Ji-Sun Jung

Anti-inflammatory mechanism of ginseng saponins in activated microglia

In the present study, we investigated the effect of ginseng extract (KRG) and total saponins (GTS) on microglial activation. KRG and GTS inhibited LPS-induced expression of iNOS, MMP-9 and proinflammatory cytokines in microglial cells. Suppression of microglial activation by ginseng was also observed in the mouse brain inflamed by LPS. Furthermore, KRG and GTS significantly suppressed NF-kappaB and MAP kinase activities, which are upstream signaling molecules in inflammation. Among the individual ginsenosides tested, Rh2, Rh3 and compound K significantly inhibited LPS-induced iNOS and cytokine expressions. Therefore, the inhibition of microglial activation by ginseng saponins may a good potential therapeutic modality for neurodegenerative diseases.

Anti-Inflammatory Mechanism of Compound K in Activated Microglia and Its Neuroprotective Effect on Experimental Stroke in Mice

Microglial activation plays a pivotal role in the pathogenesis of various neurologic disorders, such as cerebral ischemia, Alzheimers disease, and Parkinsons disease. Thus, controlling microglial activation is a promising therapeutic strategy for such brain diseases. In the present study, we found that a ginseng saponin metabolite, compound K [20-O-d-glucopyranosyl-20(S)-protopanaxadiol], inhibited the expressions of inducible nitric-oxide synthase, proinflammatory cytokines, monocyte chemotactic protein-1, matrix metalloproteinase-3, and matrix metalloproteinase-9 in lipopolysaccharide (LPS)-stimulated BV2 microglial cells and primary cultured microglia. Subsequent mechanistic studies revealed that compound K suppressed microglial activation via inhibiting reactive oxygen species, mitogen-activated protein kinases, and nuclear factor-κB/activator protein-1 activities with enhancement of heme oxygenase-1/antioxidant response element signaling. To address the anti-inflammatory effects of compound K in vivo, we used two brain disease models of mice: sepsis (systemic inflammation) and cerebral ischemia. Compound K reduced the number of Iba1-positive activated microglia and inhibited the expressions of tumor necrosis factor-α and interleukin-1β in the LPS-induced sepsis brain. Furthermore, compound K reduced the infarct volume of ischemic brain induced by middle cerebral artery occlusion and suppressed microglial activation in the ischemic cortex. The results collectively suggest that compound K is a promising agent for prevention and/or treatment of cerebral ischemia and other neuroinflammatory disorders.

Anti‐inflammatory mechanism of ginsenoside Rh1 in lipopolysaccharide‐stimulated microglia: critical role of the protein kinase A pathway and hemeoxygenase‐1 expression

J. Neurochem. (2010) 115, 1668–1680.

Antioxidant mechanism of isoflavone metabolites in hydrogen peroxide-stimulated rat primary astrocytes: critical role of hemeoxygenase-1 and NQO1 expression

J. Neurochem. (2011) 119, 909–919.

Ginsenoside Rh1 suppresses inducible nitric oxide synthase gene expression in IFN-γ-stimulated microglia via modulation of JAK/STAT and ERK signaling pathways

Microglial activation plays an important role in the pathogenesis of various neurodegenerative diseases by producing neurotoxic factors, such as pro-inflammatory cytokines and nitric oxide (NO). In the present study, we found that protopanaxatriol ginsenoside Rh1 suppresses NO, ROS, and TNF-alpha production in IFN-gamma-stimulated BV2 microglial cells. Rh1 inhibited the mRNA and protein expression of iNOS and TNF-alpha. To determine the regulatory mechanism of iNOS gene expression by Rh1, promoter analysis was performed. Rh1 significantly suppressed IFN-gamma-induced iNOS promoter activity by inhibiting DNA binding of several transcription factors, such as NF-kappaB, IRF-1, and STAT1. Furthermore, Rh1 inhibited the phosphorylation of JAK1, STAT1, STAT3, and ERK, which are upstream signaling molecules for IFN-gamma-induced iNOS gene expression. The present study demonstrates that Rh1 inhibits IFN-gamma-induced JAK/STAT and ERK signaling pathways and downstream transcription factors, and thereby iNOS gene expression. Therefore, the inhibition of microglial activation by ginsenoside Rh1 may provide potential therapeutic strategy for various neuroinflammatory diseases.

Selective inhibition of MMP-9 gene expression by mangiferin in PMA-stimulated human astroglioma cells: Involvement of PI3K/Akt and MAPK signaling pathways

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases which play a key role in invasion, migration, and angiogenesis of astrogliomas and other malignant tumors. Thus, controlling MMPs has been considered an important therapeutic strategy for prevention and/or treatment of gliomas. However, most MMP inhibitors developed so far are broad spectrum inhibitors; thus, it is necessary to develop a selective MMP inhibitor to minimize potential side effects. In the present study, we found that mangiferin, a glucosylxanthone isolated from Anemarrhena asphodeloides, specifically inhibited MMP-9 gene expression in phorbol myristate acetate (PMA)-stimulated human astroglioma U87MG, U373MG, and CRT-MG cells. However, it did not affect other MMPs, such as MMP-1, -2, -3, and -14. Mangiferin suppressed MMP-9 expression at the promoter, mRNA, and protein levels and additionally inhibited MMP-9 enzymatic activity. The Matrigel-invasion assay showed that mangiferin suppresses the in vitro invasiveness of glioma cells, which appears to be correlated with mangiferin-mediated MMP-9 inhibition. Further mechanistic studies demonstrated that mangiferin inhibits the binding of NF-κB and AP-1 to the MMP-9 promoter and suppresses the PMA-induced phosphorylation of Akt and MAP kinases, which are upstream signaling molecules in MMP-9 expression. Thus, the specific inhibition of MMP-9 by mangiferin may provide a valuable pharmacological tool for treatment of gliomas.

Anti-inflammatory effect of ginsenoside Rg5 in lipopolysaccharide-stimulated BV2 microglial cells.

Microglia are resident immune cells in the central nervous system. They play a role in normal brain development and neuronal recovery. However, overactivation of microglia causes neuronal death, which is associated with neurodegenerative diseases, such as Parkinson’s disease and Alzheimer’s disease. Therefore, controlling microglial activation has been suggested as an important target for treatment of neurodegenerative diseases. In the present study, we investigated the anti-inflammatory effect of ginsenoside Rg5 in lipopolysaccharide (LPS)-stimulated BV2 microglial cells and rat primary microglia. The data showed that Rg5 suppressed LPS-induced nitric oxide (NO) production and proinflammatory TNF-α secretion. In addition, Rg5 inhibited the mRNA expressions of iNOS, TNF-α, IL-1β, COX-2 and MMP-9 induced by LPS. Further mechanistic studies revealed that Rg5 inhibited the phophorylations of PI3K/Akt and MAPKs and the DNA binding activities of NF-κB and AP-1, which are upstream molecules controlling inflammatory reactions. Moreover, Rg5 suppressed ROS production with upregulation of hemeoxygenase-1 (HO-1) expression in LPS-stimulated BV2 cells. Overall, microglial inactivation by ginsenoside Rg5 may provide a therapeutic potential for various neuroinflammatory disorders.

Anti-inflammatory mechanism of exogenous C2 ceramide in lipopolysaccharide-stimulated microglia.

Ceramide is a major molecule among the sphingolipid metabolites which are produced in the brain and other organs and act as intracellular second messengers. Although a variety of physiological roles of ceramide have been reported in the periphery and central nervous systems, the role of ceramide in microglial activation has not been clearly demonstrated. In the present study, we examined the effects of exogenous cell permeable short chain ceramides on microglial activation in vitro and in vivo. We found that C2, C6, and C8 ceramide and C8 ceramide-1-phosphate inhibited iNOS and proinflammatory cytokines in lipopolysaccharide (LPS)-stimulated BV2 microglial cells and rat primary microglia. In addition, the administration of C2 ceramide suppressed microglial activation in the brains of LPS-exposed mice. By HPLC and LC/MS/MS analyses, we found that C2 ceramide on its own, rather than its modified form (i.e. ceramide-1-phosphate or long chain ceramides), mainly work by penetrating into microglial cells. Further mechanistic studies by using the most effective C2 ceramide among the short chain ceramides tested, revealed that C2 ceramide exerts anti-inflammatory effects via inhibition of the ROS, MAPKs, PI3K/Akt, and Jak/STAT pathways with upregulation of PKA and hemeoxygenase-1 expressions. Interestingly, we found that C2 ceramide inhibits TLR4 signaling by interfering with LPS and TLR4 interactions. Therefore, our data collectively suggests the therapeutic potential of short chain ceramides such as C2 for neuroinflammatory disorders such as Alzheimers disease and Parkinsons disease.

Protopanaxatriol ginsenoside Rh1 inhibits the expression of matrix metalloproteinases and the in vitro invasion/migration of human astroglioma cells.

Malignant gliomas are the most common and fatal brain tumors in adults. In particular, the strong invasiveness of glioma cells into the normal brain tissue makes eradication of glioma very difficult. Matrix metalloproteinases (MMPs) play a pivotal role in glioma invasion, and thus controlling MMP expression has been suggested as an important therapeutic target for brain tumors. In the present study, we investigated the effect of protopanaxatriol ginsenoside Rh1 on MMP expressions in human astroglioma U87MG and U373MG cells. RT-PCR analysis showed that Rh1 inhibits the mRNA expressions of MMP-1, -3, and -9 in PMA-stimulated U87MG and U373MG cells. Rh1 also suppressed the promoter activities of MMP-1, -3 and -9. The ELISA, Western blot, and zymographic analyses revealed that Rh1 inhibits the protein expression and/or enzymatic activity of MMP-1, -3 and -9. In accordance with the strong inhibitory effects of Rh1 on MMPs, Rh1 efficiently inhibited the invasion and migration of U87MG and U373MG glioma cells as demonstrated by Matrigel invasion assay and wound healing assay. Further mechanistic studies revealed that Rh1 inhibits MAPK and PI3K/Akt signaling pathways and downstream transcription factors such as NF-κB and AP-1, which play an important role in MMP gene expressions. The data collectively suggest that ginsenoside Rh1 may have a therapeutic potential for malignant gliomas.

Protopanaxatriol Ginsenoside Rh1 Upregulates Phase II Antioxidant Enzyme Gene Expression in Rat Primary Astrocytes: Involvement of MAP Kinases and Nrf2/ARE Signaling

Oxidative stress activates several intracellular signaling cascades that may have deleterious effects on neuronal cell survival. Thus, controlling oxidative stress has been suggested as an important strategy for prevention and/or treatment of neurodegenerative diseases. In this study, we found that ginsenoside Rh1 inhibited hydrogen peroxide-induced reactive oxygen species generation and subsequent cell death in rat primary astrocytes. Rh1 increased the expression of phase II antioxidant enzymes, such as heme oxygenase-1 (HO-1), NAD(P)H:quinone oxidoreductase 1, superoxide dismutase-2, and catalase, that are under the control of Nrf2/ARE signaling pathways. Further mechanistic studies showed that Rh1 increased the nuclear translocation and DNA binding of Nrf2 and c-Jun to the antioxidant response element (ARE), and increased the ARE-mediated transcription activities in rat primary astrocytes. Analysis of signaling pathways revealed that MAP kinases are important in HO-1 expression, and act by modulating ARE-mediated transcriptional activity. Therefore, the upregulation of antioxidant enzymes by Rh1 may provide preventive therapeutic potential for various neurodegenerative diseases that are associated with oxidative stress.