Magister Pharmaceuticae - MPharm / The declining efficacy of antimalarial drugs against resistant Plasmodium falciparum strains in several endemic regions has amplified the world’s burden of neglected diseases. This has highlighted the need for alternate strategies for chemotherapy and chemoprophylaxis. Since malaria is prevalent primarily in third world countries, it is critical for novel therapies to be affordable. Previous research has found that some antihistamines possess inherent antimalarial activity and cause a marked reversal of chloroquine resistance in vitro and in vivo. Promising results have been demonstrated when chlorpheniramine was combined with chloroquine to reverse chloroquine resistance in two African studies (Sowunmi et al, 1997; Abok., 1997).Recently, astemizole and its principle human metabolite desmethylastemizole were identified as potent inhibitors of Plasmodium falciparum at sub-micromolar concentrations in both chloroquine sensitive and chloroquine resistant parasites, showing efficacy in vitro and in two mouse models. The promising results observed with these studies warrant a more comprehensive understanding of how antihistamines interact with the malaria parasite. Additionally, analysing the different structural and mechanistic characteristics of antihistamines may lead to the design and development of effective and affordable antimalarial agents or chloroquine resistance modulators.This thesis describes the antimalarial activity of mainly off-patent (generic) antihistamines by comparing the efficacy of a total of 24 antihistamines, representing histamine1, histamine2, and histamine3 receptor antagonists, against chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum. Cyproheptadine, ketotifen, loratadine, desloratadine, 3-(1HImidazol-4-yl) propyldi (p-fluorophenyl) methyl ether hydrochloride and ciproxifan display IC50 values less than 4μg/ml. There was no significant difference in the sensitivity to antihistamines among the chloroquine sensitive and resistant parasites tested. A tricyclic nucleus appears to be an important structural scaffold for antihistamines which exhibit low IC50 values. Synergistic studies indicate that enhancement of the antimalarial effect of chloroquine on P.falciparum was observed with the ethanolamines against the chloroquine sensitive parasites.Cyproheptadine, ketotifen and desloratadine exerted a marked synergistic action with chloroquine against chloroquine sensitive and resistant parasites. Chlorpheniramine exhibited synergism with chloroquine against resistant parasites only.Microscopic studies illustrate the effect of antihistamines on parasite morphology when compared to control. Using immunofluorescence microscopy, it was seen that ketotifen decreases haemoglobin localization while cyproheptadine increases haemoglobin localization in the parasite’s food vacuole. Western blots have confirmed these results, in addition to indicating that chlorpheniramine decreases the haemoglobin content in the parasite. The results confirm that certain antihistamines do indeed cause a reduction in the growth of malaria parasites. Furthermore, the histamine1 and histamine3 receptor antagonists are most active while histamine2 receptor antagonists have no antimalarial activity. Microscopic studies suggest that antihistamines do not exert their antimalarial effect via a single mechanism of action.I wish to express my sincere appreciation to the following people and institutions whose supervision and assistance made the presentation of this thesis possible:My supervisor, Prof. Henry Leng. Thank for always believing in me. Your encouragement, kindness and calm temperament has given me the strength to complete this thesis even when times were tough. Your wisdom and understanding will always be remembered.My co-supervisor, Prof. Pete Smith. I sincerely thank you for allowing me the opportunity to work in your laboratory and for welcoming me into the department. Your kindness and welcoming attitude will forever be appreciated. Thank you for always being patient and understanding.Dr. Uschi Wiehart. Thank you for all the help in the laboratory and always being there for me. I truly value and appreciate your contribution to this thesis. Your friendship has added so much positive energy to my life. Thank you for your wisdom, inspirational advice and unfaltering encouragement Sumaya and Ntokosi, your help, advice and company in tissue culture, are truly appreciated.The UCT, Pharmacology students. Thank for all your assistance.My dearest Pharmaceutical Chemistry colleagues, Jaques Joubert, for your friendship and support and for always listening and Prof. Peter Eagles, your kindness, support and wise advice has given me strength when I needed it most. To my other School of Pharmacy colleagues. Prof. Sarel Malan and team, for your support and motivation.To my family for all your support and wisdom and to my baby brothers; Omar and Uzair for all the joy that you bring to my life.And finally to my dearest husband, Zaheer for all your love and support throughout my studies and for taking me to UCT to culture parasites every weekend

Orientador: Alexandrina Sartori / Resumo: A Esclerose múltipla é uma doença autoimune degenerativa que acomete jovens adultos, causando danos neuroaxonais e áreas de desmielinização no sistema nervoso central (SNC) devido a uma resposta autoimune mediada por linfócitos Th1, Th17 e T citotóxicos. A encefalomielite autoimune experimental (EAE) constitui seu principal modelo de estudo e mastócitos parecem contribuir para os processos inflamatórios envolvidos na patogênese da EM/EAE. Seguindo este raciocínio, substâncias estabilizadoras de mastócitos, como o fumarato de cetotifeno, poderiam afetar o desenvolvimento destas doenças através do bloqueio dos processos de exocitose e desgranulação. O objetivo principal deste trabalho foi avaliar o efeito desta droga no desenvolvimento da EAE. Para isto, camundongos C57BL/6 fêmeas submetidas à indução da EAE através da imunização com MOG/CFA e injeção de toxina pertussis, foram tratados com fumarato de cetotifeno (0,4 mg/kg via intraperitoneal) durante 11 dias, a partir do 7º dia após a indução. O efeito do tratamento no desenvolvimento clínico da EAE foi determinado pela avaliação de peso corporal e escore clínico. Posteriormente, parâmetros histopatológicos e imunológicos associados à doença, bem como a quebra da função da barreira hematoencefálica (BHE) foram avaliados. As comparações dos valores de incidência, escores clínicos diários e máximos, e de variação de peso corpóreo revelaram que o tratamento com cetotifeno reduziu a incidência e a gravidade da EAE. Este efeito pr... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor

<p>The gastrointestinal mucus gel layer and blood flow are two important mechanisms for protection at the pre-epithelial and sub-epithelial levels, respectively. <i>Helicobacter pylori</i> might circumvent these mechanisms and elicit a chronic inflammatory response with consequent ulcers in the stomach and duodenum. In this thesis, the physical state and properties of the adherent mucus gel layer was studied from the stomach to colon. Furthermore, the acute and chronic effects of <i>H. pylori</i> on the integrity of the mucus gel layer and mucosal blood flow were studied in the anesthetized rat.</p><p>A translucent mucus gel covers all studied segments of the gastrointestinal tract during fasting conditions, with the thickest layers in the colon and ileum. Carefully applied suction revealed that the mucus gel was a multi-layered structure comprising a firmly adherent layer covering the mucosa, impossible to remove, and a loosely adherent upper layer. The firmly adherent layer was thick and continuous in the corpus (80μm), antrum (154μm) and colon (116μm), but thin (<20μm) and discontinuous in the small intestine.</p><p>Following mucus removal, a rapid renewal of the loosely adherent layer ensued. The highest rate was observed in the colon with intermediate values in the small intestine. Mucus renewal in the stomach was attenuated on acute luminal application of water extracts from <i>H. pylori</i> (HPE). In animals with a chronic <i>H. pylori</i> infection the mucus renewal rate was unaffected, but the total gastric mucus gel thickness was reduced and the mucus secretory response to luminal acid (pH1) attenuated in the antrum. </p><p>HPE from type I strains acutely reduced corporal mucosal blood flow, measured with laser-Doppler flowmetry, by approximately 15%. The reduction in blood flow was mediated by a heat stable factor other than VacA and CagA. Inhibition of endogenous nitric oxide production with Nω-nitro-l-arginine augmented the decrease. However, ketotifen, a mast cell stabilizer, completely attenuated the effect of the extract as did the platelet activating factor (PAF) receptor-antagonist, WEB2086, thus depicting a detrimental role for the microvascular actions of PAF.</p>

The gastrointestinal mucus gel layer and blood flow are two important mechanisms for protection at the pre-epithelial and sub-epithelial levels, respectively. Helicobacter pylori might circumvent these mechanisms and elicit a chronic inflammatory response with consequent ulcers in the stomach and duodenum. In this thesis, the physical state and properties of the adherent mucus gel layer was studied from the stomach to colon. Furthermore, the acute and chronic effects of H. pylori on the integrity of the mucus gel layer and mucosal blood flow were studied in the anesthetized rat. A translucent mucus gel covers all studied segments of the gastrointestinal tract during fasting conditions, with the thickest layers in the colon and ileum. Carefully applied suction revealed that the mucus gel was a multi-layered structure comprising a firmly adherent layer covering the mucosa, impossible to remove, and a loosely adherent upper layer. The firmly adherent layer was thick and continuous in the corpus (80μm), antrum (154μm) and colon (116μm), but thin (&lt;20μm) and discontinuous in the small intestine. Following mucus removal, a rapid renewal of the loosely adherent layer ensued. The highest rate was observed in the colon with intermediate values in the small intestine. Mucus renewal in the stomach was attenuated on acute luminal application of water extracts from H. pylori (HPE). In animals with a chronic H. pylori infection the mucus renewal rate was unaffected, but the total gastric mucus gel thickness was reduced and the mucus secretory response to luminal acid (pH1) attenuated in the antrum. HPE from type I strains acutely reduced corporal mucosal blood flow, measured with laser-Doppler flowmetry, by approximately 15%. The reduction in blood flow was mediated by a heat stable factor other than VacA and CagA. Inhibition of endogenous nitric oxide production with Nω-nitro-l-arginine augmented the decrease. However, ketotifen, a mast cell stabilizer, completely attenuated the effect of the extract as did the platelet activating factor (PAF) receptor-antagonist, WEB2086, thus depicting a detrimental role for the microvascular actions of PAF.