Lipopolysaccharide activates nuclear factor κB in rat intestine: role of endogenous platelet‐activating factor and tumour necrosis factor

Abstract

We examined the effect of lipopolysaccharide (LPS), a cell wall constituent of Gram negative bacteria, on nuclear factor κB (NF‐κB) activation in the intestine and the roles of endogenous platelet‐activating factor (PAF), tumour necrosis factor‐α (TNF) and neutrophils. We also compared the time course of NF‐κB activation in response to PAF and LPS. Ileal nuclear extracts from LPS (8 mg kg⁻¹, IV)‐injected rats were assayed for NF‐κB‐DNA‐binding activity and identification of the subunits. Some rats were pretreated with WEB2170 (a PAF receptor antagonist), anti‐TNF antibody, or anti‐neutrophil antiserum. NF‐κB p65 was localized by immunohistochemistry. An additional group was challenged with PAF (2 μg kg⁻¹, IV) for comparison. LPS activates intestinal NF‐κB, both as p50‐p50 and p50‐p65 dimers within 15 min, and the effect peaks at 2 h. The effect is slower and more sustained than that of PAF, which peaks at 30 min. Activated NF‐κB was immunolocalized within epithelial and lamina propria cells. LPS effect was reduced by 41, 37 and 44%, respectively, in animals pretreated with WEB2170, anti‐TNF antibody, or anti‐neutrophil antiserum (Pin vivo and neutrophil activation is involved in its action. The LPS effect is mediated by both endogenous PAF and TNF. British Journal of Pharmacology (2000) 129, 307–314; doi:10.1038/sj.bjp.0703055