A relação entre risco cardiovascular e terapia hormonal na pós-menopausa é controversa. Ainda que o estrogênio endógeno possa estar associado ao menor risco cardiovascular observado em mulheres na pré-menopausa em relação às pós-menopáusicas, grandes ensaios clínicos, como o WHI, falharam em demonstrar efeito benéfico da terapia hormonal. Estes resultados podem ter sido influenciados por uma série de fatores, sendo os mais importantes: idade média das pacientes e tempo de menopausa superiores às candidatas usuais de terapia hormonal, tipo e dose dos hormônios utilizados. Desenvolvemos ensaio clínico randomizado, cross-over, com objetivo de avaliar os efeitos de dois tipos de tratamento hormonal na menopausa: tratamento oral baixa dose, associação de estradiol 17 β nasal 300 μcg e drospirenona 2 mg, diário e tratamento nâo oral, estradiol 17 β nasal diário e progesterona micronizada vaginal, 200 mg, 14 dias por mês , sobre variáveis relacionadas com inflamação e função endotelial, perfil antropométrico, metabólico e hormonal em mulheres na pós-menopausa recente e sem doença clínica evidente. Quarenta mulheres na pós-menopausa foram alocadas aleatoriamente para iniciar o tratamento hormonal por um dos dois grupos de tratamento: via oral baixa dose (n=20): ou via não oral (n=20). Ao final dos primeiros 2 meses do estudo, o grupo inicialmente tratado com terapia oral passou a receber tratamento não oral por mais 2 meses, e o grupo inicialmente tratado com terapia não oral passou a receber terapia oral também por mais 2 meses. A avaliação laboratorial foi realizada antes e ao final de 2 e 4 meses de tratamento hormonal. A amostra do estudo foi composta por mulheres com média etária de 51,2 ± 2,7 anos e tempo de amenorréia de 23,1 ± 10 meses. Após os primeiros 2 meses de tratamento, não houve diferença significativa entre os tratamentos sobre circunferência da cintura, relação cintura/quadril, índice de massa corporal e níveis de pressão arterial. Colesterol total diminuiu em ambos os tratamentos de forma semelhante. O tratamento oral teve um efeito maior em reduzir os níveis de LDL-C. HDL-C, triglicerídeos, glicemia e insulinemia de jejum, glicemia e insulinemia 2 horas após sobrecarga oral de glicose não se modificaram. PCR e FVWdiminuíram significativamente, e fibrinogênio permaneceu inalterado. Após o período de 4 meses de tratamento hormonal, não houve diferença significativa entre os tratamentos sobre circunferência da cintura, relação cintura/quadril, índice de massa corporal e níveis de pressão arterial. Durante o tratamento oral observou-se redução da circunferência da cintura e da relação cintura/ quadril em relação ao basal. Colesterol total diminuiu em ambos os grupos de tratamento, e HDL-C diminuiu discreta, mas significativamente após o tratamento oral, enquanto triglicerídeos diminuíram durante tratamento não oral. A glicemia 2 horas após sobrecarga oral de glicose apresentou valores mais elevados em relação ao basal após tratamento oral. Em contraste, glicemia e insulinemia em jejum e insulinemia 2 horas após sobrecarga oral de glicose não se modificaram. Níveis de FVW encontraram-se significativamente reduzidos após 4 meses de tratamento hormonal. Em conclusão, os resultados obtidos em nosso estudo sugerem que os tratamentos não induziram efeitos deletérios sobre variáveis relacionadas com risco cardiovascular, a curto prazo, em uma população de mulheres na pós-menopausa recente e aparentemente saudáveis. O tratamento hormonal baixa dose por via oral manteve os efeitos benéficos conhecidos do tratamento hormonal por via oral, a redução do colesterol total e do LDL-C, e evitou os efeitos nocivos tradicionalmente atribuídos à via oral: o aumento de marcadores próinflamatórios, relacionados à disfunção endotelial. O tratamento hormonal por via não oral mostrou-se também uma alternativa segura, não relacionado à modificações no perfil metabólico e nos marcadores de função endotelial. / The relationship between cardiovascular risk and hormone therapy (HT) for menopause is a contemporary and complex issue. While evidences suggest an association between endogenous estrogen and cardiovascular protection among premenopausal women, recent clinical trials have failed in demonstrate a benefic impact of HT on prevention of cardiovascular events. These results seem to be related by several factors, including selection biases like higher mean age of and time since menopause of participants, fixed type and dosages of hormones administered. A cross-over, randomized clinical trial was designed in order to evaluate the effects of two types of HT: low dose oral treatment, estradiol 17 β oral 1 mg and drospirenona 2 mg, by day and non-oral treatment, estradiol 17 β nasal 300 μcg by day and vaginal micronized progesterone, 200 mg/d, 14 days by month on variables associated with endothelial function, anthropometric, metabolic and hormonal variables on early and healthy postmenopausal women.Forty postmenopausal women were randomly allocated to start with one of the treatments: low dose oral treatment or non-oral treatment. At the end of two months, the group that started with low dose oral treatment passed to receive the non oral treatment for additional two months and vice-versa. Laboratory evaluations were performed before, at 1, 2 and 4 months of HT. The sample of the study included postmenopausal women presenting mean age of 51.2 ± 2.7 years and mean time since menopause of 23.1 ± 10 months. After 2 months, no significant differences were observed between treatments on waist circumference, waist to hip ratio, BMI and arterial pressure. Total cholesterol levels were reduced on both treatments. Low oral dose treatment had greater effect in reducing LDL cholesterol. HDL cholesterol, triglycerides, fast and 2 hours glucose and insulin levels did not change with either treatment. PCR and vW factor levels were reduced in both treatment groups and fibrinogen did not change. After 4 months of low oral dose treatment, a reduction on waist circumference and waist/circumference ratio was found. Total cholesterol was lower than basal levels on bothtreatment groups and while HDL cholesterol presented a slight but significant reduction on low oral dose treatment, triglycerides decreased significantly on non oral treatment. Two hours glucose was higher than basal levels but fast glucose and fast or 2 h insulin levels did not change after low oral dose therapy. After 4 months, vW factor decreased only on non oral treatment and PCR and fibrinogens were unchanged on both treatment groups. In conclusion, the present results suggest that the studied treatments did not induce deleterious effects on variables related to cardiovascular risk, at least at short period of time, in early postmenopausal and apparently healthy women. Low dose oral HT has maintained the well known beneficial effects on lipid profile (lower total and LDL cholesterol) and did not induced an increase on pro-inflammatory or endothelial function markers. On the other hand, non oral HT has shown to be a safe alternative, and was not related to changes on metabolic profile or markers of endothelial function.

Angiotensin II (Ang II) promotes vascular disease and hypertension, in part, by activating the interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (STAT3) signaling pathway. Extensive studies have demonstrated that SOCS3 plays an important role in suppressing the IL-6/STAT3 pathway in the immune system and in cancer biology. In contrast, the functional importance of SOCS3 in cardiovascular disease is largely unknown. Thus, the overall goal of these studies was to investigate the role of SOCS3 in models of Ang II-dependent vascular disease and hypertension. To examine direct effects of Ang II on the vessel wall, carotid arteries from SOCS3 haplodeficient (SOCS3+/-) mice and wild-type littermates (SOCS3+/+) were incubated with the peptide or vehicle for 22 hrs, followed by examination of endothelial function using acetylcholine. Relaxation to acetylcholine was similar in all arteries incubated with vehicle. A low concentration of Ang II (1 nmol/L) did not affect acetylcholine-induced vasodilation in SOCS3+/+ mice, but reduced responses in arteries from SOCS3+/- mice by ~50% (P<0.05). This Ang II-induced endothelial dysfunction in SOCS3+/- mice was prevented by inhibitors of NF-êB or STAT3, an IL-6 neutralizing antibody, or a scavenger of superoxide. Responses to nitroprusside, an endothelium-independent vasodilator, were similar in all groups. To test the importance of SOCS3 in vivo, mice were infused systemically with a pressor dose of Ang II (1.4 mg/kg per day) or vehicle for 14 days via osmotic mini-pumps. Acetylcholine-induced vasodilation in carotid and resistance arteries in brain from SOCS3+/- mice was reduced by ~60% (P<0.05). Surprisingly, genetic deficiency in SOCS3 prevented the majority of Ang II-induced endothelial dysfunction without affecting the pressor response to Ang II. To investigate potential mechanisms underlying divergent results when studying effects of local versus systemic effects of Ang II, we performed bone marrow transplantation followed by infusion of vehicle or Ang II for two weeks. Lethally irradiated WT (CD45.1) mice reconstituted with SOCS3+/- bone marrow were protected from Ang II-induced endothelial dysfunction (P<0.05), while reconstitution of irradiated SOCS3+/- mice with WT (CD45.1) bone marrow exacerbated Ang II-induced vascular dysfunction (P<0.05). WT (CD45.1) into SOCS3+/+ and SOCS3+/- into SOCS3+/- bone marrow chimeras exhibited vascular function consistent with non-irradiated controls. In addition, the pressor response to Ang II was reduced by ~50% in WT mice reconstituted with bone marrow from SOCS3+/- mice (P<0.05). These data suggest that SOCS3 exerts divergent or context-dependent effects depending on whether vascular dysfunction was due to local versus systemic administration of Ang II. SOCS3 deficiency in the vessel wall enhanced local detrimental effects of Ang II on vascular function. In contrast, bone marrow-derived cells that are haplodeficient in SOCS3 protect against systemically administered Ang II and the resulting vascular dysfunction and hypertension. To my knowledge, these are the first experimental studies that begin to define the importance of SOCS3 in Ang II-induced hypertension and endothelial dysfunction. Results obtained from these experiments provide new insight into mechanisms which regulate oxidative stress and inflammation within the vasculature. The studies also revealed that bone marrow-derived cells that are haplodeficient in SOCS3 protect against pressor and endothelial effects of Ang II. These findings may eventually contribute to the development of novel therapeutic approaches for hypertension and hypertension associated end-organ damage.

Experiments described in this thesis address the pathogenesis of aortic valve sclerosis/stenosis using a bench to bedside approach. In particular, the thesis begins with development of a technique using ultrasonic backscatter analyses to quantitate the early stages of aortic stenosis. Subsequent chapters utilized this methodology to quantitate aortic valve structural changes in a model and intervention study of aortic stenosis in rabbits. The last chapters are human studies designed to identify factors associated with presence of aortic sclerosis/stenosis; with particular interest in potential association of endothelial dysfunction/inflammation/platelet aggregation with abnormal aortic valve structure quantitated by ultrasonic backscatter. In Chapter 1 (Introduction) the relevant literature is reviewed. Development of ultrasonic backscatter to quantitate aortic sclerosis (Chapter 2) Aortic valve sclerosis (ASc) is detected when there is visual assessment of focal increases in echogenicity of the aortic valve most commonly assessed by echocardiography. However, there is no previously described method to quantitate degree of aortic valve structural abnormality as ASc is not associated with marked hemodynamic obstruction quantifiable by Doppler echocardiography. The current study used ultrasonic backscatter to quantitate aortic valve structural abnormality in patients assessed as having ASc based on valve appearances, compared to young healthy volunteers with normal aortic valves. The results of the study indicate: 1) that the mean levels of aortic valve backscatter in ASc patients are approximately 60% greater than in young healthy volunteers (ie aortic valve backscatter scores ≥ 16dB are not consistent with normal aortic valve structure), 2) ultrasonic backscatter scores in ASc patients are directly correlated with subjective scoring of sclerosis and with a positive trend with transvalvular pressure gradients in patients with mild-moderate aortic stenosis, and most importantly, 3) ultrasonic backscatter is a reproducible technique, with mean differences between estimates based on repeat echocardiograms of 2.3 ± 1.7 (9.1%). These results indicate that ultrasonic backscatter could be used as a quantitative measure of aortic valve structural abnormality in epidemiology and for examination of interventions. In vivo studies Development of an animal model of aortic stenosis with vitamin D2 (Chapter 3) The aim of the study was to develop an appropriate animal model for AS. The study used vitamin D2 alone at 25,000IU/4 days weekly (vit-D2) for 8 weeks to induce AS in rabbits. Results showed that: 1) rabbits in the vit-D2 group had significantly increased in transvalvular velocity and pressure gradients compared to rabbits in the control group (normal chow + drinking water); this was consistent for aortic valve ultrasonic backscatter scores; 2) aortic valve immunohistochemistry/histology showed marked calcification, neutral lipids, macrophage, and leukocyte infiltrations for rabbits in the vit- D2 group (ie consistent with histology of human AS); 3) significant elevation of asymmetric dimethylarginine (ADMA) concentrations in the vit-D2 group occurred compared to controls over the 8 weeks treatment period; the change in ADMA concentrations correlated significantly with the change in transvalvular pressure gradients for rabbits in the vit-D2 group; 4) rabbits in the vit-D2 group had significantly impaired endothelium-dependent acetylcholine-induced aortic relaxation, and this effect was completely abolished by the nitric oxide synthase inhibitor (L-NAME); 5) the addition of 0.5% cholesterol-supplemented diet to the vitamin D2 regimen did not accentuate the development of AS. Thus, treatment with vitamin D2 at 25,000IU/4 days weekly for 8 weeks significantly induced AS with similar aortic valve pathology to that of human AS; therefore, the model is suitable for use in examining potential therapeutic interventions in AS. Effects of ramipril on development of AS in rabbits (Chapter 4) Using this animal model, this study aimed to examine the effects of the angiotensinconverting enzyme inhibitor (ACEi) ramipril on development of AS. Rabbits (n=28) treated for 8 weeks were divided into 2 groups: (a) vitamin D2 alone (n=10) (normal chow + 25,000IU vitamin D2 in drinking water); (b) vitamin D2/Ramipril (n=12) (normal chow+25,000IU vitamin D2/Ramipril (0.5mg/kg) in drinking water). Six further rabbits constituted a normal reference group (no treatment was given). The results for comparisons between vitamin D2/ramipril vs vitamin D2 alone were as follows: 1) ramipril-treated rabbits had significantly less severe hemodynamic obstructions (p<0.05, for both) as assessed by transvalvular velocity, and aortic valve area; with borderline reduction in aortic valve backscatter (p=0.08); 2) ramipril significantly reduced plasma ADMA concentrations; 3) there was improvement in acetylcholine-induced aortic relaxation (p=0.056), with significant improvement in sodium nitroprusside-induced relaxation (p<0.05); 4) there was a strong inverse correlation between acetylcholineinduced aortic relaxation and aortic valve backscatter score (0<0.001), thus providing further evidence of the potential role of nitric oxide in retarding the development of AS in this model. These data provide a strong rationale for the inception of a randomized trial of ACE inhibition as a strategy for limitation of AS progression in humans. Human studies Aortic stenosis is associated with elevated plasma levels of asymmetric dimethylarginine (ADMA) concentrations in humans (Chapter 5). Given the findings that aortic stenosis induced by vitamin D2 in rabbits also caused elevation of plasma ADMA concentrations, a physiological inhibitor of nitric oxide synthase, a mediator and marker of endothelial dysfunction and an indicator of incremental cardiovascular risk. The study sought to determine whether plasma ADMA concentrations are elevated independently of pre-existing coronary risk factors in subjects with at least moderate aortic stenosis (n=42) compared to age-matched patients with normal aortic valves (n=42): as determined both by visual assessment and with aortic valve backscatter scores < 16dB. Results for this study were as follows: 1) plasma ADMA concentrations were not statistically different between the AS and non-AS group (median 0.59 vs 0.54 µmol/L, p=0.13, Mann-Whitney test) on univariate analysis; 2) backward stepwise multiple linear regression showed the presence of AS was a significant predictor of elevated ADMA concentrations (p=0.04, 95% CI =0.001, 0.072). 3) in addition, elevated plasma ADMA concentrations were also associated with history of atrial fibrillation (p=0.009, 95% CI=0.015, 0.100), and negatively associated with creatinine clearance (p=0.01, 95% CI=-0.002, 0.000), and the use of statin therapy (p=0.01, 95% CI=-0.081, -0.011). Therefore, in conclusion, this study found that AS is independently associated with elevation of ADMA concentrations, beyond that implied by “conventional” risk factors for endothelial dysfunction. The clinical status of AS as an incremental marker of cardiovascular risk may reflect ADMA-mediated endothelial dysfunction. Assessment of factors associated with ASc in a random ageing population study (Chapter 6). There have been few clinical studies of factors associated with ASc. Previous population studies have established that ASc is an independent correlate of incremental risk of coronary events. Having established that patients with AS have increased plasma ADMA concentrations (Chapter 5), it was now aimed to determine whether subjects with increased aortic valve backscatter scores (ASc) also have other markers of endothelial dysfunction/NO effects, independent of preexisting coronary risk factors. The study was designed to identify such anomalies, if they existed, on an incremental basis to other putative correlates of ASc, including coronary risk factors, renal dysfunction and vitamin D levels. Random selected subjects (n=253) aged between 51 to 77 years were evaluated. All patients underwent transthoracic echocardiography examination; aortic valve ultrasonic backscatter score (AVBS), was used to quantitate echogenicity of the aortic valve. Conventional coronary risk factors were identified on history. Integrity of NO generation/response was assessed via (i) plasma ADMA concentrations; (ii) inhibition of platelet aggregation by the NO donor sodium nitroprusside (SNP); (iii) aortic augmentation index (AIx), a measure of arterial stiffness/wave reflection. All putative correlations with AVBS were examined by univariate and stepwise multiple linear regression analyses. On the basis of echocardiographic appearances, ASc was present in 63 subjects (25.4%); mean AVBS scores was 14.9±4.6dB (SD) vs 11.2±3.9dB (SD) in the presence vs absence of ASc (p<0.001). Univariate analyses revealed that platelet responsiveness to NO was inversely correlated with AVBS (β=-0.16, p=0.02); but [ADMA] and AIx were not. On multiple linear regression, significant correlates of increased AVBS were: (i) advanced age (β=0.21, p=0.003), (ii) low body mass index (β=-0.23, p=0.001); and (iii) impaired platelet responsiveness to NO (β=-0.16, p=0.02). In Chapter 7, the implications of the overall findings in this thesis are discussed in relation to future perspective. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1309350 / Thesis(Ph.D.) -- School of Medicine, 2008

The endothelium plays an essential role in the regulation of vascular homeostasis and a state of endothelial dysfunction, which develops in the presence of cardiovascular risk factors, may contribute to the development and progression of cardiovascular disease. As such, the measurement of endothelial function, beyond being an experimental tool, may serve as an important tool to complement current risk assessment algorithms in the identification of high-risk patients. Flow-mediated dilation (FMD) is a non-invasive measure of peripheral conduit artery endothelial function that holds great promise. Presently, FMD suffers from methodological heterogeneity and a poor understanding of the various biological components involved in eliciting the dilatory response to a given shear stimulus. We compared both traditional and alternative methods of arterial diameter characterization with regards to their repeatability, nitric oxide-dependency, and their sensitivity in distinguishing between normal and dysfunctional endothelial responses. Our findings emphasize the importance of continuous arterial diameter measurement and suggest that the time to peak FMD is not a useful adjunctive measure of the FMD response. Given that endothelial dysfunction may be of clinical importance, strategies to correct it or prevent it from occurring may be of benefit. The 3-hydroxy-3-methylglutaryl coenzyme A inhibitors are agents that have demonstrated marked cholesterol-independent, endothelial-protective effects. We investigated the ability of rosuvastatin and atorvastatin to protect against endothelial dysfunction associated with ischemia and reperfusion (IR) injury, and chronic nitrate therapy. Using the FMD technique, we demonstrated, for the first time in humans, that acute rosuvastatin administration protects against IR-induced conduit artery endothelial dysfunction. Additionally, we demonstrated that this effect likely occurred by a cyclooxygenase-2-dependent mechanism, which may provide mechanistic insight into the observed cardio-toxicity with cyclooxygenase-2 inhibitors. In contrast, we observed that this endothelial-protective effect was lost upon sustained rosuvastatin administration, which may have important implications regarding the generation of sustained cardioprotective phenotypes. Finally, we demonstrated that atorvastatin co-administration prevented the development of tolerance and endothelial dysfunction associated with continuous transdermal nitroglycerin therapy in humans, likely through an antioxidant mechanism. Future studies are needed in disease patients to determine whether the concept of nitrate tolerance needs reconsideration in the presence of vascular-protective agents.

The endothelium plays an essential role in the regulation of vascular homeostasis and a state of endothelial dysfunction, which develops in the presence of cardiovascular risk factors, may contribute to the development and progression of cardiovascular disease. As such, the measurement of endothelial function, beyond being an experimental tool, may serve as an important tool to complement current risk assessment algorithms in the identification of high-risk patients. Flow-mediated dilation (FMD) is a non-invasive measure of peripheral conduit artery endothelial function that holds great promise. Presently, FMD suffers from methodological heterogeneity and a poor understanding of the various biological components involved in eliciting the dilatory response to a given shear stimulus. We compared both traditional and alternative methods of arterial diameter characterization with regards to their repeatability, nitric oxide-dependency, and their sensitivity in distinguishing between normal and dysfunctional endothelial responses. Our findings emphasize the importance of continuous arterial diameter measurement and suggest that the time to peak FMD is not a useful adjunctive measure of the FMD response. Given that endothelial dysfunction may be of clinical importance, strategies to correct it or prevent it from occurring may be of benefit. The 3-hydroxy-3-methylglutaryl coenzyme A inhibitors are agents that have demonstrated marked cholesterol-independent, endothelial-protective effects. We investigated the ability of rosuvastatin and atorvastatin to protect against endothelial dysfunction associated with ischemia and reperfusion (IR) injury, and chronic nitrate therapy. Using the FMD technique, we demonstrated, for the first time in humans, that acute rosuvastatin administration protects against IR-induced conduit artery endothelial dysfunction. Additionally, we demonstrated that this effect likely occurred by a cyclooxygenase-2-dependent mechanism, which may provide mechanistic insight into the observed cardio-toxicity with cyclooxygenase-2 inhibitors. In contrast, we observed that this endothelial-protective effect was lost upon sustained rosuvastatin administration, which may have important implications regarding the generation of sustained cardioprotective phenotypes. Finally, we demonstrated that atorvastatin co-administration prevented the development of tolerance and endothelial dysfunction associated with continuous transdermal nitroglycerin therapy in humans, likely through an antioxidant mechanism. Future studies are needed in disease patients to determine whether the concept of nitrate tolerance needs reconsideration in the presence of vascular-protective agents.

Ischemia-reperfusion (IR) injury occurs during myocardial infarction and during some cardiovascular surgeries. Animal studies support the role of endurance exercise training in preventing myocardial IR injury and coronary endothelial dysfunction. In human and animal studies, habitual exercise has been shown to attenuate endothelial dysfunction caused by aging and disease. It is unknown; however, if exercise can protect against vascular IR injury in humans and if so, whether these effects persist with advancing age. Using 20 minutes of forearm ischemia and the response of the brachial artery as a noninvasive surrogate model for the heart, the association between the mode of exercise training (endurance versus resistance) and vascular IR injury was examined in young healthy adults in the first study. Endothelial function, as measured by flow-mediated dilation (FMD) in the brachial artery, decreased significantly after forearm ischemia, suggesting that this noninvasive model of the heart produces significant and measureable vascular injury. These measures returned to baseline levels within 30 minutes following ischemia, illustrating the transient nature of this form of IR injury. The magnitude of injury and recovery from ischemia were not significantly different among young sedentary, endurance-trained, and resistance-trained subjects, suggesting that exercise training is not associated with protection from vascular IR injury in a young, healthy population. In the second study, the association between aging, endurance exercise training, and vascular IR injury was studied. Twenty minutes of forearm ischemia was associated with a transient fall in brachial FMD in young and older sedentary and endurance-trained subjects. Young subjects recovered more quickly from IR injury than older subjects. Within 30 minutes of injury, the endothelial function of the young group was back to baseline while blunted endothelial function persisted in older subjects for greater than 45 minutes after injury. There was no association between endurance exercise training and enhanced recovery from IR injury. These findings suggest that aging is associated with delayed recovery from vascular IR injury and that endurance training does not appear to modulate the vascular IR injury responses. / text

Cardiovascular disease remains the leading cause of death in Western societies. Endothelial dysfunction is one of the initiating steps in the development of atherosclerosis. While there is a strong correlation with a person’s genetics, lifestyle factors including smoking, physical activity, and diet can significantly increase a person’s susceptibility to the development of atherosclerosis. In addition to these lifestyle factors, there is a strong body of evidence linking exposure to environmental pollutants including persistent organic pollutants such as polychlorinated biphenyls to increased cardiovascular disease and mortality. It has been well-established that exercise protects against cardiovascular disease, but whether exercise can modulate PCB-induced cardiovascular inflammation and dysfunction is unknown. To investigate the effects of exercise on PCB-induced cardiovascular disease, two murine models of atherosclerosis, the ApoE-/- and the LDLr-/- mouse were utilized. Risk factors for cardiovascular disease including adiposity, glucose intolerance, hyperlipidemia, hypertension, oxidative stress, and inflammation, were assessed in these two models as well as mean atherosclerotic lesion size. Exercise positively modulates several risk factors associated with cardiovascular disease including hypertension, hyperlipidemia, adiposity and obesity, systemic levels of oxidative stress, inflammation, and glucose tolerance. Exercise significantly reduced mean lesion size in vehicle-treated animals. To assess the mechanism of protection of exercise in chapter 4, vascular reactivity studies were performed to measure endothelial function after exposure to PCB 77. Exercise prevented PCB-impaired endothelial function implicating the role of superoxide as a cause of impairment. Exercise upregulated phase II antioxidant enzymes. The work in this dissertation demonstrates several protective properties of exercise against PCB-induced cardiovascular disease; however, additional studies are needed to determine if exercise enhances metabolism and excretion of these environmental pollutants.

The phenomenon of platelet hyperaggregability and decreased platelet responsiveness to nitric oxide (also termed as nitric oxide resistance), documented in several cardiovascular disease states, is associated with adverse cardiovascular outcomes. The series of experiments described in this thesis address primarily some aspects of the pathophysiology, epidemiology and therapy of the phenomenon of end-organ resistance to nitric oxide (NO) in two important conditions, that are closely associated with cardiovascular risk factors and disease states:- Polycystic ovary syndrome, which is closely linked with the metabolic syndrome and premature subclinical atherosclerosis. The renin-angiotensin system, which is recognized as a significant mediator in the pathophysiology of a number of cardiovascular disease states. The first study examined the epidemiology/pathophysiology of putative platelet/endothelial dysfunction in young individuals with PCOS. The subsequent studies focused on the potential impact of the renin-angiotensin system on platelet and endothelial function. This mechanistic review is set in the context of a number of recent major clinical studies which have demonstrated surprising efficacy of certain angiotensin-converting enzyme (ACE) inhibitors (ramipril and perindopril) in the prevention of thrombotic processes. Thus we tested the hypothesis whether ACE inhibitor ramipril sensitizes platelets to NO (as a potential mechanism for improved cardiovascular outcomes) in a high risk patient cohort. In addition, particular attention will be given to the emerging role of the heptapeptide Angiotensin- (1-7), a possible physiological antagonist to Angiotensin II in the vasculature and the limitation of the current literature concerning potential effects of the renin-angiotensin system on thrombotic mechanisms. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1348615 / Thesis (Ph.D.) - University of Adelaide, School of Medicine, 2009

Experiments described in this thesis address the pathogenesis of aortic valve sclerosis/stenosis using a bench to bedside approach. In particular, the thesis begins with development of a technique using ultrasonic backscatter analyses to quantitate the early stages of aortic stenosis. Subsequent chapters utilized this methodology to quantitate aortic valve structural changes in a model and intervention study of aortic stenosis in rabbits. The last chapters are human studies designed to identify factors associated with presence of aortic sclerosis/stenosis; with particular interest in potential association of endothelial dysfunction/inflammation/platelet aggregation with abnormal aortic valve structure quantitated by ultrasonic backscatter. In Chapter 1 (Introduction) the relevant literature is reviewed. Development of ultrasonic backscatter to quantitate aortic sclerosis (Chapter 2) Aortic valve sclerosis (ASc) is detected when there is visual assessment of focal increases in echogenicity of the aortic valve most commonly assessed by echocardiography. However, there is no previously described method to quantitate degree of aortic valve structural abnormality as ASc is not associated with marked hemodynamic obstruction quantifiable by Doppler echocardiography. The current study used ultrasonic backscatter to quantitate aortic valve structural abnormality in patients assessed as having ASc based on valve appearances, compared to young healthy volunteers with normal aortic valves. The results of the study indicate: 1) that the mean levels of aortic valve backscatter in ASc patients are approximately 60% greater than in young healthy volunteers (ie aortic valve backscatter scores ≥ 16dB are not consistent with normal aortic valve structure), 2) ultrasonic backscatter scores in ASc patients are directly correlated with subjective scoring of sclerosis and with a positive trend with transvalvular pressure gradients in patients with mild-moderate aortic stenosis, and most importantly, 3) ultrasonic backscatter is a reproducible technique, with mean differences between estimates based on repeat echocardiograms of 2.3 ± 1.7 (9.1%). These results indicate that ultrasonic backscatter could be used as a quantitative measure of aortic valve structural abnormality in epidemiology and for examination of interventions. In vivo studies Development of an animal model of aortic stenosis with vitamin D2 (Chapter 3) The aim of the study was to develop an appropriate animal model for AS. The study used vitamin D2 alone at 25,000IU/4 days weekly (vit-D2) for 8 weeks to induce AS in rabbits. Results showed that: 1) rabbits in the vit-D2 group had significantly increased in transvalvular velocity and pressure gradients compared to rabbits in the control group (normal chow + drinking water); this was consistent for aortic valve ultrasonic backscatter scores; 2) aortic valve immunohistochemistry/histology showed marked calcification, neutral lipids, macrophage, and leukocyte infiltrations for rabbits in the vit- D2 group (ie consistent with histology of human AS); 3) significant elevation of asymmetric dimethylarginine (ADMA) concentrations in the vit-D2 group occurred compared to controls over the 8 weeks treatment period; the change in ADMA concentrations correlated significantly with the change in transvalvular pressure gradients for rabbits in the vit-D2 group; 4) rabbits in the vit-D2 group had significantly impaired endothelium-dependent acetylcholine-induced aortic relaxation, and this effect was completely abolished by the nitric oxide synthase inhibitor (L-NAME); 5) the addition of 0.5% cholesterol-supplemented diet to the vitamin D2 regimen did not accentuate the development of AS. Thus, treatment with vitamin D2 at 25,000IU/4 days weekly for 8 weeks significantly induced AS with similar aortic valve pathology to that of human AS; therefore, the model is suitable for use in examining potential therapeutic interventions in AS. Effects of ramipril on development of AS in rabbits (Chapter 4) Using this animal model, this study aimed to examine the effects of the angiotensinconverting enzyme inhibitor (ACEi) ramipril on development of AS. Rabbits (n=28) treated for 8 weeks were divided into 2 groups: (a) vitamin D2 alone (n=10) (normal chow + 25,000IU vitamin D2 in drinking water); (b) vitamin D2/Ramipril (n=12) (normal chow+25,000IU vitamin D2/Ramipril (0.5mg/kg) in drinking water). Six further rabbits constituted a normal reference group (no treatment was given). The results for comparisons between vitamin D2/ramipril vs vitamin D2 alone were as follows: 1) ramipril-treated rabbits had significantly less severe hemodynamic obstructions (p<0.05, for both) as assessed by transvalvular velocity, and aortic valve area; with borderline reduction in aortic valve backscatter (p=0.08); 2) ramipril significantly reduced plasma ADMA concentrations; 3) there was improvement in acetylcholine-induced aortic relaxation (p=0.056), with significant improvement in sodium nitroprusside-induced relaxation (p<0.05); 4) there was a strong inverse correlation between acetylcholineinduced aortic relaxation and aortic valve backscatter score (0<0.001), thus providing further evidence of the potential role of nitric oxide in retarding the development of AS in this model. These data provide a strong rationale for the inception of a randomized trial of ACE inhibition as a strategy for limitation of AS progression in humans. Human studies Aortic stenosis is associated with elevated plasma levels of asymmetric dimethylarginine (ADMA) concentrations in humans (Chapter 5). Given the findings that aortic stenosis induced by vitamin D2 in rabbits also caused elevation of plasma ADMA concentrations, a physiological inhibitor of nitric oxide synthase, a mediator and marker of endothelial dysfunction and an indicator of incremental cardiovascular risk. The study sought to determine whether plasma ADMA concentrations are elevated independently of pre-existing coronary risk factors in subjects with at least moderate aortic stenosis (n=42) compared to age-matched patients with normal aortic valves (n=42): as determined both by visual assessment and with aortic valve backscatter scores < 16dB. Results for this study were as follows: 1) plasma ADMA concentrations were not statistically different between the AS and non-AS group (median 0.59 vs 0.54 µmol/L, p=0.13, Mann-Whitney test) on univariate analysis; 2) backward stepwise multiple linear regression showed the presence of AS was a significant predictor of elevated ADMA concentrations (p=0.04, 95% CI =0.001, 0.072). 3) in addition, elevated plasma ADMA concentrations were also associated with history of atrial fibrillation (p=0.009, 95% CI=0.015, 0.100), and negatively associated with creatinine clearance (p=0.01, 95% CI=-0.002, 0.000), and the use of statin therapy (p=0.01, 95% CI=-0.081, -0.011). Therefore, in conclusion, this study found that AS is independently associated with elevation of ADMA concentrations, beyond that implied by “conventional” risk factors for endothelial dysfunction. The clinical status of AS as an incremental marker of cardiovascular risk may reflect ADMA-mediated endothelial dysfunction. Assessment of factors associated with ASc in a random ageing population study (Chapter 6). There have been few clinical studies of factors associated with ASc. Previous population studies have established that ASc is an independent correlate of incremental risk of coronary events. Having established that patients with AS have increased plasma ADMA concentrations (Chapter 5), it was now aimed to determine whether subjects with increased aortic valve backscatter scores (ASc) also have other markers of endothelial dysfunction/NO effects, independent of preexisting coronary risk factors. The study was designed to identify such anomalies, if they existed, on an incremental basis to other putative correlates of ASc, including coronary risk factors, renal dysfunction and vitamin D levels. Random selected subjects (n=253) aged between 51 to 77 years were evaluated. All patients underwent transthoracic echocardiography examination; aortic valve ultrasonic backscatter score (AVBS), was used to quantitate echogenicity of the aortic valve. Conventional coronary risk factors were identified on history. Integrity of NO generation/response was assessed via (i) plasma ADMA concentrations; (ii) inhibition of platelet aggregation by the NO donor sodium nitroprusside (SNP); (iii) aortic augmentation index (AIx), a measure of arterial stiffness/wave reflection. All putative correlations with AVBS were examined by univariate and stepwise multiple linear regression analyses. On the basis of echocardiographic appearances, ASc was present in 63 subjects (25.4%); mean AVBS scores was 14.9±4.6dB (SD) vs 11.2±3.9dB (SD) in the presence vs absence of ASc (p<0.001). Univariate analyses revealed that platelet responsiveness to NO was inversely correlated with AVBS (β=-0.16, p=0.02); but [ADMA] and AIx were not. On multiple linear regression, significant correlates of increased AVBS were: (i) advanced age (β=0.21, p=0.003), (ii) low body mass index (β=-0.23, p=0.001); and (iii) impaired platelet responsiveness to NO (β=-0.16, p=0.02). In Chapter 7, the implications of the overall findings in this thesis are discussed in relation to future perspective. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1309350 / Thesis(Ph.D.) -- School of Medicine, 2008

Experiments described in this thesis address the pathogenesis of aortic valve sclerosis/stenosis using a bench to bedside approach. In particular, the thesis begins with development of a technique using ultrasonic backscatter analyses to quantitate the early stages of aortic stenosis. Subsequent chapters utilized this methodology to quantitate aortic valve structural changes in a model and intervention study of aortic stenosis in rabbits. The last chapters are human studies designed to identify factors associated with presence of aortic sclerosis/stenosis; with particular interest in potential association of endothelial dysfunction/inflammation/platelet aggregation with abnormal aortic valve structure quantitated by ultrasonic backscatter. In Chapter 1 (Introduction) the relevant literature is reviewed. Development of ultrasonic backscatter to quantitate aortic sclerosis (Chapter 2) Aortic valve sclerosis (ASc) is detected when there is visual assessment of focal increases in echogenicity of the aortic valve most commonly assessed by echocardiography. However, there is no previously described method to quantitate degree of aortic valve structural abnormality as ASc is not associated with marked hemodynamic obstruction quantifiable by Doppler echocardiography. The current study used ultrasonic backscatter to quantitate aortic valve structural abnormality in patients assessed as having ASc based on valve appearances, compared to young healthy volunteers with normal aortic valves. The results of the study indicate: 1) that the mean levels of aortic valve backscatter in ASc patients are approximately 60% greater than in young healthy volunteers (ie aortic valve backscatter scores ≥ 16dB are not consistent with normal aortic valve structure), 2) ultrasonic backscatter scores in ASc patients are directly correlated with subjective scoring of sclerosis and with a positive trend with transvalvular pressure gradients in patients with mild-moderate aortic stenosis, and most importantly, 3) ultrasonic backscatter is a reproducible technique, with mean differences between estimates based on repeat echocardiograms of 2.3 ± 1.7 (9.1%). These results indicate that ultrasonic backscatter could be used as a quantitative measure of aortic valve structural abnormality in epidemiology and for examination of interventions. In vivo studies Development of an animal model of aortic stenosis with vitamin D2 (Chapter 3) The aim of the study was to develop an appropriate animal model for AS. The study used vitamin D2 alone at 25,000IU/4 days weekly (vit-D2) for 8 weeks to induce AS in rabbits. Results showed that: 1) rabbits in the vit-D2 group had significantly increased in transvalvular velocity and pressure gradients compared to rabbits in the control group (normal chow + drinking water); this was consistent for aortic valve ultrasonic backscatter scores; 2) aortic valve immunohistochemistry/histology showed marked calcification, neutral lipids, macrophage, and leukocyte infiltrations for rabbits in the vit- D2 group (ie consistent with histology of human AS); 3) significant elevation of asymmetric dimethylarginine (ADMA) concentrations in the vit-D2 group occurred compared to controls over the 8 weeks treatment period; the change in ADMA concentrations correlated significantly with the change in transvalvular pressure gradients for rabbits in the vit-D2 group; 4) rabbits in the vit-D2 group had significantly impaired endothelium-dependent acetylcholine-induced aortic relaxation, and this effect was completely abolished by the nitric oxide synthase inhibitor (L-NAME); 5) the addition of 0.5% cholesterol-supplemented diet to the vitamin D2 regimen did not accentuate the development of AS. Thus, treatment with vitamin D2 at 25,000IU/4 days weekly for 8 weeks significantly induced AS with similar aortic valve pathology to that of human AS; therefore, the model is suitable for use in examining potential therapeutic interventions in AS. Effects of ramipril on development of AS in rabbits (Chapter 4) Using this animal model, this study aimed to examine the effects of the angiotensinconverting enzyme inhibitor (ACEi) ramipril on development of AS. Rabbits (n=28) treated for 8 weeks were divided into 2 groups: (a) vitamin D2 alone (n=10) (normal chow + 25,000IU vitamin D2 in drinking water); (b) vitamin D2/Ramipril (n=12) (normal chow+25,000IU vitamin D2/Ramipril (0.5mg/kg) in drinking water). Six further rabbits constituted a normal reference group (no treatment was given). The results for comparisons between vitamin D2/ramipril vs vitamin D2 alone were as follows: 1) ramipril-treated rabbits had significantly less severe hemodynamic obstructions (p<0.05, for both) as assessed by transvalvular velocity, and aortic valve area; with borderline reduction in aortic valve backscatter (p=0.08); 2) ramipril significantly reduced plasma ADMA concentrations; 3) there was improvement in acetylcholine-induced aortic relaxation (p=0.056), with significant improvement in sodium nitroprusside-induced relaxation (p<0.05); 4) there was a strong inverse correlation between acetylcholineinduced aortic relaxation and aortic valve backscatter score (0<0.001), thus providing further evidence of the potential role of nitric oxide in retarding the development of AS in this model. These data provide a strong rationale for the inception of a randomized trial of ACE inhibition as a strategy for limitation of AS progression in humans. Human studies Aortic stenosis is associated with elevated plasma levels of asymmetric dimethylarginine (ADMA) concentrations in humans (Chapter 5). Given the findings that aortic stenosis induced by vitamin D2 in rabbits also caused elevation of plasma ADMA concentrations, a physiological inhibitor of nitric oxide synthase, a mediator and marker of endothelial dysfunction and an indicator of incremental cardiovascular risk. The study sought to determine whether plasma ADMA concentrations are elevated independently of pre-existing coronary risk factors in subjects with at least moderate aortic stenosis (n=42) compared to age-matched patients with normal aortic valves (n=42): as determined both by visual assessment and with aortic valve backscatter scores < 16dB. Results for this study were as follows: 1) plasma ADMA concentrations were not statistically different between the AS and non-AS group (median 0.59 vs 0.54 µmol/L, p=0.13, Mann-Whitney test) on univariate analysis; 2) backward stepwise multiple linear regression showed the presence of AS was a significant predictor of elevated ADMA concentrations (p=0.04, 95% CI =0.001, 0.072). 3) in addition, elevated plasma ADMA concentrations were also associated with history of atrial fibrillation (p=0.009, 95% CI=0.015, 0.100), and negatively associated with creatinine clearance (p=0.01, 95% CI=-0.002, 0.000), and the use of statin therapy (p=0.01, 95% CI=-0.081, -0.011). Therefore, in conclusion, this study found that AS is independently associated with elevation of ADMA concentrations, beyond that implied by “conventional” risk factors for endothelial dysfunction. The clinical status of AS as an incremental marker of cardiovascular risk may reflect ADMA-mediated endothelial dysfunction. Assessment of factors associated with ASc in a random ageing population study (Chapter 6). There have been few clinical studies of factors associated with ASc. Previous population studies have established that ASc is an independent correlate of incremental risk of coronary events. Having established that patients with AS have increased plasma ADMA concentrations (Chapter 5), it was now aimed to determine whether subjects with increased aortic valve backscatter scores (ASc) also have other markers of endothelial dysfunction/NO effects, independent of preexisting coronary risk factors. The study was designed to identify such anomalies, if they existed, on an incremental basis to other putative correlates of ASc, including coronary risk factors, renal dysfunction and vitamin D levels. Random selected subjects (n=253) aged between 51 to 77 years were evaluated. All patients underwent transthoracic echocardiography examination; aortic valve ultrasonic backscatter score (AVBS), was used to quantitate echogenicity of the aortic valve. Conventional coronary risk factors were identified on history. Integrity of NO generation/response was assessed via (i) plasma ADMA concentrations; (ii) inhibition of platelet aggregation by the NO donor sodium nitroprusside (SNP); (iii) aortic augmentation index (AIx), a measure of arterial stiffness/wave reflection. All putative correlations with AVBS were examined by univariate and stepwise multiple linear regression analyses. On the basis of echocardiographic appearances, ASc was present in 63 subjects (25.4%); mean AVBS scores was 14.9±4.6dB (SD) vs 11.2±3.9dB (SD) in the presence vs absence of ASc (p<0.001). Univariate analyses revealed that platelet responsiveness to NO was inversely correlated with AVBS (β=-0.16, p=0.02); but [ADMA] and AIx were not. On multiple linear regression, significant correlates of increased AVBS were: (i) advanced age (β=0.21, p=0.003), (ii) low body mass index (β=-0.23, p=0.001); and (iii) impaired platelet responsiveness to NO (β=-0.16, p=0.02). In Chapter 7, the implications of the overall findings in this thesis are discussed in relation to future perspective. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1309350 / Thesis(Ph.D.) -- School of Medicine, 2008