title: Differentially Expressed in Chondrocytes 2 (DEC2) Increases the Expression of IL-1β and Is Abundantly Present in Synovial Membrane in Rheumatoid Arthritis.
abstract: OBJECTIVE
  Patients with rheumatoid arthritis (RA) have altered circadian rhythm of circulating serum cortisol, melatonin and IL-6, as well as disturbance in the expression of clock genes ARNTL2 and NPAS2. In humans, TNFα increases the expression ARNTL2 and NPAS2 but paradoxically suppresses clock output genes DPB and PER3. Our objective was to investigate the expression of direct clock suppressors DEC1 and DEC2 (BHLHE 40 and 41 proteins) in response to TNFα and investigate their role during inflammation.
  
  
  METHODS
  Cultured primary fibroblasts were stimulated with TNFα. Effects on DEC2 were studied using RT-qPCR and immunofluorescence staining. The role of NF-κB in DEC2 increase was analyzed using IKK-2 specific inhibitor IMD-0354. Cloned DEC2 was transfected into HEK293 cells to study its effects on gene expression. Transfections into primary human fibroblasts were used to confirm the results. The presence of DEC2 was analyzed in (RA) and osteoarthritis (OA) synovial membranes by immunohistochemistry.
  
  
  RESULTS
  TNFα increased DEC2 mRNA and DEC2 was mainly detected at nuclei after the stimulus. The effects of TNFα on DEC2 expression were mediated via NF-κB. Overexpression, siRNA and promoter activity studies disclosed that DEC2 directly regulates IL-1β, in both HEK293 cells and primary human fibroblasts. DEC2 was increased in synovial membrane in RA compared to OA.
  
  
  CONCLUSIONS
  Not only ARNTL2 and NPAS2 but also DEC2 is regulated by TNFα in human fibroblasts. NF-κB mediates the effect on DEC2, which upregulates IL-1β. Circadian clock has a direct effect on inflammation in human fibroblasts.
authors.affiliation: Department of Medicine, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: Juri
authors.initials: J
authors.lastname: Olkkonen
authors.affiliation: Department of Medicine, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: Vesa-Petteri
authors.initials: VP
authors.lastname: Kouri
authors.affiliation: ORTON Orthopaedic Hospital of the Invalid Foundation, Helsinki, Finland.
authors.forename: Joel
authors.initials: J
authors.lastname: Hynninen
authors.affiliation: Department of Medicine, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: Yrjö T
authors.initials: YT
authors.lastname: Konttinen
authors.affiliation: Department of Medicine, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: Jami
authors.initials: J
authors.lastname: Mandelin
mesh_terms: D056930:ARNTL Transcription Factors / Q000378:metabolism; D001172:Arthritis, Rheumatoid / Q000473:pathology*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D001549:Benzamides / Q000494:pharmacology; D002460:Cell Line; D005347:Fibroblasts / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D051550:I-kappa B Kinase / Q000037:antagonists & inhibitors; D053583:Interleukin-1beta / Q000096:biosynthesis*; D016328:NF-kappa B / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010003:Osteoarthritis / Q000473:pathology; D011401:Promoter Regions, Genetic / Q000235:genetics; D034622:RNA Interference; D012333:RNA, Messenger / Q000096:biosynthesis; D034741:RNA, Small Interfering / Q000235:genetics; D013583:Synovial Membrane / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
chemical_list: D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D001549:Benzamides; D051550:I-kappa B Kinase; D053583:Interleukin-1beta; D016328:NF-kappa B; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; D025521:Tumor Suppressor Proteins; C486615:BMAL2 protein, human; C422085:BHLHE41 protein, human; C403671:DELEC1 protein, human; C508585:IL1B protein, human; C104264:NPAS2 protein, human; C492919:N-(3,5-bis(trifluoromethyl)phenyl)-5-chloro-2-hydroxybenzamide; C496560:IKBKB protein, human