Proteins with thiol groups interact with metal ions in the human body. They maintain their homeostasis, participate in cell signaling, protect the cell against the effects of toxic metals and detoxify them. This work is focused on proteins with thiol groups glutathione and metallothionein and their effects on selenium. The method of study is electrochemical.

Cell proliferation plays an important role in multistage chemical carcinogenesis. Again, several reports demonstrated that upregulation of metallothionein (MT) expression is associated with increased cell proliferation that may contribute to the pathogenesis of preneoplastic phenotype to frank malignancy. In this study, we evaluated the roles of early DNA damage, altered expressions of liver MT and Ki-67 nuclear antigen, and altered hepatic levels of zinc (Zn) and copper (Cu) on cell proliferation and the progression of hepatocarcinogenesis through premalignant, late premalignant and malignant transformation phases in male Sprague-Dawley rats. We have further studied the association between MT expression and cell proliferation in hepatocarcinogenesis. There was substantial induction of DNA single-strand breaks (SSBs) (P < 0.001) and development of hepatocellular premalignant lesions along with significant decrease in hepatic levels of Zn and increase in Cu content following a single, necrogenic, intraperitoneal (i.p.) injection (200 mg/Kg body weight) of diethylnitrosamine (DEN) at week 4 of the experimental protocol. Moreover, DEN + phenobarbital (PB)-treatment significantly elevated MT-, Ki-67-, and BrdU-immunoexpressions along with their immunolabeling indices. Furthermore, positive correlations between MT- and Ki-67- labeling (P = 0.0006) at various time intervals, as well as, between MT immunoreactivity and 5'-bromo-2'-deoxyuridine-labeling index (BrdU-LI) (P = 0.0007) indicate that, MT expression might be associated with Ki-67 expression and cell proliferation thereby. The study suggests that DEN treatment may lead to alteration of Zn and Cu levels resulting in early DNA damage along with elevation of MT expression that may ultimately lead to hepatic cell proliferation. The results thus provide evidence in support of the role of MT as a potential positive regulator of cell growth during the early stages of hepatocellular transformation in rats.

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Cheuk, Wai Ka. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 96-108). / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgements --- p.v / Table of contents --- p.vi / List of Tables --- p.ix / List of Figures --- p.x / Abbreviations --- p.xii / Chapter CHAPTER 1 --- General introduction / Chapter 1.1 --- Metal Contaminations in the environment --- p.1 / Chapter 1.2 --- Biology of Heavy Metal Ions --- p.3 / Chapter 1.2.1 --- Essential and non-essential metal ions --- p.3 / Chapter 1.2.2 --- Toxicities and origins of heavy metal ions --- p.5 / Chapter 1.3 --- Monitoring Of Heavy Metal Contaminations In Aquatic Environment --- p.9 / Chapter 1.3.1 --- Monitoring in chemical approach --- p.9 / Chapter 1.3.2 --- Monitoring in biological approach: biomarkers --- p.11 / Chapter 1.4 --- Metallothionein (MT) --- p.12 / Chapter 1.4.1 --- Biological functions of MT and its regulation --- p.12 / Chapter 1.4.2 --- MT isoforms --- p.14 / Chapter 1.4.3 --- Mechanisms of MT gene regulation --- p.15 / Chapter 1.4.3.1 --- Zinc pool hypothesis --- p.20 / Chapter 1.4.3.2 --- Protein kinase cascade --- p.21 / Chapter 1.5 --- Metal responsive element (MRE) --- p.22 / Chapter 1.6 --- MRE-Binding Transcription Factor-1 (MTF-1) --- p.30 / Chapter 1.6.1 --- Structure of MTF-1 --- p.30 / Chapter 1.6.2 --- Physiological functions of MTF-1 --- p.32 / Chapter 1.6.3 --- The role of MTF-1 in MT gene regulation --- p.33 / Chapter 1.6.4 --- Regulation of MTF-1 by various heavy metals --- p.34 / Chapter 1.7 --- Zebrafish (Daino reio) --- p.36 / Chapter 1.8 --- Project aim --- p.37 / Chapter CHAPTER 2 --- Materials and Methods / Chapter 2.1 --- Cell Culture --- p.40 / Chapter 2.1.1 --- ZFL cell line --- p.40 / Chapter 2.1.2 --- SJD cell line --- p.41 / Chapter 2.2 --- Alarmar blue̐ưؤ M assay --- p.41 / Chapter 2.3 --- First strand cDNA synthesis --- p.42 / Chapter 2.3.1 --- Metal treatment of the SJD and ZFL cell lines --- p.42 / Chapter 2.3.2 --- Isolation of total RNA --- p.43 / Chapter 2.3.3 --- Quantification of mRNA by spectrophotometer --- p.43 / Chapter 2.3.4 --- Reverse Transcription --- p.44 / Chapter 2.4 --- Quantifications of mRNA levels by using real-time PCR technique --- p.44 / Chapter 2.4.1 --- Primer design --- p.44 / Chapter 2.4.2 --- PCR components and cycling condition --- p.45 / Chapter 2.4.3 --- Determination of relative amount of target gene present in the samples --- p.49 / Chapter 2.5 --- Cloning of zMT-II gene promoter and its transient expression studies --- p.50 / Chapter 2.5.1 --- Purification of genomic DNA --- p.50 / Chapter 2.5.2 --- Preparation of Escherichia coli competent cell --- p.51 / Chapter 2.5.3 --- PCR-Cloning of a 1.4 kb zMT-II gene promoter --- p.51 / Chapter 2.5.4 --- Purification of plasmid DNA --- p.53 / Chapter 2.5.5 --- Transient transfection of plasmid into SJD and ZFL cells --- p.54 / Chapter 2.5.6 --- Heavy metal treatments and measurement of luciferase activities --- p.54 / Chapter CHAPTER 3 --- Results / Chapter 3.1 --- Toxicities of various heavy metal ions --- p.56 / Chapter 3.2 --- Relative mRNA fold induction of zMT in SJD and ZFL cell lines --- p.59 / Chapter 3.3 --- The zMT-II gene and its induction by metal ions in zebrafish cell-lines --- p.63 / Chapter 3.4 --- MTF-1 mRNA levels in SJD and ZFL cell lines exposed to heavy metal ions --- p.74 / Chapter CHAPTER 4 --- Discussion / Chapter 4.1 --- Comparison of metal toxicities in the two cell lines studied --- p.78 / Chapter 4.2 --- zMT gene expression study --- p.80 / Chapter 4.2.1 --- zMT mRNA regulation by heavy metal ions in the two cell lines --- p.80 / Chapter 4.2.2 --- The potential use of MT regulation as exposure biomarker --- p.82 / Chapter 4.3 --- Structure of the zMT-II gene promoter region --- p.82 / Chapter 4.4 --- Metal responsiveness of zMT-II promoter --- p.84 / Chapter 4.5 --- Mechanism of MT gene expression and the MTF-1 mRNA inductions in SJD and ZFL cell lines --- p.86 / Chapter 4.6 --- Concluding Remarks --- p.93 / References --- p.96

Os resultados obtidos no mestrado mostraram que a samambaia do campo (Pteridium aquilinum) reduz a citotoxicidade das células natural killer (NK) esplênicas e a resposta imune celular do tipo tardia (DTH) de camundongos. Entretanto, até aquele momento não era sabido qual a célula afetada pela planta causava a diminuição da DTH. Assim, o objetivo inicial deste estudo foi verificar qual a célula envolvida na diminuição da DTH. Além disto, buscou-se descobrir o mecanismo de ação imunotóxico da P. aquilinum, o principio tóxico envolvido e se este efeito poderia ser revertido pelo selênio (Se). Para tal, camundongos C57BL/6 foram administrados com extrato de P. aquilinum, por gavage, durante 30 dias e suplementados com Se por mais 30 dias e a análise histológica revelou redução significativa na área de polpa branca esplênica que foi completamente revertida pelo tratamento com Se. Ainda, foi possível verificar que a diminuição da DTH foi causada pela redução da produção de IFN&gamma; pelas células NK durante a indução da resposta imune celular. Além disto, camundongos administrados com ptaquilosídeo, por gavage, durante 14 dias mostraram a mesma redução na atividade das células NK causada pelo extrato de P. aquilinum, assim como a prevenção deste efeito pela co-administração de Se. Por fim, na análise da expressão gênica das células NK esplênicas dos camundongos tratados com ptaquilosídeo e/ou selênio pôde-se observar o aumento da expressão dos genes Mt1 e Mt2, possíveis responsáveis pelo mecanismo imunotóxico da planta, sendo posteriormente confirmado pelo aumento de metalotioneína e consequente redução de Zn2+ livre no espaço intracelular das células NK. Os resultados deste estudo claramente mostram que os efeitos imunossupressores da P. aquilinum são induzidos pelo ptaquilosídeo e são decorrentes do aumento da expressão dos genes da Mt1 e Mt2 e que a suplementação com Se pode prevenir e reverter estes efeitos tóxicos. / The results obtained in the master showed that the bracken fern (Pteridium aquilinum) reduces both the cytotoxicity of splenic natural killer cells (NK) and the delayed-type hypersensitivity (DTH) from mice. However, it was not known until that time, which cell affected by the plant that caused a decrease in DTH. Thus, the initial goal of this study was to determine which cell was involved in the reduction of DTH. Moreover, we sought to discover the mechanism of action of the P. aquilinum, the toxic principle involved and whether this effect could be reversed by selenium (Se). For that, C57BL/6 mice were treated with extract of P. aquilinum, by gavage, for 30 days and supplemented with Se for following 30 days. The histological analysis revealed a significant reduction in the splenic white pulp area that was completely reversed by treatment with Se. Still, it was verified that the decrease in DTH was caused by reduced production of IFN&gamma; by NK cells during the induction of cellular immune response. In addition, the mice administered with ptaquiloside, by gavage, for 14 days showed the same reduction in the NK cell activity caused by the extract of P. aquilinum, as well as the prevention of this effect by co-administration of Se. Finally, we could observe an increase in the expression of Mt1 and Mt2 genes in the gene expression analysis of splenic NK cells from mice treated with ptaquiloside and/or selenium. These genes were probably responsible for immunotoxic mechanism of the plant, which was confirmed later by the augment of metallothionein and consequent reduction of free Zn2+ into the intracellular space of NK cells. The results of this study clearly show that the immunosuppressive effects of P. aquilinum are induced by ptaquiloside and they are a consequence of the augment in the gene expression of Mt1 and Mt2 and that the supplementation with Se can prevent and reverse these toxic effects.

O carcinoma epidermóide é a neoplasia maligna que ocorre com maior freqüência na boca. Os pacientes portadores desta neoplasia ainda apresentam um pobre prognóstico com índices de sobrevida, em cinco anos, variando de 20 a 40% em vários estudos. Um grande número de trabalhos tem sido direcionado para identificar marcadores que auxiliem no direcionamento do tratamento e melhorem o prognóstico. A metalotioneína (MT) é uma proteína de baixo peso molecular, com alto conteúdo de cisteína e que está associada à resistência neoplásica a várias modalidades de tratamento, e que por isso tem sido estudada como fator prognóstico em uma variedade de neoplasias malignas humanas. O Fator Nuclear B desempenha um importante papel na ativação de genes que estão relacionados à imunidade, inflamação, sobrevida, apoptose, proteção celular à radiação e à quimioterapia. A proteína serina/treonina quinase Akt é um alvo downstream da quinase 3-fosfaditilinositol, desempenhando um importante papel na proliferação e no bloqueio da apoptose de células cancerígenas. Neste estudo, nós examinamos a expressão das proteínas MT, NF-kB e pAKT em 51 casos de carcinomas epidermóides de boca, através de imunoistoquímica, com a finalidade de investigar suas influências prognosticas, assim como estudar as correlações entre alguns fatores clínicos com a sobrevida. Os resultados mostraram uma associação estatisticamente significante entre a expressão pAkt e NF-kB e entre MT e NF-kB. Ao lado disso, nossos resultados mostraram que a expressão de pAkt está associada a um pior prognóstico. Nossos resultados, portanto, sugerem que a proteína pAkt pode ter implicações terapêuticas em carcinomas epidermóides de boca. / Oral squamous cell carcinoma (OSCC) is the most frequent malignant tumor of the oral cavity. In spite of improved therapeutic procedures, patients with OSCC in advanced stage generally present a poor prognosis, with an overall 5-year survival rate that ranges from 20% to 40%. An extensive effort has started to identify features of the oral tumors that predict treatment response and prognosis. The metallothionein (MT), a low-molecular weight protein with high cysteine content, seems to be related to neoplastic resistance to oncologic treatment and therefore has been studied as a prognostic factor for a variety of human malignant tumors. The nuclear factor B (NF-B) plays an important role in the activation of the genes that code for immunity, survival, inflammation, apoptosis and in the cell protection for radiation and chemotherapy. The serine/threonine protein kinase Akt is a downstream target of phosphatidylinositol-3-kinase and it plays a key regulator of cancerous cell growth. Therefore, we have examined the MT, NF-kB and pAkt expression in 51 samples of oral squamous cell carcinoma by immunohistochemistry in order to investigate their prognostic influence on oral cancer, as well as studying the correlations between clinical factors and patient survival. The results showed a significant association between pAkt and NF-kB and between MT and NF-kB expression in tumor tissue. Besides pAkt over-expression was found in OSCC clinical samples and its expression was significantly associated with a poor overall patient survival. In conclusion, our findings suggested that pAkt expression may have therapeutic implications in squamous cell carcinoma.

O carcinoma epidermóide é a neoplasia maligna que ocorre com maior freqüência na boca. Os pacientes portadores desta neoplasia ainda apresentam um pobre prognóstico com índices de sobrevida, em cinco anos, variando de 20 a 40% em vários estudos. Um grande número de trabalhos tem sido direcionado para identificar marcadores que auxiliem no direcionamento do tratamento e melhorem o prognóstico. A metalotioneína (MT) é uma proteína de baixo peso molecular, com alto conteúdo de cisteína e que está associada à resistência neoplásica a várias modalidades de tratamento, e que por isso tem sido estudada como fator prognóstico em uma variedade de neoplasias malignas humanas. O Fator Nuclear B desempenha um importante papel na ativação de genes que estão relacionados à imunidade, inflamação, sobrevida, apoptose, proteção celular à radiação e à quimioterapia. A proteína serina/treonina quinase Akt é um alvo downstream da quinase 3-fosfaditilinositol, desempenhando um importante papel na proliferação e no bloqueio da apoptose de células cancerígenas. Neste estudo, nós examinamos a expressão das proteínas MT, NF-kB e pAKT em 51 casos de carcinomas epidermóides de boca, através de imunoistoquímica, com a finalidade de investigar suas influências prognosticas, assim como estudar as correlações entre alguns fatores clínicos com a sobrevida. Os resultados mostraram uma associação estatisticamente significante entre a expressão pAkt e NF-kB e entre MT e NF-kB. Ao lado disso, nossos resultados mostraram que a expressão de pAkt está associada a um pior prognóstico. Nossos resultados, portanto, sugerem que a proteína pAkt pode ter implicações terapêuticas em carcinomas epidermóides de boca. / Oral squamous cell carcinoma (OSCC) is the most frequent malignant tumor of the oral cavity. In spite of improved therapeutic procedures, patients with OSCC in advanced stage generally present a poor prognosis, with an overall 5-year survival rate that ranges from 20% to 40%. An extensive effort has started to identify features of the oral tumors that predict treatment response and prognosis. The metallothionein (MT), a low-molecular weight protein with high cysteine content, seems to be related to neoplastic resistance to oncologic treatment and therefore has been studied as a prognostic factor for a variety of human malignant tumors. The nuclear factor B (NF-B) plays an important role in the activation of the genes that code for immunity, survival, inflammation, apoptosis and in the cell protection for radiation and chemotherapy. The serine/threonine protein kinase Akt is a downstream target of phosphatidylinositol-3-kinase and it plays a key regulator of cancerous cell growth. Therefore, we have examined the MT, NF-kB and pAkt expression in 51 samples of oral squamous cell carcinoma by immunohistochemistry in order to investigate their prognostic influence on oral cancer, as well as studying the correlations between clinical factors and patient survival. The results showed a significant association between pAkt and NF-kB and between MT and NF-kB expression in tumor tissue. Besides pAkt over-expression was found in OSCC clinical samples and its expression was significantly associated with a poor overall patient survival. In conclusion, our findings suggested that pAkt expression may have therapeutic implications in squamous cell carcinoma.

Os resultados obtidos no mestrado mostraram que a samambaia do campo (Pteridium aquilinum) reduz a citotoxicidade das células natural killer (NK) esplênicas e a resposta imune celular do tipo tardia (DTH) de camundongos. Entretanto, até aquele momento não era sabido qual a célula afetada pela planta causava a diminuição da DTH. Assim, o objetivo inicial deste estudo foi verificar qual a célula envolvida na diminuição da DTH. Além disto, buscou-se descobrir o mecanismo de ação imunotóxico da P. aquilinum, o principio tóxico envolvido e se este efeito poderia ser revertido pelo selênio (Se). Para tal, camundongos C57BL/6 foram administrados com extrato de P. aquilinum, por gavage, durante 30 dias e suplementados com Se por mais 30 dias e a análise histológica revelou redução significativa na área de polpa branca esplênica que foi completamente revertida pelo tratamento com Se. Ainda, foi possível verificar que a diminuição da DTH foi causada pela redução da produção de IFN&gamma; pelas células NK durante a indução da resposta imune celular. Além disto, camundongos administrados com ptaquilosídeo, por gavage, durante 14 dias mostraram a mesma redução na atividade das células NK causada pelo extrato de P. aquilinum, assim como a prevenção deste efeito pela co-administração de Se. Por fim, na análise da expressão gênica das células NK esplênicas dos camundongos tratados com ptaquilosídeo e/ou selênio pôde-se observar o aumento da expressão dos genes Mt1 e Mt2, possíveis responsáveis pelo mecanismo imunotóxico da planta, sendo posteriormente confirmado pelo aumento de metalotioneína e consequente redução de Zn2+ livre no espaço intracelular das células NK. Os resultados deste estudo claramente mostram que os efeitos imunossupressores da P. aquilinum são induzidos pelo ptaquilosídeo e são decorrentes do aumento da expressão dos genes da Mt1 e Mt2 e que a suplementação com Se pode prevenir e reverter estes efeitos tóxicos. / The results obtained in the master showed that the bracken fern (Pteridium aquilinum) reduces both the cytotoxicity of splenic natural killer cells (NK) and the delayed-type hypersensitivity (DTH) from mice. However, it was not known until that time, which cell affected by the plant that caused a decrease in DTH. Thus, the initial goal of this study was to determine which cell was involved in the reduction of DTH. Moreover, we sought to discover the mechanism of action of the P. aquilinum, the toxic principle involved and whether this effect could be reversed by selenium (Se). For that, C57BL/6 mice were treated with extract of P. aquilinum, by gavage, for 30 days and supplemented with Se for following 30 days. The histological analysis revealed a significant reduction in the splenic white pulp area that was completely reversed by treatment with Se. Still, it was verified that the decrease in DTH was caused by reduced production of IFN&gamma; by NK cells during the induction of cellular immune response. In addition, the mice administered with ptaquiloside, by gavage, for 14 days showed the same reduction in the NK cell activity caused by the extract of P. aquilinum, as well as the prevention of this effect by co-administration of Se. Finally, we could observe an increase in the expression of Mt1 and Mt2 genes in the gene expression analysis of splenic NK cells from mice treated with ptaquiloside and/or selenium. These genes were probably responsible for immunotoxic mechanism of the plant, which was confirmed later by the augment of metallothionein and consequent reduction of free Zn2+ into the intracellular space of NK cells. The results of this study clearly show that the immunosuppressive effects of P. aquilinum are induced by ptaquiloside and they are a consequence of the augment in the gene expression of Mt1 and Mt2 and that the supplementation with Se can prevent and reverse these toxic effects.