Neuro-hormonal host defence in endotoxin shock

Area of Science:

• Endocrinology
• Immunology
• Toxicology

Background:

• Adrenalectomy (ADX) significantly impacts physiological responses to endotoxins.
• Glucocorticoids play a crucial role in modulating the immune response to bacterial components like lipopolysaccharide (LPS).

Purpose of the Study:

• To investigate the role of adrenalectomy and glucocorticoids in modulating the sensitivity of mice to lipopolysaccharide (LPS) and its toxic moiety, lipid A (LA).
• To examine the effects of adrenalectomy on tumor necrosis factor-alpha (TNF) production and lethality induced by LPS/LA.

Main Methods:

• Mice underwent adrenalectomy (ADX) or were treated with metyrapone to inhibit glucocorticoid synthesis.
• Sensitivity to LPS and lipid A (LA) was assessed by LD100.
• Serum levels of TNF and corticosterone were measured at various time points after LPS/LA administration.
• The effect of glucocorticoid treatment on TNF production and lethality in ADX mice was evaluated.

Main Results:

• Adrenalectomy increased mouse sensitivity to LPS and LA by 500-fold.
• ADX mice exhibited 40-60 times higher serum TNF levels post-LPS/LA treatment compared to controls.
• Inhibition of glucocorticoid synthesis in intact mice also sensitized them to LPS.
• Glucocorticoid administration to ADX mice inhibited TNF production and reduced the lethal effects of LPS/LA.
• Plasma prolactin levels increased after endotoxin administration in both intact and ADX mice.

Conclusions:

• Adrenalectomy profoundly enhances sensitivity to endotoxins, mediated by increased TNF production.
• Glucocorticoids are critical in preventing excessive inflammatory responses and lethality associated with LPS/LA exposure.
• These findings highlight the critical role of the adrenal axis in regulating endotoxin tolerance.