Zerumbone ameliorates behavioral impairments and neuropathology in transgenic APP/PS1 mice by suppressing MAPK signaling

Lei Li,Xiao-Jing Zhao,Xiang-Hui Wu,Zhi-Yuan Zhang,Cai-Long Pan,Lu Xu

doi:10.1186/s12974-020-01744-1

Abstract

BackgroundAlzheimer’s disease (AD) is a major clinical problem, but there is a distinct lack of effective therapeutic drugs for this disease. We investigated the potential therapeutic effects of zerumbone, a subtropical ginger sesquiterpene, in transgenic APP/PS1 mice, rodent models of AD which exhibit cerebral amyloidosis and neuroinflammation.MethodsThe N9 microglial cell line and primary microglial cells were cultured to investigate the effects of zerumbone on microglia. APP/PS1 mice were treated with zerumbone, and non-cognitive and cognitive behavioral impairments were assessed and compared between the treatment and control groups. The animals were then sacrificed, and tissues were collected for further analysis. The potential therapeutic mechanism of zerumbone and the signaling pathways involved were also investigated by RT-PCR, western blot, nitric oxide detection, enzyme-linked immunosorbent assay, immunohistochemistry, immunofluorescence, and flow cytometry analysis.ResultsZerumbone suppressed the expression of pro-inflammatory cytokines and induced a switch in microglial phenotype from the classic inflammatory phenotype to the alternative anti-inflammatory phenotype by inhibiting the mitogen-activated protein kinase (MAPK)/nuclear factor-kappa B signaling pathway in vitro. After a treatment period of 20 days, zerumbone significantly ameliorated deficits in both non-cognitive and cognitive behaviors in transgenic APP/PS1 mice. Zerumbone significantly reduced β-amyloid deposition and attenuated pro-inflammatory microglial activation in the cortex and hippocampus. Interestingly, zerumbone significantly increased the proportion of anti-inflammatory microglia among all activated microglia, potentially contributing to reduced β-amyloid deposition by enhancing phagocytosis. Meanwhile, zerumbone also reduced the expression of key molecules of the MAPK pathway, such as p38 and extracellular signal-regulated kinase.ConclusionsOverall, zerumbone effectively ameliorated behavioral impairments, attenuated neuroinflammation, and reduced β-amyloid deposition in transgenic APP/PS1 mice. Zerumbone exhibited substantial anti-inflammatory activity in microglial cells and induced a phenotypic switch in microglia from the pro-inflammatory phenotype to the anti-inflammatory phenotype by inhibiting the MAPK signaling pathway, which may play an important role in its neuroprotective effects. Our results suggest that zerumbone is a potential therapeutic agent for human neuroinflammatory and neurodegenerative diseases, in particular AD.

Highlights

Alzheimer’s disease (AD) is a major clinical problem, but there is a distinct lack of effective therapeutic drugs for this disease
The mRNA levels of CD206, IL-10, and ARG-1, markers of the anti-inflammatory phenotype were significantly increased by zerumbone administration, indicating that zerumbone promotes a switch in microglial phenotype from the classic pro-inflammatory phenotype to the anti-inflammatory phenotype
When microglia were treated with zerumbone, none of the three inhibitors altered the secretion of inflammatory factors. These results suggested that zerumbone induced a switch in microglial polarization towards the antiinflammatory phenotype by down-regulating the Aβ stimulated activation of the extracellular signal-regulated kinase (ERK)/p38 mitogen-activated protein kinase (MAPK)/Nuclear factor-kappa B (NF-κB) signaling pathway in microglia

Summary

Introduction

Alzheimer’s disease (AD) is a major clinical problem, but there is a distinct lack of effective therapeutic drugs for this disease. The development of senile plaques composed of extracellular accumulated β-amyloid (Aβ) peptides [2] is one of the most distinct neuropathological features of AD. In AD, excessive production and inefficient clearance of Aβ lead to Aβ aggregation and trigger a pro-inflammatory response, which contributes to cell death and neural dysfunction [8]. This chronic neuroinflammation promotes Aβ liberation during amyloid precursor protein (APP) processing [9]. Controlling neuroinflammation and reducing Aβ accumulation in the AD brain are thought to be promising approaches for the treatment of AD [10]

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