Young Chul Chung

Purple sweet potato anthocyanins attenuate hepatic lipid accumulation through activating adenosine monophosphate-activated protein kinase in human HepG2 cells and obese mice

Purple sweet potato is a functional food rich in anthocyanins that possess disease-preventive properties. Anthocyanins are known to possess potent antidiabetic properties. However, the effect of the anthocyanin fraction (AF) from purple sweet potato on hepatic lipid metabolism remains unclear. Our hypothesis is that AF inhibits hepatic lipid accumulation through the activation of adenosine monophosphate-activated protein kinase (AMPK) signaling pathways in vitro and in vivo. In this study, we evaluated body weight, liver histology, and hepatic lipid content in high-fat diet (HFD)-fed ICR mice treated with AF. In addition, we characterized the underlying mechanism of AFs effects in HepG2 hepatocytes through Western blot analysis. Anthocyanin fraction (200 mg/kg per day) reduced weight gain and hepatic triglyceride accumulation and improved serum lipid parameters in mice fed an HFD for 4 weeks. Anthocyanin fraction significantly increased the phosphorylation of AMPK and acetyl-coenzyme A carboxylase (ACC) in the liver and HepG2 hepatocytes. In addition, AF down-regulated the levels of sterol regulatory element-binding protein 1 and its target genes including ACC and fatty acid synthase (FAS). The specific AMPK inhibitor compound C attenuated the effects of AF on the expression of lipid metabolism-related proteins such as SREBP-1 and FAS in HepG2 hepatocytes. The beneficial effects of AF on HFD-induced hepatic lipid accumulation are thus mediated through AMPK signaling pathways, suggesting a potential target for the prevention of obesity.

Saponins isolated from the root of Platycodon grandiflorum protect against acute ethanol-induced hepatotoxicity in mice

The protective effects of saponins isolated from the root of Platycodon grandiflorum (Changkil saponins: CKS) against alcoholic steatosis in liver injury induced by acute ethanol administration were investigated. Pretreatment with CKS prior to ethanol administration significantly prevented the increases in serum alanine aminotransferase activity, hepatic TNF-alpha level, hepatic lipid peroxidation and hepatic triglyceride level. CKS prevented ethanol-induced steatosis and necrosis, as indicated by liver histopathological studies. Additionally, CKS protected against ethanol-induced depletion of hepatic glutathione levels. CYP2E1 has been suggested as a major contributor to ethanol-induced oxidative stress and liver injury. The concurrent administration of CKS efficaciously abrogated the CYP2E1 induction and CYP2E1-dependents hydroxylation of aniline as compared to the individual treatment at higher doses. These findings suggest that CKS may prevent ethanol-induced acute liver injury, possibly through its ability to block CYP2El-mediated ethanol bioactivation and its free radical scavenging effects.

Inhibitory mechanism of saponins derived from roots of Platycodon grandiflorum on anaphylactic reaction and IgE-mediated allergic response in mast cells

The purpose of this study was to investigate the protective effects of saponins isolated from the root of Platycodi Radix (Changkil saponins: CKS) anti-allergic effects in mice and mast cells. Oral administration of CKS inhibited the dinitrophenyl (DNP)-IgE antibody-induced systemic PCA reaction in mice. CKS reduced the beta-hexosaminidase and histamine release from anti-DNP-IgE-sensitized RBL-2H3 cells. In addition, CKS inhibited the IgE antibody-induced increases in IL-4 and TNF-alphaproduction and expression in RBL-2H3 cells. In order to explore the inhibitory mechanism of CKS in PCA and mast cell degranulation, we examined the activation of intracellular signaling molecules. CKS suppressed DNP-IgE antibody-induced Syk phosphorylation. Further downstream, CKS also inhibited the phosphorylation of Akt and MAP kinases. Taken together, the in vivo/in vitro anti-allergic effects of CKS suggest possible therapeutic applications for this agent in allergic diseases through the inhibition of inflammatory cytokines and Syk-dependent signaling cascades.

Ilimaquinone induces death receptor expression and sensitizes human colon cancer cells to TRAIL-induced apoptosis through activation of ROS-ERK/p38 MAPK–CHOP signaling pathways

TRAIL induces apoptosis in a variety of tumor cells. However, development of resistance to TRAIL is a major obstacle to more effective cancer treatment. Therefore, novel pharmacological agents that enhance sensitivity to TRAIL are necessary. In the present study, we investigated the molecular mechanisms by which ilimaquinone isolated from a sea sponge sensitizes human colon cancer cells to TRAIL. Ilimaquinone pretreatment significantly enhanced TRAIL-induced apoptosis in HCT 116 cells and sensitized colon cancer cells to TRAIL-induced apoptosis through increased caspase-8, -3 activation, PARP cleavage, and DNA damage. Ilimaquinone also reduced the cell survival proteins Bcl2 and Bcl-xL, while strongly up-regulating death receptor (DR) 4 and DR5 expression. Induction of DR4 and DR5 by ilimaquinone was mediated through up-regulation of CCAAT/enhancer-binding protein homologous protein (CHOP). The up-regulation of CHOP, DR4 and DR5 expression was mediated through activation of extracellular-signal regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK) signaling pathways. Finally, the generation of ROS was required for CHOP and DR5 up-regulation by ilimaquinone. These results demonstrate that ilimaquinone enhanced the sensitivity of human colon cancer cells to TRAIL-induced apoptosis through ROS-ERK/p38 MAPK-CHOP-mediated up-regulation of DR4 and DR5 expression, suggesting that ilimaquinone could be developed into an adjuvant chemotherapeutic drug.

Saponins, especially platycodin D, from Platycodon grandiflorum modulate hepatic lipogenesis in high-fat diet-fed rats and high glucose-exposed HepG2 cells.

AMP-activated protein kinase (AMPK) plays a central role in controlling hepatic lipid metabolism through modulating the downstream acetyl CoA carboxylase (ACC) and sterol regulatory element-binding protein-1c (SREBP-1c) pathway. Saponins, particularly platycodin D, from the roots of Platycodon grandiflorum (Changkil saponins, CKS) have a variety of pharmacological properties, including antioxidant and hepatoprotective properties. The aim of this study was to investigate the effects of CKS on hepatic lipogenesis and on the expression of genes involved in lipogenesis, and the mechanisms involved. CKS attenuated fat accumulation and the induction of the lipogenic genes encoding SREBP-1c and fatty acid synthase in the livers of HFD-fed rats and in steatotic HepG2 cells. Blood biochemical analyses and histopathological examinations showed that CKS prevented liver injury. CKS and platycodin D each increased the phosphorylation of AMPK and acetyl-CoA carboxylase in HFD-fed rats and HepG2 cells. The use of specific inhibitors showed that platycodin D activated AMPK via SIRT1/CaMKKβ in HepG2 cells. This study demonstrates that CKS or platycodin D alone can regulate hepatic lipogenesis via an AMPK-dependent signalling pathway.

Platycodi Radix attenuates dimethylnitrosamine-induced liver fibrosis in rats by inducing Nrf2-mediated antioxidant enzymes

The purpose of this study was to investigate the anti-fibrotic effects of the aqueous extract of the Platycodi Radix root (Changkil: CK) on dimethylnitrosamine (DMN)-induced liver fibrosis in rats. DMN treatment for 4 weeks led to marked liver fibrosis as assessed by serum biochemistry, histopathological examination, and hepatic lipid peroxidation and collagen content. CK significantly inhibited DMN-induced increases in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, fibrosis score, and hepatic malondialdehyde and collagen content. CK also inhibited DMN-induced reductions in rat body and liver weights. Reverse transcription polymerase chain reaction (RT-PCR) and western blot analyses revealed that CK inhibited DMN-induced increases in matrix metalloproteinase-13 (MMP-13), tissue inhibitor of metalloproteinase-1 (TIMP-1), and tumor necrosis factor-α (TNF-α) mRNA, and collagen type I and α-smooth muscle actin protein. DMN-induced cyclooxygenase-2 (COX-2) expression and nuclear factor-kappa B (NF-κB) activation was reduced by CK treatment. Furthermore, CK induced activation of nuclear erythroid 2-related factor 2 (Nrf2)-mediated antioxidant enzymes such as γ-glutamylcysteine synthetase (γ-GCS), heme oxygenase-1 (HO-1), NAD(P)H quinone oxidoreductase 1 (NQO1), and glutathione-S-transferase (GST) in HepG2 cells. These results demonstrated that CK attenuates DMN-induced liver fibrosis through the activation of Nrf2-mediated antioxidant enzymes.

Cultivated ginseng inhibits 2,4-dinitrochlorobenzene-induced atopic dermatitis-like skin lesions in NC/Nga mice and TNF-α/IFN-γ-induced TARC activation in HaCaT cells

Ginseng contains many bioactive constituents, including various ginsenosides that are believed to have anti-allergic, anti-oxidant, and immunostimulatory activities; however, its effects on atopic dermatitis (AD) remain unclear. In the current study, we hypothesized that cultivated ginseng (CG) would inhibit 2,4-dinitrochlorobenzene (DNCB)-induced AD-like skin lesions in NC/Nga mice by regulating the T helper (Th)1/Th2 balance. Also, CG inhibits TNF-α/IFN-γ-induced thymus- and activation-regulated chemokine (TARC) expression through nuclear factor-kappa B (NF-κB)-dependent signaling in HaCaT cells. CG ameliorated DNCB-induced dermatitis severity, serum levels of IgE and TARC, and mRNA expression of TARC, TNF-α, IFN-γ, IL-4, IL-5, and IL-13 in mice. Histopathological examination showed reduced thickness of the epidermis/dermis and dermal infiltration of inflammatory cells in the ears. Furthermore, CG suppressed the TNF-α/IFN-γ-induced mRNA expression of TARC in HaCaT cells. CG inhibited TNF-α/IFN-γ-induced NF-κB activation. These results suggest that CG inhibited the development of the AD-like skin symptoms by modulating Th1 and Th2 responses in the skin lesions in mice and TARC expression by suppressing TNF-α/IFN-γ-induced NF-κB activation in keratinocytes, and so may be a useful tool in the therapy of AD-like skin symptoms.

3-Caffeoyl, 4-dihydrocaffeoylquinic acid from Salicornia herbacea attenuates high glucose-induced hepatic lipogenesis in human HepG2 cells through activation of the liver kinase B1 and silent information regulator T1/AMPK-dependent pathway.

SCOPE Increasing evidence indicates that polyphenols may protect against metabolic disease through activating AMP-activated protein kinase (AMPK). The aims of our study were to provide new data on the molecular mechanism(s) underlying the role of the phenolic compound, 3-caffeoyl, 4-dihydrocaffeoylquinic acid (CDCQ) from Salicornia herbacea, in the prevention of high glucose-induced lipogenesis in human HepG2 cells. METHODS AND RESULTS Nile red staining assays were used to demonstrate lipid accumulation in the cells. Expression of sterol regulatory element-binding protein-1c (SREBP-1c) and fatty acid synthase (FAS) gene at the levels of promoter activity, mRNA, and protein was demonstrated using transient transfection assays, quantitative RT-PCR, and Western blot analyses, respectively. We found that CDCQ suppressed high glucose-induced lipid accumulation in HepG2 cells. CDCQ strongly inhibited high glucose-induced FAS expression by modulating SREBP-1c activation. Moreover, the use of both a specific inhibitor and liver kinase B1 (LKB1)-siRNA transfected HepG2 cells showed that CDCQ activated AMPK via silent information regulator T1 (SIRT1) or LKB1 in HepG2 cells. CONCLUSION These results indicate that CDCQ prevented lipid accumulation by blocking the expression of SREBP-1c and FAS through LKB1/SIRT1 and AMPK activation in HepG2 cells, suggesting that CDCQ plays a potential role in the prevention of lipogenesis by AMPK activation.

S-Allyl cysteine attenuates free fatty acid-induced lipogenesis in human HepG2 cells through activation of the AMP-activated protein kinase-dependent pathway☆

S-Allyl cysteine (SAC), a nontoxic garlic compound, has a variety of pharmacological properties, including antioxidant and hepatoprotective properties. In this report, we provide evidence that SAC prevented free fatty acid (FFA)-induced lipid accumulation and lipotoxicity in hepatocytes. SAC significantly reduced FFA-induced generation of reactive oxygen species, caspase activation and subsequent cell death. Also, SAC mitigated total cellular lipid and triglyceride accumulation in steatotic HepG2 cells. SAC significantly increased the phosphorylation of AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC) in HepG2 cells. Additionally, SAC down-regulated the levels of sterol regulatory element binding protein-1 (SREBP-1) and its target genes, including ACC and fatty acid synthase. Use of a specific inhibitor showed that SAC activated AMPK via calcium/calmodulin-dependent kinase kinase (CaMKK) and silent information regulator T1. Our results demonstrate that SAC activates AMPK through CaMKK and inhibits SREBP-1-mediated hepatic lipogenesis. Therefore, SAC has therapeutic potential for preventing nonalcoholic fatty liver disease.

Protective mechanisms of Aralia continentalis extract against tert-butyl hydroperoxide-induced hepatotoxicity: in vivo and in vitro studies.

In the present work, we investigated the protective effects of the ethanol extract of Aralia continentalis roots (AC) on tert-butyl hydroperoxide (t-BHP)-induced hepatotoxicity in a cultured Hepa1c1c7 cell line and in mouse liver. Pretreatment with AC prior to the administration of t-BHP significantly prevented the increase in serum levels of hepatic enzyme markers (ALT, AST) and lipid peroxidation and reduced oxidative stress, as measured by glutathione content, in the liver. Histopathological evaluation of the livers also revealed that AC reduced the incidence of liver lesions. The in vitro study showed that AC significantly reduced t-BHP-induced oxidative injury in Hepa1c1c7 cells, as determined by cell cytotoxicity, intracellular glutathione content, lipid peroxidation, reactive oxygen species (ROS) levels, and caspase-3 activation. Also, AC up-regulated phase II genes including heme oxygenase-1 (HO-1), NAD(P)H:quinone reductase, and glutathione S-transferase. Moreover, AC induced Nrf2 nuclear translocation and ERK1/2 and p38 activation, pathways that are involved in inducing Nrf2 nuclear translocation. Taken together, these results suggest that the protective effects of AC against t-BHP-induced hepatotoxicity may, at least in part, be due to its ability to scavenge ROS and to regulate the antioxidant enzyme HO-1 via the ERK1/2 and p38/Nrf2 signaling pathways.