脂氧素A4激活Nrf2通路改善重症急性胰腺炎相关肺损伤的细胞保护机制研究

Our previous studies have showed that the “braking signal” for inflammatory - lipoxin A4 (LXA4) can ameliorate Severe acute pancreatitis (SAP)-associated lung injury (LI). It can work not only on allaying inflammation but also facilitate the expression of HO-1 via the activation of Nrf2. It is affirmed that HO-1 plays an important role in the cytoprotective effects in chronic injury, but till not confirmed that whether the HO-1 induced by LXA4 also functions beneficially in the severe inflammatory diseases - SAP. Besides, the regulatory mechanism of LXA4 on HO-1 has not been well studied. We use the HO-1-/- mice to prove if the expression of HO-1 induced by LXA4 activated of Nrf2 plays a key role in the cytoprotection and ameliorates SAP-associated LI. By luciferase report assay we will try to make it clear that whether LXA4 can be a two-way regulation of HO-1 expression via Nrf2 activation and the decrease of inflammation pathways. With a further study, by using the Nrf2-/- mice, we try to verify that whether the HO-1 expression by activation of Nrf2 play a important role in the beneficial effect of LXA4 to ameliorate SAP-associated LI. This study aims to improve the understanding of the cytoprotective effects played by LXA4 in SAP-associated LI, and to reveal the regulation mechanism of LXA4 on the expression of HO-1, especially studying the role that Nrf2 plays in the whole process. This study will provide a new idea of therapeutic method for the treatment of SAP-associated LI, and gives a potential treatment of decreasing the incidence of LI and improving the survival rate of SAP and other critical illnesses.

我们前期研究证实“炎症刹车剂”-脂氧素A4(LXA4)能改善重症胰腺炎(SAP)相关肺损伤，其除抗炎作用外还激活Nrf2诱导HO-1表达上调。慢性炎症中HO-1的细胞保护作用已得到肯定，但在SAP如此剧烈的严重炎症中是否同样发挥保护作用及LXA4对HO-1表达调节的分子机制均不清晰。我们拟通过HO-1-/-小鼠反证LXA4诱导HO-1表达在改善SAP-肺损伤中起重要的细胞保护作用；通过荧光素酶报告实验明确LXA4如何通过激活Nrf2及抑制炎症双向调节HO-1的表达；并采用Nrf2-/-小鼠证实Nrf2激活在LXA4诱导HO-1表达及改善SAP-肺损伤中起关键作用。本课题旨在突出HO-1的细胞保护是LXA4改善SAP-肺损伤的重要机制，阐明LXA4对HO-1表达的调节机制，尤其是通过Nrf2激活的作用。此研究将为SAP相关肺损伤防治提供一种新方法，降低肺损伤的发生率，有利于降低SAP病死率。

急性肺损伤(ALI)是急性胰腺炎(AP)病理生理过程中的重要事件。各种治疗方法被广泛应用于AP-ALI，但几乎没有有效控制早期炎症的方法。脂氧素A4(LXA4)是一种有效的抗炎和新型抗氧化介质，在AP-ALI中已被广泛研究，但其作为保护性介质的作用机制尚不清楚。本研究旨在明确LXA4抗AP-ALI作用的可能靶点和机制。首先，我们证实LXA4对小鼠AP-ALI有强烈的抑制作用。接下来，通过ELISA、PCR和荧光检测来评价不同的参数，结果表明LXA4在体内和体外均能减少AP诱导的炎性细胞因子的产生，并阻断活性氧(ROS)的产生。此外，TNF-α还激活了人肺微血管内皮细胞核因子E2相关因子2(NRF2)信号通路及其下游基因血红素氧合酶-1(HO-1)，LXA4进一步促进了它们的表达。本研究还提供了LXA4磷酸化Ser40并触发其核转位以激活Nrf2的证据。此外，当使用Nrf2基因敲除(Nrf2-/-)小鼠和细胞进一步评估Nrf2/HO-1通路的作用时，我们发现Nrf2表达下调部分消除了LXA4降低炎症因子水平的作用，同时取消了LXA4对AP-ALI刺激的ROS产生的抑制作用。总体而言，LXA4可能通过调节Nrf2/HO-1途径来减轻AP诱导的炎症和ROS的产生，从而减轻ALI。这些发现为AP-ALI的治疗奠定了基础。