摘要目的:探讨脾脏源性髓源性抑制细胞（MDSCs）在脓毒症诱导肾上腺损伤（SAI）中的作用及其机制。方法:采用随机数字表法将30只6～8周龄C57雄性小鼠分为正常对照组（ n＝5）、假手术组（Sham组， n＝5）、脓毒症模型组〔盲肠结扎穿孔术（CLP）组， n＝10〕和脓毒症+脾切除组（CLPS组， n＝10）。采用CLP法制备小鼠脓毒症模型；Sham组仅开腹分离盲肠后关腹，不给予盲肠结扎穿孔；CLPS组于CLP前切除脾脏；正常对照组不给予任何处理。各组于制模后24 h处死小鼠，收集外周血、脾脏、骨髓及双侧肾上腺；采用苏木素-伊红（HE）染色后光镜下观察肾上腺组织病理学改变，采用流式细胞仪测定外周血、脾脏和骨髓中MDSCs细胞比例，采用实时定量反转录-聚合酶链反应（PCR）检测肾上腺组织中MDSCs表面抗原CD11b、Gr-1和白细胞介素（IL-6、IL-1β）的mRNA表达，采用蛋白质免疫印迹试验（Western Blot）检测肾上腺组织中哺乳动物雷帕霉素靶蛋白（mTOR）通路相关蛋白总mTOR（T-mTOR）、磷酸化mTOR（p-mTOR）和天冬氨酸特异性半胱氨酸蛋白酶3（caspase-3）的蛋白表达。 结果:光镜下显示，正常对照组和Sham组肾上腺皮质、髓质完整，结构清晰；CLP组肾上腺皮质肿胀、出血，可见细胞水肿；CLPS组上述肾上腺组织损伤较CLP组明显减轻。与正常对照组和Sham组相比，CLP组外周血中MDSCs细胞比例明显增加，脾脏中MDSCs细胞比例明显降低，骨髓中MDSCs细胞比例差异无统计学意义，肾上腺组织中CD11b、Gr-1、IL-6、IL-1β的mRNA和caspase-3蛋白表达均明显增加，p-mTOR蛋白表达明显降低，T-mTOR蛋白表达差异无统计学意义；与CLP组相比，CLPS组外周血中MDSCs细胞比例明显降低（0.143±0.011比0.324±0.023， P<0.01），肾上腺组织中CD11b、Gr-1、IL-6和IL-1β的mRNA以及caspase-3的蛋白表达均明显降低〔CD11b mRNA（2 -ΔΔCt）：2.90±0.56比5.74±0.13，Gr-1 mRNA（2 -ΔΔCt）：2.71±0.14比4.59±0.46，IL-6 mRNA（2 -ΔΔCt）：2.44±0.64比5.17±1.04，IL-1β mRNA（2 -ΔΔCt）：3.58±0.52比4.44±0.26，caspase-3蛋白（caspase-3/GAPDH）：0.05±0.01比0.13±0.02，均 P<0.01〕，p-mTOR蛋白表达明显增加（p-mTOR/GAPDH：0.61±0.11比0.27±0.04， P<0.01）。 结论:脾脏是SAI中MDSCs细胞的主要来源；脾切除可减少MDSCs细胞动员，激活mTOR信号通路，从而减轻SAI。

abstractsObjective:To investigate the role and mechanism of splenic myeloid-derived suppressor cells (MDSCs) in sepsis-induced adrenal injury (SAI).Methods:Thirty male C57 mice aged 6-8 weeks were randomly divided into normal control group ( n = 5), sham operation group (Sham group, n = 5), sepsis model group [cecal ligation and perforation (CLP) group, n = 10] and sepsis+splenectomy group (CLPS group, n = 10). The sepsis model of mice was reproduced by CLP method. In Sham group, only the cecum was opened and separated, then closed, without CLP. In CLPS group, the spleen was removed before CLP. In normal control group, no challenge was given. After 24 hours, the rats were sacrificed by anesthesia, and peripheral blood, spleen, bone marrow, and bilateral adrenal glands were harvested. The pathological of adrenal gland was assessed by hematoxylin-eosin (HE) staining under optical microscope. The ratio of MDSCs in peripheral blood, spleen and bone marrow was determined by flow cytometry. The expressions of MDSCs surface antigen CD11b, Gr-1 and interleukins (IL-6, IL-1β) mRNA in adrenal tissue were measured by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). Western Blot was used to detect the expressions of mammalian rapamycin target protein (mTOR) pathway related proteins including total mTOR (T-mTOR), phosphorylation of mTOR (p-mTOR) and caspase-3. Results:The adrenal cortex and medulla of the normal control group and Sham group were intact and the structure was clear under optical microscope, while in the CLP group, the adrenal gland showed edema, cortical hemorrhage and cell edema. Compared with the CLP group, the adrenal tissue injury was significantly reduced in the CLPS group. Compared with the normal control group and Sham group, MDSCs ratio in the peripheral blood was significantly increased and significantly reduced in the spleen in the CLP group, but there was no significant difference in bone marrow, the expression levels of CD11b, Gr-1, IL-6, IL-1β mRNA and caspase-3 protein were increased significantly and p-mTOR protein expression was significantly decreased in adrenal tissue, there was no significant difference in the expression of T-mTOR protein. Compared with the CLP group, in the CLPS group, the MDSCs ratio in the peripheral blood was significantly decreased (0.143±0.011 vs. 0.324±0.023, P < 0.01), the expression levels of CD11b, Gr-1, IL-6 , IL-1β mRNA and caspase-3 protein in adrenal gland were significantly decreased [CD11b mRNA (2 -ΔΔCt): 2.90±0.56 vs. 5.74±0.13, Gr-1 mRNA (2 -ΔΔCt): 2.71±0.14 vs. 4.59±0.46, IL-6 mRNA (2 -ΔΔCt): 2.44±0.64 vs. 5.17±1.04, IL-1β mRNA (2 -ΔΔCt): 3.58±0.52 vs. 4.44±0.26, caspase-3 protein (caspase-3/GAPDH): 0.05±0.01 vs. 0.13±0.02, all P < 0.01], the p-mTOR protein expression was significantly increased (p-mTOR/GAPDH: 0.61±0.11 vs. 0.27±0.04, P < 0.01). Conclusions:The spleen is the major source of MDSCs in SAI. Splenectomy can attenuate SAI by reducing mobilization of MDSCs and activating the mTOR signaling pathway.