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Tetrahydrocurcumin, a major metabolite of curcumin, is more effective than curcumin in preventing azoxymethane-induced colon carcinogenesis
Discussion: The findings point to an anti-inflammatory role of GPx2, that seems to be associated with inflammation resolution, thus inhibiting colitis-driven carcinogenesis. In the AOM model the presence of GPx2 was associated with higher tumor numbers. Therefore, the postulated anti-carcinogenic function of GPx2 depends on the involvement of an inflammation. Keywords: GPx2, colorectal cancer, colitis, selenium doi:10.1016/j.freeradbiomed.2012.08.245 [0129] Role of selenite in differentiation of acute myeloid leukemia cells S. Misra*, M. Wallenberg, A. Barsham, M. Björnstedt, A. Fernandes Karolinska Institutet, Sweden Acute myeloid leukemia (AML) is characterized by clonal proliferation of hematological malignant neoplasm that possesses compromised ability to differentiate into mature leukocytes. Conventional chemotherapy is being persistently used to treat AML patients, often resulting in poor survival associated with side effects of chemotherapy and unfavourable cytogenetics. Thus, there exists a persuasive need to develop more effective and less toxic therapies. Inorganic selenium (as selenite) has been reported to be effective in selective killing of other form of cancer cells. Context wise, our previous investigation indicates superior cytotoxicity of selenite to primary leukemic cells when compared to conventional chemotherapeutic agents used ex vivo. Apart from it, selenite is a potential modulator of cellular differentiation. In line with these observations, the present work is aimed at understanding whether selenium exerts differentiation in a malignant cell line (NB-4) of hematopoietic origin. Our preliminary results suggest distinct differentiation effect of selenite in NB-4 cells based on cell surface CD markers and morphological evaluations. We also investigate effects on the gene expression of several oxidoreductases under these differentiation processes. Keywords: Leukemia, Oxidoreductases
Selenium,
Differentiation,
[0131] Effect of ascorbic acid on formaldehydemediated DNA oxidation and methylation in human bronchial epithelial cell lines Y. Ke*, J. Hu, J. Cheng, J. Yuan, X. Xie Shenzhen Center for Disease Control and Prevention, China Background: DNA oxidation and DNA methylation are two important biological phenomena universally exist in body cells, Formaldehyde (FA) is a well-recognized human carcinogen, its carcinogenic mechanisms are still poorly understood. Previous studies have emphasized on genetic changes. However, little is known about the epigenetic mechanisms of FA exposure. Objective: To study the intrinsic association between oxidative DNA damage and DNA methylation when exposed to FA. Methods: We measured the levels of DNA adducts in untreated and FA-treated 16HBE cells for five days. 8Hydroxydeoxyguanosine (8-OHdG), a biomarker for oxidative DNA damage, was analyzed following enzymatic hydrolysis of DNA. 7-Methylguanine (7mGua), the most suitable biomarker for the DNA adducts formed by methylating agents, was released by thermal depurination of DNA. The modified guanine adducts were separated by HPLC and quantified using electrochemical detection. Results: The levels of 8OHdG and 7-mGua in 16HBE cells treated with FA increased up to approximately 3.5- and 2.1-fold over those in the untreated cells, respectively. However, the peak of 8-OHdG appeared about 1.5 days earlier than that of 7-mGua. The addition of ascorbic acid, an antioxidant, to the FA-treated cells resulted in decrease in the cytotoxicity with a concomitant decrease in the levels of 8-OHdG, but a significant increase in the levels of 7-mGua. Conclusion: Our results suggest that FAmediated DNA methylation and DNA oxidation might play an important role in its carcinogenic mechanisms, and support the hypothesis that DNA oxidation would inhibit DNA methylation. Keywords: Ascorbic Acid, Oxidation, DNA Methylation
Formaldehyde,
DNA
doi:10.1016/j.freeradbiomed.2012.08.247 [0145]
doi:10.1016/j.freeradbiomed.2012.08.246 Influence of pyruvate on ascorbic acid-mediated cytotoxicity in tumor cells L. Eberhardt*, J. Locher, S. Rodemeister, D. Nohr University of Hohenheim, Germany
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It is well known that pharmacologic ascorbic acid concentrations have cytotoxic effects on many tumor cell lines. The proposed mechanism is based on the extracellular ascorbic acid-dependent production of H2O2. This highly membrane-permeable molecule enters the cells and subsequently triggers several intracellular pathways, finally leading to apoptosis. However, the highly metastatic melanoma cell line WM451 used in our experiments seemed to be resistant towards ascorbic acid treatment up to a concentration of 25mM, which in fact represents one of the highest concentrations used by others. We therefore tried to kill the tumor cells by direct application of the main mediator, namely hydrogen peroxide. Unfortunately, we were not able to detect a notable cytotoxic effect up to a concentration of 1mM H2O2. As there is evidence that sodium pyruvate, a component often present in cell culture media, might lead to hydrogen peroxide degradation, we then decided to repeat this experiment in a pyruvate-free environment. Under these conditions, H2O2 in fact led to a concentration-dependent killing of the cells, which in turn could be prevented by re-addition of sodium pyruvate to the medium. We therefore suggest the presence of pyruvate in some cell culture media being a reason for the ineffectiveness of ascorbic acid treatment. Keywords: ascorbic acid, pyruvate, cytotoxic action doi:10.1016/j.freeradbiomed.2012.08.248 [0180] Tetrahydrocurcumin, a major metabolite of curcumin, is more effective than curcumin in preventing azoxymethane-induced colon carcinogenesis M.H. Pan*1, C.S. Lai1, J.C. Wu1, C.T. Ho1 et al 1 National Kaohsiung Marine University, Taiwan, 2Rutgers University, USA Tetrahydrocurcumin (THC), a major metabolite of curcumin (CUR), has been demonstrated to be anticancerogenic and anti-angiogenic and prevents type II diabetes. In this present study, we investigated the chemopreventive effects and underlying molecular mechanisms of dietary administration of CUR and THC in azoxymethane (AOM)-induced colon carcinogenesis in mice. All mice were sacrificed at 6 and 23 wk, and colonic tissue was collected and examined. We found that dietary administration of both CUR and THC could reduce aberrant crypt foci and polyps formation, while THC showed a better inhibitory effect than CUR. At the molecular level, results from Western blot analysis and
immunohistochemistry staining showed that dietary CUR and THC exhibited anti-inflammatory activity by decreasing the levels of inducible NOS and COX-2 through downregulation of ERK1/2 activation. In addition, both dietary CUR and THC significantly decreased AOM-induced Wnt-1 and β-catenin protein expression, as well as the phosphorylation of GSK-3β in colonic tissue. Moreover, dietary feeding with CUR and THC markedly reduced the protein level of connexin-43, an important molecule of gap junctions, indicating that both CUR and THC might interfer with the intercellular communication of crypt cells.Taken together, these results demonstrated for the first time the in vivo chemopreventive efficacy and molecular mechanisms of dietary THC against AOM-induced colonic tumorigenesis. Keywords: Tetrahydrocurcumin, Colon carcinogenesis, AOM, Inflammation doi:10.1016/j.freeradbiomed.2012.08.249 [0188] Temporal changes in gene expression and cellular responses after exposure to different oxygen radical generating compounds in human liver carcinoma cells L. Deferme*, J.J. Briedé, J.C.S. Kleinjans Maastricht University, The Netherlands Oxidative stress plays an important role in hepatocarcinogenesis, however, our insight in the molecular responses to different oxygen radicals is fragmentary and incomplete. Since these cellular responses will differ in time, examining time-dependent changes in gene expression and correlation with phenotypical markers may provide new insights in responses to oxidants. Using electron spin resonance (ESR) spectroscopy, time dependent radical formation in a human hepatoma cell line (HepG2 cells) after exposure to menadione, tert-butyl hydroperoxide (TBH) and H2O2/Fe2+ was investigated. All compounds showed different types of radicals (superoxide anion-, hydroxyland methyl radicals) and a different time-dependent pattern. Whole genome expression was studied by an extensive time series (0.5, 1, 2, 4, 6, 8 and 24h) and correlated to different phenotypical markers of oxidative stress (apoptosis and cell cycle distribution, protein oxidation and oxidative DNA damage). Gene expression analysis resulted in 4414 differentially expressed genes upon menadione exposure, 2284 genes after TBH exposure and 483 genes after H2O2/Fe2+ treatment. In total, 136 genes were commonly modified after exposure to these 3 oxidants. Hierarchical clustering of these 136
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Selenium,
Differentiation,
[0131] Effect of ascorbic acid on formaldehydemediated DNA oxidation and methylation in human bronchial epithelial cell lines Y. Ke*, J. Hu, J. Cheng, J. Yuan, X. Xie Shenzhen Center for Disease Control and Prevention, China Background: DNA oxidation and DNA methylation are two important biological phenomena universally exist in body cells, Formaldehyde (FA) is a well-recognized human carcinogen, its carcinogenic mechanisms are still poorly understood. Previous studies have emphasized on genetic changes. However, little is known about the epigenetic mechanisms of FA exposure. Objective: To study the intrinsic association between oxidative DNA damage and DNA methylation when exposed to FA. Methods: We measured the levels of DNA adducts in untreated and FA-treated 16HBE cells for five days. 8Hydroxydeoxyguanosine (8-OHdG), a biomarker for oxidative DNA damage, was analyzed following enzymatic hydrolysis of DNA. 7-Methylguanine (7mGua), the most suitable biomarker for the DNA adducts formed by methylating agents, was released by thermal depurination of DNA. The modified guanine adducts were separated by HPLC and quantified using electrochemical detection. Results: The levels of 8OHdG and 7-mGua in 16HBE cells treated with FA increased up to approximately 3.5- and 2.1-fold over those in the untreated cells, respectively. However, the peak of 8-OHdG appeared about 1.5 days earlier than that of 7-mGua. The addition of ascorbic acid, an antioxidant, to the FA-treated cells resulted in decrease in the cytotoxicity with a concomitant decrease in the levels of 8-OHdG, but a significant increase in the levels of 7-mGua. Conclusion: Our results suggest that FAmediated DNA methylation and DNA oxidation might play an important role in its carcinogenic mechanisms, and support the hypothesis that DNA oxidation would inhibit DNA methylation. Keywords: Ascorbic Acid, Oxidation, DNA Methylation
Formaldehyde,
DNA
doi:10.1016/j.freeradbiomed.2012.08.247 [0145]
doi:10.1016/j.freeradbiomed.2012.08.246 Influence of pyruvate on ascorbic acid-mediated cytotoxicity in tumor cells L. Eberhardt*, J. Locher, S. Rodemeister, D. Nohr University of Hohenheim, Germany
S118
It is well known that pharmacologic ascorbic acid concentrations have cytotoxic effects on many tumor cell lines. The proposed mechanism is based on the extracellular ascorbic acid-dependent production of H2O2. This highly membrane-permeable molecule enters the cells and subsequently triggers several intracellular pathways, finally leading to apoptosis. However, the highly metastatic melanoma cell line WM451 used in our experiments seemed to be resistant towards ascorbic acid treatment up to a concentration of 25mM, which in fact represents one of the highest concentrations used by others. We therefore tried to kill the tumor cells by direct application of the main mediator, namely hydrogen peroxide. Unfortunately, we were not able to detect a notable cytotoxic effect up to a concentration of 1mM H2O2. As there is evidence that sodium pyruvate, a component often present in cell culture media, might lead to hydrogen peroxide degradation, we then decided to repeat this experiment in a pyruvate-free environment. Under these conditions, H2O2 in fact led to a concentration-dependent killing of the cells, which in turn could be prevented by re-addition of sodium pyruvate to the medium. We therefore suggest the presence of pyruvate in some cell culture media being a reason for the ineffectiveness of ascorbic acid treatment. Keywords: ascorbic acid, pyruvate, cytotoxic action doi:10.1016/j.freeradbiomed.2012.08.248 [0180] Tetrahydrocurcumin, a major metabolite of curcumin, is more effective than curcumin in preventing azoxymethane-induced colon carcinogenesis M.H. Pan*1, C.S. Lai1, J.C. Wu1, C.T. Ho1 et al 1 National Kaohsiung Marine University, Taiwan, 2Rutgers University, USA Tetrahydrocurcumin (THC), a major metabolite of curcumin (CUR), has been demonstrated to be anticancerogenic and anti-angiogenic and prevents type II diabetes. In this present study, we investigated the chemopreventive effects and underlying molecular mechanisms of dietary administration of CUR and THC in azoxymethane (AOM)-induced colon carcinogenesis in mice. All mice were sacrificed at 6 and 23 wk, and colonic tissue was collected and examined. We found that dietary administration of both CUR and THC could reduce aberrant crypt foci and polyps formation, while THC showed a better inhibitory effect than CUR. At the molecular level, results from Western blot analysis and
immunohistochemistry staining showed that dietary CUR and THC exhibited anti-inflammatory activity by decreasing the levels of inducible NOS and COX-2 through downregulation of ERK1/2 activation. In addition, both dietary CUR and THC significantly decreased AOM-induced Wnt-1 and β-catenin protein expression, as well as the phosphorylation of GSK-3β in colonic tissue. Moreover, dietary feeding with CUR and THC markedly reduced the protein level of connexin-43, an important molecule of gap junctions, indicating that both CUR and THC might interfer with the intercellular communication of crypt cells.Taken together, these results demonstrated for the first time the in vivo chemopreventive efficacy and molecular mechanisms of dietary THC against AOM-induced colonic tumorigenesis. Keywords: Tetrahydrocurcumin, Colon carcinogenesis, AOM, Inflammation doi:10.1016/j.freeradbiomed.2012.08.249 [0188] Temporal changes in gene expression and cellular responses after exposure to different oxygen radical generating compounds in human liver carcinoma cells L. Deferme*, J.J. Briedé, J.C.S. Kleinjans Maastricht University, The Netherlands Oxidative stress plays an important role in hepatocarcinogenesis, however, our insight in the molecular responses to different oxygen radicals is fragmentary and incomplete. Since these cellular responses will differ in time, examining time-dependent changes in gene expression and correlation with phenotypical markers may provide new insights in responses to oxidants. Using electron spin resonance (ESR) spectroscopy, time dependent radical formation in a human hepatoma cell line (HepG2 cells) after exposure to menadione, tert-butyl hydroperoxide (TBH) and H2O2/Fe2+ was investigated. All compounds showed different types of radicals (superoxide anion-, hydroxyland methyl radicals) and a different time-dependent pattern. Whole genome expression was studied by an extensive time series (0.5, 1, 2, 4, 6, 8 and 24h) and correlated to different phenotypical markers of oxidative stress (apoptosis and cell cycle distribution, protein oxidation and oxidative DNA damage). Gene expression analysis resulted in 4414 differentially expressed genes upon menadione exposure, 2284 genes after TBH exposure and 483 genes after H2O2/Fe2+ treatment. In total, 136 genes were commonly modified after exposure to these 3 oxidants. Hierarchical clustering of these 136
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