Curcumin alleviates Alzheimer's disease by inhibiting inflammatory response, oxidative stress and activating the AMPK pathway

Abstract

Background: Alzheimer's disease (AD) is a common degenerative brain disorder with limited therapeutic options. Curcumin (Cur) exhibits neuroprotective function in many diseases. We aimed to explore the role and mechanism of Cur in AD.

Materials and methods: Firstly, we established AD mice by injecting amyloid-β1-42 (Aβ1-42) solution into the hippocampus. Then, the AD mice received 150 mg/kg/d Cur for 10 consecutive days. The Morris water maze test was conducted to evaluate the cognitive function of the mice by hidden platform training and probe trials. To assess the spatial memory of the mice, spontaneous alternation behavior, the number of crossing the novel arm and the time spent in the novel arm during the Y-maze test was recorded. Hematoxylin and eosin (H&E) staining and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNAL) assay were performed to assess the pathological damage and apoptosis of brain tissues. The number of damaged neurons was inspected by Nissl staining. Immunohistochemical staining was then performed to detect Aβ1-42 deposition. The levels of tumor necrosis factor-α (TNF-a), interleukin-6 (IL-6) and interleukin-1β (IL-1β) in serum and hippocampus, the contents of super oxide dismutase (SOD) and malondialdehyde (MDA) in brain tissues were assessed by enzyme-linked immunosorbent assay (ELISA). Additionally, B-cell lymphoma-2 (Bcl-2), Bcl-2 associated X protein (Bax), RelA (p65) protein expressions and Adenosine 5'-monophosphate-activated protein kinase (AMPK) phosphorylation were tested using Western blot.

Results: Cur not only improved cognitive function and spatial memory, but also alleviated the pathological damage and apoptosis of brain tissues for AD mice. Meanwhile, upon Cur treatment, the number of damaged neurons in AD mice was decreased, the level of Aβ1-42 in AD mice was significantly decreased. Furthermore, the AD mice treated with Cur exhibited lower TNF-a, IL-6, IL-1β and MDA levels and a higher SOD content. Besides, Cur also downregulated p65 expression and upregulated AMPK phosphorylation.

Conclusion: Cur may improve AD via suppressing the inflammatory response, oxidative stress and activating the AMPK pathway, suggesting that Cur may be a potential drug for AD.

Keywords: Alzheimer’s disease; Curcumin; Inflammatory response; Oxidative stress; The AMPK pathway.