Characterizing oxidative stress induced by Aβ oligomers and the protective role of carnosine in primary mixed glia cultures

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by cognitive decline and memory loss. A critical aspect of AD pathology is represented by oxidative stress, which significantly contributes to neuronal damage and death. Microglia and astrocytes, the primary glial cells in the brain, are crucial for managing oxidative stress and supporting neuronal function. Carnosine is an endogenous dipeptide possessing a multimodal mechanism of action that includes antioxidant, anti-inflammatory, and anti-aggregant activities. The present study investigated the effects of Aβ1-42 oligomers (oAβ), small aggregates associated with the neurodegeneration observed in AD, on primary rat mixed glia cultures composed of both microglia and astrocytes, focusing on the ability of these detrimental species to induce oxidative stress. We assessed intracellular reactive oxygen species (ROS) and nitric oxide (NO) levels as markers of oxidative stress. Exposure to oAβ significantly elevated both ROS and NO intracellular levels compared to control cells. However, this effect was completely inhibited by the pre-treatment of mixed cultures with carnosine, resulting in ROS and NO levels similar to those observed in untreated (control) cells. Single-cell analysis of cellular responses to oAβ revealed heterogeneous ROS production, resulting in two distinct clusters of cells, one of which was very responsive to the treatment. The presence of carnosine counteracted the overproduction of ROS, also leading to a single, homogeneous cluster, similar to that observed in the case of control cells. Interestingly, unlike ROS response, single-cell analysis of NO production did not show any distinct clusters. Overall, our findings demonstrated the ability of carnosine to mitigate Aβ-induced oxidative stress in mixed glia cells, by rescuing ROS and NO intracellular levels, as well as to normalize the heterogeneous response to the treatment measured in terms of clusters' formation. The present study suggests a therapeutic potential of carnosine in pathologies characterized by oxidative stress including AD.