Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Elevated circulating Ang II activates neurons in the forebrain cardiovascular regulatory areas to cause sympatho-excitation and hypertension. We hypothesized that circulating Ang II causes neuronal activation in the SFO and thereby activates efferent pathways to the PVN, and chronically causes activation of aldosterone production in magnocellular neurons in PVN and SON, which amplifies neuronal activation in the PVN and central sympatho-excitatory pathways. The aim of the present study was to determine the pattern of neuronal activation in forebrain nuclei by circulating Ang II and to elucidate where in the hypothalamus Ang II may stimulate aldosterone biosynthesis. Dose related effects of circulating Ang II on BP were first assessed. Wistar rats instrumented with telemetry probes were infused subcutaneously with Ang II 150 and 500 ng/kg/min for 14 days. The subcutaneous infusion of Ang II at 150 ng/kg/min increased blood pressure gradually up to 20 mmHg and at 500 ng/kg/min up to 60 mmHg. Ang II at 500 ng/kg/min increased plasma Ang II by 4-fold. To assess effects of circulating Ang II on CNS pathways, Wistar rats were implanted subcutaneously with minipumps infusing 150 and 500 ng/kg/min Ang II for 1, 4 and 14 days. Three patterns of neuronal activation were observed by sc infusion of Ang II. The SFO was activated during the first day and remained activated for 4 days, but at 14 days showed diminished activation. MnPO did not show significant activation during the first day but, after several days the activation was high and then less by 14 days. Parvocellular PVN (pPVN), magnocellular PVN (mPVN) and SON showed an initial activation that increased over time. Chronic intracerebroventricular infusion of an aldosterone synthase inhibitor or a mineralocorticoid receptor (MR) blocker attenuated the increase in Fra expression in PVN but not SON, and prevented the decrease in SFO after 14 days infusion of Ang II. A significant increase in mRNA expression of steroidogenic acute regulatory protein (StAR), a rate limiting enzyme in aldosterone production was found in glia cells of PVN and SFO assessed by rt-PCR after 3 days subcutaneous infusion of Ang II at 500 ng/kg/min. Total expression of aldosterone synthase (CYP11B2) mRNA was increased in SFO, MnPO, SON and PVN after 3 days of infusion of Ang II. After 14 days no significant changes were observed in the expression of StAR or CYP11B2 mRNA. In comparison, in adrenal StAR mRNA expression increased after 3 days but no longer after 14 days. In contrast, CYP11B2 mRNA expression in adrenal increased after both 3 and 14 days of infusion. These findings may support our hypothesis that chronic elevation of circulating Ang II increases neuronal activity in CVOs, presumably leading to activation of the PVN and SON to induce an increase in aldosterone production in magnocelular PVN and SON. In the second phase activation of CVOs appears to diminish, but an aldosterone-dependent amplifying mechanisms, causes sustained activation of the PVN and thereby hypertension.

The intracellular delivery of molecules to modulate signaling pathways and gene expression is a powerful approach to control stem cell fate decision. For applications in gene therapy and regenerative medicine, the use of genetic material and viral vectors raise concerns because stem cells persist throughout life, and long-term effects of uncontrolled genetic modifications could affect the cellular progeny. An alternative is to deliver directly peptides or proteins using cell-permeable peptides (CPPs) which have the ability of crossing the plasma membrane and carrying cargos into cells. CPPs can therefore be used to deliver factors to direct stem cells proliferation, survival and differentiation. This thesis describes an approach to control stem cell fate based on the delivery of a CPP-conjugated bioactive peptide. A first significant contribution from this work is the development of a flow cytometric assay to accurately quantify the uptake of a panel of CPPs. This study revealed that HIV-transactivator of transcription (TAT) and Antennapedia (Antp) offered the highest level of translocation in different cell types. The uptake was improved by treating the cells with a single, low-voltage electrical pulse that selectively enhances the amount of TAT-conjugated peptides and proteins delivered by at least an order of magnitude, without causing cellular toxicity or apoptosis. Subsequently, flow cytometry, confocal microscopy, capillary electrophoresis and mass spectrometry were used to examine the intracellular fate of TAT-conjugated peptides in order to define the parameters that limit their bioactivity and point to specific sequence modifications that can improve their efficacy. The advances described in this thesis were applied to the development of TAT-eIF2B, a peptide-inhibitor of glycogen synthase kinase-3 (GSK-3). TAT-eIF2B was found to be specific for GSK-3 and had a significant positive effect on the formation of neurospheres in embryonic stem cell cultures and on the survival of myeloid progenitors in cytokine-starved fetal liver cell cultures. On the other hand, GSK-3 inhibition reduced the number of neurospheres generated by human olfactory neuroepithelium cells due to lower proliferation and increased neuronal differentiation. In summary, this work describes the development of a peptide-based technology to deliver bioactive cargoes in cells, and it demonstrates its utility for modulating the activity of a master regulator of stem cell fate decision.

The intracellular delivery of molecules to modulate signaling pathways and gene expression is a powerful approach to control stem cell fate decision. For applications in gene therapy and regenerative medicine, the use of genetic material and viral vectors raise concerns because stem cells persist throughout life, and long-term effects of uncontrolled genetic modifications could affect the cellular progeny. An alternative is to deliver directly peptides or proteins using cell-permeable peptides (CPPs) which have the ability of crossing the plasma membrane and carrying cargos into cells. CPPs can therefore be used to deliver factors to direct stem cells proliferation, survival and differentiation. This thesis describes an approach to control stem cell fate based on the delivery of a CPP-conjugated bioactive peptide. A first significant contribution from this work is the development of a flow cytometric assay to accurately quantify the uptake of a panel of CPPs. This study revealed that HIV-transactivator of transcription (TAT) and Antennapedia (Antp) offered the highest level of translocation in different cell types. The uptake was improved by treating the cells with a single, low-voltage electrical pulse that selectively enhances the amount of TAT-conjugated peptides and proteins delivered by at least an order of magnitude, without causing cellular toxicity or apoptosis. Subsequently, flow cytometry, confocal microscopy, capillary electrophoresis and mass spectrometry were used to examine the intracellular fate of TAT-conjugated peptides in order to define the parameters that limit their bioactivity and point to specific sequence modifications that can improve their efficacy. The advances described in this thesis were applied to the development of TAT-eIF2B, a peptide-inhibitor of glycogen synthase kinase-3 (GSK-3). TAT-eIF2B was found to be specific for GSK-3 and had a significant positive effect on the formation of neurospheres in embryonic stem cell cultures and on the survival of myeloid progenitors in cytokine-starved fetal liver cell cultures. On the other hand, GSK-3 inhibition reduced the number of neurospheres generated by human olfactory neuroepithelium cells due to lower proliferation and increased neuronal differentiation. In summary, this work describes the development of a peptide-based technology to deliver bioactive cargoes in cells, and it demonstrates its utility for modulating the activity of a master regulator of stem cell fate decision.

Elevated circulating Ang II activates neurons in the forebrain cardiovascular regulatory areas to cause sympatho-excitation and hypertension. We hypothesized that circulating Ang II causes neuronal activation in the SFO and thereby activates efferent pathways to the PVN, and chronically causes activation of aldosterone production in magnocellular neurons in PVN and SON, which amplifies neuronal activation in the PVN and central sympatho-excitatory pathways. The aim of the present study was to determine the pattern of neuronal activation in forebrain nuclei by circulating Ang II and to elucidate where in the hypothalamus Ang II may stimulate aldosterone biosynthesis. Dose related effects of circulating Ang II on BP were first assessed. Wistar rats instrumented with telemetry probes were infused subcutaneously with Ang II 150 and 500 ng/kg/min for 14 days. The subcutaneous infusion of Ang II at 150 ng/kg/min increased blood pressure gradually up to 20 mmHg and at 500 ng/kg/min up to 60 mmHg. Ang II at 500 ng/kg/min increased plasma Ang II by 4-fold. To assess effects of circulating Ang II on CNS pathways, Wistar rats were implanted subcutaneously with minipumps infusing 150 and 500 ng/kg/min Ang II for 1, 4 and 14 days. Three patterns of neuronal activation were observed by sc infusion of Ang II. The SFO was activated during the first day and remained activated for 4 days, but at 14 days showed diminished activation. MnPO did not show significant activation during the first day but, after several days the activation was high and then less by 14 days. Parvocellular PVN (pPVN), magnocellular PVN (mPVN) and SON showed an initial activation that increased over time. Chronic intracerebroventricular infusion of an aldosterone synthase inhibitor or a mineralocorticoid receptor (MR) blocker attenuated the increase in Fra expression in PVN but not SON, and prevented the decrease in SFO after 14 days infusion of Ang II. A significant increase in mRNA expression of steroidogenic acute regulatory protein (StAR), a rate limiting enzyme in aldosterone production was found in glia cells of PVN and SFO assessed by rt-PCR after 3 days subcutaneous infusion of Ang II at 500 ng/kg/min. Total expression of aldosterone synthase (CYP11B2) mRNA was increased in SFO, MnPO, SON and PVN after 3 days of infusion of Ang II. After 14 days no significant changes were observed in the expression of StAR or CYP11B2 mRNA. In comparison, in adrenal StAR mRNA expression increased after 3 days but no longer after 14 days. In contrast, CYP11B2 mRNA expression in adrenal increased after both 3 and 14 days of infusion. These findings may support our hypothesis that chronic elevation of circulating Ang II increases neuronal activity in CVOs, presumably leading to activation of the PVN and SON to induce an increase in aldosterone production in magnocelular PVN and SON. In the second phase activation of CVOs appears to diminish, but an aldosterone-dependent amplifying mechanisms, causes sustained activation of the PVN and thereby hypertension.

L'organisme synthétise les lipides de novo au niveau hépatique, les transforme en triglycérides, et les stocke dans le tissu adipeux. Les lipides servent à de nombreuses fonctions biologiques essentielles, telles la synthèse de membrane ou d'hormone, mais aboutissent à un excès de masse corporelle lorsqu'il y a déséquilibre. L'acide gras synthase (FAS) est une enzyme clé de la lipogenèse. Elle synthétise le palmitate à partir d'acétyl-CoA et de malonyl-CoA en présence de nicotinamide adénine dinucléotide phosphate (NADPH). Comprendre ses mécanismes de régulation est important dans l'optique de moduler son activité. La FAS est régulée positivement par la triiodothyronine (T₃) et l'insuline, l'effet est inhibé par les MCFA. La régulation est essentiellement transcriptionnelle. Muter le gène FAS, afin de l'éteindre, est létal. L'inhibition partielle à l'aide d'agents tel le C75 serait donc préférable. Malheureusement, en plus d'avoir des effets anorexiques réversibles pour C75, ces agents ont des effets neurotoxiques dévastateurs. L'inhibition partielle de la FAS par des nutriments, tels les acides gras à chaîne moyenne (MCFA), serait une solution. Le présent projet propose d'élucider les mécanismes moléculaires par lesquels les hormones modulées par la diète, telles l'insuline et la triiodothyronine T₃, influencent l'activité de la FAS et comment les MCFA inhibent cette stimulation hormonale. Comme l'effet hormonal ne semble pas être totalement transcriptionnel et qu'une implication du glucose au niveau post-transcriptionnel a aussi été suggérée, nous avons analysé l'effet de l'insuline et de la T₃ sur la stabilisation des ARN messagers et sur l'activité enzymatique de la FAS en utilisant des milieux à haute ou basse concentration en glucose. Cependant, nous n'avons pas observé de différence significative, peu importe la concentration de glucose dans le milieu de culture. Des études préalables ont aussi démontré un rôle de la phosphorylation sur la régulation transcriptionnelle de la FAS par l'insuline et le T₃. Nous avons investigué ce rôle sur l'activité de la FAS à l'aide d'inhibiteurs spécifiques. En utilisant PD98058, un inhibiteur spécifique de MEK, nous avons observé une implication de Erk1/2 dans l'induction de FAS. Avec LY 294002, un inhibiteur spécifique de PI3Kinase (PI3K), nous observons une inhibition de la FAS en présence de T₃, ce qui impliquerait la voie PI3K dans l'activation de la FAS induite par la T₃. Des études préliminaires ont montré que l'inhibition de la FAS par les MCFA se faisait très rapidement. Une courbe d'inhibition en fonction du temps a été effectuée et a révélé une inhibition dans les premières 30 minutes d'exposition. Des études de captation ont montré que les MCFA étaient absorbés par les hépatocytes. Un profil lipidique a montré que les MCFA sont métabolisés pour se retrouver dans la fraction lipidique correspondant aux triglycérides, qui nous a donné une idée des voies métaboliques empruntées. L'acide bétulinique, un inhibiteur de la CPTl, ainsi que l'Etomoxir, un inhibiteur de la DGAT, ne semble pas avoir d'effet sur l'inhibition de la FAS induite par les MCFA en présence d'insuline et de T₃, contrairement à la Triacsin C, un inhibiteur des acyl-CoA synthases, qui abolit l'effet inhibiteur. En dernier point, nous avons vérifié l'impact de la famille des « scavenger receptors » de classe B tels que SR-BI dans le transport sélectif et la captation de MCFA par la cellule. Ces derniers ne semblent aucunement impliqués dans le transport des MCFA contrairement à nos attentes. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : FAS, MCFA, Acyl-CoA, Insuline, T₃

This research investigated the changes in body adipocyte size and density as well as parameters relating to adipogenesis in growing cobia, Rachycentron canadum. The cobia from a same batch were sampled 5 , 7 , 9 , 13 , 17 , 21 , 26 and 31 weeks after hatching, Liver activities of fatty acid synthase, (FAS), mailc enzyme (ME), and glucose-6-phosphate dehydrogenase (G6PDH) as well as serum total triacylglycerol (TG), total cholesterol (TC), phospholipid (PL), non-esterified fatty acid (NEFA) were assayed. Adipocyte abundance and size spectrum in liver, ventral muscle and dorsal muscle were determined. The cobia attained an average weight of 13.6 ¡Ó 0.5 g at week 5, and were cultured in nursery outdoor ponds until an average weight 87.5 ¡Ó 3.8 g when moved to open ocean cages. They grew to an average weight 1690.8 ¡Ó 106.6 g at week 31. The crude lipid content in liver, ventral and dorsal muscle increased significantly with fish age, and were 36.1 ¡Ó 3.2 g, 14.8 ¡Ó 0.2g, 4.6 ¡Ó 0.0 g at week 31. No significant change was found in hepatic FAS activity. Hepatic ME activity increased significantly after the fish were stocked in the cages. Whilr hepatic ME activity reduced with age, TG and PL were both increased significantly with age. While adipocyte diameter in liver showed a decreasing trend as the fish grew its abundance increased significantly at week 13 and maintained between 3070¡ã3356 x 104 cell/g tissue during week 17-31. Similarly, adipocyte abundance in ventral muscle increased significantly at week 13, and maintained between 255¡ã269 x 104 cell/g tissue afterwards. There was no significant change in size of ventral muscle adipocyte as fish grew. These results indicate that the adipocyte hyperplasia occurred during week 7- 13, when body weight was 100- 400 g. Adipocyte hypertrophy was observed when the fish reached week 31, there was a sign of adipocyte hypertrophy in liver when the fish were at the last phase of nursery outdoor ponds before being moved to the offshore cages.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 35-40). Also available on the World Wide Web.

Thesis (Ph.D.)--Marshall University, 2009. / Title from document title page. Includes abstract. Document formatted into pages: contains 117 p. Includes bibliographical references p. 114.

Background and objectives: Circulating endothelial progenitor cells (EPCs) play an essential role in maintaining vascular integrity and preventing endothelial dysfunction. Decreased circulating EPC levels are frequently observed in various cardiovascular risks, including aging and diabetes. Endothelial nitric oxide synthase (eNOS) and adiponectin exert their vasculo-protective effects by directly targeting the key components of the vascular system, such as endothelial cells and smooth muscle cells. Both eNOS and adiponectin have been implicated in the mobilization and in vitro functions of EPCs. However, whether and how circulating EPCs are involved in eNOS and adiponectin-mediated vascular protection remain unclear. The objective of this study is to investigate the role of circulating EPCs in eNOS and adiponectin-mediated regulation of vascular integrity after arterial injury under both physiological and pathophysiological conditions, and to elucidate the underlying mechanisms involved. Key findings: 1. Modulation of eNOS activity in vivo by replacing the serine 1176 (S1176) with an aspartate (S1176D mutation or Dki) to mimic phosphorylation or with an alanine (S1176A mutation or Aki) to render it unphosphorylatable altered reendothelialization and subsequent endothelial function after arterial injury in mice. 2. eNOS S1176D mutation increased the number of circulating EPCs and their incorporation into regenerated endothelium, whereas eNOS S1176A or knockout (KO) impaired the mobilization and reendothelializing capacity of circulating EPCs after injury. 3. eNOS S1176D elevated circulating EPCs by promoting the proliferation and differentiation of bone marrow hematopoietic stem cells (HSCs) into EPCs and by inhibiting apoptosis of circulating EPCs. 4. Adiponectin deficiency in mice resulted in progressive decrease of circulating EPCs with aging. Systemic administration of recombinant adiponectin reversed the decreased EPCs number in adiponectin KO mice. In db(-/-) diabetic mice, adiponectin deficiency further reduced circulating EPCs number and subsequent reendothelialization after injury. Rosiglitazone (Rosi), an antidiabetic drug, induced an upregulation of EPCs number and improved reendothelialization, which were partially abolished in the absence of adiponectin. 5. In cultured EPCs, adiponectin significantly inhibited high glucose-induced premature senescence, whereas its effects on proliferation and apoptosis were not evident. High glucose instigated EPCs senescence by increasing the intracellular accumulation of reactive oxygen species (ROS), activation of p38 MAPK and expression of p16INK4A, whereas all these changes could be abolished by adiponectin through adenosine monophosphate (AMP)-activated protein kinase (AMPK) and cyclic AMP (cAMP)/protein kinase A (PKA)-dependent pathways. 6. Compared to cells from db(-/-) diabetic mice, bone marrow EPCs isolated from db(-/-) plus adiponectin double KO (DKO) mice were more susceptible to high glucose-evoked senescence, which were abrogated by adiponectin in vitro. Importantly, chronic administration of adiponectin or the anti-oxidant N-acetylcysteine (NAC) prevented both aging and diabetes-associated elevation of p16INK4A and decline of circulating EPCs in DKO mice. Conclusions: Collectively, the current study demonstrates that circulating EPCs are actively involved in the vasculo-protective effects of both eNOS and adiponectin under physiological and pathological conditions. These findings enrich our knowledge of the versatile functions of eNOS and adiponectin in vascular protection and provide solid scientific evidence supporting the use of eNOS and adiponectin as possible therapeutic targets for cardiovascular diseases. / published_or_final_version / Medicine / Doctoral / Doctor of Philosophy