Activation of Synovial Cell p38 MAP Kinase by Macrophage Migration Inhibitory Factor

LEILANI L. SANTOS, DEREK LACEY, YUANHANG YANG, MICHELLE LEECH, and ERIC F. MORAND

ABSTRACT.

Objective. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine important in animal models of rheumatoid arthritis (RA). We investigated the utilization by MIF of mitogen activated protein (MAP) kinase signalling pathways in the stimulation of fibroblast-like synoviocytes (FLS), cyclooxygenase-2 (COX-2), prostaglandin E₂ (PGE₂), and interleukin 6 (IL-6) and IL-8 expression.

Methods. Cultured human RA FLS were treated with recombinant MIF. Activation of MAPK was measured by Western blotting and blocked using specific inhibitors. The expression of COX-2, PGE₂, IL-6, and IL-8 were measured using flow cytometry, ELISA, and real-time polymerase chain reaction.

Results. MIF induced the phosphorylation of FLS p38 and extracellular-signal regulated kinase (ERK) MAP kinase. MIF significantly induced COX-2 and IL-6 protein and mRNA expression as well as PGE₂ and IL-8 production. Antagonism of p38 MAP kinase inhibited MIF induction of COX-2, PGE₂, and IL-6. In contrast, antagonism of ERK had no effect on COX-2, PGE₂, or IL-6. Neither antagonist inhibited MIF-induced IL-8.

Conclusion. MIF activates RA FLS COX-2 and IL-6 expression via p38 MAP kinase activation and induces IL-8 via p38 and ERK MAP kinase-independent pathways. (J Rheumatol 2004;31:1038-43)

Key Indexing Terms:

MIGRATION INHIBITORY FACTOR
p38 MITOGEN ACTIVATED PROTEIN KINASE
CYCLOOXYGENASE-2
PROSTAGLANDIN E₂
INTERLEUKIN 6
INTERLEUKIN 8

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From the Centre for Inflammatory Diseases, Monash University Department of Medicine, Monash Medical Centre, Clayton, Melbourne, Australia.

Supported by grants from the National Health and Medical Research Council of Australia, Arthritis Foundation of Australia, and Pfizer Global Research and Development.

L.L. Santos, PhD, Research Officer; D. Lacey, Hons, PhD Student; Y. Yang, PhD, Research Officer; M. Leech, MBBS, FRACP, PhD, Senior Lecturer, Medicine, Monash University; Consultant Rheumatologist, Southern Health; E.F. Morand, MBBS, FRACP, PhD, Associate Professor, Medicine, Monash University; Deputy Director, Rheumatology and Immunology, Southern Health.

Address reprint requests to Dr. L. Santos, Centre for Inflammatory Diseases, Monash University Department of Medicine, Monash Medical Centre, Locked Bag No 29, Clayton, Melbourne, 3168 Australia. E-mail: lanie.santos@med.monash.edu.au

Submitted June 25, 2003; revision accepted December 5, 2003.

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