Peptidylarginine deiminase 4 contributes to tumor necrosis factor α-induced inflammatory arthritis.
OBJECTIVE
Peptidylarginine deiminase 4 (PAD4) is a citrullinating enzyme that has multiple associations with inflammation. In rheumatoid arthritis, PAD4 and protein citrullination are increased in inflamed joints, and anti-citrullinated protein antibodies (ACPAs) form against citrullinated antigens are formed. ACPA immune complexes can deposit in the joint and induce the production of tumor necrosis factor α (TNFα), a critical inflammatory cytokine in the pathogenesis of rheumatoid arthritis. Further, in other settings, TNFα has been shown to induce PAD4 activity and modulate antibody formation. We undertook this study to investigate whether TNFα and PAD4 may synergistically exacerbate autoantibody production and inflammatory arthritis.


METHODS
To determine whether TNFα and PAD4 augment autoantibody production and inflammatory arthritis, we first used a multiplex assay to determine whether mice with chronic inflammatory arthritis due to overexpression of TNFα develop autoantibodies against native and citrullinated antigens. With TNF(+) PAD4(+/+) and TNF(+) PAD4(-/-) mice, we then compared serum autoantibody levels by multiplex array, lymphocyte activation by flow cytometry, total serum IgG levels by enzyme-linked immunosorbent assay, arthritis by clinical and histologic scoring, and systemic inflammation using microfluidic devices.


RESULTS
TNFα-overexpressing mice had increased levels of autoantibodies reactive against native and citrullinated antigens. PAD4(-/-) mice with TNFα-induced arthritis had lower levels of autoantibodies reactive against native and citrullinated antigens, decreased T cell activation and total IgG levels, and reduced inflammation and arthritis compared to PAD4(+/+) TNFα-overexpressing mice.


CONCLUSIONS
PAD4 mediates autoantibody production and inflammatory arthritis downstream of TNFα.
University of Wisconsin-Madison and William S. Middleton Memorial VA Hospital, Madison, Wisconsin.
Miriam A
MA
Shelef
Jeremy
J
Sokolove
Lauren J
LJ
Lahey
Catriona A
CA
Wagner
Eric K
EK
Sackmann
Thomas F
TF
Warner
Yanming
Y
Wang
David J
DJ
Beebe
William H
WH
Robinson
Anna
A
Huttenlocher
D000818:Animals; D001169:Arthritis, Experimental / Q000276:immunology* / Q000378:metabolism* / Q000473:pathology; D001323:Autoantibodies / Q000378:metabolism; D001402:B-Lymphocytes / Q000473:pathology; D002956:Citrulline / Q000378:metabolism; D004195:Disease Models, Animal; D006867:Hydrolases / Q000378:metabolism*; D007074:Immunoglobulin G / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D000080002:Protein-Arginine Deiminase Type 4; D013601:T-Lymphocytes / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology* / Q000378:metabolism*
D001323:Autoantibodies; D007074:Immunoglobulin G; D014409:Tumor Necrosis Factor-alpha; D002956:Citrulline; D006867:Hydrolases; D000080002:Protein-Arginine Deiminase Type 4; C552151:peptidylarginine deiminase 4, mouse