Siu-Yin Sylvia Lam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 123-140). / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iv / 英中譯名對照 --- p.vi / Acknowledgements --- p.vii / Table of Contents --- p.viii / Abbreviations --- p.xiii / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Overview of Carotid Body --- p.1 / Chapter 1.1.1 --- Type I Cells --- p.3 / Chapter 1.1.2 --- Type II Cells --- p.4 / Chapter 1.1.3 --- Blood Vessels --- p.5 / Chapter 1.1.4 --- Innervation --- p.5 / Chapter 1.1.5 --- Biochemistry --- p.6 / Chapter 1.1.6 --- Physiology and Function --- p.7 / Chapter 1.2 --- The Renin-Angiotensin System (RAS) --- p.8 / Chapter 1.2.1 --- Circulating RAS --- p.8 / Chapter 1.2.1.1 --- Angiotensinogen --- p.10 / Chapter 1.2.1.2 --- Renin --- p.10 / Chapter 1.2.1.3 --- Angiotensin I --- p.11 / Chapter 1.2.1.4 --- Angiotensin Converting Enzyme --- p.12 / Chapter 1.2.1.5 --- Angiotensin II --- p.12 / Chapter 1.2.1.6 --- Angiotensin II Receptors --- p.13 / Chapter 1.2.1.7 --- Angiotensin IV and Angiotensin IV Receptor --- p.15 / Chapter 1.2.2 --- Tissue RAS --- p.16 / Chapter 1.3 --- Hypoxia and Carotid Body --- p.18 / Chapter 1.4 --- Hypoxia and RAS --- p.21 / Chapter 1.5 --- Hypoxia and RAS in Carotid Body --- p.23 / Chapter 1.6 --- Aims of Study --- p.24 / Chapter 1.6.1 --- Existence of Functional Angiotensin II Receptors --- p.24 / Chapter 1.6.2 --- Regulation and Function of Angiotensin II Receptors by Chronic Hypoxia --- p.24 / Chapter 1.6.3 --- Existence of an Intrinsic Angiotensin-generating System --- p.25 / Chapter 1.6.4 --- Regulation of Local RAS by Chronic Hypoxia --- p.25 / Chapter 1.6.5 --- Studies of AT4 Receptor --- p.26 / Chapter Chapter 2 --- Materials and Methods / Chapter 2.1 --- Experimental Animals and Rat Models --- p.27 / Chapter 2.1.1 --- Rat Model of Chronic Hypoxia --- p.27 / Chapter 2.1.2 --- Isolation of Carotid Body --- p.28 / Chapter 2.2 --- Semi-quantitative Reverse Transcriptase-polymerase Chain Reaction (RT-PCR) --- p.30 / Chapter 2.2.1 --- Total RNA Extraction and Quantification --- p.30 / Chapter 2.2.2 --- Reverse Transcription (RT) --- p.31 / Chapter 2.2.3 --- Polymerase Chain Reaction (PCR) --- p.31 / Chapter 2.2.4 --- Gel Electrophoresis --- p.34 / Chapter 2.2.5 --- Optimization of Semi-quantitative RT-PCR for RAS Gene Analysis --- p.34 / Chapter 2.3 --- Northern Blotting --- p.35 / Chapter 2.3.1 --- Transfer of Denatured RNA to Nitrocellulose Membrane By Capillary Elution --- p.35 / Chapter 2.3.2 --- Hybridization --- p.36 / Chapter 2.4 --- In-situ Hybridization --- p.38 / Chapter 2.4.1 --- Linearization of Angiotensinogen cDNA --- p.38 / Chapter 2.4.2 --- Riboprobe Preparation --- p.38 / Chapter 2.4.3 --- Quantification and Gel Electrophoresis of Riboprobes --- p.39 / Chapter 2.4.4 --- In-situ Hybridization Histochemistry --- p.39 / Chapter 2.5 --- Immunohistochemistry --- p.42 / Chapter 2.5.1 --- Preparation of Cryosection --- p.42 / Chapter 2.5.2 --- Indirect Immunoperoxidase Staining --- p.42 / Chapter 2.5.3 --- Immunofluorescent Double Staining --- p.43 / Chapter 2.6 --- Western Blot Analysis --- p.45 / Chapter 2.6.1 --- Preparation of Angiotensinogen Protein --- p.45 / Chapter 2.6.2 --- Quantification of Protein Concentration --- p.45 / Chapter 2.6.3 --- Sample Preparation --- p.45 / Chapter 2.6.4 --- Sodium Dodecyl-sulphate Polyacrylamide Gel Electrophoresis (SDS-PAGE) --- p.46 / Chapter 2.6.5 --- Electroblotting and Immunodetection of Proteins --- p.46 / Chapter 2.7 --- Spectrofluorimetric Measurement and In-vitro Electrophysiology --- p.48 / Chapter 2.7.1 --- Dissociation of Carotid Body Type I Cells and Spectrofluorimetric Measurement --- p.48 / Chapter 2.7.2 --- In-vitro Electrophysiology --- p.49 / Chapter 2.8 --- Assay of ACE Activity --- p.51 / Chapter 2.8.1 --- Crude Membrane Preparation --- p.51 / Chapter 2.8.2 --- Basic Principle for ACE Activity Measurement --- p.51 / Chapter 2.8.3 --- Measurement of ACE Activity --- p.51 / Chapter 2.8.4 --- Fluorescence Measurement --- p.53 / Chapter 2.9 --- In-vitro Autoradiography and Fluorescence-labeled Binding Assay for Angiotensin IV --- p.54 / Chapter 2.9.1 --- Preparation of Frozen Tissue Sections --- p.54 / Chapter 2.9.2 --- Localization and Density of AT4 Receptor --- p.54 / Chapter 2.10 --- Statistics and Data Analysis --- p.57 / Chapter Chapter 3 --- Results / Chapter 3.1 --- Functional Expression of Angiotensin II Receptors --- p.58 / Chapter 3.1.1 --- [Ca2+]i Response to Angiotensin II --- p.58 / Chapter 3.1.2 --- Antagonistic Blockade of Angiotensin II Receptor Subtypes --- p.58 / Chapter 3.1.3 --- Expression of AT1 Receptors mRNA --- p.61 / Chapter 3.1.4 --- Cellular Localization of AT1 Receptors Protein --- p.61 / Chapter 3.2 --- Effect of Chronic Hypoxia on the Expression and Function of Angiotensin II Receptors --- p.64 / Chapter 3.2.1 --- Effect of Chronic Hypoxia on the Expression of AT1 Receptors --- p.64 / Chapter 3.2.2 --- Effect of Chronic Hypoxia on the Expression of AT2 Receptors --- p.67 / Chapter 3.2.3 --- Cellular Localization of the AT1 Receptor by Chronic Hypoxia --- p.69 / Chapter 3.2.4 --- Increase of Afferent Nerve Activities of the Carotid Body In-vitro by Angiotensin II --- p.71 / Chapter 3.2.5 --- Inhibition of Angiotensin II-mediated Response in Chronically Hypoxic Carotid Body by Losartan --- p.73 / Chapter 3.3 --- Evidence for the Existence of an Intrinsic Angiotensin-generating System --- p.75 / Chapter 3.3.1 --- Expression and Localization of Angiotensinogen mRNA --- p.75 / Chapter 3.3.2 --- Expression and Localization of Angiotensinogen Protein --- p.78 / Chapter 3.3.3 --- Expression of Renin mRNA --- p.81 / Chapter 3.3.4 --- Expression of ACE mRNA --- p.81 / Chapter 3.4 --- Effect of Chronic Hypoxia on the Locally-generated Angiotensin System --- p.85 / Chapter 3.4.1 --- Effect of Chronic Hypoxia on the Expression of Angiotensinogen mRNA --- p.85 / Chapter 3.4.2 --- Effect of Chronic Hypoxia on the Localization of Angiotensinogen mRNA --- p.87 / Chapter 3.4.3 --- Effect of Chronic Hypoxia on the Expression of Angiotensinogen Protein --- p.89 / Chapter 3.4.4 --- Effect of Chronic Hypoxia on the Expression of ACE --- p.91 / Chapter 3.5 --- Time-course Effect of Chronic Hypoxia on ACE Activity --- p.93 / Chapter 3.6 --- Preliminary Studies of AT4 Receptor --- p.98 / Chapter 3.6.1 --- In-vitro Autoradiographic Study of AT4 Receptors --- p.98 / Chapter 3.6.2 --- Localization of AT4 Receptors --- p.100 / Chapter Chapter 4 --- Discussion / Chapter 4.1 --- Functional Expression of Angiotensin II Receptors --- p.102 / Chapter 4.2 --- Upregulation and Function of Angiotensin II Receptors --- p.105 / Chapter 4.3 --- Existence of a Local RAS --- p.108 / Chapter 4.4 --- Regulation of the Local RAS --- p.112 / Chapter 4.5 --- Time-dependent Changes of ACE Activity --- p.155 / Chapter 4.6 --- Presence and Regulation of AT4 Receptor --- p.117 / Chapter 4.7 --- Conclusion --- p.120 / Chapter 4.8 --- Future Works --- p.121 / Chapter Chapter 5 --- References --- p.123

The apelin-apelin receptor (APLNR) system is an important regulator of cardiovascular homeostasis both in health and disease. Principal actions of the apelin-APLNR system are positive inotropism, vasodilatation, diuresis and a potential anti-inflammatory role in vascular tissue. The significance of this system is highlighted in heart failure and pulmonary hypertension. Preclinical models of these diseases report downregulation of apelin- APLNR, whilst knockout strains develop more severe phenotypes, more rapidly. Moreover treatment with exogenous apelin retards or prevents disease progression. In man plasma apelin concentrations are reduced in heart failure and vary with disease severity. Initial increases are reported in mild heart failure suggesting a compensatory role, but are depressed in severe heart failure. Limited data profile myocardial APLNR expression in heart failure and in keeping with plasma apelin concentrations, expression is reduced in severe heart failure. Of interest, the APLNR most closely resembles the angiotensin II type 1 receptor (AT1R), sharing similar tissue expression and sequence homology, but mediates opposing physiological actions. Furthermore, emerging preclinical data support receptor interactions between the APLNR and AT1R that modify their native signalling pathways. It is likely that the apelin-APLNR system serves to antagonise the renin-angiotensin system. Given the established role of angiotensin II, arguably the most important peptide in cardiovascular pathophysiology, any system influencing its actions merits further investigation. Current clinical studies are limited to 20 minutes infusions and understanding its cardiovascular effects requires more prolonged administration. There are concerns of tachyphylaxis and interaction with the renin-angiotensin-aldosterone system (RAAS), possibly reducing efficacy of APLNR agonism in clinical settings. In a series of randomised, blinded crossover clinical trials 60 healthy volunteers and 20 patients with chronic stable heart failure were enrolled to assess the effects of (Pyr1)apelin-13 infusion at rest, during acute and subacute infusion, exercise and upregulation of the renin-angiotensin system. I have identified that APLNR agonism is unaffected by prevailing levels of angiotensin II activity in local vascular beds and systemic haemodynamic infusions. Furthermore, the efficacy of (Pyr1)apelin-13 is retained in healthy volunteers and patients with chronic stable heart failure during acute and subacute infusions. Finally, systemic (Pyr1)apelin-13 does not alter exercise performance in healthy individuals. My findings support a role in targeting the APLNR in chronic heart failure and predict that efficacy will be retained in chronic dosing. Future research directed at other patient groups with ventricular dysfunction is merited, in order to further characterise the utility of this system. These studies are encouraging; however, longer term studies may reveal effects beyond haemodynamic alterations and examine the effects on cardiac fibrosis and endothelial function. A long acting agonist is required to fully evaluate the role of APLNR signalling in cardiovascular disease.

Fluid balance is critical for cells to maintain at homeostasis as disturbances in it can disrupt cellular function and consequently the physiology of an organism. Fluid loss for an organism can be classified as either intra- or extracellular, and it appears that different mechanisms have developed to restore homeostasis after intra- or extracellular dehydration. The renin-angiotensin system (RAS) has been shown to be an important mediator of extracellular dehydration induced fluid intake. Various lines of evidence have demonstrated the importance of the subfornical organ (SFO) to mediate fluid intake, especially due to the RAS, and we have shown that production and action of angiotensin (ANG) at the SFO is necessary for fluid intake due to ANG within the brain. Protein kinase C (PKC), specifically PKC-a;, is shown to be a necessary and sufficienty sufficient effector in the SFO to mediate brain angiotensin-II (ANG-II) polydipsia. It is also demonstrated that production of ANG from the SFO is sufficient to increase fluid intake through the ANG-II type 1 (AT1R) receptor and PKC. While production of ANG from the SFO is sufficient to increase fluid intake it is not sufficient to increase blood pressure, metabolism, or sodium appetite. Thus, production and action of ANG to activate PKC-a; is both necessary and sufficient to increase fluid intake at the SFO, and the fluid, pressor, and metabolic phenotypes of brain ANG through the SFO can be separated.

Renin is an enzyme that catalyzes the rate-limiting step in the production of angiotensin peptides, and is thus a key regulator of processes controlled by angiotensin such as blood pressure, hydromineral balance, and metabolism. Our laboratory and others have previously identified a novel isoform of renin (icRen) which, as a result of the utilization of an alternate first exon, lacks the signal peptide and first third of the pro-segment of classical secreted renin (sRen). This alternate icRen isoform thus remains within the cytoplasm of the cell, but is constitutively active. Here, we report that while sRen is the predominant form of renin expressed in most tissues during development, icRen is the predominant form of renin within the adult brain. Thus, we hypothesized that sRen and icRen play distinct physiological roles in adult mice. To examine this hypothesis, we have utilized the Cre-LoxP system to selectively delete either isoform globally or within selected cell types such as neurons and glia. We have successfully developed a "sRen-flox" model, in which endogenous mouse sRen isoform can be selectively deleted, while not affecting endogenous icRen production. Breeding these mice against the E2A-Cre, Nestin-Cre, and GFAP-Cre mouse lines resulted in global-, neuronal-, and glial-specific knockouts of sRen, respectively. Physiological characterization of resulting mice has uncovered postnatal lethality, hypotension, renal atrophy, vascular dysfunction and decreased body weight and white adipose in the global knockouts. Depletion of sRen from only neuronal or glial cells does not appear to alter any of these phenotypes at baseline. From these data, we conclude that while peripheral sRen is of primary importance to blood pressure regulation, hydromineral balance, and metabolism, central expression of this isoform is unimportant. Further, comparison of our results to published findings from global total renin knockout models indirectly supports a role for icRen in the brain. We are currently in the process of generating icRen-flox and subsequent knockout mice, which will be useful models to directly analyze the physiological role(s) of icRen.

Leptin acts within the brain to increase resting metabolic rate (RMR) and blood pressure (BP). The renin-angiotensin system (RAS) elicits similar effects in the brain, as reviewed in chapter 1, and it has previously been shown that central angiotensin II type 1 (AT1) receptors are required for leptin-mediated inductions in sympathetic nerve activity to the brown adipose tissue. Thus, we hypothesize that the brain RAS mediates the metabolic effects of leptin. To investigate the interaction between the RAS and leptin, we generated the AT1ALepR-KO mouse which lacks the AT1A receptor in leptin-sensitive cells. In chapter 2, we demonstrated that stimulation of RMR by DOCA-salt and high fat diet requires AT1A receptors in leptin receptor-expressing cells and that these cells expressing both AT1A and the leptin receptor appear to be agouti related-peptide (AgRP) neurons. In chapter 3, we investigated the role of AT1A specifically in AgRP neurons by utilizing AT1AAgRP-KO mice. Similar to AT1ALepR-KO mice, AT1AAgRP-KO mice exhibited deficits in BAT SNA responses to leptin and induction of RMR by alpha melanocyte stimulating hormone. In chapter 4, we utilized a novel transgenic mouse model to demonstrate that microglia do not express the AT1A receptor under chow or high fat diet fed conditions. Taken together, we conclude that a subset of AgRP neurons, which express both the leptin receptor and the AT1A receptor, are critical for the control of sympathetic nerve activity and ultimately RMR.

Die vorliegende Arbeit untersucht die positiven Auswirkungen des Angiotensin-II-Rezeptor-Antagonisten Telmisartan auf die endotheliale Funktion und Thrombozytenaktivierung bei Ratten mit Streptozotocin-induziertem Diabetes mellitus. In Gefäßreaktivitätsstudien, Luminometer- und Fluoreszenzmessungen und mit Hilfe der Durchflusszytometrie wurden die Wirkungen des Medikamentes überprüft. Es konnte gezeigt werden, dass sich durch Telmisartan die NO-Bioverfügbarkeit verbessert, welche maßgeblich für die endotheliale Funktion verantwortlich ist und durch Ca2+-abhängige Aktivierung der eNOS und dehnungsinduzierte, Ca2+-unabhängigen NO-Bildung beeinflusst wird. Positiv wird des Weiteren die Sensitivität der glatten Gefäßmuskelzellen gegenüber NO beeinflusst, was zur Vasodilatation führt. Die atherosklerosefördernde Superoxidbildung wird zusätzlich reduziert. Es erfolgten außerdem Messungen von thrombozytengebundenem Fibrinogen, dementsprechend der GP IIb/IIIa-Aktivität, und der VASP-Phosphorylierung, demzufolge dem NO/cGMP-Signalweg, in Thrombozyten durch FITC-markierte Antikörper mit Hilfe der Durchflusszytometrie. Es wurde gezeigt, dass die Thrombozytenaktivierung, die für den initialen Schritt der Atherosklerose verantwortlich gemacht wird, durch Telmisartan verringert wird. Alle Messungen wurden vergleichend in einer Kontroll-, Placebo- und Telmisartangruppe durchgeführt. Die beobachtete Blutdrucksenkung ist, nach früheren Betrachtungen, nicht alleine verantwortlich für die verbesserte endotheliale Funktion, welche bei dem Einsatz von AT-II-Antagonisten beobachtet wird. Telmisartan wirkt, laut einer Studie, als einziger AT-II-Antagonist als partieller PPAR-Rezeptor, so dass Insulinresistenz und metabolische Parameter verbessert werden. Über diese Wirkungen beeinflusst Telmisartan auch die endotheliale Funktion und die Thrombozytenaktivierung. Zur Reduktion von vaskulären Komplikationen bei Diabetes mellitus erscheint Telmisartan aufgrund der vorliegenden Ergebnisse als sinnvolle medikamentöse Therapie. / Diabetes is associated with endothelial dysfunction and platelet activation, which are positively modulated by chronic treatment with telmisartan.

Bibliography : leaves 162-181. / xvi, 186, [19] leaves, [13] leaves of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines the gene expression of the renin-angiotensin system (RAS) in the spontaneously hypertensive rat and the normotensive Wistar-Kyoto rat. / Thesis (Ph.D.)--University of Adelaide, Dept. of Clinical and Experimental Pharmacology, 1994

Zugl.: Giessen, Univ., Diss., 2009

Zugl.: Giessen, Universiẗat, Diss., 2009.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2002. / Härtill 6 uppsatser.