Quetiapine attenuates glial activation and proinflammatory cytokines in APP/PS1 transgenic mice via inhibition of nuclear factor-κB pathway

Abstract

Background: In Alzheimer's disease, growing evidence has shown that uncontrolled glial activation and neuroinflammation may contribute independently to neurodegeneration. Antiinflammatory strategies might provide benefits for this devastating disease. The aims of the present study are to address the issue of whether glial activation and proinflammatory cytokine increases could be modulated by quetiapine in vivo and in vitro and to explore the underlying mechanism.

Methods: Four-month-old amyloid precursor protein (APP) and presenilin 1 (PS1) transgenic and nontransgenic mice were treated with quetiapine (5mg/kg/d) in drinking water for 8 months. Animal behaviors, total Aβ levels, and glial activation were evaluated by behavioral tests, enzyme-linked immunosorbent assay, immunohistochemistry, and Western blot accordingly. Inflammatory cytokines and the nuclear factor kappa B pathway were analyzed in vivo and in vitro.

Results: Quetiapine improves behavioral performance, marginally affects total Aβ40 and Aβ42 levels, attenuates glial activation, and reduces proinflammatory cytokines in APP/PS1 mice. Quetiapine suppresses Aβ1-42-induced activation of primary microglia by decresing proinflammatory cytokines. Quetiapine inhibits the activation of nuclear factor kappa B p65 pathway in both transgenic mice and primary microglia stimulated by Aβ1-42.

Conclusions: The antiinflammatory effects of quetiapine in Alzheimer's disease may be involved in the nuclear factor kappa B pathway. Quetiapine may be an efficacious and promising treatment for Alzheimer's disease targeting on neuroinflammation.

Keywords: NF-κB; astrocyte; microglia; neuroinflammation; quetiapine.

Figure 1.

Quetiapine improves behavioral performance in amyloid precursor protein (APP)/presenilin 1 (PS1) mice. Total time spent in the center (a) and the total distance travelled in an open field test (b). c, The exploration time of mice on identical objects (A1 and A2) in the object recognition test. A t test showed that all groups of mice demonstrated equal total exploration time for each of the identical objects in the training session. d, The exploration time of mice on a familiar object (A1) and a novel object (B) in a retention trial 1 hour after training. A t test showed that all mice spent more time exploring the novel objective. e, The exploration time of mice on a familiar object (A1) and a novel object (C) in a retention trial 24 hours after training. A t test showed that transgenic mice exhibited an impaired ability to discriminate between the familiar object and a novel object C, whereas transgenic mice treated with quetiapine spent more time exploring the novel object C. Data are expressed as means±SEM, n=7 to 10 mice per group. *P<.05 vs Con; ^# P<.05 vs transgenic + water.

Figure 2.

Quetiapine marginally affects total β-amyloid (Aβ)₄₀ and Aβ₄₂ levels in APP/PS1 mice. Total Aβ₄₀ (a) and total Aβ₄₂ (b) in the cortex of transgenic mice. A t test showed a significant reduction of total Aβ₄₀ but not Aβ₄₂ in the cerebral cortex after quetiapine treatment. Total Aβ₄₀ (c) and total Aβ₄₂ (d) in the hippocampus of transgenic mice. e, Immunoblot analysis of APP and PS1 in both cortex and hippocampus following the treatment. Quantification of full-length APP and PS1 was shown in the graph. No statistcial significance was detected. Data are expressed as means±SEM, n=4 to 6 in each group. ^# P<.05 vs transgenic + water.

Figure 3.

Quetiapine attenuates microglial activation and reduces proinflammatory cytokines in APP/PS1 mice. a, Representative immunohistochemical staining with anti-ionized calcium binding adapter molecule 1 (Iba1) in hippocampus following the treatment. The scale bar represents 50 μm. Quantification of the number of Iba positive cells was shown in the graph. Two-way analysis of variance (ANOVA) showed microglial cell density was increased in transgenice mice and decreased following quetiapine treatment. (b) Enzyme-linked immunosorbent assay (ELISA) analysis of selected proinflammatory cytokines. Two-way ANOVA showed quetiapine treatment greatly attenuated the increase of interleukin 1β (IL-1β) in the cortex of transgenic mice. No statistcial significance was detected in the level of tumor necrosis factor α (TNFα). Data are expressed as means±SEM, n=5 to 8 mice per group. * P<.05 vs Con; ^# P<.05 vs transgenic + water.

Figure 4.

Quetiapine inhibits activation of astrocytes in APP/PS1 mice. A, Representatvie immunohistochemical staining using anti-glial fibrillary acidic protein (GFAP) antibody indicated reduced astroglial cell densities in brain sections of treated transgenic mice compared with untreated transgenic mice. Upper panel shows the higher magnification of the field in red frame.The scale bars represent 100 μm (upper) and 500 μm (lower). B, Quantification of cell number in the cerebral cortex showed the GFAP-positive cells were significantly greater in APP/PS1 transgenic mice compared with APP/PS1 transgenic mice treated with quetiapine. C, Immunoblot analysis of GFAP in cerebral cortex. Quantification of GFAP was shown in the graph. Data are expressed as means±SEM, n=4 to 5 mice per group. * P<.05 vs Con; ^# P<.05 vs transgenic + water.

Figure 5.

Quetiapine reduces proinflammatory cytokines in β-amyloid (Aβ)_1-42-treated primary microglia. Primary microglia were pretreated with quetiapine (10 µM) for 1 hour and then with Aβ_1–42 (25 µM) for 6 hours. a, Enzyme-linked immunosorbent assay (ELISA) analysis of interleukin 1β (IL-1β). Two-way analysis of variance (ANOVA) showed quetiapine significantly attenuated Aβ-induced IL-1β increase. b, ELISA analysis of tumor necrosis factor α (TNFα). Two-way ANOVA showed exposure of microglia to Aβ increased the secreted TNFα levels. No statistcial significance was detected after quetiapine treatment. Data are expressed as means±SEM, n=4. * P<.05 vs Con; ^# P<.05 vs Aβ.

Figure 6.

Quetiapine inhibits the activation of the nuclear factor kappa B (NF-κB) p65 pathway in vivo and in vitro. a, Immunoblot analysis of p65 in both cortex and hippocampus following the treatment. Quantification of p65 was shown in the graph. Two-way analysis of variance (ANOVA) showed quetiapine treatment significantly attenuated this increase of p65 in both cortex and hippocampus of transgenic mice. Data are expressed as means±SEM, n=6 to 9 mice per group. * P<.05 vs Con; ^# P<.05 vs transgenic + water. b, Representative immunocytochemistry showing the effect of quetiapine on β-amyloid (Aβ)_1-42-induced NF-κB p65 nuclear translocation in primary microglia. Fluorescent images (100× magnification): blue, hoechst; red, p65; green, phalloidin.