Combined effects of interleukin-1 alpha and transforming growth factor-beta 1 on modulation of human cardiac fibroblast function

During cardiac remodeling, cardiac fibroblasts (CF) are influenced by increased levels of interleukin-1 alpha (IL-1 alpha) and transforming growth factor-beta 1 (TGF beta 1). The present study investigated the interaction between these two important cytokines on function of human CF and their differentiation to myofibroblasts (CMF). CF were isolated from human atrial appendage and exposed to IL-1 alpha and/or TGF beta 1 (both 0.1 ng/ml). mRNA expression levels of selected genes were determined after 6-24 h by real-time RT-PCR, while protein levels were analyzed at 24-48 h by ELISA or western blot Activation of canonical signaling pathways (NF kappa B. Smad3, p38 MAPK) was determined by western blotting. Differentiation to CMF was examined by collagen gel contraction assays. Exposure of CF to IL-1 alpha alone enhanced levels of IL-6, IL-8, matrix metalloproteinase-3 (MMP3) and collagen III (COL3A1), but reduced the CMF markers alpha-smooth muscle actin (alpha SMA) and connective tissue growth factor (CTGF/CCN2). By contrast, TGF beta 1 alone had minor effects on IL-6, IL-8 and MMP3 levels, but significantly increased levels of the CMF markers alpha SMA, CTGF, COL1A1 and COL3A1. Co-stimulation with both IL-1 alpha and TGF beta 1 increased MMP3 expression synergistically. Furthermore, while TGF beta 1 had no effect on IL-1 alpha-induced IL-6 or IL-8 levels, co-stimulation inhibited the TGF beta 1-induced increase in alpha SMA and blocked the gel contraction caused by TGF beta 1. Combining IL-1 alpha and TGF beta 1 had no apparent effect on their canonical signaling pathways. In conclusion, IL-1 alpha and TGF beta 1 act synergistically to stimulate MMP3 expression in CF. Moreover, IL-1 alpha has a dominant inhibitory effect on the phenotypic switch of CF to CMF induced by TGF beta 1