PTEN/AKT/mTOR pathway involvement in autophagy, mediated by miR-99a-3p and energy metabolism in ammonia-exposed chicken bursal lymphocytes

Abstract

Emission of atmospheric ammonia (NH₃) is an environmental challenge because of its harmful effects on humans and animals including birds. Among all organisms, NH₃ is highly sensitive to birds. Autophagy plays a critical role in Bursa of fabricius (BF)-mediated immune responses against various hazardous substances. Therefore, we designed our work to demonstrate whether NH₃ can induce autophagy in broiler chicken BF. In this study, the downregulated levels of mammalian target of rapamycin and light chain-3 (LC-Ⅰ), as well as the upregulated levels of phosphate and tensin homology (PTEN), protein kinase B (AKT), autophagy related-5, light chain-3 (LC3-Ⅱ), Becline-1, and Dynein, were found. Our results of transmission electron microscopy displayed signs of autophagosomes/autophagic lysosomes, and immunofluorescence assay displayed that NH₃ exposure reduced the relative amount of CD8⁺ B-lymphocyte in chicken BF. Exposure of NH₃ led to energy metabolism disturbance by decreasing mRNA levels of glucose metabolism factors aconitase-2, hexokinase-1, hexokinase-2, lactate dehydrogenase-A, lactate dehydrogenase-B, pyruvate kinase, phosphofructokinase and succinate dehydrogenase complex unit-B, and adenosine triphosphates (ATPase) activities (Na⁺/K⁺ ATPase, Ca²⁺ ATPase, Mg²⁺ ATPase, and Ca/Mg²⁺ ATPase). Moreover, phosphate and tensin homology was found as target gene of microRNA-99a-3p which confirmed that high concentration of NH₃ caused autophagy in chicken BF. In summary, these findings suggested that ammonia induced autophagy via miR-99a-3p, the reduction of ATPase activity, and the alteration of autophagy-related factors, and energy metabolism mediation in BF. Our findings provide information to assess the harmful effects of NH₃ on chicken and clues for human health pathophysiology.

Keywords: ATPase; NH(3); PTEN/AKT/mTOR signaling pathway; autophagy; miR-99a-3p.