Angiotensin I-converting Enzyme Activity Research Articles

Inhibitory activities of baicalin against renin and angiotensin-converting enzyme

Context: Baicalin has been characterized as the active compound and quality control marker in Scutellaria baicalensis Georgi, traditionally used as a hypotensive herb.Objectives: To investigate the inhibitory activities of baicalin against renin and angiotensin-I converting enzyme (ACE) and their molecule mechanism of interactions.Methods: The fluorescence method using renin substrate 1(R-2932) and the spectroscopy method by Cushman were used to determine renin and ACE activities, respectively. The fluorescence quench techniques were used to characterize their interactions.Results: The results showed that baicalin inhibited renin activity with an IC50 value of 120.36 µM and inhibited ACE activity with an IC50 value of 2.24 mM in vitro. The fluorescence emission of both renin and ACE were efficiently quenched by baicalin and a complete quenching was achieved at a high concentration of baicalin. Furthermore, baicalin was more effective in quenching the fluorescence of renin (KSV = 60 × 103 M−1) than ACE (KSV = 17.1 × 103 M−1). The quenching of fluorescence of renin and ACE involved static interactions, which was characterized by the formation of quencher–enzyme complex. The baicalin–renin complex formed through three-sites binding including the active site with a binding constant of 796.15 × 1013 M−1, but there was only one binding site for the baicalin–ACE complex with a much smaller binding constant of 6.8 × 105 M−1.Conclusion: The inhibition activity of baicalin against renin was a result of the formation of stable complex through multisites binding including the active site, which could explain the higher inhibitory efficiency.

Serum angiotensin I-converting enzyme response to exercise; no differential effect of genotype

Angiotensin I-converting enzyme (ACE) plays a pivotal role in whole body fluid balance and the degradation of bradykinin. A common allelic variant with a 287 base pair insert has been...

No association betweenACEolymorphism and risk of nasopharyngeal carcinoma

Emerging evidence has shown that angiotensin I-converting enzyme (ACE) plays pivotal roles not only in the regulation of cardiovascular homeostasis but also in the process of tumorigenesis. A common ACE I/D polymorphism has been found to be functional, with the D allele displaying a higher plasma ACE level and ACE activity. The purpose of this study was to investigate whether the ACE I/D polymorphism was related to the risk of nasopharyngeal carcinoma (NPC). The study included 175 patients with NPC and 279 age- and sex-matched control subjects. The ACE I/D polymorphism was identified by a polymerase chain reaction analysis. No association was found between the ACE I/D polymorphism and risk of NPC (ID vs. II: odds ratio [OR] = 0.77, 95% confidence interval [CI] 0.51-1.17; DD vs. II: OR = 0.98, 95%CI 0.56-1.72, respectively). This finding indicates that the ACE I/D polymorphism may not play a role in susceptibility to NPC. Further studies are warranted to confirm this finding, especially in ethnically disparate populations.

Cocaine administration increases angiotensin I-converting enzyme (ACE) expression and activity in the rat striatum and frontal cortex

Some central effects of cocaine administration seem to be related to angiotensin II (Ang II) or its metabolites. Nonetheless, it is still an open question whether or not the levels of angiotensin I-converting enzyme (ACE), the main Ang II generating enzyme, are modified by cocaine administration. To evaluate the effect of acute and subchronic cocaine administration on ACE activity and mRNA expression, male rats were randomly assigned to saline or cocaine group. Acute and subchronic cocaine administration induced a significant increase in ACE activity and mRNA expression in the frontal cortex and striatum but not in the hippocampus. These results suggest that some of the Ang II related effects of cocaine upon the central nervous system can be mediated by changes on the expression and activity of ACE in the striatum and frontal cortex.

Effects of acute exercise on angiotensin I‐converting enzyme (ACE) activity in horses

Angiotensin I-converting enzyme (ACE) level measurement in blood samples is an important tool in human medicine for the detection, treatment and control of diseases such as sarcoidosis and hypertension. Recently ACE has been advocated as being correlated to athletic aptitude in human athletes and a genetic polymorphism has been shown to be responsible for the enzymatic levels in the circulation. The objective of this research was to evaluate the effects of acute exercise in horses in order to increase the understanding of a possible correlation between ACE levels in plasma and performance in equine athletes. A standardised exercise test (SET) to fatigue was conducted on 8 horses and repeated venous blood collections carried out for ACE activity measurements before, during and after the SET. Our results show an increase in ACE activity up to fatigue and a return to baseline values at 30 min post exercise.

Toxic effects of mercury, lead and gadolinium on vascular reactivity

Heavy metals have been used in a wide variety of human activities that have significantly increased both professional and environmental exposure. Unfortunately, disasters have highlighted the toxic effects of metals on different organs and systems. Over the last 50 years, the adverse effects of chronic lead, mercury and gadolinium exposure have been underscored. Mercury and lead induce hypertension in humans and animals, affecting endothelial function in addition to their other effects. Increased cardiovascular risk after exposure to metals has been reported, but the underlying mechanisms, mainly for short periods of time and at low concentrations, have not been well explored. The presence of other metals such as gadolinium has raised concerns about contrast-induced nephropathy and, interestingly, despite this negative action, gadolinium has not been defined as a toxic agent. The main actions of these metals, demonstrated in animal and human studies, are an increase of free radical production and oxidative stress and stimulation of angiotensin I-converting enzyme activity, among others. Increased vascular reactivity, highlighted in the present review, resulting from these actions might be an important mechanism underlying increased cardiovascular risk. Finally, the results described in this review suggest that mercury, lead and gadolinium, even at low doses or concentrations, affect vascular reactivity. Acting via the endothelium, by continuous exposure followed by their absorption, they can increase the production of free radicals and of angiotensin II, representing a hazard for cardiovascular function. In addition, the actual reference values, considered to pose no risk, need to be reduced.

Phenolic compounds in raw and cooked rice ( Oryza sativa L.) and their inhibitory effect on the activity of angiotensin I-converting enzyme

Whole rice has been widely studied due to the abundance of bioactive compounds in its pericarp. Some of the beneficial effects of these compounds on human health have been attributed to their antioxidant and other biological activities, such as enzyme inhibition. In this work, we evaluated the contents of total, soluble and insoluble phenolic compounds of 6 red and 10 non-pigmented genotypes of whole rice as well as their inhibitory effect on the activity of angiotensin I-converting enzyme (ACE). The effects of cooking on phenolics and their inhibitory activities were also investigated. Red genotypes showed high content of phenolics, mainly soluble compounds, at an average of 409.7 mg ferulic acid eq./100 g, whereas overall lower average levels (99.4 mg ferulic acid eq./100 g) at an approximate soluble/insoluble compound ratio of 1:1 were observed in non-pigmented rice. Pigmented rice displayed a greater inhibitory effect on ACE than non-pigmented rice. In fact, a significant correlation between the content of soluble phenolics and ACE inhibition was observed ( r = 0.8985, p < 0.05). In addition to significantly reducing the levels of total phenolics and ACE inhibition, cooking altered the soluble/insoluble compound ratio, especially among red rice genotypes.

Shaddock peels (Citrus maxima) phenolic extracts inhibit α-amylase, α-glucosidase and angiotensin I-converting enzyme activities: A nutraceutical approach to diabetes management

In this study, the interactions of free and bound phenolic-rich extracts from shaddock peels (popular in folklore for the management of diabetes and hypertension) with α-amylase and α-glucosidase (key enzymes linked to type-2 diabetes) and angiotensin I-converting enzyme (ACE) (key enzyme linked to hypertension) were assessed. The free phenolics of shaddock (Citrus maxima) peels were extracted with 80% acetone, while the bound phenolics were extracted from the alkaline and acid hydrolyzed residue with ethyl acetate; and their interaction with the enzymes were assessed. The phenolic extracts inhibited α-amylase, α-glucosidase and ACE enzyme activities in a dose-dependent manner; however, bound phenolics had significantly higher (P<0.05) α-amylase inhibitory activities, than free phenolics, which had significantly higher (P<0.05) ACE inhibitory activities. There was no significant difference (P>0.05) in their α-glucosidase inhibitory activities. The stronger inhibition of α-glucosidase when compared to α-amylase is of great pharmaceutical importance. The phenolic inhibited sodium nitroprusside induced lipid peroxidation in pancreas in a dose dependent manner. Therefore, free and bound phenolic extracts from shaddock peels could be used as nutraceutical for the management of hypertension and type-2 diabetes.

Kinetics of Enzyme Inhibition and Antihypertensive Effects of Hemp Seed (Cannabis sativa L.) Protein Hydrolysates

AbstractThe aim of this study was to determine the antihypertensive effects of enzymatic hemp seed protein hydrolysate (HPH) and its peptide fractions. Hemp seed protein isolate was digested by the sequential action of pepsin and pancreatin to mimic gastrointestinal digestion in human beings. The resultant HPH was separated by membrane ultrafiltration into peptide fractions with different sizes (&lt;1 and 1–3 kDa). The HPH led to significantly higher (P &lt; 0.05) in vitro inhibition of the activities of angiotensin I‐converting enzyme (ACE) and renin, the two main enzymes involved in abnormal blood pressure elevation (hypertension). Kinetic studies showed that HPH and peptide fractions inhibited renin and ACE activities in a mixed‐type pattern, indicating binding to areas other than the active site. Oral administration of HPH (200 mg/kg body weight) to spontaneously hypertensive rats led to significant reductions (P &lt; 0.05) in systolic blood pressure (SBP) that reached a maximum of −30 mmHg after 8 h. In contrast, the hypotensive effects of peptide fractions (&lt;1 and 1–3 kDa) had a maximum value of about −15 mmHg after 6–8 h post oral administration. The results suggest a synergistic antihypertensive effect of the peptides present within HPH; this effect was reduced significantly (P &lt; 0.05) upon separation into peptide fractions.

Angiotensin I-converting enzyme (ACE) activity and expression in rat central nervous system after sleep deprivation

Proteases are essential either for the release of neuropeptides from active or inactive proteins or for their inactivation. Neuropeptides have a fundamental role in sleep-wake cycle regulation and their actions are also likely to be regulated by proteolytic processing. Using fluorescence resonance energy transfer substrates, specific protease inhibitors and real-time PCR we demonstrate changes in angiotensin I-converting enzyme (ACE) expression and proteolytic activity in the central nervous system in an animal model of paradoxical sleep deprivation during 96 h (PSD). Male rats were distributed into five groups (PSD, 24 h, 48 h and 96 h of sleep recovery after PSD and control). ACE activity and mRNA levels were measured in hypothalamus, hippocampus, brainstem, cerebral cortex and striatum tissue extracts. In the hypothalamus, the significant decrease in activity and mRNA levels, after PSD, was only totally reversed after 96 h of sleep recovery. In the brainstem and hippocampus, although significant, changes in mRNA do not parallel changes in ACE specific activity. Changes in ACE activity could affect angiotensin II generation, angiotensin 1-7, bradykinin and opioid peptides metabolism. ACE expression and activity modifications are likely related to some of the physiological changes (cardiovascular, stress, cognition, metabolism function, water and energy balance) observed during and after sleep deprivation.

Characterization of Salt III as new possible allosteric modulator of Angiotensin I Converting Enzyme

Angiotensin I Converting Enzyme (ACE) is a glycoprotein that plays an important function in vascular and electrolyte homeostasis. Recently signaling pathways triggered by ACE was described in endothelial cells, showing that it could be a signaling transducer molecule. Several data demonstrated that inhibitors and substrates of ACE and its product Angiotensin II (AII), evoke intracellular signaling pathways activation. During the study of new AT1 receptor antagonists on blood pressure (BP), our group detected that Salt III had no classical effect in reducing BP in spontaneous hypertensive rats, but increased their BP (6 mmHg) at 15 minutes, suggesting a modulation of ACE activity. Incubating Salt III plus Angiotensin I [AI], and plasma ACE, happened a faster conversion of AI into AII when compared to control (AI plus plasma ACE), in the first 10 minutes of reaction. Pesquero group described that ACE could act as an AII receptor-like. Salt III was able to increase the binding sites of AII with ACE transfected in CHO cells. At the moment we are analyzing JNK and ERK1/2 signaling pathways triggered by ACE activation as result of interaction with Salt III. Salt III that act as an activator of AII binding ACE, and is able to modulate signaling pathways iniciated by ACE could clearly emerge as possible tool for treatment of many disorders such as in diabetes and various renal diseases.

Effects of two training protocols on Angiotensin I-converting enzyme (ACE) activity in horses

Studies in man have shown a correlation between Angiotensin I-converting enzyme (ACE) genetic polymorphisms, ACE activity in the blood and superior athletic performance in sports requiring endurance. It has been hypothesised that the same correlation occurs in horses. There is no information in the literature concerning the effects of training on ACE activity in equine plasma. Exercise training influences the activity of circulating ACE and the response observed is dependent on the exercise protocol. Thirteen horses of mixed breeds were randomly allocated 2 different training protocols to be carried out for a period of 15 weeks. Blood samples were collected from each horse before the beginning of training to determine baseline values. Subsequent sampling took place every 15 days throughout the training phase and for 8 weeks of paddock rest. Angiotensin I-converting enzyme activity was determined by automated spectrophotometry. Training for 15 weeks significantly increased plasma ACE activity, irrespective of training protocol. Differences observed in ACE activity pattern between the 2 training protocols were not statistically significant. Increase in ACE activity peaked with maximum workload. As soon as training was interrupted, ACE levels significantly decreased. Exercise training affects levels of ACE activity in equine plasma. The mechanism for this is not yet elucidated, but cardiovascular adaptation to exercise and blood pressure changes might be involved in this regulation. Exercise training produced a gradual increase in enzymatic activity and might warrant the use of ACE as a tool for fitness monitoring. Angiotensin I-converting enzyme enzymatic activity in the plasma might be directly correlated to a change in genetic expression and that variability must be taken into account when evaluating results from horses undergoing a physical training programme.

Inhibitory activity of Plantago major L. on angiotensin I-converting enzyme

Eight compounds were isolated from methanol extract of Plantago major L. leaves and investigated for their ability to inhibit angiotensin I-converting enzyme activity. Among them, compound 1 showed the most potent inhibition with rate of 28.06 ± 0.21% at a concentration of 100 μM. Compounds 2 and 8 exhibited weak activities. These results suggest that compound 1 might contribute to the ability of P. major to inhibit the activity of angiotensin I- converting enzyme.

ANTIHYPERTENSIVE EFFECT OF MUNG BEAN SPROUT EXTRACTS IN SPONTANEOUSLY HYPERTENSIVE RATS

ABSTRACT We investigated the efficacy of mung bean sprout in reducing hypertension. Different dosages of raw sprout extract (RSE) or dried sprout extracts (DSE) and enzyme-digested sprout extracts were used in a single intragastric administration test to examine the short-term effect in spontaneously hypertensive rats. Results indicated that high doses (600 mg peptide/kg body weight) extracts significantly reduced systolic blood pressure (SBP) of the rats after administration for 6–9, 3–6 and 3–9 h, respectively. Plasma angiotensin I-converting enzyme activities in the treated rats also decreased. A long-term (1 month) intervention study that consists of treatment groups of fresh sprout powder, dried sprout powder and concentrated extracts of the sprouts (RSE and DSE, respectively) was carried out. Results indicated that the sprout powders were not as efficacious as concentrated sprout extracts. SBP of the rats in the RSE and DSE groups were significantly reduced during the intervention period from week 1–4 and week 2–4, respectively. PRACTICAL APPLICATIONS The results suggested that although fresh and low doses of mung bean sprout or sprout extracts did not have apparent antihypertensive effects, high doses of sprout extracts significantly decreased blood pressure in the experimental animals. Therefore, concentrated mung bean sprout juice has potential applications in the preventive management of hypertension. It might be utilized for physiologically functional food with antihypertensive activity.

Determination of angiotensin I-converting enzyme activity in equine blood: lack of agreement between methods of analysis

Angiotensin-I converting enzyme (ACE) is a key regulator of blood pressure, electrolytes and fluid homeostasis through conversion of angiotensin I into angiotensin II. Recently, a genetic polymorphism of the ACE gene, which accounts for 47% of the variation of ACE activity in blood, has been advocated as a biomarker of athletic aptitude. Different methods of analysis and determination of ACE activity in plasma have been used in human and equine research without a consensus of a "gold standard" method. Different methods have often been used interchangeably or cited as being comparable in the existing literature; however, the actual agreement between assays has not been investigated. Therefore, in this study, we evaluated the level of agreement between three different assays using equine plasma obtained from 29 horses. Two spectrophotometric assays using Furylacryloyl-phenylalanyl-glycyl-glycine as substrate and one fluorimetric assay utilizing o-aminobenzoic acid-FRK-(Dnp)P-OH were employed. The results revealed that the measurements from the different assays were not in agreement, indicating that the methods should not be used interchangeably for measurement of equine ACE activity. Rather, a single method of analysis should be adopted to achieve comparable results and critical appraisal of the literature is needed when attempting to compare results obtained from different assays.

Effect of phlorotannins isolated from Ecklonia cava on angiotensin I-converting enzyme (ACE) inhibitory activity.

Inhibition of angiotensin I-converting enzyme (ACE) activity is the most common mechanism underlying the lowering of blood pressure. In the present study, five organic extracts of a marine brown seaweed Ecklonia cava were prepared by using ethanol, ethyl acetate, chloroform, hexane, and diethyl ether as solvents, which were then tested for their potential ACE inhibitory activities. Ethanol extract showed the strongest ACE inhibitory activity with an IC50 value of 0.96 mg/ml. Five kinds of phlorotannins, phloroglucinol, triphlorethol-A, eckol, dieckol, and eckstolonol, were isolated from ethanol extract of E. cava, which exhibited potential ACE inhibition. Dieckol was the most potent ACE inhibitor and was found to be a non-competitive inhibitor against ACE according to Lineweaver-Burk plots. Dieckol had an inducible effect on the production of NO in EAhy926 cells without having cytotoxic effect. The results of this study indicate that E. cava could be a potential source of phlorotannins with ACE inhibitory activity for utilization in production of functional foods.

251 Renin-angiotensin-aldosterone system polymorphisms: a role or a hole in occurrence and long-term prognosis of acute myocardial infarction at Tunisian older people

Myocardial infarction (MI) is one of the major causes of death all over the world. Because MI frequently occurs suddenly without any preceding clinical symptoms, the prediction of MI is clinically of great importance. Angiotensin II is produced primarily by angiotensin I-converting enzyme (ACE) within atherosclerotic lesions and ACE level correlates with the severity of vessel wall damage. We analyzed the evolution with age of the frequencies of the I/D polymorphism of the ACE, A1166C of the angiotensin II AT1 receptor (AT1R), and M235T of the angiotensinogen (AGT) gene in a healthy population and he subsequent comparison to age- and sex-matched groups of MI patients. To investigate the influence of increasing age on the incidence and remaining lifetime risk of myocardial infarction in a cohort of older men. Polymorphisms of the AGT, ACE (I/D) and AGTR1 (A1166C) genes in patients and controls were analyzed using allele-specific PCR, and PCR-rflp. A total of 140 healthy subjects and 119 individuals with MI were divided into two groups < 65 and > 65 years old. The evolution with age showed that the AGT M allele (P < 0.001) and the ACE I allele (P < 0.05) frequency decreased with age. The TT genotype frequency increased in patients with MI > 65 years (OR = 3.52; 95% CI; 3.12–5.54). The AA genotype showed a similar behaviour (OR = 2.9; 95% CI; 1.11–5.6). The DD genotype increased in the MI > 65 group (OR = 6.66; 95% CI; 2.02–21.9). Serum ACE activity was positively associated to age (r = 0.38, p = 0.000). Patients with DD genotype > 65 years was significantly higher (119.7 ± 50.8 U/L) than in patients with DD genotype < 65 years (96.9 ± 31.4 U/L, p = 0.039). The incidence of new cardiovascular disease continued to increase after age 65 but was most often diagnosed at death. These findings suggest that people aged 60 and older have a substantial amount of undiagnosed disease. We propose that the study of the allele frequency evolution in an healthy population at different ages is essential to determine risk factors for MI in case-control studies.

Inhibition of the angiotensin-converting enzyme by grape seed and skin proanthocyanidins extracted from Vitis vinífera L. cv. País

The influence of two extracts of grape skin and seeds from Vitis vinífera L. cv. País (Chilean black grapes), rich in proanthocyanidins (PAs), was evaluated on the inhibition of the angiotensin I-converting enzyme (ACE), and the inhibition was related to the type and number of subunits of the polymeric PAs chain. Size exclusion chromatography was used to purify the extract and its characterization was made by acid catalysis depolymerization followed by HPLC. ACE activity was measured by quantitative HPLC, measuring the hyppuric acid (HA) produced from the hydrolysis of hippuryl- l-histidyl- l-leucine (HHL) by ACE. Structural compositions differed significantly between both extracts: the skin extracts do not exhibit epicatechin (EC) and epicatechin gallate (ECG), and the seed extracts did not present epigallocatechin (EGC). Skin extracts have a higher mean degree of polymerization (mDP) than seed extracts and a higher inhibition power ( IC 50 = 0.14 ± 0.03 μM and IC 50 = 0.480 ± 0.03 μmol/L), respectively. The catechin ( IC 50 = 1495 ± 90 μmol/L) and epicatechin ( IC 50 = 1772 ± 121 μmol/L) monomers exerted lower inhibition than the either grape extract. The structural differences between grape skin and seed PAs could influence the ACE inhibition capacity. The larger inhibitory power of skin extract was associated to greater OH availability, higher mDP and the presence of EGC.

ACE activity is modulated by the enzyme α-galactosidase A

Fabry disease is a multisystem X-linked disorder resulting from α-galactosidase A (α-GalA) gene mutations leading to the accumulation of globotriaosylceramide mainly in endothelium compromising heart, kidney, and brain. In Fabry patients, progressive renal failure is frequently treated with angiotensin I-converting enzyme (ACE) inhibitors. We were interested in the possible interactions between ACE inhibitors therapy and the only causative therapy for Fabry disease, the enzyme replacement therapy (ERT) using recombinant human α-GalA (rhα-GalA). Our results suggest that ACE activity was significantly inhibited in plasma of Fabry patients and the blood pressure level decreased just after ERT (at the end of the rhα-GalA infusion). Interestingly, 2 weeks later, ACE activity was significantly upregulated and the plasma levels of angiotensin II increased in the patients treated with rhα-GalA following the elevations of ACE activity. The same inhibitory effect on ACE activity was also observed in rats after rhα-GalA infusion. Furthermore, ACE activity in CHO cells transfected with the human ACE was inhibited dose and time-dependently by rhα-GalA. In vitro, the incubation of plasma from healthy volunteers with rhα-GalA significantly reduced ACE activity. Finally, rhα-GalA also inhibited ACE activity and released galactose residues from purified rabbit lung ACE dose-dependently. In summary, our results suggest that rhα-GalA interacts with ACE and inhibits its activity, possibly by removing the galactose residues from the enzyme. This modulation might have profound impact on the clinical outcome of Fabry patients treated with rhα-GalA.

ACE gene polymorphism and serum ACE activity in Iranians type II diabetic patients with macroalbuminuria

There are controversial results related to the contribution of insertion (I)/deletion (D) polymorphism of the angiotensin I-converting enzyme (ACE) in the development of diabetic nephropathy. To assess the distribution of this polymorphism in diabetic patients with and without nephropathy we studied 140 unrelated type 2 diabetic patients from the Kermanshah Province of Iran with ethnic background of Kurds including 68 patients with macroalbuminuria and 72 normoalbuinuric diabetic patients as controls. Genotyping was done by polymerase chain reaction (PCR). The frequency of D allele in nephropathic and normoalbuminuric patients were 69.1 and 58.3%, respectively (P=0.061). In individuals with DD genotype the risk of macroalbuminuria increased 2.87-fold (P=0.057). Significant lower level of serum ACE activity was found in the normoalbuminuric (59.76IU/l) compared to macroalbuminuric (97.43IU/l) patients. The serum ACE activity was significantly higher in macroalbuminuric patients with ID (105.7IU/l) and ID+DD (100.7IU/l) genotypes compared to normoalbuminuric patients with the same genotypes (63.5 and 64.2IU/l, respectively). Treatment with captopril significantly (P=0.045) reduced the serum ACE activity in normoalbuminuric patients with DD genotype compared to macroalbuminuric patients with the same genotype (33.6 vs. 73.8IU/l). However, the greatest benefit effect of losartan therapy on ACE activity was observed only in macroalbuminuric patients with DD genotype compared to that in normoalbuminuric patients (61.0 vs. 109.0IU/l, P=0.06). Our study suggests the importance of ethnic origin in the development of diabetic nephropathy and demonstrates different responses to therapy according to genotype and stage of diabetes.