Comparison between radiometry and spectrophotometry for the determination of angiotensin-converting enzyme activity in cerebrospinal fluid

Determination of angiotensin-converting enzyme (ACE) activity in cerebrospinal fluid (CSF) can help for establishing the diagnosis of neurosarcoidosis. We investigated the performance characteristics of two assays for ACE determination in 57 CSF, radiometry with [glycine-1-14C] benzoyl-L-histidyl-L-leucine and spectrophotometry with furylacryloyl-phenylalanyl-L-glycyl-L-glycine (FAPGG) as substrates. We compared both kinetic assays to an ELISA specific for human ACE. Within run and between run imprecisions were 14-17% for radiometry, 6-19% for spectrophotometry and 5-8% for ELISA. The limit of detection was 0.04 U/L for radiometry, 1.0 U/L for spectrophotometry and 0.156 μg/L for ELISA. The limit of quantification was 0.06 U/L for radiometry, 1.5 U/L for spectrophotometry, but not known for ELISA. The domain for quantification was 0.06-4.0 U/L for radiometry, 1.5-24 U/L for spectrophotometry and 0.156-10 μg/L for ELISA. Deming regression and Bland-Altman plots show good correlations between the three assays, but with high slopes, because both kinetic assays use different substrates and ELISA measures ACE molecule but not activity. Radiometry was more sensitive than spectrophotometry, which has a limit of detection above most pathological levels. ELISA could be an alternative to radiometry but only after complete evaluation, determination of normal values and assessment of its clinical value. We claim for standardization of ACE determination as well as in serum as in other biological fluids, in particular CSF.

Consistent localization of SARS-CoV-2 spike glycoprotein and ACE2 over TMPRSS2 predominance in placental villi of 15 COVID-19 positive maternal-fetal dyads

INTRODUCTION

While the COVID-19 pandemic continues to have a significant global health impact, rates of maternal to infant vertical transmission remain low (<5%). Parenchymal changes of placentas from COVID-19 infected mothers have been reported by several groups, but the localization and relative abundance of SARS-CoV-2 viral proteins and cellular entry machinery has not been fully characterized within larger placental tissue cohorts.

METHODS

An extended placental tissue cohort including samples from 15 COVID-19 positive maternal-fetal dyads (with n = 5 cases with evidence of fetal transmission) in comparison with 10 contemporary COVID-19 negative controls. Using comparative immunofluorescence, we examined the localization and relative tissue abundance of SARS-CoV2 spike glycoprotein (CoV2 SP) along with the co-localization of two SARS-CoV2 viral entry proteins angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2).

RESULTS/CONCLUSIONS

CoV2 SP was present within the villous placenta in COVID-19 positive pregnancies with and without evidence of fetal transmission. We further identified the predominance of ACE2 expression in comparison with TMPRSS2. Importantly, both CoV2 SP and ACE2 expression consistently localized primarily within the outer syncytiotrophoblast layer placental villi, a key physiologic interface between mother and fetus. Overall this study provides an important basis for the ongoing evaluation of SARS-CoV-2 physiology in pregnancy and highlights the importance of the placenta as a key source of primary human tissue for ongoing diagnostic and therapeutic research efforts to reduce the global burden of COVID-19.

Involvement of the digestive system in covid-19. A review

The SARS-CoV-2 pandemic is leading to high mortality and a global health crisis. The primary involvement is respiratory; however, the virus can also affect other organs, such as the gastrointestinal tract and liver. The most common symptoms are anorexia and diarrhea. In about half of the cases, viral RNA could be detected in the stool, which is another line of transmission and diagnosis. covid19 has a worse prognosis in patients with comorbidities, although there is not enough evidence in case of previous digestive diseases. Digestive endoscopies may give rise to aerosols, which make them techniques with a high risk of infection. Experts and scientific organizations worldwide have developed guidelines for preventive measures. The available evidence on gastrointestinal and hepatic involvement, the impact on patients with previous digestive diseases and operating guidelines for Endoscopy Units during the pandemic are reviewed.

Placental barrier against COVID-19

Vertical transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and possible induction of pregnancy complications, including miscarriage, fetal malformations, fetal growth restriction and/or stillbirth, are serious concerns for pregnant individuals with COVID-19. According to clinical information, the incidence of vertical transmission of SARS-CoV-2 is limited to date. However, even if a neonate tests negative for SARS-CoV-2, frequent abnormal findings, including fetal and maternal vascular malperfusion, have been reported in cases of COVID-19-positive mothers. Primary receptor of SARS-CoV-2 is estimated as angiotensin-converting enzyme 2 (ACE2). It is highly expressed in maternal-fetal interface cells, such as syncytiotrophoblasts, cytotrophoblasts, endothelial cells, and the vascular smooth muscle cells of primary and secondary villi. However other route of transplacental infection cannot be ruled out. Pathological examinations have demonstrated that syncytiotrophoblasts are often infected with SARS-CoV-2, but fetuses are not always infected. These findings suggest the presence of a placental barrier, even if it is not completely effective. As the frequency and molecular mechanisms of intrauterine vertical transmission of SARS-CoV-2 have not been determined to date, intensive clinical examinations by repeated ultrasound and fetal heart rate monitoring are strongly recommended for pregnant women infected with COVID-19. In addition, careful investigation of placental samples after delivery by both morphological and molecular methods is also strongly recommended.

ACE2 Expression in Pancreas May Cause Pancreatic Damage After SARS-CoV-2 Infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel coronavirus that causes coronavirus disease 2019 (COVID-19) in human beings, has caused a serious public health issue.¹ Attention to pancreatic injury is lacking, which may impact patients' prognosis. In this study, we explored the expression and distribution of angiotensin-converting enzyme 2 (ACE2), the receptor of SARS-CoV-2, in the pancreas. Combined with clinical data, we showed that pancreatic injury can occur in some COVID-19 patients.

Genetic Association of Angiotensin-Converting Enzyme (ACE) Gene I/D Polymorphism with Preterm Birth in Korean Women: Case-Control Study and Meta-Analysis

Background and Objectives: The ACE gene encodes the angiotensin-converting enzyme (ACE), a component of the renin-angiotensin system. Increased ACE activity may cause abnormal regulation of placental circulation and angiogenesis, resulting in adverse pregnancy outcomes. Previous studies have reported that the insertion/deletion (I/D) polymorphism of the ACE gene is associated with the development of preterm birth (PTB). However, results of the association between ACE gene I/D and PTB are inconsistent in various populations. Therefore, we performed a case-control study and a meta-analysis to evaluate the association between ACE I/D polymorphism and PTB. Materials and Methods: We analyzed a total of 254 subjects (111 patients with PTB and 143 women at ≥38 weeks gestation) for the case-control study. For the meta-analysis, we searched Google Scholar, PubMed, and NCBI databases with the terms “ACE,” “angiotensin-converting enzyme,” “preterm birth,” “preterm delivery,” and their combinations. Results: Our results of the case-control study indicated that ACE I/D polymorphism is significantly associated with PTBs in the overdominant genetic model (odds ratio (OR) 0.57, 95% confidence interval (CI) 0.347–0.949, p = 0.029) and that the ID genotype of ACE I/D polymorphism has a protective effect for PTB (OR 0.57, 95% CI 0.333–0.986, p = 0.043). Similarly, the meta-analysis showed that the OR for the ACE gene ID genotype was 0.66 (95% CI 0.490–0.900, p < 0.01). Conclusion: The ACE gene ID genotype has a significant association with PTB and is a protective factor for PTB. A larger sample set and functional studies are required to further elucidate of our findings.

Changes in angiotensin II and angiotensin-converting enzyme of different tissues after prolonged hyperoxia exposure

Current study findings concerning changes in the renin-angiotensin system (RAS) in cases of hyperoxic acute lung injury (HALI) have shown conflicting results. This study aimed to detect the angiotensin II (Ang II) and angiotensin-converting enzyme (ACE) in a rat HALI model. Healthy male Sprague-Dawley rats were randomly assigned into three groups: the control group, HALI group and hyperbaric oxygen preconditioning (HBO₂-PC) group. HALI was induced by exposure to pure oxygen at 250 kPa for six hours. In the HBO₂-PC group, rats were exposed to oxygen at 250 kPa for 60 minutes twice daily for two consecutive days; HALI was induced at 24 hours after the last oxygen exposure.=After HALI, the lung, spleen and liver were harvested for HE staining and pathological examination. At one hour and 18 hours after HALI, the blood, liver, lung and spleen were collected for the detection of Ang II and ACE contents by enzyme-linked immunosorbent assay. Pathological examination showed the lung was significantly damaged and characteristics of HALI were observed, but there were no significant pathological changes in the liver and spleen. After HALI, Ang II and ACE contents of different tissues increased progressively over time, but the HBO₂-PC group showed reductions in the Ang II and ACE contents to a certain extent, especially at 18 hours after injury. These findings suggest prolonged hyperoxia exposure may activate the RAS, which may be associated with the pathogenesis of HALI. HBO₂-PC has a limited capability to inhibit RAS activation.

Cardiac ACE2/angiotensin 1-7/Mas receptor axis is activated in thyroid hormone-induced cardiac hypertrophy

OBJECTIVES

Thyroid hormone (TH) promotes marked effects on the cardiovascular system, including the development of cardiac hypertrophy. Some studies have demonstrated that the renin-angiotensin system (RAS) is a key mediator of the cardiac growth in response to elevated TH levels. Although some of the main RAS components are changed in cardiac tissue on hyperthyroid state, the potential modulation of the counter regulatory components of the RAS, such as angiotensin-converting enzyme type 2 (ACE2), angiotensin 1-7 (Ang 1-7) levels and Mas receptor induced by hyperthyroidism is unknown. The aim of this study was to investigate the effect of hyperthyroidism on cardiac Ang 1-7, ACE2 and Mas receptor levels.

METHODS

Hyperthyroidism was induced in Wistar rats by daily intraperitoneal injections of T4 for 14 days.

RESULTS

Although plasma Ang 1-7 levels were unchanged by hyperthyroidism, cardiac Ang 1-7 levels were increased in TH-induced cardiac hypertrophy. ACE2 enzymatic activity was significantly increased in hearts from hyperthyroid animals, which may be contributing to the higher Ang 1-7 levels observed in the T4 group. Furthermore, elevated cardiac levels of Ang 1-7 levels were accompanied by increased Mas receptor protein levels.

CONCLUSION

The counter-regulatory components of the RAS are activated in hyperthyroidism and may be contributing to modulate the cardiac hypertrophy in response to TH.

Sarcoidosis Presenting Addison's Disease

We herein describe a second Japanese case of sarcoidosis presenting Addison's disease. A 52-year-old man was diagnosed with sarcoidosis based on clinical and laboratory findings, including bilateral hilar lymphadenopathy and elevated levels of serum angiotensin-converting enzyme and lysozyme, as well as the presence of noncaseating epithelioid granulomas. The patient also exhibited general fatigue, pigmentation, weight loss, hypotension and hyponatremia, suggestive of chronic adrenocortical insufficiency. An endocrine examination confirmed primary adrenocortical insufficiency. This case suggests the direct involvement of sarcoid granuloma in the adrenal glands.

Laparoscopic fenestration of pancreatic serous cystadenoma: Minimally invasive approach for symptomatic benign disease

Serous cystadenoma (SC) is a benign pancreatic cystic tumor. Surgical resection is recommended for symptomatic forms, but laparoscopic fenestration of large symptomatic macrocystic SC was not yet described in the literature. In this study, 3 female patients underwent laparoscopic fenestration for macrocystic SC (12-14 cm). Diagnosis was established via magnetic resonance imaging and endoscopic ultrasound, with intra-cystic dosage of tumors markers (ACE and CA19-9) in 2 patients. All patients were symptomatic and operated on 15-60 mo after diagnosis. Radiological evaluation showed constant cyst growth. Patients were informed about this new surgical modality that can avoid pancreatic resection. The mean operative time was 103 min (70-150 min) with one conversion. The post-operative course was marked by a grade A pancreatic fistula in one patient and was uneventful in the other two. The hospital stay was 3, 10, and 18 d, respectively. The diagnosis of macrocystic SC was histologically-confirmed in all cases. At the last follow-up (13-26 mo), all patients were symptom-free, and radiological evaluation showed complete disappearance of the cyst. Laparoscopic fenestration, as opposed to resection, should be considered for large symptomatic macrocystic SC, thereby avoiding pancreatic resection morbidity and mortality.

New phenolic compounds from Coreopsis tinctoria Nutt. and their antioxidant and angiotensin i-converting enzyme inhibitory activities

Three new phenolic compounds, coretinphenol (1), coretincone (2), and coretinphencone (3), were isolated from the buds of Coreopsis tinctoria Nutt., together with nine known compounds, including butein (4), okanin (5), isoliquiritigenin (6), maritimetin (7), taxifolin (8), isookanin (9), marein (10), sachalinoside B (11), and 2-phenylethyl-β-d-glucoside (12). The chemical structures of these compounds were elucidated by extensive spectroscopic analysis and on the basis of their chemical reactivity. This work represents the first recorded example of the isolation of compounds 1–3, 6, 7, 9, 11, and 12 from C. tinctoria. Compounds 5–9 showed strong diphenyl(2,4,6-trinitrophenyl)iminoazanium (DPPH) radical-scavenging activity, with IC50 values of 3.35 ± 0.45, 9.6 ± 2.32, 4.12 ± 0.21, 6.2 ± 0.43, and 7.9 ± 0.53 μM, respectively. Compounds 2 and 8 exhibited angiotensin I-converting enzyme inhibitory activity, with IC50 values of 228 ± 4.47 and 145.67 ± 3.45 μM, respectively. The activities of phenolic compounds isolated from C. tinctoria support the medicinal use of this plant in the prevention of cardiovascular diseases.

Inhibition of reactive oxygen species in hypothalamic paraventricular nucleus attenuates the renin-angiotensin system and proinflammatory cytokines in hypertension

AIMS

To explore whether reactive oxygen species (ROS) scavenger (tempol) in the hypothalamic paraventricular nucleus (PVN) attenuates renin-angiotensin system (RAS) and proinflammatory cytokines (PICs), and decreases the blood pressure and sympathetic activity in angiotensin II (ANG II)-induced hypertension.

METHODS AND RESULTS

Male Sprague-Dawley rats were infused intravenously with ANG II (10 ng/kg per min) or normal saline (NS) for 4 weeks. These rats were treated with bilateral PVN infusion of oxygen free radical scavenger tempol (TEMP, 20 μg/h) or vehicle (artificial cerebrospinal fluid, aCSF) for 4 weeks. ANG II infusion resulted in increased mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA). These ANG II-infused rats also had higher levels of gp91(phox) (a subunit of NAD(P)H oxidase), angiotensin-converting enzyme (ACE), and interleukin-1 beta (IL-1β) in the PVN than the control animals. Treatment with PVN infusion of TEMP attenuated the overexpression of gp91(phox), ACE and IL-1β within the PVN, and decreased sympathetic activity and MAP in ANG II-infused rats.

CONCLUSION

These findings suggest that ANG II infusion induces elevated PICs and oxidative stress in the PVN, which contribute to the sympathoexcitation in hypertension. Inhibition of reactive oxygen species in hypothalamic paraventricular nucleus attenuates the renin-angiotensin system, proinflammatory cytokines and oxidative stress in ANG II-induced hypertension.

Measuring angiotensin-I converting enzyme inhibitory activity by micro plate assays: comparison using marine cryptides and tentative threshold determinations with captopril and losartan

To determine the angiotensin-I converting enzyme (ACE) inhibitory activity of marine cryptides, different methods were tested. ACE inhibition was measured using two synthetic substrates, (N-[3-(2-furyl) acryloyl]-Phe-Gly-Gly (FAPGG) and N-hippuryl-His-Leu hydrate salt (HHL)), and a natural one, angiotensin-I. The IC50 value (defined as the concentration of inhibitory molecule needed to inhibit 50% of the ACE activity) of the reference synthetic inhibitor captopril was in the nanomolar range (1.79-15.1 nM) when synthetic substrates were used, whereas it exhibited IC50 of micromolar range (16.71 μM) with angiotensin-I. We chose losartan, an antagonist of angiotensin-II receptor as negative control for the ACE inhibition. Losartan was also able to inhibit ACE whatever the substrate tested, with IC50 of micromolar range (17.13-146 μM). We defined this value as a limit above which molecules are not showing in vitro ACE inhibitory activity. Val-Trp (VW), Val-Tyr (VY), Lys-Tyr (KY), Lys-Trp (KW), Ile-Tyr (IY), Ala-Pro (AP), Val-Ile-Tyr (VIY), Leu-Lys-Pro (LKP), Gly-Pro-Leu (GPL), Ala-Lys-Lys (AKK), and Val-Ala-Pro (VAP) were tested as inhibitors of ACE with synthetic and natural substrates. IC50 displayed were substrate-dependent. With FAPGG as substrate, IW, VAP, KY, IY, AP, AKK, and VIY show IC50 values over the IC50 value of losartan and should not be considered as inhibitors of ACE. VY, VW, KW, and LKP exhibited IC50 value lower than the IC50 value of losartan for all substrates tested and were thus considered as good candidates for effectively decreasing hypertension. It appears that the comparison of IC50 is not consistent when IC50 values are obtained with different substrates and different methods. In vitro ACE inhibitory activity assays should always include various ACE substrates and references such as captopril and a negative control to obtain data reliable to discriminate ACE inhibitory peptides.

Childhood sarcoidosis: diagnostic issues

Childhood sarcoidosis is a rare granulomatous disorder that affects several systems including the lungs, skin, eyes, and bones. On histopathology, non-caseating granuloma is the classic feature. We present a case of late childhood sarcoidosis of the skin, lungs, and bones demonstrating granulomas with fibrinoid necrosis, making distinction from tuberculosis difficult.

Utero-placental expression of angiotensin-(1-7) and ACE2 in the pregnant guinea-pig

BACKGROUND

In humans, trophoblast invasion, vascular remodeling and placental development are critical to determine the fate of pregnancy. Since guinea-pigs (GP) and humans share common pregnancy features including extensive trophoblast invasion, transformation of the uterine spiral arteries and a haemomonochorial placenta, the GP animal model was deemed suitable to extend our knowledge on the spatio-temporal immunoreactive expression of the vasodilator arpeptide of the renin-angiotensin system, angiotensin-(1-7) [Ang-(1-7)] and its main generating enzyme, angiotensin converting enzyme 2 (ACE2).

METHODS

Utero-placental units were collected in days 15, 20, 40 and 60 of a 64-67 day long pregnancy in 25 Pirbright GP. Ang-(1-7) and ACE2 expression in utero-placental units were evaluated by immunohistochemistry.

RESULTS

Ang-(1-7) and ACE2 were detected in the endothelium and syncytiotrophoblast of the labyrinthine placenta, interlobium, subplacenta, giant cells, syncytial sprouts, syncytial streamers, and myometrium throughout pregnancy. In late pregnancy, perivascular or intramural trophoblasts in spiral and mesometrial arteries expressed both factors. Immunoreactive Ang-(1-7) and ACE2 were present in decidua and in the vascular smooth muscle of spiral, myometrial and mesometrial arteries, which also express kallikrein (Kal), the bradykinin receptor 2 (B2R), vascular endothelial growth factor (VEGF) and its type 2 receptor (KDR), but no endothelial nitric oxide synthase (eNOS). In addition, the signal of Ang-(1-7) and ACE2 was especially remarkable in giant cells, which also show Kal, B2R. eNOS, VEGF and KDR.

CONCLUSIONS

The spatio-temporal expression of Ang-(1-7) and ACE2 in GP, similar to that of humans, supports a relevant evolutionary conserved function of Ang-(1-7) and ACE2 in decidualization, trophoblast invasion, vascular remodeling and placental flow regulation, as well as the validity of the GP model to understand the local adaptations of pregnancy. It also integrates Ang-(1-7) to the utero-placental vasodilatory network. However, its antiangiogenic effect may counterbalance the proangiogenic activity of some of the other vasodilator components.

Contribution of T cell subset analysis in induced sputum in diagnosing ocular sarcoidosis

OBJECTIVE

The aim of this study was to establish a correlation between the diagnosis of ocular sarcoidosis and the presence of an elevated CD4/CD8 ratio in the induced sputum(IS) of patients with uveitis and no other systemic symptoms.

METHODS

This retrospective chart review study included all newly diagnosed uveitis patients treated between 1998-2006. IS examinations and determination of angiotensin-converting enzyme (ACE) levels were carried out. A CD4/CD8 ratio > 2.5 and an ACE level > 145 Cd/ml/min were considered abnormal. The etiology of uveitis was retrieved from the medical records.

RESULTS

Twenty males and 26 females (mean age 47 +/- 16.1 years) were enrolled. The CD4/CD8 ratio was elevated in 26 (56.5%) patients, and five (10.9%) were diagnosed as having sarcoidosis by the end of follow-up. The sensitivity and specificity of the T lymphocytes CD4/CD8 ratio in diagnosing sarcoidosis were 100% and 48.8%, respectively. CD4/CD8 ratios were not significantly different between the sarcoid and non-sarcoid groups (p > 0.05), but the former tended to have higher levels (p = 0.0991). The mean ACE level of the sarcoid patients was significantly higher than that of the non-sarcoid patients (p < 0.001).

CONCLUSION

CD4/CD8 lymphocytes ratios obtained by IS were sensitive in uveitis patients with concomitant sarcoidosis, suggesting that analysis of T cells subsets in IS may rule out an etiology of sarcoidosis in newly diagnosed uveitis patients.

Angiotensin-converting enzyme gene variant and its levels: risk factors for myocardial infarction in a South Indian population

INTRODUCTION

Recently, there has been increasing evidence that genetic variation in the angiotensin-converting enzyme (ACE) plays an important role in myocardial infarction. Therefore, the present study was carried out with the aim of investigating the association of the ACE gene insertion/deletion (I /D) polymorphism and its levels in myocardial infarction patients and their first-degree relatives (FDRs).

METHODS

206 patients with myocardial infarction, 168 FDRs and 210 control subjects were enrolled in the study. ACE I /D polymorphism was determined using the polymerase chain reaction method. Serum ACE levels were measured using the photometric method.

RESULTS

The DD genotype and ACE activity were significantly higher in patients (p-value is 0.00006 and 0.0001, respectively) and FDRs (p-value is 0.003 and 0.04, respectively) compared with the controls.

CONCLUSION

ACE DD genotype and ACE levels are important risk factors for myocardial infarction. This study indicates that the higher frequency of the DD genotype and ACE levels observed in FDRs may increase susceptibility to developing myocardial infarction.

Novel angiotensin-converting enzyme (ACE) inhibitory peptides derived from boneless chicken leg meat

Four peptides that inhibit angiotensin-converting enzyme (ACE) were separated from the hydorlysate of boneless chicken leg meat digested with artificial gastric juice (pepsin). Two peptides were identified as the peptides encrypted in myosin heavy chain. The peptide P1 (MNVKHWPWMK) corresponds to the amino acid sequence from amino acids 825 to 834 of myosin heavy chain, and the peptide P4 (VTVNPYKWLP) corresponds to the amino acid sequence from amino acids 125 to 135 of myosin heavy chain. They are novel ACE inhibitory peptides derived from chicken, and IC(50) values of P1 and P4 were determined as 228 and 5.5 microM, respectively. Although these values were much larger than 0.022 microM for captopril, a typical synthetic ACE inhibitor, they are comparable to IC(50) values reported for various ACE inhibitory peptides derived from foods. Because the peptide P4 has a relatively low IC(50) value, it is a good starting substance for designing food supplements for hypertensive patients.

Study of Serum and Tissues Angiotensin Converting Enzyme (ACE) Activity in Rat with Gentamicin Induced Renal Toxicity

PURPOSE

In this research ACE activity (as a marker of epithelial injury) was studied in rats with gentamicin induced renal toxicity.

METHODS

Male Sprague-Dawley rats were sacrificed 1, 3, 5, and 7 days after gentamicin injection, 100 mg/kg/day for 1, 3, 5, and 7 consecutive days. ACE activity was measured in serum, kidney and lung. These data were compared with normal saline-treated rats. Histological scoring of renal cortical pathology was performed on days 1, 3, 5, and 7.

RESULTS

Treatment of rats with gentamicin resulted in renal damage evidenced by proteinuria, polyuria, and decreased creatinine clearance. The damage to the kidney proximal tubule was evident by (a) the histological analysis at light microscopy and (b) the augmentation in the urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG). Kidney ACE activity decreased while lung and serum ACE activity didn't change until day 7. Lung ACE activity increased significantly on day 7. Kidney and serum ACE activity increased too. Blood pressure increased significantly on day 7. This corresponded well with the lung ACE activity increment.

CONCLUSION

These data suggest that kidney ACE activity decreased significantly just one day after gentamicin administration and prior to kidney NAG decrease.

Angiotensin-converting enzyme in sarcoidosis

Using a spectrophotometric assay with L-hippuryl-L-histidyl-L-leucine as substrate, s-angiotensin-converting enzyme (SACE) was determined in 85 sarcoidosis patients, 116 healthy controls and 150 patients with various non-sarcoid diseases. The controls showed no sex or age variation and had SACE levels of 24.4 +/- 6.2 U/ml (mean +/- 1 S.D.), giving a normal range (mean +/- 2 S.D.) of 12.0-36.8 U/ml. In contrast, the sarcoidosis patients had SACE values of 38.4 +/- 14.4 U/ml, with the highest values in cases with active sarcoidosis and duration of disease longer than two years (49.0 +/- 12.7 U/ml). A total of 41% of the sarcoidosis patients had elevated SACE, in the chronic active group 85%. Patients with renal failure, Hodgkin's disease and other malignant lymphoma had low SACE, whereas patients with lung cancer and tuberculosis had normal SACE values. Among 266 patients with non-sarcoid diseases and healthy controls, only two had slightly elevated SACE, but so far we have not found SACE above 40 U/ml in other than sarcoidosis patients. An elevated SACE is rather specific in sarcoidosis and seems to be a useful supplement to existing diagnostic measures.

Free light chains of immunoglobulins in serum from patients with rheumatoid arthritis, sarcoidosis, chronic infections and pulmonary cancer

Free light chains of immunoglobulins were measured in serum from 181 patients with rheumatoid arthritis (RA), sarcoidosis, pulmonary tuberculosis, pulmonary cancer and chronic bronchitis, i.e. patients with long-term stimulation of the immune system. Increased concentrations of light chains were found in patients with active sarcoidosis, and the light chain level appeared to be a marker of disease activity in sarcoidosis. The mean (+/- S.D.) concentration of kappa plus lambda chains in active sarcoidosis of more than two years' duration was 38.3 +/- 13.7 mg/l, that is twice the concentration of 19.4 +/- 5.5 mg/l found in normals. Some patients with seropositive RA also had increased serum values. The light chain concentrations in seropositive RA were correlated to the severity of the disease measured by clinical staging and laboratory tests. A modest increase in light chains was observed in one patient with tuberculosis, and in two patients each with chronic bronchitis and pulmonary cancer.

Isoflavone content and its potential contribution to the antihypertensive activity in soybean Angiotensin I converting enzyme inhibitory peptides

A soybean angiotensin I converting enzyme (ACE) inhibitory peptide fraction was reported to have antihypertensive activity in a rat study. The purpose of the present study was to examine if the presence of isoflavones in the soybean ACE inhibitory peptide fraction may contribute to the blood-pressure-lowering property. The isoflavone concentration in soybean samples was analyzed on a C 18 reverse-phase column using a two-step gradient solvent system. Producing soybean hydrolysate led to a nearly 40% loss of isoflavones compared with the original soybean flour, but the isoflavone composition did not change and the dominant isoflavone chemicals remained as 6''-O-malonylgenistin and 6''-O-malonyldaidzin. Ion exchange chromatography affected significantly both the content and the composition of the isoflavones. The dominant isoflavones in the ion-exchanged fraction were aglycones and nonacylated isoflavones, accounting for 95.8% of the total amount of 987.7 microg/g. It was calculated that the isoflavone content in the soybean ACE inhibitory peptide fraction was 25 times less than the minimal effective isoflavone dose reported. In vitro study also showed that adding isoflavones into both soybean flour hydrolysate and soybean ACE inhibitory peptide samples to a concentration of as high as 31.5% (w/w) did not affect ACE inhibitory activity (IC 50 values). The findings along with previously published results indicated that the contribution of isoflavones in soybean ACE inhibitory peptide fraction to the blood-pressure-lowering property in a short-term feeding study might be negligible.

Comparative expression analysis of the renin-angiotensin system components between white and brown perivascular adipose tissue

Recent studies have demonstrated that the rat adipose tissue expresses some of the components necessary for the production of angiotensin II (Ang II) and the receptors mediating its actions. The aim of this work is to characterize the expression of the renin-angiotensin system (RAS) components in perivascular adipose tissue and to assess differences in the expression pattern depending on the vascular bed and type of adipose tissue. We analyzed Ang I and Ang II levels as well as mRNA levels of RAS components by a quantitative RT-PCR method in periaortic (PAT) and mesenteric adipose tissue (MAT) of 3-month-old male Wistar-Kyoto rats. PAT was identified as brown adipose tissue expressing uncoupling protein-1 (UCP-1). It had smaller adipocytes than those from MAT, which was identified as white adipose tissue. All RAS components, except renin, were detected in both PAT and MAT. Levels of expression of angiotensinogen, Ang-converting enzyme (ACE), and ACE2 were similar between PAT and MAT. Renin receptor expression was five times higher, whereas expression of chymase, AT(1a), and AT(2) receptors were significantly lower in PAT compared with MAT respectively. In addition, three isoforms of the AT(1a) receptor were found in perivascular adipose tissue. The AT(1b) receptor was found at very a low expression level. Ang II levels were higher in MAT with no differences between tissues in Ang I. The results show that the RAS is differentially expressed in white and brown perivascular adipose tissues implicating a different role for the system depending on the vascular bed and the type of adipose tissue.

Diverse clinical presentations of orbital sarcoid

PURPOSE

To review the clinical presentation, location, systemic features, management, and natural history of orbital sarcoid.

DESIGN

Retrospective, noncomparative, interventional case series.

METHODS

Twenty patients with sarcoid and sarcoidal reactions of the orbit underwent biopsy, excision of localized mass, and systemic and local treatment at a tertiary referral center. Age, gender, onset, symptoms and signs, characterization of disease process, location, systemic disease, associated systemic features, management, and recurrence of the disease were identified.

RESULTS

Of the 20 patients studied, five were male and 15 were female. The mean age was 50.55 +/- 16.43 years (range, 18 to 77 years). The most common symptom was the presence of a palpable mass, followed by eyelid swelling. Review of the computed tomographic scans revealed four main categories of presentation: lacrimal gland infiltration (n = 11; 55%), orbital mass (n = 4; 20%), optic nerve sheath and dural involvement (n = 4; 20%), and extraocular muscle involvement (n = 1; 5%). Concurrent systemic sarcoidosis discovered after the diagnosis of orbital sarcoid was present in 10 cases (50%). The remaining showed no evidence of systemic disease at follow-up. Angiotensin converting enzyme analysis was performed in 10 cases; in only two (20%) was elevated, and in the remaining eight, it was within normal levels.

CONCLUSIONS

Orbital sarcoid has a diverse clinical presentation varying from lacrimal gland infiltration, soft tissue orbital mass, intraorbital and extraorbital optic nerve sheath and dural involvement, to extraocular muscle involvement. The orbital site most commonly involved was the lacrimal gland.

Angiotensin-Converting Enzyme Genotype Interacts With Systolic Blood Pressure to Determine Coronary Heart Disease Risk in Healthy Middle-Aged Men

The impact of the ACE I/D polymorphism on coronary heart disease (CHD) risk is modest at most, however it may act as a modifier gene. ACE genotype was determined in 2711 healthy middle-aged men (mean age 56 years) followed for 15 years. No genotype-CHD risk association was found, but when analyzed by quartiles of systolic blood pressure (SBP), compared with II homozygotes, carriage of each additional D allele was protective at lower SBP, but in the highest quartile (SBP >150 mm Hg) conferred almost 1.5 times the risk for CHD (genotype interaction P=0.003). When SBP was analyzed as a continuous variable, again a highly significant association was seen, with the hazard ratio ([95% CI]) for a 1 SD increase in SBP being 0.90 [0.70 to 1.15] for IIs and 1.40 [1.21 to 1.61] for ID/DD (genotype SBP interaction P=0.002). The D allele was protective against CHD at lower SBP but would overtake the II risk at higher SBP. In hypertension, the proinflammatory or prohypertrophic properties of angiotensin II may explain this association. The LPL S447X polymorphism also impacts on CHD risk through interaction with hypertension, and there was an additive action of these 2 polymorphisms and SBP on CHD risk (hazard ratio for 1 SD increase in SBP for combined genotypes 1.78 [1.30 to 2.45]). Thus in the presence of hypertension, common variation in "modifier" genes confers significant CHD risk.

Dipeptidase-inactivated tACE action in vivo: selective inhibition of sperm-zona pellucida binding in the mouse

The angiotensin-converting enzyme (ACE) plays a crucial role in male fertilization and is a key regulator of blood pressure. Testicular ACE (tACE), the germinal specific isozyme expressed on different promoters, exclusively carries out the role of ACE in fertility, although the site and mode of action are not well known. To investigate the contribution of tACE in fertilization, we produced transgenic mouse lines carrying a dipeptidase-inactivated mutant. Although the transgenic mice showed normal blood pressure, kidney morphology, and fertility, reduced fertilization was observed after in vitro fertilization (IVF). The sperm-zona pellucida (ZP) binding was exclusively impaired in these lines in a manner similar to that observed in an Ace knockout mouse. The dipeptidase activity was reduced in epididymal ingredients but not in the testis. Furthermore, direct application of mutant protein did not suppress sperm-ZP binding of intact sperm during IVF, implying that the dipeptidase-inactivated mutant affects sperm modification in the epididymis for ZP binding. Our results indicate that the dipeptidase-inactivated tACE acts in vivo, suggesting that tACE contributes to fertilization as a dipeptidase at least in the epididymis.

[Immunomorphological study of angiotensin-converting enzyme in coronary shunts]

Coronary bypass surgery is the operation of choice in patients with coronary atherosclerosis. However, some time later, venous shunts frequently stop functioning after successful surgery. The reasons for this include intimal hyperplasia occurring in response to release of cytokines, angiotensin II in particular. In man, the latter is formed by angiotensin-converting enzyme or chimase. The findings show that elevated ATF concentrations are found in some cells in the area of intimal hyperplasia, in macrophages and smooth muscle cells of the shunt hyperplastic intima. The increased ATF concentration in the aorto-coronary shunt cells results in the elevated levels of angiotensin II, the migration of smooth muscle cells, their hypertrophy and hyperplasia, the formation of atherosclerotic plaques, thrombosis, and circulatory disorders.

[Protection of captopril against chronic lung disease induced by hyperoxia in neonatal rats]

OBJECTIVE

This study examined the protein and mRNA contents of angiotesin converting enzyme (ACE), angiotensin II (Ang II) and type I collagen and the changes of lung histomorphology in neonatal rats with hyperoxia-induced chronic lung disease (CLD) and investigated the protection of captopril against CLD and the possible mechanism.

METHODS

A total of 240 term neonatal Wistar rats were randomly assigned into air, model, normal saline and captopril-treated groups (n=60 each). The air group was exposed to room air (FiO2=0.21) immediately after birth. The other three groups were exposed to hyperoxia (FiO2=0.9) for 21 days to induce lung injury. The captopril-treated group received captopril daily (30 mg/kg) by intragastric administration between the 7th and 21st days of hyperoxia exposure. The normal saline group was administrated with normal saline instead. At each time interval of 1, 3, 7, 14 and 21 days after experiment, six rats of each group were randomly chosen and sacrificed. The protein and mRNA levels of ACE, Ang II and type I collagen were measured by enzyme-linked immunosorbentassay, radio-immunity technique and RT-PCR. The changes of lung histomorphology were observed under a light microscope.

RESULTS

The protein and mRNA expressions of ACE, Ang II and type I collagen increased significantly in the model and normal saline groups on the 14th and peaked on the 21st days of exposure compared with those of the air group (P < 0.05 or 0.01). Captopril treatment reduced significantly the protein and mRNA expressions of ACE, Ang II and type I collagen compared the model and normal saline groups on the 14th and 21st days, although the values were significantly higher than the air group (P < 0.05 ). The histopathologic examination demonstrated broadened lung interstitium and reduced alveolar quantity and lung fibrosis was developed in the model and normal saline groups on the 14th day of exposure. Captopril treatment obviously alleviated the changes of lung histomorphology.

CONCLUSIONS

Captopril can inhibit the protein and mRNA expressions of ACE, Ang II and type I collagen and alleviate lung fibrosis in neonatal rats with hyperoxia-induced lung injury/CLD. This may contribute to one of the possible mechanisms underlying the protective effects of captopril against lung injury/CLD.

Determination of angiotensin I-converting enzyme activity in cell culture using fluorescence resonance energy transfer peptides

An assay using fluorescence resonance energy transfer peptides was developed to assess angiotensin I-converting enzyme (ACE) activity directly on the membrane of transfected Chinese hamster ovary cells (CHO) stably expressing the full-length somatic form of the enzyme. The advantage of the new method is the possibility of using selective substrates for the two active sites of the enzyme, namely Abz-FRK(Dnp)P-OH for somatic ACE, Abz-SDK(Dnp)P-OH for the N domain, and Abz-LFK(Dnp)-OH for the C domain. Hydrolysis of a peptide bond between the donor/acceptor pair (Abz/Dnp) generates detectable fluorescence, allowing quantitative measurement of the enzymatic activity. The kinetic parameter K(m) for the hydrolysis of the three substrates by ACE in this system was also determined and the values are comparable to those obtained using the purified enzyme in solution. The specificity of the activity was demonstrated by the complete inhibition of the hydrolysis by the ACE inhibitor lisinopril. Therefore, the results presented in this work show for the first time that determination of ACE activity directly on the surface of intact CHO cells is feasible and that the method is reliable and sensitive. In conclusion, we describe a methodology that may represent a new tool for the assessment of ACE activity which will open the possibility to study protein interactions in cells in culture.

Early lung injury contributes to lung fibrosis via AT1 receptor in rats

AIM

Angiotensin II is believed to play an important role in tissue repair and remodeling in lungs by the angiotensin type I (AT1) receptor via a number of potential mechanisms. However, the role of the AT1 receptor in early lung injury has not been characterized.

METHODS

Bleomycin-induced pulmonary fibrosis (PF) in rats was utilized to value the treatment with valsartan, an AT1 receptor antagonist, by measurement of body weight, wet weight of the left lung, hydroxy-proline content, mRNA expression of collagen I/III, and the degree of fibrosis in lung tissues on d 21. Tissue injury in the early phase was assessed on d 1, 3 and 7 by apoptosis, malondialdehyde content, myeloperoxidase activity, inflammatory cell count and protein content. Angiotensin converting enzyme (ACE) activity and the AT1 receptor in lung tissues were analyzed by biochemistry method and Western blotting, respectively.

RESULTS

Valsartan ameliorated PF induced by bleomycin in the rats on d 21. After bleomycin was injected intratracheally, increases in the lung AT1 receptor and ACE activity were observed by d 1, 3 and 7. Lung injury deteriorated in the early phase. Valsartan reduced the increase of the AT1 receptor, ACE activity and lung injury induced by bleomycin in the early phase.

CONCLUSION

These observations suggest that angiotensin II may play a potent role in early lung injury via the AT1 receptor. AT1 receptor antagonists should be assessed as potential new therapies for fibrotic lung disease.

A fluorescence-based protocol for quantifying angiotensin-converting enzyme activity

The determination of angiotensin-converting enzyme (ACE) activity represents a useful tool in the study of different health pathologies, such as hypertension. This protocol describes a fluorescent assay for measuring ACE activity in vitro with high precision and sensitivity. The method relies on the ability of ACE to hydrolyse the internally quenched fluorescent substrate o-aminobenzoylglycyl-p-nitro-L-phenylalanyl-L-proline. The generation of the fluorescent product o-aminobenzoylglycine can be continuously monitored, preferably using a microtiter-plate fluorometer, though the use of a conventional cuvette fluorometer would also be possible. The method has important advantages with respect to other assays, because it involves only a one-step reagent, is easy to carry out and allows the analysis of an elevated number of samples in shorter times. It can be completed in one and a half hours. In addition, the fact that all reagents are commercially available allows the rapid introduction of the assay into the laboratory.

Expression of elevated levels of pro-inflammatory cytokines in SARS-CoV-infected ACE2+ cells in SARS patients: relation to the acute lung injury and pathogenesis of SARS

The authors have previously shown that acute lung injury (ALI) produces a wide spectrum of pathological processes in patients who die of severe acute respiratory syndrome (SARS) and that the SARS coronavirus (SARS‐CoV) nucleoprotein is detectable in the lungs, and other organs and tissues, in these patients. In the present study, immunohistochemistry (IHC) and in situ hybridization (ISH) assays were used to analyse the expression of angiotensin‐converting enzyme 2 (ACE2), SARS‐CoV spike (S) protein, and some pro‐inflammatory cytokines (PICs) including MCP‐1, TGF‐β1, TNF‐α, IL‐1β, and IL‐6 in autopsy tissues from four patients who died of SARS. SARS‐CoV S protein and its RNA were only detected in ACE2⁺ cells in the lungs and other organs, indicating that ACE2‐expressing cells are the primary targets for SARS‐CoV infection in vivo in humans. High levels of PICs were expressed in the SARS‐CoV‐infected ACE2⁺ cells, but not in the uninfected cells. These results suggest that cells infected by SARS‐CoV produce elevated levels of PICs which may cause immuno‐mediated damage to the lungs and other organs, resulting in ALI and, subsequently, multi‐organ dysfunction. Therefore application of PIC antagonists may reduce the severity and mortality of SARS. Copyright © 2006 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

A high-throughput fluorimetric assay for angiotensin I-converting enzyme

Angiotensin I-converting enzyme (ACE) assays are commonly used for measuring enzymatic activity in clinical and biological samples. The fluorimetric procedure described is sensitive, rapid and involves unsophisticated procedures and inexpensive reagents. It uses the substrate hippuryl-L-histidyl-L-leucine, and the fluorescent adduct of the enzyme-catalyzed product L-histidyl-L-leucine is quantified fluorimetrically. This assay has been adapted for a 96-well plate format that produces comparable data to previously described assays and has the advantage of greater efficiency with respect to both time and reagents. The protocol can be used for routine purposes or for more detailed kinetic analyses. The apparent Km and kcat values for purified testis ACE determined from a double reciprocal plot were 3.0 mM and 195.7 s(-1), respectively. The protocol can be completed within 4 h.

Glomerular localization and expression of Angiotensin-converting enzyme 2 and Angiotensin-converting enzyme: implications for albuminuria in diabetes

Angiotensin-converting enzyme 2 (ACE2) expression has been shown to be altered in renal tubules from diabetic mice. This study examined the localization of ACE and ACE2 within the glomerulus of kidneys from control (db/m) and diabetic (db/db) mice and the effect of chronic pharmacologic ACE2 inhibition. ACE2 co-localized with glomerular epithelial cell (podocyte) markers, and its localization within the podocyte was confirmed by immunogold labeling. ACE, by contrast, was seen only in glomerular endothelial cells. By immunohistochemistry, in glomeruli from db/db mice, strong ACE staining was found more frequently than in control mice (db/db 64.6 +/- 6.3 versus db/m 17.8 +/- 3.4%; P < 0.005). By contrast, strong ACE2 staining in glomeruli from diabetic mice was less frequently seen than in controls (db/db 4.3 +/- 2.4 versus db/m 30.6 +/- 13.6%; P < 0.05). For investigation of the significance of reduced glomerular ACE2 expression, db/db mice were treated for 16 wk with a specific ACE2 inhibitor (MLN-4760) alone or combined with telmisartan, a specific angiotensin II type 1 receptor blocker. At the end of the study, glomerular staining for fibronectin, an extracellular matrix protein, was increased in both db/db and db/m mice that were treated with MLN-4760. Urinary albumin excretion (UAE) increased significantly in MLN-4760-treated as compared with vehicle-treated db/db mice (743 +/- 200 versus 247 +/- 53.9 microg albumin/mg creatinine, respectively; P < 0.05), and the concomitant administration of telmisartan completely prevented the increase in UAE associated with the ACE2 inhibitor (161 +/- 56; P < 0.05). It is concluded that ACE2 is localized in the podocyte and that in db/db mice glomerular expression of ACE2 is reduced whereas glomerular ACE expression is increased. The finding that chronic ACE2 inhibition increases UAE suggests that ACE2, likely by modulating the levels of glomerular angiotensin II via its degradation, may be a target for therapeutic interventions that aim to reduce albuminuria and glomerular injury.

No changes in lung function after a saturation dive to 2.5 MPa with intermittent reduction in $$ P_{{{{\rm O}}_{{{\rm 2}}} }} $$ during decompression

Decompression stress and exposure to hyperoxia may cause a reduction in transfer factor of the lung for carbon monoxide and in maximal aerobic capacity after deep saturation dives. In this study lung function and exercise capacity were assessed before and after a helium-oxygen saturation dive to a pressure of 2.5 MPa where the decompression rate was reduced compared with previous deep dives, and the hyperoxic exposure was reduced by administering oxygen intermittently at pressures of 50 and 30 kPa during decompression. Eight experienced divers of median age 41 years (range 29-48) participated in the dive. The incidence of venous gas microemboli was low compared with previous deep dives. Except for one subject having treatment for decompression sickness, no changes in lung function or angiotensin converting enzyme, a marker of pulmonary endothelial cell damage, were demonstrated. The modified diving procedures with respect to decompression rate and hyperoxic exposure may have contributed to the lack of changes in lung function in this dive compared with previous deep saturation dives.

Role of chymase-dependent angiotensin II formation in monocrotaline-induced pulmonary hypertensive rats

Angiotensin II-forming chymase is expressed in the pulmonary arteries of the monocrotaline-induced pulmonary hypertensive rats, but its actual role is unclear. We studied chymase-dependent angiotensin II formation in the pulmonary arteries of the monocrotaline-induced pulmonary hypertensive rats and observed the effects of an angiotensin II receptor blocker on vascular remodeling. Four weeks after the administration of monocrotaline (60 mg/kg, s.q.), echocardiographic, hemodynamic, morphometric and biochemical analyses were performed. Age-matched rats were used as controls. To evaluate the effects of an angiotensin II receptor blocker, 2 wk after beginning of monocrotaline treatment, the rats were given candesartan (10 mg/kg per day) or placebo for 2 wk. In the monocrotaline-induced pulmonary hypertensive rats, the elevated systolic pulmonary arterial pressure and right ventricular hypertrophy were observed. Medial hypertrophy of lung arterioles was also observed. Chymase activity and angiotensin II concentration, but not angiotensin-converting enzyme activity, were significantly increased in the lung. In the angiotensin II receptor blocker-treated group, both systolic pulmonary arterial pressure and right ventricular hypertrophy were significantly reduced, and arteriolar hypertrophy was also prevented. Thus, angiotensin II-forming chymase may play a role in the proliferation of the medial layer in the lung arterioles of monocrotaline-induced pulmonary hypertensive rats.

Renin-angiotensin system is an important factor in hormone refractory prostate cancer

BACKGROUND

The aim of this study was to perform a comprehensive evaluation of the renin-angiotensin system (RAS) in prostate cancer.

METHODS

We investigated the expression of RAS components in prostate cancer cells treated with hormonal agents. Real-time PCR data showed the expression of the AT1 receptor, angiotensin I converting enzyme (ACE), and angiotensin I/II (Ang-I/II) precursor in all 87 prostate tissue samples.

RESULTS

Expression of these genes in hormone refractory prostate cancer (HRPC) was significantly higher than that in normal prostate tissue and untreated prostate cancer tissue. Western blot showed that protein expression of the AT1 receptor and Ang-I/II was enhanced in LNCaP cells cultivated in steroid-free medium. When LNCaP cells were stimulated with dihydrotestosterone (DHT), estradiol (E2), dexamethasone (DEX), or anti-androgen drugs, protein expression of the AT1 receptor and Ang-I/II was augmented.

CONCLUSIONS

The present data suggest that prostatic RAS is overexpressed in HRPC tissue, and expression of its components is influenced by several kinds of hormonal stimulation.

Angiotensin-(1-7) inhibits angiotensin II-stimulated phosphorylation of MAP kinases in proximal tubular cells

Angiotensin-converting enzyme 2 (ACE2) is a homolog of ACE, which is not blocked by ACE inhibitors. High amounts of ACE2 are present in the proximal tubule, and ACE2 catalyzes generation of angiotensin 1-7 (Ang-(1-7)) by this segment. Ang-(1-7) binds to a receptor distinct from the AT1 or AT2 Ang II receptor, identified as the mas receptor. We studied the effects of Ang-(1-7) on Ang II-mediated cell signaling pathways in proximal tubule. In primary cultures of rat proximal tubular cells, activation of mitogen-activated protein kinases (MAPK) was detected by immunoblotting, in the presence or absence of agonists/antagonists. Transforming growth factor-beta1 (TGF-beta1) was measured by enzyme-linked immunosorbent assay. Ang II (5 min, 10(-7) M) stimulated phosphorylation of the three MAPK (p38, extracellular signal-related kinase (ERK 1/2), and c-Jun N-terminal kinase (JNK)). While incubation of proximal tubular cells with Ang-(1-7) alone did not significantly affect MAPK phosphorylation, Ang-(1-7) (10(-7) M) completely inhibited Ang II-stimulated phosphorylation of p38, ERK 1/2, and JNK. This inhibitory effect was reversed by the Ang-(1-7) receptor antagonist, D-Ala7-Ang-(1-7). Ang II significantly increased production of TGF-beta1 in proximal tubular cells, an effect that was partly inhibited by Ang-(1-7). Ang-(1-7) had no significant effect on cyclic 3',5'-adenosine monophosphate production in these cells. In summary, Ang-(1-7) inhibits Ang II-stimulated MAPK phosphorylation in proximal tubular cells. Generation of Ang-(1-7) by proximal tubular ACE2 could thereby serve a protective role by counteracting the effects of locally generated Ang II.

New mass spectrometric assay for angiotensin-converting enzyme 2 activity

A novel assay was developed for evaluation of mouse angiotensin-converting enzyme (ACE) 2 and recombinant human ACE2 (rACE2) activity. Using surface-enhanced laser desorption/ionization time of flight mass spectrometry (MS) with ProteinChip Array technology, ACE1 and ACE2 activity could be measured using natural peptide substrates. Plasma from C57BL/6 mice, kidney from wild-type and ACE2 knockout mice, and rACE2 were used for assay validation. Plasma or tissue extracts were incubated with angiotensin I (Ang I; 1296 m/z) or angiotensin II (Ang II; 1045 m/z). Reaction mixtures were spotted onto the ProteinChips WCX2 and peptides detected using surface-enhanced laser desorption/ionization time of flight MS. MS peaks for the substrates, Ang I and Ang II, and the generated peptides, Ang (1-7) and Ang (1-9), were monitored. The ACE2 inhibitor MLN 4760 (0.01 to 100 micromol/L) significantly inhibited rACE2 activity (IC50=3 nmol/L). Ang II was preferably cleaved by rACE2 (km=5 mumol/L), whereas Ang I was not a good substrate for rACE2. There was no detectable ACE2 activity in plasma. Assay specificity was validated in a model of ACE2 gene deletion. In kidney extract from ACE2-deficient mice, there was no generation of Ang (1-7) from Ang II. However, Ang (1-7) was produced when Ang I was used as a substrate. In conclusion, we developed a specific and sensitive assay for ACE2 activity, which used the natural endogenous peptide substrate Ang II. This approach allows for the rapid screening for ACE2, which has applications in drug testing, high-throughput enzymatic assays, and identification of novel substrates/inhibitors of the renin-angiotensin system.

Monoclonal antibodies to native mouse angiotensin-converting enzyme (CD143): ACE expression quantification, lung endothelial cell targeting and gene delivery

We demonstrated previously that the monoclonal antibody 9B9 to angiotensin-converting enzyme (ACE), which accumulates very selectively into the rat lung after systemic injection, is a powerful tool for immunotargeting of therapeutic agents or genes to the rat lung vascular bed. Bearing in mind a high research and therapeutic potential of lung targeting via ACE, we obtained a new set of rat monoclonal antibodies to different epitopes of mouse ACE in order to expand this approach to mice. Nine new monoclonal antibodies, recognizing epitopes on the N- and C-domains of catalytically active mouse ACE, were obtained and examined for their efficacy to bind ACE both in vitro and in vivo. This set of monoclonal antibodies was proved to be useful for ACE quantification (by flow cytometry and cell enzyme-linked immunosorbent assay) on the surface of different mouse ACE-expressing cells: endothelial cells, monocytes, macrophages, dendritic cells and spermatozoa. Moreover, gene delivery into mouse ACE-expressing cells using adenoviruses increased 40-fold after redirecting of these viruses to ACE (by coating these viruses with anti-ACE monoclonal antibodies). Radiolabelled (I(125)) monoclonal antibodies specifically accumulated in the mouse lung after systemic injection. Monoclonal antibodies 3G8.17, 4B10.5 and 4B10.17 demonstrated the highest level of lung uptake, 40-50% of injected dose, and high selectivity of lung uptake. Influence of monoclonal antibodies on ACE shedding was negligible, except monoclonal antibody 1D10.11. None of the tested monoclonal antibodies inhibited ACE activity in vitro. In conclusion, a new set of rat monoclonal antibodies to mouse ACE was obtained suitable to study ACE biology in mice and for ACE expression quantification on mouse cells in particular. These monoclonal antibodies also demonstrated highly efficient and selective lung accumulation and thus has the potential for targeting drugs/genes to the pulmonary vasculature in different mouse models of human lung diseases, including numerous knockout models.

Equine endometrial fibrosis correlates with 11beta-HSD2, TGF-beta1 and ACE activities

Endometrial periglandular fibrosis (EPF) contributes to embryonic and fetal loss in mares. Equine EPF correlates inversely with conception and successful gestation. In the modified Kenney endometrial biopsy classification system, EPF categories I, IIA, IIB, and III correspond to minimal, mild, moderate, and severe fibrosis (+/-inflammation), respectively. Paraffin sections of biopsy specimens were stained with H&E, and picrosirius red (specific for fibrillar collagens types I and III), to determine %EPCVF. Endometrial ACE-binding activity, TGF-beta1 and 11beta-HSD2 activities were also measured. Ultrastructural changes in EPF categories IIB and III endometria strongly suggested myofibroblastic transformation. ACE-binding activity was highest in EPF category IIB; however, endometrial TGF-beta1 and 11beta-HSD2 activities were significantly correlated to the severity of EPF (P<0.05). We conclude that, locally generated angiotensin II initiates the expression of TGF-beta1 resulting in myofibroblastic transformation. 11Beta-HSD2 in concert appears to modulate the severity of endometrial fibrosis.

Escherichia coli lipopolysaccharide inhibits renin activity in human mesangial cells

Hyperactivation of systemic renin-angiotensin system (RAS) during sepsis is well documented. However, the behavior of intrarenal RAS in the context of endotoxemia is yet to be defined. The present study evaluates the direct effect of Escherichia coli lipopolysaccharide (LPS) on immortalized human mesangial cell (HMC) RAS. Quiescent HMC were incubated with vehicle or LPS (1-100 microg/ml), and levels of angiotensin I and II (Ang I and II) and their metabolites were analyzed by high-performance liquid chromatography. In addition, angiotensin-converting enzyme (ACE) and renin activity were also investigated. Cell lysate and extracellular medium levels of Ang II were rapidly reduced (1 h) in a time- and concentration-dependent manner, reaching a significant -9 fold-change (P<0.001) after 3 h of LPS incubation. Similar results were obtained for Ang I levels (-3 fold-change, P<0.001). We ruled out Ang I and II degradation, as levels of their metabolic fragments were also significantly decreased by LPS. ACE activity was slightly increased following LPS incubation. On the other hand, renin activity was significantly inhibited, as Ang I concentration elevation following exogenous angiotensinogen administration was blunted by LPS (-60% vs vehicle, P<0.001). Renin and angiotensinogen protein levels were not affected by LPS according to Western blot analysis. Taken together, these data demonstrate for the first time that LPS significantly downregulates HMC RAS through inhibition of renin or renin-like activity. These findings are potentially related to the development of and/or recovery from acute renal failure in the context of sepsis.

Cellular immunostaining of angiotensin-converting enzyme in human coronary atherosclerotic plaques

OBJECTIVES

The aim of this study was to determine the cellular localization of angiotensin I-converting enzyme (ACE) in the atherosclerotic plaque and its correlation with inflammation and cellular proliferation.

BACKGROUND

Angiotensin I-converting enzyme inhibitors reduce the incidence of vascular events; therefore, tissue ACE may play a determinant role in the pathophysiology of the atherosclerotic plaque.

METHODS

Histology and immunocytochemistry of de novo coronary plaques retrieved with directional coronary atherectomy from 141 patients were analyzed: 87 with stable angina, 39 with subacute unstable angina, and 15 with acute unstable angina.

RESULTS

Compared with stable patients, unstable patients showed more thrombotic lesions (72% vs. 27%, p < 0.0001), smaller areas of fibrous plaque (2.3 +/- 1.2 mm2 vs. 2.8 +/- 1.1 mm2, p = 0.02), higher cellular proliferative score (0.78 +/- 0.9 vs. 0.27 +/- 0.6, p = 0.003), larger content of ACE-stained cells (26.3 +/- 23% vs. 12.6 +/- 15%, p = 0.005) and larger areas of inflammation as identified by CD68 immunostaining (29.5 +/- 22% vs. 20.2 +/- 19%, p = 0.02). A significant linear correlation was found between CD68- and ACE-stained areas (mm2) among unstable patients (r = 0.6, p = 0.0001), but it was absent among stable patients (r = 0.006, p = 0.9). Co-localization of ACE, CD68, and alpha-actin was confirmed by double immunostaining. Patients with Ki-67-positive staining as an index of cell proliferation showed also significantly larger areas of ACE immunoactivity (p = 0.004).

CONCLUSIONS

Our data demonstrate ACE immunoactivity in inflammatory and proliferative cells of coronary atherosclerotic plaques. In particular, patients with unstable angina showed larger areas of ACE immunoactive tissue and proliferating cells compared with stable patients. These observations support a role of the enzyme in the pathophysiology of coronary unstable plaques and suggest potentially different effects of ACE inhibitors according to clinical presentation.

Performance of two commonly used angiotensin-converting enzyme inhibition assays using FA-PGG and HHL as substrates

In development of fermented dairy products and protein hydrolysates with high inhibitory activity towards angiotensin-converting enzyme (ACE), it is crucial to have a reliable assay for measuring the ACE activity. In the present study, the performance of two commonly used assays based on synthetic N-derivates of tripeptides as substrates were tested with respect to reliability in determination of ACE activity per se and to the inhibitory effect of a tryptic whey protein digest and captopril. In one test, the ACE activity was calculated from the amount of hippuric acid liberated from hippuryl-His-Leu (HHL) during 30 min of incubation with ACE, as quantified after HPLC separation of reaction products. In the other assay, the ACE activity was measured directly as the rate of decrease in the absorbance at 340 nm during the first 30 min of ACE catalysed hydrolysis of furanacroloyl-Phe-Glu-Glu (FA-PGG). Both assays, in the absence of inhibitor, showed a good performance with relative standard deviation between replicate samples around 7%. In the presence of inhibitor solutions, relative standard deviations for both assays varied between 1 and 18% for the variously diluted inhibitors. Both assays gave values for the concentration of inhibitor needed to inhibit ACE by 50% similar to those previously reported for whey protein digests and captopril. Different results from the two assays, however, emphasize the importance of controlling the actual ACE-activity for comparison between assays. The limitations of each assay are discussed. Considering the fewer steps in the assay using FA-PGG as substrate, and thus less time and chemicals consumed per sample, and the simpler equipment needed, this assay is recommended for the screening of clear peptide samples.

Increased expression of monocytic angiotensin-converting enzyme in dialysis patients with cardiovascular disease

BACKGROUND

Patients with chronic renal disease suffer from accelerated atherogenesis, which is promoted by inflammation and oxidative stress. Tissue angiotensin converting enzyme (ACE) exerts proinflammatory and prooxidative effects by producing angiotensin II. Monocytes are strongly involved in the pathogenesis of atherosclerosis. They express ACE, which might contribute to their atherogenic potency. We hypothesize that dialysis patients have increased monocytic ACE expression, and that ACE expression on circulating monocytes is associated with prevalent cardiovascular disease.

METHODS

In 74 dialysis patients, ACE expression on total monocytes and monocyte subsets was measured flow-cytometrically in a whole-blood assay. A subpopulation of 22 dialysis patients was compared to an age- and gender-matched control group with intact renal function. Cardiovascular risk factors and the prevalence of cardiovascular disease were assessed. In a subgroup of patients (n = 8), monocytic ACE activity was measured in vitro and correlated with monocytic ACE expression.

RESULTS

Dialysis patients had an increased expression of monocytic ACE compared to controls. Monocytic ACE expression was higher in dialysis patients with prevalent cardiovascular disease than in those without cardiovascular disease. This association remained significant after correction for classical cardiovascular risk factors. Among monocyte subsets, CD14++CD16+ monocytes had the highest ACE expression. Monocytic ACE activity correlated with ACE surface expression.

CONCLUSIONS

The finding of increased ACE expression on monocytes of dialysis patients with cardiovascular disease links monocytes to the activated renin-angiotensin system. ACE expression was found highest among CD14++16+ monocytes, which is in accordance with a prominent role of these proinflammatory cells in atherogenesis.

Histochemical characteristics of soleus muscle in angiotensin-converting enzyme gene knockout mice

We examined the histochemical characteristics of soleus muscle in the angiotensin-converting enzyme (ACE) gene (Ace in mice, ACE in humans) knockout mice. Serial sections of soleus muscle of wild-type (Ace+/+, n=20) and heterozygous mutant (Ace+/-, n=24) mice were stained for myosin adenosine triphosphatase activity to identify different muscle fiber types. Capillaries were visualized by amylase-periodic acid-Schiff staining. ACE activity in the serum and gastrocnemius muscle was higher in male mice than in female mice. Female and male Ace+/- mice had markedly lower ACE activity in the serum and the gastrocnemius muscle than did female and male Ace+/+ mice, respectively. In both male and female mice, the composition of fiber types (type I and IIa) did not differ significantly between Ace+/+ and Ace+/- mice. There was no significant gender difference in capillary density. Ace+/- mice had significantly more capillaries around type IIa fibers (5.44 +/- 0.18 vs. 5.01 +/- 0.13, p<0.05) than Ace+/+ mice. The differences in the number of capillaries around type I fibers and in the number of capillaries around per fiber (capillary:fiber ratio) between Ace+/- and Ace+/+ mice were not significant (p<0.1). There was no significant difference in the mean cross-sectional area occupied by one capillary and the number of capillaries per fiber area between Ace+/+ and Ace+/- mice. In conclusion, knockout of the Ace gene in mice increased capillary density, as expressed by the mean number of capillaries around type IIa fibers. This finding suggests a possible mechanism for the cardioprotective effects of ACE inhibitors.

Quantitative study of testicular angiotensin-converting enzyme on the surface of human spermatozoa

Expression of testicular angiotensin-converting enzyme on the surface of human spermatozoa was studied by means of flow cytometry with monoclonal antibodies. Expression of testicular angiotensin-converting enzyme on the cell surface depended on functional and morphological characteristics of spermatozoa.

Angiotensin I-converting enzyme-dependent and neutral endopeptidase-dependent generation and degradation of angiotensin II contrarily modulate noradrenaline release: implications for vasopeptidase-inhibitor therapy?

OBJECTIVES

Vasopeptidase inhibitors inhibit neutral endopeptidase (NEP) and angiotensin I-converting enzyme (ACE). Since angiotensin (ANG) II availability is decreased by ACE inhibition but is increased by NEP inhibition, we evaluated the influence of the vasopeptidase inhibitor omapatrilat on ANG II-dependent noradrenaline (NA) release.

DESIGN

The functional relevance of ACE-dependent and NEP-dependent generation and degradation of ANG II on NA overflow was determined in pithed rats by applications of ANG I (0.1-100 microg/kg) or ANG II (0.01-10 microg/kg) after single injections of ramipril (1 mg/kg), the NEP inhibitor candoxatril (100 mg/kg), or the vasopeptidase inhibitor omapatrilat (30 mg/kg).

RESULTS

Blood pressure was equipotently decreased by ramipril and omapatrilat, but not by candoxatril. NA overflow was increased after ANG I infusions in controls (EC50 = 9.0 microg/kgANG I, Emax = 5680 pg/ml), but almost completely suppressed by ramipril and omapatrilat. Candoxatril decreased EC50 (4.1 microg/kg) and increased Emax (7259 pg/ml). NA overflow after ANG II infusions was enhanced by candoxatril or omapatrilat. Ex vivo ACE activity was extensively inhibited by ramipril or omapatrilat, whereas ex vivo NEP activity was reduced by omapatrilat and candoxatril only. In vitro, omapatrilat inhibited NEP and ACE with similar potencies (IC50 NEP/IC50 ACE = 0.4).

CONCLUSIONS

Vasopeptidase inhibitors influence ANG II-related NA release depending on their ability to modulate the availability of ANG II via ACE or NEP. After acute application, the vasopeptidase inhibitor suppresses NA release in response to ANG I due to a predominant reduction of ANG II formation. These results indicate that the ratio of ACE-inhibitory and NEP-inhibitory potencies of vasopeptidase inhibitors may be relevant for sympathetic activation in chronic therapy.