内毒素耐受与全身炎症反应综合征等危重症疾病密切相关。前期发现，过表达TRAF3或抑制其降解不能完全诱导TLR4信号所致的Kupffer细胞（KCs）内毒素耐受。据报道，叉头蛋白O3A（foxo3a）磷酸化会削弱PI3Kγ/AKT对TLR4的抑制，机制尚未清楚。课题组发现p53/鼠双微体蛋白2（MDM2）可降解磷酸化的foxo3a，foxo3a-p53-PI3Kγ是正向转录调控通路，且过表达foxo3a可显著降低内毒素刺激下KCs的凋亡。因此，推测foxo3a-p53/MDM2负反馈弧可能通过PI3Kγ/AKT调控KCs内毒素耐受的发生。本项目选择KCs为靶细胞，以foxo3a为切入点，建立体内外KCs内毒素耐受模型，通过基因敲除等方式改变KCs中foxo3a含量，探讨foxo3a-p53/MDM2负反馈弧通过PI3Kγ/AKT调控KCs内毒素耐受的确切机制，为脓毒症的治疗提供新的思路。

Endotoxin tolerance of is closely related to the occurrence and development of clinical related diseases such as systemic inflammatory response syndrome. Previous studies of our group found that over expression of tumor necrosis factor (TNF) receptor-associated factor 3 (TRAF3) or inhibiting the ubiquitination of TRAF3 could not completely induce endotoxin tolerance in Kupffer cells (KCs). Recent reports showed that the phosphorylation of forkhead box protein O3（foxo3a）reduced the transcriptional activity of TLR4 by activating PI3Kγ/AKT pathway, however, the mechanisms are not clear. It is known that p53/murine double mimute (MDM2) can degrade the phosphorylation of foxo3a. Our preliminary experiment had the following results: foxo3a promoted the transcriptional activity of p53, p53 promoted PI3Kγ expression, and overexpression of foxo3a significantly reduced the apoptosis rate when a large dose of endotoxin was used in KCs. Therefore, we hypothesized that foxo3a-p53/MDM2 negative feedback loop may play a key role in the mechanism of PI3Kγ/AKT pathway in the regulation of the endotoxin tolerance in KCs. This study will choose KCs as target cells and foxo3a as the breakthrough point, regulate foxo3a expression of KCs in vivo and in vitro using gene knockout and other approaches, to investigate the mechanism of KCs endotoxin tolerance regulated by PI3Kγ/AKT pathway through foxo3a-p53/MDM2 negative feedback loop, and provide novel ideas for treating sepsis.