Abstracts
1999 Digestive Disease Week

# 2126 HEPATIC NF-kB ACTIVATION DURING ENDOTOXEMIA IS INHIBITED BY THE STRESS RESPONSE
T A Pritts, Q Wang, Univ of Cincinnati, CChildren's Hosp Med Ctr, Shriners Hosp, Cincinnati, OH; D R Fischer, Univ of Cincinnati Med Ctr, Cincinnati, OH; X Sun, Univ of Cincinnati, CChildren's Hosp Med Ctr, Shriners Hosp, Cincinnati, OH; Josef E Fischer, Univ of Cincinnati Ctr, Cincinnati, OH; H R Wong, Univ of Cincinnati, CChildren's Hosp Med Ctr, Shriners Hosp, Cincinnati, OH; P O Hasselgren, Univ of Cincinnati, Cincinnati, OH

The transcription factor nuclear factor-kappa B (NF-kB), normally sequestered in the cytoplasm by its inhibitory protein IkB, regulates many genes involved in the inflammatory response to critical illness. Previous studies suggest that induction of the stress response improves survival during sepsis and endotoxemia and protects cells and tissues by regulating pro-inflammatory mediators. NF-kB is activated in the liver of endotoxemic mice, but the effect of the stress response on NF-kB activation in this tissue is not known. We tested the hypothesis that induction of the stress response inhibits NF-kB binding activity in liver during endotoxemia. Methods: The stress response was induced in mice by thermal heat shock (HS). Mice were anesthetized and their core temperature was raised to 42oC for three minutes by placing them in a heating chamber. Control animals received anesthesia and remained at room temperature (RT). After a two hour recovery period, mice were injected either with 12.5 mg/kg endotoxin (LPS) or a corresponding volume of sterile saline (NS). One hour later, animals were sacrificed, the liver was excised, and nuclear and cytoplasmic extracts were prepared. Hepatic IkB-a and HSP-72 levels were determined by Western blotting of cytoplasmic fractions. NF-kB binding activity was determined by electrophoretic mobility shift assay (EMSA) of nuclear fractions. Results: Hepatic levels of HSP-72 increased after heat shock, indicating induction of the stress response (figure 1, upper panel). NF-kB binding activity increased (figure 2), and IkB-a levels decreased (figure 1, lower panel) following LPS injection. These responses to endotoxemia were inhibited by prior heat shock. Conclusions: Induction of the stress response decreases NF-kB binding activity in the liver during endotoxemia, possibly by preserving cytoplasmic levels of IkB-a. The protective effect of the stress response may be partly due to decreased inflammatory response through inhibition of NF-kB.

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