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Chemokines are responsible for directing leukocyte migration and triggering firm arrest by activating integrins on leukocytes. It is now apparent that chemokines have critical biological roles beyond chemo-attraction. Throughout this thesis, I describe the importance of the CCL5/CCR5 axis in the context of the immune response and cancer biology. Specifically, CCL5 invokes dose-dependent distinct signalling events downstream of CCR5 activation in T cells. I show that nM concentrations of CCL5 mediate CD4+ T cell migration that is partially dependent on mTOR activation. CCL5 induces phosphorylation and de-activation of the repressor 4E-BP1, resulting in its dissociation from the eukaryotic initiation factor-4E to initiate protein translation. I provide evidence that CCL5 initiates rapid translation of cyclin D1 and MMP-9, known mediators of cell migration. The data demonstrated that up-regulation of chemotaxis-related proteins may “prime” T cells for efficient migration. During an immune response, recently recruited T cells are exposed to high CCL5 concentrations. The propensity of CCL5 to form higher-order aggregates at high, µM concentrations, prompted studies to investigate their effects on T cell function. I show that at these high doses, CCL5 induces apoptosis in PM1.CCR5 and MOLT4.CCR5 T cell lines. CCL5-induced cell death involves the cytosolic release of cytochrome c and caspase-9/-3 activation. Furthermore, I identified Tyrosine-339 as a critical residue within CCR5, suggesting that tyrosine phosphorylation signalling events are important in CCL5-mediated apoptosis. Our data suggest that CCL5-induced cell death, in addition to Fas/FasL mediated events, may contribute to clonal deletion of T cells during an immunological response. I subsequently examined the possible pathological consequence of aberrant CCL5/CCR5 signalling in breast cancer. Exogenous CCL5 enhances MCF-7.CCR5 proliferation, which is abolished by anti-CCR5 antibody and rapamycin. CCL5 induces the formation of the eIF4F translation initiation complex, and mediates a rapid up-regulation of cyclin D1, c-Myc and Dad-1 protein expression. Thus, our data demonstrate the potential for breast cancer cells to exploit downstream CCL5/CCR5 signalling pathways for their proliferative and survival advantage. Taken altogether, each of these studies reinforces the notion that chemokines are not only potent chemotactic mediators, but are key effectors in diverse developmental, immunological and pathological processes.

Transmissible spongiform encephalopathies (TSEs) or prion diseases are defined by infectivity and by the pathological damage they produce in the central nervous system (CNS), typically involving spongiform degeneration or vacuolation, deposition of abnormal PrP (PrPSc), glial activation and neuronal loss. Much of our understanding of the TSEs has derived from the study of murine scrapie models. The molecular basis of pathological changes is not clear, in particular the relationship between the deposition of PrPSc and neuronal dysfunction. A typical feature of TSE disease is neuronal loss, although the mechanisms leading to this loss are poorly understood. Apoptosis has been proposed as an important mechanism of TSE associated cell death, but which pathways are involved are still to be determined. The main aims of this thesis are to investigate the progression of the characteristic neuropathological changes observed in the TSE infected brain and to analyse the mechanisms involved in neuronal loss. In this study two contrasting scrapie mouse models were used : the ME7/CV model , and the 87V/VM model in which neuronal loss is targeted to different areas of the hippocampus, the CA1, and CA2 respectively. The role of the caspase-dependent pathway of apoptosis in the neuronal loss was investigated. The results of analysis of pro-apoptotic markers of disease in the two scrapie mouse models differed. The results observed in the ME7/CV scrapie mouse model suggest that apoptosis may not be the main mechanism of neuronal loss, whereas the 87V/VM model showed some indication that apoptosis may be involved. Detailed studies in the progression of neurodegenerative changes in the ME7/CV scrapie mouse model revealed that the initial pathological change observed in the hippocampus was the deposition of PrPSc followed by a glial response, spongiform change and subsequent neuronal degeneration. The role of the cytoskeleton and synaptic dysfunction in the neuronal damage observed in the CA1 of the ME7 infected hippocampus was analysed. Cytoskeletal disruption was observed in the post-synaptic dendritic spine, and the apical dendrites of CA1 neurons at 160days, a time point at which neurons are known to be lost. Changes in the expression of the pre-synaptic protein, synaptophysin and the post-synaptic protein PSD-95 were not observed until the terminal stage of disease when the neuronal loss is profound. In conclusion, this research suggests that the mechanisms of neuronal loss may follow different biochemical pathways, which might not necessarily involve an apoptotic mechanism. Cytoskeletal disruption in the post-synaptic dendritic spine plays a major role in the neuronal dysfunction observed in ME7 infected CA1 neurons, although the post synaptic density does not seem to be involved .Pre-synaptic changes and disruption to the innervation of CA1 neurons is not apparent until the end stages of disease. The trigger for this cytoskeletal disruption and the subsequent neuronal loss may be the early deposition of PrPSc in the extracellular space but the precise mechanisms involved are still to be elucidated. The identification of the key events involved in the mechanisms of neruodegeneration in TSE diseases may lead to the development of therapeutic strategies to inhibit the neurodegenerative process.

Memoria para optar al Título Profesional de Médico Veterinario / El desarrollo pulmonar es un proceso complejo y dinámico que implica una serie de interacciones entre los tejidos involucrados a través de la expresión de distintas moléculas que actúan promoviendo o inhibiendo los mecanismos del desarrollo implicados en este sistema. Para lograr identificar la expresión témporo-espacial de moléculas que participan en la diferenciación de estructuras pulmonares se utilizaron embriones de rata de la cepa Sprague dawley de 12 días post-coito a recién nacido. Se obtuvieron cortes seriados que fueron tratados con técnicas inmunohistoquímicas para detectar proliferación celular (PCNA), apoptosis (TUNEL), diferenciación celular (BMP-4), desarrollo vascular (VEGF y fvW) y método histoquímico para identificar membrana basal y surfactante pulmonar (H-PAS). El patrón de expresión de las moléculas estudiadas varió al avanzar el desarrollo, así, con PCNA se observó una gran proliferación de células mesenquimáticas y epiteliales en las etapas iniciales (E14); la diferenciación, a distintos tipos celulares observada después del pico de proliferación, es coincidente con el incremento de la inmunomarcación con BMP-4 (E16), cuya curva de expresión fue antagónica a la de PCNA, patrón que se repitió en edades más avanzadas (E18), indicando la participación de esta molécula en mecanismos de diferenciación celular. La inmunomarcación de la actividad apoptótica fue siempre menor a la de los otros anticuerpos, aumentando levemente en las últimas edades, coincidiendo con la remodelación pulmonar, lo que podría indicar que éste sería su rol principal en el desarrollo pulmonar. En las etapas iniciales, junto con el desarrollo de los primeros conductos respiratorios, se observó con VEGF-A la formación de una red vascular por vasculogénesis paralela a estas estructuras. En edades más avanzadas se detectaron en la zona periférica del esbozo pulmonar, células endoteliales inmunomarcadas con fvW, formando por angiogénesis pequeños vasos sanguíneos relacionados estrechamente a los futuros alvéolos pulmonares. Al avanzar el desarrollo (E17) ambas redes se fusionaron para lograr al momento del nacimiento, un órgano capaz de realizar una adecuada función de hematosis. La aplicación del método de PAS permitió observar, desde las primeras edades la relación de la membrana basal con la diferenciación y organización de células epiteliales de los conductos respiratorios y la desorganización de ésta en el extremo distal del conducto que se dividirá dicótomicamente, así como también un aumento de la reacción PAS positiva en el mesénquima próximo a este punto de bifurcación. La reacción de PAS permitió visualizar la actividad secretora de células diferenciadas, coincidiendo con la mayor expresión de BMP-4. Así, en E15 se detectó reacción PAS en células epiteliales de conductos respiratorios correspondientes a células caliciformes, coincidiendo con inmumarcación con BMP-4 en las mismas células. También se encontró tinción PAS en AEC II lo que se corrobora con la fuerte reacción positiva en el interior de los sacos alveolares, desde E17 hasta el nacimiento, como consecuencia de la secreción de surfactante pulmonar por estos neumocitos. Estas complejas interacciones dan como resultado un sistema respiratorio funcional que culmina después del nacimiento

<p>Tuberculosis is a devastating disease that has been plaguing humankind for millennia. Co-evolution of humans with Mycobacterium tuberculosis, the causative agent of the disease, has allowed for the pathogen to possess an abundance of survival mechanisms. The outcome of this is the ability of the bacterium to create an intracellular niche lifestyle inside host cells where it can successfully evade the host immune system. While there is a vaccine available, named the BCG vaccine, it confers little protection to adults in the pulmonary form of the disease. The lack of an effective vaccine and the rise of Multidrug-Resistant (MDR) and Extensively Drug-Resistant (XDR) tuberculosis highlight the need for more research into combating Mycobacterium tuberculosis. The purpose of this work is to enhance the field of knowledge of how mycobacterial virulence factors affect host cellular pathways so that the interactions can be exploited for novel therapeutics and vaccine development.</p><p>One of the hypotheses for the poor efficacy of the BCG vaccine is that it fails to elicit a strong CD8+ T cell response during infection. Studies have found that vaccinating mice with apoptotic bodies containing mycobacterial antigens were able to protect mice to a greater degree than BCG and that this is dependent on CD8+ T cell activation. Thus, we hypothesized that a pro-apoptotic mutant of M. tuberculosis could be utilized as a novel vaccine candidate. Through screening a library of M. tuberculosis transposon mutants, we identified an Enhanced Cell Death mutant (ECD19) that functions through caspase 3 mediated apoptosis. Sequencing revealed that the mutant has a transposon insertion in Rv2456c, a probable integral membrane transport protein. Immunogenicity testing via Enzyme-Linked ImmunoSpot (ELISPOT) and Intracellular Cytokine Staining (ICS) assays demonstrated that ECD19 induced an altered immune response when compared to the parental strain M. tuberculosis H37Rv. Additionally, ECD19 has reduced survival in an in vitro THP-1 cell model and in an in vivo mouse model. Taken together, our data suggest that Rv2456c is important to the survival of H37Rv in host cells and that deletion of the gene may enhance the immunogenicity of the bacterium.</p><p>Inappropriate dosing and poor adherence to antibiotics in the treatment of tuberculosis has led to MDR and XDR, the highest incidences of which can be found in the KwaZulu-Natal (KZN) province of South Africa. Little is known about the virulence of these strains, but it is hypothesized that the drug resistance mechanisms come at a cost to the bacteria. In an in vitro assay, we have found that clinical isolates from the KZN region induce higher levels of necrosis than virulent laboratory strains of M. tuberculosis. Additionally, our in vivo studies show that the drug-resistant isolates do not disseminate as well as susceptible strains, and in both immunocompetent and immunocompromised mouse models, mice infected with the drug-resistant strains are able to live longer than mice infected with drug-sensitive strains. As all strains are highly related on a genetic level, we can say that the drug-resistant mechanisms acquired by the strains come at a cost of reduced virulence. Thus, it is likely that higher prevalence of the MDR and XDR in the KZN province is due to the high rate of HIV+, immunocompromised individuals living in the region. </p><p>Lastly, we are interested in building on the knowledge that avirulent mycobacteria are able to induce autophagy in a murine macrophage cell line. Through the use of Mammalian Target of Rapamycin (mTOR) inhibitors and autophagy-deficient macrophages, we were able to show that Mycobacterium smegmatis is able to induce both mTOR and autophagy during infection. Additionally, we found that mycobacterial killing occurs in the absence of autophagy when mTOR is inhibited. This effect is not due to a bactericidal effect of the mTOR inhibitors. From these data, we show that there is an underappreciated role in the induction of mTOR after mycobacterial infection. By studying the interplay of mTOR and autophagy, therapies targeted to favoring host defenses could be developed.</p><p>In summary, the insights from this work enhance the knowledge of how mycobacteria are able to be successful pathogens. This data may be useful in the creation of novel vaccine candidates or the identification of potential drug targets to bolster the therapeutic options in treating those afflicted with tuberculosis.</p> / Dissertation

Head and neck cancer is the sixth leading cancer worldwide. Head and neck squamous cell carcinoma (HNSCC) accounts for more than 90% of incident cases. Despite intense, multimodality treatment regimens for HNSCC including surgery, chemotherapy, and radiation, little progress has been made over the past 30 years in improving overall survival rates. Tumor cell death induced by both conventional and targeted chemotherapy is often mediated by the BCL-2 family-dependent mitochondrial apoptotic pathway. However, initiators of this apoptotic pathway, such as p53, are more than 50% of the time mutated or deleted in HNSCC rendering the disease refractory to treatment. To counter such resistance, direct therapeutic targeting of the BCL-2 family is conceptually appealing. For this purpose, we use three clinically-available drugs: cisplatin, fenretinide, and ABT-263 (navitoclax). Both cisplatin and fenretinide are known to induce a BH3-only pro-apoptotic protein, Noxa, which binds to and inactivates multi-domain anti-apoptotic protein MCL-1 and release from its interaction with multi-domain pro-apoptotic protein BAK, followed by the phosphorylation via CDK2 for the proteasome-mediated degradation. Activated BAK can now go through conformational change for the oligomerization at the outer membrane of the mitochondria to release cytochrome c into the cytosol and induce caspase-dependent apoptotic cell death. ABT-263 directly binds to multi-domain anti-apoptotic proteins, such as BCL-2 and BCL-XL, to inhibit their activity and leads to the activation of multi-domain pro-apoptotic protein BAX to induce apoptosis. We hypothesize that combining the Noxa-inducing drugs (cisplatin or fenretinide) along with ABT-263 can efficiently induce BAX and BAK activation and significantly increase cell death in HNSCC cells by simultaneously inhibiting the activity of MCL-1, BCL-2, and BCL-XL. Combination-induced treatments in four cell lines (HN8, HN30, HN31, and UMSCC1) tested led to significant increase in apoptotic cell death. Cisplatin and ABT-263 combined treatment is inducing the expression of Noxa and leading to increase in apoptosis in HN30, HN31, UMSCC1, but not HN8. Similarly, fenretinide and ABT-263 combined treatment is inducing the expression of Noxa in all four cell lines tested and is largely relying on expression of Noxa.

The renin-angiotensin system (RAS) is a major physiological regulator of body fluid volume, electrolyte balance and blood pressure. The principal effector peptides for this system are the angiotensins, particularly angiotensin II (Ang II), whose biological cations are mediated by specific angiotensin receptors. The use of highly specific nonpeptide angiotensin antagonists has allowed identification and characterisation of two major Ang II receptor subtypes, designated AT1 and AT2. The aims of this thesis were to investigate AT1 and AT2 receptor expression at both mRNA and protein level in freshly isolated and primary cultures of rat proximal tubular (PT) cells, and to determine the effect of culture upon Ang II receptor subtype expression. The possible role of Ang II upon receptor expression was also investigated. This study demonstrated that only the AT1 receptor is expressed in freshly isolated rat PT cells, with no evidence for AT2 receptor expression. Although continuously present throughout the culture period, a significant decrease in AT1 receptor expression was observed with time. Conversely AT2 receptor expression was absent in freshly isolated cells but was observed after 24 hours in culture with expression then remaining stable throughout culture. Clearly Ang II receptor expression is not stable during culture. Primary cultures of rat PT cells exhibit a change in receptor expression similar to those observed in vivo following tissue damage and repair, with an increase in AT2 receptor expression possibly mediated by locally released Ang II. Initial studies however, involving incubation of rat PT cells with exogenous Ang II, have demonstrated no effect upon AT1 receptor mRNA expression.

Philosophiae Doctor - PhD / The abnormal death of neurons in the central nervous system of individuals suffering from neurodegenerative diseases such as Parkinson’s disease, Alzheimer’s disease, Huntington’s disease and amyotrophic lateral sclerosis, takes place by an intrinsic cell suicide programme known as apoptosis. This process is triggered by several stimuli, and consists of numerous pathways and cascades which lead to the death of neuronal cells. It is this multifactorial nature of neurodegenerative diseases that has over the years seen many researchers develop compounds that may serve as multi-target directed ligands (MTDLs) which could potentially confer neuroprotection by acting simultaneously on different receptors and target sites implicated in neurodegeneration. This study was aimed at developing MTDLs that may serve as neuroprotective agents by simultaneously (a) inhibiting N-methyl D-aspartate receptors (NMDAR) and blocking L-type voltage gated calcium channels (VGCC) thus regulating the Ca2+ influx mediated excitotoxic process; (b) inhibiting the monoamine oxidase enzymes A and -B (MAO-A/B) thus allowing increase in dopamine levels in the central nervous system and reducing the levels of the highly oxidative products produced by the activity of these enzymes; (c) possessing anti-apoptotic activity to halt the neuronal cell death process. In designing the compounds we focused on the structures of rasagiline and selegiline, two well-known MAO-B inhibitors and proposed neuroprotective agents, and of NGP1-01, a known VGCC blocker and NMDAR antagonist. The first series of compounds (reported in research article 1, Chapter 3), comprised polycyclic propargylamine and acetylene derivatives. Compounds 12, 15 and 16 from this series showed promising VGCC and NMDA receptor channel inhibitory activity ranging from 18 % to 59 % in micromolar concentrations, and compared favourably to the reference compounds. In the MAO-B assay, compound 10 exhibited weak MAO-B inhibition of 73.32 % at 300 μM. The rest of the series showed little to no activity on these target sites, despite showing significant anti-apoptotic activity. This suggested the compounds in this series to be exhibiting their neuroprotective action through some other mechanism(s) unexplored in this study.

>Magister Scientiae - MSc / Cancer is one of the leading causes of death, worldwide. Mortality tolls are estimated to reach approximately 13.1 million in 2030. These statistics suggest that current therapeutic strategies are not effective. This is partly due to the fact that the drugs used in the treatment of cancer lack selectivity and specificity, which lead to undesirable side effects and reduced drug efficacy. There is therefore a need for alternative therapeutic approaches. In view of this, the therapeutic goal of chemotherapy has shifted towards targeted drug delivery systems, which have been successfully demonstrated using nanotechnology. The nano-based drug delivery vehicles that specifically target diseased cells are appealing as they could reduce drug toxicity towards healthy tissues and be more effective at lower dosages. The main aim of this study was to develop gold nanorods (AuNRs) capable of inducing cell death in cancer cells specifically. Selectivity of the AuNRs (denoted as AGK) for cancer cells was achieved by conjugating the AuNRs to a peptide (Adipose Homing Peptide or AHP) that has high affinity and specificity for a cell surface receptor (prohibitin or PHB) that is expressed on some cancer cells. Cell death was achieved through conjugating the AuNRs to a pro-apoptotic peptide, D(KLAKLAK)2. Spherical AuNPs (AuNSs) conjugated with AHP and D(KLAKLAK)2, capable of selectively inducing apoptosis in cancer cells that express PHB, was previously reported. However, in this study the AuNSs were replaced with AuNRs. AuNRs has the ability to absorb light in the near infrared (NIR) light spectrum and converts this light energy into heat. This property of AuNRs has been used in several studies to demonstrate the application of AuNRs for the treatment of cancer using photothermal therapy (PTT). Consequently, the AuNRs described in this study can also be used for PTT. These AuNRs can induce cell death through the target specific delivery of the pro-apoptotic peptide D(KLAKLAK)2 as well as through PTT. The study showed that three human cancer cell lines (PC-3, Caco-2 and U-87) express PHB. The cytotoxicity testing of AGK AuNPs on PC-3 cells showed that these AuNRs could induce apoptosis in these cells without exposure to a NIR light source. The study also shows that AuNRs conjugated with the targeting peptide only (denoted as AG) can induce cell death in Caco-2 through PTT. This study demonstrates the potential of the AuNRs described in this study for application in the targeted elimination of cancer cells through the selective induction of PTT and apoptosis.

Sowohl NFAT- (Nukleäre Faktoren aktivierter T-Zellen) als auch MEF2- (’myosin-enhancer factor 2’) Transkriptionsfaktoren spielen eine wichtige Rolle bei der Differenzierung, Proliferation oder Apoptose vieler eukaryotischer Zellen. Sie sind in einer Vielzahl von Zellen aktiv und können dort die Transkription ihrer Zielgene nach Stimulation der Zellen mit anschließendem Calcium-Einstrom aktivieren. Dabei kooperieren sie oft mit anderen Transkriptionsfaktoren. Kurz vor Beginn dieser Arbeit erschienen zwei Veröffentlichungen, die eine Kooperation von MEF2D mit NFATc2 bei der Aktivierung des nur77-Promotors, der bei der negativen Selektion von T-Zellen aktiv ist, beschrieben. Im Rahmen dieser Arbeit sollte nun das Bindungsverhalten verschiedener NFAT-Proteine an den nur77-Promotor und ihre Kooperationsfähigkeit mit MEF2D bei der Aktivierung des nur77- und anderer Promotoren untersucht werden. Es konnte gezeigt werden, dass verschiedene NFAT-Faktoren direkt an ein Oligonukleotid des nur77-Promotors (von Position -274 bis -247 bp reichend) binden. Diese Bindung wird zwar durch eine Bindung von MEF2-Faktoren an den Promotor unterstützt, ist jedoch nicht wesentlich beeinträchtigt, wenn MEF2-Faktoren aufgrund von einer Mutation in ihrer Bindungssequenz nicht binden können. Dagegen führt eine Mutation der NFAT-Bindungsstelle zu einer aufgehobenen Bindung von NFAT-Faktoren an den Promotor. Desweiteren zeigte sich, dass nicht nur endogenes NFATc2 sondern auch verschiedene NFATc1-Isoformen an den Promotor binden können. In ihrer Fähigkeit mit MEF2D zu kooperieren, zeigte sich kein Unterschied zwischen den getesteten NFAT-Isoformen NFATc1/&#945;A, NFATc1/&#945;C oder NFATc2. So aktivierten in Transfektionsversuchen in Jurkat T-Zellen und 293 T-Zellen alle NFAT-Proteine die Luciferase-Reporter-Gen-Konstrukte gemeinsam mit MEF2D in etwa additiver Weise. Dies konnte an verschiedenen Luciferase-Reporter-Genen (nur77-gesteuert, hFasL-gesteuert und desmin-gesteuert) nachgewiesen werden, was auf eine mögliche Kooperation der verschiedenen NFAT-Faktoren mit MEF2D (und evtl. auch anderen MEF2-Faktoren) nicht nur bei der Apoptose von T-Zellen sondern auch in anderen Zellen hinweist. / NFAT- (nuclear factors of activated t cells) and MEF2- (myosin enhancer factor 2) transcription factors play an important role in the differentiation, proliferation or apoptosis of eucaryotic cells. They are activ in a variation of cells and they can activate the transcription of their target genes after stimulation of the cells with calcium influx. Both cooperate often with other transcription factors. Before the beginning of this work, there were two publications which discribed a cooperation of MEF2D with NFATc2 in the activation of the nur77 promotor, which is activ in t cells undergoing negative selection. In this work I studied the binding of different NFAT-proteins at the nur77-promotor and their ability to cooperate with MEF2D activating the nur77-promotor and other promotors. It could be shown that different NFAT-facors bind to an oligonucleotid of the nur77-promotor (reaching from position -274 to -247 bp). This binding is assisted by the binding of MEF2D to the promotor, but MEF2D binding is not essential for NFAT binding (when the MEF2-binding site is mutated). When the NFAT binding site is mutated, no binding of NFAT factors could be observed. It also could be shown, that not only NFATc2 but also different NFATc1-isoforms can bind to the promotor. There was no difference between the tested NFAT-isoforms NFATc1/&#945;A, NFATc1/&#945;C or NFATc2 in their ability to cooperate with MEF2D. All of them activated different luciferace-reporter-gene-contructs (nur77, hFasL, desmin) in transfection assays in Jurkat t-cells and 293 t-cells aproximately in addition, which might hint to a possible cooperation of different NFAT-factors with MEF2D not only in the apoptosis of t-cells but also in other cells.