Nootkatone immunomodulates alveolar macrophage via STING/TBK1/IRF3 signaling pathway inhibition to protect against LPS-induced acute lung injury.

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are characterized by diffuse pulmonary interstitial edema, alveolar edema, lung infiltration by immune cells, and acute hypoxic respiratory insufficiency. Nootkatone (NKT) is an organic compound and a bioactive sesquiterpene ketone with anti-inflammatory properties. This study aims to explore the potential protective effects of NKT in lipopolysaccharide (LPS)-induced ALI models. The study assesses the anti-inflammatory action of NKT, its effects on the metabolism of both the lungs and alveolar macrophages (AMs), and the underlying cellular mechanisms. NKT inhibits the increase in total cell, macrophage and neutrophil counts in bronchoalveolar lavage fluid of the ALI mice, as well as pro-inflammatory cytokines (IL-6, TNF-α, and IL-1β). NKT also downregulates the expressions of genes related to inflammatory mediator in AMs, including Cxcl10 (IP-10), Ccl4 (MIP-1β), Ccl3 (MIP-1α), Csf3 (G-CSF), Il22 (IL-22), Il12a (IL-12α), Il1b (IL-1β), Ccl5 (RANTES). NKT diminishes mitochondrial respiration and glycolysis in lung single cells and AMs of ALI mice almost to baseline. Treatment with NKT significantly reduces the protein expression of phospho-STING, phospho-TANK-binding kinase 1 (TBK1) and phospho-IFN regulatory factor 3 (IRF3) in the lungs and AMs, thereby inhibiting the STING/TBK1/IRF3 pathway. We report for the first time that NKT may exert its anti-inflammatory effects in LPS-induced ALI by suppressing the STING/TBK1/IRF3 signaling pathway in AMs and lungs, offering compelling evidence for further development of NKT as a treatment of ALI.