Research article
Epigallocatechin-3-gallate prevents systemic inflammation-induced memory deficiency and amyloidogenesis via its anti-neuroinflammatory properties

https://doi.org/10.1016/j.jnutbio.2012.06.011Get rights and content

Abstract

Neuroinflammation has been known to play a critical role in the pathogenesis of Alzheimer's disease (AD) through amyloidogenesis. In a previous study, we found that systemic inflammation by intraperitoneal (ip) injection of lipopolysaccharide (LPS) induces neuroinflammation and triggers memory impairment. In this present study, we investigated the inhibitory effects of epigallocatechin-3-gallate (EGCG) on the systemic inflammation-induced neuroinflammation and amyloidogenesis as well as memory impairment. ICR mice were orally administered with EGCG (1.5 and 3 mg/kg) for 3 weeks, and then the mice were treated by ip injection of LPS (250 μg/kg) for 7 days. We found that treatment of LPS induced memory-deficiency-like behavior and that EGCG treatment prevented LPS-induced memory impairment and apoptotic neuronal cell death. EGCG also suppressed LPS-induced increase of the amyloid beta-peptide level and the expression of the amyloid precursor protein (APP), β-site APP cleaving enzyme 1 and its product C99. In addition, we found that EGCG prevented LPS-induced activation of astrocytes and elevation of cytokines including tumor necrosis factor-α, interleukin (IL)-1β, macrophage colony-stimulating factor, soluble intercellular adhesion molecule-1 and IL-16, and the increase of inflammatory proteins, such as inducible nitric oxide synthase and cyclooxygenase-2, which are known factors responsible for not only activation of astrocytes but also amyloidogenesis. In the cultured astrocytes, EGCG also inhibited LPS-induced cytokine release and amyloidogenesis. Thus, this study shows that EGCG prevents memory impairment as well as amyloidogenesis via inhibition of neuroinflammatory-related cytokines released from astrocytes and suggests that EGCG might be a useful intervention for neuroinflammation-associated AD.

Introduction

Alzheimer's disease (AD) is the most common cause of dementia, accounting for 50% to 75% of all cases [1], [2]. AD is pathologically characterized by senile plaques and neurofibrillary tangles in the brain. In particular, the senile plaques are extracellular aggregates of amyloid beta-peptide (Aβ) that are cleaved from the amyloid precursor protein (APP) [3]. Postmortem studies of AD brains also found a number of pathological abnormalities including a profound loss of synapses, microglial activation and inflammatory processes [4]. Previous studies with transgenic animals revealed that neuroinflammation also accelerates amyloidogenesis in the process of cerebral amyloid deposition [5], [6], [7], [8]. In the process of neuroinflammation, various cytokines [tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-1β, etc.], chemokines [monocyte chemotactic protein (MCP)-1, macrophage-derived inflammatory mediator (MIP)-α, etc.], oxygen free radicals and reactive nitrogen species [9], and eicosanoids such as leukotriene B4 and prostaglandins [10] are important signaling molecules of neuroinflammatory responses [11].

Intraperitoneal (ip) administration of lipopolysaccharide (LPS) can induce an immediate, strong and persistent up-regulation of proinflammatory cytokines IL-1β, IL-6 and TNF-α primarily from macrophages, and these proinflammatory cytokines exert neurobiological effects [12], suggesting that systemic inflammation can affect the neurobiological condition. Systemic administration of a single dose of LPS through ip injections induces neuroinflammation that persists for 10 months, which results in the progressive loss of dopaminergic neurons in the substantia nigra [13]. Mouton et al. [14] found that single ip injection of LPS induced elevation of several cytokines, such as IL-1β, IL-6 and TNF-α, in hippocampal tissue. Erickson and Banks [15] reported that single and three repeated ip injections of LPS increased release of neuroinflammatory-related cytokines and chemokines granulocyte colony-stimulating factor, IL-1α, IL-6, MCP-1, MIP-1α and TNF-α, in mouse brain. Those inflammatory components accelerate amyloidogenesis via up-regulation of the β-secretase level and activity [16], [17]. Recently, Jaeger et al. [18] reported that systemic injection of LPS increased brain influx of blood Aβ via alteration of low density lipoprotein receptor-related protein 1 (LRP-1) in mice brain. Our previous studies also showed that systemic administration of LPS could induce memory deficiency and Aβ accumulation through the elevation of β- and γ-secretase activities [19]. Moreover, administration of anti-inflammatory agents in AD patients could reduce amyloidogenesis, suggesting that neuroinflammation may cause the pathogenesis of AD via amyloidogenesis [20]. Thus, this animal model might be useful to study underlying mechanisms of neuroinflammation-associated development of AD.

Epigallocatechin-3-gallate (EGCG) is the most abundant biologically active compound in tea. Epidemiological studies have also suggested a positive relationship between consumption of EGCG and the prevention of AD [21]. Green tea extract or EGCG has been reported to attenuate Aβ-induced neurotoxicity in cultured human neuronal cell lines and to modulate both tau pathology and Aβ-mediated cognitive impairment in transgenic mice models of AD [22], [23], [24], [25], [26]. It was also reported that green tea has anti-β-secretase activity in vitro [27]. Moreover, Rezai-Zadeh et al. [22] reported that EGCG markedly elevated the α-secretase activity and promoted soluble APP-α production in the murine neuron-like cells transfected with the human Swedish mutant form of APP (SweAPP N2a cells), as well as in primary neurons derived from Swedish mutant APP-overexpressing mice (the Tg APPsw line 2576).

In our previous studies, we found that intracerebroventricular (icv) injection of LPS induced memory deficiency and Aβ accumulation through decreased α-secretase activity as well as elevation of the β- and γ-secretase activities, and these were all reduced by EGCG [28]. We previously also demonstrated that EGCG prevented amyloidogenesis via inhibition of β-secretase activity in Aβ-injected and presenilin2 mutant transgenic mice [28], [29]. Thus, we investigated preventive effect of EGCG on the systemic neuroinflammation model via ip injection of LPS, and we investigated the possible mechanisms of EGCG effects to improve the memory deficiency in systemic LPS-injected AD mice models.

Section snippets

EGCG

Green tea-derived flavonoid EGCG was purchased from Sigma-Aldrich (St. Louis, MO, USA). In our previous memory impairment animal model, 1.5 and 3 mg/kg EGCG treatment for 3 weeks showed a neuroprotective effect [28], [29]. Therefore, a similar dose of EGCG (1.5 and 3 mg/kg) was used in the present study, which is about 1.5 times more than the dose of human consumption. The daily human consumption of green tea is about 2 mg/kg (12 g×1% yield from green tea leaf/70 kg) [30]. The average water

Effect of EGCG on the LPS-induced memory impairment as determined by behavior tests

The memory-improving effect of EGCG was assessed in mice that were continuously administered with EGCG at a dose of 1.5 or 3 mg/kg/day daily for 3 weeks (from day 1 to day 28), and then they were ip injected with 250 μg/kg/day LPS for 1 weeks (from day 22 to day 28). The mice then performed the Morris water maze test after 15 training sessions (three times per day for 5 days) as shown in Fig. 1. Similar to previous findings [19], [28], the LPS injection retarded arriving at the location of the

Discussion

The most important finding in this study is that systemic administration of LPS caused memory impairment and that EGCG suppressed the amyloidogenesis through its anti-neuroinflammatory property via modulation of cytokine release in systemic LPS-induced in vivo and in vitro models, and resulted in ameliorated memory impairment.

Many epidemiological and experimental animal studies have suggested that neuroinflammation may contribute to the occurrence and progress of AD [37], [38], [39], [40].

Acknowledgments

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government [MEST] (MRC, 2010–0029480), by a grant (No. A101836) of the Korean Health Technology R&D Project, Ministry for Health, Welfare & Family Affairs, Republic of Korea and by a grant of the Korea Ministry of Education, Science and Technology (The Regional Core Research Program/Chungbuk BIT Research-Oriented University Consortium).

References (112)

  • J.C. Breitner et al.

    Extended results of the Alzheimer's disease anti-inflammatory prevention trial

    Alzheimers Dement

    (2011)
  • K. Rezai-Zadeh et al.

    Green tea epigallocatechin-3-gallate (EGCG) reduces beta-amyloid mediated cognitive impairment and modulates tau pathology in Alzheimer transgenic mice

    Brain Res

    (2008)
  • A.M. Antonio et al.

    Antioxidants prevent ethanol-associated apoptosis in fetal rhombencephalic neurons

    Brain Res

    (2008)
  • H.S. Cho et al.

    Protective effect of the green tea component, L-theanine on environmental toxins-induced neuronal cell death

    Neurotoxicology

    (2008)
  • Y.K. Lee et al.

    (−)-Epigallocatechin-3-gallate prevents lipopolysaccharide-induced elevation of beta-amyloid generation and memory deficiency

    Brain Res

    (2009)
  • J.W. Lee et al.

    Green tea (−)-epigallocatechin-3-gallate inhibits beta-amyloid-induced cognitive dysfunction through modification of secretase activity via inhibition of ERK and NF-kappaB pathways in mice

    J Nutr

    (2009)
  • A. Rietveld et al.

    Antioxidant effects of tea: evidence from human clinical trials

    J Nutr

    (2003)
  • R. Morris

    Developments of a water-maze procedure for studying spatial learning in the rat

    J Neurosci Methods

    (1984)
  • S.M. Lee et al.

    EPO receptor-mediated ERK kinase and NF-kappaB activation in erythropoietin-promoted differentiation of astrocytes

    Biochem Biophys Res Commun

    (2004)
  • K.S. Park et al.

    Neuronal differentiation of embryonic midbrain cells by upregulation of peroxisome proliferator-activated receptor-gamma via the JNK-dependent pathway

    Exp Cell Res

    (2004)
  • H.N. Nguyen et al.

    Mutant presenilin 2 increased oxidative stress and p53 expression in neuronal cells

    Biochem Biophys Res Commun

    (2007)
  • H. Akiyama et al.

    Inflammation and Alzheimer's disease

    Neurobiol Aging

    (2000)
  • C. Bay-Richter et al.

    Changes in behaviour and cytokine expression upon a peripheral immune challenge

    Behav Brain Res

    (2011)
  • J.G. Sheng et al.

    Lipopolysaccharide-induced-neuroinflammation increases intracellular accumulation of amyloid precursor protein and amyloid beta peptide in APPswe transgenic mice

    Neurobiol Dis

    (2003)
  • A. Michelucci et al.

    Characterization of the microglial phenotype under specific pro-inflammatory and anti-inflammatory conditions: effects of oligomeric and fibrillar amyloid-beta

    J Neuroimmunol

    (2009)
  • F.E. McAlpine et al.

    Inhibition of soluble TNF signaling in a mouse model of Alzheimer's disease prevents pre-plaque amyloid-associated neuropathology

    Neurobiol Dis

    (2009)
  • D. Paris et al.

    Pro-inflammatory effect of freshly solubilized beta-amyloid peptides in the brain

    Prostaglandins Other Lipid Mediat

    (2002)
  • M.J. Gunasingh et al.

    Melatonin prevents amyloid protofibrillar induced oxidative imbalance and biogenic amine catabolism

    Life Sci

    (2008)
  • L.F. Lue et al.

    Modeling microglial activation in Alzheimer's disease with human postmortem microglial cultures

    Neurobiol Aging

    (2001)
  • G.M. Murphy et al.

    Expression of macrophage colony-stimulating factor receptor is increased in the AbetaPP(V717F) transgenic mouse model of Alzheimer's disease

    Am J Pathol

    (2000)
  • G.M. Murphy et al.

    Macrophage colony-stimulating factor augments beta-amyloid-induced interleukin-1, interleukin-6, and nitric oxide production by microglial cells

    J Biol Chem

    (1998)
  • O.M. Mitrasinovic et al.

    Overexpression of macrophage colony-stimulating factor receptor on microglial cells induces an inflammatory response

    J Biol Chem

    (2001)
  • J.B. O'Sullivan et al.

    Noradrenaline reuptake inhibitors inhibit expression of chemokines IP-10 and RANTES and cell adhesion molecules VCAM-1 and ICAM-1 in the CNS following a systemic inflammatory challenge

    J Neuroimmunol

    (2010)
  • G. Wang et al.

    Effects of chronic systemic treatment with peroxisome proliferator-activated receptor alpha activators on neuroinflammation induced by intracerebral injection of lipopolysaccharide in adult mice

    Neurosci Res

    (2011)
  • J. Apelt et al.

    [beta]-Amyloid-associated expression of intercellular adhesion molecule-1 in brain cortical tissue of transgenic Tg2576 mice

    Neurosci Lett

    (2002)
  • S. Zara et al.

    Ibuprofen and lipoic acid codrug 1 control Alzheimer's disease progression by down-regulating protein kinase C epsilon-mediated metalloproteinase 2 and 9 levels in beta-amyloid infused Alzheimer's disease rat model

    Brain Res

    (2011)
  • M. Motta et al.

    Altered plasma cytokine levels in Alzheimer's disease: correlation with the disease progression

    Immunol Lett

    (2007)
  • Y.J. Lee et al.

    Inhibitory effect of 4-O-methylhonokiol on lipopolysaccharide-induced neuroinflammation, amyloidogenesis and memory impairment via inhibition of nuclear factor-kappaB in vitro and in vivo models

    J Neuroinflammation

    (2012)
  • S. Jang et al.

    Neuroprotective effects of (−)-epigallocatechin-3-gallate against quinolinic acid-induced excitotoxicity via PI3K pathway and NO inhibition

    Brain Res

    (2010)
  • E.C.S. Franco et al.

    Modulation of microglial activation enhances neuroprotection and functional recovery derived from bone marrow mononuclear cell transplantation after cortical ischemia

    Neurosci Res

    (2012)
  • F.J. Ortega et al.

    ATP-dependent potassium channel blockade strengthens microglial neuroprotection after hypoxia–ischemia in rats

    Exp Neurol

    (2012)
  • M.A. Yenari et al.

    Microglial activation in stroke: therapeutic targets

    Neurotherapeutics

    (2010)
  • J.D. Lambert et al.

    The antioxidant and pro-oxidant activities of green tea polyphenols: a role in cancer prevention

    Arch Biochem Biophys

    (2010)
  • R.A. Isbrucker et al.

    Safety studies on epigallocatechin gallate (EGCG) preparations. Part 1: genotoxicity

    Food Chem Toxicol

    (2006)
  • R.A. Isbrucker et al.

    Safety studies on epigallocatechin gallate (EGCG) preparations. Part 2: dermal, acute and short-term toxicity studies

    Food Chem Toxicol

    (2006)
  • R.A. Isbrucker et al.

    Safety studies on epigallocatechin gallate (EGCG) preparations. Part 3: teratogenicity and reproductive toxicity studies in rats

    Food Chem Toxicol

    (2006)
  • M. Vignes et al.

    Anxiolytic properties of green tea polyphenol (−)-epigallocatechin gallate (EGCG)

    Brain Res

    (2006)
  • J.D. Lambert et al.

    Hepatotoxicity of high oral dose (−)-epigallocatechin-3-gallate in mice

    Food Chem Toxicol

    (2010)
  • C.M. Peters et al.

    Formulation with ascorbic acid and sucrose modulates catechin bioavailability from green tea

    Food Res Int

    (2010)
  • C.P. Ferri et al.
  • Cited by (0)

    View full text