Interleukin-18 stimulates fibronectin expression in primary human cardiac fibroblasts via PI3K-Akt-dependent NF-kappaB activation

• Published in: Journal of cellular physiology 2008-06, Vol.215 (3), p.697-707
• Main Authors: Reddy, Venkatapuram Seenu, Harskamp, Ralf Egan, van Ginkel, Margreet Willie, Calhoon, John, Baisden, Clinton Eugene, Kim, In-San, Valente, Anthony J, Chandrasekar, Bysani
• Format: Article
• Language: English
• Subjects: Cells, Cultured; Cytokines - metabolism; Enzyme Activation - drug effects; Fibroblasts - drug effects; Fibroblasts - enzymology; Fibroblasts - secretion; Fibronectins - genetics; Fibronectins - metabolism; Gene Expression Regulation - drug effects; Humans; I-kappa B Kinase - metabolism; Inflammation Mediators - metabolism; Intercellular Signaling Peptides and Proteins - metabolism; Interleukin-1 Receptor-Associated Kinases - metabolism; Interleukin-18 - pharmacology; Interleukin-18 - secretion; Myeloid Differentiation Factor 88 - metabolism; Myocardium - cytology; Myocardium - enzymology; NF-kappa B - metabolism; Phosphatidylinositol 3-Kinases - metabolism; Proto-Oncogene Proteins c-akt - metabolism; RNA, Messenger - genetics; RNA, Messenger - metabolism; Solubility - drug effects; TNF Receptor-Associated Factor 6 - metabolism; Transcription, Genetic - drug effects
• ISSN: 1097-4652

Fibronectin (FN), a key component of the extracellular matrix, is upregulated in cardiac tissue during myocardial hypertrophy and failure. Here we show that interleukin (IL)-18, a proinflammatory and pro-hypertrophic cytokine, stimulates FN expression in adult human cardiac fibroblasts (HCF), an effect blocked by either the IL-18BP:Fc chimera or IL-18 neutralizing antibodies. IL-18 stimulated FN promoter-reporter activity in HCF, a response attenuated by mutation of an NF-kappaB binding site in the FN promoter. Overexpression of p65 stimulated FN transcription. IL-18 stimulated in vitro (p65, p50) and in vivo NF-kappaB DNA binding activities, and induced kappaB-dependent reporter gene activity. These effects were inhibited by adenoviral transduction of dominant negative (dn) p65 (Ad.dnp65) and dnIKK2 (Ad.dnIKK2). Investigation of signaling intermediates revealed that IL-18 stimulated PI3 kinase activity (blocked by wortmannin, LY294002, or Ad.dnPI3Kp85), and Akt phosphorylation and kinase activity (blocked by SH-5 or Ad.dnAkt). Furthermore, targeting MyD88, IRAK1, TRAF6, PI3K, Akt, and NF-kappaB by RNA interference or dn expression vectors blunted IL-18 mediated FN transcription and mRNA expression. Conversely, FN stimulated IL-18 expression. These data provide the first evidence that IL-18 and FN stimulate each other's expression in HCF, and suggest a role for IL-18, FN and their crosstalk in myocardial hypertrophy and remodeling, disease states characterized by enhanced FN expression and fibrosis.