The Effect of Toll‐Like Receptor‐4 on the Behavioral Impairment in Aβ1–42 Induced AD Mouse Model

Abstract

ObjectiveTo investigate the role of toll like receptor 4 (TLR4) in the cognition impairment in β‐amyloid fragment 1–42 (Aβ1–42) induced Alzheimer's disease (AD) mouse model.MethodsTwenty four TLR4 gene knockout mice (TLR4KO, male, body weight: 25–30g) and 24 wild type mice (WT, male, body weight: 25–30g) were randomly assigned into 4 groups: Normal saline control (WT.NS, wild type mice were injected 1ul normal saline into bilateral hippocampus), AD model group (WT. Aβ, wild type mice were injected with 1ul Aβ1–42 (5ug/ul) into bilateral hippocampus), TLR4KO‐normal saline control (TLR4KO.NS, TLR4KO mice were injected with 1ul normal saline into bilateral hippocampus), and TLR4KO Aβ group (TLR4KO.Aβ, TLR4KO mice were injected with 1ul Aβ1–42 (5ug/ul) into bilateral hippocampus). Seven days after injection, the learning and memorial functions were tested using Morris Water Maze (MWM). The repeated measures analysis of variance was used to analyze navigation test, the one‐way ANOVA and LSD post‐hoc comparisons were used for probe trial analyses. HE staining was performed.; and the expression of Bcl‐2 and Caspase‐3 was assayed by Western blot, the results was analyzed by one‐way ANOVA.Results1. Compared with normal saline control groups(WT.NS), the AD groups (WT. Aβ) showed a longer escape latency (P<0.05), increased percentage of time in outer annulus (P<0.05) in the place navigation test, reduced percentage of time in the platform quadrant and decreasing times of traversing platform (P<0.05) in the spatial probe test. Compared with AD model groups(WT.Aβ), the escape latency and the percentage of time in outer annulus were decreased in TLR4KOAβ groups (P<0.05), and the percentage of time in the platform quadrant and the times of traversing platform were increased (P<0.05). There was no significant difference of swimming speed amonge each group (P>0.05). 2. Hematoxylin eosin staining showed that compared with normal saline control groups, the neurons in AD groups distribute loosely and irregularly, and more dead neurons were observed. TLR4KOAβ groups showed a attenuated damage in hippocamus compared with the AD groups. 3. The results of western blots suggested that compared with control groups, the expression of Bcl‐2 in AD groups were significant reduced (P<0.05) and the expression of Caspase‐3 were increased (P<0.05); the expression of Bcl‐2 in the TLR4KO Aβ groups were increased (P<0.05) and the level of Caspase‐3 was reduced (P<0.05) when compared with AD groups.Conclusion1. Injection of 5ug Aβ1–42 into bilateral hippocampus can obvious impaire the learning and memorial functions and induced histological damage in hippocampus of mice, which provides an effective method for establishing mouse model of AD; 2. TLR4 knockout can attenuate cognitive impairment and tissue damage induced by hippocampal injection of Aβ1–42 in the AD model, which may be partly achieved by reducing apoptosis.Support or Funding InformationThis work was supported by China National Nature Scientific Foundation (81571469 and 81271268)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.