Bovine angiotensin converting enzyme cDNA cloning and regulation. Increased expression during endothelial cell growth arrest

Association of angiotensin-converting enzyme insertion/deletion (ACE I/D) gene polymorphism with susceptibility to prostate cancer: an updated meta-analysis

Objective

This meta-analysis aims to explore the association between angiotensin-converting enzyme (ACE) insertion/deletion (I/D) gene polymorphism and susceptibility to prostate cancer (PCa).

Methods

We searched studies related to ACE I/D polymorphism and susceptibility to PCa through PubMed, Web of Science, Embase, Cochrane Library, and Scopus databases from inception to June 1, 2022. Five gene models, including allelic, dominant, recessive, homozygote, and heterozygote models, were analyzed. The pooled odds ratio (OR) was calculated using Stata 15.0 software. Publication bias was judged by the funnel plot and Egger’s test, with the robustness of the findings verified by sensitivity analysis.

Results

Eight published articles (including ten studies) were identified. The pooled results showed that ACE I/D locus polymorphism was significantly correlated with the risk of PCa under all gene models except for the heterozygous model (D vs. I: OR= 1.58, 95% CI: 1.14–2.21; DD vs. DI+II: OR=1.68, 95% CI: 1.11–2.54; DD+DI vs. II: OR=1.76, 95% CI: 1.11–2.80; DI vs. II: OR= 1.44, 95% CI: 0.99–2.10; DD vs. II: OR= 2.12, 95% CI: 1.15–3.93). Subgroup analysis based on genotype frequencies in the control group meeting Hardy-Weinberg equilibrium showed statistically significant differences in all gene models. The funnel plot and Egger’s test indicated no publication bias. The sensitivity analysis verified the robustness of the conclusions obtained in this meta-analysis.

Conclusion

ACE I/D locus polymorphism correlates to PCa risk. Allele D, genotype DD+DI, and DD at the ACE I/D locus increase susceptibility to PCa and can therefore serve as a potential diagnostic and screening molecular marker for PCa patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-022-02812-x.

A modern understanding of the traditional and nontraditional biological functions of angiotensin-converting enzyme

Angiotensin-converting enzyme (ACE) is a zinc-dependent peptidase responsible for converting angiotensin I into the vasoconstrictor angiotensin II. However, ACE is a relatively nonspecific peptidase that is capable of cleaving a wide range of substrates. Because of this, ACE and its peptide substrates and products affect many physiologic processes, including blood pressure control, hematopoiesis, reproduction, renal development, renal function, and the immune response. The defining feature of ACE is that it is composed of two homologous and independently catalytic domains, the result of an ancient gene duplication, and ACE-like genes are widely distributed in nature. The two ACE catalytic domains contribute to the wide substrate diversity of ACE and, by extension, the physiologic impact of the enzyme. Several studies suggest that the two catalytic domains have different biologic functions. Recently, the X-ray crystal structure of ACE has elucidated some of the structural differences between the two ACE domains. This is important now that ACE domain-specific inhibitors have been synthesized and characterized. Once widely available, these reagents will undoubtedly be powerful tools for probing the physiologic actions of each ACE domain. In turn, this knowledge should allow clinicians to envision new therapies for diseases not currently treated with ACE inhibitors.

Characterization of the bovine angiotensin converting enzyme promoter: essential roles of Egr-1, ATF-2 and Ets-1 in the regulation by phorbol ester

The protease angiotensin converting enzyme (ACE) is a key regulator of blood pressure homeostasis, and is responsible for proteolytic activation of angiotensin I to angiotensin II (Ang II), a potent vasoconstrictor, and proteolytic inactivation of bradykinin, a vasodilator. Recent studies have also implicated ACE and Ang II dysregulation in the progression of fibrotic tissue diseases. Although many studies have utilized bovine tissues and cells for investigating the regulation of ACE gene expression, the bovine ACE promoter has not been previously characterized. Here we present the analysis of the bovine ACE promoter. We investigated cis elements regulated by phorbol 12-myristate 13-acetate (PMA). Sequence analysis shows that the bovine ACE promoter contains several putative binding sites for the transcription factors ATF-2, Ets-1, Egr-1 and SP1/SP3. Chromatin immunoprecipitation (ChIP) indicated that the activation of the bovine ACE promoter by PMA involves histone H4 acetylation, and that PMA induced Egr-1 and ATF-2 binding to the ACE promoter, whereas Ets-1 binding was suppressed by PMA. The regulatory roles of these transcription factors in the bovine ACE gene regulation were confirmed by co-expression of either wild type or dominant negative transcription factors with the luciferase reporter constructs. The bovine and human ACE promoters share similarities in binding sites for transcription factors and PMA regulation within the core regions but contain significant differences in the distal promoter regions.

Effect of angiotensin-converting enzyme inhibition and angiotensin II type 1 receptor blockade on apoptotic changes in contralateral testis following unilateral testicular torsion

OBJECTIVES

In this experimental study, our aim was to determine whether angiotensin-converting enzyme (ACE) inhibition and angiotensin II type 1 (AT1) receptor blockade affect the apoptotic changes in contralateral testis following unilateral testicular torsion (UTT).

METHODS

Study groups consisted of 30 adult male Wistar rats. The rats were randomly separated into five groups. Group 1 was maintained as control without manipulation. Group 2 underwent the sham operation. Torsion was created by rotating the left testis 720 degrees clockwise for 4 h and maintained by fixing the testis to the scrotum in the other groups. Group 3 underwent torsion and detorsion, with saline administration after detorsion. In group 4, the same surgical procedure was done as in the detorsion group, but AT1 receptor blocker (losartan 30 mg/kg) was injected intraperitoneally for 60 min before detorsion. In group 5, the same surgical procedure was done as in the detorsion group, but ACE inhibitor (lisinopril 50 mg/kg) was injected intraperitoneally for 60 min before detorsion. Bilateral testes were removed from each rat 24 h after surgery. Apoptosis was assessed in paraffin-embedded sections stained for TUNEL method. Reticulum staining was performed to evaluate the extracellular changes semiquantitatively. Testicular biopsy score counts were performed on these sections according to Johnsen.

RESULTS

The mean apoptotic scores of group 1, group 2 and group 3 were significantly higher than that of the other groups. There was no difference between the apoptotic scores of groups 1, 2, 4 and 5. Reticulum stain was increased in group 3 as compared to other groups. The mean Johnsen biopsy score of group 3 was significantly lower than that of the other groups.

CONCLUSION

ACE inhibition and AT1 receptor blockade reduced the tubular damage and apoptosis in the contralateral testes after UTT. The beneficial effect of these drugs may arise from inhibition of ischemic process resulting from increased sympathetic activity and elimination of insults subsequent to dysregulation of RAS. These results suggest that ACE inhibitors and AT1 receptor blockers may be of potential value in patients with UTT.

Neutrophil-activating activity and platelet-activating factor synthesis in cytokine-stimulated endothelial cells: Reduced activity in growth-arrested cells

The reactivity of endothelial cells (ECs) to proinflammatory cytokines is critically important for the pathogenesis of vascular diseases. Here, we studied functional alterations of human ECs during culture under a confluent condition; i.e., the alterations of neutrophil-activating activity, platelet-activating factor (PAF) synthesis, and granulocyte-macrophage colony-stimulating factor (GM-CSF) production in cytokine-stimulated ECs. Human umbilical vein-derived ECs exhibited the increased activity in neutrophil activation, PAF synthesis, and GM-CSF production when stimulated by proinflammatory cytokines such as interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha). The activity of cytokine-stimulated ECs to stimulate superoxide release in human neutrophils and to produce PAF declined markedly in parallel as ECs became growth-arrested during culture under a confluent condition. By contrast, GM-CSF production induced by cytokine stimulation was modestly increased, and up-regulation of intercellular adhesion molecule-1 (ICAM-1) and activation of mitogen-activated protein kinases were not altered. The neutrophil-activating activity of cytokine-stimulated ECs was dependent on PAF synthesis and GM-CSF production from ECs. These findings indicate that the reduced neutrophil-activating activity in growth-arrested ECs may be, at least in part, ascribed to down-regulation of PAF synthesis.

Shedding of the Germinal Angiotensin I-Converting Enzyme (gACE) Involves a Serine Protease and Is Activated by Epididymal Fluid1

The present report describes how the soluble germinal angiotensin I-converting enzyme (gACE) appears in the epididymal fluid, where it has been identified in some laboratory rodents and domestic ungulates. We showed that this gACE results from an active proteolytic process that releases the enzyme's extracellular domain from sperm in a precise spatiotemporal location during epididymal transit and that this process involves serine protease activity. Using polyclonal antibodies against the C-terminal intracellular sequence of ACE, a fragment of approximately 10 kDa was detected on the sperm extract only in the epididymal region, where the gACE release occurs. The fluid enzyme was purified, and the cleavage site was determined by mass spectrometry to be between Arg622 and Leu623 of the mature sheep gACE sequence (equivalent to Arg627 and Arg1203 of the human mature gACE and somatic ACE sequences, respectively). Thereafter, the C-terminal Arg was removed, leaving Ala621 as a C-terminal. Using an in vitro assay, gACE cleavage from sperm was strongly increased by the presence of epididymal fluid from the release zone, and this increase was inhibited specifically by the serine protease-inhibitor AEBSF but not by para-aminobenzamidine. None of the other inhibitors tested, such as metallo- or cystein-protease inhibitors, had a similar effect on release. It was also found that this process did not involve changes in gACE phosphorylation.

Role of Two Chloride-Binding Sites in Functioning of Testicular Angiotensin-Converting Enzyme

Modeling the structure of the C-domain of bovine angiotensin-converting enzyme revealed two putative chloride-binding sites. The kinetic parameters, K(m) and k(cat), of hydrolysis of the substrate Cbz-Phe-His-Leu catalyzed by the testicular (C-domain) enzyme were determined over a wide range of chloride concentrations. Chloride anions were found to be enzyme activators at relatively low concentrations, but they inhibit enzymatic activity at high concentrations. A general scheme for the effect of chloride anions on activity of the C-domain of bovine angiotensin-converting enzyme accounting for binding the "activating" and "inhibiting" anions is suggested.

The renin angiotensin system as a therapeutic target to prevent diabetes and its complications

The role of the RAAS in development and maintenance of blood pressure is well established. In addition, the deleterious effects of angiotensin II on the heart, vasculature, and kidneys have been clearly defined. There seems to be a close relationship between endothelial dysfunction, insulin resistance (a precursor to diabetes and coronary artery disease) and angiotensin II. The signaling pathways for insulin in the vascular wall interacts with the angiotensin signaling, giving rise to potential mechanisms for development of diabetes and resulting harmful effects. A large number of clinical trials using ACE inhibitors or ARBs have shown significant reduction in secondary endpoints in the development of new onset of diabetes. Ongoing prospective studies involving ARBs (eg, the Nateglinide and Valsartan Impaired Glucose Tolerance Outcomes Research trial) and ACE inhibitors (eg, the Diabetes Re-duction Assessment with Ramipril and Rosiglita-zone Medication trial) are testing the ability of certain agents to prevent type 2 diabetes. In the meantime, it is important to recognize insulin resistance and metabolic syndrome as entities that increase the risk for cardiovascular disease. In addition to lifestyle modifications, managing endothelial dysfunction and protecting the vasculature will help prevent diabetes and cardiovascular disease.

Evidence for the negative cooperativity of the two active sites within bovine somatic angiotensin-converting enzyme

The somatic isoform of angiotensin-converting enzyme (ACE) consists of two homologous domains (N- and C-domains), each bearing a catalytic site. We have used the two-domain ACE form and its individual domains to compare characteristics of different domains and to probe mutual functioning of the two active sites within a bovine ACE molecule. The substrate Cbz-Phe-His-Leu (N-carbobenzoxy-L-phenylalanyl-L-histidyl-L-leucine; from the panel of seven) was hydrolyzed faster by the N-domain, the substrates FA-Phe-Gly-Gly (N-(3-[2-furyl]acryloyl)-L-phenylalanyl-glycyl-glycine) and Hip-His-Leu (N-benzoyl-glycyl-L-histidyl-L-leucine) were hydrolyzed by both domains with equal rates, while other substrates were preferentially hydrolyzed by the C-domain. The inhibitor captopril ((2S)-1-(3-mercapto-2-methylpropionyl)-L-proline) bound to the N-domain more effectively than to the C-domain, whereas lisinopril ((S)-N(alpha)-(1-carboxy-3-phenylpropyl)-L-lysyl-L-proline) bound to equal extent with all ACE forms. However, active site titration with lisinopril assayed by hydrolysis of FA-Phe-Gly-Gly revealed that 1 mol of inhibitor/mol of enzyme abolished the activity of either two-domain or single-domain ACE forms, indicating that a single active site functions in bovine somatic ACE. Neither of the k(cat) values obtained for somatic enzyme was the sum of k(cat) values for individual domains, but in every case the value of the catalytic constant of the hydrolysis of the substrate by the two-domain ACE represented the mean quantity of the values of the corresponding catalytic constants obtained for single-domain forms. The results indicate that the two active sites within bovine somatic ACE exhibit strong negative cooperativity.

Purification of angiotensin I converting enzyme from pig lung using concanavalin-A sepharose chromatography

Angiotensin I converting enzyme (ACE) plays a major role in blood pressure regulation, catalyzing the conversion of angiotensin I to the vasoconstrictor angiotensin II. In this report we describe a two-step affinity chromatography method for preparative purification of ACE from pig lung using Concanavalin-A Sepharose 4B and affinity chromatography on Lisinopril Sepharose 6B. The same purification scheme was used to obtain Cobalt-ACE, where zinc ion located at the active site is replaced by cobalt. Cobalt-ACE visible spectrum shows a characteristic broad peak from 500 to 600 nm. The shape and maximum absorptivity of this peak changes in presence of ACE inhibitors that bind at the catalytic site.

Temperature-induced selective death of the C-domain within angiotensin-converting enzyme molecule

Somatic angiotensin-converting enzyme (ACE) consists of two homologous domains, each domain bearing a catalytic site. Differential scanning calorimetry of the enzyme revealed two distinct thermal transitions with melting points at 55.3 and 70.5 degrees C. which corresponded to denaturation of C- and N-domains, respectively. Different heat stability of the domains underlies the methods of acquiring either single active N-domain or active N-domain with inactive C-domain within parent somatic ACE. Selective denaturation of C-domain supports the hypothesis of independent folding of the two domains within the ACE molecule. Modeling of ACE secondary structure revealed the difference in predicted structures of the two domains, which, in turn, allowed suggestion of the region 29-133 in amino acid sequence of the N-part of the molecule as responsible for thermostability of the N-domain.

The germinal isozyme of angiotensin-converting enzyme can substitute for the somatic isozyme in maintaining normal renal structure and functions

The angiotensin-converting enzyme (ACE) gene encodes two structurally related isozymes, somatic ACE and germinal ACE, that are uniquely expressed in discrete locations in the body. The importance of ACE in these cell types was revealed by generating Ace -/- mice, which exhibit multiple abnormalities including renal structural defects and functions, hypotension, and male sterility. To test the hypothesis that specific physiological functions of ACE are mediated by isozyme-specific and tissue-specific expression patterns, we have used a transgenic approach to develop mouse strains that express just one ACE isoform in the target tissue of Ace -/- mice. The mice described in this report produce germinal ACE in sperm and serum. These mice were as healthy as wild type mice, and the males were fertile. Interestingly, they had normal kidney structure, fluid homeostasis, and partially restored urine concentration despite having low blood pressure. This result demonstrated that circulating germinal ACE is sufficient for maintaining normal kidney structure and fluid homeostasis but insufficient for restoring blood pressure to normal levels.

The relevance of tissue angiotensin-converting enzyme: manifestations in mechanistic and endpoint data

Angiotensin-converting enzyme (ACE) is primarily localized (>90%) in various tissues and organs, most notably on the endothelium but also within parenchyma and inflammatory cells. Tissue ACE is now recognized as a key factor in cardiovascular and renal diseases. Endothelial dysfunction, in response to a number of risk factors or injury such as hypertension, diabetes mellitus, hypercholesteremia, and cigarette smoking, disrupts the balance of vasodilation and vasoconstriction, vascular smooth muscle cell growth, the inflammatory and oxidative state of the vessel wall, and is associated with activation of tissue ACE. Pathologic activation of local ACE can have deleterious effects on the heart, vasculature, and the kidneys. The imbalance resulting from increased local formation of angiotensin II and increased bradykinin degradation favors cardiovascular disease. Indeed, ACE inhibitors effectively reduce high blood pressure and exert cardio- and renoprotective actions. Recent evidence suggests that a principal target of ACE inhibitor action is at the tissue sites. Pharmacokinetic properties of various ACE inhibitors indicate that there are differences in their binding characteristics for tissue ACE. Clinical studies comparing the effects of antihypertensives (especially ACE inhibitors) on endothelial function suggest differences. More comparative experimental and clinical studies should address the significance of these drug differences and their impact on clinical events.

New feature of angiotensin-converting enzyme: carbohydrate-recognizing domain

Self carbohydrate-mediated dimerization of glycoprotein angiotensin-converting enzyme (ACE) was demonstrated. The dimerization was studied in the reverse micelle experimental system as a model of biomembrane situation. Asialo-ACE or agalacto-ACE was able to form a dimer, whereas deglycosylated ACE and sequentially desialylated and degalactosylated ACE failed to dimerize. ACE-ACE interaction was competitively inhibited by Neu5Ac- or Gal-terminated saccharides. The results have allowed us to propose the existence of carbohydrate-recognizing domain (CRD) on ACE molecule. The structural requirements of this CRD were estimated based on the ability of saccharides to inhibit ACE dimerization. The most effective monosaccharides with equal inhibition potencies were shown to be galactose (as GalbetaOMe) and N-acetylneuraminic acid (as Neu5AcalphaOMe). Among oligosaccharides, the most effective ones were found to be 3'SiaLac and, especially, the whole pool of ACE oligosaccharide chains and biantennae complex oligosaccharide chains of other glycoproteins. Bovine and human ACEs were shown to be similar in terms of recognition of carbohydrates.

A 105- to 94-kilodalton protein in the epididymal fluids of domestic mammals is angiotensin I-converting enzyme (ACE); evidence that sperm are the source of this ACE

SDS-PAGE analysis of luminal fluid from the ram testis and epididymis revealed a protein of about 105 kDa in the fluid in the caput epididymal region. The molecular mass of this fluid protein shifted from 105 kDa to 94 kDa in the distal caput epididymidis and remained at 94 kDa in the lower regions of the epididymis. The possible sperm origin of this protein was suggested by the decrease in intensity of a 105-kDa compound on the sperm plasma membrane extract and by its total disappearance from the fluid of animals with impaired sperm production caused by scrotal heating. The 94-kDa protein was purified from ram cauda epididymal fluid, and a rabbit polyclonal antiserum was obtained. This antiserum showed that membranes of testicular sperm and sperm from the initial caput were positive for the presence of an immunologically related antigen. The protein was immunolocalized mainly on the flagellar intermediate piece, whereas in some corpus and caudal sperm, only the apical ridge of the acrosomal vesicle was labeled. The purified protein was microsequenced: its N-terminal was not found in the sequence database, but its tryptic fragments matched the sequence of the angiotensin I-converting enzyme (ACE). Indeed, the purified 94-kDa protein exhibited a carboxypeptidase activity inhibited by specific blockers of ACE. All the soluble seminal plasma ACE activity in the ram was attributable to the 94-kDa epididymal fluid ACE. The polyclonal antiserum also showed that a soluble form of ACE appeared specifically in the caput epididymal fluid of the boar, stallion, and bull. This soluble form was responsible for all the ACE activity observed in the fluid from the distal caput to the cauda epididymidis in these species. Our results strongly suggest that the epididymal fluid ACE derives from the germinal form of ACE that is liberated from the testicular sperm in a specific epididymal area.

Characterization of AT2 receptor expression in NIH 3T3 fibroblasts

1. A high expression of angiotensin II receptors and of angiotensin-converting enzyme (ACE) activity was detected in confluent NIH 3T3 fibroblasts. 2. Characterization with selective ligands, dithiothreitol, and GTP gamma S, indicated that only the AT2 subtype was expressed. 3. AT2 receptors and ACE expression were strictly dependent on the cell density and growth phase of the cells, with AT2 receptors being expressed earlier than ACE. In contrast, high expression of AT2 receptors irrespective of their growth state was observed in NIH 3T3 cells lacking contact inhibition upon neoplastic transformation with ras. 4. Our results imply a possible relation of AT2 receptors to cell growth and cell-cell contact.

Induction of angiotensin I-converting enzyme transcription by a protein kinase C-dependent mechanism in human endothelial cells

Angiotensin I-converting enzyme (ACE) has been implicated in various cardiovascular diseases; however, little is known about the ACE gene regulation in endothelial cells. We have investigated the effect of the protein kinase C activator phorbol 12-myristate 13-acetate (PMA) on ACE activity and gene expression in human umbilical vein endothelial cells (HUVEC). Our results showed a 3- and 5-fold increase in ACE activity in the medium and in the cells, respectively, after 24-h stimulation by PMA. We also observed an increase in the cellular ACE mRNA content starting after 6 h and reaching a 10-fold increase at 24 h in response to 100 ng/ml PMA as measured by ribonuclease protection assay. This effect was mediated by an increased transcription of the ACE gene as demonstrated by nuclear run-on experiments and nearly abolished by the specific PKC inhibitor GF 109203X. Our results indicate that PMA-activated PKC strongly increases ACE mRNA level and ACE gene transcription in HUVEC, an effect associated with an increased ACE secretion. A role for early growth response factor-1 (Egr-1) as a factor regulating ACE gene expression is suggested by both the presence of an Egr-1-responsive element in the proximal portion of the ACE promoter and the kinetics of the Egr-1 mRNA increase in HUVEC treated with PMA.

Glycosylation of bovine pulmonary angiotensin-converting enzyme modulates its catalytic properties

To study the role of the oligosaccharide moiety in the catalytic properties of angiotensin-converting enzyme (ACE), we obtained asialo- and partially deglycosylated ACE by enzymatic treatment of two-domain somatic enzyme from bovine lung. Treated enzymes demonstrated appreciable, but different changes of catalytic properties in the reaction of the hydrolysis of N-substituted tripeptides, C-terminal analogs of angiotensin I and bradykinin among them, compared to those for native enzyme. Deglycosylation also altered the catalytic properties of a single N domain of bovine ACE. So, various patterns of glycosylation modulate substrate specificity of somatic ACE and may be the reason for functional heterogeneity of the enzyme.

Modulation of angiotensin-converting enzyme in cultured human vascular endothelial cells

Previous work has suggested that not all immunoreactive angiotensin-converting enzyme (ACE) in tissues or cells is in a biologically active state. We have explored this possibility in cultured human umbilical vein endothelial cells (HUVEC), one of the most widely studied in vitro endothelial cell systems. Our approach included characterization of the effect of increasing passage number on ACE activity and expression of immunoreactive ACE at the single cell level, the subcellular compartmentalization of active ACE, and the effect of phorbol ester (PMA) treatment. We found that both ACE activity and expression of ACE antigen were downregulated by cultivation (30% of ACE-positive cells at seventh passage vs. 90% in primary culture). ACE downregulation is specific (number of CD31-positive cells did not change with cultivation) and correlated with downregulation of factor VIII-antigen. The percentage of ACE-positive cells in permeabilized HUVEC at third passage was almost twice that in nonpermeabilized HUVEC (90% vs. 50%), indicating that HUVEC contain intracellular immunoreactive ACE. ACE activity, however, was similar when measured in intact cells and in cell lysates. Moreover, diazonium salt of sulfanilic acid (DASA), a membrane-impermeable ACE inhibitor, inhibited ACE activity in intact cells and in cell lysates at the same extent, thus implying that intracellular ACE is inactive. PMA (100 nM) treatment increased the percentage of ACE-positive cells at third passage from 57 to 96%. ACE activity was increased 3-fold in cell and 1.5-fold in the culture medium of PMA-treated cells. Analysis of ACE activity in intact monolayers and cell lysates of control and PMA-treated cells revealed that all enzymatically active ACE in PMA-treated cells is localized on the plasma membrane and acts as an ectoenzyme. We conclude that expression of ACE by HUVEC is downregulated by repeated passage in culture but can be restored by PMA treatment. In addition, ACE expression is heterogeneous between neighboring cells, and total immunoreactive ACE protein associated with HUVEC includes an inactive pool of the enzyme.

Alternative splicing of the mRNA coding for the human endothelial angiotensin-converting enzyme: a new mechanism for solubilization

Angiotensin converting enzyme (ACE) is a zinc metalloprotease anchored in the plasma membrane with a carboxy-terminal hydrophobic domain. In addition, the existence of a soluble form of ACE lacking the transmembrane domain has been reported. We show evidence for the existence of an mRNA specific for this isoform produced by alternative splicing. In human umbilical vein endothelial cells, two ACE mRNAs of different length (4.3 and 3.5 kb) were detected by Northern blot. Ribonuclease protection assays and the sequence of a PCR-amplified cDNA fragment show that the shortened ACE mRNA lacks the exons coding for the transmembrane domain of the protein. As this mRNA could be the source of soluble ACE, plasma ACE activity may be regulated on the level of mRNA processing.

Sequential development of angiotensin receptors and angiotensin I converting enzyme during angiogenesis in the rat subcutaneous sponge granuloma

1. The vasoconstrictor peptide antiotensin II (AII) can stimulate angiogenesis, an important process in wound healing, tumour growth and chronic inflammation. To elucidate mechanisms underlying AII-enhanced angiogenesis, we have studied a subcutaneous sponge granuloma model in the rat by use of 133Xe clearance, morphometry and quantitative in vitro autoradiography. 2. When injected directly into the sponge, AII (1 nmol day-1) increased 133Xe clearance from, and fibrovascular growth in sponge granulomas, indicating enhanced angiogenesis 6 to 12 days after implantation. This AII-enhanced angiogenesis was inhibited by daily doses (100 nmol/sponge) of the specific but subtype non-selective AII receptor antagonist (Sar1, Ile8)AII, and by the selective non-peptide AT1 receptor antagonists losartan and DuP 532. In contrast, AII-enhanced neovascularization was not inhibited by the AT2 receptor antagonist PD123319, nor was it mimicked by the AT2 receptor agonist CGP42112A (each at 100 nmol/sponge day-1). 3. AI (1 nmol/sponge day-1), the angiotensin converting enzyme (ACE) inhibitors captopril (up to 100 micrograms/sponge day-1) and lisinopril (40 micrograms/sponge day-1), or AII receptor antagonists did not affect angiogenesis in the absence of exogenous AII. 4. [125I]-(Sar1, Ile8)AII binding sites with characteristics of AT1 receptors were localized to microvessels and to non-vascular cells within the sponge stroma from 4 days after implantation, and were at higher density than in skin throughout the study. 5. [125I]-(Sar1, Ile8)AII binding sites with characteristics of AT2 receptors were localized to non-vascular stromal cells, were of lower density and appeared later than did AT1 sites. 6. The ACE inhibitor [125I]-351A bound to sites with characteristics of ACE, 14 days after sponge implantation. [125I]-351A bound less densely to sponge stroma than to skin. 7. We propose that AII can stimulate angiogenesis, acting via AT1 receptors within the sponge granuloma. AT1 and AT2 receptors and ACE develop sequentially during microvascular maturation, and the role of the endogenous angiotensin system in angiogenesis will depend on the balanced local expression of its various components. Pharmacological modulation of this balance may provide novel therapeutic approaches in angiogenesis-dependent diseases.

Electron paramagnetic resonance studies of cobalt-substituted angiotensin I-converting enzyme

Electron paramagnetic resonance (EPR) spectroscopy has been used to study the metal coordination sphere geometry in the cobalt-substituted Zn-protein angiotensin I-converting enzyme (ACE). It has been shown that ACE contains two distinct metal-binding sites. In the presence of the two structurally different inhibitors, captopril and ramiprilat, it is found that the metal binding sites are nearly structurally identical and are separated more than 10 A from each other. The metal atoms are most likely four- to five-coordinated, and it is argued that the inhibitor binds directly to the metal ion.

The endopeptidase activity and the activation by Cl- of angiotensin-converting enzyme is evolutionarily conserved: purification and properties of an an angiotensin-converting enzyme from the housefly, Musca domestica

A soluble 67 kDa angiotensin-converting enzyme (ACE) has been purified by lisinopril-Sepharose affinity column chromatography from adult houseflies, Musca domestica. The dipeptidyl carboxypeptidase activity towards benzoyl-Gly-His-Leu was inhibited by captopril (IC50 50 nM) and fosinoprilat (IC50 251 nM), two inhibitors of mammalian ACE, and was activated by Cl- (optimal Cl- concentration 600 mM). Musca ACE removed C-terminal dipeptides from angiotensin I, bradykinin [Leu5]enkephalin and [Met5]enkephalin and also functioned as an endopeptidase by hydrolysing dipeptideamides from [Leu5]enkephalinamide and [Met5]enkephalinamide, and a dipeptideamide and a tripeptideamide from substance P. Musca ACE was also able to cleave a tripeptide from both the N-terminus and C-terminus of luteinizing hormone-releasing hormone, with C-terminal hydrolysis predominating. Maximal N-terminal tripeptidase activity occurred at 150 mM NaCl, whereas the C-terminal tripeptidase activity continued to rise with increasing concentration of Cl- (0-0.5 M). Musca ACE displays properties of both the N- and C-domains of human ACE, indicating a high degree of conservation during evolution of the substrate specificity of ACE and its response to Cl-.

The cellular basis of angiotensin converting enzyme mRNA expression in rat heart

Angiotensin converting enzyme (ACE) is a key factor in the regulation of two peptide systems: the renin angiotensin system (RAS) and the kinin-kallikrein system (KKS). Since it is involved in the biosynthesis of Angiotensin II (Ang II) as well as in the degradation of bradykinin (BK) it could play an important role in cardiovascular physiology and pathophysiology. ACE is widely expressed in the heart and upregulated in pathophysiological situations such as heart failure and cardiac hypertrophy. In addition, inhibition of ACE has beneficial effects in these conditions. Whereas the regulation of cardiac ACE has been studied extensively, little is known concerning the cellular expression of ACE in cardiac tissue. To define the cellular localization of ACE mRNA expression in the rat heart, we separated coronary microvascular endothelial cells from cardiac myocytes using differential centrifugation and growth on selective media. ACE mRNA expression was measured by a specific polymerase chain reaction assay after reverse transcription (RT-PCR) in different cardiac cells. The studies showed that ACE is differentially expressed in endothelial cells as well as in cardiac myocytes. This differential regulation of ACE in myocytes and non-myocytes may play a role for the diverse actions of the cardiac angiotensin system under physiological and pathological conditions.

Cloning and expression of an evolutionary conserved single-domain angiotensin converting enzyme from Drosophila melanogaster

Mammalian somatic angiotensin converting enzyme (EC 3.4.15.1, ACE) consists of two highly homologous (N- and C-) domains encoded by a duplicated gene. We have identified an apparent single-domain (67 kDa) insect angiotensin converting enzyme (AnCE) in embryos of Drosophila melanogaster which converts angiotensin I to angiotensin II (Km, 365 microM), removes Phe-Arg from the C terminus of bradykinin (Km, 22 microM), and is inhibited by ACE inhibitors, captopril (IC50 = 1.1 x 10(-9) M) and trandolaprilat (IC50 = 1.6 x 10(-8) M). We also report the cloning and expression of a Drosophila AnCE cDNA which codes for a single-domain 615-amino acid protein with a predicted 17-amino acid signal peptide and regions with high levels of homology to both the N- and C-domains of mammalian somatic ACE, especially around the active site consensus sequence. Northern analysis identified a single 2.1-kilobase mRNA in Drosophila embryos, and Southern analysis of Drosophila genomic DNA indicates that the insect gene is not duplicated. When expressed in COS-7 cells, the AnCE protein is a secreted enzyme, which converts angiotensin I to angiotensin II and is inhibited by captopril (IC50 = 5.6 x 10(-9) M) and trandolaprilat (IC50 = 2 x 10(-8) M). The evolutionary significance of these results is discussed.

Fibroblast growth factor stimulates angiotensin converting enzyme expression in vascular smooth muscle cells. Possible mediator of the response to vascular injury

Angiotensin converting enzyme (ACE) activity contributes to the vascular response to injury because ACE inhibition limits neointima formation in rat carotid arteries after balloon injury. To investigate the mechanisms by which ACE may contribute to vascular smooth muscle cell (VSMC) proliferation, we studied expression of ACE in vivo after injury and in vitro after growth factor stimulation. ACE activity 14 d after injury was increased 3.6-fold in the injured vessel. ACE expression, measured by immunohistochemistry, became apparent at 7 d in the neointima and at 14 d was primarily in the most luminal neointimal cells. To characterize hormones that induce ACE in vivo, cultured VSMC were exposed to steroids and growth factors. Among steroids, only glucocorticoids stimulated ACE expression with an 8.0 +/- 2.1-fold increase in activity and a 6.5-fold increase in mRNA (30 nM dexamethasone for 72 h). Among growth factors tested, only fibroblast growth factor (FGF) stimulated ACE expression (4.2 +/- 0.7-fold increase in activity and 1.6-fold increase in mRNA in response to 10 ng/ml FGF for 24 h). Dexamethasone and FGF were synergistic at the indicated concentrations inducing 50.6 +/- 12.4-fold and 32.5-fold increases in activity and mRNA expression, respectively. In addition, when porcine iliac arteries were transfected with recombinant FGF-1 (in the absence of injury), ACE expression increased in neointimal VSMC, to the same extent as injured, nontransfected arteries. The data suggest a temporal sequence for the response to injury in which FGF induces ACE, ACE generates angiotensin II, and angiotensin II stimulates VSMC growth in concert with FGF.

The endothelial cell nitric oxide synthase: is it really constitutively expressed?

During the past two years, the enzyme responsible for production of endothelium-derived nitric oxide, the endothelial cell NO synthase (ecNOS) has been cloned and the gene encoding this enzyme isolated, cloned and its structure characterized. This research has provided direction for a variety of studies of regulation of the ecNOS. Several features of the ecNOS are compatible with a constitutively expressed, poorly regulated gene, including absence of a TATA box and numerous SP-1 sites. The promoter also contains a number of putative binding domains which suggest that it may be regulated by a variety of transcription factor mediated signals. In this review we will discuss evidence to support the concept that the ecNOS is a constitutively expressed gene subject to a modest degree of regulation by important physiological influences.

Identification and properties of a peptidyl dipeptidase in the housefly, Musca domestica, that resembles mammalian angiotensin-converting enzyme

[D-Ala2,Leu5]Enkephalin was readily metabolized by membranes (40,000 g pellet) prepared from heads of the housefly, Musca domestica, with Gly3-Phe4 being the major site of cleavage. This hydrolysis was only partially inhibited (40%) by 10 microM phosphoramidon, an inhibitor of endopeptidase-24.11, but was almost totally abolished in the presence of a mixture of 10 microM phosphoramidon and 10 microM captopril, a potent inhibitor of mammalian angiotensin-converting enzyme (ACE). An assay for ACE employing Bz-Gly-His-Leu as the substrate was used to confirm the presence of an ACE-like peptidyl dipeptidase activity in fly head membranes. The peptidase had a Km of 1.91 mM for Bz-Gly-His-Leu and a pH optimum of 8.2. The activity was inhibited by 100 microM EDTA and was greatly activated by ZnCl2 but not other bivalent metal ions. Captopril, lisinopril, fosinoprilat and enalaprilat, all selective inhibitors of mammalian ACE, were also good inhibitors of the insect enzyme with IC50 values of 400 nM, 130 nM, 16 nM and 290 nM respectively. An M(r) value of around 87,000 was obtained for this enzyme from gel-filtration chromatography, indicating that the insect enzyme is similar in size to mammalian testicular ACE (M(r) = 90,000-110,000) and not the larger form of the enzyme (M(r) = 150,000-180,000) found in mammalian somatic tissues. The fly peptidyl dipeptidase was released from membranes into a soluble fraction by incubating the head membranes at 37 degrees C but not at 0 degree C, suggesting that the insect ACE-like enzyme can be solubilized from cell surfaces through the activity of a membrane-bound enzyme activity. In conclusion, we have shown the existence of a peptidyl dipeptidase in membranes from the heads of M. domestica, which has similar properties to those of mammalian ACE.

Ontogeny of somatic angiotensin-converting enzyme

Angiotensin-converting enzyme or kininase II (ACE-KII) plays a central role in the control of circulating and tissue levels of angiotensin II and kinins. Both peptides have been implicated in the regulation of renal function and growth during normal development. We tested the hypothesis that the developing rat kidney expresses ACE-KII mRNA transcripts and the active enzyme and evaluated whether the developmental expression of the ACE-KII gene is related to changes in circulating angiotensin II and tissue kallikrein. ACE-KII mRNA and enzymatic activity were low in the newborn kidney; peak expression occurred on days 15 and 20 of postnatal life (16-fold versus day 1). In extrarenal tissues, ACE-KII activity and mRNA levels were also low during the newborn period in the following order of abundance: lung > kidney > aorta > heart. The lung showed a higher age-related increase in active ACE-KII and mRNA abundance (15-fold) than heart and aorta (activity, 3- to 4-fold; mRNA, 6- to 10-fold). The developmental profile of ACE-KII correlated temporally with changes in circulating angiotensin II and tissue kallikrein. Plasma angiotensin II levels were 2.5-fold higher in newborn than adult rats, whereas renal and extrarenal kallikrein-like activity increased twofold to fivefold from birth to adulthood. These results demonstrate that the ACE-KII gene is developmentally regulated in a tissue-specific manner. Tissue kinin generation and degradation, reflected by kallikrein and ACE-KII activities, are coordinately regulated during development, whereas circulating angiotensin II and tissue ACE-KII change in a reciprocal manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhancement of cytosolic calcium, prostacyclin and nitric oxide by bradykinin and the ACE inhibitor ramiprilat in porcine brain capillary endothelial cells

We studied whether primary cultured porcine brain capillary endothelial cells (PBCEC) respond to bradykinin with an enhanced intracellular cytosolic calcium concentration [Ca2+]i with subsequent formation of nitric oxide (NO) and prostacyclin (PGI2). In addition we examined whether these cells synthetize and release kinins that may accumulate during angiotensin-converting enzyme (ACE) inhibition. [Ca2+]i was assessed by the fluorescent dye Fura-2, NO formation by determination of intracellular cyclic GMP and PGI2 by a specific radioimmunoassay for 6-ketoprostaglandin F1 alpha. Bradykinin and the ACE inhibitor ramiprilat concentration-dependently increased the formation of cyclic GMP which was completely prevented by the stereospecific inhibitor of NO synthase, NG-nitro-L-arginine. Also the specific B2-kinin receptor antagonist icatibant (Hoe 140) abolished the increase in cyclic GMP as well as the ramiprilat-induced increase in PGI2 formation. The data demonstrate the existence of B2-kinin receptors and ACE activity in PBCEC. Moreover PBCEC are capable of producing and releasing kinins in amounts that lead via stimulation of B2-kinin receptors to an enhanced [Ca2+]i as well as NO and PGI2 synthesis and release, provided that degradation of kinins is prevented by inhibition of endothelial ACE activity.

Metabolism of substance P and neurokinin A by human vascular endothelium and smooth muscle

Analysis of SP and NKA metabolism by human vascular endothelium, relative to that in human plasma, identified integrative, multiple pathways for the processing of circulating SP (but not NKA) by angiotensin-converting enzyme (ACE; EC 3.4.15.1), dipeptidyl(amino)peptidase IV (DAP IV; EC 3.4.14.5), and aminopeptidase M (AmM; EC 3.4.11.2). In contrast, SP and NKA, which may diffuse into or be neurally released within the vessel wall, were both metabolized by smooth muscle neutral endopeptidase-24.11 (NEP-24.11; EC 3.4.24.11). Collectively, these studies indicate peptide-specific and site-specific differential processing of SP and NKA by human plasma and vasculature.

Regulation of angiotensin I-converting enzyme in cultured bovine bronchial epithelial cells

The purpose of this study was to determine whether angiotensin I-converting enzyme (ACE) is present in cultured bovine bronchial epithelial cells (BBECs) and whether its activity can be modulated. We found that extracts of confluent monolayers of cultured BBECs degraded [glycine-1-14C]hippuryl-L-histidyl-L-leucine at a rate of 843 +/- 66 pmol/hr/mg protein (mean +/- SEM, n = 5). In addition, we found that the enzyme was shed into the culture medium. ACE activity in BBECs was inhibited by three selective, but structurally different, ACE inhibitors (captopril, quinapril, and cisalaprilat) with an IC50 of approximately 2 nM. Increasing chloride concentration in the assay buffer resulted in an increase in BBECs ACE activity of 63%. Enzyme activity was also modulated by the presence of zinc cation in the assay buffer. Addition of dexamethasone to the culture medium was associated with a significant increase in BBECs ACE activity (P < 0.05), which was inhibited by the steroid receptor antagonist RU 38486. Western blot analysis of BBECs, tracheal and bronchial mucosal strips utilizing a cross-reacting rabbit anti-mouse ACE antibody, showed a faint 175 kDa band and additional strong 52 kDa and 47 kDa band. The mechanism of generation of the low M.W. bands is unknown. Our data indicate the presence of ACE in cultured BBECs and that enzyme activity can be modulated.

Effect of a short-term captopril treatment on serum and tissue angiotensin I-converting enzyme activity from four mammalian species. Differences using diamide in the in vitro assay

1. Angiotensin I-converting enzyme (ACE) activity was determined in serum and nine tissues from control and captopril-treated rats, mice, guinea pigs and rabbits. 2. ACE activity was determined with and without sample pretreatment with diamide (total and basal activity, respectively). 3. A very different pattern of response to captopril was observed among the different species. 4. There was no relationship between serum ACE activity and the response to captopril. 5. There were important differences in the determinations of total or basal ACE activities. 6. Endogenous ACE inhibitors were found in some tissues from mouse and rabbit.

Structure and regulated expression of angiotensin-converting enzyme and the receptor for angiotensin II

The renin-angiotensin system maintains a homeostasis of blood pressure and blood volume. One component of this system is angiotensin-converting enzyme (ACE). There are two isozymes of ACE. The protein produced by vascular endothelium is termed "somatic ACE" and is regulated as a function of the growth state of these cells in vitro. The second isozyme, "testis ACE," is only produced by developing spermatozoa. The two ACE isozymes are the result of two distinct promoter regions within the ACE gene. Angiotensin II binds to specific receptors on the surface of cells. We have isolated cDNA encoding the AT1 subtype of receptor. This subtype is responsible for the hemodynamic consequences of angiotensin.