title: JNK-dependent downregulation of FoxO1 is required to promote the survival of fibroblast-like synoviocytes in rheumatoid arthritis.
abstract: BACKGROUND
  Forkhead box O (FoxO) transcription factors integrate environmental signals to modulate cell proliferation and survival, and alterations in FoxO function have been reported in rheumatoid arthritis (RA).
  
  
  OBJECTIVE
  To examine the relationship between inflammation and FoxO expression in RA, and to analyse the mechanisms and biological consequences of FoxO regulation in RA fibroblast-like synoviocytes (FLS).
  
  
  METHODS
  RNA was isolated from RA patient and healthy donor (HD) peripheral blood and RA synovial tissue. Expression of FoxO1, FoxO3a and FoxO4 was measured by quantitative PCR. FoxO1 DNA binding, expression and mRNA stability in RA FLS were measured by ELISA-based assays, immunoblotting and quantitative PCR. FLS were transduced with adenovirus encoding constitutively active FoxO1 (FoxO1ADA) or transfected with small interfering RNA targeting FoxO1 to examine the effects on cell viability and gene expression.
  
  
  RESULTS
  FoxO1 mRNA levels were reduced in RA patient peripheral blood compared with HD blood, and RA synovial tissue FoxO1 expression correlated negatively with disease activity. RA FLS stimulation with interleukin 1β or tumour necrosis factor caused rapid downregulation of FoxO1. This effect was independent of protein kinase B (PKB), but dependent on c-Jun N-terminal kinase (JNK)-mediated acceleration of FoxO1 mRNA degradation. FoxO1ADA overexpression in RA FLS induced apoptosis associated with altered expression of genes regulating cell cycle and survival, including BIM, p27(Kip1) and Bcl-XL.
  
  
  CONCLUSIONS
  Our findings identify JNK-dependent modulation of mRNA stability as an important PKB-independent mechanism underlying FoxO1 regulation by cytokines, and suggest that reduced FoxO1 expression is required to promote FLS survival in RA.
authors.affiliation: Department of Experimental Immunology and Department of Clinical Immunology and Rheumatology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Aleksander M
authors.initials: AM
authors.lastname: Grabiec
authors.affiliation: Department of Experimental Immunology and Department of Clinical Immunology and Rheumatology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Chiara
authors.initials: C
authors.lastname: Angiolilli
authors.affiliation: Department of Experimental Immunology and Department of Clinical Immunology and Rheumatology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Linda M
authors.initials: LM
authors.lastname: Hartkamp
authors.affiliation: Department of Experimental Immunology and Department of Clinical Immunology and Rheumatology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Lisa G M
authors.initials: LG
authors.lastname: van Baarsen
authors.affiliation: Department of Experimental Immunology and Department of Clinical Immunology and Rheumatology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands GlaxoSmithKline, Stevenage, and University of Cambridge, Cambridge, UK.
authors.forename: Paul P
authors.initials: PP
authors.lastname: Tak
authors.affiliation: Department of Experimental Immunology and Department of Clinical Immunology and Rheumatology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Kris A
authors.initials: KA
authors.lastname: Reedquist
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000235:genetics* / Q000378:metabolism; D018797:Cell Cycle Proteins; D002470:Cell Survival; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D005347:Fibroblasts / Q000378:metabolism*; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000187:drug effects / Q000235:genetics*; D006801:Humans; D053583:Interleukin-1beta / Q000494:pharmacology; D015850:Interleukin-6 / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D013583:Synovial Membrane / Q000166:cytology / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D018797:Cell Cycle Proteins; C085126:FOXO1 protein, human; C499517:FOXO3 protein, human; C108803:FOXO4 protein, human; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; C508585:IL1B protein, human; C508600:IL6 protein, human; D053583:Interleukin-1beta; D015850:Interleukin-6; D012333:RNA, Messenger; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D051057:Proto-Oncogene Proteins c-akt; D048031:JNK Mitogen-Activated Protein Kinases
keywords: Cytokines; Fibroblasts; Inflammation; Rheumatoid Arthritis