College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
Ecotoxicol Environ Saf. 2022 Apr 15;235:113441. doi: 10.1016/j.ecoenv.2022.113441. Epub 2022 Mar 28.
Heat stress is directly correlated to mammary gland dysfunction in dairy cows, especially in summer. Abnormally high environmental temperature induces oxidative stress and apoptosis in bovine mammary epithelial cells (BMECs). Nicotinamide mononucleotide (NMN) has beneficial effects in maintaining the cellular physiological functions. In this study, we evaluate the protective effect of NMN on heat stress-induced apoptosis of BMECs and explore the potential underlying mechanisms. Our results showed that heat stress considerably decreased cell viability in BMECs, whereas pretreatment of BMECs with NMN (150 μM) for 24 h significantly alleviated the negative effects of heat stress on cells. NMN protected BMECs from heat stress-induced oxidative stress by inhibiting the excessive accumulation of reactive oxygen species (ROS) and increasing the activity of antioxidant enzymes. It also inhibited apoptosis by reducing the ratio of Bax/Bcl2 and blocking proteolytic the cleavage of Caspase-3 in heat stressed-BMECs. Importantly, NMN treatment could reduce mitochondrial damage through mediating the expression of mitochondrial fission and fusion-related genes, including Dynamin related protein 1 (Drp1), Mitochondrial fission 1 protein (Fis1), and Mitofusin1, 2 (MFN1, 2); and suppress endoplasmic reticulum stress through unfolded protein response regulator Glucose regulated protein 78 (GRP78), and downstream elements Recombinant activating transcription factor 4 (ATF4) and C/EBP homologous protein (CHOP). Above all, our results demonstrate that NMN supplemention attenuates heat stress-induced oxidative stress and apoptosis in BMECs by maintaining mitochondrial fission and fusion, and regulating endoplasmic reticulum stress, which provides the convincing evidence that NMN has valuable potential in alleviating mammary gland injury of dairy cows caused by environmental heat stress.
热应激与奶牛乳腺功能障碍直接相关，尤其是在夏季。异常高的环境温度会导致牛乳腺上皮细胞（BMECs）发生氧化应激和细胞凋亡。烟酰胺单核苷酸（NMN）在维持细胞生理功能方面具有有益作用。在本研究中，我们评估了 NMN 对热应激诱导的 BMEC 细胞凋亡的保护作用，并探讨了潜在的机制。结果表明，热应激显著降低了 BMECs 的细胞活力，而 NMN（150μM）预处理 24h 可显著减轻热应激对细胞的负面影响。NMN 通过抑制活性氧（ROS）的过度积累和增加抗氧化酶的活性来保护 BMECs 免受热应激引起的氧化应激。它还通过降低 Bax/Bcl2 比值和阻断热应激-BMECs 中 Caspase-3 的蛋白水解切割来抑制细胞凋亡。重要的是，NMN 通过调节线粒体分裂和融合相关基因的表达，包括动力相关蛋白 1（Drp1）、线粒体分裂 1 蛋白（Fis1）和线粒体融合蛋白 1、2（MFN1、2），减轻线粒体损伤；并通过未折叠蛋白反应调节剂葡萄糖调节蛋白 78（GRP78）和下游元件重组激活转录因子 4（ATF4）和 C/EBP 同源蛋白（CHOP）抑制内质网应激。综上所述，我们的研究结果表明，NMN 通过维持线粒体分裂和融合以及调节内质网应激来减轻热应激诱导的 BMECs 氧化应激和细胞凋亡，为 NMN 减轻奶牛环境热应激引起的乳腺损伤提供了有力证据。
