Tetrathiomolybdate Treatment Leads to the Suppression of Inflammatory Responses through the TRAF6/NFκB Pathway in LPS-Stimulated BV-2 Microglia.

Zhuo Wang,Rui-Fang Guo,Ya-Hong Zhang,Ting-Ting Huang,Hui-Ling Gao,Zhan-You Wang,Wei Zhang,Tian Lan,Pu Zhao,Chuang Guo,Na-Na Liu,Man-Li Zhong

doi:10.3389/fnagi.2018.00009

Zhuo Wang, Rui-Fang Guo + Show 10 more

Open Access

https://doi.org/10.3389/fnagi.2018.00009

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Abstract

Although the positive relationship between copper and Alzheimer's disease (AD) was reported by a lot of epidemiological data, the mechanism is not completely known. Copper is a redox metal and serves as a mediator of inflammation. Because the homeostasis of copper is altered in Aβ precursor protein (APP) and presenilin 1 (PS1) transgenic (Tg) mice, the using of copper chelators is a potential therapeutic strategy for AD. Here we report that a copper chelator, tetrathiomolybdate (TM), is a potential therapeutic drug of AD. We investigated whether TM treatment led to a decrease of pro-inflammatory cytokines in vivo and in vitro, and found that TM treatment reduced the expression of iNOS and TNF-α in APP/PS1 Tg mice through up-regulating superoxide dismutase 1 (SOD1) activity. In vitro, once stimulated, microglia secretes a variety of proinflammatory cytokines, so we utilized LPS-stimulated BV-2 cells as the inflammatory cell model to detect the anti-inflammatory effects of TM. Our results indicated that TM-pretreatment suppressed the ubiquitination of TRAF6 and the activation of NFκB without affecting the expression of TLR4 and Myd88 in vitro. By detecting the activity of SOD1 and the production of reactive oxygen species (ROS), we found that the anti-inflammatory effects of TM could be attributed to its ability to reduce the amount of intracellular bioavailable copper, and the production of ROS which is an activator of the TRAF6 auto-ubiquitination. Hence, our results revealed that TM-treatment could reduce the production of inflammatory cytokines by the suppression of ROS/TRAF6/AKT/NFκB signaling pathway.

Highlights

Microglia, as principal immune cell in the central nervous system (CNS), serves as mediator of inflammation and degenerative diseases (Gonzalez-Scarano and Baltuch, 1999)
Our results indicated that TM increased the levels of superoxide dismutase 1 (SOD1) (Figure 2A), but had no effect on GSH (Figure 2B), suggesting that TM reduced bioavailability of copper in Aβ precursor protein (APP)/presenilin 1 (PS1) Tg mice (Figure 2)
Previous study showed that proinflammatory cytokines, such as IL-6, IL1β, and tumor necrosis factor (TNF)-α, were increased in the brain of APP/PS1 Tg mice (Song et al, 2014)

Summary

Introduction

As principal immune cell in the central nervous system (CNS), serves as mediator of inflammation and degenerative diseases (Gonzalez-Scarano and Baltuch, 1999). Tetrathiomolybdate Suppresses Inflammation in Microglia that microglia can be activated by lipopolysaccharide (LPS), interferon (IFN)-γ, and β-amyloid (Aβ), promoting the production of nitric oxide (NO) and inflammatory cytokines such as, interleukin-1 beta (IL-1β) and tumor necrosis factoralpha (TNF-α; Jana et al, 2007; Lee, 2013). These inflammatory cytokines contributed to several neurodegenerative diseases, including AD and Parkinson’s disease (Liu and Hong, 2003; Block et al, 2007). TLR recruits the adaptor proteins Myd and the IL1 receptor associated kinase (IRAK)-1,4, which binds to tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6) to form complex to trigger the autopolyubiquitination of TRAF6, and subsequently triggers NF-κB activation (Wesche et al, 1997; Medzhitov et al, 1998; Deng et al, 2000; Martin and Wesche, 2002; Zhang, X. et al, 2013)

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