Proefschrift--Utrecht. / Vita. Summary in English. Includes bibliography.

Cellular proliferation is a key characteristic of hematopoietic stem and progenitor cells (HSC/HPCs) that allows for the production of all blood cell lineages during an individuals lifetime. While this feature of stem cells is strictly regulated during steadystate and stress hematopoiesis, it also contributes to the development of myeloproliferative disorders, such as chronic myelogenous leukemia, essential thrombocythemia, and polycythemia vera. It should come as no surprise then, that common treatments for these diseases often target the proliferative nature of the dysfunctional HSC/HPCs. Thus, the identification of molecular determinants of cell cycle regulation associated with these disorders could serve as targets for novel therapies. Using the hematopoietic system of the inbred mouse strains, C57BL/6J (B6) and DBA/2J (D2), it was found that the HSC/HPCs of the long-lived B6 mouse strain were less susceptible to the cytostatic agent hydroxyurea (HU) than the short-lived D2 mouse strain. A quantitative trait locus (QTL) analysis revealed a region of proximal chromosome 7 that regulates this response to HU. Congenic mouse strains were generated and phenotypic analysis confirmed that the B6 and D2 loci confer a low and high sensitivity of the HSC/HPCs to HU, respectively. We then showed that while this response of the HSC/HPCs to HU is independent of their cell cycle status, the B6 allele of this QTL confers a proliferative advantage to bone marrow cells after bone marrow transplantation. Having shown that proximal chromosome 7 regulates the response of HSC/HPCs to HU, we found it necessary to characterize the gene and protein expression profiles in order to identify the responsible candidate genes. We first analyzed mRNA expression profiles of HPCs from the parental and congenic mouse strains using gene microarrays and found that four genes within the congenic interval were differentially expressed. Real-time PCR confirmed that the expression profile of only one gene, Ndufa3, is significantly different in HPCs of B6 and D2 mice. Concurrently, we assessed the protein expression profiles of HPC-enriched mononuclear cells. Significant differences were found between the cytoplasmic and nuclear fractions of both strains, with a skewing of protein expression towards the D2 congenic strain.

FundaÃÃo de Amparo à Pesquisa do Estado do Cearà / A anemia falciforme (AF) se caracteriza por anemia hemolÃtica crÃnica e com fenÃmenos vaso-oclusivos, seguidos de lesÃes a ÃrgÃos alvos, responsÃveis pela mortalidade associada a esta doenÃa. O fenÃmeno vaso-oclusivo està associado ao processo inflamatÃrio desencadeado pela polimerizaÃÃo da HbS desoxigenada, favorecendo a impactaÃÃo das hemÃcias na microcirculaÃÃo e subseqÃente obstruÃÃo da luz do endotÃlio. Numerosas evidÃncias sugerem que a reduÃÃo da biodisponibilidade do Ãxido nÃtrico (NO) pode ser um fator que favoreÃa a vaso-oclusÃo e que os radicais livres formados induzem à peroxidaÃÃo lipÃdica e à subseqÃente produÃÃo de quantidades anormais de malonaldeÃdo (MDA), que provoca alteraÃÃo da permeabilidade da membrana eritrocitÃria. Dentre os fatores genÃticos que modulam a clÃnica da AF consta os nÃveis de HbF. A hidroxiurÃia (HU) à utilizada no tratamento da AF e alÃm de aumentar os nÃveis de HbF parece contribuir como um doador de Ãxido nÃtrico. Nesse contexto, os objetivos do presente trabalho foram avaliar o estresse oxidativo por meio da dosagem sÃrica de MDA e determinar os nÃveis de NO e de lactato desidrogenase lÃctica (LDH) em pacientes com AF em acompanhamento ambulatorial no Hospital UniversitÃrio Walter CantÃdeo (HUWC) e correlacionar com o uso da HU. Desta forma foram utilizadas 65 amostras de sangue perifÃrico de pacientes adultos com AF em uso ou nÃo de HU, e um grupo controle foi elaborado por 20 doadores do banco de sangue com HbAA. Os nÃveis de NO, MDA e LDH foram determinados por mÃtodos bioquÃmicos. Os participantes da pesquisa foram selecionados junto ao centro de hematologia e hemoterapia do Cearà (HEMOCE). Todos os indivÃduos assinaram o termo de consentimento livre e esclarecido (TCLE) e foram submetidos a um questionÃrio prÃ-estruturado. Os dados obtidos foram expressos como mÃdias  desvio padrÃo e analisados utilizando-se o programa estatÃstico SPSS15.0, utilizamos os coeficientes de correlaÃÃo de Pearsaon e de Spearman para o estudo das correlaÃÃes entre MDA, NO, LDH, HbF e Hb. Para comparar os trÃs grupos atravÃs dos nÃveis de MDA, NO e LDH obtemos os resultados atravÃs da anÃlise de deviance (ANODEV). verificamos um predomÃnio do sexo feminino, e das raÃas parda (grupo I) e negra (grupo II), sendo a grande maioria desses pacientes com idade variando de 20 a 35 anos (grupo I) e 20 a 40 anos (grupo II) e procedentes do estado de CearÃ. Em sua maioria, nÃo faziam uso de fumoetilismo e de suplementaÃÃo de vitaminas (C e E). Os nÃveis de MDA nos trÃs grupos sÃo todos diferentes, isto Ã, o grupo controle apresentou um nÃvel mÃdio de MDA superior ao grupo II, e este por sua vez superior ao grupo I. NÃo encontramos diferenÃa nos nÃveis sÃricos de NO em relaÃÃo ao uso de HU. Nos trÃs grupos observamos que apenas o grupo controle difere, apresentando uma mÃdia bem inferior a dos dois grupos de pacientes quanto aos nÃveis de LDH. Observamos uma correlaÃÃo inversamente proporcional entre os de nÃveis NO e de HbF para o grupo I, enquanto que para o grupo II nÃo houve correlaÃÃo. Em relaÃÃo à concentraÃÃo da Hb nÃo houve correlaÃÃo tanto no grupo I quanto no grupo II, com os nÃveis de NO. NÃo houve correlaÃÃo significativa entre os nÃveis de MDA e Hb e HbF para nenhum dos grupos estudados. Encontramos uma correlaÃÃo inversamente proporcional entre os nÃveis de LDH e de Hb para o grupo I. Observou-se nÃveis elevados de MDA em pacientes do grupo II que realizaram duas ou mais transfusÃes no decorrer do ano, que apresentaram Ãlcera de perna maleolar e que tiveram trÃs ou mais crises vaso-oclusivas para ambos os grupos. NÃo encontramos nenhuma relaÃÃo do NO com as variÃveis clÃnicas. CONCLUSÃO: Nossos resultados mostram que os paciente em uso de HU nÃo estÃo protegidos contra a peroxidaÃÃo lipÃdica, hemÃlise quanto ao consumo de NO disponÃvel. / The sickle-cell disease (SCD) is characterized by hemolytic chronic anemia and with vase-occlusive phenomena, followed by target organs which are responsible for the mortality associated with this disease. The vase-occlusive phenomenon is associated with the inflammatory process unleashed by the polymerization of deoxygenated HbS, which favors the polymerization of erythrocytes in the microcirculation and the subsequent obstruction of endothelia light. Several evidences suggest that the reduction of the bioavailability of the nitric oxide (NO) can be a factor to favor the vase-occlusion and that the free radicals produced give rise to the lipidic peroxidation and the subsequent production of the abnormal quantities of malonaldehyde (MDA), which induce the permeability of the red cell membrane. Among the genetic factors that modulate the clinic of the AF, there is the HbF levels. The hydroxyurea (HU) is used in the treatment of SCD and apart from increasing the HbF levels it also seems to contribute as a nitric oxide donator. In this context, the present work aims to evaluate the oxidative stress by means of seric dosage of the MDA and to determinate the levels of NO and lactate desidogenase lactica (LDH) in patients with SCD by means within the Walter CantÃdeo University Hospital (HUWC) and to correlate with the use of HU. This way, it was used 65 samples of peripheral blood of adult patients with AF with either HU or not, and a control group was composed by 20 donors of the blood bank with HbAA. The levels of NO, MDA and LDH were determined by biochemical methods. The participants of the research were selected in the Center of Hematology and Hemotherapy of Cearà State (HEMOCE). All the participants have signed a document stating free consent and approval (TCLE) and they were submitted to a previously elaborated questionnaire. The obtained data were expressed as averages  pattern deviation and analyzed by using a statistics software SPSS15.0, using Pearson and Spearman correlation coefficients for the study of the correlations among MDA, NO, LDH, HbF and Hb. In order to compare the three groups through the levels of MDA, NO and LDH, the results were obtained by means of deviance analysis (ANODEV). It has been observed a majority of females and fallow race (group I) and black (group II), in which the most part of these patients have ages in the range of 20-35 (group I) and 20-40 (group II) and come from Cearà State. Most of them did not smoke, drink alcohol nor use vitamin supplements (C and E). The levels of MDA in the three groups are all different, i. e., the control group showed an average level of MDA higher than group II, and the later higher than that of the group one. It was not verified difference in the seric levels of NO in relation to the use of HU. In the three groups, it was observed that only the control group is different, showing an average much lower than those of the other two groups of patients regarding the levels of LDH. It was also observed a correlation inversely proportional between the two levels of NO and HbF for the group I, while in the group II there was no correlation. Regarding to the concentration of Hb, there was no correlation both in the group I and in the group II, with levels of NO. There was no significantly correlation among the levels of MDA, Hb and HbF for the studied groups. It was found a correlation inversely proportional between the levels of LDH and Hb for the group I. It was observed accentuated levels of MDA in patients of group II who have made two or more transfusions throughout the year, who had leg ulcers and who had three or more vase-occlusive crises form both the groups. It was found no relation of NO with the clinic variables. CONCLUSÃO: Our results have shown that patients who use HU are not protected against lipidic peroxidation, hemolysis and consume of available NO

Aicardi-Goutières Syndrome (AGS) is a single gene, autoimmune disorder, with variable onset in the first year of life. Its clinical features exhibit similarities to several autoimmune diseases and congenital viral infections. AGS can result from mutations in ADAR1, TREX1 and SAMHD1 as well as any of the three genes that encode the protein subunits of the RNase H2 enzyme. It is hypothesised that impairment of nucleic acid metabolism results in abnormal nucleic acid species within the cell. This in turn is thought to cause the aberrant immune response that leads to AGS. The RNase H2 complex contains the catalytic RNASEH2A subunit and the auxiliary RNASEH2B and RNASEH2C subunits, which are thought to provide structural support and facilitate interactions with additional cellular proteins. RNase H2 can cleave the RNA strand of an RNA:DNA hybrid as well as 5’ of a single ribonucleotide embedded in dsDNA. Therefore, RNase H2 may have roles in several cellular processes, including DNA replication and repair, transcription, and viral infection. The aim of this PhD project was to investigate the physiological functions of RNase H2. The localisation of the RNase H2 proteins was investigated using EGFP-tagging and fluorescent microscopy. The interaction between the PIP-box of RNASEH2B and PCNA was found to localise RNase H2 and not RNase H1 to nuclear replication foci during S-phase. This suggests that RNase H2 is the dominant RNase H activity during DNA replication. Stable cell lines expressing EGFP-RNASEH2B and an alternative isoform, EGFP-RNASEH2Balt, were generated and used to perform a protein-protein interaction screen by GFP-Trap and mass spectrometry. The results indicate putative physical interactions between RNASEH2B and other factors involved in DNA replication and repair. Further evidence for a role in DNA repair was revealed when mammalian RNase H2 null cells were treated with hydroxyurea. Low doses of hydroxyurea increased ribonucleotide incorporation into genomic DNA and impaired S-phase progression. In contrast to wild-type cells, RNase H2 null cell proliferation also failed to recover from this replicative stress after HU withdrawal. However, the ribonucleotide content of genomic DNA from these cells did return to pre-hydroxyurea treatment levels. This suggests that an alternative repair pathway exists in mammalian cells, which can remove ribonucleotides from DNA in the absence of RNase H2, but that this pathway is also harmful to the cells. There is evidence that TREX1 facilitates viral infection while SAMHD1 has been shown to restrict viral infection. Therefore, experiments were performed to investigate if RNase H2 could be a viral facilitator or restriction factor. Ribonucleotides can be incorporated into viral DNA, so RNase H2 could act as a restriction factor by nicking and damaging the pre-integration complex. However, RNase H2 could also function as a facilitator of infection by processing viral RNA:DNA hybrid by-products and thus prevent the host immune response. The data obtained during this PhD project provides further evidence that RNase H2 is involved in DNA replication and repair and has contributed to the understanding of the function of RNase H2 in the cell. However, it is still unknown how mutations in RNase H2 lead to the pathology of AGS.

No description available.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / A anemia falciforme (AF) Ã uma das alteraÃÃes genÃticas mais comuns em nosso paÃs. Os haplÃtipos da &#61538;s-globina estÃo associados com a heterogeneidade clÃnica apresentada pela doenÃa. Os portadores de AF sÃo submetidos a elevados nÃveis de estresse oxidativo. A hidroxiurÃia (HU) tem sido utilizada no tratamento por sua aÃÃo de elevar os nÃveis de hemoglobina fetal e aÃÃo antioxidante. O estudo teve como objetivo investigar o impacto do uso da HU e dos haplÃtipos no perfil oxidativo nos pacientes com AF. Foram analisadas amostras de 64 pacientes acompanhados no Hospital UniversitÃrio Walter CantÃdio - HUWC e do grupo controle de 20 indivÃduos sem hemoglobinopatias. Os pacientes foram estratificados em grupos: uso de HU > 1 ano, uso de HU &#8804; 1 ano e sem uso de HU (SHU). A confirmaÃÃo do diagnÃstico e a anÃlise dos haplÃtipos foram realizadas atravÃs de estudo molecular. As dosagens do nitrito (NO2-), malonaldeÃdo (MDA), glutationa peroxidase (GSH-Px), catalase (CAT), glutationas total (GSSG+GSH), oxidada (GSSG) e reduzida (GSH) e da relaÃÃo GSSG/GSH (glutationas oxidada/reduzida) foram realizadas por espectrofotometria. Os nÃveis mÃdios de NO2-, e MDA mostraram-se mais elevados no grupo SHU, sendo significante apenas para o MDA (p < 0,05). O grupo SHU apresentou atividade mÃdia das enzimas CAT (p = 0,031) e GSH-Px (p = 0,036) inferiores aos demais grupos e maior relaÃÃo GSSG/GSH (p < 0,05). A avaliaÃÃo do estresse oxidativo em relaÃÃo aos haplÃtipos demonstrou que na populaÃÃo sem uso de HU os nÃveis de NO2- e de MDA foram semelhantes entre os grupos, com um aumento nÃo significante da GSH-Px no grupo Bantu/n em relaÃÃo ao Benin/n e do Ãndice GSSG/GSH no grupo Benin/n em relaÃÃo ao Bantu/n. Na populaÃÃo em uso de HU verificou-se um aumento nÃo significante dos nÃveis de NO2- no grupo Bantu/n em relaÃÃo ao Benin/n com resultados semelhantes de MDA entre os grupos e um aumento significante da GSH-Px (p<0,03) no grupo Benin/n em relaÃÃo ao Bantu/n. Os resultados da CAT foram semelhantes entre os grupos. A relaÃÃo GSSG/GSH foi maior, porÃm nÃo significante no grupo Bantu/n em relaÃÃo ao Benin/n. Os resultados do presente estudo reforÃam a hipÃtese de que os pacientes com AF apresentam um estado hiperoxidativo com nÃveis elevados dos produtos do estresse oxidativo e diminuÃdos do perfil antioxidante e que a hidroxiurÃia teve um impacto sobre o perfil oxidativo. No entanto, em relaÃÃo ao impacto dos haplÃtipos no estresse oxidativo, estudos posteriores com uma maior amostragem devem ser recomendados para confirmar nossos resultados, considerando que o grupo de pacientes nÃo tratados com HU foi menor que o grupo de pacientes em uso de HU, o que pode ter interferido na anÃlise estatÃstica dos resultados. / The sickle cell anemia is one of the most common genetic disorders in our country. The &#61538;-globin haplotypes are associated with the clinical heterogeneity of the disease. Individuals with sickle cell disease are subjected to high levels of oxidative stress. Hydroxyurea (HU) has been used as treatment and it increases the levels of fetal hemoglobin having an action antioxidant. The study aimed to investigate the impact of the use of HU and haplotypes in the oxidative status in patients with sickle cell anemia. Samples from 64 patients treated at the University Hospital Walter CantÃdio - HUWC and the control group of 20 individuals without hemoglobinopathies. Patients were stratified into groups: the first one using HU > 1 year, the second using HU &#8804; 1 year and the third using of HU (SHU). Confirmation of the diagnosis and analysis of haplotypes were performed by molecular study. The measurements of nitrite (NO2-), malonaldehyde (MDA), glutathione peroxidase (GSH-Px), catalase (CAT), glutathione total (GSSG+GSH), oxidized (GSSG) and reduced (GSH) and the ratio GSSG/GSH (glutathione oxidized/reduced) were performed by spectrophotometry. Mean levels of NO2- and MDA were shown to be higher in SHU group, being significant only for MDA (p < 0,05). The assessment of oxidative stress in relation to haplotypes showed that the population without the use of HU levels of NO2- and MDA were similar between groups, with an insignificant increase of GSH-Px in the Bantu/n compared with Benin/n and index GSSG/GSH in the Benin/n compared with Bantu/n. In the population using the HU there was a nonsignificant increase in the levels of NO2- in the Bantu/n compared with Benin/n with similar results between groups of MDA and a significant increase in GSH-Px (p <0.03) in the Benin/n compared with Bantu/n. The results of CAT were similar between groups. The ratio of GSSG/GSH was higher but not significant in the Bantu/n compared to Benin/n. The results of this study support the hypothesis that patients with the sickle cell anemia have a state hiperoxidativo products with high levels of oxidative stress and decreased antioxidant status and that of hydroxyurea had an impact on oxidative stress. However, regarding the impact of the haplotypes in oxidative stress, further studies with a larger sample should be recommended to confirm our results, considering that the group of patients not treated with HU was lower than the group of patients using HU, the which may have interfered in the statistical analysis of results.

Actuellement, l’Hydroxyurée est le seul traitement médicamenteux qui permet d’améliorer la qualité de vie et l’espérance de vie des patients drépanocytaires. Ses effets sont essentiellement liés à l’augmentation de l’HbF par l’inhibition de la polymérisation de l’hémoglobine S qui constitue la base physiopathologique de la drépanocytose. Cependant d’autres paramètres de réponse contribuent à l’amélioration clinique, principalement les atteintes chroniques, et ce indépendamment de l’augmentation du %HbF. Le phénotype hémolytique est associé aux globules rouges denses (DRBC) qui constituent une sous population de globules rouges présentant une densité supérieure à 1,11. L’amélioration des manifestations chroniques est associée à une diminution du %DRBC qui semble être une cible thérapeutique de l’Hydroxyurée. Par son efficacité de plus en plus démontrée, l’Hydroxyurée pourrait être le traitement de recours dans le traitement de fond de la drépanocytose, cependant son mode d’action reste encore partiellement élucidé.Ce travail a été réalisé dans le but de mieux comprendre le mode d’action de l’Hydroxyurée.La première étude consiste à déterminer les facteurs prédictifs de la diminution des DRBC sous Hydroxyurée. Après 6 mois de traitement, une diminution significative du %DRBC associée à une amélioration des paramètres d’hémolyses a été observée. Cet effet est indépendant de l’augmentation du %HbF. La diminution du %DRBC semble être plus constante que l’augmentation du %HbF sous Hydroxyurée.La deuxième étude a pour but de mettre au point une nouvelle approche de mesure de la teneur en HbF par globule rouge. L’outil de quantification actuellement utilisé donne une mesure du pourcentage moyen de l’HbF. Or la teneur en HbF par globule rouge peut varier pour un même %HbF conduisant à une variabilité de réponse clinique et biologique. Dans l’hypothèse d’un seuil d’HbF inhibant la polymérisation de l’hémoglobine S, une méthode précise de mesure de la teneur en HbF par globule rouge a été développée. Dans le cadre d’une preuve de concept, une étude de la distribution de l’HbF a été effectuée au cours du traitement par Hydroxyurée. Le suivi longitudinal montre une distribution hétérogène de l’HbF avant le début du traitement par Hydroxyurée. La distribution de l’HbF devient homogène après 6 mois sur l’ensemble des globules rouges avec une diminution rapide du nombre de globules rouges ne contenant pas d’HbF au profit des autres populations globulaires.La troisième étude a pour but d’optimiser le traitement par Hydroxyurée. En effet les atteintes rénales associées à la drépanocytose sont de plus en plus fréquentes et constituent un facteur de mortalité. Elles peuvent influencer la pharmacocinétique de l’Hydroxyurée car l’excrétion rénale constitue une voie d’élimination de l’Hydroxyurée. Nous avons d’abord développé unetechnique de mesure simple et fiable de dosage de l’Hydroxyurée. La pharmacocinétique de l’Hydroxyurée a été comparée entre les patients drépanocytaires présentant une fonction rénale normale avec ceux présentant une insuffisance rénale modérée et une hyper filtration glomérulaire. Une diminution de l’élimination de l’Hydroxyurée associée à une augmentation des concentrations plasmatiques ont été observées chez les insuffisants rénaux. La pharmacocinétique de l’Hydroxyurée semble être similaire chez les patients normo-rénaux et hyperfiltrants.Ce travail a apporté des éléments de réponse que nous jugeons important quant à l’action de l’Hydroxyurée sur les DRBC impliqués dans la vasculopathie chronique et sur la distribution de l’HbF. Nous avons également apporté une nouvelle technique de mesure de l’Hydroxyurée et montré qu’une adaptation de dose est nécessaire chez les patients ayant une insuffisance rénale. / Hydroxyurea, the only sickle-cell–disease approved drug, has proven its efficacy in ameliorating patient quality of life and life expectancy. The classical biological response of Hydroxyurea therapy is increased fetal hemoglobin (HbF) which inhibits deoxy hemoglobin S polymerization. However, other parameters also support clinical benefits of Hydroxyurea especially for chronic organ failures which are related to hemolysis. Sickle-cell–disease hemolytic phenotype is associated with dense red blood cells (DRBC) defined as having a density >1,11. Improvement of chronic clinical complications is associated with a marked decrease in %DRBC emphasizing its role as a therapeutic target for Hydroxyurea treatment. Despite the known benefits in both acute and chronic sickle-cell–disease manifestations, the mechanism action of Hydroxyurea has not been fully elucidated.This thesis was undertaken in order to investigate the mechanism of action of Hydroxyurea in sickle-cell–disease treatment.The first aim is to determine biological parameters predictive of %DRBC decrease under Hydroxyurea. A significant decrease in %DRBC after 6 months of Hydroxyurea therapy was observed. This biological response was associated with a decrease in hemolysis. However no correlation with %HbF increase was detected; the decrease in %DRBC under Hydroxyurea was more constant than the increase in %HbF.The second aim of this study was to develop a new approach for HbF determination in individual red blood cells. Indeed, routine HbF quantification only provides a mean value. However clinical amelioration is not exclusively dependent on the average %HbF, since a wide distribution of HbF content per cell could indicate a HbF content threshold for inhibition of deoxy hemoglobin S polymerization. In this context, a simple and precise method was developed in order to assay HbF content per cell. The distribution of HbF during Hydroxyurea therapy was analyzed as proof of concept. The longitudinal monitoring showed an uneven distribution of HbF before Hydroxyurea and a normal distribution in the whole red blood cells after 6 months of therapy. A rapid decrease in red blood cells not containing HbF in favor of cells expressing a high quantity of HbF was observed.The third objective consisted of Hydroxyurea therapy optimization. Chronic kidney disease is a frequent complication during sickle-cell–disease. Since Hydroxyurea is cleared from plasma partially by renal excretion, impaired renal function could potentially affect Hydroxyurea pharmacokinetics. A new simple Hydroxyurea dosage method was performed in this context.Hydroxyurea pharmacokinetic parameters were compared among sickle-cell–disease patients with normal renal function, moderate renal insufficiency and renal hyper filtration. A decrease in Hydroxyurea elimination associated with a marked plasma concentration was observed inrenally impaired patients. No significant difference was observed between renal hyper filtration and normal patients.These results provide answers about Hydroxyurea effect on DRBC which are involved in chronic vasculopathy and on HbF distribution. Hydroxyurea dosage method underpins the need for dose adjustment in renally impaired patients.

Essential thrombocythemia (ET) is a rare myeloproliferative neoplasm affecting 43.7 out of every 100,000 people in the United States. The disease is characterized by abnormally high platelet counts, mutational abnormalities in Janus Kinase 2 (JAK2)/Calreticulin (CALR)/myeloproliferative leukemia virus oncogene (MPL), and increased megakaryocyte production and differentiation. The average age of onset for patients with ET is between 65-70 years, but recent studies have demonstrated a downward trend in the age of diagnosis. Mechanistically, ET mutations cause the dimerization of JAK and upregulation of the JAK-STAT pathways. Common treatment approaches seek to use cytoreduction and platelet inhibition to lower the risk of a thrombotic event. Hydroxyurea and low-dose aspirin have been the gold-standard of treatment for ET patients. This thesis sought to compare the current available therapy with second-line treatments and investigational treatments. Anagrelide is a key second-line treatment for ET that is used in the event of intolerance to hydroxyurea. It acts through cytoreductive mechanisms which result in a decreased platelet count. Major bleeding is a severe adverse event associated with anagrelide. Interferons are another second-line defense in the treatment of ET despite a lack of FDA approval for this indication. Interferons act directly to reduce platelet counts and, unlike other drug classes, mount an immunological response against the JAK2 stem cells to reduce the allelic burden. An immunological approach to ET may be key to the sustained treatment of the disorder without a daily dosing regimen. Despite the promise of interferons, severe adverse effects limit the adherence of many patients to this class of drugs. JAK inhibitors are an investigational drug class that acts directly through the JAK-STAT pathway. JAK inhibitors have shown little efficacy in the treatment of ET and may be better suited for treatment in combination therapies. Telomerase inhibitors are one such investigational drug class that may pair well with JAK inhibitors for the treatment of ET. All of these drug classes were compared to hydroxyurea with respect to their pharmacokinetics, pharmacodynamics, and patient evaluation. Hydroxyurea and low-dose aspirin showed superiority in comparison to other drug classes due to their low toxicity profile and minimum adverse side-effects, high oral bioavailability and wide distribution, high adherence, and production of the most uniform response to reducing thrombotic events and platelet counts. The interferon drug class shows unique potential for the treatment of ET and should be placed above the second-line treatment standard of anagrelide due to its benefits in treatment of younger and pregnant patients. Interferons are the only class of drug for the treatment of ET that did not increase the risk of drug-related leukemogenic transformations. Despite non-adherence due to side-effects and lack of an oral administration, interferons are superior to anagrelide due to their longer dosing interval and immunological attack on JAK2 stem cells. Treatment of ET with anagrelide has shown similar efficacy to hydroxyurea and interferons in platelet reduction and rivals hydroxyurea in the prevention of thrombotic risk. Despite this benefit, the risk of bleeding associated with anagrelide is a significant disadvantage. Hydroxyurea and low-dose aspirin remain the current standard of treatment for patients with ET, although new approaches may soon be available.

No description available.

Οι αιμοσφαιρινοπάθειες συγκαταλέγονται ανάμεσα στις πιο κοινές μονογονιδιακές διαταραχές παγκοσμίως, συμπεριλαμβανομένης της β-θαλασσαιμίας και της δρεπανοκυτταρικής αναιμίας. Η επανενεργοποίηση των γονιδίων της γ-σφαιρίνης φαίνεται να είναι μια ενδιαφέρουσα θεραπευτική προσέγγιση για τους ασθενείς που πάσχουν από β-τύπου αιμοσφαιρινοπάθειες. Ορισμένες φαρμακευτικές ουσίες έχουν τη δυνατότητα να επάγουν παροδικά την έκφραση των γονιδίων της γ-σφαιρίνης γεγονός που βελτιώνει το φαινότυπο των ασθενών λόγω των υψηλότερων επιπέδων HbF που παρατηρούνται. Η μόνη φαρμακευτική ουσία που έχει εγκριθεί από τον FDA και χρησιμοποιείται ευρύτατα σε ασθενείς που πάσχουν από β-τύπου αιμοσφαιρινοπάθειες και συγκεκριμένα από δρεπανοκυτταρική αναιμία είναι η HU. Παρά το γεγονός ότι στην πλειονότητα των ασθενών παρατηρείται αύξηση της παραγωγής HbF μετά από αγωγή με HU (Steinberg et al. 1997), τα επίπεδα αύξησης διαφέρουν αρκετά μεταξύ των ασθενών που πάσχουν από β-θαλασσαιμία και δρεπανοκυτταρική αναιμία(Patrinos and Grosveld 2008). Σύμφωνα με τους Borg και συνεργάτες, το γονίδιο KLF10 φαίνεται να σχετίζεται με την αύξηση των επιπέδων της HbF και την ανταπόκριση ασθενών με β-τύπου αιμοσφαιρινοπάθειες σε θεραπεία με HU(Borg et al. 2012). Στην παρούσα μελέτη διερευνήθηκε η πιθανή συσχέτιση των SNP rs319133 και rs11552577, που εδράζονται στο γονίδιο KLF10, με αυξημένα επίπεδα HbF και η αξιολόγηση αυτών ως φαρμακογονιδιωματικοί δείκτες, που σχετίζονται με τη μεταβλητότητα των επιπέδων της HbF ως απόκριση στη θεραπεία με HU. Χρησιμοποιήθηκαν ασθενείς που πάσχουν από βαριά β-θαλασσαιμία, ενδιάμεση β-θαλασσαιμία, μη-θαλασσαιμικοί ασθενείς και διπλά ετερόζυγοι ασθενείς για β-θαλασσαιμία και δρεπανοκυτταρική αναιμία. Η μέθοδος γονοτύπησης που χρησιμοποιήθηκε και για τους δύο πολυμορφισμούς ήταν η PCR-RFLP. Η απουσία του πολυμορφισμού rs319133 φαίνεται να σχετίζεται με αυξημένα επίπεδα HbF στους ασθενείς που χαρακτηρίζονται από ενδιάμεση β-θαλασσαιμία συγκριτικά με ασθενείς που πάσχουν από βαριά β-θαλασσαιμία (p=0.04). Επίσης παρατηρείται μια στατιστική τάση συσχέτισης χειρότερης ανταπόκρισης στην αγωγή με HU στους διπλά ετερόζυγους ασθενείς 96 για β-θαλασσαιμία και δρεπανοκυτταρική αναιμία. Για τον δεύτερο πολυμορφισμό που μελετήθηκε δεν παρατηρήθηκαν στατιστικά σημαντικές διαφορές. Τα δεδομένα της παρούσας μελέτης υποδεικνύουν συσχέτιση του γονιδίου KLF10 με αυξημένα επίπεδα HbF. Μελέτες σε πολυπληθέστερες ομάδες θα μπορούσαν να οδηγήσουν στον εντοπισμό και άλλων πολυμορφισμών που σχετίζονται με αυξημένη έκφραση των γονιδίων της γ-σφαιρίνης. / Hemoglobinopathies are amongst the most common single gene disorders worldwide, including the thalassemias and sickle cell disease (SCD). Reactivation of the human γ-globin genes would be a therapeutic intervention for β-type hemoglobinopathies patients. Some drugs and compounds can transiently induce γ-globin gene expression and improve the disease phenotype by augmenting HbF accumulation. Only HU (hydroxyurea) is approved from the FDA and is widely used to treat patients with β-type hemoglobinopathies, in particular sickle cell disease. Although the majority of patients show an increase of HbF production upon HU treatment(Steinberg et al. 1997), the level of HbF increase differs considerably among β-thalassemia and SCD patients(Patrinos and Grosveld 2008). According to Borg et al, KLF10 appears to be significantly associated with high HbF and it may act as an important pharmacogenetic biomarker for β-type hemoglobinopathies patients who are treated with HU(Borg et al. 2012). The aim of our study was to elucidate whether there is an association of the SNPs namely rs3191333 and rs11552577 in KLF10 gene with increased levels of HbF and with response to HU treatment in β-hemoglobinopathies patients. We analyzed samples of β-thalassemia major patients, of β-thalassemia intermedia patients, of healthy (non-thalassemic) donors and samples of SCD/β–thalassemia patients who have been treated with HU. Genotyping was carried out by using PCR-RFLP. The lack of rs3191333 is associated with increased HbF levels in β–thalassemia intermedia compared to β– thalassemia major patients (p=0.04). Also, it is shown a statistical trend of worse response to HU treatment in compound heterozygote β–thalassemia-SCD patients. As far as rs11552577 is concerned no statistically significant differences were observed. Our data show that KLF10 gene is strongly associated with HbF levels. Further analyses could possibly reveal novel variants which are associates with increased expression of γ-globin genes.