C/EBP DNA-binding activity is upregulated by a glucocorticoid-dependent mechanism in septic muscle

Sepsis-induced muscle cachexia is associated with increased expression of several genes in the ubiquitin-proteasome proteolytic pathway, but little is known about the activation of transcription factors in skeletal muscle during sepsis. We tested the hypothesis that sepsis upregulates the expression and activity of the transcription factors CCAAT/enhancer binding protein (C/EBP)-β and -δ in skeletal muscle. Sepsis was induced in rats by cecal ligation and puncture, and control rats were sham operated. C/EBP-β and -δ DNA-binding activity was determined by electrophoretic mobility shift assay and supershift analysis. In addition, C/EBP-β and -δ nuclear protein levels were determined by Western blot analysis. Sepsis resulted in increased DNA-binding activity of C/EBP, and supershift analysis suggested that this reflected activation of the β- and δ-isoforms of C/EBP. Concomitantly, C/EBP-β and -δ protein levels were increased in the nuclear fraction of skeletal muscle. In additional experiments, we tested the role of glucocorticoids in sepsis-induced activation of C/EBP-β and -δ by treating rats with the glucocorticoid receptor antagonist RU-38486. This treatment inhibited the sepsis-induced activation of C/EBP-β and -δ, suggesting that glucocorticoids participate in the upregulation of C/EBP in skeletal muscle during sepsis. The present results suggest that C/EBP-β and -δ are activated in skeletal muscle during sepsis and that this response is, at least in part, regulated by glucocorticoids.