The CDK domain of p21 is a suppressor of IL‐1β‐mediated inflammation in activated macrophages

Abstract

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...

Quantifying Ca2+ Current and Permeability in ATP-gated P2X7 Receptors

“…Measures of the Pf % of recombinant P2X1R-P2X6Rs come from our published data (1,83,100) with one exception; data of recombinant hP2X2aR are previously unpublished observations. Data of the native P2X4R of mouse bone marrowderived macrophages (BMDM4) are unpublished observations of Samways and Egan obtained during a previous study (27). The red bars indicate the average adjusted Pf % of the P2X7Rs expected in the absence of Ca 2ϩ chelation by BzATP.…”

Vitamin B6 activates p53 and elevates p21 gene expression in cancer cells and the mouse colon

“…In addition, p21 protects against oxidative stress (26). Importantly, p53 and p21 are reported to be antiinflammation factors (27)(28)(29). Furthermore, p21 is a negative regulator of macrophage activation; in particular, it inhibits the lipopolysaccharide-dependent stimulation of TNF-α and IL-1β (29,30).…”

“…Importantly, p53 and p21 are reported to be antiinflammation factors (27)(28)(29). Furthermore, p21 is a negative regulator of macrophage activation; in particular, it inhibits the lipopolysaccharide-dependent stimulation of TNF-α and IL-1β (29,30). Moreover, the inhibition caused by p21 inhibits the NF-κB activity (29,30).…”

“…Furthermore, p21 is a negative regulator of macrophage activation; in particular, it inhibits the lipopolysaccharide-dependent stimulation of TNF-α and IL-1β (29,30). Moreover, the inhibition caused by p21 inhibits the NF-κB activity (29,30). Yanaka et al (7) reported the inhibitory effect of PL on the lipopolysaccharide-dependent activation of NF-κB in macrophages.…”

Reconciliation of IL-1ß loss with TRIF-biased TLR4 signaling by monophosphate lipid A.

“…Shock in response to LPS results in part from an inflammatory cytokine storm mediated primarily by monocytes and macrophages and is marked by high levels of serum IL-1(3 and TNF [114][115][116]. IL-1(3 has been directly implicated in the pathogenesis of endotoxemia, and inhibitors of its production or signaling via IL-1RI (such as Fluorofenidone [70] and Kineret® [117] protect mice from lethality of endotoxic shock.…”