Department of Medical and Molecular Genetics, School of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Herman B Wells Center for Pediatric Research, School of Medicine, Indiana University School of Medicine, 1044 West Walnut, Indianapolis, IN 46202, USA.
Herman B Wells Center for Pediatric Research, School of Medicine, Indiana University School of Medicine, 1044 West Walnut, Indianapolis, IN 46202, USA.
Stem Cell Reports. 2016 Jun 14;6(6):940-956. doi: 10.1016/j.stemcr.2016.05.002. Epub 2016 Jun 2.
Toll-like receptor 4 (TLR4) plays a central role in host responses to bacterial infection, but the precise mechanism(s) by which its downstream signaling components coordinate the bone marrow response to sepsis is poorly understood. Using mice deficient in TLR4 downstream adapters MYD88 or TRIF, we demonstrate that both cell-autonomous and non-cell-autonomous MYD88 activation are major causes of myelosuppression during sepsis, while having a modest impact on hematopoietic stem cell (HSC) functions. In contrast, cell-intrinsic TRIF activation severely compromises HSC self-renewal without directly affecting myeloid cells. Lipopolysaccharide-induced activation of MYD88 or TRIF contributes to cell-cycle activation of HSC and induces rapid and permanent changes in transcriptional programs, as indicated by persistent downregulation of Spi1 and CebpA expression after transplantation. Thus, distinct mechanisms downstream of TLR4 signaling mediate myelosuppression and HSC exhaustion during sepsis through unique effects of MyD88 and TRIF.
Toll 样受体 4(TLR4)在宿主对细菌感染的反应中发挥核心作用,但 TLR4 下游信号成分协调骨髓对败血症反应的确切机制尚不清楚。使用 TLR4 下游衔接子 MYD88 或 TRIF 缺失的小鼠,我们证明在败血症期间,细胞自主和非细胞自主的 MYD88 激活是骨髓抑制的主要原因,而对造血干细胞(HSC)功能的影响较小。相比之下,细胞内固有 TRIF 的激活严重损害了 HSC 的自我更新,而不会直接影响髓样细胞。脂多糖诱导的 MYD88 或 TRIF 激活导致 HSC 的细胞周期激活,并诱导转录程序的快速和永久性变化,这表明移植后 Spi1 和 CebpA 表达的持续下调。因此,TLR4 信号下游的不同机制通过 MyD88 和 TRIF 的独特作用介导败血症期间的骨髓抑制和 HSC 耗竭。