angiotensinogen and renin-inhibitory-peptide

The renin-angiotensin-aldosterone system (RAAS) plays a pivotal role in the regulation of blood pressure and body fluid homeostasis and is a mainstay for the treatment of cardiovascular and renal diseases. Angiotensin II and aldosterone are the two most powerful biologically active products of the RAAS, inducing all of the classical actions of the RAAS including vasoconstriction, sodium retention, tissue remodeling and pro-inflammatory and pro-fibrotic effects. In recent years, new components of the RAAS have been discovered beyond the classical pathway that have led to the identification of depressor or so-called protective RAAS pathways and the development of novel therapies targeting this system. Moreover, dual inhibitors which block the RAAS and other systems involved in the regulation of blood pressure or targeting upstream of angiotensin II by selectively deleting liver-derived angiotensinogen, the precursor to all angiotensins, may provide superior treatment for cardiovascular and renal diseases and revolutionize RAAS-targeting therapy.

Topics: Angiotensin II Type 1 Receptor Blockers; Angiotensin-Converting Enzyme Inhibitors; Angiotensinogen; Blood Pressure; Body Fluids; Enzyme Inhibitors; Homeostasis; Humans; Neprilysin; Oligopeptides; Receptor, Angiotensin, Type 2; Renin-Angiotensin System; RNA, Small Interfering

Although renin was identified as playing a part in cardiovascular homeostasis by the experiments of Goldblatt in the 1930s, neither its physiological role in organs other than the kidney nor its contribution to the genesis of essential hypertension have been defined. It is difficult to interpret studies with converting enzyme inhibitors because of their multiple pharmacological effects. Specific inhibitors of renin appropriate for clinical investigation would help to resolve many questions. Four classes of compounds have been shown to be renin inhibitors of high potency: specific antibody, general peptide inhibitors of acid proteases, analogues of angiotensinogens and peptides that are related to the amino-terminal sequence of prorenin. Of these, it is likely that angiotensinogen analogues will be the first applied in human studies. The minimal substrate for renin has the sequence: His-Pro-Phe-His-Leu-Val-Tyr. Variants of this sequence have yielded competitive inhibitors. Remarkably active compounds have recently been synthesized by reducing the peptide bond that is cleaved by renin, or by incorporating the amino acid statine, found in pepstatin. These compounds have been shown to be effective in dogs, rats and monkeys and, most recently, preliminary studies have reported their efficacy in man. Recent studies with one of these inhibitors, RIP, raise questions concerning both its specificity and site of action.

Topics: Angiotensin-Converting Enzyme Inhibitors; Angiotensinogen; Animals; Antibodies, Monoclonal; Antihypertensive Agents; Blood Pressure; Heart Rate; Humans; Hypertension; Oligopeptides; Pepstatins; Renin

Although renin was identified as playing a role in cardiovascular homeostasis by the experiments of Goldblatt in the 1930's, neither its physiologic role in organs other than the kidney nor its contribution to the genesis of essential hypertension has been defined as yet. It is difficult to interpret studies with converting enzyme inhibitors because of their multiple pharmacologic effects. Specific inhibitors of renin appropriate for clinical investigation would help resolve many questions. Four classes of compounds have been demonstrated to be renin inhibitors of high potency: specific antibody, general peptide inhibitors of acid proteases, analogs of angiotensinogens, and peptides that are related to the amino-terminal sequence of prorenin. Of these, it is likely that angiotensinogen analogs will be the first applied in human studies. The minimal substrate for renin has the sequence: His-Pro-Phe-His-Leu-Leu-Val-Tyr. Variants of this sequence have yielded competitive inhibitors. Recently, remarkably active compounds have been synthesized by reducing the peptide bond that is cleaved by renin, or by incorporating the amino acid statine, found in pepstatin. These compounds have been shown now to be effective in dogs, rats, and monkeys, and most recently, preliminary studies have reported their efficacy in humans. Recent studies with one of these inhibitors, RIP, raise questions concerning both its specificity and site of action.

Topics: Angiotensinogen; Animals; Antibodies; Dogs; Humans; Hypertension, Renal; Macaca fascicularis; Oligopeptides; Pepstatins; Protein Precursors; Rats; Renin; Time Factors

Activity of renin substrate cleavage (renin-like activity) was measured in vitro in plasma samples obtained from healthy human volunteers.. Renin-like activity was determined using FRET (Fluorescence Resonance Energy Transfer) human renin substrate. Recombinant human renin and human plasma showed dose-dependent cleavage activity of FRET human renin substrate.. Activity of recombinant human renin was completely inhibited by either a peptidergic or a non-peptidergic renin inhibitor. However, renin-like activity in human plasma was not inhibited by these renin inhibitors. In a mixture of recombinant renin and human plasma, renin inhibitors inhibited only that part of the activity caused by recombinant renin, while the activity in plasma still remained. Human plasma did not show cleavage activity of rat FRET renin substrate. Native human prorenin showed cleavage activity of human renin substrate. This activety was also completely inhibited by renin inhibitors. Immunoprecipitation with anti-renin or anti-prorenin antibodies did not reduce the activity in human plasma. Renin-like activity in human plasma was abolished by degeneration of protein when sample was heated to 95 degrees C. Activity of both recombinant renin and human plasma was significantly inhibited by a protease inhibitor cocktail.. These results suggest that the activity of renin substrate cleavage in human plasma is not mainly caused by the renin or prorenin molecule, but probably by other proteases.

Topics: Adult; Amides; Angiotensinogen; Animals; Enzyme Precursors; Fumarates; Humans; Middle Aged; Oligopeptides; Protease Inhibitors; Rats; Recombinant Proteins; Renin; Young Adult

Renin is the initial rate limiting step in the renin angiotensinogen system (RAS). To combat hypertension, various stages of the RAS can be positively affected. The aim of this study was to isolate and characterize renin inhibitory peptides from the red seaweed P. palmata for use in functional foods. Palmaria palmata protein was extracted and hydrolyzed with the food grade enzyme Papain to generate renin inhibitory peptides. Following proteolytic hydrolysis of P. palmata protein, reverse phase-high performance liquid chromatography (RP-HPLC) was employed to enrich for peptides with renin inhibitory activities. Fraction 25 (Fr-25) inhibited renin activities by 58.97% (±1.26) at a concentration of 1 mg/mL. This fraction was further characterized using nano-electrospray ionization quadropole/time-of-flight mass spectrometry (ESI-Q/TOF MS). A number of novel peptide sequences were elucidated, and the parent protein from which they were derived was determined using MS in tandem with protein database searches. All sequences were confirmed using de novo sequencing. The renin inhibitory peptide Ile-Arg-Leu-Ile-Ile-Val-Leu-Met-Pro-Ile-Leu-Met-Ala (IRLIIVLMPILMA) was chemically synthesized and its bioactivity confirmed using the renin inhibitory assay. Other stages of the RAS have recently been inhibited by bioactive peptides sourced from macroalgae, but this is the first study to isolate and characterize renin inhibitory peptides from the macroalgae.

Topics: Angiotensinogen; Chromatography, High Pressure Liquid; Oligopeptides; Papain; Plant Extracts; Renin; Rhodophyta; Seaweed; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry

The effects of angiotensin II and its precursors angiotensin I and tetradecapeptide renin substrate were investigated in isolated segments of the rat caudal artery. Each peptide constricted the rat caudal artery and also enhanced vasoconstrictor responses to sympathetic nerve stimulation (0.5 Hz, 10 s). The threshold concentrations for each peptide in enhancing sympathetic vasoconstrictor responses were lower than those required to produce vasoconstriction. Tetradecapeptide renin substrate was the least potent of the three peptides and had the slowest onset of action. Angiotensin II and angiotensin I each enhanced noradrenergic transmission to the same degree, whether perfused through the lumen or added to the adventitial surface of the artery. In contrast, tetradecapeptide renin substrate was more potent when applied to the adventitial surface. The effects of angiotensin I were blocked by the converting enzyme inhibitor enalaprilat, whereas the effects of tetradecapeptide renin substrate were unaltered by enalaprilat, or by the renin inhibitors pepstatin or a decapeptide renin inhibitor. These findings suggest that tetradecapeptide renin substrate and angiotensin I may be converted to angiotensin II within the rat caudal artery, with subsequent enhancement of noradrenergic neuroeffector function. However, the enzyme responsible for the conversion of tetradecapeptide renin substrate cannot be determined from the present findings.

Topics: Angiotensin I; Angiotensin II; Angiotensinogen; Animals; Arteries; Enalapril; Enalaprilat; Female; Male; Neurotransmitter Agents; Oligopeptides; Rats; Rats, Inbred Strains; Tail

Renin is present in vascular smooth muscle cells and has been shown to coexist with angiotensins I (AI) and II (AII) in many cell types. Accordingly, we postulated that the renin-angiotensin system controls vascular tone, not by the action of circulating renal renin but rather, by the local generation of angiotensin by vascular renin. Isolated rat hindquarters were perfused in vitro with Krebs-Henseleit buffer containing 7% albumin, and flow-adjusted to obtain a perfusion pressure of approximately 90 mmHg. Infusion of 4.8 nmol X min-1 for 5 min of AII or AI markedly increased perfusion pressure. An identical dose of the synthetic tetradecaptide of renin substrate (TDCP-RS) increased pressure similarly to AI. The pressure increase evoked by TDCP-RS was markedly decreased by captopril and by two different peptides that inhibit renin. Renin activity in the perfusate, incubated with semipurified rat renin substrate, was 21 +/- 3 pg AI X ml-1 X h-1 (mean +/- SEM) at 15 min of perfusion and 47 +/- 4 pg AI X ml-1 X h-1 at 45 min (n = 9; P less than 0.01). When TDCP-RS was infused at 4.8 nmol X min-1 for 5 min in the presence of captopril, AI in the perfusate increased linearly at a rate of 16.5 pmol X min-1 for 10 min (n = 5). The results indicate that TDCP-RS constricted the vasculature by its conversion to AII and suggest that AII was generated from a two-step hydrolysis of TDCP-RS by renin and converting enzyme. The data thus suggest that the renin-angiotensin system controls vascular tone by the local generation of AII by renin and converting enzyme in the vasculature.

Topics: Angiotensin I; Angiotensin II; Angiotensinogen; Animals; Male; Muscle Tonus; Muscle, Smooth, Vascular; Oligopeptides; Perfusion; Rats; Rats, Inbred Strains; Renin; Vasoconstrictor Agents

Renin is a proteolytic enzyme that may be inhibited in vivo by three classes of compounds: specific antibody, general peptide inhibitors of acid proteases, and substrate analogs. With the availability of highly purified renin, specific polyclonal or monoclonal antibodies have become available. The former have already been used extensively in physiological studies with intact animals. Pepstatin is an inhibitor of many acid proteases. Its in vivo application has been retarded by relative insolubility, but recent chemical modifications, particularly the addition of charged amino acids at the carboxy terminus, have rendered it more useful. The minimal substrate for renin is an octapeptide segment of the protein substrate: His-Pro-Phe-His-Leu-Leu-Val-Tyr. Variants of this sequence have resulted in competitive inhibitors that are useful in vivo. Effectiveness of a given peptide varies among different species of animals, possibly because of different substrate specificity. To support this hypothesis, it has been reported that the amino acid sequences of angiotensinogens around the site where renin cleaves may vary among species. Effectiveness of inhibitors is also dependent on the hydrophobicity of amino acids near the cleavage site. Recently, remarkably active inhibitors have been synthesized by reducing the peptide bond that is cleaved by renin. Studies with monkeys show that a peptide renin inhibitors may cause hypotension after sodium depletion and normalize blood pressure in Goldblatt hypertension to the same degree as a converting-enzyme inhibitor.

Topics: Amino Acid Sequence; Angiotensin I; Angiotensinogen; Animals; Blood Pressure; Enzyme Inhibitors; Heart Rate; Humans; Hypertension; Kinetics; Macaca fascicularis; Oligopeptides; Rats; Renin; Substrate Specificity; Swine; Teprotide

Topics: Adult; Aldosterone; Angiotensinogen; Blood Pressure; Captopril; Drug Interactions; Heart Rate; Hemodynamics; Humans; Hypertension; Male; Oligopeptides; Posture; Renin; Sodium

The angiotensin substrate analog Pro-His-Pro-Phe-His-Phe-Phe-Val-Tyr-Lys has no significant effect on blood pressure in sodium-replete monkeys (Macaca fascicularis) but blocks the pressor response to infused human renin. Pressor responses to angiotensin I and angiotensin II are not attenuated. In five studies in sodium-depleted monkeys, an infusion of 2 mg of the peptide per kg of body weight resulted in a reduction of mean arterial pressure (MAP) from 105 +/- 4 to 79 +/- 3 mm Hg, which is not significantly different from the response to 1 mg of the angiotensin I-converting enzyme inhibitor teprotide per kg. In uninephrectomized monkeys, inflation of a suprarenal aortic cuff caused an increase in MAP from 107 +/- 3 to 131 +/- 3 mm Hg. Infusion of 0.6 mg of the renin-inhibitory peptide per kg was followed by a return of blood pressure to 107 +/- 4 mm Hg--a depressor response similar to that observed with teprotide. This specific in vivo inhibitor of renin can now be applied to a wide variety of physiologic studies.

Topics: Angiotensin I; Angiotensin II; Angiotensinogen; Animals; Blood Pressure; Hypertension; Macaca fascicularis; Male; Oligopeptides; Peptidyl-Dipeptidase A; Renin; Sodium; Teprotide