DHA depletion in brain was associated with impairment on spatial learning and memory in rat. The Morris water maze test found that the n-3 deficient rats spent more time and swam a longer distance to find the hidden platform compared with the n-3 adequate group, indicating that n-3 Def rats had a poorer spatial learning ability and memory. The results suggest that learning and memory are partially related to the brain DHA status in rat. / Docosahexaenoic acid (DHA, 22-6n-3) and arachidonic acid (AA, 22:4n-6) are long-chain polyunsaturated fatty acids (LCPUFA), which are important for the structural development of mammalian central nervous system and are accumulated in large amounts in the developing brain, retina and sperm. Deficiency in DHA and AA syndromes can occur if these fatty acids and their precursors (linoleic and linolenic acid) are insufficient in diet. It had been reported that DHA deficiency in animal brain led to a poor performance in learning ability and other abnormal behavior in rodents. In addition, DHA and AA are the unique fatty acids in human milk. Many studies reported that children who were breast-fed got higher intelligent scores than those who were formula-fed. Thus, a large number of studies suggested that DHA and AA should be added into infant formula to mimic the composition of human milk. / In summary, DHA distribution, depletion and recovery were region-specific in rat brain. DHA deficiency could lead to impairment on spatial learning in rat. The underlying mechanism of learning deficit might not be attributed to changes in antioxidant enzymes in rat brain. Although impairment on spatial learning was observed in DHA-deficient rat, a meta-analysis of published data demonstrated that DHA and AA supplement in infant formula had no effect on cognitive development in children. / No significant relationship between DHA level and brain antioxidant enzyme activities was observed, including catalase (CAT), Cu-Zn superocide dismutase (Cu-Zn SOD), Mn superocide dismutase (Mn SOD) and glutathione peroxidase (GPx). These enzyme activities varied with regions of brain. A lower activity of CAT, Mn SOD and GPx in hippocampus and cortex would make them particularly susceptible to oxidation damage compared with other regions. The present results did not support the view that the spatial learning and memory impairment in DHA depletion was associated with antioxidant status in brain. / The meta-analysis indicated that breast-feeding was positively associated with a higher cognitive development than formula-feeding. However, no benefit was found for infants who received formula supplemented with DHA alone or DHA plus AA compared with those fed traditional formula based on available data. The results suggest that the beneficial effect of breast-feeding over formula-feeding can not be solely attributed to DHA and AA present in breast milk. / The objectives of present study were to (1) examine the distribution, depletion and recovery of DHA in rat brain; (2) investigate the effect DHA deficiency in rat brain on spatial learning behavior; (3) study the effect of DHA deficiency on antioxidant enzymes in rat brain; and (4) analyze whether DHA and AA supplementation has any beneficial effect on cognitive development and quantify their effect size in children by conducting a meta-analysis of the published data, and adult rats, the region with the highest DHA percentage was cortex, whereas in aged rats, both cortex and cerebellum were the regions with the highest DHA percentage. DHA concentration in rat brain increased with age. DHA was not proportionally depleted and recovered in different regions of rat brain when the rats were maintained on an n-3 fatty acid deficient diet for two generations. The present results demonstrated that the distribution of DHA and AA was region-specific. / Xiao Ying. / "August 2006." / Adviser: Zhen Yu Chen. / Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1566. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 140-156). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Tong, Kit Fong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 91-104). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.vi / Table of Contents --- p.vii / List of Figures --- p.x / List of Tables --- p.xii / List of Abbreviations --- p.xiii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Cancer --- p.2 / Chapter 1.1.1 --- Tumor development --- p.2 / Chapter 1.1.2 --- Cell cycle --- p.4 / Chapter 1.1.3 --- Apoptosis --- p.9 / Chapter 1.1.3.1 --- The extrinsic pathway --- p.14 / Chapter 1.1.3.2 --- The intrinsic pathway --- p.16 / Chapter 1.1.3.3 --- The Bcl-2 family proteins --- p.17 / Chapter 1.1.3.4 --- Execution of apoptosis --- p.20 / Chapter 1.1.4 --- Melanoma --- p.22 / Chapter 1.2 --- Polyunsaturated fatty acids (PUFAs) --- p.24 / Chapter 1.2.1 --- "Chemistry, classification, metabolic conversion and sources …" --- p.24 / Chapter 1.2.2 --- Epidemiology studies --- p.27 / Chapter 1.2.3 --- Docosahexaenoic acid (DHA) --- p.28 / Chapter 1.2.3.1 --- Sources --- p.28 / Chapter 1.2.3.2 --- DHA and cancer --- p.29 / Chapter 1.3 --- Objectives --- p.33 / Chapter Chapter 2 --- Materials and Methods --- p.34 / Chapter 2.1 --- In vitro studies of DHA on growth and survival of human cancer cells --- p.34 / Chapter 2.1.1 --- Cell cultures --- p.34 / Chapter 2.1.2 --- Studies of growth inhibition of DHA on human cancer cells --- p.35 / Chapter 2.1.2.1 --- MTT assay --- p.35 / Chapter 2.1.2.2 --- Chemiluminescent-bromodeoxyuridine (Chemi-BrdU) immunoassay --- p.36 / Chapter 2.1.3 --- Studies of growth inhibitory mechanism of DHA on A375 cells. --- p.38 / Chapter 2.1.3.1 --- DNA -flow cytometry analysis --- p.38 / Chapter 2.1.3.2 --- Western blot analysis --- p.39 / Chapter 2.1.3.3 --- Caspase inhibitor studies --- p.42 / Chapter 2.1.3.4 --- Mitochondrial membrane potential analysis --- p.42 / Chapter 2.2 --- In vivo study of the anticancer effect of DHA on A375 cells --- p.44 / Chapter 2.2.1 --- Animals --- p.44 / Chapter 2.2.2 --- Cell inoculation and treatments --- p.44 / Chapter 2.2.3 --- Western blot analysis --- p.45 / Chapter 2.3 --- Statistical analysis --- p.46 / Chapter Chapter 3 --- Results --- p.47 / Chapter 3.1 --- In vitro studies of DHA on growth and survival of human canccr cells --- p.47 / Chapter 3.1.1 --- DHA reduced proliferation and survival of human cancer cells --- p.47 / Chapter 3.1.2 --- DHA modulated cell cycle of A375 cells --- p.52 / Chapter 3.1.3 --- DHA induced apoptosis in A375 cells --- p.55 / Chapter 3.1.4 --- Caspase activations were involved in the DHA-induced apoptosis in A375 cells --- p.59 / Chapter 3.1.5 --- "Caspase 3´ة 6, 8 and 9 were activated in DHA-induced apoptosis of A375 cells" --- p.62 / Chapter 3.1.6 --- DHA dissipated mitochondrial membrane potential in A375 cells --- p.66 / Chapter 3.1.7 --- DHA triggered the mitochondrial pathway of apoptosis --- p.68 / Chapter 3.1.8 --- DHA triggered the death receptor pathway of apoptosis --- p.71 / Chapter 3.2 --- In vivo study of the anticancer effect of DHA on A375 cells --- p.74 / Chapter 3.2.1 --- Effect of DHA on the growth ofA375 xenograft in athymic Bαlb/c mice --- p.74 / Chapter 3.2.2 --- DR4 and TRAIL were upregulated by DHA treatment in A375 solid tumor --- p.77 / Chapter Chapter 4 --- Discussion --- p.79 / References --- p.91

<p>Alzheimer’s disease (AD) is a progressive neurodegenerative disorder, neuropathologically characterized by neurofibrillay tangles and deposition of amyloid-β (Aβ) peptides. Several mutations in the gene for amyloid precursor protein (APP) cause familial AD and affect APP processing leading to increased levels of Aβ42. However, the Arctic Alzheimer mutation (APP E693G) reduces Aβ levels. Instead, the increased tendency of Arctic Aβ peptides to form Aβ protofibrils is thought to contribute to the pathogenesis. </p><p>In this thesis, the pathogenic mechanisms of the Arctic mutation were further investigated, specifically addressing if and how the mutation affects APP processing. Evidence of a shift towards β-secretase cleavage of Arctic APP was demonstrated. Arctic APP did not appear to be an inferior substrate for α-secretase, but the availability of Arctic APP for α-secretase cleavage was reduced, with diminished levels of cell surface APP in Arctic cells. Interestingly, administration of the fatty acid docosahexaenoic acid (DHA) stimulated α-secretase cleavage and partly reversed the effects of the Arctic mutation on APP processing.</p><p>In contrast to previous findings, the Arctic mutation generated enhanced total Aβ levels suggesting increased Aβ production. Importantly, this thesis illustrates and explains why measures of both Arctic and wild type Aβ levels are highly dependent upon the Aβ assay used, with enzyme-linked immunosorbent assay (ELISA) and Western blot generating different results. It was shown that these differences were due to inefficient detection of Aβ oligomers by ELISA leading to an underestimation of total Aβ levels. </p><p>In conclusion, the Arctic APP mutation leads to AD by multiple mechanisms. It facilitates protofibril formation, but it also alters trafficking and processing of APP which leads to increased steady state levels of total Aβ, in particular at intracellular locations. Importantly, these studies highlight mechanisms, other than enhanced production of Aβ peptide monomers, which could be implicated in sporadic AD.</p>

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder, neuropathologically characterized by neurofibrillay tangles and deposition of amyloid-β (Aβ) peptides. Several mutations in the gene for amyloid precursor protein (APP) cause familial AD and affect APP processing leading to increased levels of Aβ42. However, the Arctic Alzheimer mutation (APP E693G) reduces Aβ levels. Instead, the increased tendency of Arctic Aβ peptides to form Aβ protofibrils is thought to contribute to the pathogenesis. In this thesis, the pathogenic mechanisms of the Arctic mutation were further investigated, specifically addressing if and how the mutation affects APP processing. Evidence of a shift towards β-secretase cleavage of Arctic APP was demonstrated. Arctic APP did not appear to be an inferior substrate for α-secretase, but the availability of Arctic APP for α-secretase cleavage was reduced, with diminished levels of cell surface APP in Arctic cells. Interestingly, administration of the fatty acid docosahexaenoic acid (DHA) stimulated α-secretase cleavage and partly reversed the effects of the Arctic mutation on APP processing. In contrast to previous findings, the Arctic mutation generated enhanced total Aβ levels suggesting increased Aβ production. Importantly, this thesis illustrates and explains why measures of both Arctic and wild type Aβ levels are highly dependent upon the Aβ assay used, with enzyme-linked immunosorbent assay (ELISA) and Western blot generating different results. It was shown that these differences were due to inefficient detection of Aβ oligomers by ELISA leading to an underestimation of total Aβ levels. In conclusion, the Arctic APP mutation leads to AD by multiple mechanisms. It facilitates protofibril formation, but it also alters trafficking and processing of APP which leads to increased steady state levels of total Aβ, in particular at intracellular locations. Importantly, these studies highlight mechanisms, other than enhanced production of Aβ peptide monomers, which could be implicated in sporadic AD.

The epidermal growth factor receptor (EGFR) is a transmembrane receptor tyrosine kinase integral in regulating cell growth, survival, and migration. EGFR signaling, which is dependent on localization of the receptor within lipid rafts, is often hijacked during colon tumorigenesis. Previous work has found that docosahexaenoic acid (DHA) is protective against colon cancer. This fatty acid is proposed to function in part by perturbing lipid rafts and thereby altering cell signaling. The overall objective of this work was to determine whether DHA alters EGFR function and signaling. We assessed EGFR localization and ligand-induced phosphorylation in YAMC cells treated with fatty acids. We found that DHA reduced the localization of EGFR to lipid rafts. Concomitant with altering receptor localization, DHA was found to increase EGFR phosphorylation. However, DHA paradoxically suppressed EGFR signal transduction. We found that DHA uniquely altered EGFR activity, and other long chain polyunsaturated fatty acid did not exert the same effect. We additionally observed similar effects on EGFR activation and signaling by feeding mice a diet enriched in fish oil (high in DHA), and this was attendant with reduced colon tumorigenesis. We next probed the mechanism by which DHA enhances EGFR phosphorylation. We found that DHA facilitates receptor dimerization to increase phosphorylation. We additionally identified Ras activation as the site of perturbation of signal transduction. DHA suppressed signal transduction by both changing the localization of EGFR within the plasma membrane and increasing receptor endocytosis and degradation. Lastly, we extended our observations into a wounding model. Although DHA uniquely altered ligand-stimulated EGFR activity, both DHA and EPA altered EGFR transactivation and signaling upon injury. This culminated in reduced wound healing in DHA and EPA treated cells. In an animal model, we found that diets enriched in either DHA or EPA altered EGFR signaling in the colonocytes of wounded animals. Overall, we found that DHA modifies EGFR signaling, which can be beneficial or detrimental for health depending on the disease state of an individual. These data help elucidate a mechanism by which DHA protects against colon cancer, as well as indicating a potential downside of n-3 PUFA therapy.

Omega-3 fatty acids, particularly docosahexaenoic (DHA) and eicospentaenoic acid (EPA), are important mediators for cardiovascular disease, fetal/infant development, neurological disorders and inflammatory diseases. Supplementation and washout studies are important for future research on the physiological effects of omega-3 fatty acids and for determination of the proper washout period for future cross-over studies. In this study, omega-3 fatty acid blood biomarker comparisons are made for the n-3 HUFA score (% of n-3 HUFAs in total HUFAs) and omega-3 index (sum of EPA + DHA) in plasma, erythrocytes, whole blood and a novel finger-tip prick blood method (FTPB) of analysis. This FTPB method of fatty acid analysis is further tested to determine the potential for its use in fatty acid analysis. In addition, gender differences in response to omega-3 fish oil supplementation are analyzed in all four blood fractions. Nine males and seven females were supplemented with 8 fish-oil capsules per day (providing 3.2 g/day EPA and 1.6 g/day DHA) for four weeks, followed by an eight-week omega-3 washout period. Venous plasma, erythrocyte and whole blood samples were collected during weeks 0, 4, 8 and 12 and FTPB samples were collected weekly during supplementation and washout fatty acid analysis was performed. EPA and DHA incorporation is lowest in magnitude in erythrocytes relative to all other blood fractions. Omega-3 blood biomarker comparisons demonstrate that the n-3 HUFA score is a more reliable measure across all blood fractions compared to the omega-3 index. In addition, the n-3 HUFA score demonstrates no differences (p > 0.05) between FTPB and whole blood analysis, providing evidence to support its usefulness as a tool for fatty acid analysis. However, differences (p < 0.05) do exist between these methods for saturated fatty acid, monounsaturated fatty acids, omega-6 polyunsaturated fatty acids (PUFAs) and omega-3 PUFAs. Baseline fatty acid levels for DHA, and the DHA:EPA and DHA:DPA ratios tend to be higher (p < 0.05) in females, and docosapentaenoic acid n-3 (DPAn-3) is higher (p > 0.05) in males across all blood fractions. Furthermore, a gender effect (p < 0.05) is seen for the DHA:EPA ratio across all blood fractions. At baseline, female DHA:EPA is higher (p < 0.05) than males with supplementation lowering both male and female values and removing any differences (p > 0.05) between genders. Washout results in a return of levels towards baseline, however, baseline levels are not fully reached. Furthermore, while gender differences do begin to reform during washout, these differences are not significant (p > 0.05). In conclusion, omega-3 fatty acid responses, particularly DHA:EPA ratio, demonstrate significant gender differences that may be related to differences in long-chain PUFA synthesis pathways between males and females. In addition, the n-3 HUFA score may be a more valuable omega-3 blood biomarker than the omega-3 index, as the n-3 HUFA score displays more consistent levels across all blood fractions. Finally, the FTPB method of analysis may be a useful tool in the measurement of fatty acid composition, however, some microwave methylation problems do exist, specifically in the phospholipid class of lipids.

Omega-3 fatty acids, particularly docosahexaenoic (DHA) and eicospentaenoic acid (EPA), are important mediators for cardiovascular disease, fetal/infant development, neurological disorders and inflammatory diseases. Supplementation and washout studies are important for future research on the physiological effects of omega-3 fatty acids and for determination of the proper washout period for future cross-over studies. In this study, omega-3 fatty acid blood biomarker comparisons are made for the n-3 HUFA score (% of n-3 HUFAs in total HUFAs) and omega-3 index (sum of EPA + DHA) in plasma, erythrocytes, whole blood and a novel finger-tip prick blood method (FTPB) of analysis. This FTPB method of fatty acid analysis is further tested to determine the potential for its use in fatty acid analysis. In addition, gender differences in response to omega-3 fish oil supplementation are analyzed in all four blood fractions. Nine males and seven females were supplemented with 8 fish-oil capsules per day (providing 3.2 g/day EPA and 1.6 g/day DHA) for four weeks, followed by an eight-week omega-3 washout period. Venous plasma, erythrocyte and whole blood samples were collected during weeks 0, 4, 8 and 12 and FTPB samples were collected weekly during supplementation and washout fatty acid analysis was performed. EPA and DHA incorporation is lowest in magnitude in erythrocytes relative to all other blood fractions. Omega-3 blood biomarker comparisons demonstrate that the n-3 HUFA score is a more reliable measure across all blood fractions compared to the omega-3 index. In addition, the n-3 HUFA score demonstrates no differences (p > 0.05) between FTPB and whole blood analysis, providing evidence to support its usefulness as a tool for fatty acid analysis. However, differences (p < 0.05) do exist between these methods for saturated fatty acid, monounsaturated fatty acids, omega-6 polyunsaturated fatty acids (PUFAs) and omega-3 PUFAs. Baseline fatty acid levels for DHA, and the DHA:EPA and DHA:DPA ratios tend to be higher (p < 0.05) in females, and docosapentaenoic acid n-3 (DPAn-3) is higher (p > 0.05) in males across all blood fractions. Furthermore, a gender effect (p < 0.05) is seen for the DHA:EPA ratio across all blood fractions. At baseline, female DHA:EPA is higher (p < 0.05) than males with supplementation lowering both male and female values and removing any differences (p > 0.05) between genders. Washout results in a return of levels towards baseline, however, baseline levels are not fully reached. Furthermore, while gender differences do begin to reform during washout, these differences are not significant (p > 0.05). In conclusion, omega-3 fatty acid responses, particularly DHA:EPA ratio, demonstrate significant gender differences that may be related to differences in long-chain PUFA synthesis pathways between males and females. In addition, the n-3 HUFA score may be a more valuable omega-3 blood biomarker than the omega-3 index, as the n-3 HUFA score displays more consistent levels across all blood fractions. Finally, the FTPB method of analysis may be a useful tool in the measurement of fatty acid composition, however, some microwave methylation problems do exist, specifically in the phospholipid class of lipids.

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Submitted by (lucia.rodrigues@ufrpe.br) on 2016-05-23T14:49:01Z No. of bitstreams: 1 Bruno Oliveira Ferreira de Souza.pdf: 1374739 bytes, checksum: 210e4bdc1715b5995117487fc1929cf5 (MD5) / Made available in DSpace on 2016-05-23T14:49:01Z (GMT). No. of bitstreams: 1 Bruno Oliveira Ferreira de Souza.pdf: 1374739 bytes, checksum: 210e4bdc1715b5995117487fc1929cf5 (MD5) Previous issue date: 2011-05-23 / Retinal degenerations are the major causes of blindness in the world, and the Age-Related Macular Degeneration (AMD) is the most important. The AMD is a slow and progressive disease with multi-factorial causes. The oxidative stress caused by light exposure is the major risk factor for this disease. Although there is no cure, dietary supplementation with ω-3 long chain polyunsaturated fatty acids (ω-3 LCPUFAs) is indicated for reduction of disease progression. The purpose of our study is evaluate the effects of dietary supplementation with ω-3 LCPUFAs in albino mice (SWISS) subjected to medium intensity light exposure. The animals were fed with a diet enriched with ω-3 LCPUFAs and exposed to white light (3000LUX) for 12 hours, and then evaluated at periods of 0, 7, 14, 21, 30, 60 and 90 days after exposure. Mice fed with a commercial diet served as controls. The retinal morphology, outer nuclear layer thickness, Retinal Pigmented Epithelium (EPR) cell number, presence and activation of microglial cells, PEDF immunolocalization, presence of apoptotic cells and retina neovascularization. Our results indicated that immediately after light exposure, supplemented animals had attenuated lesions compared to the control group. However, in subsequent periods, supplemented groups showed lesions similar or even more pronounced as the control group. These results suggest that ω-3 LCPUFAs have a dual effect on the retina, exerting an initial neuroprotection, and then exhibiting a deleterious effect to the retina. / As degenerações retinianas são a maior causa de cegueira no mundo, sendo a Degeneração Macular Associada à Idade (DMAI) a mais importante. A DMAI é uma doença de caráter lento, progressivo e de causas multifatoriais. O estresse oxidativo causado pela exposição à luz é o principal fator de risco para esta enfermidade. Embora não haja cura, a suplementação dietética com ácidos graxos polinsaturados de cadeia longa ω-3 (ω-3 LCPUFAs) é indicada para a redução da progressão da doença. O presente estudo tem como objetivo avaliar os efeitos da suplementação dietética com ω-3 LCPUFAs em camundongos albinos (SWISS) submetidos à exposição à luz de média intensidade. Os animais foram suplementados com dieta rica em ω-3 LCPUFAs e expostos à luz branca (3000LUX) por 12 horas, e em seguida avaliados nos períodos de 0, 7, 14, 21, 30, 60 e 90 dias após a exposição. Camundongos alimentados com ração comercial serviram como controle. Os grupos foram avaliados quanto a morfologia da retina, espessura da camada nuclear externa, número de células do Epitélio Pigmentar da Retina (EPR), presença e ativação de micróglias, imunolocalização de PEDF, presença de células em apoptose e neovascularizações. Nossos resultados indicaram que imediatamente após a exposição à luz, os animais suplementados tiveram alterações atenuadas em relação ao grupo controle. Entretanto, nos períodos seguintes, os grupos suplementados apresentaram lesões equivalentes ou até mesmo mais acentuadas em relação ao grupo controle. Estes resultados sugerem que os ω-3 LCPUFAs possuem um efeito dual sobre a retina, exercendo uma neuroproteção inicial e, e em seguida, atuando de maneira nociva.

A Esclerose Lateral Amiotrófica (ELA) é uma doença progressiva e fatal causada pela degeneração seletiva dos neurônios motores do cérebro e medula. Dos casos familiares de ELA (fELA), 20% são causados por mutações pontuais no gene da sod1. O ácido docosahexaenoico (C22:6, n-3, DHA) é um ácido graxo altamente insaturado, sendo um dos principais ácidos graxos da massa cinzenta do cérebro. Estudos têm correlacionado mutações de SOD1 com a formação de agregados que poderiam ser induzidos por ácidos graxos insaturados. O objetivo deste estudo foi avaliar os efeitos e mecanismos do DHA e de seus hidroperóxidos (DHAOOH) na agregação de SOD1 in vitro. As análises de dicroísmo circular (CD) mostraram mudanças na estrutura secundária de ambas as proteínas apo-SOD1WT e G93A promovidas pelo DHA, resultando em aumento de superfície hidrofóbica e formação de estruturas do tipo beta-amilóide, como mostrado pelos ensaios do bis- ANS e Tioflavina, respectivamente. Estas mudanças resultam na formação de agregados amorfos como observado por microscopia eletrônica de varredura (MEV). Espécies de alto peso molecular foram observadas nas incubações do DHA com as formas apo da SOD1 por SDS-PAGE sob condições não redutoras e também por cromatografia de exclusão por tamanho. A formação dos agregados mostrou-se dependente de resíduos de Cys na sua forma desprotonada, visto que agregados não foram observados na presença de beta-mercaptoetanol e sua formação foi inibida na presença de bloqueador de tióis e em pH ácido. Além disso, análises por cromatografia de exclusão mostraram que a agregação é dependente da insaturação e conformação cis dos ácidos graxos. Comparativamente ao DHA, os hidroperóxidos do DHA tiveram um efeito menor na agregação de SOD1, porém revelaram a propriedade de induzir a dimerização covalente de SOD1. No geral, os dados mostram que o DHA induz a agregação de SOD1, através de um processo envolvendo a exposição de superfícies hidrofóbicas, formação de pontes dissulfeto e também de possíveis cross-links envolvendo reações do tipo \"ene-tiol\". / ALS is a progressive and fatal disease caused by selective degeneration of motor neurons in the brain and spinal cord. Twenty percent of familial ALS (fALS) cases are caused mainly by point mutations in the sod1 gene. Docosahexaenoic acid (C22:6, n-3, DHA) is a highly unsaturated fatty acid, wich is one of the main fatty acids in the cerebral gray matter. Studies have linked SOD1 mutations to the formation of aggregates that could be induced by unsaturated fatty acids. The aim of this study was to evaluate the effect of DHA on aggregation of SOD1 fALS mutants in vitro and its mechanisms. CD analysis shows changes in the secondary structure of both apo-SOD1WT and G93A promoted by DHA resulting in an increase in the surface hydrophobicity and formation of structures such as beta amyloid, which was also confirmed by bis-ANS assay and Thioflavin, respectively. These changes enhance the interaction of SOD1 and DHA, leading to amorphous aggregates as revealed by FESEM. Incubation of DHA with apo-SOD1 forms results in high-molecular weight species as detected by SDS-PAGE analyses under non-reducing conditions and also by size exclusion chromatography. This appears to require Cys residues in their thiolate forms because high aggregates are not observed under reducing conditions and also by size exclusion chromatography or at acidic pH. Also, size-exclusion chromatography indicates that the mutant apo-SOD1 aggregation is dependent on the unsaturation and cis-conformation of fatty acids. Compared to the DHA, DHAOOH had a minor effect on SOD1 aggregation, however revealed the ability to induce covalent dimerization of SOD1. Overall, the data suggest a mechanism of DHA aggregation, by a process involving exposure to hydrophobic surfaces, formation of disulfide bonds and also for possible cross-links involving reactions such \"thiol-ene\".