Pathogenic responses of bradykinin system in chronic inflammatory rheumatoid disease

Bradykinin Receptors Play a Critical Role in the Chronic Post-ischaemia Pain Model

Complex regional pain syndrome type-I (CRPS-I) is a chronic painful condition resulting from trauma. Bradykinin (BK) is an important inflammatory mediator required in acute and chronic pain response. The objective of this study was to evaluate the association between BK receptors (B₁ and B₂) and chronic post-ischaemia pain (CPIP) development in mice, a widely accepted CRPS-I model. We assessed mechanical and cold allodynia, and paw oedema in male and female Swiss mice exposed to the CPIP model. Upon induction, the animals were treated with BKR antagonists (HOE-140 and DALBK); BKR agonists (Tyr-BK and DABK); antisense oligonucleotides targeting B₁ and B₂ and captopril by different routes in the model (7, 14 and 21 days post-induction). Here, we demonstrated that treatment with BKR antagonists, by intraperitoneal (i.p.), intraplantar (i.pl.), and intrathecal (i.t.) routes, mitigated CPIP-induced mechanical allodynia and oedematogenic response, but not cold allodynia. On the other hand, i.pl. administration of BKR agonists exacerbated pain response. Moreover, a single treatment with captopril significantly reversed the anti-allodynic effect of BKR antagonists. In turn, the inhibition of BKRs gene expression in the spinal cord inhibited the nociceptive behaviour in the 14th post-induction. The results of the present study suggest the participation of BKRs in the development and maintenance of chronic pain associated with the CPIP model, possibly linking them to CRPS-I pathogenesis.

Emerging and Dynamic Biomedical Uses of Ferritin

Ferritin, a ubiquitously expressed protein, has classically been considered the main iron cellular storage molecule in the body. Owing to the ferroxidase activity of the H-subunit and the nucleation ability of the L-subunit, ferritin can store a large amount of iron within its mineral core. However, recent evidence has demonstrated a range of abilities of ferritin that extends well beyond the scope of iron storage. This review aims to discuss novel functions and biomedical uses of ferritin in the processes of iron delivery, delivery of biologics such as chemotherapies and contrast agents, and the utility of ferritin as a biomarker in a number of neurological diseases.

Photobiomodulation therapy in the modulation of inflammatory mediators and bradykinin receptors in an experimental model of acute osteoarthritis

The objective of this study was to evaluate the effects of photobiomodulation therapy (PBMT) on inflammatory indicators, i.e., inflammatory mediators (TNF-α and CINC-1), and pain characterized by hyperalgesia and B1 and B2 receptor activation at 6, 24, and 48 h after papain-induced osteoarthritis (OA) in rats. Fifty-four rats were subjected to hyperalgesia evaluations and then divided randomly into three groups-a control group and two groups OA and OA PBMT group by using laser parameters at wavelength (808 nm), output power (50 mW), energy per point (4 Joules), power density (1.78 W/cm²), laser beam (0.028 cm²), and energy density (144 J/cm²)-the induction of osteoarthritis was then performed with 20-μl injections of a 4 % papain solution dissolved in 10 μl of saline solution, to which 10 μl of cysteine solution (0.03 M). The statistical analysis was performed using two-way ANOVA with Bonferroni's post hoc test for comparisons between the 6, 24, and 48 h and team points within each group, and between the control, injury, and PBMT groups, and p < 0.05 was considered to indicate a significant difference. The hyperalgesia was evaluated at 6, 24, and 48 h after the injury. PBMT at a wavelength of 808 nm and doses of 4 J, administered afterward, promotes increase at the threshold of pressure stimulus at 6, 24, and 48 h after application and promote cytokine attenuation levels (TNF and CINC-1) and bradykinin receptor (B1 and B2) along the experimental period. We conclude that photobiomodulation therapy was able to promote the reduction of proinflammatory cytokines such as TNF-α and CINC-1, to reduce the gene and protein expression of the bradykinin receptor (B1 and B2), as well as increasing the stimulus response threshold of pressure in an experimental model of acute osteoarthritis.

Genome-wide association study for acute otitis media in children identifies FNDC1 as disease contributing gene

Acute otitis media (AOM) is among the most common pediatric diseases, and the most frequent reason for antibiotic treatment in children. Risk of AOM is dependent on environmental and host factors, as well as a significant genetic component. We identify genome-wide significance at a locus on 6q25.3 (rs2932989, P_meta=2.15 × 10⁻⁰⁹), and show that the associated variants are correlated with the methylation status of the FNDC1 gene (cg05678571, P=1.43 × 10⁻⁰⁶), and further show it is an eQTL for FNDC1 (P=9.3 × 10⁻⁰⁵). The mouse homologue, Fndc1, is expressed in middle ear tissue and its expression is upregulated upon lipopolysaccharide treatment. In this first GWAS of AOM and the largest OM genetic study to date, we identify the first genome-wide significant locus associated with AOM.

Acute otitis media (AOM) is an acute infection of middle ear mucosa and among the most common pediatric diseases. Here, the authors performed a genome-wide association study to link a variant in the FNDC1 locus on 6q25.3 and differential methylation status of the FNDC1 gene with predisposition to AOM.

Bradykinin Expression in Synovial Tissues and Synovial Fluids Obtained from Patients with Internal Derangement of the Temporomandibular Joint

Bradykinin has been implicated in the pathogenesis of inflammatory arthritis by virtue of the potent pro-inflammatory properties. The purpose of this study is to investigate the expression of bradykinin in patients with internal derangement of the temporomandibular joint (TMJ). We examined 33 TMJ synovial biopsy specimens from 31 patients with internal derangement of the TMJ by an immunohistochemical technique using specific antibodies. We also determined the concentration of bradykinin in 20 synovial fluids from 18 patients with TMJ internal derangement by enzyme-linked immunosorbent assay. These data were compared with those of the control subjects. Bradykinin was predominantly localized in the synovial lining cell layer of TMJ samples obtained from patients with TMJ internal derangement. Bradykinin was also detected in 19 patients' TMJ synovial fluids and the average of bradykinin concentration in the synovial fluids of patients was higher than that of the healthy controls. Although a statistically significant correlation was not observed, these findings support the hypothesis that bradykinin may also be involved in the pathogenesis of TMJ pain and synovitis.

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

OBJECTIVES

Clinical and experimental observations have suggested that bradykinin, a major activation product of the plasma kallikrein-kinin system, is involved in the pathogenesis of arthritis, but the pathogenic role of bradykinin receptors remains inconclusive. In this study we examined whether bradykinin receptors are important in the pathogenesis of anti-collagen antibody-induced arthritis (CAIA) using double receptor-deficient (B1RB2R(-/-)) mice.

METHODS

CAIA was induced in B1RB2R(+/+) and B1RB2R(-/-) mice by injection of an anti-collagen antibody cocktail on day 0 and lipopolysaccharide on day 3. Severity of disease was evaluated by measurement of joint diameter and histological analysis. The expression of proinflammatory cytokines in joint tissue and peripheral mononuclear cells was determined by ELISA and real-time RT-PCR.

RESULTS

The absent expression of B1R and B2R mRNA in B1RB2R(-/-) mice was confirmed by RT-PCR. Although B1RB2R(+/+) mice developed severe CAIA, the severity of the disease was significantly attenuated in B1RB2R(-/-) mice. In B1RB2R(+/+) mice bearing CAIA, both B1R and B2R mRNA levels were increased in joint tissue and peripheral mononuclear cells. Compared with B1RB2R(+/+) mice, the production of IL-1β and IL-6 in joint tissue and their mRNA expression in peripheral mononuclear cells were remarkably reduced in B1RB2R(-/-) mice.

CONCLUSION

These observations provide genetic evidence that bradykinin plays an important role in the pathogenesis of CAIA. B1R, whose expression is induced in inflamed joint tissue and peripheral inflammatory cells, is important in the development of CAIA.

Fasitibant chloride, a kinin B₂ receptor antagonist, and dexamethasone interact to inhibit carrageenan-induced inflammatory arthritis in rats

BACKGROUND AND PURPOSE

Bradykinin, through the kinin B₂ receptor, is involved in inflammatory processes related to arthropathies. B₂ receptor antagonists inhibited carrageenan-induced arthritis in rats in synergy with anti-inflammatory steroids. The mechanism(s) underlying this drug interaction was investigated.

EXPERIMENTAL APPROACH

Drugs inhibiting inflammatory mediators released by carrageenan were injected, alone or in combination, into the knee joint of pentobarbital anaesthetized rats 30 min before intra-articular administration of carrageenan. Their effects on the carrageenan-induced inflammatory responses (joint pain, oedema and neutrophil recruitment) and release of inflammatory mediators (prostaglandins, IL-1β, IL-6 and the chemokine GRO/CINC-1), were assessed after 6 h.

KEY RESULTS

The combination of fasitibant chloride (MEN16132) and dexamethasone was more effective than each drug administered alone in inhibiting knee joint inflammation and release of inflammatory mediators. Fasitibant chloride, MK571, atenolol, des-Arg⁹-[Leu⁸]-bradykinin (B₂ receptor, leukotriene, catecholamine and B₁ receptor antagonists, respectively) and dexketoprofen (COX inhibitor), reduced joint pain and, except for the latter, also diminished joint oedema. A combination of drugs inhibiting joint pain (fasitibant chloride, des-Arg⁹-[Leu⁸]-bradykinin, dexketoprofen, MK571 and atenolol) and oedema (fasitibant chloride, des-Arg⁹-[Leu⁸]-bradykinin, MK571 and atenolol) abolished the respective inflammatory response, producing inhibition comparable with that achieved with the combination of fasitibant chloride and dexamethasone. MK571 alone was able to block neutrophil recruitment.

CONCLUSIONS AND IMPLICATIONS

Bradykinin-mediated inflammatory responses to intra-articular carrageenan were not controlled by steroids, which were not capable of preventing bradykinin effects either by direct activation of the B₂ receptor, or through the indirect effects mediated by release of eicosanoids and cytokines.

Anti-inflammatory synergy of MEN16132, a kinin B(2) receptor antagonist, and dexamethasone in carrageenan-induced knee joint arthritis in rats

BACKGROUND AND PURPOSE

Bradykinin, through its B(2) receptor, is involved in inflammatory processes related to arthropathies. In carrageenan and lipopolysaccharide (LPS)-induced arthritis in rat, the anti-inflammatory activity of MEN16132, a potent and selective kinin B(2) receptor antagonist, was compared with that of steroidal and nonsteroidal anti-inflammatory drugs. The interaction between MEN16132 and dexamethasone was also investigated.

EXPERIMENTAL APPROACH

Drugs, alone or in combination, were injected into the knee joint 30min before intra-articular administration of carrageenan or LPS, in pentobarbital anaesthetized rats. Effects on incapacitation, oedema, neutrophil recruitment and kallikrein system activation, in the knee joint, were assessed.

KEY RESULTS

MEN16132 and dexamethasone (10-300µg per knee) dose-dependently reduced carrageenan-induced joint pain, oedema and neutrophil infiltration, reaching a maximal inhibition of about 50%. Dexketoprofen exerted a similar analgesic activity, whereas it did not affect the other inflammatory responses. MEN16132 showed a partial inhibition of LPS-induced joint pain, whereas dexamethasone produced a full analgesic effect. Combination of MEN16132 and dexamethasone showed a strong synergistic interaction in inhibiting both carrageenan and LPS-induced knee joint inflammation. Dexamethasone did not prevent the contact activation of prekallikrein by carrageenan and the subsequent release of kallikreins and bradykinin in the synovium.

CONCLUSIONS AND IMPLICATIONS

Steroids and kinin B(2) receptor antagonists appear to relieve arthritic symptoms induced by carrageenan or LPS and act synergistically to inhibit joint inflammation. This could have interesting therapeutic implications, possibly opening the way for combination therapies in the control of inflammatory arthropathies.

The kallikrein-kinin system: from mediator of inflammation to modulator of cardioprotection

Kinin is an important mediator of hyperalgesia, inflammatory conditions and asthma. It causes pain, inflammation, increased vascular permeability and vasodilatation. Several kinin antagonists have been developed with the aim of treating these pathologies. Kinin B2 receptor agonists and kallikrein may have clinical utility in the treatment of hypertension, left ventricular hypertrophy, ischemic heart disease, congestive heart failure and diabetes. However, there is a need to know whether there is a safe therapeutic window between potential cardio-protective and pro-inflammatory effects following administration of kinin B2 receptor agonists.

Prognostic factors in arthrocentesis of the temporomandibular joint: Comparison of bradykinin, leukotriene B4, prostaglandin E2, and substance P level in synovial fluid between successful and unsuccessful cases

PURPOSE

To compare levels of bradykinin (BK), leukotriene B4 (LTB4), prostaglandin E2 (PGE2), and substance P (SP) between successful and unsuccessful cases of arthrocentesis of temporomandibular joint disorders (TMDs).

PATIENTS AND METHODS

A total of 66 joints in 66 patients with TMDs who underwent arthrocentesis were evaluated in this study. Synovial fluid diluted with saline solution was aspirated from the superior joint compartment before arthrocentesis and their concentrations of BK, LTB4, PGE2, and SP were determined by enzyme-linked immunosorbent assay. The differences in the detection rate and concentration of each mediator between successful cases and unsuccessful cases of arthrocentesis were analyzed statistically.

RESULTS

Arthrocentesis was successful for 77% (51/66) of the joints. The mean detection rate of LTB4 was significantly (P < .05) higher in the unsuccessful cases (47%) than in the successful cases (16%). The mean concentration of BK was significantly (P < .0005) higher in the unsuccessful cases (425 pg/mL) than in the successful cases (144 pg/mL). There was also a statistical correlation between the detection of LTB4 and PGE2 (P < .01).

CONCLUSIONS

Increased levels of BK and LTB4 in the synovial fluid of patients with TMDs may indicate that arthrocentesis is less likely to be a successful treatment.

Identification of a Nonpeptidic and Conformationally Restricted Bradykinin B1 Receptor Antagonist with Anti-Inflammatory Activity

We report the discovery of chroman 28, a potent and selective antagonist of human, nonhuman primate, rat, and rabbit bradykinin B1 receptors (0.4-17 nM). At 90 mg/kg s.c., 28 decreased plasma extravasation in two rodent models of inflammation. A novel method to calculate entropy is introduced and ascribed approximately 30% of the gained affinity between "flexible" 4 (Ki = 132 nM) and "rigid" 28 (Ki = 0.77 nM) to decreased conformational entropy.

Zaltoprofen, a non-steroidal anti-inflammatory drug, inhibits bradykinin-induced pain responses without blocking bradykinin receptors

Zaltoprofen, a preferential COX-2 inhibitor, exhibited a potent inhibitory action on the nociceptive responses induced by a retrograde infusion of bradykinin into the right common carotid artery in rats. However, other COX-2 preferential inhibitors such as meloxicam and etodolac did not exhibit any apparent action, and also, preferential COX-1 inhibitors mofezolac and indomethacin, COX-1 and COX-2 inhibitor loxoprofen sodium showed a weak effect. These non-steroidal anti-inflammatory drugs (NSAIDs) except for zaltoprofen, strongly inhibited an acetic acid-induced writhing response related to PGs based on COX-1, at lower doses. Zaltoprofen had a moderate inhibitory effect compared with those of the above-mentioned NSAIDs. These results suggest that the inhibitory effect of zaltoprofen on bradykinin-induced nociceptive responses is not explainable by the inhibition of cyclooxygenase (COX). So, we examined the inhibitory effect of zaltoprofen on bradykinin-induced nociceptive responses by performing several in vitro experiments. Zaltoprofen did not bind to B(1) and B(2) receptors in a radio-ligand binding assay. In the cultured dorsal root ganglion cells of mature mice, zaltoprofen completely inhibited the bradykinin-induced increase of [Ca(2+)](i), which was inhibited by B(2) antagonist D-Arg-[Hyp(3), Thi(5,8), D-Phe(7)]-bradykinin, but not by B(1) antagonist. In addition, the inhibition of zaltoprofen on the increase of [Ca(2+)](i) was observed even under extracellular Ca(2+)-free conditions. The above results suggest that zaltoprofen produces an analgesic action on bradykinin-induced nociceptive responses by blocking the B(2) receptor-mediated pathway in the primary sensory neurons. Taken together, these results suggest that zaltoprofen may serve as a potent and superior analgesic for the treatment of pain.

Cytokines and neutrophils as important mediators of platelet-activating factor-induced kinin B1 receptor expression

PAF injection into the rat paw is accompanied by the concomitant activation of NF-kappaB and neutrophil influx, which appears to be relevant to the up-regulation of kinin B1 receptors. Herein, we analyse the role of TNF-alpha and IL-1beta production for PAF-induced B1 receptor upregulation in the rat paw. Additionally, we evaluate how cytokine production and neutrophil migration fit into the temporal sequence of events leading to PAF-induced B1 receptor upregulation. In our experiments, treatment with PAF resulted in a marked increase of B1 receptor-mediated paw oedema and in situ production of TNF-alpha at 1 h and IL-1beta at 3 and 6 h later. B1 receptor-mediated paw oedema was significantly inhibited by anti-TNF-alpha antibody and by interleukin-1 receptor antagonist (IRA). TNF-alpha was necessary for the local PAF-induced IL-1beta production. NF-kappaB blocker PDTC prevented the production of both TNF-alpha and IL-1beta, indicating that cytokine production is NF-kappaB dependent. Depletion of neutrophils with an anti-PMN antibody prevented IL-1beta, but not TNF-alpha, production. Although both TNF-alpha and IL-1beta are relevant to functional B1 receptor upregulation, PAF-induced increase in B1 receptor mRNA was markedly suppressed by anti-TNF-alpha and, to a lesser extent, by IRA. B1 receptor mRNA expression was also prevented by the anti-PMN antibody. In conclusion, the activation of the TNF-alpha/neutrophil axis by PAF seems to be sufficient for B1 receptor mRNA production. However, the TNF-alpha/neutrophil axis is also necessary for IL-1beta production. These two processes might lead to the appearance of functional kinin B1 upregulation receptors in vivo after PAF treatment.

The ideal lavage volume for removing bradykinin, interleukin-6, and protein from the temporomandibular joint by arthrocentesis

PURPOSE

The aim of this study was to investigate the ideal volume of perfusate for arthrocentesis of the temporomandibular joint (TMJ) disorders (TMDs).

PATIENTS AND METHODS

We evaluated 17 joints in 17 patients with TMD in this study. Arthrocentesis of the TMJ was done by perfusion of 400 mL of Ringer's solution. The first 5 mL of perfusate was collected, and then a 5-mL sample was collected when the total volume of perfusate outflow approached 50, 100, 200, 300, and 400 mL. The concentrations of bradykinin, interleukin-6, and protein were measured by immunoassay.

RESULTS

The concentration of bradykinin, interleukin-6, and protein during arthrocentesis were effectively reduced by more than 200 mL of lavage (P <.05). With a perfusate volume of 300 to 400 mL, the protein and bradykinin were no longer detectable.

CONCLUSIONS

Arthrocentesis is effective for washing out bradykinin, interleukin-6, and protein from the TMJ, and the ideal lavage volume of perfusate for arthrocentesis is between 300 and 400 mL.

Endothelial cell phenotypes in the rheumatoid synovium: activated, angiogenic, apoptotic and leaky

Endothelial cells are active participants in chronic inflammatory diseases. These cells undergo phenotypic changes that can be characterised as activated, angiogenic, apoptotic and leaky. In the present review, these phenotypes are described in the context of human rheumatoid arthritis as the disease example. Endothelial cells become activated in rheumatoid arthritis pathophysiology, expressing adhesion molecules and presenting chemokines, leading to leukocyte migration from the blood into the tissue. Endothelial cell permeability increases, leading to oedema formation and swelling of the joints. These cells proliferate as part of the angiogenic response and there is also a net increase in the turnover of endothelial cells since the number of apoptotic endothelial cells increases. The endothelium expresses various cytokines, cytokine receptors and proteases that are involved in angiogenesis, proliferation and tissue degradation. Associated with these mechanisms is a change in the spectrum of genes expressed, some of which are relatively endothelial specific and others are widely expressed by other cells in the synovium. Better knowledge of molecular and functional changes occurring in endothelial cells during chronic inflammation may lead to the development of endothelium-targeted therapies for rheumatoid arthritis and other chronic inflammatory diseases.

Mechanisms underlying the modulatory action of platelet activating factor (PAF) on the upregulation of kinin B1 receptors in the rat paw

1. The present study evaluated the ability of the administration of platelet activating factor (PAF) to induce the upregulation of B(1) receptors in the rat paw. 2. Local treatment with PAF resulted in a time-dependent increase of oedema formation induced by the B(1) receptor agonist des-Arg(9)-BK (des-Arg(9)-bradykinin), but not by the B(2) receptor agonist tyrosine(8)-bradykinin. Functional upregulation of B(1) receptors was accompanied by a prominent increase of B(1) receptor mRNA expression in the rat paw. 3. In PAF-treated paws, des-Arg(9)-BK-induced oedema formation was significantly inhibited by the B(1) receptor antagonists des-Arg(9)-[Leu(8)]-BK and R-715. The effects of PAF pretreatment were receptor operated, as assessed by the effects of the PAF receptor antagonist WEB2086 or by desensitisation of PAF receptors. 4. The protein synthesis inhibitor cycloheximide, the anti-inflammatory steroid dexamethasone or the nuclear factor (NF-kappaB) blockers pyrrolidine-dithiocarbamate (PDTC) and Nalpha-tosyl-L-chloromethylketone significantly blocked the functional upregulation of B(1) receptors. 5. The selectin inhibitor fucoidin, an anti-CD18 antibody or an anti-rat neutrophil antiserum, also significantly prevented des-Arg(9)-BK-induced paw oedema in rats pretreated with PAF. 6. Intradermal injection of PAF induced a 25-fold increase of myeloperoxidase activity in the rat paw, a response that was significantly inhibited by fucoidin, anti-CD-18, anti-rat neutrophil antiserum or PDTC. 7. Local treatment with PAF also resulted in a marked increase of NF-kappaB activation, an effect largely prevented by PDTC or by the anti-rat neutrophil antiserum. 8. Collectively, the present results indicate that the induction of B(1) receptors following treatment with the chemotatic mediator PAF is dependent on the recruitment of neutrophils, an event that is under the control of adhesion molecules, protein synthesis and NF-kappaB activation. These findings provide new insights into the role played by cell migration and chemotatic factors on B(1) receptor upregulation in vivo.

Bradykinin increases IL-8 generation in airway epithelial cells via COX-2-derived prostanoids

Interleukin (IL)-8, the C-X-C chemokine, is a potent neutrophil chemoattractant that has been implicated in a number of inflammatory airway diseases such as cystic fibrosis. Here we tested the hypothesis that bradykinin, an inflammatory mediator and chloride secretagogue, would increase IL-8 generation in airway epithelial cells through autocrine generation of endogenous prostanoids. Bradykinin increased IL-8 generation in both a non-cystic fibrosis (A549) and cystic fibrosis epithelial cell line (CFTE29) that was inhibited by the nonselective cyclooxygenase (COX) inhibitor indomethacin and the COX-2 selective inhibitor NS-398. COX-2 was the only isoform of COX expressed in both cell lines. Furthermore, the COX substrate arachidonic acid and exogenous prostaglandin E(2) both increased IL-8 release in A549 cells. These results suggest that bradykinin may contribute to neutrophilic inflammation in the airway by generation of IL-8 from airway epithelial cells. The dependence of this response on endogenous production of prostanoids by COX-2 suggests that selective COX-2 inhibitors may have a role in the treatment of airway diseases characterized by neutrophilic inflammation such as cystic fibrosis or chronic obstructive pulmonary disease.

Functional studies of bradykinin receptors in Chinese hamster ovary cells stably expressing the human B2 bradykinin receptor

Bradykinin B1 and B2 receptors, members of the G-protein coupled receptor superfamily, are involved in inflammation and pain. Chinese hamster ovary (CHO) cells stably expressing the human B2 bradykinin receptor (CHO-B2) were used to characterize the signal transduction pathways associated with this receptor and its regulation. The selective B2 antagonist [3H]NPC17731 but not the selective B1 antagonist [3,4-prolyl-3,4-(3)H(N)]-[des-Arg10,Leu9]kallidin ([3H]DALKD) bound to CHO-B2 cell membranes with a Kd of 0.77 nM and a Bmax of 1087 fmol/mg protein. [3H]NPC17731 binding was inhibited by bradykinin ligands in the order: NPC17731 > bradykinin > kallidin >> DALKD > [des-Arg10] kallidin (DAKD), consistent with the pharmacological profile of B2 bradykinin receptors. The B2 agonist bradykinin and the B1/B2 agonist kallidin, but not the B1 agonist DAKD, increased [35S]GTP gamma S binding to the CHO-B2 cell membranes. The B2 bradykinin receptors were co-immunoprecipitated with G alpha q/11. In response to bradykinin stimulation, coupling of the B2 receptors to G alpha q/11 was increased by 10-fold. Bradykinin and kallidin, but not DAKD, induced intracellular calcium release in CHO-B2 cells, which was blocked by NPC17731 but not by DALKD. These results demonstrate that B2 bradykinin receptors directly coupled to G alpha q/11 to regulate intracellular calcium release. CHO-B2 cell is a useful system that can be applied to study the effect of potential agents that may influence the B2 receptor function.

Expression of tissue kallikrein and kinin receptors in angiogenic microvascular endothelial cells

Angiogenesis is the sprouting of new capillary blood vessels from pre-existing ones. The kinin family of vasoactive peptides, formed by the serine protease tissue kallikrein from its endogenous multifunctional protein substrate kininogen, is believed to regulate the angiogenic process. The aim of this study was to determine the expression of tissue kallikrein and kinin receptors in an in vitro model of angiogenesis. Microvascular endothelial cells from the bovine mature and regressing corpus luteum were used only if they reacted with known endothelial cell markers. At first the cultured endothelial cells began sprouting, and within four weeks formed three-dimensional, capillary-like structures. Immunolabelling for tissue prokallikrein and the mature enzyme was intense in the angiogenic endothelial cells derived from mature corpora lutea. Immunoreactivity was lower in non-angiogenic endothelial cells and least in angiogenic endothelial cultures of the regressing corpus luteum. Additionally, using specific antisense DIG-labelled probes, tissue kallikrein mRNA was demonstrated in cells of the angiogenic phenotype. Immunolabelled kinin B2 receptors, but not kinin B1 receptors, were visualised on angiogenic endothelial cells. Our results suggest an important regulatory role for kinins in the multiple steps of the angiogenic cascade that may occur in wound healing and cancer cell growth.

Pro-inflammatory properties of the kallikrein-kinin system: Potential for new drug therapy

Components of the kallikrein-kinin system are activated in response to noxious stimuli (chemical, physical or bacterial), which may lead to excessive release of kinins in the synovial joints that may produce inflammatory joint disease. The inflammatory changes observed in synovial tissue may be due to activation of B(2) receptors. Kinins also stimulate the synthesis of other pro-inflammatory agents (PGs, LTs, histamine, EDRF, PGI(2) and PAF) in the inflamed joint. B(2)-receptor antagonists may provide valuable agents as new analgesic drugs. Furthermore, it is suggested that substances to reduce activation of the kallikrein-kinin system (KKS) may provide a pharmacological basis for the synthesis of novel antirheumatic or anti-inflammatory drugs.

Characterization of bradykinin receptors in human lung fibroblasts using the binding of 3[H][Des-Arg10,Leu9]kallidin and [3H]NPC17731

Bradykinin (BK) receptors are involved in pain and inflammation. Two BK receptor subtypes, B1 and B2, have been defined based on their pharmacological properties. Both B1 and B2 receptors are G-protein coupled membrane receptors. B1 receptors are present in smooth muscle tissue, whereas B2 receptors are found in both smooth muscle tissue and neurons. [Des-Arg10,Leu9]kallidin (DALKD) is a selective B1 receptor antagonist, and NPC17731 is a selective B2 receptor antagonist. To develop binding assays for the two known BK receptor subtypes, [3H]DALKD and [3H]NPC17731 were used as selective ligands for B1 and B2 receptors respectively. Both ligands bound to the CCD-16 human lung fibroblast membranes reaching equilibrium at 25 degrees C within 30 min. Binding was stable for at least 60 min. The Kd of [3H]DALKD was 0.33 nM and Bmax was 52 fmol/mg membrane protein. The Kd of [3H]NPC17731 was 0.39 nM and Bmax was 700 fmol/mg membrane protein. Competition for [3H]DALKD binding with BK receptor agonists was in the order: [des-Arg10]KD (DAKD) > KD >> [des-Arg9]BK (DABK) > BK, and competition for [3H]DALKD binding with BK receptor antagonists was in the order: DALKD > [des-Arg10]Hoe 140 (DAHoe 140) > [des-Arg9,Leu8]BK (DALBK) > NPC17731 > Hoe 140 > DNMFBK, suggesting that [3H]DALKD bound selectively to B1 receptors. By contrast, competition for [3H]NPC17731 binding by BK agonists was in the order: BK > KD >> DAKD > DABK, and competition for [3H]NPC17731 binding by BK antagonists was in the order: NPC17731 = Hoe 140 >> DNMFBK > DAHoe 140 > DALBK > DALKD, indicating that [3H]NPC17731 labeled B2 receptors selectively. These results demonstrate that [3H]DALKD and [3H]NPC17731 can be used with CCD-16 human lung fibroblast membranes to provide a pair of binding assays for the simultaneous evaluation of B1 and B2 BK receptor subtypes.

Effect of captopril on the time-dependent variation of kaolin-induced writhing reaction

Effect of captopril, an angiotensin-converting enzyme (ACE) inhibitor, on the time-dependent variation of kaolin-induced writhing reactions was examined in mice kept under conditions of light from 07:00 to 19:00 and dark from 19:00 to 07:00. The number of writhes was counted for 60 minutes after a single intraperitoneal injection of kaolin at 01:00, 07:00, 13:00, and 19:00. The number of writhes showed a time-dependent variation, with a peak at 19:00 and a trough at 07:00 in the control group. Captopril significantly increased the number of writhes after dosing at 01:00 and 07:00 (during the active period). The ACE activity following captopril dosing was significantly lower in the 07:00 than the 19:00 trial. These results suggest that the pharmacological effect of captopril varies with the dosing time, and the enhancement of the kaolin-induced writhing reaction is greater following dosing of the agent at nighttime in mice.

The kinin antagonist hoe 140 reduces acute paw oedema in rats caused by carrageenan, bradykinin and kaolin

The present study aimed to evaluate the effect of Hoe 140, a BK receptor B(2) antagonist, on acute oedema induced by carrageenan, BK and kaolin in male Wistar Kyoto rats. Hoe 140 (0.2 mg/kg and 20 mg/kg) given ip caused significant (p<0.05 and p<0.01) inhibition of carrageenan and BK-induced paw oedema. This suggests that BK is the prime inflammatory mediator of carrageenan oedema, and that it is also a specific blocker of oedema caused by BK. Furthermore, Hoe 140 was found to be less effective in reducing kaolin-induced oedema in rats. This might reflect that BK is not a prime inflammatory mediator of kaolin-induced oedema. The possible significance of these findings is discussed.

Role of nitric oxide in the physiopathology of pain

Many painful disorders, including joint dysfunctions such as rheumatoid arthritis (RA) or temporomandibular joint disorders (TMD), are associated with hyperthermia of the overlying skin. The same is true of certain intractable chronic pain conditions, such as chronic orofacial pain, which may be associated with TMD. We suggest that this skin hyperthermia, caused by regional vasodilation, is induced by extravascular nitric oxide (NO). Extravascular NO can be produced in the affected joint by osteoblasts, chondrocytes, and macrophages, by mechanical stimulation of endothelial cells, or by stimulated neurons. In view of a strong correlation between pain and skin hyperthermia in these disorders, and the evidence that NO enhances the sensitivity of peripheral nociceptors, we also suggest that at least this kind of pain is associated with excessive local level of NO. This hypothesis can be verified by dynamic area telethermometry, assessing the effect of NO on the sympathetic nervous function. This mechanism, which is in line with the general role of NO as a mediator between different organ systems, also may be relevant to any pain associated with enhanced immune response. Clinical implications of the proposed mechanism are discussed.

Cellular, biochemical and molecular characterization of the bovine temporomandibular joint disc

The cellular and collagenous components of the bovine temporomandibular joint (TMJ) disc have been isolated and analysed. In the central regions of the disc, significant amounts of type I, II, IX and XII collagen were found. The identity of these molecules was verified with collagenase digestions, Western blot analysis and Northern blot analysis (for type II collagen). Cells isolated from the TMJ disc synthesized alkaline phosphatase, proteoglycans and collagen in culture; however, the basal rate of synthesis for these molecules was lower than that for isolated osteoblasts, articular and growthplate chondrocytes. The TMJ disc cells proliferated more rapidly in culture than osteoblasts or chondrocytes. Transforming growth factor-beta stimulated proliferation by 250%, whereas prostaglandin E2 had no effect.

Inhibition of rats adjuvant arthritis by a bradykinin antagonist Hoe 140 and its influence on kallikreins

1. This study examines the effect of Hoe 140, a bradykinin (BK) 2 receptor antagonist, indomethacin and prednisolone on chronic adjuvant arthritis of the knee in rats. We also evaluated the influence of Hoe 140 on BK-forming enzymes in the synovial and paw tissues. 2. Adjuvant arthritis was induced in male Sprague-Dawley rats in the right knee by injecting 0.05 ml of a fine suspension of heat-killed Mycobacterium tubercle bacilli in liquid paraffin (5 mg/ml). 3. Hoe 140 (1.5 mg/kg i.p.), indomethacin (2.5 mg/kg orally) and prednisolone (3.0 mg/kg orally) administration for 9 days resulted in significant suppression of knee joint swelling. Plasma and tissue kallikrein levels were raised (P < 0.01) in the synovial and paw tissues of adjuvant arthritic rats. Hoe 140 treatment reduced (P < 0.05) tissue kallikrein but increased (P < 0.01) plasma kallikrein levels in synovial tissue. 4. Hoe 140 treatment did not alter (P > 0.05) the raised plasma and tissue kallikrein levels in the paw tissue. The findings indicate that Hoe 140 may be a useful anti-inflammatory agent and BK plays a major role in this adjuvant-induced arthritis model.