Fujihara M, Ikebuchi K, Maekawa T L, Wakamoto S, Ogiso C, Ito T, Takahashi T A, Suzuki T, Sekiguchi S
Japanese Red Cross, Hokkaido Red Cross Blood Center, Sapporo, Japan.
J Immunol. 1998 Oct 1;161(7):3659-65.
Treatment of a mouse macrophage cell line, P388D1, for 1 h with bacterial LPS caused a transient increase in the level of junB mRNA expression. These cells became refractory in terms of the junB gene response to exposure to a second round of LPS or lipid A, but not to PMA. The LPS-induced desensitized state was not due to the shortening of the half-life of junB mRNA, but was suggested, by nuclear run-on analysis, to be caused by reduction of junB gene transcription. Pretreating cells with herbimycin A, a tyrosine kinase inhibitor, substantially inhibited LPS-induced expression of junB mRNA and decreased tyrosine phosphorylation of 38- to 42-kDa proteins, which comigrated with p38 and p42 mitogen-activated protein (MAP) kinases. Parallel to down-regulation of junB mRNA expression, activation of the p38 MAP kinase was markedly reduced in LPS-tolerant cells, whereas activation of p42 MAP kinase was relatively constant. The specific p38 MAP kinase inhibitor, SB202190, potently inhibited LPS-induced junB mRNA expression. These results suggest that the LPS-induced desensitization of junB gene expression occurs at or upstream of the level of gene transcription and may be involved in a defective LPS-induced p38 MAP kinase pathway.
用细菌脂多糖（LPS）处理小鼠巨噬细胞系P388D1 1小时，导致junB mRNA表达水平短暂升高。这些细胞在对第二轮LPS或脂质A暴露的junB基因反应方面变得不应答，但对佛波酯（PMA）仍有反应。LPS诱导的脱敏状态并非由于junB mRNA半衰期缩短，而是通过细胞核连续转录分析表明，是由junB基因转录减少所致。用酪氨酸激酶抑制剂赫伯霉素A预处理细胞，可显著抑制LPS诱导的junB mRNA表达，并降低与p38和p42丝裂原活化蛋白（MAP）激酶迁移率相同的38至42 kDa蛋白的酪氨酸磷酸化。与junB mRNA表达下调平行，LPS耐受细胞中p38 MAP激酶的活化明显降低，而p42 MAP激酶的活化相对恒定。特异性p38 MAP激酶抑制剂SB202190有效抑制LPS诱导的junB mRNA表达。这些结果表明，LPS诱导的junB基因表达脱敏发生在基因转录水平或其上游，可能与LPS诱导的p38 MAP激酶途径缺陷有关。
