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

Role of Vitamin K in Intestinal Health

Intestinal diseases, such as inflammatory bowel diseases (IBDs) and colorectal cancer (CRC) generally characterized by clinical symptoms, including malabsorption, intestinal dysfunction, injury, and microbiome imbalance, as well as certain secondary intestinal disease complications, continue to be serious public health problems worldwide. The role of vitamin K (VK) on intestinal health has drawn growing interest in recent years. In addition to its role in blood coagulation and bone health, several investigations continue to explore the role of VK as an emerging novel biological compound with the potential function of improving intestinal health. This study aims to present a thorough review on the bacterial sources, intestinal absorption, uptake of VK, and VK deficiency in patients with intestinal diseases, with emphasis on the effect of VK supplementation on immunity, anti-inflammation, intestinal microbes and its metabolites, antioxidation, and coagulation, and promoting epithelial development. Besides, VK-dependent proteins (VKDPs) are another crucial mechanism for VK to exert a gastroprotection role for their functions of anti-inflammation, immunomodulation, and anti-tumorigenesis. In summary, published studies preliminarily show that VK presents a beneficial effect on intestinal health and may be used as a therapeutic drug to prevent/treat intestinal diseases, but the specific mechanism of VK in intestinal health has yet to be elucidated.

A critical role of endothelial cell protein C receptor in the intestinal homeostasis in experimental colitis

Crohn’s disease and ulcerative colitis are the two forms of disorders of the human inflammatory bowel disease with unknown etiologies. Endothelial cell protein C receptor (EPCR) is a multifunctional and multiligand receptor, which is expressed on the endothelium and other cell types, including epithelial cells. Here, we report that EPCR is expressed in the colon epithelial cells, CD11c⁺, and CD21⁺/CD35⁺ myeloid cells surrounding the crypts in the colon mucosa. EPCR expression was markedly decreased in the colon mucosa during colitis. The loss of EPCR appeared to associate with increased disease index of the experimental colitis in mice. EPCR^−/− mice were more susceptible to dextran sulfate sodium (DSS)-induced colitis, manifested by increased weight loss, macrophage infiltration, and inflammatory cytokines in the colon tissue. DSS treatment of EPCR^−/− mice resulted in increased bleeding, bodyweight loss, anemia, fibrin deposition, and loss of colon epithelial and goblet cells. Administration of coagulant factor VIIa significantly attenuated the DSS-induced colon length shortening, rectal bleeding, bodyweight loss, and disease activity index in the wild-type mice but not EPCR^−/− mice. In summary, our data provide direct evidence that EPCR plays a crucial role in regulating the inflammation in the colon during colitis.

Human recombinant activated protein C-coated stent for the prevention of restenosis in porcine coronary arteries

Activated protein C (APC), an endogenous protein, inhibits inflammation and thrombosis and interrupts the coagulation cascade. Here, we investigated the effect of human recombinant APC on the development of neointimal hyperplasia in porcine coronary arteries. Yukon Choice bare metal stents were coated with 2.6 µg APC/mm(2). Under general anesthesia, APC-coated and bare stents were implanted in the left anterior descending and circumflex coronary arteries of 10 domestic pigs. During the 4-week follow-up, animals were treated with dual antiplatelet therapy and neointimal hyperplasia was evaluated via histology. Scanning electron microscopy indicated successful but unequal coating of stents with APC; nearly complete drug release occurred within 4 h. Enzyme-linked immunosorbent assay revealed that intracoronary stent implantation rapidly increased the levels of monocyte chemoattractant protein-1, an effect that was inhibited by APC release from the coated stent. Fibrin deposition and adventitial inflammation were significantly decreased 1 month after implanting APC-coated stents versus bare stents, paralleled by significantly smaller neointimal area (0.98 ± 0.92 vs. 1.44 ± 0.91 mm(2), P = 0.028), higher lumen area (3.47 ± 0.94 vs. 3.06 ± 0.91 mm(2), P = 0.046), and lower stenosis area (22.2 ± 21.2% vs. 32.1 ± 20.1%, P = 0.034). Endothelialization was complete with APC-coated but not bare (90%) stents. P-selectin immunostaining revealed significantly fewer activated endothelial cells in the neointima in the APC group (4.6 ± 1.9 vs. 11.6 ± 4.1%, P < 0.001). Thus, short exposure of coronary arteries to APC reduced inflammatory responses, neointimal proliferation, and in-stent restenosis, offering a promising therapy to improve clinical outcomes of coronary stenting. However, coating stents with APC for prolonged, controlled drug release remains technically challenging.

Engineering activated protein C to maximize therapeutic efficacy

The anticoagulant-activated protein C (APC) acts not solely as a crucial regulator of thrombus formation following vascular injury, but also as a potent signalling enzyme with important functions in the control of both acute and chronic inflammatory disease. These properties have been exploited to therapeutic effect in diverse animal models of inflammatory disease, wherein recombinant APC administration has proven to effectively limit disease progression. Subsequent clinical trials led to the use of recombinant APC (Xigris) for the treatment of severe sepsis. Although originally deemed successful, Xigris was ultimately withdrawn due to lack of efficacy and an unacceptable bleeding risk. Despite this apparent failure, the problems that beset Xigris usage may be tractable using protein engineering approaches. In this review, we detail the protein engineering approaches that have been utilized to improve the therapeutic characteristics of recombinant APC, from early studies in which the distinct anti-coagulant and signalling activities of APC were separated to reduce bleeding risk, to current attempts to enhance APC cytoprotective signalling output for increased therapeutic efficacy at lower APC dosage. These novel engineered variants represent the next stage in the development of safer, more efficacious APC therapy in disease settings in which APC plays a protective role.

Tissue hemostasis and chronic inflammation in colon biopsies of patients with inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterized by a chronic inflammation accompanied by procoagulation settings. However, tissue hemostasis in IBD patients was only incidentally reported. Accordingly, the current study characterizes changes in tissue hemostasis components in a colon inflammatory setting. Serial cryostat sections of endoscopic mucosal biopsy specimens taken from 26 consecutive IBD patients diagnosed de novo and normal colon resection specimens taken from 6 patients were immunohistochemically stained with monoclonal anti-human tissue factor (TF), tissue factor pathway inhibitor (TFPI), thrombomodulin (TM), as well as CD3 and CD68 positive cells. The hemostatic components studied differed significantly from the control subjects. Up-regulation predominated in the case of TF while down-regulation was mainly found in TM and TFPI in IBD. In the control sections, TF was observed in a few fibroblast-shaped cells in the lamina propria, while in the majority of IBD sections, TF positively stained small microvessels, infiltrating mononuclear cells and fibroblast-shaped cells tightly surrounding the colon crypts. Thrombomodulin intensively stained the endothelium of the small capillary vessels in the control, whereas such staining mainly accompanied infiltrating mononuclear cells of the IBD subjects. Tissue factor pathway inhibitor positively stained the endothelium of the small capillary vessels in the control group, whereas in the IBD group endothelial cells presented only weak TFPI staining. The mean number of CD3-positive lymphocytes in IBD was 23.3 ± 14.3, but the mean number of CD68-positive cells was 114.5 ± 55.8. In the control sections, it was 4.1 ± 2.4 and 39.6 ± 17.9, respectively. There was no relationship between CD3 and CD68 (+) cells and the hemostasis markers studied. The results of the current study indicate a shift of tissue hemostasis toward the procoagulant state irrespective of the severity of inflammatory infiltration. In addition, TF distribution in the colon sections of IBD patients may indicate a role in the restoration of the barrier function in injured intestinal mucosa.

Unexpected role of anticoagulant protein C in controlling epithelial barrier integrity and intestinal inflammation

The protein C (PC) pathway is a well-characterized coagulation system. Endothelial PC receptors and thrombomodulin mediate the conversion of PC to its activated form, a potent anticoagulant and anti-inflammatory molecule. Here we show that the PC pathway is expressed on intestinal epithelial cells. The epithelial expression of PC and endothelial PC receptor is down-regulated In patients with inflammatory bowel disease. PC(-/-)/PC(Tg) mice, expressing only 3% of WT PC, developed spontaneous intestinal inflammation and were prone to severe experimental colitis. These mice also demonstrated spontaneous elevated production of inflammatory cytokines and increased intestinal permeability. Structural analysis of epithelial tight junction molecules revealed that lack of PC leads to decreased JAM-A and claudin-3 expression and an altered pattern of ZO-1 expression. In vitro, treatment of epithelial cells with activated PC led to protection of tight junction disruption induced by TNF-α, and in vivo, topical treatment with activated PC led to mucosal healing and amelioration of colitis. Taken together, these findings demonstrate that the PC pathway is a unique system involved in controlling intestinal homeostasis and inflammation by regulating epithelial barrier function.

Role of tumor necrosis factor-α in the extraintestinal thrombosis associated with colonic inflammation

BACKGROUND

Inflammatory bowel diseases (IBDs) are associated with a hypercoagulable state and an increased risk of thromboembolism, with accelerated thrombus formation occurring both within the inflamed bowel and in distant tissues. While the IBD-associated prothrombogenic state has been linked to the inflammatory response, the mediators that link inflammation and thrombosis remain poorly defined. The objective of this study was to assess the role of tumor necrosis factor alpha (TNF-α) in the enhanced extraintestinal microvascular thrombosis that accompanies colonic inflammation.

METHODS

TNF-α concentration was measured in plasma, colon, and skeletal muscle of control mice and in mice with dextran sodium sulfate (DSS)-induced colitis. A light/dye injury method was used to induce microvascular thrombosis in cremaster microvessels. The effects of exogenous TNF-α on thrombus formation were determined in control mice. DSS-enhanced thrombus formation was evaluated in wildtype (WT) mice treated with an anti-TNF-α antibody (±an anti-IL-1β antibody) and in TNF-α receptor-deficient (TNFr(-/-) ) mice.

RESULTS

DSS colitis enhanced thrombus formation in cremaster arterioles. A similar response was produced by TNF-α administration in control mice. TNF-α concentration was elevated in plasma, colon, and skeletal muscle. Immunoblockade of TNF-α or genetic deficiency of the TNF-α receptor blunted the thrombotic response of arterioles to DSS colitis. Additional protection was noted in mice receiving antibodies to both TNF-α and IL-1β.

CONCLUSIONS

Our findings implicate TNF-α in the enhanced microvascular thrombosis that occurs in extraintestinal tissue during colonic inflammation, and suggests that the combined actions of TNF-α and IL-1β accounts for most of the colitis-enhanced thrombotic response.

A novel integrative network approach to understand the interplay between cardiovascular disease and other complex disorders

There is accumulating evidence that the proteins encoded by the genes associated with a common disorder interact with each other, participate in similar pathways and share GO terms. It has been anticipated that the functional modules in a disease related functional linkage network can be integrated with bibliomics to reveal association with other complex disorders. In this study, the cardiovascular disease functional linkage network (CFN) containing 1536 nodes and 3345 interactions was constructed using proteins encoded by 234 genes associated with the disease. Integration of CFN with bibliomics showed that 227 out of 566 functional modules are significantly associated with one or more diseases. Analysis of functional modules revealed the possible regulatory roles of SP1 and CXCL12 in the pathogenesis of cardiovascular disease (CVD) and modulation of their activities may be considered as potential therapeutic tools. The integration of CFN with bibliomics also indicated significant relations of CVD with other complex disorders. In a stratified map the members of 227 functional modules and 58 diseases in 15 disease classes were combined. In this map, leprosy, listeria monocytogenes, myasthenia, hemorrhagic diathesis and Protein S deficiency, which were not previously reported to be associated with CVD, showed significant associations. Several cancers arising from epithelial cells were also found to be linked to other diseases through hub proteins, VEGFA and PTGS2.

Haemostatic system in inflammatory bowel diseases: New players in gut inflammation

Inflammation and coagulation constantly influence each other and are constantly in balance. Emerging evidence supports this statement in acute inflammatory diseases, such as sepsis, but it also seems to be very important in chronic inflammatory settings, such as inflammatory bowel disease (IBD). Patients with Crohn’s disease and ulcerative colitis have an increased risk of thromboembolic events, and several abnormalities concerning coagulation components occur in the endothelial cells of intestinal vessels, where most severe inflammatory abnormalities occur. The aims of this review are to update and classify the type of coagulation system abnormalities in IBD, and analyze the strict and delicate balance between coagulation and inflammation at the mucosal level. Recent studies on possible therapeutic applications arising from investigations on coagulation abnormalities associated with IBD pathogenesis will also be briefly presented and critically reviewed.

Activated protein C action in inflammation

Activated protein C (APC) is a natural anticoagulant that plays an important role in coagulation homeostasis by inactivating the procoagulation factor Va and VIIIa. In addition to its anticoagulation functions, APC also has cytoprotective effects such as anti-inflammatory, anti-apoptotic, and endothelial barrier protection. Recently, a recombinant form of human APC (rhAPC or drotrecogin alfa activated; known commercially as 'Xigris') was approved by the US Federal Drug Administration for treatment of severe sepsis associated with a high risk of mortality. Sepsis, also known as systemic inflammatory response syndrome (SIRS) resulting from infection, is a serious medical condition in critical care patients. In sepsis, hyperactive and dysregulated inflammatory responses lead to secretion of pro- and anti-inflammatory cytokines, activation and migration of leucocytes, activation of coagulation, inhibition of fibrinolysis, and increased apoptosis. Although initial hypotheses focused on antithrombotic and profibrinolytic functions of APC in sepsis, other agents with more potent anticoagulation functions were not effective in treating severe sepsis. Furthermore, APC therapy is also associated with the risk of severe bleeding in treated patients. Therefore, the cytoprotective effects, rather than the anticoagulant effect of APC are postulated to be responsible for the therapeutic benefit of APC in the treatment of severe sepsis.

The protein C pathway and pathologic processes

Alterations in expression of protein C (PC) pathway components have been identified in patients with active inflammatory disease states. While the PC pathway plays a pivotal role in regulating coagulation and fibrinolysis, activated PC (aPC) also exhibits cytoprotective properties. For example, PC-deficient mice challenged in septic/endotoxemic models exhibit phenotypes that include hypotension, disseminated intravascular coagulation, elevated inflammatory mediators, neutrophil adhesion to the microvascular endothelium, and loss of protective endothelial and epithelial cell barriers. Further, inflammatory bowel disease has been correlated with diminished endothelial PC receptor and thrombomodulin levels in the intestinal mucosa. Downregulated expression of the cofactor, protein S, as well as PC, is also associated with ischemic stroke. Studies to elucidate further the structural elements that differentiate the various functions of PC will serve to identify novel therapeutic approaches toward regulating these and other diseases.