RESUMO
BACKGROUND: The bradykinin potentiating peptides (BPPs) are oligopeptides found in different animal venoms. BPPs isolated from Bothrops jararaca venom were the first natural inhibitors described for somatic angiotensin I-converting enzyme (ACE). They were used in the structural modeling for captopril development, a classical ACE inhibitor widely used to treat human hypertension. METHODS: We evaluated the effect of BPP-5a on cardiovascular parameters of conscious Wistar (WTs) and spontaneously hypertensive rats (SHRs). RESULTS: In SHR, BPP-5a showed potent cardiovascular effects, at doses ranging from 0.47 to 710 nmol/kg. The maximal changes in mean arterial pressure (MAP) and heart rate (HR) were found at the dose of 2.37 nmol/kg (Δ MAP: -38 ± 4 mmHg, p < 0.01; Δ HR: -71 ± 17 bpm, p < 0.05). Reductions in MAP and HR occurred throughout 6 hours of post-injection period. In contrast to active site-directed ACE inhibitors, no ACE inhibition, evaluated by the Ang I pressor effect, or bradykinin potentiation was observed during the antihypertensive effect of the pentapeptide. In vitro assays showed no effects of BPP-5a upon argininosuccinate synthetase and B(1), B(2), AT(1), AT(2) or Mas receptors. Ex vivo assays showed that BPP-5a induced endothelium-dependent vasorelaxation in isolated aortic rings of SHRs and WTs. CONCLUSIONS: Although the BPP-5a is considered an ACE inhibitor, our results indicate that its antihypertensive effect is exerted via a unique target, a nitric-oxide-dependent mechanism.
Assuntos
Inibidores da Enzima Conversora de Angiotensina/farmacologia , Bradicinina/metabolismo , Hipertensão/tratamento farmacológico , Oligopeptídeos/farmacologia , Venenos de Víboras/farmacologia , Motivos de Aminoácidos , Animais , Pressão Sanguínea/efeitos dos fármacos , Bradicinina/efeitos dos fármacos , Endotélio Vascular/efeitos dos fármacos , Endotélio Vascular/fisiologia , Frequência Cardíaca/efeitos dos fármacos , Hipertensão/fisiopatologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Óxido Nítrico/metabolismo , Subunidades Proteicas/metabolismo , Ratos , Ratos Endogâmicos SHR , Vasodilatação/efeitos dos fármacos , Peçonhas/químicaRESUMO
Angiotensin-converting enzyme (ACE) inhibitors were developed based on proline-rich oligopeptides found in the venom of Bothrops jararaca (Bj) previously known as bradykinin-potentiating peptides (BPPs). However, the exact mechanism of action of BPPs remains unclear. The role of the ACE in the cardiovascular effects of two of naturally proline-rich oligopeptides (Bj-BPP-7a and Bj-BPP-10c) was evaluated in vitro and in vivo. Bj-BPP-7a does not potentiate the cardiovascular response to bradykinin and is a weak inhibitor of ACE C and N sites (K(i) = 40,000 and 70,000 nM, respectively), whereas Bj-BPP-10c is a strong bradykinin potentiator and inhibitor of the ACE C site (K(i) = 0.5 versus 200 nM for N site). Strikingly, both peptides, in doses ranging from 0.47 to 71 nmol/kg, produced long-lasting reduction (>6 h) in the mean arterial pressure of conscious spontaneously hypertensive rats (maximal change, 45 +/- 6 and 53 +/- 6 mm Hg for Bj-BPP-7a and Bj-BPP-10c, respectively). The fall in blood pressure was accompanied by variable degrees of bradycardia. In keeping with the absence of relationship between ACE-inhibitory and antihypertensive activities, no changes in the pressor effect of angiotensin I or in the hypotensive effect of bradykinin were observed at the peak of the cardiovascular effects of both peptides. Our results indicate that the antihypertensive effect of two Bj-BPPs containing the motif Ile-Pro-Pro is unrelated to their ability for inhibiting ACE or potentiating bradykinin (BK), indicating as a major component ACE and BK-independent mechanisms. These results are in line with previous observations suggesting ACE inhibition-independent mechanisms for angiotensin I-converting enzyme inhibitor.
Assuntos
Inibidores da Enzima Conversora de Angiotensina/farmacologia , Sistema Cardiovascular/efeitos dos fármacos , Venenos de Crotalídeos/química , Oligopeptídeos/farmacologia , Peptidil Dipeptidase A/metabolismo , Angiotensina I/farmacologia , Inibidores da Enzima Conversora de Angiotensina/química , Inibidores da Enzima Conversora de Angiotensina/metabolismo , Animais , Anti-Hipertensivos/química , Anti-Hipertensivos/metabolismo , Anti-Hipertensivos/farmacologia , Pressão Sanguínea/efeitos dos fármacos , Bothrops , Bradicinina/farmacologia , Células CHO , Cricetinae , Cricetulus , Relação Dose-Resposta a Droga , Feminino , Cobaias , Frequência Cardíaca/efeitos dos fármacos , Humanos , Íleo/efeitos dos fármacos , Íleo/fisiologia , Técnicas In Vitro , Masculino , Contração Muscular/efeitos dos fármacos , Oligopeptídeos/química , Oligopeptídeos/metabolismo , Peptidil Dipeptidase A/genética , Ratos , Ratos Endogâmicos SHR , Ratos WistarRESUMO
Angiotensin-(1-7) [Ang-(1-7)] causes endothelial-dependent vasodilation mediated, in part, by NO release. However, the molecular mechanisms involved in endothelial NO synthase (eNOS) activation by Ang-(1-7) remain unknown. Using Chinese hamster ovary cells stably transfected with Mas cDNA (Chinese hamster ovary-Mas), we evaluated the underlying mechanisms related to receptor Mas-mediated posttranslational eNOS activation and NO release. We further examined the Ang-(1-7) profile of eNOS activation in human aortic endothelial cells, which constitutively express the Mas receptor. Chinese hamster ovary-Mas cells and human aortic endothelial cell were stimulated with Ang-(1-7; 10(-7) mol/L; 1 to 30 minutes) in the absence or presence of A-779 (10(-6) mol/L). Additional experiments were performed in the presence of the phosphatidylinositol 3-kinase inhibitor wortmannin (10(-6) mol/L). Changes in eNOS (at Ser1177/Thr495 residues) and Akt phosphorylation were evaluated by Western blotting. NO release was measured using both the fluorochrome 2,3-diaminonaphthalene and an NO analyzer. Ang-(1-7) significantly stimulated eNOS activation (reciprocal phosphorylation/dephosphorylation at Ser1177/Thr495) and induced a sustained Akt phosphorylation (P<0.05). Concomitantly, a significant increase in NO release was observed (2-fold increase in relation to control). These effects were blocked by A-779. Wortmannin suppressed eNOS activation in both Chinese hamster ovary-Mas and human aortic endothelial cells. Our findings demonstrate that Ang-(1-7), through Mas, stimulates eNOS activation and NO production via Akt-dependent pathways. These novel data highlight the importance of the Ang-(1-7)/Mas axis as a putative regulator of endothelial function.