INTRODUCTION: Interleukin (IL)-6 is induced in the heart during endotoxemia. We investigated endotoxin-induced IL-6 in vitro and its modulation by IL-1beta and tumor necrosis factor (TNF)-alpha. Whether lipopolysaccharide (LPS) would stimulate nuclear factor (NF)-kappaB intranuclear translocation was also examined. We hypothesized that IL-6 production is enhanced with LPS and cytokine challenge and that LPS stimulates NF-kappaB 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 microg/ml) and in the presence of TNF-alpha or IL-1beta. IL-6 mRNA was amplified using reverse-transcription polymerase chain reaction. Myoblasts were treated with LPS and stained for the p65 subunit of NF-kappaB. RESULTS: LPS stimulated IL-6 protein and mRNA expression (P < 0.05). IL-1beta increased IL-6 when combined with TNF-alpha (P < 0.05). In the presence of LPS, TNF-alpha lowered IL-6 production, which was further reduced upon addition of IL-1beta. LPS activated NF-kappaB 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-kappaB in response to LPS was evident in a myogenic cell line.
INTRODUCTION: Interleukin (IL)-6 is induced in the heart during endotoxemia. We investigated endotoxin-induced IL-6 in vitro and its modulation by IL-1beta and tumor necrosis factor (TNF)-alpha. Whether lipopolysaccharide (LPS) would stimulate nuclear factor (NF)-kappaB intranuclear translocation was also examined. We hypothesized that IL-6 production is enhanced with LPS and cytokine challenge and that LPS stimulates NF-kappaB 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 microg/ml) and in the presence of TNF-alpha or IL-1beta. IL-6 mRNA was amplified using reverse-transcription polymerase chain reaction. Myoblasts were treated with LPS and stained for the p65 subunit of NF-kappaB. RESULTS: LPS stimulated IL-6 protein and mRNA expression (P < 0.05). IL-1beta increased IL-6 when combined with TNF-alpha (P < 0.05). In the presence of LPS, TNF-alpha lowered IL-6 production, which was further reduced upon addition of IL-1beta. LPS activated NF-kappaB 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-kappaB in response to LPS was evident in a myogenic cell line.