Age-Related and Region-Specific Morphological and Molecular Alterations of Astrocytes and Microglia Following Chronic Oxidative Stress in Male Wistar Rats

Aging is associated with chronic pro-inflammatory background and increased risk of susceptibility to oxidative stress and neurodegenerative processes. However, age-dependent morphological and molecular changes in glial cells under chronic oxidative stress remain insufficiently characterized. This study aimed to investigate age- and region-specific alterations in astrocytes and microglia in the hippocampus and the entorhinal cortex (EntC) of adult (4–6 months) and old (22–24 months) male Wistar rats following chronic AlCl3 administration (100 mg/kg/day for 60 days). Spatial learning and memory were assessed using the Morris water maze. GFAP+ astrocytes and Iba1+ microglia were evaluated by immunohistochemistry and morphometry. Hippocampal 4-HNE and pTau (Ser404) were assessed by ELISA and Western blotting, respectively. Hippocampal expression of Tnf, Tgfb, Mmp9, Bdnf, Ntrk2, and Gpx4 was evaluated by RT-qPCR, while serum MMP-9 and HSP-70 concentrations were measured by ELISA. Aging was associated with increased glial cell size in both brain regions, elevated hippocampal Tnf expression, decreased Tgfb and Ntrk2 expression, and increased serum MMP-9 and HSP-70 serum concentrations. In adult rats, AlCl3 exposure was accompanied by changes in astrocytic morphology and increased Iba1+ cell density in the EntC, whereas molecular compensatory mechanisms remained preserved in the hippocampus. Only old AlCl3-treated rats demonstrated reduced success in locating the former platform position in the Morris water maze and significantly elevated hippocampal 4-HNE levels, consistent with increased lipid peroxidation. Although hippocampal pTau (Ser404) immunoreactivity showed an age-related increase, no statistically significant effect of AlCl3 exposure or age + AlCl3 was detected. In this group, AlCl3 exposure was associated with increased Iba1+ cell density in both regions, hypertrophic astrocytic morphology in the hippocampus, and reduced astrocytic area with fragmented processes in the EntC. These changes coincided with decreased hippocampal Bdnf and Gpx4 expression, as well as co-existence of reduced serum MMP-9 and HSP-70 concentrations. Overall, these findings demonstrate that aging influences region-specific glial morphological alterations and associated molecular responses to chronic AlCl3-induced oxidative stress. This model demonstrated a translational approach to provide insights regarding mechanisms of age-related neurodegeneration.