Leung, Chun Yin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 155-169). / Abstracts in English and Chinese. / Title Page --- p.i / Acknowledgements --- p.ii / Table of Content --- p.iii / List of Figures --- p.viii / List of Graphs --- p.x / List of Tables x --- p.iv / Abbreviations --- p.xvii / Abstract --- p.xviii / Abstract (Chinese) --- p.xx / Chapter Chapter 1: --- General Introduction / Chapter 1.1 --- Introduction to retinoids --- p.2 / Chapter 1.2 --- Role of endogenous retinoic acid in embryonic development --- p.3 / Chapter 1.3 --- Regulation of retinoic acid in embryonic development --- p.5 / Chapter 1.3.1 --- Retinoic acid synthesis and degradation --- p.5 / Chapter 1.3.2 --- Retinoic acid signaling --- p.8 / Chapter 1.4 --- Effect of excess vitamin AJ RA on embryogenesis --- p.8 / Chapter 1.4.1 --- Examples of human animal studies --- p.9 / Chapter 1.4.2 --- Mechanisms of retinoid teratogenesis --- p.11 / Chapter 1.4.2.1 --- Apoptosis --- p.11 / Chapter 1.4.2.2 --- Altered proliferation --- p.12 / Chapter 1.4.2.3 --- Altered cell migration --- p.12 / Chapter 1.4.2.4 --- Altered differentiation --- p.13 / Chapter 1.4.3 --- Critical period of RA administration caused specific Malformations --- p.14 / Chapter 1.5 --- Effect of vitamin A/ RA deficiency on embryogenesis --- p.15 / Chapter 1.6 --- Excess and deficiency of RA cause similar types of malformations --- p.17 / Chapter 1.6.1 --- Retinoic acid-induced renal malformations mouse model --- p.18 / Chapter 1.7 --- Strategy of thesis --- p.19 / Chapter Chapter 2: --- General Materials and Methods / Chapter 2.1 --- Mouse maintenance and mating methods --- p.23 / Chapter 2.2 --- All-trans retinoic acid preparation and injection --- p.23 / Chapter 2.3 --- Whole mount in situ hybridization --- p.24 / Chapter 2.3.1 --- Riboprobe synthesis --- p.24 / Chapter 2.3.1.1 --- Bacterial culture --- p.24 / Chapter 2.3.1.2 --- DNA plasmids extraction --- p.24 / Chapter 2.3.1.3 --- Linearization of plasmid --- p.25 / Chapter 2.3.1.4 --- Purification of linearized plasmid --- p.26 / Chapter 2.3.1.5 --- In vitro transcription and labeling --- p.26 / Chapter 2.3.2 --- Sample collection --- p.27 / Chapter 2.3.3 --- Hybridization --- p.28 / Chapter 2.3.4 --- Post hybridization wash and antibody development --- p.29 / Chapter 2.3.4.1 --- Embryo powder preparation --- p.30 / Chapter 2.3.4.2 --- Pre-absorption of antibody --- p.30 / Chapter 2.3.5 --- Post-antibody and staining --- p.31 / Chapter 2.4 --- Real-time quantitative reverse transcription -polymerase chain reaction (RT-PCR) --- p.32 / Chapter 2.4.1 --- Sample collection --- p.32 / Chapter 2.4.2 --- RNA extraction --- p.32 / Chapter 2.4.3 --- Reverse transcription into cDNA --- p.33 / Chapter 2.4.4 --- Quantitative real-time PCR --- p.33 / Chapter 2.4.5 --- Preparation of cDNA standards --- p.34 / Chapter 2.5 --- High pressure liquid chromatography (HPLC) --- p.35 / Chapter 2.5.1 --- Chromatographic system --- p.35 / Chapter 2.5.2 --- Standards preparation --- p.35 / Chapter 2.5.3 --- Embryo sample collection and preparation --- p.36 / Chapter 2.5.4 --- HPLC conditions --- p.36 / Chapter 2.5.5 --- Sample recovery --- p.37 / Chapter 2.5.6 --- Bradford assay --- p.38 / Chapter 2.6 --- RA-responsive cell line --- p.38 / Chapter 2.6.1 --- Cell culture --- p.39 / Chapter 2.6.2 --- Seeding and loading sample to 96-well plate --- p.40 / Chapter 2.6.3 --- X-gal staining --- p.41 / Chapter Chapter 3: --- Time and Dose Responses to RA / Chapter 3.1 --- Introduction --- p.43 / Chapter 3.1.1 --- Time response to RA --- p.43 / Chapter 3.1.2 --- Dose response to RA --- p.45 / Chapter 3.1.3 --- Other factors affecting susceptibilities to RA --- p.46 / Chapter 3.2 --- Experimental design --- p.48 / Chapter 3.3 --- Materials and methods --- p.50 / Chapter 3.3.1 --- Time response to RA --- p.50 / Chapter 3.3.2 --- Dose response to RA --- p.50 / Chapter 3.3.3 --- Examination of fetuses --- p.51 / Chapter 3.3.4 --- Statistical analysis --- p.51 / Chapter 3.4 --- Results --- p.53 / Chapter 3.4.1 --- Time response --- p.53 / Chapter 3.4.1.1 --- Time response to RA-induced resorption --- p.53 / Chapter 3.4.1.2 --- Time response to RA-induced renal malformations --- p.54 / Chapter 3.4.1.3 --- Time response to RA-induced changes in growth parameters --- p.57 / Chapter 3.4.1.4 --- Time response to RA-induced non-renal malformations --- p.60 / Chapter 3.4.2 --- Dose response --- p.64 / Chapter 3.4.2.1 --- Dose response to RA-induced resorption --- p.64 / Chapter 3.4.2.2 --- Dose response to RA-induced renal malformations --- p.65 / Chapter 3.4.2.3 --- Dose response to RA-induced changes in growth parameters --- p.68 / Chapter 3.4.2.4 --- Dose response to RA-induced non-renal malformations --- p.71 / Chapter 3.5 --- Discussion --- p.74 / Chapter Chapter 4: --- Effect of Teratogenic Dose of RA on RA Synthesis and Endogenous RA Levels in the Embryo / Chapter 4.1 --- Introduction --- p.79 / Chapter 4.1.1 --- RA synthesis in embryo --- p.79 / Chapter 4.1.2 --- Detection of endogenous RA in embryo --- p.81 / Chapter 4.2 --- Experimental design --- p.83 / Chapter 4.3 --- Materials and methods --- p.84 / Chapter 4.3.1 --- Localization of mRNA transcripts in whole embryo by in situ hybridization --- p.84 / Chapter 4.3.2 --- Vibratome sectioning --- p.85 / Chapter 4.3.2.1 --- Preparation of Gloop --- p.85 / Chapter 4.3.2.2 --- Sample preparation and sectioning --- p.85 / Chapter 4.3.3 --- Quantification of mRNA expression levels in whole embryo and in metanephros by real-time RT-PCR --- p.86 / Chapter 4.3.4 --- Detection of RA levels in whole embryo by HPLC --- p.87 / Chapter 4.3.5 --- Detection of RA levels in metanephros by RA-responsive cell line --- p.87 / Chapter 4.3.6 --- Statistical analysis --- p.88 / Chapter 4.4 --- Results --- p.89 / Chapter 4.4.1 --- Comparison of mRNA expression levels of different iso forms of RA synthesizing enzymes Raldh and RA catabolizing enzymes Cyp26 between embryos of RA-treated and vehicle-treated control mice at various time points after treatment --- p.89 / Chapter 4.4.2 --- Comparison of mRNA expression levels of different iso forms of RA synthesizing enzymes Raldh and RA catabolizing enzymes Cyp26 between metanephroi of embryos of RA-treated and vehicle-treated control mice at various time points after treatment --- p.93 / Chapter 4.4.3 --- Comparison of the in situ hybridization pattern of different iso forms of Raldh between embryos of RA-treated and vehicle-treated control mice at different time points after treatment --- p.95 / Chapter 4.4.3.1 --- In situ hybridization pattern of Raldh 1 --- p.96 / Chapter 4.4.3.2 --- In situ hybridization pattern of Raldh2 --- p.97 / Chapter 4.4.3.3 --- In situ hybridization pattern of Raldh3 --- p.100 / Chapter 4.4.4 --- Comparison of the in situ hybridization pattern of Cyp26al and Cyp26bl between embryos of RA-treated and vehicletreated control mice at different time points after treatment --- p.101 / Chapter 4.4.4.1 --- In situ hybridization pattern of Cyp26al --- p.101 / Chapter 4.4.4.2 --- In situ hybridization pattern of Cyp26bl --- p.102 / Chapter 4.4.5 --- Comparison of RA levels between embryos of RA-treated and vehicle-treated control mice at different time points after treatment --- p.103 / Chapter 4.4.6 --- Comparison of RA levels between metanephroi of embryos of RA-treated and vehicle-treated control mice at different time points after treatment --- p.105 / Chapter 4.5 --- Discussion --- p.106 / Chapter Chapter 5: --- Effect of Supplementation with Low Doses of RA on RA Teratogenesis / Chapter 5.1 --- Introduction --- p.111 / Chapter 5.1.1 --- RA supplementation --- p.111 / Chapter 5.1.2 --- Wilms' tumor suppressor gene Wtl --- p.112 / Chapter 5.1.3 --- Apoptosis --- p.113 / Chapter 5.2 --- Experimental design --- p.115 / Chapter 5.3 --- Materials and methods --- p.117 / Chapter 5.3.1 --- Oral gavage of low dose of RA --- p.117 / Chapter 5.3.2 --- Determination of Wtl expression level by real-time quantitative RT-PCR --- p.117 / Chapter 5.3.3 --- Preparation of paraffin sections and TUNEL staining --- p.118 / Chapter 5.3.3.1 --- Sample collection --- p.118 / Chapter 5.3.3.2 --- "Dehydration, embedding and sectioning" --- p.118 / Chapter 5.3.3.3 --- TUNEL staining --- p.119 / Chapter 5.3.4 --- Statistical analysis --- p.121 / Chapter 5.4 --- Results --- p.122 / Chapter 5.4.1 --- Time response to RA supplementation in rescuing kidney development --- p.122 / Chapter 5.4.2 --- Dose response to RA supplementation in rescuing kidney development --- p.127 / Chapter 5.4.3 --- RA supplementation restored various growth parameters --- p.132 / Chapter 5.4.4 --- RA supplementation rescued non-renal malformations --- p.134 / Chapter 5.4.5 --- Wtl expression in the metanephros after RA supplementation --- p.142 / Chapter 5.4.6 --- Apoptotic cell death in the metanephros after RA supplementation --- p.143 / Chapter 5.5 --- Discussion --- p.145 / Chapter Chapter 6: --- Conclusion and Future Perspectives --- p.150 / References --- p.155 / Figures / Graphs

Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2016-04-13T13:00:25Z No. of bitstreams: 1 PDF - Rayanne Sales de Araújo Batista.pdf: 2799391 bytes, checksum: bfd7e21254a6a5383f8798d74f80923d (MD5) / Approved for entry into archive by Secta BC (secta.csu.bc@uepb.edu.br) on 2016-06-13T20:27:28Z (GMT) No. of bitstreams: 1 PDF - Rayanne Sales de Araújo Batista.pdf: 2799391 bytes, checksum: bfd7e21254a6a5383f8798d74f80923d (MD5) / Made available in DSpace on 2016-06-13T20:28:54Z (GMT). No. of bitstreams: 1 PDF - Rayanne Sales de Araújo Batista.pdf: 2799391 bytes, checksum: bfd7e21254a6a5383f8798d74f80923d (MD5) Previous issue date: 2015-03-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Retinoic acid (RA), widely used in dermatological and cosmetic products, has low stability in the presence of air and light, with sensitivity to heat and oxidation, so it is particularly important to implement the quality control of its finished products performing tests indicators of stability. Therefore, the objective was to develop an analytical method to evaluate the thermal stability of an RA cream formulation through the correlation of analytical techniques, high performance liquid chromatography with ultraviolet detection efficiency (HPLC-UV), differential scanning calorimetry (DSC) and vibrational absorption spectroscopy in the infrared Fourier transform spectroscopy (FTIR). Previously been established chromatographic conditions for development of the analytical method using HPLC-UV system, which was subjected to analytical tests specified in RE ANVISA Nº 899/2003 for validation. For evaluation of the thermal stability the cream samples were subjected to thermal stress in an oven at temperatures of 60, 70 and 80 °C and subsequently analyzed by HPLC-UV over the period of 0, 24, 48 and 72 h. DSC analyzes and FTIR spectra were carried out from the binary mixture (BM) of the RA and excipients of the cream formulation to investigate possible physical and/or chemical interactions. According to the data obtained it was possible to develop an analytical method by validated HPLC-UV, and based thereon, for analyzing and quantifying the RA content cream formulation, it has been found that from 70 ° C caused a decrease in the content of RA, and 0-order kinetics; and 80 ° C, followed a kinetic order 2 by setting up a reaction of bimolecular type. The analytical techniques DSC and FTIR showed the absence of chemical and physical interaction in most MB among the components of the formulation, except only for the carrier sodium metabisulfite. Thus, we can infer that it has a well-defined thermal behavior and compatibility of its components. / O ácido retinoico (AR), largamente utilizado em produtos dermatológicos e cosméticos, apresenta baixa estabilidade na presença de ar e luz, com sensibilidade ao calor e à oxidação, assim, é particularmente importante implementar o controle de qualidade de seus produtos acabados realizando ensaios indicadores de estabilidade. Logo, objetivou-se desenvolver um método analítico para avaliar a estabilidade térmica de uma formulação creme de AR através da correlação de técnicas analíticas, cromatografia líquida de alta eficiência com detecção ultravioleta (CLAE-UV), calorimetria exploratória diferencial (DSC) e espectroscopia vibracional de absorção na região do infravermelho com transformada de Fourier (FTIR). Previamente foram estabelecidas as condições cromatográficas para desenvolvimento do método analítico utilizando um sistema de CLAE-UV, o qual foi submetido aos testes analíticos especificados na RE ANVISA nº 899/2003 para validação do mesmo. Para avaliação da estabilidade térmica, as amostras do creme foram submetidas a estresse térmico em estufa nas temperaturas de 60, 70 e 80 º C, e posteriormente analisadas por CLAE-UV no período de 0, 24, 48 e 72 h. As análises de DSC e dos espectros de FTIR foram realizadas a partir das misturas binárias (MB) do AR e excipientes da formulação creme a fim de investigar possíveis interações físicas e/ou químicas. De acordo com os dados obtidos foi possível desenvolver um método analítico por CLAE-UV validado, e com base no mesmo, para análise e quantificação do teor de AR em formulação creme, constatou-se que a partir de 70 ° C ocorreu redução no teor de AR, e cinética de ordem 0; a 80 ° C, obedeceu uma cinética de ordem 2, configurando uma reação do tipo bimolecular. As técnicas analíticas DSC e FTIR mostraram a ausência de interação física e química na maioria das MB entre os componentes da formulação, com exceção apenas para o excipiente metabissulfito de sódio. Desta forma, podemos inferir que a mesma apresenta um comportamento térmico bem definido e compatibilidade entre seus componentes.

O carcinoma epidermóide de boca, neoplasia maligna de boca mais comum, pode originar-se de lesões potencialmente malignas. O ácido retinóico, que atua no crescimento e diferenciação celular, tem sido comumente estudado como um possível quimioterápico na prevenção dessa progressão. Embora o mecanismo pelo qual o ácido retinóico previne essa progressão, e promove a parada do crescimento celular, não esteja estabelecido, sabe-se que os genes homeobox são importantes alvos do ácido retinóico durante o desenvolvimento embrionário e diferenciação tecidual. Este estudo visa determinar se a modulação da expressão desses genes está envolvida na inibição do crescimento pelo ácido retinóico em carcinoma epidermóide de boca. Para isso, foi realizado PCR array para avaliar a expressão de 84 genes homeobox na linhagem celular de carcinoma epidermóide de boca sensível ao ácido retinóico SSC-25, comparando com a linhagem resistente, SSC-9, após o tratamento com ácido retinóico por sete dias. Os resultados mostraram nove genes com perda de expressão e quatro com alta expressão. A validação por qPCR de 7 desses genes confirmou os resultados. Desses, três genes(ALX1, DLX3, TLX1) foram selecionados para terem a expressão avaliada em amostras tratadas por 3, 5 e 7 dias. O gene ALX1 apresentou baixa expressão apenas no dia 7. O gene DLX3 apresentou baixa expressão no terceiro dia com maior decréscimo no sétimo. Já o gene TLX1, mostrou baixa significativa no quinto dia, com valores semelhantes no sétimo. Os dados mostram genes homebox são modulados pelo ácido retinóico em linhagens de carcinoma epidermóide de boca. No entanto, esses genes não parecem ser alvo direto da inibição do crescimento promovida pelo ácido retinóico. / Oral squamous cell carcinoma, the most frequent oral cancer, may arise from potentially malignant oral lesions. Retinoic acid, which plays a role in cell growth and differentiation, has been frequently studied as a possible chemotherapeutic agent in the prevention of this progression. While the mechanism by which retinoic acid prevents progression and suppresses cell growth has not been completely elucidated, it is known that homeobox genes represent important targets of retinoic acid during embryogenesis and differentiation. The present study aims to determine if modulation of the expression of these genes is involved in inhibition of OSCC cell growth by retinoic acid. In order to achieve this goal a PCR array was performed to evaluate the expression of 84 homeobox genes in retinoic acid sensitive SCC-25 cells compared to retinoic acid resistant SCC-9 cells following treatment with retinoic acid for 7 days. Results showed that 9 homeobox genes are downregulated and 4 are upregulated by retinoic acid. The validation confirmed these results. Three genes (ALX1, DLX3, TLX1) were selected for having their expression evaluated on samples treated with retinoic acid for 3, 5 and 7 days. Three different patterns of gene expression were observed. Gene ALX1 showed down-regulation only on day 7. Homeobox gene DLX3 showed reduced expression on day 3 and decreased expression on day 7. TLX1 showed a substantial down-regulation on day 5 with similar values on. The data presented show that a number of homeobox genes are modulated by retinoic acid in oral squamous cell carcinoma cell lines. However, these genes do not appear to be direct targets of growth suppression trigged by retinoic acid.

<p>Vitamin A and metabolites (retinoids) are crucial for normal epidermal maturation. Physiological effects are mediated by retinoic acid (RA) that activates nuclear retinoic acid receptors (RARs) in complexes with retinoid X receptors (RXRs), resulting in altered gene transcription.</p><p>Psoriasis is a common disease with unknown etiology. Lesions display inflammation, hyperproliferation, and disturbed epidermal maturation. Treatments include topical or oral synthetic retinoids that allegedly bind to and activate the RARs.</p><p>The mRNA expression of retinoid receptors RARα/γ and RXRα was studied in normal and psoriatic skin samples. RARα and RXRα were significantly reduced in psoriatic plaques as compared to non-lesional and normal skin. <i>In situ</i> immunofluorescence detection revealed altered distribution patterns of the receptor proteins in lesional skin. All three receptor proteins were more intensely detected in the lower half of the epidermis but were significantly reduced in the superficial epidermis compared to both normal and non-lesional skin. </p><p>In order to evaluate the retinoid signaling system in psoriatic lesions, we compared the effect of topical RA on the expression of the cellular RA-binding protein II (CRABPII) in psoriatic and normal skin. CRABPII was induced by RA on mRNA and protein level in non-lesional and normal skin but not in lesional skin, where the basal expression of CRABPII was already up-regulated.</p><p>Changes in retinoid signaling during keratinocyte differentiation <i>in vitro </i>were studied by measuring retinoid receptor and RAR-ligand levels<i>.</i> Exposure to differentiation-inducing levels of calcium, phorbol myristate acetate (PMA) or interferon-γ (IFNγ) led to increased RAR-ligand levels but PMA and IFNγ caused receptor protein loss due to increased proteasomal degradation. Since an increased IFNγ level is a hallmark of psoriatic inflammation, this might be a cause of altered retinoid signaling in lesional epidermis.</p><p><i>Conclusion:</i> Keratinocyte differentiation is accompanied by alterations in the retinoid signaling system. In psoriatic lesions, this system appears to be dysfunctioning due to reduced retinoid receptor levels, which might be an important event in the pathogenesis of the disease.</p>

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Vitamin A and metabolites (retinoids) are crucial for normal epidermal maturation. Physiological effects are mediated by retinoic acid (RA) that activates nuclear retinoic acid receptors (RARs) in complexes with retinoid X receptors (RXRs), resulting in altered gene transcription. Psoriasis is a common disease with unknown etiology. Lesions display inflammation, hyperproliferation, and disturbed epidermal maturation. Treatments include topical or oral synthetic retinoids that allegedly bind to and activate the RARs. The mRNA expression of retinoid receptors RARα/γ and RXRα was studied in normal and psoriatic skin samples. RARα and RXRα were significantly reduced in psoriatic plaques as compared to non-lesional and normal skin. In situ immunofluorescence detection revealed altered distribution patterns of the receptor proteins in lesional skin. All three receptor proteins were more intensely detected in the lower half of the epidermis but were significantly reduced in the superficial epidermis compared to both normal and non-lesional skin. In order to evaluate the retinoid signaling system in psoriatic lesions, we compared the effect of topical RA on the expression of the cellular RA-binding protein II (CRABPII) in psoriatic and normal skin. CRABPII was induced by RA on mRNA and protein level in non-lesional and normal skin but not in lesional skin, where the basal expression of CRABPII was already up-regulated. Changes in retinoid signaling during keratinocyte differentiation in vitro were studied by measuring retinoid receptor and RAR-ligand levels. Exposure to differentiation-inducing levels of calcium, phorbol myristate acetate (PMA) or interferon-γ (IFNγ) led to increased RAR-ligand levels but PMA and IFNγ caused receptor protein loss due to increased proteasomal degradation. Since an increased IFNγ level is a hallmark of psoriatic inflammation, this might be a cause of altered retinoid signaling in lesional epidermis. Conclusion: Keratinocyte differentiation is accompanied by alterations in the retinoid signaling system. In psoriatic lesions, this system appears to be dysfunctioning due to reduced retinoid receptor levels, which might be an important event in the pathogenesis of the disease.

Retinoic Acid Metabolism Blocking Agents (RAMBAs) increase the endogenous levels of all-trans retinoic acid (RA) by inhibiting CYP26 enzymes. Thus they are believed to mimic the effects of retinoid treatment. Their mechanism of action and effects on vitamin A metabolism in keratinocytes are however uncertain. To explore this and the function of CYP26 in human skin was the main purpose of the project. The effects of two RAMBAs (talarozole and liarozole) on the expression of retinoid biomarkers in epidermis were studied in vivo and in vitro. Normal human skin (n=16) exposed to topical talarozole for 9 days showed similar response as previously reported for topical RA, even though no skin inflammation occurred. Lamellar ichthyosis patients (n=11) treated systemically with liarozole showed variable clinical improvement after 4 weeks with only mild effects on the retinoid biomarkers and the expression did not always correlate at the protein and mRNA levels. In these studies the proinflammatory transcripts IL-1α and TNFα were down-regulated by RAMBAs. In vitro, using an organotypic epidermis model we first studied how the RA metabolism was affected by adding RA and/or RAMBAs. We next examined the effects of the same agents on the expression of vitamin A metabolising enzymes in monolayer cultures of proliferating and differentiating keratinocytes. The results show among other things that CYP26 A1 and B1 are both involved in the catabolism of RA, and that talarozole potently increases the level of endogenous RA, primarily by inhibiting CYP26B1. However the drug´s biological effects cannot be solely attributed to increased RA levels. In conclusion, RAMBAs are promising new drugs for treatment of skin disorders, but further studies on their mechanism of action are needed.

Η ριβονουκλεάση P (RNase P) είναι το ένζυμο που ευθύνεται για την ωρίμανση του 5΄ άκρου των πρόδρομων μορίων tRNA συμμετέχοντας έτσι στην πρωτεΐνοσύνθεση. H RNase P καταλύει την ενδονουκλεολυτική θραύση ενός φωσφοδιεστερικού δεσμού παρουσία ιόντων Mg2+ παράγοντας προϊόντα με 3΄ υδροξυλικά και 5΄ φωσφορικά άκρα. Η πλειοψηφία των RNase P ενζύμων που έχουν μελετηθεί μέχρι σήμερα είναι ριβονουκλεοπρωτεΐνες αποτελούμενες από μια RNA και πρωτεϊνικές υπομονάδες. Η RNA υπομονάδα της βακτηριακής RNase P είναι ένα από τα πρώτα καταλυτικά RNA που μελετήθηκαν. Η RNase P και το ριβόσωμα είναι τα μόνα γνωστά ριβοένζυμα που είναι συντηρημένα και στις τρείς φυλογεννετικές περιοχές. Δεδομένης της ζωτικής σημασίας των λεμφοκυττάρων στην ακεραιότητα του ανοσολογικού συστήματος και στην παθογένεια ευρέος φάσματος δερματολογικών και μη νοσημάτων, σκοπός της παρούσας εργασίας ήταν η ανάπτυξη μεθοδολογίας για την απομόνωση και τον καθαρισμό της RNase P από περιφερικά λεμφοκύτταρα υγιών μαρτύρων, ο προσδιορισμός της ενζυμικής της δραστικότητας, καθώς και η μελέτη της in vitro επιδράσεως δυο συνθετικών ρετινοειδών, του 13-cis ρετινοϊκού οξέος και της ασιτρετίνης, της αμινογλυκοσίδης νεομυκίνης Β, όπως και της διφωσφορικής χλωροκίνης στην δραστικότητα της λεμφοκυτταρικής RNase P. Το ένζυμο καθαρίστηκε με τη χρήση κατιοντοανταλλακτικής χρωματογραφίας φωσφοκυτταρίνης και προσδιορίστηκαν οι βέλτιστες συνθήκες δραστικότητάς του.Μετά από μελέτη της επίδρασης των συνθετικών ρετινοϊδών και της νεομυκίνης Β στην δραστικότητα της RNase P, προέκυψε ότι και τα τρία προκαλούν μια δοσοεξαρτώμενη αναστολή της δραστικότητας της RNase Ρ των ανθρωπίνων λεμφοκυττάρων. Η διφωσφορική χλωροκίνη δεν επηρεάζει τη δραστικότητα της λεμφοκυτταρικής RNase P. Λεπτομερής κινητική ανάλυση έδειξε πως η αναστολή που προκαλείται από την ασιτρετίνη είναι συναγωνιστικού τύπου, ενώ αυτή από την νεομυκίνη Β είναι μη συναγωνιστικού τύπου.Η κινητική σταθερά Km της λεμφοκυτταρικής RNase P βρέθηκε ότι ισούται με 245 nM και η Vmax με 0.42 pmol/min. Συμπερασματικά, η απομόνωση της RNase P από ανθρώπινα περιφερικά λεμφοκύτταρα καθιστά δυνατή τη μελέτη της πιθανής ανάμιξης αυτού του ριβοενζύμου στους παθογενετικούς μηχανισμούς διαφόρων αυτοάνοσων, φλεγμονωδών και νεοπλασματικών δερματοπαθειών και μπορεί να διευκολύνει τη περαιτέρω ανάπτυξη της βασιζομένης στην RNase P τεχνολογίας για τη γονιδιακή θεραπεία δερματικών και μη παθήσεων. / Ribonuclease P (RNase P) is the enzyme responsible for the 5΄ maturation of the precursor tRNA molecules, participating in tRNA biogenesis and therefore in protein synthesis. It catalyses the endonucleolytic cleavage of a phosphodiester bond in the presence of Mg2+ and results in the production of molecules that bear 3΄ hydroxyl and 5΄ phosphoric ends. Most forms of RNase P are ribonucleoproteins consisting of an essential RNA and protein subunits. The RNA component of the bacterial RNase P was one of the first identified catalytic RNAs. So far, RNase P and the ribosome are the only ribozymes known to be conserved in all kingdoms of life (bacteria, archaea and eucarya). In view of the vital importance of lymphocytes for an effective immune system, we proceeded to the RNase P isolation from human peripheral lymphocytes. The enzyme was purified with cation exchange phosphocellulose chromatography and the optimal conditions were determined. Herein, it was investigated the effect of the synthetic retinoids (cis-retinoic acid and acitretin), neomycin B, as well as chloroquine diphosphate, on the RNase P activity. Cis-retinoic acid, acitretin and neomycin B exerted a dose-dependent inhibitory effect on RNase P activity from human lymphocytes, wlile the activity was not affected in the presence of chloroquine diphosphate. A detailed kinetic analysis showed that the inhibition caused by acitretin was of competitive type, whereas that caused by neomycin B was of noncompetitive type. The kinetic constant Km of RNase P activity isolated from lymphocytes for the tRNA maturation reaction has been estimated equal to 245 nM and the Vmax value has been estimated equal to 0.42 pmol/min. Finally, the isolation of RNase P from human peripheral lymphocytes will enable the study of the possible involvement of this ribozyme in the pathogenetic mechanisms of diverse autoimmune, inflammatory and neoplastic cutaneous disorders and may facilitate the further development of RNase P-based technology for gene therapy of infectious and neoplastic dermatoses.

Neuroblastoma (NB) is the most common solid tumor of early infancy. Despite a significant improvement in the general survival rate for children with cancer, the prognosis of high-risk NB remains low, at about 30%, despite the use of intensive chemo-radiotherapy followed by differentiation therapy with retinoic acid (RA). Relapses in this category of NB are often due to the emergence of multi-drug and RA-resistant minimal residual cancer cells. The use of natural 13-cis RA, as a single chemo-preventive agent, has improved the survival rate to 50% for high-risk NB patients. However, the prevalence of RA-resistance is high in high-risk NB, and in solid cancers, in general. RA-resistance in cancer cells is mediated by a number of factors. Loss of RA-induced expression of the putative tumor suppressor gene, retinoic acid receptor-beta (RARβ), is one of the most common factors that have been reported in RAresistant phenotypes of a wide range of cancer cells. The transcriptional regulation of RAR(β) gene and other retinoid responsive-genes is believed to be regulated by the ligand-dependent transactivation of the homo- or heterodimer complexes of the retinoic acid receptor (RAR) and retinoid X receptor (RXR) subtypes, namely alpha (α), beta (β) and gamma (γ). It is believed that the anti-cancer activities of natural all-trans RA and 13-cis RA are mediated through activation of RAR-complexes. The loss of RA-induced RAR β expression can be caused by aberrant recruitment of chromatin structure modifying enzymes, histone deacetylases (HDACs), which have major roles in the global regulation of gene transcription. However, the mechanism of RA-resistance in NB cells is unclear. This thesis set out to identify the molecular mechanism of RA-resistance and to develop a new therapeutic approach to overcome RA-resistance in NB cells. The data in this thesis demonstrated that deregulation or over-expression of proto-oncogene MYCN caused a total RA-resistance in NB cells in vitro and in vivo, despite the strong induction of RARI3 expression. The data also indicated that the activation of RAR-dependent pathways by aRA or 13RA alone is not sufficient to overcome MYCN-mediated RA-resistance in NB cells. In the light of this observation, this thesis went on to examine whether combined targeting activation of RAR and RXR subtypes with receptor specific ligands could enhance the therapeutic efficacy of the retinoid signaling pathway. NB cells were treated with a panel of receptor-specific retinoids, namely aRA, l3RA, 9RA (RAR-specific), CD 417, CD 2314 (RARβ-specific), CD 666 (RARγ-specific), CD 336 (RARα-specific), CD 3640, CD 2872 (RXR-specific), as a single agent or in combination at a low concentration of 0.1 ??M. The results showed that combined targeting activation of RARα and RXR was not only the most effective combination, but also overcame MYCN-mediated RA-resistance in NB cells in vitro.Collectively, these data demonstrated the combined targeting activation of RAR and RXRs as a new approach to enhance the efficacy of retinoid therapy and overcome RA-resistance in the treatment of high-risk NB, and other cancers. The emerging therapeutic potential of HDAC inhibitors (HDACi) as front line anti-cancer agents, or adjuvants to other agents such as RA, has suggested a new approach in the treatment of cancer. However, the molecular mechanism of the remarkably specific anticancer actions of HDACi is still largely speculation. The data presented in this study was the first to demonstrate a novel sequential order and the dosage-dependent roles of basal p21Wafl expression and G2/M arrest as protective mechanisms against HDACi-induced apoptosis. In addition, this thesis also examined and compared the therapeutic efficacy of HDACi as a single agent and in combination with other anti-cancer agents such as RA, IFNα and chemotherapeutic agents. Evaluation of the therapeutic effects of combinations of aRA, IFN and HDACi showed that combination of HDACi and IFNα exhibited the strongest synergy against NB cells in vitro. Treatment of MYCN transgenic mice, which consistently develop abdominal NB tumors that closely mirror the human disease in both physiological and biological aspects, with hydroxamic acid-based HDACi, trichostatin A (TSA), alone reduced tumor growth by nearly 50%, compared to the solvent control and IFNα alone, which had no effect on NB tumor growth. The most exciting finding was that the combination of HDACi and IFNα synergistically reduced tumor mass and angiogenesis by over 80% without any apparent systemic side-effects. The therapeutic effect of treatment with HDACi correlated with the induction of acetylation of histone 4 protein (H4) in both tumor and organ tissues, indicating a wide therapeutic index for HDACi in vivo. Collectively, the data in this study have demonstrated basal p21 Wafl expression as a potential marker of sensitivity to HDACi-based therapy, and the therapeutic efficacy of a novel combination of HDACi with IFNα in vivo. These preclinical data have provided an evidence-based rationale for a clinical trial of the combination of HDACi and IFNα in the treatment of high risk NB.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 120-147).