Cardiac angiotensin-converting enzyme activity in myocardial infarction

Structure–activity relationship study between Ornithyl-Proline and Lysyl-Proline based tripeptidomimics as angiotensin-converting enzyme inhibitors

A designed library of tripeptidomimics of Ornithyl-Proline (Orn-Pro) and Lysyl-Proline (Lys-Pro) conjugated with various unnatural amino acids and carboxylic acid derived heterocyclics was synthesized and screened for possible inhibitors of angiotensin-converting enzyme (ACE). Among the tripeptidomimics 10[MTP-Orn-Pro], 11[HTP-Orn-Pro], 14[TA-Orn-Pro] and 20[BPA-Orn-Pro] showed prominent inhibition with IC50 values in micromolar concentrations. Structure-activity relationship study indicated that C3 side chain of Orn as compared to C4 side chain of Lys at P1' position was better suited to inhibit ACE, with propionic acid (C3) derived heterocyclics and unnatural amino acids.

Novel peptidomimics as angiotensin-converting enzyme inhibitors: a combinatorial approach

One of the efficient mode of treatments of chronic hypertension and cardiovascular disorders has been to restrain the formation of angiotensin-II by inhibiting the action of angiotensin-converting enzyme (ACE) on angiotensin-I. A number of ACE inhibitors (ACEIs) have been put to therapeutic use during the last two decades. The efforts continue towards achieving superior molecules or drugs with improved affinities, better bioavailability and thus long duration of action with minimum side effects. The present work evolves around similar objectives. In order to understand the mode of interaction of inhibitors with the active site of the enzyme and subsequently to have lead compounds as possible inhibitors the novel dipeptidomimics and tripeptidomimics have been designed and synthesized using combinatorial chemistry approach. A Focussed library of 10 di- and tri-peptides, eight dipeptidomemics and forty tripeptidomemics was generated. The pharmacophoric heterocyclic moieties and the amino acids have been selected to have affinities with the S1, S1', and S2' subsites of the active site of the enzyme. ACE inhibition studies clearly demonstrated the structural-activity relationships within these classes of peptidomimics. The dipeptidomimics interacted only with S1' and S2' subsites, whereas the tripeptidomemics had additional interaction with S1 subsite, which accounted for their significant ACE inhibition potencies. The in-vitro screening of these peptidomimics have resulted in identification of four promising tripeptidomimics 34[2-benzimidazolepropionyl-Val-Trp], 35[5hydroxytryptophanyl-Val-Trp], 40[2-benzimidazolepropionyl-Ile-Trp] and 45[2-benzimidazolepropionyl-Lys-Trp] with IC50 values in micromolar concentrations.

Aldosterone stimulates angiotensin-converting enzyme expression and activity in rat neonatal cardiac myocytes

BACKGROUND

Members of the nuclear receptor family proteins function as transcription factors upon ligand binding and thereby regulate gene expression in host cells. Aldosterone, the high-affinity endogenous ligand for the mineralocorticoid receptor, induces cardiac hypertrophy and fibrosis in a variety of animal models, but the transcriptional targets for aldosterone in the myocardium are not well-described.

METHODS AND RESULTS

Using quantitative reverse transcription-polymerase chain reaction method, we show that in cultured rat neonatal cardiomyocytes, aldosterone stimulates expression of angiotensin converting enzyme (ACE) in a concentration and time-dependent manner. Aldosterone (50 and 100 nM) increased levels of ACE mRNA by 1.8- and 2.2-fold, respectively. Aldosterone-induced ACE gene expression was blocked by spironolactone (1 microM), a mineralocorticoid receptor antagonist. In contrast, the expressions of the type I angiotensin receptor was not induced by aldosterone in either cardiac myocytes or fibroblasts. Consistent with the increased ACE mRNA level, 100 nM aldosterone also induced a 2-fold increase in ACE activity in cardiac myocytes.

CONCLUSION

ACE gene expression may be a target for mineralocorticoid receptors in the myocardium, supporting the notion that at least some of the known adverse effects of aldosterone on the myocardium are mediated by increased angiotensin II.

Effects of perindopril on aldosterone production in the failing human heart

The present study was designed to examine whether the production of aldosterone from the heart is suppressed by angiotensin-converting enzyme (ACE) inhibition in patients with heart failure. Forty-one patients with left ventricular systolic dysfunction were randomly divided into either the perindopril group (n = 21, perindopril 4 mg/day) or the placebo group (n = 20). Plasma levels of aldosterone and ACE activity were measured in the anterior interventricular vein, coronary sinus, and aortic root during cardiac catheterization. The levels of aldosterone as well as ACE activity were significantly higher at the anterior interventricular vein and the coronary sinus than at the aortic root in the placebo group (aldosterone: 92.1 +/- 9.0 vs 70.6 +/- 8.3 pg/ml [p <0.001]; 90.3 +/- 9.2 vs 70.6 +/- 8.3 pg/ml [p <0.001], respectively; ACE activity: 13.6 +/- 0.8 vs 12.2 +/- 0.7 IU/L [p <0.001], 13.4 +/- 0.8 vs 12.2 +/- 0.7 IU/L [p <0.001], respectively). On the other hand, there were no differences in the levels of aldosterone or ACE activity between the anterior interventricular vein and aortic root or between the coronary sinus and aortic root (aldosterone: 68.1 +/- 8.4 vs 69.9 +/- 9.4 pg/ml [p = NS]; 67.3 +/- 8.9 vs 69.9 +/- 9.4 pg/ml [p = NS], respectively; ACE activity: 9.7 +/- 0.8 vs 9.9 +/- 0.8 IU/L [p = NS]; 9.8 +/- 0.8 vs 9.9 +/- 0.8 IU/L, respectively) in the perindopril group. The levels of aldosterone as well as ACE activity were significantly lower at the anterior interventricular vein and coronary sinus in the perindopril group than in the placebo group. The difference in the level of aldosterone between the anterior interventricular vein and aortic root (Delta aldosterone [anterior interventricular vein - aortic root]) had a significant positive correlation with that of ACE activity (Delta ACE [anterior interventricular vein - aortic root]) (r = 0.536, p <0.001), whereas ACE activity in the aortic root had no significant correlation with either the aldosterone levels in the aortic root or Delta aldosterone (anterior interventricular vein - aortic root). Perindopril suppressed cardiac aldosterone production by mainly suppressing cardiac ACE activity in patients with heart failure. Thus, aldosterone production is activated in the failing ventricle and is suppressed by perindopril mainly via the suppression of cardiac ACE activity in patients with heart failure.

Aldosterone is produced from ventricles in patients with essential hypertension

This study was designed to examine whether aldosterone is produced from the hearts of patients with essential hypertension without left ventricular systolic dysfunction (LVSD). The study population consisted of 20 patients with essential hypertension without LVSD and 22 control subjects. Plasma levels of aldosterone, serum ACE activity, and B-type natriuretic peptide levels were measured in the anterior interventricular vein (AIV), coronary sinus, and aortic root during cardiac catheterization. The plasma aldosterone levels were significantly higher in AIV and coronary sinus than in aortic root (99+/-11 versus 88+/-10 pg/mL, P<0.01, and 100+/-12 versus 88+/-10 pg/mL, P<0.01, respectively) in the hypertension group. On the other hand, there were no significant differences in aldosterone levels for these sites in the control group. There were no significant differences in ACE activity levels between aortic root, AIV, and coronary sinus in either the hypertension or control group. The levels of B-type natriuretic peptide were significantly higher in AIV than in aortic root in both groups. The difference in aldosterone levels between AIV and aortic root (Delta Aldo[AIV-Ao]) had a significant positive correlation with the difference in ACE activity between AIV and aortic root (DeltaACE[AIV-Ao]) (r=0.501, P<0.05) in the hypertension group. Both Delta Aldo[AIV-Ao] and DeltaACE[AIV-Ao] had a significant positive correlation with diastolic blood pressure (r=0.498, P<0.05; r=0.577, P<0.01, respectively) in the hypertension group. We conclude that production of aldosterone is activated in the left ventricles in patients with essential hypertension without LVSD in proportion to the severity of hypertension.

Pathophysiological significance and clinical application of ANP and BNP in patients with heart failure

Plasma levels of ANP and BNP increase in accordance with the severity of the heart failure. In severe cases, the amount of BNP secreted surpasses that of ANP. The main secretion site of BNP is the ventricles, and that of ANP is the atria. However, ANP is also secreted from the ventricles as heart failure advances, and thus the ventricles are important sites for both BNP and ANP. It is well known that myocardial stretch is a key factor in the stimulation of the secretion of ANP and BNP, although neurohumoral factors also play a role in the secretion mechanism. The major physiological effects of ANP and BNP are vasodilation, natriuresis, and inhibition of the renin-angiotensin-aldosterone (RAA) and the sympathetic nervous systems; all of which are supposed to suppress the progression of heart failure. The inhibitory action of ANP and BNP on the RAA system has been considered to be an extra-cardiac effect. We recently reported the activation of an angiotensin-converting enzyme and aldosterone production in failing human hearts. ANP and BNP, however, would inhibit aldosterone production, not only in the adrenal cortex but also in cardiac tissue. ANP, and especially BNP, are useful markers of the heart's status during treatment for heart failure. The infusion of synthetic ANP (hANP) or BNP (Nesiritide®) is effective in the treatment of acute heart failure. In Japan, BNP occupies an important position in the diagnosis of chronic heart failure, as ANP does in the treatment of acute heart failure.Key words: natriuretic peptide, heart failure, myocardial infarction, cardiomyopathy, aldosterone.

Aldosterone production is activated in failing ventricle in humans

BACKGROUND

Recent reports have indicated that aldosterone is produced in extra-adrenal tissues in animals. The present study was designed to examine whether aldosterone is produced in human heart.

METHODS AND RESULTS

Plasma levels of aldosterone, BNP, and angiotensin-converting enzyme were measured in anterior interventricular vein (AIV), coronary sinus (CS), and aortic root (Ao), respectively, in 20 patients with left ventricular systolic dysfunction (LVSD), 25 patients with LV diastolic dysfunction (LVDD), and 23 control subjects. Aldosterone levels were significantly higher in AIV and CS than Ao in LVSD (98+/-10 versus 72+/-9 pg/mL, P:<0.001, and 97+/-11 versus 72+/-9 pg/mL, P:<0.001, respectively) and LVDD (87+/-10 versus 71+/-9 pg/mL, P:<0.01, and 84+/-10 versus 71+/-9 pg/mL, P:<0.01, respectively) groups, but no differences were observed in levels for these sites in the control group. Levels of ACE activity and BNP also were higher in AIV than Ao in both LV dysfunction groups. The difference in aldosterone levels between AIV and Ao and those in BNP and angiotensin-converting enzyme had a significant positive correlation with LVEDP and a significant negative correlation with LV ejection fraction in the LVSD group.

CONCLUSIONS

Production of aldosterone, angiotensin-converting enzyme, and BNP are activated in failing human ventricle in proportion to severity.

The plasma levels of dehydroepiandrosterone sulfate are decreased in patients with chronic heart failure in proportion to the severity

Dehydroepiandrosterone sulfate (DHEAS) is the major secretory steroid of the human adrenal glands. The secretion of DHEAS decreases with aging. The incidence of heart failure also rises in the elderly population. We measured the plasma levels of DHEAS and cortisol in 49 patients with chronic heart failure (CHF) and 32 age-matched controls and assessed its relation to plasma levels of A-type natriuretic peptide and B-type natriuretic peptide, biochemical markers of heart failure. Plasma levels of DHEAS were significantly lower in patients with CHF than in controls, whereas there was no significant difference in plasma levels of cortisol between the two groups. In stepwise regression analysis, the plasma level of DHEAS was significantly and independently correlated with age (beta = -0.451; P < 0.0001) and the plasma level of B-type natriuretic peptide (beta = -0.338; P < 0.001), and the plasma cortisol/DHEAS ratio was significantly and independently correlated with the plasma levels of A-type natriuretic peptide (beta = 0.598; P < 0.0001) and thiobarbituric acid-reactive substances (a marker of oxidative stress; beta = 0.252; P < 0.01) and age (beta = 0.171; P < 0.05). These results indicate that the plasma levels of DHEAS are decreased in patients with CHF in proportion to its severity and that oxidative stress is associated with decreased levels of DHEAS in patients with CHF.