Alterations in the stoichiometric balance between members of Bcl-2 and Fas apoptotic pathway could lead to the pathogenesis of systemic lupus erythematosus (SLE). We showed that patients with SLE displayed increased expression in antiapoptotic members of the Bcl-2 and Fas apoptotic pathways in isolated mononuclear cells. Further, mice (Bcl2l11(-/-)Fas(lpr/lpr)) lacking the Bcl-2 pro-apoptotic member, Bim (Bcl2l11(-/-)) and and with an lpr mutation in the gene encoding Fas (Fas(lpr/lpr)) developed severe SLE-like disease by 16 weeks of age unlike Bcl2l11(-/-) or Fas(lpr/lpr) mice. Bcl2l11(-/-)Fas(lpr/lpr) antigen-presenting cells (APCs) were markedly activated, and their numbers were increased in lymphoid tissues and in kidneys, yet numerous TUNEL-positive cells were observed in glomeruli of Bcl2l11(-/-)Fas(lpr/lpr) mice. These data demonstrate that dysregulation of the Bcl-2 or Fas pathways can alter the function of APCs, thereby leading to SLE pathogenesis.

Significant morbidity and mortality can be attributed to inflammatory diseases; therefore, a greater understanding of the mechanisms involved in the progression of inflammation is crucial. Here, we demonstrate that p21 (WAF1/CIP1) , an established suppressor of cell cycle progression, is a inhibitor of IL-1b synthesis in macrophages. Mice deficient in p21 (p21 À/À ) display increased susceptibility to endotoxic shock, which is associated with increased serum levels of IL-1b. Administration of IL-1 receptor antagonist reduces LPS-induced lethality in p21 À/À mice. Analysis of isolated macrophages, which are one of the central producers of IL-1b, reveals that deficiency for p21 led to more IL-1b mRNA and pro-protein synthesis following TLR ligation. The increase in IL-1b pro-protein is associated with elevated secretion of active IL-1b by p21 À/À macrophages. siRNA-mediated knockdown of p21 in human macrophages results in increased IL-1b secretion as well. A peptide mapping strategy shows that the cyclin-dependent-kinase (CDK)-binding domain of p21 is sufficient to reduce the secretion of IL-1b by p21 À/À macrophages. These data suggest a novel role for p21 and specifically for the CDK-binding domain of p21 (WAF1/CIP1) in inhibiting inflammation. IntroductionThe pleiotropic cytokine IL-1b is required for the progression of numerous inflammatory disorders [1]. As key components of the innate immune response, monocytes and macrophages play an important role in the initiation and/or progression of inflammatory disease, largely through secretion of IL-1b, which contributes significantly to pathogenesis. Current treatments for diseases such as rheumatoid arthritis, gout, and periodic fever syndromes include the IL-1 receptor antagonist anakinra (Kineret s , Amgen) SHORT COMMUNICATIONÃ These authors contributed equally to this work. 820[2]; yet this therapy is ineffective in a cohort of patients [3]. Therefore, a better understanding of the mechanisms by which IL-1b production is regulated remains crucial for the development of new therapies to treat inflammatory diseases.Here, we investigate the role that p21 (WAF1/CIP1) (p21) plays in the production of IL-1b and development of inflammatory disease. As a member of the Cip/Kip family of cyclin-dependent kinase (CDK) inhibitors, p21 induces blockade of cell cycle progression via inhibition of the activity of CDK/cyclin complexes as well as that of proliferating cell nuclear antigen (PCNA) [4]. p21 binds to CDK and cyclins through two distinct domains on the N-terminus and to PCNA via its C-terminus [5]. Mice deficient in p21 show no developmental or reproductive abnormalities, although the mice display sensitivity to radiation [6] and develop a form of lupus-like disease [6][7][8]. Furthermore, a paucity of p21 expression is observed in synovial tissue from rheumatoid arthritis patients compared with osteoarthritis controls [9]. Because of the implication of p21 in the pathogenesis of lupus and rheumatoid arthritis and the importance of IL-1b in these and other inflamm...

Objective: Rheumatoid arthritis (RA) is characterized by hyperplasia of the synovial lining, inflammation, and destruction of cartilage and bone. Since there are only a few detectable cells undergoing apoptosis in the joint, it is possible that a defect in apoptosis may contribute to synovial hyperplasia. This study sought to identify and characterize the direct role of apoptotic regulators in a mouse model of inflammatory arthritis.Methods. Using a serum transfer model, experimental arthritis was induced in mice lacking the proapoptotic Bcl-2 family genes Bak (Bak ؊/؊ ), Bax (Bax ؊/؊ ), or Bim (Bim ؊/؊ ), as compared with wild-type (WT) control mice. Physical examination for edema of the ankles and histopathologic analysis of ankle sections were used to determine the severity of arthritis. The serum and ankles were examined for production of chemokines and cytokines using enzyme-linked immunosorbent or Luminex-based assays.Results. Bim ؊/؊ mice displayed increased severity and prolongation of arthritis. In contrast, Bak ؊/؊ and Bax ؊/؊ mice showed no difference in the severity of arthritis as compared with WT mice. In addition, Bim ؊/؊ mice had elevated levels of proinflammatory chemokines and cytokines, decreased joint and serum production of antiinflammatory cytokines, fewer TUNEL-positive cells, and reduced levels of active caspase 3 as compared with WT mice.Conclusion. These studies are the first to demonstrate a role for the proapoptotic Bcl-2 protein Bim in the effector phase of RA. The findings indicate that Bim potentially functions to repress the effector phase of arthritis by regulating the milieu of the joint and serum, and by inducing apoptosis.

Objective. Rheumatoid arthritis (RA) is a destructive autoimmune disease characterized by an increased inflammation in the joint. Therapies that activate the apoptotic cascade may have potential for use in RA; however, few therapeutic agents fit this category. The purpose of this study was to examine the potential of Bim, an agent that mimics the action of Bcl-2 homology 3 (BH3) domain-only proteins that have shown success in preclinical studies of cancer, in the treatment of autoimmune disease.Methods. Synovial tissues from RA and osteoarthritis patients were analyzed for the expression of Bim and CD68 using immunohistochemistry. Macrophages from Bim -/-mice were examined for their response to lipopolysaccharide (LPS) using flow cytometry, realtime polymerase chain reaction analysis, enzyme-linked immunosorbent assay, and immunoblotting. Bim -/-mice were stimulated with thioglycollate or LPS and examined for macrophage activation and cytokine production. Experimental arthritis was induced using the K/BxN serum-transfer model. A mimetic peptide corresponding to the BH3 domain of Bim (TAT-BH3) was administered as a prophylactic agent and as a therapeutic agent. Edema of the ankles and histopathologic analysis of ankle tissue sections were used to determine the severity of arthritis, its cellular composition, and the degree of apoptosis.