Effects of human soluble thrombomodulin on experimental glomerulonephritis

Circulating Thrombomodulin: Release Mechanisms, Measurements, and Levels in Diseases and Medical Procedures

Thrombomodulin (TM) is a type-I transmembrane protein that is mainly expressed on endothelial cells and plays important roles in many biological processes. Circulating TM of different forms are also present in biofluids, such as blood and urine. Soluble TM (sTM), comprised of several domains of TM, is the major circulating TM which is generated by either enzymatic or chemical cleavage of the intact protein under different conditions. Under normal conditions, sTM is present in low concentrations (<10 ng/mL) in the blood but is elevated in several pathological conditions associated with endothelial dysfunction such as cardiovascular, inflammatory, infection, and metabolic diseases. Therefore, sTM level has been examined for monitoring disease development, such as disseminated intravascular coagulation (DIC), sepsis and multiple organ dysfunction syndrome in patients with novel coronavirus disease 2019 (COVID-19) recently. In addition, microvesicles (MVs) that contain membrane TM (MV-TM) have been found to be released from activated cells which also contribute to levels of circulating TM in certain diseases. Several release mechanisms of sTM and MV-TM have been reported, including enzymatic, chemical, and TM mutation mechanisms. Measurements of sTM and MV-TM have been developed and explored as biomarkers in many diseases. In this review, we summarize all these advances in three categories as follows: (1) release mechanisms of circulating TM, (2) methods for measuring circulating TM in biological samples, and (3) correlation of circulating TM with diseases. Altogether, it provides a whole picture of recent advances on circulating TM in health and disease.

Recombinant human soluble thrombomodulin attenuates anti-glomerular basement membrane glomerulonephritis in Wistar-Kyoto rats through anti-inflammatory effects

BACKGROUND

Since recombinant human soluble thrombomodulin (RH-TM) has anti-inflammatory properties through neutralizing high-mobility group box 1 protein (HMGB1), the protective effects of RH-TM were examined in anti-glomerular basement membrane (GBM) glomerulonephritis (GN) in Wistar-Kyoto rats.

METHODS

Rats were injected with nephrotoxic serum (NTS) to induce anti-GBM GN on Day 0, and were given either RH-TM or vehicle from Day 0 to Day 6. Rats were sacrificed 7 days after NTS injection.

RESULTS

RH-TM-treated rats had decreased proteinuria and serum creatinine level. RH-TM significantly reduced the percentage of glomeruli with crescentic features and fibrinoid necrosis. In addition, RH-TM-treated rats had significantly reduced glomerular ED1+ macrophage accumulation as well as reduced renal cortical proinflammatory cytokine expression. Furthermore, RH-TM had a potent effect in reducing intercellular adhesion molecule-1 (ICAM-1) expression in kidneys and urine. RH-TM significantly reduced renal cortical mRNA levels for toll-like receptor -2 and -4, known as receptors for HMGB1, and their downstream adopter protein, myeloid differentiation primary respond protein 88 (MyD88).

CONCLUSIONS

We showed for the first time that anti-inflammatory effects, which were characterized by reduced glomerular macrophage influx concomitant with a marked reduction in proinflammatory cytokines, were involved in the mechanism of attenuating experimental anti-GBM GN by RH-TM. The observed effects might be attributable to the downregulation of ICAM-1 by reducing the HMGB1/TLR/MyD88 signaling pathway.

Therapeutic Potential of Thrombomodulin in Renal Fibrosis of Nephrotoxic Serum Nephritis in Wistar-Kyoto Rats

BACKGROUND

Recombinant human soluble thrombomodulin (rhTM) was approved in 2008 and has been used for treatment of disseminated intravascular coagulation in Japan. The antifibrotic effects of rhTM in acute exacerbation of idiopathic pulmonary fibrosis are well established, but the therapeutic potential of rhTM in renal fibrosis remains poorly understood.

METHODS

Nephrotoxic serum nephritis (NTS-N) was induced in 22 female Wistar-Kyoto (WKY) rats on day 0. Rats were administered either rhTM or vehicle intraperitoneally, every day from day 4 to day 55. Rats were sacrificed on day 56 when renal fibrosis was established and renal morphological investigations were performed. In vitro, rat renal fibroblasts (NRK-49F) were pretreated with rhTM or saline, and expression levels of profibrogenic gene induced by thrombin were analyzed by real-time reverse transcription polymerase chain reaction.

RESULTS

Compared to WKY-GN-vehicle rats, the body weights of WKY-GN-rhTM rats were significantly greater on day 55. By day 56, rhTM had significantly reduced serum creatinine levels in NTS-N. On the other hand, urinary protein excretion was comparable between the two treatment groups throughout the study. The percentage of Masson trichrome-positive areas in WKY-GN-rhTM rats was significantly lower compared to that in WKY-GN-vehicle rats. Glomerular fibrin deposition was significantly reduced in WKY-GN-rhTM rats. In addition, rhTM significantly reduced the renal cortical mRNA expression levels of TNF-α, Toll-like receptor 4, MYD88, TGF-β, αSMA, collagen I, collagen III, fibronectin, and protease-activated receptor 1 (PAR1), a thrombin receptor. In vitro, thrombin stimulation of NRK-49F cells significantly enhanced the mRNA expression levels of αSMA and PAR1, and these upregulations were significantly reduced by pretreatment with rhTM.

CONCLUSIONS

Administration of rhTM after establishment of crescentic glomerulonephritis (GN) attenuated the subsequent development of renal fibrosis in NTS-N, possibly in part by inhibiting thrombin-mediated fibrogenesis. Our results suggest that rhTM may offer a therapeutic option for limiting the progression of chronic kidney disease in crescentic GN.

Recombinant thrombomodulin ameliorates autoimmune vasculitis via immune response regulation and tissue injury protection

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is characterized by necrotizing vasculitis with the presence of pathogenic ANCA. ANCA can potentially cause neutrophil activation and induce neutrophil extracellular traps (NETs), resulting in endothelial damage as well as activation of autoreactive B cells and alternative complement pathway. Recombinant thrombomodulin (rTM) protects the endothelium from vascular injury during disseminated intravascular coagulation, thus we hypothesized that rTM ameliorates necrotizing vasculitis in AAV. In this study, rTM was administered in an experimental AAV rat model. Treatment of experimental AAV rats with rTM improved pulmonary hemorrhage and glomerulonephritis, with a suppression of ANCA production and NETs formation. In addition, in vitro experiments showed that rTM bound to neutrophils via Mac-1 (macrophage-1 antigen) and inhibited ANCA-induced NETs formation accompanied by a suppression of histone citrullination, leading to a protection of the endothelium from NETs toxicity. Additionally, rTM affected lymphocytes leading to the inhibition of pro-inflammatory cytokine/chemokin in PBMC during the antibody production process, which might indirectly be involved in the reduction of pathogenic ANCA. Our data revealed that the rTM could ameliorate autoimmune vasculitis through a combination of different biological mechanisms.

Recombinant human soluble thrombomodulin reduces the severity and incidence of necrotizing enterocolitis in a newborn rat model

PURPOSE

Necrotizing enterocolitis (NEC) remains the leading cause of death in preterm infants. Recombinant human soluble thrombomodulin (rTM) has been reported to have anti-inflammatory effects as well as antithrombogenic effects. The aim of this study was to evaluate the effect of rTM in a rat NEC model.

METHODS

NEC was induced by enteral feeding with hyperosmolar formula, gavage administration of lipopolysaccharide and asphyxia stress. Controls were fed by their mother ad libitum. In the treatment group, rTM was administered subcutaneously twice (once each on the first and second day). All animals surviving beyond 96 h or that developed signs of distress were euthanized. The ileum was harvested for a histological evaluation and the measurement of the mRNA and protein expression.

RESULTS

The rate of NEC-like intestinal injury in the treatment group (9/25, 36%) was significantly lower than in the NEC group (25/34, 73.5%). Tissue levels of TNF-α, IL-6 and HMGB1 were significantly elevated in the NEC group, whereas those in the treatment group were decreased to similar values as in the control group.

CONCLUSIONS

Our experimental study showed that rTM is able to reduce the severity and incidence of NEC. It may be an alternative option for the treatment of NEC.

Disseminated Intravascular Coagulation: An Update on Pathogenesis, Diagnosis, and Therapeutic Strategies

Disseminated intravascular coagulation (DIC) is an acquired clinicobiological syndrome characterized by widespread activation of coagulation leading to fibrin deposition in the vasculature, organ dysfunction, consumption of clotting factors and platelets, and life-threatening hemorrhage. Disseminated intravascular coagulation is provoked by several underlying disorders (sepsis, cancer, trauma, and pregnancy complicated with eclampsia or other calamities). Treatment of the underlying disease and elimination of the trigger mechanism are the cornerstone therapeutic approaches. Therapeutic strategies specific for DIC aim to control activation of blood coagulation and bleeding risk. The clinical trials using DIC as entry criterion are limited. Large randomized, phase III clinical trials have investigated the efficacy of antithrombin (AT), activated protein C (APC), tissue factor pathway inhibitor (TFPI), and thrombomodulin (TM) in patients with sepsis, but the diagnosis of DIC was not part of the inclusion criteria. Treatment with APC reduced 28-day mortality of patients with severe sepsis, including patients retrospectively assigned to a subgroup with sepsis-associated DIC. Treatment with APC did not have any positive effects in other patient groups. The APC treatment increased the bleeding risk in patients with sepsis, which led to the withdrawal of this drug from the market. Treatment with AT failed to reduce 28-day mortality in patients with severe sepsis, but a retrospective subgroup analysis suggested possible efficacy in patients with DIC. Clinical studies with recombinant TFPI or TM have been carried out showing promising results. The efficacy and safety of other anticoagulants (ie, unfractionated heparin, low-molecular-weight heparin) or transfusion of platelet concentrates or clotting factor concentrates have not been objectively assessed.

The involvement of endothelial mediators in leprosy

Leprosy is a chronic infectious disease that requires better understanding since it continues to be a significant health problem in many parts of the world. Leprosy reactions are acute inflammatory episodes regarded as the central etiology of nerve damage in the disease. The activation of endothelium is a relevant phenomenon to be investigated in leprosy reactions. The present study evaluated the expression of endothelial factors in skin lesions and serum samples of leprosy patients. Immunohistochemical analysis of skin samples and serum measurements of VCAM-1, VEGF, tissue factor and thrombomodulin were performed in 77 leprosy patients and 12 controls. We observed significant increase of VCAM-1 circulating levels in non-reactional leprosy (p = 0.0009). The immunostaining of VEGF and tissue factor was higher in endothelium of non-reactional leprosy (p = 0.02 for both) than healthy controls. Patients with type 1 reaction presented increased thrombomodulin serum levels, compared with non-reactional leprosy (p = 0.02). In type 2 reaction, no significant modifications were observed for the endothelial factors investigated. The anti-inflammatory and antimicrobial activities of the endotfhelial factors may play key-roles in the pathogenesis of leprosy and should be enrolled in studies focusing on alternative targets to improve the management of leprosy and its reactions.

Coagulation and inflammation

The protein C anticoagulant pathway is critical for controlling microvascular thrombosis and is initiated when thrombin binds to thrombomodulin (TM) on the surface of the endothelium. Protein C activation is augmented by an endothelial cell protein C receptor (EPCR). EPCR is shed from the vasculature by inflammatory mediators and thrombin. EPCR binds to activated neutrophils in a process that involves proteinase 3 and Mac-1 and appears to inhibit leukocyte extravasation. EPCR can undergo translocation from the plasma membrane to the nucleus where it re-directs gene expression. During translocation, EPCR can carry activated protein C (APC) to the nucleus, possibly accounting for the ability of APC to modulate inflammatory mediator responses in the endothelium. TNF-α and other inflammatory mediators can down-regulate EPCR and TM. Inhibition of protein C pathway function increases cytokine elaboration, endothelial cell injury and leukocyte extravasation in response to endotoxin and infusion of APC reverses these processes. In vitro, APC has been reported to inhibit TNF-α elaboration from monocytes and to block leukocyte adhesion to selectins. Since thrombin can elicit many inflammatory responses in microvascular endothelium, loss of control of microvascular thrombin generation due to impaired protein C pathway function probably contributes to microvascular dysfunction in sepsis.

The multifaceted role of the renal microvasculature during acute kidney injury

Pediatric acute kidney injury (AKI) represents a complex disease process for clinicians as it is multifactorial in cause and only limited treatment or preventatives are available. The renal microvasculature has recently been implicated in AKI as a strong therapeutic candidate involved in both injury and recovery. Significant progress has been made in the ability to study the renal microvasculature following ischemic AKI and its role in repair. Advances have also been made in elucidating cell-cell interactions and the molecular mechanisms involved in these interactions. The ability of the kidney to repair post AKI is closely linked to alterations in hypoxia, and these studies are elucidated in this review. Injury to the microvasculature following AKI plays an integral role in mediating the inflammatory response, thereby complicating potential therapeutics. However, recent work with experimental animal models suggests that the endothelium and its cellular and molecular interactions are attractive targets to prevent injury or hasten repair following AKI. Here, we review the cellular and molecular mechanisms of the renal endothelium in AKI, as well as repair and recovery, and potential therapeutics to prevent or ameliorate injury and hasten repair.

The emerging role of coagulation proteases in kidney disease

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

Characterization of soluble thrombomodulin levels in patients with stage 3-5 chronic kidney disease

OBJECTIVE

This study aims to test the serum levels of soluble thrombomodulin (TM) in patients with chronic kidney disease (CKD)3-5 and to assess their connection with the different stages and severity of disease.

METHODS

Sixty-seven patients with CKD are included, disease severity was evaluated accordingly to CKD staging and clinical data is collected. Nineteen healthy volunteers served as healthy controls. Serum soluble TM is analyzed by ELISA.

RESULTS

The levels of soluble TM in all patients with CKD were significantly higher than those of healthy controls (p < 0.001). CKD5 patients showed higher serum levels of soluble TM, in comparison to CKD4 patients (p = 0.001), CKD3 patients (p < 0.001), and healthy controls (p < 0.001). The correlation analysis revealed significant correlation between serum soluble TM and disease severity (r = 0.714, p < 0.001). Serum soluble TM was found to be correlated with eGFR (r = -0.766; p < 0.001) and serum creatinine (r = 0.778, p < 0.001).

CONCLUSION

Soluble TM concentrations significantly increase in the CKD patients and are associated with the severity of the disease. Soluble TM may play critical roles in the development of CKD, as a biomarker of endothelial cells damage, anticoagulation and anti-inflammation.

Thrombomodulin expression regulates tumorigenesis in bladder cancer

Background

The identification of potential tumor markers will help improve therapeutic planning and patient management. Thrombomodulin (TM) is a sensitive urothelial marker. TM was reported to be one of the endogenous anti-metastatic factors and has diagnostic and prognostic values for the progression of carcinoma. In the present study, we examine the role of TM in bladder cancer.

Methods

We studied the role of TM in tumor behavior and related signaling pathways in vitro using the human bladder cancer cell lines HT1376, HT1197, J82 and T24, and in vivo using animal models. We also selected clinical specimens from 100 patients with bladder cancer for immunohistochemical staining to evaluate the predictive capacity of TM in tumor invasiveness.

Results

The data revealed that positive immunoreactivity for TM was inversely correlated with clinical stage and DNA methyltransferase 1 immunoreactivity. Decreased TM expression could predict the aggressive tumor growth and advanced clinical stage in bladder cancer. When TM was inhibited, tumor growth rate and invasion ability were augmented in vitro and in vivo. The underlying changes included increased cell proliferation, enhanced epithelial-mesenchymal transition (EMT) and angiogenesis. Moreover, inhibition of NF-κB activation significantly increased TM expression and attenuated tumor aggressiveness in bladder cancer.

Conclusions

TM plays an important role in bladder cancer tumor aggressiveness in vitro and in vivo and is a clinically significant predictor that may represent a suitable therapeutic target for bladder cancer.

Effect of eculizumab and recombinant human soluble thrombomodulin combination therapy in a 7-year-old girl with atypical hemolytic uremic syndrome due to anti-factor H autoantibodies

Atypical hemolytic uremic syndrome (aHUS), which is defined as non-Shiga toxin-associated hemolytic uremic syndrome, is a type of thrombotic microangiopathy. This syndrome presents with hemolytic anemia, thrombocytopenia, and acute kidney injury. Excessive complement activation due to genetic disorders of the complement system or production of autoantibodies to factor H (FH) causes the disease. We report a successful treatment course using eculizumab and recombinant human soluble thrombomodulin (rTMD) for a 7-year-old girl with aHUS due to anti-FH autoantibodies. Although her chief complaints were abdominal pain and loose stools, we were finally able to diagnose her with aHUS because Shiga toxin-producing Escherichia coli was not detected in her feces and a hemolytic assay analyzing FH function was positive. We administrated rTMD to our patient because of signs of disseminated intravascular coagulation. Soon after the therapeutic intervention, the platelet count began to increase and abdominal pain was moderately improved. Plasma exchange limited the efficacy of her disease. Therefore, we administered eculizumab, monoclonal humanized antibody against C5, 3 weeks after admission. Platelet counts immediately increased and kidney function gradually recovered. Genetic disorders were not detected. However, anti-FH autoantibody was observed. There were no symptoms for recurrence of aHUS or kidney dysfunction for 15 months, as a result of the administration of eculizumab every other week. In conclusion, combination therapy of eculizumab and rTMD was effective for an aHUS patient. This therapy may be helpful for improving the prognosis and long-term kidney function of aHUS patients.

Thrombomodulin domain 1 ameliorates diabetic nephropathy in mice via anti-NF-κB/NLRP3 inflammasome-mediated inflammation, enhancement of NRF2 antioxidant activity and inhibition of apoptosis

AIMS/HYPOTHESIS

Chronic inflammatory processes have been increasingly shown to be involved in the pathogenesis of diabetes and diabetic nephropathy. Recently, we demonstrated that a lectin-like domain of thrombomodulin (THBD), which is known as THBD domain 1 (THBDD1) and which acts independently of protein C activation, neutralised an inflammatory response in a mouse model of sepsis. Here, therapeutic effects of gene therapy with adeno-associated virus (AAV)-carried THBDD1 (AAV-THBDD1) were tested in a mouse model of type 2 diabetic nephropathy.

METHODS

To assess the therapeutic potential of THBDD1 and the mechanisms involved, we delivered AAV-THBDD1 (10(11) genome copies) into db/db mice and tested the effects of recombinant THBDD1 on conditionally immortalised podocytes.

RESULTS

A single dose of AAV-THBDD1 improved albuminuria, renal interstitial inflammation and glomerular sclerosis, as well as renal function in db/db mice. These effects were closely associated with: (1) inhibited activation of the nuclear factor κB (NF-κB) pathway and the NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome; (2) promotion of nuclear factor (erythroid-derived 2)-like 2 (NRF2) nuclear translocation; and (3) suppression of mitochondria-derived apoptosis in the kidney of treated mice.

CONCLUSIONS/INTERPRETATION

AAV-THBDD1 gene therapy resulted in improvements in a model of diabetic nephropathy by suppressing the NF-κB-NLRP3 inflammasome-mediated inflammatory process, enhancing the NRF2 antioxidant pathway and inhibiting apoptosis in the kidney.

Effect of thrombomodulin on the development of monocrotaline-induced pulmonary hypertension

PURPOSE

The purpose of the present study was to investigate whether thrombomodulin (TM) prevents the development of pulmonary hypertension (PH) in monocrotaline (MCT)-injected rats.

METHODS

Human recombinant TM (3 mg/kg/2 days) or saline were given to MCT-injected male Sprague-Dawley rats for 19 (n = 14) or 29 (n = 11) days. Control rats (n = 6) were run for 19 days. The mean pulmonary artery pressure (mPAP), right ventricular hypertrophy (RVH), percentages of muscularized peripheral arteries (%muscularization), and medial wall thickness of small muscular arteries (%MWT) were measured. To determine inflammatory and coagulation responses, broncho-alveolar lavage fluid (BALF) was analyzed in another set of rats (n = 29). Western blotting for endothelial nitric oxide synthase (eNOS) and phosphorylated eNOS (peNOS) in the lung tissue was performed in separate rats (n = 13). Survival was determined in 60 rats.

RESULTS

MCT increased mPAP, RVH, %muscularization, and %MWT. TM treatment significantly reduced mPAP, %muscularization, and %MWT in peripheral arteries with an external diameter of 50-100 μm in 19 days after MCT injection, but the effect was lost after 29 days. MCT increased the levels of tumor necrosis factor alpha, monocyte chemoattractant protein-1, and thrombin-antithrombin complex in BALF. Expression of eNOS increased in MCT rats, while peNOS decreased. The relative amount of peNOS to total eNOS increased in MCT/TM rats compared to MCT/Vehicle rats. A Kaplan-Meier survival curve showed no difference with and without TM.

CONCLUSION

Although the administration of TM might slightly delay the progression of MCT-induced PH, the physiological significance for treatment is limited, since the survival rate was not improved.

Recombinant thrombomodulin of different domains for pharmaceutical, biomedical, and cell transplantation applications

Thrombomodulin (TM) is a membrane glycoprotein mainly expressed by vascular endothelial cells and is involved in many physiological and pathological processes, such as coagulation, inflammation, cancer development, and embryogenesis. Human TM consists of 557 amino acids divided into five distinct domains: N-terminal lectin-like domain (designated as TMD1); six epidermal growth factor (EGF)-like domain (TMD2); Ser/Thr-rich domain (TMD3); transmembrane domain (TMD4); and cytoplasmic tail domain (TMD5). The different domains are responsible for different biological functions of TM. In the past decades, various domains of TM have been cloned and expressed for TM structural and functional study. Further, recombinant TMs of different domains show promising antithrombotic and anti-inflammatory activity in both rodents and primates and a recombinant soluble TM has been approved for therapeutic application. This review highlights recombinant TMs of diverse structures and their biological functions, as well as the complex interactions of TM with factors involved in the related biological processes. Particularly, recent advances in exploring recombinant TM of different domains for pharmaceutical, biomedical, and cell transplantation applications are summarized.

Thrombomodulin as a regulator of the anticoagulant pathway: implication in the development of thrombosis

Thrombomodulin is a cell surface-expressed glycoprotein that serves as a cofactor for thrombin-mediated activation of protein C (PC), an event further amplified by the endothelial cell PC receptor. The PC pathway is a major anticoagulant mechanism that downregulates thrombin formation and hedges thrombus formation. The objectives of this review were to review recent findings regarding thrombomodulin structure, its involvement in the regulation of hemostasis and further discuss the implication, if any, of the genetic polymorphisms in the thrombomodulin gene in the risk of development of thrombosis. We performed a literature search by using electronic bibliographic databases. Although the direct evaluation of risk situations associated with thrombomodulin mutations/polymorphisms could be of clinical significance, it appears that mutations that affect the function of thrombomodulin are rarely associated with venous thromboembolism. However, several polymorphisms are reported to be associated with increased risk for arterial thrombosis. Additionally studies on knock out mice as well studies on humans bearing rare mutations suggest that thrombomodulin dysfunction may be implicated in the pathogenesis of myocardial infraction.

The role of thrombomodulin lectin-like domain in inflammation

Thrombomodulin (TM) is a cell surface glycoprotein which is widely expressed in a variety of cell types. It is a cofactor for thrombin binding that mediates protein C activation and inhibits thrombin activity. In addition to its anticoagulant activity, recent evidence has revealed that TM, especially its lectin-like domain, has potent anti-inflammatory function through a variety of molecular mechanisms. The lectin-like domain of TM plays an important role in suppressing inflammation independent of the TM anticoagulant activity. This article makes an extensive review of the role of TM in inflammation. The molecular targets of TM lectin-like domain have also been elucidated. Recombinant TM protein, especially the TM lectin-like domain may play a promising role in the management of sepsis, glomerulonephritis and arthritis. These data demonstrated the potential therapeutic role of TM in the treatment of inflammatory diseases.

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.

Soluble thrombomodulin reduces inflammation and prevents microalbuminuria induced by chronic endothelial activation in transgenic mice

Chronic kidney disease pathogenesis involves both tubular and vascular injuries. Despite abundant investigations to identify the risk factors, the involvement of chronic endothelial dysfunction in developing nephropathies is insufficiently explored. Previously, soluble thrombomodulin (sTM), a cofactor in the activation of protein C, has been shown to protect endothelial function in models of acute kidney injury. In this study, the role for sTM in treating chronic kidney disease was explored by employing a mouse model of chronic vascular activation using endothelial-specific TNF-α-expressing (tie2-TNF) mice. Analysis of kidneys from these mice after 3 mo showed no apparent phenotype, whereas 6-mo-old mice demonstrated infiltration of CD45-positive leukocytes accompanied by upregulated gene expression of inflammatory chemokines, markers of kidney injury, and albuminuria. Intervention with murine sTM with biweekly subcutaneous injections during this window of disease development between months 3 and 6 prevented the development of kidney pathology. To better understand the mechanisms of these findings, we determined whether sTM could also prevent chronic endothelial cell activation in vitro. Indeed, treatment with sTM normalized increased chemokines, adhesion molecule expression, and reduced transmigration of monocytes in continuously activated TNF-expressing endothelial cells. Our results suggest that vascular inflammation associated with vulnerable endothelium can contribute to loss in renal function as suggested by the tie2-TNF mice, a unique model for studying the role of vascular activation and inflammation in chronic kidney disease. Furthermore, the ability to restore the endothelial balance by exogenous administration of sTM via downregulation of specific adhesion molecules and chemokines suggests a potential for therapeutic intervention in kidney disease associated with chronic inflammation.

Systemic versus localized coagulation activation contributing to organ failure in critically ill patients

In the pathogenesis of sepsis, inflammation and coagulation play a pivotal role. Increasing evidence points to an extensive cross-talk between these two systems, whereby inflammation not only leads to activation of coagulation but coagulation also considerably affects inflammatory activity. The intricate relationship between inflammation and coagulation may not only be relevant for vascular atherothrombotic disease in general but has in certain clinical settings considerable consequences, for example in the pathogenesis of microvascular failure and subsequent multiple organ failure, as a result of severe infection and the associated systemic inflammatory response. Molecular pathways that contribute to inflammation-induced activation of coagulation have been precisely identified. Pro-inflammatory cytokines and other mediators are capable of activating the coagulation system and downregulating important physiological anticoagulant pathways. Activation of the coagulation system and ensuing thrombin generation is dependent on an interleukin-6-induced expression of tissue factor on activated mononuclear cells and endothelial cells and is insufficiently counteracted by physiological anticoagulant mechanisms and endogenous fibrinolysis. Interestingly, apart from the overall systemic responses, a differential local response in various vascular beds related to specific organs may occur.

Liposomal Formulations of Thrombomodulin Increase Engraftment after Intraportal Islet Transplantation

Early destruction of donor islet grafts due to an instant blood-mediated inflammatory reaction (IBMIR) remains a major obstacle in islet transplantation. Thrombomodulin plays an important role in limiting coagulation and inflammatory events through a variety of effects. In this study, we investigated the ability of thrombomodulin (TM), when reconstituted as a liposomal formulation, to enhance early syngeneic islet engraftment by minimizing or abrogating the IBMIR. Administration of TM significantly improved early engraftment of syngeneic islets after intraportal transplantation in diabetic mice. In the absence of treatment, conversion to euglycemia was observed among 46.6% (7/15) of recipients. In contrast, administration of TM led to euglycemia in 93.3% (14/15) of recipients ( p = 0.0142). Recipients that received TM exhibited a lower incidence of primary nonfunction and better glucose control over a 30-day period after transplantation. Fibrin deposition ( p < 0.05), neutrophil infiltration ( p < 0.05), expression of TNF-α and IL-β mRNA ( p < 0.05), as well as NF-κB activity ( p < 0.05) were significantly reduced in the liver of islet recipients having been treated with liposomal TM. These data demonstrate that TM significantly improves early syngeneic islet engraftment through effects that target both coagulation and inflammatory pathways.

The protein C pathway in tissue inflammation and injury: pathogenic role and therapeutic implications

Inflammation and coagulation are closely linked interdependent processes. Under physiologic conditions, the tissue microcirculation functions in anticoagulant and anti-inflammatory fashions. However, when inflammation occurs, coagulation is also set in motion and actively participates in enhancing inflammation. Recently, novel and unexpected roles of hemostasis in the humoral and cellular components of innate immunity have been described. In particular, the protein C system, besides its well-recognized role in anticoagulation, plays a crucial role in inflammation. Indeed, the protein C system is now emerging as a novel participant in the pathogenesis of acute and chronic inflammatory diseases, such as sepsis, asthma, inflammatory bowel disease, atherosclerosis, and lung and heart inflammation, and may emerge as unexpected therapeutic targets for intervention.

The protein C pathway in tissue inflammation and injury: pathogenic role and therapeutic implications

Inflammation and coagulation are closely linked interdependent processes. Under physiologic conditions, the tissue microcirculation functions in anticoagulant and anti-inflammatory fashions. However, when inflammation occurs, coagulation is also set in motion and actively participates in enhancing inflammation. Recently, novel and unexpected roles of hemostasis in the humoral and cellular components of innate immunity have been described. In particular, the protein C system, besides its well-recognized role in anticoagulation, plays a crucial role in inflammation. Indeed, the protein C system is now emerging as a novel participant in the pathogenesis of acute and chronic inflammatory diseases, such as sepsis, asthma, inflammatory bowel disease, atherosclerosis, and lung and heart inflammation, and may emerge as unexpected therapeutic targets for intervention.

Combination effect of antithrombin and recombinant human soluble thrombomodulin in a lipopolysaccharide induced rat sepsis model

Introduction

Recombinant human soluble thrombomodulin (rhsTM) is newly developed for the treatment of DIC. The purpose of this study was to evaluate the efficacy of the concomitant administration of rhsTM and antithrombin (AT).

Methods

In the first series, rats were treated with either 62.5, 125, 250 or 500 IU/kg (n = 6, each) of AT or 0.125, 0.25, 0.5 or 1.0 mg/kg (n = 6, each) of rhsTM followed by lipopolysaccharide (LPS) injection. 8 h later, the fibrinogen level was examined. In the second series, TM group was pretreated with 0.25 mg/kg of rhsTM, AT group was pretreated with 125 IU/kg of AT, AT/TM group was pretreated with both AT and rhsTM, and control group was pretreated with saline (n = 7, each). The platelet count, fibrinogen, ALT, LDH and high-mobility group box 1 (HMGB1) levels were measured. In addition, histologic changes in liver were examined. In the third series, survival was calculated up to 24 h.

Results

Both AT and rhsTM produced a linear dose-response with regard to the fibrinogen level, with 125 IU/kg of AT and 0.25 mg/kg of rhsTM producing equivalent effects. The combined administration of AT and rhsTM significantly reduced the decrease in the platelet count and the fibrinogen level (P < 0.05, 0.01, respectively). The elevations in ALT and LDH were significantly suppressed in all treatment groups. The HMGB1 level and the histologic changes tended to indicate damage reduction. Survival was significantly better only in AT/TM group (P < 0.01).

Conclusions

The coadministration of AT and rhsTM might be effective for the treatment of severe sepsis.

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

BACKGROUND

Inflammation and thrombosis coexist in several disorders. Although it is recognized that leukocytes may induce a procoagulant state at sites of inflammation, the critical molecular determinants of this process remain largely unknown.

METHODS AND RESULTS

To examine mechanisms of inflammation-induced thrombosis, we developed a murine model of thrombotic glomerulonephritis (TGN), a known cause of acute renal failure in patients. This model, induced by lipopolysaccharide and antibody to the glomerular basement membrane, led to rapid glomerular neutrophil recruitment, thrombotic glomerular lesions with endothelial cell injury, and renal dysfunction. In mice immunodepleted of neutrophils or lacking the leukocyte-specific integrin Mac-1, neutrophil recruitment, endothelial injury, glomerular thrombosis, and acute renal failure were markedly attenuated despite the robust generation of renal cytokines. Neutrophil elastase is a likely effector of Mac-1 because its activity was reduced in Mac-1-deficient mice and the phenotype in mice deficient in Mac-1 or neutrophil elastase was similar. Platelets accumulated in glomerular capillaries within 4 hours of TGN before evidence of thrombosis. Platelet immunodepletion before TGN markedly exacerbated hematuria (hemorrhage), inflammation, and injury, whereas thrombocytopenic Mac-1-deficient mice remained resistant to disease, indicating that initial glomerular platelet deposition protects the vessel wall from neutrophil-mediated sequelae. The subsequent thrombosis relied on the interaction of Mac-1 on recruited neutrophils with glycoprotein Ibalpha on platelets as antibody-mediated disruption of this interaction attenuated TGN without affecting renal neutrophil accumulation.

CONCLUSIONS

These observations establish Mac-1 on neutrophils as a critical molecular link between inflammation and thrombosis and suggest it as an attractive target for antithrombotic therapy.

Coagulation and innate immune responses: can we view them separately?

The horseshoe crab is often referred to as a "living fossil," representative of the oldest classes of arthropods, almost identical to species in existence more than 500 million years ago. Comparative analyses of the defense mechanisms used by the horseshoe crab that allowed it to survive mostly unchanged throughout the millennia reveal a common ancestry of the coagulation and innate immune systems that are totally integrated-indeed, almost inseparable. In human biology, we traditionally view the hemostatic pathways and those regulating innate immune responses to infections and tissue damage as entirely separate entities. But are they? The last couple of decades have revealed a remarkable degree of interplay between these systems, and the linking cellular and molecular mechanisms are rapidly being delineated. In this review, we present some of the major points of intersection between coagulation and innate immunity. We attempt to highlight the potential impact of these findings by identifying recently established paradigms that will hopefully result in the emergence of new strategies to treat a range of inflammatory and hemostatic disorders.

Crosstalk between inflammation and thrombosis

Inflammation shifts the hemostatic mechanisms in favor of thrombosis. Multiple mechanisms are at play including up regulation of tissue factor leading to the initiation of clotting, amplification of the clotting process by augmenting exposure of cellular coagulant phospholipids, inhibition of fibrinolysis by elevating plasminogen activator inhibitor 1 (PAI-1) and decreases in natural anticoagulant pathways, particularly targeted toward down regulation of the protein C anticoagulant pathway through multiple mechanisms. The decreased function of the natural anticoagulant pathways may be particularly problematic because these appear to play a role in dampening inflammatory responses. The protein C anticoagulant pathway provides a useful model for the impact of inflammation on coagulation. This pathway plays a major role in preventing microvascular thrombosis. The pathway is initiated when thrombin binds to thrombomodulin (TM) on the surface of the endothelium. An endothelial cell protein C receptor (EPCR) augments protein C activation by the thrombin-TM complex more than 10-fold in vivo. EPCR is shed from the endothelium by inflammatory mediators and thrombin. EPCR binds to activated neutrophils in a process that involves proteinase 3 and Mac-1 and appears to inhibit leukocyte extravisation. EPCR can undergo translocation from the plasma membrane to the nucleus where it redirects gene expression. During translocation it can carry activated protein C (APC) to the nucleus, possibly accounting for the ability of APC to modulate inflammatory mediator responses in the endothelium. TNF alpha and other inflammatory mediators can down-regulate EPCR and TM and IL-6 can depress levels of protein S in experimental animals. Inhibition of protein C pathway function increases cytokine elaboration, endothelial cell injury and leukocyte extravisation in response to endotoxin, processes that are decreased by infusion of APC. In vitro, APC inhibits TNF alpha elaboration from monocytes and to block leukocyte adhesion to selectins. Since thrombin can elicit many inflammatory responses in microvascular endothelium, loss of control of microvascular thrombin generation due to impaired protein C pathway function probably contributes to microvascular dysfunction in sepsis.

Thrombomodulin improves early outcomes after intraportal islet transplantation

Primary islet nonfunction due to an instant blood mediated inflammatory reaction (IBMIR) leads to an increase in donor islet mass required to achieve euglycemia. In the presence of thrombin, thrombomodulin generates activated protein C (APC), which limits procoagulant and proinflammatory responses. In this study, we postulated that liposomal formulations of thrombomodulin (lipo-TM), due to its propensity for preferential uptake in the liver, would enhance intraportal engraftment of allogeneic islets by inhibiting the IBMIR. Diabetic C57BL/6J mice underwent intraportal transplantation with B10.BR murine islets. In the absence of treatment, conversion to euglycemia was observed among 29% of mice receiving 250 allo-islets. In contrast, a single infusion of lipo-TM led to euglycemia in 83% of recipients (p = 0.0019). Fibrin deposition (p < 0.0001), neutrophil infiltration (p < 0.0001), as well as expression TNF-alpha and IL-beta (p < 0.03) were significantly reduced. Significantly, thrombotic responses mediated by human islets in contact with human blood were also reduced by this approach. Lipo-TM improves the engraftment of allogeneic islets through a reduction in local thrombotic and inflammatory processes. As an enzyme-based pharmacotherapeutic, this strategy offers the potential for local generation of APC at the site of islet infusion, during the initial period of elevated thrombin production.

Soluble thrombomodulin protects ischemic kidneys

Altered coagulation and inflammation contribute to the pathogenesis of ischemic renal injury. Thrombomodulin is a necessary factor in the anticoagulant protein C pathway and has inherent anti-inflammatory properties. We studied the effect of soluble thrombomodulin (sTM) in a hypoperfusion model of ischemic kidney injury. To markedly reduce infrarenal aortic blood flow and femoral arterial pressures, we clamped the suprarenal aorta of rats, occluding them 90%, for 60 min. Reversible acute kidney injury (AKI) occurred at 24 h in rats subjected to hypoperfusion. Histologic analysis at 24 h revealed acute tubular necrosis (ATN), and intravital two-photon microscopy showed flow abnormalities in the microvasculature and defects of endothelial permeability. Pretreatment with rat sTM markedly reduced both I-R-induced renal dysfunction and tubular histologic injury scores. sTM also significantly improved microvascular erythrocyte flow rates, reduced microvascular endothelial leukocyte rolling and attachment, and minimized endothelial permeability to infused fluorescence dextrans, assessed by intravital quantitative multiphoton microscopy. Furthermore, sTM administered 2 h after reperfusion protected against ischemia-induced renal dysfunction at 24 h and improved survival. By using an sTM variant, we also determined that the protective effects of sTM were independent of its ability to generate activated protein C. These data suggest that sTM may have therapeutic potential for ischemic AKI.

The protein C pathway in inflammatory bowel disease: the missing link between inflammation and coagulation

Traditionally described as a major anti-coagulant system, the protein C (PC) pathway, consisting of thrombomodulin, the endothelial cell protein C receptor and activated PC (APC), is gaining increasing attention as an important regulator of microvascular inflammation. Although they possess several anti-inflammatory and cytoprotective functions, the expression and function of the components of the PC pathway is downregulated during inflammation. Recent evidence suggests that the PC pathway is defective in patients with inflammatory bowel disease (IBD) and that restoring its function has anti-inflammatory effects on cultured intestinal microvascular endothelial cells and in animal models of colitis. Here, we propose that the PC pathway has an important role in governing intestinal microvascular inflammation and might provide a novel therapeutic target in the management of IBD.

EF6265, a novel plasma carboxypeptidase B inhibitor, protects against renal dysfunction in rat thrombotic glomerulonephritis through enhancing fibrinolysis

BACKGROUND/AIM

Plasma carboxypeptidase B is a physiological fibrinolysis inhibitor. In the present study, the effects of EF6265, a novel specific plasma carboxypeptidase B inhibitor, on renal dysfunction in a rat thrombotic glomerulonephritis model were examined.

METHODS

The model was induced by injection of anti-glomerular basement membrane serum and lipopolysaccharide to rats. Renal microthrombosis was histologically evaluated by phosphotungstic acid-hematoxylin staining for fibrin thrombi. Renal dysfunction was evaluated on the basis of plasma levels of blood urea nitrogen as well as renal edemas and urine volume.

RESULTS

The glomerular microthrombi observed in a positive control group were significantly reduced after a short-term treatment (4 h) with EF6265 at a dose which enhanced fibrinolysis. The elevation of blood urea nitrogen and renal edema formation decreased, and the reduction of the urine volume improved after a long-term treatment (21 h) with EF6265. In addition, EF6265 had a protective activity against multiple organ dysfunction, because it reduced plasma lactate dehydrogenase and alanine aminotransferase levels and mortality in this model.

CONCLUSION

EF6265, which inhibits plasma carboxypeptidase B, showed a protective effect on thrombotic renal dysfunction in thrombotic glomerulonephritis through enhancing the fibrinolysis.

Efficacy and safety of recombinant human soluble thrombomodulin (ART-123) in disseminated intravascular coagulation: results of a phase III, randomized, double-blind clinical trial

BACKGROUND

Soluble thrombomodulin is a promising therapeutic natural anticoagulant that is comparable to antithrombin, tissue factor pathway inhibitor and activated protein C.

OBJECTIVES

We conducted a multicenter, double-blind, randomized, parallel-group trial to compare the efficacy and safety of recombinant human soluble thrombomodulin (ART-123) to those of low-dose heparin for the treatment of disseminated intravascular coagulation (DIC) associated with hematologic malignancy or infection.

METHODS

DIC patients (n = 234) were assigned to receive ART-123 (0.06 mg kg(-1) for 30 min, once daily) or heparin sodium (8 U kg(-1) h(-1) for 24 h) for 6 days, using a double-dummy method. The primary efficacy endpoint was DIC resolution rate. The secondary endpoints included clinical course of bleeding symptoms and mortality rate at 28 days.

RESULTS

DIC was resolved in 66.1% of the ART-123 group, as compared with 49.9% of the heparin group [difference 16.2%; 95% confidence interval (CI) 3.3-29.1]. Patients in the ART-123 group also showed more marked improvement in clinical course of bleeding symptoms (P = 0.0271). The incidence of bleeding-related adverse events up to 7 days after the start of infusion was lower in the ART-123 group than in the heparin group (43.1% vs. 56.5%, P = 0.0487).

CONCLUSIONS

When compared with heparin therapy, ART-123 therapy more significantly improves DIC and alleviates bleeding symptoms in DIC patients.

SYNERGISTIC EFFECTS OF RECOMBINANT HUMAN SOLUBLE THROMBOMODULIN AND FLUID-VOLUME RESUSCITATION IN A RAT LETHAL CRUSH INJURY MODEL

Severe crush injury results in a high mortality rate because of acute circulatory failure and hyperkalemia. The purpose of this study was to evaluate whether administration of prophylactic-recombinant human soluble thrombomodulin (rhsTM) and/or fluid-volume resuscitation before reperfusion attenuates severe crush injury in rats. Both hindlimbs of anesthetized rats were compressed for 6 h under blocks weighing 3.5 kg each, followed by 3 h of reperfusion. In the first group, fluid resuscitation with normal saline (1 mL/kg/h) was performed throughout the experiment. In the second group, volume resuscitation treatment with normal saline (10 mL/kg/h) was initiated 60 min before the end of the crush period and was continued until the end of the experiment. In the third group, normal saline-resuscitation treatment plus rhsTM (3 mg/kg) was performed. In the fourth group, volume resuscitation treatment plus rhsTM was performed. Blood samples were collected 6 h after the end of the crush period. Complete blood count and platelets were measured. In addition, serum lactate, base deficit, serum potassium, creatine phosphokinase, blood urea nitrogen, creatinine, myoglobin, and some cytokines were evaluated. In another experiment, survival of each group was monitored for 72 h after the end of the crush period. Combined administration of rhsTM and volume resuscitation significantly decreased hemoconcentration and hyperkalemia. The serum interleukin-6 level and mortality were also significantly improved in the combination group compared with those in the other groups. We conclude that prophylactic combination of rhsTM administration and volume resuscitation may be an effective therapy for severe crush injury.

Thrombomodulin expression in colorectal carcinoma is protective and correlates with survival

Thrombomodulin (TM) is an endothelial receptor that exhibits anticoagulant, antifibrinolytic and anti-inflammatory activity by inhibiting thrombin and cellular adhesion. In this study, the expression and significance of TM was examined in primary colorectal cancer and its prognostic implications explored. TM immunostaining was performed on formalin-fixed, paraffin-embedded tissue sections, from primary lesions of 200 patients with colorectal carcinoma. Institutional Ethical approval was granted and clinical data retrieved from patients' records. All normal colonic tissue expressed TM on endothelial cells. TM tumour cell expression was demonstrated in 53 (26.5%) cases and 147 (73.5%) showed no neoplastic cell staining. On univariate and multivariate analysis TM expression on tumour cells correlated significantly with tumour stage, differentiation, Jass score and 5 year survival. TM expression decreases as overall stage and tumour size increase (P=0.03). In all, 91% TM positive tumours were well differentiated and 85% of TM negative tumours were poorly differentiated (P<0.01). Five year survival rates of patients with positive and negative TM expression were 71 and 41%, respectively. Survival rate was poorer in those patients who were TM negative compared with those who were positive (P<0.01). A total of 101 (50.5%) of the cases were node negative. In this group, 5 year survival rates of patients with positive and negative TM expression were 87.5 and 37.8%, respectively, demonstrating a poorer survival rate for those who are node negative and TM negative at the time of surgery (P<0.001). This study demonstrates that loss of TM is a key indicator in tumour biology and prognosis.

The N-terminal domain of thrombomodulin sequesters high-mobility group-B1 protein, a novel antiinflammatory mechanism

Thrombomodulin (TM) is an endothelial anticoagulant cofactor that promotes thrombin-mediated formation of activated protein C (APC). We have found that the N-terminal lectin-like domain (D1) of TM has unique antiinflammatory properties. TM, via D1, binds high-mobility group-B1 DNA-binding protein (HMGB1), a factor closely associated with necrotic cell damage following its release from the nucleus, thereby preventing in vitro leukocyte activation, in vivo UV irradiation-induced cutaneous inflammation, and in vivo lipopolysaccharide-induced lethality. Our data also demonstrate antiinflammatory properties of a peptide spanning D1 of TM and suggest its therapeutic potential. These findings highlight a novel mechanism, i.e., sequestration of mediators, through which an endothelial cofactor, TM, suppresses inflammation quite distinctly from its anticoagulant cofactor activity, thereby preventing the interaction of these mediators with cell surface receptors on effector cells in the vasculature.

The N-terminal domain of thrombomodulin sequesters high-mobility group-B1 protein, a novel antiinflammatory mechanism

Thrombomodulin (TM) is an endothelial anticoagulant cofactor that promotes thrombin-mediated formation of activated protein C (APC). We have found that the N-terminal lectin-like domain (D1) of TM has unique antiinflammatory properties. TM, via D1, binds high-mobility group-B1 DNA-binding protein (HMGB1), a factor closely associated with necrotic cell damage following its release from the nucleus, thereby preventing in vitro leukocyte activation, in vivo UV irradiation-induced cutaneous inflammation, and in vivo lipopolysaccharide-induced lethality. Our data also demonstrate antiinflammatory properties of a peptide spanning D1 of TM and suggest its therapeutic potential. These findings highlight a novel mechanism, i.e., sequestration of mediators, through which an endothelial cofactor, TM, suppresses inflammation quite distinctly from its anticoagulant cofactor activity, thereby preventing the interaction of these mediators with cell surface receptors on effector cells in the vasculature.

Thrombomodulin-protein C-EPCR system: integrated to regulate coagulation and inflammation

Late in the 18th century, William Hewson recognized that the formation of a clot is characteristic of many febrile, inflammatory diseases (Owen C. A History of Blood Coagulation. Rochester, Minnesota: Mayo Foundation; 2001). Since that time, there has been steady progress in our understanding of coagulation and inflammation, but it is only in the past few decades that the molecular mechanisms linking these 2 biologic systems have started to be delineated. Most of these can be traced to the vasculature, where the systems most intimately interact. Thrombomodulin (TM), a cell surface-expressed glycoprotein, predominantly synthesized by vascular endothelial cells, is a critical cofactor for thrombin-mediated activation of protein C (PC), an event further amplified by the endothelial cell protein C receptor (EPCR). Activated PC (APC), in turn, is best known for its natural anticoagulant properties. Recent evidence has revealed that TM, APC, and EPCR have activities that impact not only on coagulation but also on inflammation, fibrinolysis, and cell proliferation. This review highlights recent insights into the diverse functions of this complex multimolecular system and how its components are integrated to maintain homeostasis under hypercoagulable and/or proinflammatory stress conditions. Overall, the described advances underscore the usefulness of elucidating the relevant molecular pathways that link both systems for the development of novel therapeutic and diagnostic targets for a wide range of inflammatory diseases.

Crosstalk between inflammation and thrombosis

Inflammation shifts the hemostatic mechanisms in favor of thrombosis. Multiple mechanisms are at play including up regulation of tissue factor leading to the initiation of clotting, amplification of the clotting process by augmenting exposure of cellular coagulant phospholipids, inhibition of fibrinolysis by elevating plasminogen activator inhibitor 1 (PAI-1) and decreases in natural anticoagulant pathways, particularly targeted toward down regulation of the protein C anticoagulant pathway through multiple mechanisms. The decreased function of the natural anticoagulant pathways may be particularly problematic because these appear to play a role in dampening inflammatory responses. The protein C anticoagulant pathway provides a useful model for the impact of inflammation on coagulation. This pathway plays a major role in preventing microvascular thrombosis. The pathway is initiated when thrombin binds to thrombomodulin (TM) on the surface of the endothelium. An endothelial cell protein C receptor (EPCR) augments protein C activation by the thrombin-TM complex more than 10-fold in vivo. EPCR is shed from the endothelium by inflammatory mediators and thrombin. EPCR binds to activated neutrophils in a process that involves proteinase 3 and Mac-1 and appears to inhibit leukocyte extravisation. EPCR can undergo translocation from the plasma membrane to the nucleus where it redirects gene expression. During translocation it can carry activated protein C (APC) to the nucleus, possibly accounting for the ability of APC to modulate inflammatory mediator responses in the endothelium. TNF alpha and other inflammatory mediators can down-regulate EPCR and TM and IL-6 can depress levels of protein S in experimental animals. Inhibition of protein C pathway function increases cytokine elaboration, endothelial cell injury and leukocyte extravisation in response to endotoxin, processes that are decreased by infusion of APC. In vitro, APC inhibits TNF alpha elaboration from monocytes and to block leukocyte adhesion to selectins. Since thrombin can elicit many inflammatory responses in microvascular endothelium, loss of control of microvascular thrombin generation due to impaired protein C pathway function probably contributes to microvascular dysfunction in sepsis.

Beyond sepsis: activated protein C and ischemia-reperfusion injury

OBJECTIVE

To review potential clinical situations beyond sepsis in which activated protein C might be an effective treatment.

DATA SOURCE

Published articles between 1970 and 2003 on experimental and clinical studies of activation of both coagulation and inflammation in various disease states.

DATA SYNTHESIS AND CONCLUSION

The efficacy of activated protein C in sepsis might rely on the fact that it can modulate both coagulation and inflammation. Therefore, administration of activated protein C could be beneficial in disease states that are also characterized by the simultaneous activation of these systems. Ischemia-reperfusion injury of various organs may represent such a state. Indeed, the involvement of the protein C system has been demonstrated in various experimental studies of ischemia-reperfusion, including studies in renal ischemia-reperfusion syndromes, coronary atherosclerosis and acute coronary syndromes, and intestinal ischemia and reperfusion. In some of these models, activated protein C administration, or other interventions in the protein C system, was shown to be beneficial.

Novel functions of thrombomodulin in inflammation

The objective of this study was to review the mechanisms by which thrombomodulin (TM) may modulate inflammation. The data were taken from published research performed by other laboratories and our own experimental results. TM is a transmembrane glycoprotein receptor and cofactor for thrombin in the protein C anticoagulant system. Recent studies have revealed that TM has activities, both dependent and independent of either protein C or thrombin, that affect biological systems beyond the coagulation pathway. This review highlights recent insights, provided by in vitro and in vivo analyses, into how the unique structural domains of TM effectively modify coagulation, fibrinolysis, and inflammation in health and disease. A paradigm is presented to describe how these apparently distinct functions are integrated to maintain homeostasis under stress conditions. Finally, we explore the potential diagnostic and therapeutic utility of dissecting out the structure-function correlates of TM. We conclude that TM plays a central role in regulating not only hemostasis but also inflammation, thus providing a close link between these processes. Elucidation of the molecular mechanisms by which TM functions will likely provide novel targets for therapeutic intervention.

Thrombomodulin

Since its discovery as a critical cofactor in the initiation of the protein C (PC) anticoagulant pathway [1,2], biochemical and structural investigations, combined with in vivo analyses of genetically engineered mice have revealed new, and in part PC- and thrombin-independent aspects of thrombomodulin (TM) function in fibrinolysis and inflammation, and in embryogenesis. This review summarizes more recent structural and functional investigations of TM, gives an overview of the association of TM gene polymorphisms with human disease, and provides a synopsis of what is know about TM function in disease states of thrombosis, stroke, arteriosclerosis, and cancer. Newly emerging aspects of TM function in inflammation and embryogenesis are presented and discussed in detail.

Anti-monocyte chemoattractant protein-1 gene therapy attenuates renal injury induced by protein-overload proteinuria

It has been postulated that protein filtered through glomeruli activates tubular epithelial cells, which secrete vasoactive and inflammatory substances including chemokines, leading to tubulointerstitial renal injury. The present study was designed to investigate the role of monocyte chemoattractant protein-1 (MCP-1) in this process and to evaluate the effectiveness of a kidney-targeted gene transfer technique using hydrodynamic pressure. Naked plasmid encoding 7ND (an MCP-1 antagonist) or a control plasmid was introduced into the left kidney of rats. Three days after gene transfer (day 0), intraperitoneal administration of bovine serum albumin (10 mg/g body wt per day) was started and continued for 14 or 21 d. RT-PCR showed that 7ND mRNA was expressed only in the gene-transfected kidney. Immunostaining showed that 7ND protein was localized in the interstitial cells. Macrophage infiltration was significantly reduced in the left kidney of rats treated with 7ND on days 14 and 21. In the right kidney, such effects were not observed. 7ND also attenuated tubular damage and decreased the number of apoptotic cells. Computer-assisted analysis revealed that the areas positively stained for alpha-smooth muscle actin (alpha SMA), fibronectin-EDA, type I collagen, and collagen fibrils were significantly reduced in the 7ND-treated kidney on day 21. Furthermore, 7ND gene therapy significantly reduced MCP-1 and TGF-beta 1 mRNA expression. These results demonstrate that MCP-1 plays an important role in the development of tubulointerstitial inflammation, tubular damage, and fibrosis induced by proteinuria. The fact that 7ND gene therapy had little effect on the contralateral kidney indicates that 7ND acted locally. This strategy may have a potential usefulness as a gene therapy against tubulointerstitial renal injury.

Anticoagulant therapy in acute lung injury

OBJECTIVE

To review the rationale for evaluating anticoagulant therapies in acute lung injury (ALI) and to review selected data regarding the effectiveness of anticoagulants in animals and human patients with ALI and acute respiratory distress syndrome.

DATA SOURCES

Published literature on coagulation alterations and anticoagulant strategies in ALI during the past 25 yrs.

DATA EXTRACTION AND SYNTHESIS

In the lung, alveolar and interstitial fibrin deposition are the hallmarks of early phase ALI. Local procoagulant activity and reduced fibrinolysis constitute the rationale for anticoagulant use in the treatment of ALI. An activated complex of tissue factor and factor VIIa triggers procoagulant activity in the lung, with subsequent thrombin formation and fibrin deposition. Increased pulmonary vascular permeability and leukocyte accumulation have been successfully prevented in animals treated with tissue factor/activated factor VII pathway inhibitor. In humans, a phase II study evaluating tissue factor pathway inhibitor in the treatment of severe sepsis suggested that lung function in acute respiratory distress syndrome patients was improved. However, the phase III trial failed to demonstrate a survival benefit; data regarding respiratory dysfunction have not yet been published. Heparin, despite effectively inhibiting thrombin formation, has not shown consistent benefits in reducing lung injury, and its efficacy has not yet been evaluated in a controlled study. Antithrombin administration in animals has shown consistent benefits with ALI, but clinical studies have failed to demonstrate reductions in mortality and lung injury. Activated protein C administration has been shown to improve survival and lung function in both animal and clinical studies. Soluble thrombomodulin has been shown to improve ALI in animals, and it is currently being evaluated in humans with sepsis. Finally, plasminogen activators may improve gas exchange in ALI, but studies in humans are limited.

Pitavastatin-induced thrombomodulin expression by endothelial cells acts via inhibition of small G proteins of the Rho family

OBJECTIVE

3-hydroxyl-3-methyl coenzyme A reductase inhibitors (statins) can function to protect the vasculature in a manner that is independent of their lipid-lowering activity. The main feature of the antithrombotic properties of endothelial cells is an increase in the expression of thrombomodulin (TM) without induction of tissue factor (TF) expression. We investigated the effect of statins on the expression of TM and TF by endothelial cells.

METHODS AND RESULTS

The incubation of endothelial cells with pitavastatin led to a concentration- and time-dependent increase in cellular TM antigen and mRNA levels. In contrast, the expression of TF mRNA was not induced under the same conditions. A nuclear run-on study revealed that pitavastatin accelerates TM transcription rate. The stimulation of TM expression by pitavastatin was prevented by either mevalonate or geranylgeranylpyrophosphate. Specific inhibition of geranylgeranyltransferase-I and Rac/Cdc42 by GGTI-286 and Clostridium sordellii lethal toxin, respectively, enhanced TM expression, whereas inactivation of Rho by Clostridium botulinum C3 exoenzyme was ineffective.

CONCLUSIONS

Statins regulate TM expression via inhibition of small G proteins of the Rho family; Rac/Cdc42. A statin-mediated increase in TM expression by endothelial cells may contribute to the beneficial effects of statins on endothelial function.