Methionine alleviates heat stress-induced ferroptosis in bovine mammary epithelial cells through the Nrf2 pathway.

Heat stress (HS) triggers mammary gland degradation, accompanied by apoptosis and autophagy in bovine mammary epithelial cells, negatively affecting milk performance and mammary gland health. Ferroptosis is iron-mediated regulated cell death caused by over production of lipid peroxides, however, the relationship between ferroptosis and HS in bovine mammary epithelial cells has not been clarified. Methionine (Met) plays a notable role in alleviating HS affecting the mammary glands in dairy cows, but the underlying mechanisms require further exploration. Therefore, we evaluated the regulatory effect and mechanism of Met in alleviating HS-induced ferroptosis by using bovine mammary epithelial cell line (MAC-T) as an in vitro model. The results showed that Met improved cell vitality, restored mitochondrial function; reduced the content of various reactive oxygen species (ROS), especially hydrogen peroxide (H2O2) and superoxide anion (O2·-); had positive effects on antioxidant enzyme activity, namely glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD). More importantly, Met reduced labile iron protein (LIP) levels; increased iron storage and simultaneously decreased the levels of lipid reactive oxygen species (lipid ROS) and malondialdehyde (MDA), which all caused by HS in MAC-T. Mechanistically, Met increased the protein expression levels of glutathione peroxidase 4 (GPX4), solute carrier family 7, member 11 (SLC7A11) and ferritin heavy chain 1 (FTH1) by activating nuclear factor E2-related factor 2 (Nrf2) expression. Additionally, the protection effect of Met was cut off in MAC-T cells after interference with Nrf2, manifesting in decresing the protein expression levels of GPX4, SLC7A11 and FTH1,and increasing the levels of LIP and lipid ROS. Our findings indicate that Met eases HS-induced ferroptosis in MAC-T through the Nrf2 pathway, revealing that Met produces a marked effect on easing HS-induced bovine mammary gland injury in dairy cows.

[Meteorological Characteristics, Influence Analysis and Prediction of PM2.5 Concentration in Taiyuan City].

Based on the pollutant concentration data of Taiyuan City from 2016 to 2020 and the surface meteorological data of the national benchmark meteorological observation station in the same period, the variation characteristics of PM2.5 concentration in Taiyuan City and the effects of meteorological conditions such as humidity, precipitation, wind, and mixing layer thickness on PM2.5 concentration were analyzed. At the same time, the causes of pollutant concentration changes were discussed, and the PM2.5 concentration prediction model based on the LSTM neural network was established. The results showed that the number of days of heavy pollution in Taiyuan City from 2016 to 2020 was the highest in winter, of which the maximum number of days in 2017 was 28 days. The PM2.5 concentration was generally high in autumn and winter and low in spring and summer. The PM2.5 concentration on weekends was higher than that on weekdays. The daily variation in PM2.5 concentration roughly presented a bimodal distribution, which appeared around 09:00 and 23:00 to 01:00 the following day. Except for relative humidity and winter temperature, other air pressure, wind speed, and PM concentration showed negative correlations in the four seasons. The pollution sources affecting the increase in PM2.5 concentration in Taiyuan City were mainly located in the NE-ENE-E direction, and the pollution in the northwest was not relatively apparent. In flood season, when the precipitation reached the level of moderate rain (rainfall ≥ 10 mm), it had an obvious effect on the reduction of PM2.5 concentration. The increase in atmospheric mixing layer height was very beneficial to the diffusion and dilution of PM2.5 in the vertical direction. The strong northwest air flow in winter, low relative humidity, high pressure control on the ground, and high height of the mixing layer belonged to the cluster most conducive to the reduction in PM2.5 concentration. Using the LSTM model for modeling, the R2 of PM2.5 concentration prediction was as high as 0.95, which was significantly better than that of the traditional tree model and linear regression model (R2<0.60). The residual of the prediction results was close to the normal distribution, of which the absolute error of 84.2% prediction results was less than 20 µg·m-3, and the MAE, MAPE, and RMSE of the model were 38.17, 17.19%, and 20.6, respectively.

Nicotinamide mononucleotide alleviates heat stress-induced oxidative stress and apoptosis in BMECs through reducing mitochondrial damage and endoplasmic reticulum stress.

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.

SIRT3 protects bovine mammary epithelial cells from heat stress damage by activating the AMPK signaling pathway.

With global warming, heat stress has become an important challenge for the global dairy industry. Sirtuin 3 (SIRT3), an important mitochondrial NAD+dependent decarboxylase and a major regulator of cellular energy metabolism and antioxidant defense, is integral to maintaining normal mitochondrial function. The aim of this study was to assess the protective effect of SIRT3 on damage to bovine mammary epithelial cells (BMECs) induced by heat stress and to explore its potential mechanism. Our results indicate that SIRT3 is significantly downregulated in heat-stressed mammary tissue and high-temperature-treated BMECs. SIRT3 knockdown significantly increased the expression of HSP70, Bax, and cleaved-caspase 3 and inhibited the production of antioxidases, thus promoting ROS production and cell apoptosis in BMECs. In addition, SIRT3 knockdown can aggravate mitochondrial damage by mediating the expression of genes related to mitochondrial fission and fusion, including dynamin-related protein 1, mitochondrial fission 1 protein, and mitochondrial fusion proteins 1and 2. In addition, SIRT3 knockdown substantially decreased AMPK phosphorylation in BMECs. In contrast, SIRT3 overexpression in high-temperature treatment had the opposite effect to SIRT3 knockdown in BMECs. SIRT3 overexpression reduced mitochondrial damage and weakened the oxidative stress response of BMECs induced by heat stress and promoted the phosphorylation of AMPK. Taken together, our results indicate that SIRT3 can protect BMECs from heat stress damage through the AMPK signaling pathway. Therefore, the reduction of oxidative stress by SIRT3 may be the primary molecular mechanism underlying resistance to heat stress in summer cows.

Investigating disordered many-body system with entanglement in momentum space.

We study the entanglement in momentum space of the ground state of a disordered one-dimensional fermion lattice model with attractive interaction. We observe two components in the entanglement spectrum, one of which is related to paired-fermion entanglement and contributes to the long-range correlation in position space. The vanishing point of it indicates the localization phenomenon in the ground state of this model. Additionally, by method of entanglement spectrum, we provide a new evidence to show the transition of two phases induced by interaction, and find that this phase transition is not influenced by the disorder. Our result show key characteristics in entanglement for different phases in the system, and provide a novel perspective to understand localization phenomena.

Methionine protects against hyperthermia-induced cell injury in cultured bovine mammary epithelial cells.

The aim of this study was to investigate the effects of methionine on cell proliferation, antioxidant activity, apoptosis, the expression levels of related genes (HSF-1, HSP70, Bax and Bcl-2) and the expression levels of protein (HSP70) in mammary epithelial cells, after heat treatment. Methionine (60 mg/L) increased the viability and attenuated morphological damage in hyperthermia-treated bovine mammary epithelial cells (BMECs). Additionally, methionine significantly reduced lactate dehydrogenase leakage, malondialdehyde formation, nitric oxide, and nitric oxide synthase activity. Superoxide dismutase, catalase, and glutathione peroxidase enzymatic activity was increased significantly in the presence of methionine. Bovine mammary epithelial cells also exhibited a certain amount of HSP70 reserve after methionine pretreatment for 24 h, and the expression level of the HSP70 gene and protein further increased with incubation at 42 °C for 30 min. Compared to the control, the expression of HSF-1 mRNA increased, and there was a significantly reduced expression of Bax/Bcl-2 mRNA and a reduced activity of caspase-3 against heat stress. Methionine also increased survival and decreased early apoptosis of hyperthermia-treated BMECs. Thus, methionine has cytoprotective effects on hyperthermia-induced damage in BMECs.

Cytoprotection of methionine on hyperthermia-induced damage in bovine mammary epithelial cells.

The protective effects of methionine against hyperthermia-induced damage in bovine mammary epithelial cells (BMEC) were studied. We have investigated the effects of methionine on proliferation, antioxidant activity, and apoptosis of the mammary epithelial cells of dairy cow after heat treatment. The structure of BMEC membrane was damaged by hyperthermia. Methionine (30 and 60 mg/L) efficiently increased cell viability and attenuated morphological damages in hyperthermia-treated BMEC. It significantly reduced lactate dehydrogenase leakage and malondialdehyde formation, whereas superoxide dismutase activity increased significantly. It also increased cell survival and decreased early apoptosis. Methionine therefore is cytoprotective on hyperthermia-induced damage in BMEC by increasing intracellular antioxidant levels and decreasing lipid peroxidation.

Upregulation of heat shock protein 32 in Sertoli cells alleviates the impairments caused by heat shock-induced apoptosis in mouse testis.

Heat stress results in apoptosis in testicular germ cells. A small heat shock protein (hsp), hsp32, is induced by heat stress in the testis, but little is known about its definitive function in physiological processes. To clarify the underlying role of hsp32, hsp32 expression and related signals in the heat shock pathway were analysed in mouse testes and Sertoli cells after heat stress in vivo and in vitro; meanwhile, expression of hsp32 was silenced only in the Sertoli cells using three different small interfering RNAs (siRNAs) to further verify the functional role of hsp32 in Sertoli cells, and hsp32-derived carbon monoxide (CO) contents in cultured media were analysed to clarify whether hsp32-derived CO involve in the apoptosis regulation mechanisms. The results from the in vivo experiment showed that the high expression levels of hsp32 (P < 0.05) were observed whether chronic, moderate or acute, transient heat exposure. The in vitro experiment showed that acute, transient heat exposure resulted in increases in Sertoli cells apoptosis (P < 0.01), the expression of hsp32 and caspase-3 activity; hsp32-siRNA knockdown of hsp32 expression resulted in upregulated apoptosis (P < 0.01) and caspase-3 activity (P < 0.01) in the Sertoli cells and hyperthermia increases CO (P < 0.01) release by Sertoli cells. The results suggested that upregulating hsp32 in Sertoli cells inhibits caspase-3 activity and alleviates heat-induced impairments in mouse testis; hsp32-derived CO may involve in the regulation mechanism.

[Effects of daidzein on sperm quality, testis gain and testosterone in mice].

OBJECTIVE: To evaluate the effects of daidzein on sperm quality of male mice. METHODS: Three different doses of daidzein were supplemented to pubertal male mice for 21 days(5 mg/kg, 100 mg/kg, 1,000 mg/kg ration). The viability of sperm was determined by eosin-Y, the acrosome was observed by Wright-Giemsa staining, and the testosterone was measured by radioimmunoassay. RESULTS: Daidzein at the dose of 5 mg/kg ration significantly increased serum testosterone levels (P < 0.01), prompted testis gain (P < 0.05), and improved spermatozoa quality. Daidzein at dose of 1,000 mg/kg ration could inhibit the secretion of serum testosterone (P < 0.01), without significant variation in spermatozoa quality. Daidzein at dose of 100 mg/kg ration did not significantly affect sperm quality and other index. CONCLUSIONS: Daidzein can affect sperm quality and in dosage-dependant ways.