Causes of death in patients with rheumatoid arthritis over a 40-year period : with special emphasis on autopsy

Rheumatoid arthritis (RA) patients have premature mortality. Contrary to the general population, mortality in RA has not declined over time. This study aimed to evaluate determinants of mortality in RA by examining causes of death (CoDs) over time, accuracy of CoD diagnoses, and contribution of RA medication to CoDs. This study further evaluated detection rate of reactive systemic amyloid A amyloidosis, which is an important contributor to RA mortality. CoDs were examined in 960 RA patients between 1971 and 1991 (Study population A) and in 369 RA patients autopsied from 1952 to 1991, with non-RA patients serving as the reference cases (Study population B). In Study population B, CoDs by the clinician before autopsy were compared to those by the pathologist at autopsy to study accuracy of CoD diagnoses. In Study population B, autopsy tissue samples were re-examined systematically for amyloidosis (90% of patients) and clinical data for RA patients was studied from 1973. RA patients died most frequently of cardiovascular diseases (CVDs), infections, and RA. RA deaths declined over time. Coronary deaths showed no major change in Study population A, but, in Study population B, coronary deaths in RA patients increased from 1952 to 1991, while non-RA cases had a decrease in coronary deaths starting in the 1970s. Between CoD diagnoses by the clinician and those by the pathologist, RA patients had lower agreement than non-RA cases regarding cardiovascular (Kappa reliability measure: 0.31 vs. 0.51) and coronary deaths (0.33 vs. 0.46). Use of disease modifying anti-rheumatic drugs was not associated with any CoD. In RA patients, re-examination of autopsy tissue samples doubled the prevalence of amyloid compared with the original autopsy: from 18% to 30%. In the amyloid-positive RA patients, amyloidosis was diagnosed before autopsy in only 37%; and they had higher inflammatory levels and longer duration of RA than amyloid-negative RA patients. Of the RA patients with amyloid, only half had renal failure or proteinuria during lifetime. In RA, most important determinants of mortality were CVDs, RA, and infections. In RA patients, RA deaths decreased over time, but this was not true for coronary deaths. Coronary death being less accurately diagnosed in RA may indicate that coronary heart disease (CHD) often goes unrecognized during lifetime. Thus, active search for CHD and its effective treatment is important to reduce cardiovascular mortality. Reactive amyloidosis may often go undetected. In RA patients with proteinuria or renal failure, as well as with active and long-lasting RA, a systematic search for amyloid is important to enable early diagnosis and early enhancement of therapy. This is essential to prevent clinical manifestations of amyloidosis such as renal failure, which has a poor prognosis.

Consenso em reumatologia pediátrica: parte I - definição dos critérios de doença inativa e remissão em artrite idiopática juvenil/artrite reumatóide juvenil

Não há critérios universalmente aceitos para a remissão clínica em artrite idiopática juvenil/artrite reumatóide juvenil (AIJ/ARJ). OBJETIVO: formar consenso sobre estes critérios. MÉTODOS: foi utilizado um inquérito pelo método Delphi para reunir os critérios vigentes e utilizados por especialistas em reumatologia pediátrica (RP) no mundo todo. A análise dos resultados constituiu a base para uma Consensus Conference utilizando a nominal group technique (NGT) para alcançar o consenso nas questões não resolvidas após a análise dos questionários deste inquérito. Cento e trinta RP de 34 países responderam ao inquérito e 20 RP de nove países elegeram os critérios durante dois dias, em processo de discussão estruturada, para formar consenso pela NGT. RESULTADOS: os critérios de doença inativa deveriam incluir: 1) nenhuma articulação com artrite em atividade; 2) ausência de febre, rash, serosite, esplenomegalia ou linfadenopatia generalizada atribuída à AIJ/ARJ; 3) ausência de uveíte em atividade; 4) VHS ou PCR negativas (se ambos forem testados, ambos devem ser normais); 5) a avaliação global pelo médico deve indicar o melhor escore possível, indicando doença inativa. CONCLUSÕES: de acordo com o voto de consenso, seis meses contínuos de doença inativa são necessários para se considerar um paciente em estado de remissão com medicação; 12 meses contínuos de doença inativa e sem medicação são necessários para considerar um paciente em estado de remissão sem medicação. O critério para remissão sem medicação deve prever com acurácia de 95% a probabilidade inferior a 20% de recaída em cinco anos.

Consenso em reumatologia pediátrica: parte II - definição de melhora clínica para o lúpus eritematoso sistêmico e dermatomiosite juvenil

OBJETIVO: avaliar as medidas de atividade e critérios de melhora clínica para o lúpus eritematoso sistêmico juvenil (LESJ) e dermatomiosite juvenil (DMJ), desenvolvidos por meio de consenso entre especialistas. MÉTODOS E RESULTADOS: para o LESJ, as medidas essenciais em cinco domínios e as respectivas variáveis foram: 1) avaliação global pelo médico por escala analógica visual de 0-10 cm; 2) avaliação da qualidade de vida relacionada à saúde (índice Físico - CHQ-PF50); 3) avaliação da atividade pelos pais/paciente por escala analógica visual de 0-10 cm; 4) avaliação renal (proteinúria 24 h); e 5) avaliação global da atividade por instrumento específico (SLEDAI ou ECLAM). A definição preliminar de melhora clínica para o JSLE foi: melhora > 50% em pelo menos 2 das 5 variáveis e não mais que uma com piora > 30%, a qual não pode ser a proteinúria de 24h em casos com envolvimento renal. Os seis domínios e as respectivas variáveis selecionadas para a atividade na DMJ foram: 1) avaliação global pelo médico por escala analógica visual de 0-10 cm; 2) avaliação da força muscular proximal por meio de teste específico - CMAS-Childhood Myositis Assessment Scale 0-52; 3) avaliação da capacidade funcional (CHAQ); 4) avaliação da atividade pelos pais/paciente por escala analógica visual de 0-10 cm; 5) avaliação da qualidade de vida relacionada à saúde (Índice Físico - CHQ-PF50); 6) avaliação global da atividade por meio de instrumento específico (DAS - Disease Activity Score). A definição preliminar de melhora clínica para a DMJ foi: pelo menos 3 de quaisquer das 6 variáveis com melhora > 20% e não mais que uma com piora > 30%, a qual não pode ser o CMAS. CONCLUSÕES: estas variáveis foram testadas em uma casuística representativa e mostraram propriedades estatísticas adequadas de responsividade e validade discriminativa, podendo ser estudadas em ensaios terapêuticos.

A reumatologia em um curso de medicina com aprendizagem baseada em problemas

OBJETIVO: Apresentar a experiência de uma instituição brasileira no ensino da Reumatologia na graduação médica, cujo projeto pedagógico é estruturado em metodologias ativas de aprendizado. MÉTODOS: Realizou-se um estudo descritivo, com abordagem qualitativa dos conteúdos referentes à Reumatologia no curso de Medicina do Centro Universitário do Estado do Pará (Cesupa). RESULTADOS: O sistema musculoesquelético é abordado no segundo e sétimo semestres, nos módulos referentes ao sistema locomotor e Clínica Médica II, respectivamente, sendo que cada etapa e cada atividade apresentam objetivos específicos mínimos. Além do conteúdo teórico, no sétimo semestre, os alunos realizam atendimentos no ambulatório de Reumatologia, quando existe maior ênfase na elaboração correta de anamnese e exame físico. No internato, os alunos retornam ao ambulatório de Reumatologia e, neste momento, as habilidades de diagnóstico, de investigação e de terapêutica são as mais exigidas. CONCLUSÃO: Ainda há muito para evoluir em busca de um modelo ideal para o ensino da Reumatologia, porém, cumprindo as principais recomendações disponíveis para a boa prática do ensino na graduação, podemos proporcionar ao futuro médico conhecimento, habilidade e experiências capazes de ajudá-lo na condução desses pacientes.

Consenso 2012 da Sociedade Brasileira de Reumatologia para o tratamento da artrite reumatoide

OBJETIVO: Elaborar recomendações para o tratamento da artrite reumatoide no Brasil. MÉTODO: Revisão da literatura com seleção de artigos baseados em evidência e opinião de especialistas da Comissão de Artrite Reumatoide da Sociedade Brasileira de Reumatologia. RESULTADOS E CONCLUSÕES: 1) A decisão terapêutica deve ser compartilhada com o paciente; 2) imediatamente após o diagnóstico, uma droga modificadora do curso da doença (DMCD) deve ser prescrita e o tratamento ajustado para atingir remissão; 3) o tratamento deverá ser conduzido por reumatologista; 4) o tratamento inicial inclui DMCD sintéticas; 5) o metotrexato é a droga de escolha; 6) pacientes que não alcançaram resposta após a utilização de dois esquemas de DMCD sintéticas devem ser avaliados para DMCD biológicas; 7) excepcionalmente, DMCD biológicas poderão ser consideradas mais precocemente; 8) recomenda-se preferencialmente o uso de agentes anti-TNF como terapia biológica inicial; 9) após falha terapêutica a uma primeira DMCD biológica, outros biológicos poderão ser utilizados; 10) ciclofosfamida e azatioprina podem ser consideradas em manifestações extra-articulares graves; 11) recomenda-se a utilização de corticoide oral em baixas doses e por curtos períodos; 12) os anti-inflamatórios não hormonais devem sempre ser prescritos em associação à DMCD; 13) avaliações clínicas devem ser mensais no início do tratamento; 14) terapia física, reabilitação e terapia ocupacional são indicadas; 15) deve-se recomendar tratamento cirúrgico para correção de sequelas; 16) métodos de terapia alternativa não substituem a terapia tradicional; 17) deve-se orientar planejamento familiar; 18) orienta-se a busca ativa e o manejo de comorbidades; 19) atualizar e documentar a vacinação do paciente; 20) doenças transmissíveis endêmico-epidêmicas devem ser investigadas e tratadas.

Consenso 2012 da Sociedade Brasileira de Reumatologia sobre o manejo de comorbidades em pacientes com artrite reumatoide

OBJETIVO: Elaborar recomendações da Comissão de Artrite Reumatoide da Sociedade Brasileira de Reumatologia (SBR) para o manuseio das comorbidades em artrite reumatoide (AR). MÉTODOS: Revisão da literatura e opinião de especialistas da Comissão de AR da SBR. RESULTADOS E CONCLUSÕES: Recomendações: 1) Diagnosticar e tratar precoce e adequadamente as comorbidades; 2) O tratamento específico da AR deve ser adaptado às comorbidades; 3) Inibidores da enzima conversora da angiotensina (IECA) ou bloqueadores dos receptores de angiotensina II (BRA) são preferidos no tratamento da hipertensão arterial sistêmica; 4) Em pacientes com AR e diabetes mellitus, deve-se evitar o uso contínuo de dose cumulativa alta de corticoides; 5) Sugere-se o uso de estatinas para manter níveis de LDL menor que 100 mg/dL e índice aterosclerótico menor que 3,5 em pacientes com AR e comorbidades; 6) A síndrome metabólica deve ser tratada; 7) Recomenda-se a realização de exames para a investigação de aterosclerose subclínica; 8) Maior vigilância para um diagnóstico precoce de neoplasia oculta; 9) Medidas de prevenção para trombose venosa são sugeridas; 10) Recomenda-se a realização de densitometria óssea em pacientes com AR acima de 50 anos, e naqueles com idade menor com corticoide maior que 7,5 mg por mais de três meses; 11) Pacientes com AR e osteoporose devem evitar quedas, e devem ser aconselhados a aumentarem a ingestão de cálcio, aumentarem a exposição solar e fazerem atividade física; 12) Suplementação de cálcio e vitamina D é sugerida.Autilização de bisfosfonatos é sugerida para pacientes com escore T menor que -2,5 na densidade mineral óssea; 13) Recomenda-se equipe multidisciplinar, com participação ativa do médico reumatologista no tratamento das comorbidades.

Sistema web based per la somministrazione di questionari online per la reumatologia

Viene presentato un sito web per definire e somministrare questionari clinici per la reumatologia. In particolare viene definito il questionario PRO-CLARA creato dal prof. Fausto Salaffi.

Artrites microcristalinas : experiência da consulta de osteoartrose e artrites microcristalinas do Serviço de Reumatologia do Centro Hospitalar Lisboa Norte, E.P.E.

Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2014

Efeito da ingestão de uma infusão de gengibre no fluxo salivar, grau de xerostomia e qualidade de vida em indivíduos com síndrome de Sjögren primário do Instituto Português de Reumatologia

Dissertação para obtenção do grau de Mestre no Instituto Superior de Ciências da Saúde Egas Moniz

Grammar and disciplinary culture : a corpus-based study

The present study provides a usage-based account of how three grammatical structures, declarative content clauses, interrogative content clause and as-predicative constructions, are used in academic research articles. These structures may be used in both knowledge claims and citations, and they often express evaluative meanings. Using the methodology of quantitative corpus linguistics, I investigate how the culture of the academic discipline influences the way in which these constructions are used in research articles. The study compares the rates of occurrence of these grammatical structures and investigates their co-occurrence patterns in articles representing four different disciplines (medicine, physics, law, and literary criticism). The analysis is based on a purpose-built 2-million-word corpus, which has been part-of-speech tagged. The analysis demonstrates that the use of these grammatical structures varies between disciplines, and further shows that the differences observed in the corpus data are linked with differences in the nature of knowledge and the patterns of enquiry. The constructions in focus tend to be more frequently used in the soft disciplines, law and literary criticism, where their co-occurrence patterns are also more varied. This reflects both the greater variety of topics discussed in these disciplines, and the higher frequency of references to statements made by other researchers. Knowledge-building in the soft fields normally requires a careful contextualisation of the arguments, giving rise to statements reporting earlier research employing the constructions in focus. In contrast, knowledgebuilding in the hard fields is typically a cumulative process, based on agreed-upon methods of analysis. This characteristic is reflected in the structure and contents of research reports, which offer fewer opportunities for using these constructions.

Eläinruumis - seuraeläin : Erittävä ruumis englantilaisessa lääketieteessä ja kohteliaisuuskulttuurissa 1700-1780

Tutkielmani tarkastelee käsityksiä ruumiista englantilaisessa kulttuurissa n. 1700-1780. Ruumiin historia on varsin uusi historiantutkimuksen ala ja sitä on leimannut feministinen tutkimusote, joka on keskittynyt diskurssiin naisen ruumiista ja seksuaalisuudesta. Itse kuitenkin lähestyn ruumista sen sivuutetun ulottuvuuden, ruumiineritteiden, kautta ja yhdistän käsitykset myös toiminnan tasolle. Tarkastelen erittävää ruumiista kulttuurihistoriallisesti sijoittamalla sen kahteen 1700-luvulla merkittävään kontekstiin: lääketieteeseen ja kohteliaisuuskulttuuriin. Tällä pyrin paitsi avaamaan ruumiiseen ja ruumiineritteisiin liittyvien käsitysten kirjoa myös osoittamaan näiden kahden kontekstin väliset vuorovaikutussuhteet. Lääketieteen ja kohteliaisuuskulttuurin puitteissa käsittelen erittävää ruumista mahdollisimman kokonaisvaltaisesti niin fysiologian, terveydenhoidon, hajujen, hy­gienian, aineellisen kulttuurin kuin sosiaalisten suhteiden kannalta, käyttäen lähteinäni mm. lääketieteellisiä tekstejä, kaunokirjallisuutta, matkakertomuksia, päiväkirjoja, kirjeitä, lehtiä ja muuta kohteliasta kirjallisuutta. Käsitykset erittävästä ruumiista osoittautuvat moninaisiksi, jopa ristiriitaisiksi. Toi­saalta lääketiede korostaa ruumiin avoimuutta ja eritteiden vapautta, toisaalta kohteliaisuus vaatii ruumiintoimintojen suhteen pidättyväisyyttä. Tämän moninai­suuden pohjalta kritisoin mm. Norbert Eliaksen sivilisaatioteoriaa ja osoitan näiden vastakkaisten käsitysten tilannesidonnaisuuden, joka mahdollistaa nii­den samanaikaisen olemassaolon. Kohteliaat herrasmiehet ja -naiset ovatkin kovin kiinnostuneita erittävistä ruumiistaan: ihmiset tarkkailevat eritteitään saadakseen tietoa ruumiin sisältä sekä toisten eritteitä karsiakseen kaiken eläimellisen ympäriltään ja kaunokirjallisuudessa ne ovat naurun ja huvituksen lähde. Vuorovai­kutus lääketieteellisen ja kohteliaan kulttuurin välillä osoittautuukin varsin tiiviiksi: kohteliaisuuden takana vaikuttavat periaatteet näkyvät myös lääketieteessä ja toisaalta lääketiede tunkeutuu mm. kohteliaaseen kieleen, hämärtäen näin kontekstien välistä rajaa.

Adenoviral Gene Therapy for Advanced Head and Neck Cancer

Advanced stage head and neck cancers (HNC) with distant metastasis, as well as prostate cancers (PC), are devastating diseases currently lacking efficient treatment options. One promising developmental approach in cancer treatment is the use of oncolytic adenoviruses, especially in combination therapy with conventional cancer therapies. The safety of the approach has been tested in many clinical trials. However, antitumor efficacy needs to be improved in order to establish oncolytic viruses as a viable treatment alternative. To be able to test in vivo the effects on anti-tumor efficiency of a multimodal combination therapy of oncolytic adenoviruses with the standard therapeutic combination of radiotherapy, chemotherapy and Cetuximab monoclonal antibody (mAb), a xenograft HNC tumor model was developed. This model mimics the typical clinical situation as it is initially sensitive to cetuximab, but resistance develops eventually. Surprisingly, but in agreement with recent findings for chemotherapy and radiotherapy, a higher proportion of cells positive for HNC cancer stem cell markers were found in the tumors refractory to cetuximab. In vitro as well as in vivo results found in this study support the multimodal combination therapy of oncolytic adenoviruses with chemotherapy, radiotherapy and monoclonal antibody therapy to achieve increased anti-tumor efficiency and even complete tumor eradication with lower treatment doses required. In this study, it was found that capsid modified oncolytic viruses have increased gene transfer to cancer cells as well as an increased antitumor effect. In order to elucidate the mechanism of how oncolytic viruses promote radiosensitization of tumor cells in vivo, replicative deficient viruses expressing several promising radiosensitizing viral proteins were tested. The results of this study indicated that oncolytic adenoviruses promote radiosensitization by delaying the repair of DNA double strand breaks in tumor cells. Based on the promising data of the first study, two tumor double-targeted oncolytic adenoviruses armed with the fusion suicide gene FCU1 or with a fully human mAb specific for human Cytotoxic T Lymphocyte-Associated Antigen 4 (CTLA-4) were produced. FCU1 encodes a bifunctional fusion protein that efficiently catalyzes the direct conversion of 5-FC, a relatively nontoxic antifungal agent, into the toxic metabolites 5-fluorouracil and 5-fluorouridine monophosphate, bypassing the natural resistance of certain human tumor cells to 5-fluorouracil. Anti-CTLA4 mAb promotes direct killing of tumor cells via apoptosis and most importantly immune system activation against the tumors. These armed oncolytic viruses present increased anti-tumor efficacy both in vitro and in vivo. Furthermore, by taking advantage of the unique tumor targeted gene transfer of oncolytic adenoviruses, functional high tumor titers but low systemic concentrations of the armed proteins were generated. In addition, supernatants of tumor cells infected with Ad5/3-24aCTLA4, which contain anti-CTLA4 mAb, were able to effectively immunomodulate peripheral blood mononuclear cells (PBMC) of cancer patients with advanced tumors. -- In conclusion, the results presented in this thesis suggest that genetically engineered oncolytic adenoviruses have great potential in the treatment of advanced and metastatic HNC and PC.

Zebrafish as a model of Parkinson's disease

Parkinson’s disease (PD) is the second most common neurodegenerative disease among the elderly. Its etiology is unknown and no disease-modifying drugs are available. Thus, more information concerning its pathogenesis is needed. Among other genes, mutated PTEN-induced kinase 1 (PINK1) has been linked to early-onset and sporadic PD, but its mode of action is poorly understood. Most animal models of PD are based on the use of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MPTP is metabolized to MPP+ by monoamine oxidase B (MAO B) and causes cell death of dopaminergic neurons in the substantia nigra in mammals. Zebrafish has been a widely used model organism in developmental biology, but is now emerging as a model for human diseases due to its ideal combination of properties. Zebrafish are inexpensive and easy to maintain, develop rapidly, breed in large quantities producing transparent embryos, and are readily manipulated by various methods, particularly genetic ones. In addition, zebrafish are vertebrate animals and results derived from zebrafish may be more applicable to mammals than results from invertebrate genetic models such as Drosophila melanogaster and Caenorhabditis elegans. However, the similarity cannot be taken for granted. The aim of this study was to establish and test a PD model using larval zebrafish. The developing monoaminergic neuronal systems of larval zebrafish were investigated. We identified and classified 17 catecholaminergic and 9 serotonergic neuron populations in the zebrafish brain. A 3-dimensional atlas was created to facilitate future research. Only one gene encoding MAO was found in the zebrafish genome. Zebrafish MAO showed MAO A-type substrate specificity, but non-A-non-B inhibitor specificity. Distribution of MAO in larval and adult zebrafish brains was both diffuse and distinctly cellular. Inhibition of MAO during larval development led to markedly elevated 5-hydroxytryptamine (serotonin, 5-HT) levels, which decreased the locomotion of the fish. MPTP exposure caused a transient loss of cells in specific aminergic cell populations and decreased locomotion. MPTP-induced changes could be rescued by the MAO B inhibitor deprenyl, suggesting a role for MAO in MPTP toxicity. MPP+ affected only one catecholaminergic cell population; thus, the action of MPP+ was more selective than that of MPTP. The zebrafish PINK1 gene was cloned in zebrafish, and morpholino oligonucleotides were used to suppress its expression in larval zebrafish. The functional domains and expression pattern of zebrafish PINK1 resembled those of other vertebrates, suggesting that zebrafish is a feasible model for studying PINK1. Translation inhibition resulted in cell loss of the same catecholaminergic cell populations as MPTP and MPP+. Inactivation of PINK1 sensitized larval zebrafish to subefficacious doses of MPTP, causing a decrease in locomotion and cell loss in one dopaminergic cell population. Zebrafish appears to be a feasible model for studying PD, since its aminergic systems, mode of action of MPTP, and functions of PINK1 resemble those of mammalians. However, the functions of zebrafish MAO differ from the two forms of MAO found in mammals. Future studies using zebrafish PD models should utilize the advantages specific to zebrafish, such as the ability to execute large-scale genetic or drug screens.

Experimental and computational studies on lipoprotein lipolysis at acidic pH

Atherosclerosis is a disease of the arteries; its characteristic features include chronic inflammation, extra- and intracellular lipid accumulation, extracellular matrix remodeling, and an increase in extracellular matrix volume. The underlying mechanisms in the pathogenesis of advanced atherosclerotic plaques, that involve local acidity of the extracellular fluid, are still incompletely understood. In this thesis project, my co-workers and I studied the different mechanisms by which local extracellular acidity could promote accumulation of the atherogenic apolipoprotein B-100 (apoB-100)-containing plasma lipoprotein particles in the inner layer of the arterial wall, the intima. We found that lipolysis of atherogenic apoB-100-containing plasma lipoprotein particles (LDL, IDL, and sVLDL) by the secretory phospholipase A2 group V (sPLA2-V) enzyme, was increased at acidic pH. Also, the binding of apoB-100-containing plasma lipoprotein particles to human aortic proteoglycans was dramatically enhanced at acidic pH. Additionally, lipolysis by sPLA2-V enzyme further increased this binding. Using proteoglycan-affinity chromatography, we found that sVLDL lipoprotein particles consist of populations, differing in their affinities toward proteoglycans. These populations also contained different amounts of apolipoprotein E (apoE) and apolipoprotein C-III (apoC-III); the amounts of apoC-III and apoE per particle were highest in the population with the lowest affinity toward proteoglycans. Since PLA2-modification of LDL particles has been shown to change their aggregation behavior, we also studied the effect of acidic pH on the monolayer structure covering lipoprotein particles after PLA2-induced hydrolysis. Using molecular dynamics simulations, we found that, in acidity, the monolayer is more tightly packed laterally; moreover, its spontaneous curvature is negative, suggesting that acidity may promote lipoprotein particles fusion. In addition to extracellular lipid accumulation, the apoB-100-containing plasma lipoprotein particles can be taken up by inflammatory cells, namely macrophages. Using radiolabeled lipoprotein particles and cell cultures, we showed that sPLA2-V-modification of LDL, IDL, and sVLDL lipoproteins particles, at neutral or acidic pH, increased their uptake by human monocyte-derived macrophages.

Cholesterol Disturbances in Inherited Neurodegenerative Diseases : Studies on Npc1, Ppt1 and Ctsd deficient mice

The central nervous system (CNS) is the most cholesterol-rich organ in the body. Cholesterol is essential to CNS functions such as synaptogenesis and formation of myelin. Significant differences exist in cholesterol metabolism between the CNS and the peripheral organs. However, the regulation of cholesterol metabolism in the CNS is poorly understood compared to our knowledge of the regulation of cholesterol homeostasis in organs reached by cholesterol-carrying lipoprotein particles in the circulation. Defects in CNS cholesterol homeostasis have been linked to a variety of neurodegenerative diseases, including common diseases with complex pathogenetic mechanisms such as Alzheimer s disease. In spite of intense effort, the mechanisms which link disturbed cholesterol homeostasis to these diseases remain elusive. We used three inherited recessive neurodegenerative disorders as models in the studies included in this thesis: Niemann-Pick type C (NPC), infantile neuronal ceroid lipofuscinosis and cathepsin D deficiency. Of these three, NPC has previously been linked to disturbed intracellular cholesterol metabolism. Elucidating the mechanisms with which disturbances of cholesterol homeostasis link to neurodegeneration in recessive inherited disorders with known genetic lesions should shed light on how cholesterol is handled in the healthy CNS and help to understand how these and more complex diseases develop. In the first study we analyzed the synthesis of sterols and the assembly and secretion of lipoprotein particles in Npc1 deficient primary astrocytes. We found that both wild type and Npc1 deficient astrocytes retain significant amounts of desmosterol and other cholesterol precursor sterols as membrane constituents. No difference was observed in the synthesis of sterols and the secretion of newly synthesized sterols between Npc1 wild type, heterozygote or knockout astrocytes. We found that the incorporation of newly synthesized sterols into secreted lipoprotein particles was not inhibited by Npc1 mutation, and the lipoprotein particles were similar to those excreted by wild type astrocytes in shape and size. The bulk of cholesterol was found to be secreted independently of secreted NPC2. These observations demonstrate the ability of Npc1 deficient astrocytes to handle de novo sterols, and highlight the unique sterol composition in the developing brain. Infantile neuronal ceroid lipofuscinosis is caused by the deficiency of a functional Ppt1 enzyme in the cells. In the second study, global gene expression studies of approximately 14000 mouse genes showed significant changes in the expression of 135 genes in Ppt1 deficient neurons compared to wild type. Several genes encoding for enzymes of the mevalonate pathway of cholesterol biosynthesis showed increased expression. As predicted by the expression data, sterol biosynthesis was found to be upregulated in the knockout neurons. These data link Ppt1 deficiency to disturbed cholesterol metabolism in CNS neurons. In the third study we investigated the effect of cathepsin D deficiency on the structure of myelin and lipid homeostasis in the brain. Our proteomics data, immunohistochemistry and western blotting data showed altered levels of the myelin protein components myelin basic protein, proteolipid protein and 2 , 3 -cyclic nucleotide 3 phosphodiesterase in the brains of cathepsin D deficient mice. Electron microscopy revealed altered myelin structure in cathepsin D deficient brains. Additionally, plasmalogen-derived alkenyl chains and 20- and 24-carbon saturated and monounsaturated fatty acids typical for glycosphingolipids were found to be significantly reduced, but polyunsaturated species were significantly increased in the knockout brains, pointing to a decrease in white matter. The levels of ApoE and ABCA1 proteins linked to cholesterol efflux in the CNS were found to be altered in the brains of cathepsin D deficient mice, along with an accumulation of cholesteryl esters and a decrease in triglycerols. Together these data demonstrate altered myelin architecture in cathepsin D deficient mice and link cathepsin D deficiency to aberrant cholesterol metabolism and trafficking. Basic research into rare monogenic diseases sheds light on the underlying biological processes which are perturbed in these conditions and contributes to our understanding of the physiological function of healthy cells. Eventually, understanding gained from the study of disease models may contribute towards establishing treatment for these disorders and further our understanding of the pathogenesis of other, more complex and common diseases.