• Nutrition Research and Practice
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• 제14권6호
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• pp.593-605
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• 2020

BACKGROUND/OBJECTIVES: Alzheimer's disease is common age-related neurodegenerative condition characterized by amyloid beta (Aβ) accumulation that leads cognitive impairment. In the present study, we investigated the protective effect of paeoniflorin (PF) against Aβ-induced neuroinflammation and the underlying mechanism in C6 glial cells. MATERIALS/METHODS: C6 glial cells were treated with PF and Aβ_25-35, and cell viability, nitric oxide (NO) production, and pro-inflammatory cytokine release were measured. Furthermore, the mechanism underlying the effect of PF on inflammatory responses and Aβ degradation was determined by Western blot. RESULTS: Aβ_25-35 significantly reduced cell viability, but this reduction was prevented by the pretreatment with PF. In addition, PF significantly inhibited Aβ_25-35-induced NO production in C6 glial cells. The secretion of interleukin (IL)-6, IL-1β, and tumor necrosis factor-alpha was also significantly reduced by PF. Further mechanistic studies indicated that PF suppressed the production of these pro-inflammatory cytokines by regulating the nuclear factor-kappa B (NF-κB) pathway. The protein levels of inducible NO synthase and cyclooxygenase-2 were downregulated and phosphorylation of NF-κB was blocked by PF. However, PF elevated the protein expression of inhibitor kappa B-alpha and those of Aβ degrading enzymes, insulin degrading enzyme and neprilysin. CONCLUSIONS: These findings indicate that PF exerts protective effects against Aβ-mediated neuroinflammation by inhibiting NF-κB signaling, and these effects were associated with the enhanced activity of Aβ degradation enzymes.

• The Korean Journal of Physiology and Pharmacology
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• 제24권1호
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• pp.27-37
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• 2020

Neuroinflammation is an important process underlying a wide variety of neurodegenerative diseases. Carvacrol (CAR) is a phenolic monoterpene commonly used as a food additive due to its antibacterial properties, but it has also been shown to exhibit strong antioxidative, anti-inflammatory, and neuroprotective effects. Here, we sought to investigate the effects of CAR on inflammation in the hippocampus and prefrontal cortex, as well as the molecular mechanisms underlying these effects. In our study, lipopolysaccharide was injected into the lateral ventricle of rats to induce memory impairment and neuroinflammation. Daily administration of CAR (25, 50, and 100 mg/kg) for 21 days improved recognition, discrimination, and memory impairments relative to untreated controls. CAR administration significantly attenuated expression of several inflammatory factors in the brain, including interleukin-1β, tumor necrosis factor-α, and cyclooxygenase-2. In addition, CAR significantly increased expression of brain-derived neurotrophic factor (BDNF) mRNA, and decreased expression of Toll-like receptor 4 (TLR4) mRNA. Taken together, these results show that CAR can improve memory impairment caused by neuroinflammation. This cognitive enhancement is due to the anti-inflammatory effects of CAR medicated by its regulation of BDNF and TLR4. Thus, CAR has significant potential as an inhibitor of memory degeneration in neurodegenerative diseases.

• The Korean Journal of Physiology and Pharmacology
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• 제20권1호
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• pp.41-51
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• 2016

Adult hippocampal dentate granule neurons are generated from neural stem cells (NSCs) in the mammalian brain, and the fate specification of adult NSCs is precisely controlled by the local niches and environment, such as the subventricular zone (SVZ), dentate gyrus (DG), and Toll-like receptors (TLRs). Epigallocatechin-3-gallate (EGCG) is the main polyphenolic flavonoid in green tea that has neuroprotective activities, but there is no clear understanding of the role of EGCG in adult neurogenesis in the DG after neuroinflammation. Here, we investigate the effect and the mechanism of EGCG on adult neurogenesis impaired by lipopolysaccharides (LPS). LPS-induced neuroinflammation inhibited adult neurogenesis by suppressing the proliferation and differentiation of neural stem cells in the DG, which was indicated by the decreased number of Bromodeoxyuridine (BrdU)-, Doublecortin (DCX)- and Neuronal Nuclei (NeuN)-positive cells. In addition, microglia were recruited with activating TLR4-NF-${\kappa}B$ signaling in the adult hippocampus by LPS injection. Treating LPS-injured mice with EGCG restored the proliferation and differentiation of NSCs in the DG, which were decreased by LPS, and EGCG treatment also ameliorated the apoptosis of NSCs. Moreover, pro-inflammatory cytokine production induced by LPS was attenuated by EGCG treatment through modulating the TLR4-NF-${\kappa}B$ pathway. These results illustrate that EGCG has a beneficial effect on impaired adult neurogenesis caused by LPS-induced neuroinflammation, and it may be applicable as a therapeutic agent against neurodegenerative disorders caused by inflammation.

• Biomolecules & Therapeutics
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• 제26권2호
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• pp.210-217
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• 2018

Neuroinflammation is an immune response within the central nervous system against various proinflammatory stimuli. Abnormal activation of this response contributes to neurodegenerative diseases such as Parkinson disease, Alzheimer's disease, and Huntington disease. Therefore, pharmacologic modulation of abnormal neuroinflammation is thought to be a promising approach to amelioration of neurodegenerative diseases. In this study, we evaluated the synthetic flavone derivative 3',4'-dihydroxyflavone, investigating its anti-neuroinflammatory activity in BV2 microglial cells and in a mouse model. In BV2 microglial cells, 3',4'-dihydroxyflavone successfully inhibited production of chemokines such as nitric oxide and prostaglandin $E_2$ and proinflammatory cytokines such as tumor necrosis factor alpha, interleukin 1 beta, and interleukin 6 in BV2 microglia. It also inhibited phosphorylation of mitogen-activated protein kinase (MAPK) and nuclear factor $(NF)-{\kappa}B$ activation. This indicates that the anti-inflammatory activities of 3',4'-dihydroxyflavone might be related to suppression of the proinflammatory MAPK and $NF-{\kappa}B$ signaling pathways. Similar anti-neuroinflammatory activities of the compound were observed in the mouse model. These findings suggest that 3',4'-dihydroxyflavone is a potential drug candidate for the treatment of microglia-related neuroinflammatory diseases.

• Journal of Ginseng Research
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• 제43권4호
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• pp.499-507
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• 2019

Background: Ginsenoside Rb1 (Rb1), a dominant component from the extract of Panax ginseng root, exhibits neuroprotective functions in many neurological diseases. This study was intended to investigate whether Rb1 can attenuate cisplatin-induced memory impairments and explore the potential mechanisms. Methods: Cisplatin was injected intraperitoneally with a dose of 5 mg/kg/wk, and Rb1 was administered in drinking water at the dose of 2 mg/kg/d to rats for 5 consecutive wk. The novel objects recognition task and Morris water maze were used to detect the memory of rats. Nissl staining was used to examine the neuron numbers in the hippocampus. The activities of superoxide dismutase, glutathione peroxidase, cholineacetyltransferase, acetylcholinesterase, and the levels of malondialdehyde, reactive oxygen species, acetylcholine, tumor necrosis factor-${\alpha}$, interleukin-$1{\beta}$, and interleukin-10 were measured by ELISA to assay the oxidative stress, cholinergic function, and neuroinflammation in the hippocampus. Results: Rb1 administration effectively ameliorates the memory impairments caused by cisplatin in both novel objects recognition task and Morris water maze task. Rb1 also attenuates the neuronal loss induced by cisplatin in the different regions (CA1, CA3, and dentate gyrus) of the hippocampus. Meanwhile, Rb1 is able to rescue the cholinergic neuron function, inhibit the oxidative stress and neuroinflammation in cisplatin-induced rat brain. Conclusion: Rb1 rescues the cisplatin-induced memory impairment via restoring the neuronal loss by reducing oxidative stress and neuroinflammation and recovering the cholinergic neuron functions.

• Biomolecules & Therapeutics
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• 제27권5호
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• pp.442-449
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• 2019

This study sought to evaluate the effects of Asiatic acid in LPS-induced BV2 microglia cells and 1-methyl-4-phenyl-pyridine ($MPP^+$)-induced SH-SY5Y cells, to investigate the potential anti-inflammatory mechanisms of Asiatic acid in Parkinson's disease (PD). SH-SY5Y cells were induced using $MPP^+$ to establish as an in vitro model of PD, so that the effects of Asiatic acid on dopaminergic neurons could be examined. The NLRP3 inflammasome was activated in BV2 microglia cells to explore potential mechanisms for the neuroprotective effects of Asiatic acid. We showed that Asiatic acid reduced intracellular production of mitochondrial reactive oxygen species and altered the mitochondrial membrane potential to regulate mitochondrial dysfunction, and suppressed the NLRP3 inflammasome in microglia cells. We additionally found that treatment with Asiatic acid directly improved SH-SY5Y cell viability and mitochondrial dysfunction induced by $MPP^+$. These data demonstrate that Asiatic acid both inhibits the activation of the NLRP3 inflammasome by downregulating mitochondrial reactive oxygen species directly to protect dopaminergic neurons from, and improves mitochondrial dysfunction in SH-SY5Y cells, which were established as a model of Parkinson's disease. Our finding reveals that Asiatic acid protects dopaminergic neurons from neuroinflammation by suppressing NLRP3 inflammasome activation in microglia cells as well as protecting dopaminergic neurons directly. This suggests a promising clinical use of Asiatic acid for PD therapy.

• Molecules and Cells
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• 제42권10호
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• pp.702-710
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• 2019

Neuroinflammation is an important contributor to the pathogenesis of neurodegenerative disorders including Parkinson's disease (PD). We previously reported that our novel synthetic compound KMS99220 has a good pharmacokinetic profile, enters the brain, exerts neuroprotective effect, and inhibits $NF{\kappa}B$ activation. To further assess the utility of KMS99220 as a potential therapeutic agent for PD, we tested whether KMS99220 exerts an anti-inflammatory effect in vivo and examined the molecular mechanism mediating this phenomenon. In 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated mice, oral administration of KMS99220 attenuated microglial activation and decreased the levels of inducible nitric oxide synthase and interleukin 1 beta ($IL-1{\beta}$) in the nigrostriatal system. In lipopolysaccharide (LPS)-challenged BV-2 microglial cells, KMS99220 suppressed the production and expression of $IL-1{\beta}$. In the activated microglia, KMS99220 reduced the phosphorylation of $I{\kappa}B$ kinase, c-Jun N-terminal kinase, and p38 MAP kinase; this effect was mediated by heme oxygenase-1 (HO-1), as both gene silencing and pharmacological inhibition of HO-1 abolished the effect of KMS99220. KMS99220 induced nuclear translocation of the transcription factor Nrf2 and expression of the Nrf2 target genes including HO-1. Together with our earlier findings, our current results show that KMS99220 may be a potential therapeutic agent for neuroinflammation-related neurodegenerative diseases such as PD.

• Molecules and Cells
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• 제45권12호
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• pp.950-962
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• 2022

Aging is a major risk factor for common neurodegenerative diseases. Although multiple molecular, cellular, structural, and functional changes occur in the brain during aging, the involvement of caveolin-2 (Cav-2) in brain ageing remains unknown. We investigated Cav-2 expression in brains of aged mice and its effects on endothelial cells. The human umbilical vein endothelial cells (HUVECs) showed decreased THP-1 adhesion and infiltration when treated with Cav-2 siRNA compared to control siRNA. In contrast, Cav-2 overexpression increased THP-1 adhesion and infiltration in HUVECs. Increased expression of Cav-2 and iba-1 was observed in brains of old mice. Moreover, there were fewer iba-1-positive cells in the brains of aged Cav-2 knockout (KO) mice than of wild-type aged mice. The levels of several chemokines were higher in brains of aged wild-type mice than in young wild-type mice; moreover, chemokine levels were significantly lower in brains of young mice as well as aged Cav-2 KO mice than in their wild-type counterparts. Expression of PECAM1 and VE-cadherin proteins increased in brains of old wild-type mice but was barely detected in brains of young wild-type and Cav-2 KO mice. Collectively, our results suggest that Cav-2 expression increases in the endothelial cells of aged brain, and promotes leukocyte infiltration and age-associated neuroinflammation.

• BMB Reports
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• 제56권5호
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• pp.308-313
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• 2023

Phenotypic features such as ataxia and loss of motor function, which are characteristics of Parkinson's disease (PD), are expected to be very closely related to cerebellum function. However, few studies have reported the function of the cerebellum. Since the cerebellum, like the cerebrum, is known to undergo functional and morphological changes due to neuroinflammatory processes, elucidating key functional factors that regulate neuroinflammation in the cerebellum can be a beneficial therapeutic approach. Therefore, we employed PD patients and MPTP-induced PD mouse model to find cytokines involved in cerebellar neuroinflammation in PD and to examine changes in cell function by regulating related genes. Along with the establishment of a PD mouse model, abnormal shapes such as arrangement and number of Purkinje cells in the cerebellum were confirmed based on histological finding, consistent with those of cerebellums of PD patients. As a result of proteome profiling for neuroinflammation using PD mouse cerebellar tissues, fetuin-A, a type of cytokine, was found to be significantly reduced in Purkinje cells. To further elucidate the function of fetuin-A, neurons isolated from cerebellums of embryos (E18) were treated with fetuin-A siRNA. We uncovered that not only the population of neuronal cells, but also their morphological appearances were significantly different. In this study, we found a functional gene called fetuin-A in the PD model's cerebellum, which was closely related to the role of cerebellar Purkinje cells of mouse and human PD. In conclusion, morphological abnormalities of Purkinje cells in PD mice and patients have a close relationship with a decrease of fetuin-A, suggesting that diagnosis and treatment of cerebellar functions of PD patients might be possible through regulation of fetuin-A.

• Journal of Ginseng Research
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• 제48권4호
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• pp.384-394
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• 2024

Background: Herpes simplex virus type 1 (HSV-1), known to latently infect the host's trigeminal ganglion, can lead to severe herpes encephalitis or asymptomatic infection, potentially contributing to neurodegenerative diseases like Alzheimer's. The virus generates reactive oxygen species (ROS) that significantly impact viral replication and induce chronic inflammation through NF-κB activation. Nuclear factor E2-related factor 2 (Nrf2), an oxidative stress regulator, can prevent and treat HSV-1 infection by activating the passive defense response in the early stages of infection. Methods and results: Our study investigated the antiviral effects of ginsenoside Rg5, an Nrf2 activator, on HSV-1 replication and several host cell signaling pathways. We found that HSV-1 infection inhibited Nrf2 activity in host cells, induced ROS/NF-κB signaling, and triggered inflammatory cytokines. However, treatment with ginsenoside Rg5 inhibited ROS/NF-κB signaling and reduced inflammatory cytokines through NRF2 induction. Interestingly, the Nrf2 inhibitor ML385 suppressed the expression of NAD(P)H quinone oxidoreductase 1(NQO1) and enhanced the expression of KEAP1 in HSV-1 infected cells. This led to the reversal of VP16 expression inhibition, a protein factor associated with HSV-1 infection, thereby promoting HSV-1 replication. Conclusion: These findings suggest for the first time that ginsenoside Rg5 may serve as an antiviral against HSV-1 infection and could be a novel therapeutic agent for HSV-1-induced neuroinflammation.