Characterization and functional consequences of underexpression of clusterin in rheumatoid arthritis.
We previously compared by microarray analysis gene expression in rheumatoid arthritis (RA) and osteoarthritis (OA) tissues. Among the set of genes identified as a molecular signature of RA, clusterin (clu) was one of the most differentially expressed. In the present study we sought to assess the expression and the role of CLU (mRNA and protein) in the affected joints and in cultured fibroblast-like synoviocytes (FLS) and to determine its functional role. Quantitative RT-PCR, Northern blot, in situ hybridization, immunohistochemistry, and Western blot were used to specify and quantify the expression of CLU in ex vivo synovial tissue. In synovial tissue, the protein was predominantly expressed by synoviocytes and it was detected in synovial fluids. Both full-length and spliced isoform CLU mRNA levels of expression were lower in RA tissues compared with OA and healthy synovium. In synovium and in cultured FLS, the overexpression of CLU concerned all protein isoforms in OA whereas in RA, the intracellular forms of the protein were barely detectable. Transgenic overexpression of CLU in RA FLS promoted apoptosis within 24 h. We observed that CLU knockdown with small interfering RNA promoted IL-6 and IL-8 production. CLU interacted with phosphorylated IkappaBalpha. Differential expression of CLU by OA and RA FLS appeared to be an intrinsic property of the cells. Expression of intracellular isoforms of CLU is differentially regulated between OA and RA. We propose that in RA joints, high levels of extracellular CLU and low expression of intracellular CLU may enhance NF-kappaB activation and survival of the synoviocytes.
Devauchelle
Valérie
V
Institut Cochin, Département d'Immunologie, 27 rue du Faubourg Saint-Jacques, 75674 Paris Cedex 14, France.
Essabbani
Abdellatif
A
De Pinieux
Gonzague
G
Germain
Stéphane
S
Tourneur
Léa
L
Mistou
Sylvie
S
Margottin-Goguet
Florence
F
Anract
Philippe
P
Migaud
Henri
H
Le Nen
Dominique
D
Lequerré
Thierry
T
Saraux
Alain
A
Dougados
Maxime
M
Breban
Maxime
M
Fournier
Catherine
C
Chiocchia
Gilles
G
D001172:Arthritis, Rheumatoid / Q000235:genetics / Q000378:metabolism*; D002470:Cell Survival; D002478:Cells, Cultured; D051152:Clusterin / Q000032:analysis / Q000172:deficiency* / Q000235:genetics; D005347:Fibroblasts / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D016328:NF-kappa B / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010003:Osteoarthritis / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D021381:Protein Transport; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D034741:RNA, Small Interfering / Q000187:drug effects / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013582:Synovial Fluid / Q000737:chemistry / Q000378:metabolism; D013583:Synovial Membrane / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D019076:Transgenes; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D051152:Clusterin; D015850:Interleukin-6; D016209:Interleukin-8; D016328:NF-kappa B; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C439524:TNF protein, human; D014409:Tumor Necrosis Factor-alpha; D051550:I-kappa B Kinase