Hydroxytyrosol mitigates Mycoplasma gallisepticum-induced pulmonary injury through downregulation of the NF-κB/NLRP3/IL-1β signaling pathway in chicken

In this study, the anti-inflammatory and antiapoptotic effects of hydroxytyrosol (HT) in Mycoplasma gallisepticum (MG)-infected chicken were investigated, and the underlying molecular mechanisms were explored. The results revealed severe ultrastructural pathological changes after MG infection in the lung tissue of chicken, including inflammatory cell infiltration, thickening of the lung chamber wall, visible cell swelling, mitochondrial cristae rupture, and ribosome shedding. MG possibly activated the nuclear factor κB (NF-κB)/nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3)/interleukin (IL)-1β signaling pathway in the lung. However, HT treatment significantly ameliorated MG-induced pathological damage of the lung. HT reduced the magnitude of pulmonary injury after MG infection by reducing apoptosis and releasing the proinflammatory factors. Compared with the MG-infected group, the HT-treated group exhibited significant inhibition of the expression of NF-κB/NLRP3/IL-1β signaling-pathway-related genes; for example, the expressions of NF-κB, NLRP3, caspase-1, IL-1β, IL-2, IL-6, IL-18, and TNF-α significantly decreased (P < 0.01 or <0.05). In conclusion, HT effectively inhibited MG-induced inflammatory response and apoptosis and protected the lung by blocking the activation of NF-κB/NLRP3/IL-1β signaling pathway and reducing the damage caused by MG infection in chicken. This study revealed that HT may be a suitable and effective anti-inflammatory drug against MG infection in chicken.