Glaesserella parasuis serotype 5 induces pyroptosis via the RIG-I/MAVS/NLRP3 pathway in swine tracheal epithelial cells

Glaesserella parasuis (G. parasuis) is a common Gram-negative commensal bacterium in the upper respiratory tract of swine that can cause Glässer's disease under stress conditions. Pyroptosis is an important immune defence mechanism of the body that plays a crucial role in clearing pathogen infections and endogenous danger signals. This study aimed to investigate the mechanism of G. parasuis serotype 5 SQ (GPS5-SQ)-induced pyroptosis in swine tracheal epithelial cells (STECs). The results of the present study demonstrated that GPS5-SQ infection induces pyroptosis in STECs by enhancing the protein level of the N-terminal domain of gasdermin D (GSDMD-N) and activating the NOD-like receptor protein 3 (NLRP3) inflammasome. Furthermore, the levels of pyroptosis-related proteins, including GSDMD-N and cleaved caspase-1 were considerably decreased in STECs after the knockdown of retinoic acid inducible gene-I (RIG-I) and mitochondrial antiviral signaling protein (MAVS). These results indicated that GPS5-SQ might trigger pyroptosis through the activation of the RIG-I/MAVS/NLRP3 signaling pathway. More importantly, the reactive oxygen species (ROS) scavenger N-acetylcysteine (NAC) repressed the activation of the RIG-I/MAVS/NLRP3 signaling and rescued the decrease in Occludin and zonula occludens-1 (ZO-1) after GPS5-SQ infection. Overall, our findings show that GPS5-SQ can activate RIG-I/MAVS/NLRP3 signaling and destroy the integrity of the epithelial barrier by inducing ROS generation in STECs, shedding new light on G. parasuis pathogenesis.