A tissue kallikrein in the synovial fluid of patients with rheumatoid arthritis

An Extensive Study of the Functional Polymorphisms of Kinin-Kallikrein System in Rheumatoid Arthritis Susceptibility

Objectives

This study aims to examine the following functional polymorphisms in rheumatoid arthritis (RA) susceptibility: (i) the 587C>T of kininogen gene, (ii) the 287 bp Alu repeat insertion of angiotensin converting enzyme gene, (iii) the 9 bp insertion of bradykinin receptor 2 gene, (iv) the -58T>C of bradykinin receptor 2 gene, and (v) the -699G>C of bradykinin receptor 1 gene.

Patients and methods

The study included 136 RA patients (27 males; 109 females; mean age 60.8 years; range 39 to 75 years) and 149 ethnic matching controls (30 males, 119 females; mean age 56.2 years; range 35 to 78 years). Polymerase chain reaction coupled with restriction assay was performed for 587C>T, -58T>C, and -699G>C.

Results

Rheumatoid arthritis patients and controls carried the wild type allele of 587C>T; therefore, produced the high molecular weight kininogen. No significant difference was observed in genotype or allele distribution of the studied functional polymorphisms between RA patients and controls.

Conclusion

Kinin-kallikrein system related genes might not be major RA susceptibility loci.

N-methyl pyrrolidone promotes ankle fracture healing by inhibiting inflammation via suppression of the mitogen-activated protein kinase signaling pathway

N-methyl pyrrolidone (NMP), a small bioactive molecule, has the potential to stimulate bone formation and inhibit osteoclast differentiation. The aim of the present study was to investigate the effect of NMP on the inflammatory response and underlying molecular mechanisms in MG-63 cells. The mRNA and protein expression of cytokines from peripheral blood in children with or without ankle fracture were determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and ELISA, respectively. MG-63 cells were pre-treated with/without NMP and stimulated with 1 µM bradykinin (BK). The production of cytokines from MG-63 cells was assessed by western blotting and RT-qPCR. The expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) mRNA and protein were measured using western blotting and/or RT-qPCR. Western blotting was used to examine the activation level of mitogen activated protein kinase. Compared with healthy children, levels of tumor necrosis factor (TNF-α), interleukin (IL)-1β and IL-6 mRNA and protein were upregulated in children with ankle fracture. NMP treatment did not induce cytotoxicity in MG-63 cells. The BK-induced upregulation of TNF-α, IL-1β, IL-6, iNOS and COX-2 mRNA and protein was reversed in a dose-dependent manner by NMP. Furthermore, NMP downregulated the activation of c-Jun NH2-terminal kinase and p38 pathways, but not the extracellular signal-related kinase pathway. Therefore, the results of the current study demonstrate that NMP inhibits inflammation dependent on the mitogen-activated protein kinase pathway in MG-63 cells, indicating that it may be beneficial in the healing of fractures.

Bradykinin regulates osteoblast differentiation by Akt/ERK/NFκB signaling axis

Bradykinin (BK), a well known mediator of pain and inflammation, is also known to be involved in the process of bone resorption. The present study therefore evaluated the role of BK in osteoblast lineage commitment. Our data showed that BK inhibits the migration of bone marrow mesenchymal stem cells, but does not affect their viability. Moreover, BK also inhibits osteoblastic differentiation by significantly downregulating the levels of mRNAs for osteopontin, runX2, col24, osterix, osteocalcin genes and bone mineralization (P < 0.05). Further, BK was found to elicit the BK receptors (BDKR1 and BDKR2) mediated activation of ERK1/2 and Akt pathways, which finally led to the activation of NFκB. BK also promoted the osteoclast differentiation of bone marrow derived preosteoclast cells by upregulating the expression of c-fos, NFATC1, TRAP, clcn7, cathK, and OSCAR genes and increasing TRAP activity through NFκB pathway. In conclusion, our data suggest that BK decreases the differentiation of osteoblasts with concomitant increase in osteoclast formation and thus provides new insight into the mechanism of action of BK in modulating bone resorption.

Non-canonical signalling and roles of the vasoactive peptides angiotensins and kinins

GPCRs (G-protein-coupled receptors) are among the most important targets for drug discovery due to their ubiquitous expression and participation in cellular events under both healthy and disease conditions. These receptors can be activated by a plethora of ligands, such as ions, odorants, small ligands and peptides, including angiotensins and kinins, which are vasoactive peptides that are classically involved in the pathophysiology of cardiovascular events. These peptides and their corresponding GPCRs have been reported to play roles in other systems and under pathophysiological conditions, such as cancer, central nervous system disorders, metabolic dysfunction and bone resorption. More recently, new mechanisms have been described for the functional regulation of GPCRs, including the transactivation of other signal transduction receptors and the activation of G-protein-independent pathways. The existence of such alternative mechanisms for signal transduction and the discovery of agonists that can preferentially trigger one signalling pathway over other pathways (called biased agonists) have opened new perspectives for the discovery and development of drugs with a higher specificity of action and, therefore, fewer side effects. The present review summarizes the current knowledge on the non-canonical signalling and roles of angiotensins and kinins.

Synovial fluid levels of bradykinin correlate with biochemical markers for cartilage degradation and inflammation in knee osteoarthritis

OBJECTIVE

To determine the content of bradykinin (BK) and markers of cartilage degradation and inflammation in the synovial fluid (SF) of patients with knee osteoarthritis (OA), and to evaluate correlations with biomarkers or clinical parameters.

METHODS

SFs were obtained from 30 patients with knee OA. Levels of basal and generated BK, cartilage oligomeric matrix protein (COMP), interleukin (IL) 1, IL-6, IL-8 and matrix metalloprotease (MMP) 1, MMP-3, MMP-13 and sulfated glycosaminoglycans (GAGs) were measured by enzyme-linked immunosorbent assay (ELISA) or colorimetric assays.

RESULTS

The mean concentration of basal BK (in the presence of peptidase and protease inhibitors to avoid degradation and de novo formation of BK) was 422 pg/ml (95% confidence interval, CI, 281-563) whereas that of in vitro generated BK (in the presence of peptidase inhibitors SFs were incubated 60 min at 37°C to measure the potential capability to generate BK) was 3427 pg/ml (2591-4264). The content of MMP-13, IL-1α, and IL-1β was under assay sensitivity. Basal BK levels positively correlated (Spearman's rank correlation) with GAGs (40 μg/ml, 26-54, r = 0.4834, P = 0.0308) and IL-6 (553 pg/ml, 171-935, r = 0.3946, P = 0.0377) similarly to the generated BK (GAGs, r = 0.4563, P = 0.0431; IL-6, r = 0.5605, P = 0.0019). Statistical analysis of basal BK and biomarkers was significant (P = 0.0483). When applying a stepwise logistic regression analysis considering biomarkers together with clinical parameters, results indicated that K/L radiographic OA grade and COMP improved the model (P = 0.0032).

CONCLUSION

The presence of BK in the knee OA SF and its correlations with cartilage degradation and inflammation markers of OA support its participation in OA pathology.

Kallikreins, kininogens and kinin receptors on circulating and synovial fluid neutrophils: role in kinin generation in rheumatoid arthritis

OBJECTIVES

Neutrophils traffic into and have the capacity to generate kinins in SF of RA patients. The aim of this study was to assess the expression of kallikreins, kininogens and kinin receptors in circulating and SF neutrophils, as well as synovial tissue of RA patients, and to assess kinin generation in SF.

METHODS

Neutrophils were isolated from blood and SF of RA patients and blood of healthy volunteers. Expression of kallikreins, kininogens and kinin receptors in neutrophils and synovial tissue was assessed by immunocytochemistry using specific antibodies, with visualization by brightfield and confocal microscopy. Levels of basal and generated kinins in SF of RA patients were measured by ELISA.

RESULTS

Kinin labelling was significantly reduced, indicating the loss of the kinin moiety from kininogen on circulating (P < 0.001) and SF neutrophils (P < 0.05) of RA patients. Immunolabelling of tissue kallikrein was also decreased, whereas kinin B(1) and B(2) receptor expression was increased in circulating and SF neutrophils of RA patients. Immunolabelling of kallikreins and kinin receptor proteins was similar in RA and normal synovial tissues. The basal kinin level in SF of RA patients was 5.7 +/- 6.1 ng/ml and the mean concentration of kinins generated in vitro was 80.6 +/- 56.3 ng/ml. The capacity for kinin generation was positively correlated with measures of disease activity.

CONCLUSIONS

Kallikrein-kinin proteins on neutrophils play an important role in kinin generation and the pathophysiology of RA. Specific kallikrein and kinin receptor antagonists may be useful as IA therapies for inflamed joints.

Bradykinin potentiates cytokine-induced prostaglandin biosynthesis in osteoblasts by enhanced expression of cyclooxygenase 2, resulting in increased RANKL expression

OBJECTIVE

Bradykinin (BK) stimulates bone resorption in vitro and synergistically potentiates interleukin-1 (IL-1)-induced bone resorption and prostaglandin (PG) formation, suggesting that kinins are important in inflammation-induced bone loss. The present study was undertaken to study 1) the role of the kinin B1 and B2 receptors in the synergistic interaction with IL-1 and tumor necrosis factor alpha (TNFalpha), 2) the molecular mechanisms involved in synergistic enhancement of PG formation, and 3) the effects of kinins on cytokine-induced expression of RANKL, RANK, and osteoprotegerin (OPG) (the latter being crucial molecules in osteoclast differentiation).

METHODS

Formation of PGs, expression of enzymes involved in arachidonic acid metabolism, and expression of RANKL, RANK, and OPG were assessed in the human osteoblastic cell line MG-63 and in mouse calvarial bones. The role of NF-kappaB and MAP kinases was studied using pharmacologic inhibitors.

RESULTS

PGE(2) formation and cyclooxygenase 2 (COX-2) protein expression were induced by IL-1beta and potentiated by kinins with affinity for the B1 or B2 receptors, resulting in PGE(2)-dependent enhancement of RANKL. The enhancements of PGE(2) formation and COX-2 were markedly decreased by inhibition of p38 and JNK MAP kinases, whereas inhibition of NF-kappaB resulted in abolishment of the PGE(2) response with only slight inhibition of COX-2.

CONCLUSION

Kinin B1 and B2 receptors synergistically potentiate IL-1- and TNFalpha-induced PG biosynthesis in osteoblasts by a mechanism involving increased levels of COX-2, resulting in increased RANKL. The synergistic stimulation is dependent on NF-kappaB and MAP kinases. These mechanisms might help to explain the enhanced bone resorption associated with inflammatory disorders, including that in rheumatoid arthritis.

The role of plasma high molecular weight kininogen in experimental intestinal and systemic inflammation

Inflammation is accompanied by activation of the plasma kallikrein-kinin system (KKS). KKS activation has been demonstrated in a variety of inflammatory human diseases. To further explore the participation of KKS in arthritis and inflammatory bowel disease, we used two experimental animal models in arthritis and enterocolitis. We found that activation of KKS is associated with arthritis induced by intraperitoneal injection of peptidoglycan-polysaccharide polymers (PG-PS) as well as the enterocolitis and systemic inflammation induced also by PG-PS when injected into the intestinal wall of genetically susceptible Lewis rats. We postulated that KKS participates in the pathogenesis of inflammatory reactions involved in cellular injury, coagulation, fibrinolysis, kinin formation, complement activation, cytokine secretion, and release of proteases. We demonstrated that therapy with a specific plasma kallikrein inhibitor modulated the experimental enterocolitis, arthritis, and systemic inflammation. The fact that deficiency of plasma high molecular weight kininogen in the genetically susceptible Lewis rat results in decreased chronic enterocolitis and systemic inflammation also supports our hypothesis. We suggest that KKS plays a similar role in idiopathic human intestinal inflammatory disease and arthritis, making kallikrein-kinin system proteins appealing targets for drug therapy in chronic inflammatory diseases such as rheumatoid arthritis and Crohn's disease.

The role of plasma high molecular weight kininogen in experimental intestinal and systemic inflammation

Inflammation is accompanied by activation of the plasma kallikrein-kinin system (KKS). KKS activation has been demonstrated in a variety of inflammatory human diseases. To further explore the participation of KKS in arthritis and inflammatory bowel disease, we used two experimental animal models in arthritis and enterocolitis. We found that activation of KKS is associated with arthritis induced by intraperitoneal injection of peptidoglycan-polysaccharide polymers (PG-PS) as well as the enterocolitis and systemic inflammation induced also by PG-PS when injected into the intestinal wall of genetically susceptible Lewis rats. We postulated that KKS participates in the pathogenesis of inflammatory reactions involved in cellular injury, coagulation, fibrinolysis, kinin formation, complement activation, cytokine secretion, and release of proteases. We demonstrated that therapy with a specific plasma kallikrein inhibitor modulated the experimental enterocolitis, arthritis, and systemic inflammation. The fact that deficiency of plasma high molecular weight kininogen in the genetically susceptible Lewis rat results in decreased chronic enterocolitis and systemic inflammation also supports our hypothesis. We suggest that KKS plays a similar role in idiopathic human intestinal inflammatory disease and arthritis, making kallikrein-kinin system proteins appealing targets for drug therapy in chronic inflammatory diseases such as rheumatoid arthritis and Crohn's disease.

Kallikrein cascade and cytokines in inflamed joints

Rheumatoid arthritis is a chronic multi-system disease of unknown aetiology. The current hypothesis is that an unknown antigen triggers an autoimmune response in a genetically susceptible individual. The predominant pathological change is that of an inflammatory synovitis, characterised by cellular infiltrates and angiogenesis, with subsequent bone and cartilage destruction. These pathological changes are as a result of the activation of a variety of cells, inflammatory mediators, and effector molecules. The pro-inflammatory kinins and cytokines appear to play a central role in the pathogenesis of rheumatoid arthritis. Sufficient evidence exists that establishes a key role for the kallikrein-kinin cascade in inflamed joints. In addition, there appears to be an inter-relationship between cytokines and kinins in the inflammatory process. Kinins induce the release of cytokines, and cytokines have been shown to augment the effects of kinins. This may lead to an enhancement and perpetuation of the inflammatory process. In this review, we report a first study, correlating markers of disease with the kallikrein-kinin cascade and with cytokines.

Evidence for activation of the tissue kallikrein-kinin system in nociceptive transmission and inflammatory responses of mice using a specific enzyme inhibitor

The pharmacological activity of phenylacetyl-Phe-Ser-Arg-N-(2, 4-dinitrophenyl)-ethylenediamine (TKI), a tissue kallikrein specific inhibitor, was assessed using models of nociception and inflammation in mice. Injection of TKI (13.6 - 136 micromol kg(-1), i.p. or 41 - 410 micromol kg(-1), s.c.) produced a dose-related inhibition of the acetic acid-induced writhes (by 37 to 85% or 34 to 80%, respectively). The antinociceptive activity of TKI (41 micromol kg(-1), i.p.) was maximal after 30 min injection and lasted for 120 min. The effect was unaltered by pretreatment with naloxone (8.2 micromol kg(-1), s.c.) or bilateral adrenalectomy. TKI (41 and 136 micromol kg(-1), i.p.) produced a dose-related decrease of the late phase of formalin-induced nociception by 79 and 98%, respectively. At 136 micromol kg(-1), i.p., TKI also shortened the duration of paw licking in the early phase by 69%. TKI (41 and 136 micromol kg(-1), i.p.) also reduced the capsaicin-induced nociceptive response (by 51 to 79%). TKI (41 micromol kg(-1), i.p. or 410 micromol kg(-1), s.c.) reduced the oedematogenic response, from the second to the fifth hour after carrageenin injection by 36 to 30% or by 47 to 39%, respectively. Pretreatment with TKI (41 micromol kg(-1), i.p.) reduced the capsaicin-induced neurogenic inflammation in the mouse ear by 54%. It is concluded that TKI presents antinociceptive and antiinflammatory activities mediated by inhibition of kinin formation by tissue kallikrein in mice. The results also indicate that the tissue kallikrein-dependent pathway contributes to kinin generation in nociceptive and inflammatory processes in mice.

High-molecular-weight kininogen is a binding protein for tissue prokallikrein

Human tissue prokallikrein, a zymogen of the kallikrein-kinin system, circulates in plasma bound to neutrophils. Because plasma kininogens contribute to the assembly of kinin-generating components on blood cells, these proteins were assessed for their ability to complex the kallikrein precursor. Using ligand blot and direct binding assays, biotinylated prokallikrein was found to bind only to high-molecular-weight kininogen and not to the low-molecular-weight form. The interaction was specific, reversible, and saturable yielding an estimated dissociation constant K(D)=690 nM and a 1:1 stoichiometry. Specific kininogen binding of tissue prokallikrein also occurred at physiological plasma protein concentrations. These results provide the first evidence for a novel function of high-molecular-weight kininogen as a binding protein for tissue prokallikrein that could serve to localize the kallikrein precursor on the neutrophil surface.

Generation of kinins in synovial fluid from patients with arthropathy

An enzyme-linked immunosorbent assay method is described for the measurement of kinin formation in synovial fluid from patients with rheumatoid and osteoarthritis (RA and OA). Basal kinin concentrations were less than 6 ng/ml in synovial fluid collected in the presence of inhibitors of kinin forming (kininogenase) and kinin metabolising (kininase) enzymes. During incubation of synovial fluid in the presence of kininase inhibitors alone, kinins were produced rapidly over the first 10 min, but production ceased completely within 30 min due to inhibition of the endogenous kininogenases; the rate of kinin generation during the early rapid phase correlated well with the plateau kinin concentration. Plateau kinin levels in synovial fluid from 15 patients with OA and RA ranged from 98 to 427 ng/ml, with a median value of 148 ng/ml. This study demonstrates clearly that synovial fluid from arthritis patients has the capacity to produce kinins. Although the number of patients was small, the amount of kinin generated in vitro varied over a wide range and a relationship between intra-articular kinin formation and clinical features may become apparent in a larger group of patients. The technique could also be used to investigate other biological systems in which a role has been proposed for kinins.

Augmented plasma and tissue kallikrein like activity in synovial fluid of patients with inflammatory articular diseases

We studied some of the components of the kininogen-kallikrein-kinin system, simultaneously, in plasma and synovial effusions of patients with inflammatory articular diseases. Plasma and tissue kallikrein like activity and kininogen levels were evaluated. Active plasma and tissue kallikreins in plasma and synovial fluid were detected by their amidase activity upon specific chromogenic substrates. Kininogen levels were determined by a bioassay. Both specific amidase activity of plasma and tissue kallikreins were augmented in synovial effusions in relation to their own plasma activity. Kininogen levels in synovial fluid tended to be diminished in relation to plasma, however statistical significance was not reached. The consumption of kininogen is probably related to kinin production. This finding together with increased activities of plasma and tissue kallikreins reinforce the involvement of kinins in pathogenesis of inflammatory articular diseases.

Hoe 140 a new potent and long acting bradykinin-antagonist: in vivo studies

1. The potency, duration of action and tolerability of Hoe 140, a novel and highly potent bradykinin (BK) antagonist in vitro, has been tested in different in vivo models and compared with the well-known BK antagonist D-Arg-[Hyp2, Thi5,8, D-Phe7]BK. 2. Hoe 140 is highly potent and long acting in inhibiting BK-induced hypotensive responses in the rat. Four hours after s.c. administration of 20 nmol kg-1, inhibition still amounted to 60% whereas the effect of 200 nmol kg-1 of D-Arg-[Hyp2, Thi5,8, D-Phe7]BK was not significant. 3. BK-induced bronchoconstriction in guinea-pigs was strongly inhibited by Hoe 140. The magnitude and duration of inhibition confirmed the findings obtained in the blood pressure experiments in the rat. 4. Carrageenin-induced inflammatory oedema of the rat paw was considerably inhibited at i.v. doses between 0.1 and 1 mg kg-1. 5. In conscious dogs, intravenous doses of 0.01 and 0.1 mg kg-1 of Hoe 140 and D-Arg-[Hyp2, Thi5,8, D-Phe7]BK were well tolerated. At doses of 1 mg kg-1 adverse effects occurred that were attributed to the residual BK agonistic activity of both compounds. 6. Hoe 140 has been shown to be a highly potent and long acting BK antagonist in vivo in different animal species and models. This makes it appropriate to investigate further the physiological and pathophysiological role of BK.

Identification of tissue kallikrein messenger RNA in human neutrophils

Expression of tissue kallikrein in human neutrophils has been suggested by previous studies using enzymatic and immunochemical techniques. Secretion of this potent biological factor by neutrophils would be of marked significance in the inflammatory process. The present study utilized the polymerase chain reaction following reverse transcriptase generation of total neutrophils cDNA to demonstrate the presence of tissue kallikrein mRNA in the human neutrophils. In addition, use of sequence-specific primers demonstrated the presence of mRNA for the hGK-1 gene, but not for the hPK gene product or the gene for prostate-specific antigen. These results confirm that tissue kallikrein is present in neutrophils and may be secreted as part of the inflammatory process.

Cultured human synovial fibroblasts rapidly metabolize kinins and neuropeptides

Kinins and substance P have been implicated in the pathogenesis of inflammatory arthritis by virtue of their abilities to induce vasodilation, edema, and pain. The relative biological potencies of these peptides in vivo would depend at least in part upon their rates of catabolism in the joint. We hypothesized that human synovial lining cells may regulate intraarticular levels of kinins and neuropeptides via degradation by cell surface-associated peptidases. We exposed intact human synovial fibroblasts to kinins and substance P, in the presence or absence of specific peptidase inhibitors, and measured the amount of intact substrate remaining and degradation product(s) generated over time. Aminopeptidase M (AmM; EC 3.4.11.2), neutral endopeptidase-24.11 (NEP-24.11; EC 3.4.24.11), and dipeptidyl(amino)peptidase IV (DAP IV; EC 3.4.14.5) were identified on the cell surface of synovial cells. Bradykinin degradation was due entirely to NEP-24.11 (1.39 +/- 0.29 nmol/min per well). Lysylbradykinin was also degraded by NEP-24.11 (0.80 +/- 0.19 nmol/min per well); however, in the presence of phosphoramidon, AmM-mediated conversion to bradykinin (3.74 +/- 0.46 nmol/min per well) could be demonstrated. The combined actions of NEP-24.11 (0.93 +/- 0.15 nmol/min per well) and DAP IV (0.84 +/- 0.18 nmol/min per well) were responsible for the degradation of substance P. AmM (2.44 +/- 0.33 nmol/min per well) and NEP-24.11 (1.30 +/- 0.45 nmol/min per well) were responsible for the degradation of the opioid peptide, [Leu5]enkephalin. The identity of each of the three peptidases was confirmed via synthetic substrate hydrolysis, inhibition profile, and immunological identification. The profiles of peptidase enzymes identified in cells derived from rheumatoid and osteoarthritic joints were identical. These data demonstrate the human synovial fibroblast to be a rich source of three specific peptidases and suggest that it may play a prominent role in regulating peptide levels in the joint.

Mediators of joint swelling and damage in rheumatoid arthritis and pristane induced arthritis

Joint swelling and tenderness in rheumatoid arthritis (RA) probably result from IgG aggregates activating complement with the consequent attraction of polymorphonuclear leucocytes (PMNs) and the liberation of their granule enzymes such as kininogenases. By contrast IL-1 and TNF are the major stimulants of cartilage and bone loss although other agents contribute. The fundamental drive for the production of these mediators is unknown but a role for heat shock proteins is suggested from work on pristane induced arthritis.

Kallikreins and kinins: mediators in inflammatory joint disease?

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Identification of a tissue kallikrein in human polymorphonuclear leucocytes

We have identified a tissue kallikrein in polymorphonuclear (PMN) leucocytes of normal human blood and bone marrow by immunocytochemistry, radioimmunoassay and enzymology. Immunoreactive tissue kallikrein was visualized in the mature neutrophil leucocytes and in immature forms such as metamyelocytes and myelocytes. No tissue kallikrein was detected in eosinophil leucocytes, lymphocytes, macrophages, megakaryocytes and platelets. So far, we have failed to observe immunoreactivity to tissue kallikrein in basophils. The presence of tissue kallikrein in extracts prepared from PMN leucocytes isolated from peripheral blood was demonstrated by immunodiffusion, dot-blotting and by radioimmunoassay. The kininogenase and amidase activity of the extracts resembled that of tissue kallikrein in being resistant to soya bean trypsin inhibitor and sensitive to trasylol. The amidase activity attributable to tissue kallikrein was completely inhibited by specific antisera.