Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement
The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.
The C-Terminus of the Cyclin Dependent Kinase Inhibitor p21(WAF1/CIP1) Suppresses Cytokine Production and Inflammatory Arthritis
Mavers1, Melissa, Agrawal2, Hemant, Balomenos3, Dimitrios, Perlman4, Harris R.
Saint Louis University School of Medicine, St. Louis, MO
Northwestern University Feinberg School of Medicine, Chicago, IL
Centro Nacional de Biotecnología, Madrid, Spain
Northwestern University, Chicago, IL
Rheumatoid arthritis (RA) is a destructive autoimmune disease of unknown etiology. Previous studies demonstrated reduced expression of cyclin dependent kinase (CDK) inhibitors, which suppress cell cycle progression, in RA joints. We have shown that the CDK inhibitor p21 also suppresses inflammatory cytokine production by macrophages (MF), including IL-1b, IL-6, and TNFa. Furthermore, deficiency for p21 results in increased severity of lipopolysaccharide (LPS)-induced endotoxic shock. Herein, we further elucidate the role of p21 in suppression of inflammatory disease and determine the domain of p21 important for this function.
Wild-type (Wt) or p21-/- mice (C57BL/6) were injected intraperitoneally (i.p.) with 300 mL K/BxN serum and ankle circumference was measured over 725 days. Ankles were then harvested and embedded in paraffin for sections, which were stained for histochemical or immunohistochemical analysis and scored by a pathologist blinded to the study. For peptide studies, a polycationic peptide derived from HIV-1 Tat was fused to p21-mimetic peptides. Thioglycollate-elicited peritoneal MF were incubated with peptide (10 mM) for 2 hr, followed by 6 hr of 10 ng/ml LPS stimulation (in the presence of peptide). Supernatants were then collected and analyzed for various cytokines by multiplexed bead array. For in vivo studies, Wt B6;129 mice were injected i.p. with 10 mg/kg peptide 30 minutes prior to K/BxN serum and daily throughout.
Mice deficient for p21 developed more severe arthritis, with enhanced ankle swelling, joint destruction, and inflammatory infiltrate, as compared to Wt mice. Furthermore, the disease failed to fully resolve in p21-/- mice. To determine the domain of p21 important in suppression of cytokine production, MF were treated with Tat-conjugated peptides corresponding to several domains of p21 prior to, and during, incubation with LPS. Peptides corresponding to amino acids (aa) 4665 and aa 141160 reduced the production of inflammatory cytokines as compared to a control peptide. In vivo treatment with these peptides demonstrated that the aa 141160 peptide was superior in suppressing inflammatory arthritis, with 36.1-, 6.4-, and 3.6-fold reductions in ankle swelling at days 2, 4, and 7 post-K/BxN serum injection, respectively, as compared to control peptide.
These data demonstrate a pivotal role for the CDK inhibitor p21 in the suppression of inflammation. A peptide corresponding to aa 141160, which significantly reduces cytokine production and the severity of inflammatory arthritis, contains the proliferating cell nuclear antigen binding domain and a putative cyclin-binding domain. Therefore, therapies using mimics to this p21 domain may have potential in the treatment of inflammatory disease.
To cite this abstract, please use the following information:
Mavers, Melissa, Agrawal, Hemant, Balomenos, Dimitrios, Perlman, Harris R.; The C-Terminus of the Cyclin Dependent Kinase Inhibitor p21(WAF1/CIP1) Suppresses Cytokine Production and Inflammatory Arthritis [abstract]. Arthritis Rheum 2009;60 Suppl 10 :151