Abstract The aim of the present study was to describe the effects of different types of cold exposures on blood pressure (BP) and heart rate (HR) and to test how these cold-induced effects are modulated by antihypertensive drugs representing different kind of mechanisms of action. The tested drugs represented the following antihypertensive drug subgroups: metoprolol from beta-blocking agents, carvedilol from alfa- and beta-blocking agents, lisinopril from angiotensin converting enzyme inhibitors, eprosartan from angiotensin II antagonists, amlodipine from calcium channel blockers and hydrochlorothiazide from diuretics. The main outcome measures were the levels and changes in systolic (SBP) and diastolic blood pressure (DBP) and HR before, during and after cold exposure. The normotensive and mildly hypertensive subjects were exposed either to –15°C for 15 minutes (with winter clothing), 5°C for 45 minutes (minimal clothing) or to a cold pressor test (CPT). Before measurements at –15°C, metoprolol, carvedilol, lisinopril, eprosartan, hydrochlorothiazide or placebo were given for a week in a double-blind and crossover manner. In one test procedure (5°C and CPT) the test subjects ingested amlodipine for three days or were without drug ingestion before the tests in a crossover manner. Both SBP and DBP were markedly increased by all types of cold exposure. Cold-induced rises of SBP/DBP were higher during the exposure to 5°C and –15°C (19–35/20–24 mmHg) than during CPT (13/16 mmHg). Metoprolol, carvedilol, lisinopril, eprosartan and amlodipine decreased the level of BP during the exposure to 5°C and –15°C compared to placebo or no drug. The antihypertensive drugs, with dosages used in this study, did not affect the cold-induced rise of BP compared to no drug or placebo. HR increased during CPT, but decreased during exposure to 5°C and –15°C. Metoprolol and carvedilol decreased HR during exposure to –15°C compared to placebo. The present study demonstrates for the first time the effects of antihypertensive drugs on BP in hypertensive subjects exposed to cold similar to normal outdoor exposure in winter. Although the magnitude of the cold-induced rise in BP was not affected by the drugs, the drug-induced decrease in the level of BP kept the peak values in the cold closer to the recommended threshold limit values. / Tiivistelmä Tutkimuksen tarkoituksena oli selvittää eri mekanismeilla vaikuttavien verenpainelääkkeiden vaikutusta verenpainevasteisiin ja sydämen lyöntitiheyteen kylmässä sekä verrata erilaisten kylmäaltistusten vaikutusta verenpaineeseen ja sydämen lyöntitiheyteen. Tutkitut lääkkeet edustivat seuraavia verenpainelääkeryhmiä: metoprololi beetasalpaajia, karvediloli yhdistettyjä alfa- ja beetasalpaajia, lisinopriili ACE-estäjiä, eprosartaani angiotensiini II antagonisteja, amlodipiini kalsiumestäjiä ja hydroklooritiatsidi diureetteja. Tärkeimmät mitatut vasteet olivat systolisen ja diastolisen verenpaineen ja sydämen lyöntitiheyden tasot ja muutokset ennen kylmäaltistusta, kylmäaltistuksen aikana ja sen jälkeen. Lisäksi mitattiin lämpötilavasteita ja tuntemuksia. Normo- ja hypertensiiviset koehenkilöt altistettiin joko –15°C:seen 15 minuutin ajaksi (talvivaatetuksessa), 5°C:seen 45 minuutin ajaksi (minimaalisella vaatetuksella) tai tehtiin ns. käden kylmävesitesti (CPT). Testisarjoissa (–15°C) metoprololi, karvediloli, lisinopriili, eprosartaani ja hydroklooritiatsidi tai plasebo annettiin viikon ajan kaksoissokko- ja vaihtovuoromenetelmällä. Yhdessä testisarjassa (5°C ja CPT) koehenkilöt ottivat amlodipiinia 3 päivän ajan tai olivat ilman lääkettä ennen testikertoja vaihtovuoroisessa järjestyksessä. Kaikki kylmäaltistustyypit nostivat merkittävästi sekä systolista että diastolista verenpainetta. Systolisen ja diastolisen verenpaineen nousu oli korkeampi koko kehon kylmäaltistuksissa (5°C tai –15°C) (19–35/20–24 mmHg) kuin ns. kylmävesitestissä (13/16 mmHg). Metoprololi, karvediloli, lisinopriili, eprosartaani ja amlodipiini laskivat verenpaineen tasoja koko kehon kylmäaltistuksessa verrattuna plaseboon. Yksikään verenpainelääkkeistä ei vaikuttanut merkittävästi kylmän aiheuttamaan verenpaineen nousuun verrattuna tutkimuskertaan ilman lääkettä tai plaseboon. Sydämen lyöntitiheys nousi ns. kylmävesitestin aikana, mutta laski koko kehon kylmäaltistuksissa (5°C ja –15°C). Metoprololi ja karvediloli laskivat sydämen lyöntiheyttä kylmäaltistuksessa (–15°C) verrattuna plaseboon. Tämä tutkimus kuvaa ensimmäistä kertaa, kuinka verenpainelääkkeet vaikuttavat verenpainetasoihin ja -vasteisiin kylmäaltistuksessa, joka simuloi tyypillisiä ulko-olosuhteita talvella. Vaikka lääkkeet eivät estäneet kylmän aiheuttamaa verenpaineen nousua, ne laskivat verenpaineen tasoa, jolloin verenpaine pysyi kylmässäkin lähempänä suositusrajoja.

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No. of bitstreams: 2 Dissertação - Álvaro Paulo Silva Souza - 2014.pdf: 2481064 bytes, checksum: 21b6308dc6b1eefeb3619cad7c3ab0a7 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2014-09-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / According to the World Health Organization (2013),cardiovascular diseases(CVD) are the major causes of death world wide. High blood pressure is the main risk factors for these diseases. The Renin-angiotensin System (RAS) is a important regulator of the cardiovascular functions. Among the components of the RAS, we can highlight the Angiotensin-(1-7) [Ang (1-7)]. It is known that the vasodilator effect of Ang-(1-7) is endothelium-dependent. Hypertension cause changes in the vascular structure and function, especially in the endothelium cells, leading to endothelial dysfunction and, consequently, impairment in the vasodilator effect of Ang (1-7). However, it has been shown that some classes of antihypertensive drugs (Angiotensin II receptor blockers, angiotensin-converting enzyme inhibitors and Calcium channel blocker) improve the endothelial function. However, it is unknown if these drugs are able to improve the vasorelaxant effect of Ang-(1-7) in pressure-overload condition. Since several studies have pointed to Ang-(1-7)/Mas axis as a therapeutic potential for cardiovascular disease, is very important to understand the influence of the anti hypertensive drugs on the vascular effects of Ang-(1-7). Thus, the purpose of this study was to evaluate the influence of anti hypertensive drugs on the vascular effects of Angiotensin-(1-7) in pressure-overload rats. Wistar rats were submitted to abdominal aorta coarctation (ACo). Sham surgery was performed in the controls group. After 21 days of coarctation, blood pressure (BP) was recorded by carotid artery catheterization. Subsequently,the vasorelaxant effect of Ang-(1-7) were evaluated in aortic rings with or without acute pre-treatment (in vitro) of losartan 1µmol/L, captopril 1µmol/L or amlodipine 1µmol/L. To evaluate the effect of chronic treatment (in vivo), the ACo animals received the following treatments after surgery procedure: losartan 1 or 5 mg/kg/day, captopril 1 or 5 mg/kg/day, amlodipine 1 or 5 mg/kg/day, or DIZE 1 or 5 mg/kg/day. At the end of treatment, the aortic rings were isolated and the vasorrelaxant effect of Ang-(1-7) was evaluated. The increase of the BP was confirmed in the ACo rats. None of the treatment was able to reduce the blood pressure in ACo rats. Pressure overload decreased the relaxation induced by Ang (1-7) in isolated aortic rings. The in vitro pre treatment with losartan, captopril or amlodipine restored the vasorelaxant effect promoted by Ang-(1-7).A-779 or L-NAME blunted the vasorelaxant effect of Ang-(1-7) in aortic rings from CoA rats in presence of losartan.The in vivo treatment with losartan 1 mg/kg/day, captopril 1 mg/kg/day, amlodipine 1 mg/kg/day or DIZE 1 and 5 mg/kg/day was not effective in improving the vasorelaxant effect of Ang (1-7) in CoA aortic rings. However, losartan 5 mg/kg/day, captopril 5 mg/kg/day or amlodipine 5 mg/kg/Day improved the vasorelaxant effect of Ang-(1-7) in aortic rings from CoA rats. These results demonstrate that treatment in vitro or in vivo with some antihypertensive drugs (losartan, captopril and amlodipine) was able to improve the vasorelaxation effect of Ang (1-7) in the aorta from pressure-overloaded animals through mechanisms independent of blood pressure reduction. Therefore, the use of Ang-(1-7) associated with sub-pressor doses of antihypertensive agents may be a new therapeutic tool for the hypertension treatment. / Segundo a Organização Mundial de Saúde (2013), as doenças cardiovasculares (DCV) são as maiores causas de morte no mundo, sendo a Hipertensão Arterial um dos principais fatores de risco. O Sistema Renina-Angiotensina (SRA) é um sistema fundamental para a regulação das funções cardiovasculares. Dentre os componentes do SRA, podemos destacar a Angiotensina-(1-7) [Ang-(1-7)]. Sabe-se que o efeito vasodilatador da Ang-(1-7) é dependente do endotélio. A hipertensão arterial acarreta conseqüências sobre a estrutura vascular, de forma especial no endotélio, acarretando a disfunção endotelial, nesta condição o efeito vasodilatador da Ang-(1-7) fica prejudicado. No entanto, tem sido demonstrado que algumas classes de anti- hipertensivos (BRA, iECA e BCC) são importantes na melhora da função endotelial. Porém, ainda não se sabe se estes fármacos podem melhorar o efeito vasorrelaxante da Ang-(1-7) em condições de sobrecarga pressórica. Como diversos trabalhos tem apontado a Ang-(1-7)/ Receptor Mas como um potencial terapêutico para as doenças cardiovasculares, é de grande importância um melhor conhecimento sobre a influência de fármacos anti-hipertensivos nos efeitos vasculares da Ang-(1-7). Desta forma, a proposta do trabalho foi avaliar a influência de fármacos anti-hipertensivos nos efeitos vasculares da Angiotensina-(1-7) em ratos submetidos à sobrecarga pressórica. Para isto, ratos Wistar foram submetidos à coarctação da aorta abdominal (CoA). Como controles, foram utilizados animais onde foi realizado o procedimento cirúrgico fictício (Sham). Decorridos 21 dias da coarctação, a pressão arterial (PA) foi registrada pela canulação da artéria carótida. Posteriormente, o efeito vasorrelaxante da Ang-(1-7) foi avaliado em anéis de ratos CoA com ou sem o pré-tratamento agudo (in vitro) de losartan 1 µmol/L, captopril 1 µmol/L ou anlodipino 1 µmol/L. Para avaliar o efeito do tratamento crônico (in vivo), os animais receberam os seguintes tratamentos:losartan 1 ou 5 mg/kg/dia, captopril 1 ou 5 mg/kg/dia, anlodipino 1 ou 5 mg/kg/dia ou DIZE 1 ou 5 mg/kg/dia.Ao final do tratamento, os anéis de aorta de ratos foram isolados para a realização da curva de Ang-(1-7). Os animais CoA apresentaram aumento da PA e nenhum dos tratamentos foi capaz de reduzir a pressão arterial. A sobrecarga pressórica diminuiu o relaxamento induzido por Ang-(1-7) nos anéis de aorta isolados. O pré-tratamento in vitro com losartan, captopril ou anlodipino restaurou o efeito vasorrelaxante promovido por Ang-(1-7). Entretanto, em anéis de aorta de ratos CoA pré-tratados “in vitro” com losartan e A-779 ou losartan e L-NAME, tiveram o vasorrelaxamento promovido por Ang-(1-7) abolido. Já o tratamento in vivo nos animais CoA com losartan 1 mg/kg/dia, captopril 1 mg/kg/dia, anlodipino 1 mg/kg/dia ou DIZE 1 e 5 mg/kg/dia não foram efetivos em melhorar o efeito vasorrelaxante da Ang-(1-7). No entanto, o tratamento com losartan 5 mg/kg/dia, captopril 5 mg/kg/dia ou anlodipino 5 mg/kg/dia melhorou a resposta vasorrelaxante da Ang-(1-7) em animais CoA. Estes resultados demonstram que o tratamento in vitro ou in vivo com alguns anti-hipertensivos (losartan, captopril ou anlodipino) foi capaz de melhorar o vasorrelaxamento promovido por Ang-(1-7) em aorta de animais submetidos à sobrecarga pressórica por mecanismos independentes da pressão arterial. Portanto, a utilização de Ang-(1-7) associada a doses sub-pressóricas de fármacos anti- hipertensivos pode ser uma nova ferramenta terapêutica para o tratamento da hipertensão arterial.

Angiotensin converting enzyme (ACE) catalyzes the conversion of angiotensin I (Ang I) to angiotensin II (AngII). ACE also cleaves the terminal dipeptide of vasodilating hormone bradykinin (a nonapeptide) to its inactive form. Therefore, inhibition of ACE is one of the treatments of hypertension. A number of ACE inhibitory antihypertensive drugs are known. ‘Oxidative stress’ is another disease state caused by an imbalance in the production of oxidants and antioxidants in the body. A number of studies suggest that hypertension and oxidative stress are interdependent. Therefore, ACE inhibitors having antioxidant property are considered beneficial for the treatment of hypertension. Generally, selenium compounds exhibit better antioxidant behavior than their sulfur analogues. Therefore, we have synthesized a number of selenium analogues of captopril, an ACE inhibitor used as antihypertensive drug. Similar to captopril, the selenium analogues of captopril exhibited excellent ACE inhibition property. It was observed that these compounds are very good scavengers of peroxynitrite (PN), a strong oxidizing as well as nitrating agent found in vivo. The orientation of the chiral centers in these compounds was found to be very important for their ACE inhibition behavior. A number of selenocysteine- and cysteine-containing dipeptides and tripeptides were synthesized as inhibitors of ACE. It was observed that the ACE inhibition properties of these compounds depend on various factors such as orientation of the amino functionality, substitution at the C-terminal of the inhibitor, ring size of the proline moiety or the availability of the terminal acid group in carboxylate form etc. A structure-function correlation was drawn for the ACE inhibition properties of the peptide-based selenium-or sulfur-containing compounds. These studies reveal that the antioxidant properties do not depend on the side-chain functional groups, but they depend on the availability of selenium or sulfur centers. Selenium-based compounds were found to be better antioxidants than those containing sulfur moieties. In conclusion, the present study reveals that the replacement of sulfur atom in captopril and its analogues by selenium enhances the antioxidant activity. The reaction products of lactoperoxidase (LPO)-catalyzed iodination of Ang II were separated and characterized. It was observed that LPO-catalyzed iodination of Ang II takes place preferentially at the tyrosine residue. LPO-catalyzed iodination of Ang II is inhibited by commonly used antithyroid drugs such as MMI, MTU, PTU and also by antihypertensive drug captopril. It was also observed that the monoiodo Ang I is a better substrate for ACE compared to the natural substrate Ang I. The site of nitration of Ang II by PN was also determined by MS-MS analyses. This study reveals that the nitration takes place at the tyrosine residue.