Cardiovascular diseases are considered the first cause of death in westernized societies. They are directly linked to atherosclerosis, a clinical condition characterized by a thickening of the arterial wall. Atherosclerosis is in his turn linked to various genetic and environmental factors; among those factors are high oxidized LDL levels and endothelial dysfunction. In the present study, we have analyzed in vitro the effect of myeloperoxidase oxidized LDL on endothelial cells at the level of fibrinolysis and cell motility.<p>In the first part of the work, we measured fibrinolysis in real time at the surface of endothelial cells. Our results suggest that myeloperoxidase oxidized LDL interferes with the regulation of fibrinolysis by endothelial cells by decreasing their pro-fibrinolytic activity. This effect was not related to a modification in expression of major regulators of fibrinolysis such as PAI-1 and t-PA. Our data link the current favorite hypothesis that oxidized LDL has a causal role in atheroma plaque formation with an old suggestion that fibrin may also play a causal role. A model that best explains our results would be as follows: oxidized LDL increases fibrin deposition on endothelial cells which will increase their permeability resulting in more oxidized LDL infiltration into the subendothelial space of the arterial wall initiating atherogenesis. <p>In the second part of the work, we investigated the effect of myeloperoxidase oxidized LDL at the level of endothelial cell motility. We have shown that oxidized LDL is able to decrease cell migration, wound healing and tubulogenesis in endothelial cells. Those effects were not associated with any alteration at the level of neither cell viability nor proliferation. Subsequent gene expression analyses enabled us to link the oxidized LDL induced phenotypical changes in the cells to a change in expression of both microRNA-22 and Heme Oxygenase 1 genes. Our observations suggest a novel role of oxidized LDL not only as an important factor in the initiation of atheromatous lesions, but also as a potential player in the progression of the atherosclerosis disease by impeding blood vessel repair and wound healing at the sites of lesions.<p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Diversas doenças estão associadas com a formação de novos vasos a parti vasos pré-existentes, ou angiogênese. Dentre elas está a aterosclerose (Griffioen & Molema, 2000). Pesquisas recentes demonstram que a hipercolesterolemia, que têm um papel importante na fisiologia da aterosclerose, também pode prejudicar a ação de fatores angiogênicos (Jang et.al., 2000). A hipercolesterolemia que é decorrente de aumento de LDL no plasma ocasiona um aumento no tempo de permanência desta partícula na circulação (Yasunobu, 2001). Contudo, a LDL pode sofrer modificação na circulação, dando origem a uma subfração mais eletronegativa da LDL, a LDL (-). A LDL (-) pode prejudicar cada etapa da angiogênese, desregulando a função endotelial (Tai et. al., 2006). Em nosso estudo, vimos que apesar da LDL (-) ter estimulado a miga celular, esta partícula inibiu a formação de túbulos in vitro. A LDL (-) não foi capa afetar a angiogênese in vivo. / A large number of diseases is associated with formation of new blood vessels out of pre-existing capillaries, or angiogenesis. These diseases include the atherosclerosis (Griffioen & Molema, 2000). Resents researches demonstrate that the hypercholesterolemia, that have a important role in the physiology of the atherosclerosis, can impaired the angiogenesis (Jang et. al., 2000) . The hypercholesterolemia that is decurrente of high levels of LDL in the plasma causes an increase in the time of permanence this particle in the circulation (Yasunobu, 2001). However, the LDL can to suffer modification in the circulation, giving rise to a subfration more eletronegative from LDL, the LDL (-). The LDL (-) could impair each one of the steps of the angiogenesis, thereby dysregulating endothelial function (Tai et. al., 2006). In our study, see that despite the LDL (-) have stimulated the cell migration, this particle inhibited the Tube formation in vitro. The LDL (-) didn\'t affect the angiogenesis in vivo.

Abstract Coronary heart disease (CHD) is a clinical manifestation of atherosclerosis. It is a major cause of mortality and morbidity both in Finland and globally. Even after the best known treatments a significant residual risk of CHD remains. A low plasma HDL cholesterol level (HDL, high-density lipoprotein) is a common lipid abnormality in patients affected by premature CHD and also a component of the metabolic syndrome, a cluster of risk factors for atherosclerosis associated with central obesity. In this study, a phenotype of low HDL cholesterol level and premature CHD was investigated in two Northern Finnish family populations. The aim was to find new biological factors accounting for the elevated CHD risk in the phenotype. In the subjects of family population I, plasma levels of antibodies (IgG, IgM, IgA) against experimental epitopes (malondialdehyde-acetaldehyde-modified, copper-oxidized) of oxidized LDL (low-density lipoprotein) particles were measured. In the subjects of family population II, capacity of HDL fractions (total HDL, HDL2 and HDL3) to accept cholesterol from a THP-1 experimental foam cell model was assayed (cholesterol efflux). In addition, a phospholipid composition of their HDL fractions (HDL2 and HDL3) was measured using liquid chromatography-mass spectrometry. The antibody levels were not related to CHD or to HDL cholesterol level. Instead, the cholesterol efflux to HDL2 fraction was clearly impaired in CHD, which was associated with the low HDL cholesterol level of the patients. The impaired cholesterol efflux to HDL2 fraction was primarily in conjunction with the metabolic syndrome. The phospholipid composition of HDL fractions was different between the affected and the non-affected subjects. As an example, characteristic of the metabolic syndrome were elevated contents of palmitic, palmitoleic or oleic acids relative to linoleic acid in lysophosphatidylcholines and phosphatidylcholines. In conclusion, the HDL fraction is both functionally and compositionally modified in the phenotype of low HDL cholesterol level and premature CHD. Especially the cholesterol efflux capacity of the HDL2 fraction and thus its many functional properties may be impaired. There are many characteristic features in the phospholipid composition of the HDL in the phenotype which were detected in HDL2 and HDL3 fractions. / Tiivistelmä Sepelvaltimotauti on ateroskleroosin kliininen ilmenemismuoto. Se on merkittävimpiä kuolleisuuden ja sairastavuuden aiheuttajia niin Suomessa kuin maailmalla. Parhaillakin tunnetuilla hoidoilla sepelvaltimotaudille jää huomattava jäännösriski. Plasman matala HDL-kolesterolitaso (HDL, high-density lipoprotein) on yleinen lipidipoikkeavuus varhaista sepelvaltimotautia sairastavilla ja myös eräs metabolisen oireyhtymän, eli keskivartalolihavuuteen liittyvän ateroskleroosin riskitekijäkasauman, komponentti. Tässä väitöskirjassa tutkittiin matalan HDL-kolesterolitason ja varhaisen sepelvaltimotaudin fenotyyppiä kahdessa pohjoissuomalaisessa sukuaineistossa. Tavoitteena oli löytää uusia biologisia tekijöitä fenotyypin kohonneen sepelvatimotautiriskin taustalta. Ensimmäisen aineiston henkilöiden plasmasta mitattiin vasta-ainetasoja (IgG, IgM, IgA) LDL-hiukkasten (LDL, low-density lipoprotein) kokeellisia hapettuneita epitooppeja (malonidialdehydi-asetaldehydi-modioitu ja kuparilla hapetettu LDL) vastaan. Toisessa aineistossa mitattiin henkilöiden HDL-fraktioiden (kokonais-HDL, HDL2 ja HDL3) kykyä saada aikaan kolesterolin ulosvirtausta kokeellisesta THP-1 vaahtosolumallista. Lisäksi heidän HDL-fraktioidensa (HDL2, HDL3) fosfolipidikoostumus mitattiin nestekromatografi-massaspektrometri-laitteistolla. Vasta-ainetasot eivät liittyneet sepelvaltimotautiin tai HDL-kolesterolitasoon. Sen sijaan kolesterolin ulosvirtaus HDL2-fraktioon oli selkeästi alentunut sepelvaltimotaudissa, mikä liittyi potilaiden pieneen HDL-kolesterolipitoisuuteen. Alentunut ulosvirtaus HDL2-fraktioon liittyikin ensisijaisesti metaboliseen oireyhtymään. HDL-fraktioiden fosfolipidikoostumus erosi terveiden ja sairaiden välillä. Esimerkiksi metabolisessa oireryhtymässä tunnusomaista oli lysofosfatidyylikoliinien ja fosfatidyylikoliinien sisältämän palmitiinihapon, palmitoleiinihapon tai oleiinihapon suurentunut määrä suhteessa niiden sisältämän linoleenihapon määrään. Loppupäätelmä on, että matalan HDL-kolesterolitason ja varhaisen sepelvaltimotaudin fenotyypin HDL-fraktio on sekä toiminnaltaan että koostumukseltaan muuntunut. Erityisesti HDL2-fraktion kyky saada aikaan kolesterolin ulosvirtausta ja näin ollen sen monet toiminnalliset ominaisuudet voivat olla alentuneet. Fenotyypin HDL:n fosfolipidikoostumuksessa on monia tunnusomaisia piirteitä, joita havaittiin sekä HDL2- että HDL3-fraktiossa.

Diversas doenças estão associadas com a formação de novos vasos a parti vasos pré-existentes, ou angiogênese. Dentre elas está a aterosclerose (Griffioen & Molema, 2000). Pesquisas recentes demonstram que a hipercolesterolemia, que têm um papel importante na fisiologia da aterosclerose, também pode prejudicar a ação de fatores angiogênicos (Jang et.al., 2000). A hipercolesterolemia que é decorrente de aumento de LDL no plasma ocasiona um aumento no tempo de permanência desta partícula na circulação (Yasunobu, 2001). Contudo, a LDL pode sofrer modificação na circulação, dando origem a uma subfração mais eletronegativa da LDL, a LDL (-). A LDL (-) pode prejudicar cada etapa da angiogênese, desregulando a função endotelial (Tai et. al., 2006). Em nosso estudo, vimos que apesar da LDL (-) ter estimulado a miga celular, esta partícula inibiu a formação de túbulos in vitro. A LDL (-) não foi capa afetar a angiogênese in vivo. / A large number of diseases is associated with formation of new blood vessels out of pre-existing capillaries, or angiogenesis. These diseases include the atherosclerosis (Griffioen & Molema, 2000). Resents researches demonstrate that the hypercholesterolemia, that have a important role in the physiology of the atherosclerosis, can impaired the angiogenesis (Jang et. al., 2000) . The hypercholesterolemia that is decurrente of high levels of LDL in the plasma causes an increase in the time of permanence this particle in the circulation (Yasunobu, 2001). However, the LDL can to suffer modification in the circulation, giving rise to a subfration more eletronegative from LDL, the LDL (-). The LDL (-) could impair each one of the steps of the angiogenesis, thereby dysregulating endothelial function (Tai et. al., 2006). In our study, see that despite the LDL (-) have stimulated the cell migration, this particle inhibited the Tube formation in vitro. The LDL (-) didn\'t affect the angiogenesis in vivo.