The protective role of Astragaloside IV in adriamycin-induced renal injury: A focus on macrophage polarization and PPARγ activation

Astragali Radix (AR), a homologous of medicine and food, has been extensively recorded to possess a nephroprotective impact on individuals suffering from chronic kidney disease (CKD). Astragaloside IV (ASIV) is one of the prominent bioactive constituents derived from AR. This study aimed to investigate how ASIV promotes M2 polarization of macrophages and whether this contributes to the protection of podocytes from injury, using a combination of lipidomics and molecular biology techniques.The effect of ASIV on adriamycin (ADR)-induced renal injury in rats was evaluated in vivo, with a particular emphasis on elucidating the potential involvement of macrophages. The M1 polarization model of RAW264.7 cells induced by ADR was established in vitro. The impact of ASIV on ADR-induced macrophage polarization was comprehensively assessed by measuring the expression levels of M1 and M2 macrophage marker proteins, along with their associated mRNA profiles. Flow cytometry was employed to analyze surface marker expression, while Western blot (WB) was used to quantify protein levels, and real-time quantitative PCR (qPCR) allowed for the measurement of gene expression. Notably, we found that the macrophage supernatant intervened by ASIV was found to have a protective effect against podocyte injury, which was evaluated through cell adhesion and apoptosis assays. Innovatively, we explored the mechanism by which ASIV affects macrophage polarization from the perspective of lipid metabolism, using lipidomics methods. During this process, the role of peroxisome proliferator-activated receptor gamma (PPARγ) in macrophage polarization caught our attention. This receptor is closely associated with lipid metabolites, as confirmed by molecular docking. ASIV has been shown to effectively ameliorate kidney injury, with macrophages playing a pivotal role in renal podocyte repair process. The protein and mRNA expressions of ARG-1, CD206 and IL-10, M2 macrophage markers, was increased by ASIV and M2 macrophages polarization was promoted by ASIV (P < 0.05). In addition, it was observed that the supernatant of macrophages intervened by ASIV exerts a protective effect on podocyte injury, which was confirmed through podocyte adhesion assays and cell apoptosis experiments. This study suggests that ASIV enhances the M2 polarization of macrophages, and the supernatant from these polarized macrophages has a protective effect on podocytes. From the perspective of lipid metabolism, the underlying mechanism of this effect may involve the modulation of sphingolipids, arachidonic acid, glycerophospholipids, and other lipid metabolites, which activate the receptor PPARγ, thereby exerting protective effects on podocytes.