Protein lysine acetylation played an important role in NH3-induced AEC2 damage and pulmonary fibrosis in piglets

Abstract

Gaseous ammonia (NH₃), as a main air pollutant in pig farms and surrounding areas, directly affects animal and human health. The lung, as an important organ for gas exchange in the respiratory system, is damaged after NH₃ exposure, but the underlying mechanism needs to be further explored. In this study, seven weeks old piglets were exposed to 50 ppm NH₃ for 30 days, and displayed pulmonary fibrosis. Then, the toxicological mechanism of NH₃-induced pulmonary fibrosis was explored from the aspects of whole genome wide protein expression and post-translational modification. Totally, 404 differentially expressed proteins (DEPs) and 136 differentially lysine acetylated proteins (DAPs) were identified. The expression or lysine acetylation levels of proteins involved in mitochondrial energy metabolism including fatty acid oxidation (CPT1A, ACADVL, ACADS, HADHA, and HADHB), TCA cycle (IDH2 and MDH2), and oxidative phosphorylation (NDUFB7, NDUFV1, ATP5PB, ATP5F1A, COX5A, and COX5B) were significantly changed after NH₃ exposure, which suggested that NH₃ disrupted mitochondrial energy metabolism in the lung of piglets. Next, we found that type 2 alveolar epithelial cells (AEC2) damaged after NH₃ exposure in vivo and in vitro. Integrin-linked kinase (ILK) was enriched in focal adhesion pathway, and showed significantly up-regulated acetylation levels at K191 (FC = 2.99) and K209 sites (FC = 1.52) after NH₃ exposure. We illustrated that ILK-K191 hyper-acetylation inhibited AEC2 proliferation and induced AEC2 apoptosis by down-regulating pAKT-S473 in vitro. In conclusion, for the first time, our study revealed that protein acetylation played an important role in the process of NH₃-induced pulmonary fibrosis in piglets. Our findings provided valuable insights into toxicological harm of NH₃ to human health.

Keywords: AEC2 damage; Ammonia; Piglets; Protein lysine acetylation; Pulmonary fibrosis.