The introduction of antiretroviral drugs has dramatically increased the lifespan of human immunodeficiency virus (HIV)-infected patients, shifting the major concern towards long-term morbidity and mortality, particularly an increased risk of cardiovascular complications. Antiretroviral therapy has been proposed to be one of the contributing factors. However, existing evidence for the role of antiretroviral therapy in the development of cardiovascular diseases is controversial. Therefore, in the present thesis, the effects of several antiretroviral drugs on the vascular system were investigated. In view of the contribution of vascular inflammation in the development of cardiovascular diseases, the first study examined the effects of acute treatment of efavirenz, indinavir, saquinavir, lopinavir and ritonavir on the release of major inflammatory markers, interleukin (IL)-8, soluble intercellular adhesion molecule 1 (ICAM-1) and monocyte adhesion molecule 1 (MCP-1) in human umbilical vein endothelial cells in the absence or presence of lipopolysaccharide, a pro-inflammatory stimulus. The results demonstrated that efavirenz and the combination of lopinavir and ritonavir, at concentrations present in human plasma, reduced the IL-8 release, but not that of soluble ICAM-1 and MCP-1 in endothelial cells exposed to lipopolysaccharide. The data, therefore, suggest that efavirenz and lopinavir plus ritonavir may possibly have anti-inflammatory effects. Since these findings seems to contradict with the increased incidence of cardiovascular diseases associated with antiretroviral therapy, in vivo experiments were performed to further characterized the effects of antiretroviral drugs on the cardiovascular system. In the second study, the atherogenic effects of long-term treatment (eight weeks) with efavirenz, abacavir and lamivudine, alone or in combination (as used clinically), were investigated in apolipoprotein E deficient (Apo-E-/-) mice (hyperlipidemic/atherosclerotic model) and the corresponding wild-type mice of both genders. All drug treatments had no effects on the lipid profile, nitrotyrosine expression in the liver (an indication of oxidative stress) and the degree of atherosclerotic lesions in all mice. Efavirenz and lamivudine did not have any significant effects on acetylcholine- and sodium nitroprusside-induced relaxations in all mice. Abacavir and the combination of the three drugs did not have any effects on acetylcholine-induced relaxation in aortae of wild-type mice, but impaired acetylcholine-induced relaxation in those of male Apo-E-/- mice without affecting sodium nitroprusside-induced relaxation. The reduction in relaxation was likely mediated by the cyclooxygenase pathway since indomethacin restored the reduction in relaxation. In male Apo-E-/- mice, IL-6 levels were increased by abacavir and the combined treatment, whereas serum amyloid P component (SAP) levels remained unchanged. Although no differences in the development of atherosclerotic lesions were observed, female Apo-E-/- mice receiving abacavir had better lipid profiles, no impairment in acetylcholine-induced relaxation and decreased serum IL-6 and SAP levels compared to male Apo-E-/- mice, revealing a vasculoprotective role of the female gender. In conclusion, the data suggest that certain, but not all, antiretroviral drugs may increase the risk of cardiovascular diseases, and that this risk may be exacerbated in hyperlipidemia but reduced in females. Antiretroviral drugs should be cautiously prescribed to HIV-infected patients to minimize cardiovascular adverse effects. / published_or_final_version / Pharmacology and Pharmacy / Master / Master of Philosophy

Congenital heart disease (CHD) is the most common type of birth defect affecting eight out of every 1,000 newborns, causing more deaths in the first year of life than any other birth defect. A significant fraction of CHD is associated with abnormal valve structure and function. A detailed understanding of the early signaling events that regulate and guide cardiac valve formation is required to identify new therapeutic targets. Here, I focus on the role of Type III Transforming Growth Factor β Receptor (TGFβR3) in Endocardial epithelial to mesenchymal transformation (EMT), a critical step in valvular development. Using an in vitro assay of endocardial EMT I used small molecule inhibitors to establish that ALK2 and ALK3 are both required for endocardial EMT. Specifically, I demonstrated that ALK2 and ALK3 are downstream of TGFβR3. Finally, I used small molecule inhibitors of the NF-κB pathway to implicate this signaling system in endocardial EMT. These studies identify and clarify the role of specific pathways endocardial EMT which furthers our understanding of TGFβR3 signaling and early valve formation.

An Investigation was undertaken to determine the effects of beta-hydroxy thujaplicin and gamma-thujaplicin, used as the sodium salts, on blood pressure and heart rate in the rat. Attempts were made to discover the sites and modes of action of these two compounds. Gamma-thujaplicin 30mg/kg. produced either a vasopressor or a vasodepressor response in anesthetized rats. The pressor response was usually more pronounced, than the vasodepressor response. Tachycardia occurred with either blood pressure response. To determine whether the central nervous system was necessary for the vasopressor and tachycardiac response, pithed rats were used. In these preparations gamma-thujaplicin produced only a fall in blood pressure and a decrease in heart rate. The effect of adrenergic blocking drugs on the response to gamma-thujaplicin was investigated. In the anesthetized rat the vasopressor response was reduced significantly by both phenoxybenzamine and pronethalol; however, the heart rate was unaffected. In the pithed rat the vasodepressor response produced by gamma-thujaplicin was not affected by pronethalol; however, gamma-thujaplicin produced a significantly greater decrease in heart rate after treatment with pronethalol. To determine whether gamma-thujaplicin had adrenergic alpha-receptor or beta-receptor blocking properties its effect on blood pressure responses to noradrenaline and isoproterenol was investigated. Gamma-thujaplicin was found to reduce the vasopressor effect of intravenous noradrenaline 0.5ug/kg. but had no effect on the vasopressor response produced by isoproterenol 0.25ug/kg. The pressor response to intravenous physostigmine salicylate 40ug/kg. was unaffected by gamma-thujaplicin. The increase in heart rate and blood pressure produced by gamma-thujaplicin, with injections repeated every fifteen minutes, was greatly reduced after the second dose. It is concluded that in the anesthetized rats the vasopressor and tachycardiac response produced by gamma-thujaplicin were of central origin while the vasodepressor effect was a result of direct action on vascular smooth muscle. The vasopressor response could involve the stimulation, via sympathetic nerves, of alpha-adrenergic receptors of vascular smooth muscle. Gamma-thujaplicin can produce alpha-adrenergic receptor, blockade to exogenous noradrenaline, but not to endogenously released noradrenaline since the response to intravenous physostigmine was not affected by the tropolone. Beta-hydroxy thujaplicin 10mg/kg. caused a vasopressor response in all anesthetized and pithed rats tested. The vasopressor response was abolished by phenoxybenzamine in both anesthetized and pithed rats. Beta-hydroxy thujaplicin did not alter isoproterenol induced tachycardia or the vasopressor response produced by physostigmine salicylate. It is concluded that beta-hydroxy thujaplicin caused its vasopressor effect in rats by acting directly on the alpha-adrenergic receptors of vascular smooth muscle. / Medicine, Faculty of / Anesthesiology, Pharmacology and Therapeutics, Department of / Graduate

The IKs current constitutes part of the repolarisation reserve in the human myocardium, and whilst it does not play a major role at resting heart rates, it becomes a crucial component of repolarisation in the setting of increased sympathetic tone and high heart rates. The formation of the IKs current requires the KCNQ1 α-subunit and the KCNE1 β-subunit. Mutations in either of these subunits can lead to long QT syndrome types 1 and 5, respectively. Loss-of-function mutations in the IKs channel can reduce the repolarisation reserve and lead to action potential prolongation, predisposing to lethal cardiac arrhythmias such as torsades de pointes and ventricular fibrillation. It is widely recognised that the IKs channel requires the minor membrane phospholipid PIP2 for its function, and previous work in this laboratory found that mutations in a PIP2-binding region in KCNQ1 led to retention of the channel in the endoplasmic reticulum, suggesting that PIP2 may play a role in anterograde trafficking. Here, the rapamycin-inducible dimerisation system was used to manipulate levels of PIP2 and/or PI4P at the plasma membrane or Golgi, and the effect of this on IKs channel trafficking and function was investigated using molecular biology, confocal microscopy and electrophysiology. Despite difficulties with optimising the rapamycin-induced dimerisation system, it was observed that the IKs channel does not require PIP2 for anterograde trafficking, but is heavily reliant on PIP2 for channel opening. In addition, activation of the β1-adrenergic receptor (β 1-AR) led to an increase in the IKs current amplitude. The potential interplay between β1-AR and PIP2 signalling was also explored by depleting PIP2 during β1-AR stimulation. PIP2 depletion was less effective at inhibiting the IKs current during β1-AR stimulation, but this requires further investigation. In conclusion, the results suggest that the IKs channel is reliant on PIP2 for function, but not anterograde trafficking.

by Chun-Ping Li. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1989. / Bibliography: leaves 135-159.

Thesis (M. Med. Sc.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 43-48).

Thesis (Ph. D.)--University of Hong Kong, 1991.

Abstract Right heart failure may be caused by several etiologic factors such as pulmonary embolism, post coronary bypass, chronic obstructive pulmonary disease (COPD) and right heart infarction. Traditionally, treatment has consisted of fluid loading (volume expansion) and the use of inotropic agents. In the present series of studies, an experimental model of acute right heart failure was developed using right heart infarct. Treatment with drugs chosen to specifically improve right heart performance was then evaluated. The drugs used in this series were aminophlline, adenosine, nitric oxide (NO) and losartan. Aminophylline transiently improved cardiac index and pulmonary vascular resistance, but simultaneously caused an increase in heart rate and a decrease in stroke volume. Although it may reduce right heart afterload, aminophylline did not improve overall cardiac function in this experimental model of right heart infarction. Adenosine affected an increase in cardiac index during the adenosine infusion and in stroke index, while pulmonary vascular resistance and mean pulmonary pressure were decreased. There was a marked decrease in systemic vascular resistance as a result of the drug. Heart rate remained unchanged by the infusion. Discontinuation of the drug resulted in a rapid reversal of the hemodynamic changes. The continuous infusion of adenosine therefore appears to cause an effective arterial vasodilation, with a consequent unloading of right heart afterload. NO treatment significantly reduced right heart afterload. A significant deterioration was observed in cardiac output as well as in left and right ventricle stroke work indices. The use of NO in this model of right heart infarct affected a decrease in both right heart afterload and left heart preload, with an overall deterioration in global hemodynamics. Losartan was shown to decrease central venous pressure and wedge pressure, while cardiac output, left ventricle stroke work and stroke volume all showed improvement. Compared to the control animals, pulmonary vascular resistance, systemic vascular resistance and systemic pressures were unaffected by the drug, as was heart rate. An inhibition of angiotensin II action may therefore be of benefit in the treatment of right heart failure symptoms during the first hours after right heart infarct.

No description available.

published_or_final_version / Pharmacology / Doctoral / Doctor of Philosophy