Macleaya cordata extract modulates inflammation via inhibition of the NF-κB and MAPK signaling pathways in porcine alveolar macrophages induced by Glaesserella parasuis.

Glässer's disease in pigs is associated with infection by Glaesserella parasuis and is characterized by pneumonia-like symptoms, fibrinous polyserositis, polyarthritis, and meningitis. Macleaya cordata, a commonly used traditional Chinese medication, has been shown to have anti-inflammatory, antiviral, antioxidative, antimicrobial, insecticidal, and antitumor properties. However, the anti-inflammatory effects of M. cordata on G. parasuis stimulation are still poorly understood. This study explored the anti-inflammatory effects and mechanisms of M. cordata extract on G. parasuis-induced inflammatory responses, via the nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways, in porcine alveolar macrophages (PAMs). Porcine alveolar macrophages, when stimulated with G. parasuis, initiated transcription of interleukin (IL)-1α, IL-1β, IL-6, IL-8, and tumor necrosis factor alpha (TNF-α). Furthermore, p65, IκBα, p38, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) phosphorylation were upregulated via the NF-κB and MAPK signaling pathways. However, treatment with M. cordata extract inhibited transcription of IL-1α, IL-1β, IL-6, IL-8, and TNF-α and reduced p65, IκBα, p38, ERK, and JNK phosphorylation, by inhibiting activation of the NF-κB and MAPK signaling pathways in PAMs induced by G. parasuis. These findings reveal that M. cordata extract can reverse the inflammatory effect initiated by G. parasuis in vitro and that it possesses significant immunosuppression activity; thus, it may offer a novel strategy for controlling and treating G. parasuis infection.