Satoru Motokawa

Serum amyloid A-induced IL-6 production by rheumatoid synoviocytes

In this study, we investigated the role of serum amyloid A protein (SAA) in the production of interleukin‐6 (IL‐6) using rheumatoid arthritis fibroblast‐like synoviocytes (RA‐FLS). Recombinant SAA stimulation induced the production of pro‐inflammatory cytokine, IL‐6, from RA‐FLS. The signaling events induced by SAA included the activation of the mitogen‐activated protein kineases, p38 and JNK1/2 and the activation of nuclear factor‐kappa B (NF‐κB). Inhibitor studies have shown SAA‐induced IL‐6 production to be down‐regulated by NF‐κB inhibition and partially inhibited by p38 or JNK inhibitors. Our findings demonstrate that SAA is a significant inducer of IL‐6, which is critically involved in RA pathogenesis.

CP690,550 inhibits oncostatin M-induced JAK/STAT signaling pathway in rheumatoid synoviocytes

IntroductionInterleukin (IL)-6-type cytokines exert their effects through activation of the Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling cascade. The JAK/STAT pathways play an important role in rheumatoid arthritis, since JAK inhibitors have exhibited dramatic effects on rheumatoid arthritis (RA) in clinical trials. In this study, we investigated the molecular effects of a small molecule JAK inhibitor, CP690,550 on the JAK/STAT signaling pathways and examined the role of JAK kinases in rheumatoid synovitis.MethodsFibroblast-like synoviocytes (FLS) were isolated from RA patients and stimulated with recombinant oncostatin M (OSM). The cellular supernatants were analyzed using cytokine protein chips. IL-6 mRNA and protein expression were analyzed by real-time PCR method and ELISA, respectively. Protein phosphorylation of rheumatoid synoviocytes was assessed by Western blot using phospho-specific antibodies.ResultsOSM was found to be a potent inducer of IL-6 in FLS. OSM stimulation elicited rapid phosphorylation of STATs suggesting activation of the JAK/STAT pathway in FLS. CP690,550 pretreatment completely abrogated the OSM-induced production of IL-6, as well as OSM-induced JAK/STAT, and activation of mitogen-activated kinases (MAPKs) in FLS.ConclusionsThese findings suggest that IL-6-type cytokines contribute to rheumatoid synovitis through activation of the JAK/STAT pathway in rheumatoid synoviocytes. Inhibition of these pro-inflammatory signaling pathways by CP690,550 could be important in the treatment of RA.

Effects of Janus kinase inhibitor tofacitinib on circulating serum amyloid A and interleukin‐6 during treatment for rheumatoid arthritis

The Janus kinase inhibitor tofacitinib is currently being investigated as a disease‐modifying agent in rheumatoid arthritis (RA). We investigated the in‐vivo effects of tofacitinib treatment for 4 weeks on elevated circulating acute‐phase serum amyloid (SAA) levels in 14 Japanese patients with RA. SAA levels fell from 110·5 ± 118·5 μg/ml (mean ± standard deviation) at treatment initiation to 15·3 ± 13·3 μg/ml after 4 weeks treatment with tofacitinib. The reduction in SAA levels was greater in patients receiving tofacitinib plus methotrexate compared with those receiving tofacitinib monotherapy. Tofacitinib was also associated with reduced serum interleukin (IL)‐6, but had no effect on serum levels of soluble IL‐6 receptor. Patients were divided into groups with adequate (normalization) and inadequate SAA responses (without normalization). Serum IL‐6 levels were reduced more in the group with adequate SAA response compared with those with inadequate SAA response. These results suggest that tofacitinib down‐regulates the proinflammatory cytokine, IL‐6, accompanied by reduced serum SAA levels in patients with active RA. The ability to regulate elevated serum IL‐6 and SAA levels may explain the anti‐inflammatory activity of tofacitinib.

Venous thromboembolism after total joint arthroplasty: results from a Japanese multicenter cohort study

IntroductionReal-world evidence of the effectiveness of pharmacological thromboprophylaxis for venous thromboembolism (VTE) is limited. Our objective was to assess the effectiveness and safety of thromboprophylactic regimens in Japanese patients undergoing joint replacement in a real-world setting.MethodOverall, 1,294 patients (1,073 females and 221 males) who underwent total knee arthroplasty (TKA) and 868 patients (740 females and 128 males) who underwent total hip arthroplasty (THA) in 34 Japanese national hospital organization (NHO) hospitals were enrolled. The primary efficacy outcome was the incidence of deep vein thrombosis (DVT) detected by mandatory bilateral ultrasonography up to post-operative day (POD) 10 and pulmonary embolism (PE) up to POD28. The main safety outcomes were bleeding (major or minor) and death from any cause up to POD28.ResultsPatients undergoing TKA (n = 1,294) received fondaparinux (n = 360), enoxaparin (n = 223), unfractionated heparin (n = 72), anti-platelet agents (n = 45), or no medication (n = 594). Patients undergoing THA (n = 868) received fondaparinux (n = 261), enoxaparin (n = 148), unfractionated heparin (n = 32), anti-platelet agents (n = 44), or no medication (n = 383). The incidence rates of sonographically diagnosed DVTs up to POD10 were 24.3% in patients undergoing TKA and 12.6% in patients undergoing THA, and the incidence rates of major bleeding up to POD28 were 1.2% and 2.3%, respectively. Neither fatal bleeding nor fatal pulmonary embolism occurred. Significant risk factors for postoperative VTE identified by multivariate analysis included gender (female) in both TKA and THA groups and use of a foot pump in the TKA group. Only prophylaxis with fondaparinux reduced the occurrence of VTE significantly in both groups. Propensity score matching analysis (fondaparinux versus enoxaparin) showed that the incidence of DVT was lower (relative risk 0.70, 95% confidence interval (CI) 0.58 to 0.85, P = 0.002 in TKA and relative risk 0.73, 95% CI 0.53 to 0.99, P = 0.134 in THA) but that the incidence of major bleeding was higher in the fondaparinux than in the enoxaparin group (3.4% versus 0.5%, P = 0.062 in TKA and 4.9% versus 0%, P = 0.022 in THA).ConclusionsThese findings indicate that prophylaxis with fondaparinux, not enoxaparin, reduces the risk of DVT but increases bleeding tendency in patients undergoing TKA and THA.Trial registrationUniversity Hospital Medical Information Network Clinical Trials Registry: UMIN000001366. Registered 11 September 2008.

Influence of Janus Kinase Inhibition on Interleukin 6-mediated Induction of Acute-phase Serum Amyloid A in Rheumatoid Synovium

Objective. Inhibition of intracellular signal transduction is considered to be a therapeutic target for chronic inflammation. The new Janus kinase (JAK)3 inhibitor CP690,550 has shown efficacy in the treatment of rheumatoid arthritis (RA). We investigated the influence of JAK/STAT inhibition using CP690,550 on the induction of acute-phase serum amyloid A (SAA), which is triggered by interleukin 6 (IL-6) stimulation in rheumatoid fibroblast-like synoviocytes (RA-FLS). Methods. IL-6-stimulated gene expression of the acute-phase serum amyloid A genes (A-SAA; encoded by SAA1+SAA2) and SAA4 was analyzed by reverse transcriptase-polymerase chain reaction. The intracellular signaling pathway mediating the effects of CP690,550 on IL-6-stimulated JAK/STAT activation was assessed by measuring the phosphorylation levels using Western blots. Results. IL-6 trans-signaling induced A-SAA messenger RNA (mRNA) expression in RA-FLS. By contrast IL-6 stimulation did not affect SAA4 mRNA expression, which is expressed constitutively in RA-FLS. IL-6 stimulation elicited rapid phosphorylation of JAK2 and STAT3, which was blunted by CP690,550. CP690,550 abrogated IL-6-mediated A-SAA mRNA expression in RA-FLS. Similarly, CP690,550 inhibited IL-6-mediated A-SAA mRNA expression in human hepatocytes. Conclusion. Our data indicated that CP690,550 blocked IL-6-induced JAK2/STAT3 activation, as well as the induction of A-SAA. Inhibition of IL-6-mediated proinflammatory signaling pathways by CP690,550 may represent a new antiinflammatory therapeutic strategy for RA and AA amyloidosis.

IgG-class anti-PF4/heparin antibodies and symptomatic DVT in orthopedic surgery patients receiving different anti-thromboembolic prophylaxis therapeutics

BackgroundHeparin-induced thrombocytopenia (HIT) is a thromboembolic complication that can occur with unfractionated heparin (UFH) or low molecular weight heparin (LMWH). Our objective was to determine and compare the incidence of IgG-class HIT antibodies in patients undergoing total hip arthroplasty (THA) or total knee arthroplasty (TKA) with different antithrombotic prophylaxis therapies and their contributions to the occurrence of venous thromboembolism (VTE).MethodsA prospective observational study was performed for 374 Japanese patients undergoing THA or TKA to determine the incidence of VTE. IgG-class anti-PF4/heparin antibodies were measured using IgG-specific EIA before and after the operation.ResultsIn the clinical outcome, the incidence of symptomatic deep vein thrombosis (DVT) was 15.0% (56/374, TKA; 35, THA; 21) and pulmonary emboli (PE) were not observed. The total seroconversion incidence of IgG-class PF4/heparin antibodies was 19.8% (74/374). The seroconversion incidence of IgG-class PF4/heparin antibodies was higher in patients receiving UFH (32.7%) compared to those receiving LMWH (9.5%) or fondaparinux (14.8%). Furthermore, the seroconversion incidence was significantly higher in patients undergoing TKA compared to those undergoing THA. Based on multivariate analysis, seroconversion of the IgG-class PF4/heparin antibodies was independent a risk factor for symptomatic DVT.ConclusionOur findings show that the seroconversion of IgG-class anti-PF4/heparin antibodies differed with various anti-thrombotic prophylaxis therapeutics and was associated with the risk of DVT in a subset of patients undergoing total joint arthroplasty (TKA and THA).

Serum amyloid A protein stimulates CCL20 production in rheumatoid synoviocytes

OBJECTIVE Although serum amyloid A (SAA) has been used as a marker of inflammation, its role in leucocyte recruitment and angiogenesis has not been well established in RA. CCL20 is a chemokine involved in the migration of CCR6-expressing Th17 cells. To study the contribution of SAA to the recruitment of Th17 cells, we investigated the effects of SAA on CCL20 production by RA synoviotytes. METHODS Synoviocytes isolated from RA patients were stimulated with recombinant SAA and cellular supernatants were analysed by CCL20-specific ELISA. CCL-20 mRNA expression was analysed by RT-PCR. RESULTS SAA is a most potent inducer of CCL20 secretion in RA synoviocytes compared with other inflammatory cytokines (IL-1beta, TNF-alpha and IL-17A). SAA stimulation induced CCL20 mRNA expression in RA synoviocytes, which was not affected by polymyxin B pre-treatment. SAA-induced CCL20 production was down-regulated by NF-kappaB inhibition and partially by c-jun N-terminal kinase (JNK) inhibition. SAA-induced CCL20 production was also suppressed by dexamethasone or FK506. CONCLUSION These findings suggest that SAA may be implicated in the recruitment of lymphocytes, including CCR6-expressing Th17 cells, in RA synovium by up-regulating CCL20 production in synoviocytes.

Mechanical prophylaxis is a heparin-independent risk for anti-platelet factor 4/heparin antibody formation after orthopedic surgery

Platelet-activating antibodies, which recognize platelet factor 4 (PF4)/heparin complexes, induce spontaneous heparin-induced thrombocytopenia (HIT) syndrome or fondaparinux-associated HIT without exposure to unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH). This condition mostly occurs after major orthopedic surgery, implying that surgery itself could trigger this immune response, although the mechanism is unclear. To investigate how surgery may do so, we performed a multicenter, prospective study of 2069 patients who underwent total knee arthroplasty (TKA) or hip arthroplasty. Approximately half of the patients received postoperative thromboprophylaxis with UFH, LMWH, or fondaparinux. The other half received only mechanical thromboprophylaxis, including dynamic (intermittent plantar or pneumatic compression device), static (graduated compression stockings [GCSs]), or both. We measured anti-PF4/heparin immunoglobulins G, A, and M before and 10 days after surgery using an immunoassay. Multivariate analysis revealed that dynamic mechanical thromboprophylaxis (DMT) was an independent risk factor for seroconversion (odds ratio [OR], 2.01; 95% confidence interval [CI], 1.34-3.02; P = .001), which was confirmed with propensity-score matching (OR, 1.99; 95% CI, 1.17-3.37; P = .018). For TKA, the seroconversion rates in patients treated with DMT but no anticoagulation and in patients treated with UFH or LMWH without DMT were similar, but significantly higher than in patients treated with only GCSs. The proportion of patients with ≥1.4 optical density units appeared to be higher among those treated with any anticoagulant plus DMT than among those not treated with DMT. Our study suggests that DMT increases risk of an anti-PF4/heparin immune response, even without heparin exposure. This trial was registered to www.umin.ac.jp/ctr as #UMIN000001366.

Inhibition of Janus kinase/signal transducer and activator of transcription (JAK/STAT) signalling pathway in rheumatoid synovial fibroblasts using small molecule compounds

Janus kinase (JAK) inhibitors have been developed as anti‐inflammatory agents and have demonstrated clinical efficacy in rheumatoid arthritis (RA). We investigated if JAK‐3‐selective inhibition alone could disrupt cytokine signalling in rheumatoid synovial fibroblasts. In‐vitro studies were performed using synovial fibroblasts isolated from patients with RA. Levels of activated JAK and signal transducer and activator of transcription (STAT) proteins were detected by immunoblot analysis. Target‐gene expression levels were measured by reverse transcription–polymerase chain reaction (RT–PCR) or real‐time PCR. The JAK inhibitors CP‐690,550 and INCB028050 both suppressed activation of JAK‐1/‐2/‐3 and downstream STAT‐1/‐3/‐5, as well as the expression levels of target proinflammatory genes (MCP‐I, SAA1/2) in oncostatin‐M (OSM)‐stimulated rheumatoid synovial fibroblasts. In contrast, the JAK‐3‐selective inhibitor, PF‐956980, suppressed STAT‐1/‐5 activation but did not affect STAT‐3 activation in OSM‐stimulated rheumatoid synovial fibroblasts. In addition, PF‐956980 significantly suppressed MCP‐1 gene expression, but did not block SAA1/2 gene expression in OSM‐stimulated rheumatoid synovial fibroblasts. These data suggest that JAK‐3‐selective inhibition alone is insufficient to control STAT‐3‐dependent signalling in rheumatoid synovial fibroblasts, and inhibition of JAKs, including JAK‐1/‐2, is needed to control the proinflammatory cascade in RA.

Serum amyloid A triggers the mosodium urate -mediated mature interleukin-1β production from human synovial fibroblasts

BackgroundMonosodium urate (MSU) has been shown to promote inflammasome activation and interleukin-1β (IL-1β) secretion in monocyte/macrophages, but the cellular pathway and nod-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome activation in synovial tissues, remain elusive. In this study, we investigated the effects of MSU on synovial fibroblasts to elucidate the process of MSU-mediated synovial inflammation.MethodsHuman synovial fibroblasts were stimulated with MSU in the presence or absence of serum amyloid A (SAA). The cellular supernatants were analyzed by immunoblotting using anti-IL-1β or anti-caspase-1 antibodies. IL-1β or NLRP3 mRNA expressions were analyzed by real-time PCR or reverse transcription-PCR (RT-PCR) method.ResultsNeither SAA nor MSU stimulation resulted in IL-1β or interleukin-1α (IL-1α) secretions and pro-IL-1β processing in synovial fibroblasts. However, in SAA-primed synovial fibroblasts, MSU stimulation resulted in the activation of caspase-1 and production of active IL-1β and IL-1α. The effect of SAA on IL-1β induction was impaired in cells by silencing NLRP3 using siRNA or treating with caspase-1 inhibitor. In addition, SAA induced the secretion of cathepsin B and NLRP3 mRNA expression in synovial fibroblasts.ConclusionsOur data demonstrate that exposure of human synovial fibroblasts to SAA promotes MSU-mediated caspase-1 activation and IL-1β secretion in the absence of microbial stimulation. These findings provide insight into the molecular processes underlying the synovial inflammatory condition of gout.