Interleukin-1 alpha stimulates proinflammatory cytokine expression in human cardiac myofibroblasts

Turner NA, Das A, Warburton P, O'Regan DJ, Ball SG, Porter KE. Interleukin-1 alpha stimulates proinflammatory cytokine expression in human cardiac myofibroblasts. Am J Physiol Heart Circ Physiol 297: H1117-H1127, 2009. First published July 31, 2009; doi:10.1152/ajpheart.00372.2009.-Cardiac myofibroblasts (CMF) play a key role in infarct repair and scar formation following myocardial infarction (MI) and are also an important source of proinflammatory cytokines. We postulated that interleukin-1 alpha (IL-1 alpha), a potential early trigger of acute inflammation post-MI, could stimulate human CMF to express additional proinflammatory cytokines. Furthermore, we hypothesized that these effects may be modulated by the anti-inflammatory cytokine interleukin-10 (IL-10). Human CMF were cultured from atrial biopsies from multiple patients. Interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and cardiotrophin-1 (CT-1) mRNA expression and secretion were measured using quantitative real-time RT-PCR and enzyme-linked immunosorbent assay. IL-1 alpha (0.001-10 ng/ml, 0-6 h) stimulated IL-1 beta, TNF-alpha, and IL-6 mRNA expression with distinct temporal and concentration profiles, resulting in increased cytokine secretion. The response to IL-1 alpha was much greater than with TNF-alpha. Neither IL-1 alpha nor TNF-alpha treatment modulated CT-1 mRNA expression. Immunoblotting with phosphospecific antibodies revealed that IL-1 alpha stimulated the extracellular signal-regulated kinase (ERK)-1/2, p38 mitogen-activated protein kinase (MAPK), c-Jun NH(2)-terminal kinase (JNK), phosphatidylinositol 3-kinase (PI 3-kinase)/protein kinase B (Akt), and nuclear factor (NF)-kappa B signaling pathways. Pharmacological inhibitor studies indicated roles for PI 3-kinase/Akt and NF-kappa B pathways in mediating IL-1 beta expression, and for NF-kappa B and p38 MAPK pathways in mediating TNF-alpha expression. IL-1 alpha-induced IL-6 mRNA expression was reduced by p38 MAPK inhibition, but increased by ERK and JNK pathway inhibitors. IL-10 produced a consistent but modest reduction in IL-1 alpha-induced IL-6 mRNA levels (not IL-1 beta or TNF-alpha), but this was not reflected by reduced IL-6 protein secretion. In conclusion, IL-1 alpha stimulates human CMF to express IL-1 beta, TNF-alpha, and IL-6 via specific signaling pathways, responses that are unaffected by IL-10 exposure.