Geisel J, Cook J A, Ashton S H, Wise W C, Halushka P V
Department of Physiology, Medical University of South Carolina, Charleston 29425.
Am J Physiol. 1994 Oct;267(4 Pt 1):C1067-72. doi: 10.1152/ajpcell.1994.267.4.C1067.
Lipopolysaccharide (LPS) induces macrophage protein and eicosanoid synthesis. Previous studies have shown that LPS induction of eicosanoid metabolism is transcription dependent and that prostaglandin (PG) H synthase is the committed step in the conversion of arachidonic acid (AA) to thromboxane (Tx) B2. LPS tolerance induced by sublethal in vivo injections of LPS renders rats resistant to LPS in vivo and macrophages refractory to LPS-stimulated eicosanoid synthesis in vitro. This study examined potential activity and content changes in constitutive and mitogen inducible PGH synthase in LPS-stimulated control and tolerant macrophages. TxB2 levels were measured to evaluate basal PGH synthase activity and stimulation by Salmonella enteritidis LPS (50 micrograms/ml), calcium ionophore A-23187, and AA. All tolerant macrophage groups demonstrated decreased TxB2 synthesis. TxB2 synthesis stimulated by AA in tolerant cells was decreased by 70% (P < 0.05) compared with control macrophages. In subsequent studies changes in PGH synthase content were examined in rat peritoneal macrophages from tolerant and control rats incubated with and without LPS. Immunoblot analysis of PGH synthase-1 (constitutive) demonstrated no increase in cells stimulated with LPS compared with basal but was diminished by 62 +/- 9% (n = 4, P < 0.05) in tolerant macrophages compared with control cells. Immunoblot analysis of PGH synthase-2 (mitogen inducible) demonstrated induction in response to LPS that was maximal between 12 and 24 h. PGH synthase-2 was also induced in tolerant macrophages in response to LPS but was less than in control cells. The results demonstrate that endotoxin tolerance is associated with reduced activity and content of PGH synthase-1 and a decreased LPS induction of PGH synthase-2.(ABSTRACT TRUNCATED AT 250 WORDS)
脂多糖（LPS）可诱导巨噬细胞合成蛋白质和类二十烷酸。以往研究表明，LPS诱导类二十烷酸代谢是转录依赖性的，且前列腺素（PG）H合酶是花生四烯酸（AA）转化为血栓素（Tx）B2的关键步骤。体内注射亚致死剂量LPS诱导的LPS耐受性使大鼠在体内对LPS产生抗性，并使巨噬细胞在体外对LPS刺激的类二十烷酸合成产生抗性。本研究检测了LPS刺激的对照和耐受性巨噬细胞中组成型和丝裂原诱导型PGH合酶的潜在活性和含量变化。通过测量TxB2水平来评估基础PGH合酶活性以及肠炎沙门氏菌LPS（50微克/毫升）、钙离子载体A-23187和AA的刺激作用。所有耐受性巨噬细胞组的TxB2合成均减少。与对照巨噬细胞相比，耐受性细胞中AA刺激的TxB2合成减少了70%（P<0.05）。在随后的研究中，检测了来自耐受性和对照大鼠的腹膜巨噬细胞在有或无LPS孵育情况下PGH合酶含量的变化。对PGH合酶-1（组成型）的免疫印迹分析表明，与基础水平相比，LPS刺激的细胞中PGH合酶-1没有增加，但与对照细胞相比，耐受性巨噬细胞中的PGH合酶-1减少了62±9%（n = 4，P<0.05）。对PGH合酶-2（丝裂原诱导型）的免疫印迹分析表明，LPS刺激可诱导PGH合酶-2，在12至24小时达到最大值。LPS刺激也可诱导耐受性巨噬细胞中的PGH合酶-2，但低于对照细胞。结果表明，内毒素耐受性与PGH合酶-1的活性和含量降低以及LPS对PGH合酶-2的诱导减少有关。（摘要截短于250字）
