Endo Yukinori, Blinova Ksenia, Romantseva Tatiana, Golding Hana, Zaitseva Marina
Center for Biologics Evaluation and Research (CBER), Food and Drug Administration (FDA), Bethesda, Maryland, United States of America.
PLoS One. 2014 May 28;9(5):e98517. doi: 10.1371/journal.pone.0098517. eCollection 2014.
Prostaglandin E2 (PGE2) is induced in vivo by bacterial products including TLR agonists. To determine whether PGE2 is induced directly or via IL-1β, human monocytes and macrophages were cultured with LPS or with Pam3CSK4 in presence of caspase-1 inhibitor, ZVAD, or IL-1R antagonist, Kineret. TLR agonists induced PGE2 in macrophages exclusively via IL-1β-independent mechanisms. In contrast, ZVAD and Kineret reduced PGE2 production in LPS-treated (but not in Pam3CSK4-treated) monocytes, by 30-60%. Recombinant human IL-1β augmented COX-2 and mPGES-1 mRNA and PGE2 production in LPS-pretreated monocytes but not in un-primed or Pam3CSK4-primed monocytes. This difference was explained by the finding that LPS but not Pam3CSK4 induced phosphorylation of IRF3 in monocytes suggesting activation of the TRIF signaling pathway. Knocking down TRIF, TRAM, or IRF3 genes by siRNA inhibited IL-1β-induced COX-2 and mPGES-1 mRNA. Blocking of TLR4 endocytosis during LPS priming prevented the increase in PGE2 production by exogenous IL-1β. Our data showed that TLR2 agonists induce PGE2 in monocytes independently from IL-1β. In the case of TLR4, IL-1β augments PGE2 production in LPS-primed monocytes (but not in macrophages) through a mechanism that requires TLR4 internalization and activation of the TRIF/IRF3 pathway. These findings suggest a key role for blood monocytes in the rapid onset of fever in animals and humans exposed to bacterial products and some novel adjuvants.
前列腺素E2（PGE2）在体内由包括TLR激动剂在内的细菌产物诱导产生。为了确定PGE2是直接诱导产生还是通过白细胞介素-1β（IL-1β）诱导产生，将人单核细胞和巨噬细胞与脂多糖（LPS）或Pam3CSK4一起在半胱天冬酶-1抑制剂ZVAD或IL-1受体拮抗剂Kineret存在的情况下培养。TLR激动剂仅通过不依赖IL-1β的机制在巨噬细胞中诱导PGE2产生。相反，ZVAD和Kineret使LPS处理的（而非Pam3CSK4处理的）单核细胞中PGE2的产生减少30%-60%。重组人IL-1β增加了LPS预处理的单核细胞中环氧合酶-2（COX-2）和微粒体前列腺素E合酶-1（mPGES-1）的信使核糖核酸（mRNA）以及PGE2的产生，但在未预处理或Pam3CSK4预处理的单核细胞中则没有增加。这种差异可以通过以下发现来解释：LPS而非Pam3CSK4诱导单核细胞中干扰素调节因子3（IRF3）的磷酸化，提示TIR结构域衔接蛋白诱导干扰素β（TRIF）信号通路被激活。通过小干扰RNA（siRNA）敲低TRIF、TRAM或IRF3基因可抑制IL-1β诱导的COX-2和mPGES-1 mRNA。在LPS预处理期间阻断TLR4的内吞作用可防止外源性IL-1β使PGE2产生增加。我们的数据表明，TLR2激动剂在单核细胞中独立于IL-1β诱导PGE2产生。就TLR4而言，IL-1β通过一种需要TLR4内化和TRIF/IRF3通路激活的机制增加LPS预处理的单核细胞（而非巨噬细胞）中PGE2的产生。这些发现提示血液单核细胞在接触细菌产物和一些新型佐剂的动物和人类发热的快速发作中起关键作用。
