Oestrogens inhibit interleukin 1beta-mediated nitric oxide synthase expression in articular chondrocytes through nuclear factor-kappa B impairment

• Published in: Annals of the rheumatic diseases 2007-03, Vol.66 (3), p.345-350
• Main Authors: Richette, Pascal, Dumontier, Marie-France, Tahiri, Khadija, Widerak, Magdalena, Torre, Antoine, Benallaoua, Mourad, Benallaloua, Mourad, Rannou, François, Corvol, Marie-Therese, Savouret, Jean-François
• Format: Article
• Language: English
• Subjects: Animals; Cartilage, Articular - cytology; Cartilage, Articular - drug effects; Cartilage, Articular - enzymology; Cartilage, Articular - metabolism; Cells, Cultured; Chondrocytes - drug effects; Chondrocytes - enzymology; Chondrocytes - metabolism; Dose-Response Relationship, Drug; Estradiol - pharmacology; Estrogen Receptor alpha - metabolism; Estrogen Receptor alpha - physiology; Female; Interleukin-1beta - antagonists & inhibitors; Interleukin-1beta - pharmacology; NF-kappa B - metabolism; NF-kappa B - physiology; Nitric Oxide - biosynthesis; Nitric Oxide Synthase - genetics; Nitric Oxide Synthase - metabolism; Promoter Regions, Genetic; Rabbits; Signal Transduction - drug effects; Transcriptional Activation - drug effects; Translocation, Genetic - drug effects
• ISSN: 0003-4967

To investigate the presence and functionality of oestrogen receptor alpha (ERalpha) in interleukin (IL)1beta-treated rabbit articular chondrocytes in culture, and to determine the mechanisms of 17beta oestradiol (E2) effects on IL1beta-induced inducible nitric oxide synthase (iNOS) expression. The presence and functionality of ERalpha were investigated by immunocytochemistry and transient expression of an E2-responsive reporter construct. iNOS expression and production were determined by transient expression of a chimeric iNOS promoter-luciferase construct and protein immunoblotting. Nitric oxide (NO) production was determined by the Griess reaction. DNA-binding activities of nuclear factor-kappaB (NF-kappaB) and activated protein 1 were determined by electrophoretic mobility shift assay (EMSA)-ELISA assays. Nuclear translocation of p65 was studied by immunocytochemistry. ERalpha was identified in the nucleus of chondrocytes. ERalpha efficiently transactivated a transiently expressed E2-responsive construct. On IL1beta treatment, ERalpha partially diffused from its nuclear localisation into the cytoplasm and its transactivation ability was impaired. Nevertheless, E2, tamoxifen and raloxifene efficiently inhibited IL1beta-induced NO production (-34%, -31% and -36%, respectively). E2 decreased IL1beta-induced iNOS protein expression (-40%). Transient expression of an iNOS promoter construct strongly suggested that iNOS expression was inhibited at the transcriptional level, and EMSA-ELISA assays showed that E2 reduced (-60%) the IL1beta-induced p65 DNA-binding capacity. Finally, the p65 nuclear translocation induced by IL1beta was also strongly decreased by E2. Our data support a reciprocal antagonism between oestrogens and IL1beta, ultimately resulting in the decrease of cytokine-dependent NO production through transcriptional inhibition of iNOS expression. This effect was associated with selective inhibition of p65 DNA binding and nuclear translocation.