Modulation of interleukin-6 in cardiac myoblasts during endotoxemia

Abstract

Introduction. Interleukin (IL)-6 is induced in the heart during endotoxemia. We investigated endotoxin-induced IL-6 in vitro and its modulation by IL-1β and tumor necrosis factor (TNF)-α. Whether lipopolysaccharide (LPS) would stimulate nuclear factor (NF)-κB intranuclear translocation was also examined. We hypothesized that IL-6 production is enhanced with LPS and cytokine challenge and that LPS stimulates NF-κB intranuclear translocation in a myogenic cell line. Methods. Rat H9c2 cardiac myoblasts were grown in culture. IL-6 protein was determined by enzyme-linked immunosorbent assay after LPS (10 μg/ml) and in the presence of TNF-α or IL-1β. IL-6 mRNA was amplified using reverse-transcription polymerase chain reaction. Myoblasts were treated with LPS and stained for the p65 subunit of NF-κB. Results. LPS stimulated IL-6 protein and mRNA expression ( P < 0.05). IL-1β increased IL-6 when combined with TNF-α ( P < 0.05). In the presence of LPS, TNF-α lowered IL-6 production, which was further reduced upon addition of IL-1β. LPS activated NF-κB showing p65 subunit cellular localization within 30 min. Conclusions. In cardiac myoblasts, IL-6 is either enhanced or reduced depending on interactions between LPS and cytokine challenge. Enhanced nuclear translocation of NF-κB in response to LPS was evident in a myogenic cell line.