angiotensin-iii and Heart-Failure

The pathophysiology of heart failure (HF) and hypertension are thought to involve brain renin-angiotensin system (RAS) hyperactivity. Angiotensin III, a key effector peptide in the brain RAS, provides tonic stimulatory control over blood pressure (BP) in hypertensive rats. Aminopeptidase A (APA), the enzyme responsible for generating brain angiotensin III, constitutes a potential therapeutic target for hypertension treatment. We focus here on studies of RB150/firibastat, the first prodrug of the specific and selective APA inhibitor EC33 able to cross the blood-brain barrier. We consider its development from therapeutic target discovery to clinical trials of the prodrug. After oral administration, firibastat crosses the gastrointestinal and blood-brain barriers. On arrival in the brain, it is cleaved to generate EC33, which inhibits brain APA activity, lowering BP in various experimental models of hypertension. Firibastat was clinically and biologically well tolerated, even at high doses, in phase I trials conducted in healthy human subjects. It was then shown to decrease BP effectively in patients of various ethnic origins with hypertension in phase II trials. Brain RAS hyperactivity leads to excessive sympathetic activity, which can contribute to HF after myocardial infarction (MI). Chronic treatment with oral firibastat (4 or 8 weeks after MI) has been shown to normalize brain APA activity in mice. This effect is accompanied by a normalization of brain RAS and sympathetic activities, reducing cardiac fibrosis and hypertrophy and preventing cardiac dysfunction. Firibastat may therefore represent a novel therapeutic advance in the clinical management of patients with hypertension and potentially with HF after MI.

Topics: Angiotensin II; Angiotensin III; Animals; Antihypertensive Agents; Brain; Clinical Trials as Topic; Disulfides; Glutamyl Aminopeptidase; Heart Failure; Humans; Hypertension; Myocardial Infarction; Renin-Angiotensin System; Sulfonic Acids

Renin plays a major role in the control of blood pressure and water and electrolyte metabolism and it is clear that blocking of this system is particularly effective in the treatment of essential hypertension and heart failure. A large number of converting enzyme inhibitors have been synthesized. Converting enzyme inhibitors are remarkably active in heart failure and they reduce microalbuminuria and possibly maintain glomerular function. Blocking of the renin-angiotensin system by converting enzyme inhibitors is not accompanied by hypotension or reflex stimulation of the sympathetic nervous system. Converting enzyme inhibitors represent a major therapeutic advance in the field of cardiovascular and renal disease but the long-term effects of decreased angiotensin II levels are unknown. There are other ways to inhibit the renin-angiotensin system. The recent discovery of orally-active non-peptide angiotensin II antagonists opens a range of fascinating prospects. Another approach consists in inhibiting the reaction of renin on angiotensinogen, which is remarkably selective. Although it is too early to know whether these new approaches will be less active, more active or as active as current converting enzyme inhibitors, they may constitute a progress in relation to currently available treatments.

Topics: Angiotensin II; Angiotensin III; Angiotensin-Converting Enzyme Inhibitors; Animals; Heart Failure; Humans; Hypertension; Renin-Angiotensin System

Inhibition of brain angiotensin III by central infusion of aminopeptidase A (APA) inhibitor firibastat (RB150) inhibits sympathetic hyperactivity and heart failure in rats after myocardial infarction (MI). This study evaluated effectiveness of systemic treatment with firibastat compared with AT1R blocker, losartan.. MI was induced by ligation of left coronary artery in male Wistar rats. Rats were treated from 1 to 5 weeks after MI in protocol 1 with vehicle, or firibastat at 50 mg/kg/d subcutaneously (s.c.) or 150 mg/kg/d oral, once daily, and in protocol 2, with vehicle, firibastat 150 mg/kg or losartan 50 mg/kg oral twice daily. At 5 weeks, left ventricle function was evaluated by echocardiography and Millar catheter. After MI, rats developed moderate severe heart failure. Both s.c. and oral firibastat inhibited brain APA and attenuated left ventricle dysfunction. Oral firibastat and losartan similarly improved left ventricular end diastolic pressure. However, whereas firibastat improved dP/dtmax, losartan lowered dP/dtmax and left ventricular peak systolic pressure, and increased plasma creatinine by ~50%. On the other hand, losartan more effectively inhibited cardiac fibrosis.. Inhibition of the brain renin-angiotensin system by oral APA inhibitor is at least as effective as oral AT1R blocker to inhibit cardiac dysfunction after MI but without hypotension or renal dysfunction.

Topics: Administration, Oral; Angiotensin II Type 1 Receptor Blockers; Angiotensin III; Animals; Brain; Disease Models, Animal; Disulfides; Enzyme Inhibitors; Fibrosis; Glutamyl Aminopeptidase; Heart Failure; Injections, Subcutaneous; Losartan; Male; Myocardial Infarction; Rats, Wistar; Signal Transduction; Sulfonic Acids; Ventricular Function, Left; Ventricular Pressure; Ventricular Remodeling