title: Catabolic cytokines disrupt the circadian clock and the expression of clock-controlled genes in cartilage via an NFкB-dependent pathway.
abstract: OBJECTIVE
  To define how the catabolic cytokines (Interleukin 1 (IL-1) and tumor necrosis factor alpha (TNFα)) affect the circadian clock mechanism and the expression of clock-controlled catabolic genes within cartilage, and to identify the downstream pathways linking the cytokines to the molecular clock within chondrocytes.
  
  
  METHODS
  Ex vivo cartilage explants were isolated from the Cry1-luc or PER2::LUC clock reporter mice. Clock gene dynamics were monitored in real-time by bioluminescence photon counting. Gene expression changes were studied by qRT-PCR. Functional luc assays were used to study the function of the core Clock/BMAL1 complex in SW-1353 cells. NFкB pathway inhibitor and fluorescence live-imaging of cartilage were performed to study the underlying mechanisms.
  
  
  RESULTS
  Exposure to IL-1β severely disrupted circadian gene expression rhythms in cartilage. This effect was reversed by an anti-inflammatory drug dexamethasone, but not by other clock synchronizing agents. Circadian disruption mediated by IL-1β was accompanied by disregulated expression of endogenous clock genes and clock-controlled catabolic pathways. Mechanistically, NFкB signalling was involved in the effect of IL-1β on the cartilage clock in part through functional interference with the core Clock/BMAL1 complex. In contrast, TNFα had little impact on the circadian rhythm and clock gene expression in cartilage.
  
  
  CONCLUSIONS
  In our experimental system (young healthy mouse cartilage), we demonstrate that IL-1β (but not TNFα) abolishes circadian rhythms in Cry1-luc and PER2::LUC gene expression. These data implicate disruption of the chondrocyte clock as a novel aspect of the catabolic responses of cartilage to pro-inflammatory cytokines, and provide an additional mechanism for how chronic joint inflammation may contribute to osteoarthritis (OA).
authors.affiliation: Faculty of Life Sciences, University of Manchester, A.V. Hill Building, Oxford Road, Manchester, M13 9PT, UK.
authors.forename: B
authors.initials: B
authors.lastname: Guo
authors.affiliation: Faculty of Life Sciences, University of Manchester, A.V. Hill Building, Oxford Road, Manchester, M13 9PT, UK.
authors.forename: N
authors.initials: N
authors.lastname: Yang
authors.affiliation: Faculty of Life Sciences, University of Manchester, A.V. Hill Building, Oxford Road, Manchester, M13 9PT, UK.
authors.forename: E
authors.initials: E
authors.lastname: Borysiewicz
authors.affiliation: Faculty of Life Sciences, University of Manchester, A.V. Hill Building, Oxford Road, Manchester, M13 9PT, UK.
authors.forename: M
authors.initials: M
authors.lastname: Dudek
authors.affiliation: Faculty of Life Sciences, University of Manchester, A.V. Hill Building, Oxford Road, Manchester, M13 9PT, UK.
authors.forename: J L
authors.initials: JL
authors.lastname: Williams
authors.affiliation: Faculty of Life Sciences, University of Manchester, A.V. Hill Building, Oxford Road, Manchester, M13 9PT, UK; Department of Chronopharmacology, School of Pharmacy, Taishan Medical University, Chang Cheng Road, Shandong, 271016, PR China.
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.affiliation: MRC Laboratory of Molecular Biology, Neurobiology Division, Francis Crick Ave, Cambridge, CB2 0QH, UK.
authors.forename: E S
authors.initials: ES
authors.lastname: Maywood
authors.affiliation: Faculty of Life Sciences, University of Manchester, A.V. Hill Building, Oxford Road, Manchester, M13 9PT, UK.
authors.forename: A
authors.initials: A
authors.lastname: Adamson
authors.affiliation: MRC Laboratory of Molecular Biology, Neurobiology Division, Francis Crick Ave, Cambridge, CB2 0QH, UK.
authors.forename: M H
authors.initials: MH
authors.lastname: Hastings
authors.affiliation: Murdoch Childrens Research Institute, Parkville, Victoria, 3052, Australia.
authors.forename: J F
authors.initials: JF
authors.lastname: Bateman
authors.affiliation: Faculty of Life Sciences, University of Manchester, A.V. Hill Building, Oxford Road, Manchester, M13 9PT, UK.
authors.forename: M R H
authors.initials: MR
authors.lastname: White
authors.affiliation: Wellcome Trust Centre for Cell Matrix Research, University of Manchester, Oxford Road, Manchester, M13 9PT, UK.
authors.forename: R P
authors.initials: RP
authors.lastname: Boot-Handford
authors.affiliation: Faculty of Life Sciences, University of Manchester, A.V. Hill Building, Oxford Road, Manchester, M13 9PT, UK. Electronic address: qing-jun.meng@manchester.ac.uk.
authors.forename: Q J
authors.initials: QJ
authors.lastname: Meng
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism*; D057906:Circadian Clocks / Q000235:genetics*; D016207:Cytokines / Q000096:biosynthesis / Q000235:genetics*; D004247:DNA / Q000235:genetics*; D004195:Disease Models, Animal; D005786:Gene Expression Regulation; D051379:Mice; D008822:Mice, Transgenic; D016328:NF-kappa B / Q000096:biosynthesis / Q000235:genetics*; D010003:Osteoarthritis / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D016207:Cytokines; D016328:NF-kappa B; D004247:DNA
keywords: Cartilage; Circadian clock; Cytokine; Inflammation; Osteoarthritis