Elevated Glucose Levels Increase Oxidative Stress in Human Cerebral Microvascular Endothelial Cells

Abstract

Although glucose is the primary fuel source for cerebral metabolism and function, chronic exposure to high glucose levels impairs cerebral endothelial cell function and increases the risk of cerebrovascular accidents (CVA). Indeed, hyperglycemia is linked to an increased risk and prevalence of ischemic stroke, primarily attributed to the detrimental impact of glucose on cerebral endothelial cell function. The direct and indirect effects of glucose on brain endothelial cells are complex and not well understood. It is known that hyperglycemia can induce a profound pro-oxidative state with deleterious effects on peripheral vascular function resulting in pathologic outcome. The experimental aim of this study was to determine, in vitro, the effect of elevated glucose concentrations on cerebral endothelial cell oxidative stress. Human cerebral microvascular endothelial cells (hCMECs) were cultured (3rd passage) and incubated with culture media containing 5 mM D-glucose (normal glucose condition [NG]), 6.5 mM glucose (concentration representative of impaired fasting glucose [IFG]), and 8 mM (concentration representative of type 2 diabetes [T2D]) for 3 hours. Cells were harvested and intracellular reactive oxygen species (ROS) production was determined using CellROX Deep Red Reagent and expression of key anti-oxidant defense proteins, superoxide dismutase 1 (SOD-1) and catalase, were determined by capillary electrophoresis immunoassay. In separate experiments, the effect of each glucose condition was determined in the presence of the ROS scavenger, vitamin C (200 μmol). Cells treated with glucose concentration representing IFG (137+8 %) and T2D (162+12%) significantly increased intracellular ROS compared with NG (98+3 %). Concordantly, expression of SOD-1 and catalase were significantly higher in hCMECs treated with glucose concentration representing IFG (190.2+17.8 AU; 134.7+15.4 AU, respectively) and T2D (186.7+19.6 AU; 137.2+17.5 AU, respectively) compared with NG (24.4+1.8 AU; 65.6+4.3 AU, respectively). Pretreatment of cells with vitamin C prevented the increase in ROS in both the IFG and T2D conditions. Of note, there were no significant differences in ROS or the expression of SOD-1 and catalase in hCMECs between the IFG and T2D glucose conditions. In conclusion, glucose concentrations associated with IFG and T2D markedly increased ROS in hCMECs. In addition, there was a compensatory increase in SOD-1 and catalase to counteract the increase in cellular oxidative burden. Similar effects between the IFG and T2D glucose conditions on the oxidative milieu of hCMECs is consistent with the similar clinical cerebrovascular risk burden between these pathologic conditions. Glucose-induced increased oxidative stress in cerebral endothelial cells may contribute to the increased risk of CVA, such as ischemic stroke, associated with IFG and T2D. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.