Demethyleneberberine alleviates Pseudomonas aeruginosa-induced acute pneumonia by inhibiting the AIM2 inflammasome and oxidative stress.

BACKGROUND: Acute pneumonia induced by Pseudomonas aeruginosa is characterized by massive infiltration of inflammatory cell and the production of reactive oxygen species (ROS), which lead to severe and transient pulmonary inflammation and acute lung injury. However, P.aeruginosa infection is resistant to multiple antibiotics and causes high mortality in clinic, the search for alternative prophylactic and therapeutic strategies is imperative.

PURPOSE: This study was aimed to investigate the anti-inflammatory and antioxidant effects of DMB, a novel derivative of berberine, and explore the role of AIM2 inflammasome in P. aeruginosa-induced acute pneumonia.

METHODS: Acute pneumonia mice were established by tracheal injection of P. aeruginosa suspension. Pathological changes of lung tissue were observed by its appearance and H&E staining. The lung coefficient ratio was measured to evaluate pulmonary edema. Inflammatory factors were detected by qRT-PCR, western blotting and immunohistochemistry. ROS and other indicators of oxidative damage were analyzed by flow cytometry and specific kit. Proteins related to AIM2 inflammasome were detected by western blotting.

RESULTS: Compared with the P. aeruginosa-induced group, DMB ameliorated pulmonary edema, hyperemia, and pathological damage based on its appearance and H&E staining in DMB groups. First, DMB attenuated the inflammatory response induced by P.aeruginosa. Compared with the P. aeruginosa-induced group, the lung coefficient ratio was decreased by 31.5%, the MPO activity of lung tissue was decreased by 44.0%, the mRNA expression levels of TNF-α, IL-1β and IL-6 were decreased by 64.8%, 51.2% and 64.0% respectively, and those protein expression levels were decreased by 40.1%, 42.8% and 47.8% respectively, and the number of white blood cells, neutrophils and monocytes were decreased by 53.5%, 29.4% and 13.7% in high dose (200mg/kg) DMB group. Second, DMB alleviates oxidative stress in the lung tissue during P. aeruginosa-induced acute pneumonia. Compared with the P. aeruginosa-induced group, the level of GSH was increased by 42.5% and MDA was decreased by 49.5% in high dose DMB group. Moreover, the western blotting results showed that DMB markedly suppressed the expression of AIM2, ASC, Cleaved caspase1 and decreased the secretion of IL-1β. Additionally, these results were also confirmed by in vitro experiments using MH-S and BEAS-2B cell lines.

CONCLUSIONS: Taken together, these results indicated that DMB ameliorates P. aeruginosa-induced acute pneumonia through anti-inflammatory, antioxidant effects, and inhibition of AIM2 inflammasome activation.