A3 CROHN’S DISEASE PROTEOLYTIC MICROBIOTA ENHANCES INFLAMMATION THROUGH PAR2 PATHWAY IN GNOTOBIOTIC MICE

Background

An imbalance in host proteases has been implicated in inflammatory bowel disease (IBD). Recent evidence implicates microbial proteolytic activity (PA) in ulcerative colitis but whether it also plays a role in Crohn’s disease (CD) remains unclear.

Purpose

We therefore investigated the colitogenic potential and underlying pathways of proteolytic CD microbiota.

Method

Adult germ-free (GF) C57BL/6 mice were colonized with CD microbiota selected based on high (CD-HPA) or low fecal proteolytic activity (CD-LPA), and from healthy controls with LPA (HC-LPA), after which total fecal proteolytic, elastolytic and mucolytic activity were analyzed in the mice. Microbial community was assessed by 16S rRNA gene sequencing. Immune function and colonic injury were investigated by inflammatory gene expression (NanoString) and histology. Colitis severity and underlying pathways were investigated in C57BL/6, Nucleotide-binding Oligomerization Domain-2 knock-out (Nod2^-/-), and Protease-Activated Receptor 2 (PAR2) cleavage resistant mice (R38E-PAR2) subjected to 2% dextran sodium sulfate in drinking water for 5 days followed by 2 days on water.

Result(s)

Colonization with HC-LPA or CD-LPA lowered baseline fecal proteolytic activity compared with GF mice, which was paralleled by lower acute inflammatory cell infiltrate. CD-HPA further increased proteolytic activity compared with GF mice. Fecal supernatants from CD-LPA or HC-LPA colonized mice had lower in vitro PAR2 cleavage compared to supernatants from GF and CD-HPA colonized mice. Several genes, such as Map kinases, Rhoa, Myd88, and Tollip, were increased in GF mice compared to colonized mice. 18 genes related to inflammation and barrier function (e.g., Mapk2k6, Tnf, Claudin1) were differentially expressed between CD-LPA and CD-HPA. CD-HPA mice had lower alpha diversity, distinct microbial profiles, and higher fecal proteolytic activity compared with CD-LPA. Abundance of several beneficial species (e.g., Akkermansia muciniphilia) was decreased while other taxa were increased (e.g., Hungattella hathewayi) in CD-HPA compared to CD-LPA. H. hathewayi as well as the serine protease K04772 were transcriptionally increased in fecal samples from CD-HPA colonized mice. C57BL/6 and Nod2^-/- mice, but not R38E-PAR2 mice, colonized with CD-HPA developed earlier and more severe colitis compared with mice colonized with CD-LPA.

Conclusion(s)

CD proteolytic microbiota is proinflammatory through a PAR2 pathway. H. hathewayi correlates with the proinflammatory phenotype through the serine protease K04772 in this model. The results support a role of microbial PA in CD, which could constitute a biomarker for identifying patients who would benefit from anti-proteolytic therapies.

Disclosure of Interest

None Declared

Aircraft noise exposure induces pro-inflammatory vascular conditioning and amplifies vascular dysfunction and impairment of cardiac function after myocardial infarction

AIMS

Traffic noise may play an important role in the development and deterioration of ischemic heart disease. Thus, we sought to determine the mechanisms of cardiovascular dysfunction and inflammation induced by aircraft noise in a mouse model of myocardial infarction (MI) and in humans with incident MI.

METHODS AND RESULTS

C57BL/6J mice were exposed to noise alone (average sound pressure level 72 dB; peak level 85 dB) up to 4d, resulting in pro-inflammatory aortic gene expression in the myeloid cell adhesion/diapedesis pathways. Noise alone promoted adhesion and infiltration of inflammatory myeloid cells in vascular/cardiac tissue, paralleled by an increased percentage of leukocytes with a pro-inflammatory, reactive oxygen species (ROS)-producing phenotype and augmented expression of Nox-2/phospho-NFκB in peripheral blood. Ligation of the LAD resulted in worsening of cardiac function, pronounced cardiac infiltration of CD11b+ myeloid cells and Ly6Chigh monocytes and induction of interleukin (IL) 6, IL-1β, CCL-2 and Nox-2, being aggravated by noise exposure prior to MI. MI induced stronger endothelial dysfunction and more pronounced increases in vascular ROS in animals preconditioned with noise. Participants of the population-based Gutenberg Health Cohort Study (median follow-up:11.4y) with incident MI revealed elevated CRP at baseline and worse LVEF after MI in case of a history of noise exposure and subsequent annoyance development.

CONCLUSION

Aircraft noise exposure before MI substantially amplifies subsequent cardiovascular inflammation and aggravates ischemic heart failure, facilitated by a pro-inflammatory vascular conditioning. Our translational results suggest, that measures to reduce environmental noise exposure will be helpful in improving clinical outcome of subjects with MI.

The relationship between direct care providers' physical activity behaviour and perceived physical activity needs for people with intellectual disabilities

BACKGROUND

The promotion of physical activity and the decrease of inactivity and sedentary behaviour are crucial for a healthy lifestyle and positive quality of life. People with intellectual disabilities are at increased risk of inactivity and sedentary behaviour. Therefore, it is important to increase their physical activity by implementing physical activity guidelines in their daily life. Professional direct care providers can play a decisive role in supporting people with intellectual disabilities to participate in physical activity, but the engagement of direct care providers with this role may be reflective of their own attitudes and beliefs towards physical activity. Therefore, the link between the implementation of current physical activity guidelines for people with intellectual disabilities and direct care providers' own beliefs and behaviour with regard to physical activity is investigated.

METHOD

A total of 104 direct care providers completed self-reported questionnaires about their own physical activity behaviour (IPAQ-SF), recommendations for people with intellectual disabilities (adaption of EMIQ-HP) and questions regarding global physical activity guidelines. They were also asked about potential barriers and facilitators for the recommendation of physical activity in open-ended questions.

RESULTS

Personal physical activity behaviour is related to the recommended physical activity for people with intellectual disabilities (moderate-to-vigorous physical activity: r_s  = 0.408, P = 0.005). However, recommended physical activity behaviour for people with intellectual disabilities is significantly lower than direct care providers' own physical activity behaviour (P < 0.001). 47.1% of the respondents recommended people with intellectual disabilities to participate in less than the 150 min of moderate intensity physical activity per week for that is recommended in global physical activity guidelines.

CONCLUSION

Direct care providers may hold stereotypical views and insecurities about the potential harms associated with people with intellectual disabilities participating in physical activity. Therefore, the dissemination of physical activity recommendations for people with intellectual disabilities should be a major target for health professionals, social workers and scientists to address direct care providers' concerns. Furthermore, we need to emphasise the benefits of regular physical activity to professional direct care providers and directly to people with intellectual disabilities.

Nox2+ myeloid cells drive vascular inflammation and endothelial dysfunction in heart failure after myocardial infarction via angiotensin II receptor type 1

Background

Ischemic heart failure (HF) ensuing myocardial infarction (MI) leads to impaired left ventricular function, reduced cardiac output and counterregulatory activation of angiotensin II (AngII) levels. Furthermore, it is characterized by the initiation of a systemic inflammatory response.

Objective

We aimed to elucidate the impact of myelomonocytic cells and their activation by angiotensin II on vascular endothelial function in a mouse model of HF after MI.

Results

HF was induced in male C57BL/6J mice by permanent ligation of the left anterior descending coronary artery. Compared to sham, HF mice had significantly impaired endothelial function accompanied by enhanced mobilization of Sca-1+c-Kit+ hematopoietic stem cells and Sca-1-c-Kit+ common myeloid and granulocyte-macrophage progenitors in the bone marrow as well as increased vascular infiltration of CD11b+Ly6G-Ly6Chigh monocytes and accumulation of CD11b+ F4/80+ macrophages, assessed by flow cytometry. Using mice with Cre-inducible expression of diphtheria toxin receptor in myeloid cells, we selectively depleted lysozyme M+ myelomonocytic cells for 10 d starting 28d after MI. While the cardiac phenotype remained unaltered until 38d post MI, myeloid cell depletion attenuated vascular accumulation of Nox2+CD45+ cells, endothelial dysfunction, oxidative stress and vascular expression of adhesion molecules and angiotensin II receptor type 1 (AT1R). Pharmacological blockade of this receptor for 4 weeks did not significantly alter cardiac function, but mimicked the effects of myeloid cell depletion: Telmisartan (20 mg/kg/d, fed to C57BL/6J mice) diminished bone marrow myelopoesis and myeloid ROS production, attenuated endothelial leukocyte rolling and vascular accumulation of CD11b+Ly6G-Ly6Chigh monocytes and macrophages, resulting in improved vascular function with less abundance of Nox2+CD45+ cells.

Conclusion

Endothelial dysfunction in HF ensuing MI is mediated by inflammatory Nox2+ myeloid cells infiltrating the vessel wall that can be targeted by AT1R blockade.

Funding Acknowledgement

Type of funding source: None

Tissue factor cytoplasmic tail regulates myeloid cell derived superoxide formation and TGF-beta 1 driven cardiac remodeling in myocardial infarction

Background

In the setting of myocardial infarction (MI), patients with coronary no-reflow and/or delayed presentation after onset of symptoms (sub-acute MI) are inflicted by severe thrombo-inflammation and are marked by worse clinical outcome. However, it is unclear whether tissue factor (TF) contributes to outcome post MI solely by the regulatory functions of its cytoplasmic tail independently of its coagulation activity.

Purpose

We analyzed the role of the TF cytoplasmic domain in the recruitment of myeloid cells into the infarcted myocardium and the consequences on cardiac remodeling, scar formation, development of heart failure and survival post MI.

Methods

Twelve Patients enrolled in the MICAT (Mainzer Intracoronary Database, ClinicalTrials.gov Identifier: NCT02180178) study were examined. Patients with sub-acute MI and stable coronary artery disease were defined and monocytes were isolated from peripheral blood mononuclear cells (PBMCs). Human heart samples acquired from the left ventricular wall of explanted hearts following cardiac transplantation or obtained during implantation of left ventricular assist device. Samples were investigated for downstream analysis of protein by western blots, RNA quantification and cryo-sectioning. MI was induced in 9 to 12 weeks old male C57BL/6J mice, mice specifically lacking the cytoplasmic tail (CT) of TF (TFΔCT mice) and TFfl/flLysMCre+/− mice by permanent ligation of the left anterior descending artery. Left ventricular function was assessed by High-Frequency Ultrasound System. Infiltration of immune cells into the infarcted myocardium was analyzed by performing flow cytometric analysis after enzymatic digestion of the myocardium. Superoxide levels were quantified by HPLC-based measurement of dihydroethidium derived oxidation product 2-hydroxy ethidium.

Results

Circulating monocytes in patients with sub-acute MI showed increased nitrosative stress as well as increased phosphorylation of TF CT along with TGF-β1 and NF-kB inflammatory activation, which was recapitulated in cardiac tissue of end-stage heart failure patients with chronic MI. MI results in phosphorylation of the CT of TF within myeloid cells. Using mice with conditional knockout of TF on myeloid cells or TFΔCT mice, we found that this regulatory intracellular domain of TF within myeloid cells is required for cardiac infiltration of inflammatory Ly6Chigh TF+ monocytes, Rac-1 GTPase and superoxide formation of gp91phox + myeloid cells in MI. TGF-β1 dependent SMAD2 activation and cardiac collagen deposition as late sequel of MI was reduced in TFΔCT mice, resulting in attenuated cardiac dysfunction and reduced mortality.

Conclusion

We conclude that, TF CT drives NADPH-oxidase derived superoxide formation, thrombo-inflammation and cardiac fibrosis. Therefore, it might serve as putative biomarker and risk predictor in MI

Funding Acknowledgement

Type of funding source: None

A48 COLITIS FAVORS THE EXPANSION OF BACTERIA THAT ACTIVATE PAR2 AMPLIFYING INFLAMMATORY RESPONSE

Background

Proteolytic imbalance has been described in patients with inflammatory bowel disease (IBD) and in different models of experimental colitis. Although the proteases reported to be increased are mainly from the host, the role of bacterial proteases has recently emerged, as they can promote inflammation, in part, through activation of Protease-activated receptors (PARs). PAR2 deficient mice are resistant to inflammation and PAR2 activation affects multiple aspects of the tissue response to injury. However, PAR2 communicates with other receptors such as toll-like and other PARs, which are important in multiple immune signaling pathways. Thus, the direct implication of PAR2 in colitis, and specifically the activation of the external domain by microbial proteases, remains unclear.

Aims

To study the role of PAR2 and bacterial proteases in experimental colitis.

Methods

C57BL/6 and protease-resistant PAR2 (R38E-PAR2) mice, in which activation site of PAR2 is missing, were given 3.5% dextran sodium sulfate (DSS) in drinking water for 5 days followed by 2 days of water. Control C57BL/6 (wild-type) and R38E-PAR2 mice received only water. Percent weight change was evaluated along the study. Fecal microbiota (16S Ilumina), expression of proinflammatory genes (Nanostring), gut permeability (Ussing chamber), proteolytic activities (colorimetric assay) and bacterial translocation (plating) were measured in all mice at sacrifice. Inflammation was determined by analyzing stool consistency, fecal blood and by microscopic scores (Cooper score). Bacteria with proteolytic activity were isolated using agar-media with protein as main nutrient and bacterial capacity to release the external domain of PAR2 was tested in cells harbouring luciferase at the PAR2 N terminus.

Results

Wild-type, but not R38E-PAR2 mice, had increased expression of several pro-inflammatory genes, such as tnf, map3k and tlr, gut dysfunction and increased intestinal permeability, increased bacterial translocation into spleen and altered microbiota profiles following DSS treatment. DSS induced colitis in both mouse strains, but clinical and microscopic scores were significantly lower in R38E-PAR2 compared with wild-type mice. DSS increased the abundance of opportunistic pathogens such as Enterococcus and Staphylococcus only in wild-type mice. Proteolytic phenotype of these bacteria, and their capacity to cleave the external domain of PAR2, was confirmed.

Conclusions

Mice lacking the activation site of PAR2 are protected from DSS-induced colitis. DSS treatment leads to expansion of bacteria releasing active proteases, which may mediate injury through PAR2. These results suggest that intestinal injury promotes microbial proteolytic imbalance which in turn, exacerbates inflammation.

Funding Agencies

CAG, CCC, CIHR

Do we have to reduce the recall period? Validity of a daily physical activity questionnaire (PAQ24) in young active adults

Background

Combining the strengths of physical activity (PA) diaries and questionnaires may be needed to improve the unsatisfying measurement quality of existing PA questionnaires. This study investigated the construct validity of a short PA questionnaire (Physical Activity Questionnaire for 24 h [PAQ24]) with a recall period of one day.

Methods

In this cross-sectional study, participants completed the PAQ24 on seven consecutive days while wearing an accelerometer (GENEActiv). Thereafter, the Global Physical Activity Questionnaire (GPAQ) was completed. Spearman correlation coefficients and Bland-Altman analysis were used to assess construct validity.

Results

Overall, 50 active adults (11 women, mean age = 25.1 ± 2.5) participated. Relative agreements between Total PA of PAQ24 and accelerometer were 0.37 ≤ ρ ≤ 0.72 for each day with satisfying agreement on five out of seven days. Weekly relative agreement for Total PA was moderate (ρ = 0.44). Relative agreements between PAQ24 and GPAQ were ρ = 0.43 for Total PA. Daily and weekly absolute agreements were poor indicated by wide limits of agreement.

Conclusions

In contrast to weekly Total PA, the majority of daily results of the PAQ24 showed satisfying construct validity. A short recall period may improve the measurement quality of PA questionnaires, but measurement errors and the costs of multiple administrations must be considered in future studies.

Tissue factor at the crossroad of coagulation and cell signaling

The tissue factor (TF) pathway plays a central role in hemostasis and thrombo-inflammatory diseases. Although structure-function relationships of the TF initiation complex are elucidated, new facets of the dynamic regulation of TF's activities in cells continue to emerge. Cellular pathways that render TF non-coagulant participate in signaling of distinct TF complexes with associated proteases through the protease-activated receptor (PAR) family of G protein-coupled receptors. Additional co-receptors, including the endothelial protein C receptor (EPCR) and integrins, confer signaling specificity by directing subcellular localization and trafficking. We here review how TF is switched between its role in coagulation and cell signaling through thiol-disulfide exchange reactions in the context of physiologically relevant lipid microdomains. Inflammatory mediators, including reactive oxygen species, activators of the inflammasome, and the complement cascade play pivotal roles in TF procoagulant activation on monocytes, macrophages and endothelial cells. We furthermore discuss how TF, intracellular ligands, co-receptors and associated proteases are integrated in PAR-dependent cell signaling pathways controlling innate immunity, cancer and metabolic inflammation. Knowledge of the precise interactions of TF in coagulation and cell signaling is important for understanding effects of new anticoagulants beyond thrombosis and identification of new applications of these drugs for potential additional therapeutic benefits.

Atherothrombosis and Thromboembolism: Position Paper from the Second Maastricht Consensus Conference on Thrombosis

Atherothrombosis is a leading cause of cardiovascular mortality and long-term morbidity. Platelets and coagulation proteases, interacting with circulating cells and in different vascular beds, modify several complex pathologies including atherosclerosis. In the second Maastricht Consensus Conference on Thrombosis, this theme was addressed by diverse scientists from bench to bedside. All presentations were discussed with audience members and the results of these discussions were incorporated in the final document that presents a state-of-the-art reflection of expert opinions and consensus recommendations regarding the following five topics: 1. Risk factors, biomarkers and plaque instability: In atherothrombosis research, more focus on the contribution of specific risk factors like ectopic fat needs to be considered; definitions of atherothrombosis are important distinguishing different phases of disease, including plaque (in)stability; proteomic and metabolomics data are to be added to genetic information. 2. Circulating cells including platelets and atherothrombosis: Mechanisms of leukocyte and macrophage plasticity, migration, and transformation in murine atherosclerosis need to be considered; disease mechanism-based biomarkers need to be identified; experimental systems are needed that incorporate whole-blood flow to understand how red blood cells influence thrombus formation and stability; knowledge on platelet heterogeneity and priming conditions needs to be translated toward the in vivo situation. 3. Coagulation proteases, fibrin(ogen) and thrombus formation: The role of factor (F) XI in thrombosis including the lower margins of this factor related to safe and effective antithrombotic therapy needs to be established; FXI is a key regulator in linking platelets, thrombin generation, and inflammatory mechanisms in a renin-angiotensin dependent manner; however, the impact on thrombin-dependent PAR signaling needs further study; the fundamental mechanisms in FXIII biology and biochemistry and its impact on thrombus biophysical characteristics need to be explored; the interactions of red cells and fibrin formation and its consequences for thrombus formation and lysis need to be addressed. Platelet-fibrin interactions are pivotal determinants of clot formation and stability with potential therapeutic consequences. 4. Preventive and acute treatment of atherothrombosis and arterial embolism; novel ways and tailoring? The role of protease-activated receptor (PAR)-4 vis à vis PAR-1 as target for antithrombotic therapy merits study; ongoing trials on platelet function test-based antiplatelet therapy adjustment support development of practically feasible tests; risk scores for patients with atrial fibrillation need refinement, taking new biomarkers including coagulation into account; risk scores that consider organ system differences in bleeding may have added value; all forms of oral anticoagulant treatment require better organization, including education and emergency access; laboratory testing still needs rapidly available sensitive tests with short turnaround time. 5. Pleiotropy of coagulation proteases, thrombus resolution and ischaemia-reperfusion: Biobanks specifically for thrombus storage and analysis are needed; further studies on novel modified activated protein C-based agents are required including its cytoprotective properties; new avenues for optimizing treatment of patients with ischaemic stroke are needed, also including novel agents that modify fibrinolytic activity (aimed at plasminogen activator inhibitor-1 and thrombin activatable fibrinolysis inhibitor.

Tissue factor pathways linking obesity and inflammation

Obesity is a major cause for a spectrum of metabolic syndrome-related diseases that include insulin resistance, type 2 diabetes, and steatosis of the liver. Inflammation elicited by macrophages and other immune cells contributes to the metabolic abnormalities in obesity. In addition, coagulation activation following tissue factor (TF) upregulation in adipose tissue is frequently found in obese patients and particularly associated with diabetic complications. Genetic and pharmacological evidence indicates that TF makes significant contributions to the development of the metabolic syndrome by signaling through G protein-coupled protease activated receptors (PARs). Adipocyte TF-PAR2 signaling contributes to diet-induced obesity by decreasing metabolism and energy expenditure, whereas hematopoietic TF-PAR2 signaling is a major cause for adipose tissue inflammation, hepatic steatosis and inflammation, as well as insulin resistance. In the liver of mice on a high fat diet, PAR2 signaling increases transcripts of key regulators of gluconeogenesis, lipogenesis and inflammatory cytokines. Increased markers of hepatic gluconeogenesis correlate with decreased activation of AMP-activated protein kinase (AMPK), a known regulator of these pathways and a target for PAR2 signaling. Clinical markers of a TF-induced prothrombotic state may thus indicate a risk in obese patient for developing complications of the metabolic syndrome.

The tick-derived inhibitor Ixolaris prevents tissue factor signaling on tumor cells

BACKGROUND

Tissue factor (TF) is frequently overexpressed in cancer cells and correlated with more aggressive tumor phenotypes and poor prognosis. In addition to promoting coagulation-dependent metastasis and cancer-associated thrombosis, tumor cell-expressed TF mediates direct cell signaling involving the protease-activated receptor (PAR) 2. Ixolaris is a tick-derived inhibitor of the TF-factor (F)VIIa-Xa coagulation initiation complex which blocks primary tumor growth and angiogenesis in glioblastoma and melanoma models.

METHODS

In this study we address the anti-tumor effects of Ixolaris in TF-VIIa-PAR2 signaling-dependent breast cancer models, a xenograft model of highly aggressive human MDA-MB-231 mfp cells and a syngeneic model of PAR2-deficient and replete PyMT mouse mammary carcinoma cells.

RESULTS

Ixolaris potently inhibited the procoagulant activity of human MDA-MB-231mfp or murine PyMT breast cancer cells. Ixolaris blocked signaling by the ternary TF-FVIIa-FXa complex, and, surprisingly, at higher concentrations also the binary TF-FVIIa complex on MDA-MB-231 cells. We show that Ixolaris interacts with certain residues in the human VIIa protease domain that are involved in PAR2 cleavage. In contrast to human VIIa, Ixolaris was a poor inhibitor of murine TF-FVIIa signaling and did not attenuate PAR2-dependent tumor growth in a syngeneic mouse model of breast cancer progression.

CONCLUSION

These data show that Ixolaris inhibits PAR2 cleavage specifically by human TF signaling complexes and suggest that Ixolaris may block tumor growth of human cell models with ectopic FVIIa expression through inhibition of direct TF-FVIIa-PAR2 signaling as well as its anticoagulant activity.

Splice variants of tissue factor promote monocyte-endothelial interactions by triggering the expression of cell adhesion molecules via integrin-mediated signaling

BACKGROUND

TF is highly expressed in cancerous and atherosclerotic lesions. Monocyte recruitment is a hallmark of disease progression in these pathological states.

OBJECTIVE

To examine the role of integrin signaling in TF-dependent recruitment of monocytes by endothelial cells.

METHODS

The expression of flTF and asTF in cervical cancer and atherosclerotic lesions was examined. Biologic effects of the exposure of primary microvascular endothelial cells (MVEC) to truncated flTF ectodomain (LZ-TF) and recombinant asTF were assessed.

RESULTS

flTF and asTF exhibited nearly identical expression patterns in cancer lesions and lipid-rich plaques. Tumor lesions, as well as stromal CD68(+)  monocytes/macrophages, expressed both TF forms. Primary MVEC rapidly adhered to asTF and LZ-TF, and this was completely blocked by anti-β1 integrin antibody. asTF- and LZ-TF-treatment of MVEC promoted adhesion of peripheral blood mononuclear cells (PBMCs) under orbital shear conditions and under laminar flow; asTF-elicited adhesion was more pronounced than that elicited by LZ-TF. Expression profiling and western blotting revealed a broad activation of cell adhesion molecules (CAMs) in MVEC following asTF treatment including E-selectin, ICAM-1 and VCAM-1. In transwell assays, asTF potentiated PMBC migration through MVEC monolayers by ∼3-fold under MCP-1 gradient.

CONCLUSIONS

TF splice variants ligate β1 integrins on MVEC, which induces the expression of CAMs in MVEC and leads to monocyte adhesion and transendothelial migration. asTF appears more potent than flTF in eliciting these effects. Our findings underscore the pathophysiologic significance of non-proteolytic, integrin-mediated signaling by the two naturally occurring TF variants in cancer and atherosclerosis.

Tissue factor and cell signalling in cancer progression and thrombosis

The close link between coagulation activation and clinical cancer is well established and recent progress has defined underlying molecular pathways by which tumour cells interact with the haemostatic system to promote cancer progression. Tumour type-specific oncogenic transformations cause constitutive and hypoxia-dependent upregulation of tissue factor (TF) in cancer cells, but TF expressed by vascular, stromal and inflammatory cells also contributes to the procoagulant character of the tumour microenvironment. A growing body of genetic and pharmacological evidence implicates signalling by protease activated receptors (PARs) and specifically by tumour cell-expressed TF-VIIa-PAR2 in the induction of an array of proangiogenic and immune modulating cytokines, chemokines and growth factors. Specific inhibition of this pathway results in attenuated tumour growth and angiogenesis. PARs are increasingly recognised as targets for proteases outside the coagulation system and emerging evidence indicates that alternative protease signalling pathways synergise with the coagulation system to promote tumour growth, angiogenesis and metastasis. The elucidation of new therapeutic targets in tumour-promoting protease signalling pathways requires new diagnostic approaches to identify patients that will benefit from tailored therapy targeting procoagulant or signalling aspects of the TF pathway.

Vascular and dendritic cell coagulation signaling in sepsis progression

The intrinsic signaling networks of the coagulation pathways have recently emerged as crucial determinants for survival in sepsis and systemic inflammatory response syndromes. Protease activated receptor (PAR) 1 is central to both lethality promoting and vascular protective signaling. In the vascular anticoagulant pathway, EPCR/aPC-PAR1 signaling prevents vascular leakage and genetic or acute deficiencies in this pathway promote lethality. In addition, coagulation signaling acts directly on cells of the innate immune system. Dendritic cell (DC) thrombin-PAR1 signaling is coupled to the migration promoting sphingosine 1 phosphate receptor 3 (S1P3). Thrombin generated in the lymphatic compartment perturbs DCs to promote systemic inflammation and disseminated intravascular coagulation in severe sepsis. Signaling-selective aPC variants and selective modulators of the S1P receptor system attenuate sepsis lethality, suggesting novel therapeutic approaches that can be employed to rebalance alterations in the coagulation signaling pathways in severe inflammatory disorders.

TF:FVIIa-specific activation of CREB upregulates proapoptotic proteins via protease-activated receptor-2

BACKGROUND

Tissue factor (TF) and factor (F) VIIa are the primary initiators of the coagulation cascade, but also promote non-hemostatic events, such as angiogenesis and tumor growth, via activation of protease activated receptor-2 (PAR2). Our previous findings indicated that the TF:FVIIa complex activates signal transducer and activator of transcription (STAT) signaling, leading to cell survival in TF-transfected baby hamster kidney (BHK) cells.

METHODS

Using BHK TF, keratinocytes (HaCaT) and human umbilical vein endothelial cells (HUVEC), FVIIa-induced phosphorylation and activation of the transcription factor cyclic AMP-responsive binding protein (CREB) were tested and compared to that elicited by thrombin and FXa. In addition, the effect of these factors on cell survival and expression of apoptosis-associated proteins was monitored.

RESULTS

Factor VIIa led to a TF-dependent, but TF cytoplasmic domain-independent phosphorylation and activation of CREB in BHK TF, HaCaT and HUVEC. CREB activation was sensitive to blockade of the extracellular-signal regulated kinase 1/2 pathway and PAR2. Surprisingly, FVIIa decreased cell survival in HaCaT cells but not other cell types and upregulated the pro-apoptotic proteins Bak and Puma in a CREB-dependent manner. Factor Xa, but not FIIa, induced phosphorylation of CREB, but did not have an effect on apoptosis.

CONCLUSION

TF:FVIIa induces CREB phosphorylation and activation in several cell types, but TF:FVIIa induces pro-apoptotic proteins and apoptosis only in selected cell types.

Allosteric regulation of the cofactor-dependent serine protease coagulation factor VIIa

The integration of structure and function analysis of the tissue factor-factor VIIa complex has provided a detailed view of the functional surface of the extrinsic activation complex. An incomplete zymogen to enzyme transition is responsible for the strict cofactor dependence of catalytic function of factor VIIa. The mutational analysis demonstrates that factor VIIa is allosterically regulated by specific conformational linkages that involve the cofactor binding site, the catalytic cleft, and the macromolecular substrate exosite. Regions of the flexible activation domain appear to play an important role in the allosteric regulation of this cofactor-dependent coagulation serine protease.

Specificity of coagulation factor signaling

Coagulation serine proteases signal through protease-activated receptors (PARs). Thrombin-dependent PAR signaling on platelets is essential for the hemostatic response and vascular thrombosis, but regulation of inflammation by PAR signaling is now recognized as an important aspect of the pro- and anti-coagulant pathways. In tissue factor (TF)-dependent initiation of coagulation, factor (F) Xa is the PAR-1 or PAR-2-activating protease when associated with the transient TF-FVIIa-FXa complex. In the anticoagulant protein C (PC) pathway, the thrombin-thrombomodulin complex activates PC bound to the endothelial cell PC receptor (EPCR), which functions as a required coreceptor for activated PC-mediated signaling through endothelial cell PAR-1. Thus, the pro- and anti-inflammatory receptor cascades are mechanistically coupled to immediate cell signaling, which precedes systemic coagulant or anticoagulant effects. In contrast to the substrate-like recognition of PARs by thrombin, TF- or EPCR-targeted activation of PARs generates cell-type specificity, PAR selectivity and protease receptor cosignaling with the G-protein-coupled PAR response. Protease receptors are thus major determinants of the biological outcome of coagulation factor signaling on vascular cells.

Molecular regulation of blood clotting in tumor biology

TF expression is a hallmark of cancer progression. The procoagulant functions of TF that lead to thrombin generation are critically important to support metastasis, in part through the generation of fibrin that assures prolonged arrest of tumor cells in target organs. In addition, the coagulation initiation complex, i.e. TF-VIIa-Xa, generates autocrine cell signaling though protease activated receptors. A cooperation of the TF cytoplasmic domain with protease signaling may explain the diverse contributions of TF to metastasis and angiogenesis.

Sulfur isotope effects associated with oxidation of sulfide by O2 in aqueous solution

Normal sulfur isotope effects averaging epsilon = -5.2 +/- 1.4% (s.d.) were consistently observed for the oxidation of sulfide in aqueous solution. Reaction products were sulfate, thiosulfate and sulfite at pH 10.8-11 in distilled water; S0 was formed in two experiments with synthetic seawater at pH 8-9.5. Because the -5.2% normal isotope effect differs significantly from the previously measured +2% inverse effect associated with anaerobic oxidation of sulfide by photosynthetic bacteria, stable sulfur isotopic measurements are potentially useful for distinguishing aerobic vs. anaerobic sulfide oxidation in marine and freshwater sulfureta.

Mechanistic coupling of protease signaling and initiation of coagulation by tissue factor

The crucial role of cell signaling in hemostasis is clearly established by the action of the downstream coagulation protease thrombin that cleaves platelet-expressed G-protein-coupled protease activated receptors (PARs). Certain PARs are cleaved by the upstream coagulation proteases factor Xa (Xa) and the tissue factor (TF)--factor VIIa (VIIa) complex, but these enzymes are required at high nonphysiological concentrations and show limited recognition specificity for the scissile bond of target PARs. However, defining a physiological mechanism of PAR activation by upstream proteases is highly relevant because of the potent anti-inflammatory in vivo effects of inhibitors of the TF initiation complex. Activation of substrate factor X (X) by the TF--VIIa complex is here shown to produce enhanced cell signaling in comparison to the TF--VIIa complex alone, free Xa, or Xa that is generated in situ by the intrinsic activation complex. Macromolecular assembly of X into a ternary complex of TF--VIIa--X is required for proteolytic conversion to Xa, and product Xa remains transiently associated in a TF--VIIa--Xa complex. By trapping this complex with a unique inhibitor that preserves Xa activity, we directly show that Xa in this ternary complex efficiently activates PAR-1 and -2. These experiments support the concept that proinflammatory upstream coagulation protease signaling is mechanistically coupled and thus an integrated part of the TF--VIIa-initiated coagulation pathway, rather than a late event during excessive activation of coagulation and systemic generation of proteolytic activity.

Gene induction by coagulation factor Xa is mediated by activation of protease-activated receptor 1

Cell signaling by coagulation factor Xa (Xa) contributes to pro-inflammatory responses in vivo. This study characterizes the signaling mechanism of Xa in a HeLa cell line that expresses protease-activated receptor 1 (PAR-1) but not PAR-2, -3, or -4. Xa induced NF-kappaB in HeLa cells efficiently but with delayed kinetics compared to thrombin. This delay caused no difference in gene expression patterns, as determined by high-density microarray analysis. Both proteases prominently induced the angiogenesis-promoting gene Cyr61 and connective tissue growth factor. Inhibition of PAR-1 cleavage abolished MAP kinase phosphorylation and gene induction by Xa, demonstrating that Xa signals through PAR-1 and not through a novel member of the PAR family. Activation of cell surface prothrombin with the snake venom enzyme Ecarin also produced PAR-1-dependent signaling. However, though the response to Ecarin was completely blocked by the thrombin inhibitor hirudin, the response to Xa was not. This suggests that the Xa response is not mediated by locally generated thrombin. The concentration dependence of Xa for PAR-1 activation is consistent with previously characterized Xa-mediated PAR-2 signaling, suggesting that local concentration of Xa on the cell surface, rather than sequence-specific recognition of the PAR scissile bond, determines receptor cleavage. This study demonstrates that PAR-1 cleavage by Xa can elicit the same cellular response as thrombin, but mechanistic differences in receptor recognition may be crucial for specific roles for Xa in signaling during spatial or temporal separation from thrombin generation.

Role of zymogen and activated factor X as scaffolds for the inhibition of the blood coagulation factor VIIa-tissue factor complex by recombinant nematode anticoagulant protein c2

Recombinant nematode anticoagulant protein c2 (rNAPc2) is a potent, factor Xa (fXa)-dependent small protein inhibitor of factor VIIa-tissue factor (fVIIa.TF), which binds to a site on fXa that is distinct from the catalytic center (exo-site). In the present study, the role of other fX derivatives in presenting rNAPc2 to fVIIa.TF is investigated. Catalytically active and active site blocked fXa, as well as a plasma-derived and an activation-resistant mutant of zymogen fX bound to rNAPc2 with comparable affinities (K(D) = 1-10 nm), and similarly supported the inhibition of fVIIa.TF (K(i)* = approximately 10 pm). The roles of phospholipid membrane composition in the inhibition of fVIIa.TF by rNAPc2 were investigated using TF that was either detergent-solubilized (TF(S)), or reconstituted into membranes, containing phosphatidylcholine (TF(PC)) or a mixture of phosphatidylcholine and phosphatidylserine (TF(PCPS)). In the absence of the fX derivative, inhibition of fVIIa.TF was similar for all three conditions (K(i) approximately 1 microm), whereas the addition of the fX derivative increased the respective inhibition by 35-, 150-, or 100,000-fold for TF(S), TF(PC), and TF(PCPS). The removal of the gamma-carboxyglutamic acid-containing domain from the fX derivative did not affect the binding to rNAPc2, but abolished the effect of factor Xa as a scaffold for the inhibition of fVIIa.TF by rNAPc2. The overall anticoagulant potency of rNAPc2, therefore, results from a coordinated recognition of an exo-site on fX/fXa and of the active site of fVIIa, both of which are properly positioned in the ternary fVIIa.TF.fX(a) complex assembled on an appropriate phospholipid surface.

Residue Met(156) contributes to the labile enzyme conformation of coagulation factor VIIa

Serine protease activation is typically controlled by proteolytic cleavage of the scissile bond, resulting in spontaneous formation of the activating Ile(16)-Asp(194) salt bridge. The initiating coagulation protease factor VIIa (VIIa) differs by remaining in a zymogen-like conformation that confers the control of catalytic activity to the obligatory cofactor and receptor tissue factor (TF). This study demonstrates that the unusual hydrophobic Met(156) residue contributes to the propensity of the VIIa protease domain to remain in a zymogen-like conformation. Mutation of Met(156) to Gln, which is found in the same position of the highly homologous factor IX, had no influence on the amidolytic and proteolytic activity of TF-bound VIIa. Furthermore, the mutation did not appreciably stabilize the labile Ile(16)-Asp(194) salt bridge in the absence of cofactor. VIIa(Gln156) had increased affinity for TF, consistent with a long range conformational effect that stabilized the cofactor binding site in the VIIa protease domain. Notably, in the absence of cofactor, amidolytic and proteolytic function of VIIa(Gln156) were enhanced 3- and 9-fold, respectively, compared with wild-type VIIa. The mutation thus selectively influenced the catalytic activity of free VIIa, identifying the Met(156) residue position as a determinant for the zymogen-like properties of free VIIa.

The role of catalytic cleft and exosite residues of factor VIIa for complex formation with tissue factor pathway inhibitor

The extrinsic coagulation pathway is initiated by the binding of plasma factor VIIa (VIIa) to the cell surface receptor tissue factor (TF). Formation of the TF-VIIa complex results in allosteric activation of VIIa as well as the creation of an extended macromolecular substrate binding exosite that greatly enhances proteolytic activation of substrate factor X. The catalytic function of the TF-VIIa complex is regulated by a specific Kunitz-type inhibitor, tissue factor pathway inhibitor (TFPI). TFPI inhibition of the TF-VIIa complex was enhanced by the presence of Xa. This study investigates the relative contribution of catalytic cleft and exosite residues in VIIa for inhibitory complex formation with TFPI. VIIa protease domain residues Q176, T239 and E296 are involved in the formation of stable inhibitor complex with free TFPI. Kinetic analysis further demonstrated a predominant role of the S2' subsite residue Q176 for the initial complex formation with TFPI. In contrast, no significant reductions in inhibition by TFPI-Xa were found for each of the mutants in complex with phospholipid reconstituted TF. However, reduced rates of inhibition of the VIIa Gla-domain (R36) and Q176 mutant by TFPI-Xa were evident when TF was solubilized by detergent micelles. These data demonstrate docking of the TFPI-Xa complex with the macromolecular substrate exosite and the catalytic cleft, in particular the S2' subsite. The masking of the mutational effect by the presence of phospholipid shows a critical importance of Xa Gla-domain interactions in stabilizing the quaternary TF-VIIa-Xa-TFPI complex.

Role of residue Phe225 in the cofactor-mediated, allosteric regulation of the serine protease coagulation factor VIIa

Functional regulation by cofactors is fundamentally important for the highly ordered, consecutive activation of the coagulation cascade. The initiating protease of the coagulation system, factor VIIa (VIIa), retains zymogen-like features after proteolytic cleavage of the activating Arg(15)-Ile(16) peptide bond and requires the binding of the cofactor tissue factor (TF) to stabilize the protease domain in an active enzyme conformation. Structural comparison of TF-bound and free VIIa failed to provide a conclusive mechanism for this catalytic activation. This study provides novel insight into the cofactor-dependent regulation of VIIa by demonstrating that the side chain of Phe(225), an aromatic residue that is common to allosterically regulated serine proteases, is necessary for optimal TF-mediated activation of VIIa's catalytic function. However, mutation of Phe(225) did not abolish the cofactor-induced stabilization of the Ile(16)-Asp(194) salt bridge, previously considered the primary switch mechanism for activating VIIa. Moreover, mutation of other residue side chains in the VIIa protease domain resulted in a reduced level of or no stabilization of the amino-terminal insertion site upon TF binding, with little or no effect on the TF-mediated enhancement of catalysis. This study thus establishes a crucial role for the aromatic Phe(225) residue position in the allosteric network that transmits the activating switch from the cofactor interface to the catalytic cleft, providing insight into the highly specific conformational linkages that regulate serine protease function.

Diverse functions of protease receptor tissue factor in inflammation and metastasis

Accumulating evidence suggests that protease receptors and their cognate protease ligands play important roles in cell-signaling events that regulate cell adhesion and migration in inflammation as well as tumor invasion and metastasis. Tissue factor (TF), the cell surface receptor for the serine protease VIIa and the initiator of the coagulation pathways, supports metastatic implantation by activating extracellular, protease-dependent signaling pathways and by intracellular links to the actin cytoskeleton. The adhesion of TF-expressing tumor cells can be mediated by interactions of the receptor-protease complex with specific matrix-associated inhibitors, suggesting a novel bridging mechanism by which proteases participate in migratory functions of cells.

Novel drugs for neuropathic pain

Neuropathic pain is often inadequately controlled by conventional analgesics. Because the aetiology of neuropathic pain is only partially understood, specific treatment approaches have not been defined. A variety of pharmacological treatments have been proposed. However, for only a small minority of drugs used in neuropathic pain has the scientific evidence been evaluated in a satisfactory manner. The present review of the recent literature reveals the potential of certain novel drugs in treatment of neuropathic pain.

Dimerization of tissue factor supports solution-phase autoactivation of factor VII without influencing proteolytic activation of factor X

Tissue factor (TF) is a transmembrane receptor that initiates the thrombogenic cascade by assembly with the serine protease factor VII or VIIa (VII/VIIa) resulting in formation of the bimolecular active complex TF.VIIa. Chemical cross-linking studies identified that a minor population of TF forms dimers on the surface of cells, possibly influencing TF.VIIa proteolytic function as a result of dimerization. We here investigate the effects of dimerization of the extracellular domain of TF on the proteolytic function of the TF. VIIa complex. The leucine zipper dimerization domain of the yeast transcriptional factor GCN4 (LZ) was genetically fused at the C-terminus of the extracellular domain of TF separated by a short linker (TF(L)LZ). TF(L)LZ homodimerized with a K(d) similar to that of the LZ peptide. Tryptophan fluorescence indicated that the two TF moieties were in close proximity and parallel orientation in TF(L)LZ. TF(L)LZ dimers bound two molecules of VIIa, and VIIa binding did not influence the TF dimer equilibrium. Dimerization influenced neither amidolytic nor the factor X activation activities of the TF. VIIa complexes. Notably, dimer TF(L)LZ efficiently promoted the autoactivation of VII to VIIa in solution in contrast to monomeric TF(L)LZ or TF(1)(-)(218). Thus, TF dimerization on cells may serve to "prime" the initiation of the coagulation pathway by generating active TF.VIIa complexes for the subsequent activation of downstream macromolecular substrates.

Exosite interactions determine the affinity of factor X for the extrinsic Xase complex

The initiation of coagulation results from the activation of factor X by an enzyme complex (Xase) composed of the trypsin-like serine proteinase, factor VIIa, bound to tissue factor (TF) on phospholipid membranes. We have investigated the basis for the protein substrate specificity of Xase using TF reconstituted into vesicles of phosphatidylcholine, phosphatidylserine, or pure phosphatidylcholine. We show that occupation of the active site of VIIa within Xase by a reversible inhibitor or an alternate peptidyl substrate is sufficient to exclude substrate interactions at the active site but does not alter the affinity of Xase for factor X. This is evident as classical competitive inhibition of peptidyl substrate cleavage but as classical noncompetitive inhibition of factor X activation by active site-directed ligands. This implies that the productive recognition of factor X by Xase arises from a multistep reaction requiring an initial interaction at sites on the enzyme complex distinct from the active site (exosites), followed by active site interactions and bond cleavage. Exosite interactions determine protein substrate affinity, whereas the second binding step influences the maximum catalytic rate for the reaction. We also show that competitive inhibition can be achieved by interfering with exosite binding using factor X derivatives that are expected to have limited or abrogated interactions with the active site of VIIa within Xase. Thus, substrate interactions at exosites, sites removed from the active site of VIIa within the enzyme complex, determine affinity and binding specificity in the productive recognition of factor X by the VIIa-TF complex. This may represent a prevalent strategy through which distinctive protein substrate specificities are achieved by the homologous enzymes of coagulation.

Reversible regulation of tissue factor-induced coagulation by glycosyl phosphatidylinositol-anchored tissue factor pathway inhibitor

Endothelial and tumor cells synthesize tissue factor pathway inhibitor (TFPI-1), which regulates tissue factor (TF) function by TF. VIIa. Xa. TFPI-1 quaternary complex formation (where VIIa and Xa are coagulation factors) and by translocation of these complexes into glycosphingolipid-rich microdomains of the cell membrane. Recombinant TFPI-1 added exogenously to cells is targeted to a degradation pathway. This study analyzes whether quaternary complex formation with endogenous TFPI-1 results also in internalization and degradation. We demonstrate that endogenous TFPI-1 and recombinant TFPI-1 differ in their distribution on the cell surface. Recombinant TFPI-1 is found in phospholipid- and glycosphingolipid-rich membrane domains, whereas endogenous TFPI-1 preferentially localizes to glycosphingolipid-rich microdomains. On quaternary complex formation, endogenous TFPI-1 remains protease sensitive and accessible for antibodies on intact cells, demonstrating that it is not appreciably internalized. Rather, regulation of TF by TFPI-1 is restored within 12 hours, consistent with dissociation of quaternary complexes on the cell surface. Endogenous TFPI-1 can be released from the cell surface by phospholipase treatment, indicating that TFPI-1 either is a glycosyl phosphatidylinositol (GPI)-anchored protein or binds to a GPI-linked receptor. We demonstrate that expression of a recombinant GPI-anchored form of TFPI-1 targets TF. VIIa complexes to glycosphingolipid-rich membrane fractions. Thus, GPI anchoring of TFPI-1 is sufficient for regulation of TF. VIIa complex function by a pathway of reversible inhibition rather than internalization and degradation.

Tumor cell adhesion and migration supported by interaction of a receptor-protease complex with its inhibitor

Tissue factor (TF), the cell-surface receptor for coagulation factor VIIa, supports metastasis. Equally important for this process are (a) interactions of the TF cytoplasmic domain, which binds the mobility-enhancing actin-binding protein 280, and (b) the formation of a proteolytically active TF-VIIa complex on the tumor cell surface. In primary bladder carcinoma cells, we find that this complex localizes to the invasive edge, in proximity to tumor-infiltrating vessels that stain intensely for TF pathway inhibitor (TFPI-1), the major inhibitor of the protease activity of the complex. In culture, binding of VIIa to TF-expressing tumor cells is sufficient to allow cell adhesion, migration, and intracellular signaling on immobilized TFPI-1. Immobilized heparin, a mimic for extracellular matrix-associated proteoglycans, binds physiological concentrations of TFPI-1 in a conformation that supports TF-VIIa-dependent cell adhesion. Consistent with a functional role of TFPI-1 in complex extracellular matrices, we show that TF cooperates with integrin-mediated adhesion and migration on composite matrices that contain ligands for both integrins and the TF-VIIa complex. This study thus provides evidence for a novel mechanism of protease-supported migration that is independent of proteolytic matrix degradation but rather involves protease-dependent bridging of TF's extracellular domain to an ECM-associated inhibitor.

Engineered recombinant factor VII Q217 variants with altered inhibitor specificities

Recombinant factor VII with residue 217 (chymotrypsinogen numbering system) converted to alanine (VIIQ217A), glutamic acid (VIIQ217E), or glycine (VIIQ217G) was characterized. In a prothrombin time assay, VIIQ217E demonstrated 100%, VIIQ217A 15%, and VIIQ217G <1% clotting activities relative to wild-type VII. Binding of VIIQ217A and VIIQ217G to TF was comparable to that of wild-type VII to TF. All the variants were readily activated by factor Xa. Autoactivation in the presence of TF was efficient with VIIQ217E, slow with VIIQ217A, but undetected with VIIQ217G. Relative to wild-type VII added at the same concentration, VIIQ217E had no effect on the PT of normal plasma, whereas VIIQ217A slightly and VIIQ217G dramatically prolonged the clotting time in a dose-dependent manner. Activation of macromolecular substrates paralleled this functional inhibition. The k(cat)/K(M) values for factor X activation in the presence of TF were 2.4 for VIIaQ217E as compared to 1.9 (M(-)(1) s(-)(1) x 10(7)) for wild-type VIIa, 1.57 for VIIaQ217A, and 0.05 with VIIaQ217G. In comparison to wild-type VIIa, VIIaQ217E cleaved the chromogenic substrate S2765 (Z-D-Arg-Gly-Arg-pNA) with 10-fold higher k(cat). Analysis of the interactions with the inhibitors TFPI and antithrombin III demonstrated that VIIaQ217A but not VIIaQ217E or VIIaQ217G was inhibited less efficiently by TFPI either in the presence or in the absence of factor Xa. In contrast, VIIaQ217A association with antithrombin III in the presence of heparin was the fastest among the variants with a second-order rate constant of 2.31 (x10(3) M(-)(1) min(-)(1)), as compared to 0.47 and 1.47 for VIIaQ217E and wild-type VIIa, respectively. Our results demonstrate that residue Q(217) is important in regulating substrate and, more importantly, inhibitor recognition by VIIa.