Glucocorticoid Effect on Radiographic Progression in Placebo Arms of Rheumatoid Arthritis Biologics Trials

Objective.To assess the effect of glucocorticoids (GC) on damage progression in placebo-biologic arms of rheumatoid arthritis (RA) biologics trials.Methods.Posthoc metaanalysis of 2 infliximab (IFX) trials (established and early RA) and 1 tocilizumab (TCZ) trial (established RA).Results.The proportion of patients receiving GC was 38%–64%, baseline damage was 11–82 Sharp/van der Heijde points, and progression in the placebo groups was 0.5–4.8 points in 6 months. In the pooled IFX studies, GC cotreatment reduced 6-month progression by 2.6 points (95% CI 0.6–4.5). In the TCZ study (progression rate 0.5 Genant points), no such difference was seen.Conclusion.GC cotreatment may affect results in RA trials.

Glucocorticoid Suppression of IGF I Transcription in Osteoblasts

Glucocorticoids have profound effects on bone formation, decreasing IGF I transcription in osteoblasts, but the mechanisms involved are poorly understood. We previously showed that the bp +34 to+ 192 region of the rat IGF I exon 1 promoter was responsible for repression of IGF I transcription by cortisol in cultures of osteoblasts from fetal rat calvariae (Ob cells). Here, site-directed mutagenesis was used to show that a binding site for members of the CAAT/enhancer binding protein family of transcription factors, within the +132 to +158 region of the promoter, mediates this glucocorticoid effect. EMSAs demonstrated that cortisol increased binding of osteoblast nuclear proteins to the +132 to +158 region of the IGF I promoter. Supershift assays showed that CAAT/enhancer binding protein α, β, and δ interact with this sequence, and binding of CAAT/enhancer binding protein δ, in particular, was increased in the presence of cortisol. Northern blot analysis showed that CAAT/enhancer binding protein δ and β transcripts were increased by cortisol in Ob cells. Further, cortisol increased the transcription of these genes and increased the stability of CAAT/enhancer binding protein δ mRNA. In conclusion, cortisol represses IGF I transcription in osteoblasts, and CAAT/enhancer binding proteins appear to play a role in this effect.

Delineation of the insulin-responsive sequence in the rat cytosolic aspartate aminotransferase gene: binding sites for hepatocyte nuclear factor-3 and nuclear factor I

Expression of the rat cytosolic aspartate aminotransferase gene is stimulated by glucocorticoids and repressed by insulin in the liver. The regulation by insulin and part of the glucocorticoid effect are mediated by a distal region in the promoter. A 142 bp fragment (-1844 to -1702) confers hormonal sensitivity to the heterologous thymidine kinase promoter in transient-transfection assays in H4IIEC3 hepatoma cells. Footprinting and gel-shift assays showed that several nuclear proteins bind to this region at conserved CCAAT-enhancer binding protein (C/EBP), activator protein (AP-1) and E-box sequences. Hepatocyte nuclear factor-3α (HNF-3)α and β bind to sequences upstream of a glucocorticoid-responsive element (GRE) half-site as demonstrated by supershift experiments. Nuclear factor I (NFI)-like proteins bind downstream of the GRE half-site. These sites around the GRE motif overlap with five insulin responsive element (IRE) -like sequences (TG/ATTT). The effect of insulin was not prevented by any single mutation in the IRE-like sites. However, mutation of two IRE sites (namely IREc and d) prevented the insulin effect although only marginally affecting the glucocorticoid effect. The results suggest that the effect of insulin is due to a complex interplay of factors requiring the synergistic contribution of at least two sites and underline the contribution of HNF-3 and NFI-like proteins.

The Effect of Glucocorticoids on the Expression of L-Selectin on Polymorphonuclear Leukocyte

When active bone marrow release is induced by inflammatory stimuli, it is associated with an increase in L-selectin expression on circulating polymorphonuclear leukocyte (PMN). This contrasts sharply with glucocorticoid-induced granulocytosis that is associated with decreased L-selectin expression on PMN. The present study was designed to determine if the reduced L-selectin expression observed after glucocorticoid treatment is the result of suppression of L-selectin synthesis in the bone marrow. New Zealand white rabbits treated with dexamethasone (2.0 mg/kg, a single dose intravenously) were shown to have decreased L-selectin expression on circulating PMN 12 to 24 hours after treatment (P < .01) with a return to baseline levels by 48 hours. When dexamethasone was administered 48 hours after the bone marrow PMN were pulse labeled with the thymidine analogue, 5′-bromo-2′-deoxyuridine (BrdU), L-selectin expression on BrdU-labeled PMN released from the bone marrow was decreased (P< .01). Dexamethasone decreased L-selectin expression on segmented PMN in the bone marrow (P < .05) but not on PMN already in the circulation. We conclude that glucocorticoids decrease L-selectin expression on circulating PMN by downregulating L-selectin expression in the maturation pool of bone marrow and speculate that this is an important glucocorticoid effect that influences the recruitment of PMN into inflammatory sites.