上皮-树突状细胞转分化在脓毒症性AKI中的作用及机制研究

Septic acute kidney injury (AKI) significantly increases mortality of critical patients. Systemic inflammatory response disorder as a result of immune dysfunction could be the underlying cause of persistent AKI. The phenomenon of epithelial-dendritic cell (DC) transition (EDT) has received much concern as it is closely related to the pathogenesis of chronic inflammatory diseases. However, none research of EDT in the field of septic AKI has ever been reported. Our previous study first found that hemorrhagic shock upregulated DC-SIGN expression in renal tubular epithelial cells, increased inflammatory response in kidneys and renal functional injury. On the pilot experiment, these phenomena also have been observed in the septic mouse models. In addition, the expression of receptor for advanced glycation end products (RAGE) was increased markedly and E-cadherin was suppressed in renal tissue. Therefore, we raised the hypothesis that sepsis induces renal tubular epithelial cells trans-differentiate into DC through “RAGE-E-cadherin-DC-SIGN” signaling pathway. We will use the septic mouse model by cecal ligation and puncture, and a series of research methods such as cell culture, plasmid transfection and RAGE gene knockout to validate this hypothesis at molecular, cellular and organic levels. This research will provide a new mechanism and also propose a novel clinical treatment for septic AKI.

脓毒症性急性肾损伤（AKI）导致患者死亡率显著升高。免疫功能紊乱引发的炎症反应失控是AKI持续存在的重要原因。已证实上皮-树突状细胞转分化（epithelial-dendritic cell/DC transition，EDT）参与慢性炎症反应，但在脓毒症性AKI中的作用及机制均无报道。我们前期研究首次发现，失血性休克大鼠肾小管上皮细胞DC-SIGN表达上调，并向DC转分化，加重肾组织损伤。预实验显示，脓毒症诱导小鼠肾脏发生EDT；肾组织RAGE表达升高，E-cadherin降低，故推测EDT可能参与脓毒症性AKI过程，其机制可能为“RAGE-E-cadherin-DC-SIGN”通路。本课题拟盲肠结扎穿孔法建立小鼠脓毒症模型，采用细胞培养、质粒转染及RAGE基因敲除等技术，从分子、细胞及器官水平阐明脓毒症性AKI中的EDT现象及机制。本课题研究成果将为脓毒症性AKI的临床治疗提供新思路。

脓毒症性急性胃肠道损伤（Acute gastrointestinal injury, AGI）与患者不良预后相关。免疫功能紊乱引发的炎症反 应失控是AGI持续存在的重要原因。已有研究发现上皮-树突状细胞转分化（epithelial-dendritic cell/DC transition，EDT）参与慢性炎症反应，但在脓毒症性AGI中的作用及机制均未见报道。我们在研究中发现，脓毒症小鼠肠上皮细胞发生EDT现象，且EDT标志物DC-SIGN表达水平与体内的脓毒症打击时间及体外的LPS浓度均呈正相关。在利用siRNA沉默DC-SIGN的表达之后，脓毒症小鼠的肠道、肺、肝脏、肾脏的病理损伤均显著减轻，且TNF-α、IL-1β、IL-6、IL-10、IFN-γ水平明显下降。更重要的是，DC-SIGN表达抑制后提高了脓毒症小鼠的生存率。进一步的研究发现，DC-SIGN 的siRNA抑制炎症反应可能是通过抑制ERK1/2及 NF-kB/p65的磷酸化来实现。而当使用SCH772984抑制ERK1/2时，DC-SIGN表达并未受影响，提示ERK1/2为DC-SIGN下游蛋白。该研究为揭示了脓毒症炎症反应新的调控机制，有望为脓毒症治疗提供新的靶点。