Os compostos fenólicos são substâncias amplamente distribuídas no reino vegetal, em particular nas frutas e em outros vegetais. Estes compostos, destacando-se flavonoides e os ácidos fenólicos, devido à estrutura molecular, podem apresentar a capacidade de inibir processos oxidativos. Além do mais, estão relacionados com a redução de risco de doenças crônicas não transmissíveis tais como: cardiovasculares, câncer, aterosclerose, entre outras. Considerando a elevada produção de caju em território brasileiro e a possibilidade da existência de compostos com potencial antioxidante no pedúnculo de caju , este trabalho teve por objetivo avaliar quantitativa e qualitativamente os compostos fenólicos, particularmente os ácidos fenólicos, e identificar a participação destes em processos metabólicos do organismo animal. Foram caracterizados quimicamente três clones distintos de pedúnculos de caju (CCP-76, CCP-09, BRS-189 e CCP-76 tratado) e na análise química, apresentaram um elevado teor de ácidos graxos monoinsaturados, predominando o ácido oléico, e de fenólicos totais. Os ácidos fenólicos identificados foram: gálico, protocatecuíco, p-cumárico, ferúlico, caféico e salicílico. Foram obtidos extratos aquoso (EAq) e alcoólico (EAlc) e frações de ácidos fenólicos a partir dos pedúnculos e, avaliados em sistemas modelo β-caroteno/ácidolinoléico e em Rancimat. As frações de ácidos fenólicos exibiram expressiva atividade antioxidante no primeiro sistema e os extratos, no segundo, demonstraram fatores de proteção superior ao antioxidante sintético BHT. Pôde-se também verificar a capacidade antioxidante dos extratos e frações do clone CCP-76 no sistema de varredura do radical DPPH. Em ensaio experimental com ratos, em condição normal, foi administrado EAq (80 e 240 mg/kg, v.o.) ou fração de ácidos fenólicos livres (40 e 120 mg/kg, v.o.) obtidos do pedúnculo de caju CCP-76. Neste estudo, não se observou potencialização de todos os antioxidantes enzimáticos (superóxido dismutase, catalase e glutationas peroxidase e redutase), contudo pôde-se verificar a redução dos níveis de lipoperoxidação no tecido cerebral dando indícios de aumento do estado antioxidante nos animais. Também foi avaliado o potencial antioxidante do EAq e da fração de ácidos fenólicos livres sobre o dano hepático em ratos tratados com tetracloreto (CCl4) de carbono. A administração deste teve seu efeito corroborado pela avaliação dos parâmetros bioquímicos, ou seja, aumento exacerbado das enzimas hepáticas no plasma: alanina transaminase (ALT) e aspartato transaminase (AST); decréscimo da atividades da enzimas antioxidantes no fígado e elevação da produção de peróxidos lipídicos no tecido hepático. Nos ratos que receberam EAq (480 mg/kg, v.o.) não se observou alteração comparando-os aos animais tratados apenas com CCl4 . No entanto, a administração de fração de ácidos fenólicos livres, nas duas doses (40 e 120 mg/kg, v.o.), evidenciou pronunciado efeito contra a lesão hepática, com níveis reduzidos de AL T e AST plasmáticas, aumento da atividade das enzimas antioxidantes no fígado e prevenindo a lipoperoxidação hepática mediada pelo radical CCl3• a partir do CCl4. Estudos histológicos do tecido hepático confirmaram as avaliações bioquímicas exibindo preservação tecidual, supressão de degeneração vacuolar macro e microgoticular e de sinais necróticos nos ratos tratados com a fração de ácidos fenólicos livres do pedúnculo de caju. / Phenolic compounds are widely distributed in the plant kingdom, particularly fruits and vegetables. Due to their chemical structure, these compounds, in particular flavonoids and phenolic acids, are able to inhibit oxidative processes. Furthermore, can be used to reduce the risk of non-transmissible chronic diseases such as cardiovascular diseases, cancer and atherosclerosis. Taking into consideration the large production of cashew in Brazil and the possible existence of potentially antioxidant compounds present in the cashew apples, the aim of this study was to quantitatively and qualitatively evaluate the presence of phenolic compounds in cashew apple, particularly phenolic acids, and identify their role in metabolic processes in animals. The cashew apples of three distinct clones (CCP-76, CCP-09, BRS-189 and CCP-76 (processed)) were studied. The determination of fatty acids yielded a high concentration of monounsaturated fatty acids, mainly oleic acid, and of total phenolic compound. The phenolic acids found were: gallic, proteocatechuic, p-cumaric, ferulic, caffeic and salicylic acids. Both aqueous (EAq) and ethanolic (EAlc) extracts and phenolic acid fractions were obtained from the cashew apples and were evaluated in a β-carotene/linoleate model system and Rancimat test. The phenolic acid fractions presented an expressive antioxidant activity in the β-carotene/linoleate model system and the extracts, by the Rancimat test presented a protection factor higher than that of antioxidant additive, BHT. We also observed the antioxidant capacity of the extracts and fractions of the CCP-76 clone in the DPPH radical scavenging assay. In an experimental assay with rats, the EAq (80 and 240 mg/kg) or the free phenolic acid fraction (40 and 120 mg/kg) obtained from the cashew apple of CCP-76 clone was administered via the oral route. In this study, the enhancement of enzymatic antioxidants (superoxide dismutase, catalase, glutathione peroxidase and reductase) was not observed, nevertheless, a decrease in the amount of lipoperoxidation in the brain tissue was observed, suggesting that the ingestion of cashew might increase the antioxidative state in animals. Also, the antioxidant activity of EAq and of the free phenolic acid fraction from the cashew apple of CCP-76 clone was verified on the liver damage induced by carbon tetrachloride. The liver damage caused by the administration of carbon tetrachloride was detected by biochemical parameters, namely, the increase in the serum concentrations of alanine transaminase (ALT) and aspartate transaminase (AST) as well as a decrease in the activities of antioxidant enzymes and an increase in peroxidation in the liver. Rats who received EAq (480 mg/kg, p.o.) did not present alterations in any of the parameters evaluated, compared to the animals treated with carbon tetrachloride. On the other hand, the administration of free the phenolic acid fraction in doses of 40 and 120 mg/kg, p.o., had a pronounced effect in protecting against hepatic lesion, which was evidenced by the decrease in plasma ALT and AST, enhancing the activity of antioxidant enzymes and preventing lipoperoxidation mediated by the CCl3• radical generated by carbon tetrachloride. Histological studies were able to confirm the biochemical alterations observed in that the liver tissue obtained from rats treated with phenolic acid fractions extracted from cashew apple of CCP-76 clone presented a preserved tissue structure and suppression of macro and microgoticular vacuolar degeneration as well as of signs of necrosis.

<p>Upotrebom 50% etanola i 50% acetona kao ekstragensa izvr&scaron;ena je ekstrakcija delova ploda kestena: srž ploda, braon spoljna kora ploda, crvena unutra&scaron;nja kora ploda, ceo plod (bez ježevica), kao i drveta: li&scaron;će, resa, ježevice, stara i mlada kora stabla. Ispitivani su pitomi kesten, lovranski marun i kalemljeni italijanski marun. Nakon određivanja prinosa suvog ekstrakta, primenom standardnih spektrofotometrijskih metoda određen je sadržaj fenolnih jedinjenja, flavonoida i kondenzovanih tanina. Iako je primenom 50% acetona kao ekstragensa dobijen veći prinos fenolnih materija, flavonoida i kondenzovanih tanina, za proizvodnju ekstrakata se preporučuje 50% etanol kao ekstragens, jer obezbeđuje sasvim zadovoljavajuće rezultate, a prihvatljiviji je sa aspekta znatno niže toksičnosti.<br />Ekstrakt lista lovranskog maruna i rese pitomog kestena roda 2007. godine &scaron;tite eritrocite od hemolize izazvane H₂O₂.<br />Glavne komponente hidrolizata nakon metanolizacije ekstrakata su dimetil estar dehidrodigalne kiseline i metil estar dilaktona elaginske i valoneinske kiseline. Kvantitativnom LC/MS i HPLC/DAD analizom najveći sadržaj elagitanina je utvrđen za ekstrakt ježevica (170,6 mg/g ekstrakta).<br />Izv&scaron;eno je ispitivanje antioksidativne aktivnosti ekstrakata u odnosu na 1,1-difenil-2-pikrilhidrazil (DPPH), hidroksi (^&bull;OH) i superoksidni anjon (^&bull;O₂^-) radikale. Kapacitet ekstrakata za transformaciju organskih hidrofilnih radikala, ispitan kao sposobnost redukcije spin probe Tempon je najveći za ekstrakt rese pitomog kestena (A = 18,1%), dok ekstrakti lista pitomog kestena i mlade kore drveta ispoljavaju slabu aktivnost. Ispitivanje protektivnog delovanja ekstrakata u odnosu na UV zračenje određeno je kao sposobnost uklanjanja ^&bull;OH i ^&bull;O₂^- radikala nastalih nakon zračenja. Ekstrakti koji ispoljavaju pozitivne, ali relativno niske RI vrednosti za proizvodnju obe vrste radikala ^&bull;OH i ^&bull;O₂^- su spoljna braon kora lovranskog maruna, resa sa kalemljenog italijanskog maruna i list lovranskog maruna. Negativne RI vrednosti dobijene za ostale ekstrakte ukazuju na prooksidativnu aktivnost u vodenom rastvoru izloženom UV zračenju. Ekstrakti rese, lista i ježevica ispoljavaju aktivnost u cilju preveniranja/otklanjanja lipidne peroksidacije membrane eritrocita.<br />Ispitivanjem<em> in vitro</em> antioksidativne aktivnosti primenom MTT testa je utvrđeno da ekstrakti rese i ježevica pitomog kestena i lista lovranskog maruna imaju izuzetno visoku antioksidativnu aktivnost u ćeliji. Naročito je povoljna činjenica da deluju u niskim koncentracijama (0,02 mg/ml). Antimikrobna aktivnost ekstrakata <em>C. sativa </em>određena je u odnosu na (G+) bakterije: <em>S. aureus, S. lutea, B. cereus, L. lactis ssp. lactis, M. pyrogenes var. albus</em>, kao i na (G-) bakterije: <em>P. mirabilis i S. typhimurium</em>. Značajnu antimikrobnu aktivnost daju ekstrakti kore drveta, ježevica i spoljne braon kore ploda. Ekstrakti srži ploda i celog ploda nisu ispoljili antimikrobnu aktivnost. Postoji značajna i jako značajna korelacija između antimikrobne aktivnosti ekstrakata, kao i antimikrobne i antioksidativne aktivnosti u odnosu na superoksid anjon radikale. Ekstrakti lista, ježevica, spoljne braon i unutra&scaron;nje crvene kore ploda, kao i kore drveta <em>C. sativa</em> Mill. dobijeni primenom 50% etanola kao ekstragensa predstavljaju značajan izvor komponenata sa farmakolo&scaron;kim delovanjem u cilju smanjenja nivoa oksidativnog stresa, poseduju visok kapacitet sprečavanja lipidne peroksidacije, deluju u pravcu preveniranja/otklanjanja lipidne peroksidacije i za&scaron;tite membrane eritrocita, imaju visoku <em>in vitro</em> antioksidativnu aktivnost, a ispoljavaju i značajnu antimikrobnu aktivnost.</p> / <p>Parts of chestnut such as: seeds (without spiny burs), peeled chestnut, red internal seed coat and brown seed coat, as well as parts of the trees: leaf, catkin, spiny burs, young and old chestnut bark have been extracted by 50% ethanol and 50% acetone as an extragent. Three cultivars of <em>Castanea sativa</em> Mill.: sweet chestnut, Lovran&#39;s marrone and grafted Italian marrone were examined. After determination of the yield of dry extract, the content of total phenolic compounds, flavonoids and condensed tannins are determined by application of standard spectrophotometrics methods. Although, the highest content of total phenolics, flavonoids and condensed tannins are obtained by 50% acetone as extragents, for production of extracts 50% ethanol is more suitable, regards much lower toxicity.<br />Extracts of the leaf of Lovran&#39;s marrone and catkin of sweet chestnut native in 2007, protect erythrocytes from hemolysis provoked by H₂O₂.<br />Dehydrodigallic acid dimethyl ester, ellagic acid and valoneic acid dilactone methyl ester are the main compounds in all hydrolysates after methanolisation. The highest content of ellagitannin was detected in extract of spiny burs (170.6 mg/g extract), by application of quantitative LC/MS and HPLC/DAD analysis.<br />The examination of antioxidant activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl (^&bull;OH) and superoxide (^&bull;O2^-) radicals have been done. Capacity of extracts for removal of organic, hydrophilic radicals, exanimate as potential of reduction of spin probe Tempon is highest in extract of catkin of sweet chestnut (A = 18.1%), while extracts of catkin, leaf and spiny burs almost have no antioxidative activity. The evaluation of UV-protective activity of extracts is determinated as capacity for removal of ^&bull;OH and O₂^- radicals generated after irradiation. Extracts which showed positive, but relative low RI values for production of both radical species, OH and ^&bull;O₂ radicals, are brown seed coat of Lovran&#39;s marrone, catkin of grafted Italian marrone and leaf of Lovran&#39;s marrone. Negative RI values obtained for other extracts show that these have prooxidative activity in aqueous solution exposed to UV radiation. Extracts of catkin, leaf and spiny burs expressed activity to prevent/remove lipid peroxidation in the membrane of erythrocytes.<br />Examination of antioxidant activity <em>in vitro</em> by application of MTT test have been detected especially high antioxidant activity of extracts of catkin, spiny bur of sweet chestnut and leaf of Lovran&rsquo;s marrone in the cell. Particularly is favorable that extracts acting in low concentration (0.02 mg/ml). Antimicrobial activity of extracts of <em>C. sativa</em> was determinated against Gram-positive bacteria:<em> S. aureus, S. lutea, B. cereus, L. lactis ssp. lactis, M. pyrogenes var. albus</em>, as well as Gram-negative bacteria: <em>P. mirabilis and S. typhimurium</em>. The significant antimicrobial activity shows extracts of bark, spiny burs and brown seed coat. Extracts of peeled chestnut and seeds didn&rsquo;t show any antimicrobial activity. The very significant and significant correlation existed between antimicrobial activity of extracts, as well as antimicrobial activity and scavenging of^&bull;O2^- radical. Extracts of leaf, spiny burs, brown seed coat and red internal seed coat, as well as bark of <em>C. sativa</em> Mill. produced by 50% ethanol as extragent represent important resource of components with pharmacological activity in reducing level of oxidative stress, possess high activity to prevent/remove lipid peroxidation and protection of the membrane of erythrocytes, have high<em> in vitro</em> antioxidant activity, and also express significant antimicrobial activity.</p>

Thesis (M. Sc. (Zoology)) -- University of Limpopo, 2015 / The unprecedented expansion in human population and industry, since the industrial revolution in the late 1700s, has led to increased anthropogenic activities which have indisputably impacted freshwater ecosystems and biological communities therein, including fish. Although this has understandably been the focus, under natural aquatic conditions, no organism is only affected by pollution. Parasites have also been shown in a number of interdisciplinary studies to affect the health of aquatic hosts (amphibians, crustaceans, fish, and mammals). This is illustrated in a number of comprehensive studies the detrimental effects parasites exacerbate when their hosts (fish) are stressed. Therefore, the ability of parasites to interact with anthropogenic stressors, as well as effects they have on the genetic, cellular or tissue level of their host is crucial in conservation and sustaining aquatic biodiversity. As such, the present study examined the combined effects of pollution and metazoan parasites on the health and oxidative stress biomarkers, evaluated for the first time for silver carp, Hypophthalmichthys molitrix (Valenciennes, 1844) and rednose mudfish, Labeo rosae Steindachner, 1894, in one of South Africa’s impacted freshwater ecosystems, Flag Boshielo Dam, Olifants River System, Limpopo Province. Seasonal surveys were conducted from February 2012–January 2013. A total of 111 H. molitrix and 116 L. rosae fish specimens were collected using conventional angling gear, scoop and gill nets with stretched mesh sizes of 30–110 mm. The two selected cyprinid fish species were assessed for oxidative stress biomarkers [Glutathione S-transferase (GST), lipid peroxidation (MDA) and Total Antioxidant Capacity (TAC)] and parasitism of metazoan parasites. Concentrations of biomarkers of oxidative damage and antioxidant defense in the gill and liver tissue were measured to assess how these major organs of the immune system responded to oxidative stress associated with parasitic infections. In addition, water quality analyses were carried out by testing an assay of physico-chemical parameters to establish the level of contamination. Fish health was assessed using the Health Assessment Index (HAI), refined Parasite Index (PI), Inverted Parasite Index (IPI) and Condition Factor (K) protocols. Relative to previous studies at Flag Boshielo Dam, water quality results showed an increase of nutrients, major ions and several metals which may have adverse effects that may comprise fish health; however, this dam remains moderately polluted in a mesotrophic state. The fish health assessment results indicated that H. molitrix was more affected in terms of the necropsy and parasite based assessments (HAI, IPI and K) with mean±SD of 65.68±35.51; 68.29±25; 0.82±0.20, respectively, as compared to 39.14±22.44; 28.79±18.33; 1.17±0.21 for L. rosae during the study. In addition, significantly higher parasitic infections (mean prevalence of infection with any species of parasite = 45.3±0.13) were observed for H. molitrix than L. rosae (12.0±0.05). Furthermore, there was considerable variation in biomarker concentration between highly infected and non-infected fish, for and between each species and tissues with regard to parasite infection, suggesting that the specific functions of each tissue are associated with their susceptibility to oxidative stress, as well as their ability to defend against oxidative damage. These results illustrate that although fish are affected by aquatic contaminants they are to an extent affected by parasites, which may act synergistically on the health of the two fish species. Most importantly, it was suggested that knowledge on the parasites of alien H. molitrix when compared to indigenous L. rosae may give an indication of how adaptive this fish are to new localities as well as expands the information on the rarely studied biology, epizootiology and ecological interactions of these two cyprinid species. Keywords: Health Assessment Index, refined Parasite Index, Inverted Parasite Index, Condition Factor, water quality, lipid peroxidation, Glutathione S-transferase, Total Antioxidant Capacity, Hypophthalmichthys molitrix, Labeo rosae, Flag Boshielo Dam.

Philosophiae Doctor - PhD / The role of phenolic acids in mitigating salt stress tolerance have been well documented. However, there are contradicting reports on the effect of exogenously applied phenolic acids on the growth and development of various plants species. A general trend was observed where phenolic acids were shown to inhibit plant growth and development, with the exception of a few documented cases. One of these such cases is presented in this thesis. This study investigates the role of exogenously applied p-coumaric acid (p-CA) on physio-biochemical and molecular responses of chia seedlings under salt stress. This study is divided into three parts. Part one (Chapter 3) focuses on the impact of exogenous p-coumaric acid on the growth and development of chia seedlings. In this section, chia seedlings were supplemented with exogenous p-CA and the various biochemical and plant growth parameters were measured. The results showed that exogenous p-CA enhanced the growth of chia seedlings. An increase in chlorophyll, proline and superoxide oxide contents were also observed in the p-CA treatment relative to the control. We suggested that the increase in chia seedling growth could possibly be via the activation of reactive oxygen species-signalling pathway involving O2− under the control of proline accumulation (Chapter 3). Given the allopathy, nature of p-coumaric acid it is noteworthy that the response observed in this study may be species dependent, as contrasting responses have been reported in other plant species. Part two (Chapter 4) of this study investigates the influence of piperonylic acid (an inhibitor of endogenous p-coumaric acid) on the growth and development of chia seedlings. In trying to illustrate whether p-CA does play a regulatory role in enhancing pseudocereal plant growth, we treated chia seedlings with the irreversible inhibitor of C4H enzyme, to inhibit the biosynthesis of endogenous p-CA. In this section, chia seedlings were treated with piperonylic acid and changes in plant growth, ROS-induced oxidative damage, p-CA content and antioxidant capacity was monitored. Inhibition of endogenous p-CA restricted chia seedling growth by enhancing ROS-induced oxidative damage as seen for increased levels of superoxide, hydrogen peroxide and the extent of lipid peroxidation. Although an increase in antioxidant activity was observed in response to piperonylic acid, this increase was not sufficient to scavenge the ROS molecules to prevent oxidative damage and ultimate cellular death manifested as reduced plant growth. The results presented in this section support our hypothesis that p-CA play an important regulatory role in enhancing chia seedling growth and development as shown in Chapter 3. Part three (Chapter 5) seeks to identify and functionally characterise p-coumaric acid induced putative protein biomarkers under salt stress conditions in chia seedlings. Previous studies have shown that p-CA reversing the negative effect caused by NaCl-induced salt stress. While these studies were able to demonstrate the involvement of p-CA in promoting plant growth under salt stress conditions, they focussed primarily on the physiological aspect, which lacks in-depth biochemical and molecular analysis (ionomic and proteomic data) which could help in detecting the genes/proteins involved in salt stress tolerance mechanisms. A comparative ionomics and proteomic study was conducted, with the aim of elucidating the pivotal roles of essential macro elements and/or key protein markers involved in p-CA induced salt stress tolerance in chia seedlings. With the exception of Na, all the other macro elements were decreased in the salt treatment. Contrary to what was observed for the salt treatment most of the macro elements were increased in the p-CA treatment. However, the addition of exogenous p-CA to salt stressed seedlings showed an increase in essential macro elements such as Mg and Ca which have been shown to play a key role in plant growth and development. In the proteomic analysis we identified 907 proteins associated with shoots across all treatments. Interestingly, only eight proteins were conserved amongst all treatments. A total of 79 proteins were unique to the p-CA, 26 to the combination treatment (NaCl + p-CA) and only two proteins were unique to the salt stress treatment. The unique proteins identified in each of the treatments were functionally characterised to various subcellular compartments and biological processes. Most of the positively identified proteins were localised to the chloroplast and plays key roles in photosynthesis, transportation, stress responses and signal transduction pathways. Moreover, the protein biomarkers identified in this study (especially in the p-CA treatment) are putative candidates for genetic improvement of salt stress tolerance in plants.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease, with poor prognosis and no cure. Substantial evidence implicates inflammation and associated oxidative stress as a potential mechanism for ALS, especially in patients carrying the SOD1 mutation and, therefore, lacking anti-oxidant defense. The brain is particularly vulnerable to oxidation due to the abundance of polyunsaturated fatty acids, such as docosahexaenoic acid (DHA), which can give rise to several oxidized metabolites. Accumulation of a DHA peroxidation product, CarboxyEthylPyrrole (CEP) is dependent on activated inflammatory cells and myeloperoxidase (MPO), and thus marks areas of inflammation-associated oxidative stress. At the same time, generation of an alternative inactive DHA peroxidation product, ethylpyrrole, does not require cell activation and MPO activity. While absent in normal brain tissues, CEP is accumulated in the central nervous system (CNS) of ALS patients, reaching particularly high levels in individuals carrying a SOD1 mutation. ALS brains are characterized by high levels of MPO and lowered anti-oxidant activity (due to the SOD1 mutation), thereby aiding CEP generation and accumulation. Due to DHA oxidation within the membranes, CEP marks cells with the highest oxidative damage. In all ALS cases CEP is present in nearly all astrocytes and microglia, however, only in individuals carrying a SOD1 mutation CEP marks >90% of neurons, thereby emphasizing an importance of CEP accumulation as a potential hallmark of oxidative damage in neurodegenerative diseases.

Les métaux et les métalloïdes sont naturellement présents dans l’ensemble de la biosphère et les premières formes de vie ont su bénéficier des plus abondants comme macronutriments. Catégorisés dans le tableau périodique des éléments selon leurs caractéristiques chimiques, les métaux sont également divisés en deux grandes catégories : les métaux essentiels et non essentiels. Se retrouvent parmi les métaux essentiels, le sélénium, le calcium et le zinc, nécessaires aux fonctionnements cellulaires tandis que le cadmium, le plomb et le mercure sont des exemples de métaux dits non essentiels puisqu’ils ne sont pas requis pour les fonctions biologiques. Cependant, peu importe leur essentialité, les métaux peuvent engendrer des effets délétères lorsque leur concentration intracellulaire dépasse un certain seuil, propre à la nature chimique, ou spéciation, de chaque métal et de la tolérance de chaque organisme. Si la toxicité d’un métal dépend de sa spéciation, sa spéciation est également dépendante des conditions du milieu, qu’il soit aquatique ou cellulaire. De plus, la spéciation d’un métal est déterminante de sa biodisponibilité, et donc, de sa bioaccumulation. Considérant que les activités anthropiques et les points de sources naturelles ponctuels contribuent à la remobilisation et à l’augmentation des concentrations de métaux dans les écosystèmes, notamment les milieux aquatiques, déterminer la spéciation des métaux afin de mieux prédire leur biodisponibilité et leur bioaccumulation par les organismes est essentiel. L‘objectif général de cette thèse est d’étudier, par l’entremise de trois modèles d’organismes aquatiques, la bioaccumulation des métaux à l’interface rivière-estuaire, leur gestion intracellulaire et, plus particulièrement pour le mercure, son effet toxicologique suivant sa distribution subcellulaire. Dans un premier temps, nous avons mené une étude sur les facteurs biogéochimiques influençant la distribution et la bioaccumulation du mercure et des éléments de terres rares par la mye commune (Mya arenaria) à l’embouchure de la rivière Romaine et Mingan dans la région de la Côte-Nord au Québec. Nous avons également mesuré les concentrations d’éléments traces essentiels et d’autres métaux non essentiels dans une perspective d’évaluation du risque et des bénéfices à la consommation de cette espèce pour quatre groupes de population. Par la signature isotopique de soufre des myes, nos résultats ont démontré que les myes influencées par les eaux marines accumulaient des concentrations plus faibles de mercure total, de méthylmercure et de terres rares. Nous avons observé que la matière organique des sédiments joue un rôle dans la rétention du mercure total et du méthylmercure dans ce compartiment tandis que les éléments de terres étaient davantage liés à la concentration de fer. Nous avons également identifié les sédiments comme un compartiment de transfert de ces métaux vers les myes. En ce qui a trait à l’évaluation du risque à la consommation, à la suite de la comparaison des concentrations de métaux non essentiels à des valeurs de référence, la consommation des myes de tous les secteurs à l’étude ne pose pas de risque pour la santé des consommateurs.trices. En contrepartie, l’évaluation de l’apport nutritionnel a indiqué que les myes présentent une source élevée en fer et en sélénium et que leur consommation est recommandée. Dans un second temps, nous avons évalué la gestion intracellulaire de métaux selon leurs caractéristiques chimiques dans le foie de la perchaude (Perca flavescens) du lac Saint-Pierre, une espèce de poisson exposée chroniquement à de faibles concentrations polymétalliques. Par l’entremise de résultats suivant l’approche de fractionnement subcellulaire, nous avons démontré des profils de distribution subcellulaire distincts entre les métaux selon leur classification chimique. Les métaux de classe A et intermédiaires étaient préférentiellement associés aux fractions sensibles. Nos résultats ont démontré une distribution subcellulaire divergente entre le méthylmercure, le cadmium et le cuivre. Contrairement au cadmium et au cuivre qui sont associés à la fraction protéines thermosensibles du cystosol (HSP), le méthylmercure est davantage lié aux fractions sensibles. Finalement, une comparaison des proportions de méthylmercure, de cuivre et de cadmium entre la perchaude et d’autres espèces de poissons a permis de confirmer que les métaux se distribuent dans le milieu intracellulaire en raison de leur affinité et sans égard à la bioaccumulation, réfutant ainsi le principe de débordement subcellulaire. Finalement, nous avons lié la distribution subcellulaire du méthylmercure dans le foie du grand brochet (Esox lucius) d’une sous-section de la rivière Saint-Maurice à un marqueur de stress oxydant. Considérant le foie total, nos résultats ont permis de corréler les concentrations de méthylmercure et de sélénium à une augmentation de la peroxydation des lipides dans le foie. Cette relation soulève un intérêt afin d’approfondir les connaissances sur les mécanismes cellulaires pouvant exacerber les effets conjoints potentiels entre le méthylmercure et le sélénium. De plus, nous avons observé une corrélation positive entre la concentration de méthylmercure associée à la fraction mitochondriale et l’augmentation de la peroxydation des lipides dans le foie, jusqu'alors indéterminée. Les résultats de cette thèse mettent en lumière la pertinence et la nécessité de considérer la spéciation des métaux, leur bioaccumulation et leur distribution subcellulaire dans l’évaluation de leurs effets indésirables, puisque ces processus sont intrinsèquement liés. / Metals and metalloids are naturally present throughout the biosphere and the first forms of life were able to benefit from the most abundant as macronutrients. Categorized in the periodic table of elements according to their chemical characteristics, metals are also divided into two main categories: essential and non-essential metals. Among the essential metals are selenium, calcium, and zinc, necessary for cellular functions, while cadmium, lead and mercury are examples of so-called non-essential metals since they are not required for biological functions. However, regardless of their essentiality, metals can cause deleterious effects when their intracellular concentration exceeds a certain threshold, specific to the chemical nature, or speciation, of each metal and the tolerance of each organism. If the toxicity of a metal depends on its speciation, its speciation is also dependent on the conditions of the environment, whether aquatic or cellular. Moreover, the speciation of a metal determines its bioavailability, and therefore, its bioaccumulation. Considering that anthropogenic activities and point natural sources contribute to the remobilization and increase of metal concentrations in ecosystems, especially aquatic environments, assessing the speciation of metals to better predict their bioavailability and their bioaccumulation by organisms is essential. The general objective of this thesis is to study, through three models of aquatic organisms, the bioaccumulation of metals at the river-estuary interface, their intracellular handling and, in particular for mercury, its toxicological effect according to its subcellular distribution. First, we conducted a study on the biogeochemical factors influencing the distribution and bioaccumulation of mercury and rare earth elements by the soft-shell clam (Mya arenaria) at the mouth of the Romaine and Mingan rivers in the Côte-Nord region of Quebec. We also measured the concentrations of essential trace elements and other non-essential metals to assess health concerns and nutritional benefits for four population subgroups. Through the isotopic sulfur signature of clams, our results demonstrated that clams influenced by marine waters accumulated lower concentrations of total mercury, methylmercury, and rare earth elements. We observed that organic matter plays a role in the retention of total mercury and methylmercury in sediments whilst the retention of rare earth elements was more related to the iron concentration in sediments. We have also identified sediments as a transfer compartment of these metals to clams. Considering the health risk and benefits following the consumption of soft-shell clams, the comparison of the concentrations of non-essential metals with reference values for food safety, showed that their consumption should not pose a health risk to the consumer. On the other hand, the evaluation of the nutritional intake indicated that clams are a high source of iron and selenium. Second, we evaluated the intracellular management of metals according to their chemical characteristics in the liver of yellow perch (Perca flavescens) from Lake Saint-Pierre, a species of fish chronically exposed to low polymetallic concentrations. Through results following the subcellular partitioning approach, we demonstrated distinct subcellular distribution patterns between metals according to their chemical classification. Class A and intermediate metals were preferentially associated with metal-sensitive fractions. Our results showed a divergent subcellular distribution between methylmercury, cadmium, and copper. Unlike cadmium and copper which are associated with the heat-stable protein (HSP) fraction, methylmercury was bound to the metal-sensitive fractions. Finally, a comparison of the proportions of methylmercury, copper, and cadmium between yellow perch and other species of fish confirmed that metals distribute in the intracellular environment due to their chemical affinity and regardless of the bioaccumulation level, thus refuting the principle of the spillover effect. Finally, we linked the subcellular distribution of methylmercury in the liver of northern pike (Esox lucius) from a subsection of the Saint-Maurice River to an oxidative stress biomarker. Considering the total liver, our results correlated methylmercury and selenium concentrations with an increase in lipid peroxidation in the whole liver. This relationship raises the interest to deepen our knowledge on the cellular mechanisms that can exacerbate the potential joint effects of methylmercury and selenium. Moreover, among the subcellular fractions, we observed a positive correlation between the concentration of methylmercury associated with the mitochondrial fraction and the increase of lipid peroxidation in the whole liver, which was hitherto undetermined. The results of this thesis highlight the relevance and the need to consider the speciation of metals, their bioaccumulation, and their subcellular distribution in the assessment of their adverse effects, since these processes are intrinsically linked.

Объектами исследования являются полифенольные антиоксиданты. Целью выпускнoй квалификационной работы является исследование антиоксидантных свойств полифенольных соединений с позиции механизмов их действия. В работе рассмотрены причины возникновения окислительного стресса, система антиоксидантной защиты и существующие методы исследования антиоксидантных свойств соединений. В процессе работы предложенными методами оценена хелатирующая способность полифенолов по отношению к ионам железа (II) и (III), исследована зависимость антиоксидантных свойств от рН, определены значения условных констант устойчивости и их зависимость от рН. / The objects of research are polyphenolic antioxidants. The purpose of the final qualifying work is to study the antioxidant properties of polyphenolic compounds from the perspective of their mechanisms of action. The paper considers the causes of oxidative stress, the system of antioxidant protection and existing methods for studying the antioxidant properties of compounds. In the process of work, the proposed methods evaluated the chelating ability of polyphenols with respect to iron (II) and (III) ions, investigated the dependence of antioxidant properties on pH, determined the values of conditional stability constants and their dependence on pH.

For peanuts, roasted at 170 °C, the formation of selected glycerol-bound oxidized fatty acids (GOFAs), namely 9-oxononanoic acid (9-ONA), azelaic acid (AZA) and octanoic acid, was observed by GC-MS (EI). The content of octanoic acid as well as AZA increased with continuous roasting time (from 59 mg/kg peanut oil to 101 mg/kg peanut oil and from not detectable to 8 mg/kg peanut oil, respectively), whereas the content of 9-ONA initially decreased from 25 mg/kg peanut oil to 8 mg/kg peanut oil (20 min) and increased again up to 37 mg/kg peanut oil following roasting for 40 min. Due to its aldehyde function, 9-ONA could contribute to amino acid side chain modifications as a result of lipation, which could directly influence the functional properties of peanut proteins. Both 9-ONA and octanoic acid are potential markers of thermal processes. Furthermore, in model experiments using methyl linoleate and methyl oleate, up to 18 oxidized fatty acids could be identified as methyl esters, 9-ONA as well as octanoic acid as major components and a faster formation of GOFAs under roasting conditions (170 °C, 20 min). In addition, 9-ONA contributes to the formation of AZA and octanoic acid in both free and bound form as a result of oxidative subsequent reactions in presence of iron (III).

L’arthrose (OA) est une maladie dégénérative et multifactorielle caractérisée par une destruction de cartilage, une formation d’ostéophytes et une inflammation au niveau de la membrane synoviale. Le 4-hydroxynonénal (HNE), un produit final de la peroxydation lipidique, a été identifié récemment comme un facteur catabolique et un médiateur inflammatoire dans le cartilage arthrosique humain. Notre projet vise à étudier l’effet du HNE sur la régulation de la prostaglandine E2 synthase-1 microsomale (mPGES-1) et de la protéine activante 5-lipoxygénase (FLAP)/5-lipoxygénase (5-LOX) dans les chondrocytes arthrosiques humains. Lorsque les cellules sont traitées une seule fois avec 10 µM HNE, les résultats de Western blot et de PCR en temps réel montrent que l’expression de la cyclooxygénase-2 (COX-2) et de la mPGES-1 augmente de manière significative et atteint respectivement le maximum après 8 et 16 heures d’incubation puis diminue graduellement. Cependant, lorsque les cellules sont traitées plusieurs fois avec 10 µM HNE à 2 heures d’intervalle, l’expression de la COX-2 et de la mPGES-1 augmente en fonction du temps sans subir une baisse après 24 heures d’incubation. Le HNE induit l’activité du promoteur de la mPGES-1 via l’activation du facteur de transcription Egr-1. L’investigation de la 2ème voie du métabolisme de l’acide arachidonique, à savoir 5-LOX/FLAP, montre que le HNE induit l’expression de FLAP après 24 heures de stimulation et celle de 5-LOX seulement après 48 heures. Ceci semble survenir à l’étape de transcription au cours de laquelle HNE induit l’expression de l’ARNm et l’activité du promoteur du gène 5-LOX. Nous avons démontré aussi que le niveau de leukotriène B4 (LTB4) augmente et suit le même profil que celui de la 5-LOX. L’étude des mécanismes moléculaires susceptibles d’être impliqués dans la régulation de la 5-LOX/FLAP par le HNE montre que ce dernier stimule leur expression via l’action de prostaglandine E2 (PGE2) et du facteur de croissance transformant-beta 1 (TGF-β1). En conclusion, notre étude démontre que le HNE induit à court-terme d’incubation la voie de COX-2/mPGES-1 puis par la suite stimule celle de FLAP/5-LOX à long-terme d’incubation dans les chondrocytes arthrosiques humains. Ces résultats suggèrent que la mPGES-1 et 5-LOX/FLAP sont des potentielles cibles thérapeutiques intéressantes pour contrôler la production de PGE2 et LTB4 dans OA. / 4-hydroxynonenal (HNE), a lipid peroxidation end-product, is produced abundantly in osteoarthritic (OA) articular tissues. Recently, we reported that HNE-induced cyclooxygenase-2 (COX-2) decreased gradually in human OA chondrocytes after 8 h of incubation. This study aimed to investigate whether COX-2 down-regulation is attributed to HNE depletion and is responsible for the switch from COX-2 to 5-lipoxygenase-activating protein (FLAP)/5-lipoxygenase (5-LOX). Treatment of chondrocytes with 10 µM HNE induced prostaglandin E2 (PGE2) release as well as COX-2 and microsomal prostaglandin E2 synthase-1 (mPGES-1) expression at the protein and mRNA levels, with a plateau reached at 8-16 h of incubation, followed by a subsequent decline. However, 8 repeated treatments with 10 µM HNE prevented the reduction of COX-2 and mPGES-1 expression. We demonstrated that HNE induced mPGES-1 promoter activity mainly through transcription factor Egr-1 activation. On the other hand, when COX-2 expression decreased, leukotriene B4 (LTB4) level rose after a long period of stimulation (48 and 72 h). At the mRNA level, HNE induced FLAP and 5-LOX expression after 24 and 48 h of stimulation, respectively. The addition of a nonspecific COX-2 inhibitor (naproxen) to cultured chondrocytes revealed that FLAP and 5-LOX regulation by HNE required PGE2 production. Furthermore, our data showed that 10 µM HNE significantly induced transforming growth factor-beta 1 (TGF-β1) production. The addition of anti-TGF-β antibody to culture medium reduced HNE-induced 5-LOX/FLAP expression by 40%, indicating the involvement of a TGF-β1-dependent mechanism. Our data demonstrate that the shunt to the FLAP/5-LOX pathway in HNE-induced human OA chondrocytes is attributed to COX-2 inhibition, probably due to HNE depletion. PGE2 and TGF-β1 are suggested to be involved in this regulation. Further experiments are in progress to determine other molecular mechanisms underlying this switch in OA chondrocytes.

De nombreuses études ont montré que l'exposition de cultures cellulaires à des particules α conduit à des changements biologiques importants autant dans les cellules irradiées que dans les cellules bystander non-irradiées. L'étude des réponses biologiques non-ciblées dans des cultures cellulaires exposées à de faibles fluences d’ions lourds permet d’estimer les risques pour la santé du rayonnement spatial et de la radiothérapie. Nous avons caractérisé les mécanismes sous-jacents de l'induction d'effets stressants dans des cultures confluentes de fibroblastes normaux humains exposés à de faibles fluences d’ions fer de 1000 MeV/u (transfert d'énergie linéique (TEL) ~151 keV/µm), d’ions silicium de 600 MeV/u (TEL ~50 keV/µm) ou d’ions carbone de 290 MeV/u (TEL ~13 keV/µm). Nous avons comparé ces résultats avec ceux obtenus dans des cultures cellulaires exposées, en parallèle, à de faibles fluences de particules α de 0,92 MeV/u (TEL ~109 keV/µm). L'induction de dommages à l'ADN, les changements dans l'expression des gènes, la carbonylation des protéines et la peroxydation lipidique durant les 24 h suivant l'exposition de cultures confluentes à de faibles doses (0,2 cGy et plus) d’ions fer ou d'ions silicium ont très largement contribué à la propagation d’effets stressants des cellules irradiées aux cellules bystander non-irradiées. Pour une dose moyenne de 0,2 cGy, seules ~1 et 3 % des cellules seraient irradiées dans le noyau par un ion, respectivement, fer ou silicium. Les immunoblots ont révélés des augmentations significatives des niveaux de phospho-TP53 (sérine 15), p21Waf1 (CDKN1A), HDM2, phospho-ERK1/2, de carbonylation des protéines et de peroxydation lipidique dans les 24 h suivant l’exposition. L'ampleur de ces réponses suggère la participation de cellules non ciblées dans les effets observés. De plus, lorsque les populations cellulaires irradiées ont été ré-ensemencées dans un milieu de culture frais peu après l'irradiation, les niveaux de ces marqueurs ont aussi augmentés durant 24 h. Ensemble, ces résultats montrent un effet rapidement propagé et persistant. Des analyses in situ réalisées dans des cultures cellulaires confluentes ont montré que la formation de foyers de la protéine 53BP1, marqueur de dommages à l'ADN, touchait un nombre de cellules plus important que celui auguré par la fraction de cellules traversées dans le noyau par un ion fer ou silicium. Cet effet est exprimé dès 15 min suivant l'exposition, atteint son maximum 1 h après l’exposition puis diminue jusqu’à 24 h. Une tendance similaire s'est produite après exposition à une dose moyenne absorbée de 0,2 cGy de particules α de 3,7 MeV, mais non après 0,2 cGy d’ions carbone de 290 MeV/u.Des analyses utilisant des puits de cultures intégrant une fine épaisseur de CR-39, détecteur solide de traces nucléaires, et permettant ainsi l’identification des cellules irradiées aux ions fer ou silicium, confirment la participation de cellules bystander dans la réponse au stress. Des études mécanistiques ont, de plus, indiqué que les jonctions gap permettant la communication intercellulaire, certaines voies de la réparation de l’ADN, ainsi que le métabolisme oxydatif participent à la propagation des effets non ciblés induit par des radiations de haut TEL. Nous avons également examiné la contribution possible des particules secondaires produites le long des traces d’ions primaires dans les réponses biologiques. Les simulations réalisées avec le code de transport de particules FLUKA ont révélé que la dose due aux produits de fragmentation, autres que les électrons, est inférieure à 1 % de la dose absorbée dans les cultures cellulaires exposées à des ions lourds. De plus, la dose radiale des ions lourds secondaires est limitée à ~10-20 µm autour de l’ion primaire. Ainsi, ces derniers sont peu susceptibles de contribuer de manière significative à la réponse biologique observée dans des cellules non ciblées par des ions lourds primaires / Widespread evidence indicates that exposure of cell cultures to α particles results in significant biological changes in both the irradiated and non-irradiated bystander cells in the population. The induction of non-targeted biological responses in cell cultures exposed to low fluences of high charge (Z) and high energy (E) particles is relevant to estimates of the health risks of space radiation and to radiotherapy. Here, we investigated the mechanisms underlying the induction of stressful effects in confluent normal human fibroblast cultures exposed to low fluences of 1000 MeV/u iron ions (linear energy transfer (LET) ~151 keV/µm), 600 MeV/u silicon ions (LET ~50 keV/µm) or 290 MeV/u carbon ions (LET ~13 keV/µm). We compared the results with those obtained in cell cultures exposed, in parallel, to low fluences of 0.92 MeV/u α particles (LET ~109 keV/µm).Induction of DNA damage, changes in gene expression, protein carbonylation and lipid peroxidation during 24 h after exposure of confluent cultures to mean doses as low as 0.2 cGy of iron or silicon ions strongly supported the propagation of stressful effects from irradiated to bystander cells. At a mean dose of 0.2 cGy, only ~1 and 3 % of the cells would be targeted through the nucleus by an iron or silicon ion, respectively. Within 24 h post-irradiation, immunoblot analyses revealed significant increases in the levels of phospho-TP53 (serine 15), p21Waf1 (also known as CDKN1A), HDM2, phospho-ERK1/2, protein carbonylation and lipid peroxidation. The magnitude of the responses suggested participation of non-targeted cells in the response. Furthermore, when the irradiated cell populations were subcultured in fresh medium shortly after irradiation, greater than expected increases in the levels of these markers were also observed during 24 h. Together, the results imply a rapidly propagated and persistent bystander effect. In situ analyses in confluent cultures showed 53BP1 foci formation, a marker of DNA damage, in more cells than expected based on the fraction of cells traversed through the nucleus by an iron or silicon ion. The effect was expressed as early as 15 min after exposure, peaked at 1 h and decreased by 24 h. A similar tendency occurred after exposure to a mean absorbed dose of 0.2 cGy of 3.7 MeV α particles, but not after 0.2 cGy of 290 MeV/u carbon ions.Analyses in dishes that incorporate a CR-39 solid state nuclear track detector bottom identified the cells irradiated with iron or silicon ions and further supported the participation of bystander cells in the stress response. Mechanistic studies indicated that gap junction intercellular communication, DNA repair, and oxidative metabolism participate in the propagation of the induced effects.We also considered the possible contribution of secondary particles produced along the primary particle tracks to the biological responses. Simulations with the FLUKA multi-particle transport code revealed that fragmentation products, other than electrons, in cells cultures exposed to HZE particles comprise <1 % of the absorbed dose. Further, the radial spread of dose due to secondary heavy ion fragments is confined to approximately 10-20 µm Thus, the latter are unlikely to significantly contribute to the stressful effects in cells not targeted by primary HZE particles.