Increased prevalence of MEFV exon 10 variants in Japanese patients with adult-onset Still's disease.

Autoinflammatory diseases include a large spectrum of monogenic diseases, e.g. familial Mediterranean fever (FMF), as well as complex genetic trait diseases, e.g. adult-onset Still's disease (AOSD). In populations where FMF is common, an increased MEFV mutation rate is found in patients with rheumatic diseases. The aim of this study was to examine MEFV mutations in Japanese patients with AOSD. Genomic DNA was isolated from 49 AOSD patients and 105 healthy controls, and exons 1, 2, 3 and 10 of the MEFV gene genotyped by direct sequencing. MEFV mutation frequencies in AOSD patients were compared with controls. We found no significant difference in overall allele frequencies of MEFV variants between AOSD patients and controls. However, MEFV exon 10 variants (M694I and G632S) were significantly higher in AOSD patients than controls (6.1 versus 0%). In addition, there was no significant difference between MEFV variant carriers and non-carriers with clinical manifestations, but the monocyclic clinical course of the AOSD disease phenotype was observed less frequently in patients without MEFV variants. AOSD patients had significantly higher frequencies of MEFV exon 10 mutations, suggesting that low-frequency variants of MEFV gene may be one of the susceptibility factors of AOSD.

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.

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.

Expression of CD64 on polymorphonuclear neutrophils in patients with familial Mediterranean fever.

Familial Mediterranean fever (FMF) is an autoinflammatory disease characterized by recurrent episodes of fever and serosal or synovial inflammation. We examined the utility of CD64 (FcγRI) expression in polymorphonuclear neutrophils (PMNs) as clinical and biological parameters in patients with FMF. We studied 12 Japanese FMF patients (mean age; 22·8 ± 15·5 years, male/female: 2/10), along with rheumatoid arthritis patients (RA, n = 38 male/female: 6/32, mean age; 52·2 ± 15·3 years), systemic lupus erythematosus (SLE, n = 15 male/female: 0/15, mean age; 38·5 ± 15·9 years) and 12 healthy subjects (male/female: 3/9, mean age; 37·9 ± 17·2 years). CD64 expression on PMNs was determined using flow cytometry. The quantitative expression of CD64 in patients with FMF (2439·6 ± 2215·8 molecules per PMN) was significantly higher than in healthy subjects (547·8 ± 229·5, P = 0·003) or in patients with RA (606·5 ± 228·2, P < 0·0001) and SLE (681·3 ± 281·1, P = 0·004). The increased CD64 expression on PMNs isolated from untreated FMF patients was down-regulated by colchicine treatment. NACHT-LRR-PYD-containing protein 3 (NLRP3) activation using MurNAc-L-Ala-D-isoGln (MDP) resulted in increased CD64 expression on PMNs from healthy subjects. Our results suggest that quantitative measurement of CD64 expression on PMNs can be a valuable tool to discriminate between FMF and autoimmune diseases.

Induction of interleukin-23 p19 by serum amyloid A (SAA) in rheumatoid synoviocytes.

In this study, we investigated the roles of serum amyloid A (SAA) in T helper 17 (Th17)-related cytokine induction in rheumatoid arthritis (RA) synoviocytes. Synoviocytes isolated from rheumatoid arthritis (RA) patients were stimulated with recombinant SAA and IL-23 expression was investigated using reverse transcriptase-polymerase chain reaction and Western blot. The involvement of mitogen-activated protein kineases (MAPKs) and nuclear factor (NF)-κB in SAA-induced interleukin (IL)-23 p19 expression was investigated using pharmacological inhibitors. In RA synoviocytes, SAA induced the expression of IL-23 p19 and p40 mRNA expression. The SAA-stimulated expression of p19 was rapid (< 3 h), and insensitive to polymyxin B treatment. This SAA-stimulated expression of IL-23 p19 was inhibited completely by inhibitors of NF-κB, p38MAPK and dexamethasone. Interestingly, the SAA-induced IL-23, p19 and p40 production was accompanied by enhanced expression of IL-1ß, but not transforming growth factor-ß. These results indicate that SAA is a significant inducer of IL-23 and IL-1ß in RA synoviocytes and potentially activates the IL-23/IL-17 pathway in the RA synovium. Our data present a novel interaction between inflammation and autoimmunity by an acute-phase protein.