Angiotensin-I converting enzyme (ACE): structure, biological roles, and molecular basis for chloride ion dependence

Proteomic Analysis of Human Macrophages Overexpressing Angiotensin-Converting Enzyme

Angiotensin converting enzyme (ACE) exerts strong modulation of myeloid cell function independently of its cardiovascular arm. The success of the ACE-overexpressing murine macrophage model, ACE 10/10, in treating microbial infections and cancer opens a new avenue into whether ACE overexpression in human macrophages shares these benefits. Additionally, as ACE inhibitors are a widely used antihypertensive medication, their impact on ACE expressing immune cells is of interest and currently understudied. In the present study, we utilized mass spectrometry to characterize and assess global proteomic changes in an ACE-overexpressing human THP-1 cell line. Additionally, proteomic changes and cellular uptake following treatment with an ACE C-domain selective inhibitor, lisinopril-tryptophan, were also assessed. ACE activity was significantly reduced following inhibitor treatment, despite limited uptake within the cell, and both RNA processing and immune pathways were significantly dysregulated with treatment. Also present were upregulated energy and TCA cycle proteins and dysregulated cytokine and interleukin signaling proteins with ACE overexpression. A novel, functionally enriched immune pathway that appeared both with ACE overexpression and inhibitor treatment was neutrophil degranulation. ACE overexpression within human macrophages showed similarities with ACE 10/10 murine macrophages, paving the way for mechanistic studies aimed at understanding the altered immune function.

Prediction of endogenous mineralocorticoid receptor activity by depressor effects of mineralocorticoid receptor antagonists in patients with primary aldosteronism

Patients with primary aldosteronism have an increased risk of developing cardiovascular disease. The response to mineralocorticoid receptor antagonists varies among individuals, indicating diverse mineralocorticoid receptor activities in these patients. This study explored the factors linked to the efficacy of blood pressure reduction through mineralocorticoid receptor antagonists in patients with primary aldosteronism. We examined the relationship between the reduction in blood pressure and patient characteristics in a group of 41 patients with primary aldosteronism (24 males, mean age 55 ± 13 years, including 34 patients diagnosed with bilateral primary aldosteronism) before and after undergoing treatment with mineralocorticoid receptor antagonists. Significant reductions in office blood pressure were observed 3 and 6 months after treatment initiation. Single correlation analyses showed that the urinary chloride-to-potassium ratio displayed the strongest positive association with blood pressure reduction, surpassing plasma aldosterone concentration, plasma renin activity, and urinary sodium-to-potassium ratio, at 3 and 6 months. Multiple correlation analyses revealed a consistent and independent positive correlation between the urinary chloride-to-potassium ratio and blood pressure reduction at 3 and 6 months. The optimal threshold for the urinary chloride-to-potassium ratio with respect to its ability to lower blood pressure, was determined as 3.18. These results imply that the urinary chloride-to-potassium ratio may be independently associated with the effectiveness of blood pressure reduction facilitated by mineralocorticoid receptor antagonists. Moreover, it could potentially serve as a valuable predictor of the effectiveness of these agents and function as an indicator of endogenous mineralocorticoid receptor activity in patients with primary aldosteronism.

Angiotensin-converting enzyme I/D gene polymorphism and risk of type 2 diabetes mellitus in Iranian individuals

This study aimed to examine the relationship between type 2 diabetes mellitus (T2DM) and renin-angiotensin system gene polymorphisms in the Iranian population. Additionally, we performed a straightforward meta-analysis of the present articles to better understand this role. A total of 100 Iranian individuals, 50 patients with T2DM, and 50 age-matched healthy individuals were included in this study. DNA was extracted using the salting-out approach, polymerase chain reaction was used to amplify the angiotensin-converting enzyme (ACE) gene, electrophoresis techniques were used, and genotyping was performed. We also searched PubMed, Web of Science, Scopus, and Google Scholar databases for papers published in 2023. We found a significantly higher frequency of I/D genotype in the patient group than in the control group, and the risk of T2DM was 10 times higher in individuals with the I/D genotype (OR, 10 [95% CI, 3.7 to 27]; p < 0.0001) and also 2.85 time higher in individuals with the D allele OR, 2.85 [95% CI, 1.55 to 5.24]; p < 0.001). The ACE polymorphism alleles D and I/D genotypes may increase the risk of developing T2DM in an Iranian population.

Structural insights into the inhibitory mechanism of angiotensin-I-converting enzyme by the lactotripeptides IPP and VPP

Human somatic angiotensin-1-converting enzyme (sACE) is composed of a catalytic N-(nACE) and C-domain (cACE) of similar size with different substrate specificities. It is involved in the regulation of blood pressure by converting angiotensin I to the vasoconstrictor angiotensin II and has been a major focus in the development of therapeutics for hypertension. Bioactive peptides from various sources, including milk, have been identified as natural ACE inhibitors. We report the structural basis for the role of two lacototripeptides, Val-Pro-Pro and Ile-Pro-Pro, in domain-specific inhibition of ACE using X-ray crystallography and kinetic analysis. The lactotripeptides have preference for nACE due to altered polar interactions distal to the catalytic zinc ion. Elucidating the mechanism of binding and domain selectivity of these peptides also provides important insights into the functional roles of ACE.

A Comprehensive Review on Potential Molecular Drug Targets for the Management of Alzheimer's Disease

Alzheimer's disease (AD) is an onset and incurable neurodegenerative disorder that has been linked to various genetic, environmental, and lifestyle factors. Recent research has revealed several potential targets for drug development, such as the prevention of Aβ production and removal, prevention of tau hyperphosphorylation, and keeping neurons alive. Drugs that target numerous ADrelated variables have been developed, and early results are encouraging. This review provides a concise map of the different receptor signaling pathways associated with Alzheimer's Disease, as well as insight into drug design based on these pathways. It discusses the molecular mechanisms of AD pathogenesis, such as oxidative stress, aging, Aβ turnover, thiol groups, and mitochondrial activities, and their role in the disease. It also reviews the potential drug targets, in vivo active agents, and docking studies done in AD and provides prospects for future drug development. This review intends to provide more clarity on the molecular processes that occur in Alzheimer's patient's brains, which can be of use in diagnosing and preventing the condition.

Inhibitory effects of the anthocyanins from Lycium ruthenicum Murray on angiotensin-I-converting enzyme: in vitro and molecular docking studies

BACKGROUND

Lycium ruthenicum Murray (LRM), a perennial shrub plant belonging to the Solanaceae family, is rich in anthocyanins, which have anti-inflammatory, antioxidant, lipid-lowering, intestinal flora regulating, and other pharmacological qualities. This study was primarily aimed to investigate the inhibitory effect of different anthocyanin purities from LRM on angiotensin-I-converting enzyme (ACE) activity in vitro. Moreover, the inhibitory mechanism was further analyzed by molecular docking technology.

RESULTS

Two main anthocyanin isomers were identified by ultra-performance liquid chromatography-tandem mass spectrometry and proton/carbon-13 nuclear magnetic resonance, namely petunidin-3-O-[rhamnopyranosyl-(trans-p-coumaroyl)]-5-O-(β-d-glucopyranoside) (trans-Pt3R5G) and petunidin-3-O-[rhamnopyranosyl-(cis-p-coumaroyl)]-5-O-(β-d-glucopyranoside) (cis-Pt3R5G), with a molar ratio of 9:1. Three purification grades of Pt3R5G all showed excellent inhibitory effects on ACE, with the half maximal inhibitory concentration (IC50 ) values being 0.562, 0.421, and 0.106 mg·mL-1 . Increasing the purity may reduce the IC50 within a certain concentration range. An enzymatic kinetic experiment showed that the inhibitory effect of Pt3R5G on ACE was reversible and non-competitive: Pt3R5G and substrate were not in competition for the active sites of ACE. Molecular docking technology further revealed the possible mechanism was that Pt3R5G and ACE amino acid residues were interacting by hydrogen bonds to exert the inhibitory effect.

CONCLUSION

The results indicated that Pt3R5G from LRM was highly effective at inhibiting ACE activity in vitro, with the hydrogen bonds of Pt3R5G and ACE amino acid residues exerting the inhibition. As a potential plant-based ACE inhibitor, Pt3R5G can be used as a functional ingredient for antihypertensive effects. © 2023 Society of Chemical Industry.

Molecular Structure of Phosphoserine Aminotransferase from Saccharomyces cerevisiae

Phosphoserine aminotransferase (PSAT) is a pyridoxal 5′-phosphate-dependent enzyme involved in the second step of the phosphorylated pathway of serine biosynthesis. PSAT catalyzes the transamination of 3-phosphohydroxypyruvate to 3-phosphoserine using L-glutamate as the amino donor. Although structural studies of PSAT have been performed from archaea and humans, no structural information is available from fungi. Therefore, to elucidate the structural features of fungal PSAT, we determined the crystal structure of Saccharomyces cerevisiae PSAT (ScPSAT) at a resolution of 2.8 Å. The results demonstrated that the ScPSAT protein was dimeric in its crystal structure. Moreover, the gate-keeping loop of ScPSAT exhibited a conformation similar to that of other species. Several distinct structural features in the halide-binding and active sites of ScPSAT were compared with its homologs. Overall, this study contributes to our current understanding of PSAT by identifying the structural features of fungal PSAT for the first time.

Characterization of the First Animal Toxin Acting as an Antagonist on AT1 Receptor

The renin-angiotensin system (RAS) is one of the main regulatory systems of cardiovascular homeostasis. It is mainly composed of angiotensin-converting enzyme (ACE) and angiotensin II receptors AT1 and AT2. ACE and AT1 are targets of choice for the treatment of hypertension, whereas the AT2 receptor is still not exploited due to the lack of knowledge of its physiological properties. Peptide toxins from venoms display multiple biological functions associated with varied chemical and structural properties. If Brazilian viper toxins have been described to inhibit ACE, no animal toxin is known to act on AT1/AT2 receptors. We screened a library of toxins on angiotensin II receptors with a radioligand competition binding assay. Functional characterization of the selected toxin was conducted by measuring second messenger production, G-protein activation and β-arrestin 2 recruitment using bioluminescence resonance energy transfer (BRET) based biosensors. We identified one original toxin, A-CTX-cMila, which is a 7-residues cyclic peptide from Conus miliaris with no homology sequence with known angiotensin peptides nor identified toxins, displaying a 100-fold selectivity for AT1 over AT2. This toxin shows a competitive antagonism mode of action on AT1, blocking Gαq, Gαi3, GαoA, β-arrestin 2 pathways and ERK_1/2 activation. These results describe the first animal toxin active on angiotensin II receptors.

Single-cell profiling identifies ACE+ granuloma macrophages as a nonpermissive niche for intracellular bacteria during persistent Salmonella infection

Macrophages mediate key antimicrobial responses against intracellular bacterial pathogens, such as Salmonella enterica. Yet, they can also act as a permissive niche for these pathogens to persist in infected tissues within granulomas, which are immunological structures composed of macrophages and other immune cells. We apply single-cell transcriptomics to investigate macrophage functional diversity during persistent S. enterica serovar Typhimurium (STm) infection in mice. We identify determinants of macrophage heterogeneity in infected spleens and describe populations of distinct phenotypes, functional programming, and spatial localization. Using an STm mutant with impaired ability to polarize macrophage phenotypes, we find that angiotensin-converting enzyme (ACE) defines a granuloma macrophage population that is nonpermissive for intracellular bacteria, and their abundance anticorrelates with tissue bacterial burden. Disruption of pathogen control by neutralizing TNF is linked to preferential depletion of ACE+ macrophages in infected tissues. Thus, ACE+ macrophages have limited capacity to serve as cellular niche for intracellular bacteria to establish persistent infection.

Structural Characterization of Functionally Important Chloride Binding Sites in the Marine Vibrio Alkaline Phosphatase

Enzyme stability and function can be affected by various environmental factors, such as temperature, pH, and ionic strength. Enzymes that are located outside the relatively unchanging environment of the cytosol, such as those residing in the periplasmic space of bacteria or extracellularly secreted, are challenged by more fluctuations in the aqueous medium. Bacterial alkaline phosphatases (APs) are generally affected by ionic strength of the medium, but this varies substantially between species. An AP from the marine bacterium Vibrio splendidus (VAP) shows complex pH-dependent activation and stabilization in the 0-1.0 M range of halogen salts and has been hypothesized to specifically bind chloride anions. Here, using X-ray crystallography and anomalous scattering, we have located two chloride binding sites in the structure of VAP, one in the active site and another one at a peripheral site. Further characterization of the binding sites using site-directed mutagenesis and small-angle X-ray scattering showed that upon binding of chloride to the peripheral site, structural dynamics decreased locally, resulting in thermal stabilization of the VAP active conformation. Binding of the chloride ion in the active site did not displace the bound inorganic phosphate product, but it may promote product release by facilitating rotational stabilization of the substrate-binding Arg129. Overall, these results reveal the complex nature and dynamics of chloride binding to enzymes through long-range modulation of electronic potential in the vicinity of the active site, resulting in increased catalytic efficiency and stability.

Cryo-EM reveals mechanisms of angiotensin I-converting enzyme allostery and dimerization

Hypertension (high blood pressure) is a major risk factor for cardiovascular disease, which is the leading cause of death worldwide. The somatic isoform of angiotensin I‐converting enzyme (sACE) plays a critical role in blood pressure regulation, and ACE inhibitors are thus widely used to treat hypertension and cardiovascular disease. Our current understanding of sACE structure, dynamics, function, and inhibition has been limited because truncated, minimally glycosylated forms of sACE are typically used for X‐ray crystallography and molecular dynamics simulations. Here, we report the first cryo‐EM structures of full‐length, glycosylated, soluble sACE (sACE^S1211). Both monomeric and dimeric forms of the highly flexible apo enzyme were reconstructed from a single dataset. The N‐ and C‐terminal domains of monomeric sACE^S1211 were resolved at 3.7 and 4.1 Å, respectively, while the interacting N‐terminal domains responsible for dimer formation were resolved at 3.8 Å. Mechanisms are proposed for intradomain hinging, cooperativity, and homodimerization. Furthermore, the observation that both domains were in the open conformation has implications for the design of sACE modulators.

Chokeberry (A. melanocarpa (Michx.) Elliott)—A Natural Product for Metabolic Disorders?

Abnormal metabolism of substances in the body can result in metabolic disorders which include obesity, cardiovascular diseases, diabetes, hypertension, chronic kidney disease, liver disease, or cancer. Foods rich in antioxidants can help to prevent and treat various types of disorders. Chokeberry fruits are rich in polyphenols, especially cyanidins, and therefore, can show a beneficial health effect. The aim of this study was to summarize and systematize reports about the effects of chokeberry on various metabolic parameters. Studies from 2000 to 2021, published in the PubMed and Google Scholar databases, were reviewed. The review of studies shows that chokeberry may have a positive effect in dyslipidemia and hypertension and may increase the body’s antioxidant defense mechanisms. The anti-inflammatory effect, in turn, may translate into a reduction in the risk of metabolic disorders over a longer period of use. Changes in glucose levels were reported by studies in which the intervention lasted more than 10 weeks in patients with carbohydrate metabolism disorders. The effects of protecting the liver, inhibiting platelet aggregation, lowering uric acid levels, and having a protective effect on the kidneys require additional confirmation in human clinical trials. Consumption of chokeberry fruit did not impact on anthropometric measurements; however, it seems that chokeberry fruit can be recommended in many metabolic disorders due to the richness of bioactive ingredients.

Basal VEGF-A and ACE Plasma Levels of Metastatic Colorectal Cancer Patients Have Prognostic Value for First-Line Treatment with Chemotherapy Plus Bevacizumab

Simple Summary

Molecular biology knowledge has enabled the incorporation of targeted therapies, such as the anti-angiogenic drug bevacizumab, into combined chemotherapy regimens for the treatment of metastatic colorectal cancer. However, to date, there are no reliable useful biomarkers to predict the efficacy of this anti-angiogenic therapy. The objective of this prospective study was to evaluate potential circulating plasma biomarkers in mCRC patients prior to the start of first-line treatment with chemotherapy plus bevacizumab. We found that high VEGF-A and low ACE plasma levels were associated with poor OS after treatment. Moreover, a simple scoring system combining both biomarkers efficiently stratified patients into high- or low-risk groups, which allows the selection of patients for anti-angiogenic therapy.

Abstract

The identification of factors that respond to anti-angiogenic therapy would represent a significant advance in the therapeutic management of metastatic-colorectal-cancer (mCRC) patients. We previously reported the relevance of VEGF-A and some components of the renin–angiotensin-aldosterone system (RAAS) in the response to anti-angiogenic therapy in cancer patients. Therefore, this prospective study aims to evaluate the prognostic value of basal plasma levels of VEGF-A and angiotensin-converting enzyme (ACE) in 73 mCRC patients who were to receive bevacizumab-based therapies as a first-line treatment. We found that high basal VEGF-A plasma levels were significantly associated with worse overall survival (OS) and progression-free survival (FPS). On the other hand, low ACE levels were significantly associated with poor OS. Importantly, a simple scoring system combining the basal plasma levels of VEGF-A and ACE efficiently stratified mCRC patients, according to OS, into high-risk or low-risk groups, prior to their treatment with bevacizumab. In conclusion, our study supports that VEGF-A and ACE may be potential biomarkers for selecting those mCRC patients who will most benefit from receiving chemotherapy plus bevacizumab treatment in first-line therapy. Additionally, our data reinforce the notion of a close association between the RAAS and the anti-angiogenic response in cancer.

An exploration of ACE inhibitory peptides derived from gastrointestinal protease hydrolysate of milk using a modified bioassay-guided fractionation approach coupled with in silico analysis

An improved bioassay-guided fractionation was performed to effectively screen angiotensin-I converting enzyme inhibitory (ACEI) peptides from milk protein hydrolysate. The aqueous normal phase liquid chromatography, namely hydrophilic interaction liquid chromatography (HILIC), was used as a format of solid-phase extraction (SPE) short column for the first fractionation, then the HILIC-SPE fraction with the best ACEI activity (IC₅₀ = 61.75 ± 5.74 µg/mL; IC₅₀ = half-maximal inhibitory concentration) was obtained when eluted by 95% acetonitrile + 0.1% formic acid (fraction F1). The best HILIC-SPE fraction was further fractionated using reversed-phase (RP)-SPE short column. The best RP-SPE fraction was obtained when eluted by 20% acetonitrile + 0.1% formic acid (fraction P3) with an ACEI activity of IC₅₀ 36.22 ± 1.18 µg/mL. After the 2-step fractionation, the IC₅₀ value of fraction P3 significantly decreased by 8.92-fold when compared with the crude hydrolysate. Several peptides were identified from fraction P3 using liquid chromatography-tandem mass spectrometry. The in silico analysis of these identified sequences based on the BIOPEP database predicted that HLPLPLL (HL-7) was the most active peptide against angiotensin-converting enzyme (ACE). The HL-7 derived from β-casein showed a potent ACEI activity (IC₅₀ value is 16.87 ± 0.3 µM). The contents of HL-7 in the gastrointestinal protease hydrolysate and RP-SPE fraction originated from 1 mg of milk proteins were quantified using a multiple reaction monitoring mode upon liquid chromatography-tandem mass spectrometry analysis to give 19.86 ± 1.14 pg and 14,545.8 ± 572.9 pg, respectively. Besides, the kinetic study indicated that HL-7 was a competitive inhibitor and the result was rationalized using the docking simulation. The study demonstrated an efficient screening of ACEI peptides from commercially available milk powders using a simple SPE process instead of a sophisticated instrument such as HPLC. Moreover, the potent ACEI peptide HL-7 uncovered by this method could be a natural ACE inhibitor.

Angiotensin converting enzyme (ACE)

BACKGROUND

Angiotensin converting enzyme (ACE) was isolated as a 'hypertensinconverting enzyme'. There have been considerable advances in understanding the metabolic role of ACE in the body. This review attempts to highlight the role of ACE enzyme in the physiological and pathological processes occurring in the organs in which it is localized.

METHODS

The literature was searched from the websites of the National Library of Medicine (http://www.ncbi.nlm.nih.gov/) and Pub Med Central, the U.S. National Library of Medicine's digital archive of life sciences journal literature.

RESULTS

The involvement of ACE in regulation of blood pressure forms its central action but it has a role to play in a variety of physiological processes occurring in the organs in which it is localized like the lungs, macrophages, brain, pancreas, liver etc. It has also been implicated in the pathogenesis of a number of diseases including COVID-19.

CONCLUSIONS

More studies need to be carried out in order to validate the use of ACE levels in the diagnosis and monitoring of the diseases associated, and facilitate the use of ACE inhibitors and Angiotensin Receptor Blockers in the management of the same, so this wonder molecule can be utilized to its full potential.

In silico analysis and characterization of medicinal mushroom cystathionine beta-synthase as an angiotensin converting enzyme (ACE) inhibitory protein

Angiotensin-converting enzyme (ACE) regulates blood pressure and has been implicated in several conditions including lung injury, fibrosis and Alzheimer's disease. Medicinal mushroom Ganordema lucidum (Reishi) cystathionine beta-synthase (GlCBS) was previously reported to possess ACE inhibitory activities. However, the inhibitory mechanism of CBS protein remains unreported. Therefore, this study integrates in silico sequencing, structural and functional based-analysis, protein modelling, molecular docking and binding affinity calculation to elucidate the inhibitory mechanism of GlCBS and Lignosus rhinocerus (Tiger milk mushroom) CBS protein (LrCBS) towards ACE. In silico analysis indicates that CBSs from both mushrooms share high similarities in terms of physical properties, structural properties and domain distribution. Protein-protein docking analysis revealed that both GlCBS and LrCBS potentially modulate the C-terminal domain of ACE (C-ACE) activity via regulation of chloride activation and/or prevention of substrate entry. GICBS and LrCBS were also shown to interact with ACE at the same region that presumably inhibits the function of ACE.

Relationship of angiotensin converting enzyme (I/D) polymorphism (rs4646994) and coronary heart disease among a male Iraqi population with type 2 diabetes mellitus

BACKGROUND

Insertion deletion (I/D) polymorphism (rs4646994) in the angiotensin-converting enzyme (ACE) has a substantial effect on coronary heart disease (CHD). The amplification of an Alu repetitive element in an intron of the ACE has shown three potential genotypes of I/I and D/D as homozygous, and I/D as heterozygous.

OBJECTIVE

The objective of this study was to investigate the association between the ACE gene polymorphism and CHD among male Iraqi patients with and without type2 diabetes mellitus (T2DM).

METHODS

A case-control study of total 217 male subjects participated in this study, divided into three groups; Group 1 including 86 CHD patients with T2DM, group 2 including 78 CHD patients without T2DM, and group 3 including 53 age and sex-matched healthy individuals (as a control group). Genotyping of ACE (I/D) gene was performed using polymerase chain reaction (PCR) technique.

RESULTS

The II allele was significantly more frequent in CHD patients without T2DM compared to the control population, but not from those patients with T2DM (p < 0.05). Nonetheless, the ID allele was significantly more frequent in each of CHD with T2DM and control populations compared to the CHD without T2DM. The DD allele was significantly more frequent in CHD patients with T2DM compared to each of CHD patients without T2DM and control populations (p < 0.05).

CONCLUSION

We conclude that the D/D and I/D genotypes are implicated as risk factors for development of CHD with T2DM, but not CHD without T2DM among the male Iraqi population. However, larger sample sizes are needed to monitor the CHD patients and to validate this study.

ACE2 and ACE: structure-based insights into mechanism, regulation and receptor recognition by SARS-CoV

Angiotensin converting enzyme (ACE) is well-known for its role in blood pressure regulation via the renin–angiotensin aldosterone system (RAAS) but also functions in fertility, immunity, haematopoiesis and diseases such as obesity, fibrosis and Alzheimer’s dementia. Like ACE, the human homologue ACE2 is also involved in blood pressure regulation and cleaves a range of substrates involved in different physiological processes. Importantly, it is the functional receptor for severe acute respiratory syndrome (SARS)-coronavirus (CoV)-2 responsible for the 2020, coronavirus infectious disease 2019 (COVID-19) pandemic. Understanding the interaction between SARS-CoV-2 and ACE2 is crucial for the design of therapies to combat this disease. This review provides a comparative analysis of methodologies and findings to describe how structural biology techniques like X-ray crystallography and cryo-electron microscopy have enabled remarkable discoveries into the structure–function relationship of ACE and ACE2. This, in turn, has enabled the development of ACE inhibitors for the treatment of cardiovascular disease and candidate therapies for the treatment of COVID-19. However, despite these advances the function of ACE homologues in non-human organisms is not yet fully understood. ACE homologues have been discovered in the tissues, body fluids and venom of species from diverse lineages and are known to have important functions in fertility, envenoming and insect–host defence mechanisms. We, therefore, further highlight the need for structural insight into insect and venom ACE homologues for the potential development of novel anti-venoms and insecticides.

ACE2 in the Era of SARS-CoV-2: Controversies and Novel Perspectives

Angiotensin-converting enzyme 2 (ACE2) is related to ACE but turned out to counteract several pathophysiological actions of ACE. ACE2 exerts antihypertensive and cardioprotective effects and reduces lung inflammation. ACE2 is subjected to extensive transcriptional and post-transcriptional modulation by epigenetic mechanisms and microRNAs. Also, ACE2 expression is regulated post-translationally by glycosylation, phosphorylation, and shedding from the plasma membrane. ACE2 protein is ubiquitous across mammalian tissues, prominently in the cardiovascular system, kidney, and intestine. ACE2 expression in the respiratory tract is of particular interest, in light of the discovery that ACE2 serves as the initial cellular target of severe acute respiratory syndrome (SARS)-coronaviruses, including the recent SARS-CoV2, responsible of the COronaVIrus Disease 2019 (COVID-19). Since the onset of the COVID-19 pandemic, an intense effort has been made to elucidate the biochemical determinants of SARS-CoV2-ACE2 interaction. It has been determined that SARS-CoV2 engages with ACE2 through its spike (S) protein, which consists of two subunits: S1, that mediates binding to the host receptor; S2, that induces fusion of the viral envelope with the host cell membrane and delivery of the viral genome. Owing to the role of ACE2 in SARS-CoV2 pathogenicity, it has been speculated that medical conditions, i.e., hypertension, and/or drugs, i.e., ACE inhibitors and angiotensin receptor blockers, known to influence ACE2 density could alter the fate of SARS-CoV-2 infection. The debate is still open and will only be solved when results of properly designed experimental and clinical investigations will be made public. An interesting observation is, however that, upon infection, ACE2 activity is reduced either by downregulation or by shedding. These events might precipitate the so-called "cytokine storm" that characterizes the most severe COVID-19 forms. As evidence accumulates, ACE2 appears a druggable target in the attempt to limit virus entry and replication. Strategies aimed at blocking ACE2 with antibodies, small molecules or peptides, or at neutralizing the virus by competitive binding with exogenously administered ACE2, are currently under investigations. In this review, we will present an overview of the state-of-the-art knowledge on ACE2 biochemistry and pathophysiology, outlining open issues in the context of COVID-19 disease and potential experimental and clinical developments.

A study in first-episode psychosis patients: does angiotensin I-converting enzyme (ACE) activity associated with genotype predict symptoms severity reductions after treatment with the atypical antipsychotic risperidone?

BACKGROUND

Our previous studies showed increased angiotensin I-converting enzyme (ACE) activity in chronic schizophrenia (SCZ) patients compared to healthy control (HC) volunteers, and the relevance of combining ACE genotype and activity for predicting SCZ was suggested.

METHODS

ACE activity was measured in plasma of ACE insertion/deletion (I/D) genotyped HC volunteers (N = 53) and antipsychotic-naïve first-episode psychosis (FEP) patients (N = 45), assessed at baseline (FEB-B) and also after 2-months (FEP-2M) of treatment with the atypical antipsychotic risperidone.

RESULTS

ACE activity measurements showed significant differences among HC, FEP-B and FEP-2M groups (F = 5.356, df = 2, p = 0.005), as well as between HC and FEP-2M (post-hoc Tukey's multiple comparisons test, p = 0.004). No correlation was observed for ACE activity increases and symptom severity reductions in FEP as assessed by total PANSS (r = -0.131, p = 0.434). FEP subgrouped by ACE I/D genotype showed significant ACE activity increases, mainly in the DD genotype subgroup. No correlation between ACE activity and age was observed in FEP or HC groups separately (r = 0.210, p = 0.392), but ACE activity levels differences observed between these groups were influenced by age.

CONCLUSIONS

The importance of measuring the ACE activity in blood plasma, associated to ACE I/D genotyping to support the follow-up of FEP patients did not show correlation with general symptoms amelioration in the present study. However, new insights into the influence of age and I/D genotype for ACE activity changes in FEP individuals upon treatment was demonstrated.

Cl- as a bona fide signaling ion

Cl^- is the major extracellular (Cl^-_out) and intracellular (Cl^-_in) anion whose concentration is actively regulated by multiple transporters. These transporters generate Cl^- gradients across the plasma membrane and between the cytoplasm and intracellular organelles. [Cl^-]_in changes rapidly in response to cell stimulation and influences many physiological functions, as well as cellular and systemic homeostasis. However, less appreciated is the signaling function of Cl^-. Cl^- interacts with multiple proteins to directly modify their activity. This review highlights the signaling function of Cl^- and argues that Cl^- is a bona fide signaling ion, a function deserving extensive exploration.

Advances in Structural Biology of ACE and Development of Domain Selective ACE-inhibitors

BACKGROUND

The Angiotensin-I converting enzyme (ACE) is one of the most important components of the renin-angiotensin-aldosterone system controlling blood pressure and renal functions. Inhibitors of ACE are first line therapeutics used in the treatment of hypertension and related cardiovascular diseases. Somatic ACE consists of two homologous catalytic domains, the C- and N-domains. Recent findings have shown that although both domains are highly homologous in structure, they may have different physiological functions. The C-domain is primarily involved in the control of blood pressure, in contrast to the N-domain that is engaged in the regulation of hematopoietic stem cell proliferation. The currently available ACE inhibitors have some adverse effects that can be attributed to the non-selective inhibition of both domains. In addition, specific Ndomain inhibitors have emerged as potential antifibrotic drugs. Therefore, ACE is still an important drug target for the development of novel domain-selective drugs not only for the cardiovascular system but also for other systems.

OBJECTIVE

Detailed structural information about interactions in the protein-ligand complex is crucial for rational drug design. This review highlights the structural information available from crystallographic data which is essential for the development of domain selective inhibitors of ACE.

METHODS

Over eighty crystal complexes of ACE are placed into the Protein Database. An overview of X-ray ACE complexes with various inhibitors in C- and N-domains and an analysis of their binding mode have given mechanistic explanation of the structural determinants of selective ligand binding. In addition, ACE domain selective inhibitors with dual modes of action in complexes with ACE are also discussed.

CONCLUSION

Selectivity of ACE inhibitors for the N- and C-domain is controlled by subtle differences in the amino-acids forming the active site. Reported studies of crystal complexes of inhibitors in the C- and N-domains revealed that most selective inhibitors interact with non-conserved amino-acids between domains and have distinct interactions with the residues in the S2 and S2' subsites of the ACE catalytic site. Moreover, unusual binding of the second molecule of inhibitors in the binding cavity opens new possibilities of exploiting more distant regions of the catalytic center in structure-based design of novel drugs.

Simultaneous determination of nine trace concentration angiotensin peptides in human serum using ultra high performance liquid chromatography with tandem mass spectrometry with sephadex LH-20 gel solid-phase extraction

The renin-angiotensin system is a highly complex enzymatic system consisting of multiple peptide hormones, enzymes, and receptors. Here, an assay to simultaneously quantify eight angiotensin peptides and bradykinin in human serum was developed and validated, using ultra high performance liquid chromatography coupled with tandem mass spectrometry. A pre-concentration method of Sephadex LH-20 gel solid-phase extraction was first applied for analysis of angiotensin peptides from serum sample. The triple quadrupole mass spectrometer was operated in the positive ion mode and multiple reaction monitoring was used for drug quantification. The analytical time was within 5 min, much raising the analysis efficiency. Limits of detection ranged from 0.9 to 1.3 pg/mL, and displayed the same level of sensitivity compared with radioimmunoassay. The method was successfully applied to 22 healthy human serum samples, giving the concentrations of angiotensin I, angiotensin II, angiotensin III, angiotensin IV, angiotensin 1-9, angiotensin 1-7, angiotensin 1-5, Asn¹ ,Val⁵ -Angiotensin II, and bradykinin for reference. This novel metabolic profile study of vasoactive peptides based on gel solid-phase extraction concentration provided not only an accurate quantitative assay of the serum concentrations, but also a promising methodology for evaluating the diagnostic values of the various peptides.

Structural analysis of a Vibrio phospholipase reveals an unusual Ser-His-chloride catalytic triad

Phospholipases can disrupt host membranes and are important virulence factors in many pathogens. VvPlpA is a phospholipase A₂ secreted by Vibrio vulnificus and essential for virulence. Its homologs, termed thermolabile hemolysins (TLHs), are widely distributed in Vibrio bacteria, but no structural information for this virulence factor class is available. Herein, we report the crystal structure of VvPlpA to 1.4-Å resolution, revealing that VvPlpA contains an N-terminal domain of unknown function and a C-terminal phospholipase domain and that these two domains are packed closely together. The phospholipase domain adopts a typical SGNH hydrolase fold, containing the four conserved catalytic residues Ser, Gly, Asn, and His. Interestingly, the structure also disclosed that the phospholipase domain accommodates a chloride ion near the catalytic His residue. The chloride is five-coordinated in a distorted bipyramid geometry, accepting hydrogen bonds from a water molecule and the amino groups of surrounding residues. This chloride substitutes for the most common Asp/Glu residue and forms an unusual Ser-His-chloride catalytic triad in VvPlpA. The chloride may orient the catalytic His and stabilize the charge on its imidazole ring during catalysis. Indeed, VvPlpA activity depended on chloride concentration, confirming the important role of chloride in catalysis. The VvPlpA structure also revealed a large hydrophobic substrate-binding pocket that is capable of accommodating a long-chain acyl group. Our results provide the first structure of the TLH family and uncover an unusual Ser-His-chloride catalytic triad, expanding our knowledge on the biological role of chloride.

Angiotensin-converting enzyme activity in Cavalier King Charles Spaniels with an ACE gene polymorphism and myxomatous mitral valve disease

OBJECTIVES

Myxomatous mitral valve disease (MMVD) is the most common heart disease in the dog. It is particularly common in the Cavalier King Charles Spaniel (CKCS) breed and affected dogs are frequently managed with angiotensin-converting enzyme inhibitors (ACE-I). We have previously identified a canine ACE gene polymorphism associated with a decrease in angiotensin-converting enzyme (ACE) activity. The aim of this study was to evaluate for the prevalence of the ACE polymorphism in CKCS with mitral valve disease and to determine whether the presence of the polymorphism is associated with alterations in ACE activity at different stages of cardiac disease.

METHODS

Seventy-three dogs with a diagnosis of mitral valve disease were evaluated and a blood sample was drawn for ACE polymorphism genotyping and ACE activity measurement.

RESULTS

Forty-three dogs were homozygous for the ACE polymorphism; five were heterozygous and 25 were homozygous wild type. The mean age and the median severity of disease were not different for dogs with the polymorphism and dogs with the wild-type sequence. The median baseline ACE activity was significantly lower for the ACE polymorphism (27.0 U/l) than the wild-type sequence dogs (31.0 U/l) (P=0.02). Dogs with more severe disease and the ACE polymorphism had significantly lower levels of ACE activity than dogs with the wild-type sequence (P=0.03).

CONCLUSION

The CKCS appears to have a high prevalence of the ACE variant. Dogs with the ACE variant had lower levels of ACE activity even in more advanced mitral valve disease than dogs without the variant. The clinical significance of this finding and its impact on the need for ACE-I in dogs with the polymorphism and heart disease deserves further study.

Angiotensin converting enzyme 1 in the median preoptic nucleus contributes to chronic intermittent hypoxia hypertension

Obstructive sleep apnea is associated with hypertension and cardiovascular disease. Chronic intermittent hypoxia is used to model the arterial hypoxemia seen in sleep apnea patients and is associated with increased sympathetic nerve activity and a sustained diurnal increase in blood pressure. The renin angiotensin system has been associated with hypertension seen in chronic intermittent hypoxia. Angiotensin converting enzyme 1, which cleaves angiotensin I to the active counterpart angiotensin II, is present within the central nervous system and has been shown to be regulated by AP‐1 transcription factors, such as ΔFosB. Our previous study suggested that this transcriptional regulation in the median preoptic nucleus contributes to the sustained blood pressure seen following chronic intermittent hypoxia. Viral mediated delivery of a short hairpin RNA against angiotensin converting enzyme 1 in the median preoptic nucleus was used along with radio‐telemetry measurements of blood pressure to test this hypothesis. FosB immunohistochemistry was utilized in order to assess the effects of angiotensin converting enzyme 1 knockdown on the activity of nuclei downstream from median preoptic nucleus. Angiotensin converting enzyme 1 knockdown within median preoptic nucleus significantly attenuated the sustained hypertension seen in chronic intermittent hypoxia. Angiotensin converting enzyme 1 seems to be partly responsible for regulating downstream regions involved in sympathetic and blood pressure control, such as the paraventricular nucleus and the rostral ventrolateral medulla. The data suggest that angiotensin converting enzyme 1 within median preoptic nucleus plays a critical role in the sustained hypertension seen in chronic intermittent hypoxia.

Crystal structures of sampatrilat and sampatrilat-Asp in complex with human ACE - a molecular basis for domain selectivity

Angiotensin‐1‐converting enzyme (ACE) is a zinc metallopeptidase that consists of two homologous catalytic domains (known as nACE and cACE) with different substrate specificities. Based on kinetic studies it was previously reported that sampatrilat, a tight‐binding inhibitor of ACE, K_i = 13.8 nm and 171.9 nm for cACE and nACE respectively [Sharma et al., Journal of Chemical Information and Modeling (2016), 56, 2486–2494], was 12.4‐fold more selective for cACE. In addition, samAsp, in which an aspartate group replaces the sampatrilat lysine, was found to be a nonspecific and lower micromolar affinity inhibitor. Here, we report a detailed three‐dimensional structural analysis of sampatrilat and samAsp binding to ACE using high‐resolution crystal structures elucidated by X‐ray crystallography, which provides a molecular basis for differences in inhibitor affinity and selectivity for nACE and cACE. The structures show that the specificity of sampatrilat can be explained by increased hydrophobic interactions and a H‐bond from Glu403 of cACE with the lysine side chain of sampatrilat that are not observed in nACE. In addition, the structures clearly show a significantly greater number of hydrophilic and hydrophobic interactions with sampatrilat compared to samAsp in both cACE and nACE consistent with the difference in affinities. Our findings provide new experimental insights into ligand binding at the active site pockets that are important for the design of highly specific domain selective inhibitors of ACE.

Database

The atomic coordinates and structure factors for N‐ and C‐domains of ACE bound to sampatrilat and sampatrilat‐Asp complexes (6F9V, 6F9R, 6F9T and 6F9U respectively) have been deposited in the Protein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers University, New Brunswick, NJ (http://www.rcsb.org/).

An investigation of the pH dependence of copper-substituted anthrax lethal factor and its mechanistic implications

Anthrax lethal factor (LF) is a zinc-dependent endopeptidase involved in the cleavage of proteins critical to the maintenance of host signaling pathways during anthrax infections. Although zinc is typically regarded as the native metal ion in vivo, LF is highly tolerant to metal substitution, with its replacement by copper yielding an enzyme (CuLF) 4.5-fold more active than the native zinc protein (at pH 7). The current study demonstrates that by careful choice of the buffer, ionic strength, pH and substrate, the activity ratio of CuLF and native LF can be increased to >40-fold. Using a fluorogenic LF substrate, such optimized assay conditions can be exploited to detect LF concentrations as low as 2 pM. In contrast to the zinc form, CuLF was found to be inhibited by bromide and iodide ions, to be resistant to metal loss under acidic conditions, and to display a sharp pH dependence with significantly shifted alkaline limb towards more acidic conditions. The alkaline limb in the enzyme's pH profile is suggested to originate from changes in the protonation state of the metal-bound water molecule which serves as the nucleophile in the catalytic mechanism. Based on these observations and studies on other zinc proteases, a minimal mechanism for LF is proposed.

Isolation, purification and the anti-hypertensive effect of a novel angiotensin I-converting enzyme (ACE) inhibitory peptide from Ruditapes philippinarum fermented with Bacillus natto

A novel ACE inhibitory peptide (Val-Ile-Ser-Asp-Glu-Asp-Gly-Val-Thr-His) with a high anti-hypertensive effect isolated from Ruditapes philippinarum fermented with Bacillus natto.

Many Faces of Renin-angiotensin System - Focus on Eye

The renin-angiotensin system (RAS), that is known for its role in the regulation of blood pressure as well as in fluid and electrolyte homeostasis, comprises dozens of angiotensin peptides and peptidases and at least six receptors. Six central components constitute the two main axes of the RAS cascade. Angiotensin (1-7), an angiotensin converting enzyme 2 and Mas receptor axis (ACE2-Ang(1-7)-MasR) counterbalances the harmful effects of the angiotensin II, angiotensin converting enzyme 1 and angiotensin II type 1 receptor axis (ACE1-AngII-AT1R) Whereas systemic RAS is an important factor in blood pressure regulation, tissue-specific regulatory system, responsible for long term regional changes, that has been found in various organs. In other words, RAS is not only endocrine but also complicated autocrine system. The human eye has its own intraocular RAS that is present e.g. in the structures involved in aqueous humor dynamics. Local RAS may thus be a target in the development of new anti-glaucomatous drugs. In this review, we first describe the systemic RAS cascade and then the local ocular RAS especially in the anterior part of the eye.

Angiotensin Converting Enzyme Regulates Cell Proliferation and Migration

Background

The angiotensin-I converting enzyme (ACE) plays a central role in the renin-angiotensin system, acting by converting the hormone angiotensin-I to the active peptide angiotensin-II (Ang-II). More recently, ACE was shown to act as a receptor for Ang-II, and its expression level was demonstrated to be higher in melanoma cells compared to their normal counterparts. However, the function that ACE plays as an Ang-II receptor in melanoma cells has not been defined yet.

Aim

Therefore, our aim was to examine the role of ACE in tumor cell proliferation and migration.

Results

We found that upon binding to ACE, Ang-II internalizes with a faster onset compared to the binding of Ang-II to its classical AT1 receptor. We also found that the complex Ang-II/ACE translocates to the nucleus, through a clathrin-mediated process, triggering a transient nuclear Ca²⁺ signal. In silico studies revealed a possible interaction site between ACE and phospholipase C (PLC), and experimental results in CHO cells, demonstrated that the β3 isoform of PLC is the one involved in the Ca²⁺ signals induced by Ang-II/ACE interaction. Further studies in melanoma cells (TM-5) showed that Ang-II induced cell proliferation through ACE activation, an event that could be inhibited either by ACE inhibitor (Lisinopril) or by the silencing of ACE. In addition, we found that stimulation of ACE by Ang-II caused the melanoma cells to migrate, at least in part due to decreased vinculin expression, a focal adhesion structural protein.

Conclusion

ACE activation regulates melanoma cell proliferation and migration.

Lysozyme and bilirubin bind to ACE and regulate its conformation and shedding

Angiotensin I-converting enzyme (ACE) hydrolyzes numerous peptides and is a critical participant in blood pressure regulation and vascular remodeling. Elevated tissue ACE levels are associated with increased risk for cardiovascular and respiratory disorders. Blood ACE concentrations are determined by proteolytic cleavage of ACE from the endothelial cell surface, a process that remains incompletely understood. In this study, we identified a novel ACE gene mutation (Arg532Trp substitution in the N domain of somatic ACE) that increases blood ACE activity 7-fold and interrogated the mechanism by which this mutation significantly increases blood ACE levels. We hypothesized that this ACE mutation disrupts the binding site for blood components which may stabilize ACE conformation and diminish ACE shedding. We identified the ACE-binding protein in the blood as lysozyme and also a Low Molecular Weight (LMW) ACE effector, bilirubin, which act in concert to regulate ACE conformation and thereby influence ACE shedding. These results provide mechanistic insight into the elevated blood level of ACE observed in patients on ACE inhibitor therapy and elevated blood lysozyme and ACE levels in sarcoidosis patients.

Insertion/deletion polymorphism in intron 16 of ACE gene in idiopathic recurrent spontaneous abortion: case-control study, systematic review and meta-analysis

The insertion/deletion (I/D) polymorphism in intron 16 of the angiotensin I-converting enzyme gene (ACE) has been extensively studied as a predisposing factor for idiopathic recurrent spontaneous abortion (IRSA). A case-control study including 149 women with ≥3 spontaneous abortions and 149 controls was performed to test the association of ACE I/D polymorphism with IRSA. A systematic review was conducted of previous case-control studies, with strict selection criteria for meta-analyses. We also aimed to evaluate the potential differences in summary estimates between studies defining IRSA as ≥2 and ≥3 spontaneous abortions. Genotyping was performed by PCR, and systematic review conducted using PubMed and Scopus. There was no association of the polymorphism with IRSA in Slovenian women. Sixteen case-control studies, showing substantial differences regarding IRSA definition and selection criteria for women were identified. Meta-analysis was performed and included four studies defining IRSA as ≥2 spontaneous abortions and the current study, which defined IRSA as ≥3 spontaneous abortions. Based on random effects model, meta-analysis conducted on 1192 patients and 736 controls showed no association with IRSA under dominant(DD+IDvsII) and recessive(DDvsID+II) genetic models. Well-designed studies are needed to evaluate the role of ACE I/D polymorphism in IRSA defined as ≥3 spontaneous abortions.

Ocular renin-angiotensin system with special reference in the anterior part of the eye

The renin-angiotensin system (RAS) regulates blood pressure (BP) homeostasis, systemic fluid volume and electrolyte balance. The RAS cascade includes over twenty peptidases, close to twenty angiotensin peptides and at least six receptors. Out of these, angiotensin II, angiotensin converting enzyme 1 and angiotensin II type 1 receptor (AngII-ACE1-AT1R) together with angiotensin (1-7), angiotensin converting enzyme 2 and Mas receptor (Ang(1-7)-ACE2-MasR) are regarded as the main components of RAS. In addition to circulating RAS, local RA-system exists in various organs. Local RA-systems are regarded as tissue-specific regulatory systems accounting for local effects and long term changes in different organs. Many of the central components such as the two main axes of RAS: AngII-ACE1-AT1R and Ang(1-7)-ACE2-MasR, have been identified in the human eye. Furthermore, it has been shown that systemic antihypertensive RAS- inhibiting medications lower intraocular pressure (IOP). These findings suggest the crucial role of RAS not only in the regulation of BP but also in the regulation of IOP, and RAS potentially plays a role in the development of glaucoma and antiglaucomatous drugs.