Crocetin attenuates inflammation and amyloid-β accumulation in APPsw transgenic mice

Abstract

Background: Crocetin, an agent derived from saffron, has multiple pharmacological properties, such as neuroprotective, anti-oxidant, and anti-inflammatory actions. These properties might benefit the treatment of Alzheimer's disease (AD). In the present study, we tested whether crocetin attenuates inflammation and amyloid-β (Aβ) accumulation in APPsw transgenic mice, AD mouse models. Cell viability and the levels of Aβ40 and Aβ42 in HeLa cells stably transfected with Swedish mutant APP751 were evaluated. Mice with Swedish mutant APP751 transgene were used as transgenic mouse models of AD, and were orally administrated with crocetin. Aβ protein and inflammatory cytokines were measured with ELISA. NF-κB and P53 were measured with western blot assay. Learning and memory were analyzed with Morris water maze and novel object recognition tests.

Results: Crocetin significantly reduced Aβ40 and Aβ42 secretion in Hela cells without effecting cell viability. In AD transgenic mice, crocetin significantly reduced the pro-inflammatory cytokines and enhanced anti-inflammatory cytokine in plasma, suppressed NF-κB activation and P53 expression in the hippocampus, decreased Aβ in various brain areas, and improved learning and memory deficits.

Conclusion: Crocetin improves Aβ accumulation-induced learning and memory deficit in AD transgenic mice, probably due to its anti-inflammatory and anti-apoptotic functions.

Keywords: Alzheimer’s disease (AD); Aβ accumulation; Crocetin; NF-κB; P53.

Fig. 1

Effect of crocetin on cell viability and the levels of Aβ42 and Aβ40 in APPsw-transfected cells. Cells were treated with crocetin at the indicated concentrations for 8 h. Pb (80 mg/L) was employed as a positive control. Cell viability was measured using MTT assay, and the levels of Aβ42 and Aβ40 in cultured medium were measured using a sandwich ELISA. Crocetin did not affect the viability of APPsw-transfected cells (a), but reduced the levels of Aβ40 (b) and Aβ42 (c) in a dose-dependent manner. (n = 4) ∗ p < 0.05; ∗∗ p < 0.01; ∗∗∗ p < 0.001

Fig. 2

Crocetin treatment reduced levels of insoluble Aβ in AD mice. Effect of crocetin on the levels of insoluble Aβ in the hippocampus (a), cerebellum (b) and cerebral cortex (c) in APPsw transgenic (Tg) mice. Brain tissue of mice was collected from 15 months old wild-type mice (WT) and APPsw transgenic mice. (n = 6, * p < 0.05, compared with WT; # p < 0.05, compared with TG)

Fig. 3

Effects of crocetin on the Morris water maze test in wild-type and AD mice. a Escape latency in different groups. b Time spent in target quandrant in different groups. (8–9 mice in each experimental group) ∗ p < 0.05, compared with the wild-type mice (WT) group; # p < 0.05, compared with TG control group

Fig. 4

Effect of crocetin on novel object recognition test. (WT group: n = 10; Tg group: n = 6; 10 mg/kg/day group: n = 10; 30 mg/kg/day group: n = 10; ∗ p < 0.01, compared with the WT group. # p < 0.01, compared with the TG control group)

Fig. 5

Effect of crocetin on the level of NF-κB-p65 (b) and p53 in the hippocampus. a Representative western blot images using 10 μg of protein from the hippocampus of each group. Quantitative bar graphs of protein levels of NF-κB-p65 (b) and p53 (c) to actin (n = 3/group). ∗ p < 0.05, compared with the WT group; # p < 0.05, compared with the TG control group

Fig. 6

Effect of crocetin on plasma pro-inflammatory and anti-inflammatory cytokines in plasma of AD mice. The levels of TNF-α (a), IL-1β (b), IL-8 (c), IL-6 (d) and IL-10 (e) were measured in plasma from age-matched wild-type mice and transgenic AD mouse models. (n = 6/group) ∗ p < 0.05, compared with the WT group; # p < 0.05, compared with the TG control group