, including cytokine release, platelet–leukocyte interactions and neutrophil extracellular trap formation. Then we will summarize the current evidence on the beneficial effects of P2Y₁₂ antagonists during various clinical inflammatory diseases, especially during sepsis, acute lung injury, asthma, atherosclerosis, and cancer.

Comparative analysis of obesity-related cardiometabolic and renal biomarkers in human plasma and serum

The search for biomarkers associated with obesity-related diseases is ongoing, but it is not clear whether plasma and serum can be used interchangeably in this process. Here we used high-throughput screening to analyze 358 proteins and 76 lipids, selected because of their relevance to obesity-associated diseases, in plasma and serum from age- and sex-matched lean and obese humans. Most of the proteins/lipids had similar concentrations in plasma and serum, but a subset showed significant differences. Notably, a key marker of cardiovascular disease PAI-1 showed a difference in concentration between the obese and lean groups only in plasma. Furthermore, some biomarkers showed poor correlations between plasma and serum, including PCSK9, an important regulator of cholesterol homeostasis. Collectively, our results show that the choice of biofluid may impact study outcome when screening for obesity-related biomarkers and we identify several markers where this will be the case.

Effect of the anticoagulant, storage time and temperature of blood samples on the concentrations of 27 multiplex assayed cytokines - Consequences for defining reference values in healthy humans

Cytokines are potentially useful biomarkers of sepsis and other inflammatory conditions. Many cytokines can be released by leukocytes and platelets after sampling. The sampling and processing techniques are consequently critically important to measure the in vivo levels. We therefore examined the effects of four different anticoagulants, EDTA, citrate, lepirudin, heparin compared to serum, on the levels of 27 different cytokines. The effects of storage temperature, freezing and thawing on the plasma cytokines were examined. Cytokines were analysed using a multiplex immunoassay. The cytokine levels in serum were significantly higher compared with plasma, consistent with release of cytokines in vitro during coagulation. In general, the lowest values for all cytokines were found in EDTA samples, stored on crushed ice, centrifuged within 4h and thereafter stored at -80°C. MCP-1 and MIP-1β levels were highest in heparin plasma and storage of blood for up to 4h at room temperature significantly increased the interleukin (IL)-2, IL-6, IL-8, IFN-γ and GM-CSF levels in EDTA plasma, indicating post-sampling release. In contrast, the IP-10 levels were unaffected by sample storage at both temperatures. Our results indicate that the cytokines were more stable in plasma than in whole blood after sampling. Thus, cytokines should be analysed in EDTA plasma samples stored on ice and centrifuged within 4h. Based on these data, the reference ranges of 27 cytokines in EDTA plasma in 162 healthy human donors were calculated.

A protease-activated receptor 1 antagonist protects against global cerebral ischemia/reperfusion injury after asphyxial cardiac arrest in rabbits

Cerebral ischemia/reperfusion injury is partially mediated by thrombin, which causes brain damage through protease-activated receptor 1 (PAR1). However, the role and mechanisms underlying the effects of PAR1 activation require further elucidation. Therefore, the present study investigated the effects of the PAR1 antagonist SCH79797 in a rabbit model of global cerebral ischemia induced by cardiac arrest. SCH79797 was intravenously administered 10 minutes after the model was established. Forty-eight hours later, compared with those administered saline, rabbits receiving SCH79797 showed markedly decreased neuronal damage as assessed by serum neuron specific enolase levels and less neurological dysfunction as determined using cerebral performance category scores. Additionally, in the hippocampus, cell apoptosis, polymorphonuclear cell infiltration, and c-Jun levels were decreased, whereas extracellular signal-regulated kinase phosphorylation levels were increased. All of these changes were inhibited by the intravenous administration of the phosphoinositide 3-kinase/Akt pathway inhibitor LY29004 (3 mg/kg) 10 minutes before the SCH79797 intervention. These findings suggest that SCH79797 mitigates brain injury via anti-inflammatory and anti-apoptotic effects, possibly by modulating the extracellular signal-regulated kinase, c-Jun N-terminal kinase/c-Jun and phosphoinositide 3-kinase/Akt pathways.

Comparative study of the effect of rivaroxaban and fondaparinux on monocyte's coagulant activity and cytokine release

OBJECTIVES

Tissue factor (TF) exposed on activated monocytes and macrophages is involved in thrombosis through activation of factor X and cytokine release, responsible for inflammation and thrombosis. We investigated the effect of two anti-factor Xa drugs: rivaroxaban, a direct anti-Xa inhibitor, and fondaparinux, an antithrombin dependent anti-Xa inhibitor, on monocyte/macrophage procoagulant activity and cytokine release.

METHODS

Rivaroxaban and fondaparinux were tested at pharmacological concentrations on LPS-activated monocytes and on THP-1 cells, a human monocytic cell line, to assess 1) TF expression by flow cytometry 2) prothrombinase activity by its coagulant activity and 3) cytokine release in cell supernatants by antibody based cytokine array and ELISA for IL-8 and TNFα.

RESULTS AND CONCLUSION

Rivaroxaban and fondaparinux did not modify TF expression level on activated cells. In contrast procoagulant activity associated to monocytes and macrophages was dose dependently inhibited by rivaroxaban, but not significantly by fondaparinux. These results could explain why patients undergoing major orthopedic surgery with rivaroxaban prophylaxis were able to achieve significant reductions in venous thromboembolism, compared with drugs commonly used, i.e. fondaparinux and low molecular weight heparin. In addition, rivaroxaban and fondaparinux suppressed some chemokine secretion produced by activated macrophages. This may also contribute to their antithrombotic effect in clinic.

Evaluation on potential contributions of protease activated receptors related mediators in allergic inflammation

Protease activated receptors (PARs) have been recognized as a distinctive four-member family of seven transmembrane G protein-coupled receptors (GPCRs) that can be cleaved by certain serine proteases. In recent years, there has been considerable interest in the role of PARs in allergic inflammation, the fundamental pathologic changes of allergy, but the potential roles of PARs in allergy remain obscure. Since many of these proteases are produced and actively involved in the pathologic process of inflammation including exudation of plasma components, inflammatory cell infiltration, and tissue damage and repair, PARs appear to make important contribution to allergy. The aim of the present review is to summarize the expression of PARs in inflammatory and structural cells, the influence of agonists or antagonists of PARs on cell behavior, and the involvement of PARs in allergic disorders, which will help us to better understand the roles of serine proteases and PARs in allergy.

Association of thrombomodulin Ala455Val dimorphism and inflammatory cytokines with carotid atherosclerosis in the Chinese Han population

Background and methods

It has been reported that C/T dimorphism at position 1418 of the thrombomodulin gene causes a cytosine (C) transition to thymidine (T), resulting in an alanine (A) to valine (V) substitution at amino acid position 455 (TM455). TM455 had been found not only in African American and American whites, but also in whites in The Netherlands and Sweden. Among these populations, the C/C genotype is predominant, although the distribution of this dimorphism is different. Thrombomodulin is an important anticoagulant protein that is downregulated in endothelial cells overlying atherosclerotic plaques and is also an anti-inflammatory molecule. TM455 is located in the last epidermal growth factor-like repeat of thrombomodulin, which is functionally important for protein C activation and thrombin binding. The distribution of thrombomodulin polymorphism and association between TM455, inflammatory cytokines, and carotid atherosclerosis in the Chinese Han population is unclear.

Methods

This thrombomodulin dimorphism was analyzed by allele-specific amplification in 144 patients with carotid atherosclerosis and in 384 healthy controls. TM455 was found in the Chinese Han population, but the genotype frequency and distribution of each genotype in this population differed substantially from that in other ethnic subgroups. The C/T and T/T genotypes were predominant in the Chinese Han population, and the frequency of the T allele in this population (63.8%) was much higher than that in whites in The Netherlands (18%), Sweden (26.1%), and the US (18.4%), and in blacks in the US (7.6%). The frequencies of these single nucleotide polymorphisms complied well with the Hardy-Weinberg equilibrium in healthy individuals. The C allele was significantly more common among patients with carotid atherosclerosis than in controls (P < 0.05). The frequency of the C allele was 45.5% in patients and 36.2% in controls. The thrombomodulin Ala455 genotypes C/C and C/T were significantly more common than the T/T genotype in patients with carotid atherosclerosis in the Chinese Han population. In addition, higher baseline levels of tumor necrosis factor alpha (55.45 ± 11.58 pg/mL versus 52.70 ± 10.74 pg/mL; P < 0.05), interleukin-6 (31.53 ± 10.51 pg/mL versus 27.73 ± 8.37 pg/mL; P < 0.01), and C-reactive protein (6.65 ± 2.01 mg/L versus 4.06 ± 1.03 mg/L; P < 0.01) were observed in patients with carotid atherosclerosis than in controls. Interestingly, compared with baseline inflammatory cytokine levels in those with the Val/Val genotype, higher baseline tumor necrosis factor alpha, interleukin-6, and C-reactive protein levels were observed for the Ala/Ala genotype in both patients with carotid atherosclerosis and healthy controls.

Conclusion

Our results support a significant association between thrombomodulin Ala455Val dimorphism, inflammatory cytokines, and carotid atherosclerosis in the Chinese Han population.

RNA interference-based silencing reveals the regulatory role of fatty acid-binding protein 4 in the production of IL-6 and vascular endothelial growth factor in 3T3-L1 adipocytes

The fatty acid-binding protein 4 (FABP4) is believed to play an important role in maintaining glucose and lipid homeostasis. However, the physiological functions of FABP4 in adipocytes have not been fully elucidated because of difficulties associated with the effective transfection of small interfering RNA (siRNA) to differentiated adipocytes. The aim of this study was to clarify the physiological roles of FABP4 in adipocytes by establishing an efficient, universal technique for endogenous gene silencing in fully differentiated 3T3-L1 cells. Confocal-based three-dimensional observations demonstrated that, in traditionally cultured 3T3-L1 cells, multilayers of undifferentiated cells were formed. As a result, small interfering RNA failed to reach many of the differentiated cells. To solve this problem, we developed a reliable method, denoted as density-based separation followed by replating of enriched adipocytes in a monolayer (DREAM) and, using the developed method, succeeded in a significant knockdown of FABP4. Loss-of-function analyses revealed that FABP4 regulates the expression of IL-6 and vascular endothelial growth factor (VEGF) mediated by the protease-activated receptor 1 (PAR1), a thrombin receptor, in adipocytes. In addition, the basal IL-6 production was partially suppressed by PAR1 knockdown. Moreover, we also demonstrated that IL-6 stimulates the proliferation of primary endothelial cells isolated from murine adipose tissue. These findings indicate that FABP4 may have a crucial role in modulating IL-6 and vascular endothelial growth factor as angiogenesis inducers stimulated by the cellular action of thrombin on adipocytes via PAR1. These findings promise to be helpful for developing an understanding of physiological counterparts with respect to the inflammatory and angiogenic properties of adipose tissue.

Age-related decrease in cerebrovascular-derived neuroprotective proteins: effect of acetaminophen

As the population ages, the need for effective methods to maintain brain function in older adults is increasingly pressing. Vascular disease and neurodegenerative disorders commonly co-occur in older persons. Cerebrovascular products contribute to the neuronal milieu and have important consequences for neuronal viability. In this regard vascular derived neuroprotective proteins, Such as vascular endothelial growth factor (VEGF), pigment epithelium-derived factor (PEDF), and pituitary adenylate cyclase activating peptide (PACAP) are important for maintaining neuronal viability, especially in the face of injury and disease. The objective of this study is to measure and compare levels of VEGF, PEDF and PACAP released from isolated brain microvessels of Fischer 344 rats at 6, 12, 18, and 24 months of age. Addition of acetaminophen to isolated brain microvessels is employed to determine whether this drug affects vascular expression of these neuroprotective proteins. Experiments on cultured brain endothelial cells are performed to explore the mechanisms/mediators that regulate the effect of acetaminophen on endothelial cells. The data indicate cerebrovascular expression of VEGF, PEDF and PACAP significantly decreases with age. The age-associated decrease in VEGF and PEDF is ameliorated by addition of acetaminophen to isolated brain microvessels. Also, release of VEGF, PEDF, and PACAP from cultured brain endothelial cells decreases with exposure to the oxidant stressor menadione. Acetaminophen treatment upregulates VEGF, PEDF and PACAP in brain endothelial cells exposed to oxidative stress. The effect of acetaminophen on cultured endothelial cells is in part inhibited by the selective thrombin inhibitor hirudin. The results of this study suggest that acetaminophen may be a useful agent for preserving cerebrovascular function. If a low dose of acetaminophen can counteract the decrease in vascular-derived neurotrophic factors evoked by age and oxidative stress, this drug might be useful for improving brain function in the elderly.

Physiological status alters immunological regulation of bovine follicle differentiation in dairy cattle

Lactation in dairy cattle is associated with a multitude of endocrine, metabolic and immunological changes that not only influence animal health, but also affect fertility, and in particular ovarian function. We have previously generated a global transcriptomic profile of bovine follicular tissue using RNA sequencing. This study aimed to: identify key immune-related transcriptional changes that occur during follicle differentiation and luteinisation using ingenuity pathway analysis (IPA); and determine if a compromised model of stress (i.e. lactation) influences the temporal expression of these genes. Ovarian follicular tissue from Holstein-Friesian non-lactating heifers (n=17) and lactating cows (n=16) was compared at three stages of preovulatory follicle development: (A) the newly selected dominant follicle in the luteal phase (Selection); (B) the follicular phase before the LH surge (Differentiation), and (C) the preovulatory phase after the LH surge (Luteinisation). IPA revealed an over-representation of immune-related pathways in theca compared with granulosa cells during differentiation; these were related to leucocyte extravasation and chemotaxis. Conversely, luteinisation was characterised by over-representation of immune-related pathways in granulosa compared with theca cells; these were related to inflammation and innate immune response. Notably, comparison of follicles from heifers and lactating cows revealed a large number of differentially expressed genes associated with immune cell subpopulations and chemotaxis. In conclusion, identification of immune-related canonical pathways during follicle development supports the hypothesis that ovulation is an inflammatory event. This process is influenced by the physiological status of lactation and likely contributes to compromised peri-ovulatory follicle function by impairing the inflammatory process of ovulation.

Inhibition of proinflammatory cytokines by SCH79797, a selective protease-activated receptor 1 antagonist, protects rat kidney against ischemia-reperfusion injury

Renal ischemia-reperfusion injury (I/R) is the most common cause of acute renal failure. It is partially mediated by thrombin as it is attenuated by thrombin inhibition or deletion of its receptor protease-activated receptor 1 (PAR1). However, the role of PAR1 in renal I/R injury needs to be further elucidated. The present study investigated the effect of PAR1 antagonist, SCH79797 (SCH), on renal protection and downstream effectors involved. Male Wistar rats were pretreated with SCH (25 μg/kg i.p.) or vehicle, 15 min before 45 min of clamping of left renal pedicle after right nephrectomy. To investigate the involvement of phosphatidylinositol 3-kinase (PI3K)/Akt, a group of rats was subjected to pretreatment with an inhibitor of PI3K/Akt (LY 29004, 3 mg/kg i.p.) before renal ischemia and SCH treatment. A sham-operated group served as control and received saline. All rats were killed 24 h after reperfusion or sham operation, and blood samples collected and kidney tissues processed either for immunostaining and histological assessment or for biochemical analysis. SCH79797 markedly attenuated kidney damage histologically and by improving serum creatinine. Both plasma and protein expression of P selectin were markedly reduced as well as neutrophil infiltration, cytokine-induced neutrophil chemoattractant 1, and tumor necrosis factor α. These protective effects of blocking PAR1 receptor were abolished by preadministration of LY29004. These results suggest that PAR1 mediates renal I/R injury and that blocking PAR1 using SCH limits renal injury by an anti-inflammatory effect possibly signaling via PI3K/Akt.

Thrombomodulin and its role in inflammation

The goal is to provide an extensive review of the physiologic role of thrombomodulin (TM) in maintaining vascular homeostasis, with a focus on its anti-inflammatory properties. Data were collected from published research. TM is a transmembrane glycoprotein expressed on the surface of all vascular endothelial cells. Expression of TM is tightly regulated to maintain homeostasis and to ensure a rapid and localized hemostatic and inflammatory response to injury. By virtue of its strategic location, its multidomain structure and complex interactions with thrombin, protein C (PC), thrombin activatable fibrinolysis inhibitor (TAFI), complement components, the Lewis Y antigen, and the cytokine HMGB1, TM exhibits a range of physiologically important anti-inflammatory, anti-coagulant, and anti-fibrinolytic properties. TM is an essential cofactor that impacts on multiple biologic processes. Alterations in expression of TM and its partner proteins may be manifest by inflammatory and thrombotic disorders. Administration of soluble forms of TM holds promise as effective therapies for inflammatory diseases, and infections and malignancies that are complicated by disseminated intravascular coagulation.

A newly synthetic vitamin E derivative, E-Ant-S-GS, attenuates lung injury caused by cecal ligation and puncture-induced sepsis in rats

BACKGROUND

Cytokine activation and the ensuing spread of damage to distant organs play a central role in sepsis caused by generalized peritonitis, which accompanies surgical conditions such as gastrointestinal perforation. Anti-inflammatory properties have been discovered in endogenous substances such as vitamin E; we evaluated, in a rat model of peritonitis-induced sepsis, the newly synthetic vitamin E derivative E-Ant-S-GS, in which the endogenous substances vitamin E, glutathione, 5-OH-anthranilic acid, and succinic acid are chemically linked.

METHODS

We used a model of sepsis in male Wistar rats with the cecal ligation and puncture (CLP) method. To evaluate the anti-inflammatory effects of E-Ant-S-GS, we measured serum interleukin-6 (IL-6) levels at various times after CLP. To assess the effects of E-Ant-S-GS in acute lung injury, we evaluated histologically lung tissue 12 hours after CLP by hematoxylin-eosin staining. In addition, myeloperoxidase (MPO) activity and expression of protease-activated receptor 1 (PAR1) and high mobility group box 1 (HMGB1) in the lung were determined.

RESULTS

Serum IL-6 levels increased progressively after the CLP procedure; this cytokine induction was attenuated by E-Ant-S-GS. Increased MPO activity in lung tissue and marked changes in lung histology caused by CLP-induced sepsis were also ameliorated by E-Ant-S-GS. In addition, E-Ant-S-GS suppressed the upregulation of PAR1 and HMGB1 in the lungs after CLP.

CONCLUSION

The newly synthetic vitamin E derivative E-Ant-S-GS showed anti-inflammatory actions and organ-protective effects in a rat model of sepsis, suggesting its potential clinical use as a therapeutic agent against systemic inflammation.

Neurovascular dysfunction, inflammation and endothelial activation: implications for the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is an age-related disorder characterized by progressive cognitive decline and dementia. Alzheimer's disease is an increasingly prevalent disease with 5.3 million people in the United States currently affected. This number is a 10 percent increase from previous estimates and is projected to sharply increase to 8 million by 2030; it is the sixth-leading cause of death. In the United States the direct and indirect costs of Alzheimer's and other dementias to Medicare, Medicaid and businesses amount to more than $172 billion each year. Despite intense research efforts, effective disease-modifying therapies for this devastating disease remain elusive. At present, the few agents that are FDA-approved for the treatment of AD have demonstrated only modest effects in modifying clinical symptoms for relatively short periods and none has shown a clear effect on disease progression. New therapeutic approaches are desperately needed. Although the idea that vascular defects are present in AD and may be important in disease pathogenesis was suggested over 25 years ago, little work has focused on an active role for cerebrovascular mechanisms in the pathogenesis of AD. Nevertheless, increasing literature supports a vascular-neuronal axis in AD as shared risk factors for both AD and atherosclerotic cardiovascular disease implicate vascular mechanisms in the development and/or progression of AD. Also, chronic inflammation is closely associated with cardiovascular disease, as well as a broad spectrum of neurodegenerative diseases of aging including AD. In this review we summarize data regarding, cardiovascular risk factors and vascular abnormalities, neuro- and vascular-inflammation, and brain endothelial dysfunction in AD. We conclude that the endothelial interface, a highly synthetic bioreactor that produces a large number of soluble factors, is functionally altered in AD and contributes to a noxious CNS milieu by releasing inflammatory and neurotoxic species.

Cellular regulation of blood coagulation: a model for venous stasis

We have adapted the corn-trypsin inhibitor whole-blood model to include EA.hy926 as an endothelium surrogate to evaluate the vascular modulation of blood coagulation initiated by relipidated recombinant tissue factor (rTf) and a cellular Tf surrogate, lipopolysaccharide (LPS)-stimulated THP1 cells (LPS-THP-1). Compared with bare tubes, EA.hy926 with rTf decreased the rate of thrombin formation, ITS accumulation, and the production of fibrinopeptide A. These phenomena occurred with increased rates of factor Va (fVa) inactivation by cleavages at R(506) and R(306). Thus, EA.hy926 provides thrombin-dependent protein C activation and APC fVa inactivation. Comparisons of rTf with LPS-THP-1 showed that the latter gave reduced rates for TAT formation but equivalent fibrinopeptide A, and fV activation/inactivation. In the presence of EA.hy926, the reverse was obtained; with the surrogate endothelium and LPS-THP-1 the rates of TAT generation, fibrinopeptide release, and fV activation were almost doubled, whereas cleavage at R(306) was equivalent. These observations suggest cooperativity between the 2 cell surrogates. These data suggest that the use of these 2 cell lines provides a reproducible quasi-endothelial quasi-inflammatory cytokine-stimulated monocyte system that provides a method to evaluate the variations in blood phenotype against the background of stable inflammatory cell activator and a stable vascular endothelial surrogate.

Acanthamoeba culbertsoni elicits soluble factors that exert anti-microglial cell activity

Acanthamoeba culbertsoni is an opportunistic pathogen that causes granulomatous amoebic encephalitis (GAE), a chronic and often fatal disease of the central nervous system (CNS). A hallmark of GAE is the formation of granulomas around the amoebae. These cellular aggregates consist of microglia, macrophages, lymphocytes, and neutrophils, which produce a myriad of proinflammatory soluble factors. In the present study, it is demonstrated that A. culbertsoni secretes serine peptidases that degrade chemokines and cytokines produced by a mouse microglial cell line (BV-2 cells). Furthermore, soluble factors present in cocultures of A. culbertsoni and BV-2 cells, as well as in cocultures of A. culbertsoni and primary neonatal rat cerebral cortex microglia, induced apoptosis of these macrophage-like cells. Collectively, the results indicate that A. culbertsoni can apply a multiplicity of cell contact-independent modes to target macrophage-like cells that exert antiamoeba activities in the CNS.

Changes in amniotic fluid concentration of thrombin-antithrombin III complexes in patients with preterm labor: evidence of an increased thrombin generation

OBJECTIVE

Preterm labor is associated with excessive maternal thrombin generation, as evidenced by increased circulating thrombin-antithrombin (TAT) III complexes concentration. In addition to its hemostatic functions, thrombin has uterotonic properties that may participate in the mechanism leading to preterm birth in cases of intrauterine bleeding. Thrombin also has a proinflammatory role, and inflammation is associated with increased thrombin generation. The aim of this study was to determine whether intra-amniotic infection/inflammation (IAI) is associated with increased amniotic fluid (AF) thrombin generation in women with preterm and term deliveries.

STUDY DESIGN

This cross-sectional study included the following groups: (1) mid-trimester (n = 74); (2) term not in labor (n = 39); (3) term in labor (n = 25); (4) term in labor with IAI (n = 22); (5) spontaneous preterm labor (PTL) who delivered at term (n = 62); (6) PTL without IAI who delivered preterm (n = 59); (7) PTL with IAI (n = 71). The AF TAT III complexes concentration was measured by enzyme linked immunosorbent assay (ELISA). Non-parametric statistics were used for analysis.

RESULTS

(1) TAT III complexes were identified in all AF samples; (2) patients with PTL who delivered preterm, with and without IAI, had a higher median AF TAT III complexes concentration than those with an episode of PTL who delivered at term (p < 0.001, p = 0.03, respectively); (3) among patients with PTL without IAI, elevated AF TAT III complexes concentration were independently associated with a shorter amniocentesis-to-delivery interval (hazard ratio, 1.5; 95% CI, 1.07-2.1); (4) among patients at term, those with IAI had a higher median AF TAT III complexes concentration than those without IAI, whether in labor or not in labor (p = 0.02); (5) there was no significant difference between the median AF TAT III complexes concentration of patients at term with and without labor; (6) patients who had a mid-trimester amniocentesis had a lower median AF TAT III complexes concentration than that of patients at term not in labor (p < 0.001).

CONCLUSIONS

We present herein a distinct difference in the pattern of intra-amniotic thrombin generation between term and preterm parturition. PTL leading to preterm delivery is associated with an increased intra-amniotic thrombin generation regardless of the presence of IAI. In contrast, term delivery is associated with an increased intra-amniotic thrombin generation only in patients with IAI.

Thrombin increases inflammatory cytokine and angiogenic growth factor secretion in human adipose cells in vitro

Background

Abdominal obesity is associated with pro-thrombotic and inflammatory states. Therefore, the purpose of this study was to examine the expression of thrombin receptors (PAR1 and PAR4) human adipose tissue and whether thrombin stimulates an inflammatory cytokine and growth factor profile in human adipose tissue.

Methods

Human adipose tissue, isolated preadipocytes and differentiated adipocytes were used in this study. PAR1 and PAR4 mRNA and protein were detected by RT-PCR and immunoblot analysis in both adipose tissue and adipose microvessels. In separate studies, IL-1β, IL-6, MCP-1, TNF-α, IL-10, FGF-2, VEGF, and PDGF production were measured from adipose tissue (n = 5), adipocytes (n = 5), and preadipocytes (n = 3) supernatants with and without thrombin (1 or 10 U/ml; 24 hrs) treatment.

Results

Thrombin increased cytokine secretion of IL-1β, IL-6, MCP-1 and TNF-α and growth factor secretion of VEGF from adipocytes along with MCP-1 and VEGF from preadipocytes. The direct thrombin inhibitor lepirudin given in conjunction with thrombin prevented the thrombin-mediated increase in cytokine and growth factor secretion.

Conclusion

Here we show that thrombin PAR1 and PAR4 receptors are present and that thrombin stimulates inflammatory cytokine generation and growth factor release in human adipose tissue and cells in vitro. These data suggest that thrombin may represent a molecular link between obesity and associated inflammation.

Over-expression of the thrombin receptor (PAR-1) in the placenta in preeclampsia: a mechanism for the intersection of coagulation and inflammation

OBJECTIVE

Preeclampsia (PE) is characterized by excessive thrombin generation, which has been implicated in the multiple organ damage associated with the disease. The biological effects of thrombin on coagulation and inflammation are mediated by protease-activated receptor-1 (PAR-1), a G protein-coupled receptor. The aim of this study was to determine whether preterm PE is associated with changes in placental expression of PAR-1.

STUDY DESIGN

This cross-sectional study included two groups matched for gestational age at delivery: (1) patients with preterm PE (<37 weeks of gestation; n = 26) and (2) a control group of patients with preterm labor without intra-amniotic infection (n = 26). Placental tissue microarrays were immunostained for PAR-1. Immunoreactivity of PAR-1 in the villous trophoblasts was graded as negative, weak-positive, or strong-positive.

RESULTS

(1) The proportion of cases with strong PAR-1 immunoreactivity was significantly higher in placentas of patients with PE than in placentas from the control group (37.5% (9/24) vs. 8.7% (2/23); p = 0.036, respectively). (2) PAR-1 immunoreactivity was found in the cellular compartments of the placental villous tree, mainly in villous trophoblasts and stromal endothelial cells. (3) PAR-1 was detected in 92.3% (24/26) of the placentas of women with PE and in 88.5% (23/26) of the placentas from the control group.

CONCLUSION

Placentas from pregnancies complicated by preterm PE had a significantly higher frequency of strong PAR-1 expression than placentas from women with spontaneous preterm labor. This observation is consistent with a role for PAR-1 as a mediator of the effect of thrombin on coagulation and inflammation in PE. We propose that the effects of thrombin in PE are due to increased thrombin generation and higher expression of PAR-1, the major receptor for this enzyme.

Inflammatory angiogenesis in atherogenesis--a double-edged sword

The adventitia and the outer layers of media of an atherosclerosis-prone arterial wall are vascularized by vasa vasorum. Upon growth of an atherosclerotic lesion in the intima, neovascular sprouts originating from the adventitial vasa vasorum enter the lesion, the local proangiogenic micromilieu in the lesion being created by intramural hypoxia, by increased intramural oxidant stress, and by inflammatory cell infiltration (macrophages, T cells and mast cells). The angiogenic factors present in the lesions include various growth factors, chemokines, cytokines, proteinases, and several other factors possessing direct or indirect angiogenic activities, while the current list of antiangiogenic factors is smaller. An imbalance between endogenous inducers and inhibitors of angiogenesis, with a predominance of the former ones, is essential for the development of neovessels during the progression of the lesion. By providing oxygen and nutrients to the cells of atherosclerotic lesions, neovascularization initially tends to prevent cellular death and so contributes to plaque growth and stabilization. However, the inflammatory cells may induce rupture of the fragile neovessels, and so cause intraplaque hemorrhage and ensuing plaque destabilization. Pharmacological inhibition of angiogenesis in atherosclerotic plaques with ensuing inhibition of lesion progression has been achieved in animal models, but clinical studies aiming at regulation of angiogenesis in the atherosclerotic arterial wall can be designed only after we have reached a firm conclusion about the role of angiogenesis at various stages of lesion development--good or bad.

Proteinases and signalling: pathophysiological and therapeutic implications via PARs and more

Proteinases like thrombin, trypsin and tissue kallikreins are now known to regulate cell signaling by cleaving and activating a novel family of G-protein-coupled proteinase-activated receptors (PARs 1-4) via exposure of a tethered receptor-triggering ligand. On their own, short synthetic PAR-selective PAR-activating peptides (PAR-APs) mimicking the tethered ligand sequences can activate PARs 1, 2 and 4 and cause physiological responses both in vitro and in vivo. Using the PAR-APs as sentinel probes in vivo, it has been found that PAR activation can affect the vascular, renal, respiratory, gastrointestinal, musculoskeletal and nervous systems (both central and peripheral nervous system) and can promote cancer metastasis and invasion. In general, responses triggered by PARs 1, 2 and 4 are in keeping with an innate immune inflammatory response, ranging from vasodilatation to intestinal inflammation, increased cytokine production and increased or decreased nociception. Further, PARs have been implicated in a number of disease states, including cancer and inflammation of the cardiovascular, respiratory, musculoskeletal, gastrointestinal and nervous systems. In addition to activating PARs, proteinases can cause hormone-like effects by other signalling mechanisms, like growth factor receptor activation, that may be as important as the activation of PARs. We, therefore, propose that the PARs themselves, their activating serine proteinases and their associated signalling pathways can be considered as attractive targets for therapeutic drug development. Thus, proteinases in general must now be considered as 'hormone-like' messengers that can signal either via PARs or other mechanisms.

Thrombin receptor agonist Peptide immobilized in microspheres stimulates reparative processes in rats with gastric ulcer

The effect of synthetic thrombin receptor (PAR1) agonist peptide encapsulated in microspheres made of lactic and glycolic acid copolymer on tissue reparation was studied in rats with acetate-induced ulcer. PAR1 agonist peptide was immobilized in biodegraded lactic and glycolic acid microspheres by double emulgation, the kinetics of peptide release was analyzed, and the dynamics of ulcer healing was studied in experimental (administration of microspheres with the peptide into the stomach) and two control groups (administration of saline or spheres without peptide). Thrombin receptor agonist peptide gradually released from lactic and glycolic acid microspheres into the stomach shortened the inflammation phase and shifted the proliferation phase to the earlier period, thus accelerating healing of experimental ulcers in rats.

Role of the thrombin/protease-activated receptor 1 pathway in intestinal ischemia-reperfusion injury in rats

CXC chemokines, including human interleukin-8 and rat cytokine-induced neutrophil chemoattractant-1, play a crucial role in the pathogenesis of intestinal inflammation induced by ischemia-reperfusion (I-R). Thrombin and its specific receptor, protease-activated receptor 1 (PAR1), act as important players in inflammation. However, the association between thrombin activation and chemokine production during I-R has not been well studied. We investigated whether thrombin and PAR1 might be involved in the pathophysiology of intestinal I-R, using an in vivo model. Intestinal damage was induced by clamping the superior mesenteric artery for 30 min followed by reperfusion in male Wistar rats. Thrombin-antithrombin complex was measured as an indicator of thrombin activation. PAR1 expression in the intestine was evaluated by real-time PCR. The severity of the intestinal mucosal injury was evaluated on the distal segment of the ileum by several biochemical markers and histological findings. Reperfusion significantly increased the serum levels of thrombin-antithrombin complex and enhanced PAR1 expression in the intestinal mucosa. The levels of both intraluminal hemoglobin and protein were significantly increased in the I-R group. The mucosal myeloperoxidase activity and expressions and/or productions of cytokine-induced neutrophil chemoattractant-1 and TNF-alpha were significantly increased after I-R. These increases were inhibited by the treatment of rat with antithrombin intravenously before I-R at a dose of 30 U/kg. These results suggest that the thrombin/PAR1 pathway plays an important role in the production of these cytokines during I-R and that antithrombin exerts potent anti-inflammatory effects on this injury via inhibition of proinflammatory cytokines.

Genetic polymorphism in the fibrinolytic system and endometriosis

OBJECTIVE

Although most women experience retrograde menses during their reproductive life, endometriosis develops only in a small percentage. We hypothesized that persistence of a fibrin matrix in peritoneal pockets, as a result of hypofibrinolysis, could allow menstrually deposited endometrial fragments to initiate endometriosis. Fibrinolysis is modulated by several factors, and polymorphisms in the plasminogen activator inhibitor-1 (PAI-1) gene are considered to be one of the important determinants. The objective of this study was to evaluate PAI-1 genotypes in a group of women with or without endometriosis.

METHODS

In 118 women (75 with laparoscopically confirmed endometriosis and 43 controls), genomic DNA was extracted from blood and the PAI-1 promoter genotype was determined by polymerase chain reaction amplification of DNA using specific primers for the 4G or 5G allele followed by gel electrophoresis. A portion of the polymerase chain reaction product was purified and sequenced to confirm the gel electrophoresis results.

RESULTS

Endometriosis was more likely in patients with 4G/5G (odds ratio 38; 95% confidence interval [CI] 6-229) or 4G/4G (odds ratio 441; 95% CI 53-3,694) compared with 5G/5G PAI-1 genotype. Fifty-two of 75 women with endometriosis (69 %, 95% CI 58-79%) had the 4G/4G genotype compared with only 5 of 43 (12%; 95% CI 4-25%) controls. In contrast, the 5G/5G genotype associated with normal fibrinolysis was found in 2 of 75 (3%; 95% CI 0-9%) women with endometriosis compared with 24 of 43 (56%; 95% CI 40-71%) controls.

CONCLUSION

Hypofibrinolysis, associated with the 4G allele of the PAI-1 gene, was found significantly more often in women with endometriosis compared with controls. Persistence of fibrin matrix could support the initiation of endometriotic lesions in the peritoneal cavity, explaining why some women with retrograde menstruation develop endometriosis while others do not.

LEVEL OF EVIDENCE

II-2.

Thrombin receptor expression is upregulated in prostate cancer

BACKGROUND

Aberrant expression of protease-activated receptors (PARs) has been associated with increased angiogenesis, tumor growth, and metastasis of various cancers. We assessed the status of PAR1 expression in prostate cancer.

METHODS

The study compared the abundance levels of PAR1 RNA and protein using real-time reverse-transcriptase polymerase chain reaction and immunoblotting in freshly resected prostate tissues from early localized-stage disease (n=9) to those from patients with advanced metastatic disease (n=7). PAR1 expression and localization was evaluated using immunohistochemical staining of prostate specimens with benign prostatic hyperplasia (n=27), early- (n=32) and advanced-stage (n=22) prostate cancer. Association analyses of PAR1 expression with expression of VEGF-family of growth factors, their receptors, and clinicopathological characteristics of the patients were also performed.

RESULTS

PAR1 RNA expression in advanced-stage prostate was 2.39-fold higher (P=0.024) and its protein expression was 2.75-fold higher (P=5.89x10(-5)) when compared with early-stage prostate cancer. PAR1 expression was localized to endothelial cells in vascular network of prostate tumor areas. The expression of PAR1 correlated statistically significantly with advanced disease stage (P=0.0006) and pre-operative PSA levels (P=0.005) in these samples.

CONCLUSIONS

These findings demonstrate that PAR1 expression is increased in prostate cancer. Its predominant expression in vascular network suggests that it may play a direct and crucial role in angiogenesis and could be a relevant target for therapeutic interventions to control or to prevent disease progression.

Effect of synthetic peptide thrombin receptor agonist encapsulated in microparticles based on lactic and glycolic acid copolymer on healing of experimental skin wounds in mice

PAR1 peptide thrombin receptor agonist (PAR1-AP) was encapsulated in microcorpuscles based on lactic and glycolic acid copolymer. The desorption profile of the preparation was studied in vitro and its wound-healing effects were studied on a model of cut skin wound in mice. The study showed that 90% PAR1-AP was desorbed over 6 h, but the peptide was detected in eluates from the microparticle surface after 23 h. The desorbed peptide retained its physiological activity and was capable of activating PAR1 receptors on human platelets. The study of the dynamics of experimental skin wound healing in mice showed lower number of macrophages in the wounds treated with PAR1-AP microparticles compared to the control (open wounds and wounds covered with microparticles) and higher number of fibroblasts on day 3 of tissue reparation. Hence, PAR1-AP desorbed from microparticles shortened the inflammation phase in the wound. On day 7 the best healing parameters were also observed in wounds treated with PAR1-AP microparticles, which attests to shortening of the proliferation phase and acceleration of wound healing.

Absence of proteinase-activated receptor-1 signaling affords protection from bleomycin-induced lung inflammation and fibrosis

Activation of the coagulation cascade is commonly observed in the lungs of patients with both acute and chronic inflammatory and fibrotic lung disorders, as well as in animal models of these disorders. The aim of this study was to examine the contribution of the major thrombin receptor, proteinase-activated receptor-1 (PAR-1), during the acute inflammatory and chronic fibrotic phases of lung injury induced by intratracheal instillation of bleomycin in mice. Inflammatory cell recruitment and increases in bronchoalveolar lavage fluid (BALF) protein were attenuated by 56 +/- 10% (P < 0.05) and 53 +/- 12% (P < 0.05), respectively, in PAR-1-deficient (PAR-1-/-) mice compared with wild-type (WT) mice. PAR-1-/- mice were also protected from bleomycin-induced pulmonary fibrosis with total lung collagen accumulation reduced by 59 +/- 5% (P < 0.05). The protection afforded by PAR-1 deficiency was accompanied by significant reductions in pulmonary levels of the potent PAR-1-inducible proinflammatory and profibrotic mediators, monocyte chemoattractant protein-1 (MCP-1), transforming growth factor-beta-1 (TGF-beta1), and connective tissue growth factor/fibroblast-inducible secreted protein-12 (CTGF/FISP12). In addition, PAR-1 was highly expressed in inflammatory and fibroproliferative lesions in lung sections obtained from patients with fibrotic lung disease. These data show for the first time that PAR-1 signaling plays a key role in experimentally induced lung injury, and they further identify PAR-1 as one of the critical receptors involved in orchestrating the interplay between coagulation, inflammation, and remodeling in response to tissue injury.

Proteinase-activated receptors: transducers of proteinase-mediated signaling in inflammation and immune response

Serine proteinases such as thrombin, mast cell tryptase, trypsin, or cathepsin G, for example, are highly active mediators with diverse biological activities. So far, proteinases have been considered to act primarily as degradative enzymes in the extracellular space. However, their biological actions in tissues and cells suggest important roles as a part of the body's hormonal communication system during inflammation and immune response. These effects can be attributed to the activation of a new subfamily of G protein-coupled receptors, termed proteinase-activated receptors (PARs). Four members of the PAR family have been cloned so far. Thus, certain proteinases act as signaling molecules that specifically regulate cells by activating PARs. After stimulation, PARs couple to various G proteins and activate signal transduction pathways resulting in the rapid transcription of genes that are involved in inflammation. For example, PARs are widely expressed by cells involved in immune responses and inflammation, regulate endothelial-leukocyte interactions, and modulate the secretion of inflammatory mediators or neuropeptides. Together, the PAR family necessitates a paradigm shift in thinking about hormone action, to include proteinases as key modulators of biological function. Novel compounds that can modulate PAR function may be potent candidates for the treatment of inflammatory or immune diseases.

Impaired Angiogenesis in the Aged

The process of angiogenesis, during which new blood vessels are formed, is impaired during aging. This Perspective describes many of the myriad components of the angiogenic response that are altered with age. In addition, the impact of impaired angiogenesis on wound healing, vascular disease, and cancer in the aged is discussed.

Increased Thrombin Activity after Allergen Challenge

In addition to its central role in hemostasis, thrombin may play a role in inflammation and remodeling. To investigate the contribution of thrombin to allergic airway inflammation in asthma, we used an enzymatic assay to determine thrombin activity in bronchoalveolar lavage fluid obtained from 19 subjects with atopic asthma before (Day 0) and 48 hours after (Day 2) segmental bronchoprovocation with antigen. Thrombin activity increased from 0 (0, 2.9) on Day 1 to 41.1 (0.3, 75.6) U x 10(-3)/ml on Day 2 (p = 0.002) and correlated with total protein levels in lavage fluid on Day 2 (r = 0.885, p < 0.001). After antigen challenge, thrombin activity also showed significant correlations with interleukin-5 (r = 0.66, p = 0.002), transforming growth factor beta1 (r = 0.70, p < 0.001), fibronectin (r = 0.85, p < 0.001) and tissue factor (r = 0.55, p = 0.03) levels in lavage fluid. Furthermore, Day 2, but not Day 0 lavage fluid, induced proliferation of human airway fibroblasts. This mitogenic effect was significantly reduced with hirudin, a specific thrombin inhibitor. Taken together, our findings suggest that allergen-driven airway inflammation in asthma is associated with enhanced potential for fibroblast proliferation that is related, at least in part, to increased thrombin activity. We propose that enhanced thrombin activity provides a potential link between allergic inflammation and initiation of airway remodeling.

Thalidomide protects endothelial cells from doxorubicin-induced apoptosis but alters cell morphology

Antiangiogenesis agents are now being used in clinical trials to reduce the risk of recurrence of cancer. Several of these agents, however, are associated with thrombosis, especially when used in combination with chemotherapy. Antiangiogenesis and thrombosis are both endothelial-related activities, and we therefore evaluated one presumed antiangiogenesis agent (thalidomide) on intact cultured endothelial cells, and on cultured endothelial cells injured by preincubation with doxorubicin. We evaluated cell viability, caspase-3 activation, morphology of cells using light microscopy, and protease activated receptor-1 (PAR-l) expression. In our experiments, doxorubicin induced a dose- and incubation time-dependent and caspase-3-mediated apoptosis of endothelial cells. Thalidomide alone caused no changes in intact endothelial cells in terms of morphology, cell viability or activation of caspase-3. In contrast, when thalidomide was added to doxorubicin-injured endothelial cells, there was protection from cell death, increase in viability of endothelial cells, induction of differentiation and formation of neotubules. Doxorubicin reduced the expression of thrombin receptor, PAR-1, as evaluated by immunostaining and flow cytometry. Thalidomide did not alter PAR-1 expression in untreated cells but restored its expression reduced by doxorubicin. These findings suggest that thalidomide may be procoagulant, not by enhancing doxorubicin-mediated endothelial cell injury, but by altering the expression of PAR-1 on injured endothelium and resulting in endothelial dysfunction, which may explain hypercoagulability in patients treated with chemotherapy followed by thalidomide.

Three-dimensional in vitro culture of endometrial explants mimics the early stages of endometriosis

OBJECTIVE

To reproduce the earliest phases of endometriosis using a new in vitro model in which cells from a cultured endometrial fragment can proliferate, invade, reconstitute new endometrial-like tissue, and generate blood vessels.

DESIGN

Experimental in vitro study.

SETTING

A hospital-based academic research institute.

PATIENT(S)

Five normal ovulating women undergoing surgery for various benign gynecological indications.

INTERVENTION(S)

Endometrial samples obtained from the fundus of the uterine cavity were placed in a three-dimensional fibrin matrix culture system.

MAIN OUTCOME MEASURE(S)

Degree of proliferation of stromal cells and invasion of the fibrin matrix, gland, and stroma formation, vessel sprouting, and immunohistochemical characterization of various cellular components.

RESULT(S)

During the first week of culture, an endometrial cell outgrowth was observed from the original fragments in 120 of 144 wells (83.3%). Subsequently, cell outgrowths could be quantified in 132 (91.6%), 129 (89.5%), and 127 (88.1%) of the wells after 15, 60, and 90 days, respectively. An invasion of the matrix by the human endometrial cells led to the formation of tubular structures that coalesced into tissue, architecturally resembling endometrium and in which the glands were immunohistochemically positive for cytokeratin. New capillaries, immunohistochemically positive for CD31 and vimentin, sprouted from the endometrial outgrowths at the beginning of the fifth week of culture.

CONCLUSION(S)

These data show that cells from endometrial explants can proliferate and invade a fibrin matrix in vitro generating new glands, stroma, and vessels consistent with endometriosis. The three-dimensional fibrin matrix used in the present study provides an opportunity to observe the earliest biological events of endometriosis in a quantifiable way.

Inhibition of interleukin-12 expression by alpha-thrombin in human peripheral blood mononuclear cells: a potential mechanism for modulating Th1/Th2 responses

In addition to its central role in blood coagulation and hemostasis, human alpha-thrombin is a powerful regulator of inflammatory responses and is known to affect cell-mediated immunity. Interleukin (IL)-12 is a strong promoter of the development of Th1-type lymphocytes and its downregulation implies a positive feedback mechanism for development of Th2 responses. We have previously shown that thrombin enhances the release of IL-6, a Th2-related cytokine, in human peripheral blood mononuclear cells (PBMC). Here we show that thrombin downregulates IL-12 production at both protein and mRNA levels in human PBMC. The inhibition of IL-12 production was accompanied by an enhanced release of IL-10, which inhibits Th1-related processes and promotes Th2-type responses. The use of proteolytically inactive thrombin and of the specific thrombin receptor agonist peptide, SFLLRN, reveals that this downregulation is thrombin-specific and requires thrombin proteolytic activity. In addition, activation of coagulation inhibits IL-12 production in whole blood cultures, confirming the tight relationship between the coagulation pathway, where thrombin is a key enzyme, and inflammation. Decreased IL-12 production appears to be related also to IL-10 production, since the addition of an anti-IL-10 monoclonal antibody to thrombin-treated PBMC resulted in a partial restoration of IL-12 production. In conclusion, the observation that thrombin significantly affects the production of IL-12, as well as of IL-10, implies a concerted role orchestrated by thrombin in PBMC that could be crucial to effective immunity and inflammation.

Atorvastatin limits the pro-inflammatory response of rat aortic smooth muscle cells to thrombin

Thrombin, a serine protease, plays an important role in the progression of atherosclerosis. How atorvastatin could limit the pro-inflammatory response to thrombin was studied in cultured rat aortic smooth muscle cells. The variations in expression of interleukin-6, heme oxygenase-1, p(22phox) and Mox-1 mRNAs were evaluated by reverse transcriptase-polymerase chain reaction (RT-PCR). Interleukin-6 release was determined using the B9 cell assay. Nuclear factor-kappa B (NF-kappaB) translocation was analysed by electrophoretic mobility shift assay (EMSA) and RhoA protein translocation by Western blot. Thrombin activated interleukin-6 secretion and mRNA expression in smooth muscle cells in a dose-dependent manner. The greatest effect on mRNA expression was obtained after 1 h of stimulation. Preincubation (72 h) of the cells with various concentrations of atorvastatin prevented this effect. Simultaneous addition of mevalonate overcame this statin effect. Thrombin was without effect on p(22phox) and heme oxygenase-1 mRNA expression but, after 3 h of stimulation, induced a two-fold increase in that of Mox-1. Preincubation with atorvastatin dose-dependently downregulated this Mox-1 mRNA expression. In addition, thrombin induced NF-kappaB translocation and membrane translocation of RhoA in smooth muscle cells which were both prevented by pre-treatment of the cells by atorvastatin. These data demonstrate the ability of atorvastatin to prevent the induction by thrombin of a pro-inflammatory phenotype in smooth muscle cells.

Extracellular mediators in atherosclerosis and thrombosis: lessons from thrombin receptor knockout mice

It is well appreciated that thrombin as well as other proteases can act as signaling molecules that specifically regulate cells by cleaving and activating members of a novel class of protease-activated receptors (PARs). The utility of gene knockout strategies to define and better comprehend the physiological role of specific proteins is perhaps best exemplified in the field of thrombin receptors. The development of PAR knockout mice has provided the unique opportunity to identify and characterize new members of this novel family of GPCRs, evaluate the interaction of PARs jointly expressed in common cells and tissues, and better understand the role of PARs in thrombosis, restenosis, vascular remodeling, angiogenesis, and inflammation. Presently, 4 members of the PAR family have been cloned and identified. In this review, we examine experimental evidence gleaned from PAR-/- mouse models as well as how the use of PAR-/- mice has provided insights toward understanding the physiological role of thrombin in cells of the vascular system and vascular pathology.