Changes In Angiotensin-converting Enzyme Research Articles

Investigation of the Interaction Between Angiotensin-Converting Enzyme (ACE) and ACE-Inhibitory Tripeptide from Casein.

Angiotensin-converting enzyme (ACE) inhibitory peptides exhibit antihypertensive effects by inhibiting ACE activity, and the study of the interaction between ACEs and inhibitory peptides is important for exploring new therapeutic strategies. In this study, the ACE-inhibitory peptide isolated from casein hydrolysate with the amino acid sequence Leu-Leu-Tyr (LLY) exhibited high ACE-inhibitory activity and stability, which holds significant implications for biochemistry and pharmaceutical applications. Furthermore, systematic investigations were conducted on the interaction between ACE and LLY through various approaches. The Lineweaver-Burk plot indicated the non-competitive inhibition pattern of LLY, suggesting that it binds to the enzyme at the non-active site, and the results were further validated by a molecular docking study. Additionally, multispectral experiments and atomic force microscopy were conducted to further elucidate the underlying mechanism of peptide activity. The findings indicated that LLY could induce a conformational change in ACE, thereby inhibiting its activity. This study contributes to a deeper understanding of the mechanism of action of ACE-inhibitory peptides and bears important significance for drug development in hypertension.

Alterations of whole body glucose metabolism in a feline SARS-CoV-2 infection model.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been especially devastating to patients with comorbidities, including metabolic and cardiovascular diseases. Elevated blood glucose during SARS-CoV-2 infection increased mortality of patients with COVID-19, although the mechanisms are not well understood. It has been previously demonstrated that glucose transport and utilization is a crucial pathway for other highly infectious RNA viruses. Thus, we hypothesized that SARS-CoV-2 infection could lead to alterations in cellular and whole body glucose metabolism. Specific pathogen-free domestic cats were intratracheally inoculated with USA-WA1/2020 (wild-type) SARS-CoV-2 or vehicle-inoculated, then euthanized at 4- and 8-days postinoculation (dpi). Blood glucose and cortisol concentrations were elevated at 4 and 8 dpi. Blood ketones, insulin, and angiotensin II concentrations remained unchanged throughout the experimental timeline. SARS-CoV-2 RNA was detected in the lung and heart, without changes in angiotensin-converting enzyme 2 (ACE2) RNA expression. In the lung, SARS-CoV-2 infection increased glucose transporter 1 (GLUT1) protein levels at 4 and 8 dpi, whereas GLUT4 level was only upregulated at 8 dpi. In the heart, GLUT-1 and -4 protein levels remained unchanged. Furthermore, GLUT1 level was upregulated in the skeletal muscle at 8 dpi, and AMPK was activated in the hearts of infected cats. SARS-CoV-2 infection increased blood glucose concentration and pulmonary GLUT protein levels. These findings suggest that SARS-CoV-2 infection induces metabolic reprogramming primarily in the lung to support viral replication. Furthermore, this translational feline model mimicked human COVID-19 and could be used to explore novel therapeutic targets to treat metabolic disease during SARS-CoV-2 infection.NEW & NOTEWORTHY Our study on a feline model of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, mirroring human COVID-19, revealed alterations in whole body and cellular glucose metabolism. Infected cats developed mild hyperglycemia, increased protein levels of glucose transporters in the lung, and AMPK activation in the heart. These findings suggest that SARS-CoV-2 infection induces metabolic reprogramming in the cardiorespiratory system to support viral replication. Understanding these mechanisms could lead to novel antiviral therapeutic strategies.

MicroRNA-185 Inhibits SARS-CoV-2 Infection through the Modulation of the Host's Lipid Microenvironment.

With the emergence of the novel betacoronavirus Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), there has been an urgent need for the development of fast-acting antivirals, particularly in dealing with different variants of concern (VOC). SARS-CoV-2, like other RNA viruses, depends on host cell machinery to propagate and misregulate metabolic pathways to its advantage. Herein, we discovered that the immunometabolic microRNA-185 (miR-185) restricts SARS-CoV-2 propagation by affecting its entry and infectivity. The antiviral effects of miR-185 were studied in SARS-CoV-2 Spike protein pseudotyped virus, surrogate virus (HCoV-229E), as well as live SARS-CoV-2 virus in Huh7, A549, and Calu-3 cells. In each model, we consistently observed microRNA-induced reduction in lipid metabolism pathways-associated genes including SREBP2, SQLE, PPARG, AGPAT3, and SCARB1. Interestingly, we also observed changes in angiotensin-converting enzyme 2 (ACE2) levels, the entry receptor for SARS-CoV-2. Taken together, these data show that miR-185 significantly restricts host metabolic and other pathways that appear to be essential to SAR-CoV-2 replication and propagation. Overall, this study highlights an important link between non-coding RNAs, immunometabolic pathways, and viral infection. miR-185 mimics alone or in combination with other antiviral therapeutics represent possible future fast-acting antiviral strategies that are likely to be broadly antiviral against multiple variants as well as different virus types of potential pandemics.

Gaussian Accelerated Molecular Dynamics Simulations Investigation on the Mechanism of Angiotensin-Converting Enzyme (ACE) C-Domain Inhibition by Dipeptides.

Angiotensin-converting enzyme (ACE)-inhibitory peptides extracted from food proteins can lower blood pressure by inhibiting ACE activity. A recent study showed that the inhibitory activity of IY (Ile-Tyr, a dipeptide derived from soybean protein) against ACE was much higher than that of LL (Leu-Leu), although they had similar hydrophobic and predicted activity values. It was difficult to reveal the deep molecular mechanism underlying this phenomenon by traditional experimental methods. The Apo and two complex systems (i.e., ACE–LL and ACE–IY) were therefore subjected to 1 μs long Gaussian accelerated molecular dynamics (GaMD) simulations. The results showed that the binding of IY can cause obvious contraction of the active site of ACE, mainly manifested by a significant lateral shift of α13, α14, and α15. In addition, hinge 2 and hinge 3 were more stable in the ACE–IY system, while these phenomena were not present in the ACE–LL system. Moreover, the α10 of the IY-bound ACE kept an inward state during the simulation progress, which facilitated the ACE to remain closed. However, for the LL-bound ACE, the α10 switched between two outward states. To sum up, our study provides detailed insights into inhibitor-induced conformational changes in ACE that may help in the design of specific inhibitors targeting ACE for the treatment of hypertension.

The Risk of COVID-19 in People Having a Particular Set of Gene

These risk factors of advancing age, male gender and co-existing health conditions like cancer, cardiovascular diseases, diabetes and obesity do not fully explain why some people have no or mild symptoms whereas others have severe symptoms. Genomewide association study (GWAS) identify a 3p21.31 gene cluster as a genetic susceptibility locus in patients with COVID-19 with respiratory failure. They also found a higher risk among persons with blood group A and protective effect for blood group O than among patients with other blood groups. The particular haplotype in a region of chromosome 3 is contributed to modern humans by neandertals. Another Neanderthal haplotype on chromosome 12 is associated with a 22% reduction in relative risk of becoming severely ill with COVID-19. The ApoE e4e4 homozygous genotype was found to increase the risk of severe COVID-19. Change in angiotensin converting enzyme (ACE) 2 gene was also found to be associated with increased risk of COVID-19, cardiovascular and pulmonary conditions.

Integrated Bioinformatics Analysis Reveals Key Candidate Genes and Cytokine Pathways Involved in COVID-19 After Rhinovirus Infection in Asthma Patients

BackgroundRhinovirus (RV) is the most common pathogen involved in asthma, and COVID-19, caused by SARS-COV-2, may be more severe in asthma patients. Here, we applied integrated bioinformatics to identify potential key genes and cytokine pathways after RV infection in asthma, and analyzed changes in angiotensin-converting enzyme 2 (ACE2), the cellular receptor of SARS-COV-2.Material/MethodsThe gene expression profile dataset GSE149273 was downloaded from NCBI-GEO, which included 90 samples of non-infected, RVA, and RVC. Differentially expressed genes (DEGs) were identified using t tests in the limma R package, and subsequently investigated by GO, KEGG, and DO analysis. Moreover, the expression of ACE2 and the proportion of immune cells were further analyzed to determine the effects of RV on cytokines.ResultsA total of 555 DEGs of RVA and 421 of RVC were identified. There were 415 DEGs in RVA and RVC, of which 406 were upregulated and 9 were downregulated. The functional enrichment analysis showed that most DEGs were obviously enriched in cytokines, and were mainly enriched in “influenza” and “hepatitis C, chronic”. In addition, the expression of ACE2 increased significantly and the proportion of immune cytokines significantly changed after RV infection. Our results suggest that RV can activate the cytokine pathway associated with COVID-19 by increasing ACE2.ConclusionsThe DEGs and related cytokine pathways after asthma RV infection identified using integrated bioinformatics in this study elucidate the potential link between RV and COVID-19.

Intra-Renal Angiotensin Levels Are Increased in High-Fructose Fed Rats in the Extracorporeal Renal Perfusion Model.

Overconsumption of fructose leads to metabolic syndrome as a result of hypertension, insulin resistance, and hyperlipidemia. In this study, the renal function of animals submitted to high fructose intake was analyzed from weaning to adulthood using in vivo and ex vivo methods, being compared with a normal control group. We investigated in ex vivo model of the role of the renin Angiotensin system (RAS) in the kidney. The use of perfused kidney from animals submitted to 8-week fructose treatment showed that high fructose intake caused metabolic and cardiovascular alterations that were consistent with other studies. Moreover, the isolated perfused kidneys obtained from rats under high fructose diet showed a 33% increase in renal perfusion pressure throughout the experimental period due to increased renal vascular resistance and a progressive fall in the glomerular filtration rate, which reached a maximum of 64% decrease. Analysis of RAS peptides in the high fructose group showed a threefold increase in the renal concentrations of angiotensin I (Ang I) and a twofold increase in angiotensin II (Ang II) levels, whereas no change in angiotensin 1-7 (Ang 1-7) was observed when compared with the control animals. We did not detect changes in angiotensin converting enzyme (ACE) activity in renal tissues, but there is a tendency to decrease. These observations suggest that there are alternative ways of producing Ang II in this model. Chymase the enzyme responsible for Ang II formation direct from Ang I was increased in renal tissues in the fructose group, confirming the alternative pathway for the formation of this peptide. Neprilysin (NEP) the Ang 1-7 forming showed a significant decrease in activity in the fructose vs. control group, and a tendency of reduction in ACE2 activity. Thus, these results suggest that the Ang 1-7 vasodilator peptide formation is impaired in this model contributing with the increase of blood pressure. In summary, rats fed high fructose affect renal RAS, which may contribute to several deleterious effects of fructose on the kidneys and consequently an increase in blood pressure.

Association of angiotensin-converting enzyme gene I/D polymorphism with chronic obstructive pulmonary disease: a meta-analysis.

Objectives:We conducted a meta-analysis of published studies on the angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism associated with the risk of chronic obstructive pulmonary disease, as well as with pulmonary function and circulating angiotensin-converting enzyme changes.Methods:A literature search, quality assessment and data extraction were completed independently and in duplicate.Results:A total of 16 articles were meta-analysed, including 12 articles (2113 patients and 8786 controls) for chronic obstructive pulmonary disease risk and eight articles (11,664 subjects) for pulmonary and circulating phenotypes. In overall and subgroup analyses, no significance was noted between the I/D polymorphism and chronic obstructive pulmonary disease risk under all genetic models (P>0.05), without heterogeneity or publication bias. Carriers of II, ID and II plus ID genotypes had significantly lower levels of circulating angiotensin-converting enzyme than those with the DD genotype (weighted mean difference −13.35, −8.13 and −10.74 U/L, respectively, P<0.001). For forced expiratory volume in one second (FEV1)/forced vital capacity, carriers of the DD genotype had marginally lower levels than those with the DD genotype (weighted mean difference –1.66, P=0.034). Furthermore in the case of FEV1 of 50% or greater of predicted FEV1, FEV1 was marginally lower in ID genotype carriers than DD genotype carriers (weighted mean difference −3.50, P=0.056).Conclusions:Our meta-analytical findings demonstrated that the ACE gene I/D polymorphism was not associated with the risk of chronic obstructive pulmonary disease.

ACE Phenotyping as a Guide Toward Personalized Therapy With ACE Inhibitors.

Angiotensin-converting enzyme (ACE) inhibitors (ACEI) are widely used in the management of cardiovascular diseases but with significant interindividual variability in the patient's response. To investigate whether interindividual variability in the response to ACE inhibitors is explained by the "ACE phenotype"-for example, variability in plasma ACE concentration, activity, and conformation and/or the degree of ACE inhibition in each individual. The ACE phenotype was determined in plasma of 14 patients with hypertension treated chronically for 4 weeks with 40 mg enalapril (E) or 20 mg E + 16 mg candesartan (EC) and in 20 patients with hypertension treated acutely with a single dose (20 mg) of E with or without pretreatment with hydrochlorothiazide. The ACE phenotyping included (1) plasma ACE concentration; (2) ACE activity (with 2 substrates: Hip-His-Leu and Z-Phe-His-Leu and calculation of their ratio); (3) detection of ACE inhibitors in patient's blood (indicator of patient compliance) and the degree of ACE inhibition (ie, adherence); and (4) ACE conformation. Enalapril reduced systolic and diastolic blood pressure in most patients; however, 20% of patients were considered nonresponders. Chronic treatment results in 40% increase in serum ACE concentrations, with the exception of 1 patient. There was a trend toward better response to ACEI among patients who had a higher plasma ACE concentration. Due to the fact that "20% of patients do not respond to ACEI by blood pressure drop," the initial blood ACE level could not be a predictor of blood pressure reduction in an individual patient. However, ACE phenotyping provides important information about conformational and kinetic changes in ACE of individual patients, and this could be a reason for resistance to ACE inhibitors in some nonresponders.

Chronic treatment with Ang-(1-7) reverses abnormal reactivity in the corpus cavernosum and normalizes diabetes-induced changes in the protein levels of ACE, ACE2, ROCK1, ROCK2 and omega-hydroxylase in a rat model of type 1 diabetes.

Angiotensin-(1-7) [Ang-(1-7)] may have beneficial effects in diabetes mellitus-induced erectile dysfunction (DMIED) but its molecular actions in the diabetic corpus cavernosum (CC) are not known. We characterized the effects of diabetes and/or chronic in vivo administration of Ang-(1-7) on vascular reactivity in the rat corpus cavernosum (CC) and on protein expression levels of potential downstream effectors of the renin-angiotensin-aldosterone system (RAAS) such as angiotensin-converting enzyme (ACE), ACE2, Rho kinases 1 and 2 (ROCK1 and ROCK2), and omega-hydroxylase, the cytochrome-P450 enzyme that metabolizes arachidonic acid to form the vasoconstrictor, 20-hydroxyeicosatetraenoic acid. Streptozotocin-treated rats were chronicically administered Ang-(1-7) with or without A779, a Mas receptor antagonist, during weeks 4 to 6 of diabetes. Ang-(1-7) reversed diabetes-induced abnormal reactivity to vasoactive agents (endothelin-1, phenylepherine, and carbachol) in the CC without correcting hyperglycemia. Six weeks of diabetes led to elevated ACE, ROCK1, ROCK 2, and omega-hydroxylase and a concomitant decrease in ACE2 protein expression levels that were normalized by Ang-(1-7) treatment but not upon coadministration of A779. These data are supportive of the notion that the beneficial effects of Ang-(1-7) in DMIED involve counterregulation of diabetes-induced changes in ACE, ACE2, Rho kinases, and omega-hydroxylase proteins in the diabetic CC via a Mas receptor-dependent mechanism.

Dietary restriction in the periconceptional period in normal-weight or obese ewes results in increased abundance of angiotensin-converting enzyme (ACE) and angiotensin type 1 receptor (AT1R) in the absence of changes in ACE or AT1R methylation in the adrenal of the offspring

Exposure to dietary restriction during the periconceptional period in either normal or obese ewes results in increased adrenal growth and a greater cortisol response to stress in the offspring, but the mechanisms that programme these changes are not fully understood. Activation of the angiotensin type 1 receptor (AT1R) has been demonstrated to stimulate adrenal growth and steroidogenesis. We have used an embryo transfer model in the sheep to investigate the effects of exposure to dietary restriction in normal or obese mothers from before and 1 week after conception on the methylation status, expression, abundance and localisation of key components of the renin-angiotensin system (RAS) in the adrenal of post-natal lambs. Maternal dietary restriction in normal or obese ewes during the periconceptional period resulted in an increase in angiotensin-converting enzyme (ACE) and AT1R abundance in the absence of changes in the methylation status or mRNA expression of ACE and AT1R in the adrenal of the offspring. Exposure to maternal obesity alone also resulted in an increase in adrenal AT1R abundance. There was no effect of maternal dietary restriction or obesity on ACE2 and AT2R or on ERK, calcium/calmodulin-dependent kinase II abundance, and their phosphorylated forms in the lamb adrenal. Thus, weight loss around the time of conception, in both normal-weight and obese ewes, results in changes within the intra-adrenal RAS consistent with increased AT1R activation. These changes within the intra-adrenal RAS system may contribute to the greater adrenal stress response following exposure to signals of adversity in the periconceptional period.

Intrarenal Distributions and Changes of Angiotensin-Converting Enzyme and Angiotensin-Converting Enzyme 2 in Feline and Canine Chronic Kidney Disease

ABSTRACTAngiotensin-converting enzyme (ACE) is a key enzyme in the renin-angiotensin system (RAS). ACE2 is a newly identified member of the RAS. The present immunohistochemical study focused on changes in intrarenal ACE and ACE2 immunoreactivity in feline and canine chronic kidney disease (CKD). ACE immunoreactivity was predominantly observed in the brush border of the proximal tubules in dogs and cats. ACE immunoreactivity was lower in CKD kidneys than in normal kidneys, and quantitative analysis demonstrated negative correlations between ACE and renal tissue damage in dogs. ACE2 immunoreactivity was also detected in the proximal tubules; it increased or decreased with CKD in dogs, depending on the renal region assessed. The changes in ACE and ACE2 in CKD were associated with the plasma creatinine concentration in dogs. Findings from dogs with glomerulonephritis were similar to those from dogs with non-glomerulonephritis. The present study suggests that changes in the intrarenal expression of ACE and ACE2 contribute to the pathological mechanisms of canine CKD, but not to the mechanisms of feline CKD.

Circulating ACE is a predictor of weight loss maintenance not only in overweight and obese women, but also in men

Circulating angiotensin-converting enzyme (ACE) was identified as a predictor of weight loss maintenance in overweight/obese women of the Diogenes project. To investigate whether ACE acted also as a predictor in men of the Diogenes study and to compare it with that in women. Subjects, who lost ≥ 8% of body weight induced by low-caloric diet in an 8-week weight loss period, were assigned to weight loss maintenance with dietary intervention for 6 months. 125 overweight/obese healthy men from eight European countries who completed whole intervention. Concentrations and activity of serum ACE at baseline and after the 8-week weight loss, in addition to anthropometric and physiological parameters. Serum ACE concentration decreased by 11.3 ± 10.6% during the weight loss period in men. A greater reduction is associated with less body weight regain during the maintenance period (r=0.227, P=0.012). ACE change was able to predict a weight regain ≤ 20% after 6 months, with an odds ratio of 1.59 (95% confidence interval (CI): 1.09-2.33, P=0.016) for every 10% reduction, which was independent of body mass index and weight loss. The prediction power was weaker in men than in women, but without a significant sex difference (P=0.137). In pooled subjects (N=218), the odds ratio was 1.96 (95% CI: 1.46-2.64, P<0.001). A greater reduction of ACE during weight loss is favorable for weight maintenance in both men and women. This can offer useful information for personalized advice to improve weight loss maintenance. It also confirms the role of ACE in the metabolic pathways of weight regulation.

Aldosterone-induced kidney injury is mediated by NFκB activation

BackgroundAldosterone induces inflammation and fibrosis in the kidney, while nuclear factor κB (NFκB) plays key roles in inflammation mediated by various cytokines. Here, we determined the roles of NFκB activation in aldosterone-induced kidney injury.MethodsWe used unilaterally nephrectomized rats with or without continuous aldosterone infusion and 0.9% saline as drinking water for 3 weeks. IMD-1041, an IKKβ inhibitor, and spironolactone were orally administered to inhibit NFκB and mineralocorticoid receptor, respectively.ResultsThe aldosterone-infused rats exhibited severe kidney injury, hypertension, and increased expression of pro-inflammatory and fibrotic proteins, osteopontin, fibrinogen, collagen type I, and PAI-1. Western blotting confirmed NFκB activation by aldosterone by the increased amount of p65 in the nuclear fraction of the kidney, and oral IMD-1041 prevented the kidney injury and lessened the increase in pro-inflammatory and fibrotic proteins without significant changes in blood pressures. In addition, changes in angiotensin-converting enzyme 2 (ACE2), which has been found to act as a protective factor in various kidney injury models, were examined. Immunofluorescence studies revealed the presence of ACE2 in the brush-border membrane of the proximal convoluted tubules and markedly blunted ACE2 staining in aldosterone-infused rats. The decrease in amount of ACE2 protein was confirmed by Western blotting, and IMD-1041 also prevented the decrease in ACE2. The administration of spironolactone also abolished the effects of aldosterone.ConclusionOur results suggest that aldosterone induces kidney injury via activation of NFκB and mineralocorticoid receptor, and that decreased ACE2 expression may play an important role in aldosterone-induced kidney injury.

Nocturnal fructose feeding increases renal ACE2 activity in mice

The objective was to study renal morphology and angiotensin converting enzyme (ACE) activity in an animal model of metabolic syndrome. C57Bl/6 male mice were given: 1) tap water 2) 24 h access to 10% fructose water or 3) 12 h access to fructose water (dark period) and water (light period) for 8 weeks. Regular chow was available ad libitum. Mice on 12 h fructose consumed more total fructose and gained more weight than those with 24 h access. Upon conclusion of the dietary regimen, kidneys were collected for morphologic studies using PAS staining, immunohistochemical staining for ACE and ACE2 and ACE/ACE2 activity. ACE/ACE2 enzyme activity was measured using a mass spectrometric assay with endogenous peptide substrates. Immunohistochemical staining showed a stronger presence of ACE2 in the 12 h group over control and 24 h. ACE staining appeared unchanged. ACE2 activity in the 12 h group was 4 fold higher than in control and 24 h groups (C = 0.6±0.2, 24h = 0.6±0.08 vs. 12h = 2.5±0.4; p&lt;0.05). ACE activity was not different between groups. Pathological changes were unremarkable except for mesangial expansion in the 12 h (C = 0.84±0.01, 24h = 0.88±0.01 vs. 12h = 0.92±0.009; p&lt;0.05). Results document that the renal effects of fructose water are dependent on the timing and volume of consumption. Increased nocturnal fructose water intake is associated with elevated ACE2 activity without changes in ACE. Supported by NIH grant R01 HL09356

Alterations in Circulatory and Renal Angiotensin-Converting Enzyme and Angiotensin-Converting Enzyme 2 in Fetal Programmed Hypertension

Antenatal betamethasone treatment is a widely accepted therapy to accelerate lung development and improve survival in preterm infants. However, there are reports that infants who receive antenatal glucocorticoids exhibit higher systolic blood pressure in their early adolescent years. We have developed an experimental model of programming whereby the offspring of pregnant sheep administered clinically relevant doses of betamethasone exhibit elevated blood pressure. We tested the hypothesis as to whether alterations in angiotensin-converting enzyme (ACE), ACE2, and neprilysin in serum, urine, and proximal tubules are associated with this increase in mean arterial pressure. Male sheep were administered betamethasone (2 doses of 0.17 mg/kg, 24 hours apart) or vehicle at the 80th day of gestation and delivered at term. Sheep were instrumented at adulthood (1.8 years) for direct conscious recording of mean arterial pressure. Serum and urine were collected and proximal tubules isolated from the renal cortex. Betamethasone-treated animals had elevated mean arterial pressure (97+/-3 versus 83+/-2 mm Hg; P<0.05) and a 25% increase in serum ACE activity (48.4+/-7.0 versus 36.0+/-2.7 fmol/mL per minute) but a 40% reduction in serum ACE2 activity (18.8+/-1.2 versus 31.4+/-4.4 fmol/mL per minute). In isolated proximal tubules, ACE2 activity and expression were 50% lower in the treated sheep with no significant change in ACE or neprilysin activities. We conclude that antenatal steroid treatment results in the chronic alteration of ACE and ACE2 in the circulatory and tubular compartments, which may contribute to the higher blood pressure in this model of fetal programming-induced hypertension.

Expression of Angiotensin-converting Enzyme Changes Major Histocompatibility Complex Class I Peptide Presentation by Modifying C Termini of Peptide Precursors

We recently reported a mouse model called ACE 10/10 in which macrophages overexpress the carboxypeptidase angiotensin-converting enzyme (ACE). These mice have an enhanced inflammatory response to tumors that markedly inhibits tumor growth. Here, we show that ACE modifies the C termini of peptides for presentation by major histocompatibility complex (MHC) class I molecules. The peptide-processing activity of ACE applies to antigens from either the extracellular environment (cross-presentation) or antigens produced endogenously. Consistent with its role in MHC class I antigen processing, ACE localizes to the endoplasmic reticulum. ACE overexpression does not appear to change the overall supply of peptides available to MHC class I molecules. The immunization of wild type mice previously given ACE 10/10 macrophages enhances the efficiency of antigen-specific CD8+ T cell priming. These data reveal that ACE is a dynamic participant in fashioning the peptide repertoire for MHC class I molecules by modifying the C termini of peptide precursors. Manipulation of peptidase expression by antigen-presenting cells may ultimately prove a useful strategy to enhance the immune response.

Cyclical variation of serum neutral endopeptidase lost in asthmatics: A pilot study

Angiotensin converting enzyme (ACE) and neutral endopeptidase (NEP) are two metalloproteases, which have both been isolated from the airways. With the knowledge that young girls experience a worsening of asthma with fluctuations in oestrogen levels, we attempted to establish whether there is a change in ACE or NEP levels throughout the menstrual cycle, accounting for unhydrolysed inflammatory mediators in the airways. Asthmatics and normal controls ( n = 7) were studied through the follicular and luteal phases of the menstrual cycle. Peak flow rates and serum ACE levels showed no significant difference in either group. There was a four-fold increase in NEP levels in the follicular phase of normal women. Asthmatics had high levels of NEP throughout the cycle, in both the follicular and luteal phases. These results demonstrate an alteration of normal physiology in asthmatics, which might be a natural response to background inflammation.

Central and peripheral renin-angiotensin systems in ouabain-induced hypertension

Chronic subcutaneous infusion of ouabain causes hypertension via central pathways involving angiotensin type 1 (AT(1)) receptor stimulation. The present study assessed plasma and tissue ANG I and II levels as well as AT1 receptor and angiotensin-converting enzyme (ACE) mRNA levels and binding densities by real-time PCR and in vitro autoradiography in relevant brain nuclei and peripheral tissues (heart and kidney) in rats at 1 and/or 2 wk after start of ouabain infusion at 50 microg/day. After 2 wk (but not after 1 wk), blood pressures significantly increased (+15 mmHg). At 2 wk, plasma ANG I and II levels were markedly suppressed by ouabain. In contrast, in the heart and kidneys, ANG I levels were not affected, and ANG II levels tended to decrease, whereas in the hypothalamus ANG II content clearly increased. At 1 wk, no changes in ACE and AT1 receptor densities were seen. After 2 wk, there were significant decreases in AT(1) receptor mRNA and densities in the organum vasculosum of the lamina terminalis (OVLT), subfornical organ (SFO), and paraventricular nucleus (PVN). ACE densities decreased only in the OVLT and SFO, but ACE mRNA showed more variable responses (decrease in OVLT vs. increase in PVN). In the kidneys, at 2 wk both AT1 receptor and ACE densities were decreased, but mRNA abundance did not change. The heart showed no significant changes. The increase in hypothalamic ANG II content and associated decreases in central AT1 receptor and ACE densities support the involvement of the brain renin-angiotensin system in the central hypertensive mechanism of action of ouabain.

Central and peripheral renin‐angiotensin systems in ouabain‐induced hypertension 1

Chronic subcutaneous infusion of ouabain causes hypertension via central pathways involving AT1 receptor stimulation. The present study assessed plasma and tissue Ang I and II levels as well as AT1 receptor and angiotensin converting enzyme (ACE) mRNA levels and binding densities by real–time PCR and in vitro autoradiography in relevant brain nuclei and peripheral tissues (heart and kidney) in rats at 1 and/or 2 weeks after start of ouabain infusion at 50 μg/day. After 2 weeks (but not after 1 week) blood pressures significantly increased (+15 mmHg). At 2 weeks, plasma Ang II levels were markedly suppressed by ouabain from 15 ± 4 to 3 ± 1 pg/ml. In contrast, in the heart and kidneys Ang I levels were not affected and Ang II levels tended to decrease, whereas in the hypothalamus Ang II content clearly increased from 3 ± 2 to 18 ± 6 pg/g. At 1 week, no changes in ACE and AT1 receptor densities were seen. After 2 weeks, there were significant decreases in AT1 receptor mRNA by 30–50% and densities by ~15% in the organum vasculosum of the laminae terminalis (OVLT), subfornical organ (SFO) and paraventricular nucleus (PVN), as well as decreases in ACE densities in the OVLT and SFO by 25–50%. In the kidneys, at 2 weeks both AT1 receptor and ACE densities were decreased but mRNA abundance did not change. The heart showed no significant changes. The increase in hypothalamic Ang II content and associated decreases in central AT1 receptor and ACE densities support the involvement of the brain RAS in the central hypertensive mechanism of action of ouabain.