Gyu Hwan Park

[6]-Gingerol attenuates β-amyloid-induced oxidative cell death via fortifying cellular antioxidant defense system.

β-Amyloid (Aβ) is involved in the formation of senile plaques, the typical neuropathological marker for Alzheimers disease (AD) and has been reported to cause apoptosis in neurons via oxidative and/or nitrosative stress. In this study, we have investigated the neuroprotective effect and molecular mechanism of [6]-gingerol, a pungent ingredient of ginger against Αβ(25-35)-induced oxidative and/or nitrosative cell death in SH-SY5Y cells. [6]-Gingerol pretreatment protected against Aβ(25-35)-induced cytotoxicity and apoptotic cell death such as DNA fragmentation, disruption of mitochondrial membrane potential, elevated Bax/Bcl-2 ratio, and activation of caspase-3. To elucidate the neuroprotective mechanism of [6]-gingerol, we have examined Aβ(25-35)-induced oxidative and/or nitrosative stress and cellular antioxidant defense system against them. [6]-Gingerol effectively suppressed Aβ(25-35)-induced intracellular accumulation of reactive oxygen and/or nitrogen species and restored Aβ(25-35)-depleted endogenous antioxidant glutathione levels. Furthermore, [6]-gingerol treatment up-regulated the mRNA and protein expression of antioxidant enzymes such as γ-glutamylcysteine ligase (GCL) and heme oxygenase-1 (HO-1), the rate limiting enzymes in the glutathione biosynthesis and the degradation of heme, respectively. The expression of aforementioned antioxidant enzymes seemed to be mediated by activation of NF-E2-related factor 2 (Nrf2). These results suggest that [6]-gingerol exhibits preventive and/or therapeutic potential for the management of AD via augmentation of antioxidant capacity.

Neuroprotective effects of liquiritigenin isolated from licorice roots on glutamate-induced apoptosis in hippocampal neuronal cells.

The progressive death of neurons following exposure to high concentrations of glutamate leads to loss of learning and memory and pathogenesis of neurodegenerative disorders. Therefore, identification of drugs that protect against glutamate-mediated neuronal cell death is a good strategy for prevention and treatment of neurodegenerative diseases. In this study, we isolated liquiritigenin, an active compound found in licorice roots, by column chromatography and examined its protective effects against glutamate-mediated apoptotic stimuli in a mouse hippocampus-derived neuronal cell line (HT22 cells). Cell viability was significantly recovered following treatment with 50μM liquiritigenin up to 77.50±1.93% over the control (100.00±5.62%), whereas cell viability following 5mM glutamate treatment was decreased to 52.52±4.82%. Liquiritigenin effectively reduced glutamate-induced early apoptosis through inhibition of Ca(2+) influx, intracellular reactive oxygen species (ROS) production, and lipid peroxidation. In addition, the levels of Bcl-2 and full-length Bid were protected, and that of mitochondrial Bax was reduced by liquiritigenin. Liquiritigenin suppressed not only the release of apoptosis-inducing factor (AIF), but also activation of mitogen-activated protein kinases (MAPKs) such as p38, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK). Therefore, the active component in licorice roots, liquiritigenin, might facilitate development of drug leads for neurodegenerative disorders.

Genipin as a novel chemical activator of EBV lytic cycle

Epstein-Barr virus (EBV) is a ubiquitous gammaherpesvirus that causes acute infection and establishes life-long latency. EBV causes several human cancers, including Burkitt’s lymphoma, nasopharyngeal and gastric carcinoma. Antiviral agents can be categorized as virucides, antiviral chemotherapeutic agents, and immunomodulators. Most antiviral agents affect actively replicating viruses, but not their latent forms. Novel antiviral agents must be active on both the replicating and the latent forms of the virus. Gardenia jasminoides is an evergreen flowering plant belonging to the Rubiaceae family and is most commonly found growing wild in Vietnam, Southern China, Taiwan, Japan, Myanmar, and India. Genipin is an aglycone derived from an iridoid glycoside called geniposide, which is present in large quantities in the fruit of G. jasminoides. In this study, genipin was evaluated for its role as an antitumor and antiviral agent that produces inhibitory effects against EBV and EBV associated gastric carcinoma (EBVaGC). In SNU719 cells, one of EBVaGCs, genipin caused significant cytotoxicity (70 μM), induced methylation on EBV C promoter and tumor suppressor gene BCL7A, arrested cell-cycle progress (S phases), upregulated EBV latent/lytic genes in a dose-dependent manner, stimulated EBV progeny production, activated EBV F promoter for EBV lytic activation, and suppressed EBV infection. These results indicated that genipin could be a promising candidate for antiviral and antitumor agents against EBV and EBVaGC.

Critical Role of AMPK/FoxO3A Axis in Globular Adiponectin‐Induced Cell Cycle Arrest and Apoptosis in Cancer Cells

Adiponectin predominantly secreted from adipose tissue has exhibited potent anti‐proliferative properties in cancer cells via modulating cell cycle and apoptosis. FoxO3A, a Forkhead box O member of the transcription factor, plays a critical role in modulating expression of genes involved in cell death and/or survival. In this study, we investigated the role of FoxO3A signaling in anti‐cancer activities of adiponectin. Herein, we have shown that treatment with globular adiponectin (gAcrp) increases p27 but decreases cyclinD1 expression in human hepatoma (HepG2) and breast (MCF‐7) cancer cells. Gene ablation of FoxO3A prevented gAcrp‐induced increase in p27 and decreased in cyclin D1 expression, and further ameliorated cell cycle arrest by gAcrp, indicating a critical role of FoxO3A in gAcrp‐induced cell cycle arrest of cancer cells. Moreover, treatment with gAcrp also induced caspase‐3/7 activation and increased Fas ligand (FasL) expression in both HepG2 and MCF‐7 cells. Transfection with FoxO3A siRNA inhibited gAcrp‐induced caspase‐3/7 activation and FasL expression, suggesting that FoxO3A signaling also plays an important role in gAcrp‐induced apoptosis of cancer cells. We also found that gene silencing of AMPK prevented gAcrp‐induced nuclear translocation of FoxO3A in HepG2 and MCF‐7 cells. In addition, suppression of AMPK also blocked gAcrp‐induced cell cycle arrest and further attenuated gAcrp‐induced caspase‐3/7 activation, indicating that AMPK signaling plays a pivotal role in both gAcrp‐induced cell cycle arrest and apoptosis via acting as an upstream signaling of FoxO3A. Taken together, our findings demonstrated that AMPK/FoxO3A axis plays a cardinal role in anti‐proliferative effect of adiponectin in cancer cells. J. Cell. Physiol. 231: 357–369, 2016.

Protective effect of Codium fragile against UVB-induced pro-inflammatory and oxidative damages in HaCaT cells and BALB/c mice

Acute exposure to ultraviolet (UV) radiation causes pro-inflammatory responses via diverse mechanisms including oxidative stress. Codium fragile is a green alga of Codiales family and has been reported to exhibit anti-edema, anti-allergic, anti-protozoal and anti-mycobacterial activities. In this study, we have investigated a novel anti-inflammatory potential of C. fragile using in vitro cell culture as well as in vivo animal models. In HaCaT cells, buthanol and ethylacetate fractions of 80% methanol C. fragile extract (CFB or CFE) and a single compound, clerosterol (CLS) isolated from CFE attenuated UVB (60 mJ/cm(2))-induced cytotoxicity and reduced expression of pro-inflammatory proteins including cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), and tumor necrosis factor-α (TNF- α). Moreover, CFB, CFE and CLS effectively suppressed UVB-induced production of pro-inflammatory mediators such as prostaglandin E2 (PGE2) and nitric oxide (NO). In another experiment, topical application of CFB, CFE or CLS prior to UVB irradiation (200 mJ/cm(2)) on BALB/c mice, inhibited the UVB-elevated protein levels of COX-2, iNOS, and TNF-α. Furthermore, CFB, CFE and CLS suppressed oxidative damages caused by UVB irradiation for example lipid peroxidation and/or protein carbonylation, which seemed to be mediated by up-regulation of antioxidant defense enzymes. These results suggest that C. fragile could be an effective therapeutic agent providing protection against UVB-induced inflammatory and oxidative skin damages.

Evaluation of the in vitro/in vivo drug interaction potential of BST204, a purified dry extract of ginseng, and its four bioactive ginsenosides through cytochrome P450 inhibition/induction and UDP-glucuronosyltransferase inhibition

We evaluated the potential of BST204, a purified dry extract of ginseng, to inhibit or induce human liver cytochrome P450 enzymes (CYPs) and UDP-glucuronosyltransferases (UGTs) in vitro to assess its safety. In vitro drug interactions of four bioactive ginsenosides of BST204, S-Rg3, R-Rg3, S-Rh2, and R-Rh2, were also evaluated. We demonstrated that BST204 slightly inhibited CYP2C8, CYP2D6, CYP2C9, and CYP2B6 activities with IC50 values of 17.4, 26.8, 31.5, and 49.7μg/mL, respectively. BST204 also weakly inhibited UGT1A1, UGT1A9, and UGT2B7 activities with IC50 values of 14.5, 26.6, and 31.5μg/mL, respectively. The potential inhibition by BST204 of the three UGT activities might be attributable to S-Rg3, at least in part, as its inhibitory pattern was similar to that of BST204. However, BST204 showed no time-dependent inactivation of the nine CYPs studied. In addition, BST204 did not induce CYP1A2, 2B6, or 3A4/5. On the basis of an in vivo interaction studies, our data strongly suggest that BST204 is unlikely to cause clinically significant drug-drug interactions mediated via inhibition or induction of most CYPs or UGTs involved in drug metabolism in vivo. Our findings offer a clearer understanding and possibility to predict drug-drug interactions for the safe use of BST204 in clinical practice.

Anti-tumor activity of WK88-1, a novel geldanamycin derivative, in gefitinib-resistant non-small cell lung cancers with Met amplification.

Although epidermal growth factor receptor‐tyrosine kinase inhibitors (EGFR‐TKIs) have been introduced for the treatment of non‐small cell lung cancer (NSCLC), the emergence of secondary T790M mutation in EGFR or amplification of the Met proto‐oncogene restrain the clinical success of EGFR‐TKIs. Since heat shock protein‐90 (Hsp90) stabilizes various oncoproteins including EGFR and c‐Met, the inhibition of Hsp90 activity appears as a rational strategy to develop anticancer drugs. Despite preclinical efficacy of geldanamycin‐anasamycin (GA)‐derivatives containing benzoquinone moiety as Hsp90 inhibitors, the hepatotoxicity of these GA‐derivatives restricts their therapeutic benefit. We have prepared WK‐88 series of GA‐derivatives, which lack the benzoquinone moiety. In this study, we have examined the anticancer effects of WK88‐1 in Met‐amplified‐ and gefitinib‐resistant (HCC827GR) NSCLC cells and its parental HCC827 cells. Treatment with WK88‐1 reduced the cell viability in both HCC827 and HCC827GR cells, which was associated with marked decrease in the constitutive expression of Hsp90 client proteins, such as EGFR, ErbB2, ErbB3, Met and Akt. Moreover, WK88‐1 attenuated phosphorylation of these Hsp90 client proteins and reduced the anchorage‐independent growth of HCC827GR cells. Administration of WK88‐1 did not cause hepatotoxicity in animals and significantly reduced the growth of HCC827GR cells xenograft tumors in nude mice. Our study provides evidence that ErbB3 might be a client for Hsp90 in Met‐amplified NSCLCs. In conclusion, we demonstrate that inhibition of Hsp90 dampens the activation of EGFR‐ or c‐Met‐mediated survival of Met‐amplified NSCLCs and that WK88‐1 as a Hsp90 inhibitor alleviates gefitinib resistance in HCC827GR cells.

Protective Effect of Arabinoxylan against Scopolamine-Induced Learning and Memory Impairment

The purpose of this study is to investigate the memory enhancing effect and underlying molecular mechanism of arabinoxylan (AX), a major component of dietary fiber in wheat against scopolamine (SCO)-induced amnesia in Sprague-Dawley (SD) rats. Diverse behavior tests including Y-maze, Morris water maze, and passive avoidance tests were performed to measure cognitive functions. SCO significantly decreased the spontaneous alterations in Y-maze test and step-through latency in passive avoidance test, whereas increased time spent to find the hidden platform in Morris water maze test compared with the sham control group. In contrast, oral administration of AX (25 mg/kg and 50 mg/kg) effectively reversed the SCO-induced cognitive impairments in SD rats. Furthermore, AX treatment up-regulated the expression of brain-derived neurotrophic factor (BDNF) in the cortex and hippo-campus via promoting activation of cAMP response element binding protein (CREB). Therefore, our findings suggest that AX can improve SCO-induced learning and memory impairment possibly through activation of CREB and up-regulation of BDNF levels, thereby exhibiting a cognition-enhancing potential.

Effect of high-fat diet on cognitive impairment in triple-transgenic mice model of Alzheimer's disease

High-fat diet (HFD)-induced obesity is a risk factor for cognitive impairment in Alzheimers disease (AD). It has been reported that two typical neuropathological markers of AD, β-amyloid (Aβ) peptide and hyperphosphorylated protein tau can cause neuronal apoptosis via oxidative stress, which ultimately leads to cognitive dysfunction. In this study, we tried to explore the molecular pathway underlying memory impairment in young AD transgenic mice model in response to HFD. We maintained non-transgenic control mice (non-Tg) and triple transgenic AD (3xTg-AD) mice aged 8 weeks on either normal diet (ND) containing 10% fat or HFD (60% fat) for 16 weeks. Cognitive functions were evaluated by Morris water maze and Y-maze tests. Behavioral tests showed a significant memory impairment in 3xTg-AD mice fed with HFD. HFD did not alter the levels of Aβ and phospho-tau protein in the cortical region regardless of groups. However, 3xTg-AD mice fed with HFD exhibited increased neuronal oxidative stress and apoptosis as assessed by augmentation of lipid peroxidation, activation of caspase-3 and elevated ratio of Bax/Bcl-2. Furthermore, HFD markedly reduced the activation of redox-sensitive transcription factor NF-E2-related factor 2 (Nrf2) by suppressing its up-stream regulatory protein kinase B/Akt as well as down-stream targets such as heme oxygenase-1 and manganese superoxide dismutase in these mice. Our findings suggest that HFD may accelerate cognitive impairment by enhancing oxidative stress and aggravating neuronal apoptosis via inactivation of Nrf2 signaling pathway.

Sargassum fulvellum Protects HaCaT Cells and BALB/c Mice from UVB-Induced Proinflammatory Responses

Ultraviolet (UV) radiation has been reported to induce cutaneous inflammation such as erythema and edema via induction of proinflammatory enzymes and mediators. Sargassum fulvellum is a brown alga of Sargassaceae family which has been demonstrated to exhibit antipyretic, analgesic, antiedema, antioxidant, antitumor, fibrinolytic, and hepatoprotective activities. The purpose of this study is to investigate anti-inflammatory effects of ethylacetate fraction of ethanol extract of Sargassum fulvellum (SFE-EtOAc) in HaCaT keratinocytes and BALB/c mice. In HaCaT cells, SFE-EtOAc effectively inhibited UVB-induced cytotoxicity (60 mJ/cm2) and the expression of proinflammatory proteins such as cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α), and inducible nitric oxide synthase (iNOS). Furthermore, SFE-EtOAc significantly reduced UVB-induced production of proinflammatory mediators including prostaglandin E2 (PGE2) and nitric oxide (NO). In BALB/c mice, topical application of SFE-EtOAc prior to UVB irradiation (200 mJ/cm2) effectively suppressed the UVB-induced protein expression of COX-2, iNOS, and TNF-α and subsequently attenuated generation of PGE2 and NO as well. In another experiment, SFE-EtOAc pretreatment suppressed UVB-induced reactive oxygen species production and exhibited an antioxidant potential by upregulation of antioxidant enzymes such as catalase and Cu/Zn-superoxide dismutase in HaCaT cells. These results suggest that SFE-EtOAc could be an effective anti-inflammatory agent protecting against UVB irradiation-induced skin damages.