Enhancement of phosphorylation and transcriptional activity of the glucocorticoid receptor in human synovial fibroblasts by nimesulide, a preferential cyclooxygenase 2 inhibitor

Objective. To examine the effect of 2 nonsteroidal antiinflammatory drugs ( NSAIDs), nimesulide (NIM), a preferential cyclooxygenase 2 (COX-2) inhibito r, and naproxen (NAP), on the functional parameters and transcriptional act ivity of the glucocorticoid receptor (GR) system in cultured human synovial fibroblasts (HSF). Methods. HSF were incubated with NIR;I (0.3, 3, and 30 mu g/ml), NAP (15, 3 0, and 90 mu g/ml), and dexamethasone (DEX; 0.01, 0.1, and 1 mu M) on a tim e- and dose-dependent basis. The numbers of GR binding sites per cell were determined by radioligand receptor assay. Total cellular, cytoplasmic, or n uclear GR protein was measured by Western analysis using a specific anti-hu man GR antibody. Phosphorylation of GR was determined by specific immunopre cipitation of protein extracts from P-32-orthophosphate-labeled HSF. Mitoge n-activated protein kinase p44/42 (MAPK) phosphorylation was followed by We stern analysis using a specific anti-phosphoMAPK antibody. Levels of activa ted nuclear GR capable of binding specifically to a P-32-labeled oligonucle otide harboring the glucocorticoid/hormone response element (GRE) were eval uated by gel electrophoretic mobility shift analysis. The effects of NIM an d DEX on transcriptional activation of the mouse mammary tumor virus (MMTV) promoter was determined by transfecting HSF with MMTV-luciferase (reporter gene) constructs. Results. NIM had no effect on the number of GR binding sites, in contrast t o NAP and DEX. NIM and NAP did not influence cellular GR protein levels or nucleocytoplasmic shuttling, although DEX lowered GR messenger RNA and prot ein levels after 48 hours. NIR;I, but not NAP, markedly increased MAPK phos phorylation (suggesting an increase in MAPK cascade activity), GR phosphory lation, GR binding to GRE, and transcriptional activation of MMTV promoter through the GRE site in the promoter, Conclusion. This study is the first to report that the antiinflammatory eff ects of NLM, an NSAID, may be partly related to its activation of the GR sy stem.