Soy Isoflavones Protects Against Stroke by Inhibiting Keap1/NQO1/Nrf2/HO-1 Signaling Pathway: Network Pharmacology Analysis Combined with the Experimental Validation.

Objectives: Ischemic stroke is a severe neurological disorder with high morbidity, mortality, and disability rates, posing a substantial burden on patients, families, and healthcare systems. Soy isoflavone (SI), a naturally occurring phytoestrogen, has demonstrated promising neuroprotective effects. This study aimed to evaluate the anti-stroke efficacy of SI and elucidate its underlying mechanisms through integrated phytochemical profiling, network pharmacology, and both in vitro and in vivo experimental validation. Methods: Active constituents of SI were extracted via reflux and identified using liquid chromatography-mass spectrometry (LC-MS). Network pharmacology was employed to predict therapeutic targets and signaling pathways. The neuroprotective effects of SI were first assessed in PC12 cells subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) injury in vitro. For in vivo evaluation, transient cerebral ischemia-reperfusion injury was induced using the bilateral common carotid artery occlusion (BCCAO) model in adult male ICR rats (27.3 ± 1.8 g; 6-8 weeks old), obtained from the Shanghai Experimental Animal Center, Chinese Academy of Sciences. Forty-eight rats were randomly assigned into four groups (n = 12): sham, model (BCCAO), SI-treated (100 mg/kg, oral gavage for 5 days), and edaravone (EDA)-treated (10 mg/kg, i.p., positive control). All procedures were approved by the Institutional Animal Care and Use Committee of Changchun Normal University (Approval No. 2024003, 13 March 2024) and conducted in accordance with the NIH guidelines and ARRIVE 2.0 reporting standards. Results: In vitro, SI significantly enhanced PC12 cell viability from 57.23 ± 2.88% to 80.76 ± 4.43% following OGD/R. It also reduced intracellular Ca(2+) by 58.42%, lactate dehydrogenase (LDH) release by 37.67%, caspase-3 activity by 55.05%, and reactive oxygen species (ROS) levels by 74.13% (p < 0.05). A flow cytometry analysis revealed that OGD/R increased the apoptosis rate from 5.34% (control) to 30.85% (model group), which was significantly attenuated by SI treatment, especially in the 560 µg/mL group (20.00%), followed by the 140 and 280 µg/mL groups. In vivo, SI improved neurological scores from 8.3 ± 1.09 to 6.8 ± 1.68, reduced cerebral infarction volume by 18.49%, and alleviated brain edema by 10.42% (p < 0.05). SI also decreased malondialdehyde (MDA) and LDH levels by 31.15% and 39.46%, respectively, while increasing the activity of antioxidant enzymes: superoxide dismutase (SOD) by 11.70%, catalase (CAT) by 26.09%, and glutathione peroxidase (GSH-px) by 27.55% (p < 0.01). Scratch assay results showed that SI restored the impaired migratory ability of the OGD/R-treated PC12 cells, further supporting its role in cellular repair. A Western blot analysis demonstrated the upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and NAD(P)H:quinone oxidoreductase 1 (NQO1) and the downregulation of Kelch-like, ECH-associated protein 1 (Keap1) in the cerebral ischemia-reperfusion model. Conclusions: These findings indicate that soy isoflavone confers significant neuroprotective effects against cerebral ischemia-reperfusion injury by enhancing endogenous antioxidant defense mechanisms, reducing oxidative stress, inhibiting apoptosis, and promoting cell migration. The protective effects are likely mediated through the activation of the Nrf2/Keap1 signaling pathway, supporting the therapeutic potential of SI in ischemic stroke treatment.