Ets-1/DDRGK1调控的内质网应激在哺乳期纳米氧化锌暴露致乳蛋白β-casein合成减少中的机制研究

乳蛋白β-casein是乳汁中最主要的营养成分之一，其合成减少导致婴儿营养不足及罹患各种疾病风险增加，而内质网应激能够影响乳蛋白合成。前期研究表明，哺乳期纳米氧化锌（ZNPs）暴露导致乳腺β-casein合成减少，但机制不明确。申请人预试验发现，哺乳期ZNPs暴露导致乳腺上皮细胞发生内质网应激，调控内质网稳态的蛋白DDRGK1显著下调，其转录因子Ets-1的转录活性下降；上调Ets-1转录活性，DDRGK1表达增加，β-casein合成恢复。因此提出科学假说：ZNPs通过影响Ets-1转录活性调控DDRGK1水平，诱导内质网应激，进而影响β-casein的合成。本项目拟通过体内、外实验，利用染色质免疫共沉淀、免疫荧光等技术，探究ZNPs导致β-casein合成减少的机制，并阐明Ets-1/DDRGK1介导的内质网应激在其中发挥的调控作用。本课题的顺利进行将为ZNPs的安全应用提供参考依据。

β-Casein is one of the most important nutrients in milk. The decrease of its synthesis leads to malnutrition and increased risk of various diseases in infants. Endoplasmic reticulum stress can affect milk protein synthesis. Previous studies have shown that zinc oxide nanoparticle (ZNP) exposure during lactation can reduce the synthesis of β-casein in mammary gland, but the mechanism is not clear. The applicant's preliminary studies found that lactation ZNPs exposure led to endoplasmic reticulum stress in breast epithelial cells, significantly down-regulated the protein DDRGK1 regulating endoplasmic reticulum homeostasis, and down-regulated the transcription activity of Ets-1. Then, the applicant up-regulated Ets-1 transcriptional activity, which increased the expression of DDRGK1, and restored the synthesis of β-casein. Therefore, a scientific hypothesis is proposed: the ZNPs regulate the level of DDRGK1 by affecting the transcriptional activity of Ets-1, which induces endoplasmic reticulum stress, thus affecting the synthesis of β-casein. This project aims to explore the mechanism of ZNPs induced reduction of β-casein synthesis and elucidate the regulatory role of Ets-1/DDRGK1 mediated endoplasmic reticulum stress through in vivo and in vitro experiments, using chromatin immunoprecipitation and immunofluorescence techniques. The successful implementation of this project will provide a reference for the security application of ZNPs.