The differential expression of corticosteroid receptor isoforms in corticosteroid-resistant and -sensitive patients with rheumatoid arthritis.
OBJECTIVE
A proportion of patients with rheumatoid arthritis (RA) fail to respond adequately to corticosteroid (CS) therapy. Using an in vitro CS sensitivity bioassay, we have subdivided RA patients into steroid-sensitive (SS) and -resistant (SR) subgroups and this correlates with clinical responses to CS therapy. CSs exert their effects via the CS receptor (CR), which exists as two main isoforms, CRalpha and CRbeta. CRbeta can function as a negative inhibitor of CRalpha. We have hypothesized that steroid resistance in RA patients is due in part to a relative over-expression of the CRbeta.


METHODS
Peripheral blood mononuclear cells (PBMCs) were isolated from SS and SR RA patients. CRalpha and CRbeta mRNA expression was determined by quantitative real time polymerase chain reaction (qRT-PCR). The ratio of CRbeta/CRalpha mRNA expression was determined. CRalpha and CRbeta protein expression by PBMCs was analysed by flow cytometry.


RESULTS
qRT-PCR analysis showed a trend towards higher expression of both CRbeta and basal CRbeta/CRalpha ratio in SR RA patients. Stimulation of PBMCs in vitro with concanavalin-A induced a significantly higher CRbeta mRNA expression, and CRbeta/CRalpha ratio in SR RA patients compared with SS patients, which was not inhibited by hydrocortisone. Flow cytometry showed that the percentage of PBMCs staining for CRbeta protein was significantly lower in the SS RA group (SS 43.3 +/- 14.8% vs SR 88.6 +/- 8.6%; P < 0.0010). The mean intensity of fluorescence CRbeta staining was higher in the SR RA patients (P < 0.001).


CONCLUSIONS
We show for the first time that CRbeta is over-expressed in SR RA patients and that hydrocortisone fails to inhibit concanavalin-A stimulated increase in CRbeta mRNA in SR RA patients. This mechanism may contribute in part to the CS hyporesponsiveness seen in some RA patients.
Kozaci
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DL
Bone & Joint Research Unit, Barts and The London, Queen Mary's School of Medicine & Dentistry, University of London, Charterhouse Square, London EC1M 6BQ, UK.
Chernajovsky
Y
Y
Chikanza
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IC
D000305:Adrenal Cortex Hormones / Q000494:pharmacology* / Q000627:therapeutic use; D000328:Adult; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000188:drug therapy; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D003208:Concanavalin A / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D006854:Hydrocortisone / Q000494:pharmacology; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000473:pathology; D008297:Male; D008875:Middle Aged; D020033:Protein Isoforms / Q000097:blood / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D011987:Receptors, Steroid / Q000097:blood* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods
D000305:Adrenal Cortex Hormones; D000893:Anti-Inflammatory Agents; D020033:Protein Isoforms; D012333:RNA, Messenger; D011987:Receptors, Steroid; D003208:Concanavalin A; D006854:Hydrocortisone