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Plusieurs recherches s’adressent à étudier les nouvelles interactions qui peuvent avoir lieu entre les différentes sous-unités des cytokines ainsi que les récepteurs associés. L’objectif général de la thèse est d’étudier la formation de nouveaux complexes impliquant le récepteur soluble EBI3 et la cytokine CLCF1, déterminer leurs voies de signalisation et examiner l’impact de ces interactions sur l’induction de nouvelles fonctions biologiques. EBI3 est un récepteur soluble qui participe à la formation de trois cytokines composites: IL-27 (EBI3/p28), IL-35 (EBI3/p35) et IL-39 (EBI3/p19). Celles-ci appartiennent à la famille IL-12 des cytokines. L’IL-27 est une cytokine pléiotropique qui exerce à la fois des fonctions pro-inflammatoires qui se caractérisent principalement par la différenciation des cellules Th1 et des fonctions anti-inflammatoires associées à l’inhibition de la différenciation des cellules Th17 et à la production du GM-CSF. L’IL-35 est une cytokine connue pour induire des effets immunosuppresseurs tandis que l’IL-39 a été récemment identifiée pour induire l’inflammation chez les souris atteintes du lupus. Étant donné que l’EBI3 ne forme pas des complexes covalents avec les sous-unités p28, p35 et p19, nous avons voulu savoir si les effets d’EBI3 pourraient passer par la formation d’un composé différent des cytokines IL-27, IL-35 et IL-39. Nous avons démontré que l’EBI3 induit une trans-signalisation en formant un complexe alternatif avec l’IL-6. Des effets similaires de type pro-inflammatoire ont été observés avec les complexes IL-6/sIL-6Rα et EBI3/IL-6. En effet, les deux cytokines activent la chaîne gp130, induisent la phosphorylation de STAT3 et augmentent l’expression des chemiokines par les cellules endothéliales humaines. CLCF1 appartient à la famille IL-6 des cytokines monomériques. L’efficacité de la sécrétion du CLCF1 augmente en présence du CLF, un récepteur soluble aux cytokines. Des mutations dans les gènes codant pour CLCF1 ou CLF induisent le syndrome de la transpiration induite par le froid appelé "Crisponi" ou "CISS". La liaison entre le CNTF, une cytokine qui peut avoir des effets protecteurs semblables au CLCF1 au niveau du système nerveux central, et l’apolipoprotéine E a été observée in vitro (1). Nous avons émis l’hypothèse que CLCF1 pourrait également former un complexe avec l’apoE. Nous avons démontré que CLCF1 se lie avec les différentes isoformes d’apoE, à savoir, apoE2, apoE3 et apoE4. L’apoE est une protéine impliquée dans le transport des lipides et qui se trouve principalement à la surface des chylomicrons, VLDL et une fraction des HDL. Nous avons observé que CLCF1 interagit avec les lipoprotéines en présence et absence d’apoE. L’impact de la liaison du CLCF1 avec l’apoE ou avec les lipoprotéines a été examiné sur les cellules qui expriment la chaîne CNTFRα. / Several researches aimed to study new interactions that take place between the different subunits of cytokines and related receptors. The general goal of this thesis is to study the formation of new complexes involving the soluble receptor EBI3 and the cytokine CLCF1, determine their signaling pathways, and examine the impact of these interactions on the induction of new biological functions. EBI3 is a soluble receptor participating in the formation of three composite cytokines: IL-27 (EBI3/p28), IL-35 (EBI3/p35), and IL-39 (EBI3/p19). These cytokines belong to the IL-12 family. IL-27 is a pleiotropic cytokine that exerts both pro-inflammatory functions characterized by the differentiation of Th1 cells, and anti-inflammatory functions associated with the inhibition of Th17 cells differentiation and the production of GM-CSF. IL-35 is known to induce an immunosuppressive effects while IL-39 has recently been identified to induce inflammation in mice with lupus. Since EBI3 doesn’t form a covalent complexes with p28, p35 and p19 subunits, we wanted to know if the effects of EBI3 could go through the formation of a different compound than that of IL-27, IL-35 and IL-39. We have shown that EBI3 induces a trans-signaling pathway by forming a complex with IL-6. Both IL-6/sIL-6Rα and EBI3/IL-6 complexes share similar pro-inflammatory effects. Indeed, both cytokines activate gp130 chain, induce phosphorylation of STAT3, and increase the expression of chemiokines by human endothelial cells. CLCF1 belongs to the IL-6 family of monomeric cytokines. CLCF1 is efficiently secreted in the presence of CLF, a soluble cytokine receptor. Mutations in the genes coding for CLCF1 or CLF cause the cold-induced sweating syndrome also called "Crisponi" or "CISS". The interaction between CNTF, a cytokine which may have similar protective effects as CLCF1 at the central nervous system, and apolipoprotein E was observed in vitro (1). We hypothesized that CLCF1 could also form a complex with apoE. We demonstrated that CLCF1 binds with different apoE isoforms, namely, apoE2, apoE3, and apoE4. ApoE is a protein involved in lipid transport and is located primarily on the surface of chylomicrons, VLDL, and a fraction of HDL. We observed that CLCF1 interacts with lipoproteins in the presence and absence of apoE. The impact of CLCF1 interaction with apoE or lipoproteins was examined on cells expressing the chain CNTFRα.

Atualmente, as demências tornam-se mais prevalentes e constituem-se como um importante problema de saúde pública mundial. A Degeneração Lobar Frontotemporal (DLFT) e a Doença de Alzheimer (DA) são as de maior incidência. A investigação dos fatores de risco para as demências degenerativas inscreve-se entre os temas mais relevantes das neurociências e a avaliação dos fatores de risco de natureza genética tem produzido contribuições importantes. Na DLFT, mutações no gene TARDBP, codificador da proteína nuclear TDP-43, estão entre as ocorrências genéticas mais descritas, enquanto que para a DA, o alelo 4 do gene da apolipoproteína E (APOE) é o principal fator de risco. Pacientes com diagnóstico clínico de DLFT (n=47) e de DA provável (n=30) recebidos do ambulatório do Grupo de Neurologia Cognitiva e do Comportamento (GNCC) da Clínica Neurológica do HC-FMUSP foram convidados a participar do estudo. Amostras de sangue foram coletadas para a realização da extração de DNA linfocitário. Os éxons de 1-6 do gene TARDBP foram amplificados por PCR e seus produtos foram sequenciados em sequenciador automático. Os polimorfismos do gene APOE foram determinados através da técnica de PCR em tempo real. A análise do gene da TDP-43 em pacientes com DLFT mostrou a presença de uma mutação na região do éxon 6 do TARDBP (g.14935A>G) em um paciente do sexo masculino, com idade de 54 anos e diagnóstico de demência semântica. Na genotipagem dos pacientes de DA, foi observado que a metodologia utilizada, através de PCR em tempo real mostrou-se eficiente em detectar os polimorfismos do gene APOE, fornecendo resultados compatíveis quando comparados aos demais estudos brasileiros publicados anteriormente / Brazil is one of the developing countries that are undergoing a process of demographic transition in which the elderly represents a significant proportion of the total population. Neurodegenerative illnesses most commonly appear at such ages. Frontotemporal lobar degeneration (FTLD) and Alzheimers disease (AD) are the most frequent causes for dementia. The investigation of risk factors for degenerative dementia is a relevant subject of neurosciences and the evaluation of the nature of genetic risk factors has produced the most important contributions. Mutations in TARDBP gene, the encoder of the TDP-43 nuclear protein, appear as the most frequent genetic occurrences for FTLD, whereas, in DA, the 4 allele of the apolipoprotein E (APOE) is the major genetic risk factor. Patients with clinical diagnosis of FTLD types of families and sporadic (n=47) and probable AD (n=30) from the ambulatory of Cognitive Neurology Group and Behavior (CNGB) of Neurological Clinic of HC-FMUSP were invited to participate in this study. Blood samples were collected for lymphocytic DNA extraction. The APOE gene polymorphisms are being determined through the real time PCR technique. The 1-6 exons of TARDBP gene were amplified by PCR and their products were sequenced in automated sequencer. The TDP-43 gene analysis in patients with FTLD showed the presence of one mutation in the region of exon 6 TARDBP gene in a male patient of 54 years old, with diagnoses of semantic dementia. Regarding DA patients genotyping, the real time methodology has been shown as an efficient approach to detect APOE polymorphisms, presenting data similar to those observed in other Brazilian studies

Η HDL είναι ένα μείγμα λιποπρωτεϊνικών σωματιδίων υψηλής πυκνότητας, που ανάλογα με τη σύσταση τους σε λιπίδια μπορούν να είναι δισκοειδή ή σφαιρικά. Η κύρια αθηροπροστατευτική δράση της HDL, οφείλεται στο γεγονός ότι η συγκεκριμένη λιποπρωτεΐνη συλλέγει την περίσσεια χοληστερόλης από τους περιφερικούς ιστούς και τη μεταφέρει στο ήπαρ όπου καταβολίζεται. Επιπλέον, έχει αντιφλεγμονώδη και αντιοξειδωτική δράση. Η κύρια πρωτεΐνη της HDL είναι η απολιποπρωτεΐνη Α-Ι (apoA-I). Ωστόσο, πρόσφατα αποδείχθηκε ότι σε πειραματόζωα με έλλειψη στην apoA-I και κατά συνέπεια στην κλασσική HDL, η απολιποπρωτεΐνη Ε (apoE) αλληλεπιδρά με τον μεταφορέα λιπιδίων ABCA1 προάγοντας την de novo σύνθεση HDL σωματιδίων. Στην παρούσα μελέτη, στόχος ήταν η εύρεση της περιοχής της apoE που είναι υπεύθυνη για την λειτουργική αλληλεπίδραση με τον ABCA1 για το σχηματισμό HDL. Για το σκοπό αυτό, ανασυνδυασμένοι αδενοϊοί που εξέφραζαν καρβοξυ-τελικές συντετμημένες μορφές της apoE4 (AdGFP-E4[1-259], AdGFP-E4[1-229], AdGFP-E4[1-202], AdGFP-E4[1-185]), χορηγήθηκαν σε ποντίκια με έλλειψη στην ApoA-I σε δόση 8x108 pfu και πέντε μέρες μετά τη μόλυνση δείγματα πλάσματος αναλύθηκαν για το σχηματισμό HDL. Κλασματοποίηση των λιποπρωτεϊνών του πλάσματος με υπερφυγοκέντρηση σε διαβάθμιση πυκνότητας καθώς και FPLC χρωματογραφία αποκάλυψε ότι όλες οι συντετμημένες μορφές της apoE4 προάγουν το σχηματισμό HDL. Ανάλυση ηλεκτρονικής μικροσκοπίας με αρνητική χρώση των HDL κλασμάτων, επιβεβαίωσε ότι όλες οι συντετμημένες μορφές της apoE4 είναι ικανές να προάγουν το σχηματισμό σωματιδίων με διάμετρο στην περιοχή της HDL. Τα δεδομένα αυτά οδηγούν στο συμπέρασμα ότι η αμινοτελική περιοχή της apoE που εκτείνεται από τα αμινοξέα 1 έως 185 αρκεί για το σχηματισμό HDL σωματιδίων in vivo. Αυτά τα ευρήματα, ανοίγουν το δρόμο στην έρευνα για το σχεδιασμό βιολογικών φαρμάκων με βάση την apoE για τη θεραπεία της δυσλιπιδαιμίας, της αθηροσκλήρωσης και της στεφανιαίας νόσου. / HDL is a mixture of high density lipoprotein particles that depending on the lipid composition may be discoidal or spherical. The main atheroprotective property of HDL is reverse cholesterol transport, a process that unloads excess cholesterol from peripheral tissues and transports it to the liver for catabolism. HDL has also anti-inflammatory and antioxidant properties. The main protein of HDL is apolipoprotein A-I (apoA-I). However, recently it was shown that in the absence of apoA-I and consequently classical HDL, apolipoprotein E (apoE) interacts functionally with the lipid transporter ABCA1, promoting the de novo synthesis of HDL-like particles. The present study focused on the identification of the domain of apoE that is responsible for the functional interaction with ABCA1 and the formation of apoE-containing HDL. Recombinant attenuated adenoviruses expressing carboxy-terminal truncated forms of apoE4 (apoE4[1-259], apoE4[1-229], apoE4[1-202], and apoE4[1-185]) were administered to apoA-I-deficient mice at a low dose of 8x108 pfu and five days post-infection plasma samples were isolated and analyzed for HDL formation. Fractionation of plasma lipoproteins of the infected mice by density gradient ultracentrifugation and FPLC revealed that all forms were capable of promoting HDL formation. Negative staining electron microscopy analysis of the HDL density fractions confirmed that all C-terminal truncated forms of apoE4 promoted the formation of particles with diameters in the HDL region. Taken together, these data establish that the aminoterminal 1 to 185 region of apoE suffices for the formation of HDL particles in vivo. These findings may have important ramifications in the design of apoE-based biological drugs for the treatment of dyslipidemia, atherosclerosis and coronary heart disease.

Atualmente, as demências tornam-se mais prevalentes e constituem-se como um importante problema de saúde pública mundial. A Degeneração Lobar Frontotemporal (DLFT) e a Doença de Alzheimer (DA) são as de maior incidência. A investigação dos fatores de risco para as demências degenerativas inscreve-se entre os temas mais relevantes das neurociências e a avaliação dos fatores de risco de natureza genética tem produzido contribuições importantes. Na DLFT, mutações no gene TARDBP, codificador da proteína nuclear TDP-43, estão entre as ocorrências genéticas mais descritas, enquanto que para a DA, o alelo 4 do gene da apolipoproteína E (APOE) é o principal fator de risco. Pacientes com diagnóstico clínico de DLFT (n=47) e de DA provável (n=30) recebidos do ambulatório do Grupo de Neurologia Cognitiva e do Comportamento (GNCC) da Clínica Neurológica do HC-FMUSP foram convidados a participar do estudo. Amostras de sangue foram coletadas para a realização da extração de DNA linfocitário. Os éxons de 1-6 do gene TARDBP foram amplificados por PCR e seus produtos foram sequenciados em sequenciador automático. Os polimorfismos do gene APOE foram determinados através da técnica de PCR em tempo real. A análise do gene da TDP-43 em pacientes com DLFT mostrou a presença de uma mutação na região do éxon 6 do TARDBP (g.14935A>G) em um paciente do sexo masculino, com idade de 54 anos e diagnóstico de demência semântica. Na genotipagem dos pacientes de DA, foi observado que a metodologia utilizada, através de PCR em tempo real mostrou-se eficiente em detectar os polimorfismos do gene APOE, fornecendo resultados compatíveis quando comparados aos demais estudos brasileiros publicados anteriormente / Brazil is one of the developing countries that are undergoing a process of demographic transition in which the elderly represents a significant proportion of the total population. Neurodegenerative illnesses most commonly appear at such ages. Frontotemporal lobar degeneration (FTLD) and Alzheimers disease (AD) are the most frequent causes for dementia. The investigation of risk factors for degenerative dementia is a relevant subject of neurosciences and the evaluation of the nature of genetic risk factors has produced the most important contributions. Mutations in TARDBP gene, the encoder of the TDP-43 nuclear protein, appear as the most frequent genetic occurrences for FTLD, whereas, in DA, the 4 allele of the apolipoprotein E (APOE) is the major genetic risk factor. Patients with clinical diagnosis of FTLD types of families and sporadic (n=47) and probable AD (n=30) from the ambulatory of Cognitive Neurology Group and Behavior (CNGB) of Neurological Clinic of HC-FMUSP were invited to participate in this study. Blood samples were collected for lymphocytic DNA extraction. The APOE gene polymorphisms are being determined through the real time PCR technique. The 1-6 exons of TARDBP gene were amplified by PCR and their products were sequenced in automated sequencer. The TDP-43 gene analysis in patients with FTLD showed the presence of one mutation in the region of exon 6 TARDBP gene in a male patient of 54 years old, with diagnoses of semantic dementia. Regarding DA patients genotyping, the real time methodology has been shown as an efficient approach to detect APOE polymorphisms, presenting data similar to those observed in other Brazilian studies

A study of hyperglycemia and its effects on endothelial activation, macrophage recruitment, and atherosclerotic plaque development in mice. Hyperglycemic mice demonstrated greater VCAM but not ICAM expression along the endothelium, increased macrophage presence within the subendothelial space of these regions, and a greater volume of plaque in adulthood. / Cardiovascular disease is the leading cause of death in the world today. Atherosclerosis is the formation of plaque in the arteries and a major underlying cause of these fatalities. Type I and II diabetes are each strong independent risk factors for atherosclerosis. This study examines the effects of hyperglycemia on early atherosclerosis. Hyperglycemia did not promote atherosclerosis in the absence of hypercholesterolemia. Hyperglycemic mice demonstrated greater VCAM, but not ICAM, expression in regions of the endothelium susceptible to atherogenesis, prior to initiation of plaque development. Regions correlating to upregulation of VCAM exhibited a greater quantity of macrophages infiltrating the intima. This study suggests a unique and important role for VCAM in early atherosclerotic development and may explain the accelerated atherosclerotic plaque progression seen in hyperglycemic mice. This study also identifies VCAM as a potential target for the development of therapies to block or slow atherosclerotic plaque development in people with diabetes. / Thesis / Master of Science (MSc) / Cardiovascular disease is the leading cause of death in the world today. A major underlying cause of cardiovascular disease is atherosclerosis – a condition involving the thickening of the artery wall. Type I and II diabetes are each strong independent risk factors for atherosclerosis. The purpose of this study is to examine the effects of high blood glucose (hyperglycemia) on early events leading to atherosclerosis. This study found that hyperglycemia was not sufficient to promote atherosclerosis unless plasma cholesterol levels were also elevated. Hyperglycemia appeared to induce atherosclerosis by increasing the expression of factors responsible for recruiting white blood cells to the artery wall. This is consistent with the observation that hyperglycemic mice also had significantly more macrophages in the sites of plaque development. This study implicates one macrophage-recruitment factor in particular, vascular cell adhesion molecule (VCAM), as playing an important and unique role in the initiation of atherosclerosis by hyperglycemia. Therefore, VCAM is a possible target for the development of therapies to block or slow the development of atherosclerosis in individuals with diabetes.

Telomeres are the outermost parts of linear chromosomes. They consist of tandemly repeated non-coding short nucleotide sequences (TTAGGG in all vertebrates), in humans spanning over the last 2 to 15 kilobase pairs of the chromosome. Due to the end-replication problem, telomeres shorten with each cellular division. A critically short telomere will trigger the cell to enter a state of cellular senescence or to apoptose. The rate of telomere shortening can be accelerated by factors such as oxidative stress and inflammation. Taken together, this contributed to making telomere length a candidate biomarker of health and aging. Studies have shown that leukocyte telomere length progressively shortens with age, and that it independent of age is associated with age-related morbidity, lifestyle factors, and mortality. This thesis was aimed at exploring the relationships of leukocyte telomere length with various functional and structural attributes of the brain. In Paper I, telomere length was shown to be longer among non-demented carriers of the apolipoprotein E (APOE) ε4 allele, a well-established risk factor for Alzheimer’s disease. However, the rate of telomere shortening was greater among the ε4 carriers, possibly due to the higher levels of oxidative stress and inflammation associated with this allele. Furthermore, performance on episodic memory tests was inversely related to telomere length among ε4 carriers. The results may contribute to a better understanding of the pathophysiology related to the APOE ε4 allele. The volume of the hippocampus, a structure in the brain critical for episodic memory function, was in Paper II found to be inversely related to telomere length among non-demented APOE ε3/ε3 carriers. No correlation between hippocampal volume and telomere length was discernible among ε4 carriers, but they fit the pattern exhibited by the ε3/ε3 carriers as they tended to have smaller hippocampi and longer telomere length compared with the ε3/ε3 carriers. The results are possibly explained by a low proliferative activity among subjects with smaller hippocampi, which might also explain the inverse association between telomere length and episodic memory performance in Paper I. In Paper III, we describe results corroborating earlier findings of shorter telomere length among individuals suffering from depression. Moreover, we found that the shorter telomere length among the patients to a large extent could be linked to a hypocortisolemic state; a state which has been associated with chronic stress. The findings corroborate the link between telomere length and stress, and underline the role of stress in depressive illness. Two prominent manifestations of the aging brain are atrophy and white matter hyperintensities. In Paper IV, we report that white matter hyperintensities and cerebral subcortical atrophy were associated with shorter telomere length in aged non-demented individuals. Cortical atrophy was not associated with telomere length. Inflammation may be the underlying cause of the associations, as it is linked to telomere attrition, subcortical atrophy, and white matter hyperintensities. Taken together, these results show that leukocyte telomere length has the potential of being used as a biomarker for structural and functional attributes of the brain. Furthermore, the findings can provide new insights into mechanisms of disease and aging of the brain

Patients with Alzheimer's disease (AD) often have a family history of the disease, implicating genetics as a major risk factor. Three genes are currently known to cause familial early-onset AD (<65 years): the amyloid precursor protein (APP) and the presenilins (PSEN1 and PSEN2). For the much more common late-onset disease (>65 years), only the APOE gene has repeatedly been associated to AD, where the ε4 allele increases disease risk and decreases age at onset. As APOE ε4 only explains part of the total estimated disease risk, more genes are expected to contribute to AD. This thesis has focused on the study of genetic risk factors involved in AD. In the first study, we conducted a linkage analysis of six chromosomes previously implicated in AD in a collection of affected relative pairs from Sweden, the UK and the USA. An earlier described linkage peak on chromosome 10q21 could not be replicated in the current sample, while significant linkage was demonstrated to chromosome 19q13 where the APOE gene is located. The linkage to 19q13 was further analyzed in the second study, demonstrating no significant evidence of genes other than APOE contributing to this peak. In the third study, the prevalence of APP duplications, a recently reported cause of early-onset AD, was investigated. No APP duplications were identified in 141 Swedish and Finnish early-onset AD patients, implying that this is not a common disease mechanism in the Scandinavian population. In the fourth study, genes with altered mRNA levels in the brain of a transgenic AD mouse model (tgAPP-ArcSwe) were identified using microarray analysis. Differentially expressed genes were further analyzed in AD brain. Two genes from the Wnt signaling pathway, TCF7L2 and MYC, had significantly increased mRNA levels in both transgenic mice and in AD brains, implicating cell differentiation and possibly neurogenesis in AD.

Cyclic-AMP dependent protein kinase A (PKA) regulates traffic of multiple proteins at different stages along the constitutive secretory pathway. PKA effects are regulated by protein phosphatases, which reverse the actions of PKA by dephosphorylation of PKA-substrates. Localization of specific PKA effects is mediated by the binding of A-kinase anchoring proteins (AKAPs). Apolipoprotein E (apoE) is an important regulator of lipid metabolism and atherosclerosis, and represents a large proportion of total protein constitutively secreted from macrophages. The signalling and trafficking pathways regulating secretion of apoE are unknown. Catalase is a peroxisomal enzyme which contributes to defence against hydrogen peroxide (H2O2). The primary hypothesis of this thesis is PKA and related protein phosphatase pathways are involved in the regulation of apoE secretion. The secondary hypothesis is that these pathways also regulate cellular clearance of H2O2. In Chapter Three, I have investigated the role of PKA in apoE secretion from primary human macrophages. Structurally distinct inhibitors of PKA (H89, KT5720, inhibitory peptide PKI14-22) all decreased basal secretion of apoE by between 50-80% whereas apoE mRNA or cellular protein are unaffected. Disruption of PKA-AKAP anchoring also significantly inhibited apoE secretion from human macrophages. Secretion of apoE was not immediately stimulated by PKA activity, suggesting that although PKA activity may be permissive for apoE secretion, it is in itself insufficient to stimulate apoE secretion above basal levels. Data from confocal microscopy and live cell imaging revealed PKA inhibition paralysed apoE vesicular movement from and to the plasma membrane. In Chapter Four, I investigated the effects of protein phosphatase 2B (PP2B) inhibition on apoE secretion by cyclosporin A (CsA). This was found to dose- and time-dependently inhibit secretion of apoE from primary human macrophages and increased cellular accumulation of apoE without affecting apoE mRNA levels. The role of PP2B in regulating apoE secretion was confirmed by using additional peptide and chemical inhibitors of PP2B. This effect was independent of the known inhibition of ABCA1 by CsA. Live cell imaging and confocal microscopy all demonstrated that inhibition of PP2B did not affect the apparent cellular distribution of apoE. Biochemical and microscopy studies indicated distinct mechanisms for PKA and PP2B regulation of apoE secretion. Chapter Five identified PKA-anchoring AKAPs in human macrophages, and investigated AKAP220 expression and its role in PKA-dependent processes relevant to atherosclerosis. AKAP220 protein was absent in human monocytes but was detectable after their differentiation into macrophages, with stable expression during late stages of maturation. It was also present in Chinese Hamster Ovary cells (CHO) cells. AKAP220 silencing had no effects on lipoprotein cholesteryl ester accumulation, total cellular apoE levels, apoE secretion or cholesterol efflux from human macrophages. Confocal microscopy in CHO cells revealed peroxisomal localisation of AKAP220. Catalase activity was confirmed to be PKA-regulated process, and AKAP220 was found to be a negative regulator of catalase activity, such that cell lysate catalase activity increased during AKAP220 silencing. AKAP220 silencing also decreased basal secretion of H2O2, detected using a sensitive and specific Amplex?? Red assay kit from intact CHO monolayers. In conclusion, this thesis has provided evidence that apoE secretion occurs via PKA- and PP2B-dependent pathways in human macrophages, and has identified the A-kinase anchoring protein AKAP220 as a regulator of cellular H2O2 clearance. These results will provide a basis for future investigations into the roles of PKA-related pathways in apoE secretion and catalase activity.

Background: Parkinson’s disease (PD) is a complex disease with a multi-factorial aetiology, comprising both genetic and environmental risk factors. The disease pathology is progressive and neurodegenerative where dopaminergic nerve cell death occurs predominantly in the substantia nigra pars compacta (SNpc) with the subsequent loss of the dopamine neurotransmitter in the basal ganglia. The most significant risk factors for PD include an advancing age and a family history of the disease, while environmental and lifestyle risk factors such as pesticide exposure and smoking are widely accepted as risk altering exposures. Currently up to 10% of PD is attributed to Mendelian inherited PD at one of 13 PARK loci in 9 genes. The pursuit of common susceptibility alleles for idiopathic PD has proven challenging with only a few loci reproducibility associated with an altered risk. The aim of this thesis is to study, using a candidate gene case-control design, the potential role of genetic variants in PD. The APOE candidate gene was hypothesized to modify the risk of PD as it is a proven modifier of Alzheimer’s disease (AD). The common pathological finding in PD of elevated levels of iron within the SNpc is proposed to increase the oxidative state of the nerve cells and predispose the dopaminergic neurons to apoptosis. Therefore, susceptibility alleles within the candidate genes that regulate iron metabolism and homeostasis are hypothesized to alter iron metabolism and predispose to iron-induced neurodegeneration in PD. Missense variants and common “tagging” SNPs with the HFE, Transferrin and Transferrin Receptor genes are investigated extensively in this thesis. Finally, autosomal recessively inherited PD can result from mutations in the parkin gene at the PARK2 locus. The final hypothesis explored in this thesis suggests that non-deleterious missense variants in the parkin gene modify the risk for developing sporadic PD. Further genetic variation in the parkin gene such as exon rearrangements is a frequently reported mutation where heterozygosity for these rearrangements may increase the risk of PD. Heterozygous deletions or duplications of exons in the parkin gene provide technical challenges for their detection. In this thesis a novel assay for the detection of these mutations is investigated. Methods: Genotyping was performed using PCR-RFLP for genetic variants in the APOE (E2 and E4 alleles), HFE (C282Y, H63D and S65C), Transferrin receptor (TfR; S142G), Transferrin (Tfn; P570S and G258S), IREB2 genes (L159V) and the parkin gene (S167N, R366W and V380L) in a cohort of 425 PD cases and 387 controls recruited from throughout Queensland, Australia. A tagged SNP high-throughput genotyping approach was then employed to try to replicate single SNP associations in 6 iron-related genes using a cohort of 1034 PD cases and 774 controls. These genetic variants were analysed for direct association with PD risk, age of onset effects as well as potential gene x gene (GxG) and gene x environment (GxE) interactions. Additionally, a quantitative PCR assay was developed to detect heterozygous deletions and duplications within the parkin gene and utilised to screen 43 YOPD cases for these mutations. Results: The initial study of the HFE C282Y variant revealed a significant protective association with PD in the two independent cohorts studied. Further study did not reveal significant associations with PD for the other HFE variants or missense variants within the Tfn and TfR genes. When analysed for GxE interactions, the C282Y, P589S and G277S variants showed evidence for an increased risk of PD in synergy with pesticide and herbicide exposure. Carriers of the risk variant and with toxin exposure were at two-fold increased risk of PD, although the number of individuals in this category was small. A further investigation of the role of common genetic polymorphisms in iron genes revealed only one of the 20 SNPs genotyped using high-throughput multiplex methods, remained significantly associated with PD after correction for age and sex. The rs198855 SNP is downstream of the HFE gene and further implicates a role for HFE in PD. The APOE E4 allele demonstrated modifying effects for the age of PD onset, restricted to the female cases. Analysis of the parkin missense variants also demonstrated a modifying effect on the age of PD onset in carriers of the S167N variant, with putative interactions between the APOE E4 allele, a family history of PD and toxin exposure that further reduced the age of onset. Twenty individuals of the 43 YOPD cases screened demonstrated heterozygous parkin exon rearrangements using the novel qPCR method. Conclusions: Non-synonymous variants within iron-related genes or the parkin gene putatively interact with herbicide and pesticide exposure to increase the risk of PD or modify the phenotype, highlighting the need for future studies to address the multi-factorial aetiology of PD in their study design and analysis. This thesis provides evidence for the association between genetic variation within the HFE locus and PD and for the APOE E4 allele as a modifier of PD.