PAF activates NF-"B in small intestinal epithelial cells in rats

PAF (platelet-activating factor) is a phospholipid mediator which may play an important role in bowel inflammation and injury. PAF injected into rats at 2 μg/kg, iv, produces bowel necrosis. We have shown that PAF at a lower dose (1.5 μg/kg) induces the gene expression of proinflammatory mediators, e.g., TNF and type II PLA₂. In this study we examined the effect of PAF on NF-κB which regulates the transcription of many genes of proinflammatory cytokines including TNF. Anesthetized young S.D. rats were injected with PAF at 1.25 or 1.5 μg/kg, iv. (Preliminary results showed that 1 μg/kg PAF had no effect on NF-κB activation). These doses caused only transient hypotension and no gross bowel necrosis. Heal epithelial cells from sham control and PAF-treated rats were isolated 30 min after injection. Nuclei were isolated, proteins extracted and nuclear translocation of NF-κB was analyzed by electrophoretic mobility shift assay using a [³²P]-labeled oligonucleotide probe specific for NF-κB. We found that ileal epithelial cells of sham controls have a constitutive low level of NF-κB activity within nuclei. PAF at both 1.25 and 1.5 μg/kg significantly increased NF-κB translocation into the nucleus. Thus, NF-κB could mediate the upregulation of proinflammatory cytokines produced by epithelial cells after PAF administration.