Dihydromikanolide Inhibits ROS‐Mediated NLRP3 Inflammation via Antioxidant Nrf2 Activation and Mitophagy Induction in LPS/ATP‐Stimulated Macrophages

Dihydromikanolide (DHK) is a natural product in Mikania species. We examined the anti‐inflammatory molecular mechanisms of DHK employing in vitro RAW264.7 macrophages and in vivo BALB/c mice under LPS/ATP stimulation. We found that DHK suppressed NLRP3 inflammasome, procaspase‐1 activation and then pro‐inflammatory IL1β expression in LPS/ATP‐stimulated RAW264.7 cells. Notably, DHK‐triggered autophagy in RAW264.7 cells was demonstrated by increased LC3‐II accumulation, p62/SQSTM1 expression, Beclin‐1/Bcl‐2 ratio and PI3K/AKT/mTOR phosphorylation. Besides, DHK increased Parkin and Pink‐1 protein expressions implying mitophagy induction in RAW264.7 cells. Interestingly, DHK enhanced Nrf2 nuclear translocation and provoked antioxidant HO‐1, NQO‐1 and γ‐GCLC expressions in RAW264.7 cells. Nrf2 knockdown reversed DHK‐inhibited LPS/ATP‐stimulated IL1β expression in RAW264.7 cells. Interestingly, LPS/ATP‐stimulated NLRP3 inflammasome and IL1β expression were inhibited by DHK, Mito‐TEMPO (a mitochondrial ROS inhibitor), or N ‐acetylcysteine (a ROS inhibitor). In vivo study revealed that DHK attenuated wet/dry weight ratio of lung tissue, lung neutrophil intrusions and pulmonary oedema, and reduced the increased total cells, neutrophils, TNFα and IL1β expression in bronchoalveolar lavage fluid (BALF) in LPS‐stimulated BALB/c mice. DHK alleviated LPS‐induced pathological alterations of lung through inhibiting NLRP3 inflammation, enhancing antioxidant Nrf2 pathway and inducing mitophagy in LPS‐stimulated BALB/c mice. Dihydromikanolide may be a potential therapeutic agent for inflammatory diseases.