黄芪membranaceus-derived外泌体递送花萼素以协调Nrf2/SLC7A11/GPX4轴对抗帕金森病中的铁凋亡

【ETHNOPHARMACOLOGICAL RELEVANCE】Astragalus membranaceus (Fisch.) Bunge (Fabaceae) is documented in Shennong's Classic of Materia Medica to treat Qi deficiency-induced cerebral blood stasis and limb tremor resembling Parkinson's disease (PD). Its primary bioactive component, calycosin (CA), exerts anti-ferroptosis effects; however, its ability to cross the blood-brain barrier (BBB) is severely limited. Herbal-derived exosomes isolated from Astragalus membranaceus act as homologous natural nanocarriers to overcome this limitation; however, the anti-PD efficacy and nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent ferroptosis regulatory mechanism of Astragalus membranaceus-derived exosomes (AS-Exos) loaded with CA (AS-Exos-CA) remain unelucidated.

【AIM OF THE STUDY】To construct AS-Exos-CA, verify both its BBB-crossing capacity and neuroprotective effect on dopaminergic neurons, and investigate whether its anti-ferroptosis protection relies on the Nrf2/SLC7A11/GPX4 axis, to provide modern pharmacological evidence for the ethnopharmacological application of Astragalus membranaceus against PD.

【MATERIALS AND METHODS】AS-Exos were isolated by ultracentrifugation and characterized using NTA and TEM. HPLC was employed to screen the optimal CA-loading ratio for preparing AS-Exos-CA and measure its encapsulation efficiency. PKH26 and DiR fluorescence labeling were used to assess cellular uptake and BBB penetration of AS-Exos-CA in PC12 cells and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mice, respectively. Motor function, dopaminergic neuron survival, ferroptosis-related oxidative stress, iron metabolism and mitochondrial ultrastructure were assessed to evaluate the therapeutic effects of AS-Exos-CA in MPTP-induced PD mice. 1-methyl-4-phenylpyridinium ion (MPP+)-injured PC12 cells combined with the Nrf2-specific inhibitor ML385 were used to verify the Nrf2-dependent mechanism mediating AS-Exos-CA-derived protection.

【RESULTS】AS-Exos-CA displayed typical vesicle morphology, was efficiently taken up by PC12 cells, and significantly accumulated in mouse brain 12 h after intravenous injection. Compared with free CA and AS-Exos, AS-Exos-CA more effectively ameliorated motor deficits, rescued dopaminergic neurons, mitigated mitochondrial injury and iron deposition, restored glutathione (GSH), and lowered malondialdehyde (MDA) and reactive oxygen species (ROS) levels. AS-Exos-CA facilitated Nrf2 nuclear translocation and up-regulated the downstream expression of SLC7A11 and GPX4. ML385 abolished its in vitro anti-ferroptotic actions, verifying the essential role of Nrf2 signaling.

【CONCLUSION】AS-Exos serve as homologous herbal nanocarriers, enhancing CA penetration across the BBB for brain delivery. AS-Exos-CA exerts robust neuroprotection against PD largely by inhibiting neuronal ferroptosis via the Nrf2/SLC7A11/GPX4 pathway. This herbal exosome-based nanoformulation overcomes the biocompatibility limitations of synthetic nanomaterials and represents a promising disease-modifying strategy for PD, thereby advancing the modern investigation of Qi-tonifying herbal medicines in degenerative central nervous system (CNS) disorders.