Toll-like receptor 4: the missing link of the cerebral innate immune response triggered by circulating gram-negative bacterial cell wall components
Toll-like receptor 4: the missing link of the cerebral innate immune response triggered by circulating gram-negative bacterial cell wall components
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DOI：
10.1096/fj.00-0339com
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发表时间：
2001-01-01
期刊：
影响因子：
4.8
通讯作者：
Rivest, S
中科院分区：
文献类型：
--
作者：
Laflamme, N;Rivest, S
最近对Toll人类同源物的表征可能是先天免疫反应中导致NF-kappaB活性和促炎基因转录的转导事件的缺失环节。事实上，CD14并不被认为直接参与细胞信号传导，而是一种或多种哺乳动物toll样受体（tlr）与脂多糖（LPS）受体协同作用，以区分微生物病原体或其产物并启动跨膜信号传导。哺乳动物细胞可以表达多达10种不同的tlr，尽管TLR4在革兰氏阴性细菌和LPS应答中的重要性现在得到了TLR4突变小鼠对LPS耐药这一事实的支持。我们研究了TLR4在基础条件下以及对全身LPS和IL-1 β注射的反应。首先利用RNA分离和PCR技术，利用校对聚合酶扩增大鼠TLR4 cDNA。用Tri-Reagent从大鼠肝组织中分离总RNA，用Superscript II逆转录酶和序列5‘-T12(GAC)N-3’的退化3'端寡核苷酸引物逆转录成cDNA。轻脑膜、脉络膜丛、膜下器官、终板血管器官、正中隆起、后脑区均可见杂交阳性信号。分散的小细胞在脑实质内也显示出令人信服的杂交信号。少数明确的核显示TLR4阳性转录：乳突上核、耳蜗核和外侧网状核。脑室周围器官、轻脑膜和chp也表现出LPS受体mCD14的组成性表达。与内毒素血症期间编码mCD14的基因的强烈上调相反，LPS和IL-1 β都没有引起整个中枢神经系统中TLR4 mRNA水平的令人信服的增加。在免疫挑战动物的脑组织中发现编码TLR4的基因下调。mCD 14和TLR4的组成性表达可能解释了大脑中的先天免疫反应，该反应起源于循环LPS存在时缺乏血脑屏障的结构。
The recent characterization of human homologues of Toll may be the missing link for the transduction events leading to NF-kappaB activity and proinflammatory gene transcription during innate immune response. Indeed, CD14 is not thought to participate directly in the cell signaling, but rather one or more of the mammalian Toll-like receptors (TLRs) acts in concert with the lipopolysaccharide (LPS) receptor to discriminate between microbial pathogens or their products and initiate transmembrane signaling. Mammalian cells may express as many as 10 distinct TLRs, although the importance of TLR4 in response to gram-negative bacteria and LPS is now supported by the fact that TLR4-mutated mice are LPS resistant. We investigated the expression of TLR4 across the rat brain under basal conditions and in response to systemic LPS and IL-1 beta injection. We first cloned the rat TLR4 cDNA via RNA isolation and polymerase chain reaction (PCR) amplification with a proofreading polymerase. Total RNA was isolated from the rat liver tissue using Tri-Reagent and reverse transcribed into cDNA using Superscript II reverse transcriptase and an oligonucleotide primer with a degenerate 3' end of sequence 5'-T12(GAC)N-3'. Positive hybridization signal was found in the leptomeninges, choroid plexus (chp), subfornical organ, organum vasculosum of the lamina terminalis, median eminence, and area postrema. Scattered small cells also displayed a convincing hybridization signal within the brain parenchyma. Few well-defined nuclei exhibited positive TLR4 transcript: the supramamillary nucleus, cochlear nucleus, and the lateral reticular nucleus. The circumventricular organs, the leptomeninges, and chp also exhibited constitutive expression of the LPS receptor mCD14. In contrast to the strong up-regulation of the gene encoding mCD14 during endotoxemia, neither LPS nor IL-1 beta caused a convincing increase in the TLR4 mRNA levels across the CNS. A down-regulation of the gene encoding TLR4 was found in the cerebral tissue of immune-challenged animals. The constitutive expression of both mCD 14 and TLR4 may explain the innate immune response in the brain, which originates from the structures devoid of blood-brain barrier in presence of circulating LPS.