Cytokine synthesis in the liver of endotoxin-tolerant and normal rats during hemorrhagic shock.

In the present study the effects of endotoxin tolerance on hemorrhagic shock were investigated with particular focus on hepatic alterations. The following questions were addressed: (i) does hemorrhagic shock induce cytokine formation and heat shock response in the liver; and (ii) does endotoxin tolerance alter these reactions. Endotoxin tolerance was induced by repetitive daily injections of LPS for 5 days. Hemorrhagic shock was induced by hypovolemia (MAP 35 +/- 5 mmHg). After 3 h, the animals were resuscitated by re-infusion of homologous blood. m-RNA was isolated from liver biopsies and the mRNA levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), interleukin-10 (IL-10) and heat shock protein 70 (HSP-70) were determined by RT-PCR. TNF-alpha was measured by ELISA in serum samples and in the supernatants of whole blood cultures. It was found that endotoxin tolerance reduced mortality caused by hemorrhagic shock from 80% to 20%. In parallel, TNF-alpha production in response to LPS in vivo and in vitro was significantly decreased. During hemorrhage and after resuscitation. increased mRNA levels were detected in hepatic biopsies for TNF-alpha, IL-6, IL-10 and HSP-70, with highest levels immediately after re-infusion. Endotoxin-tolerant rats produced significantly lower levels of TNF-alpha, while no differences were found for IL-10 and HSP-70. Within 30 min after reperfusion, significantly higher levels of IL-6 mRNA were found in hepatic biopsies from tolerant rats; these differences disappeared 2 h after reperfusion.