A role for bradykinin in the development of anti-collagen antibody-induced arthritis

Endothelial cell sphingosine 1-phosphate receptor 1 restrains VE-cadherin cleavage and attenuates experimental inflammatory arthritis

In rheumatoid arthritis, inflammatory mediators extravasate from blood into joints via gaps between endothelial cells (ECs), but the contribution of ECs is not known. Sphingosine 1-phosphate receptor 1 (S1PR1), widely expressed on ECs, maintains the vascular barrier. Here, we assessed the contribution of vascular integrity and EC S1PR1 signaling to joint damage in mice exposed to serum-induced arthritis (SIA). EC-specific deletion of S1PR1 or pharmacological blockade of S1PR1 promoted vascular leak and amplified SIA, whereas overexpression of EC S1PR1 or treatment with an S1PR1 agonist delayed SIA. Blockade of EC S1PR1 induced membrane metalloproteinase-dependent cleavage of vascular endothelial cadherin (VE-cadherin), a principal adhesion molecule that maintains EC junctional integrity. We identified a disintegrin and a metalloproteinase domain 10 (ADAM10) as the principal VE-cadherin "sheddase." Mice expressing a stabilized VE-cadherin construct had decreased extravascular VE-cadherin and vascular leakage in response to S1PR1 blockade, and they were protected from SIA. Importantly, patients with active rheumatoid arthritis had decreased circulating S1P and microvascular expression of S1PR1, suggesting a dysregulated S1P/S1PR1 axis favoring vascular permeability and vulnerability. We present a model in which EC S1PR1 signaling maintains homeostatic vascular barrier function by limiting VE-cadherin shedding mediated by ADAM10 and suggest this signaling axis as a therapeutic target in inflammatory arthritis.

The effect of bradykinin 1 receptor antagonist BI 1026706 on pulmonary inflammation after segmental lipopolysaccharide challenge in healthy smokers

BACKGROUND

Bradykinin 1 receptor (B1R) signalling pathways may be involved in the inflammatory pathophysiology of chronic obstructive pulmonary disease (COPD). B1R signalling is induced by inflammatory stimuli or tissue injury and leads to activation and increased migration of pro-inflammatory cells. Lipopolysaccharide (LPS) lung challenge in man is an experimental method of exploring inflammation in the lung whereby interference in these pathways can help to assess pharmacologic interventions in COPD. BI 1026706, a potent B1R antagonist, was hypothesized to reduce the inflammatory activity after segmental lipopolysaccharide (LPS) challenge in humans due to decreased pulmonary cell influx.

METHODS

In a monocentric, randomized, double-blind, placebo-controlled, parallel-group, phase I trial, 57 healthy, smoking subjects were treated for 28 days with either oral BI 1026706 100 mg bid or placebo. At day 21, turbo-inversion recovery magnitude magnetic resonance imaging (TIRM MRI) was performed. On the last day of treatment, pre-challenge bronchoalveolar lavage fluid (BAL) and biopsies were sampled, followed by segmental LPS challenge (40 endotoxin units/kg body weight) and saline control instillation in different lung lobes. Twenty-four hours later, TIRM MRI was performed, then BAL and biopsies were collected from the challenged segments. In BAL samples, cells were differentiated for neutrophil numbers as the primary endpoint. Other endpoints included assessment of safety, biomarkers in BAL (e.g. interleukin-8 [IL-8], albumin and total protein), B1R expression in lung biopsies and TIRM score by MRI as a measure for the extent of pulmonary oedema.

RESULTS

After LPS, but not after saline, high numbers of inflammatory cells, predominantly neutrophils were observed in the airways. IL-8, albumin and total protein were also increased in BAL samples after LPS challenge as compared with saline control. There were no significant differences in cells or other biomarkers from BAL in volunteers treated with BI 1026706 compared with those treated with placebo. Unexpectedly, neutrophil numbers in BAL were 30% higher and MRI-derived extent of oedema was significantly higher with BI 1026706 treatment compared with placebo, 24 h after LPS challenge. Adverse events were mainly mild to moderate and not different between treatment groups.

CONCLUSIONS

Treatment with BI 1026706 for four weeks was safe and well-tolerated in healthy smoking subjects. BI 1026706 100 mg bid did not provide evidence for anti-inflammatory effects in the human bronchial LPS challenge model.

TRIAL REGISTRATION

The study was registered on January 14, 2016 at ClinicalTrials.gov (NCT02657408).

Receptor tyrosine kinases Tyro3, Axl, and Mertk differentially contribute to antibody-induced arthritis

Tyro3, Axl, and Mertk (abbreviated TAMs) comprise a family of homologous type 1 receptor tyrosine kinases (RTKs) that have been implicated as inhibitory receptors that dampen inflammation, but their roles in the pathogenesis of rheumatoid arthritis remains understudied. Here, to investigate TAMs in an inflammatory arthritis model, antibody-induced arthritis in single TAM-deficient mice (Tyro3- KO, Axl-KO, Mertk-KO) was induced by K/BxN serum injection. Subsequently, joint inflammation and cytokine levels, as well as the expression of Fcγ Rs and complement receptors were assessed in WT and TAM-deficient mice. Compared with littermate control mice, Axl-/- and Mertk-/- mice developed more severe antibody-induced arthritis, while in contrast, Tyro3-/- mice showed diminished joint inflammation. Concomitantly, the levels of cytokines in joints of Axl-/- and Mertk-/- mice were also significantly increased, while cytokines in the Tyro3-/- joint tissues were decreased. At the molecular and cellular level, TAMs showed distinct expression patterns, whereby monocytes expressed Axl and Mertk, but no Tyro3, while neutrophils expressed Axl and Tyro3 but little Mertk. Moreover, expression of Fcγ receptors and C5aR showed different patterns with TAMs expression, whereby FcγRIV was higher in monocytes of Axl-/- and Mertk-/- mice compared to wild-type mice, while Tyro3-/- neutrophils showed lower expression levels of FcγRI, FcγRIII and FcγRIV. Finally, expression of C5aR was increased in Mertk-/- monocytes, and was decreased in Tyro3-/- neutrophils. These data indicate that Axl, Mertk and Tyro3 have distinct functions in antibody-induced arthritis, due in part to the differential regulation of cytokines production, as well as expression of FcγRs and C5aR. Video Abstract.

A comprehensive insight into effects of resveratrol on molecular mechanism in rheumatoid arthritis: A literature systematic review

AIM

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease, which is characterized by massive pain and destruction of synovial joints, leads to bone erosion, damage to cartilage, and disability. Several studies suggested that resveratrol supplementation may be effective in the prevention and management of RA. Therefore, a systematic review was conducted to summarize published studies that assess the effect of resveratrol supplementation on the complications of RA.

METHODS

A comprehensive search to identify in vitro, animal, and human studies investigating the impact of resveratrol on the complications of RA was performed up to February 2022. Two independent reviewers evaluated studies based on inclusion/exclusion criteria and performed data extraction.

RESULTS

All studies examining the effects of resveratrol supplementation on the complications of RA were included. From a total of 571 retrieved articles, 32 studies were eligible for the current systematic review. The evidence reviewed here indicates that resveratrol supplementation may exert beneficial effects on the complications of RA by attenuating inflammation and oxidative stress, modulating the immune response, and down-regulating the messenger RNA expression of genes related to inflammatory pathways.

CONCLUSION

Due to the promising therapeutic effects of resveratrol on RA complications and limited number of human studies in this subject, further clinical trials are suggested.

ATP spreads inflammation to other limbs through crosstalk between sensory neurons and interneurons

Neural circuits between lesions are one mechanism through which local inflammation spreads to remote positions. Here, we show the inflammatory signal on one side of the joint is spread to the other side via sensory neuron-interneuron crosstalk, with ATP at the core. Surgical ablation or pharmacological inhibition of this neural pathway prevented inflammation development on the other side. Mechanistic analysis showed that ATP serves as both a neurotransmitter and an inflammation enhancer, thus acting as an intermediary between the local inflammation and neural pathway that induces inflammation on the other side. These results suggest blockade of this neural pathway, which is named the remote inflammation gateway reflex, may have therapeutic value for inflammatory diseases, particularly those, such as rheumatoid arthritis, in which inflammation spreads to remote positions.

Soluble CD13 induces inflammatory arthritis by activating the bradykinin receptor B1

CD13, an ectoenzyme on myeloid and stromal cells, also circulates as a shed, soluble protein (sCD13) with powerful chemoattractant, angiogenic, and arthritogenic properties, which require engagement of a G protein-coupled receptor (GPCR). Here we identify the GPCR that mediates sCD13 arthritogenic actions as the bradykinin receptor B1 (B1R). Immunofluorescence and immunoblotting verified high expression of B1R in rheumatoid arthritis (RA) synovial tissue and fibroblast-like synoviocytes (FLSs), and demonstrated binding of sCD13 to B1R. Chemotaxis, and phosphorylation of Erk1/2, induced by sCD13, were inhibited by B1R antagonists. In ex vivo RA synovial tissue organ cultures, a B1R antagonist reduced secretion of inflammatory cytokines. Several mouse arthritis models, including serum transfer, antigen-induced, and local innate immune stimulation arthritis models, were attenuated in Cd13-/- and B1R-/- mice and were alleviated by B1R antagonism. These results establish a CD13/B1R axis in the pathogenesis of inflammatory arthritis and identify B1R as a compelling therapeutic target in RA and potentially other inflammatory diseases.

Identification of Human Kinin-Forming Enzyme Inhibitors from Medicinal Herbs

The goal of this study was to assess the pharmacological effects of black tea (Camellia sinensis var. assamica) water extract on human kinin-forming enzymes in vitro. Tea is a highly consumed beverage in the world. Factor XII (FXII, Hageman factor)-independent- and -dependent activation of prekallikrein to kallikrein leads to the liberation of bradykinin (BK) from high-molecular-weight kininogen (HK). The excessive BK production causes vascular endothelial and nonvascular smooth muscle cell permeability, leading to angioedema. The prevalence of angiotensin-converting enzyme inhibitor (ACEI)-induced angioedema appears to be through BK. Both histamine and BK are potent inflammatory mediators. However, the treatments for histamine-mediated angioedema are unsuitable for BK-mediated angioedema. We hypothesized that long-term consumption of tea would reduce bradykinin-dependent processes within the systemic and pulmonary vasculature, independent of the anti-inflammatory actions of polyphenols. A purified fraction of the black tea water extract inhibited both kallikrein and activated FXII. The black tea water extracts inhibited factor XII-induced cell migration and inhibited the production of kallikrein on the endothelial cell line. We compared the inhibitory effects of the black tea water extract and twenty-three well-known anti-inflammatory medicinal herbs, in inhibiting both kallikrein and FXII. Surprisingly, arjunglucoside II specifically inhibited the activated factor XII (FXIIa), but not the kallikrein and the activated factor XI. Taken together, the black tea water extract exerts its anti-inflammatory effects, in part, by inhibiting kallikrein and activated FXII, which are part of the plasma kallikrein–kinin system (KKS), and by decreasing BK production. The inhibition of kallikrein and activated FXII represents a unique polyphenol-independent anti-inflammatory mechanism of action for the black tea.

Cold-induced urticarial autoinflammatory syndrome related to factor XII activation

Hereditary autoinflammatory diseases are caused by gene mutations of the innate immune pathway, e.g. nucleotide receptor protein 3 (NLRP3). Here, we report a four-generation family with cold-induced urticarial rash, arthralgia, chills, headache and malaise associated with an autosomal-dominant inheritance. Genetic studies identify a substitution mutation in gene F12 (T859A, resulting in p.W268R) which encodes coagulation factor XII (FXII). Functional analysis reveals enhanced autocatalytic cleavage of the mutated protein and spontaneous FXII activation in patient plasma and in supernatant of transfected HEK293 cells expressing recombinant W268R-mutated proteins. Furthermore, we observe reduced plasma prekallikrein, cleaved high molecular weight kininogen and elevated plasma bradykinin. Neutrophils are identified as a local source of FXII. Interleukin-1β (IL-1β) is upregulated in lesional skin and mononuclear donor cells exposed to recombinant mutant proteins. Treatment with icatibant (bradykinin-B2-antagonist) or anakinra (interleukin-1-antagonist) reduces disease activity in patients. In conclusion, our findings provide a link between contact system activation and cytokine-mediated inflammation.

Systemic autoinflammatory syndromes such as cryopyrin-associated periodic syndrome (CAPS) are rare and often involve genes related to the inflammasome. Here, the authors report a syndrome characterised by systemic inflammation and cold-induced urticarial rash associated with a Factor XII-activating mutation.

The plasma contact system as a modulator of innate immunity

PURPOSE OF REVIEW

The contact system is a plasma protease cascade, which activates the proinflammatory kallikrein-kinin system and the procoagulant intrinsic coagulation pathway. Recent advances demonstrating the novel functions of this system as a key player of innate immune system will be introduced in the present review.

RECENT FINDINGS

The role of the contact system is to initiate and participate in pathophysiological responses to injury, mainly the processes of coagulation and inflammation. The past few years have seen substantial progress, showing a new role of this system in regulation of innate immunity. The relationship between high-molecular-weight kininogen and lipopolysaccharide (LPS) has been investigated and a new function of high-molecular-weight kininogen has been identified as the critical LPS carrier supporting endotoxemia. In contrast, the role of high-molecular-weight kininogen in Klebsiella pneumoniae sepsis is limited. Coagulation factor XII (FXII) plays a detrimental role in murine wound healing and host defense against K. pneumoniae sepsis. In the pathogenesis of arthritis and colitis, the activation of plasma kallikrein and downstream cleavage of high-molecular-weight kininogen and release of bradykinin constitutes a critical pathway in the innate immune mechanism, whereas FXII is not important.

SUMMARY

Current findings indicate that the plasma contact system functions as an important constituent of innate immune system, contributing to the pathogenesis of the immunological and infectious diseases.

Development of a Novel Diagnostic Biomarker Set for Rheumatoid Arthritis Using a Proteomics Approach

Background

Rheumatoid arthritis (RA) is an autoimmune disease that starts with inflammation of the synovial membrane. Studies have been conducted to develop methods for efficient diagnosis of RA and to identify the mechanisms underlying RA development. Blood samples can be useful for detecting disturbance of homeostasis in patients with RA. Nanoliquid chromatography-tandem mass spectrometry (LC-MS/MS) is an efficient proteomics approach to analyze blood sample and quantify serum proteins.

Methods

Serum samples of 18 healthy controls and 18 patients with RA were analyzed by LC-MS/MS. Selected candidate biomarkers were validated by enzyme-linked immunosorbent assay (ELISA) using sera from 43 healthy controls and 44 patients with RA.

Results

Thirty-eight proteins were significantly differentially expressed by more than 2-fold in healthy controls and patients with RA. Based on a literature survey, we selected six candidate RA biomarkers. ELISA was used to evaluate whether these proteins effectively allow distinguishing patients with RA from healthy controls and monitoring drug efficacy. SAA4, gelsolin, and vitamin D-binding protein were validated as potential biomarkers of RA for screening and drug efficacy monitoring of RA.

Conclusions

We identified a panel of three biomarkers for RA which has potential for application in RA diagnosis and drug efficacy monitoring. Further, our findings will aid in understanding the pathogenesis of RA.

The Coagulation Factors Fibrinogen, Thrombin, and Factor XII in Inflammatory Disorders-A Systematic Review

Background

The interaction of coagulation factors has been shown to go beyond their traditional roles in hemostasis and to affect the development of inflammatory diseases. Key molecular players, such as fibrinogen, thrombin, or factor XII have been mechanistically and epidemiologically linked to inflammatory disorders like multiple sclerosis (MS), rheumatoid arthritis (RA), and colitis.

Objectives

To systematically review the evidence for a role of coagulation factors, especially factor XII, fibrinogen, and thrombin in inflammatory disorders like MS, RA, and bowel disorders.

Methods

A systematic literature search was done in the PubMed database to identify studies about coagulation factors in inflammatory diseases. Original articles and reviews investigating the role of the kallikrein–kinin and the coagulation system in mouse and humans were included.

Results

We identified 43 animal studies dealing with inflammatory disorders and factors of the kallikrein–kinin or the coagulation system. Different immunological influences are described and novel molecular mechanisms linking coagulation and inflammation are reported.

Conclusion

A number of studies have highlighted coagulation factors to tip the balance between hemostasis and thrombosis and between protection from infection and extensive inflammation. To optimize the treatment of chronic inflammatory disorders by these factors, further studies are necessary.

The Plasma Kallikrein-Kininogen Pathway Is Critical in the Pathogenesis of Colitis in Mice

The kallikrein-kinin system (KKS) consists of two serine proteases, prekallikrein (pKal) and factor XII (FXII), and a cofactor, high-molecular-weight kininogen (HK). Upon activation of the KKS, HK is cleaved to release bradykinin. Although the KKS is activated in humans and animals with inflammatory bowel disease (IBD), its role in the pathogenesis of IBD has not been characterized. In the present study, we determined the role of the KKS in the pathogenesis of IBD using mice that lack proteins involved in the KKS. In two colitis models, induced by dextran sulfate sodium (DSS) or 2,4,6-trinitrobenzene sulfonic acid (TNBS), mice deficient in HK, pKal, or bradykinin receptors displayed attenuated phenotypes, including body weight loss, disease activity index, colon length shortening, histological scoring, and colonic production of cytokines. Infiltration of neutrophils and inflammatory monocytes in the colonic lamina propria was reduced in HK-deficient mice. Reconstitution of HK-deficient mice through intravenous injection of HK recovered their susceptibility to DSS-induced colitis, increased IL-1β levels in the colon tissue and bradykinin concentrations in plasma. In contrast to the phenotypes of other mice lacking other proteins involved in the KKS, mice lacking FXII had comparable colonic inflammation to that observed in wild-type mice. The concentration of bradykinin was significantly increased in the plasma of wild-type mice after DSS-induced colitis. In vitro analysis revealed that DSS-induced pKal activation, HK cleavage, and bradykinin plasma release were prevented by the absence of pKal or the inhibition of Kal. Unlike DSS, TNBS-induced colitis did not trigger HK cleavage. Collectively, our data strongly suggest that Kal, acting independently of FXII, contributes to experimental colitis by promoting bradykinin release from HK.

Inhibition of plasma kallikrein-kinin system to alleviate renal injury and arthritis symptoms in rats with adjuvant-induced arthritis

BACKGROUND

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease. Impairment of kidney functions in RA was observed. However, the mechanism of kidney injury of RA has not been clear. Plasma kallikrein-kinin system (KKS) was involved in inflammatory processes in kidney disease.

AIM

This study aimed to explore the role of plasma KKS in immune reactions and kidney injury of RA.

RESULTS

The paw of AA rats appeared to be swelling and redness, the arthritis index was significantly increased on the 18, 21 and 24 d after injection and secondary inflammation in multi-sites was observed. Kidney dysfunction accompanied with inflammatory cell infiltration, tubular epithelial cell mitochondrial swelling and vacuolar degeneration, renal glomerular foot process fusions and glomerular basement membrane thickening were observed in AA rats. The expressions of neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (Kim-1) in kidney of AA rats were increased. In addition, expressions of BK, PK, B1R and B2R in the renal tissue of AA rats were up-regulated. Pro-inflammatory cytokines IL-2, IFN-γ and TNF-α were increased and anti-inflammatory cytokines IL-4 and IL-10 were low in kidney. Plasma kallikrein (PK) inhibitor PKSI-527 attenuated arthritis signs and renal damage, and inhibited BK, PK, B1R and B2R expressions. The protein expressions of P38, p-P38 and p-JNK and IFN-γ and TNF-α were inhibited by PKSI-527.

CONCLUSIONS

These findings demonstrate that plasma KKS activation contributed to the renal injury of AA rats through MAPK signaling pathway. Plasma KKS might be a potential target for RA therapy.

Oxidative stress in inflammatory cells of patient with rheumatoid arthritis: clinical efficacy of dietary antioxidants

Rheumatoid arthritis (RA) is an autoimmune disease responsible for significant human morbidity in modern life. However, oxidative stress is one of the key markers for determining pathophysiology of patients with RA. The interaction between cellular immune system and body's endogenous and/or exogenous antigens produce reactive oxygen species (ROS) and reactive nitrogen species (RNS) in autoimmune disease like RA. ROS and RNS include highly toxic superoxide (O₂^-) and peroxynitrite (ONOO^-) radicals, which activate the signaling cascades of inflammatory cells to synthesize pro-inflammatory cytokines and chemokines. Previous studies reported that Th1 cytokines could promote the development of autoimmune disorders like RA, whereas the Th2 cytokines may attenuate the same diseases. An increased awareness of the relationship between food and health led to a tremendous increase of antioxidant research in the last decade. Evaluation of the efficacy of dietary antioxidants is also becoming highly acceptable in RA research. A number of dietary phytomolecules are already established as having antioxidant activity in isolated synovial cellular infiltrate or peripheral blood neutrophils and lymphocytes. This review aims to highlight the oxidative stress in inflammatory cells of patients with RA and to summarize the clinical relevance of dietary antioxidants as a first step in assessing beneficial effect, safety and dose safety ratio in patients with RA.

Factor XII-Driven Inflammatory Reactions with Implications for Anaphylaxis

Anaphylaxis is a life-threatening allergic reaction. It is triggered by the release of pro-inflammatory cytokines and mediators from mast cells and basophils in response to immunologic or non-immunologic mechanisms. Mediators that are released upon mast cell activation include the highly sulfated polysaccharide and inorganic polymer heparin and polyphosphate (polyP), respectively. Heparin and polyP supply a negative surface for factor XII (FXII) activation, a serine protease that drives contact system-mediated coagulation and inflammation. Activation of the FXII substrate plasma kallikrein leads to further activation of zymogen FXII and triggers the pro-inflammatory kallikrein-kinin system that results in the release of the mediator bradykinin (BK). The severity of anaphylaxis is correlated with the intensity of contact system activation, the magnitude of mast cell activation, and BK formation. The main inhibitor of the complement system, C1 esterase inhibitor, potently interferes with FXII activity, indicating a meaningful cross-link between complement and kallikrein-kinin systems. Deficiency in a functional C1 esterase inhibitor leads to a severe swelling disorder called hereditary angioedema (HAE). The significance of FXII in these disorders highlights the importance of studying how these processes are integrated and can be therapeutically targeted. In this review, we focus on how FXII integrates with inflammation and the complement system to cause anaphylaxis and HAE as well as highlight current diagnosis and treatments of BK-related diseases.

A critical role for plasma kallikrein in the pathogenesis of autoantibody-induced arthritis

The plasma kallikrein-kinin system (KKS) consists of serine proteases, prekallikrein (pKal) and factor XII (FXII), and a cofactor, high-MW kininogen (HK). Upon activation, activated pKal and FXII cleave HK to release bradykinin. Activation of this system has been noted in patients with rheumatoid arthritis, and its pathogenic role has been characterized in animal arthritic models. In this study, we generated 2 knockout mouse strains that lacked pKal and HK and determined the role of KKS in autoantibody-induced arthritis. In a K/BxN serum transfer-induced arthritis (STIA) model, mice that lacked HK, pKal, or bradykinin receptors displayed protective phenotypes in joint swelling, histologic changes in inflammation, and cytokine production; however, FXII-deficient mice developed normal arthritis. Inhibition of Kal ameliorated arthritis severity and incidence at early stage STIA and reduced the levels of major cytokines in joints. In addition to releasing bradykinin from HK, Kal directly activated monocytes to produce proinflammatory cytokines, up-regulated their C5aR and FcRIII expression, and released C5a. Immune complex increased pKal activity, which led to HK cleavage. The absence of HK is associated with a decrease in joint vasopermeability. Thus, we identify a critical role for Kal in autoantibody-induced arthritis with pleiotropic effects, which suggests that it is a new target for the inhibition of arthritis.-Yang, A., Zhou, J., Wang, B., Dai, J., Colman, R. W., Song, W., Wu, Y. A critical role for plasma kallikrein in the pathogenesis of autoantibody-induced arthritis.

An essential role of high-molecular-weight kininogen in endotoxemia

High-molecular-weight kininogen (HK) is a plasma protein. Yang et al. show that HK binds LPS and supports endotoxemia. Blockade of their binding attenuates circulating LPS level. Therefore, HK is essential for endotoxemia and is a new target for LPS clearance and sepsis treatment.

In this study, we show that mice lacking high-molecular-weight kininogen (HK) were resistant to lipopolysaccharide (LPS)-induced mortality and had significantly reduced circulating LPS levels. Replenishment of HK-deficient mice with human HK recovered the LPS levels and rendered the mice susceptible to LPS-induced mortality. Binding of HK to LPS occurred through the O-polysaccharide/core oligosaccharide, consistent with the ability to bind LPS from K. pneumoniae, P. aeruginosa, S. minnesota, and different E. coli strains. Binding of LPS induced plasma HK cleavage to the two-chain form (HKa, containing a heavy chain [HC] and a light chain [LC]) and bradykinin. Both HKa and the LC, but not the HC, could disaggregate LPS. The light chain bound LPS with high affinity (K_d = 1.52 × 10⁻⁹ M) through a binding site in domain 5 (DHG15). A monoclonal antibody against D5 significantly reduced LPS-induced mortality and circulating LPS levels in wild-type mice. Thus, HK, as a major LPS carrier in circulation, plays an essential role in endotoxemia.

The plasma contact system, a protease cascade at the nexus of inflammation, coagulation and immunity

The contact system is a potent procoagulant and proinflammatory plasma protease cascade that is initiated by binding ("contact")-induced, auto-activation of factor XII zymogen. Formed active serine protease FXIIa then cleaves plasma prekallikrein to kallikrein that in turn liberates the mediator bradykinin from its precursor high molecular weight kininogen. Bradykinin induces inflammation with implications for host defense and innate immunity. FXIIa also triggers the intrinsic pathway of coagulation that has been shown to critically contribute to thrombosis. Vice versa, FXII deficiency impairs thrombosis in animal models without inducing abnormal excessive bleeding. Recent work has established the FXIIa-driven contact system as promising target for anticoagulant and anti-inflammatory drugs. This review focuses on the biochemistry of the contact system, its regulation by endogenous and exogenous inhibitors, and roles in disease states. This article is part of a Special Issue entitled: Proteolysis as a Regulatory Event in Pathophysiology edited by Stefan Rose-John.

Mixed effects of caffeic acid phenethyl ester (CAPE) on joint inflammation, bone loss and gastrointestinal inflammation in a murine model of collagen antibody-induced arthritis

OBJECTIVE

To investigate the effect of caffeic acid phenethyl ester (CAPE) on local and systemic inflammation and bone loss in collagen antibody-induced arthritis (CAIA) mice.

METHODS

Four groups of mice (n = 8 per group) were allocated; control, CAPE (1 mg/kg), CAIA and CAIA + CAPE (1 mg/kg). Local inflammation and bone loss were evaluated using clinical paw scores, in vivo micro-computed tomography (micro-CT), histological assessment and tartrate-resistant acid phosphatase (TRAP) staining. Serum levels of C-reactive protein (CRP) and C-terminal telopeptide (CTX-1) were measured by ELISA. Jejunum and colon sections were evaluated histopathologically for damage and toxicity.

RESULTS

Greater paw scores and percentage change in paw volume were observed in CAIA + CAPE compared to the control groups (p < 0.05). Bone volume over time remained unchanged (p = 0.94) and the number of multinucleated TRAP-positive cells was greatest in CAIA + CAPE mice (p < 0.05). CRP and CTX-1 levels did not differ between groups. CAIA + CAPE mice exhibited lower colon toxicity scores and a reduced percentage of cavitated goblet cells in the colon crypts compared with CAIA mice (p = 0.026 and p = 0.003, respectively). Histopathology in the jejunum was not altered.

CONCLUSION

CAPE did not reduce paw inflammation or bone loss in CAIA mice. CAPE reduced histopathological changes in the colon of CAIA mice.

Contact pathway of coagulation and inflammation

The contact system, also named as plasma kallikrein-kinin system, consists of three serine proteinases: coagulation factors XII (FXII) and XI (FXI), and plasma prekallikrein (PK), and the nonenzymatic cofactor high molecular weight kininogen (HK). This system has been investigated actively for more than 50 years. The components of this system and their interactions have been elucidated from in vitro experiments, which indicates that this system is prothrombotic by activating intrinsic pathway, and proinflammatory by producing bioactive peptide bradykinin. Although the activation of the contact system have been implicated in various types of human disease, in only a few instances is its role clearly defined. In the last 10 years, our understanding of the contact system, particularly its biology and (patho)physiology has greatly increased through investigations using gene-modified animal models. In this review we will describe a revitalized view of the contact system as a critical (patho)physiologic mediator of coagulation and inflammation.