Uma atividade funcional para uma via alternativa de geração de angiotensina II, como a elastase-2 foi sugerida em estudos realizados anteriormente em nosso laboratório no leito arterial mesentérico isolado de rato. No presente estudo, caracterizamos com o uso de substratos e inibidores seletivos a presença de via alternativa de geração de Ang II, independente da ECA, em carótida de ratos. Determinamos ainda a expressão do RNAm da elastase-2 nesta preparação arterial. Em anéis isolados de carótida de ratos analisamos o efeito vasoconstritor dos peptídeos Ang II, Ang I, TDP, [Pro11-D-Ala12]-Ang I (um substrato resistente a ECA) na ausência e presença de inibidores de proteases. Ang II e seus precursores produziram efeito vasoconstritor dependente da concentração em carótidas de ratos, de forma sensível ao losartan (1 M). Na presença de captopril (10 M) a resposta vasoconstritora produzida pela Ang I foi inibida, mas a resposta contrátil induzida pelo TDP e [Pro11-D-Ala12]-Ang I não foi alterada. Na presença de quimostatina (100 M) o efeito produzido pelo TDP e [Pro11-D-Ala12]-Ang I foi abolido enquanto que a curva cumulativa de Ang I foi significativamente deslocada para a direita. Inibidor Ac-AAPL-CK (seletivo para elastase-2) aboliu completamente a resposta contrátil induzida pelo PDA e não alterou o efeito vasoconstritor da Ang II. Na presença de captopril e quimostatina a resposta vasoconstritora dos peptídeos Ang I, TDP e [Pro11-D-Ala12]-Ang I foram inibidas, enquanto a resposta contrátil da Ang II não foi alterada em artéria carótida. A presença de RNAm da elastase-2 na carótida, juntamente com os dados funcionais apresentados aqui sugerem a participação desta enzima na via alternativa de geração de Ang II em carótidas de ratos. Embora a formação de Ang II a partir Ang I seja descrita como essencialmente dependente da ECA, nossos resultados sugerem a existência de vias alternativas de geração de Ang II sensível a quimostatina e Ac-AAPL-CK em artéria carótida de ratos. Muito provavelmente a elastase-2 seja a enzima responsável pela geração de Ang II nessa preparação. / We have recently described a chymostatin-sensitive elastase-2 as the major angiotensin (Ang) II-forming enzyme in the perfusate of rat mesenteric arterial bed (MAB). In the present study we investigated the role of this enzyme in generating Ang II in the isolated rat carotid artery rings by analyzing the vasoconstrictor effect of Ang II, Ang I, tetradecapetide renin-substrate (TDP), [Pro11-D-Ala12]-Ang I (an ACE-resistant substrate) in the absence and presence of proteases inhibitors. Ang II and its precursors produced a dose-dependent vasoconstrictor effect in vascular preparation that was blocked by losartan (1 M). In carotid rings, captopril (10M) abolished the responses induced by Ang I but did not affect those induced by TDP and [Pro11-D-Ala12]-Ang I. In the presence of chymostatin (100 M) alone, the effects induced by [Pro11-D-Ala12]-Ang I and TDP were abolished while the concentration-response curve to Ang I was shifted to the right. Ac-AAPL-CK (selective elastase-2 inhibitor) inhibited the responses induced by [Pro11-D-Ala12]-Ang I but did not affect Ang II-induced effects. In the presence of captopril and chymostatin, the vasoconstrictor effects of Ang I, TDP, and PDA were completely blocked while those induced by Ang II were not affected in rat artery carotid. Although Ang II formation from Ang I is essentially dependent on ACE in carotid artery, our results suggest the existence of an alternative chymostatin-sensitive pathway in rat arteries, most probably involving elastase-2.

Background: Diabetes mellitus is a chronic disease that manifests as an increased level of glucose in the blood. According to the World Health Organization (WHO), 347 million people have diabetes worldwide. In year 2004, 3.4 million people died from the consequences of high blood glucose. In the Swedish population the prevalence of diabetes is estimated to 3-4 %, out of which 85-90% are Type 2. Among senior citizens a prevalence of diabetes is seen in Sweden up to 14 - 15%. Diabetes is increasing globally, particularly in developing countries, which is probably a consequence of the increased prevalence of overweight and obesity combined with low physical activity. Angiotensin converting enzyme (ACE) inhibitors are the first-line therapy in the treatment of high blood pressure among diabetics and patients suffering from congestive heart failure. The action of these inhibitors results in a decreased formation of angiotensin 2, an endogenous hormone peptide that raises the blood pressure by contracting the blood vessels. ACE inhibitors are also beneficial in the treatment of patients with renal insufficiency.Objective: The aim of this project was, with the help of published clinical trials and meta-analysis, to examine the effect of ACE inhibitors on cardiovascular diseases and mortality in type 2 diabetic and diabetic in hypertensive patients.Results: Appraisals of clinical trials within the frame of this project revealed thatACE inhibitor in patients with diabetes reduces:- Myocardial infarction (NNT = 37 during 4.5 years),- Development of stroke (NNT = 32 during 2.8 years),- Cardiovascular events (NNT = 29 during 4.5 years),- Total mortality (NNT = 20 during 2.8 years).- Left ventricular dysfunction (NNT = 6 during 3.4 years)- Complications that usually occur in association with diabetes such as nephropathy (NNT = 83 during 5 years).Conclusion: ACE inhibitors are considered well-established and safe drugs. Despite that, only 38% of the patients with diabetic in Sweden are prescribed ACE inhibitors or angiotensin II antagonists. Due to the high efficacy of ACE-inhibitors among patients with diabetes (i.e. treating 15 high-risk diabetic patients with ACE-inhibitors for a median of 4.5 years prevents one incidence of myocardial infarction, stroke, or cardiovascular mortality) measures ought to be taken in favour of a more widespread use of ACE-inhibitors among patients with diabetes. This will result not only in medical benefits, but also in reducing cost of caring for the elderly diabetics in the community. For most diabetic patients it is very cost effective to prescribe an ACE-inhibitor therapy.

Nous avons montré que l'enzyme de conversion de l'angiotensine (ACE) est un nouveau marqueur de la cellule souche hématopoïétique et identifie l’émergence de l'hématopoïèse dans tous les sites hématogènes de l’embryon humain. L'ACE fait partie du système rénine-angiotensine (SRA) dont la fonction principale est d'agir sur l'angiotensine I pour former l'angiotensine II (AngII), un puissant vasoconstricteur.De plus, nous montrons que les principaux composants du SRA (les récepteurs AT1 et AT2, l’angiotensinogène et la rénine) sont exprimés dans la même région de l'embryon qui exprime l'ACE, suggérant ainsi l’existence d’un SRA local dans l'embryon précoce. Des tests fonctionnels, conduits in vitro chez l'embryon de la souris, montrent que l’Ang II stimule dans la culture l'émergence des progéniteurs hématopoïétiques, effet qui peut être bloqué par un antagoniste spécifique de l’AT1. Ces observations suggèrent pour la première fois, le rôle direct du SRA dans l’émergence hématopoïétique au cours de l’ontogenèse. De plus, nous mettons en évidence l'existence d'un SRA local dans la moelle osseuse (MO) adulte et nous montrons que les principaux éléments de ce système sont surexprimés dans la MO de patients atteints de leucémie aiguë myéloïde, aussi bien dans les blastes que dans les cellules stromales. Ces observations suggèrent une contribution du SRA à la dérégulation de la niche observée dans les hémopathies.Ainsi, la présence d’un SRA local dans la niche hématopoïétique intra-embryonnaire et dans la MO chez l’adulte place ce système dans une position stratégique comme acteur important de l’émergence et de la régulation du système sanguin définitif. / We have shown that the angiotensin-converting enzyme (ACE) is a new marker of human hematopoietic stem cells and also identifies emerging hematopoiesis in all hemogenic sites inside the human embryo. ACE is a key component of renin-angiotensin system (RAS) as it catalyses the production of angiotensin II (Ang II) well known for its effect in the control of blood pressure, through AT1 and AT2 receptors.Furthermore, we observe the presence of the main elements of the RAS (AT1, AT2 receptors, angiotensinogen and renin) in the same region of the embryo expressing ACE, meaning that a local RAS exists in the embryo. Functional in vitro analyses, carried out in mouse model, show a stimulatory effect of AngII in the hematopoietic precursors emergence, an effect inhibited by a specific AT1 antagonist. These observations suggest for the first time a direct role of RAS in the emergence of hematopoiesis during ontogeny. In addition, our data indicate the presence of a local RAS inside the adult bone marrow (BM). This system is overexpressed in the BM of acute myeloid leukemia (AML) patients, both in hematopoietic cells and in stromal cells suggesting a RAS contribution to the bone marrow niche deregulation, always observed in these hemopathies.Therefore, the existence of a local RAS in the intraembryonic niche and in the adult bone marrow suggests that this system is an important actor in the emergence and regulation of the definitive blood system.

The Angiotensin II Type 1 (AT1) receptor is the main receptor responsible for the effects of the renin-angiotensin system, and its expression pattern is altered in several diseases. [11C]Methyl-Losartan has been developed based on the clinically used AT1 receptor antagonist Losartan. The aim of this work is to characterize the pharmacokinetics, repeatability and reliability of measurements, binding specificity and selectivity of [11C]Methyl-Losartan in rats using in vivo small animal positron emission tomography (PET) imaging, ex vivo biodistribution and in vitro autoradiography methods. Also, we aim to measure the presence of metabolites in the kidney and plasma using high-performance liquid chromatography. We have demonstrated in vivo that [11C]Methyl-Losartan is taken up in the AT1 receptor-rich kidneys and that it is displaceable by selective AT1 receptor antagonists. Using ex vivo biodistribution, we have confirmed these results and demonstrated that [11C]Methyl-Losartan binds selectively to the AT1 receptor over the AT2, Mas and β-adrenergic receptors. In vitro autoradiography results confirmed these renal binding selectivity studies. [11C]Methyl-Losartan was also shown to have one and two C-11 labeled metabolites in the plasma and kidneys, respectively. In conclusion, [11C]Methyl-Losartan is a promising agent for studying the AT1 receptor in rat models with normal and altered AT1 receptor expression using small animal PET imaging.

Para avaliar a participação do Sistema Renina Angiotensina (SRA) sobre a Hipertrofia Cardíaca de ratos submetidos ao treinamento resistido foram usados 64 Ratos Wistar divididos em: Controle (CO), Treinado (TR), Controle ou Treinado tratados com Losartan (LOS; 20mg/Kg/d) e Controle ou Treinado tratados com NaCl (SAL; 1% água). Os grupos treinados realizaram quatro séries de 12 repetições, 5x/sem/8sem, com 65-75% de 1 Repetição Máxima (1RM). Hipertrofia cardíaca (HC), obtida pelo peso úmido do VE corrigida pelo Peso Corporal (PC) e pelo Ecocardiograma, foi observada no grupo TR com nenhum prejuízo da função ventricular. Tanto a atividade da ECA, sistêmica e local no coração, quanto a atividade da renina não foram alteradas pelo treinamento. Pelo Western blotting, não foi observada alteração na expressão protéica do peptídeo angiotensina II e do receptor de angiotensina II AT2 com o treinamento, mas observou-se aumento de 31,4% na expressão dos receptores de angiotensina II AT1 no grupo TR. A administração do antagonista do receptor AT1 (Losartan) preveniu a HC em resposta ao treinamento. O mesmo não foi observado com a administração do NaCl para inibir a atividade da Renina. Esses resultados sugerem que o receptor AT1 participa da HC induzida pelo treinamento resistido sem a necessidade de aumento na concentração da angiotensina II cardíaca. Um possível mecanismo seria a ativação direta dos receptores AT1 pelo estiramento mecânico dos cardiomiócitos. / Besides the well-known effects of Ang II in stimulating pathological pressure-overload cardiac hypertrophy, little information is available regarding the role of Renin-Angiotensin-System (RAS) in the exercise training-induced cardiac hypertrophy. 64 male Wistar rats were divided into 6 groups: Sedentary, Trained, Sedentary or Trained + Losartan (20mg/Kg/d, n=7) and Sedentary or Trained + Salt (NaCl 1%). The exercise protocol was: 4 x 12 bouts, 5x/week during eight weeks, with 65-75% of 1 Repetition Maximum (1RM). Using LV weight/body weight ratio and echocardiography (ECHO) we have observed cardiac hypertrophy in the Trained group without any impairment in ventricular function. Concerning RAS, neither ACE, analyzed by fluorometric assay (systemic and local in the heart), nor Renin, by RIA, activities were altered after resistance training. In addition, using Western blotting analysis, no change was observed in cardiac Ang II and AT2 receptor levels while the AT1 receptor expression was upregulated in Trained groups by 31,4%. Administration of the AT1 receptor antagonist (losartan) prevented left ventricle hypertrophy in response to the resistance training. The administration of salt, to inhibit the renin activity, did not prevent the cardiac hypertrophy. These results suggest that the AT1 receptor participates in resistance-training-induced cardiac hypertrophy without an increase in Ang II concentration in the heart. A possible mechanism is the direct activation of the AT1 receptor by mechanical stretching of cardiomyocytes.

The renin-angiotensin system plays a central role in the maintenance of blood pressure. Angiotensin II, the main effector of this system, results from the action of angiotensin-converting enzyme (ACE) on angiotensin I. Angiotensin II, maintains vasomotor tone via its vasoconstrictor action, and also increases salt and water retention by stimulating the release of aldosterone. ACE inhibitors, such as captopril, enalapril and lisinopril, are highly effective in the treatment of hypertension and congestive cardiac failure. Previous studies have suggested that angiotensin converting enzyme (ACE) production may be enhanced during pharmacological inhibition of the enzyme. Little is known, however about the mechanism of this induction. After demonstrating increases in circulating ACE protein in cardiac failure patients receiving the ACE inhibitor captopril, a rat model was used to study this effect. A sensitive enzyme linked immunosorbent assay for rat ACE was developed and a partial cDNA for rat ACE cloned to enable examination of ACE mRNA and protein expression during enzyme inhibition with enalapril. Rat lung ACE mRNA increased by 156% (p<0.05) and ACE protein doubled within 3 hours of administering a single dose of enalapril. Testicular ACE mRNA also increased by 300% (p<0.05) within 2 hours and returned to pretreatment levels by 6 hours. The angiotensin II antagonist saralasin similarly caused a significant (p<0.0001) 800% enhancement of mRNA expression. Aldosterone pretreatment of rats prior to enalapril administration was found to abolish this mRNA induction. These findings indicate that increased ACE expression during inhibition results from reduced levels of angiotensin II with consequent reduced stimulation of the angiotensin 11 receptor and its effects, such as aldosterone release. This suggests that ACE levels are regulated by a negative feedback loop involving the distal components of the renin-angiotensin system, namely angiotensin II and aldosterone. In situ hybridisation and immunohistochemical techniques were employed to localise the site of this inductive response in rat tissue sections. It was found that lung macrophages were markedly induced to produce ACE, as was ACE in seminiferous tubules. ACE induction was also noted in the expected sites of renal tubular epithelium and glomerular tissue. Interestingly, ACE expression was also enhanced in cardiac valves. In these studies it has been conclusively demonstrated that new ACE expression is induced by enzyme inhibitor therapy. A variety of techniques have been developed that will allow futher study of ACE in rat tissues.

Insulin resistance (IR) is considered to be an important factor influencing the progression of atherosclerosis and is associated with higher morbidity and mortality. IR is a common feature of diabetes mellitus Type 2 and obesity. Many authors consider IR being the crucial abnormality of the metabolic syndrome which is characterized by the essential hypertension, hyperliproteinemia, visceral obesity, endothel dysfunction and many other abnormalities. Impaired insulin action (IR) is also described in diabetes mellitus Type 1, however this phenomenon has not been fully explained. The subjects of dissertation thesis was directed on the IR importance in diabetic Type 1 patients as well as on the renin angiotensin system inhibition in patients with IR and metabolic syndrome with impaired glucose homeostasis. Hyperinsulinemic euglycemic clamp is used in combination with indirect calorimetry to estimate the IR in vivo in humans. In our project we focused on a) the existence of the metabolic inflexibility phenomenon in type 1 diabetic patients b) the methodological evaluation of the hyperinsulinemic euglycemic clamp procedure in the same group c) the influence of renin angiotensin system inhibition with angiotensin II type 1 receptor inhibitor telmisartan in patients with metabolic syndrome and impaired glucose...

The locus coeruleus (LC) is a putative site of action for angiotensin II in the brain. Immunocytochemical studies have identified angiotensin II-like immunoreactive material in nerve terminals innervating the LC, and the LC contains one of the highest densities of angiotensin II receptor binding sites in the rat brain. Recent studies using selective neurotoxins suggest that the binding sites for angiotensin II in the LC are present on noradrenergic perikarya. Angiotensin II receptors are now known to exist as two subtypes that are distinguishable both pharmacologically and biochemically. Radioligand binding studies using agonists and antagonists selective for these angiotensin II receptor subtypes indicate that the rat LC contains a mixture of the two known angiotensin II receptor subtypes, but that the PD123177-sensitive AIIβ receptor subtype is predominant. Comparisons of spontaneously hypertensive rats with normotensive rats indicates that angiotensin II and its receptors in the LC are elevated in the hypertensive rat strain. Studies of the biochemical and physiological actions of angiotensin II in the LC have not yet established an agreed-upon function for angiotensin II in this nucleus.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19606号 / 医博第4113号 / 新制||医||1015(附属図書館) / 32642 / 京都大学大学院医学研究科医学専攻 / (主査)教授 小池 薫, 教授 YOUSSEFIAN Shohab, 教授 川村 孝 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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