脓毒症急性肾损伤(AKI)发病机制与肾小管节段交互作用有关，即S1节段传感LPS效应诱发S2节段氧化应激损伤。我们既往研究证实SP-D 92C为脓毒症AKI易感基因，但机制不明。深入研究发现外源性SP-D调节S1节段分泌sema 3A，据此提出假说：SP-D 92C致脓毒症AKI易感机制，与92C型SP-D蛋白胶原尾部活化S1节段mTOR依赖sema 3A分泌通路，加剧肾小管节段交互作用有关。本项目应用人SP-D 92C和92T敲入小鼠构建脓毒症模型，活体双光子成像比较肾脏氧化应激及肾小管节段交互作用差异; 培养SP-D KO小鼠S1和S2节段，荧光染色观察92C或92T型SP-D蛋白不同结构域与S1节段TLR4或SIRP-a受体结合，分析活化下游mTOR或SHP1通路对sema 3A分泌影响，明确其结合S2节段sema 3A受体后促氧化应激作用，揭示基因变异在脓毒症AKI中的分子机制。

The mechanisms of sepsis-induced acute kidney injury(AKI) is related with renal tubular segments “crosstalk”, that is S1 Segment of renal tubular sensing Endotoxin which may induce oxidative stress injury of S2 Segment. It has been observed by our clinical study that sepsis patients with SP-D 92C allele(rs721917) were susceptible to AKI,however the related mechanisms is still unknown. Our previous results showed sema 3A secretion from S1 segment could be modulated by exogenous SP-D. Based on this we hypothesize “the mechanisms of sepsis patients with SP-D 92C allele is more susceptible to AKI is related with mTOR-dependent sema 3A secretion pathway enhancing tubular S1 and S2 segments crosstalk activated by collagen tail of 92C type SP-D protein”, the humanized knock-in mice with different alleles(92C or 92T) will be used to set up sepsis model, the renal oxidative stress reaction and in vivo renal tubular S1 and S2 segments “cross talk” will be compared. The S1 segments of renal tubular from SP-D knockout mice will be separated and cultured to detect whether the different domains of SP-D 92C or SP-D 92T protein combined TLR4 or SIRP-a receptor on S1 segment renal tubular epithelial cells, the effects of activated mTOR or SHP1 pathway on sema 3A secretion will be analyzed, the influence of sema 3A binding on its receptor to tubular S2 segment oxidative stress will also be detected.The project aims to explore the molecule mechanisms of gene variation in sepsis-induced AKI.