ACE phenotyping in Gaucher disease

Patients with Gaucher disease display systemic elevation of ACE2, which is impacted by therapy status and genotype

Gaucher disease (GD) has a high carrier rate among Ashkenazi Jews.The most common disease-causing variant in this population N370S, is also prevalent pan-ethnically. This has led to speculations of some protective effect for carriers of this variant. During the recent COVID-19 pandemic, GD patients reportedly had a surprisingly low infection rate and mild symptoms considering their disease status. As SARS-CoV-2 gains entry into the cell via membrane-bound angiotensin-converting enzyme 2 (ACE2), we speculated that differences in levels of soluble ACE2 in GD patients could contribute to this protective state. While ACE is known to be elevated in GD, to our knowledge, ACE2 levels have not been explored. We measured serum and macrophage-bound levels of ACE and ACE2 by ELISA and western blot, respectively, in GD patients and age- and sex-matched controls. Our results reveal a significant elevation of both serum and macrophage-bound ACE and ACE2 in GD patients compared to healthy controls. This elevation appears to be mitigated by GD treatment. Moreover, the most robust ACE2 elevation was observed in N370S homozygotes, and was not effected by treatment. Since coronaviruses use the ACE2 receptor as a gateway for host cell entry, we speculate that elevated circulating ACE2 may serve as a decoy. This might explain the observed mild infections in GD patients during the COVID-19 pandemic.

ACE Phenotyping in Human Blood and Tissues: Revelation of ACE Outliers and Sex Differences in ACE Sialylation

Angiotensin-converting enzyme (ACE) metabolizes a number of important peptides participating in blood pressure regulation and vascular remodeling. Elevated ACE expression in tissues (which is generally reflected by blood ACE levels) is associated with an increased risk of cardiovascular diseases. Elevated blood ACE is also a marker for granulomatous diseases. Decreased blood ACE activity is becoming a new risk factor for Alzheimer's disease. We applied our novel approach-ACE phenotyping-to characterize pairs of tissues (lung, heart, lymph nodes) and serum ACE in 50 patients. ACE phenotyping includes (1) measurement of ACE activity with two substrates (ZPHL and HHL); (2) calculation of the ratio of hydrolysis of these substrates (ZPHL/HHL ratio); (3) determination of ACE immunoreactive protein levels using mAbs to ACE; and (4) ACE conformation with a set of mAbs to ACE. The ACE phenotyping approach in screening format with special attention to outliers, combined with analysis of sequencing data, allowed us to identify patient with a unique ACE phenotype related to decreased ability of inhibition of ACE activity by albumin, likely due to competition with high CCL18 in this patient for binding to ACE. We also confirmed recently discovered gender differences in sialylation of some glycosylation sites of ACE. ACE phenotyping is a promising new approach for the identification of ACE phenotype outliers with potential clinical significance, making it useful for screening in a personalized medicine approach.

Ratiometric fluorescence detection of the angiotensin-converting enzyme via single-excitation and double-emission biomass-derived carbon quantum dots

Efficient and rapid detection of angiotensin-converting enzyme (ACE) activity is important for preventing hypertension and the discovery of new angiotensin-converting enzyme inhibitors (ACEI). In this work, a single-excitation and double-emission biomass-derived carbon quantum dots (CQDs) was prepared and applied for ratiometric fluorescence detection of ACE. Fresh banyan leaves were extracted with ethanol and acetone, and the extracted solution was used as the precursor to produce the carbon quantum dots (BL-CQDs) with single-excitation and double-emission properties. The synthesized BL-CQDs is about 1.7 nm, has a graphene-like structure, contains a variety of hydrophilic functional groups on the surface, and has good fluorescence properties. Its fluorescence intensity ratio (I677/I460) is linear with ACE activity in the range of 0.02-0.8 U l-1. The regression equation is△F=2.5371CACE-0.0311. The method was successfully applied to the determination of ACE activity in pig lung and human serum, and the inhibitory efficiency of the flavonoid extract and captopril tablets on ACE activity was also investigated, which can be applied to the screening of ACEI. The survival rate and fluorescence imaging of Bel-7404 cells under the condition of high concentration BL-CQDs showed BL-CQDs had low cytotoxicity and good biocompatibility. These results indicate that the BL-CQDs can be used as an excellent fluorescent probe, providing a new method for screening ACE activity and plant-derived ACEI.

Macrophage angiotensin-converting enzyme reduces atherosclerosis by increasing peroxisome proliferator-activated receptor α and fundamentally changing lipid metabolism

AIMS

The metabolic failure of macrophages to adequately process lipid is central to the aetiology of atherosclerosis. Here, we examine the role of macrophage angiotensin-converting enzyme (ACE) in a mouse model of PCSK9-induced atherosclerosis.

METHODS AND RESULTS

Atherosclerosis in mice was induced with AAV-PCSK9 and a high-fat diet. Animals with increased macrophage ACE (ACE 10/10 mice) have a marked reduction in atherosclerosis vs. WT mice. Macrophages from both the aorta and peritoneum of ACE 10/10 express increased PPARα and have a profoundly altered phenotype to process lipids characterized by higher levels of the surface scavenger receptor CD36, increased uptake of lipid, increased capacity to transport long chain fatty acids into mitochondria, higher oxidative metabolism and lipid β-oxidation as determined using 13C isotope tracing, increased cell ATP, increased capacity for efferocytosis, increased concentrations of the lipid transporters ABCA1 and ABCG1, and increased cholesterol efflux. These effects are mostly independent of angiotensin II. Human THP-1 cells, when modified to express more ACE, increase expression of PPARα, increase cell ATP and acetyl-CoA, and increase cell efferocytosis.

CONCLUSION

Increased macrophage ACE expression enhances macrophage lipid metabolism, cholesterol efflux, efferocytosis, and it reduces atherosclerosis. This has implications for the treatment of cardiovascular disease with angiotensin II receptor antagonists vs. ACE inhibitors.

Urinary ACE Phenotyping as a Research and Diagnostic Tool: Identification of Sex-Dependent ACE Immunoreactivity

BACKGROUND

Angiotensin-converting enzyme (ACE) is highly expressed in renal proximal tubules, but ACE activity/levels in the urine are at least 100-fold lower than in the blood. Decreased proximal tubular ACE has been associated with renal tubular damage in both animal models and clinical studies. Because ACE is shed into urine primarily from proximal tubule epithelial cells, its urinary ACE measurement may be useful as an index of tubular damage.

OBJECTIVE AND METHODOLOGY

We applied our novel approach-ACE phenotyping-to characterize urinary ACE in volunteer subjects. ACE phenotyping includes (1) determination of ACE activity using two substrates (ZPHL and HHL); (2) calculation of the ratio of hydrolysis of the two substrates (ZPHL/HHL ratio); (3) quantification of ACE immunoreactive protein levels; and (4) fine mapping of local ACE conformation with mAbs to ACE.

PRINCIPAL FINDINGS

In normal volunteers, urinary ACE activity was 140-fold less than in corresponding plasma/serum samples and did not differ between males and females. However, urinary ACE immunoreactivity (normalized binding of 25 mAbs to different epitopes) was strongly sex-dependent for the several mAbs tested, an observation likely explained by differences in tissue ACE glycosylation/sialylation between males and females. Urinary ACE phenotyping also allowed the identification of ACE outliers. In addition, daily variability of urinary ACE has potential utility as a feedback marker for dieting individuals pursuing weight loss.

CONCLUSIONS/SIGNIFICANCE

Urinary ACE phenotyping is a promising new approach with potential clinical significance to advance precision medicine screening techniques.

Petukhov P, Kurilova OV, Ilinsky VV, Trakhtman PE, Dadali EL, Samokhodskaya LM, Kamalov AA, Kost OA. Blood ACE Phenotyping for Personalized Medicine: Revelation of Patients with Conformationally Altered ACE

Background: The angiotensin-converting enzyme (ACE) metabolizes a number of important peptides participating in blood pressure regulation and vascular remodeling. Elevated blood ACE is a marker for granulomatous diseases and elevated ACE expression in tissues is associated with increased risk of cardiovascular diseases. Objective and Methodology: We applied a novel approach -ACE phenotyping-to find a reason for conformationally impaired ACE in the blood of one particular donor. Similar conformationally altered ACEs were detected previously in 2-4% of the healthy population and in up to 20% of patients with uremia, and were characterized by significant increase in the rate of angiotensin I hydrolysis. Principal findings: This donor has (1) significantly increased level of endogenous ACE inhibitor in plasma with MW less than 1000; (2) increased activity toward angiotensin I; (3) M71V mutation in ABCG2 (membrane transporter for more than 200 compounds, including bilirubin). We hypothesize that this patient may also have the decreased level of free bilirubin in plasma, which normally binds to the N domain of ACE. Analysis of the local conformation of ACE in plasma of patients with Gilbert and Crigler-Najjar syndromes allowed us to speculate that binding of mAbs 1G12 and 6A12 to plasma ACE could be a natural sensor for estimation of free bilirubin level in plasma. Totally, 235 human plasma/sera samples were screened for conformational changes in soluble ACE. Conclusions/Significance: ACE phenotyping of plasma samples allows us to identify individuals with conformationally altered ACE. This type of screening has clinical significance because this conformationally altered ACE could not only result in the enhancement of the level of angiotensin II but could also serve as an indicator of free bilirubin levels.

Glucosylsphingosine (Lyso-Gb1) as a reliable biomarker in Gaucher disease: a narrative review

BACKGROUND

Gaucher disease (GD) is a rare, inherited, autosomal recessive disorder caused by a deficiency of the lysosomal enzyme, acid β-glucosidase. Its diagnosis is achieved via measurements of acid β-glucosidase activity in either fresh peripheral blood leukocytes or dried blood spots, and confirmed by identifying characteristic mutations in the GBA1 gene. Currently, several biomarkers are available for disease monitoring. Chitotriosidase has been used over the last 20 years to assess the severity of GD, but lacks specificity in GD patients. Conversely, the deacylated form of glucosylceramide, glucosylsphingosine (also known as lyso-Gb1), represents a more reliable biomarker characterized by its high sensitivity and specificity in GD.

MAIN TEXT

Herein, we review the current literature on lyso-Gb1 and describe evidence supporting its usefulness as a biomarker for diagnosing and evaluating disease severity in GD and monitoring treatment efficacy.

CONCLUSION

Lyso-Gb1 is the most promising biomarker of GD, as demonstrated by its reliability in reflecting disease burden and monitoring treatment response. Furthermore, lyso-Gb1 may play an important role in the onset of monoclonal gammopathy of uncertain significance, multiple myeloma, and Parkinson's disease in GD patients.

Patient centered guidelines for the laboratory diagnosis of Gaucher disease type 1

Gaucher disease (GD) is an autosomal recessive lysosomal storage disorder due to the deficient activity of the acid beta-glucosidase (GCase) enzyme, resulting in the progressive lysosomal accumulation of glucosylceramide (GlcCer) and its deacylated derivate, glucosylsphingosine (GlcSph). GCase is encoded by the GBA1 gene, located on chromosome 1q21 16 kb upstream from a highly homologous pseudogene. To date, more than 400 GBA1 pathogenic variants have been reported, many of them derived from recombination events between the gene and the pseudogene. In the last years, the increased access to new technologies has led to an exponential growth in the number of diagnostic laboratories offering GD testing. However, both biochemical and genetic diagnosis of GD are challenging and to date no specific evidence-based guidelines for the laboratory diagnosis of GD have been published. The objective of the guidelines presented here is to provide evidence-based recommendations for the technical implementation and interpretation of biochemical and genetic testing for the diagnosis of GD to ensure a timely and accurate diagnosis for patients with GD worldwide. The guidelines have been developed by members of the Diagnostic Working group of the International Working Group of Gaucher Disease (IWGGD), a non-profit network established to promote clinical and basic research into GD for the ultimate purpose of improving the lives of patients with this disease. One of the goals of the IWGGD is to support equitable access to diagnosis of GD and to standardize procedures to ensure an accurate diagnosis. Therefore, a guideline development group consisting of biochemists and geneticists working in the field of GD diagnosis was established and a list of topics to be discussed was selected. In these guidelines, twenty recommendations are provided based on information gathered through a systematic review of the literature and two different diagnostic algorithms are presented, considering the geographical differences in the access to diagnostic services. Besides, several gaps in the current diagnostic workflow were identified and actions to fulfill them were taken within the IWGGD. We believe that the implementation of recommendations provided in these guidelines will promote an equitable, timely and accurate diagnosis for patients with GD worldwide.

An observational study to investigate the relationship between plasma glucosylsphingosine (lyso-Gb1) concentration and treatment outcomes of patients with Gaucher disease in Japan

BACKGROUND

Gaucher disease (GD) is an autosomal recessive disease caused by GBA1 mutations resulting in glucosylceramide accumulation in macrophages. GD is characterized by hepatosplenomegaly, anemia, thrombocytopenia, bone complications, and neurological complications. Glucosylsphingosine (lyso-Gb1), a deacylated form of glucosylceramide, has been identified as a promising biomarker for the diagnosis and treatment response in GD. The aim of this study was to examine the relationship between plasma lyso-Gb1 and therapeutic goals for GD (improvements in hepatomegaly, splenomegaly, anemia, thrombocytopenia, bone pain, and bone crisis), as well as disease type and GBA1 mutation type, in Japanese patients with GD receiving velaglucerase alfa, an enzyme replacement therapy (ERT). Furthermore, this study compared the plasma lyso-Gb1 concentration observed in Japanese patients included in this study with that observed in a previous non-Japanese clinical study.

RESULTS

This non-interventional, open-label, multicenter observational cohort study (October 2020 to March 2021) included a total of 20 patients (of any age) with GD (type 1: n = 8; type 2: n = 9; type 3: n = 3) treated with velaglucerase alfa for ≥ 3 months. Median (minimum-maximum) duration of velaglucerase alfa treatment was 49.5 (3-107) months. A total of 14 (70.0%) patients achieved all therapeutic goals (i.e., 100% achievement; improvements in hepatomegaly, splenomegaly, anemia, thrombocytopenia, bone pain, and bone crisis). Overall, median (minimum-maximum) lyso-Gb1 concentration was 24.3 (2.1-150) ng/mL. Although not statistically significant, numerically lower plasma lyso-Gb1 concentrations were observed in patients with 100% achievement compared with those without; no statistically significant difference in plasma lyso-Gb1 concentration was observed between patients with different disease type or mutation type. Furthermore, lyso-Gb1 concentrations observed in Japanese patients were numerically lower than that observed in a previous study of non-Japanese patients with GD receiving ERT.

CONCLUSIONS

In this study, high achievement rates of therapeutic goals with low lyso-Gb1 concentration were observed, demonstrating a correlation between therapeutic goals and lower plasma lyso-Gb1 concentration in Japanese patients with GD treated with velaglucerase alfa. This study further suggests that plasma lyso-Gb1 concentration may be a useful biomarker for treatment response in patients with GD.

Predictive potential of ACE phenotyping in extrapulmonary sarcoidosis

Elevated ACE expression in tissues (reflected by blood ACE levels) is associated with increased risk of cardiovascular diseases and is also a marker for granulomatous diseases. We developed a new approach for characterization of ACE status in the blood—ACE phenotyping and established normal values of ACE levels 50–150% of control pooled plasma. ACE phenotyping was performed in citrated plasma of 120 patients with known interstitial lung diseases. In the 1st set of 100 patients we found 22 patients with ACE levels > 150%; ACE phenotyping also objectively identified the presence of ACE inhibitors in the plasma of 15 patients. After excluding these patients and patient with ACE mutation that increases ACE shedding, 17 patients were identified as a suspicious for systemic sarcoidosis based on elevation of blood ACE (> 150% of mean). A new parameter that we have established–ACE immunoreactivity (with mAb 9B9)—allowed us to detect 22 patients with decreased values (< 80%) of this parameter, which may indicate the presence of ACE in the blood that originates from macrophages/dendritic cells of granulomas. In the remaining 20 patients, this new parameter (mAbs binding/activity ratio) was calculated using 3 mAbs (9B9, 3A5 and i1A8—having overlapping epitopes), and 8 patients were identified as having decreases in this parameter, thus increasing dramatically the sensitivity for detection of patients with systemic sarcoidosis. Whole body PET scan confirmed extrapulmonary granulomas in some patients with lower immunoreactivity towards anti-ACE mAbs. ACE phenotyping has novel potential to noninvasively detect patients with systemic sarcoidosis.

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.

Human Angiotensin I-Converting Enzyme Produced by Different Cells: Classification of the SERS Spectra with Linear Discriminant Analysis

Angiotensin I-converting enzyme (ACE) is a peptidase widely presented in human tissues and biological fluids. ACE is a glycoprotein containing 17 potential N-glycosylation sites which can be glycosylated in different ways due to post-translational modification of the protein in different cells. For the first time, surface-enhanced Raman scattering (SERS) spectra of human ACE from lungs, mainly produced by endothelial cells, ACE from heart, produced by endothelial heart cells and miofibroblasts, and ACE from seminal fluid, produced by epithelial cells, have been compared with full assignment. The ability to separate ACEs’ SERS spectra was demonstrated using the linear discriminant analysis (LDA) method with high accuracy. The intervals in the spectra with maximum contributions of the spectral features were determined and their contribution to the spectrum of each separate ACE was evaluated. Near 25 spectral features forming three intervals were enough for successful separation of the spectra of different ACEs. However, more spectral information could be obtained from analysis of 50 spectral features. Band assignment showed that several features did not correlate with band assignments to amino acids or peptides, which indicated the carbohydrate contribution to the final spectra. Analysis of SERS spectra could be beneficial for the detection of tissue-specific ACEs.

Quantitation of a Urinary Profile of Biomarkers in Gaucher Disease Type 1 Patients Using Tandem Mass Spectrometry

Gaucher disease is a rare inherited disorder caused by a deficiency of the lysosomal acid beta-glucocerebrosidase enzyme. Metabolomic studies by our group targeted several new potential urinary biomarkers. Apart from lyso-Gb₁, these studies highlighted lyso-Gb₁ analogs −28, −26, −12 (A/B), +2, +14, +16 (A/B), +30, and +32 Da, and polycyclic lyso-Gb₁ analogs 362, 366, 390, and 394 Da. The main objective of the current study was to develop and validate a robust UPLC-MS/MS method to study the urine distribution of these biomarkers in patients. Method: Urine samples were purified using solid-phase extraction. A 12 min UPLC-MS/MS method was developed. Results: Validation assays revealed high precision and accuracy for creatinine and lyso-Gb₁. Most lyso-Gb₁ analogs had good recovery rates and high intra- and interday precision assays. Biomarker-estimated LOD and LOQ levels ranged from 56–109 pM to 186–354 pM, respectively. Comparison between GD patients and healthy controls showed significant differences in most biomarker levels. Typically, treated GD patients presented lower biomarker levels compared to untreated patients. Conclusions: These data suggest that the metabolites investigated might be interesting GD biomarkers. More studies with a larger cohort of patients will be needed to better understand the clinical significance of these GD biomarkers.

Gaucher Disease for Hematologists

Gaucher disease (GD) is a rare hereditary lysosomal storage disease that arises due to deficiency of glucocerebrosidase. Early diagnosis is very important for starting proper treatment and preventing complications. Splenomegaly, anemia, and thrombocytopenia are the most common findings in GD and so most patients are initially referred to hematologists. The Turkish Society of Hematology established its Rare Hematological Diseases Subcommittee in 2015. One of the main topics of this subcommittee was to increase and improve awareness and education of rare diseases among hematologists in Turkey. This review presents GD with an overview of its clinical features, pathophysiology, and treatment options for hematologists.

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.

Gaucher disease: an update

Gaucher disease is a lysosomal storage disease affecting the bone marrow, spleen, liver, and nervous system. In Romania we follow up over 70 adult patients with Gaucher disease, who benefit from fully covered therapy. There is a need to screen for Gaucher disease, to diagnose early the condition and to use the best available therapy. This is a review of recent studies on Gaucher disease and is dedicated to trainees in medicine.

Epitope mapping of novel monoclonal antibodies to human angiotensin I-converting enzyme

Angiotensin I-converting enzyme (ACE, CD143) plays a crucial role in blood pressure regulation, vascular remodeling, and immunity. A wide spectrum of mAbs to different epitopes on the N and C domains of human ACE have been generated and used to study different aspects of ACE biology, including establishing a novel approach-conformational fingerprinting. Here we characterized a novel set of 14 mAbs, developed against human seminal fluid ACE. The epitopes for these novel mAbs were defined using recombinant ACE constructs with truncated N and C domains, species cross-reactivity, ACE mutagenesis, and competition with the previously mapped anti-ACE mAbs. Nine mAbs recognized regions on the N domain, and 5 mAbs-on the C domain of ACE. The epitopes for most of these novel mAbs partially overlap with epitopes mapped onto ACE by the previously generated mAbs, whereas mAb 8H1 recognized yet unmapped region on the C domain where three ACE mutations associated with Alzheimer's disease are localized and is a marker for ACE mutation T877M. mAb 2H4 could be considered as a specific marker for ACE in dendritic cells. This novel set of mAbs can identify even subtle changes in human ACE conformation caused by tissue-specific glycosylation of ACE or mutations, and can detect human somatic and testicular ACE in biological fluids and tissues. Furthermore, the high reactivity of these novel mAbs provides an opportunity to study changes in the pattern of ACE expression or glycosylation in different tissues, cells, and diseases, such as sarcoidosis and Alzheimer's disease.

Interstitial lung disease in lysosomal storage disorders

Lysosomes are intracellular organelles that are responsible for degrading and recycling macromolecules. Lysosomal storage diseases (LSDs) are a group of inherited diseases caused by mutations affecting genes that encode the function of the lysosomal enzymes. Three LSDs are associated with lung involvement and/or interstitial lung disease (ILD): Gaucher disease (GD); Niemann-Pick disease, also known as acid sphingomyelinase deficiency (ASMD); and Fabry disease (FD). In GD and in ASMD, analysis of bronchoalveolar lavage fluid and lung biopsy can be informative, showing foamy cells. In GD, ILD is rare. Enzyme replacement therapy (ERT) has been available since 1991 and has greatly changed the natural history of GD, with pulmonary failure and death reported before the ERT era. In ASMD, ILD is frequent and is usually associated with spleen enlargement, low platelet cell count and low level of high-density lipoprotein-cholesterol. Results of ERT are promising regarding preliminary results of olipudase alfa in paediatric and adult ASMD populations. The most frequent respiratory manifestation in FD is COPD-like symptoms regardless of smoking habit and dyspnoea due to congestive heart failure. Early diagnosis of these three LSDs is crucial to prevent irreversible organ damage. Early initiation of ERT can, at least in part, prevent organ failure.

ACE overexpression in myeloid cells increases oxidative metabolism and cellular ATP

Angiotensin-converting enzyme (ACE) affects blood pressure. In addition, ACE overexpression in myeloid cells increases their immune function. Using MS and chemical analysis, we identified marked changes of intermediate metabolites in ACE-overexpressing macrophages and neutrophils, with increased cellular ATP (1.7-3.0-fold) and Krebs cycle intermediates, including citrate, isocitrate, succinate, and malate (1.4-3.9-fold). Increased ATP is due to ACE C-domain catalytic activity; it is reversed by an ACE inhibitor but not by an angiotensin II AT1 receptor antagonist. In contrast, macrophages from ACE knockout (null) mice averaged only 28% of the ATP levels found in WT mice. ACE overexpression does not change cell or mitochondrial size or number. However, expression levels of the electron transport chain proteins NDUFB8 (complex I), ATP5A, and ATP5β (complex V) are significantly increased in macrophages and neutrophils, and COX1 and COX2 (complex IV) are increased in macrophages overexpressing ACE. Macrophages overexpressing ACE have increased mitochondrial membrane potential (24% higher), ATP production rates (29% higher), and maximal respiratory rates (37% higher) compared with WT cells. Increased cellular ATP underpins increased myeloid cell superoxide production and phagocytosis associated with increased ACE expression. Myeloid cells overexpressing ACE indicate the existence of a novel pathway in which myeloid cell function can be enhanced, with a key feature being increased cellular ATP.

Overexpression of ACE in Myeloid Cells Increases Immune Effectiveness and Leads to a New Way of Considering Inflammation in Acute and Chronic Diseases

PURPOSE OF REVIEW

To review recent studies exploring how myeloid cell overexpression of angiotensin-converting enzyme (ACE) affects the immune response and to formulate an approach for considering the effectiveness of inflammation in cardiovascular disease RECENT FINDINGS: While it is widely appreciated that the renin-angiotensin system affects aspects of inflammation through the action of angiotensin II, new studies reveal a previously unknown role of ACE in myeloid cell biology. This was apparent from analysis of two mouse lines genetically modified to overexpress ACE in monocytes/macrophages or neutrophils. Cells overexpressing ACE demonstrated an increased immune response. For example, mice with increased macrophage ACE expression have increased resistance to melanoma, methicillin-resistant Staphylococcus aureus, a mouse model of Alzheimer's disease, and ApoE-knockout-induced atherosclerosis. These data indicate the profound effect of increasing myeloid cell function. Further, they suggest that an appropriate way to evaluate inflammation in both acute and chronic diseases is to ask whether the inflammatory infiltrate is sufficient to eliminate the immune challenge. The expression of ACE by myeloid cells induces a heightened immune response by these cells. The overexpression of ACE is associated with immune function beyond that possible by wild type (WT) myeloid cells. A heightened immune response effectively resolves disease in a variety of acute and chronic models of disease including models of Alzheimer's disease and atherosclerosis.

Tissue ACE phenotyping in lung cancer

Background

Pulmonary vascular endothelium is the main metabolic site for Angiotensin I-Converting Enzyme (ACE)-mediated degradation of several biologically-active peptides (angiotensin I, bradykinin, hemo-regulatory peptide Ac-SDKP). Primary lung cancer growth and lung cancer metastases decrease lung vascularity reflected by dramatic decreases in both lung and serum ACE activity. We performed precise ACE phenotyping in tissues from subjects with lung cancer.

Methodology

ACE phenotyping included: 1) ACE immunohistochemistry with specific and well-characterized monoclonal antibodies (mAbs) to ACE; 2) ACE activity measurement with two ACE substrates (HHL, ZPHL); 3) calculation of ACE substrates hydrolysis ratio (ZPHL/HHL ratio); 4) the pattern of mAbs binding to 17 different ACE epitopes to detect changes in ACE conformation induced by tumor growth (conformational ACE fingerprint).

Results

ACE immunostaining was dramatically decreased in lung cancer tissues confirmed by a 3-fold decrease in ACE activity. The conformational fingerprint of ACE from tumor lung tissues differed from normal lung (6/17 mAbs) and reflected primarily higher ACE sialylation. The increase in ZPHL/HHL ratio in lung cancer tissues was consistent with greater conformational changes of ACE. Limited analysis of the conformational ACE fingerprint in normal lung tissue and lung cancer tissue form the same patient suggested a remote effect of tumor tissue on ACE conformation and/or on “field cancerization” in a morphologically-normal lung tissues.

Conclusions/Significance

Local conformation of ACE is significantly altered in tumor lung tissues and may be detected by conformational fingerprinting of human ACE.

Tissue ACE phenotyping in prostate cancer

Epithelial cells of prostate express significant level of ACE and, as a result, seminal fluid has 50-fold more ACE than plasma. The substitution of highly specialized prostate epithelial cells by tumor cells results in dramatic decrease in ACE production in prostate tissues. We performed detailed characterization of ACE status in prostate tissues from patients with benign prostate hyperplasia (BPH) and prostate cancer (PC) using new approach- ACE phenotyping, that includes evaluation of: 1) ACE activity with two substrates (HHL and ZPHL); 2) the ratio of the rates of their hydrolysis (ZPHL/HHL ratio); 3) the ratio of immunoreactive ACE protein to ACE activity; 4) the pattern of mAbs binding to different epitopes on ACE – ACE conformational fingerprint - to reveal conformational changes in prostate ACE due to prostate pathology. ACE activity dramatically decreased and the ratio of immunoreactive ACE protein to ACE activity increased in PC tissues. The catalytic parameter, ZPHL/HHL ratio, increased in prostate tissues from all patients with PC, but was did not change for most |BPH patients. Nevertheless, prostate tissues of several patients diagnosed with BPH based on histology, also demonstrated decreased ACE activity and increased immunoreactive ACE protein/ACE activity and ZPHL/HHL ratios, that could be considered as more early indicators of prostate cancer development than routine histology. Thus, ACE phenotyping of prostate biopsies has a potential to be an effective approach for early diagnostics of prostate cancer or at least for differential diagnostics of BPH and PC.

Conformational fingerprint of blood and tissue ACEs: Personalized approach

Background

The pattern of binding of monoclonal antibodies (mAbs) to 18 epitopes on human angiotensin I-converting enzyme (ACE)–“conformational fingerprint of ACE”–is a sensitive marker of subtle conformational changes of ACE due to mutations, different glycosylation in various cells, the presence of ACE inhibitors and specific effectors, etc.

Methodology/Principal findings

We described in detail the methodology of the conformational fingerprinting of human blood and tissue ACEs that allows detecting differences in surface topography of ACE from different tissues, as well detecting inter-individual differences. Besides, we compared the sensitivity of the detection of ACE inhibitors in the patient’s plasma using conformational fingerprinting of ACE (with only 2 mAbs to ACE, 1G12 and 9B9) and already accepted kinetic assay and demonstrated that the mAbs-based assay is an order of magnitude more sensitive. This approach is also very effective in detection of known (like bilirubin and lysozyme) and still unknown ACE effectors/inhibitors which nature and set could vary in different tissues or different patients.

Conclusions/Significance

Phenotyping of ACE (and conformational fingerprinting of ACE as a part of this novel approach for characterization of ACE) in individuals really became informative and clinically relevant. Appreciation (and counting on) of inter-individual differences in ACE conformation and accompanying effectors make the application of this approach for future personalized medicine with ACE inhibitors more accurate. This (or similar) methodology can be applied to any enzyme/protein for which there is a number of mAbs to its different epitopes.