The Upregulation of NDUFB3 Is Implicated in Mitochondrial Dysfunction and Neuronal Apoptosis in Ischemic Stroke

Background: Mitochondrial dysfunction is a central event in the pathogenesis of ischemic stroke. The roles of specific mitochondrial complex subunits, such as NDUFA4 and NDUFB3, in cerebral ischemia–reperfusion injury remain poorly defined. This study aims to investigate the dynamic expressions and functional impact of NDUFA4 and NDUFB3 in ischemic stroke. Methods: A transient middle cerebral artery occlusion (MCAO) model was established in male C57BL/6J mice. Label-free quantitative proteomics and Western blotting were employed to analyze protein expression in the ischemic penumbra. Highly differentiated PC12 cells were subjected to oxygen-glucose deprivation/reperfusion (OGD/R) or glutamate excitotoxicity to mimic ischemic injury in vitro. The functional consequences of NDUFB3 knockdown and overexpression were assessed by measuring ATP levels, reactive oxygen species (ROS), mitochondrial membrane potential (ΔΨm), and apoptosis. The involvement of the JNK-mediated mitochondrial apoptotic pathway was also examined. Results: Proteomic analysis revealed a significant upregulation of NDUFA4 and NDUFB3 in the ischemic penumbra of MCAO mice, as verified by western blot. In highly differentiated PC12 cells, both OGD/R and glutamate exposure induced a time-dependent increase in these proteins in mitochondrial fractions. Functional studies demonstrated that NDUFB3 knockdown significantly rescued OGD/R-induced mitochondrial dysfunction, as indicated by restored ATP production, reduced ROS generation, and stabilized ΔΨm. Furthermore, NDUFB3 silencing attenuated apoptosis by inhibiting JNK phosphorylation and decreasing BAX levels. Conversely, overexpression of NDUFB3 alone was sufficient to induce mitochondrial abnormalities, including loss of ΔΨm and elevated oxidative stress in highly differentiated PC12 cells. Conclusions: Ischemic injury triggers the upregulation of mitochondrial complex subunits NDUFA4 and NDUFB3. While this may initially act as a compensatory response, our findings identify NDUFB3 as a critical mediator of ischemic stroke pathology, whose overexpression drives mitochondrial dysfunction and apoptosis. In contrast, the suppression of NDUFB3 provides protection against ischemic injury. Therefore, NDUFB3 may be a potential candidate therapeutic target for reducing mitochondrial damage in ischemic stroke, but this role requires further validation in additional experimental and translational models.