Investigation of Reactive Oxygen Species Management in Biological and Pathological Processes by Fluorescence Imaging

Neural damage caused by ischemia/stroke is initiated by excess reactive oxygen species (ROS). Different cell types and even same cell type, but in different regions in hippocampus are found to have differential susceptibility to ischemia/stroke. ROS levels have been found to be different in different cell types or neurons in different regions of hippocampus. However, the mechanism behind this scenario has not been fully understood.\ud We, for the first time, used a roGFP2 based GSH sensor to monitor the OGD-RP induced redox change of GSH system in mitochondria and cytoplasm from 3 different cell types (HeLa cell culture, pyramidal cells and astrocytes found in OHSC) in real-time. We observed that GSH in cytoplasm was insensitive to OGD-RP, while noticeable changes were found in mitochondria. Mitochondrial GSH get more reduced in OGD, but more oxidized in RP, and that the magnitude of change either in OGD or RP is larger in pyramidal cells than in astrocytes, not significant in HeLa cells. Heterogeneities in ROS production, antioxidant capacity of GSH and mitochondria membrane potential are responsible for the redox changes of GSH system under contrasting pathological conditions, different cellular compartments and various cell types. \ud In order to understand the differential susceptibility to OGD-RP in hippocampal CA1 and CA3, we study on ROS related critical molecules such NAD(P)H, H2O2 and GSH. During OGD-RP, NAD(P)H consumption is higher in CA3 because it is used more rapidly as reducing equivalents to maintain larger antioxidant pool in this subfield. Mitochondrial H2O2 and the oxidation degree of mitochondrial GSH are both lower in CA3 during OGD-RP. This can be ascribed to larger Trx2 pool in CA3 since Trx2 can scavenge H2O2 more fast and efficient than GSH system and is able to maintain lower H2O2 and GSH at lower oxidation degree