SIRT1介导胰岛素信号及炎症通路串话对脓毒症内稳态失衡的作用

Sepsis is a challenging problem in the treatment and research of the severe trauma and burn injury. The excessive activation of macrophages is the key step in the pathophysiological mechanism of sepsis. The insulin-PI3K-Akt and LPS-TLR4-NF-κB are the two important signaling pathways involved in the activation of the macrophages. Deacetylase SIRT1 could promote the signal transduction of insulin-PI3K-Akt and inhibit the inflammatory factors production mediated by LPS-TLR4-NF-κB. Recently, we found that the activity of SIRT1 in the macrophages decreased significantly during sepsis and the activation of SIRT1 could increase the survival rate of septic animals, with improved hyperglycemia, decreased levels of inflammatory factors, alleviated organ injuries and obvious improvement of the internal environment imbalance, indicating that the SIRT1 might play a key role in the functional regulation of macrophages. However, the exact molecular mechanism remains unclear. The present study is aimed: ① to clarify the cellular biological effects, key molecular targets and mechanism of the crosstalk regulation between insulin signaling and inflammatory pathway mediated by SIRT1 in macrophages; ② to prove the effectiveness and mechanism of the SIRT1-regulated macrophage activity on the inhibition of uncontrolled inflammation in sepsis and the correction of internal environment imbalance. This study could provide the theoretical basis for the exploration of the novel effective treatment for sepsis.

脓毒症是严重创（烧）伤治疗和研究的难点问题，巨噬细胞过度活化是其病理生理机制的关键环节。巨噬细胞存在胰岛素-PI3K-Akt及LPS-TLR4-NF-κB两条重要信号通路参与其活化；去乙酰化酶SIRT1促进胰岛素-PI3K-Akt信号转导，可抑制LPS-TLR4-NF-κB介导的炎性因子生成。课题组前期发现：脓毒症时巨噬细胞内SIRT1活性明显下调，激活SIRT1能显著提高脓毒症动物的生存率，伴有高血糖改善、炎性因子水平下降、内脏器官损伤减轻、及机体内稳态失衡明确好转，显示脓毒症时SIRT1调控巨噬细胞功能具有重要作用，但相关分子机制尚不清楚。本研究拟：①阐明SIRT1介导巨噬细胞胰岛素信号及炎症通路间串话调控的细胞生物学效应、关键分子靶点和机制；②期望证明SIRT1调节巨噬细胞活化状态对抑制脓毒症失控性炎症反应和纠正内稳态失衡的有效性和作用机制。为探索有效治疗脓毒症的新途径提供理论依据。

脓毒症是严重（烧）创伤治疗和研究的难点问题，巨噬细胞过度活化是其病理生理机制的关键环节。本项目围绕调控巨噬细胞的适度活化，以抗衡脓毒症患者内稳态失调的机制进行深入探讨，我们发现脓毒症时SIRT1的转录水平，翻译水平及活性均受到显著抑制，而激活SIRT1则可以抑制脓毒症时体内的炎症反应，降低脓毒症小鼠死亡率，明确了SIRT1与脓毒症疾病发生发展过程中炎症反应的相关性。SIRT1可以通过靶向调控Notch，IRF8，RORα的乙酰化水平，lncRNAs的稳定性，最终作用于LPS/TLR4-NF-κB通路中的关键分子抑制其活化；SIRT1抑制Akt的乙酰化水平增强insulin/PI3K-Akt通路的活化，insulin/PI3K-Akt通路的活化进一步抑制LPS/TLR4-NF-κB通路的活化，从而抑制巨噬细胞炎症因子的释放，促进抗炎因子的表达，该部分结果表明SIRT1作为重要的活性分子通过乙酰化作用介导着巨噬细胞胰岛素信号及炎症通路间的串话调节。我们体外研究发现高糖可以显著下调SIRT1的转录水平及翻译水平，为深入研究靶向SIRT1的调控机制，我们对巨噬细胞microRNAs及mRNAs进行测序分析，发现下调miR138，miR199a的表达减轻小鼠脏器的损伤，缓解脓毒症疾病的恶化，而SIRT1是这两个miRNAs的直接靶标，其对脓毒症疾病的调控依赖于SIRT1的表达及活性；该部分研究证实脓毒症时，应激性高血糖以及microRNAs的表达异常，均导致SIRT1的功能受到干扰，加速脓毒症疾病的恶化。综上研究，SIRT1在脓毒症疾病发生发展中发挥着关键的调控作用，其作用于insulin-PI3K/Akt信号通路，控制LPS-TLR4/NF-κB信号通路的激活，保障巨噬细胞的适度激活，保护脏器的功能，对抗脓毒症内稳态的失衡。