Effects of perturbations of the hypothalamic-pituitary-adrenal axis on the acute phase response: Altered C/EBP and acute phase response gene expression in lipopolysaccharide-treated rats

In this study, we investigated the influence of long term perturbations of the hypothalamic-pituitary-adrenal axis on the acute phase response elicited following lipopolysaccharide (LPS) challenge in rats. Specifically, we examined the effects of either long term absence of glucocorticoids (adrenalectomized rats treated with placebo chronic release pellets) or extended exposure to pharmacologic levels of glucocorticoids (adrenalectomized rats treated with dexamethasone chronic release pellets) on the expression of selected acute phase proteins and various members of the CCAAT/enhancer-binding protein (C/EBP) family of transcription factors. Both hypothalamic-pituitary-adrenal axis manipulations resulted in a reduction of the acute phase response as assessed by the LPS-mediated induction of acute phase proteins and C/EBP gene expression, with dexamethasone treatment exhibiting a greater inhibitory effect than adrenalectomy. Induction of hemopexin, alpha(1)-acid glycoprotein, alpha(2)-macroglobulin, GADD153, C/EBP beta, and C/EBP delta mRNAs by LPS were all abolished in dexamethasone-treated rats. These findings have direct implications for patients undergoing chronic high dose glucocorticoid therapy.