CYC1 Silencing Exacerbates Hypoxia-Induced Neuronal Death via Mitochondrial Apoptosis under Hyperglycemia

Cytochrome c1 (CYC1) is a subunit of mitochondrial complex III, which is known to play a key role in ischemic brain injury. However, the functional role of CYC1 in hyperglycemic cerebral ischemia/reperfusion remains unclear. In this study, we investigated the effect of CYC1 gene knockdown in an in vitro model mimicking hyperglycemic ischemia/reperfusion. HT22 cells with normal CYC1 expression (wild-type) and CYC1-knockdown cells were exposed to 4 h of hypoxia under high-glucose and acidic conditions, followed by reoxygenation. Assessments were conducted at 0, 6, and 12 h post-reoxygenation. Cell viability (CCK-8), cell injury (LDH release), ROS production (DHE probe), mitochondrial membrane potential (JC-1 probe), and apoptosis (TUNEL staining) were evaluated. CYC1 knockdown reduced cell viability, increased LDH release and ROS production, decreased mitochondrial membrane potential, and upregulated expression of Cyt c, cleaved caspase-3, and AIF, indicative of activation of the mitochondrial apoptotic pathway. These results indicate that CYC1 deficiency exacerbates hippocampal neuronal injury under hypoxic, high-glucose, and acidic conditions mimicking diabetic cerebral ischemia.