Protective role of selenium on ammonia-mediated nephrotoxicity via PI3K/AKT/mTOR pathway: Crosstalk between autophagy and cytokine release

Sirtuin 5 alleviates apoptosis and autophagy stimulated by ammonium chloride in bovine mammary epithelial cells

Ammonia (NH3) is an irritating and harmful gas that affects cell apoptosis and autophagy. Sirtuin 5 (SIRT5) has multiple enzymatic activities and regulates NH3-induced autophagy in tumor cells. In order to determine whether SIRT5 regulates NH3-induced bovine mammary epithelial cell apoptosis and autophagy, cells with SIRT5 overexpression or knockdown were generated and in addition, bovine mammary epithelial cells were treated with SIRT5 inhibitors. The results showed that SIRT5 overexpression reduced the content of NH3 and glutamate in cells by inhibiting glutaminase activity in glutamine metabolism, and reduced the ratio of ADP/ATP. The results in the SIRT5 knockdown and inhibitor groups were comparable, including increased content of NH3 and glutamate in cells by activating glutaminase activity, and an elevated ratio of ADP/ATP. It was further confirmed that SIRT5 inhibited the apoptosis and autophagy of bovine mammary epithelial cells through reverse transcription-quantitative PCR, western blot, flow cytometry with Annexin V FITC/PI staining and transmission electron microscopy. In addition, it was also found that the addition of LY294002 or Rapamycin inhibited the PI3K/Akt or mTOR kinase signal, decreasing the apoptosis and autophagy activities of bovine mammary epithelial cells induced by SIRT5-inhibited NH3. In summary, the PI3K/Akt/mTOR signal involved in NH3-induced cell autophagy and apoptosis relies on the regulation of SIRT5. This study provides a new theory for the use of NH3 to regulate bovine mammary epithelial cell apoptosis and autophagy, and provides guidance for improving the health and production performance of dairy cows.

Thrombospondin-1-mediated crosstalk between autophagy and oxidative stress orchestrates repair of blast lung injury

Coal mining carries inherent risks of catastrophic gas explosions capable of inflicting severe lung injury. Using complementary in vivo and in vitro models, we explored mechanisms underlying alveolar epithelial damage and repair following a gas explosion in this study. In a rat model, the gas explosion was demonstrated to trigger inflammation and injury within the alveolar epithelium. The following scRNA-sequencing revealed that alveolar epithelial cells exhibited the most profound transcriptomic changes after gas explosion compared to other pulmonary cell types. In the L2 alveolar epithelial cells, the blast was found to cause autophagic flux by inducing autophagosome formation, LC3 lipidation, and p62 degradation. Transcriptomic profiling of the L2 cells identified PI3K-Akt and p53 pathways as critical modulators governing autophagic and oxidative stress responses to blast damage. Notably, Thrombospondin-1 (Thbs1) was determined for the first time as a pivotal node interconnecting these two pathways. The findings of this study illuminate intricate mechanisms of alveolar epithelial injury and recovery after blast trauma, highlighting autophagic and oxidative stress responses mediated by Thbs1-associated PI3K-Akt and p53 pathways as high-value therapeutic targets, and strategic modulation of these pathways in future studies may mitigate lung damage by reducing oxidative stress while engaging endogenous tissue repair processes like autophagy.

Inhalation of ammonia promotes apoptosis and induces autophagy in hepatocytes via Bax/BCl-2 and m-TOR/ATG5/LC-3bII axes

Ammonia (NH3) is an irritating gas and atmospheric pollutant that endangers the health of humans and animals by stimulating respiratory tract's mucosa and causing liver damage. However, physiological role of ammonia gas in hepatotoxicity remains unclear. To investigate the hepatotoxic effects of inhaled ammonia gas, experiments were conducted using mouse model exposed to 100 ppm of ammonia gas for 21 days. The exposed mice exhibited signs of depression, emaciation, and reduced growth. This study revealed that inhalation of ammonia led to significant decrease in water (P < 0.0001) and food intake (P < 0.05), resulting in slower growth. Histopathological analysis showed that ammonia stress alters the microstructure of the liver by enlarging the gap between hepatic lobule and fibrosis. Moreover, ammonia-induced stress significantly reduces the expression of the anti-apoptotic protein BCl-2 (P < 0.001), while elevates the mRNA expression of the pro-apoptotic gene Bax (P < 0.001). Furthermore, ammonia inhalation significantly increases the protein expression of LC-3bII (P < 0.05) and the mRNA expression of autophagy-related gene 5 (ATG5) (P < 0.05) and p62 (P < 0.05) while remarkably decreases the mRNA expression of mammalian target of rapamycin (m-TOR) (P < 0.05). In conclusion, this study demonstrates that inhalation of ammonia gas causes liver damage and suggests autophagy happening via m-TOR/p62/LC-3bII and pro-apoptosis effect mediated by Bax/BCl-2 in the liver damage caused by ammonia inhalation. Our study provides a new perspective on ammonia-induced hepatotoxicity.

Bile duct ligation elevates 5-HT levels in cerebral cortex of rats partly due to impairment of brain UGT1A6 expression and activity via ammonia accumulation

Hepatic encephalopathy (HE) is often associated with endogenous serotonin (5-HT) disorders. However, the reason for elevated brain 5-HT levels due to liver failure remains unclear. This study aimed to investigate the mechanism by which liver failure increases brain 5-HT levels and the role in behavioral abnormalities in HE. Using bile duct ligation (BDL) rats as a HE model, we verified the elevated 5-HT levels in the cortex but not in the hippocampus and striatum, and found that this cortical 5-HT overload may be caused by BDL-mediated inhibition of UDP-glucuronosyltransferase 1A6 (UGT1A6) expression and activity in the cortex. The intraventricular injection of the UGT1A6 inhibitor diclofenac into rats demonstrated that the inhibition of brain UGT1A6 activity significantly increased cerebral 5-HT levels and induced HE-like behaviors. Co-immunofluorescence experiments demonstrated that UGT1A6 is primarily expressed in astrocytes. In vitro studies confirmed that NH4Cl activates the ROS-ERK pathway to downregulate UGT1A6 activity and expression in U251 cells, which can be reversed by the oxidative stress antagonist N-acetyl-l-cysteine and the ERK inhibitor U0126. Silencing Hepatocyte Nuclear Factor 4α (HNF4α) suppressed UGT1A6 expression whilst overexpressing HNF4α increased Ugt1a6 promotor activity. Meanwhile, both NH4Cl and the ERK activator TBHQ downregulated HNF4α and UGT1A6 expression. In the cortex of hyperammonemic rats, we also found activation of the ROS-ERK pathway, decreases in HNF4α and UGT1A6 expression, and increases in brain 5-HT content. These results prove that the ammonia-mediated ROS-ERK pathway activation inhibits HNF4α expression to downregulate UGT1A6 expression and activity, thereby increasing cerebral 5-HT content and inducing manic-like HE symptoms. This is the first study to reveal the mechanism of elevated cortical 5-HT concentration in a state of liver failure and elucidate its association with manic-like behaviors in HE.

Toxic Kidney Damage in Rats Following Subchronic Intraperitoneal Exposure to Element Oxide Nanoparticles

Chronic diseases of the urogenital tract, such as bladder cancer, prostate cancer, reproductive disorders, and nephropathies, can develop under the effects of chemical hazards in the working environment. In this respect, nanosized particles generated as by-products in many industrial processes seem to be particularly dangerous to organs such as the testes and the kidneys. Nephrotoxicity of element oxide particles has been studied in animal experiments with repeated intraperitoneal injections of Al2O3, TiO2, SiO2, PbO, CdO, CuO, and SeO nanoparticles (NPs) in total doses ranging from 4.5 to 45 mg/kg body weight of rats. NPs were synthesized by laser ablation. After cessation of exposure, we measured kidney weight and analyzed selected biochemical parameters in blood and urine, characterizing the state of the excretory system. We also examined histological sections of kidneys and estimated proportions of different cells in imprint smears of this organ. All element oxide NPs under investigation demonstrated a nephrotoxic effect following subchronic exposure. Following the exposure to SeO and SiO2 NPs, we observed a decrease in serum creatinine and urea, respectively. Exposure to Al2O3 NPs caused an increase in urinary creatinine and urea, while changes in total protein were controversial, as it increased under the effect of Al2O3 NPs and was reduced after exposure to CuO NPs. Histomorphological changes in kidneys are associated with desquamation of the epithelium (following the exposure to all NPs except those of Al2O3 and SiO2) and loss of the brush border (following the exposure to all NPs, except those of Al2O3, TiO2, and SiO2). The cytomorphological evaluation showed greater destruction of proximal sections of renal tubules. Compared to the controls, we observed statistically significant alterations in 42.1% (8 of 19) of parameters following the exposure to PbO, CuO, and SeO NPs in 21.1% (4 of 19)-following that, to CdO and Al2O3 NPs-and in 15.8% (3 of 19) and 10.5% (2 of 19) of indicators, following the exposure to TiO2 and SiO2 nanoparticles, respectively. Histomorphological changes in kidneys are associated with desquamation of epithelium and loss of the brush border. The cytomorphological evaluation showed greater destruction of proximal sections of renal tubules. The severity of cyto- and histological structural changes in kidneys depends on the chemical nature of NPs. These alterations are not always consistent with biochemical ones, thus impeding early clinical diagnosis of renal damage. Unambiguous ranking of the NPs examined by the degree of their nephrotoxicity is difficult. Additional studies are necessary to establish key indicators of the nephrotoxic effect, which can facilitate early diagnosis of occupational and nonoccupational nephropathies.

Selenium and Selenoproteins in Health

Selenium is a trace mineral that is essential for health. After being obtained from food and taken up by the liver, selenium performs various physiological functions in the body in the form of selenoproteins, which are best known for their redox activity and anti-inflammatory properties. Selenium stimulates the activation of immune cells and is important for the activation of the immune system. Selenium is also essential for the maintenance of brain function. Selenium supplements can regulate lipid metabolism, cell apoptosis, and autophagy, and have displayed significant alleviating effects in most cardiovascular diseases. However, the effect of increased selenium intake on the risk of cancer remains unclear. Elevated serum selenium levels are associated with an increased risk of type 2 diabetes, and this relationship is complex and nonlinear. Selenium supplementation seems beneficial to some extent; however, existing studies have not fully explained the influence of selenium on various diseases. Further, more intervention trials are needed to verify the beneficial or harmful effects of selenium supplementation in various diseases.

Roles of selenoprotein K in oxidative stress and endoplasmic reticulum stress under selenium deficiency in chicken liver

Selenoprotein K (SELENOK) is a major part of selenoprotein family. Selenoproteins have been proven playing vital roles in a variety of physiological processes. However, as a necessary supplement to the body of trace elements, how SELENOK regulates necroptosis in chicken liver has none clear claim. The purpose of this study was to cover the mechanism of SELENOK act in necroptosis of chicken liver. By feeding Se-deficiency diet for 1-day-old hyline chickens, we successfully built SELENOK-deficiency and discussed the regulation SELENOK have done. The test of liver function showed there has dysfunction appeared in the -Se groups. Results of TEM showed necroptosis occurred in the 35-Se group. After that western blot and qRT-PCR results prompted us SELENOK-deficiency caused large accumulation of ROS, enhanced endoplasmic reticulum stress, abnormally elevated HSPs family expression, and activated RIPK1-RIPK3 complex. In order to show the regulation of SELENOK in chicken liver, we artificially knocked off SELENOK gene in LMH cells. Through AO/EB staining we also found necroptosis in the siRNA-Se group. Furthermore, the results in LMH cells were coincided with those in chicken (Gallus gallus) liver. Our experiment clarified the molecular mechanism of SELENOK in the regulation and liver necroptosis, and provided reference for the healthy feeding mode of broilers.