RESUMEN
Lipids are a diverse and ubiquitous group of compounds, which have several biological functions such as structural components of cell membranes, energy storage, and participation in signaling pathways. Free radicals or reactive oxygen species could attack polyunsaturated fatty acid esterified to phospholipids generating oxidized products. Once oxidized, lipids are able to modify amino acids residues in proteins leading to modulation signaling pathways and cellular redox balance. Furthermore, alteration of lipid homeostasis is also linked to development and progression of neurodegenerative diseases. The purposes of this study were (i) to investigate the role of lipids in protein aggregation, (ii) to investigate the plasma lipidome of an ALS rat model (SOD1G93A rats), and (iii) to investigate the effect of high-fat diet in plasma lipidome of an ALS rat model. In chapters 1 and 2, the interaction between cytochrome c (cytc) and cardiolipin hydroperoxide (CLOOH), as well as cholesterol hydroperoxide (ChOOH) promoted protein aggregation. Mass spectrometry analysis of tryptic peptides from CLOOH-containing reaction revealed K72 and H26 consistently modified by 4- hydroxynonenal (4-HNE). Further, adduction of K27, K73 and K88 were detected with 4- oxynonenal (4-ONE). For the first time, we characterized the dityrosine cross-linked peptides at Y48-Y74, Y48-97 and Y74-Y97 in oligomeric cytc. Similarly, ChOOH-containing reaction showed dityrosine cross-linked peptides at Y48-Y48, Y48-Y74 and Y48-Y97 in dimeric cytc. In accordance to previous studies, the proposed mechanism under covalent protein oligomerization mediated by lipid hydroperoxide could be related to modification of lysine and tyrosine residues. In chapter 3, we characterized the lipid composition of blood plasma in amyotrophic lateral sclerosis (ALS), since dysregulation of lipid metabolism is increasingly associated with neuropathology. Using untargeted lipidomics approach based on liquid chromatography coupled to mass spectrometry, we found main alterations in triglycerides, phospholipids and sphingolipids in symptomatic ALS rats relative to controls. Additionally, for the first time we reported acylceramides species in the plasma. In order to investigate the source of these lipid alterations, we analyzed the lipid content of fractioned lipoproteins. Triglycerides and phospholipids were found in very low-density lipoprotein (VLDL), while acylceramides and hexosylceramides were found enriched in high-density lipoprotein (HDL). In chapter 4, high-fat diet containing lard or high-fish oil as much as 60% of total lipids has both the largest change on plasma lipid composition. Overall survival was not statistically different when compared to control diet. Increased levels of acylceramides, hexosylceramides and acylcarnitines were observed in ALS rats fed a control diet or high-fat diet in comparison to WT controls. Importantly, untargeted lipidomic analysis of blood plasma highlighted acylceramide d18:1/24:1+20:4 as potential biomarkers of ALS progression. Thus, our lipidomic analysis provides a novel insight into the molecular level event driving molecular dysregulation in ALS. Additional research is needed to determine the effect of plasma lipid alteration on motor neuron process and energetic metabolism. Collectively, our findings reinforce the idea that lipids play a relevant role in modulating cellular processes linked to protein aggregation and neurodegeneration
Os lipídeos são moléculas que possuem várias funções biológicas importantes, atuando como componente de membranas celulares, servindo com fonte de reserva de energia e participando de vias de sinalização. Os ácidos graxos poli-insaturados esterificados aos fosfolipídeos, por exemplo, são potenciais alvos para o ataque de radicais livres gerando produtos oxidados que são capazes de modificar resíduos de aminoácidos em proteínas levando a modulação das vias de sinalização e balanço redox. Por outro lado, alteração na homeostase do metabolismo dos lipídeos está relacionada ao desenvolvimento e progressão de doenças neurodegenerativas. Tendo em vista a importância dos lipídeos nos processos biológicos, os objetivos desse estudo foram (i) investigar o papel dos lipídeos na agregação proteica (capítulo 1 e 2), (ii) investigar as alterações na composição lipídica do plasma de rato modelo SOD1G93A de esclerose lateral amiotrófica (ELA) (capítulo 3) e (iii) investigar o efeito da suplementação de dietas hiperlipídicas na composição lipídica do plasma de rato modelo SOD1G93A (capítulo 4). No capítulo 1 e 2, a interação do citocromo c (citc) com hidroperóxido de cardiolipina (CLOOH) e hidroperóxido de colesterol (ChOOH) promove a agregação covalente do citc. Análise por nLC-MS/MS dos peptídeos digeridos identificou resíduos de lisina (K72) e histidina (H26) modificado por 4-hidroxininenal (4-HNE), enquanto os resíduos K27, K73 e K88 foram modificados por 4-oxinonenal (4-ONE). Pela primeira vez, nós caracterizamos ditirosinas (Y48-Y74, Y48-97 e Y74-Y97) na reação do citc com CLOOH. Também foram caracterizadas ditirosinas envolvendo os resíduos Y48-Y48, Y48-Y74 e Y48-Y97 na reação com ChOOH. Esses resultados corroboram com estudos anteriores que sugerem um mecanismo de agregação proteica envolvendo a perda da carga positiva de lisina e formação de ditirosina pela combinação de radicais de tirosil. No capítulo 3, a análise da composição lipídica do plasma de ratos SOD1G93A utilizando LC-MS/MS revelou alterações significativas na composição de triglicérides, glicerofosfolipídeos e esfingolipídeos em ratos sintomáticos comparado com os assintomáticos. É importante destacar que pela primeira vez acilceramidas foram identificadas em plasma de rato modelo para ALS. Análise da composição lipídica de lipoproteínas isoladas, maior fonte de lipídeos circulantes no plasma, mostraram alterações de triglicérides e glicerofosfolipídeos em VLDL. As acilceramidas e as hexosilceramidas, por sua vez, foram encontradas em maior abundância em HDL. No capítulo 4, a suplementação com dietas hiperlipídicas (rica em banha de porco e óleo de peixe) alterou significativamente o perfil lipídico do plasma em relação a doença. Contudo, não foi observado aumento significativo na sobrevida dos ratos ALS comparado com dieta controle. Independente da dieta, a concentração plasmática de acilcarnitina, hexosilceramidas e acilceramidas foram significativamente aumentadas em ratos ALS comparado com WT. A análise do perfil lipídico do plasma mostrou que a acilceramida d18:1/24:1+20:4 pode ser um potencial marcador de progressão da ALS. Dessa forma, os resultados mostrados fornecem uma visão enriquecedora sobre o evento a nível molecular que conduz a desregulação lipídica na ELA. Coletivamente, nossos resultados reforçam a importância dos lipídeos na modulação dos processos celulares ligados a agregação de proteínas e na neurodegeneração
Asunto(s)
Animales , Masculino , Ratas , Esclerosis Amiotrófica Lateral/fisiopatología , Lípidos/análisis , Espectrometría de Masas/instrumentación , Dieta Alta en Grasa/efectos adversos , Agregación Patológica de Proteínas/clasificaciónRESUMEN
The oocyst wall of coccidian parasites is a robust structure that is resistant to a variety of environmental and chemical insults. This resilience allows oocysts to survive for long periods, facilitating transmission from host to host. The wall is bilayered and is formed by the sequential release of the contents of two specialized organelles - wall forming body 1 and wall forming body 2 - found in the macrogametocyte stage of Coccidia. The oocyst wall is over 90 percent protein but few of these proteins have been studied. One group is cysteine-rich and may be presumed to crosslink via disulphide bridges, though this is yet to be investigated. Another group of wall proteins is rich in tyrosine. These proteins, which range in size from 8-31 kDa, are derived from larger precursors of 56 and 82 kDa found in the wall forming bodies. Proteases may catalyze processing of the precursors into tyrosine-rich peptides, which are then oxidatively crosslinked in a reaction catalyzed by peroxidases. In support of this hypothesis, the oocyst wall has high levels of dityrosine bonds. These dityrosine crosslinked proteins may provide a structural matrix for assembly of the oocyst wall and contribute to its resilience.
Asunto(s)
Animales , Eimeria/citología , Oocistos/química , Eimeria/químicaRESUMEN
A comparative study of the collagen of the foot of Lamellidens Sp. and that of the unmodified part of the foot in Mytilus edulis shows marked differences in physical properties, amino acid composition and in the degree of stabilization. But both conform to type I collagen of vertebrates. In these respects, the latter shows agreement with the features characteristic of byssus collagen, which is highly crosslinked, involving dimers and trimers of tyrosine. It is suggested that such differences may reflect the different functions of the organs concerned, the foot of Lamellidens being a locomotary organ of the animal, while the foot of Mytilus edulis is modified for anchorage of the animal. The vertigial part though not morphologically modified shows the essential compositional characteristics of the byssus being a mere remanant of it.