RESUMO
The present study investigated the protective actions of des-aspartate-angiotensin I (DAA-I) in mice that were intranasally administered 2-chloroethyl ethyl sulfide (CEES), a half sulfur mustard. The protection was dose-dependent, and an oral dose of 75 mg kg⻹ per day administered 18 h post exposure and for the following 13 days, offered maximum protection that increased survival by a third. DAA-I attenuated the early processes of inflammation seen in the CEES-inoculated mice. DAA-I attenuated (i) elevated pulmonary ROS, and gp91-phox protein of NADPH oxidase, a non phagocytic enzyme that generates superoxide and subsequent ROS; (ii) intercellular adhesion molecule-1 (ICAM⻹) that is involved in the extravasation of circulating leucocytes; and (iii) myeloperoxidase activity, which is a surrogate enzymatic measurement of neutrophil infiltration. These actions led to improved histological lung structures, and survival of type-1 pneumocytes. The action of DAA-I on animal survival was blocked by losartan, a selective angiotensin AT1 receptor blocker, indicting that the AT1 receptor mediates the protection. The presence of elevated PGE2 and PGI2 in lung supernatants of DAA-I treated CEES-inoculated mice indicates that the two prostaglandins are involved in signaling the protective actions of DAA-I. This finding complements earlier studies showing that DAA-I acts on an indomethacin-sensitive angiotensin AT1 receptor. The findings of the present study are the first demonstration of an angiotensin peptide as an effective antidote for CEES intoxication. DAA-I is also an effective therapeutic intervention against CEES that was instituted at 18 h post exposure, and challenges conventional assumptions of limited efficacy with delayed action against alkylating agents.
Assuntos
Angiotensina I/análogos & derivados , Pulmão/efeitos dos fármacos , Pulmão/patologia , Gás de Mostarda/análogos & derivados , Angiotensina I/farmacologia , Animais , Líquido da Lavagem Broncoalveolar/química , Dinoprostona/metabolismo , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Epoprostenol/metabolismo , Molécula 1 de Adesão Intercelular/metabolismo , Losartan/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Gás de Mostarda/toxicidade , NADPH Oxidases/metabolismo , Peroxidase/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Receptores Imunológicos/metabolismo , Transdução de SinaisRESUMO
Angiotensin II is known to act primarily on the angiotensin AT(1) receptors to mediate its physiological and pathological actions. Des-aspartate-angiotensin I (DAA-I) is a bioactive angiotensin peptide and have been shown to have contrasting vascular actions to angiotensin II. Previous work in this laboratory has demonstrated an overwhelming vasodepressor modulation on angiotensin II-induced vasoconstriction by DAA-I. The present study investigated the involvement of the AT(1) receptor in the actions of DAA-I on angiotensin II-induced vascular actions in the renal vasculature of normotensive Wistar-Kyoto rats (WKY), spontaneously hypertensive rats (SHR) and streptozotocin (STZ)-induced diabetic rats. The findings revealed that the angiotensin receptor in rat kidney homogenate was mainly of the AT(1) subtype. The AT(1) receptor density was significantly higher in the kidney of the SHR. The increase in AT(1) receptor density was also confirmed by RT-PCR and Western blot analysis. In contrast, AT(1) receptor density was significantly reduced in the kidney of the streptozotocin-induced diabetic rat. Perfusion with 10(-9)M DAA-I reduced the AT(1) receptor density in the kidneys of WKY and SHR rats suggesting that the previously observed vasodepressor modulation of the nonapeptide could be due to down-regulation or internalization of AT(1) receptors. RT-PCR and Western blot analysis showed no significant changes in the content of AT(1) receptor mRNA and protein. This supports the suggestion that DAA-I causes internalization of AT(1) receptors. In the streptozotocin-induced diabetic rat, no significant changes in renal AT(1) receptor density and expression were seen when its kidneys were similarly perfused with DAA-I.
Assuntos
Angiotensina I/análogos & derivados , Rim , Receptor Tipo 1 de Angiotensina/metabolismo , Angiotensina I/genética , Angiotensina I/metabolismo , Angiotensina I/farmacologia , Angiotensina II/química , Angiotensina II/genética , Angiotensina II/metabolismo , Bloqueadores do Receptor Tipo 1 de Angiotensina II/metabolismo , Animais , Diabetes Mellitus Experimental , Rim/irrigação sanguínea , Rim/efeitos dos fármacos , Losartan/metabolismo , Masculino , Ratos , Ratos Endogâmicos SHR , Ratos Endogâmicos WKY , Receptor Tipo 1 de Angiotensina/genéticaRESUMO
In an earlier single-dose escalation study to evaluate the safety and pharmacokinetics of orally administered des-aspartate-angiotensin I (DAA-I) in healthy subjects, the plasma level of DAA-I could not be determined because DAA-I is rapidly degraded in the circulation. The present study investigated the oral bioavailability of DAA-I by measuring the prostaglandin E2 metabolite (PGEM) in the plasma samples of the same trial. PGEM is a stable derivative of PGE2, which has been shown to be a biomarker of DAA-I. The data show that plasma from two of the three subjects who were orally administered the efficacious preclinical dose of 0.70 mg/kg DAA-I exhibited a significant PGEM peak at 5-6 h postdose. Plasma of subjects who were administered 0.08 and 1.5 mg/kg DAA-I, the subefficacious and two-times efficacious dose, respectively, did not exhibit a similar PGEM peak. This observation is concordant with the known in vivo actions of DAA-I, especially its hypoglycemic action where maximum efficacy occurred at a dose of 0.7 mg/kg, and decreased to nil at the two-times efficacious dose. The onset of the PGEM peak at 5-6 h postdose was closed to the 4-h onset of absorption of [C14]DAA-I seen in preclinical rat studies, albeit the absorption kinetics between rodents and humans are not identical. The occurrence of polymorphism of enzymes involved in the formation and degradation of PGE2 is common, and this has been attributed to contributing to the variation in response, onset and peak PGEM observed among the three subjects who were administered the efficacious dose.
Assuntos
Angiotensina I/análogos & derivados , Dinoprostona/análogos & derivados , Angiotensina I/administração & dosagem , Angiotensina I/farmacocinética , Disponibilidade Biológica , Dinoprostona/sangue , Relação Dose-Resposta a Droga , HumanosRESUMO
The present study investigated the hypoglycemic action of des-aspartate-angiotensin I (DAA-I), a metabolite of angiotensin I, in two animal models of type 2 diabetes. The rationale was based on our earlier studies demonstrating that DAA-I acts on the angiotensin AT(1) receptor and exerts responses opposing those of angiotensin II and on recent reports that curtailment of angiotensin II formation by angiotensin converting enzyme inhibitors and blockade of the AT(1) receptor attenuate hyperglycemia in type 2 diabetics and diabetic animals. Diabetic KKAy mice and GK rats were administered orally (by gavage) one of the following doses of DAA-I: 400, 600, or 800 nmol/kg.d for 4 and 6 wk, respectively. Control diabetic animals were similarly administered water. Blood glucose of each animal was determined fortnightly by oral glucose tolerance test and blood insulin on the last day of treatment. Animals were killed, and the levels of plasma membrane glucose transporter-4 and cytosolic tyrosine-phosphorylated insulin receptor substrate-1 in hind limb skeletal muscles were determined by Western blot in insulin-challenged and nonchallenged animals. Orally administered DAA-I had no effect on blood insulin level but exerted dose-dependent hypoglycemic action in KKAy mice and GK rats after 4 and 6 wk of treatment, respectively. At the maximal effective dose of 600 nmol/kg, insulin induced a significant increase in plasma membrane glucose transporter-4 and cytosolic tyrosine-phosphorylated insulin receptor substrate-1. These findings show that DAA-I is not an insulin secretagogue and exerts hypoglycemic action by attenuating insulin resistance, the first such demonstration indicating that the nonapeptide is involved in glycemic regulation.
Assuntos
Angiotensina I/farmacologia , Diabetes Mellitus Tipo 2/tratamento farmacológico , Transportador de Glucose Tipo 4/metabolismo , Hipoglicemiantes/farmacologia , Angiotensina I/administração & dosagem , Angiotensina I/análogos & derivados , Animais , Glicemia/metabolismo , Western Blotting , Peso Corporal/efeitos dos fármacos , Diabetes Mellitus Experimental/tratamento farmacológico , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Tipo 2/metabolismo , Teste de Tolerância a Glucose , Hipoglicemiantes/administração & dosagem , Imunoprecipitação , Insulina/sangue , Resistência à Insulina , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Músculo Esquelético/metabolismo , Fosfodiesterase I/metabolismo , Distribuição Aleatória , Ratos , Ratos WistarRESUMO
Human chymase is a serine proteinase that converts angiotensin (Ang) I to Ang II independent of angiotensin converting enzyme (ACE) in vitro. The effects of chymase on systemic hemodynamics and left ventricular function in vivo were studied in nine conscious baboons instrumented with a LV micromanometer and LV minor axis and wall thickness sonomicrometer crystal pairs. Measurements were made at baseline and after [Pro11DAla12] Ang I, a specific substrate for human chymase, was given in consecutive fashion as a 0.1 mg bolus, an hour-long intravenous infusion of 5 mg, a 3 mg bolus, and after 5 mg of an Ang II receptor antagonist. [Pro11DAla12]Ang I significantly increased LV systolic and diastolic pressure, LV end-diastolic and end systolic dimensions and the time constant of LV relaxation and significantly decreased LV fractional shortening and wall thickening. Administration of a specific Ang II receptor antagonist reversed all the hemodynamic changes. In separate studies, similar results were obtained in six of the baboons with ACE blockade (20 mg, intravenous captopril). Post-mortem studies indicated that chymase-like activity was widely distributed in multiple tissues. Thus, in primates, Ang I is converted into Ang II by an enzyme with chymase-like activity. This study provides the first in vivo evidence of an ACE-independent pathway for Ang II production.
Assuntos
Angiotensina II/biossíntese , Angiotensina II/farmacologia , Angiotensina I/análogos & derivados , Serina Endopeptidases/metabolismo , Função Ventricular Esquerda/efeitos dos fármacos , Angiotensina I/metabolismo , Antagonistas de Receptores de Angiotensina , Animais , Artefatos , Captopril/farmacologia , Quimases , Estado de Consciência , Diástole/efeitos dos fármacos , Relação Dose-Resposta a Droga , Feminino , Hemodinâmica/efeitos dos fármacos , Infusões Intra-Arteriais , Masculino , Mastócitos/metabolismo , Papio , Peptidil Dipeptidase A/metabolismo , Sístole/efeitos dos fármacos , Distribuição TecidualRESUMO
We report here a comparative analysis of the involvement of a number of components of the renin-angiotensin system in the performance of simple and complex forms of drinking behavior and thirst-associated non-drinking types of behavior. On central (intracerebroventricular) microinjection, [des-Asp1]-angiotensin I at doses equieffective to those of angiotensins II and III was found to be involved only in the performance of simple (taking water from the bowl) and linked forms of activity (comfort behavior, stress grooming, orientational-investigative, and feeding behavior). Angiotensin II was involved in the central mechanisms of complex acquired drinking behavior, selectively modulating its key stages (initial, final), while angiotensin III was involved only in the mechanisms of reproduction of the complex skill. All three substances induced "innate patterns of behavior" specific for each compound, these occurring at fixed periods of time after intracerebral microinjection. The effects of these substances were selectively suppressed by the AT1 receptor blocker losartan potassium.
Assuntos
Instinto , Peptídeos/farmacologia , Sistema Renina-Angiotensina/efeitos dos fármacos , Sede/efeitos dos fármacos , Angiotensina I/análogos & derivados , Angiotensina I/farmacologia , Angiotensina II/farmacologia , Angiotensina III/farmacologia , Animais , Comportamento Animal/fisiologia , Ingestão de Líquidos/efeitos dos fármacos , Masculino , Ratos , Ratos Wistar , Sede/fisiologia , Fatores de TempoRESUMO
Central mechanisms of angiotensin involvement in initiation and realization of operant forms of drinking behavior were investigated. It was suggested that intracerebroventricular microinjection of angiotensin-II and angiotensin-IIl specifically affected the learned forms of drinking behavior. The experiments demonstrated that [des-Asp1]-angiotensin-I produced only the natural forms of drinking behavior. Angiotensins modulated specific forms of thirst-associated behavior such as exploring, grooming, and ingestive behavior. Injections of AT1 receptor antagonist losartan were associated with acute water intake decrease and sharp operant behavior inactivation.
Assuntos
Angiotensinas/farmacologia , Comportamento de Ingestão de Líquido/fisiologia , Aprendizagem , Sistema Renina-Angiotensina/fisiologia , Sede , Angiotensina I/administração & dosagem , Angiotensina I/análogos & derivados , Angiotensina I/farmacologia , Angiotensina II/administração & dosagem , Angiotensina II/farmacologia , Bloqueadores do Receptor Tipo 1 de Angiotensina II/farmacologia , Angiotensina III/administração & dosagem , Angiotensina III/farmacologia , Angiotensinas/fisiologia , Animais , Injeções Intraventriculares , Losartan/farmacologia , Masculino , Ratos , Ratos WistarRESUMO
Des-aspartate-angiotensin I (DAA-I) is an endogenous angiotensin peptide and a prototype angiotensin receptor agonist (ARA). It acts on the angiotensin AT1 receptor and antagonises the deleterious actions of angiotensin II. DAA-I attenuates animal models of human disease in which angiotensin II has been implicated, such as cardiac hypertrophy, neointima formation, arteriosclerosis, renal failure, post-infarction injuries, diabetes, viral infection, chemical-induced inflammation, heat stroke, cancer, and gamma radiation lethality. DAA-I crosses Caco-2 cells and is effective at sub-nanomolar concentrations. These two properties are responsible for its oral efficacy. A single dose-escalation study was conducted to evaluate the safety, tolerability and pharmacokinetics of orally administered DAA-I in 18 healthy subjects. DAA-I was safe and well tolerated by the subjects, who were administered either 0.08, 0.70 or 1.50 mg/kg of the compound. The heart rate and systolic and diastolic blood pressures determined at each post-dose measurement remained within the clinically acceptable range. Across all cohorts, DAA-I had no substantial effect on blood pressures compared with placebo. Electrocardiographs (ECGs) were normal, and none of the subjects complained of chest discomfort. All clinical laboratory tests obtained before and after DAA-I and placebo treatment were normal. Pharmacokinetic analysis over a 12-h period following DAA-I administration did not show any increase of its level beyond basal concentration. This is in line with studies showing that intravenously administered DAA-I is rapidly metabolized and has a short half-life. We postulate that, during its short systemic sojourn, DAA-I exerts its actions via biased agonism on the angiotensin AT1 receptor.The ClinicalTrial.gov assignment number for this study is NCT02666196.
Assuntos
Angiotensina I/análogos & derivados , Administração Oral , Adulto , Angiotensina I/administração & dosagem , Angiotensina I/farmacocinética , Relação Dose-Resposta a Droga , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
Des-Leu10-angiotensin I is a nonapeptide generated from angiotensin I by the action of carboxypeptidase-like activities residing in the human platelet and mast cell. This nonapeptide was found to inhibit rabbit lung angiotensin-converting enzyme (peptidyl-dipeptide hydrolase, EC 3.4.15.1) with a Ki of 3.1 X 10(-7) M. The mechanism of inhibition was competitive. Inhibition of human serum angiotensin-converting enzyme by des-Leu10-angiotensin I was comparable in magnitude to inhibition by bradykinin and angiotensin III. These results suggest that limited proteolysis of angiotensin I by cells resident in vascular tissue may result in the generation of an endogenous inhibitor of angiotensin-converting enzyme. Such pathways may play roles in controlling levels of vasoactive peptides at local vascular sites.
Assuntos
Angiotensina I/farmacologia , Inibidores da Enzima Conversora de Angiotensina , Angiotensinas/farmacologia , Angiotensina I/análogos & derivados , Animais , Bradicinina/farmacologia , Captopril/farmacologia , Humanos , Cinética , Pulmão/enzimologia , Peptidil Dipeptidase A/sangue , CoelhosRESUMO
BACKGROUND: [Pro(11)(D)-Ala(12)] angiotensin I is an ACE-resistant substrate specific for chymase. We used this peptide to determine whether a functionally significant non-ACE angiotensin (Ang) II-generating pathway exists in human dorsal hand veins. METHODS AND RESULTS: Using a modified Aellig technique, we studied the response to Ang I and [Pro(11)(D)-Ala(12)] Ang I in dorsal hand veins in vivo in patients with coronary heart disease. We measured the venoconstrictor effect of each peptide given before and after a 6.25-mg oral dose of the ACE inhibitor captopril or matching placebo. Placebo or captopril was given in a double-blind, randomized fashion. Ang I induced a mean+/-SEM venoconstrictor response of 45+/-11%, 40+/-10%, 55+/-8%, and 4+/-4% before placebo, after placebo, before captopril, and after captopril, respectively. Hence, the response to Ang I was reproducible and was reduced significantly only after treatment with captopril (P=0.002). [Pro(11)(D)-Ala(12)] Ang I induced a mean venoconstrictor response of 42+/-9%, 49+/-9%, 48+/-10%, and 54+/-11% before placebo, after placebo, before captopril, and after captopril, respectively. Hence, captopril had no significant effect on the response to [Pro(11)(D)-Ala(12)] Ang I. CONCLUSIONS: We have demonstrated that [Pro(11)(D)-Ala(12)] Ang I is able to induce venoconstriction in humans in vivo. With this specific pharmacological probe, we have shown that a non-ACE pathway capable of generating Ang II exists in human veins in vivo and is potentially functionally important. This pathway is likely to involve the enzyme chymase.
Assuntos
Angina Pectoris/fisiopatologia , Angiotensina I/análogos & derivados , Angiotensina I/farmacologia , Vasoconstrição/efeitos dos fármacos , Veias/efeitos dos fármacos , Veias/fisiopatologia , Administração Oral , Angina Pectoris/tratamento farmacológico , Angiotensina I/metabolismo , Angiotensina II/biossíntese , Antagonistas de Receptores de Angiotensina , Inibidores da Enzima Conversora de Angiotensina/administração & dosagem , Anti-Hipertensivos/administração & dosagem , Compostos de Bifenilo/administração & dosagem , Captopril/administração & dosagem , Doença Crônica , Quimases , Relação Dose-Resposta a Droga , Método Duplo-Cego , Mãos/irrigação sanguínea , Humanos , Infusões Intravenosas , Irbesartana , Pessoa de Meia-Idade , Peptidil Dipeptidase A/metabolismo , Reprodutibilidade dos Testes , Serina Endopeptidases/metabolismo , Especificidade por Substrato , Tetrazóis/administração & dosagemRESUMO
The present study investigated the action of des-aspartate-angiotensin I (DAA-I) on the pressor action of angiotensin II in the renal and mesenteric vasculature of WKY, SHR and streptozotocin (STZ)-induced diabetic rats. Angiotensin II-induced a dose-dependent pressor response in the renal vasculature. Compared to the WKY, the pressor response was enhanced in the SHR and reduced in the STZ-induced diabetic rat. DAA-I attenuated the angiotensin II pressor action in renal vasculature of WKY and SHR. The attenuation was observed for DAA-I concentration as low as 10(-18) M and was more prominent in SHR. However, the ability of DAA-I to reduce angiotensin II response was lost in the STZ-induced diabetic kidney. Instead, enhancement of angiotensin II pressor response was seen at the lower doses of the octapeptide. The effect of DAA-I was not inhibited by PD123319, an AT2 receptor antagonist, and indomethacin, a cyclo-oxygenase inhibitor in both WKY and SHR, indicating that its action was not mediated by angiotensin AT2 receptor and prostaglandins. The pressor responses to angiotensin II in mesenteric vascular bed were also dose-dependent but smaller in magnitude compared to the renal vasculature. The responses were significantly smaller in SHR but no significant difference was observed between STZ-induced diabetic and WKY rat. Similarly, PD123319 and indomethacin had no effect on the action of DAA-I. The findings reiterate a regulatory role for DAA-I in vascular bed of the kidney and mesentery. By being active at circulating level, DAA-I subserves a physiological role. This function appears to be present in animals with diseased state of hypertension and diabetes. It is likely that DAA-I functions are modified to accommodate the ongoing vascular remodeling.
Assuntos
Angiotensina Amida/metabolismo , Angiotensina II/administração & dosagem , Angiotensina I/administração & dosagem , Diabetes Mellitus Experimental/metabolismo , Circulação Renal/efeitos dos fármacos , Circulação Esplâncnica/efeitos dos fármacos , Vasoconstritores/administração & dosagem , Angiotensina I/análogos & derivados , Animais , Pressão Sanguínea/efeitos dos fármacos , Vasos Sanguíneos/metabolismo , Rim/irrigação sanguínea , Rim/metabolismo , Masculino , Ratos , Ratos Endogâmicos SHR , Ratos Endogâmicos WKY , Circulação Renal/fisiologia , Circulação Esplâncnica/fisiologiaRESUMO
Conformational properties of the angiotensin II precursor, angiotensin I (AngI) and analogues containing the paramagnetic amino acid TOAC (2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid) at positions 0, 1, 3, 5, 8, 9, and 10, were examined by EPR, CD, and fluorescence. The conformational data were correlated to their activity in muscle contraction experiments and to their properties as substrates of the angiotensin I-converting enzyme (ACE). Biological activity studies indicated that TOAC0-AngI and TOAC1-AngI maintained partial potency in guinea pig ileum and rat uterus. Kinetic parameters revealed that only derivatives labeled closer to the N-terminus (positions 0, 1, 3, and 5) were hydrolyzed by ACE, indicating that peptides bearing the TOAC moiety far from the ACE cleavage site (Phe8-His9 peptide bond) were susceptible to hydrolysis, albeit less effectively than the parent compound. CD spectra indicated that AngI exhibited a flexible structure resulting from equilibrium between different conformers. While the conformation of N-terminally-labeled derivatives was similar to that of the native peptide, a greater propensity to acquire folded structures was observed for internally-labeled, as well as C-terminally labeled, analogues. These structures were stabilized in secondary structure-inducing agent, TFE. Different analogues gave rise to different ß-turns. EPR spectra in aqueous solution also distinguished between N-terminally, internally-, and C-terminally labeled peptides, yielding narrower lines, indicative of greater mobility for the former. Interestingly, the spectra of peptides labeled at, or close, to the C-terminus, showed that the motion in this part of the peptides was intermediate between that of N-terminally and internally-labeled peptides, in agreement with the suggestion of turn formation provided by the CD spectra. Quenching of the Tyr4 fluorescence by the differently positioned TOAC residues corroborated the data obtained by the other spectroscopic techniques. Lastly, we demonstrated the feasibility of monitoring the progress of ACE-catalyzed hydrolysis of TOAC-labeled peptides by following time-dependent changes in their EPR spectra.
Assuntos
Angiotensina I/análogos & derivados , Contração Muscular/efeitos dos fármacos , Relação Quantitativa Estrutura-Atividade , Angiotensina I/química , Angiotensina I/farmacologia , Animais , Óxidos N-Cíclicos/química , Feminino , Cobaias , Peptidil Dipeptidase A/metabolismo , Conformação Proteica , Ratos , Especificidade por SubstratoRESUMO
DAA-I (des-aspartate-angiotensin I), an endogenous angiotensin, had been shown earlier to ameliorate animal models of cardiovascular diseases via the angiotensin AT1 receptor and prostaglandins. The present study investigated further the action of DAA-I on the release of PGE2, PGI2, PGF2α and TXA2 in HUVEC. 10(-11)-10(-8)M DAA-I and 15min incubation specifically released PGE2 and PGI2. The release was inhibited by losartan and indomethacin but not by PD123319 and NS398 indicating that the angiotensin AT1 receptor and COX-1 mediate the release. At concentrations higher than 10(-7)M, DAA-I mimics the action of angiotensin II by releasing TXA2 but had no effect on the production of PGF2α. At similar concentrations and 4h incubation, DAA-I increased the release of the 4 prostaglandins via the angiotensin AT1 receptor and COX-2, again mimicking the action of angiotensin II. HUVEC that were preincubated with DAA-I or angiotensin II, released similar profiles of prostaglandins when incubated with arachidonic acid after the angiotensin had been washed off. We postulate that the internalized DAA-I/receptor complex remains active and mediates the conversion of arachidonic acid to the respective prostaglandins. The release of PGE2 and PGI2 via the angiotensin AT1 receptor and COX-1 is a novel specific action of DAA-I and is likely responsible for its beneficial effects seen in earlier studies. This specific action is definable as a biased agonism of the angiotensin AT1 receptor, which identifies DAA-I as a novel biased agonist and potential therapeutic that is able to produce specific prostaglandins at nanomolar concentrations.
Assuntos
Angiotensina I/análogos & derivados , Dinoprostona/metabolismo , Epoprostenol/metabolismo , Células Endoteliais da Veia Umbilical Humana/efeitos dos fármacos , Células Endoteliais da Veia Umbilical Humana/metabolismo , Receptor Tipo 1 de Angiotensina/agonistas , Receptor Tipo 1 de Angiotensina/metabolismo , Angiotensina I/farmacologia , Ácido Araquidônico/farmacologia , Humanos , Fatores de TempoRESUMO
ACE inhibitors and ARBs (angiotensin receptor blockers) have been shown to attenuate radiation injuries in animal models of lethal gamma irradiation. These two classes of drug act by curtailing the actions of angiotensin II-linked inflammatory pathways that are up-regulated during gamma radiation in organ systems such as the brain, lung, kidney, and bone marrow. ACE inhibitors inhibit ACE and attenuate the formation of angiotensin II from angiotensin I; ARBs block the angiotensin AT1 receptor and attenuate the actions of angiotensin II that are elicited through the receptor. DAA-I (des-aspartate-angiotensin I), an orally active angiotensin peptide, also attenuates the deleterious actions of angiotensin II. It acts as an agonist on the angiotensin AT1 receptor and elicits responses that oppose those of angiotensn II. Thus, DAA-I was investigated for its anticipated radioprotection in gamma irradiated mice. DAA-I administered orally at 800 nmole/kg/day for 30 days post exposure (6.4 Gy) attenuated the death of mice during the 30-day period. The attenuation was blocked by losartan (50 nmole/kg/day, i.p.) that was administered sequential to DAA-I administration. This shows that the radioprotection was mediated via the angiotensin AT1 receptor. Furthermore, the radioprotection correlated to an increase in circulating PGE2 of surviving animals, and this suggests that PGE2 is involved in the radioprotection in DAA-I-treated mice. At the hematopoietic level, DAA-I significantly improved two syndromes of myelosuppression (leucopenia and lymphocytopenia), and mice pre-treated with DAA-I prior to gamma irradiation showed significant improvement in the four myelodysplastic syndromes that were investigated, namely leucopenia, lymphocytopenia, monocytopenia and thrombocytopenia. Based on the known ability of PGE2 to attenuate the loss of functional hematopoietic stem and progenitor cells in radiation injury, we hypothesize that PGE2 mediated the action of DAA-I. DAA-I completely attenuated the increase in circulating level of two inflammatory cytokines, TNFα and IL-6, in irradiated mice; and this shows that DAA-I exerted additional anti-inflammatory actions, which could also have contributed to its radioprotection. These findings show that DAA-I acts via a novel mechanism of action on the angiotensin AT1 receptor to specifically release PGE2, which mediates radioprotection in the gamma irradiated mice.
Assuntos
Angiotensina I/análogos & derivados , Raios gama/efeitos adversos , Síndromes Mielodisplásicas/tratamento farmacológico , Protetores contra Radiação/farmacologia , Angiotensina I/farmacologia , Inibidores da Enzima Conversora de Angiotensina/farmacologia , Animais , Dinoprostona/metabolismo , Feminino , Interleucina-6/metabolismo , Losartan/farmacologia , Camundongos , Camundongos Endogâmicos BALB C , Síndromes Mielodisplásicas/metabolismo , Síndromes Mielodisplásicas/radioterapia , Receptor Tipo 1 de Angiotensina/metabolismo , Fator de Necrose Tumoral alfa/metabolismoRESUMO
Des-aspartate angiotensin I (DAA-I), an endogenous nonapeptide, counteracts several effects of angiotensin II on vascular tone. The aim of this study was to investigate the acute protective effect of DAA-I on endothelial function in the spontaneously hypertensive rat (SHR) as well as its effect on angiotensin II-induced contractions and oxidative stress. Aortic rings were incubated with DAA-I (0.1µM) for 30min prior to the assessment of angiotensin II-induced contractions (0.1nM-10µM) in WKY and SHR aortas. Total nitrate and nitrite levels were assessed using a colorimetric method and reactive oxygen species (ROS) were measured by dihydroethidium (DHE) fluorescence and lucigenin-enhanced chemiluminescence. The effect of DAA-I was also assessed against endothelium-dependent and -independent relaxations to acetylcholine and sodium nitroprusside, respectively. Angiotensin II-induced contractions were significantly reduced by DAA-I, losartan and tempol. Incubation with ODQ (soluble guanylyl cyclase inhibitor) and removal of the endothelium prevented the reduction of angiotensin II-induced contractions by DAA-I. Total nitrate and nitrite levels were increased in DAA-I, losartan and tempol treated-SHR tissues while ROS level was reduced by DAA-I and the latter inhibitors. In addition, DAA-I significantly improved the impaired acetylcholine-induced relaxation in SHR aortas whilst sodium nitroprusside-induced endothelium-independent relaxation remained unaffected. The present findings indicate that improvement of endothelial function by DAA-I in the SHR aorta is mediated through endothelium-dependent release of nitric oxide and inhibition of angiotensin II-induced oxidative stress.
Assuntos
Angiotensina II/toxicidade , Angiotensina I/análogos & derivados , Hipertensão/induzido quimicamente , Hipertensão/tratamento farmacológico , Estresse Oxidativo/efeitos dos fármacos , Angiotensina I/farmacologia , Angiotensina I/uso terapêutico , Animais , Aorta Torácica/efeitos dos fármacos , Aorta Torácica/metabolismo , Relação Dose-Resposta a Droga , Hipertensão/metabolismo , Masculino , Técnicas de Cultura de Órgãos , Estresse Oxidativo/fisiologia , Ratos , Ratos Endogâmicos SHR , Ratos Endogâmicos WKYRESUMO
The review describes DAA-I (des-aspartate-angiotensin-I) as a prototype of a novel class of drugs that acts as agonists on the angiotensin AT1 receptor or ARAs (angiotensin receptor agonists). DAA-I is a component of the renin angiotensin system. Earlier studies showed that it was rapidly metabolized to angiotensin III. However, when administered at doses below the Km of enzymes, DAA-I produces specific actions that antagonize the deleterious actions of angiotensin II. DAA-I exerts protective actions in animal models of eight human pathologies in which angiotensin II is implicated. The pathologies include cardiac hypertrophy, neointima growth and cardiovascular hypertrophy, myocardial-ischemia reperfusion injury, hyperglycemia and insulin resistance, chemical induced inflammation, and exercise-induced skeletal muscle inflammation. Binding of DAA-I to the angiotensin AT1 receptors releases prostaglandins, which could either function as autocrines/paracrines or second messengers and attenuate the deleterious actions of angiotensin II. It is possible that in in vivo DAA-I functions as a physiological antagonist to angiotensin II, and exogenous DAA-I is a novel class of angiotensin receptor drug that could rival the angiotensin receptor blockers.
Assuntos
Angiotensina I/análogos & derivados , Receptor Tipo 1 de Angiotensina/metabolismo , Angiotensina I/metabolismo , Angiotensina I/farmacologia , Angiotensina I/uso terapêutico , Animais , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/fisiologia , Cardiomegalia/tratamento farmacológico , Cardiomegalia/metabolismo , Humanos , Hiperglicemia/tratamento farmacológico , Hiperglicemia/metabolismo , Traumatismo por Reperfusão Miocárdica/tratamento farmacológico , Traumatismo por Reperfusão Miocárdica/metabolismoRESUMO
Bioassay studies have indicated that angiotensin I (Ang I), but not angiotensin II (Ang II), is degraded by the intact lung. The present study was an attempt to isolate and quantify pulmonary metabolites of Ang I. The pulmonary vascular bed of the rat was isolated and perfused at 4-6 ml/min (< 20 mm Hg) with oxygenated Krebs buffer containing 5% bovine serum albumin. [3H-Leu10]Ang I (3-10 ng) was administered, and pulmonary effluent samples were collected every 15 sec for 5 min. Peptides were isolated by Dowex chromatography and separated by thin layer chromatography. 3H-labeled peptides were eluted from the thin layer chromatography plate, and the Ang I and [des-Asp1]Ang I levels were estimated by RIA. These peptides were shown to be hydrolyzed by purified converting enzyme with the release of His-3H-Leu. About 25% of the [3H]Ang I administered was isolated as [3H-des-Asp1]Ang I, and this percentage increased to 33% after treatment with teprotide. These studies clearly demonstrate that [des-Asp1]Ang I is a major pulmonary metabolite of Ang I and suggest the presence of a pulmonary aminopeptidase which hydrolyzes Ang I but not Ang II.
Assuntos
Angiotensina I/metabolismo , Angiotensinas/metabolismo , Pulmão/metabolismo , Angiotensina I/análogos & derivados , Animais , Reações Cruzadas , Cinética , Masculino , Perfusão , Radioimunoensaio , RatosRESUMO
The observation that angiotensin III is present in the circulation of the rat in amounts similar to those of angiotensin II has led to the notion that it may, in part, be formed by the action of converting enzyme on des-Asp-angiotensin I without the prior formation of angiotensin II. This possibility was studied in conscious rats using a combination of RIA and chromatographic techniques which allowed the separate measurement of angiotensin I, des-Asp-angiotensin I, angiotensin II, and angiotensin III in rat blood. Infusion of des-Asp1-[Ile5]angiotensin I at 50, 150, and 450 ng/kg . min resulted in a progressive increase in the plasma concentration of angiotensin III up to 279 +/- 50 (SD) pg/ml compared to 9 +/- 9 (SD) pg/ml after dextrose infusion. Regardless of the infusion of des Asp-[Ile5]angiotensin I, plasma angiotensin III made up a constant 46 +/- 8% (+/- SD) of the total immunoactive material, the remainder being composed of smaller metabolic fragments, indicating a rapid rate of clearance of angiotensin III. Captopril completely inhibited the rise in angiotensin III after des-Asp1-[Ile5]angiotensin I infusion. A substance which chromatographed as des-Asp-[Ile5]angiotensin I was detected in rat blood and made up 19% of the angiotensin I immunoactive material, while angiotensin III made up 44% of the angiotensin II immunoactive material. These results confirm that des-Asp1-[Ile5]angiotensin I is a substrate for converting enzyme in the rat, and the presence of a chromatographically similar substance in the circulation suggests that at least part of the angiotensin III in rat blood may be formed by the action of converting enzyme on endogenous des-Asp-angiotensin I. (Endocrinology 108: 406, 1981)
Assuntos
Angiotensina III/metabolismo , Angiotensina II/análogos & derivados , Angiotensina I/metabolismo , Angiotensinas/metabolismo , Angiotensina I/administração & dosagem , Angiotensina I/análogos & derivados , Angiotensina I/sangue , Angiotensina II/sangue , Angiotensina III/sangue , Animais , Captopril/farmacologia , Relação Dose-Resposta a Droga , Hormônios/administração & dosagem , Infusões Parenterais , Masculino , Peptidil Dipeptidase A/metabolismo , RatosRESUMO
Human des-angiotensin I renin substrate, a cleavage product of the renin reaction, was generated in plasma and from semipurified renin substrate by exhaustive incubation with renin and was quantitated by a direct RIA. An increase in the Michaelis-Menten constant of the renin-substrate reaction, from 2000 to 5000 ng angiotensin I equivalents of renin substrate/ml, with no change in maximal velocity was observed upon addition of this semipurified protein to plasma. It is suggested that this phenomenon of competitive inhibition of the renin reaction by des-angiotensin I renin substrate accounts for discrepancies in the determination of renin substrate concentration and possibly has physiological significance for feedback inhibition of angiotensin I generation.
Assuntos
Angiotensinogênio/farmacologia , Angiotensinas/farmacologia , Renina/antagonistas & inibidores , Angiotensina I/análogos & derivados , Angiotensinogênio/sangue , Ligação Competitiva , Humanos , Cinética , Fragmentos de Peptídeos/sangue , Fragmentos de Peptídeos/farmacologiaRESUMO
Angiotensinogen and the product of its hydrolysis by renin, des-angiotensin I-angiotensinogen, were quantitated in human plasma and in cerebrospinal fluid (CSF) by a direct RIA. This assay was developed using polyclonal antibodies raised against pure human angiotensinogen. The antibodies recognized only primate angiotensinogen and des-angiotensin I-angiotensinogen. Results obtained with the direct RIA were compared with those of the indirect assay which measures angiotensinogen through angiotensin I liberated by an excess of renin. Both assays gave almost identical results in normal subjects whereas in three different conditions characterized by a high renin level (severe hypertension plus low sodium diet, converting enzyme inhibition, and adrenal insufficiency) higher results were obtained by the direct assay. This difference between the results of both methods was attributed to des-angiotensin I-angiotensinogen accumulation which is detected only in the direct assay. CSF angiotensinogen had similar immunochemical properties to plasma angiotensinogen and could also be measured by the direct RIA. Isoelectric focusing of plasma angiotensinogen and des-angiotensin I-angiotensinogen revealed a similar microheterogeneity. Microheterogeneity was also a characteristic of CSF angiotensinogen, but its isoelectric point was more basic than plasma angiotensinogen.