Tumor necrosis factor alpha-induced interleukin-32 is positively regulated via the Syk/protein kinase Cdelta/JNK pathway in rheumatoid synovial fibroblasts.

Abstract

OBJECTIVE Interleukin-32 (IL-32) is a recently discovered cytokine that appears to play a critical role in human rheumatoid arthritis (RA). It is highly expressed in synovium and fibroblast-like synoviocytes (FLS) from RA patients, but not in patients with osteoarthritis (OA). This study was undertaken to assess IL-32 levels in RA synovial fluid (SF) and to investigate the secretion and regulation of IL-32 in RA FLS. METHODS FLS and SF were obtained from the joints of RA patients. The secretion and expression of IL-32 and activation of signaling molecules were examined by enzyme-linked immunosorbent assay, immunoblotting, immunoprecipitation, reverse transcriptase-polymerase chain reaction, and small interfering RNA (siRNA) transfection. RESULTS IL-32 levels were high in RA SF compared with OA SF. Furthermore, RA FLS expressed and secreted IL-32 when stimulated with tumor necrosis factor alpha (TNFalpha). TNFalpha-induced expression of IL-32 was significantly suppressed, in a dose-dependent manner, by inhibitors of Syk, protein kinase Cdelta (PKCdelta), and JNK and by knockdown of these kinases and c-Jun with siRNA. We also observed that PKCdelta mediated the activation of JNK and c-Jun, and experiments using specific inhibitors and siRNA demonstrated that Syk was the upstream kinase for the activation of PKCdelta. CONCLUSION The present findings suggest that IL-32 may be a newly identified prognostic biomarker in RA, thereby adding valuable knowledge to the understanding of this disease. The results also demonstrate that the production of IL-32 in RA FLS is regulated by Syk/PKCdelta-mediated signaling events.

DOI: 10.1002/art.24299
050100150200920102011201220132014201520162017
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@article{Mun2009TumorNF, title={Tumor necrosis factor alpha-induced interleukin-32 is positively regulated via the Syk/protein kinase Cdelta/JNK pathway in rheumatoid synovial fibroblasts.}, author={Se Hwan Mun and Jie Wan Kim and Seong Su Nah and Na Young Ko and Jun Ho Lee and Ju Dong Kim and Do Kyun Kim and Hyuk Soon Kim and Ji Da Choi and Soo Hyun Kim and Chang Keun Lee and Seung Hwa Park and Bo Kyung Kim and Hyung Sik Kim and Young Mi Kim and Wahn Soo Choi}, journal={Arthritis and rheumatism}, year={2009}, volume={60 3}, pages={678-85} }