Innate Immune Regulation by HSF1 in Liver Inflammatory Injury

项目总结 肝脏缺血再灌注损伤(IRI)是一种以先天免疫为主的局部无菌炎症反应。 肝移植、切除和出血后肝功能障碍和衰竭的主要原因 令人震惊。氧化应激已被认为是肝脏IRI发病机制中的一个重要因素。 IR激活肝巨噬细胞(Kupffer细胞)产生活性氧(ROS)，导致无菌 肝脏发炎。ROS是一种内源性“危险”信号，可以从坏死区或应激区释放出来 触发NLRP3炎症体激活的细胞。最近的研究表明，NLRP3的激活 炎症体需要依赖ROS的NEK7，这是一种参与有丝分裂细胞分裂的丝氨酸-苏氨酸激酶。 NEK7直接与NLRP3结合并促进炎症反应，提示NEK7是一种必不可少的 在炎症反应中触发先天免疫的中介物。已有研究表明，激活 抗氧化防御系统防止ROS诱导的肝损伤，而NLRP3接头蛋白的破坏 ASC可降低肝脏IRI的炎症反应。此外，具有髓系特异性HSF1基因敲除(HSF1M-)的小鼠 Ko)增强NLRP3功能，通过激活转录加重IR诱导的肝损伤 因子X盒结合蛋白(XBP1)。最终，热休克蛋白1的激活增加了β-连环蛋白的活性，从而导致 ROS的产生和NLRP3的激活减少。尽管这些结果指向hsf1-β-catenin轴 HSF1作为一种新的肝脏炎性损伤中天然免疫的主开关，其机制尚不清楚 调节NEK7功能，导致NLRP3活化减少，以应对IR诱导的应激。这个 TLR4/TRAF6轴介导了NOX2依赖的ROS的产生，这是激活TLR4/TRAF6的关键 TXNIP。TLR信号通路可与转化生长因子β激活的激酶1相互作用而启动 炎症级联反应，而NEK7的激活促进NLRP3炎症体途径。因此，TXNIP 和TAK1可能在HSF1介导的肝脏NEK7功能调节中起重要作用 炎症性损伤。这项建议的总体目标是剖析细胞因子的功能和分子机制。 HSF1对IR应激肝脏中NEK7功能的调节假设是HSF1调节 NEK7通过以下途径介导肝脏IRI的天然免疫反应：1)抑制TAK1活性；2)抑制 TXNIP激活。为了验证这一假设，提出了以下具体目标：i)通过 在IR应激的肝脏中，哪种HSF1控制TAK1-NEK7的相互作用；以及ii)通过什么机制确定 HSF1对IR应激肝脏TXNIP-NEK7轴的调节作用这些研究将增加对 IR诱导的肝脏炎症中先天免疫的肝脏调节网络。这些发现也将产生深远的影响 器官移植和其他方面对缺血性组织损伤治疗调节的意义 无菌炎症疾病状态。

PROJECT SUMMARY Liver ischemia and reperfusion injury (IRI), an innate immunity-dominant local sterile inflammatory response, is a major cause for hepatic dysfunction and failure following liver transplantation, resection, and hemorrhagic shock. Oxidative stress has been recognized as an important factor in the pathogenesis of hepatic IRI, in which IR activates liver macrophages (Kupffer cells) to generate reactive oxygen species (ROS), leading to sterile inflammation in the liver. ROS is an endogenous `danger' signal and can be released from necrotic or stressed cells to trigger NLRP3 inflammasome activation. Recent study revealed that activation of the NLRP3 inflammasome required ROS-dependent NEK7, a serine-threonine kinase involved in mitotic cell division. NEK7 directly binds to NLRP3 and promotes inflammatory response, suggesting that NEK7 is an essential mediator to trigger innate immunity during inflammatory response. It has been shown that activation of antioxidant defense system prevents ROS-induced liver damage whereas disruption of NLRP3 adaptor protein ASC reduces inflammatory response in liver IRI. Moreover, mice with myeloid-specific HSF1 knockout (HSF1M- KO) enhanced NLRP3 functions and exacerbated IR-induced liver damage through activation of transcription factor X-box-binding protein (XBP1). Ultimately, HSF1 activation increased β-catenin activity leading to reduced ROS production and NLRP3 activation. Although these results point towards the HSF1-β-catenin axis as a novel master-switch of innate immunity in liver inflammatory injury, it remains unknown how HSF1 modulates NEK7 function leading to reduced NLRP3 activation in response to IR-induced stress. The TLR4/TRAF6 axis mediates the NOX2-dependent production of ROS, which is crucial for the activation of TXNIP. TLR signaling can interact with transforming growth factor β-activated kinase 1 (TAK1) to initiate inflammatory cascade whereas activation of NEK7 promotes NLRP3 inflammasome pathway. Thus, TXNIP and TAK1 are likely to be essential for the HSF1-mediated regulation of NEK7 functions during liver inflammatory injury. The overall goal of this proposal is to dissect the functions and molecular mechanisms of HSF1-dependent regulation of NEK7 function in IR-stressed livers. The hypothesis is that HSF1 regulates NEK7-mediated innate immune responses in hepatic IRI by: 1) controlling TAK1 activity; and 2) inhibiting TXNIP activation. To test this hypothesis, the following specific aims are proposed: i) dissect mechanisms by which HSF1 controls the TAK1-NEK7 interaction in IR-stressed liver; and ii) determine mechanisms by which HSF1 regulates the TXNIP-NEK7 axis in IR-stressed liver. These studies will increase the understanding of the hepatic regulatory network of innate immunity in IR-induced liver inflammation. These findings will also have far reaching implications for therapeutic modulation of ischemic tissue damage in organ transplantation and other sterile inflammatory disease states.