Jung Ok Ban

Green Tea (-)-Epigallocatechin-3-Gallate Inhibits β-Amyloid-Induced Cognitive Dysfunction through Modification of Secretase Activity via Inhibition of ERK and NF-κB Pathways in Mice

Alzheimers disease (AD) is characterized by the extracellular deposition of beta-amyloid peptide (Abeta) in cerebral plaques. Abeta is derived from the beta-amyloid precursor protein (APP) by the enzymes alpha-, beta- and gamma-secretase. Compounds that enhance alpha-secretase, but inhibit beta- or gamma-secretase activity, have therapeutic potential in the treatment of AD. Green tea, or its major polyphenolic compound, has been shown to have neuroprotective effects. In this study, we investigated the possible effects of (-)-epigallocatechin-3-gallate (EGCG) on memory dysfunction caused by Abeta through the change of Abeta-induced secretase activities. Mice were pretreated with EGCG (1.5 or 3 mg/kg body weight in drinking water) for 3 wk before intracerebroventricular administration of 0.5 microg Abeta(1-42). EGCG dose-dependently reduced the Abeta(1-42)-induced memory dysfunction, which was evaluated using passive avoidance and water maze tests. Abeta(1-42) induced a decrease in brain alpha-secretase and increases in both brain beta- and gamma-secretase activities, which were reduced by EGCG. In the cortex and the hippocampus, expression of the metabolic products of the beta- and gamma-secretases from APP, C99, and Abeta also were dose-dependently suppressed by EGCG. Paralleled with the suppression of beta- and gamma-secretases by EGCG, we found that EGCG inhibited the activation of extracellular signal-regulated kinase and nuclear transcription factor-kappaB in the Abeta(1-42)-injected mouse brains. In addition, EGCG inhibited Abeta(1-42)-induced apoptotic neuronal cell death in the brain. To further test the ability of EGCG to affect memory, EGCG (3 mg/kg body weight) was administered in drinking water for 1 wk to genetically developed preseniline 2 (PS2) mutant AD mice. Compared with untreated mutant PS2 AD mice, treatment with EGCG enhanced memory function and brain alpha-secretase activity but reduced brain beta- and gamma-secretase activities as well as Abeta levels. Moreover, EGCG inhibited the fibrillization of Abeta in vitro with a half maximal inhibitory concentration of 7.5 mg/L. These studies suggest that EGCG may be a beneficial agent in the prevention of development or progression of AD.

l-Theanine, an amino acid in green tea, attenuates β-amyloid-induced cognitive dysfunction and neurotoxicity: Reduction in oxidative damage and inactivation of ERK/p38 kinase and NF-κB pathways

Amyloid beta (Abeta)-induced neurotoxicity is a major pathological mechanism of Alzheimer disease (AD). In this study, we investigated the inhibitory effect of l-theanine, a component of green tea (Camellia sinensis), on Abeta(1-42)-induced neuronal cell death and memory impairment. Oral treatment of l-theanine (2 and 4 mg/kg) for 5 weeks in the drinking water of mice, followed by injection of Abeta(1-42) (2 microg/mouse, icv), significantly attenuated Abeta(1-42)-induced memory impairment. Furthermore, l-theanine reduced Abeta(1-42) levels and the accompanying Abeta(1-42)-induced neuronal cell death in the cortex and hippocampus of the brain. Moreover, l-theanine inhibited Abeta(1-42)-induced extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase as well as the activity of nuclear factor kappaB (NF-kappaB). l-Theanine also significantly reduced oxidative protein and lipid damage and the elevation of glutathione levels in the brain. These data suggest that the positive effects of l-theanine on memory may be mediated by suppression of ERK/p38 and NF-kappaB as well as the reduction of macromolecular oxidative damage. Thus, l-theanine may be useful in the prevention and treatment of AD.

Anti-inflammatory and arthritic effects of thiacremonone, a novel sulfurcompound isolated from garlic via inhibition of NF-κB

IntroductionSulfur compounds isolated from garlic exert anti-inflammatory properties. We recently isolated thiacremonone, a novel sulfur compound from garlic. Here, we investigated the anti-inflammatory and arthritis properties of thiacremonone through inhibition of NF-κB since NF-κB is known to be a target molecule of sulfur compounds and an implicated transcription factor regulating inflammatory response genes.MethodsThe anti-inflammatory and arthritis effects of thiacremone in in vivo were investigated in 12-O-tetradecanoylphorbol-13-acetate-induced ear edema, carrageenan and mycobacterium butyricum-induced inflammatory and arthritis models. Lipopolysaccharide-induced nitric oxide (NO) production was determined by Griess method. The DNA binding activity of NF-κB was investigated by electrophoretic mobility shift assay. NF-κB and inducible nitric oxide synthetase (iNOS) transcriptional activity was determined by luciferase assay. Expression of iNOS and cyclooxygenase-2 (COX-2) was determined by western blot.ResultsThe results showed that topical application of thiacremonone (1 or 2 μg/ear) suppressed the 12-O-tetradecanoylphorbol-13-acetate-induced (1 μg/ear) ear edema. Thiacremonone (1-10 mg/kg) administered directly into the plantar surface of hind paw also suppressed the carrageenan (1.5 mg/paw) and mycobacterium butyricum (2 mg/paw)-induced inflammatory and arthritic responses as well as expression of iNOS and COX-2, in addition to NF-κB DNA-binding activity. In further in vitro study, thiacremonone (2.5-10 μg/ml) inhibited lipopolysaccharide (LPS, 1 μg/ml)-induced nitric oxide (NO) production, and NF-κB transcriptional and DNA binding activity in a dose dependent manner. The inhibition of NO by thiacremonone was consistent with the inhibitory effect on LPS-induced inducible nitric oxide synthase (iNOS) and COX-2 expression, as well as iNOS transcriptional activity. Moreover, thiacremonone inhibited LPS-induced p50 and p65 nuclear translocation, resulting in an inhibition of the DNA binding activity of the NF-κB. These inhibitory effects on NF-κB activity and NO generation were suppressed by reducing agents dithiothreitol (DTT) and glutathione, and were abrogated in p50 (C62S)-mutant cells, suggesting that the sulfhydryl group of NF-κB molecules may be a target of thiacremonone.ConclusionsThe present results suggested that thiacremonone exerted its anti-inflammatory and anti-arthritic properties through the inhibition of NF-κB activation via interaction with the sulfhydryl group of NF-κB molecules, and thus could be a useful agent for the treatment of inflammatory and arthritic diseases.

Suppression of NF-κB and GSK-3β is involved in colon cancer cell growth inhibition by the PPAR agonist troglitazone

Peroxisome proliferator-activated receptor (PPAR)-gamma agonists such as troglitazone, pioglitazone and thiazolidine have been shown to induce apoptosis in human colon cancer cells. The molecular mechanism of PPARgamma agonist-induced apoptosis of colon cancer cells, however, is not clear. Glycogen synthase kinase-3beta (GSK-3beta) is an indispensable element for the activation of nuclear factor-kappa B (NF-kappaB) which plays a critical role in the mediation of survival signals in cancer cells. To investigate the mechanisms of PPARgamma agonist-induced apoptosis of colon cancer cells, we examined the effect of troglitazone (0-16muM) on the activation of GSK-3beta and NF-kappaB. Our study showed that the inhibitory effect of troglitazone on colon cancer cell growth was associated with inhibition of NF-kappaB activity and GSK-3beta expression in a dose-dependent manner. Cells were arrested in G(0)/G(1) phase followed by the induction of apoptosis after treatment of troglitazone with concomitant decrease in the expression of the G(0)/G(1) phase regulatory proteins; Cdk2, Cdk4, cyclin B1, D1, and E as well as in the anti-apoptosis protein Bcl-2 along with an increase in the expression of the pro-apoptosis-associated proteins; Caspase-3, Caspase-9 and Bax. Transient transfection of GSK-3beta recovered troglitazone-induced cell growth inhibition and NF-kappaB inactivation. In contrast, co-treatment of troglitazone with a GSK-3beta inhibitor (AR-a014418) or siRNA against GSK-3beta, significantly augmented the inhibitory effect of troglitazone on the NF-kappaB activity, the cancer cell growth and on the expression of G(0)/G(1) phase regulatory proteins and pro-apoptosis regulatory proteins. These results suggest that the PPARgamma agonist, troglitazone, inhibits colon cancer cell growth via inactivation of NF-kappaB by suppressing GSK-3beta activity.

Anti-inflammatory effect of 4-O-methylhonokiol, a novel compound isolated from Magnolia officinalis through inhibition of NF-κB

The bioactive constituents isolated from the bark of Magnolia officinalis such as magnolol, honokiol and obovatol have anti-inflammatory properties through the inactivation of NF-kappaB which is an important factor in the regulation of inflammatory reaction. We recently isolated neolignan compound, 4-O-methylhonokiol, from M. officinalis. In the present study, we investigated whether or not 4-O-methylhonokiol inhibits inflammatory reaction through the inhibition of NF-B activity [corrected]. The results showed that 4-O-methylhonokiol (2.5-10 microM) inhibited LPS (1 microg/ml)-induced NO generation in macrophage Raw 264.7 cells in a concentration-dependent manner with IC(50) value 9.8 microM. The inhibition of NO generation by 4-O-methylhonokiol was consistent with the inhibitory effect on the expression as well as transcriptional activity of inducible nitric oxide synthase (iNOS). In addition, 4-O-methylhonokiol inhibited the LPS-induced transcriptional and DNA binding activities of NF-kappaB as well as p50 and p65 translocation into the nucleus. Topical application of 4-O-methylhonokiol (0.1-1 mg/ear) inhibited 12-O-tetradecanoylphorbol-13-acetate-induced inflammatory ear edema formation, NF-kappaB activity, and iNOS and COX-2 expression. The present results provided evidence that 4-O-methylhonokiol has anti-inflammatory properties through inhibition of the NF-kappaB pathway, and suggested that 4-O-methylhonokiol can be used as an anti-inflammatory agent.

Potential therapeutic effects of functionally active compounds isolated from garlic

The medicinal properties of functionally active organosulfur compounds such as allin, diallyl disulfide, S-allylmercaptocysteine, and S-trityl-L-cysteine isolated from garlic have received great attention from a large number of investigators who have studied their pharmacological effects for the treatment of various diseases. These organosulfur compounds are able to prevent for development of cancer, cardiovascular, neurological, and liver diseases as well as allergy and arthritis. There have been also many reports on toxicities and pharmacokinetics of these compounds. The aim of this study is to review a variety of experimental and clinical reports, and describe the effectiveness, toxicities and pharmacokinetics, and possible mechanisms of pharmaceutical actions of functionally active compounds isolated from garlic.

Anti-proliferate and pro-apoptotic effects of 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyranone through inactivation of NF-κB in Human Colon Cancer Cells

Many natural compounds have been shown to prevent cancer cell growth through the redox regulation of transcription factors. NF-κB, a redox transcription factor, has been implicated in the apoptotic cell death of several cancer cells. This study examined whether or nor 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyranone (DDMP) isolated from onions can modulate the activity of NF-κB, thereby induce the apoptotic cell death of colon cancer cells. Treatment with different DDMP concentrations (0.5–1.5 mg/mL) for various periods (0–48 h) inhibited the growth of colon cancer cells (SW620 and HCT116) followed by the induction of apoptosis in a dose dependent manner. It was also found that DDMP modulated tumor necrosis factor-α (TNF-α) and tetradeanoyl phorbol acetate (TPA)-induced NF-κB transcriptional and DNA binding activity. Moreover, DDMP suppressed the NF-κB target anti-apoptotic genes (Bcl-2), whereas it induced the expression of the apoptotic genes (Bax, cleaved caspase-3 and cleaved PARP). These results suggest that DDMP from onions inhibit colon cancer cell growth by inducing apoptotic cell death through the inhibition of NF-κB.

Thiacremonone, a sulfur compound isolated from garlic, attenuates lipid accumulation partially mediated via AMPK activation in 3T3-L1 adipocytes

Garlic extracts exert anti-cancer and anti-inflammatory effects. However, the anti-adipogenic effect of garlic-derived compounds remains unclear. In this study, we examined the effect of thiacremonone, a sulfur compound isolated from garlic, on adipocyte differentiation using 3T3-L1 cells. We found that thiacremonone significantly inhibited 3T3-L1 differentiation via down-regulation of adipogenesis-related transcription factors and adipogenic markers. The inhibitory effect mainly occurred at the early phase of differentiation in 3T3-L1 cells. There was no cytotoxic effect of thiacremonone in 3T3-L1 cells and treatment of differentiating 3T3-L1 cells with thiacremonone resulted in AMPK activation, which led to an attenuated expression of acetyl CoA carboxylase-1 (ACC-1), an essential enzyme for the synthesis and usage of fatty acids. Moreover, thiacremonone enhanced the mRNA level of carnitine palmitoyltransferase (CPT-1). The modulating effect of thiacremonone on expressions of genes involved in lipolysis was partially abrogated by treatment with compound C, an AMPK inhibitor. Taken together, these results indicated that thiacremonone-induced AMPK activation, inhibition of ACC-1 expression and concomitant recovery of CPT-1 expression resulted in the suppression of intracellular lipid droplet levels, suggesting that thiacremonone may induce reduction of lipid synthesis and increases in fatty acid oxidation partially mediated via AMPK activation. Thiacremonone may be a promising compound for the treatment of obesity.

4-O-methylhonokiol attenuated β-amyloid-induced memory impairment through reduction of oxidative damages via inactivation of p38 MAP kinase☆

Oxidative stress induced neuronal cell death by accumulation of β-amyloid (Aβ) is a critical pathological mechanism of Alzheimers disease (AD). Intracerebroventrical infusion of Aβ(1-42) (300 pmol/day per mouse) for 14 days induced neuronal cell death and memory impairment, but pre-treatment of 4-O-methylhonokiol (4-O-MH), a novel compound extracted from Magnolia officinalis for 3 weeks (0.2, 0.5 and 1.0 mg/kg) prior to the infusion of Aβ(1-42) and during the infusion dose dependently improved Aβ(1-42)-induced memory impairment and prevented neuronal cell death. Additionally, 4-O-MH reduced Aβ(1-42) infusion-induced oxidative damages of protein and lipid but reduced glutathione levels in the cortex and hippocampus. Aβ(1-42) infusion-induced activation of astrocytes and p38 mitogenic activated protein (MAP) kinase was also prevented by 4-O-MH in mice brains. In further study using culture cortical neurons, p38 MAP kinase inhibitor abolished the inhibitory effect of 4-O-MH (10 μM) on the Aβ(1-42) (5 μM)-induced reactive oxidative species generation and neuronal cell death. These results suggest that 4-O-MH might prevent the development and progression of AD through the reduction of oxidative stress and neuronal cell death via inactivation of p38 MAP kinase pathway.

Thiacremonone Augments Chemotherapeutic Agent–Induced Growth Inhibition in Human Colon Cancer Cells through Inactivation of Nuclear Factor-κB

Chemotherapeutic strategies commonly use multiple agents to overcome drug resistance and to lower drug toxicity. Activation of nuclear factor-κB (NF-κB) is implicated in drug resistance in cancer cells. Previously, we reported that thiacremonone, a novel sulfur compound isolated from garlic, inhibited NF-κB and cancer cell growth with IC50 values about 100 μg/mL in colon cancer cells. In the present study, we tested whether thiacremonone could increase susceptibility of cancer cells to chemotherapeutics through inactivation of NF-κB. Colon cancer cells were cotreated with thiacremonone (50 μg/mL, half dose of IC50) and lower doses of each chemotherapeutic agent (half dose of IC50) for 24 hours. NF-κB activity was completely abrogated in cells treated with a combination of thiacremonone and docetaxel, whereas thiacremonone on its own did not alter NF-κB activity. This combined drug effect was also found with other anticancer drugs in colon cancer and in other cancer cells. In good correlation with inhibition of cell growth and NF-κB activity, the combination treatment also regulated NF-κB target genes. Oral treatment of mice with thiacremonone (1 mg/kg) by administering it in drinking water for 4 weeks significantly augmented docetaxel (1 mg/kg, i.p., four times)–induced decrease of tumor growth accompanied with regulation of NF-κB activity and NF-κB target genes. These results warrant carefully designed clinical studies investigating the combination of thiacremonone and commonly used chemotherapeutic agents for the treatment of human cancers. (Mol Cancer Res 2009;7(6):870–9)