NF-κB is a transcription factor which regulates many genes involved in the expression of pro-inflammatory cytokines and adhesion molecules. We have previously shown that: (1) PAF (1.5 μ/kg, IV) activated NF-κB, mainly as p50 homodimer, in rat intestine; (2) LPS induced intestinal PAF production and injury, which was blocked by PAF antagonists. Here we examined whether LPS activates NF-κB in rat small intestine and whether it was via endogenous PAF production. Young Sprague-Dawley rats were injected IV with PAF (1.5 μ/kg), LPS (8mg/kg) or vehicle (saline). At 30 min, 1 hr, 90 min and 2 hr, ileal nuclear extracts were assessed for NF-κB DNA-binding activity by electrophoretic mobility shift assay using a [32P]-labeled oligonucleotide probe specific for NF-κB. Supershift experiments were done to identify the NF-κB subunits. We found that LPS (8mg/kg) activated NF-κB in the intestine, predominantly as p50-p65 heterodimer. This effect was maximum 2 hr after injection. In contrast, PAF activates NF-κB, predominantly as p50-p50 homodimer, and the effect peaked at 30 min. Further, LPS-induced NF-κB activation was partially inhibited by WEB 2086 (PAF antagonist). Thus, LPS induces NF-κB activation via both PAF-dependent and PAF-independent pathways.

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