Laboratory of Human Molecular Genetics, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, Poznan, Poland.
Am J Physiol Cell Physiol. 2011 Jun;300(6):C1337-44. doi: 10.1152/ajpcell.00276.2010. Epub 2011 Feb 23.
Inflammation plays an important role in host defenses against infectious agents and injury, but it also contributes to the pathophysiology of atherosclerosis. Signal transducer and activated transcription 1 (STAT1) has been identified as a point of convergence for the cross talk between the pro-inflammatory cytokine interferon γ (IFNγ) and the Toll-like receptor-4 (TLR4) ligand LPS in immune cells. However, there is no information available on the role of STAT1 in TLR4-mediated progression of atherosclerosis and on potential synergism between lipopolysaccharides (LPS) and IFNγ signaling in cells from the vasculature. Cultured human microvascular endothelial cells (HMECs) exposed to LPS activated STAT1 in a delayed manner that was inhibited by cycloheximide treatment. Pretreatment of HMECs as well as primary vascular smooth muscle cells (VSMCs) with IFNγ followed by LPS resulted in a significant increase in STAT1 phosphorylation compared with both factors alone. Increased STAT1 protein levels, strictly mediated by IFNγ, correlated with the augmented STAT1 phosphorylation that was absent in TLR4(-/-) cells. As assessed by PCR, Western analysis, and ELISA, this coincided with increased expression of the chemokine interferon gamma-induced protein 10 kDa (IP-10) and the adhesion molecule ICAM-1 in a TLR4-dependent manner.The STAT1-inhibitor fludarabine markedly reduced these effects as well as IFNγ and LPS-dependent adhesion of U937 cells to endothelial cells, emphasizing the potential importance of STAT1 in the integration of both signals. With the established roles of IFNγ and TLRs in atherosclerotic pathology, the STAT1-dependent signal integration between IFNγ and TLR in ECs and VSMCs in response to exogenous and endogenous atherogenic ligands could result in amplification of pro-inflammatory responses in the damaged vessel and be a novel mechanism involved in the initiation and progression of atherosclerosis.
炎症在宿主防御感染因子和损伤方面起着重要作用，但它也促成了动脉粥样硬化的病理生理学。信号转导子和转录激活子 1（STAT1）已被确定为促炎细胞因子干扰素 γ（IFNγ）和 Toll 样受体 4（TLR4）配体 LPS 在免疫细胞中相互作用的交汇点。然而，目前尚无关于 STAT1 在 TLR4 介导的动脉粥样硬化进展中的作用以及脂多糖（LPS）和 IFNγ 信号在血管细胞中潜在协同作用的信息。暴露于 LPS 的培养人微血管内皮细胞（HMEC）以延迟方式激活 STAT1，该方式可被环己酰亚胺处理抑制。IFNγ 预处理 HMEC 以及原发性血管平滑肌细胞（VSMC），然后用 LPS 处理，与单独使用两种因子相比，STAT1 磷酸化显著增加。IFNγ 严格介导的 STAT1 蛋白水平增加与增强的 STAT1 磷酸化相关，而在 TLR4（-/-）细胞中不存在这种磷酸化。如通过 PCR、Western 分析和 ELISA 评估的那样，这与趋化因子干扰素γ诱导的 10 kDa 蛋白（IP-10）和粘附分子 ICAM-1 的表达增加一致，这种增加依赖于 TLR4。STAT1 抑制剂氟达拉滨显著降低了这些效应，以及 IFNγ 和 LPS 依赖性 U937 细胞与内皮细胞的粘附，强调了 STAT1 在整合两种信号中的潜在重要性。鉴于 IFNγ 和 TLRs 在动脉粥样硬化发病机制中的作用，IFNγ 和 TLR 在 ECs 和 VSMCs 中对细胞外和内源性动脉粥样硬化配体的 STAT1 依赖性信号整合可能导致受损血管中促炎反应的放大，并成为参与动脉粥样硬化起始和进展的新机制。
