A natural sesquiterpene lactone isolinderalactone attenuates lipopolysaccharide-induced inflammatory response and acute lung injury through inhibition of NF-κB pathway and activation Nrf2 pathway in macrophages

Abstract

Isolinderalactone is the main sesquiterpene lactone isolated from Lindera aggregata, a traditional Chinese medicine widely used to treat pain and inflammation. Although isolinderalactone has been demonstrated to possess anti-cancer effect, its anti-inflammatory activity and underlying mechanism has not been well characterized. Herein, isolinderalactone was able to significantly inhibit the production of NO and PGE₂ by reducing the expressions of iNOS and COX2 in LPS-stimulated RAW264.7 macrophages and BMDMs, and decreased the mRNA levels of IL-1β, IL-6, and TNF-α in LPS-induced RAW264.7 cells. In vivo, isolinderalactone effectively alleviated LPS-induced acute lung injury (ALI), which manifested as reduction in pulmonary inflammatory infiltration, myeloperoxidase activity, and production of PGE₂, IL-1β, IL-6, TNF-α, and malondialdehyde. Furthermore, isolinderalactone inhibited phosphorylation of IKKα/β, phosphorylation and degradation of IκBα, and nuclear translocation of NF-κB p65, thereby blocking NF-κB pro-inflammatory pathway. Meanwhile, isolinderalactone reduced the intracellular ROS through promoting the activation of Nrf2-HMOX1 antioxidant axis. By using drug affinity responsive target stability assay and molecular docking, isolinderalactone was found to covalently interact with IKKα/β and Keap1, which may contribute to its anti-inflammatory action. Additionally, a thiol donor β-mercaptoethanol significantly abolished isolinderalactone-mediated anti-inflammatory action in vitro, indicating the crucial role of the unsaturated lactone of isolinderalactone on its anti-inflammatory effects. Taken together, isolinderalactone protected against LPS-induced ALI in mice, which may be associated with its inhibition of NF-κB pathway and activation of Nrf2 signaling in macrophages.

Keywords: Acute lung injury; Anti-inflammatory activity; IKKα/β-NF-κB pathway; Isolinderalactone; Keap1-Nrf2 pathway; Macrophages.