Selenomethionine protects against ammonia-induced apoptosis through inhibition of endoplasmic reticulum stress in pig kidneys

Ammonia (NH3) emission is a common threat to farm animals. Selenium (Se) is known for its antioxidant property and can resist several stressors affecting farm animals. The aims of this study were (I) to determine how excess NH3 exert nephrotoxic effects in pigs and (II) to investigate whether selenomethionine has an alleviative effect on NH3 toxicity. Two diets supplemented with different doses of Se (0.22 mg/kg or 0.50 mg/kg) and two concentrations of NH3 (< 5 mg/m(3) or 89.8 mg/m(3)) were used in a 2 x 2 factorial design trial for a period of 30 days. The results showed that NH3 exposure caused apoptosis and increased the number of apoptotic cells in pig kidneys. Further, the activities of antioxidant enzymes were decreased, and the transcriptional and translational levels of endoplasmic reticulum stress-related genes, Bcl-2 and Caspase family members were increased under NH3 exposure. In addition, Wnt/beta-catenin signaling pathway was suppressed after NH3 treatment. Dietary supplement with selenomethionine appears to offer protection against NH3-induced kidney injury in pigs and the pathologic changes above were alleviated. Our findings provide additional insight into the mechanism of NH3 toxicity in pigs while elucidating the role of Se as a potential antidote against NH3 poisoning.