378 - Overexpression of Glutaredoxin Averts F-Actin Loss in Spines of Primary Cortical Neurons Derived from Mouse Model of Alzheimer's Disease

Abstract

Oxidative stress is known to be one of the major contributors towards the pathogenesis of Alzheimer’s disease (AD) potentially leading to amyloid plaques, neurofibrillary tangles and loss of dendritic spine morphology. As a marker for ongoing oxidative stress, we observed increased levels of reactive oxygen species (ROS) in primary cortical neurons from APPSwe/PS1ΔE9 (APP/PS1) transgenic mouse model of AD, compared to wild type littermates. Thiol oxidation and protein glutathionylation are important targets during oxidative stress, resulting in perturbation of cellular thiol homeostasis. Glutaredoxins and other thiol disuflide oxidoreductases are important enzymes involved in reversing protein thiol oxidation in the brain. We hypothesized that overexpressing Grx1 (glutaredoxin) may partially reverse the adverse effects of oxidative stress in AD neurons. We overexpressed human glutaredoxin using AAV6 virus and confirmed overexpression of glutaredoxin using biochemical and immunostaining methods. Actin, an important neuronal cytoskeletal filament, is important for maintenance of spine morphology and function. It is also a target of cellular oxidation undergoing gluathionylation, leading to its conversion from the functional fibrillar form (F-actin) to the globular (G-actin) form. Other studies from our laboratory have shown increased actin oxidation in early stages of AD-related pathology leading to synaptic dysfunction using a combination of cellular, in vivo and post-mortem human brain samples. We also observed loss of F-actin in APP/PS1 neurons compared to their wild-type littermates, as indicated by reduced phalloidin staining. Importantly, overexpression of Grx1 reversed this F-actin loss, and preserved the F-actin microarchitecture in spines. Our results suggest that thiol oxidation events, such as protein glutathionylation including that of actin, play an important role in the synaptic structural and functional deficits seen in AD.