Ammonia inhalation-induced inflammation and structural impairment in the bursa of fabricius and thymus of broilers through NF-κB signaling pathway

Ammonia (NH3) is a toxic, environmental pollutant, and irritant gas. Previous studies reported the toxic effects of NH3 which led to inflammation in various organs of chicken. However, the exact mechanism of NH3-induced inflammation in chicken lymphoid organs bursa of fabricius (BF) and thymus is still elusive. Thus, this study was designed to investigate NH3-induced inflammation in chicken BF and thymus. Experimental chickens were divided into low (5.0 mg/m(3)), middle (10.0-15.0 mg/m(3)), and high (20.0-45.0 mg/m(3)) NH3-treated groups. To investigate NH3-induced inflammation in chicken's BF and thymus, histological observation, NO content and iNOS activity, inflammatory cytokine contents, and mRNA levels were performed by light microscopy, microplate spectrophotometer, ELISA assay, and qRT-PCR. The finding of the present study showed that NH3 exposure reduced BF and thymus index, increased nitric oxide (NO) content and inducible nitric oxide synthase (iNOS) activity, inflammatory cytokine contents and mRNA levels of nuclear factor-kappa B (NF-kappa B), cyclooxygenase-2 (Cox-2), tumor necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6), IL-10, IL-1 beta, IL-18, toll-like receptor 2A (TLR-2A), and iNOS. Histopathological examination revealed signs of inflammation including increased nuclear debris and vacuoles in the cortex and medulla of thymus and bursal follicles. Conclusively, our findings displayed that NH3 exposure affects the normal function of BF and thymus and led inflammation. The data provided a new ground for NH3-induced toxicity and risk assessment in chicken production.