Structural and genomic analysis of single nucleotide polymorphisms in human host factor endothelial protein C receptor (EPCR) reveals complex interplay with malaria parasites

Plasmodium parasites responsible for malaria follow a complex life cycle of which half takes place inside the human host. Parasites present diverse antigens at different stages of their life cycle and interact with many surface molecules to attach to and enter host cells. The CIDRα1 domain of Plasmodium falciparum Erythrocyte Membrane Protein 1 (PfEMP1) in infected erythrocytes adheres to one such vascular receptor endothelial protein C receptor (EPCR). EPCR is implicated in the pathogenesis of severe malaria as preferential binding of CIDRα1 to endothelium results in widespread sequestration of infected erythrocytes leading to endothelium inflammation and severe disease. A single EPCR variant S219G is clinically reported to provide protection from severe malaria. In this work, we have collated all single nucleotide polymorphisms (SNPs) in EPCR from dbSNP. We structurally mapped the SNPs on the three-dimensional complex of EPCR and PfEMP1 CIDRα1. Analysis shows that most EPCR mutations lie on the receptor surface and are non-conservative. Of the 11 mutations in the CIDRα1-interaction region of EPCR, S88P, L96V/I, and R98L/H/P/C are seen with comparably higher occurrences in diverse populations. Our structural analysis details a framework of the interactions between the parasite ligand and host factor EPCR. These structural glimpses provide a blueprint for designing both field-based variant sequencing studies and vaccine development.

Co-culture of mesenchymal stem cell spheres with hematopoietic stem cells under hypoxia: a cost-effective method to maintain self-renewal and homing marker expression

BACKGROUND

Hematopoietic stem cell (HSC) transplantation is considered a possible treatment option capable of curing various diseases. The aim of this study was the co-culturing of mesenchymal stem cell (MSC) spheres with HSCs under hypoxic condition to enhance the proliferation, self-renewal, stemness, and homing capacities of HSCs.

METHODS AND RESULTS

HSCs were expanded after being subjected to different conditions including cytokines without feeder (Cyto), co-culturing with adherent MSCs (MSC), co-culturing with adherent MSCs + hypoxia (MSC + Hyp), co-culturing with MSCs spheres (Sph-MSC), co-culturing with MSCs spheres + hypoxia (Sph-MSC + Hyp), co-culturing with MSC spheres + cytokines (Sph-MSC + Cyto). After 10 days, total nucleated cell (TNC) and CD34⁺/CD38^- cell counts, colony-forming unit assay (CFU), long-term culture initiating cell (LTC-IC), the expression of endothelial protein C receptor (EPCR), nucleostemin (NS), nuclear factor I/X (Nfix) CXCR4, and VLA-4 were evaluated. The TNC, CD34⁺/CD38^- cell count, CFU, and LTC-IC were higher in the Sph-MSC + Hyp and Sph-MSC + Cyto groups as compared with those of the MSC + Hyp group (P < 0.001). The expanded HSCs co-cultured with MSC spheres in combination with hypoxia expressed more EPCR, CXCR4, VLA-4, NS, and Nfix mRNA. The protein expression was also more up-regulated in the Sph-MSC + Cyto and Sph-MSC + Hyp groups.

CONCLUSION

Co-culturing HSCs with MSC spheres under hypoxic condition not only leads to higher cellular yield but also increases the expression of self-renewal and homing genes. Therefore, we suggest this approach as a simple and non-expensive strategy that might improve the transplantation efficiency of HSCs.

Immunohistochemical study of dissociation and association of adherens junctions in splenic sinus endothelial cells

It is not yet clear whether cellular junctions between splenic sinus endothelial cells are open or closed. In order to clarify this, immunolocalization of thrombomodulin (TM), endothelial protein C receptor (EPCR), protease-activated receptor 1 (PAR1), sphingosine 1-phosphate receptor 1 (S1P₁), β-catenin phosphorylated at Try142 (β-catenin Y142) and β-catenin phosphorylated at Try654 (β-catenin Y654), which are related proteins that regulate dissociation and association of the adherens junctions of endothelial cells, are examined in rats using laser microscopy and electron microscopy. TM, EPCR, PAR1 and S1P₁ were colocalized in the entire circumference of the endothelial cells, as well as in the caveolar membranes and junctional membranes of adjacent endothelial cells. These molecules may protect the adherens junctions of the endothelial cells. On the other hand, β-catenin Y142 and β-catenin Y 654 colocalized with α-catenin and β-catenin, respectively and in addition, β-catenin Y142 and β-catenin Y 654 were localized in the vicinity of the adherens junctions of the endothelial cells from immunogold electron microcopy. The adherens junctions are considered to be partially dissociated at the site where β-catenin Y142 and β-catenin Y 654 are localized. Thus, the system that protects the adherens junctions and the system that dissociates them may concurrently coexist in the endothelial cells and dissociation and association of the adherens junctions may be constantly repeated at the cell boundary of the endothelial cells.

Platelet-derived calpain cleaves the endothelial protease-activated receptor 1 to induce vascular inflammation in diabetes

Diabetes mellitus is a major risk factor for cardiovascular disease. Platelets from diabetic patients are hyperreactive and release microparticles that carry activated cysteine proteases or calpains. Whether platelet-derived calpains contribute to the development of vascular complications in diabetes is unknown. Here we report that platelet-derived calpain1 (CAPN1) cleaves the protease-activated receptor 1 (PAR-1) on the surface of endothelial cells, which then initiates a signaling cascade that includes the activation of the tumor necrosis factor (TNF)-α converting enzyme (TACE). The latter elicits the shedding of the endothelial protein C receptor and the generation of TNF-α, which in turn, induces intracellular adhesion molecule (ICAM)-1 expression to promote monocyte adhesion. All of the effects of CAPN1 were mimicked by platelet-derived microparticles from diabetic patients or from wild-type mice but not from CAPN1^−/− mice, and were not observed in PAR-1-deficient endothelial cells. Importantly, aortae from diabetic mice expressed less PAR-1 but more ICAM-1 than non-diabetic mice, effects that were prevented by treating diabetic mice with a calpain inhibitor as well as by the platelet specific deletion of CAPN1. Thus, platelet-derived CAPN1 contributes to the initiation of the sterile vascular inflammation associated with diabetes via the cleavage of PAR-1 and the release of TNF-α from the endothelial cell surface.

Elevated levels of soluble Endothelial protein C receptor in rheumatoid arthritis and block the therapeutic effect of protein C in collagen-induced arthritis

BACKGROUND

Endothelial protein C receptor (EPCR) is a membranous protein that can be combined with a variety of ligands and plays important roles in anticoagulant and anti-inflammation. Recent reports have shown that surface EPCR expression on T cells is negatively associated with Th17 differentiation and is co-expressed with other immunosuppressive molecules, such as The programmed cell death 1 (PD-1) and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4). Hence, we hypothesized that EPCR may play a critical role in rheumatoid arthritis (RA) disease progression that is mediated by Th17 differentiation. In order to explore the role of EPCR on RA disease pathogenesis, we detected membranous EPCR (mEPCR) expression in CD4⁺ T cells and soluble EPCR (sEPCR) expression in the sera of RA patients.

METHODS

The proportion of CD4⁺/EPCR⁺ T cells in the peripheral blood of RA patients was detected by flow cytometry, and the expression of sEPCR in the sera of RA patients was detected by enzyme-linked immunosorbent assay (ELISA). For in vitro experiments, protein C (PC) and EPCR recombinant proteins were used to block peripheral blood mononuclear cell (PBMC) activation and to detect Th17 differentiation. For in vivo experiments in DBA/1 mice with collagen-induced arthritis (CIA), we administered PC and EPCR recombinant proteins, monitored disease progression, and evaluated the role of EPCR in disease progression.

RESULTS

The proportion of CD4⁺/EPCR⁺ T cells in the peripheral blood of RA patients was lower than that of osteoarthritis (OA) patients, while the expression level of sEPCR in the sera of RA patients was concomitantly higher than that in OA patients. Subsequent analysis revealed that sEPCR expression was positively correlated with rheumatoid factors (RF) and other inflammatory indicators in RA patients. Further studies confirmed that sEPCR administration alleviated the progression of collagen-induced arthritis and partially blocked the therapeutic effect of PC in CIA mice.

CONCLUSION

Soluble EPCR is associated with RA disease progression and induces disease remission in CIA mice by inhibiting Th17 differentiation.

Urinary EPCR and dermcidin as potential novel biomarkers for severe adult OSA patients

BACKGROUND

Due to low predictive values of obstructive sleep apnea (OSA) screening tools, there is a need for biomarker for screening of OSA patients at an early stage. The aim of the study was to evaluate differentially expressed proteins in blood and urine samples of OSA patients.

METHODS

In this study, we used isobaric tagging for relative and absolute quantification (iTRAQ) based proteomics approach to identify differentially expressed proteins, which were subsequently verified and validated using enzyme-linked immunosorbent assay (ELISA) technique in adult OSA patients.

RESULTS

Seventeen differentially expressed proteins were selected from iTRAQ data for verification, based on their clinical significance and reproducibility among different iTRAQ experiment sets. Five of these proteins (plasma = 2; urine = 3) were further validated in plasma (non-OSA- = 42; OSA = 198) and urine samples (non-OSA = 46; OSA = 197). ROC curve analysis for all OSA vs. non-OSA subjects ensured optimal diagnostic utility of two urinary proteins: Endothelial protein c receptor (EPCR) (AUC = 73%, cut-off: 35 pg/ml) and dermcidin (AUC = 74%, cut-off: 4.6 pg/ml). For severe OSA, diagnostic accuracy significantly improved with AUC as 88% and 82% for EPCR (cut-off: 46 pg/ml) and dermcidin (cut-off: 5.2 pg/ml) respectively. Sensitivity and specificity of combined performance of both urinary proteins for severe OSA were 94% and 91% respectively.

CONCLUSION

In this study, urinary EPCR and dermcidin emerged as novel biomarkers for screening severe OSA patients.

Isolation of Human Skin Epidermal Stem Cells Based on the Expression of Endothelial Protein C Receptor

Skin epidermis is a continuous self-renewal tissue maintained by interfollicular epidermal stem cells (IESCs) that reside in the basal layer of epidermis. IESCs also contribute to the repair and regeneration of the epidermis during wound healing. The great plasticity and easy accessibility afforded by IESCs make them a promising source of stem cells for scientific research and clinical applications. Thus, simple methods to isolate and define pure and viable IESCs are a valuable resource. Here, we provide a method for isolating IESCs from human skin epidermis. This method relies exclusively on selecting cells with a higher expression of the endothelial protein C receptor, using fluorescence-activated cell sorting.

Activated protein C suppresses osteoclast differentiation via endothelial protein C receptor, protease-activated receptor-1, sphingosine 1-phosphate receptor, and apolipoprotein E receptor 2

INTRODUCTION

Bone remodeling relies on a delicate balance between formation and resorption of bone tissues, processes in which bone-forming osteoblasts and bone-resorbing osteoclasts play central roles. Recently, we reported that anticoagulant activated protein C (APC) promotes osteoblast proliferation, but the role of the blood coagulation system in bone remodeling remains unclear. In this study, to further elucidate the relationship between bone remodeling and blood coagulation, we investigated the effect of APC on osteoclast differentiation.

MATERIALS AND METHODS

Normal human osteoclast precursor cells were cultured in their growth medium including soluble RANKL, M-CSF, and FBS, and on days 4 and 7, the culture medium was replaced with the same medium containing various concentrations of APC, protein C (PC), sphingosine 1-phosphate (S1P) receptor agonist, FTY720, or APC+various substances without FBS. On day 8, TRAP-positive multinucleated cells (≥3 nuclei) were counted manually using a light microscope. The effects of APC on NF-κB and NFATc1 activation were evaluated using specific ELISA.

RESULTS

APC suppressed RANKL-induced osteoclast differentiation, and this APC-induced suppression of osteoclast differentiation was inhibited by zymogen protein C and aprotinin, a serine protease inhibitor. Immunohistochemistry and RT-PCR analyses suggested that endothelial protein C receptor (EPCR) and protease-activated receptor-1 (PAR-1) were expressed in osteoclast precursor cells and osteoclasts. Both anti-PAR-1 antibody and anti-EPCR antibody (RCR-252), which blocks APC binding to EPCR, inhibited the APC-induced suppression of osteoclast differentiation. FTY720 had no effect on osteoclast differentiation. However, FTY 720 and S1P receptor antagonist, VP 23019, inhibited the APC-induced suppression of osteoclast differentiation. On the other hand, recombinant soluble human ApoER2 and anti-human ApoER2 inhibited the APC-induced suppression of osteoclast differentiation. Further, APC had no effect on NF-κB and NFATc1 activation.

CONCLUSIONS

APC suppresses human osteoclast differentiation mainly by inhibiting the formation of multinucleated cells via EPCR, PAR-1, S1P receptor, and ApoER2 in a manner that depends on APC protease activity.

The Endothelial Protein C Receptor Is a Potential Stem Cell Marker for Epidermal Keratinocytes

Endothelial protein C receptor (EPCR) is a specific receptor for anticoagulant protein C and expressed by human epidermis and cultured keratinocytes. Here we investigated whether: (a) the level of EPCR in keratinocytes is associated with their growth potential; and (b) EPCR is a potential marker for human epidermal stem cells. Human keratinocytes isolated from foreskins or adult skin tissues were transfected with EPCR siRNA or EPCR overexpressing plasmids. Cell proliferation, long term proliferation potential, colony forming efficiency (CFE), and in vitro epidermal regeneration ability of EPCR^high and EPCR^l °^w cells were assessed. The expression and colocalization of EPCR with stem cell markers p63, integrin β1, and activation of MAP kinases were detected by flow cytometry, immunofluorescence staining, or Western blot. Results showed that EPCR was highly expressed by the basal layer of skin epidermis. EPCR^high cells were associated with the highest levels of p63 and integrin β1. Most EPCR^high cells were smaller in size, formed larger colonies and had a greater long term growth potential, CFE, holoclone formation, and in vitro epidermal regeneration ability when compared to EPCR^l °^w cells. Blocking EPCR resulted in keratinocyte apoptosis, particularly in nondifferentiated conditions. Cell proliferation and p63 expression were reduced by blocking EPCR and enhanced by overexpressing this receptor. These data indicate that EPCR can regulate p63, is associated with highly proliferative keratinocytes, and is a potential human epidermal stem cell marker. Stem Cells 2017;35:1786-1798.

Endothelial protein C receptor polymorphisms and risk of sepsis in a Chinese population

Objective

To examine the potential relationship of EPCR polymorphisms and the risk of sepsis in a Chinese population.

Methods

Snapshot SNP genotyping assays and DNA sequencing methods were used to detect polymorphisms of the EPCR gene, rs2069948C/T (2532C/T) and rs867186A/G (6936A/G), in 64 patients with sepsis and in 113 controls. Soluble EPCR (sEPCR) was measured by ELISA.

Results

There were significant differences in the allele and genotype frequencies of EPCR gene rs2069948C/T and allele frequencies of rs867186A/G between male and female patients and controls. Females carrying rs2069948 C/T genotype or T allele and males carrying rs867186 A allele were associated with a significantly increased risk of sepsis. Plasma sEPCR levels of sepsis patients were higher than controls and showed no correlation with EPCR gene polymorphisms.

Conclusions

EPCR polymorphisms may be associated with increased risk of sepsis, but this has no effect on the release of sEPCR in patients with sepsis.

Endothelial markers are associated with pancreatic necrosis and overall prognosis in acute pancreatitis: A preliminary cohort study

BACKGROUND

Endothelial injury is believed to play an important role in the evolution of pancreatic microcirculatory dysfunction and pancreatic necrosis (PN) in patients with acute pancreatitis (AP). The aim of this study was to investigate the role of three endothelial markers (von Willebrand factor, vWF; E-selectin; endothelial protein C receptor, EPCR) in the early phase of AP, especially the relationship between endothelial markers and PN.

METHODS

From March 2015 to March 2016, 57 AP patients admitted within 72 h of symptom onset in our hospital were included for this study. Blood samples were taken on admission and the clinical characteristics and outcomes of these patients were recorded. The levels of vWF, E-selectin and EPCR were measured using ELISA for analysis and compared with other severity markers of AP.

RESULTS

All the three markers were significantly different in healthy control, mild, moderate and severe AP patients. Moreover, the endothelial markers, especially vWF, also showed significant difference in patients with different extent of PN, as well as those with or without MODS. Additionally, the levels of endothelial markers correlated well with other commonly used markers of AP severity.

CONCLUSION

Elevated endothelium-related mediators (vWF, E-selectin and EPCR) appear to participate in the development of PN and may be a potential indicator of overall prognosis. Our results may help clinicians better understand the pathophysiological process of the development of PN.

Fondaparinux upregulates thrombomodulin and the endothelial protein C receptor during early-stage reperfusion in a rat model of myocardial infarction

INTRODUCTION

Fondaparinux (FDX) was demonstrated to be cardioprotective in a rat model of myocardial ischemia reperfusion. In this model, FDX reduced infarct size after 2h of reperfusion, involving the activation of the survivor activating factor enhancement (SAFE) pathway as early as 30min post-reperfusion. Our aim was to study if this cardioprotection could be explained by anti-inflammatory mechanisms and a protective effect on vessels.

METHODS

Wistar male rats were subjected to 40minutes (min) of myocardial ischemia, followed by 30min or 2h of reperfusion. Rats were randomized into four groups: control 30min (n=7), FDX 30min (n=7), control 2h (n=7), and FDX 2h (n=7). The FDX groups received 10mg/kg injection of FDX 10min prior to initiating reperfusion. We studied: 1) mRNA expression of endothelial markers, such as thrombomodulin (TM), endothelial protein C receptor (EPCR), and tissue factor (TF) and 2) proteic expression of ICAM-1, NF-κB, IκB, and JNK. Leukocyte infiltration was assessed by histochemistry. We also evaluated TM and EPCR mRNA expression in a model of isolated rat mesenteric arteries incubated with FDX.

RESULTS

FDX upregulated the expression of TM and EPCR mRNA in the models of myocardial infarction and isolated mesenteric arteries. No difference was observed between the treated and control groups regarding the expression of pro-inflammatory signaling proteins, adhesion molecules, and leukocyte infiltration after 2h of reperfusion.

CONCLUSION

The cardioprotective effect of FDX at early-stage reperfusion could be related to vascular protection, yet not to an anti-inflammatory effect.

Cell painting with an engineered EPCR to augment the protein C system

The protein C (PC) system conveys beneficial anticoagulant and cytoprotective effects in numerous in vivo disease models. The endothelial protein C receptor (EPCR) plays a central role in these pathways as cofactor for PC activation and by enhancing activated protein C (APC)-mediated protease-activated receptor (PAR) activation. During inflammatory disease, expression of EPCR on cell membranes is often diminished thereby limiting PC activation and APC's effects on cells. Here a caveolae-targeting glycosylphosphatidylinositol (GPI)-anchored EPCR (EPCR-GPI) was engineered to restore EPCR's bioavailability via "cell painting." The painting efficiency of EPCR-GPI on EPCR-depleted endothelial cells was time- and dose-dependent. The EPCR-GPI bioavailability after painting was long lasting since EPCR surface levels reached 400 % of wild-type cells after 2 hours and remained > 200 % for 24 hours. EPCR-GPI painting conveyed APC binding to EPCR-depleted endothelial cells where EPCR was lost due to shedding or shRNA. EPCR painting normalised PC activation on EPCR-depleted cells indicating that EPCR-GPI is functional active on painted cells. Caveolin-1 lipid rafts were enriched in EPCR after painting due to the GPI-anchor targeting caveolae. Accordingly, EPCR painting supported PAR1 and PAR3 cleavage by APC and augmented PAR1-dependent Akt phosphorylation by APC. Thus, EPCR-GPI painting achieved physiological relevant surface levels on endothelial cells, restored APC binding to EPCR-depleted cells, supported PC activation, and enhanced APC-mediated PAR cleavage and cytoprotective signalling. Therefore, EPCR-GPI provides a novel tool to restore the bioavailability and functionality of EPCR on EPCR- depleted and -deficient cells.

Progesterone attenuates thrombin-induced endothelial barrier disruption in the brain endothelial cell line bEnd.3: The role of tight junction proteins and the endothelial protein C receptor

This study examines the effects of progesterone on blood-brain barrier (BBB) integrity following thrombin administration. Thrombin is expressed in many diseases which affect neural tissue and is associated with breakdown of the BBB. Progesterone has shown protective effects on the BBB in stroke and traumatic brain injury.

METHODS

Mouse brain endothelial (bEnd.3) cells were treated with progesterone (20 μmol/l) for 24h before thrombin administration (60 U/ml). BBB permeability was measured by transendothelial electrical resistance (TEER), because TEER decrease is associated with BBB compromise. Tight junction (TJ) proteins (occludin, claudin-5, and zonula occludens-1) and endothelial protein C receptor (EPCR) were analyzed.

RESULTS

Thrombin decreased TEER and progesterone prevented that decrease. TJ proteins and EPCR were also decreased after thrombin treatment and progesterone treatment blocked that effect.

CONCLUSION

Progesterone can attenuate thrombin-induced BBB disruption by blocking the degradation of TJ proteins and EPCR in bEnd.3 cells.

MPTP/MPP+ suppresses activation of protein C in Parkinson's disease

Endothelial dysfunction and disruption of the blood-brain barrier have been found to be associated with Parkinson's disease (PD). However, the mechanisms underlying these effects have yet to be elucidated. It has also been found that activated protein C (APC) displays neuroprotective properties. Presently, the effects of APC on PD remain unknown. Using a 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) neurotoxin rodent model of PD, we found that administration of MPTP can reduce expression of endothelial protein C receptor (EPCR), an N-glycosylated type I membrane protein that has the ability to enhance protein C activation. However, the use of MPTP does not alter levels of thrombomodulin. These findings were verified in an in vitro study showing that 1-methyl-4-phenylpyridinium (MPP+) treatment leads to suppression of EPCR along with reduction of protein C activation in human primary endothelial cells. Importantly, our results display that activation of the transcriptional factor SP1 is involved in the inhibitory effects of MPTP/MPP+ on EPCR expression. We found that using 300 nM of the SP1 inhibitor MIT can abolish the effects of MPP+ on EPCR expression. Consistently, SP1 silencing using small RNA interference was able to prevent the inhibitory effects of MPTP/MPP+ on the reduction of EPCR expression and impairment of protein C activation. Importantly, our results indicate that overexpression of SP1 inhibits EPCR promoter activity. Our study suggests that EPCR-APC may be a potential therapeutic target for endothelial dysfunction in PD.

Activated protein C: A regulator of human skin epidermal keratinocyte function

Activated protein C (APC) is a physiological anticoagulant, derived from its precursor protein C (PC). Independent of its anticoagulation, APC possesses strong anti-inflammatory, anti-apoptotic and barrier protective properties which appear to be protective in a number of disorders including chronic wound healing. The epidermis is the outermost skin layer and provides the first line of defence against the external environment. Keratinocytes are the most predominant cells in the epidermis and play a critical role in maintaining epidermal barrier function. PC/APC and its receptor, endothelial protein C receptor (EPCR), once thought to be restricted to the endothelium, are abundantly expressed by skin epidermal keratinocytes. These cells respond to APC by upregulating proliferation, migration and matrix metalloproteinase-2 activity and inhibiting apoptosis/inflammation leading to a wound healing phenotype. APC also increases barrier function of keratinocyte monolayers by promoting the expression of tight junction proteins and re-distributing them to cell-cell contacts. These cytoprotective properties of APC are mediated through EPCR, protease-activated receptors, epidermal growth factor receptor or Tie2. Future preventive and therapeutic uses of APC in skin disorders associated with disruption of barrier function and inflammation look promising. This review will focus on APC’s function in skin epidermis/keratinocytes and its therapeutical potential in skin inflammatory conditions.

Activated protein C and its potential applications in prevention of islet β-cell damage and diabetes

Activated protein C (APC) is derived from its precursor, protein C (PC). Originally thought to be synthesized exclusively by the liver, recent reports have shown that PC is also produced by many other cells including pancreatic islet β cells. APC functions as a physiological anticoagulant with anti-inflammatory, anti-apoptotic, and barrier-stabilizing properties. APC exerts its protective effects via an intriguing mechanism requiring combinations of endothelial PC receptor, protease-activated receptors, epidermal growth factor receptor, Tie2 or CD11b, depending on cell types. Diabetes is a chronic condition resulted from the body's inability to produce and/or properly use insulin. The prevalence of diabetes has risen dramatically and has become one of the major causes of premature mortality and morbidity worldwide. Diabetes prevention is an ideal approach to reduce this burden. Type 1 and type 2 diabetes are the major forms of diabetes mellitus, and both are characterized by an autoimmune response, intraislet inflammation, β-cell apoptosis, and progressive β-cell loss. Protecting β-cell from damage is critical in both prevention and treatment of diabetes. Recent in vitro and animal studies show that APC's strong anti-inflammatory and anti-apoptotic properties are beneficial in preventing β-cell destruction and diabetes in the NOD mouse model of type 1 diabetes. Future preventive and therapeutic uses of APC in diabetes look very promising.

Enhanced effect of inhibition of thrombin on endothelium in murine endotoxaemia: specific inhibition of thrombocytopenia

INTRODUCTION

In systemic endotoxaemia, bacterial lipopolysaccharide causes the rapid expression of tissue factor (TF) and disseminated intravascular coagulation and in animal models, anticoagulants limit pathology and promote survival. Recent studies have emphasised the importance of TF expressed by mononuclear cells for initiating thrombin generation during endotoxaemia and suggested that endothelial cell TF is of little relevance. However, the precise importance of endothelium for intravascular thrombin generation has not been established. In this study, we compared the effect of equivalent levels of hirudin tethered to either endothelium or platelets and monocytes.

MATERIALS AND METHODS

CD31-Hir-Tg mice express a vesicle-targeted, membrane-tethered hirudin fusion protein on endothelium, platelets and monocytes. Bone marrow chimeras between these mice and C57BL/6 were generated The level of intravascular hirudin expressed during endotoxaemia was quantified by inhibition studies using an anti-hirudin antibody and reference to the circulating thrombin anti-thrombin complexes generated in control mice given soluble hirudin.

RESULTS AND CONCLUSIONS

Antibody inhibition studies indicated that individual chimeras expressed similar levels of hirudin fusion protein on endothelium alone as on platelets and leukocytes combined and accordingly, the levels of thrombin anti-thrombin complexes and fibrinogen in each chimera were similar, indicating equivalent inhibition of thrombin generation. However, mice with hirudin on endothelium alone developed significantly less thrombocytopenia. These results suggest a hitherto unrecognized role of endothelium in thrombin-dependent platelet sequestration during endotoxaemia. The data have implications for the development of therapeutic strategies based on targeted anticoagulation to limit disseminated intravascular coagulation.

Adenosine regulates thrombomodulin and endothelial protein C receptor expression in folliculostellate cells of the pituitary gland

Adenosine stimulates the release of interleukin 6 (IL-6) and vascular endothelial growth factor from folliculostellate cells of the anterior pituitary gland indicating that such cells are also involved in the communication between the immune and endocrine systems during stress and inflammation. In order to understand the precise actions of adenosine on folliculostellate cells, DNA microarray analysis was used to determine global changes in gene expression. Hierarchical clusters revealed, of the genes that had altered expression, the majority were suppressed and many, such as B cell translocation gene 2 and cyclin-dependent kinase inhibitor 2b were related to cell cycle arrest or inhibition of proliferation. Several of the up-regulated genes were associated with cytokine signalling or membrane receptor activity. The most notable of these being IL-6, sulfiredoxin 1, endothelial protein C receptor (EPCR) and thrombomodulin (THBD) which can all play a role in controlling inflammation. The EPCR and THBD pathway is well known in anti-coagulation but also has anti-inflammatory and anti-apoptotic properties. Up-regulation of EPCR and THBD in folliculostellate cells was confirmed by qRT-PCR and western blotting analysis and their expression were also demonstrated in many of the hormone-secreting cells of the anterior pituitary gland. Our findings suggest that adenosine can stimulate expression of stress and inflammation related genes from folliculostellate cells of the anterior pituitary gland. These genes include EPCR and THBD, neither of which has been previously identified in the pituitary gland.