Hajishengallis George, Martin Michael, Schifferle Robert E, Genco Robert J
Department of Oral Biology, State University of New York at Buffalo, 14214, USA.
Infect Immun. 2002 Dec;70(12):6658-64. doi: 10.1128/IAI.70.12.6658-6664.2002.
We investigated counteracting interactions between the lipopolysaccharides (LPS) from Escherichia coli (Ec-LPS) and Porphyromonas gingivalis (Pg-LPS), which induce cellular activation through Toll-like receptor 4 (TLR4) and TLR2, respectively. We found that Ec-LPS induced tolerance in THP-1 cells to subsequent tumor necrosis factor alpha (TNF-alpha) and interleukin 1 beta (IL-1beta) induction by Pg-LPS, though the reverse was not true, and looked for explanatory differential effects on the signal transduction pathway. Cells exposed to Pg-LPS, but not to Ec-LPS, displayed persisting expression of IL-1 receptor-associated kinase without apparent degradation, presumably allowing prolonged relay of downstream signals. Accordingly, cells pretreated with Pg-LPS, but not with Ec-LPS, were effectively activated in response to subsequent exposure to either LPS molecule, as evidenced by assessing nuclear factor (NF)-kappaB activity. In fact, Pg-LPS primed THP-1 cells for enhanced NF-kappaB activation and TNF-alpha release upon restimulation with the same LPS. This was a dose-dependent effect and correlated with upregulation of surface TLR2 expression. Furthermore, we observed inhibition of NF-kappaB-dependent transcription in a reporter cell line pretreated with Ec-LPS and restimulated with Pg-LPS (compared to cells pretreated with medium only and restimulated with Pg-LPS), but not when the reverse treatment was made. Although Pg-LPS could not make cells tolerant to subsequent activation by Ec-LPS, Pg-LPS inhibited Ec-LPS-induced TNF-alpha and IL-6 release when the two molecules were added simultaneously into THP-1 cell cultures. Pg-LPS also suppressed P. gingivalis FimA protein-induced NF-kappaB-dependent transcription in the 3E10/huTLR4 reporter cell line, which does not express TLR2. This rules out competition for common signaling intermediates, suggesting that Pg-LPS may block component(s) of the TLR4 receptor complex. Interactions between TLR2 and TLR4 agonists may be important in the regulation of inflammatory reactions.
我们研究了来自大肠杆菌的脂多糖（Ec-LPS）和牙龈卟啉单胞菌的脂多糖（Pg-LPS）之间的拮抗相互作用，它们分别通过Toll样受体4（TLR4）和TLR2诱导细胞活化。我们发现Ec-LPS可诱导THP-1细胞对随后Pg-LPS诱导的肿瘤坏死因子α（TNF-α）和白细胞介素1β（IL-1β）产生耐受，尽管反之则不成立，并且我们寻找了对信号转导途径的解释性差异效应。暴露于Pg-LPS而非Ec-LPS的细胞显示白细胞介素1受体相关激酶持续表达且无明显降解，推测这允许下游信号的延长传递。因此，用Pg-LPS预处理而非Ec-LPS预处理的细胞在随后暴露于任何一种LPS分子时均能有效活化，通过评估核因子（NF）-κB活性可证明这一点。事实上，Pg-LPS使THP-1细胞在再次用相同LPS刺激时增强NF-κB活化和TNF-α释放。这是一种剂量依赖性效应且与表面TLR2表达上调相关。此外，我们观察到在用Ec-LPS预处理并再次用Pg-LPS刺激的报告细胞系中NF-κB依赖性转录受到抑制（与仅用培养基预处理并再次用Pg-LPS刺激的细胞相比），但反过来处理时则未观察到这种情况。尽管Pg-LPS不能使细胞对随后Ec-LPS的活化产生耐受，但当将这两种分子同时添加到THP-1细胞培养物中时，Pg-LPS可抑制Ec-LPS诱导的TNF-α和IL-6释放。Pg-LPS还抑制牙龈卟啉单胞菌FimA蛋白在不表达TLR2的3E10/huTLR4报告细胞系中诱导的NF-κB依赖性转录。这排除了对共同信号中间体的竞争，表明Pg-LPS可能阻断TLR4受体复合物的成分。TLR2和TLR4激动剂之间的相互作用在炎症反应调节中可能很重要。
