Time-Dependent Effects of Individual and Combined Treatments With Nebivolol, Lisinopril, and Valsartan on Blood Pressure and Vascular Reactivity to Angiotensin II and Norepinephrine.

Clinical guidelines suggest the combination of 2 drugs as a strategy to treat hypertension. However, some antihypertensive combinations have been shown to be ineffective. Therefore, it is necessary to determine whether differences exist between the results of monotherapy and combination therapy by temporal monitoring of the responses to angiotensin II and norepinephrine, which are vasoconstrictors involved in the development of hypertension. Thus, the purpose of this work was to determine the vascular reactivity to angiotensin II and norepinephrine in spontaneously hypertensive rat (SHR) aortic rings after treatment with valsartan, lisinopril, nebivolol, nebivolol-lisinopril, and nebivolol-valsartan for different periods of time. In this study, male SHR and Wistar Kyoto normotensive (WKY) rats were divided into 7 groups treated for 1, 2, and 4 weeks: (1) WKY + vehicle, (2) SHR + vehicle; (3) SHR + nebivolol; (4) SHR + lisinopril; (5) SHR + valsartan; (6) SHR + nebivolol-lisinopril; and (7) SHR + nebivolol-valsartan. Blood pressure was measured by the tail-cuff method, and vascular reactivity was determined from the concentration-response curve to angiotensin II and norepinephrine in aortic rings. The results showed that the combined and individual treatments reduced mean blood pressure at all times evaluated. All treatments decreased vascular reactivity to angiotensin II; however, in the case of lisinopril and nebivolol-lisinopril, the effect observed was significant up to 2 weeks. All treatments decreased the reactivity to norepinephrine up to week 4. These results show a time-dependent difference in vascular reactivity between the pharmacological treatments, with nebivolol-valsartan and nebivolol-lisinopril being both effective combinations. Additionally, the results suggest crosstalk between the renin-angiotensin and sympathetic nervous systems to reduce blood pressure and to improve treatment efficacy.

Differences in the expression of the renin angiotensin system and the kallikrein-kinin system during the course of myocardial infarction in male and female Wistar rats.

BACKGROUND: There is some evidence that components of the renin-angiotensin system and kallikrein-kinin system are not similarly regulated in both sexes. The aim of this work was to analyze the expression of angiotensin-converting enzyme, angiotensin-converting enzyme 2, angiotensin 1 receptor, angiotensin 2 receptor, beta-1 receptor, and beta-2 receptor during the evolution of myocardial infarction. METHODS: Thirty-six male and 36 female Wistar rats were used. Myocardial infarction was induced. Six groups of both sexes were formed, (n=6): (a) sham; (b) 48 h myocardial infarction; (c) one week myocardial infarction; (d) two weeks myocardial infarction; (e) three weeks myocardial infarction and (f) four weeks myocardial infarction. The expression was evaluated by real-time polymerase chain reaction on the penumbra of left ventricle. RESULTS: The mRNA expression of most biomarkers was lower in females than in males. During acute infarction, an increase of all protein expression was found in female and at two weeks while in the male only biomarker changes occurred at three weeks. In addition, in male biomarkers mRNA expression decreased during chronic infarction while in females it did not. CONCLUSIONS: The renin-angiotensin system and kallikrein-kinin system biomarkers expression occurs at earlier times in the female than in the male rat. In addition, during chronic myocardial infarction these biomarkers remained unchanged in females while in males they decreased.

The α1D-adrenoreceptor antagonist BMY 7378 reverses cardiac hypertrophy in spontaneously hypertensive rats.

OBJECTIVE: The α1D-adrenoreceptor (α1D-AR) is involved in angiotensin II-induced vascular remodeling and hypertension. Whether α1D-AR plays a role in hypertension-associated cardiac hypertrophy is unclear. Here we investigated effects of BMY 7378, a selective α1D-AR antagonist, on cardiac status in aged spontaneously hypertensive rats (SHR). METHODS: Male SHR were studied during the phase of developing hypertension (5 and 10 weeks old) and once hypertension was established (20 and 30 weeks old) to assess the evolution of cardiac hypertrophy. Age-matched WKY rats were studied as controls. Thirty-week-old SHR were treated for 4 weeks with BMY 7378 (10 mg/kg per day, o.a.), or captopril (angiotensin-converting enzyme inhibitor, 40 mg/kg per day, o.a.) (as a positive control). Blood pressure and cardiac function were measured in vivo, cardiac hypertrophy by histology, and α1D-AR protein expression by immunofluorescence. RESULTS: By 30 weeks of age, SHR exhibited significant hypertension and cardiac hypertrophy. BMY 7378 and captopril decreased blood pressure and improved hemodynamic parameters and cardiac function in treated SHR vs. untreated SHR (P < 0.05). Histology showed increased cardiomyocyte size, fibrosis, and left ventricular hypertrophy in SHR hearts. BMY 7378 ameliorated fibrosis and cardiac hypertrophy, but had no effect on cardiomyocyte size in SHR. Effects of BMY 7378 were associated with increased α1D-AR protein expression in SHR. CONCLUSION: Our data indicate that pharmacological antagonism of α1D-AR reduces blood pressure and associated cardiac hypertrophy in aged SHR. These findings suggest that the α1D-AR plays a pathophysiological role in the development of hypertension and cardiac target organ damage in SHR.

Combined Antihypertensive Therapies That Increase Expression of Cardioprotective Biomarkers Associated With the Renin-Angiotensin and Kallikrein-Kinin Systems.

Antihypertensive pharmacological treatments focus on the use of angiotensin-converting enzyme (ACE) inhibitors, AT1 receptor antagonists, and beta-blockers as single and combined treatments. The effect of single treatments on the mRNA expression of some components of the renin-angiotensin system has been studied, but not the effect of combined treatments. This study determined the expression of the AT1, AT2, B1, and B2 receptors and of the enzymes ACE and ACE2 in hypertensive rats treated with captopril-propranolol or losartan-propranolol. Methods: The mRNA expression of the receptors and enzymes was determined by reverse transcription-quantitative polymerase chain reaction in the aorta of spontaneously hypertensive rats under different treatments. Results: Rats under combined treatments showed a decrease in the expression of AT1 and ACE, and an increase in the expression of the B1 receptor (captopril + propranolol group: 0.43 ± 0.046, 2.243 ± 0.269, 3.356 ± 0.418; Group: losartan + propranolol: 0.727 ± 0.071, 0.852 ± 0.102, 1.277 ± 0.131 compared to the spontaneously hypertensive group: 1 ± 0.212, 1 ± 0.192, 1 ± 0.214). This decrease in the expression of ACE and AT1 suggests a reduction in the expression of Ang II that could be related to a lower response to this vasoconstrictor. An increase in the expression of B1 would improve vasodilation, which would be a beneficial effect of combined therapies for hypertension.

Sex Differences in Vascular Reactivity to Angiotensin II During the Evolution of Myocardial Infarction.

The influence of sex on the vascular response during the progression of myocardial infarction (MI) has not been extensively studied. In this work, we analyzed the differences of the vasoconstriction induced by angiotensin II (Ang II) in the absence and presence of valsartan (200 nM) on the aortic rings of male and female Wistar rats at 2, 4, 24, and 48 hours and 1, 2, 3, and 4 weeks after induction of MI. In the aortic rings of males, an increase was observed in the contractile response that lasts up to 4 weeks; on females, this effect is diminished since 48 hours until reaching sham group values at 2 weeks of coronary occlusion. The incubation of valsartan generated greater reduction on vasoconstriction in males than females. In relation to the determination of infarct areas, we found them between 30% and 40% in all experimental groups. In addition, the index of hypertrophy was determined and no significant changes were observed in female rats, while in males we reported an increase at 2, 3, and 4 weeks. In conclusion, we found differences in vascular reactivity due to sex, as well as on the response of Ang II via AT1 during the evolution of MI.

Combination of ß Adrenergic Receptor Block and Renin-Angiotensin System Inhibition Diminished the Angiotensin II-Induced Vasoconstriction and Increased Bradykinin-Induced Vasodilation in Hypertension.

In hypertension, the combination therapy is frequently used to obtain a better therapeutic effect and reduce adverse effects. One effective combination is with inhibitors and ß-blockers of renin-angiotensin system. Although the mechanisms of action of each drug are already known, the antihypertensive mechanism is more complex and therefore the combined treatment mechanism is unclear. Specifically, the effect of the treatments of angiotensin-converting enzyme inhibitor or AT1 receptor antagonist with ß-blocker on the angiotensin II and bradykinin reactivity has not been studied. For this reason, we evaluated the interaction between propranolol and captopril or losartan on vascular reactivity to bradykinin and angiotensin II in spontaneously hypertensive rat. We constructed concentration-response curves to angiotensin II and bradykinin after treatment of SHR with propranolol-captopril or propranolol-losartan by using rat aortic rings. While losartan or captopril with propranolol potentiated bradykinin-induced vasodilation effect, the propranolol-losartan interaction decreased the angiotensin II-induced vasoconstriction. In addition, the combinations did not reduce the heart rate significantly. These results suggest that the combined therapy decreased blood pressure to normotensive values and showed less effect for angiotensin II and greater effect for bradykinin than monotherapy which could contribute in the antihypertensive effect.

Antihypertensive Properties of a Novel Morphologic Derivative (4-tert-buthyl-2,6-bis(thiomorpholine-4-ilmethyl)phenol).

We evaluated the antihypertensive properties of 4-tert-buthyl-2,6-bis(thiomorpholine-4-ilmethyl)phenol (TBTIF). Spontaneously hypertensive rats were treated with TBTIF or captopril (both at 1 mg·kg⁻¹·d⁻¹ intramuscularly for 4 days), and their blood pressure (BP) was assessed. In some experiments, concentration response curves to angiotensin I or angiotensin II were generated in rat aortic rings and in the absence or presence of Ang-(1-7), N(G)-monomethyl L-arginine, or both; additionally, the angiotensin-converting enzyme (ACE) and ACE2 mRNA levels were quantified in the aortic rings using reverse transcription-polymerase chain reaction. TBTIF diminished BP and reduced angiotensin I- or angiotensin II-induced vasoconstriction. The presence of Ang-(1-7) induced a greater reduction in vasoconstriction, and this effect was reversed by L-N(G)-monomethyl arginine. Moreover, TBTIF decreased the mRNA of ACE and increased the mRNA of ACE2. In conclusion, TBTIF diminished rat BP through nitric oxide-dependent and nitric oxide-independent mechanisms. In contrast to captopril, TBTIF exhibits better antihypertensive properties through mechanisms that involve ACE2.

Ang (1-7) is a modulator of the vasoconstrictor actions of Ang I and Ang II.

INTRODUCTION: The role of angiotensin (Ang) (1-7) on the vasoconstrictor effect induced by angiotensins could be different in the presence of an ACE inhibitor or an ARB because Ang II is formed through several pathways. Therefore, the role of Ang (1-7) in Ang I and Ang II contraction was evaluated in aortas from Wistar rats after 48-hour coronary occlusion treated with captopril or losartan. METHODS: Concentration-response curves to Ang I or Ang II were conducted in the absence or presence of Ang (1-7) and A779: a) sham group; b) 48-hour coronary occlusion; c) treated with captopril or d) losartan (3.1 mg/kg, i.m.). RESULTS: Captopril caused a significant increase in the contractile effect of Ang I and Ang II, while losartan reduced it. The presence of Ang (1-7) in the captopril group showed a reduction of the contraction compared to the sham group, while the treatment with losartan did not show a significant difference. Ang (1-7) presents effects different from Ang I or Ang II. CONCLUSION: Ang (1-7) showed a modulatory role, suggesting Ang I did as well after treatment with an ACE inhibitor but not with an AT1 receptor antagonist.

Comparative effects of a novel angiotensin-converting enzyme inhibitor versus captopril on plasma angiotensins after myocardial infarction.

The compound 4-tert-butyl-2,6-bis(thiomorpholin-4-ylmethyl)phenol (TBTIF) has molecular characteristics similar to angiotensin-converting enzyme (ACE) inhibitors of the sulfhydryl subclass. To assess its value as a new therapeutic agent, we performed a comparative analysis of the effect of TBTIF versus captopril on the circulating levels of angiotensin (Ang) peptides and bradykinin as well as ACE and ACE2 expression after myocardial infarction. Male Wistar rats were divided into four groups: (1) sham-operated rats; (2) rats subjected to 48 h of coronary artery ligation; (3) rats administered captopril (1 mg/kg, i.m.), and (4) a similar group of rats given TBTIF (1 mg/kg, i.m.). Both drugs were administered 30 min before coronary artery ligation and again 24 h later. Acute myocardial infarction lowered both systolic and left ventricular systolic blood pressures compared to the sham group and increased plasma levels of Ang I, Ang II, Ang(1-7) and Ang(1-12). Administration of either captopril or TBTIF reversed the increases in plasma angiotensins. Interestingly, the levels of plasma Ang(1-7) achieved by administration of TBTIF reached values higher than those recorded with captopril. Both agents reversed the decreases in plasma concentrations of bradykinin; in addition, TBTIF upregulated ACE expression, while both agents suppressed the ACE2 upregulation induced by myocardial infarction. These results demonstrate a beneficial effect of the novel compound TBTIF in suppressing the acute surge in the circulating renin-angiotensin system activity induced by myocardial infarction. The greater effects of this compound in augmenting plasma Ang(1-7) concentrations may be highly significant as drugs which augment the concentration of this heptapeptide will exert cardioprotective actions in part by suppressing the hypertrophic and profibrotic actions of Ang II.