Lipopolysaccharide-triggered desensitization of TNF-alpha mRNA expression involves lack of phosphorylation of I kappa B alpha in a murine macrophage-like cell line, P388D1

Activation of nuclear factor kappa B (NF-kappa B) is thought to be required for cytokine production by lipopolysaccharide (LPS)-responsive cells. Here , we investigated the contribution of NF-kappa B in preventing LPS-induced transcription of the tumor necrosis factor alpha (TNF-alpha) gene in a muri ne macrophage cell line, P388D1, when tolerance was induced in the cells wi th a short exposure to a higher dose of LPS. Electrophoretic mobility shift assays with the kappa B elements of the murine TNF-alpha promoter and enha ncer revealed that unclear mobilization of heterodimers of p65/p50, c-rel/p 50 and p65/c-rel, and homodimers of p65 was markedly reduced in LPS-toleran t cells, whereas that of p50 homodimers was only slightly increased. Wester n blot analysis showed that the phosphorylation of Ser(32) on I kappa B alp ha and its transient degradation did not occur in LPS-tolerant cells, These results thus suggest that desensitization of TNF-alpha gene expression in this LPS-tolerant state is closely associated with down-regulation of trans activating NF-kappa B and may involve a defect in the LPS-induced I kappa B alpha kinase pathway.