Compromised calcium homeostasis in the central nervous system (CNS) is implicated as a major contributor in the pathology of neurodegeneration. Dysregulation of Ca2+ homeostasis initiates downstream Ca2+–dependent events that lead to apoptotic and/or necrotic cell death. Increases in the intracellular free calcium concentration ([Ca2+]i) may be the result of Ca2+ influx from the extracellular environment or Ca2+ release from intracellular Ca2+ stores such as the endoplasmic reticulum (ER). Influx from the extracellular environment is controlled predominantly by voltage gated calcium channels (VGCC), such as L–type calcium channels (LTCC) and ionotropic glutamate receptors, such as the N–methyl–D–aspartate (NMDA) receptors. Ca2+ release from the ER occurs through the inositol–1,4,5–triphosphate receptors (IP3Rs) or ryanodine receptors (RyRs) via IP3–induced or Ca2+–induced mechanisms. Mitigation of Ca2+ overload through these Ca2+ channels offers an opportunity for pharmacological interventions that may protect against neuronal death. In the present study the ability of a novel series of polycyclic compounds, both the pentacycloundecylamines and triquinylamines, to regulate calcium influx through LTCC was evaluated in PC12 cells using calcium imaging with Fura–2/AM in a fluorescence microplate reader. We were also able for the first time to determine IC50 values for these compounds as LTCC blockers. In addition, selected compounds were evaluated for their ability to offer protection in apoptosis–identifying assays such as the lactate dehydrogenase release assay (LDH–assay), trypan blue staining assay and immunohistochemistry utilizing the Annexin V–FITC stain for apoptosis. We were also able to obtain single crystal structures for the tricyclo[6.3.0.02,6]undecane–4,9–dien–3,11–dione (9) and tricyclo[6.3.0.02,6]undecane–3,11–dione (10) scaffolds as well as a derivative, N–(3–methoxybenzyl)–3,11–azatricyclo[6.3.0.02,6]undecane (14f). We also evaluated the possibility that the polycyclic compounds might be able to modulate Ca2+ flux through intracellular Ca2+ channels. Computational methods were utilized to accurately predicted IC50 values and develop a QSAR model with marginal error. The linear regression model delivered r2 = 0.83, which indicated a favorable correlation between the predicted and experimental IC50 values. This model could thus serve as valuable predictor for future structural design and optimization efforts. Data obtained from the crystallographic analysis confirmed the NMR–data based structural assignments done for these compounds in previous studies. Obtaining structural information gave valuable insight into the differences in size and geometric constrains, which are key features for the LTCC activity of these compounds. vii In conclusion, we found that all of the compounds evaluated were able to attenuate Ca2+ influx through the LTCC, with some compounds having IC50 values comparable with known LTCC blockers such as nimodipine. Representative compounds were evaluated for their ability to afford protection against apoptosis induced by 200 ?M H2O2. With the exception of compound 14c (the most potent LTCC blocker in the series, IC50 = 0.398 ?M), most compounds were able to afford protection at two or more concentrations evaluated. Compound 14c displayed inherent toxicity at the highest concentrations evaluated (100 ?M). We concluded that compounds representing both types of structures (pentacycloudecylamines and triquinylamines) have the ability to attenuate excessive Ca2+ influx through the LTCC. In general the aza–pentacycloundecylamines (8a–c) were the most potent LTCC blocker which also had the ability to offer protection in the cell viability assays. However, NGP1–01 (7a) had the most favorable pharmacological profile overall with good activity as an LTCC blocker (IC50 = 86 ?M) and the ability to significantly attenuate cell death in the cell viability assays, exhibiting no toxicity. In addition to their ability to modulate Ca2+ influx from the extracellular environment, these compounds also displayed the ability to modulate Ca2+ flux through intracellular Ca2+ channels. The mechanisms by which they act on intracellular Ca2+ channels still remains unclear, but from this preliminary study it would appear that these compounds are able to partially inhibiting Ca2+–ATPase activity whilst possibly simultaneously inhibiting the IP3R. In the absence of extracellular Ca2+ these compounds showed the ability in inhibit voltage–induced Ca2+ release (VICaR), possibly by modulating the gating charge of the voltage sensor being the dihydropyridine receptors. In future studies it might be worthwhile to do an expanded QSAR study and evaluate the aza–pentacycloundecylamines. To clarify the mechanisms by which the polycyclic compounds interact with intracellular Ca2+ channels we should examine the direct interaction with the individual Ca2+ channels independently. The polycyclic compounds evaluated in this study demonstrate potential as multifunctional drugs due to their ability to broadly regulate calcium homeostasis through multiple pathways of Ca2+ entry. This may prove to be more effective in diseases where perturbed Ca2+ homeostasis have devastating effects eventually leading to excitotoxicity and cell death. / Thesis (Ph.D. (Pharmaceutical Chemistry))--North-West University, Potchefstroom Campus, 2012.

O estuário de Santos abriga o maior porto da América Latina e um dos maiores complexos industriais do Brasil. Na década de 1970 foi considerado um dos maiores exemplos de degradação ambiental em ambientes costeiros, e apesar da melhora na qualidade ambiental observada nos últimos anos algumas áreas deste estuário apresentam sedimentos ainda altamente contaminados com compostos tóxicos e genotóxicos, especialmente os Hidrocarbonetos Policíclicos Aromáticos (HPA). Operações de dragagem para manutenção das atividades portuárias são necessárias e consequentemente durante este processo pode ocorrer a ressuspensão de contaminantes presentes nesses sedimentos, tornando-os disponíveis novamente na coluna d\'água. Desta forma é interessante ter uma estratégia eficiente e aplicável no monitoramento da qualidade dessas águas. O Blue rayon (BR) é um adsorvente seletivo para compostos policíclicos com três ou mais anéis fundidos em sua molécula e tem sido utilizado com sucesso no monitoramento de HPA e atividade mutagênica em ambientes aquáticos. Este trabalho teve como objetivo padronizar o uso da técnica de Blue rayon in situ ancorado, onde as fibras são fixas a uma distância padronizada dos sedimentos, associada ao teste de Salmonella/microssoma em microssuspensão a ser aplicada no monitoramento das águas desse estuário. Foram selecionados três pontos de amostragem com diferentes características e sedimentos com variados níveis de contaminação. As duas campanhas iniciais foram realizadas com o objetivo de avaliar a eficiência do BR e de escolher a linhagem de Salmonella mais sensível aos compostos mutagênicos possivelmente presentes nos extratos obtidos bem como verificar a presença de HPA. As cinco campanhas posteriores foram realizadas para verificar o comportamento e a eficiência da estratégia previamente definida no monitoramento das águas desse estuário utilizando experimentos de dose resposta. Os resultados obtidos nas duas primeiras campanhas mostraram que as águas do ponto 1, que contém os sedimentos mais contaminados e recebe os efluentes da COSIPA, apresentam maior contaminação por HPA e atividade genotóxica mais elevada que o ponto 2. Também foi possível determinar que a linhagem de Salmonella YG1041 foi a mais sensível para detectar atividade mutagênica tanto no ponto 1 quanto no ponto 2. Nas cinco campanhas subsequentes as maiores potências mutagênicas foram também observadas no ponto 1 com valores máximos de 5.100 e 36.000 revertentes/g de BR para a linhagem YG1041 na ausência e na presença de ativação metabólica (S9) respectivamente. Nos pontos 2 e 3 as potências observadas foram similares entre si, com valores em torno de 1.000 revertentes/g de BR. Com base nos resultados obtidos nas duas etapas deste trabalho pode-se concluir que a o Blue rayon utilizado in situ a uma distância padronizada dos sedimento associado ao teste de Salmonella/microssoma em microssuspensão com a linhagem YG1041 na presença e na ausência de ativação metabólica (S9) é uma ferramenta que pode ser aplicada no monitoramento da qualidade do estuário de Santos. / Santos estuary is the major Latin American harbor and one of the largest industrial complex of Brazil. In the 1970s, it was considered one of the major examples of coastal degradation. Due to enforcement actions the quality of the environment has improved in the last years in relation to the chemical parameters and toxicity but unfortunately the sediment is still contaminated with toxic and genotoxic compounds especially Polycyclic Aromatic Hydrocarbons (PAHs). For the maintenance of the port activities sediment dredging is needed and during this process contaminants resuspension can occur, leading to the contamination of the water column. Therefore it is interesting to have an efficient strategy that can be used for the water quality monitoring of this area. The Blue rayon is a selective adsorbent to polycyclic compounds containing three or more fused rings and has been successfully used in the monitoring of PAHs and mutagenic activity in aquatic environments. The objective of this work was to evaluate a modified blue rayon hanging technique, denominated in this work \"Blue rayon anchored technique\", where the fibers are placed at a fixed distance from the sediment, associated with the Salmonella/microsome microsuspension assay in order to monitor the water quality of Santos estuary. Three sites with different sources and sediment contamination levels were selected in this study. Two initial samplings were performed in order to evaluate the efficiency of the BR modified technique and find the most sensitive strain of Salmonella typhimurium to the mutagens possibly present in the those waters as well as verify the presence of PAHs. Five subsequent samplings were performed to verify the performance and efficiency of the defined strategy in the estuary water quality monitoring using dose response experiments. In the two initial samplings, the water from the site containing the most contaminated sediment and under influence of COSIPA (site 1) presented higher mutagenic activity and higher levels of PAHs. It was also possible to verify the highest sensitivity of the YG1041 strain in the detection of the mutagenic activity in both sites analyzed. In the subsequent five samplings, higher mutagenic potencies were again observed for site 1, reaching 5,100 and 36,000 revertants per gram of BR for the YG1 041 strain in the absence and presence of S9 respectively. Sites 2 and: presented similar potencies, around 1000 revertants per gram of BR. Based on the obtained results we can conclude that the Blue rayon anchored technique associated with the Salmonella/microsome microsuspension assay with the YG1041 strain in the presence and absence of S9 is an suitable tool to monito Santos estuarine waters.

Among heat shock proteins, Hsp90 is unusual because it is not required for the proper folding of most cellular proteins but rather is disproportionally linked to the activation of signal transduction proteins including over forty kinases and many steroid hormone receptors. Mutated forms of many Hsp90 clients are causative agents in cancer, making Hsp90 a promising pharmacological target. Many small molecular inhibitors have been identified that competitively bind to the ATP binding site of Hsp90, some of which are in clinical trials as anticancer agents. Although the activation of kinase and hormone receptor clients by Hsp90 and its co-chaperones has been extensively studied, the molecular mechanism of client protein activation is poorly understood. Hsp90 is a dimeric chaperone containing three domains: the N-terminal (N) and middle (M) domains contribute directly to ATP binding and hydrolysis and the C-terminal (C) domain mediates dimerization. At physiological concentration, Hsp90 predominantly forms dimers, but the possibility that full-length monomers might also function in cells has not been tested. In Chapter 3, we used a single-chain strategy to design a full-length Hsp90 monomer (NMCC). The resulting construct was predominantly monomeric at physiological concentration and did not function to support yeast viability as the sole Hsp90. NMCC Hsp90 was also defective at ATP hydrolysis and the activation of kinase and steroid hormone receptor clients in yeast cells. The ability to support yeast growth was rescued by the addition of a coiled-coil dimerization domain, indicating that the parental single-chain construct is functionally defective because it is monomeric. After finding that a full-length Hsp90 monomer containing only one ATPase site was unable to support yeast viability or activate Hsp90 clients, we set out to further explore the role of ATPase activity in client protein activation. Approximately 10 % of the yeast proteome binds to Hsp90 making it important to study Hsp90 function in the cellular environment where all binding partners are present. In Chapter 4, we observed that co-expression of different Hsp90 subunits in Saccharomyces cerevisiae caused unpredictable synthetic growth defects due to cross-dimerization. We engineered super-stabilized Hsp90 dimers that resisted cross-dimerization with endogenous Hsp90 and alleviated the synthetic growth defect. We utilized these super-stabilized dimers to analyze the ability of ATPase mutant homodimers to activate known Hsp90 client proteins in yeast cells. We found that ATP binding and hydrolysis by Hsp90 are both required for the efficient maturation of the glucocorticoid hormone receptor (GR) and v-src confirming the critical role of ATP hydrolysis in the maturation of steroid hormone receptors and kinases in vivo. In addition to its role in the activation of signal transduction client proteins, Hsp90 has been shown to suppress the in vitro aggregation of numerous hard-to-fold proteins. In Chapter 5, we examine the role of charge in Hsp90 anti-aggregation activity. The charge on Hsp90 is largely concentrated in two highly acidic regions. We found that deletion of both charge-rich regions dramatically impaired Hsp90 anti-aggregation activity. Addition of an acid-rich region with a distinct amino acid sequence to our double-deleted Hsp90 construct rescued the anti-aggregation activity of Hsp90 indicating that the net charge contributes to its anti-aggregation activity. The in vitro anti-aggregation activity of Hsp90 studied in Chapter 5 occurs in the absence of ATP. However, all of the biologically important functions of Hsp90 in cells identified to date, including the maturation of kinases and nuclear steroid hormone receptors, clearly require ATP hydrolysis. Why does Hsp90 robustly hinder the aggregation of hard-to-fold proteins without ATP in vitro, but in vivo uses ATP hydrolysis for all of its essential functions? By utilizing separation of function Hsp90 variants (that specifically lack in vitro anti-aggregation activity) we have begun to address this question. We find that anti-aggregation deficient Hsp90 is unable to support yeast growth under stressful conditions, potentially due to reduced cellular expression. Interestingly, the ATP-independent anti-aggregation activity of Hsp90 has no measureable impact on cellular function. Thus, hindering the aggregation of most hard-to- fold proteins by Hsp90 (independent of ATP hydrolysis) does not appear to be important for cell function. These results suggest a cellular model where the Hsp40/60/70 machinery is responsible for hindering the aggregation of most hard-to-fold proteins while Hsp90 assists in the maturation of a select set of clients in an ATP-dependent fashion, potentially aided by its inherent anti-aggregation properties.

Grâce à l’utilisation de catalyseurs sacrifiables issus, la plupart du temps, du groupe principal ou de la première période des éléments de transition, des nouvelles méthodologies de synthèse pour accéder à des molécules complexes ont été développées au cours de cette thèse. i) Des bicyclolactones ont été synthétisées par addition intramoléculaire de β-cétoesters sur des diènes-1,3 catalysée par un système coopératif de Bi(OTf)₃ et d’HOTf. ii) le motif 7-alcynylcycloheptatriène a été étudié et a permis d’accéder sélectivement à différents produits issus soit d’une cycloisomérisation d’énynes-1,6 ou d’une hydroarylation d’allènes, en fonction du caractère dur ou mou de l’acide de Lewis utilisé. iii) Ce motif a ensuite été utilisé comme plateforme pour accéder à des molécules polycycliques en présence d’acides de Lewis ou à des bromophénylallènes en présence d’un agent de bromation. Les bromoallènes ainsi formés ont pu être engagé dans des réactions de couplages C-C et C-N ou dans une réaction de CH-propargylation. iv) La N-éthylation réductrice d’imines en présence d’éthanol et d’un complexe de fer facilement accessible a été étudiée et a conduit à la formation d’amines tertiaires portant trois substituants différents. / Due to the use of sacrificial catalysts, most of the time derived from main group elements or 1st row transition metal, new methodologies were developed in this thesis to access complex molecules. i) Bicyclolactones were synthesized by an intramolecular addition of β-ketoesters into 1,3-dienes catalyzed by a cooperative Bi(OTf)₃ / HOTf catalytic system. ii) The 7-alkynylcyclohepatriene moiety was studied and afforded different products provided by a cycloisomerization of 1,6-enynes or an hydroarylation of allenes. The selectivity of this reaction is dependent of the soft or hard character of the Lewis acids engaged. iii) Afterward, the 7-alkynylcycloheptatriene moeity was used as a plateform to access various polycyclic molecules in presence of Lewis acids or bromophenylallenes in presence of a bromation agent. Thus the bromoallene formed can be engaged in C-C and C-N cross coupling reactions or in a CH propargylation reaction. iv) The reductive ethylation of imines using ethanol and a simple iron complex was developed and led to the formation of tertiary amines with three different substituents.

<p>Systemic fungal infections brought about by <em>Cryptococcus</em> species are associated with some of the highest mortality rates of any infectious disease. Alarmingly these pathogens have overtaken tuberculosis as the second greatest killer among Sub-Saharan AIDS patients and are an emerging disease among immunocompetent populations on the Pacific Coast of North America. This clinical threat has been exacerbated by our inability to discover novel compounds that specifically target fungal cellular architecture at the genus level. To confront this challenge, we have made a concerted effort to biologically prospect the vast chemical potential of Actinomycete bacteria isolated from diverse and underexplored niches around the world. A novel phenotypic screen was developed whereby bacterial small molecule producers were co-cultured on agar plates in an intimate setting with evolutionary distant fungal pathogens <em>Candida albicans</em> and <em>Cryptococcus neoformans</em>. Diffusible small molecules released by the organisms created a signaling environment that stimulated profound phenotypic changes both in the Actinomycetes and the pathogens. We were able to discern a unique relationship whereby the growth of <em>C. neoformans</em> was specifically inhibited by Nigerian soil Actinomycete isolate curated as WAC 2288. Further bioactivity guided purification and chemical analysis lead to the identification of ibomycin, a previously undescribed 34 membered macrolactone decorated with seven sugar moieties. A draft genome of WAC 2288 revealed a 140kb gene cluster containing 12 type I PKS modules and downstream capacity to generate rare sugars are responsible for ibomycin biosynthesis. Purification of ibomycin analogs has revealed that the terminal vancosamine on the molecule is dispensable for bioactivity, establishing a chemical antecedent for target identification through affinity chromatography. Throughout these studies the unprecedented anticryptococcal activity of ibomycin is consistently recapitulated. Future work on the molecule may validate ibomycin as an effective antifungal therapy.</p> / Master of Science (MSc)

The dissertation describes a novel method for plant drug discovery based on mutation and selection of plant cells. Despite the industry focus on chemical synthesis, plants remain a source of potent and complex bioactive metabolites. Many of these have evolved as defensive compounds targeted on key proteins in the CNS of herbivorous insects, for example the insect dopamine transporter (DAT). Because of homology with the human DAT protein some of these metabolites have high abuse potential, but others may be valuable in treating drug dependence. This dissertation redirects the evolution of a native Lobelia species toward metabolites with greater activity at this therapeutic target, i.e. the human DAT. This was achieved by expressing the human DAT protein in transgenic plant cells and selecting gain-of-function mutants for survival on medium containing a neurotoxin that is accumulated by the human DAT. This created a sub-population of mutants with increased DAT inhibitory activity. Some of the active metabolites in these mutants are novel (i.e. not detectable in wild-type cells). Others are cytoprotective, and also protect DAergic neurons against the neurotoxin. This provides proof-of-concept for a novel plant drug discovery platform, which is applicable to many different therapeutic target proteins and plant species.

Sepsis is the leading cause of death among critically ill patients and the 10th most common cause of death overall in the United States. The mortality rates increase with severity of the disease, ranging from 15% for sepsis to 60% for septic shock. Patient with sepsis can present varied clinical symptoms depending on the personal predisposition, causal microorganism, organ system involved, and disease severity. To facilitate sepsis diagnosis, the first sepsis consensus definitions was published in 1991 and then updated in 2001. Early recognition of a sepsis patient followed with timely and appropriate treatment and management strategies have been shown to significantly reduce sepsis-related mortality, and allows care to be provided at lower costs. Despite the rapid progress in the knowledge of pathophysiological mechanisms of sepsis and its treatment in the last two decades, identifying patient with sepsis and therapeutic approaches to sepsis and its complications remains challenging to critical care clinicians. Hence, the objectives of this thesis were to 1) evaluate the test characteristics of the two sepsis consensus definitions and delineate the differences in patient profile among patients meeting or not meeting sepsis definitions; 2) determine the relationship between the changes in several physiological parameters before sepsis onset and sepsis, and to determine whether these parameters could be used to identify sepsis in critically ill adults; 3) evaluate the effect of corticosteroids therapy on patient mortality. Data used in this thesis were prospectively collected from an electronic medical record system for all the adult patients admitted into the seven critical care units (ICUs) in a tertiary medical center. Besides analyzing data at the ICU stay level, we investigated patient information in various time frames, including 24-hour, 12-hour, and 6-hour time windows. In the first study of this thesis, the 1991 sepsis definition was found to have a high sensitivity of 94.6%, but a low specificity of 61.0%. The 2001 sepsis definition had a slightly increased sensitivity but a decreased specificity, which was 96.9% and 58.3%, respectively. The areas under the ROC curve for the two consensus definitions were similar, but less than optimal. The sensitivity and area under the ROC curve of both definitions were lower at the 24-hour time window level than those of the unit stay level, though the specificity increased slightly. At the time window level, the 1991 definitions performed slightly better than the 2001 definition. In the second study, minimum systolic blood pressure performed the best, followed by maximum respiratory rate in discriminating sepsis patients from SIRS patients. Maximum heart rate and maximum respiratory rate can differentiate sepsis patients from non-SIRS patients fairly well. The area under ROC of the combination of five physiological parameters was 0.74 and 0.90 for comparing sepsis to non-infectious SIRS patients and comparing sepsis to non-SIRS patients, respectively. Parameters typically performed better in 24-hour windows compared to 6-hour or 12-hour windows. In the third study, significantly increased hospital mortality and ICU mortality were observed in the group treated with low-dose corticosteroids than the control group based on the propensity score matched comparisons, and multivariate logistic regression analyses after adjustment for propensity score alone, covariates, or propensity score (in deciles) and covariates. This thesis advances the existing knowledge by systemically evaluating the test characteristics for the 1991 and 2001 sepsis consensus definitions, delineating physiological signs and symptoms of deterioration in the preceding 24 hours prior to sepsis onset, assessing the prediction performances of single or combined physiological parameters, and examining the use of corticosteroids treatment and survival among septic shock patients. In addition, this thesis sets an innovative example on how to use data from electronic medical records as these surveillance systems are becoming increasingly popular. The results of these studies suggest that a more parsimonious set of definitional criteria for sepsis diagnosis are needed to improve sepsis case identification. In addition, continuously monitored physiological parameters could help to identify patients who show signs of deterioration prior to developing sepsis. Last but not least, caution should be used when considering a recommendation on the use of low dose corticosteroids in clinical practice guidelines for the management of sepsis.

Malaria is caused by a protozoan parasite, Plasmodium falciparum, which is responsible for over 500,000 deaths per year worldwide. Although malaria medicines are working well in many parts of the world, antimalarial drug resistance has emerged as one of the greatest challenges facing malaria control today. Since the malaria parasites are once again developing widespread resistance to antimalarial drugs, this can cause the spread of malaria to new areas and the re-emergence of malaria in areas where it had already been eradicated. Therefore, the discovery and characterization of novel antimalarials is extremely urgent. A previous drug screen in Dr. Chakrabarti's lab identified several natural products (NPs) with antiplasmodial activities. The focus of this study is to characterize the hit compounds using Principal Component Analysis (PCA) to determine structural uniqueness compared to known antimalarial drugs. This study will compare multiple libraries of different compounds, such as known drugs, kinase inhibitors, macrocycles, and top antimalarial hits discovered in our lab. Prioritizing the hit compounds by their chemical uniqueness will lessen the probability of future drug resistance. This is an important step in drug discovery as this will allow us to increase the interpretability of the datasets by creating new uncorrelated variables that will successively maximize variance. Characterization of the Natural Product inspired compounds will enable us to discover potent, selective, and novel antiplasmodial scaffolds that are unique in the 3-dimensional chemical space and will provide critical information that will serve as advanced starting points for the antimalarial drug discovery pipeline.