Chemogenetic emulation of intraneuronal oxidative stress affects synaptic plasticity

Abstract

Overproduction of reactive oxygen species (ROS) and oxidative cell damage are commonly associated with most brain pathologies [1, 2]. Dysregulation of redox homeostasis in the aging brain is thought to be responsible for impaired synaptic transmission and plasticity, leading to reduced neuronal computational capacity and learning and memory deficits. Studying the contribution of oxidative stress to the development of diseases, such as age-related dementia and Alzheimer’s disease, is complex due to the lack of methods for modeling isolated oxidative damage in individual cell types [3]. We introduce a chemogenetic approach utilizing D-amino acid oxidase (DAAO) from yeast to produce hydrogen peroxide intraneuronally, which is one of the most stable ROS [4]. H2O2 generation was evaluated in primary cultured neurons and acute mouse brain slices through the utilization of a genetically encoded fluorescent biosensor, HyPer7, to validate the methodology [5]. The changes in the fluorescence signal of HyPer7 after treating neurons that expressed DAAO with D-Norvaline (D-Nva), a substrate for DAAO, confirmed the targeted production of H2O2 through chemogenetics. Using electrophysiological recordings in acute brain slices, we demonstrated that intraneuronal oxidative stress induced by chemogenetics did not affect basal synaptic transmission and the probability of neurotransmitter release from presynaptic terminals. However, it diminished long-term potentiation (LTP) at the single-cell level. Astrocytes have the ability to metabolize d-amino acids, rendering the proposed approach ineffective in vivo experiments. Consequently, in vivo testing of the tool was necessary for validation. To achieve this, an optical setup for exciting and detecting the HyPer7 signal was developed and implanted into the mouse brain via optical fibers. By using this approach, we were able to demonstrate the generation of H2O2 in DAAO-expressing neurons in vivo, upon intraperitoneal administration of D-amino acids. The results demonstrate that using a DAAO-based chemogenetic tool, along with electrophysiological recordings, clarifies numerous unanswered queries regarding the part of ROS-dependent signaling in typical brain activities and the impact of oxidative stress on the development of cognitive aging and preliminary neurodegenerative stages. The suggested method is valuable for detecting initial indicators of neuronal oxidative stress. Additionally, it can be used for evaluating probable antioxidants that can effectively combat neuronal oxidative harm.