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

Abstract

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-1α (IL-1α), 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-1β (IL-1β), tumor necrosis factor-α (TNF-α), 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-1α (0.001–10 ng/ml, 0–6 h) stimulated IL-1β, TNF-α, and IL-6 mRNA expression with distinct temporal and concentration profiles, resulting in increased cytokine secretion. The response to IL-1α was much greater than with TNF-α. Neither IL-1α nor TNF-α treatment modulated CT-1 mRNA expression. Immunoblotting with phosphospecific antibodies revealed that IL-1α stimulated the extracellular signal-regulated kinase (ERK)-1/2, p38 mitogen-activated protein kinase (MAPK), c-Jun NH2-terminal kinase (JNK), phosphatidylinositol 3-kinase (PI 3-kinase)/protein kinase B (Akt), and nuclear factor (NF)-κB signaling pathways. Pharmacological inhibitor studies indicated roles for PI 3-kinase/Akt and NF-κB pathways in mediating IL-1β expression, and for NF-κB and p38 MAPK pathways in mediating TNF-α expression. IL-1α-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-1α-induced IL-6 mRNA levels (not IL-1β or TNF-α), but this was not reflected by reduced IL-6 protein secretion. In conclusion, IL-1α stimulates human CMF to express IL-1β, TNF-α, and IL-6 via specific signaling pathways, responses that are unaffected by IL-10 exposure.