Sea buckthorn extract mitigates chronic obstructive pulmonary disease by suppression of ferroptosis via scavenging...

Sea buckthorn (Hippophae rhamnoides), a traditional Tibetan medicinal herb, exhibits protective effects against cardiovascular and respiratory diseases. Although Sea buckthorn extract (SBE) has been confirmed to alleviate airway inflammation in mice, its therapeutic effect and underlying mechanism on chronic obstructive pulmonary disease (COPD) requires further clarification.

To elucidate the alleviative effect and molecular mechanism of SBE on lipopolysaccharides (LPS)/porcine pancreatic elastase (PPE)-induced COPD by blocking ferroptosis.

The anti-ferroptotic effects of SBE were evaluated in human BEAS-2B bronchial epithelial cells using CCK8, RT-qPCR, western blotting, and transmission electron microscopy. Transwell was employed to detect chemotaxis of neutrophils. COPD model was induced by intranasally administration of LPS/PPE in mice and measured by alterations of histopathology, inflammation, and ferroptosis. RNA-sequencing, western blotting, antioxidant examination, flow cytometry, DARTS, CETSA, and molecular docking were then used to investigate its anti-ferroptotic mechanisms.

In vitro, SBE not only suppressed erastin- or RSL3-induced ferroptosis by suppressing lipid peroxides (LPOs) production and glutathione (GSH) depletion, but also suppressed ferroptosis-induced chemotactic migration of neutrophils via reducing mRNA expression of chemokines. In vivo, SBE ameliorated LPS/PPE-induced COPD phenotypes, and inhibited the generation of LPOs, cytokines, and chemokines. RNA-sequencing showed that p53 pathway and mitogen-activated protein kinases (MAPK) pathway were implicated in SBE-mediated anti-ferroptotic action. SBE repressed erastin- or LPS/PPE-induced overactivation of p53 and MAPK pathway, thereby decreasing expression of diamine acetyltransferase 1 (SAT1) and arachidonate 15-lipoxygenase (ALOX15), and increasing expression of glutathione peroxidase 4 (GPX4) and solute carrier family 7 member 11 (SLC7A11). Mechanistically, erastin-induced elevation of reactive oxygen species (ROS) was reduced by SBE through directly scavenging free radicals, thereby contributing to its inhibition of p53 and MAPK pathways. CETSA, DARTS, and molecular docking further showed that ROS-generating enzyme nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4) may be the target of SBE. Overexpression of NOX4 partially impaired the anti-ferroptotic activity of SBE.

Our results demonstrated that SBE mitigated COPD by suppressing p53 and MAPK pro-ferroptosis pathways via directly scavenging ROS and blocking NOX4. These findings also supported the clinical application of Sea buckthorn in COPD therapy.