Serum starvation is a routine protocol for synchronizing nuclear donor cells to G0/G1 phase during somatic cell nuclear transfer (SCNT). However, abrupt serum deprivation can cause serious stress to the cells cultured in vitro, which might result in endoplasmic reticulum (ER) stress, chromosome damage, and finally reduce the success rate of SCNT. In the present study, the effects of tauroursodeoxycholic acid (TUDCA), an effective ER stress-relieving drug, on the nuclear donor cells under serum deprivation condition as well as following SCNT procedures were first assessed in the bovine. The results showed that TUDCA significantly reduced ER stress and cell apoptosis in those nuclear donor cells. Moreover, it significantly decreased the expression of Hdac1 and Dnmt1, and increased the level of H3K9 acetylation in nuclear donor cells compared with control group. SCNT reconstructed embryos cloned from TUDCA-treated donor cells showed significantly higher fusion, cleavage, blastocyst formation rate, total cell number in day 7 blastocysts, and lower apoptotic index than that from control group. In addition, the expression of Hdac1, Dnmt1 and Bax was significantly lower in blastocysts derived from TUDCA-treated donor cells than that from control group. In conclusion, TUDCA significantly reduced the ER stress of nuclear donor cells under serum starvation condition, and significantly improved the developmental competence of following SCNT reconstructed embryos when these TUDCA-treated cells were used as the nuclear donors.

Hypoxia training enhances the endurance capacity of athletes. This response may in part be attributed to the hypoxia-induced increase in antioxidant capacity in skeletal muscles. Nuclear factor erythroid 2-related factor 2 (Nrf2), a key transcription factor which regulates the expression of genes via binding to the antioxidant-response element (ARE) of these genes, plays a crucial role in stimulating the body's defense system and potentially responds to hypoxia. Meanwhile, hypoxia-inducible factor-1α (HIF-1α) is an important player in protecting cells from hypoxic stress. The purpose of this study was to investigate the effects of acute hypoxia exposure with different durations on the activation of Nrf2-ARE pathway and a possible regulatory role of HIF-1α in these responses.

Large-scale breeding environments often lead to oxidative stress. Macrophages play an important role in the immune system and are vulnerable to reactive oxygen species (ROS), which result in macrophage death. Curcumin is the main active component of turmeric and exerts antioxidant effects. Here, we measured the activity of some antioxidant enzymes and chose the Nrf2-Keap1 signaling pathway to study the protective effects of curcumin on macrophages under oxidative stress in vitro. We used RAW264.7 cells as a research model, and oxidative damage was induced by hydrogen peroxide (H2O2). Cell viability was measured by an MTT assay. Flow cytometry was used to measure cellular ROS and apoptosis. The effect of curcumin on Nrf2-Keap1 signaling pathway-related genes was analyzed by qRT-PCR. Furthermore, the translocation of Nrf2 protein was also investigated by Western blot analysis of total and nuclear proteins. All curcumin-treated groups exhibited increased activity of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX). Low- and middle-dose curcumin decreased malondialdehyde (MDA) and ROS levels, but high-dose curcumin increased MDA and ROS production. We found that low-dose curcumin protected cells from apoptosis, while apoptosis in the middle- and high-dose curcumin-treated groups were stagnant in the early stage. Furthermore, middle-dose curcumin upregulated Nrf2 expression after H2O2 treatment for 4 h. Low- and middle-dose curcumin could activate Nrf2 and promote it to migrate into nuclei. The translocation of Nrf2 to the nucleus to upregulate the expression of haemoxygenase-1 (HO-1) was promoted in the low- and middle-dose curcumin-treated groups. The middle-dose curcumin-treated group also exhibited enhanced expression of glutamate-cysteine ligase, a modifier subunit (GLCM), but inhibited transcription of glutamate-cysteine ligase, a catalytic subunit (GCLC). Curcumin resisted oxidants by increasing the activity of antioxidant enzymes and activating the Nrf2-Keap1 pathway, which could potentially promote cell survival.