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Monoamine oxidase (MAO) is an oxidative enzyme that deaminates a variety of amine substrates, including the neurotransmitter dopamine. The enzymatic reaction requires molecular oxygen and produces hydrogen peroxide as a by-product. MAO is localised in the outer mitochondrial membrane and exists as two isoforms, MAO-A and MAO-B, which are differentially expressed in the body and differ in their substrate and inhibitor specificities. Previous studies have suggested that MAO-generated reactive oxygen species (ROS) contribute to oxidative stress in the cell and can directly inhibit electron transport, cause damage to mitochondrial DNA and enhance cell death signalling. In this study the role of MAO in cell death was investigated in dopaminergic neuroblastoma (SH-SY5Y) cells, in three diverse models of mitochondrially-mediated apoptosis. The relevance of MAO in cell death signalling was confirmed with the use of two unrelated MAO inhibitors and the creation of stable SH-SY5Y cell lines that either over express MAO-A or have reduced levels of MAO-A. The study is the first to over express MAO-A using recombinant technology and to use miRNA to stably knock-down MAO-A expression in human neuronal cells. Results confirm that MAO-A is involved in modulating cell death but the mechanism and extent of the involvement depends on the apoptotic inducer. In classical apoptosis induced by staurosporine (STS), cells undergo rapid morphological and biochemical changes indicative of mitochondrially-mediated apoptosis, which is partly dependent on ROS production by MAO-A and induction of mitogen-activated protein kinase (MAPK) signalling cascades. MAO-A protein and catalytic activity are increased in this model, however the mechanism by which this occurs is unknown and is not a result of increased gene transcription. In death induced by growth factor withdrawal, the MAO-A gene is up regulated via p38 and JNK MAPK pathways, which occurs downstream of caspase activation. In both the STS and growth factor withdrawal models, MAO inhibition reduced apoptosis. Most significantly reduced levels of MAO-A expression in 'knock down' cells protected against cell death induced by the complex I inhibitor rotenone, suggesting that MAO has an important role in mitochondrial function. Over expression of MAO-A resulted in stress and apoptosis, followed by a period of cellular senescence and eventually death by necrosis. These data compliment the effects of chronic exposure to oxidative stress in ageing and neurodegeneration. For the first time this work has shown that the MAO-A isoform is an important regulator of STS-induced apoptosis, that MAO-A gene expression is regulated by JNK signalling, and that MAO-A is significantly involved in mitochondrial dysfunction induced by complex I inhibition. These data raise important questions regarding predisposition to the development of neurodegenerative diseases such as Parkinson's disease and to approaches used for their treatment.

A Dissertation Submitted to the Faculty of Health Sciences, University of the Witwatersrand, in the Fulfilment of the Requirements for the Degree for Master of Science in Medicine (Pharmaceutics) Department of Pharmacy and Pharmacology, University of the Witwatersrand, Johannesburg, 2016 / MT2016

Neurogenesis is the process by which functionally integrated neurons are generated from progenitor cells. In the adult mammalian brain two sites of high density cell division have been identified that contain neural progenitor cells retaining the ability to generate new neurons: the subgranular zone of the hippocampus (SGZ) and the subventricular zone (SVZ) lining the lateral ventricles in the forebrain. Several studies have suggested that SVZ neural progenitor cells in the adult brain can migrate into regions other than the olfactory bulb after either administration of growth factors, induction of neuronal cell loss or injury. Brain-derived neurotrophic factor (BDNF) and fibroblast growth factor (FGF-2) play major roles in regulating the survival and fate of progenitor cells in the adult mammalian brain. To determine the effect of BDNF or FGF-2 on neurogenesis in the injured adult brain, BDNF or FGF-2 were over-expressed in the subventricular zone (SVZ) via recombinant adeno-associated virus (AAV1/2) delivery and newly generated cells were identified using bromodeoxyuridine (BrdU; 150mg/kg intraperitoneal) labelling. Selective striatal cell loss was induced in a subgroup of rats by unilateral striatal injection of the excitotoxin quinolinic acid (QA) 21 days after AAV1/2 injection and 24 hours prior to BrdU labeling. The results of this thesis demonstrate that BDNF augments the recruitment, neuronal differentiation and survival of progenitor cells in both neurogenic and non-neurogenic regions of the unlesioned or QA lesioned brain. BDNF also appears to contribute to the persistence of newly generated neurons in the QA lesioned striatum. Our results provide the first evidence demonstrating the neurogenic effect of BDNF on compensatory striatal neurogenesis in the injured adult brain and suggest that enhanced BDNF expression may be a viable strategy for inducing or augmenting endogenous neural progenitor cell neurogenesis. Unlike the effect of BDNF, FGF-2 appears to have no effect on proliferation and/or survival of neural progenitor cells in either the normal or damaged brain. FGF-2 appears to be unable to act as a positive mediator of SVZ progenitor cell proliferation and neurogenesis in this study. However, FGF-2 may be having an inhibitory effect on progenitor cell differentiation. The negative result of the FGF-2 study may be of major significance in indicating the potential requirement of additional factors interacting with FGF-2 to influence neurogenesis. The results from the FGF-2 study contribute to the research field in highlighting the complexity of the mammalian neurogenic process. This thesis highlights the need for further investigation into multiple factor interactions, tighter regulation of the transgenic protein expression from the AAV1/2 delivery vector or alternative progenitor cell labelling paradigms. However, it does show that if neurogenesis can be induced or augmented exogenously, neural progenitor cells may provide a substrate for repair in the adult brain and dramatically change therapeutic approaches towards the treatment of neurodegenerative diseases.

Neurogenesis is the process by which functionally integrated neurons are generated from progenitor cells. In the adult mammalian brain two sites of high density cell division have been identified that contain neural progenitor cells retaining the ability to generate new neurons: the subgranular zone of the hippocampus (SGZ) and the subventricular zone (SVZ) lining the lateral ventricles in the forebrain. Several studies have suggested that SVZ neural progenitor cells in the adult brain can migrate into regions other than the olfactory bulb after either administration of growth factors, induction of neuronal cell loss or injury. Brain-derived neurotrophic factor (BDNF) and fibroblast growth factor (FGF-2) play major roles in regulating the survival and fate of progenitor cells in the adult mammalian brain. To determine the effect of BDNF or FGF-2 on neurogenesis in the injured adult brain, BDNF or FGF-2 were over-expressed in the subventricular zone (SVZ) via recombinant adeno-associated virus (AAV1/2) delivery and newly generated cells were identified using bromodeoxyuridine (BrdU; 150mg/kg intraperitoneal) labelling. Selective striatal cell loss was induced in a subgroup of rats by unilateral striatal injection of the excitotoxin quinolinic acid (QA) 21 days after AAV1/2 injection and 24 hours prior to BrdU labeling. The results of this thesis demonstrate that BDNF augments the recruitment, neuronal differentiation and survival of progenitor cells in both neurogenic and non-neurogenic regions of the unlesioned or QA lesioned brain. BDNF also appears to contribute to the persistence of newly generated neurons in the QA lesioned striatum. Our results provide the first evidence demonstrating the neurogenic effect of BDNF on compensatory striatal neurogenesis in the injured adult brain and suggest that enhanced BDNF expression may be a viable strategy for inducing or augmenting endogenous neural progenitor cell neurogenesis. Unlike the effect of BDNF, FGF-2 appears to have no effect on proliferation and/or survival of neural progenitor cells in either the normal or damaged brain. FGF-2 appears to be unable to act as a positive mediator of SVZ progenitor cell proliferation and neurogenesis in this study. However, FGF-2 may be having an inhibitory effect on progenitor cell differentiation. The negative result of the FGF-2 study may be of major significance in indicating the potential requirement of additional factors interacting with FGF-2 to influence neurogenesis. The results from the FGF-2 study contribute to the research field in highlighting the complexity of the mammalian neurogenic process. This thesis highlights the need for further investigation into multiple factor interactions, tighter regulation of the transgenic protein expression from the AAV1/2 delivery vector or alternative progenitor cell labelling paradigms. However, it does show that if neurogenesis can be induced or augmented exogenously, neural progenitor cells may provide a substrate for repair in the adult brain and dramatically change therapeutic approaches towards the treatment of neurodegenerative diseases.

Neurogenesis is the process by which functionally integrated neurons are generated from progenitor cells. In the adult mammalian brain two sites of high density cell division have been identified that contain neural progenitor cells retaining the ability to generate new neurons: the subgranular zone of the hippocampus (SGZ) and the subventricular zone (SVZ) lining the lateral ventricles in the forebrain. Several studies have suggested that SVZ neural progenitor cells in the adult brain can migrate into regions other than the olfactory bulb after either administration of growth factors, induction of neuronal cell loss or injury. Brain-derived neurotrophic factor (BDNF) and fibroblast growth factor (FGF-2) play major roles in regulating the survival and fate of progenitor cells in the adult mammalian brain. To determine the effect of BDNF or FGF-2 on neurogenesis in the injured adult brain, BDNF or FGF-2 were over-expressed in the subventricular zone (SVZ) via recombinant adeno-associated virus (AAV1/2) delivery and newly generated cells were identified using bromodeoxyuridine (BrdU; 150mg/kg intraperitoneal) labelling. Selective striatal cell loss was induced in a subgroup of rats by unilateral striatal injection of the excitotoxin quinolinic acid (QA) 21 days after AAV1/2 injection and 24 hours prior to BrdU labeling. The results of this thesis demonstrate that BDNF augments the recruitment, neuronal differentiation and survival of progenitor cells in both neurogenic and non-neurogenic regions of the unlesioned or QA lesioned brain. BDNF also appears to contribute to the persistence of newly generated neurons in the QA lesioned striatum. Our results provide the first evidence demonstrating the neurogenic effect of BDNF on compensatory striatal neurogenesis in the injured adult brain and suggest that enhanced BDNF expression may be a viable strategy for inducing or augmenting endogenous neural progenitor cell neurogenesis. Unlike the effect of BDNF, FGF-2 appears to have no effect on proliferation and/or survival of neural progenitor cells in either the normal or damaged brain. FGF-2 appears to be unable to act as a positive mediator of SVZ progenitor cell proliferation and neurogenesis in this study. However, FGF-2 may be having an inhibitory effect on progenitor cell differentiation. The negative result of the FGF-2 study may be of major significance in indicating the potential requirement of additional factors interacting with FGF-2 to influence neurogenesis. The results from the FGF-2 study contribute to the research field in highlighting the complexity of the mammalian neurogenic process. This thesis highlights the need for further investigation into multiple factor interactions, tighter regulation of the transgenic protein expression from the AAV1/2 delivery vector or alternative progenitor cell labelling paradigms. However, it does show that if neurogenesis can be induced or augmented exogenously, neural progenitor cells may provide a substrate for repair in the adult brain and dramatically change therapeutic approaches towards the treatment of neurodegenerative diseases.

Neurogenesis is the process by which functionally integrated neurons are generated from progenitor cells. In the adult mammalian brain two sites of high density cell division have been identified that contain neural progenitor cells retaining the ability to generate new neurons: the subgranular zone of the hippocampus (SGZ) and the subventricular zone (SVZ) lining the lateral ventricles in the forebrain. Several studies have suggested that SVZ neural progenitor cells in the adult brain can migrate into regions other than the olfactory bulb after either administration of growth factors, induction of neuronal cell loss or injury. Brain-derived neurotrophic factor (BDNF) and fibroblast growth factor (FGF-2) play major roles in regulating the survival and fate of progenitor cells in the adult mammalian brain. To determine the effect of BDNF or FGF-2 on neurogenesis in the injured adult brain, BDNF or FGF-2 were over-expressed in the subventricular zone (SVZ) via recombinant adeno-associated virus (AAV1/2) delivery and newly generated cells were identified using bromodeoxyuridine (BrdU; 150mg/kg intraperitoneal) labelling. Selective striatal cell loss was induced in a subgroup of rats by unilateral striatal injection of the excitotoxin quinolinic acid (QA) 21 days after AAV1/2 injection and 24 hours prior to BrdU labeling. The results of this thesis demonstrate that BDNF augments the recruitment, neuronal differentiation and survival of progenitor cells in both neurogenic and non-neurogenic regions of the unlesioned or QA lesioned brain. BDNF also appears to contribute to the persistence of newly generated neurons in the QA lesioned striatum. Our results provide the first evidence demonstrating the neurogenic effect of BDNF on compensatory striatal neurogenesis in the injured adult brain and suggest that enhanced BDNF expression may be a viable strategy for inducing or augmenting endogenous neural progenitor cell neurogenesis. Unlike the effect of BDNF, FGF-2 appears to have no effect on proliferation and/or survival of neural progenitor cells in either the normal or damaged brain. FGF-2 appears to be unable to act as a positive mediator of SVZ progenitor cell proliferation and neurogenesis in this study. However, FGF-2 may be having an inhibitory effect on progenitor cell differentiation. The negative result of the FGF-2 study may be of major significance in indicating the potential requirement of additional factors interacting with FGF-2 to influence neurogenesis. The results from the FGF-2 study contribute to the research field in highlighting the complexity of the mammalian neurogenic process. This thesis highlights the need for further investigation into multiple factor interactions, tighter regulation of the transgenic protein expression from the AAV1/2 delivery vector or alternative progenitor cell labelling paradigms. However, it does show that if neurogenesis can be induced or augmented exogenously, neural progenitor cells may provide a substrate for repair in the adult brain and dramatically change therapeutic approaches towards the treatment of neurodegenerative diseases.

Diss. (sammanfattning) Umeå : Univ., 2004. / Härtill 4 uppsatser.