Astragalus polysaccharide as a protective agent against peritoneal dialysis-associated peritoneal injury: Role of the Nrf2/SLC7A11 axis in ferroptosis regulation.

Astragalus polysaccharide (APS) is an active component in Astragalus membranaceus. It has immunoregulatory, antioxidant-stress, anti-inflammatory, and anti-fibrotic actions. APS has favorable therapeutic effects upon tissue injury, but its effects on peritoneal mesothelial cells (PMCs) ferroptosis-associated peritoneal injury have not been reported. In this study, high-glucose peritoneal dialysis solutions (PDS) were found to induce ferroptosis similarly to erastin, a well-established ferroptosis inducer. Different concentrations of APS were administered in vitro and in vivo, with ferrostatin-1 employed as a positive control to validate ferroptosis inhibition. Firstly, high levels of Fe2+, increased reactive oxygen species, lipid peroxide and malondialdehyde, as well as a reduction in glutathione levels, were measured in PMCs from the erastin- and PDS-treated groups. Then, a reduction in mitochondrial volume, shrinkage of mitochondrial membranes, and a decreased number of mitochondrial cristae were observed by transmission electron microscopy, and the mesothelial-mesenchymal transition of PMCs was assessed by Western blot and reverse transcription quantitative real-time PCR in the erastin- and PDS-treated groups. APS treatment could partially reverse these above changes induced by PDS and erastin in a dose-dependent manner. Furthermore, in vivo results also confirmed that PDS and sorafenib could induce peritoneal injury by inducing PMCs ferroptosis and APS treatment could improve peritoneal ferroptosis and fibrosis. Mechanistically, down-regulation of nuclear factor erythroid 2-related factor 2 (Nrf2), solute carrier family 7 member 11 (SLC7A11), and glutathione peroxidase 4 (GPX4) were detected in PDS, erastin-treated PMCs in vitro and sorafenib-treated peritoneal tissue in vivo. APS treatment could increase nuclear translocation of Nrf2 and activate the SLC7A11/GPX4 signaling pathway in vitro and in vivo, thereby rescuing peritoneal injury and ameliorating peritoneal fibrosis.