Department of Pediatrics, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan.
J Biomed Sci. 2011 Aug 15;18(1):56. doi: 10.1186/1423-0127-18-56.
Notch and TLR pathways were found to act cooperatively to activate Notch target genes and to increase the production of TLR-induced cytokines in macrophages. However, the mechanism of LPS-induced Notch activation and its role in sepsis still remains unclear.
We analyzed the expression patterns of Notch components in a LPS-stimulated murine macrophage cell line using real-time PCR and western blotting. The role of DAPT, a gamma-secretase inhibitor that is known to be a potent Notch inhibitor, in LPS-induced cytokine release and experimental sepsis in mice was also explored. Student's t-test was used to analyze the difference between the two groups.
We found that Notch signaling was activated after LPS stimulation. The expression of Jagged 1, a Notch ligand, induced by LPS occurred in a JNK-dependent manner. In addition, Notch target genes were upregulated by early Notch-independent activation followed by delayed Notch-dependent activation after LPS stimulation. Disruption of Notch signaling by DAPT attenuated the LPS-induced inflammatory responses, including vascular endothelial growth factor (VEGF) and high-mobility group box chromosomal protein 1 (HMGB1), both in vitro and in vivo and partially improved experimental sepsis survival.
These findings support the existence of a synergistic effect of Notch signaling and the LPS pathway both in vitro and in vivo. Therefore, in the future Notch inhibitors may be utilized as adjunctive agents for the treatment of sepsis syndrome.
Notch 和 TLR 通路被发现协同作用，激活 Notch 靶基因，并增加巨噬细胞中 TLR 诱导细胞因子的产生。然而，LPS 诱导 Notch 激活的机制及其在脓毒症中的作用仍不清楚。
我们使用实时 PCR 和 Western blot 分析了 LPS 刺激的鼠巨噬细胞系中 Notch 成分的表达模式。还探讨了 DAPT（一种已知是强效 Notch 抑制剂的γ-分泌酶抑制剂）在 LPS 诱导的细胞因子释放和小鼠实验性脓毒症中的作用。使用学生 t 检验分析两组之间的差异。
我们发现 LPS 刺激后 Notch 信号被激活。LPS 诱导的 Jagged 1（Notch 配体）的表达以 JNK 依赖性方式发生。此外，LPS 刺激后，早期 Notch 非依赖性激活后 Notch 依赖性激活上调了 Notch 靶基因。DAPT 破坏 Notch 信号减弱了 LPS 诱导的炎症反应，包括血管内皮生长因子 (VEGF) 和高迁移率族蛋白 B1 (HMGB1)，无论是在体外还是体内，并且部分改善了实验性脓毒症的生存。
这些发现支持 Notch 信号和 LPS 通路在体外和体内均存在协同作用。因此，在未来 Notch 抑制剂可能被用作治疗脓毒症综合征的辅助剂。
