Noriko Yamabe

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.

Resveratrol attenuates the anticancer efficacy of paclitaxel in human breast cancer cells in vitro and in vivo

It was reported recently that resveratrol could sensitise a number of cancer cell lines to the anticancer actions of several other cancer drugs, including paclitaxel. In the present study, we further investigated whether resveratrol could sensitise human breast cancer cells to paclitaxel-induced cell death. Unexpectedly, we found that resveratrol strongly diminished the susceptibility of MDA-MB-435s, MDA-MB-231 and SKBR-3 cells to paclitaxel-induced cell death in culture, although this effect was not observed in MCF-7 cells. Using MDA-MB-435s cells as a representative model, a similar observation was made in athymic nude mice. Mechanistically, the modulating effect of resveratrol was partially attributable to its inhibition of paclitaxel-induced G(2)/M cell cycle arrest, together with an accumulation of cells in the S-phase. In addition, resveratrol could suppress paclitaxel-induced accumulation of reactive oxygen species (ROS) and subsequently the inactivation of anti-apoptotic Bcl-2 family proteins. These observations suggest that the strategy of concomitant use of resveratrol with paclitaxel is detrimental in certain types of human cancers. Given the widespread use of resveratrol among cancer patients, this study calls for more preclinical and clinical testing of the potential benefits and harms of using resveratrol as a dietary adjuvant in cancer patients.

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.

Beneficial effect of 17β-estradiol on hyperglycemia and islet β-cell functions in a streptozotocin-induced diabetic rat model☆

The modulating effect of estrogen on glucose homeostasis remains a controversial issue at present. In this study, we sought to determine the beneficial effect of 17β-estradiol (E₂) on hyperglycemia and islet β-cell functions in streptozotocin (STZ)-induced diabetic rats. Male Sprague-Dawley rats were injected i.p. with STZ to induce a relatively mild diabetic condition. The rats were then treated with E₂ orally at 500 μg/kg body weight/day for 15 days to evaluate the modulating effect on hyperglycemia, insulin secretion, and islet β-cell proliferation. E₂ administration for 10 days significantly lowered plasma glucose levels, increased plasma insulin levels, and improved glucose tolerance by attenuating insulin response to oral glucose loading. These beneficial effects of E₂ were accompanied by increases in islet number and volume, rate of islet cell proliferation, and the amount of insulin secreted. The growth-stimulatory effect of E₂ on islet cells was linked to the functions of the estrogen receptor α. Notably, these protective effects of E₂ on diabetic conditions were basically not observed when the STZ-treated rats had a more severe degree of islet damage and hyperglycemia. Taken together, we conclude that E₂ can promote the regeneration of damaged pancreatic islets by stimulating β-cell proliferation in diabetic rats, and this effect is accompanied by improvements in glucose tolerance and a decrease in plasma glucose levels. These findings suggest that oral administration of E₂ may be beneficial in diabetic patients with an accelerated loss of islet β-cells.

Beneficial effects of natural phenolics on levodopa methylation and oxidative neurodegeneration

Levodopa (L-DOPA) is widely used for symptomatic management in Parkinsons disease. We recently showed that (-)-epigallocatechin-3-gallate, a tea polyphenol, not only inhibits L-DOPA methylation, but also protects against oxidative hippocampal neurodegeneration. In the present study, we sought to determine several other common dietary phenolics, namely, tea catechins [(+)-catechin and (-)-epicatechin] and a representative flavonoid (quercetin), for their ability to modulate L-DOPA methylation and to protect against oxidative hippocampal injury. A combination of in vitro biochemical assays, cell culture-based mechanistic analyses, and in vivo animal models was used. While both tea catechins and quercetin strongly inhibit human liver catechol-O-methyltransferase (COMT)-mediated O-methylation of L-DOPA in vitro, only (+)-catechin exerts a significant inhibition of L-DOPA methylation in both peripheral compartment and striatum in rats. The stronger in vivo effect of (+)-catechin on L-DOPA methylation compared to the other dietary compounds is due to its better bioavailability in vivo. In addition, (+)-catechin strongly reduces glutamate-induced oxidative cytotoxicity in HT22 mouse hippocampal neurons in vitro through inactivation of the nuclear factor-κB signaling pathway. Administration of (+)-catechin also exerts a strong neuroprotective effect in the kainic acid-induced oxidative hippocampal neurodegeneration model in rats. In conclusion, (+)-catechin is a dietary polyphenolic that may have beneficial effects in L-DOPA-based treatment of Parkinson patients by inhibiting L-DOPA methylation plus reducing oxidative neurodegeneration.

Growth‐stimulatory effect of resveratrol in human cancer cells

Earlier studies have shown that resveratrol could induce death in several human cancer cell lines in culture. Here we report our observation that resveratrol can also promote the growth of certain human cancer cells when they are grown either in culture or in athymic nude mice as xenografts. At relatively low concentrations (≤5u2009µM), resveratrol exerted a significant growth‐stimulatory effect in the MDA‐MB‐435s human cancer cells, but this effect was not observed in several other human cell lines tested. Analysis of cell signaling molecules showed that resveratrol induced the activation of JNK, p38, Akt, and NF‐κB signaling pathways in these cells. Further analysis using pharmacological inhibitors showed that only the NF‐κB inhibitor (BAY11‐7082) abrogated the growth‐stimulatory effect of resveratrol in cultured cells. In athymic nude mice, resveratrol at 16.5u2009mg/kg body weight enhanced the growth of MDA‐MB‐435s xenografts compared to the control group, while resveratrol at the 33u2009mg/kg body weight dose did not have a similar effect. Additional analyses confirmed that resveratrol stimulated cancer cell growth in vivo through activation of the NF‐κB signaling pathway. Taken together, these observations suggest that resveratrol at low concentrations could stimulate the growth of certain types of human cancer cells in vivo. This cell type‐specific mitogenic effect of resveratrol may also partly contribute to the procarcinogenic effect of alcohol consumption (rich in resveratrol) in the development of certain human cancers.

Estriol has different effects from 17β-estradiol in modulating mouse splenocyte function under inflammatory conditions

Estriol (E3), an endogenous estrogen predominantly produced during human pregnancy, has been suggested to play an important role in modulating the immune system function during pregnancy. The present study sought to investigate the ability of E3 to alter splenocyte functions in non-immunized naïve BALB/c female mice and also in mice injected with complete Freund’s adjuvant (CFA), and the effect of E3 was compared with that of 17β-estradiol (E2). When mice were injected with CFA, their spleen weight index (i.e., wet organ wet/whole body weight) was increased by ~ 300%, but co-administration of E3 almost completely suppressed splenomegaly. E3 also reduced cytokine production and reduced ERK and p38 activation in both splenocytes and peritoneal exudate cells from CFA-treated animals. In comparison, while E2 had a similar but slightly weaker effect than E3 in reducing splenomegaly, it had a rather different effect from E3 on cytokine production and ERK activation in splenocytes and peritoneal exudate cells from CFA-treated mice. Under naïve immunological conditions, E3 and E2 had very similar effects on splenocyte functions. Both of them transiently increased the percentages of splenic CD4+ and CD8+ cells. They also increased the proliferation of splenocytes ex vivo, and stimulated production of interferon-γ and interleukin-2. Altogether, these data show that E3 and E2 have different effects on splenocyte functions when the animals are under experimentally induced inflammatory conditions.

Mechanism of Ascorbate-Induced Cell Death in Human Pancreatic Cancer Cells: Role of Bcl-2, Beclin 1 and Autophagy

The present study investigates the anticancer effect of ascorbate in MIA-PaCa-2 human pancreatic cancer cells using both in vitro and in vivo models, with a focus on assessing the role of oxidative stress and autophagy as important mechanistic elements in its anticancer actions. We showed that ascorbate suppresses the growth of human pancreatic cancer cells via the induction of oxidative stress and caspase-independent cell death. Ascorbate induces the formation of autophagosomes and the presence of autophagy inhibitors suppresses ascorbate-induced cell death. These data suggest that the induction of autophagosome formation contributes to ascorbate-induced pancreatic cancer cell death.

Estriol blunts postprandial blood glucose rise in male rats through regulating intestinal glucose transporters

Despite increased total food intake in healthy, late-stage pregnant women, their peak postprandial blood sugar levels are normally much lower than the levels seen in healthy nonpregnant women. In this study, we sought to determine whether estriol (E3), an endogenous estrogen predominantly produced during human pregnancy, contributes to the regulation of the postprandial blood glucose level in healthy normal rats. In vivo studies using rats showed that E3 blunted the speed and magnitude of the blood glucose rise following oral glucose administration, but it did not appear to affect the total amount of glucose absorbed. E3 also did not affect insulin secretion, but it significantly reduced the rate of intestinal glucose transport compared with vehicle-treated animals. Consistent with this finding, expression of the sodium-dependent glucose transporter 1 and 2 was significantly downregulated by E3 treatment in the brush-border membrane and basolateral membrane, respectively, of enterocytes. Most of the observed in vivo effects were noticeably stronger with E3 than with 17β-estradiol. Using differentiated human Caco-2 enterocyte monolayer culture as an in vitro model, we confirmed that E3 at physiologically relevant concentrations could directly inhibit glucose uptake via suppression of glucose transporter 2 expression, whereas 17β-estradiol did not have a similar effect. Collectively, these data showed that E3 can blunt the postprandial glycemic surge in rats through modulating the level of intestinal glucose transporters.

Abstract 229: Omega-3 fatty acids strongly induce apoptosis in human breast cancer cells in vitro and in vivo via formation of reactive oxygen species and caspase 8 activation

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DCnn[Hypothesis] The present study sought to investigate the in vitro and in vivo anticancer effect of two representative omega-3 fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), with a focus on assessing the role of fatty acid-induced oxidative stress and apoptosis as mechanisms for their anticancer actions.nn[Methods] We used in vitro cell culture of MCF-7 human breast cancer cells and in vivo athymic nude mice model to study the effect of omega-3 fatty acids on cancer cell proliferation and the mechanism of the cell death.nn[Results] In vitro studies showed that DHA and EPA each strongly reduced the viability and DNA synthesis of MCF-7 human breast cancer cells in culture, and they also promoted cell death via apoptosis. Mechanistically, accumulation of reactive oxygen species and activation of caspase 8 contributed critically to the induction of apoptotic cell death. Co-presence of antioxidants or a selective inhibition or knockdown of caspase 8 each effectively abrogated the cytotoxic effect of DHA. Using athymic nude mice as an in vivo model, we found that feeding animals with 5% fish oil-containing diet for 6 weeks significantly reduced the growth of MCF-7 human breast cancer cells through inhibition of cancer cell proliferation as well as promotion of cell death. Using 3-nitrotyrosine as a parameter, we confirmed that fish oil diet significantly increased 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 significantly increased DHA and EPA levels in both normal and tumorous mammary tissues by 329 and 300%, respectively.nn[Conclusion] The results of this investigation clearly showed that omega-3 fatty acids strongly inhibited human breast cancer proliferation both in vitro and in vivo via formation of reactive oxygen species and induction of apoptosis by caspase 8 activation. This study calls for further studies in human subjects to assess the effectiveness of fish oil as a dietary supplement in the treatment of certain types of cancers.nnNote: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.nnCitation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 229.