ROS from menadione induces astrocytic damage: protective effects of apocynin

Abstract only availableOxidative stress is a core cause of neurodegenerative diseases such as Alzheimer's disease. When cells are under oxidative stress, they will produce a high amount of reactive oxygen species (ROS). ROS are small and highly reactive and include compounds such as oxygen ions, free radicals, and peroxides. Understanding what triggers oxidative stress and how to ameliorate its damaging effects is a crucial step in discovering a cure for Alzheimer's disease. Menadione, a vitamin precursor of K2, is an oxidative compound that is capable of delivering ROS to the cells. Apocynin, a natural organic compound that has been isolated from Picrorhiza curroa grown in the Himalayan Mountains, is an inhibitor of NADPH oxidase, an enzyme for ROS production in cells. In this experiment, we studied whether apocynin may neutralize the effects of menadione using an immortalized astrocyte cell line DITNC. Astrocytes are glial cells that play a crucial role in the brain by providing necessary nutrient to surrounding neurons. We had three sample groups and treated each group with different drugs. The first group was the control, the second group was treated with menadione, and the third group was treated with both menadione and apocynin. After treating the cells, we recorded morphological changes of the cells by taking pictures of each sample group at three different time intervals (30 min, 1 and 2 hours). In addition to the morphological evidence, we also did a MTT assay to assess cell viability and later a data analysis based on the result from the MTT test. MTT assay measures mitochondrial activity and thus indirectly measures cell viability. Both morphological data and MTT analysis showed menadione caused DITNC cell damage with decreased mitochondrial activity. When cells are treated with menadione, they formed processes, shrink, and then round up. We also found apocynin protects against the oxidative damage caused by menadione to a certain extent. Since apocynin is an inhibitor of NADPH oxidase, this also indicates oxidative stress is generated by NADPH oxidase, suggesting apocynin may be a potential means to treat Alzheimer's disease.Alzheimer disease program project grant 2P01 AG018357 to G. Su

Amyloid-beta toxicity in neurons and potential botanical compounds for prevention of Alzheimer's disease

Title from PDF of title page (University of Missouri--Columbia, viewed on October 24, 2012).The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Dissertation advisor: Dr. Grace Y. SunIncludes bibliographical references.Vita.Ph. D. University of Missouri-Columbia 2011."May 2011"[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Alzheimer's disease (AD) is characterized by a progressive decline in memory and cognitive function together with increased oxidative stress in the brain. Although there is increasing evidence indicating the involvement of oligomeric amyloid-beta peptides (A[beta]) in mediating oxidative damage to neurons, the mechanism(s) about how these peptides alter neuronal functions remains elusive. Recent studies from our laboratory have demonstrated the effects of N-methyl-D-aspartic acid (NMDA) and oligomeric A[beta] to produce reactive oxygen species (ROS) from NADPH oxidase, and stimulate downstream signaling pathways leading to activation of mitogen-activated protein kinases (MAPKs) and cytosolic phospholipase A2 (cPLA2) in neurons. In this study, we investigated the effects of prolonged exposure of neurons to oligomeric A[beta] and their response to NMDA-induced Ca2+ influx, release of arachidonic acid (AA), mitochondrial dysfunction, and ROS production. Results demonstrated that prolonged exposure of neurons to A[beta] caused mitochondrial dysfunction, a decrease in NMDA-induced Ca2+ influx and AA release, and an increase in levels of ROS. Neuronal impairments induced by A[beta] could be blocked by gp91ds-tat, a specific inhibitor for NADPH oxidase as well as other ROS scavengers, including the botanical phenolic compound, epigallochatechin-gallate (EGCG) from green tea. These studies thus identified the involvement of NADPH oxidase as a source of ROS in the cytotoxic effects of A[beta]. These results also provide a neuron model for identifying novel botanical antioxidants to protect against neurotoxic effects of A[beta] oligomers