High-yield dairy cows are usually subject to high-intensive cell metabolism and produce excessive reactive oxygen species (ROS). Once ROS is beyond the threshold of scavenging ability, it can induce oxidative stress, imperilling the reproductive performance of cows. The study was to investigate the effects of vitamin E (VE) on H₂O₂-induced proliferation and apoptosis of bovine granulosa cells and the underlying molecular mechanism. Granulosa cells were pretreated with VE for 24 hr and then treated with H₂O₂ for 6 hr. The results showed that VE treatment decreased the intracellular ROS levels, increased the MDA content, and improved the antioxidant enzyme activity in a dose-dependent manner. Furthermore, VE treatment promoted the proliferation and inhibited apoptosis in granulosa cells by up-regulation of CCND1 and BCL2 levels and down-regulation of P21, BAX, and CASP3 levels. The cytoprotective effects of VE were attributed to the activation of the NRF2 signalling pathway. Knockdown of the NRF2 impaired the cytoprotective effects of VE on granulosa cells. Besides, the PI3K/AKT and ERK1/2, but not the p38 signalling pathway is involved in the regulation of VE-mediated cell proliferation and apoptosis. The PI3K/AKT inhibitor LY294002 and ERK1/2 inhibitor SCH772984 inhibited the VE-induced granulosa cell proliferation and promoted apoptosis, whereas the p38 inhibitor SB203580 had the opposite effects. These results were confirmed by proliferation and apoptosis-related gene expression at mRNA and protein levels. The results also showed that the PI3K/AKT inhibitor LY294002 and ERK1/2 inhibitor SCH772984 inhibited VE-induced NRF2, GCLC, GCLM, and HO-1 expression, whereas the p38 inhibitor SB203580 not. Overall, the results demonstrated that VE-regulated granulosa cell proliferation and apoptosis via NRF2-mediated defence system by activating the PI3K/AKT and ERK1/2 signalling pathway.

中文翻译：

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维生素E通过激活PI3K/AKT和ERK1/2信号通路通过NRF2介导的防御机制调节牛颗粒细胞凋亡

高产奶牛通常受到高强度细胞代谢的影响，并产生过量的活性氧（ROS）。一旦活性氧超过清除能力的阈值，就会引起氧化应激，危及奶牛的繁殖性能。本研究旨在探讨维生素E（VE）对H ₂ O ₂诱导的牛颗粒细胞增殖和凋亡的影响及其潜在分子机制。颗粒细胞用 VE 预处理 24 小时，然后用 H ₂ O _{2 处理}6小时。结果表明，VE处理以剂量依赖性方式降低细胞内ROS水平，增加MDA含量，提高抗氧化酶活性。此外，VE 处理通过上调 CCND1 和 BCL2 水平以及下调 P21、BAX 和 CASP3 水平来促进颗粒细胞的增殖和抑制细胞凋亡。VE 的细胞保护作用归因于 NRF2 信号通路的激活。NRF2 的敲低削弱了 VE 对颗粒细胞的细胞保护作用。此外，PI3K/AKT 和 ERK1/2 参与调控 VE 介导的细胞增殖和凋亡，但不涉及 p38 信号通路。PI3K/AKT抑制剂LY294002和ERK1/2抑制剂SCH772984抑制VE诱导的颗粒细胞增殖并促进细胞凋亡，而 p38 抑制剂 SB203580 则具有相反的效果。这些结果通过 mRNA 和蛋白质水平的增殖和凋亡相关基因表达得到证实。结果还表明，PI3K/AKT 抑制剂 LY294002 和 ERK1/2 抑制剂 SCH772984 抑制了 VE 诱导的 NRF2、GCLC、GCLM 和 HO-1 的表达，而 p38 抑制剂 SB203580 则没有。总体而言，结果表明 VE 通过激活 PI3K/AKT 和 ERK1/2 信号通路，通过 NRF2 介导的防御系统调节颗粒细胞增殖和凋亡。和 HO-1 表达，而 p38 抑制剂 SB203580 则不然。总体而言，结果表明 VE 通过激活 PI3K/AKT 和 ERK1/2 信号通路，通过 NRF2 介导的防御系统调节颗粒细胞增殖和凋亡。和 HO-1 表达，而 p38 抑制剂 SB203580 则不然。总体而言，结果表明 VE 通过激活 PI3K/AKT 和 ERK1/2 信号通路，通过 NRF2 介导的防御系统调节颗粒细胞增殖和凋亡。