Abstract
We investigated the mechanisms that induce atrophy of the chicken bursa of Fabricius (BF) upon lipopolysaccharide (LPS) treatment in young chicks. LPS treatment resulted in ∼36% decrease in bursal weight within 36 h (P < 0.01). Histological analysis showed infiltration of eosinophilic heterophils and nucleated oval shaped RBCs in or near blood vessels of the BF from LPS-treated chicks. Scanning electron micrographs showed severe erosion and breaks in the mucosal membrane at 12 h and complete exuviation of bursal mucosal epithelial cells at 36 h. We observed decreased cell proliferation (low PCNA positivity) and increased apoptosis (high TUNEL and ssDNA positivity) in the BF 12-72 h after LPS treatment. RNA-seq analysis of the BF transcriptome showed 736 differentially expressed genes with most expression changes (637/736) 12 h after LPS treatment. KEGG pathway analysis identified TLR4-MAPK-NF-κB/AP-1 as the key signaling pathway affected in response to LPS stimulation. These findings indicate LPS activates the TLR4-MAPK-NF-κB/AP-1 signaling pathway that mediates acute atrophy of the chicken bursa of Fabricius by inducing inflammation and apoptosis.
Highlights
The bursa of Fabricius (BF) is an avian specific immune organ
BF plays a significant role in serovar Typhimurium (STm) infection in poultry [16], only few scientific reports have described the transcriptional changes in BF following STm infection in avian species
We found that LPS stimulation markedly reduced bursal weight and index
Summary
The bursa of Fabricius (BF) is an avian specific immune organ. Salmonella enterica serovar Typhimurium (STm) is a gram-negative facultative anaerobic bacterium that causes serious clinical disease in newly hatched chicks [11], which is characterized by severe diarrhea, dehydration, and increased mortality [12]. STm infection results in immune suppression, cytokine imbalance and disruption of lymphoid tissue architecture [13]. The JNK signaling pathway plays a critical role during STm-induced thymic injury in mice [14, 15]. BF plays a significant role in STm infection in poultry [16], only few scientific reports have described the transcriptional changes in BF following STm infection in avian species
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