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

The Redox Protein High-Mobility Group Box 1 in Cell Death and Cancer

Significance: As a redox-sensitive protein, high-mobility group box 1 (HMGB1) is implicated in regulating stress responses to oxidative damage and cell death, which are closely related to the pathology of inflammatory diseases, including cancer. Recent Advances: HMGB1 is a nonhistone nuclear protein that acts as a deoxyribonucleic acid chaperone to control chromosomal structure and function. HMGB1 can also be released into the extracellular space and function as a damage-associated molecular pattern protein during cell death, including during apoptosis, necrosis, necroptosis, pyroptosis, ferroptosis, alkaliptosis, and cuproptosis. Once released, HMGB1 binds to membrane receptors to shape immune and metabolic responses. In addition to subcellular localization, the function and activity of HMGB1 also depend on its redox state and protein posttranslational modifications. Abnormal HMGB1 plays a dual role in tumorigenesis and anticancer therapy (e.g., chemotherapy, radiation therapy, and immunotherapy) depending on the tumor types and stages. Critical Issues: A comprehensive understanding of the role of HMGB1 in cellular redox homeostasis is important for deciphering normal cellular functions and pathological manifestations. In this review, we discuss compartmental-defined roles of HMGB1 in regulating cell death and cancer. Understanding these advances may help us develop potential HMGB1-targeting drugs or approaches to treat oxidative stress-related diseases or pathological conditions. Future Directions: Further studies are required to dissect the mechanism by which HMGB1 maintains redox homeostasis under different stress conditions. A multidisciplinary effort is also required to evaluate the potential applications of precisely targeting the HMGB1 pathway in human health and disease. Antioxid. Redox Signal. 39, 569-590.

Circulating Histones in Sepsis: Potential Outcome Predictors and Therapeutic Targets

Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection and is associated with high morbidity and mortality. Circulating histones (CHs), a group of damage-associated molecular pattern molecules mainly derived from neutrophil extracellular traps, play a crucial role in sepsis by mediating inflammation response, organ injury and death through Toll-like receptors or inflammasome pathways. Herein, we first elucidate the molecular mechanisms of histone-induced inflammation amplification, endothelium injury and cascade coagulation activation, and discuss the close correlation between elevated level of CHs and disease severity as well as mortality in patients with sepsis. Furthermore, current state-of-the-art on anti-histone therapy with antibodies, histone-binding proteins (namely recombinant thrombomodulin and activated protein C), and heparin is summarized to propose promising approaches for sepsis treatment.

Proximate Mediators of Microvascular Dysfunction at the Blood-Brain Barrier: Neuroinflammatory Pathways to Neurodegeneration

Current projections are that by 2050 the numbers of people aged 65 and older with Alzheimer's disease (AD) in the US may increase threefold while dementia is projected to double every 20 years reaching ~115 million by 2050. AD is clinically characterized by progressive dementia and neuropathologically by neuronal and synapse loss, accumulation of amyloid plaques, and neurofibrillary tangles (NFTs) in specific brain regions. The preclinical or presymptomatic stage of AD-related brain changes may begin over 20 years before symptoms occur, making development of noninvasive biomarkers essential. Distinct from neuroimaging and cerebrospinal fluid biomarkers, plasma or serum biomarkers can be analyzed to assess (i) the presence/absence of AD, (ii) the risk of developing AD, (iii) the progression of AD, or (iv) AD response to treatment. No unifying theory fully explains the neurodegenerative brain lesions but neuroinflammation (a lethal stressor for healthy neurons) is universally present. Current consensus is that the earlier the diagnosis, the better the chance to develop treatments that influence disease progression. In this article we provide a detailed review and analysis of the role of the blood-brain barrier (BBB) and damage-associated molecular patterns (DAMPs) as well as coagulation molecules in the onset and progression of these neurodegenerative disorders.

Novel Mechanisms of Herbal Therapies for Inhibiting HMGB1 Secretion or Action

High mobility group box 1 (HMGB1) is an evolutionarily conserved protein and is constitutively expressed in virtually all types of cells. In response to microbial infections, HMGB1 is secreted from activated immune cells to orchestrate rigorous inflammatory responses. Here we review the distinct mechanisms by which several herbal components inhibit HMGB1 action or secretion, such as by modulating inflammasome activation, autophagic degradation, or endocytic uptake. In light of the reciprocal interactions between these cellular processes, it is possible to develop more effective combinational herbal therapies for the clinical management of inflammatory diseases.

The efficacy of recombinant human soluble thrombomodulin for the treatment of shiga toxin-associated hemolytic uremic syndrome model mice

BACKGROUND

Recombinant human soluble thrombomodulin (rhTM) is a promising therapeutic natural anticoagulant that is comparable to antithrombin, tissue factor pathway inhibitor and activated protein C. In order to clarify the efficacy of rhTM for the treatment of typical hemolytic uremic syndrome (t-HUS), we examined changes in renal damage in t-HUS mice treated with rhTM or vehicle alone.

METHODS

We used severe and moderate t-HUS mice injected with shiga toxin (Stx) and lipopolysaccharide (LPS). The severe t-HUS mice were divided into two subgroups [an rhTM subgroup (Group A) and a saline subgroup (Group B)] along with the moderate t-HUS mice [an rhTM subgroup (Group C) and a saline subgroup (Group D)]. Groups E and F were healthy mice treated with rhTM or saline, respectively.

RESULTS

All mice in Group B died at 80-90 h post-administration of Stx2 and LPS whereas all mice in Group A remained alive. Loss of body weight, serum creatinine level, endothelial injury and mesangiolysis scores at 24 h after administration in the t-HUS mice treated with rhTM were lower than those in t-HUS mice treated with saline. The levels of hemoglobin at 6 h and platelet counts at 24 h after administration in Group A were higher than those in Group B. Serum interleukin (IL)-6, IL-1β and tumor necrotic factor (TNF)-α levels at 24 h after administration in Group A were lower than those in Group B. Serum C5b-9 levels at 24 h after the administration and serum fibrinogen degradation product (FDP) at 72 h after the administration of Stx2 and LPS were lower in Group A than in Group B.

CONCLUSIONS

These results indicate that rhTM might afford an efficacious treatment for t-HUS model mice via the inhibition of further thrombin formation and amelioration of hypercoagulant status.

Thrombomodulin in the management of acute cholangitis-induced disseminated intravascular coagulation

AIM: To evaluate the need for thrombomodulin (rTM) therapy for disseminated intravascular coagulation (DIC) in patients with acute cholangitis (AC)-induced DIC.

METHODS: Sixty-six patients who were diagnosed with AC-induced DIC and who were treated at our hospital were enrolled in this study. The diagnoses of AC and DIC were made based on the 2013 Tokyo Guidelines and the DIC diagnostic criteria as defined by the Japanese Association for Acute Medicine, respectively. Thirty consecutive patients who were treated with rTM between April 2010 and September 2013 (rTM group) were compared to 36 patients who were treated without rTM (before the introduction of rTM therapy at our hospital) between January 2005 and January 2010 (control group). The two groups were compared in terms of patient characteristics at the time of DIC diagnosis (including age, sex, primary disease, severity of cholangitis, DIC score, biliary drainage, and anti-DIC drugs), the DIC resolution rate, DIC score, the systemic inflammatory response syndrome (SIRS) score, hematological values, and outcomes. Using logistic regression analysis based on multivariate analyses, we also examined factors that contributed to persistent DIC.

RESULTS: There were no differences between the rTM group and the control group in terms of the patients’ backgrounds other than administration. DIC resolution rates on day 9 were higher in the rTM group than in the control group (83.3% vs 52.8%, P < 0.01). The mean DIC scores on day 7 were lower in the rTM group than in the control group (2.1 ± 2.1 vs 3.5 ± 2.3, P = 0.02). The mean SIRS scores on day 3 were significantly lower in the rTM group than in the control group (1.1 ± 1.1 vs 1.8 ± 1.1, P = 0.03). Mortality on day 28 was 13.3% in the rTM group and 27.8% in the control group; these rates were not significantly different (P = 0.26). Multivariate analysis identified only the absence of biliary drainage as significantly associated with persistent DIC (P < 0.01, OR = 12, 95%CI: 2.3-60). Although the difference did not reach statistical significance, primary diseases (malignancies) (P = 0.055, OR = 3.9, 95%CI: 0.97-16) and the non-use of rTM had a tendency to be associated with persistent DIC (P = 0.08, OR = 4.3, 95%CI: 0.84-22).

CONCLUSION: The add-on effects of rTM are anticipated in the treatment of AC-induced DIC, although biliary drainage for AC remains crucial.

Anti-inflammatory functions of protein C require RAGE and ICAM-1 in a stimulus-dependent manner

By binding β₂-integrins both ICAM-1 and the receptor for advanced glycation end products (RAGE) mediate leukocyte recruitment in a stimulus-dependent manner. Using different inflammatory mouse models we investigated how RAGE and ICAM-1 are involved in anti-inflammatory functions of protein C (PC; Ceprotin, 100 U/kg). We found that, depending on the stimulus, RAGE and ICAM-1 are cooperatively involved in PC-induced inhibition of leukocyte recruitment in cremaster models of inflammation. During short-term proinflammatory stimulation (trauma, fMLP, and CXCL1), ICAM-1 is more important for mediation of anti-inflammatory effects of PC, whereas RAGE plays a major role after longer proinflammatory stimulation (TNFα). In contrast to WT and Icam-1^−/− mice, PC had no effect on bronchoalveolar neutrophil emigration in RAGE^−/− mice during LPS-induced acute lung injury, suggesting that RAGE critically mediates PC effects during acute lung inflammation. In parallel, PC treatment effectively blocked leukocyte recruitment and improved survival of WT mice and Icam-1-deficient mice in LPS-induced endotoxemia, but failed to do so in RAGE-deficient mice. Exploring underlying mechanisms, we found that PC is capable of downregulating intracellular RAGE and extracellular ICAM-1 in endothelial cells. Taken together, our data show that RAGE and ICAM-1 are required for the anti-inflammatory functions of PC.

How does the brain limit the severity of inflammation and tissue injury during bacterial meningitis?

The most devastating CNS bacterial infection, bacterial meningitis, has both acute and long-term neurologic consequences. The CNS defends itself against bacterial invasion through a combination of physical barriers (i.e. blood-brain barrier, meninges, and ependyma), which contain macrophages that express a range of pattern-recognition receptors that detect pathogens before they gain access to the CNS and cerebrospinal fluid. This activates an antipathogen response consisting of inflammatory cytokines, complement, and chemoattractants. Regulation of the antipathogen inflammatory response is essential for preventing irreversible brain injury and protecting stem cell populations in the ventricle wall. The severity of brain inflammation is regulated by the clearance of apoptotic inflammatory cells and neurons. Death signaling pathways are expressed by glia to stimulate apoptosis of neutrophils, lymphocytes, and damaged neurons and to regulate in flammation and remove necrotic cells. The emerging group of neuroimmunoregulatory molecules adjusts the balance of the anti-inflammatory and proinflammatory response to provide optimal conditions for effective clearance of pathogens and apoptotic cells but reduce the severity of the inflammatory response to prevent injury to brain cells, including stem cell populations. The neuroimmunoregulatory molecules and other CNS anti-inflammatory pathways represent potential therapeutic targets capable of reducing brain injury caused by bacterial infection.

Lack of the lectin-like domain of thrombomodulin worsens Shiga toxin-associated hemolytic uremic syndrome in mice

Shiga toxin (Stx)-producing Escherichia coli is a primary cause of diarrhea-associated hemolytic uremic syndrome (HUS), a disorder of thrombocytopenia, microangiopathic hemolytic anemia, and acute renal failure. The pathophysiology of renal microvascular thrombosis in Stx-HUS is still ill-defined. Based on evidence that abnormalities in thrombomodulin (TM), an anticoagulant endothelial glycoprotein that modulates complement and inflammation, predispose to atypical HUS, we assessed whether impaired TM function may adversely affect evolution of Stx-HUS. Disease was induced by coinjection of Stx2/LPS in wild-type mice (TM(wt/wt)) and mice that lack the lectin-like domain of TM (TM(LeD/LeD)), which is critical for its anti-inflammatory and cytoprotective properties. After Stx2/LPS, TM(LeD/LeD) mice exhibited more severe thrombocytopenia and renal dysfunction than TM(wt/wt) mice. Lack of lectin-like domain of TM resulted in a stronger inflammatory reaction after Stx2/LPS with more neutrophils and monocytes/macrophages infiltrating the kidney, associated with PECAM-1 and chemokine upregulation. After Stx2/LPS, intraglomerular fibrin(ogen) deposits were detected earlier in TM(LeD/LeD) than in TM(wt/wt) mice. More abundant fibrin(ogen) deposits were also found in brain and lungs. Under basal conditions, TM(LeD/LeD) mice exhibited excess glomerular C3 deposits, indicating impaired complement regulation in the kidney that could lead to local accumulation of proinflammatory products. TM(LeD/LeD) mice with HUS had a higher mortality rate than TM(wt/wt) mice. If applicable to humans, these findings raise the possibility that genetic or acquired TM defects might have an impact on the severity of microangiopathic lesions after exposure to Stx-producing E. coli infections and raise the potential for using soluble TM in the treatment of Stx-HUS.

Danger signals activating the immune response after trauma

Sterile injury can cause a systemic inflammatory response syndrome (SIRS) that resembles the host response during sepsis. The inflammatory response following trauma comprises various systems of the human body which are cross-linked with each other within a highly complex network of inflammation. Endogenous danger signals (danger-associated molecular patterns; DAMPs; alarmins) as well as exogenous pathogen-associated molecular patterns (PAMPs) play a crucial role in the initiation of the immune response. With popularization of the “danger theory,” numerous DAMPs and PAMPs and their corresponding pathogen-recognition receptors have been identified. In this paper, we highlight the role of the DAMPs high-mobility group box protein 1 (HMGB1), interleukin-1α (IL-1α), and interleukin-33 (IL-33) as unique dual-function mediators as well as mitochondrial danger signals released upon cellular trauma and necrosis.

Thrombomodulin: a bifunctional modulator of inflammation and coagulation in sepsis

Deregulated interplay between inflammation and coagulation plays a pivotal role in the pathogenesis of sepsis. Therapeutic approaches that simultaneously target both inflammation and coagulation hold great promise for the treatment of sepsis. Thrombomodulin is an endogenous anticoagulant protein that, in cooperation with protein C and thrombin-activatable fibrinolysis inhibitor, serves to maintain the endothelial microenvironment in an anti-inflammatory and anticoagulant state. A recombinant soluble form of thrombomodulin has been approved to treat patients suffering from disseminated intravascular coagulation (DIC) and has thus far shown greater therapeutic potential than heparin. A phase II clinical trial is currently underway in the USA to study the efficacy of thrombomodulin for the treatment of sepsis with DIC complications. This paper focuses on the critical roles that thrombomodulin plays at the intersection of inflammation and coagulation and proposes the possible existence of interactions with integrins via protein C. Finally, we provide a rationale for the clinical application of thrombomodulin for alleviating sepsis.

Gradual increase of high mobility group protein b1 in the lungs after the onset of acute exacerbation of idiopathic pulmonary fibrosis

The pathogenesis of acute exacerbation of idiopathic pulmonary fibrosis (IPF) remains to be elucidated. To evaluate the roles of inflammatory mediators in acute exacerbation, the concentrations of high mobility group protein B1 (HMGB1), a chief mediator of acute lung injury, and 18 inflammatory cytokines were measured in the bronchoalveolar lavage fluid, serially sampled from seven IPF patients after the onset of acute exacerbation. HMGB1 gradually increased in the alveolar fluid after the onset of acute exacerbation, in positive correlation with monocytes chemotactic protein-1 (MCP-1), a potent fibrogenic mediator. In the lung tissues of eight IPF patients autopsied after acute exacerbation, intense cytoplasmic staining for HMGB1 was observed in the alveolar epithelial cells in alveolar capillary augmented lesions, where the capillary endothelial cells remarkably reduced the expression of thrombomodulin, an intrinsic antagonist of HMGB1. These results suggest pathogenic roles for HMGB1 and MCP-1 in the late phase of acute exacerbation of IPF.

Using Complementary and Alternative Medicines to Target the Host Response during Severe Influenza

It is now accepted that an overwhelming inflammatory response is the cause of human deaths from avian H5N1 influenza infection. With this in mind we sought to examine the literature for examples of complementary and alternative medicines that reduce inflammation, and to place the results of this search in the context of our own work in a mouse model of influenza disease, using a pharmaceutical agent with anti-inflammatory properties. Two Chinese herbs, Angelica sinensis (Dang Gui) and Salvia miltiorrhiza (Danshen), have been recently shown to protect mice during lethal experimental sepsis via inhibition of the novel inflammatory cytokine High Mobility Group Box 1 protein (HMGB1). Biochanin A, a ligand of the peroxisome proliferator activated receptors (PPAR) alpha and gamma and the active isoflavone in Trifolium pratense (red clover), has anti-inflammatory properties, and thus could be used as an influenza treatment. This is of great interest since we have recently shown that gemfibrozil, a drug used to treat hyperlipidemia in humans and a synthetic ligand of PPAR alpha, significantly reduces the mortality associated with influenza infections in mice. The inflammation-modulating abilities of these natural agents should be considered in light of what is now known about the mechanisms of fatal influenza, and tested as potential candidates for influenza treatments in their own right, or as adjunct treatments to antivirals.

HMGB1 contributes to kidney ischemia reperfusion injury

High-mobility group box 1 (HMGB1), a nuclear factor released extracellularly as an inflammatory cytokine, is an endogenous ligand for Toll-like receptor 4 (TLR4). TLR4 activation mediates kidney ischemia-reperfusion injury (IRI), but whether HMGB1 contributes to IRI is unknown. Here, treating wild-type mice with neutralizing anti-HMGB1 antibody protected them against kidney IRI, evidenced by lower serum creatinine and less tubular damage than untreated mice. Mice treated with anti-HMGB1 had significantly less tubulointerstitial infiltration by neutrophils (day 1) and macrophages (day 5) and markedly reduced apoptosis of tubular epithelial cells. Furthermore, anti-HMGB1 antibody-treated IRI kidneys had significantly lower levels of IL-6, TNFα, and monocyte chemoattractant protein 1 (MCP1). mRNA, which are downstream of HMGB1. Conversely, administration of rHMGB1 after reperfusion exacerbated kidney IRI in wild-type mice. TLR4 deficient (TLR4(-/-)) mice were protected against kidney IRI; administration of neither anti-HMGB1 antibody nor rHMGB1 affected this renoprotection. In conclusion, endogenous HMGB1 promotes kidney damage after IRI, possibly through the TLR4 pathway. Administration of a neutralizing antibody to HMGB1 either before or soon after ischemia-reperfusion affords significant protection, suggesting therapeutic potential for acute kidney injury.

DAMPening inflammation by modulating TLR signalling

Damage-associated molecular patterns (DAMPs) include endogenous intracellular molecules released by activated or necrotic cells and extracellular matrix (ECM) molecules that are upregulated upon injury or degraded following tissue damage. DAMPs are vital danger signals that alert our immune system to tissue damage upon both infectious and sterile insult. DAMP activation of Toll-like receptors (TLRs) induces inflammatory gene expression to mediate tissue repair. However, DAMPs have also been implicated in diseases where excessive inflammation plays a key role in pathogenesis, including rheumatoid arthritis (RA), cancer, and atherosclerosis. TLR activation by DAMPs may initiate positive feedback loops where increasing tissue damage perpetuates pro-inflammatory responses leading to chronic inflammation. Here we explore the current knowledge about distinct signalling cascades resulting from self TLR activation. We also discuss the involvement of endogenous TLR activators in disease and highlight how specifically targeting DAMPs may yield therapies that do not globally suppress the immune system.

Complement factor H, a marker of self protects against experimental autoimmune encephalomyelitis

The CNS innate immune response is a "double-edged sword" representing a fine balance between protective antipathogen responses and detrimental neurocytotoxic effects. Hence, it is important to identify the key regulatory mechanisms involved in the control of CNS innate immunity and which could be harnessed to explore novel therapeutic avenues. In analogy to the newly described neuroimmune regulatory proteins also known as "don't eat me" signals (CD200, CD47, CD22, fractalkine, semaphorins), we herein identify the key role of complement regulator factor H (fH) in controlling neuroinflammation initiated in an acute mouse model of Ab-dependent experimental autoimmune encephalomyelitis. Mouse fH was found to be abundantly expressed by primary cultured neurons and neuronal cell lines (N1E115 and Neuro2a) at a level comparable to BV2 microglia and CLTT astrocytes. Mouse neurons expressed other complement regulators crry and low levels of CD55. In the brain, the expression of fH was localized to neuronal bodies and axons, endothelial cells, microglia but not oligodendrocytes and myelin sheaths and was dramatically reduced in inflammatory experimental autoimmune encephalomyelitis settings. When exogenous human fH was administered to disease Ab-dependent experimental autoimmune encephalomyelitis animals, there was a significant decrease in clinical score, inflammation, and demyelination, as compared with PBS-injected animals. We found that the accumulation of human fH in the brain parenchyma protected neurons from complement opsonization, axonal injury, and leukocyte infiltration. Our data argue for a key regulatory activity of fH in neuroprotection and provide novel therapeutic avenues for CNS chronic inflammatory diseases.

Thrombomodulin suppresses invasiveness of HT1080 tumor cells by reducing plasminogen activation on the cell surface through activation of thrombin-activatable fibrinolysis inhibitor

Cell malignancy is negatively correlated with the expression of thrombomodulin (TM), a thrombin receptor expressed on the surface of various cells, including tumor cells. TM accelerates thrombin-activatable fibrinolysis inhibitor (TAFI) activation catalyzed by thrombin. The active form of TAFI (TAFIa) contributes to inhibition of plasmin formation through its carboxypeptidase B (CPB)-like activity. Here, we examined whether TM- and tumor cell-dependent TAFI activation participates in controlling pericellular fibrinolysis and cell invasion. Human fibrosarcoma HT1080 cells retained the ability to activate both prothrombin and plasminogen, but did not express TM. HT1080 cells mediated activation of TAFI in plasma in the presence of soluble-type TM (sTM) through cell-dependent prothrombin activation. HT1080 cells stably expressing TM (TM-HT1080) mediated plasma TAFI activation without added sTM, but HT1080 (wild-type) and Mock-transfected HT1080 cells (Mock) did not. Production of TAFIa suppressed cell-mediated plasminogen activation. Matrigel invasion by wild-type and Mock cells was enhanced two-fold by diluted plasma (10%), whereas the plasma-induced invasion of TM-HT1080 cells (65% of wild-type invasion) was lower than those of wild-type and Mock cells. Cell invasion by TM-HT1080 was partially enhanced by addition of a TAFIa/CPB inhibitor. These results suggest that TM suppresses pericellular fibrinolysis and plasma-induced tumor cell invasion, and that it is mediated, at least in part, by plasma TAFI activation.

Significance of thrombomodulin release from gingival epithelial cells in periodontitis patients

BACKGROUND AND OBJECTIVE

Thrombomodulin, a cell transmembrane glycoprotein, binds to thrombin and converts it from a procoagulant protease to an anticoagulant enzyme that activates protein C. Thrombomodulin is very important in regulating the function of thrombin. Elevated soluble thrombomodulin is present in the gingival crevicular fluid of subjects with periodontitis. The objective of the present study was to investigate the mechanisms about the elevated soluble thrombomodulin in gingival crevicular fluid.

MATERIAL AND METHODS

Gingival sections from six patients with chronic periodontitis and from three periodontally healthy subjects were immunostained for thrombomodulin detection. Thrombomodulin levels were investigated in the gingival crevicular fluid of 11 subjects with chronic periodontitis. The effects of neutrophil enzymes on thrombomodulin release and on thrombomodulin in the gingival crevicular fluid were examined by an enzyme-linked immunosorbent assay or by Western blotting.

RESULTS

The expression of gingival epithelial thrombomodulin was lost or decrease near infiltrating neutrophils. Thrombomodulin was rapidly released from gingival epithelial cells by neutrophil enzymes, and gingival crevicular fluid with periodontitis included the proteolytic cleavage thrombomodulin using immunoblotting analysis. The thrombomodulin release was not caused by rapid cell damage, on lactate dehydrogenase assay. There were significant differences in thrombomodulin content between gingival crevicular fluid samples from healthy and diseased sites, regardless of the degree of probing depth.

CONCLUSION

Neutrophil enzymes induced rapid thrombomodulin release from the membrane surface of gingival epithelial cells. This might explain the thrombomodulin increase in gingival crevicular fluid with local diseased gingiva. Elevation of thrombomodulin in gingival crevicular fluid may be a potential marker of epithelial cell membrane injury.

High-mobility group box 1 restores cardiac function after myocardial infarction in transgenic mice

AIMS

High-mobility group box 1 (HMGB1) is a nuclear DNA-binding protein and is released from necrotic cells, inducing inflammatory responses and promoting tissue repair and angiogenesis. To test the hypothesis that HMGB1 enhances angiogenesis and restores cardiac function after myocardial infarction (MI), we generated transgenic mice with cardiac-specific overexpression of HMGB1 (HMGB1-Tg) using alpha-myosin heavy chain promoter.

METHODS AND RESULTS

The left anterior descending coronary artery was ligated in HMGB1-Tg and wild-type littermate (Wt) mice. After coronary artery ligation, HMGB1 was released into circulation from the necrotic cardiomyocytes of HMGB1-overexpressing hearts. The size of MI was smaller in HMGB1-Tg than in Wt mice. Echocardiography and cardiac catheterization demonstrated that cardiac remodelling and dysfunction after MI were prevented in HMGB1-Tg mice compared with Wt mice. Furthermore, the survival rate after MI of HMGB1-Tg mice was higher than that of Wt mice. Immunohistochemical staining revealed that capillary and arteriole formation after MI was enhanced in HMGB1-Tg mice.

CONCLUSION

We report the first in vivo evidence that HMGB1 enhances angiogenesis, restores cardiac function, and improves survival after MI. These results may provide a novel therapeutic approach for left ventricular dysfunction after MI.

A novel function of the receptor for advanced glycation end-products (RAGE) in association with tumorigenesis and tumor differentiation of HCC

Background

The expression of the receptor for advanced glycation end products (RAGE) has an impact on the mechanisms giving rise to characteristic features of various cancer cells. The purpose of this study was to elucidate the clinicopathological relevance of the level of RAGE expression in patients with hepatocellular carcinoma (HCC) and to explore the effect of RAGE expression on the characteristic features of HCC.

Methods

The expression of RAGE was assessed in paired cancer and noncancerous tissues with HCC, using reverse-transcription polymerase chain reaction (RT-PCR), and immunohistochemistry. The quantitative RT-PCR data were analyzed in association with the clinicopathological factors of the patients with HCC. In in vitro experiments, the survival of RAGE-transfected Cos7 and mock-transfected Cos7 cells was compared under hypoxic conditions. In addition, after reducing RAGE levels in RAGE-transfected Cos7 cells by siRNA, similar experiments were performed.

Results

The expression of RAGE mRNA was lower in normal liver than in hepatitis and highest in HCC. Furthermore, in HCC, it was high in well- and moderately differentiated tumors but declined as tumors dedifferentiated to poorly differentiated HCC. Furthermore, HCC lines resistant to hypoxia were found to have higher levels of RAGE expression, and RAGE transfectant also showed significantly prolonged survival under hypoxia.

Conclusions

Our results suggest that HCC during the early stage of tumorigenesis with less blood supply may acquire resistance to stringent hypoxic milieu by hypoxia-induced RAGE expression.

Crucial role of the protein C pathway in governing microvascular inflammation in inflammatory bowel disease

Endothelial protein C receptor (EPCR) and thrombomodulin (TM) are expressed at high levels in the resting microvasculature and convert protein C (PC) into its activated form, which is a potent anticoagulant and antiinflammatory molecule. Here we provide evidence that in Crohn disease (CD) and ulcerative colitis (UC), the 2 major forms of inflammatory bowel disease (IBD), there was loss of expression of endothelial EPCR and TM, which in turns caused impairment of PC activation by the inflamed mucosal microvasculature. In isolated human intestinal endothelial cells, administration of recombinant activated PC had a potent antiinflammatory effect, as demonstrated by downregulated cytokine-dependent cell adhesion molecule expression and chemokine production as well as inhibited leukocyte adhesion. In vivo, administration of activated PC was therapeutically effective in ameliorating experimental colitis as evidenced by reduced weight loss, disease activity index, and histological colitis scores as well as inhibited leukocyte adhesion to the inflamed intestinal vessels. The results suggest that the PC pathway represents a new system crucially involved in governing intestinal homeostasis mediated by the mucosal microvasculature. Restoring the PC pathway may represent a new therapeutic approach to suppress intestinal inflammation in IBD.

Immune regulation by microvascular endothelial cells: directing innate and adaptive immunity, coagulation, and inflammation

An effective immune response depends not only on the proper activation, regulation, and function of immune cells, but also on their distribution and retention in diverse tissue microenvironments where they encounter a number of stimuli and other cell types. These activities are mediated by endothelial cells, which form specialized microcirculatory networks used by immune cells under both physiological and pathological circumstances. Endothelial cells represent a highly heterogeneous population of cells with the ability to interact with and modulate the function of immune cells. This review is focused on the role of microvascular endothelial cells in innate and adaptive immunity, inflammation, coagulation, angiogenesis, and the therapeutic implications of targeting endothelial cells in selected autoimmune and chronic inflammatory disorders.

A guide to murine coagulation factor structure, function, assays, and genetic alterations

Murine blood coagulation factors and function are quite similar to those of humans. Because of this similarity and the adaptability of mice to genetic manipulation, murine coagulation factors and inhibitors have been extensively studied. These studies have provided significant insights into human hemostasis. They have also provided useful experimental models for evaluation of the pathophysiology and treatment of thrombosis. This review contains recommendations for obtaining, processing and assaying mouse blood hemostatic components, and it summarizes the extensive literature on murine coagulation factor structure and function, assays and genetic alteration. It is intended to be a convenient reference source for investigators of hemostasis and thrombosis.

The lectin-like domain of thrombomodulin interferes with complement activation and protects against arthritis

BACKGROUND

Thrombomodulin (TM) is predominantly a vascular endothelial cell plasma membrane glycoprotein that, via distinct structural domains, interacts with multiple ligands, thereby modulating coagulation, fibrinolysis, complement activation, inflammation and cell proliferation. We previously reported that by mediating signals that interfere with mitogen-activated protein kinase and nuclear factor kappaB pathways, the amino-terminal C-type lectin-like domain of TM has direct anti-inflammatory properties.

METHODS

In the current study, we use murine models of acute inflammatory arthritis and biochemical approaches to assess the mechanism by which the lectin-like domain of TM modifies disease progression.

RESULTS

Mice lacking the lectin-like domain of TM (TM(LeD/LeD)mice) develop inflammatory arthritis that is more rapid in onset and more severe than that developed in their wildtype counterparts. In two models of arthritis, treatment of mice with recombinant soluble lectin-like domain of TM significantly suppresses clinical evidence of disease and diminishes monocyte/macrophage infiltration into the synovium, with weaker expression of the pro-inflammatory high mobility group box chromosomal protein 1. While thrombin-TM mediated activation of thrombin activatable fibrinolysis inhibitor inactivates complement factors C3a and C5a, we show that TM has a second independent mechanism to regulate complement: the lectin-like domain of TM directly interferes with complement activation via the classical and lectin pathways.

CONCLUSIONS

These data extend previous insights into the mechanisms by which TM modulates innate immunity, and highlight its potential as a therapeutic target for inflammatory diseases.

The interactions between inflammation and coagulation

Inflammation initiates clotting, decreases the activity of natural anticoagulant mechanisms and impairs the fibrinolytic system. Inflammatory cytokines are the major mediators involved in coagulation activation. The natural anticoagulants function to dampen elevation of cytokine levels. Furthermore, components of the natural anticoagulant cascades, like thrombomodulin, minimise endothelial cell dysfunction by rendering the cells less responsive to inflammatory mediators, facilitate the neutralisation of some inflammatory mediators and decrease loss of endothelial barrier function. Hence, downregulation of anticoagulant pathways not only promotes thrombosis but also amplifies the inflammatory process. When the inflammation-coagulation interactions overwhelm the natural defence systems, catastrophic events occur, such as manifested in severe sepsis or inflammatory bowel disease.