RESUMO
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
The bradykinin-potentiating peptides from Bothrops jararaca venom are the most potent natural inhibitors of the angiotensin-converting enzyme. The biochemical and biological features of these peptides were crucial to demonstrate the pivotal role of the angiotensin-converting enzyme in blood pressure regulation. In the present study, seven bradykinin-potentiating peptides were identified within the C-type natriuretic peptide precursor cloned from snake brain. The bradykinin-potentiating peptides deduced from the B. jararaca brain precursor are strong in vitro inhibitors of the angiotensin-converting enzyme (nanomolar range), and also potentiate the bradykinin effects in ex vivo and in vivo experiments. Two of these peptides are novel bradykinin-potentiating peptides, one of which displays high specificity toward the N-domain active site of the somatic angiotensin-converting enzyme. In situ hybridization studies revealed the presence of the bradykinin-potentiating peptides precursor mRNAs in distinct regions of the B. jararaca brain, such as the ventromedial hypothalamus, the paraventricular nuclei, the paraventricular organ, and the subcommissural organ. The biochemical and pharmacological properties of the brain bradykinin-potentiating peptides, their presence within the neuroendocrine regulator C-type natriuretic peptide precursor, and their expression in regions of the snake brain correlated to neuroendocrine functions, strongly suggest that these peptides belong to a novel class of endogenous vasoactive peptides.
Assuntos
Inibidores da Enzima Conversora de Angiotensina/farmacologia , Encéfalo/metabolismo , Peptídeo Natriurético Tipo C , Oligopeptídeos/farmacologia , Fragmentos de Peptídeos/farmacologia , Precursores de Proteínas/genética , Sequência de Aminoácidos , Inibidores da Enzima Conversora de Angiotensina/química , Animais , Bioensaio , Pressão Sanguínea/efeitos dos fármacos , Bothrops , Bradicinina/farmacologia , Química Encefálica , Sinergismo Farmacológico , Cobaias , Íleo/efeitos dos fármacos , Técnicas In Vitro , Masculino , Dados de Sequência Molecular , Contração Muscular/efeitos dos fármacos , Peptídeo Natriurético Tipo C/biossíntese , Oligopeptídeos/química , Oligopeptídeos/genética , Especificidade de Órgãos , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/genética , Precursores de Proteínas/química , Precursores de Proteínas/metabolismo , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos , Especificidade por SubstratoRESUMO
The bradykinin-potentiating peptides from Bothrops jararaca venom are the most potent natural inhibitors of the angiotensin-converting enzyme. The biochemical and biological features of these peptides were crucial to demonstrate the pivotal role of the angiotensin-converting enzyme in blood pressure regulation. In the present study, seven bradykinin-potentiating peptides were identified within the C-type natriuretic peptide precursor cloned from snake brain. The bradykinin-potentiating peptides deduced from the B. jararaca brain precursor are strong in vitro inhibitors of the angiotensin-converting enzyme (nanomolar range), and also potentiate the bradykinin effects in ex vivo and in vivo experiments. Two of these peptides are novel bradykinin-potentiating peptides, one of which displays high specificity toward the N-domain active site of the somatic angiotensin-converting enzyme. In situ hybridization studies revealed the presence of the bradykinin-potentiating peptides precursor mRNAs in distinct regions of the B. jararaca brain, such as the ventromedial hypothalamus, the paraventricular nuclei, the paraventricular organ, and the subcommissural organ. The biochemical and pharmacological properties of the brain bradykinin-potentiating peptides, their presence within the neuroendocrine regulator C-type natriuretic peptide precursor, and their expression in regions of the snake brain correlated to neuroendocrine functions, strongly suggest that these peptides belong to a novel class of endogenous vasoactive peptides.