IntroductionActivation of the inflammasome has been implicated in the pathology of various auto-inflammatory and autoimmune diseases. While the NLRP3 inflammasome has been linked to arthritis progression, little is known about its synovial regulation or contribution to joint histopathology. Regulators of inflammation activation, such as interleukin (IL)-10, may have the potential to limit the inflammasome-driven arthritic disease course and associated structural damage. Hence, we used IL-10-deficient (IL-10KO) mice to assess NLRP3 inflammasome-driven arthritic pathology.MethodsAntigen-induced arthritis (AIA) was established in IL-10KO mice and wild type controls. Using histological and radiographic approaches together with quantitative real-time PCR of synovial mRNA studies explored the regulation of inflammasome components. These were combined with selective blocking agents and ex vivo investigative studies in osteoclast differentiation assays.ResultsIn AIA, IL-10KO mice display severe disease with increased histological and radiographic joint scores. Here, focal bone erosions were associated with increased tartrate resistant acid phosphatase (TRAP)-positive cells and a localized expression of IL-1ß. When compared to controls, IL-10KO synovium showed increased expression of Il1b, Il33 and NLRP3 inflammasome components. Synovial Nlrp3 and Casp1 expression further correlated with Acp5 (encoding TRAP), while neutralization of IL-10 receptor signaling in control mice caused increased expression of Nlrp3 and Casp1. In ex vivo osteoclast differentiation assays, addition of exogenous IL-10 or selective blockade of the NLRP3 inflammasome inhibited osteoclastogenesis.ConclusionThese data provide a link between IL-10, synovial regulation of the NLRP3 inflammasome and the degree of bone erosions observed in inflammatory arthritis.
Acknowledgements: Research funding was provided by Arthritis Research UK fellowships 19234 and 20305 (to GWJ) and grants 19796, 19381, 18286 (to SAJ).
Authors' contributions: CJG, GWJ, MAN and ASW performed all animal experiments, tissue processing, histology scoring, and contributed to the drafting of the manuscript. CJG and ZN performed all real-time PCR and immunoassays. AKH, ANM and MAN participated in the radiographic studies and design of scoring criteria. CJG, AKH, FLC, ACB, ASW and MR performed all osteoclast studies including data analysis and assay development. AKH participated in the statistical evaluation of data. RC, LAO, MAC and IRH provided necessary research reagents and AABR synthesized the CRID3. RC, LAO and MAC provide necessary technical expertise relating to the inhibition of the inflammasome and interpretation of results. PRT, IRH, ASW and SAJ designed experiments and evaluated all results. CJG, GWJ and SAJ wrote the manuscript. All authors read and approved the manuscriptElectronic supplementary material: https://static-content.springer.com/esm/art%3A10.1186%2Fs13075-014-0419-y/MediaObjects/13075_2014_419_MOESM1_ESM.pdf
Additional file 1:Oligonucleotide primer sequences for real-time PCR. Oligonucleotide primer sequences for each of the inflammatory mediators measured in the study. All sequences are listed in the 5'-3' direction. (PDF 42 KB)