Rosmarinic acid alleviates septic acute respiratory distress syndrome in mice by suppressing the bronchial epithelial RAS-mediated ferroptosis.

Activating angiotensin-converting enzyme 2 (ACE2) is an important player in the pathogenesis of septic-related acute respiratory distress syndrome (ARDS). Rosmarinic acid (RA) as a prominent polyphenolic secondary metabolite derived from Rosmarinus officinalis modulates ACE2 in sepsis remains unclear, although its impact on ACE inhibition and septic-associated lung injury has been explored. The study investigated the ACE2 expression in lipopolysaccharide (LPS)-induced lungs in mice and BEAS2B cells. Additionally, molecular docking, protein-protein interaction (PPI) network analysis, and western blotting were employed to predict and evaluate the molecular mechanism of RA on LPS-induced ferroptosis in vivo and in vitro. LPS-induced glutathione peroxidase 4 (GPX4) downregulation, ACE/ACE2 imbalance, and alteration of frequency of breathing (BPM), minute volume (MV), and the expiratory flow at 50% expired volume (EF) were reversed by captopril pretreatment in vitro and in vivo. RA notably inhibited the infiltration into the lungs of neutrophils and monocytes with increased amounts of GPX4 and ACE2 proteins, lung function improvement, and decreased inflammatory cytokines levels and ER stress in LPS-induced ARDS in mice. Molecular docking showed RA was able to interact with ACE and ACE2. Moreover, combined with different pharmacological inhibitors to block ACE and ferroptosis, RA still significantly inhibited inflammatory cytokines Interleukin-1ß (IL-1ß), tumor necrosis factor-α (TNF-α), and C-X-C motif chemokine 2 (CXCL2) levels, as well as improved lung function, and enhanced GPX4 expression. Particularly, the anti-ferroptosis effect of RA in LPS-induced septic ARDS is RAS-dependent.