Due to the current rise of exposure to natural and synthetic compounds in our daily life, the debate concerning the safety of many substances is becoming increasingly relevant. The estrogenic activity of various compounds, described as xenoestrogens, is the major part of this debate. Humans beings are exposed to these substances from different environmental contaminations ranging from conscious intake of estrogenic substances, as in contraception or in hormone replace therapy (HRT), to unconscious exposure, from food, the use of synthetic material in daily life and air and water pollution. At this point the need for methods to investigate the activity and the safety of these substances is becoming increasingly important. Classical methods for the analysis of the estrogenic activity of substances, like batteries of in vivo test systems on the rat uterotrophic assay are not able to describe the different pathways of action of recently discovered estrogenic substances. This evidence was already shown by the Organization for Economic Cooperation and Development (OECD), introducing new test guidelines for the investigation of effects of endocrine disruptors (according to enhanced Test Guideline 407). As reviewed by Nilsson (Nilsson et al., 2001), after the interaction of the estrogens with the Estrogen Receptor (ER) in the cells, the mechanism of activation possible is not only via direct binding of the ER to the Estrogen Responsive Elements (EREs) present in the promoter region of the target gene, very well described for many target genes, but that also other mechanisms are used: the interaction of the ER with the AP 1, Sp 1 and NFkB modes, that are discovered but not yet comprehensively described. The aim of my work is to produce a microarray DNA chip for the investigation of the estrogenic activity of different compounds present in the environment. The chip will consist of a selection of 100 genes that are estrogen responsive and it will cover the spectrum of activities of estrogenic compounds in various organs of the body. In the gene selection, genes were chosen that are estrogen responsive in the classical target tissues of estrogens, linked to reproduction, like uterus and mammary gland, and also in tissues not related to reproduction like liver, bones and capillars. In addition, other genes are included to monitor different pathways that are related to disease states; control of cell proliferation, apoptosis or cancer related genes. Currently these kinds of investigations are already in process, but by other methods which are more time consuming and with a lower throughput e.g. the gene expression profiling using the real time RT-PCR. The use of microarray’s satisfies the need for a less time consuming, high throughput method, to obtain a fast characterization of the gene expression finger print of the candidate substances and their mechanism of action in the organism. In my work I investigated the estrogenic potency of different Xenoestrogens that commonly occur in our daily life, in rat cells and tissue using well known estrogen sensitive genes like C3, Clu, IGFBP1 and CaBP9k. I focused on their effect on cell proliferation, studying PCNA expression. For the first time sensitivity of the gene CA2 was proofed in liver and uterus. A new identified mRNA sequence, r52, was characterized for its sensitivity to estrogenic exposure. This sequence was investigated at the molecular level expanding the known nucleic sequence. I produce a microarray chip with 16 genes to investigate the estrogenic potency of different compounds. As proof of principle of the microarray method completely produced in house I compared the result of gene expression obtained by the chip to that obtained by real time RT PCR finding a similarity of results. This new established method is less sensitive than the real-time RT PCR but allows a high throughput of gene expression analysis producing at the end a more complete picture of the expression signature of a compound.

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Due to the current rise of exposure to natural and synthetic compounds in our daily life, the debate concerning the safety of many substances is becoming increasingly relevant. The estrogenic activity of various compounds, described as xenoestrogens, is the major part of this debate. Humans beings are exposed to these substances from different environmental contaminations ranging from conscious intake of estrogenic substances, as in contraception or in hormone replace therapy (HRT), to unconscious exposure, from food, the use of synthetic material in daily life and air and water pollution. At this point the need for methods to investigate the activity and the safety of these substances is becoming increasingly important. Classical methods for the analysis of the estrogenic activity of substances, like batteries of in vivo test systems on the rat uterotrophic assay are not able to describe the different pathways of action of recently discovered estrogenic substances. This evidence was already shown by the Organization for Economic Cooperation and Development (OECD), introducing new test guidelines for the investigation of effects of endocrine disruptors (according to enhanced Test Guideline 407). As reviewed by Nilsson (Nilsson et al., 2001), after the interaction of the estrogens with the Estrogen Receptor (ER) in the cells, the mechanism of activation possible is not only via direct binding of the ER to the Estrogen Responsive Elements (EREs) present in the promoter region of the target gene, very well described for many target genes, but that also other mechanisms are used: the interaction of the ER with the AP 1, Sp 1 and NFkB modes, that are discovered but not yet comprehensively described. The aim of my work is to produce a microarray DNA chip for the investigation of the estrogenic activity of different compounds present in the environment. The chip will consist of a selection of 100 genes that are estrogen responsive and it will cover the spectrum of activities of estrogenic compounds in various organs of the body. In the gene selection, genes were chosen that are estrogen responsive in the classical target tissues of estrogens, linked to reproduction, like uterus and mammary gland, and also in tissues not related to reproduction like liver, bones and capillars. In addition, other genes are included to monitor different pathways that are related to disease states; control of cell proliferation, apoptosis or cancer related genes. Currently these kinds of investigations are already in process, but by other methods which are more time consuming and with a lower throughput e.g. the gene expression profiling using the real time RT-PCR. The use of microarray’s satisfies the need for a less time consuming, high throughput method, to obtain a fast characterization of the gene expression finger print of the candidate substances and their mechanism of action in the organism. In my work I investigated the estrogenic potency of different Xenoestrogens that commonly occur in our daily life, in rat cells and tissue using well known estrogen sensitive genes like C3, Clu, IGFBP1 and CaBP9k. I focused on their effect on cell proliferation, studying PCNA expression. For the first time sensitivity of the gene CA2 was proofed in liver and uterus. A new identified mRNA sequence, r52, was characterized for its sensitivity to estrogenic exposure. This sequence was investigated at the molecular level expanding the known nucleic sequence. I produce a microarray chip with 16 genes to investigate the estrogenic potency of different compounds. As proof of principle of the microarray method completely produced in house I compared the result of gene expression obtained by the chip to that obtained by real time RT PCR finding a similarity of results. This new established method is less sensitive than the real-time RT PCR but allows a high throughput of gene expression analysis producing at the end a more complete picture of the expression signature of a compound.