These findings raise the question of whether inhibition of JAK-3 alone
is sufficient to disrupt cytokine signalling and ameliorate the rheumatoid inflammatory processes. Although the importance of JAK-3 in the development and activation of the lymphoid lineage has been well characterized [5, 6], its role in non-lymphoid-cell activation PS-341 has not been explored fully. We therefore analysed the role of JAK-3 in rheumatoid synovitis using synovial fibroblasts isolated from patients with RA. JAK inhibitors, CP-690,550 and INCB028050 were obtained from Sellck (Houston, TX, USA). PF-956980 was obtained from Sigma-Aldrich Japan (Tokyo, Japan). Human oncostain-M (OSM) was purchased from Peprotech
(Rocky Hills, NJ, USA). Phosphospecific antibodies against JAK-1 (Tyr1022/1023), JAK-2 (Tyr1007/1008), STAT-1 (Tyr701), STAT-3 (Tyr705) and STAT-5 (Tyr694) were purchased from Cell Signaling Technology (Beverly, MA, USA). Phosphospecific antibody against JAK-3 (Tyr980) was purchased from Santa Cruz Biotechnology (Santa Cruz, CA, USA). For immunohistochemical analysis, formalin-fixed and paraffin-embedded tissue blocks were cut into 4-μm-thick sections. SCH772984 manufacturer The sections were deparaffinized in xylene and subsequently rehydrated in sequential ethanol (100–70%). After washing three times with 10 mM phosphate-buffered saline (PBS, pH 7·4), antigen retrieval was carried out in a microwave at 95°C for 20 min in 10 mM citrate buffer (pH 6·0), then by washing three times in PBS for 10 min. The sections were treated with peroxidase-blocking 3-oxoacyl-(acyl-carrier-protein) reductase solution (Dako Japan, Kyoto, Japan) for 5 min, and incubated with 1:1000 dilution of anti-phospho-JAK-1,-2,-3, anti-CD3, CD68 and anti-vimentin (Dako Japan) antibodies. A standardized two-step method with Envision plus (Dako) was used for detection. The reaction products were visualized using diaminobenzidine as a chromogen (Dako) and counterstained with Mayer’s haematoxylin (Dako). Synovial tissue was obtained from patients with RA or osteoarthritis (OA) at the time
of total joint replacement or synovectomy. Synovium was minced and incubated with 1 mg/ml collagenase type VIII (Sigma-Aldrich, St Louis, MO, USA) in serum-free RPMI-1640 medium (Life Technologies, Grand Island, NY, USA) for 1 h at 37°C, filtered, washed extensively and cultured in Dulbecco’s modified Eagle’s medium (DMEM) (Life Technologies) supplemented with 10% fetal bovine serum (FBS) in a humidified 5% CO2 atmosphere. Fibroblast-like synoviocytes (synovial fibroblasts) were used from passages 4 to 7, during which time they are a homogeneous population of cells (<1% CD45-positive). The whole study was approved by the Ethics Committees Nagasaki Medical Center and informed consent was obtained from each of the individuals.