Oxidative stress and nitric oxide synthase in skeletal muscles of rats with post-infarction, compensated chronic heart failure

AIM

Involvement of oxidative stress and nitric oxide synthase (NOS) isoforms in skeletal muscle cellular adaptations to chronic heart failure (CHF) is controversial, and possible muscle fibre-type heterogeneity in the oxidative stress and NOS responses to CHF have not been examined. Consequently, we hypothesized that the changes in determinants of elevated oxidative and nitrosylative stress associated with CHF would occur in skeletal muscle and would be similar in predominantly type I slow twitch muscle (soleus) and type II fast twitch muscle (plantaris) of rats.

METHODS

The purpose of this study was to measure NOS isoforms (endothelial, inducible and neuronal NOS) and antioxidant enzymes (SOD-1, SOD-2, catalase) by protein immunoblot as well as markers of oxidative stress by biochemical assays in soleus and plantaris muscle sections of the rat hind limb. This was performed for control and post-infarction, compensated CHF rats.

RESULTS

Twelve weeks after coronary artery ligation-induced moderate CHF, soleus exhibited decreased SOD-1, SOD-2 and eNOS, but increased iNOS and nNOS isoforms assessed by immunoblot. This was associated with elevated lipid and DNA oxidative damage assessed by biochemical assays. In contrast, plantaris muscle exhibited no changes in antioxidant enzymes or NOS isoforms, and had lower lipid and DNA oxidative damage.

CONCLUSION

These observations suggest a heretofore unreported muscle fibre-type-specific response of oxidative stress and NOS isoforms to CHF is of importance in understanding the cellular mechanisms of skeletal muscle dysfunction in CHF.

Activity of Angiotensin-Converting Enzyme in Hereditary Stress-Induced Arterial Hypertension

We measured activity of angiotensin-converting enzyme in plasma and tissue of NISAG and normotensive WAG rats. In different organs of NISAG rats, activity of this enzyme did not differ from the corresponding values of WAG rats, although enzyme activity in the plasma of NISAG rats was significantly lower than that of WAG rats. Since NISAG rats are characterized by low activity of renin in the renal cortex, it is hypothesized that NISAG rats simulate the low-renin hypertension, in which inhibition of activity of the angiotensin-production system results from elevation of arterial pressure of central origin.

Expression of Metallopeptidases and Kinin Receptors in Swine Oropharyngeal Tissues: Effects of Angiotensin I-Converting Enzyme Inhibition and Inflammation

Angiotensin I-converting enzyme inhibitors (ACEi) cause both chronic and acute side effects, including rare but potentially life-threatening angioedema (AE). The main hypothesis to be tested in this study was that metallopeptidases and kinin receptors are present in oropharyngeal tissues and that their expression is modulated by ACEi and inflammation. Novel real-time polymerase chain reaction analysis was developed and allowed the relative quantification of tissue's gene expression for neprilysin, membrane-bound aminopeptidase P (mAPP), and both B1 and B2 kinin receptor subtypes in tongue, parotid gland, and laryngeal tissue (areas especially involved in the gravest clinical forms of AE) and in kidney in a porcine model (single injection or 7-day ACEi oral treatments applied or lipopolysaccharide injected as a positive inflammatory control). The results provide evidence of the expression and activities of kininases in oropharyngeal tissues in the swine. ACEi treatment modulated the expression of neutral endopeptidase and mAPP mRNA, but the corresponding enzyme activities and that of angiotensin I-converting enzyme (ACE) were generally stable in tissues. The 7-day ACEi treatment up-regulated both kinin receptor mRNAs in the oropharynx and the B1 receptor mRNA in the lingual vascular endothelium (immunohistochemistry). The inhibition of ACE in plasma is responsible for an accumulation of bradykinin and des-arginine9-bradykinin generated during activation of the contact system with glass beads. The expression of critical components of the kallikrein-kinin system in the oropharyngeal tissues supports the role of kinins in ACEi-induced AE.

The number of lymph node metastases in gastric cancer correlates with the angiotensin I-converting enzyme gene insertion/deletion polymorphism

PURPOSE

In the present study, we aimed to substantiate the putative significance of angiotensin I-converting enzyme (ACE) on gastric cancer biology by investigating the influence of its gene polymorphism on gastric cancer progression.

EXPERIMENTAL DESIGN

Genomic DNA was purified from peripheral blood mononuclear cells or tissue specimens. Amplified ACE gene fragments were separated on agarose gels. D or I alleles were identified by the presence of 190- or 490-bp fragments, respectively. Local expression of ACE was investigated by immunohistochemistry.

RESULTS

Twenty-four of 113 (21%) gastric cancer patients had the II, 57 (51%) the ID, and 32 (28%) the DD genotype. The distribution of the ACE genotypes did not differ significantly from the control group of 189 patients without gastric cancer. However, the ACE genotypes correlated with the number of lymph node metastases and the Unio Internationale Contra Cancrum (UICC) tumor stage. Patients with the II genotype had a highly significantly smaller number of lymph node metastases (P < 0.001) and a significantly lower UICC tumor stage (P = 0.01) than patients with the DD genotype. No correlation was found between tumor type, tumor location, local tumor growth, distant metastases, and the ACE genotype. The expression of ACE in gastric cancer was investigated by immunohistochemistry in 100 of 113 patients. ACE was expressed by endothelial cells in all (100%) specimens and by tumor cells in 56 (56%) specimens.

CONCLUSIONS

Our study shows that ACE is expressed locally in gastric cancer and that the gene polymorphism influences metastatic behavior.

A continuous fluorescent assay for the determination of plasma and tissue angiotensin I-converting enzyme activity

A continuous assay using internally quenched fluorescent peptides with the general sequence Abz-peptidyl-(Dnp)P-OH (Abz = ortho-aminobenzoic acid; Dnp = 2,4-dinitrophenyl) was optimized for the measurement of angiotensin I-converting enzyme (ACE) in human plasma and rat tissues. Abz-FRK(Dnp)P-OH, which was cleaved at the Arg-Lys bond by ACE, was used for the enzyme evaluation in human plasma. Enzymatic activity was monitored by continuous recording of the fluorescence (lambda ex = 320 nm and lambda em = 420 nm) at 37 degrees C, in 0.1 M Tris-HCl buffer, pH 7.0, with 50 mM NaCl and 10 microM ZnCl2. The assays can be performed directly in the cuvette of the fluorimeter and the hydrolysis followed for 5 to 10 min. ACE measurements in the plasma of 80 healthy patients with Hip-His-Leu and with Abz-FRK(Dnp)P-OH correlated closely (r = 0.90, P < 0.001). The specificity of the assay was demonstrated by the complete inhibition of hydrolysis by 0.5 microM lisinopril or captopril. Abz-FRK(Dnp)P-OH cleavage by ACE was monitored in rat lung, kidney, heart, and liver homogenates in the presence of a cocktail of inhibitors containing trans-epoxy-succinyl-L-leucylamido-(4-guanido)-butene, pepstatin, phenyl-methylsulfonyl fluoride, N-tosyl-L-phenylalanyl-chloromethyl ketone, and N-tosyl-lysyl-chloromethyl ketone to prevent undesirable hydrolysis. ACE activity in lung, heart and kidney homogenates, but not in liver homogenates, was completely abolished by 0.5 microM lisinopril or captopril. The advantages of the method are the procedural simplicity and the high sensitivity providing a rapid assay for ACE determinations.

Development and characterization of rat monoclonal antibodies to denatured mouse angiotensin-converting enzyme

Four new rat monoclonal antibodies, generated to denatured mouse somatic angiotensin-converting enzyme (ACE, CD143), detect mouse ACE with high sensitivity in Western blotting. Epitope mapping for the monoclonal antibodies--B12, 4G6 and 5C4--was also performed. Two monoclonal antibodies--B12 and 5C4--are directed to various epitopes on the N-domain--i.e., they recognized only the somatic isoform of mouse ACE. The monoclonal antibody H7 recognized an epitope on the C-domain of mouse ACE. The monoclonal antibody 4G6 was directed to a sequence on the N-domain of mouse ACE, which is homologous to a region of the C-domain and, as a result, also recognizes mouse testicular ACE (tACE) by means of Western blotting. In paraffin-embedded mouse tissues, all monoclonal antibodies detected all known expression sites of somatic ACE (sACE), e.g., the epithelial cells of the kidney proximal tubules, intestine and epididymis, and heterogeneously in endothelial cells. The monoclonal antibodies 4G6 and H7 additionally stained mouse tACE in spermatozoa and in mature spermatids. The monoclonal antibody 4G6 also demonstrated cross-reactivity with sACE from a broad spectrum of animal species, including human, rat, rabbit and bovine. However, this monoclonal antibody did not recognize the testicular isoform of ACE of these species. This set of monoclonal antibodies is useful for identifying even subtle changes in mouse ACE conformation because of denaturation. These monoclonal antibodies are also sensitive tools for the detection of mouse ACE in biological fluids and tissues by using proteomics approaches. Their high reactivity in paraffin-embedded tissues opens up opportunities to study possible changes in the pattern of ACE expression in knockout mouse models and may prove useful for correlating ACE expression in these models with human diseases.

Calcium Channel Blockades Exhibit Anti-Inflammatory and Antioxidative Effects by Augmentation of Endothelial Nitric Oxide Synthase and the Inhibition of Angiotensin Converting Enzyme in the NG-Nitro-L-Arginine Methyl Ester-Induced Hypertensive Rat Aorta: Vasoprotective Effects beyond the Blood Pressure-Lowering Effects of Amlodipine and Manidipine

Long-acting dihydropyridine calcium channel blockades have been shown to limit the progression of atherosclerosis and decrease the incidence of cardiovascular events in humans and animals. To investigate the vasoprotective effects beyond the blood pressure-lowering effects of these agents, amlodipine (20 mg/kg/ day) and manidipine (10 mg/kg/day) were administered by gavage to N(G)-nitro-L-arginine methyl ester (L-NAME)-induced hypertensive rats for 2 weeks. L-NAME treatment (0.7 mg/ml in drinking water) significantly decreased the gene and protein expression of endothelial nitric oxide synthase (eNOS) and increased nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, vascular cell adhesion molecule-1 (VCAM-1), and monocyte chemoattractant protein-1 (MCP-1) mRNA levels in the aorta, as determined by Western blotting and reverse transcription (RT)-polymerase chain reaction (PCR). Amlodipine and manidipine normalized the decreased expression of eNOS gene and protein, and attenuated the overexpression of NADPH oxidase, VCAM-1, and MCP-1 mRNA. Furthermore, amlodipine and manidipine prevented the L-NAME-induced increase in the angiotensin converting enzyme (ACE) mRNA content, thereby restoring control levels in the aorta. On the other hand, hydralazine treatment had no such effect in L-NAME treated rats. Furthermore, the increased expression of manganese superoxide dismutase (Mn-SOD) by L-NAME treatment was not affected by amlodipine, manidipine, or hydralazine. We concluded that the direct anti-inflammatory and antioxidative effects of calcium channel blockades in the aorta of rats with L-NAME-induced hypertension were not likely to have been mediated by the blood pressure-lowering action of these agents, but instead these beneficial effects appear to have been mediated by an augmentation of eNOS expression and by the inhibition of the expression of ACE.

Hypercholesterolemia stimulates angiotensin peptide synthesis and contributes to atherosclerosis through the AT1A receptor

BACKGROUND

Hypercholesterolemia-induced atherosclerosis is attenuated by either pharmacological antagonism of AT1 receptors or AT1A receptor deficiency. However, the mechanism underlying the pronounced responses to angiotensin II (Ang II) antagonism has not been determined. We hypothesized that hypercholesterolemia stimulates the production of angiotensin peptides to provide a rationale for the profound effect of AT1A receptor deficiency on atherogenesis.

METHODS AND RESULTS

Atherosclerotic lesions were analyzed in LDL receptor-deficient mice. Immunocytochemical analysis demonstrated that atherosclerotic lesions contained all the components of the conventional pathway for Ang II synthesis. AT1A receptor deficiency caused a marked decrease in atherosclerotic lesion size in both the aortic root and arch of male and female mice, without a discernible effect on composition. AT1A receptor deficiency-induced reductions in atherosclerosis were independent of systolic blood pressure and measurements of oxidation and chemoattractants. Aortic AT2 receptor mRNA expression was not altered in AT1A receptor-deficient mice, and AT2 receptor deficiency had no effect on lesion area or cellular composition. Hypercholesterolemia greatly augmented the systemic renin-angiotensin system, as demonstrated by large increases in plasma concentrations of angiotensinogen and angiotensin peptides (Ang II, III, IV, and 4-8). These increases were ablated in hypercholesterolemic AT1A receptor-deficient mice.

CONCLUSIONS

AT1A receptor deficiency had a striking effect in reducing hypercholesterolemia-induced atherosclerosis in LDL receptor-negative mice. Hypercholesterolemia was associated with increased systemic angiotensinogen and angiotensin peptides, which were reduced in AT1A receptor-deficient mice. These results demonstrate that hypercholesterolemia-induced stimulation of angiotensin peptide production provides a basis for the marked effect of AT1A receptor deficiency in reducing atherosclerosis.

Individual differences in renal ACE activity in healthy rats predict susceptibility to adriamycin-induced renal damage

BACKGROUND

In man, differences in angiotensin-converting enzyme (ACE) levels, related to ACE (I/D) genotype, are associated with renal prognosis. This raises the hypothesis that individual differences in renal ACE activity are involved in renal susceptibility to inflicted damage. Therefore, we studied the predictive effect of renal ACE activity for the severity of renal damage induced by a single injection of adriamycin in rats.

METHODS

Renal ACE activity (Hip-His-Leu cleavage by cortical homogenates) was determined by renal biopsy in 27 adult male Wistar rats. After 1 week of recovery, proteinuria was induced by adriamycin [1.5 mg/kg intravenously (i.v.) n = 18; controls, saline i.v. n = 9]. Proteinuria was measured every 2 weeks. After 12 weeks, rats were sacrificed and their kidneys harvested.

RESULTS

As anticipated, adriamycin elicited nephrotic range proteinuria, renal interstitial damage and mild focal glomerulosclerosis. Baseline renal ACE positively correlated with the relative rise in proteinuria after adriamycin (r = 0.62, P<0.01), renal interstitial alpha-smooth muscle actin (r = 0.49, P<0.05), interstitial macrophage influx (r = 0.56, P<0.05), interstitial collagen III (r = 0.53, P<0.05), glomerular alpha-smooth muscle actin (r = 0.74, P<0.01) and glomerular desmin (r = 0.48, P<0.05). Baseline renal ACE did not correlate with focal glomerulosclerosis (r = 0.22, NS). In controls, no predictive values for renal parameters were observed.

CONCLUSION

Individual differences in renal ACE activity predict the severity of adriamycin-induced renal damage in this outbred rat strain. This supports the assumption that differences in renal ACE activity predispose to a less favourable course of renal damage.

Developmental changes in pulmonary and renal angiotensin-converting enzyme concentration in fetal and neonatal horses

Angiotensin-converting enzyme (ACE) has an active role in the control of blood pressure and body fluid homeostasis both before and after birth. This study investigated the ontogeny of pulmonary and renal ACE concentrations in fetal and neonatal horses. Fetal pulmonary ACE concentration increased from 250 days towards term (c. 335 days). Newborn foals showed significantly higher mean concentrations of pulmonary ACE (4.40 +/- 0.62 nmol min(-1) mg protein(-1)) than both fetuses during late gestation (1.23 +/- 0.51 nmol min(-1) mg protein(-1)) and animals aged 1 day to 2 weeks of postnatal age (0.85 +/- 0.15 nmol min(-1) mg protein(-1)). Renal ACE was detected in fetal horses from 100 days of gestation but showed no developmental trend during the second half of gestation or in early postnatal life. Overall in the fetus, mean concentrations of renal ACE were also approximately 10 times lower than mean pulmonary values. Renal ACE concentration may be related to the functional immaturity of the equine kidneys. The increase in pulmonary ACE concentration seen towards term in the fetal horse may be induced by the prepartum cortisol surge that occurs very close to delivery in this species. Therefore, premature delivery in this species may interrupt the onset of ACE production in the fetal lungs and circumvent the normal maturation of the renin-angiotensin system.

Atrial Natriuretic Peptide Helps Prevent Late Remodeling After Left Ventricular Aneurysm Repair

BACKGROUND

Left ventricular aneurysm repair (LVR) reduces LV wall stress and improves LV function. However, as we reported previously, the initial improvement of LVR was short-term because of LV remodeling but could be maintained longer with postoperative use of an angiotensin-converting enzyme (ACE) inhibitor. Atrial natriuretic peptide (ANP) has been used to treat patients with heart failure by natriuretic and vasodilatory actions. Recent reports have suggested that ANP inhibits the rennin-angiotensin system. In this study, the effects of ANP after LVR were evaluated.

METHODS AND RESULTS

Rats that had an LV aneurysm 4 weeks after left anterior descending artery ligation underwent LVR by plicating the LV aneurysm and were randomized into 2 groups: LVR+A group was intravenously administrated with 10 microg/h of carperitide, recombinant alpha-hANP, by osmotic-pump for 4 weeks, and the LVR group was given normal saline. Echocardiography revealed better LV remodeling and function in LVR+A group than in LVR group. Four weeks after LVR, left ventricular end diastolic pressure (LVEDP) and Tau were significantly lower in LVR+A group (LVEDP: 10+/-4 in LVR+A group versus 18+/-6 mm Hg in LVR group, Tau: 13+/-2 versus 17+/-2ms). End-systolic elastance (Ees) was higher in LVR+A group (Ees: 0.34+/-0.2 versus 0.19+/-0.11 mm Hg/microL). The levels of myocardial ACE activity in LVR+A group was significantly lower than in LVR group. The mRNA expressions of brain natriuretic peptide and transforming growth factor beta1 inducing fibrosis significantly decreased in LV myocardium in LVR+A group. Histologically, myocardial fibrosis was significantly reduced in LVR+A group.

CONCLUSIONS

Intravenous administration of ANP had beneficial effects on LV remodeling, function, and fibrosis after LVR. ANP could be a useful intravenous infusion drug for postoperative management after LV repair surgery.

Tissue distribution of ACE2 protein, the functional receptor for SARS coronavirus. A first step in understanding SARS pathogenesis

Severe acute respiratory syndrome (SARS) is an acute infectious disease that spreads mainly via the respiratory route. A distinct coronavirus (SARS-CoV) has been identified as the aetiological agent of SARS. Recently, a metallopeptidase named angiotensin-converting enzyme 2 (ACE2) has been identified as the functional receptor for SARS-CoV. Although ACE2 mRNA is known to be present in virtually all organs, its protein expression is largely unknown. Since identifying the possible route of infection has major implications for understanding the pathogenesis and future treatment strategies for SARS, the present study investigated the localization of ACE2 protein in various human organs (oral and nasal mucosa, nasopharynx, lung, stomach, small intestine, colon, skin, lymph nodes, thymus, bone marrow, spleen, liver, kidney, and brain). The most remarkable finding was the surface expression of ACE2 protein on lung alveolar epithelial cells and enterocytes of the small intestine. Furthermore, ACE2 was present in arterial and venous endothelial cells and arterial smooth muscle cells in all organs studied. In conclusion, ACE2 is abundantly present in humans in the epithelia of the lung and small intestine, which might provide possible routes of entry for the SARS-CoV. This epithelial expression, together with the presence of ACE2 in vascular endothelium, also provides a first step in understanding the pathogenesis of the main SARS disease manifestations.

Pulmonary injury follows systemic inflammatory reaction in infrarenal aortic surgery

OBJECTIVE

To investigate whether an inflammatory response occurs in patients undergoing infrarenal aortic abdominal aneurysm repair, the localization and timing (ischemia and/or reperfusion) of this activation, and finally whether it affects postoperative pulmonary function.

DESIGN

Prospective, observational study.

SETTING

Academic referral center in Italy.

PATIENTS

We included 12 patients undergoing infrarenal aortic abdominal aneurysm repair and 12 patients undergoing major abdominal surgery.

INTERVENTIONS

Timed measurement of gene activation (angiotensinogen, angiotensin type 1 receptor, angiotensin-converting enzyme, and interleukin-6 genes) in muscle biopsies by reverse transcriptase-polymerase chain reaction (RT-PCR), and prospective assessment of interleukin-6 plasma concentration and pulmonary function (Pao2/FIO2 and Pao2/PAO2 ratios).

MEASUREMENTS AND MAIN RESULTS

After 30 mins of aortic clamping, angiotensinogen, angiotensin type 1 receptor, angiotensin-converting enzyme, and interleukin-6 genes were all overexpressed at RT-PCR studies in quadriceps muscle of patients undergoing aortic abdominal aneurysm repair, and the overexpression persisted after reperfusion. In situ hybridization and immunohistochemistry revealed that the inflammatory response was localized in endothelial cells. A significant increase in plasma interleukin-6 concentrations was then detectable at 6 and 12 hrs after reperfusion in aortic abdominal aneurysm surgery compared with patients undergoing abdominal surgery (p < .05). The increase in interleukin-6 plasma concentration was then followed (12 and 24 hrs after surgery) by a significant reduction of Pao2/ FIO2 and Pao2/PAO2 ratios (p < .05 vs. abdominal surgery).

CONCLUSIONS

The present study shows that a) during aortic surgery, the genes for interleukin-6 and for the components of the local renin-angiotensin system (angiotensinogen, angiotensin-converting enzyme, and angiotensin type 1 receptor subtype) are activated early in the ischemic muscle, and activation persists during reperfusion; b) interleukin-6 plasma concentration increases only in patients with tissue ischemia (aortic abdominal aneurysm), whereas no changes are detectable in patients with abdominal surgery; and finally c) the occurrence of systemic inflammatory reaction with increased interleukin-6 plasma concentrations is followed by impaired pulmonary function.

Correlation of surrogate markers of Gaucher disease. Implications for long-term follow up of enzyme replacement therapy

BACKGROUND

The excessive storage of cellular debris in the lysosomal storage disorders triggers a variety of cellular responses. Some of these responses are maladaptative and result in the pathology of these diseases. To some extent, cellular responses are specific to the stored material, which influences the pathophysiology of the disease and results in some of its characteristic features.

METHODS

A large body of data has been collected for three biochemical (surrogate) markers of Gaucher Disease: angiotensin converting enzyme (ACE), tartrate-resistant acid phosphatase (TRAP) and chitotriosidase (CHITO) using currently available enzyme analysis. Follow up data was gathered in a group of 18 patients.

RESULTS

The three markers are correlated between each other and are useful indicators of the disease progress and its response to enzyme replacement therapy (ERT). Retrospective analysis of clinical records and comparison of chitotriosidase values with the baseline Severity Score Index (SSI) allowed prediction of the response patterns for this marker when long-term ERT (>24 months) was evaluated.

CONCLUSIONS

The less severely affected patients are more likely to normalize their chitotriosidase activities after long term ERT.

Renin-angiotensin system expression in rat bone marrow haematopoietic and stromal cells

The existence of a bone marrow renin-angiotensin system (RAS) is evidenced by the association of renin, angiotensin converting enzyme (ACE), and angiotensin (Ang) II and its AT(1) and AT(2) receptors with both normal and disturbed haematopoiesis. The expression of RAS components by rat unfractionated bone marrow cells (BMC), haematopoietic-lineage BMC and cultured marrow stromal cells (MSC) was investigated to determine which specific cell types may contribute to a local bone marrow RAS. The mRNAs for angiotensinogen, renin, ACE, and AT(1a) and AT(2) receptors were present in BMC and in cultured MSC; ACE2 mRNA was detected only in BMC. Two-colour flow fluorocytometry analysis showed immunodetectable angiotensinogen, ACE, AT(1) and AT(2) receptors, and Ang II, as well as binding of Ang II to AT(1) and AT(2) receptors, in CD4(+), CD11b/c(+), CD45R(+) and CD90(+) BMC and cultured MSC; renin was found in all cell types with the exception of CD4(+) BMC. Furthermore, Ang II was detected by radioimmunoassay in MSC homogenates as well as conditioned culture medium. The presence of Ang II receptors in both haematopoietic-lineage BMC and MSC, and the de novo synthesis of Ang II by MSC suggest a potential autocrine-paracrine mechanism for local RAS-mediated regulation of haematopoiesis.

Rheumatologic manifestations of sarcoidosis

PURPOSE OF REVIEW

This review emphasizes the importance of the rheumatological signs and symptoms in the presentation of sarcoidosis. Often the presence of musculoskeletal findings may lead to the diagnosis of the disease and the institution of the appropriate treatment.

RECENT FINDINGS

There have been significant advances in the treatment of sarcoidosis with the use of biologic agents for recalcitrant and severe manifestations of the disease as well as some new data regarding pathogenetics and new applications of diagnostic imaging studies such as positron emission tomography scanning.

SUMMARY

Although pulmonary disease is the most frequent manifestation of sarcoidosis, musculoskeletal symptoms are not only common, but may be the initial presentation of this systemic inflammatory process and could mimic other arthritic and autoimmune disorders. This article focuses on the rheumatological aspects of sarcoidosis and includes a review of the most recent literature, which shows new data on the diagnosis, pathogenesis, and treatment of this condition.

Modification of the furanacryloyl-l-phenylalanylglycylglycine assay for determination of angiotensin-I-converting enzyme inhibitory activity

Angiotensin-I-converting enzyme (ACE, EC 3.4.15.1) plays a central role in the regulation of blood pressure in man. The objective of this study was to evaluate and modify the furanacryloyl-L-phenylalanylglycylglycine (FAPGG) assay method for quantification of ACE activity. The fixed time conditions developed for assay of ACE activity were as follows: 0.8 mM FAPGG, 175 + or - 10 units l(-1) ACE, incubation at 37 degrees C for 30 min and enzyme inactivation with 100 mM ethylenediaminetetra-acetic acid (EDTA). Hydrolysis of FAPGG to FAP and GG was quantified by measuring the decrease in absorbance at 340 nm. It was shown that increasing the level ACE activity in the assay from 155 to 221 + or - 15 units l(-1) resulted in a corresponding increase in the apparent IC(50) value for Captopril from 9.10 to 39.40 nM. Similar trends in the apparent IC50 values for a whey protein hydrolysate were obtained. The results demonstrate the requirement for carefully controlling ACE activity levels in the assay in order to obtained comparable and reproducible values for the inhibitory potency of ACE inhibitors.

Oxidative stress in the pathogenesis of thoracic aortic aneurysm: protective role of statin and angiotensin II type 1 receptor blocker

OBJECTIVE

The pathogenesis of thoracic aortic aneurysms (TAA) is still unclear. A recent investigation indicated that angiotensin II, a potent activator of NADH/NADPH oxidase, plays an important role in aneurysmal formation. We investigated the potential role of p22phox-based NADH/NADPH oxidase in the pathogenesis of TAA.

METHODS

Human thoracic aneurysmal (n=40) and non-aneurysmal (control, n=39) aortic sections were examined, and the localization of p22phox, an essential component of the oxidase, and its expressional differences were investigated by immunohistochemistry and Western blot. In situ reactive oxygen species (ROS) generation was examined by the dihydroethidium method, and the impact of medical treatment on p22phox expression was investigated by multiple regression analysis.

RESULTS

In situ production of ROS and the expression of p22phox increased markedly in TAA throughout the wall, and Western blot confirmed the enhanced expression of p22phox. The expression was more intense in the regions where monocytes/macrophages accumulated. In these inflammatory regions, numerous chymase-positive mast cells and angiotensin converting enzyme-positive macrophages were present. Their localization closely overlapped the in situ activity of matrix metalloproteinase and the expression of p22phox. Multiple regression analysis revealed that medical treatment with statin and angiotensin II type 1 receptor blocker (ARB) suppressed p22phox expression in TAA.

CONCLUSION

Our findings indicate the role of p22phox-based NADH/NADPH oxidase and the local renin-angiotensin system in the pathogenesis of TAA. Statin and ARB might have inhibitory effects on the formation of aneurysms via the suppression of NADH/NADPH oxidase.

Angiotensin-converting enzyme (CD143) is abundantly expressed by dendritic cells and discriminates human monocyte-derived dendritic cells from acute myeloid leukemia-derived dendritic cells

OBJECTIVES

The pattern of angiotensin-converting enzyme (ACE) expression in dendritic cells (DC) and macrophages derived from normal monocytes vs that in DC derived from acute myeloid leukemia blasts was investigated.

MATERIALS AND METHODS

ACE expression was quantified by flow cytometry using a set of monoclonal antibodies (mAbs) directed against five different epitopes on the ACE molecule and by enzyme activity measurement.

RESULTS

The binding pattern of a set of anti-ACE mAbs to the surface of blood cells and their progeny, as revealed by FACS, showed lineage and epitope specificity. Differentiation of monocytes to macrophages and DC was accompanied by a dramatic increase in ACE expression. ACE activity was 50-fold higher in macrophages and 150-fold higher in DC than in monocytes. ACE level normalized per cell revealed that DC expressed 1300-fold more ACE than did monocytes. In contrast, DC derived from acute myeloid leukemia blasts did not show an elevated level of ACE, although they acquired DC markers CD80, CD40, and CD86 upon cytokine or calcium ionophore treatment.

CONCLUSIONS

ACE expression becomes the first marker to functionally distinguish DC generated from monocytes and leukemic blast cells. Given that ACE plays an important role in the hydrolysis of many peptides, as well as in the presentation of some antigens to immune cells, these data suggest that elevated ACE expression on the surface of DC is not just a reflection of the general activation of monocytes during differentiation; rather, it may be physiologically important for the functioning of these cells.

Angiotensin II influences ovarian follicle development in the transgenic (mRen-2)27 and Sprague-Dawley rat

There is accumulating evidence that local renin-angiotensin systems (RASs) influence cell growth and organ function in a variety of tissues including the ovary. The first aim of this study was to characterise the cellular location of RAS components in the rat ovary. This was facilitated by the use of the hypertensive transgenic (mRen-2)27 rat which overexpresses renin and angiotensin in extra-renal tissues. Comparisons were made with normal Sprague-Dawley (SD) rats. The second aim was to determine if the upregulated RAS of the transgenic (mRen-2)27 rat and infusion of angiotensin II (ANG II) in SD rats influences follicle number and litter size. Gene expression, immunohistochemical and autoradiographic techniques were used to identify a discrete RAS including ANG II receptors in the ovarian stroma, follicles (particularly atretic) and to a lesser extent corpora lutea. The RAS at these sites was most abundant in homozygous (HMZ) followed by heterozygous (HTZ) (mRen-2)27 rats and then SD rats. Large antral and preovulatory follicles and litter size were reduced in (mRen-2)27 rats. In HMZ (mRen-2)27 rats and SD rats infused with ANG II, angiotensin 1a (AT(1a)) receptor mRNA in the ovarian stroma was lower than control SD rats and was associated with a reduction in large antral and preovulatory follicles. These findings indicate that upregulation of the ovarian RAS in the rat influences follicular development and, potentially, reproductive capacity.

Using spectrophotometry to determine in vitro turnover rates of peptides in plasma

A new method for determination of first-order elimination constants for dipeptides is presented. The peptides are hydrolysed by plasma enzymes into amino acids, and ortho-phthaldialdehyde (OPA) is used to react with free primary amino groups. The concentration of free amino groups can, thus, be followed using simple spectrophotometry. A mathematical model for the concentration of free primary amino groups with time is presented through which the elimination constant, and thus the half life, can be determined by curve fitting. The method is applied to inhibitors of angiotensin-converting enzyme derived from the primary structure of milk proteins. The results show that these dipeptides have in vitro half lives ranging from 4.3-64 min, when incubated with 50% rat plasma. This explains why these casokinins in vivo only cause a very moderate and short-lasting inhibition. The model for calculation of elimination constant is limited to dipeptides that do not contain a C-terminal proline. The derivatization method can be applied to longer peptides as a crude indicator of peptide hydrolysis, but does not allow calculation of their elimination constants per se.

Mast cell chymase expression inHelicobacter pylori-associated gastritis

AIMS

To study the role of mast cell chymase in the inflammatory processes of human chronic gastritis. Experimental studies have shown that mast cell chymase stimulates inflammatory cell accumulation, and contributes to angiotensin II formation.

METHODS AND RESULTS

Tissue sections from human stomachs with Helicobacter pylori-associated gastritis (surgery/autopsy n = 20; biopsy n = 16) and normal stomachs (n = 10) were studied using immunohistochemical single and double labelling techniques. Monoclonal antibodies used were directed against mast cell chymase, tryptase, neutrophils (CD66b, elastase, and myeloperoxidase), macrophages, T-lymphocytes, and interleukin (IL)-4. The expression of angiotensin-converting enzyme and angiotensin II type 1 receptor was investigated using immunohistochemical analysis and the reverse transcription-polymerase chain reaction. The number of chymase-positive mast cells was significantly higher (P < 0.0001) in H. pylori-associated gastritis than in normal stomachs. Increased expression of chymase in inflamed mucosa was closely related to an increase in the accumulation of neutrophils, macrophages, T-lymphocytes, and IL-4-positive cells. The expression of angiotensin-converting enzyme and angiotensin II type 1 receptor was not altered in gastritis specimens.

CONCLUSIONS

These observations suggest that mast cell chymase may be an important mediator in the inflammatory processes of human H. pylori-associated gastritis.

[Renal protective effect of angiotensin II receptor antagonist on growth hormone-treated nephrotic rats]

OBJECTIVE

Children with nephrotic syndrome are always associated with retardation of growth. Growth hormone (GH) administration to these children can stimulate their growth, but it plays an important role in glomerulosclerosis. Thus these children would take a risk to use it to improve their growth. This study was designed to investigate the effect of GH on the kidney of rats with adriamycin-induced nephropathy (AN) and its mechanism, and to observe the renoprotective effect of angiotensin II (AngII) receptor antagonist, irbesartan, in GH-treated AN rats.

METHODS

Rats were divided into the following groups: normal control rats, AN rats, GH-treated AN rats and GH plus irbesartan-treated AN rats. There were 8 developing male SD rats (120-130 g) in each group. Urinary protein was measured at weeks 3, 6 and 9. Blood pressure, serum creatinine, BUN, albumin, cholesterol, triglyceride, as well as ACE activity and AngII concentration of the kidney were detected at the end of the study. Renal pathological changes were evaluated also. Immunohistochemistry was used to examine the protein expressions of TGF beta(1), collagen IV and fibronectin in glomeruli.

RESULTS

Glomerular sclerosis score of GH-treated AN rats (49.4 +/- 9.8) was significantly higher than that of AN rats (12.8 +/- 5.5, P < 0.01), and this score of GH-treated AN rats plus irbesartan (26.2 +/- 7.5) was significantly lower than the score of GH-treated AN rats (P < 0.01). The changes of urinary protein, hyperlipidemia and hypoalbuminemia in rats of each group consisted with the degree of glomerular injury in rats of each group. There was azotemia in GH-treated AN rats, but rats in the other groups did not have azotemia. ACE activity of kidney was significantly (P < 0.01) increased in GH-treated AN rats [(28.1 +/- 4.1) U/mg pro] and GH-treated AN rats plus irbesartan [(27.6 +/- 3.4) U/mg pro] compared with that in AN rats [(14.6 +/- 4.4) U/mg pro]. AngII concentrations in the kidney of GH-treated AN rats [(17.8 +/- 3.3) pg/mg pro] and GH-treated AN rats plus irbesartan [(27.3 +/- 5.1) pg/mg pro] were significantly higher than that in AN rats [(8.3 +/- 1.9) pg/mg pro] (P < 0.01). The protein expressions of TGF-beta(1), collagen IV and fibronectin in GH-treated AN rats were the most distinct in all groups. These expressions were significantly (P < 0.05) reduced in GH-treated AN rats plus irbesartan.

CONCLUSION

GH is able to exacerbate adriamycin-induced nephropathy in rats, which was partly through activating renal tissue RAS and initiating the function of the AngII-TGF beta(1)-ECM axis. Angiotensin II receptor antagonist, irbesartan, has some renal protective effects on AN rats treated with GH.

Angiotensin I-converting enzyme is expressed by erythropoietic cells of normal and myeloproliferative bone marrow

It is proposed that a locally active, intrinsic renin-angiotensin system (RAS) exists in the bone marrow (BM) and plays a role in regulating haematopoiesis. Angiotensin II type I receptor has been detected on erythroid burst-forming unit-derived cells; its antagonist losartan and angiotensin I-converting enzyme (ACE) inhibitors can suppress erythropoiesis. The possible role of ACE/RAS in BM was investigated by evaluating ACE expression in normal BM, several myeloproliferative disorders and myelodysplasia. Immunohistochemical studies showed that erythroid elements expressed ACE protein in both normal and disturbed haematopoiesis. The presence of ACE in erythroid cells suggests another mechanism for direct ACE inhibitor activity in erythropoiesis.

Differential localisation of the renin–angiotensin system in de-novo lesions and in-stent restenotic lesions in in-vivo human coronary arteries

OBJECTIVE

Different components of the renin-angiotensin system (RAS) have been demonstrated in atherosclerotic plaques. However, the involvement of the RAS in in-stent restenosis is not clear. We studied the differential immunolocalisation of angiotensin converting enzyme (ACE) and the angiotensin II type 1 (AT1) receptor in de-novo stenotic lesions and in-stent restenotic lesions in human coronary arteries.

METHODS

Using a pullback atherectomy catheter, biopsies from de-novo coronary lesions (n=19) and in-stent restenotic lesions (n=19) were obtained. The biopsies were immunostained for vascular smooth muscle cells (VSMCs), macrophages, ACE and the AT1 receptor.

RESULTS

In biopsies from de-novo stenotic lesions ACE-positive macrophages were more numerous than in in-stent restenotic lesions (P=0.002). Moreover, in the latter lesions, ACE-positive macrophages decreased when the time interval of stent implantation was longer. On the other hand, in-stent restenotic lesions contained predominantly young VSMCs, which abundantly expressed AT1 receptors.

CONCLUSIONS

Lesional ACE expression is not a prominent feature of in-stent restenotic lesions. In contrast, AT1 receptors are abundantly expressed on young VSMCs. In de-novo lesions ACE and AT1 receptors were found on macrophages and VSMCs, which were present in all specimens.

Differential tissue and enzyme inhibitory effects of the vasopeptidase inhibitor omapatrilat in the rat

Vasopeptidase inhibitors simultaneously inhibit angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP). The present study characterized the tissue distributions of ACE and NEP, and assessed the effects of the vasopeptidase inhibitor omapatrilat on ACE and NEP in rat tissues. In vivo ACE and NEP inhibition was studied by in vitro autoradiography and using the ACE inhibitor radioligand (125)I-MK351A and the NEP inhibitor radioligand (125)I-RB104 in rats that received oral omapatrilat (40 mg x day(-1) x kg(-1)) for 3 days. In vitro autoradiography was used to examine the distribution of ACE and NEP in the kidney, aorta, heart, adrenal gland, lung, intestine, liver, spleen and brain, and to assess enzyme inhibition after oral omapatrilat. Omapatrilat inhibited plasma ACE and increased plasma renin activity (P <0.01). Tissue ACE was inhibited by 70-95% (P <0.01), except in the brain, where ACE was not inhibited. NEP was inhibited by 87% in the kidney and by 20-40% in atria, aorta, adrenal gland, lung, liver and intestine; it was not inhibited in the brain, the ventricle or the spleen. Omapatrilat is a potent vasopeptidase inhibitor that significantly inhibits tissue ACE and NEP, with the degree of inhibition varying according to the enzyme and the tissue under assessment. The degree and site of tissue enzyme inhibition by vasopeptidase inhibitors may be relevant to end-organ protection as well as to the side-effect profiles of these agents.

Angiotensin I conversion to angiotensin II stimulates cortical collecting duct sodium transport

Angiotensin (Ang) II directly stimulates epithelial sodium channel activity in the rabbit cortical collecting duct. Because Ang I and converting enzyme analogues might be present in the distal nephron, this raises the possibility of intraluminal generation of Ang II. Conversion of Ang I to Ang II was monitored by Ang II-dependent changes in intracellular sodium concentration as a reflection of sodium transport across the apical membrane. This involved imaging-based fluorescence microscopy with sodium-binding benzofuran isophthalate in isolated, perfused, cortical collecting-duct segments from rabbit kidney. Principal and intercalated cells were differentiated by rhodamine-conjugated peanut lectin. Control principal cell intracellular sodium concentration, during perfusion with 25 mmol/L NaCl and zero sodium in the bath plus monensin (10(-5) mol/L) averaged 5.8+/-0.14 mmol/L (n=156). The increase in intracellular sodium concentration, when luminal NaCl was increased from 25 to 150 mmol/L, was elevated by 3.5-fold in the presence of intraluminal Ang I (10(-6) mol/L). Also, the effects of Ang I on sodium transport were not significantly different from the effects of Ang II (10(-9) mol/L). Ang I was used in micromolar concentrations to ensure that there was sufficient substrate available for conversion to Ang II. Inhibition of the angiotensin-converting enzyme with captopril reduced the stimulatory effect of Ang I. These results suggest that intraluminal conversion of Ang I to Ang II can occur in the cortical collecting duct, resulting in enhanced apical sodium entry.

Properties and distribution of angiotensin I converting enzyme

This review summarizes some basic properties and distribution of angiotensin I converting enzyme (ACE). ACE is one of several biologically important ectoproteins that exists in both membrane-bound and soluble forms. Localized on the surface of various cells, ACE is inserted at the cell membrane via its carboxyl terminus. Human plasma ACE originates from endothelial cells while other body fluids may contain ACE that originates from epithelial, endothelial or germinal cells. The two isoforms of ACE, the two-domain somatic form and the single domain germinal form, convert angiotensin I to angiotensin II, and metabolize kinins and many other biologically active peptides, including substance P, chemotactic peptide and opioid peptides. The broad spectrum of substrates for ACE and its wide distribution throughout the body indicates that this enzyme, in addition to an important role in cardiovascular homeostasis, may be involved in additional physiologic processes such as neovascularization, fertilization, atherosclerosis, kidney and lung fibrosis, myocardial hypertrophy, inflammation and wound healing. Future research should explore the possible functions of tissue ACE and its systemic role as a pressor agent. ACE inhibitors have achieved widespread use in the treatment of hypertension and the protection of end-organ damage in cardiovascular and renal diseases. Potential problems related to side effects and compliance of such therapy need to be addressed. A safer way of producing therapeutic effects is promised by the delivery of the ACE antisense sequences by a vector producing a permanent inhibition of ACE and long-term control of blood pressure in hypertensive patients.

AT1 receptor blockade improves vasorelaxation in experimental renal failure

It is not known whether angiotensin II type 1 receptor antagonists can influence the function and morphology of small arteries in renal failure. We investigated the effect of 8-week losartan therapy (20 mg/kg per day) on isolated mesenteric resistance arteries by wire and pressure myographs in 5/6 nephrectomized rats. Plasma urea nitrogen was elevated 1.6-fold after nephrectomy, and ventricular synthesis of atrial and B-type natriuretic peptides was increased 2.2-fold and 1.7-fold, respectively, whereas blood pressure was not affected. Losartan did not influence these variables. The endothelium-mediated relaxation to acetylcholine was impaired in nephrectomized rats in the absence and presence of nitric oxide synthase and cyclooxygenase inhibition. Blockade of calcium-activated potassium channels by charybdotoxin and apamin reduced the remaining acetylcholine response, and this effect was less marked in nephrectomized than in sham-operated rats. Relaxation to levcromakalim, a vasodilator acting through adenosine triphosphate-sensitive potassium channels, was also impaired after nephrectomy. The arteries of nephrectomized rats showed eutrophic inward remodeling: Wall-to-lumen ratio was increased without change in wall cross-sectional area. All changes in arterial relaxation and morphology were normalized by losartan therapy. Aortic ACE content, measured by autoradiography, directly correlated to the plasma level of urea nitrogen, suggesting that renal failure has an enhancing influence on the vascular renin-angiotensin system. Losartan normalized relaxation and morphology of resistance arteries in experimental renal failure, independent of its influence on blood pressure, impaired kidney function, or volume overload. The mechanism of improved vasodilation by losartan may include enhanced relaxation through potassium channels.

Chronic hypoxia activates a local angiotensin-generating system in rat carotid body

Evidence exists for the presence of a functional angiotensin system in the carotid body, which can modulate the excitability of the carotid body chemoreceptors. In the present study, the effect of chronic hypoxia on the expression and localization of the angiotensinogen (AGT) and angiotensin-converting enzyme (ACE), the two critical components of an intrinsic angiotensin-generating system in the rat carotid body, are investigated by in situ hybridization histochemistry, semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis. In situ hybridization showed that the messenger RNA (mRNA) expression of AGT was localized within the type-I glomus cells of the carotid body, which was subjected to be upregulated under the stress of chronic hypoxia. RT-PCR further confirmed a significant increase in the expression of AGT mRNA by chronic hypoxia. Consistently, Western blot analysis demonstrated that chronic hypoxia could elicit the upregulation of AGT protein in chronically hypoxic carotid bodies when compared with their normoxic controls. On the other hand, there was a slight but significant increase in ACE mRNA expression during chronic hypoxia. This study suggests that chronic hypoxia can activate a local angiotensin-generating system in the carotid body, notably its obligatory component AGT. The activation of such an intrinsic, angiotensin-generating system in the carotid body during chronic hypoxia should be important in the modulation of cardiopulmonary adaptation in the hypoxic ventilatory response and the electrolyte as well as water homeostasis.

Angiotensin-converting enzyme gene polymorphism interacts with left ventricular ejection fraction and brain natriuretic peptide levels to predict mortality after myocardial infarction

OBJECTIVES

The goal of this study was the exploration of the associations between the angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and post-myocardial infarction (MI) outcomes, especially any interaction with the accepted clinical prognostic markers brain natriuretic peptide (BNP) and left ventricular ejection fraction (LVEF).

BACKGROUND

The ACE gene I/D polymorphism has been implicated in the development of MI, hypertension, and left ventricular hypertrophy. We examined the association of ACE I/D and prognosis after acute MI.

METHODS

Patients incurring acute MI were genotyped for the ACE I/D polymorphism. Clinical data included assays of neurohormones, radionuclide ventriculography, and mortality over a mean 2.6 years of follow-up.

RESULTS

Patients (n = 978) had a mean age of 62.1 years, and 78% were male. Overall genotype frequencies were II 23.2%, ID 49.5%, and DD 27.3%. Chi-square analysis revealed an association between the ACE D allele and death after MI (88 of 103 who died were DD or ID; p < 0.05), with an odds ratio for mortality of 8.03 (95% confidence interval, 2.16 to 29.88). Patients with the DD genotype had higher (p < 0.05) plasma BNP, N-terminal BNP (N-BNP), and endothelin-1 levels within 96 h after MI than grouped ID/II patients. Multivariate analysis indicated ACE genotype, age, and previous MI were independent predictors of death (p < 0.05). Patients with an ACE D allele in combination with either a lower than median LVEF or greater than median BNP had a higher mortality (p < 0.001 and p < 0.025, respectively) than the risk associated with the D allele itself.

CONCLUSIONS

Angiotensin-converting enzyme genotyping may provide additional prognostic information in patients after MI in combination with the proven utility of LVEF, plasma BNP, and N-BNP measurements.

Bronchoalveolar and serological parameters reflecting the severity of sarcoidosis

The aim of the present study was to determine which bronchoalveolar lavage fluid (BALF) and serological parameters reflect the severity of newly diagnosed pulmonary sarcoidosis. Seventy-four previously untreated sarcoid patients were categorised into three groups: 10 patients with Löfgren's syndrome, 51 patients with stable disease and 13 patients with progressing disease requiring systemic steroid treatment. Total BALF cell count, percentage of alveolar lymphocytes and lymphocyte CD4/ CD8 ratio were not associated with severity of disease. Interestingly, a significant increase in percentages of BALF neutrophils (5.2 +/- 1.1%) and eosinophils (1.7 +/- 0.6%) was observed in sarcoid patients with progressing disease. Elevated percentages of these two cell types were the only BALF parameters associated with a more frequent necessity for systemic steroid therapy. This association between an elevated percentage of BALF neutrophils and the necessity for steroid treatment was observed in advanced as well as early sarcoidosis (radiological types I and II). Serum levels of soluble interleukin-2 receptor and neopterin were significantly elevated in progressing disease compared to stable disease or Löfgren's syndrome. The present results demonstrate that increased percentages of neutrophils (>3.0%) and eosinophils (>1%) in bronchoalveolar lavage fluid from newly diagnosed pulmonary sarcoidosis is associated with a significantly higher risk of necessity for steroid therapy and may be helpful markers of progressive disease. Furthermore, of the serological parameters investigated, only serum levels of soluble interleukin-2 receptor and neopterin were associated with disease severity.

Characterization of renal angiotensin-converting enzyme 2 in diabetic nephropathy

ACE2, initially cloned from a human heart, is a recently described homologue of angiotensin-converting enzyme (ACE) but contains only a single enzymatic site that catalyzes the cleavage of angiotensin I to angiotensin 1-9 [Ang(1-9)] and is not inhibited by classic ACE inhibitors. It also converts angiotensin II to Ang(1-7). Although the role of ACE2 in the regulation of the renin-angiotensin system is not known, the renin-angiotensin system has been implicated in the pathogenesis of diabetic complications and in particular in diabetic nephropathy. Therefore, the aim of this study was to assess the possible involvement of this new enzyme in the kidney from diabetic Sprague-Dawley rats to compare and contrast it to ACE. ACE2 and ACE gene and protein expression were measured in the kidney after 24 weeks of streptozocin diabetes. ACE2 and ACE mRNA levels were decreased in diabetic renal tubules by approximately 50% and were not influenced by ACE inhibitor treatment with ramipril. By immunostaining, both ACE2 and ACE protein were localized predominantly to renal tubules. In the diabetic kidney, there was reduced ACE2 protein expression that was prevented by ACE inhibitor therapy. The identification of ACE2 in the kidney, its modulation in diabetes, and the recent description that this enzyme plays a biological role in the generation and degradation of various angiotensin peptides provides a rationale to further explore the role of this enzyme in various pathophysiological states including diabetic complications.

Progression from compensated hypertrophy to failure in the pressure-overloaded human heart: structural deterioration and compensatory mechanisms

BACKGROUND

The progression of compensated hypertrophy to heart failure (HF) is still debated. We investigated patients with isolated valvular aortic stenosis and differing degrees of left ventricular (LV) systolic dysfunction to test the hypothesis that structural remodeling, as well as cell death, contributes to the transition to HF.

METHODS AND RESULTS

Structural alterations were studied in LV myectomies from 3 groups of patients (group 1: ejection fraction [EF] >50%, n=12; group 2: EF 30% to 50%, n=12; group 3: EF <30%, n=10) undergoing aortic valve replacement. Control patients were patients with mitral valve stenosis but normal LV (n=6). Myocyte hypertrophy was accompanied by increased nuclear DNA and Sc-35 (splicing factor) content. ACE and TGF-beta1 were upregulated correlating with fibrosis, which increased 2.3-, 2.2-, and 3.2-fold over control in the 3 groups. Myocyte degeneration increased 10, 22, and 32 times over control. A significant correlation exists between EF and myocyte degeneration or fibrosis. Ubiquitin-related autophagic cell death was 0.5 per thousand in control and group 1, 1.05 in group 2, and 6.05 per thousand in group 3. Death by oncosis was 0 per thousand in control, 3 per thousand in group 1, and increased to 5 per thousand (groups 2 and 3). Apoptosis was not detectable in control and group 3, but it was present at 0.02 per thousand in group 1 and 0.01 per thousand in group 2. Cardiomyocyte mitosis was never observed.

CONCLUSIONS

These structure-function correlations confirm the hypothesis that transition to HF occurs by fibrosis and myocyte degeneration partially compensated by hypertrophy involving DNA synthesis and transcription. Cell loss, mainly by autophagy and oncosis, contributes significantly to the progression of LV systolic dysfunction.

Isoforms of angiotensin I-converting enzyme in the development and differentiation of human testis and epididymis

Angiotensin I-converting enzyme (ACE; CD143, Kininase II, EC 3.4.15.1) is known to be crucial for male fertility in animal models. We therefore studied its testicular (tACE) and somatic (sACE) isoforms in foetal and adult human testis and epididymis using monoclonal antibodies and cRNA probes. During spermatogenesis, tACE was found only in differentiating germ cells and was the only isoform within the seminiferous tubules of adult men. Although tACE mRNA was present in spermatocytes, tACE protein was initially found in post-meiotic step 3 spermatids and increased markedly during further differentiation. The enzyme was strictly confined to the adluminal membrane site of elongating spermatids and was localized at the neck and midpiece region of released and ejaculated spermatozoa. In contrast, sACE was expressed heterogeneously in Leydig cells and endothelial cells of the testicular interstitium, and homogeneously along the luminal surface of epithelial cells lining the ductuli efferents, corpus and cauda of epididymis, and vas deferens. The cell- and site-restricted pattern of sACE corresponded to that found in foetal tissues except an additional and transient expression of sACE in foetal germ cells and foetal Sertoli cells. Our study documents for the first time in humans the regulation and unique cellular distribution of ACE isoforms during the ontogenesis of the lower male genital tract.

Oxidized-LDL through LOX-1 increases the expression of angiotensin converting enzyme in human coronary artery endothelial cells

BACKGROUND AND OBJECTIVES

Our previous studies have shown that oxidized low-density lipoprotein (ox-LDL) and angiotensin II (Ang II) influence each other's action in endothelial cells. This study was designed to examine the regulation by ox-LDL of the expression of angiotensin converting enzyme (ACE) gene in human coronary artery endothelial cells (HCAECs). In addition, we studied the effect of the HMG CoA reductase inhibitor simvastatin on this interaction.

METHODS AND RESULTS

Cultured HCAECs were incubated with ox-LDL (10-80 microg/ml) for 1-24 h. Ox-LDL increased the expression of ACE in a concentration- and time-dependent fashion. The upregulation of ACE expression in response to ox-LDL was mediated by its endothelial receptor LOX-1, since pretreatment of HCAECs with a blocking antibody to LOX-1 prevented the expression of ACE (P<0.01). Native-LDL had no significant effect on ACE expression. In this process, ox-LDL-induced activation of mitogen-activated protein kinase (MAPK p42/44) played an important role, since pretreatment of HCAECs with the MAPK p42/44 inhibitor (PD98059, 10 microM) inhibited MAPK activation and subsequently attenuated the expression of ACE (P<0.01 vs. ox-LDL alone). In other experiments, we pretreated HCAECs with simvastatin (10 microM) and then exposed the cells to ox-LDL. Simvastatin markedly attenuated ox-LDL-induced MAPK activation, and concurrently reduced ACE expression (P<0.01 vs. ox-LDL alone).

CONCLUSIONS

Our observations provide direct evidence that ox-LDL via LOX-1 activation induces ACE gene expression in HCAECs, and MAPK activation plays a signal transduction role in this process. Simvastatin, which inhibits MAPK activation, also blocks ox-LDL-mediated upregulation of ACE.

Shear stress magnitude and directionality modulate growth factor gene expression in preconditioned vascular endothelial cells

OBJECTIVE

The purpose of this study was to simultaneously monitor the transcriptional levels of 12 endothelial growth factor genes in response to alterations in wall shear stress (WSS) under conditions relevant to the development of intimal hyperplasia, a major cause of arterial bypass graft failure.

METHODS

Human umbilical vein endothelial cells were preconditioned in vitro under steady flow (WSS, 15 dynes/cm(2)) for 24 hours before being subjected to WSS at 25 (Delta = +10), 15 (Delta = 0), 5 (Delta = -10), 2.5 (Delta = -12.5), and 0 (Delta = -15) dynes/cm(2) or low magnitude WSS reversal (-2.5 dynes/cm(2)) for 6 hours. A focused complementary DNA array was used to simultaneously measure messenger RNA expression levels for END1, endothelial nitric oxide synthase (NOS3), platelet-derived growth factor A, platelet-derived growth factor B (PDGFB), acidic fibroblast growth factor, basic fibroblast growth factor, transforming growth factor-alpha, transforming growth factor-beta, vascular endothelial growth factor, insulin-like growth factor-1, epidermal growth factor, and angiotensin converting enzyme.

RESULTS

Preconditioning significantly (P <.05) increased the fold expression of NOS3 (4.1 +/- 1.4), basic fibroblast growth factor (3.90 +/- 1.16), vascular endothelial growth factor (3.39 +/- 1.04), and insulin-like growth factor-1 (2.8 +/- 0.7) but decreased END1 (0.47 +/- 0.05) and PDGFB (0.70 +/- 0.04) messenger RNA expression levels relative to no-flow controls, an effect that was sustained on removal from flow for 6 hours. Notably, the ratio of END1/NOS3 expression was diminished (0.11 +/- 0.03) relative to that of cells maintained in static culture. Although few differences in gene expression from baseline (15 dynes/cm(2)) were measured in cells exposed to either constant (Delta = 0) or step decreases (Delta = -10, -12.5, or -15 dynes/cm(2)) in WSS, marked changes were seen in the group exposed to a step increase in WSS (Delta = +10) or to WSS reversal. Low magnitude retrograde WSS evoked significant (P <.05) transcriptional changes in multiple genes, including elevated END1 (4.1 +/- 0.5), platelet-derived growth factor A (1.5 +/- 0.2), PDGFB (2.3 +/- 0.3), and transforming growth factor-beta (1.5 +/- 0.2) levels, but depressed NOS3 (0.60 +/- 0.17) levels, and a marked increase in END1/NOS3 (6.7 +/- 1.6) when compared with equal magnitude antegrade WSS (2.5 dynes/cm(2)).

CONCLUSION

These results support the implementation of a preconditioning phase for in vitro WSS studies to establish a physiologic baseline. Our findings complement previous macroscale findings and are consistent with a cellular mechanism involving increased END1 and PDGFB levels, but decreased NOS3 levels, leading to intimal hyperplasia at regions of low magnitude reversing WSS.

Presence of cellular renin-angiotensin system in chromaffin cells of bovine adrenal medulla

The presence of a local renin-angiotensin system has been established in organs that serve as angiotensin targets. In this study, the expression of angiotensinogen mRNA and subcellular localization of renin, angiotensin-converting enzyme, and angiotensin II were investigated in bovine adrenal medullary cells in primary culture. By light microscopy, expression of angiotensinogen mRNA, immunoreactive renin, angiotensin-converting enzyme, and angiotensin II were readily detectable only in the chromaffin cells. The density distribution of renin and angiotensin II in sucrose gradients suggested a concentration in chromaffin granules, a localization directly confirmed by immunoelectron microscopy. Reverse transcriptase-polymerase chain reaction and sequencing confirmed the expression of angiotensinogen in bovine chromaffin cells and the adrenal medulla. In addition, in vitro autoradiography indicated that both angiotensin-converting enzyme and angiotensin type 1 receptors were present in the adrenal medulla. These results provide the first direct evidence that chromaffin cells in the adrenal medulla are not only the target for angiotensin but should also be considered as potential local angiotensin-generating and -storing cells.

Effects of dietary salt changes on renal renin-angiotensin system in rats

Renin (RA) and angiotensin-converting enzyme (ACE) activities and angiotensinogen, ANG I, and ANG II levels were measured in the kidney (cortex and medulla) and plasma of Wistar-Kyoto rats on a low-sodium (LS; 0.025% NaCl; n = 8), normal-sodium (NS; 1% NaCl; n = 7), or high-sodium (HS; 8% NaCl; n = 7) diet for 21 days. RA, ANG I, and ANG II levels increased in a manner inversely related to sodium content of the diet in both plasma and renal tissues. The LS diet resulted in a 16-, 2.8-, and 1.8-fold increase in plasma RA, ANG I, and ANG II levels, respectively, compared with those in HS rats. In the renal cortex and medulla, RA, ANG I, and ANG II levels were also increased by diminution of dietary salt content but, in contrast to plasma, ANG II levels increased much more than RA or ANG I levels [5.4 (cortex)- and 4.7 (medulla)-fold compared with HS rats]. In summary, we demonstrated variations of ANG II levels in the kidney during dietary salt modifications. Our results confirm that RA and ACE activity are not the steps limiting intrarenal ANG II levels. Nevertheless, despite RA and ACE activity differences between renal cortex and medulla, ANG I and ANG II levels are equivalent in these two tissues; these results argue against a compartmentalization of RAS in these two intrarenal areas.

Association of angiotensin-converting enzyme with low-density lipoprotein in aortic valvular lesions and in human plasma

BACKGROUND

Recent studies have demonstrated that lesions of aortic sclerosis and stenosis share several similarities with lesions of atherosclerosis. In atherosclerosis, angiotensin-converting enzyme (ACE) is expressed by a subset of macrophages. This study was undertaken to determine whether ACE might be present in aortic sclerosis or stenosis lesions.

METHODS AND RESULTS

Immunohistochemistry was performed on 26 paraffin-embedded human aortic valves. Monospecific antibodies were used to identify ACE, macrophages, angiotensin II type 1 receptor (AT-1 receptor), angiotensin II, and apolipoprotein B. Human low-density lipoprotein (LDL) and high-density lipoprotein (HDL) were isolated from plasma of normal volunteers by sequential density-gradient ultracentrifugation. ACE was not present in normal valves but was present in all valves with aortic sclerosis or stenosis lesions. ACE was detected on a subset of lesion macrophages but was present primarily in an extracellular distribution, where it colocalized with apolipoprotein B. ACE was detected by Western blotting on plasma LDL but not on HDL isolated from normal volunteers. Angiotensin II, the enzymatic product of ACE, was colocalized with ACE in valve lesions. ACE also was colocalized with apolipoprotein B in an adjacent coronary atherosclerotic plaque.

CONCLUSIONS

ACE is present in aortic sclerosis and stenosis lesions, where it may participate in lesion development, as is evidenced by the presence of its enzymatic product, angiotensin II. The observation of an association of ACE with LDL in both lesions and plasma suggests that LDL may deliver ACE to lesions and has implications for the role of ACE-containing LDL in other diseases, such as atherosclerosis.

Bradykinin potentiation by ACE inhibitors: a matter of metabolism

1. Studies in isolated cells overexpressing ACE and bradykinin type 2 (B(2)) receptors suggest that ACE inhibitors potentiate bradykinin by inhibiting B(2) receptor desensitization, via a mechanism involving protein kinase C (PKC) and phosphatases. Here we investigated, in intact porcine coronary arteries, endothelial ACE/B(2) receptor 'crosstalk' as well as bradykinin potentiation through neutral endopeptidase (NEP) inhibition. 2. NEP inhibition with phosphoramidon did not affect the bradykinin concentration-response curve (CRC), nor did combined NEP/ACE inhibition with omapatrilat exert a further leftward shift on top of the approximately 10 fold leftward shift of the bradykinin CRC observed with ACE inhibition alone. 3. In arteries that, following repeated exposure to 0.1 microM bradykinin, no longer responded to bradykinin ('desensitized' arteries), the ACE inhibitors quinaprilat and angiotensin-(1-7) both induced complete relaxation, without affecting the organ bath fluid levels of bradykinin. This phenomenon was unaffected by inhibition of PKC or phosphatases (with calphostin C and okadaic acid, respectively). 4. When using bradykinin analogues that were either completely or largely ACE-resistant ([Phe(8)psi(CH(2)-NH)Arg(9)]-bradykinin and [deltaPhe(5)]-bradykinin, respectively), the ACE inhibitor-induced shift of the bradykinin CRC was absent, and its ability to reverse desensitization was absent or significantly reduced, respectively. Caveolar disruption with filipin did not affect the quinaprilat-induced effects. Filipin did however reduce the bradykinin-induced relaxation by approximately 25-30%, thereby confirming that B(2) receptor-endothelial NO synthase (eNOS) interaction occurs in caveolae. 5. In conclusion, in porcine arteries, in contrast to transfected cells, bradykinin potentiation by ACE inhibitors is a metabolic process, that can only be explained on the basis of ACE-B(2) receptor co-localization on the endothelial cell membrane. NEP does not appear to affect the bradykinin levels in close proximity to B(2) receptors, and the ACE inhibitor-induced bradykinin potentiation precedes B(2) receptor coupling to eNOS in caveolae.

Induction of angiotensin converting enzyme in neointima after intravascular stent placement

BACKGROUND

To investigate the morphological changes of the arterial wall and the expression of angiotensin converting enzyme (ACE) in the arterial wall after stent placement in a canine model.

METHODS

Seventeen mongrel dogs underwent stent placement (Gianturco's Z stent) in the aorta. Six animals were sacrificed at 4 weeks after stent implantation, and the other 5 animals at 12 weeks. The normal aorta was harvested from 6 dogs. The specimens were stained with hematoxylin-eosin (H&E) as well as by immunohistochemistry (smooth muscle specific a-actin, and ACE). Histomorphometric analysis was performed using the sections stained with H&E and smooth muscle specific a-actin.

RESULTS

The total intimal area was significantly increased at all time points as compared with the control aorta. The a-actin positive intimal area was also significantly increased at all time points as compared with the control aorta. In the control aorta, luminal endothelial cells as well as a-actin positive medial cells occasionally exhibited faint cytoplasmic staining for ACE. In the 4- and 12-week stented aorta, a-actin positive cells in the neointima and media as well as macrophages in the adventitia stained strongly positive for ACE.

CONCLUSIONS

ACE was induced in the neointima after stent placement of the canine aorta. Considering its multiple biological actions, ACE may be associated with the pathogenesis of neointimal hyperplasia after stent placement.

Effects of thyroid hormones on pulmonary and renal angiotensin-converting enzyme concentrations in fetal sheep near term

In the sheep fetus, pulmonary and renal concentrations of angiotensin-converting enzyme (ACE) increase towards term in parallel with the prepartum surges in plasma cortisol and tri-iodothyronine (T(3)). The ontogenic change in pulmonary ACE has been shown to be induced, at least in part, by cortisol but the role of the thyroid hormones is unknown. Therefore, this study investigated the effects of thyroid hormones on tissue ACE concentration in fetal sheep during late gestation. Pulmonary and renal ACE concentrations were measured in sheep fetuses after experimental manipulation of thyroid hormone status by fetal thyroidectomy and exogenous hormone infusion. In intact fetuses, pulmonary and renal ACE concentrations increased between 127-132 and 142-145 days of gestation (term 145 +/- 2 days), coincident with the prepartum rises in plasma cortisol and T(3). The ontogenic increment in pulmonary ACE concentration was abolished when the prepartum surge in T(3), but not cortisol, was prevented by fetal thyroidectomy. At 143-145 days, ACE concentration in the lungs and kidneys of the thyroidectomised fetuses were both lower than those in the intact fetuses. In intact fetuses at 127-132 days, pulmonary ACE was upregulated by intravenous infusions of either cortisol (2-3 mg/kg per day) or T(3) (8-12 microg/kg per day) for 5 days. Renal ACE was unaffected by cortisol or T(3) infusion. Therefore, thyroid hormones have an important role in the developmental control of pulmonary and renal ACE concentration in the sheep fetus towards term. In addition, the prepartum rise in plasma T(3) appears to mediate, in part, the maturational effect of cortisol on pulmonary ACE concentration.

Relationship of serum ACE inhibition to oral dose of enalapril in normotensive volunteers

OBJECTIVES

To determine the relationship between oral dose of enalapril and parameters describing serum angiotensin converting enzyme (ACE) inhibition.

METHODS

Four different oral doses of enalapril maleate (2.5, 5, 10 and 20 mg) were administered to six healthy normotensive volunteers, in a four-period crossover study. Serum ACE inhibition profiles were determined in each case using a synthetic substrate, hippuryl-histidyl-leucine (HHL). Pharmacodynamic parameters of the drug (Emax and AUEC0-->24) were calculated and their relationship to oral doses investigated using linear regression analysis.

RESULTS

There was no significant relationship between drug dose and the two pharmacodynamic parameters (Emax and AUEC0-->24). The r2 values were 0.548 (F=3.63, P=0.153) and 0.6360 (F=5.24, P=0.106) for Emax and AUEC0-->24, respectively.

CONCLUSION

The extent of serum ACE inhibition, as the main determinant of the blood pressure lowering effect of enalapril, is not dose-dependent within the single dose range of 2.5-20 mg.

Angiotensin converting enzyme in bovine ovarian follicular fluid and its relationship with oestradiol and progesterone

CONTENT

The purpose of the present study was to identify angiotensin converting enzyme (ACE) in bovine ovarian follicular fluid and to relate the ACE activity to the phase of the oestrous cycle, pregnancy, and the follicular fluid concentrations of oestradiol and progesterone. The ACE activity was similar to that found in bovine serum and was completely inhibited by the specific ACE inhibitor captopril. The 50% inhibitory concentration (IC50) was 1.4 x 10(-8) mol/l (range 0.8 x 10(-8) to 5.0 x 10(-8) mol/l; n=6), which is similar to that found in bovine and human serum. The ACE activity did not differ in the pre-ovulatory and luteal phase, pregnancy or cystic follicles. It correlated with the follicular fluid concentration of progesterone in cycling cows (rho=0.476; p < 0.005; n=36), but did not correlate with the diameter of the follicles, the follicular fluid concentration of oestradiol or the ratio between the oestradiol and progesterone concentrations. The demonstration of ACE in bovine ovarian follicular fluid provides further evidence for the presence of a local renin-angiotensin system in the bovine ovary.