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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Efficacité d’un analogue d’Imiqualines, l’EAPB0503 : Un nouveau traitement prometteur contre la Leishmaniose Cutanée / Efficacy of the Imiqualine analog EAPB0503 against Cutaneous Leishmaniasis : A promising new treatment paradigm

El Hajj, Rana 22 June 2018 (has links)
La leishmaniose cutanée (LC) est une infection parasitaire classifiée par l’Organisation de Santé Mondiale (WHO) comme étant une des maladies tropicales négligées non-contrôlées. Dans la région du Moyen Orient, la LC est généralement endémique en Syrie et elle est causée principalement par Leishmania tropica et Leishmania major. La LC a été récemment introduite à des pays non endémiques, suite au déplacement intense des réfugiés Syriens échappant à la crise. Les interventions thérapeutiques contre la LC incluent des traitements locaux, systémiques et physiques. En revanche, le risque élevé de sélection et de résistance des parasites aux traitements actuels suscitent une quête sérieuse, pour trouver de nouvelles approches thérapeutiques. L’Imiquimod est un composé immunomodulateur approuvé pour utilisation clinique, et présente une efficacité vis-à-vis de certaines espèces de Leishmania. Dans cette étude, notre intérêt s’est focalisé sur l’efficacité d’un analogue de l’Imiquimod, l’EAPB0503, contre les stades promastigotes et amastigotes de L.tropica et L.major.Nos résultats montrent que l’Imiquimod et particulièrement l’EAPB0503 affectent les deux espèces. L’Imiquimod affecte majoritairement la motilité des promastigotes des deux espèces, alors que l’EAPB0503 affecte la motilité des promastigotes de L. major mais surtout l’invasion des promastigotes de L. tropica dans les macrophages. Les deux composés réduisent la réplication des amastigotes, avec un effet plus prominent de l’EAPB0503. Cet effet est médié par l’augmentation de l’expression du récepteur toll-Like-7 (TLR7), particulièrement pour l’Imiquimod et d’une manière moins importante pour l’EAPB0503. Les deux composés induisent l’activation de la voie de signalisation canonique de NF-κB. Ceci conduit à une production des cytokines pro-inflammatoires, et une diminution des cytokines anti-inflammatoires expliquant l’activité leishmanicide des deux composés. L’EAPB0503 semble agir via un autre TLR que l’imiquimod, comme il induit une expression plus élevée des transcrits TLR8 et TLR9, conférant une protection contre l’infection.Collectivement, nos résultats montrent l’effet de l’Imiquimod contre l’espèce la plus aggressive, L. tropica, et souligne l’activité plus puissante de l’EAPB0503 contre les deux espèces. De plus, cette étude montre le mécanisme d’action de ces deux composés, qui vraisemblablement activent des TLRs différents, mais finissent par induire la voie NF-κB et la réponse immunitaire correspondante. Ces résultats soulignent l’importance des drogues immuno-modulatrices contre la LC et ouvrent des perspectives sur des études précliniques puis cliniques de ces composés. / Cutaneous Leishmaniasis (CL) is a parasitic infection classified by the WHO as one of the most uncontrolled spreading neglected diseases. In the Middle East Region, CL is mostly endemic in Syria where it is mainly caused by Leishmania tropica and Leishmania major. CL has been lately introduced to under endemic countries, following the large-scale displacement of refugees from Syria fleeing the crisis. Therapeutic interventions against CL include local, systemic and physical treatments. However, the high risk for selection and spread of drug-resistant parasites is high; consequently new therapeutic approaches are still needed. Imiquimod is an FDA approved immunomodulatory compound with a tested efficacy against some leishmania species. In this study, our interest was to investigate the efficacy of an Imiquimod analog, EAPB0503 in comparison to the original compound, against promastigote and amastigote stages of L.tropica and L.major.We showed that Imiquimod affects the motility of promastigotes of both strains. EAPB0503 affected L. major promastigotes’ motility and impaired the invasion of L.tropica promastigotes into macrophages. Both drugs reduced amastigote replication, with a higher potency of EAPB0503. This activity is due to the upregulation of Toll-Like Receptor-7 (TLR7), mainly by Imiquimod, and to a lesser extent by EAPB0503. Importantly, both drugs activated the NF-κB canonical pathway leading to production of pro-inflammatory cytokines and upregulation of i-NOS levels. A decrease of anti-inflammatory cytokines secretion was obtained, explaining the leishmanicidal activity of both drugs. Importantly, EAPB0503 led to a prominent increase in TLR8 and TLR9 transcripts, presumably conferring protection against the infection.Collectively, our findings show the effect of Imiquimod against both strains especially, the aggressive L. tropica strain. We also show that EAPB0503 displays a more potent in vitro leishmanicidal activity than Imiquimod. These drugs seemingly activate different TLRs, but both activate the canonical NF-κB pathway and its subsequent mediated immune response. These results highlight the promising effect of immunomodulatory drugs against CL and warrant an in depth in vivo preclinical then clinical studies of these compounds.
2

Analyses transcriptomiques et protéomiques de la résistance à l'antimoine et de son mode d'action chez la forme amastigote du parasite Leishmania infantum

El Fadili, Karima January 2007 (has links)
No description available.
3

Rôle des lipides dans l’infestation, la virulence, et la transformation des promastigotes en amastigotes et implication des acides gras dans la pathogénie de Leishmania / Role of lipids in infestation, virulence, and transformation of promastigotes into amastigotes and involvement of fatty acids in the pathogenesis of Leishmania

Bouazizi, Hana 26 June 2018 (has links)
Les parasites Leishmania sont les agents responsables de la leishmaniose viscérale (LV), mucocutanée (LM) ou cutanée (LC) chez l'homme et de la leishmaniose canine (CanL). Ces parasites sont phagocytés par les macrophages humains et animaux où ils vont se transformer de promastigote en amastigote. Nous avons identifié et analysé les lipides impliqués dans le processus de transformation dans le complexe de Leishmania donovani et infantum. Quatre classes de lipides, les phospholipides, les acides gras libres, les triglycérides et les stérols ont été étudiés. De même, nous avons analysé la composition en acides gras des lipides totaux chez neuf espèces de Leishmania isolées en Tunisie, dont quatre souches de L. infantum, deux souches de L. major et deux souches de L. tropica et une souche de L. infantum de chien. Durant nos premiers travaux, la composition en acides gras des lipides totaux a été analysée et nos résultats montrent une augmentation des acides gras et du cholestérol et une diminution des triglycérides et de l'ergostérol durant la transition entre les promastigotes et les amastigotes. En ce qui concerne les classes de phospholipides, nous avons trouvé une proportion accrue de sphingomyéline et de phosphatidylsérine et une proportion réduite de phosphatidylinositol et de lysophosphatidyléthanolamine. Pour la composition en acides gras, une augmentation significative des acides gras n-7 a été observée chez les amastigotes, quant aux acides gras n-6 totaux, ils ont diminué chez les PL. Plusieurs changements ont également été observés au niveau des TG et des acides gras libres, en particulier, les acides gras n-7 et 20: 4n-6 ont été fortement augmentés, alors que les acides gras n-9 et les précurseurs n-6 ont diminué. Pour la deuxième étude, les résultats trouvés dans nos premiers travaux qui concernent la présence de proportions très élevés de 18 : 2n-6 contre de faible proportion de l’AA (20 :4n-6) ainsi que l’absence ou la très faible proportion de 18 :3n-3 ont été confirmés. De plus, L. major présentait une proportion plus élevée de 14 : 0 (acide myristique), 18: 3n-6 (acide gamma-linoléique) et une plus faible proportion de n-3, y compris 18: 3n-3 (acide alphalinoléique) et 22: 6n-3 (acide docosahexaénoïque) comparé à L. infantum et L. tropica. Après la supplémentation de l'acide oléique (AO), l'acide arachidonique (AA) et l’acide docosahexaénoïque (DHA) sur deux souches de L. infantum utilisées pour infecter les macrophages : un isotype MON-24 responsable de la leishmaniose cutanée et un MON-1 causant la leishmaniose viscérale ; nous avons constatés que les AA et DHA augmentaient la virulence du parasite, tandis que L’AO diminuait leur virulence / Leishmania parasites are the causative agents of visceral (LV), mucocutaneous (LM) or cutaneous (LC) leishmaniasis in humans, canine leishmaniasis in dogs (CanL), and leishmaniases in other mammals .The parasites are phagocytosed by human and animal macrophages where they will transform from promastigote to amastigote. We identified and analyzed the lipids involved in the transformation process in the Leishmania donovani complex. Four classes of lipids, phospholipids (PL), free fatty acids (FA), triglycerides (TG) and sterols were studied.Similarly, we analyzed the fatty acid composition of total lipids in nine Tunisian Leishmania isolates, including five strains of L. infantum (four human and one canine), two strains of L. major and two strains of L. tropica.In our early work, the fatty acid composition of total lipids was analyzed and our results show an increase in fatty acids and cholesterol and a decrease in triglycerides and ergosterol during the transformation of promastigotes into amastigotes. For phospholipid classes, we found an increase in sphingomyelin and phosphatidylserines and a decrease in phosphatidylinositols and lysophosphatidylethanolamines during processing. For the fatty acid composition, a significant increase of n-7 fatty acids was observed in amastigotes, as for n-6 total fatty acids, they decreased in PLs. Several changes have also been observed in TG and free fatty acids, in particular, n-7 and 20: 4n-6 fatty acids have been greatly increased, whereas n-9 fatty acids and n-6 ??precursors have been significantly increased. decreased.The study of the fatty acid composition of the 9 Tunisian strains of Leishmania confirmed, in the first place, our results found in our first works concerning the presencevery high proportions of 18: 2n-6 against low proportion of AA (20: 4n-6) as well as the absence or very low proportion of 18: 3n-3.In addition, the comparison of the fatty acid compositions of the three species studied: L. infantum, L. major and L. tropica showed that L. major had a higher proportion of 14: 0 (myristic acid), 18: 3n- 6 (gamma-linoleic acid) and a lower proportion of n-3, including18: 3n-3 (alpha-linoleic acid) and 22: 6n-3 (docosahexaenoic acid) compared to L. infantum and L. tropica. After supplementation of oleic acid (AO), arachidonic acid (AA) and docosahexaenoic acid (DHA) on two L. infantum strains used to infect macrophages: a MON-24 isotype responsible for cutaneous and a MON-1
4

Étude des éléments régulateurs « cis » et « trans » impliqués dans la stabilité du transcrit de l'amastine au stade intracellulaire chez « Leishmania »

Dupé, Aurélien January 2013 (has links)
Le genre Leishmania regroupe des parasites protozoaires transmis par piqûre d’un insecte vecteur et qui sont responsables des leishmanioses. Le cycle de Leishmania alterne entre promastigotes dans l’appareil digestif de l’insecte et amastigotes dans les phagolysosomes des macrophages d’un hôte mammifère. Les delta-amastines sont une famille de protéines membranaires qui jouent potentiellement un rôle dans la virulence. L’expression exclusivement au stade intracellulaire de l’un de ces gènes est permise par une accumulation préférentielle de l’ARNm et la stimulation de la traduction, toutes deux chez les amastigotes. L’objectif de cette thèse est de caractériser les mécanismes permettant l’expression différentielle de l’ARNm de la delta-amastine. Ces organismes ont divergé rapidement des autres eucaryotes, ce qui engendre plusieurs différences fonctionnelles, dont notamment l’absence de régulation transcriptionnelle. Notre hypothèse est que la présence d’une région riche en uridines (URE) dans l’extrémité 3’ non traduite (3’UTR) du transcrit peut être impliquée dans la dégradation de l’ARNm. Nous démontrons que le URE est responsable d’une dégradation du transcrit au stade promastigote, par un phénomène indépendant de la déadénylation. Nous avons identifié une protéine à domaine Alba, LiAlba20, liant l’ARNm de la delta-amastine dans une région proche de l’URE. La suppression de cette protéine réduit l’accumulation du transcrit au stade amastigote. Ainsi, deux mécanismes complémentaires sont responsables de l’expression différentielle de ce transcrit. Le génome de Leishmania code pour une seconde protéine à domaine Alba, LiAlba13. Ces protéines interagissent ensemble, mais LiAlba13 n’affecte pas l’abondance de l’ARNm de la delta-amastine. Les protéines Alba ont une évolution exceptionnelle puisqu’elles stabilisent l’ADN chez les Archaea, et sont retrouvées dans les complexes RNase P/MRP chez les eucaryotes supérieurs. Nos résultats montrent qu’elles régulent l’expression de protéines spécifiques du stade amastigote, ce qui concorde avec les récents travaux chez d’autres parasites protozoaires. Ces protéines sont cytoplasmiques dans les deux stades de développement. Cependant, pendant la différenciation, elles s’accumulent dans le flagelle et le nucléole, respectivement décrits comme senseur et coordinateur de la réponse au stress. Nos travaux suggèrent donc l’implication du flagelle et du nucléole dans la coordination de la régulation de facteurs de virulence pendant la différenciation du parasite. / The Leishmania genus encompasses protozoan parasites which are transmitted through the bite of an insect vector and are responsible for leishmaniasis. The Leishmania life cycle alternates between promastigote forms within the gut of the insect vector and amastigotes which multiply in the phagolysosomal vacuoles of the mammalian host’s macrophages. Delta-amastins are part of a multigenic family of membrane proteins that potentially act in parasite virulence. One of the delta-amastin's exclusive expression in the intracellular stage is mediated by mRNA accumulation and translation stimulation, both taking place in the amastigote stage. The aim of this thesis is to characterize the mechanisms implicated in the differential expression of delta-amastin mRNA. Leishmania splits early in evolution from other eukaryotes and this split correlates with many functional differences, including the absence of transcriptional control of gene expression. Our hypothesis is that the presence of a uridine-rich element (URE) within the 3’ untranslated region (3’UTR) of the transcript might be implicated in an mRNA decay mechanism. We reveal that the URE is responsible for a fast mRNA decay only in the promastigote stage, performed by an unusual deadenylation-independent pathway. We next identified an Alba domain protein, LiAlba20, which binds to the delta-amastin mRNA in a region flanking the URE. Depletion of this protein leads to a reduced mRNA accumulation in the amastigote stage specifically. Therefore, we identified two complementary mechanisms taking part in the transcript’s differential expression. The Leishmania genome encodes a second Alba domain protein, LiAlba13. These proteins interact together, but LiAlba13 does not affect the delta-amastin mRNA level during the parasite life cycle. Alba domain proteins have a remarkable evolution, being involved in DNA stabilization in Archaea and subunits of the RNAses P/MRP complexes in higher eukaryotes. In addition, our data show that these proteins regulate stage-specific protein expression, which is in agreement with recent works in other protozoan parasites. Alba domain proteins are constitutively expressed in the cytoplasm of both parasite life cycle stages. Nevertheless, during the differentiation, those proteins accumulate in flagellar and nucleolus compartments, respectively described as sensor and stress response coordinators in higher eukaryotes. Our work suggests that the flagellum is implicated in the coordination of stage-specific transcript expression in response to stress in Leishmania.
5

Étude globale des gènes différemment exprimés entre les différents stades de vie et espèces du parasite leishmania à l'aide d'approches génomiques

Rochette, Annie January 2008 (has links)
Le parasite protozoaire Leishmania possède un cycle de vie dimorphique; le stade promastigote présent chez l'insecte vecteur et le stade amastigote présent dans les phagolysosomes des macrophages de l'hôte vertébré. L'étude des gènes exprimés préférentiellement ou spécifiquement au stade intracellulaire pourrait nous en apprendre d'avantage sur les mécanismes de survie du parasite à l'intérieur des macrophages. Parmi les gènes exprimés préférentiellement au stade amastigote nous avons identifié la famille des amastines qui codent pour des protéines de surface. Cette famille est présente chez plusieurs espèces de Leishmania où on retrouve en moyenne 50 membres. Toutes les amastines possèdent une séquence signature de 11 acides aminés qui leur est unique. La majorité des amastines sont plus abondantes au stade amastigote et cette régulation implique des séquences situées en 3'UTR. La comparaison des génomes de deux espèces de Leishmania causant des pathologies distinctes, soit L. major et L. infantum a révélé une grande conservation au niveau de la synténie du génome. Cela suggère que ce qui est responsable de chaque pathologie se situe au niveau des quelques gènes uniques à chaque espèce ou encore au niveau de l'expression différentielle des gènes communs. Pour identifier de nouveaux gènes exprimés au stade intracellulaire et également identifier des gènes impliqués dans le tropisme, une analyse du transcriptome entier a été effectuée à l'aide de la technologie de puces à ADN. Lors de cette étude, où des parasites intracellulaires ont été utilisés, les résultats ont montré que chez L. infantum, 7.1 % des gènes étaient différemment exprimés entre les deux stades tandis que 9.3% l'étaient chez L. major. Parmi ces gènes modulés très peu (=10%) sont communs aux deux espèces. Une expérience indépendante avec les puces a été réalisée avec des parasites axéniques de L. infantum, pour comparer les deux stades de développement mais aussi pour évaluer la pertinence du système de culture axénique pour les amastigotes par rapport aux amastigotes obtenus de macrophages ou d'animaux infectés. Cette expérience a révélé que 12.8% des gènes étaient modulés entre les deux stades et que parmi ces gènes très peu étaient en commun avec ceux identifiés chez les amastigotes intracellulaires.
6

Studies Aimed at the Synthesis of Anti-Infective Agents

Kanwar, Ankush 20 April 2018 (has links)
Infectious diseases continue to be a major concern worldwide. They are the second leading cause of death after heart disease. Factors such as an increasing global population, travel, urbanization, global climate change and evolution of pathogens have made infectious diseases more common. Infectious diseases, particularly neglected tropical diseases (NTDs) result in many deaths worldwide. Malaria and leishmaniasis are two common (NTDs) which affect low income countries around the globe. Low cost drugs with novel mechanism of action are required to tackle the growing resistances of parasites against current drugs used in the developing world, where most of the cases occur. The first part of this manuscript (chapters 1 - 3) describes the synthesis of novel analogs active against Leishmania donovani parasite which causes leishmaniasis. Leishmaniasis is a vector-borne complex group of diseases transmitted through the bite of an infected female sand-fly. Its clinical manifestations range from the less severe (cutaneous) to fatal (visceral) forms depending upon infecting species, immunity of host and the environment. Reports have suggested the role of Heat shock protein 90 (Hsp 90) in the differentiation of the Leishmania parasite from the promastigote stage to the pathogenic amastigote stage inside the host. A series of tetrahydro-indazole, tetrahydro-pyrazolo pyridine and radicicol hybrid compounds were prepared based on known Hsp 90 inhibitors, SNX2112 and NVP-AUY922. The synthetic approach allowed us to generate a diverse library of analogs which were used to probe the hydrophobic pocket of Hsp 90 active site. The most active compound, was found to be twice more active as the clinically used drug, Miltefosine, in an infected macrophage assay with an IC50 = 0.88 µM. The second part of this manuscript (chapters 4 - 5) describes the synthesis of xanthurenic acid analogs as antimalarial drugs. Xanthurenic acid (XA) is a vital component for the gametogenesis of the Plasmodium inside the mosquito’s gut. Gametogenesis plays an important part in the continuation of the parasite’s life cycle. A series of xanthurenic acid analogs were synthesized with the aim of inducing premature exflagellation of the microgametes, thus blocking the key step required for the transmission of parasites from humans to the mosquito. A biotinylated xanthurenic acid analog and a clickable xanthurenic acid analog were also synthesized which will help us investigate the mechanism of action of xanthurenic acid in inducing gametogenesis in mosquito. In the preliminary screening efforts in an exflagellation assay, analog 4.40 showed promising activity and was more active in inducing exflagellation than xanthurenic acid. An exflagellation assay of other analogs is currently being pursued. Further investigations into the molecular target and mechanism of action are underway with the biotinylated xanthurenic acid analog.
7

Identificação de ligantes da metacaspase de Leishmania (Leishmania) amazonensis pela técnica de \"Phage Display\". / Identification of ligands of Leishmania (Leishmania) amazonensis metacaspase using Phage Display.

Mauricio Scavassini Penã 23 November 2012 (has links)
Durante o ciclo de vida da Leishmania, amastigotas vivem no interior de fagolisossomas de células fagocíticas de hospedeiros vertebrados, enquanto promastigotas vivem no interior do vetor invertebrado. Proteases intracelulares como as caspases são as principais efetoras no processo apoptótico. Metacaspases (MCAs) são formas evolutivas distantes das caspases de metazoários, presentes em protozoários, plantas e fungos, e vistas como potenciais alvos para combate dos parasitas sem prejuízo do hospedeiro. Ligantes e moduladores das metacaspases são até hoje desconhecidos. O Phage Display é uma técnica baseada na expressão de proteínas sintéticas nos capsidíos de fagos, usada com o propósito de selecionar ligantes de proteínas, células ou tecidos. Produzimos a metacaspase recombinante de Leishmania L. amazonensis e aplicamos Phage Display para buscar peptídeos ligantes dessa enzima. Esses peptídeos permitiram identificar potenciais proteínas ligantes da MCA, como quinases e cinesinas, que fornecem informações sobre a regulação e controle de sua atividade. Futuramente testaremos se peptídeos ativadores da MCA poderão induzir apoptose do parasita e serem usados como drogas para o tratamento da leishmaniose. / During its life cycle, Leishmania amastigotes live inside phagolysosomes of phagocytic cells of vertebrate hosts, while promastigotes live inside the invertebrate vector. Intracellular proteases such as caspases are key effectors in the apoptotic process. Metacaspases (MCAs) are distant evolutionary forms of metazoan caspases found in protozoa, plants and fungi, and seen as potential targets to destroy the parasites without damage to the host. Ligands and modulators of metacaspases are so far unknown. Phage Display is a technique based on the expression of synthetic proteins in the phage capsid, and is used for selecting ligands of proteins, cells or tissues. We have produced the recombinant metacaspase of Leishmania (L.) amazonensis and employed Phage Display to find peptide ligands of this enzyme. These peptides led to the identification of potential binding proteins of the MCA, such as kinases and kinesin, which provide information about the regulation and control of MCA´s activity. In the future we will test whether peptide activators of MCA nduce apoptosis of the parasite and can be used as drugs for the treatment of leishmaniasis.
8

Synthesis of Novel Agents for the treatment of Infectious and Neurodegenerative diseases

Eduful, Benjamin Joe 02 April 2018 (has links)
Infectious and neurodegenerative diseases continue to be a major concern worldwide. In spite of the great advances in drug therapy for treating various infectious and neurodegenerative diseases, there is still an urgent need for new and improved drugs due to increasing drug resistance among pathogens, emergence of new pathogens, ease of transmission of infections, ineffective available treatments, toxicity associated with current standard of care, aging populations and the lack of better alternative treatment options. The first part of this manuscript (chapters 1 - 5) describes the synthesis of novel agents active against Leishmania donovani. According to the World Health Organization (WHO), a significant number of deaths worldwide can be attributed to infectious diseases – particularly neglected tropical diseases (NTDs), one of which is leishmaniasis - a complex and clinically diverse disease transmitted through the bite of an infected female phlebotomine sand-fly. The pathogen that causes leishmaniasis develops through a complex life cycle via different morphological changes. Its clinical presentations range from the less severe (cutaneous) to lethal/fatal (visceral) forms depending upon the level of systemic involvement, infecting species and the endemic environment. Treatments (and vaccines) must be species-specific to be particularly effective since sensitivity to commonly used drugs is largely species-specific. Heat shock protein 90 (Hsp 90) has been shown to promote the differentiation of the protozoan parasite that causes leishmaniasis from the promastigote stage to the amastigote pathogenic stages. To this end a series of compounds were prepared based on known Hsp 90 inhibitors, SNX2112 and XL888. The synthetic approach allows the probing of a hydrophobic pocket and rapid access to a collection of anti-leishmanial compounds. The most active compound, was found to be more than twice as active as the climivally used drug, miltefosine, in an infected J774 macrophage at IC50 = 0.65 µM. The second part of this manuscript (chapters 6 - 9) describes the synthesis novel anti-Alzheimer’s agents. Alzheimer’s disease is a progressive neurodegenerative disease believed to be caused by tau hyperphosphorylation and plaque aggregation in the brain. It is known to affect about 44 million people worldwide and it is marked as the 6th leading cause of death in the United States. Slingshot homology-1 (SSH1) proteins, important protein phosphatases, are promising targets for the discovery of a new generation of small molecule inhibitors as treatment for Alzheimer’s disease, since SSH1 is known to contribute to both tau hyperphosphorylation and plaque aggregation in the brain. Through structure and activity relationships (SAR) studies, two (2) series of compounds were synthesized, thiazoles and pyridones, bearing a carboxylic acid or phosphonic acid functionality as inhibitors of SSH1 enzymes. In the preliminary screening efforts against SSH1 phosphatase activity, the thiazole series were found to be more potent at inhibiting the phosphatase activity than the pyridone series. Among the active thiazole series, eight (8) analogs exhibited significant inhibitory activity over the initial hit compound, observed via phosphatase inhibition curves (using a pNPP phosphatase assay). Further investigations into the molecular target (SSH1) are currently underway.
9

Avaliação do potencial antileishmania dos compostos naturais isolados ácido úsnico, cumarin, quercetina e reserpina sobre as formas promastigotas e amastigotas de Leishmania Chagasi

Martins, Amely Branquinho 19 August 2008 (has links)
Made available in DSpace on 2015-05-14T12:59:23Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 4714773 bytes, checksum: e1d2845582482ef401e124b0aa366365 (MD5) Previous issue date: 2008-08-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Leishmaniases are a complex of infectious parasitic diseases caused by species of the Leishmania genus. These diseases comprise a large spectrum of manifestations ranging from localized self-healing cutaneous lesions to fatal visceral infections. In Brazil, the visceral leishmaniasis is caused by Leishmania chagasi which affects ca. 2 million people every year with estimated 90% of cases occurring in Northeastern. Current treatments of leishmaniasis are based on first line pentavalent antimonials or other drugs like amphotericin B and pentamidine. Toxicity of those drugs, their high sideeffects, besides the high cost of treatment, difficulty for administering them and the surge of resistance are their great drawbacks. These aspects have stimulated the search for new leishmanicide agents, like the isolation and identification of natural compounds which could provide new therapeutic models for the treatment of leishmaniases. It was aimed in the present work a comparative evaluation of potentially antileishmania natural isolate compounds and their action on promastigote and amastigote forms of Leishmania chagasi by observing the cycle of this parasite in vitro. Assays were carried out with usnic acid, coumarin, quercetin, and reserpine which showed to have significant antileishmanial activity on promastigote forms of Leishmania chagasi, presenting IC50 equal to 0.0417; 1.07; 0.271 and 1.7 mM, respectively. It was possible in our experimental conditions of standardized cultivation of parasites, to establish their life cycle in vitro, by observing their metamorphosis from promastigote to mastigote. The in vitro life cycle was characterized by parasite cultivations with establishment of: 1) lag (initial), log or exponential and stationary stages of promastigotes; 2) transformation of promastigotes to intracellular amastigotes by infection of murine macrophages; this step favoured the promastigotes infectivity; and 3) amastigote isolation and transformation to promastigotes completing the cycle. Furthermore, it was also possible to establish the in vitro transformation of promastigotes in axenic amastigotes of Leishmania chagasi and its use for the evaluation of antileishmanial activity. In this case, the natural compound usnic acid exhibited antileishmanial activity against axenic amastigote forms with IC50 of 1,16 mM. It was not observed any similarity of IC50 on antileishmanial activity of usnic acid and pentamidine between the axenic amastigote and promastigote forms. This demonstrates that it is important to characterize the action of compound on each life form of the parasites. It is concluded that all assayed compounds carried out in this work had antileishmanial activity on promastigote forms, mainly, and the effect of concentration was different between promastigote, of lower IC50 values, and axenic amastigotes forms, of greater IC50 values. / As leishmanioses constituem-se por um complexo de doenças infectoparasitárias, causadas por parasitas do gênero Leishmania, e apresentam um espectro de sintomas variando de simples lesões cutâneas de cicatrização espontânea a lesões viscerais letais. A leishmaniose visceral, causada pela espécie Leishmania chagasi, no Brasil infecta cerca de duas mil pessoas por ano, sendo cerca de 90% dos casos no Nordeste. Os tratamentos atuais são baseados em compostos antimôniais pentavalentes, ou na utilização de outras drogas como a anfotericina B e a pentamidina. A toxicidade desses agentes, com efeitos colaterais graves, o alto custo dos tratamentos, as dificuldades de administração e o surgimento de resistência são grandes desvantagens, tornando essencial a busca por novos agentes leishmanicidas, como a identificação de compostos naturais isolados, que podem fornecer novos modelos terapêuticos no tratamento das leishmanioses. A presente pesquisa teve como objetivo avaliar comparativamente o potencial antileishmania de compostos naturais isolados sobre as formas promastigotas e amastigotas de Leishmania chagasi, estabelecendo o ciclo do parasito in vitro. Os compostos naturais ensaiados, ácido úsnico, cumarina, quercetina e reserpina apresentaram significativa atividade antileishmania sobre as formas promastigotas de Leishmania chagasi, com IC50 igual a 0,0417; 1,07; 0,271 e 1,7 mM respectivamente. Nas condições de cultivo padronizadas no presente estudo foi possível estabelecer o ciclo de vida in vitro dos parasitos, com passagem destes pelas duas principais formas de vida: promastigotas e amastigotas. O ciclo in vitro foi caracterizado pelo cultivo das promastigotas com estabelecimento: 1) das fases: lag (inicial), log ou exponencial e estacionária dos parasitos; 2) transformação das formas promastigotas em amastigotas intracelulares, pela infecção de macrófagos murinos, o que favoreceu a infectividade das promastigotas; e 3) pelo isolamento das formas amastigotas e transformação destas em promastigotas novamente, completando o ciclo. Além disto, foi também possível estabelecer a transformação in vitro das promastigotas em amastigotas axênicas de L. chagasi e o cultivo das formas axênicas para ensaios de ação antileishmania sobre essa forma. Nesse caso, o composto natural isolado ácido úsnico apresentou atividade antileishmania sobre amastigotas axênicas de L. chagasi, com IC50 igual a 1,16 mM. Não foi observada similaridade da IC50 na atividade antileishmania do ácido úsnico e da pentamidina entre as formas amastigotas axênicas e promastigotas, o que demonstra a importância de caracterizar a ação dos compostos sobre cada forma de vida dos parasitos. Conclui-se que os compostos isolados têm atividade antileishmania sobre as formas promastigotas e o ácido úsnico sobre as formas amastigotas axênicas de L. chagasi.

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