Objective: Exposure to PM2.5 will increase the risk of respiratory disease and increase the burden of social health care. Astragaloside Ⅳ (Ast-IV) is one of the main biologically active substances form Chinese herb Astragalus membranaceus, which owns various pharmacological effects. Ferroptosis is a novel form of cell death characterized by accumulation of iron-dependent lipid reactive oxygen species (ROS). It is not clear whether there are typical features of ferroptosis in PM2.5-induced lung injury. This study investigates whether PM2.5-induced lung injury in mice has a special form of ferroptosis and the specific protective mechanism of Ast-IV.

Subjects and methods: Forty-two male C57BL/6J mice were randomly divided into six groups (n = 7 per group): NS group (normal saline), Ast group (Ast-IV 100 mg/kg), PM2.5 group, Ast-L group (Ast-IV 50 mg/kg + PM2.5), Ast-H group (Ast-IV 100 mg/kg + PM2.5) and Era group (Ast-IV 100 mg/kg + erastin 20 mg/kg + PM2.5). Mice were pre-treated with Ast-IV intraperitoneally for three days. Then, PM2.5 (7.5 mg/kg) was given by non-invasive tracheal instillation to induce lung injury. The ferroptosis' agonist erastin was used to verify the mechanism of Ast-IV anti-ferroptosis. 12 h after PM2.5 stimulation, the mice were euthanized. Bronchoalveolar lavage fluid (BALF) and serum were collected for oxidative stress and cytokine determination. Lung tissues were collected for glutathione (GSH), tissue iron content, histology, immunofluorescence, transmission electron microscopy, and western blot analysis.

Results: Ast-IV reduced the lung wet-dry ratio and the levels of interleukin 6 (IL-6), tumor necrosis factor-α (TNF-α) and interleukin 1β (IL-1β) in serum. Ast-IV could also improve the oxidative stress level in BALF, restore the GSH level in the lung tissue, and reduce the iron content in the lung tissue. Western blot outcomes revealed that Ast-IV regulated the ferroptosis signaling pathway via the Nrf2/SLC7A11/GPX4 axis to protect PM2.5-mediated lung injury.

Conclusion: The protective effect of Ast-IV on PM2.5-induced lung injury in mice might be related to the inhibition of ferroptosis in lung tissue. Anti-ferroptosis might be a new mechanism of Ast-IV on PM2.5-induced lung injury.