Impact of IL-6 signaling on hepatic thrombopoietin production, platelet turnover and platelet activation upon acute inflammation (thrombo-inflammation)

白介素6(IL-6)是一种急性期细胞因子，参与炎症反应。在IL-6经典信号转导中，靶细胞被IL-6通过膜结合的IL-6受体(IL-6R)刺激，该受体在配体结合时与信号受体蛋白gp130结合，导致Janus激酶(JAK)和转录因子(STAT)的激活。只表达gp130的细胞可以对与IL-6R的可溶性形式结合的IL-6做出反应，这一过程被称为反式信号转导。不同的研究小组证实了血小板中sIL-6R和gp130的存在，IL-6可能通过激活JAK2和STAT3而激活血小板，加速血栓的形成。通过IL-6和sIL-6R的细胞因子信号在急性心肌梗死(AMI)期间被观察到，并且与心血管事件的发生率相关。此外，IL-6信号通过促血小板生成素(TPO)刺激血小板生成来调节血小板的产生。最近，我们报道了肝部分切除(PHX)后，通过激活Ashwell Morell受体(AMR)/IL-6R-JAK2-STAT信号通路，导致剩余肝组织TPO表达和释放增加，血小板计数迅速恢复。IL-6R在确保止血的这些过程中起着至关重要的作用。在新的初步研究中，我们能够通过Asgr1和IL-6R在肝脏中的表达增强，从而导致TPO血浆水平的升高，为急性心肌梗死后血小板转换率的提高提供证据。此外，在Lgp130-CD4-CRE小鼠中，血小板计数的增加表明gp130和CD4+T细胞参与了血小板数量的控制。此外，我们还发现IL-6信号在血小板活化中起作用，但IL-6反式信号不足以调节血小板的激活。到目前为止，将IL-6信号与血小板周转和产生以及血小板激活和血小板介导性炎症联系起来的途径和蛋白质在很大程度上是未知的。在这里，我们假设IL-6信号是TPO动态平衡、血小板激活和血栓形成与相关炎症(血栓炎症)的主要调节因子。因此，我们希望试验性地遵循当前提案中的三个主要目标。首先，我们想要详细验证IL-6信号对肝脏TPO表达和释放的影响。第二，我们想要研究IL-6信号在实验性小鼠(急性心肌梗死小鼠模型)的血小板激活和血小板介导的炎症中的作用。第三，我们将分析急性心肌梗死患者的血小板周转，这可能导致血小板活化升高和表面糖基化的变化，特别是作为第一种翻译方法的唾液酸丢失。

Interleukin-6 (IL-6) is an acute phase cytokine and involved in inflammation. In IL-6 classical signaling, target cells are stimulated by IL-6 via the membrane bound IL-6 receptor (IL-6R) that associates with the signaling receptor protein gp130 upon ligand binding leading to the activation of Janus kinases (JAKs) and the activation of transcription factors (STATs). Cells that only express gp130 can respond to IL-6 bound to the soluble form of the IL-6R, a process that has been termed trans-signaling. The presence of sIL-6R and gp130 in platelets was confirmed by different groups and IL-6 might be able to activate platelets and to accelerate thrombus formation via activation of JAK2 and STAT3. Cytokine signaling via IL-6 and sIL-6R is observed during acute myocardial infarction (AMI) and associated with cardiovascular event rates. Furthermore, IL-6 signaling modulates platelet production by stimulating thrombopoiesis through thrombopoietin (TPO). Recently, we reported that platelet counts were rapidly restored after partial hepatectomy (PHx) via activation of the Ashwell Morell receptor (AMR)/IL-6R-JAK2-STAT signaling pathway leading to elevated TPO expression and release from the remaining liver tissue. The IL-6R plays a crucial role in these processes to ensure hemostasis. In new preliminary studies, we were able to provide evidence for an enhanced platelet turnover after AMI with enhanced expression of Asgr1 and IL-6r in the liver resulting in enhanced TPO plasma levels. Furthermore, elevated platelet counts in Lgp130-CD4-Cre mice suggest that gp130 and CD4+ T-cells are involved in the control of platelet numbers. Besides, we found that IL-6 signaling plays a role in platelet activation but that IL-6 trans-signaling is not sufficient to modulate platelet activation. To date, the pathways and proteins that link IL-6 signaling and platelet turnover and production as well as platelet activation and platelet-mediated inflammation are largely unknown. Here, we hypothesize that IL-6 signaling is a major regulator of TPO homeostasis, platelet activation and thrombosis with associated inflammation (thrombo-inflammation). Therefore, we want to experimentally follow three major objectives in the current proposal. First, we want to validate the impact of IL-6 signaling on TPO expression and release in liver in detail. Second, we want to investigate the role of IL-6 signaling in platelet activation and platelet mediated inflammation in experimental mice (mouse model of AMI). Third, we will analyze the platelet turnover in patients with AMI that might lead to elevated platelet activation and to changes in surface glycosylation, specifically loss of sialic acid as a first translational approach.