Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Decreased Collagen Induced Arthritis (CIA) Severity in MAPK Kinase 6 Deficient Mice: Pivotal Role of Th1 and Th17 Cytokines.

Hammaker1,  Deepa, Topolewski2,  Katharyn, Edgar2,  Meghan, Boyle1,  David L., Firestein1,  Gary S.

UCSD School of Medicine, La Jolla, CA
UCSD School of Medicine

Purpose:

MKK3 and MKK6 are upstream kinases that activate p38 MAP kinase and regulate distinct subsets of cytokines. Previous studies suggest that both kinases suppress innate immune responses and arthritis severity in passive K/BxN arthritis. However, their function in an adaptive model of inflammatory arthritis has is not known. This study evaluated whether these kinases play a role in collagen induced arthritis (CIA).

Method:

Wild type (WT), MKK6-/-, and MKK3-/- mice were immunized on days 0 and 21 with type II bovine collagen in complete Freund's adjuvant. Joint histology was evaluated on synovitis, bone erosion, extra-articular inflammation and proteoglycan damage (max score=16). Serum anti-collagen antibodies were measured by ELISA. Cytokines in joints extracts and serum was determined by multiplex analysis. Splenocytes isolated 14 days after immunization were cultured with concanavalin A (Con A), type II collagen (CII), or medium and supernatants were assayed for cytokines.

Results:

Arthritis severity was significantly lower in MKK6-/- mice than WT mice, while MKK3-/- mice had intermediate disease severity (p=0.03 for each compared to WT).

Scores of WT, MKK6-/- and MKK3-/- mice on day 35 were 12±1.5, 7±1.8, and 8±2.4, respectively. Histological evaluation showed significantly decreased bone erosion in MKK6-/- mice compared with WT mice (1.2±0.5 vs. 2.7±0.5, p=0.03). Decreased synovitis (50% inhibition), and proteoglycan loss (40% inhibition) were observed in MKK6-/- mice compared with WT mice. Surprisingly, inflammation and bone destruction were similar in WT and MKK3-/- mice. Anti-collagen antibodies levels in MKK6-/- mice were decreased by 45±12% compared with WT (p=0.004), but titers in MKK3-/- mice were the same as WT. Synovial IL-6, MMP3 and MMP13 gene expression was reduced by 66–79% in MKK6-/- mice compared with WT (p<0.02 for each). Expression of these genes was modestly reduced in MKK3-/- joints but did not reach statistical significance. T cell differentiation was evaluated by examining in vitro splenocyte cytokine profiles. IL-17 production in response to Con A and CII in MKK6-/- mice was reduced by 80±7% and 82±16% compared with WT and were normal in MKK3-/- cells (p<=0.03 for MKK6-/-). IFNg production by Con A-stimulated splenocytes was inhibited by 85±5% in MKK6-/- compared with WT mice (p=0.025). IL-4 levels were not altered by MKK3 or MKK6 deficiency.

Conclusion:

MKK6 deficiency suppressed CIA and joint destruction while MKK3 had an intermediate effect. Lower disease severity in MKK6-/- mice was due to decreased adaptive immune responses, especially the production of antibodies and Th1/Th17 cytokines. These data suggest that targeting MKK6 has a potential benefit in complex diseases involving adaptive immune responses like rheumatoid arthritis.

To cite this abstract, please use the following information:
Hammaker, Deepa, Topolewski, Katharyn, Edgar, Meghan, Boyle, David L., Firestein, Gary S.; Decreased Collagen Induced Arthritis (CIA) Severity in MAPK Kinase 6 Deficient Mice: Pivotal Role of Th1 and Th17 Cytokines. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :635
DOI: 10.1002/art.28403

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