Involvement of the nuclear orphan receptor NURR1 in the regulation of corticotropin-releasing hormone expression and actions in human inflammatory arthritis.
OBJECTIVE
To examine the regulation and mode of action of peripheral corticotropin-releasing hormone (CRH) in human inflammatory arthritis.


METHODS
CRH messenger RNA (mRNA) levels were measured in normal and inflamed synovial tissue and in primary synoviocytes prior to and following cytokine stimulation. Primary synoviocytes were transiently transfected with CRH promoter/reporter constructs, and promoter activity in response to cytokines was assessed. Immunohistochemical staining established CRH receptor expression, and Northern blot analysis confirmed that the nuclear transcription factors NUR77 and NURR1 contributed to synovial CRH receptor-mediated signaling. Primary synoviocytes were treated with pro- and antiinflammatory mediators, and the time course of NURR1 and NUR77 modulation was examined. Nuclear extracts were analyzed by electrophoretic mobility shift assay to determine NURR1 binding to the CRH promoter/enhancer.


RESULTS
CRH mRNA was up-regulated in the synovial tissue in rheumatoid arthritis (RA), psoriatic arthritis (PsA), and sarcoid arthritis, but not in normal synovium. Inflammatory cytokines, such as interleukin-1beta and tumor necrosis factor alpha, enhanced the transcriptional activity of the human CRH promoter and increased levels of CRH mRNA in primary synoviocytes. Synovial CRH functioned in a paracrine manner to induce NURR1 and NUR77. NURR1 was abundantly expressed in the inflammatory cells of both RA and PsA synovium. NURR1 and NUR77 were differentially regulated, and NURR1 was the major cytokine-regulated member of the NURR subfamily as well as the mediator of cytokine- and CRH-dependent inflammatory responses in synovium. Furthermore, glucocorticoids dramatically suppressed cytokine- and CRH-induced synovial NURR1 mRNA.


CONCLUSIONS
These data demonstrate the involvement of the transcription factor NURR1 in the regulation of CRH expression and activity in human inflammatory arthritis.
Murphy
E P
EP
Department of Rheumatology, Education and Research Center, St. Vincent's University Hospital, Dublin, Ireland.
McEvoy
A
A
Conneely
O M
OM
Bresnihan
B
B
FitzGerald
O
O
D001172:Arthritis, Rheumatoid / Q000378:metabolism* / Q000473:pathology; D015152:Blotting, Northern; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D003346:Corticotropin-Releasing Hormone / Q000096:biosynthesis* / Q000235:genetics; D017077:Culture Media, Conditioned / Q000494:pharmacology; D017931:DNA Primers / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015232:Dinoprostone / Q000494:pharmacology; D006801:Humans; D007124:Immunoenzyme Techniques; D007375:Interleukin-1 / Q000494:pharmacology; D007719:Knee Joint / Q000473:pathology; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2; D012333:RNA, Messenger / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013583:Synovial Membrane / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015854:Up-Regulation
D017077:Culture Media, Conditioned; D017931:DNA Primers; D004268:DNA-Binding Proteins; D007375:Interleukin-1; C539821:NR4A1 protein, human; C539882:NR4A2 protein, human; D009419:Nerve Tissue Proteins; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D005576:Colforsin; D003346:Corticotropin-Releasing Hormone; D015232:Dinoprostone