Ki Sung Kang

Docosahexaenoic acid induces apoptosis in MCF-7 cells in vitro and in vivo via reactive oxygen species formation and caspase 8 activation.

Background The present study sought to further investigate the in vitro and in vivo anticancer effects of a representative omega-3 fatty acid, docosahexaenoic acid (DHA), with a focus on assessing the induction of oxidative stress and apoptosis as an important mechanism for its anticancer actions. Methodology/Principal Findings In vitro studies showed that DHA strongly reduces the viability and DNA synthesis of MCF-7 human breast cancer cells in culture, and also promotes cell death via apoptosis. Mechanistically, accumulation of reactive oxygen species and activation of caspase 8 contribute critically to the induction of apoptotic cell death. Co-presence of antioxidants or selective inhibition or knockdown of caspase 8 each effectively abrogates the cytotoxic effect of DHA. Using athymic nude mice as an in vivo model, we found that feeding animals the 5% fish oil-supplemented diet for 6 weeks significantly reduces the growth of MCF-7 human breast cancer cells in vivo through inhibition of cancer cell proliferation as well as promotion of cell death. Using 3-nitrotyrosine as a parameter, we confirmed that the fish oil-supplemented diet significantly increases oxidative stress in tumor cells in vivo. Analysis of fatty acid content in plasma and tissues showed that feeding animals a 5% fish oil diet increases the levels of DHA and eicosapentaenoic acid in both normal and tumorous mammary tissues by 329% and 300%, respectively. Conclusions/Significance DHA can strongly induce apoptosis in human MCF-7 breast cancer cells both in vitro and in vivo. The induction of apoptosis in these cells is selectively mediated via caspase 8 activation. These observations call for further studies to assess the effectiveness of fish oil as a dietary supplement in the prevention and treatment of human breast cancer.

The anti-melanogenic effect of pycnogenol by its anti-oxidative actions

Pycnogenol is a natural plant extract from pine bark that contains compounds that have anti-oxidative, free-radical scavenging properties. In this work, utilizing cultured B16 melanoma cells (B16 cells), pycnogenol was investigated for its ability to inhibit tyrosinase activity and melanin biosynthesis. We also examined the anti-oxidative power of pycnogenol by measuring its suppressive effect against peroxynitrite (ONOO-), superoxide (.O2), nitric oxide (NO.), and hydroxyl radical (.OH)-scavenging activities using an electron spin resonance spectrometer. Results show that pycnogenol had a strong anti-tyrosinase activity and suppressed melanin biosynthesis. Further, our results showed that through its anti-oxidative properties, pycnogenol suppressed .O2) NO., ONOO-, and .OH in in vitro assays, and reactive species, ONOO-, .O2, and NO., while up-regulating the reduced glutathione/oxidized glutathione ratio in B16 cells. Based on the findings, we propose that pycnogenol exerts anti-melanogenic activity via its anti-oxidative actions.

Stimulatory effect of intracerebroventricular administration of orexin A on food intake in the zebrafish, Danio rerio

Orexin is a potent orexigenic neuropeptide implicated in feeding regulation of mammals. However, except for the case of goldfish, the involvement of orexin in the feeding behavior of teleost fish has not well been studied. Therefore, we investigated the role of orexin on food intake using a zebrafish (Danio rerio) model. We examined the effect of feeding status on orexin-like immunoreactivity and the expression level of orexin transcript in the brain. The number of neuronal cells showing orexin-like immunoreactivity in the hypothalamic region, including the posterior tuberal nucleus, was significantly increased in fish fasted for 7days. Orexin precursor mRNA levels in the brain obtained from fish fasted for 7 days were higher than those in fish that had been fed normally. We then investigated the effect of intracerebroventricular (ICV) administration of orexin A on food intake. Cumulative food intake was significantly increased by ICV administration of orexin A (at 0.3 and 3 pmol/g body weight, BW) during a 60-min observation period after treatment. The orexin A-induced orexigenic action (at 0.3 pmol/g BW) was blocked by treatment with an orexin receptor antagonist, SB334867, at 10 pmol/g BW. These results indicate that orexin A acts as feeding regulator in the zebrafish.

Stereospecific anticancer effects of ginsenoside Rg3 epimers isolated from heat-processed American ginseng on human gastric cancer cell

Background Research has been conducted with regard to the development of methods for improving the pharmaceutical effect of ginseng by conversion of ginsenosides, which are the major active components of ginseng, via high temperature or high-pressure processing. Methods The present study sought to investigate the anticancer effect of heat-processed American ginseng (HAG) in human gastric cancer AGS cells with a focus on assessing the role of apoptosis as an important mechanistic element in its anticancer actions. Results and Conclusion HAG significantly reduced the cancer cell proliferation, and the contents of ginsenosides Rb1 and Re were markedly decreased, whereas the peaks of less-polar ginsenosides [20(S,R)-Rg3, Rk1, and Rg5] were newly detected. Based on the activity-guided fractionation of HAG, ginsenoside 20(S)-Rg3 played a key role in inducing apoptosis in human gastric cancer AGS cells, and it was generated mainly from ginsenoside Rb1. Ginsenoside 20(S)-Rg3 induced apoptosis through activation of caspase-3, caspase-8, and caspase-9, as well as regulation of Bcl-2 and Bax expression. Taken together, these findings suggest that heat-processing serves as an increase in the antitumor activity of American ginseng in AGS cells, and ginsenoside 20(S)-Rg3, the active component produced by heat-processing, induces the activation of caspase-3, caspase-8, and caspase-9, which contributes to the apoptotic cell death.

EPA, an omega‐3 fatty acid, induces apoptosis in human pancreatic cancer cells: Role of ROS accumulation, caspase‐8 activation, and autophagy induction

In a recent study, we showed that eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two common omega‐3 fatty acids, can cause ROS accumulation and subsequently induce caspase‐8‐dependent apoptosis in human breast cancer cells (Kang et al. [2010], PLoS ONE 5: e10296). In this study, we showed that the pancreas has a unique ability to accumulate EPA at a level markedly higher than several other tissues analyzed. Based on this finding, we sought to further investigate the anticancer actions of EPA and its analog DHA in human pancreatic cancer cells using both in vitro and in vivo models. EPA and DHA were found to induce ROS accumulation and caspase‐8‐dependent cell death in human pancreatic cancer cells (MIA‐PaCa‐2 and Capan‐2) in vitro. Feeding animals with a diet supplemented with 5% fish oil, which contains high levels of EPA and DHA, also strongly suppresses the growth of MIA‐PaCa‐2 human pancreatic cancer xenografts in athymic nude mice, by inducing oxidative stress and cell death. In addition, we showed that EPA can concomitantly induce autophagy in these cancer cells, and the induction of autophagy diminishes its ability to induce apoptotic cell death. It is therefore suggested that combination of EPA with an autophagy inhibitor may be a useful strategy in increasing the therapeutic effectiveness in pancreatic cancer. J. Cell. Biochem. 114: 192–203, 2012.

Dual beneficial effects of (-)-epigallocatechin-3-gallate on levodopa methylation and hippocampal neurodegeneration: in vitro and in vivo studies.

Background A combination of levodopa (L-DOPA) and carbidopa is the most commonly-used treatment for symptom management in Parkinsons disease. Studies have shown that concomitant use of a COMT inhibitor is highly beneficial in controlling the wearing-off phenomenon by improving L-DOPA bioavailability as well as brain entry. The present study sought to determine whether (-)-epigallocatechin-3-gallate (EGCG), a common tea polyphenol, can serve as a naturally-occurring COMT inhibitor that also possesses neuroprotective actions. Methodology/Principal Findings Using both in vitro and in vivo models, we investigated the modulating effects of EGCG on L-DOPA methylation as well as on chemically induced oxidative neuronal damage and degeneration. EGCG strongly inhibited human liver COMT-mediated O-methylation of L-DOPA in a concentration-dependent manner in vitro, with an average IC 50 of 0.36 µM. Oral administration of EGCG moderately lowered the accumulation of 3-O-methyldopa in the plasma and striatum of rats treated with L-DOPA + carbidopa. In addition, EGCG also reduced glutamate-induced oxidative cytotoxicity in cultured HT22 mouse hippocampal neuronal cells through inactivation of the nuclear factor κB-signaling pathway. Under in vivo conditions, administration of EGCG exerted a strong protective effect against kainic acid-induced oxidative neuronal death in the hippocampus of rats. Conclusions/Significance These observations suggest that oral administration of EGCG may have significant beneficial effects in Parkinsons patients treated with L-DOPA and carbidopa by exerting a modest inhibition of L-DOPA methylation plus a strong neuroprotection against oxidative damage and degeneration.

Evaluation of loganin, iridoid glycoside from Corni Fructus, on hepatic and renal glucolipotoxicity and inflammation in type 2 diabetic db/db mice.

Previously, we have reported that Corni Fructus possessed hypoglycemic and hypocholesterolemic effects in streptozotocin-induced type 1 diabetic rats and diet-induced hypercholesterolemic rats. Herein, we have focused on the effect and mechanism of loganin, a major iridoid glycoside of Corni Fructus, on the type 2 diabetic db/db mice. Loganin was orally administered to db/db mice at a dose of 20 or 100 mg/kg body weight daily for 8 weeks. The biochemical factors and expressions of protein and mRNA related to lipid metabolism, inflammation, advanced glycation endproducts, and its receptor were measured. In loganin-treated db/db mice, hyperglycemia and dyslipidemia were ameliorated in both the serum and hepatic tissue; however, in the kidney, only triglyceride was reduced. The enhanced oxidative stress was alleviated by loganin through a decrease in thiobarbituric acid-reactive substances (liver and kidney) and reactive oxygen species (serum, liver, and kidney), as well as augmentation of the oxidized to reduced glutathione ratio (liver and kidney). The marked lipid-regulatory effect of loganin was exerted in the liver of type 2 diabetic mice via suppressing mRNA expressions related to lipid synthesis and adjusting the abnormal expression of peroxisome proliferator-activated receptor α and sterol regulatory-element binding protein in the nucleus. Furthermore, loganin inhibited advanced glycation endproduct formation and the expression of its receptor, and nuclear factor-kappa B-induced inflammation in the hepatic tissue of db/db mice. Loganin exhibits protective effects against hepatic injury and other diabetic complications associated with abnormal metabolic states and inflammation caused by oxidative stress and advanced glycation endproduct formation.

Stereospecific effects of ginsenoside 20-Rg3 inhibits TGF-β1-induced epithelial–mesenchymal transition and suppresses lung cancer migration, invasion and anoikis resistance

The epithelial-mesenchymal transition (EMT) is a pivotal cellular process during which epithelial polarized cells become motile mesenchymal-appearing cells, which, in turn, promotes the metastatic potential of cancer. Ginseng is a perennial plant belonging to the genus Panax that exhibits a wide range of pharmacological and physiological activities. Ginsenosides 20-Rg3, which is the active component of ginseng, has various medical effects, such as anti-tumorigenic, anti-angiogenesis, and anti-fatiguing activities. In addition, ginsenosides 20(S)-Rg3 and 20(R)-Rg3 are epimers, and this epimerization is produced by steaming. However, the possible role of 20(S)-Rg3 and 20(R)-Rg3 in the EMT is unclear. We investigated the effect of 20(S)-Rg3 and 20(R)-Rg3 on the EMT. Transforming growth factor-beta 1 (TGF-β1) induces the EMT to promote lung adenocarcinoma migration, invasion, and anoikis resistance. To understand the repressive role of 20(S)-Rg3 and 20(R)-Rg3 in lung cancer migration, invasion, and anoikis resistance, we investigated the potential use of 20(S)-Rg3 and 20(R)-Rg3 as inhibitors of TGF-β1-induced EMT development in A549 lung cancer cells in vitro. Here, we show that 20(R)-Rg3, but not 20(S)-Rg3, markedly increased expression of the epithelial marker E-cadherin and repressed Snail upregulation and expression of the mesenchymal marker vimentin during initiation of the TGF-β1-induced EMT. 20(R)-Rg3 also inhibited the TGF-β1-induced increase in cell migration, invasion, and anoikis resistance of A549 lung cancer cells. Additionally, 20(R)-Rg3 markedly inhibited TGF-β1-regulated matrix metalloproteinase-2 and activation of Smad2 and p38 mitogen activated protein kinase. Taken together, our findings provide new evidence that 20(R)-Rg3 suppresses lung cancer migration, invasion, and anoikis resistance in vitro by inhibiting the TGF-β1-induced EMT.

Behavioral effect of neuropeptides related to feeding regulation in fish

The hypothalamus, limbic system, and brainstem play an important role in the regulation of instinctive behavior. Many kinds of hypothalamic neuropeptides, such as orexin, ghrelin, neuropeptide Y, melanin‐concentrating hormone, pituitary adenylate cyclase‐activating polypeptide, corticotropin‐releasing hormone, and diazepam‐binding inhibitor‐derived peptides, including the octadecaneuropeptide, have been implicated in the regulation of appetite and energy homeostasis in various models, including rodents and goldfish. Several of these neuropeptides also influence locomotor or psychomotor activity in rats and mice. The aim of this paper is to review the current knowledge on the psychophysiological effects of neuropeptides involved in the regulation of food intake in fish, and to examine their significance from a comparative point of view.

Neuronal gap junctions are required for NMDA receptor-mediated excitotoxicity: implications in ischemic stroke.

N-methyl-D-aspartate receptors (NMDARs) play an important role in cell survival versus cell death decisions during neuronal development, ischemia, trauma, and epilepsy. Coupling of neurons by electrical synapses (gap junctions) is high or increases in neuronal networks during all these conditions. In the developing CNS, neuronal gap junctions are critical for two different types of NMDAR-dependent cell death. However, whether neuronal gap junctions play a role in NMDAR-dependent neuronal death in the mature CNS was not known. Using Fluoro-Jade B staining, we show that a single intraperitoneal administration of NMDA (100 mg/kg) to adult wild-type mice induces neurodegeneration in three forebrain regions, including rostral dentate gyrus. However, the NMDAR-mediated neuronal death is prevented by pharmacological blockade of neuronal gap junctions (with mefloquine, 30 mg/kg) and does not occur in mice lacking neuronal gap junction protein, connexin 36. Using Western blots, electrophysiology, calcium imaging, and gas chromatography-mass spectrometry in wild-type and connexin 36 knockout mice, we show that the reduced level of neuronal death in knockout animals is not caused by the reduced expression of NMDARs, activity of NMDARs, or permeability of the blood-brain barrier to NMDA. In wild-type animals, this neuronal death is not caused by upregulation of connexin 36 by NMDA. Finally, pharmacological and genetic inactivation of neuronal gap junctions in mice also dramatically reduces neuronal death caused by photothrombotic focal cerebral ischemia. The results indicate that neuronal gap junctions are required for NMDAR-dependent excitotoxicity and play a critical role in ischemic neuronal death.