Modulation of glucocorticoid receptor expression, inflammation, and cell apoptosis in septic guinea pig lungs using methylprednisolone

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Abstract
The use of glucocorticoids for treatment of sepsis has waxed and waned during the past several decades, and recent randomized controlled trials have evoked a reassessment of this therapy. Most glucocorticoid actions are mediated by its specific intracellular receptors (GRs). Thus we initially evaluated whether sepsis and high-dose corticosteroid therapy can regulate guinea pig pulmonary expression of GRs: active receptor, GRα, and dominant negative receptor, GRβ. Sepsis induction by LPS injection (300 μg/kg ip) decreased mRNA and protein levels of GRα and increased protein expression of GRβ in lungs. High-dose methylprednisolone (40 mg/kg ip), administered simultaneously with LPS, markedly potentiated the decrease in GRα expression but slightly affected the increase in GRβ expression. Consequently, this led to a significant reduction in GRα nuclear translocation. Nevertheless, methylprednisolone treatment strongly eliminated LPS induction of NF-κB activity, as determined by NF-κB nuclear translocation and by gel mobility shift assays. Furthermore, the LPS-induced increase in inflammatory cells in bronchoalveolar lavage fluid was blunted by administration of the corticosteroid. On the other hand, immunofluorescent staining for cleaved caspase-3 showed a marked increase in this proapoptotic marker in lung sections, and terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling (TUNEL) represented an enhanced appearance of cell apoptosis in lungs and spleen when methylprednisolone was given together with LPS. Cell apoptosis is now considered to play a role in the pathogenesis of septic syndrome. We thus suggest that the action of glucocorticoids at high doses to accelerate sepsis-induced cell apoptosis may overwhelm their therapeutic advantages in septic shock.