Abstract: Background　Breast cancer is one of the major chronic diseases that seriously threatens the health of women around the world，and the incidence is on the rise. Depression is the most common psychological comorbidity in breast cancer patients and can promote the progression of breast cancer. PKR-like endoplasmic reticulum kinase（PERK）/eukaryotic initiation factor 2α（eIF2α）-mediated microglial polarization plays a key role in the occurrence and development of depression and breast cancer，but the mechanism of action in breast cancer complicated by depression is still unclear. Objective　To explore the mechanism of PERK/eIF2α axis-mediated microglial polarization in promoting depression in breast cancer. Methods　Animal experiments were conducted from May 2022 to December 2022. A total of 30 mice were randomly divided into control group（control group），tumor-bearing group（4T1 group），model group（model group），agonist group（CCT020312 group），and inhibitor group（ISRIB group），with 6 mice in each group，and the tumor volume was calculated for 21 days. Sugar-water preference test and open-field test were used to evaluate depressive-like behavior in mice. Hematoxylin-eosin（HE） staining was used to evaluate tumor morphology and hippocampal neuronal morphology. Immunofluorescence（IF） was used to observe the levels of CD86/ionic calcium-binding adapter molecule 1（Iba-1） and CD206/Iba-1 in hippocampus. Western blot was used to detect the protein levels of PERK，eIF2α，activating transcription factor 4（ATF4） and C/EBP homologous protein （CHOP），which are key factors in the PERK/eIF2α axis of hippocampal tissue. Results　The sugar water preference，total exercise distance，times in the central area，and distance from central district in the model group were lower than those in the control group，and the depression-like behavior was higher than that in the control group，and the difference was statistically significant（P<0.05）. The tumor volume in the model group was higher than that in the 4T1 group，and the tumor volume in the CCT020312 group was higher than that in the model group，and the differences were statistically significant（P<0.05）. The sugar water preference and reduction of total exercise distance，times in the central area，and distance from central district in the CCT020312 group were lower than those in the model group，while those in the ISRIB group were higher than the model group，and the difference was statistically significant（P<0.05）。The results of HE staining showed that the tumor cells in the 4T1 group，model group and the CCT020312 group were tightly arranged，with a large nucleocytoplasmic ratio and more nuclear division images，while the tumor cells in the were tightly arranged，with a large nucleocytoplasmic ratio and most obvious nuclear division in CCT020312 group. In the ISRIB group，large areas of plaque-like necrosis and cell debris appeared in the tumor tissues，which became larger along the interspace of living cells and reduced mitosis.The neurons atrophied in the 4T1 group，and neurons in the Model group and CCT020312 groups showed different degrees of atrophy，cytoplasmic concentration increasing，nuclear hyper staining and cell necrosis，with the CCT020312 group being the most obvious. The ISRIB group showed a decrease in cytoplasmic concentration and the number of nuclear hyperchromations. The results of immunofluorescence staining showed that the protein levels of CD86/Iba-1 and CD206/Iba-1 in the model group were higher than those in the 4T1 group，the levels of CD86/Iba-1 protein in the CCT020312 group were higher than those in the model group，and the levels of CD206/Iba-1 protein were lower than those in the model group，the levels of CD206/Iba-1 protein in the ISRIB group were higher than those in the Model group，and the levels of CD86/Iba-1 protein were lower than those in the Model group，and the difference was statistically significant（P<0.05）. The results of Western blot showed that the levels of PERK，eIF2α，ATF4 and CHOP in the CCT020312 group were higher than those in the model group，and the levels of the above proteins in the ISRIB group were lower than those in the model group，and the differences were statistically significant（P<0.05）. Conclusion　The mechanism of depression complicated by breast cancer may be related to the PERK/eIF2α axis-mediated imbalance of microglial polarization and the induction of hippocampal neuron inflammation.

Key words: Breast cancer complicated by depression, PERK/eIF2α axis, Microglial polarization

摘要： 背景　乳腺癌是严重威胁全球女性居民健康的重大慢性疾病之一，发病率呈上升趋势。抑郁症是乳腺癌患者最常见的心理共病，可促进乳腺癌的进展。PKR样内质网激酶（PERK）/真核起始因子2α（eIF2α）轴介导的小胶质细胞极化在抑郁症和乳腺癌的发生发展中均起到关键作用，但其在乳腺癌并发抑郁症中的作用机制尚不明确。目的　探究PERK/eIF2α轴介导小胶质细胞极化促进乳腺癌并发抑郁症的作用机制。方法　2022年5月-2022年12月进行动物实验。选取30只小鼠，随机分为空白对照组（Control组）、荷瘤组（4T1组）、模型组（Model组）、激动剂组（CCT020312组）、抑制剂组（ISRIB组），每组6只，连续干预21 d，计算瘤体体积；采用糖水偏好试验、旷场试验评估小鼠抑郁样行为；采用苏木素-伊红（HE）染色评价肿瘤形态、海马神经元形态；采用免疫荧光法（IF）观察海马组织CD86/离子钙结合适配器分子1（Iba-1）与CD206/Iba-1水平；采用Western blot法检测海马组织PERK/eIF2α轴的关键因子PERK、eIF2α、激活转录因子4（ATF4）、C/EBP同源蛋白（CHOP）的蛋白水平。结果　Model组糖水偏好度、运动总距离、中央区次数、中央区距离低于Control组，抑郁样行为高于Control组，差异有统计学意义（P<0.05）；Model组肿瘤体积高于4T1组，CCT020312组肿瘤体积高于Model组，差异均有统计学意义（P<0.05）；CCT020312组糖水偏好度和降低旷场试验中的运动总距离、中央区次数、中央区距离低于Model组，而ISRIB组则高于Model组，差异均有统计学意义（P<0.05）。HE染色结果显示，4T1组、Model组和CCT020312组小鼠肿瘤细胞排列紧密，核质比大，CCT020312组核分裂增加明显；ISRIB组肿瘤组织中出现大面积斑块状坏死和细胞碎片，细胞间隙变大，有丝分裂现象减少；4T1组小鼠神经元萎缩，Model组、CCT020312组神经元表现出不同程度的萎缩、细胞质浓度增加、核深染和细胞坏死，以CCT020312组最为明显；ISRIB组显示出细胞质浓度、核深染数目减少。免疫荧光染色结果显示，Model组CD86/Iba-1、CD206/Iba-1蛋白水平均高于4T1组，CCT020312组CD86/Iba-1蛋白水平高于Model组，CD206/Iba-1蛋白水平低于Model组，ISRIB组CD206/Iba-1蛋白水平高于Model组，CD86/Iba-1蛋白水平低于Model组，差异有统计学意义（P<0.05）；Western blot检测结果显示，CCT020312组的PERK、eIF2α、ATF4、CHOP蛋白水平高于Model组，ISRIB组的上述蛋白水平低于Model组，差异均有统计学意义（P<0.05）。结论　乳腺癌并发抑郁症的机制可能与PERK/eIF2α轴介导小胶质细胞极化失衡，诱导海马神经元炎症有关。

关键词: 乳腺癌并发抑郁症, PERK/eIF2α 轴, 小胶质细胞极化