Jason Jungsik Song

Selective tyrosine kinase inhibition by imatinib mesylate for the treatment of autoimmune arthritis

Tyrosine kinases play a central role in the activation of signal transduction pathways and cellular responses that mediate the pathogenesis of rheumatoid arthritis. Imatinib mesylate (imatinib) is a tyrosine kinase inhibitor developed to treat Bcr/Abl-expressing leukemias and subsequently found to treat c-Kit-expressing gastrointestinal stromal tumors. We demonstrate that imatinib potently prevents and treats murine collagen-induced arthritis (CIA). We further show that micromolar concentrations of imatinib abrogate multiple signal transduction pathways implicated in RA pathogenesis, including mast cell c-Kit signaling and TNF-alpha release, macrophage c-Fms activation and cytokine production, and fibroblast PDGFR signaling and proliferation. In our studies, imatinib attenuated PDGFR signaling in fibroblast-like synoviocytes (FLSs) and TNF-alpha production in synovial fluid mononuclear cells (SFMCs) derived from human RA patients. Imatinib-mediated inhibition of a spectrum of signal transduction pathways and the downstream pathogenic cellular responses may provide a powerful approach to treat RA and other inflammatory diseases.

Plasma carboxypeptidase B downregulates inflammatory responses in autoimmune arthritis

The immune and coagulation systems are both implicated in the pathogenesis of rheumatoid arthritis (RA). Plasma carboxypeptidase B (CPB), which is activated by the thrombin/thrombomodulin complex, plays a procoagulant role during fibrin clot formation. However, an antiinflammatory role for CPB is suggested by the recent observation that CPB can cleave proinflammatory mediators, such as C5a, bradykinin, and osteopontin. Here, we show that CPB plays a central role in downregulating C5a-mediated inflammatory responses in autoimmune arthritis. CPB deficiency exacerbated inflammatory arthritis in a mouse model of RA, and cleavage of C5a by CPB suppressed the ability of C5a to recruit immune cells in vivo. In human patients with RA, genotyping of nonsynonymous SNPs in the CPB-encoding gene revealed that the allele encoding a CPB variant with longer half-life was associated with a lower risk of developing radiographically severe RA. Functionally, this CPB variant was more effective at abrogating the proinflammatory properties of C5a. Additionally, expression of both CPB and C5a in synovial fluid was higher in patients with RA than in those with osteoarthritis. These findings suggest that CPB plays a critical role in dampening local, C5a-mediated inflammation and represents a molecular link between inflammation and coagulation in autoimmune arthritis.

Regulation of tissue inflammation by thrombin-activatable carboxypeptidase B (or TAFI).

Thrombin-activatable procarboxypeptidase B (proCPB or thrombin-activatable fibrinolysis inhibitor or TAFI) is a plasma procarboxypeptidase that is activated by the thrombin-thrombomodulin complex on the vascular endothelial surface. The activated CPB removes the newly exposed carboxyl terminal lysines in the partially digested fibrin clot, diminishes tissue plasminogen activator and plasminogen binding, and protects the clot from premature lysis. We have recently shown that CPB is catalytically more efficient than plasma CPN, the major plasma anaphylatoxin inhibitor, in inhibiting bradykinin, activated complement C3a, C5a, and thrombin-cleaved osteopontin in vitro. Using a thrombin mutant (E229K) that has minimal procoagulant properties but retains the ability to activate protein C and proCPB in vivo, we showed that infusion of E229K thrombin into wild-type mice reduced bradykinin-induced hypotension but it had no effect in proCPB-deficient mice, indicating that the beneficial effect of E229K thrombin is mediated through its activation of proCPB and not protein C. Similarly proCPB-deficient mice displayed enhanced pulmonary inflammation in a C5a-induced alveolitis model and E229K thrombin ameliorated the magnitude of alveolitis in wild-type but not proCPB-deficient mice. ProCPB-deficient mice also displayed enhanced arthritis in an inflammatory arthritis model. Thus, our in vitro and in vivo data support the thesis that thrombin-activatable CPB has broad anti-inflammatory properties. By specific cleavage of the carboxyl terminal arginines from C3a, C5a, bradykinin and thrombin-cleaved osteopontin, it inactivates these active inflammatory mediators. Along with the activation of protein C, the activation of proCPB by the endothelial thrombin-thrombomodulin complex represents a homeostatic feedback mechanism in regulating thrombins pro-inflammatory functions in vivo.

Thrombin-activatable carboxypeptidase B cleavage of osteopontin regulates neutrophil survival and synoviocyte binding in rheumatoid arthritis.

OBJECTIVE Osteopontin (OPN) is a proinflammatory cytokine that plays an important role in the pathogenesis of rheumatoid arthritis (RA). OPN can be cleaved by thrombin, resulting in OPN-R and exposing the cryptic C-terminal alpha4beta1 and alpha9beta1 integrin-binding motif (SVVYGLR). Thrombin-activatable carboxypeptidase B (CPB), also called thrombin-activatable fibrinolysis inhibitor, removes the C-terminal arginine from OPN-R, generating OPN-L and abrogating its enhanced cell binding. We undertook this study to investigate the roles of OPN-R and OPN-L in synoviocyte adhesion, which contributes to the formation of invasive pannus, and in neutrophil survival, which affects inflammatory infiltrates in RA. METHODS Using specifically developed enzyme-linked immunosorbent assays, we tested the synovial fluid of patients with RA, osteoarthritis (OA), and psoriatic arthritis (PsA) to determine OPN-R, OPN-L, and full-length OPN (OPN-FL) levels. RESULTS Elevated levels of OPN-R and OPN-L were found in synovial fluid samples from RA patients, but not in samples from OA or PsA patients. Increased levels of OPN-R and OPN-L correlated with increased levels of multiple inflammatory cytokines, including tumor necrosis factor alpha and interleukin-6. Immunohistochemical analyses revealed robust expression of OPN-FL, but only minimal expression of OPN-R, in RA synovium, suggesting that cleaved OPN is released into synovial fluid. In cellular assays, OPN-FL, and to a lesser extent OPN-R and OPN-L, had an antiapoptotic effect on neutrophils. OPN-R augmented RA fibroblast-like synoviocyte binding mediated by SVVYGLR binding to alpha4beta1, whereas OPN-L did not. CONCLUSION Thrombin activation of OPN (resulting in OPN-R) and its subsequent inactivation by thrombin-activatable CPB (generating OPN-L) occurs locally within inflamed joints in RA. Our data suggest that thrombin-activatable CPB plays a central homeostatic role in RA by regulating neutrophil viability and reducing synoviocyte adhesion.

Chemerin158K Protein Is the Dominant Chemerin Isoform in Synovial and Cerebrospinal Fluids but Not in Plasma

Background: Chemerin is a chemokine/adipokine whose activity depends on proteolytic processing. Results: Specific ELISAs demonstrate that in plasma the precursor is dominant, whereas in synovial fluid from arthritis patients and CSF from glioblastoma patients, chem158K dominates. Low levels of active chem157S were found. Conclusion: Chemerin proteolysis occurs during inflammation. Significance: This is the first report about levels of different chemerin isoforms in biological samples. Chemerin is a chemoattractant involved in immunity that may also function as an adipokine. Chemerin circulates as an inactive precursor (chem163S), and its activation requires proteolytic cleavages at its C terminus, involving proteases involved in coagulation, fibrinolysis, and inflammation. However, the key proteolytic steps in prochemerin activation in vivo remain to be established. Previously, we have shown that C-terminal cleavage of chem163S by plasmin to chem158K, followed by a carboxypeptidase cleavage, leads to the most active isoform, chem157S. To identify and quantify the in vivo chemerin isoforms in biological specimens, we developed specific ELISAs for chem163S, chem158K, and chem157S, using antibodies raised against peptides from the C terminus of the different chemerin isoforms. We found that the mean plasma concentrations of chem163S, chem158K, and chem157S were 40 ± 7.9, 8.1 ± 2.9, and 0.7 ± 0.8 ng/ml, respectively. The total level of cleaved and noncleaved chemerins in cerebrospinal fluids was ∼10% of plasma levels whereas it was elevated ∼2-fold in synovial fluids from patients with arthritis. On the other hand, the fraction of cleaved chemerins was much higher in synovial fluid and cerebrospinal fluid samples than in plasma (∼75%, 50%, and 18% respectively). Chem158K was the dominant chemerin isoform, and it was not generated by ex vivo processing, indicating that cleavage of prochemerin at position Lys-158, whether by plasmin or another serine protease, represents a major step in prochemerin activation in vivo. Our study provides the first direct evidence that chemerin undergoes extensive proteolytic processing in vivo, underlining the importance of measuring individual isoforms.

Brief Report: Carboxypeptidase B Serves as a Protective Mediator in Osteoarthritis

We previously demonstrated that carboxypeptidase B (CPB) protects against joint erosion in rheumatoid arthritis by inactivating complement component C5a. We also found that levels of CPB are abnormally high in the synovial fluid of individuals with another joint disease, osteoarthritis (OA). We undertook this study to investigate whether CPB plays a role in the pathogenesis of OA.

Application of the 2016 EULAR/ACR/PRINTO Classification Criteria for Macrophage Activation Syndrome in Patients with Adult-onset Still Disease

Objective. To evaluate the clinical significance of the 2016 European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR)/Pediatric Rheumatology International Trials Organization (PRINTO) classification criteria for macrophage activation syndrome (MAS) in patients with adult-onset Still disease (AOSD). Methods. We performed a retrospective analysis of patients with AOSD with fever who were admitted to Severance Hospital between 2005 and 2016. The patients with AOSD were evaluated for MAS using the 2016 classification criteria for MAS. Clinical features, laboratory findings, and overall survival were analyzed. Logistic regression analysis was used to evaluate the factors associated with in-hospital mortality. Results. Among 64 patients with AOSD, 36 (56.3%) were classified as having MAS. The overall survival rate was significantly lower in patients with MAS than in those without (67% vs 100%, p < 0.001). Multivariate analysis showed that a low erythrocyte sedimentation rate, a low albumin level, an increase in ferritin of over 2 folds, and the development of MAS on admission were significantly associated with mortality in patients with AOSD. Conclusion. The 2016 EULAR/ACR/PRINTO classification criteria for MAS are potentially useful for the identification of patients with AOSD at high risk for a poor outcome. Febrile patients with AOSD should be monitored with the 2016 classification criteria for MAS in the early diagnosis and proper treatment of MAS.

Application of the 2013 ACR/EULAR classification criteria for systemic sclerosis to patients with Raynaud’s phenomenon

IntroductionWe investigated how many patients, who presented with Raynaud’s phenomenon (RP) and who had not been classified as systemic sclerosis (SSc), would be reclassified as SSc, if the 2013 American College of Rheumatology (ACR)/the European League Against Rheumatism (EULAR) classification criteria were used. We also analyzed the predictive values of the reclassification as SSc in those patients.MethodsWe consecutively enrolled 64 patients with RP and 60 patients with SSc. We applied the new classification criteria to them, reclassified them, and compared variables between those who were newly classified as SSc and those who were not or previously classified as SSc.ResultsSeventeen of 64 patients (26.5%), who presented with RP, but did not fulfill the 1980 ACR classification criteria, were newly classified as SSc by the 2013 ACR/EULAR classification criteria. The newly classified patients as SSc showed increased frequencies of sclerodactyly, digital tip ulcer, telangiectasia, abnormal nailfold capillaries and the presence of anti-centromere antibody, compared to those not and telangiectasia and anti-centromere antibody, compared to the previously classified patients. For the reclassification as SSc, the variables with independent predictive value were sclerodactyly (odds ratio (OR) 60.025), telangiectasia (OR 13.353) and the presence of anti-centromere antibody (OR 11.168).ConclusionsOverall, 26.5% of the patients, who presented with RP, but who did not fulfill the 1980 ACR classification criteria, were newly classified as SSc according to the 2013 ACR/EULAR classification criteria. Sclerodactyly, telangiectasia, and the presence of anti-centromere antibody had independent predictive value for reclassifying patients with RP as SSc.

Active tuberculosis risk with tumor necrosis factor inhibitors after treating latent tuberculosis.

BackgroundActive tuberculosis (TB) risk increases during anti–tumor necrosis factor (TNF) therapy; therefore, latent TB infection (LTBI) screening is recommended in potential TNF inhibitor users. It is unclear whether anti-TNF therapy increases the risk of active TB infection even after standard LTBI treatment. ObjectiveThe objective of this study was to compare the risk of active TB development in LTBI-positive versus LBTI-negative TNF inhibitor users following the current national LTBI treatment guidelines for LTBI. MethodsWe retrospectively studied 949 TNF inhibitor users with immune-mediated inflammatory diseases from 2005 to 2012 at the Yonsei University Health System. We compared the incidence of active TB among LTBI-positive TNF inhibitor users treated according to national guidelines (n = 256) and LTBI-negative TNF inhibitor users (n = 521), using Poisson regression. ResultsThe active TB incidence was 1107 per 100,000 patient-years in LTBI-positive TNF inhibitor users who received standard LTBI treatment and 490 per 100,000 patient-years in LTBI-negative TNF inhibitor users. Analysis showed that despite this numerical trend active TB risk was not statistically significantly elevated in LTBI-positive versus LTBI-negative TNF inhibitor users (incidence risk ratio, 2.15; P = 0.24; 95% confidence interval, 0.6–7.7). ConclusionsThis study demonstrated no statistically significantly increased risk of active TB in LTBI-positive TNF inhibitor users who received standard LTBI treatment compared with LTBI-negative TNF inhibitor users.

Anti-Sm is associated with the early poor outcome of lupus nephritis.

We investigated whether anti‐Smith (Sm) is associated with the outcome of kidney biopsy‐proven lupus nephritis.