Tumor necrosis factor-alpha (TNF-alpha) is a pleiotropic cytokine produced by activated macrophages. IL-6 is a multifunctional cytokine that plays a central role in both innate and acquired immune responses. We investigated the signaling pathway involved in IL-6 production stimulated by INF-alpha in cultured myoblasts. INF-alpha caused concentration-dependent increases in IL-6 production. INF-alpha-mediated IL-6 production was attenuated by focal adhesion kinase (FAK) mutant and siRNA. Pretreatment with phosphatidylinositol 3-kinase inhibitor (PI3K; Ly294002 and wortmannin), Akt inhibitor, NF-kappa B inhibitor (pyrrolidine dithiocarbamate, PDTC), and I kappa B protease inhibitor (L-I-tosylamido-2-phenyl phenylethyl chloromethyl ketone. TPCK) also inhibited the potentiating action of INF-alpha. INF-alpha increased the FAK, PI3K, and Akt phosphorylation. Stimulation of myoblasts with INF-alpha activated IKB kinase alpha/beta (IKK alpha/beta), I kappa B alpha phosphorylation, p65 phosphorylation, and kappa B-luciferase activity. INF-alpha mediated an increase of kappa B-luciferase activity which was inhibited by Ly294002, wortmannin, Akt inhibitor, PDTC and TPCK or FAK, PI3K, and Akt mutant. Our results suggest that INF-a increased IL-6 production in myoblasts via the FAK/PI3K/Akt and NF-kappa B signaling pathway. J. Cell. Physiol. 223: 389-396, 2010. (c) 2010 Wiley-Liss, Inc.
