Objective: To investigate the role of astrocyte overactivation in hippocampal adult-born neurons (ABNs) in a mouse model of sepsis-associated encephalopathy (SAE).
Methods: Fifty SPF-grade male C57BL/6 mice, aged 8-10 weeks, weighing 22-26 g, were selected. The mice were randomly divided into four groups using a random number table: sham operation + vehicle group (group SV), sham operation + astrocyte ablation agent L-α-aminoadipic acid (L-AAA) group (group SL), CLP + vehicle group (group CV), and CLP + L-AAA group (group CL), 10 mice in each group. The SAE mouse model was established using cecal ligation and puncture (CLP). Mice underwent lateral ventricular cannulation 14 days before surgery. L-AAA 20 μg/μl was slowly infused into the lateral ventricle daily for 5 consecutive days using a microinjection pump via an injection needle inserted through the cannula in groups SL and CL, while an equal volume of vehicle 4 μl was infused at the same time in groups SV and CV. The total movement distance was measured using the open field test, exploration time was recorded in the novel object recognition test to calculate the discrimination index, and the number of alternations and arm entries were recorded in the Y-maze test to calculate the spontaneous alternation rate. Western blot was used to detect the protein levels of glial fibrillary acidic protein (GFAP), complement C3, doublecortin (DCX), TNF-α, IL-6, and IL-1β in the hippocampus. Immunofluorescence staining was performed to detect GFAP and C3 co-localization, GFAP-positive cell count, and DCX-positive cell count in the hippocampal dentate gyrus (DG) region.
Results: Compared with groups SV and SL, group CV showed significantly decreased discrimination index, spontaneous alternation rate, and DCX protein content in the hippocampus, along with significantly increased protein levels of GFAP, C3, TNF-α, IL-6, and IL-1β. Additionally, the numbers of GFAP and C3 co-localized cells, GFAP-positive cells, and DCX-positive cells in the hippocampal DG region were significantly reduced (P < 0.05). Compared with group CV, group CL exhibited significantly increased discrimination index, spontaneous alternation rate, and DCX protein content, as well as significantly decreased protein levels of GFAP, C3, TNF-α, IL-6, and IL-1β. Moreover, the numbers of GFAP and C3 co-localized cells, GFAP-positive cells, and DCX-positive cells in the hippocampal DG region were significantly increased (P < 0.05).
Conclusion: In SAE mice induced by CLP, activation of A1-type astrocytes in the hippocampal DG region promotes the release of pro-inflammatory cytokines, leading to impaired development of ABNs in the hippocampal DG and resulting in cognitive dysfunction. Early administration of the astrocyte ablation agent L-AAA can alleviate cognitive impairment in SAE mice. |
