The co-expression of circRNA and mRNA in the thymuses of chickens exposed to ammonia

Ammonia (NH3) is one of major air pollutants in intensive poultry houses, affecting chicken health. Circular RNA (circRNA) is a novel type of RNA that can regulate gene expression and be associated with various biological activities. However, the changes of circRNA caused by excess NH3 in chickens have not been investigated. We found differentially expressed genes and morphological changes in the thymuses of chickens exposed to NH3 on day 42. We used a combination of RNA deep sequencing, qRT-PCR, and bioinformatic analysis to explore regulatory mechanism of circRNA and mRNA. Transcriptional profiling results showed that 5 circRNA genes and 100 mRNA genes were significantly dyregulated by high NH3. The results from GO items showed that immune response and the regulation of cytokine production were involved in the mechanisms of chickens exposed to NH3. Co-expression analysis found that circRNA-mRNA network was correlated with oxidative stress and inflammation. NH3 exposure decreased mRNA expression of antioxidant-related genes (GPx and GST4) and increased the mRNA expression of inflammation-related genes (IL-1 beta, IL-6, IL-8, and iNOS) in chicken thymuses. Histopathologic analysis demonstrated that NH3 caused inflammatory injury in chicken thymuses. In conclusion, the co-expression of circRNA and mRNA took part in chicken thymus inflammatory injury caused by NH3. Our study further enriches the mechanism of NH3 toxicity on chickens, which may be valuable for human and animal health protection.