AS-IV Attenuates Oxidative Stress-Induced Apoptosis in Zebrafish via Modulation of the AKT/NRF2/HO-1/Caspase-3 Signaling Axis

As the primary active component of <i>Astragalus membranaceus</i>, Astragaloside IV (AS-IV) is widely recognized in pharmacological research for its multifaceted therapeutic potential, particularly its antioxidative, immunostimulatory, and cardioprotective properties. Oxidative stress is an important mechanism in the induction of many diseases. The present study investigates the antioxidative mechanism of Astragaloside IV in zebrafish, using menaquinone exposure to induce oxidative stress conditions. The findings revealed that AS-IV effectively attenuated oxidative stress-induced mortality and morphological abnormalities in zebrafish. AS-IV exhibited a concentration-dependent protective effect against developmental abnormalities, with progressive reduction in pericardial effusion, body curvature, and growth retardation observed at higher doses. Moreover, AS-IV treatment not only effectively reduced reactive oxygen species (ROS) accumulation and attenuated oxidative DNA damage but also significantly decreased apoptosis in the cardiac region of zebrafish embryos under oxidative stress conditions. Western blot analysis revealed that AS-IV treatment significantly reduced the protein levels of both Cleaved Caspase-3 and γ-H2AX, indicating its ability to inhibit DNA damage-induced apoptosis. AS-IV mediates its antioxidant defense mechanisms through the activation of the nuclear factor erythroid 2-related factor 2 (NRF2) signaling pathway, inducing the significant upregulation of cytoprotective enzymes. This molecular mechanism underlies the observed phenotypic improvements in oxidative stress-related damage. Upstream analysis demonstrated that AS-IV activates NRF2 primarily through protein kinase B (AKT/PKB) pathway modulation, independent of KEAP1 regulation. Comprehensive mechanistic analysis reveals that Astragaloside IV mitigates oxidative stress-induced apoptosis in zebrafish through coordinated regulation of the AKT/NRF2/HO-1/Caspase-3 signaling axis.