
Prostaglandin E2induces interleukin-6 expression in human chondrocytes via cAMP/protein kinase A- and phosphatidylinositol 3-kinase-dependent NF-κB activation
Author(s) -
Pu Wang,
Fei Zhu,
Κωνσταντίνος Κωνσταντόπουλος
Publication year - 2010
Publication title -
american journal of physiology. cell physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.432
H-Index - 181
eISSN - 1522-1563
pISSN - 0363-6143
DOI - 10.1152/ajpcell.00508.2009
Subject(s) - forskolin , protein kinase a , signal transduction , endocrinology , chemistry , medicine , ly294002 , chondrocyte , wortmannin , microbiology and biotechnology , phosphatidylinositol , pi3k/akt/mtor pathway , adenylyl cyclase , prostaglandin e , protein kinase b , kinase , biology , stimulation , biochemistry , in vitro
Elevated levels of prostaglandin (PG)E(2) and interleukin (IL)-6 have been reported in the cartilage and synovial fluid from patients with arthritic disorders. PGE(2) regulates IL-6 production in numerous different cells including macrophages and synovial fibroblasts. Although PGE(2) stimulates IL-6 expression in human chondrocytes, the underlying signaling pathway of this process has yet to be delineated. Here, we investigate the mechanism of IL-6 induction in human T/C-28a2 chondrocytes treated with exogenously added PGE(2). PGE(2) induces IL-6 mRNA and protein expression via a cAMP-dependent pathway, reaching maximal levels after 60 min of stimulation before declining to baseline levels at 6 h. Forskolin, an adenylyl cyclase activator, also stimulates IL-6 expression in human chondrocytes in a dose- and time-dependent fashion. Inhibition of downstream effectors of cAMP activity such as protein kinase A (PKA) or phosphatidylinositol 3 kinase (PI3K) blocks PGE(2)- and forskolin-induced IL-6 upregulation. Simultaneous inhibition of PKA and PI3K reduces IL-6 expression in stimulated chondrocytes well below the basal levels of untreated cells. Gel shift, supershift, and chromatin immunoprecipitation assays reveal the activation and binding of the nuclear factor (NF)-kappaB p65 subunit to the IL-6 promoter, which is markedly suppressed by selective PI3K or PKA pharmacological inhibitors. p65 knockdown completely abrogates IL-6 mRNA synthesis in PGE(2)- and forskolin-primed chondrocytes. Cumulatively, our data show that PGE(2) and forskolin induce IL-6 expression in human chondrocytes via cAMP/PKA and PI3K-dependent pathways, which in turn regulate the activation and binding of p65 to the IL-6 promoter.