Paeoniflorin Attenuates Radiation-Induced Brain Injury Associated with Modulation of Microglial Polarization and ERK/MAPK Signaling

Abstract Background: Radiation-induced brain injury (RIBI) is a common side effect of cranial radiotherapy that severely impairs patients’ neurological function and quality of life. Currently, effective and safe remedies for RIBI remain limited. Paeoniflorin (PF), a key component of total glucosides of paeony (TGP) extracted from the root of Paeonia lactiflora, is a traditional Chinese herbal compound with well-documented anti-inflammatory, antioxidant, and neuroprotective benefits. Our prior research demonstrated that TGP alleviates RIBI; however, its deeper protective mechanisms are still unknown. Purpose: The purpose of this study was to investigate the protective mechanisms of TGP against RIBI, focusing on the effects of PF on microglial polarization. Methods: In vivo, we assessed the effects of TGP on microglial polarization using immunofluorescence colocalization analysis. In vitro, we evaluated the effects of PF on microglial polarization through CCK-8, qRT-PCR, flow cytometry, Western blot, and ELISA. Additionally, we utilized network pharmacology, molecular docking, and molecular dynamics simulations, together with qRT-PCR and Western blotting, to investigate the key pathway molecules involved in PF’s modulation of microglial polarization. Results: In vivo, TGP attenuated radiation-induced alterations in microglial polarization by decreasing the expression of M1-associated markers and increasing the expression of M2-associated markers. Consistently, PF modulated radiation-induced BV2 cell polarization by decreasing the level of M1-associated marker expression and increasing the level of M2-associated marker expression. Mechanistic analyses suggest that ERK signaling may be involved in the regulation of microglial polarization induced by the PF. Conclusion: TGP and its major bioactive component, PF, may attenuate RIBI by modulating microglial polarization, with the ERK signaling pathway potentially involved in this process, supporting the potential of PF as a candidate strategy for RIBI.