Fig. 4: Downregulation of LCN2 alleviated sepsis-related synaptic and cognitive impairments.

A Experimental design sketch. C57 mice were randomly divided into 3 groups. In the control group, mice were bilaterally injected with AAV-Sh-vector in the DG region and injected intraperitoneally with normal saline. In the model (Mod) group, mice were bilaterally injected with AAV-Sh-vector in the DG region and injected intraperitoneally with LPS. In the preventive (Pre) group, mice were bilaterally injected with AAV-Sh-LCN2 in the DG region and received intraperitoneal injections of LPS. Following the treatment, behavioral, electrophysiological, and biochemical tests were performed. B Fluorescence microscopy confirmed GFP expression in the hippocampus 4 weeks after injection. C Brain tissues (hippocampus) were homogenized, and LCN2 protein level was detected by immunoblotting. D Quantitative analysis of LCN2 expression was conducted, (n = 4). E The open-field test measured the total distance covered in the three groups, (n = 8–12). F The novel object recognition test measured the preference, (n = 8–12). Y-mase test: the duration G and crossing number H in the novel arm were measured, (n = 8–12). I Hippocampal DG-CA1 Long-Term Potentiation was recorded using the MED64 system. J The normalized mean slope of fEPSPs was recorded in hippocampal slices, (n = 5–6 slices from 5 to 6 mice). K Brain tissues (hippocampus) from the three groups were homogenized and synaptic associated protein were detected by immunoblotting. Actin was used as a loading control. L Quantitative analysis of the PSD95, SYT, (n = 4). M Representative dendrite from Golgi-impregnated hippocampal neurons, (Scale bar: 200 μm). Sholl analysis (Scale bar: 50 μm), (n = 10) and averaged spine density of CA1 region, (Scale bar: 2 μm), (n = 30) (N). Sholl analysis (Scale bar: 50 μm), (n = 10), and averaged spine density of CA3 region, (Scale bar: 2 μm), (n = 30) (O). Sholl analysis (Scale bar: 50 μm), (n = 10) and averaged spine density of DG region (Scale bar: 2 μm), (n = 30) (P). Data are presented as Mean ± SEM, one-way or two-way ANOVA was used for statistical analysis. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001, versus LPS group.