HuR/HIF – SIRT1 Signaling Axis in Liver Transplant Rejuvenation

摘要 原位肝移植(OLT)是终末期肝病患者治疗的金标准。 患有肝源性肿瘤的。然而，捐献器官的稀缺促使使用扩展的标准。 “边缘”肝脏，特别容易受到缺血-再灌注损伤(IRI)，这容易导致 急性/慢性排斥反应，可能需要再次移植。我们引入了器官的概念 “返老还童”，即供体肝脏从IRI过敏状态转变为体内平衡状态。 IRI抗性。我们还提出SIRT1脱乙酰基酶是IR应激与肝脏之间的一个变阻器 在小鼠和人的原位肝移植中都有年轻化的作用。我们最近发现了新的肝脏抵抗调节剂。 对抗热和冷缺血应激反应，即人类抗原R(HUR)和低氧诱导因子 (HIF-1α)。我们还发现了Ikaros(IKZF1)，作为巨噬细胞激活的标志，并加剧了 肝脏IRI。重要的是，我们还发现，保存肝细胞功能/改善人类临床结果 OLT患者与肝活检组织中HUR/HIF-1α升高但Ikaros水平降低相关 样本。我们假设肝细胞HUR/HIF-1α和巨噬细胞Ikaros之间的串扰提供了一个 调节供体肝脏对IR应激和再灌流介导的肝损伤适应性的新方法。 具体目的1：探讨原位肝移植中肝细胞HUR/HIF-1与SIRT1的α串扰机制。 假设：肝细胞SIRT1激活，受不同的缺氧/复氧(H/R)要求控制 HUR(热H/R)与HIF-1α(冷H/R)相比，为调节供体肝脏对IR应激的适应性提供了新的手段。 1.1：SIRT1的功能依赖于Hur信号在氧化应激中的抗炎反应。1.2： HUR/HIF-1α信号在小鼠肝脏缺血模型中是温度应激依赖的。1.3：HIF-1α 对照冷诱导的IRI-OLT。1.4：HUR控制热诱导的IRI-OLT。 具体目的2：阐明IRI-OLT中巨噬细胞Ikaros与SIRT1的串扰机制。 假设：巨噬细胞Ikaros信号通过抑制SIRT1转录和M2而加重IRI-OLT 巨噬细胞极化。Ikaros-sirt1髓系轴影响肝脏HUR/HIF1α缺氧感测回路 在IRI-OLT中。2.2：巨噬细胞Ikaros信号依赖于SIRT1转录实现M2极化。 具体目标3：明确低温机械保存下人肝复壮的机制。 假设：在体外缺氧处理过程中操纵缺氧诱导因子-1α/sirt 1轴可改善肝细胞功能 返老还童的人肝拒绝移植，因为先前存在的质量很差。3.1：药理学 HIF-1α蛋白稳定剂与SIRT1协同改善人体肝功能。3.2：预调节 激活/稳定缺氧诱导因子-1α的PHD-抑制剂与增强的SIRT1信号协同改善 发炎，促进细胞保护，恢复人体肝脏活力。这些实验具有很高的相关性 改进捐赠者肝脏捐赠(DBD和DCD)，并改善目前器官供应的质量/规模。

ABSTRACT Orthotopic liver transplantation (OLT) is the gold standard of care in patients with end-stage liver disease and those with tumors of hepatic origin. However, the scarcity of donor organs prompted the use of extended criteria “marginal” livers, which are particularly susceptible to ischemia-reperfusion injury (IRI), which predispose to acute/chronic rejection, and may require re-transplantation. We have introduced the concept of organ “rejuvenation”, i.e., conversion of the donor liver from the state of IRI-hypersensitivity to the homeostatic state of IRI-resistance. We have also proposed that SIRT1 deacetylase serves as a rheostat linking IR-stress with liver rejuvenation in both, mouse and human OLT. We have recently identified new regulators of hepatic resistance against warm vs. cold ischemia stress responses, i.e., Human Antigen R (HuR) and Hypoxia-Inducible Factor (HIF-1α). We have also discovered Ikaros (IKZF1), acts as a macrophage activation marker and exacerbates liver IRI. Importantly, we also found that preserved hepatocellular function/improved clinical outcomes in human OLT patients were associated with increased HuR/HIF-1α but depressed Ikaros levels in the liver biopsy samples. We hypothesize that crosstalk between hepatocyte HuR / HIF-1α and macrophage Ikaros provides a new means to regulate the adaptation of donor livers to IR-stress and reperfusion-mediated hepatic damage. Specific Aim 1: Determine mechanisms of hepatocyte HuR / HIF-1α crosstalk with SIRT1 in IRI-OLT. Hypothesis: Hepatocyte SIRT1 activation, controlled by distinct hypoxia/reoxygenation (H/R) requirements for HuR (warm H/R) vs. HIF-1α (cold H/R), provide new means to regulate adaptation of donor livers to IR-stress. 1.1: SIRT1 function is dependent on HuR signaling for anti-inflammatory responses in oxidative stress. 1.2: HuR/HIF-1α signaling in a mouse model of hepatic ischemia is temperature stress-dependent. 1.3: HIF-1α controls cold-induced IRI-OLT. 1.4: HuR controls warm-induced IRI-OLT. Specific Aim 2: Delineate mechanisms of macrophage Ikaros crosstalk with SIRT1 in IRI-OLT. Hypothesis: Macrophage Ikaros signaling exacerbates IRI-OLT by repressing SIRT1 transcription and M2 macrophage polarization. 2.1: Ikaros-SIRT1 myeloid axis influences hepatic HuR/HIF1α hypoxia sensing circuit in IRI-OLT. 2.2: Macrophage Ikaros signaling depends on SIRT1 transcription for M2 polarization. Specific Aim 3: Define mechanism of human liver rejuvenation under hypothermic machine preservation. Hypothesis: Manipulation of HIF-1α / SIRT1 axis during ex-vivo HMP improves hepatocellular function to rejuvenate human livers declined for transplantation due to preexisting poor quality. 3.1: Pharmacological stabilizer of HIF-1α protein synergizes with SIRT1 to improve human liver function. 3.2: Preconditioning with PHD-inhibitor, which activates/stabilizes HIF-1α, synergizes with enhanced SIRT1 signaling to ameliorate inflammation, promote cytoprotection, and rejuvenate human livers. These experiments are of high relevance to refine donor liver donation (DBD and DCD) as well as to improve quality/size of the current organ supply.