Overexpression Of Angiotensin-converting Enzyme Research Articles

Angiotensin converting enzyme 2 attenuates angiotensin II‐mediated phosphorylation of MAP kinase and Akt in neurons

Our lab has reported that overexpression of angiotensin converting enzyme 2 (ACE2) in the brain blunts the development of angiotensin‐II (Ang‐II)‐induced hypertension and sympathetic activation. Yet, the signaling mechanisms are still elusive. Hypothesis: Ang‐II‐mediated phosphorylation of MAP kinase and Akt in neurons is attenuated by ACE2 overexpression. A Neuro‐2a cell line overexpressing ACE2 was generated by stable transfection with an expression plasmid for human ACE2 (N2AhACE2). Control and N2AhACE2 cells were treated with 100 nM Ang‐II or vehicle, in presence and absence of inhibitors. Phosphorylation of p38 MAP kinase (Thr180/Thr182) and Akt (Ser473) by Ang‐II in control cells (2‐ and 1.5‐fold increase, respectively, p<0.05) (Western blot), was prevented by ACE2 overexpression. Pretreatment with DX600 (ACE2 inhibitor) for 30 min had no effect in control cells, but restored Ang‐II‐induced phosphorylation in N2AhACE2. In addition, Ang‐II‐induced expression of AT1R (1.8‐fold increase vs. vehicle, p<0.05) was blunted by Losartan (AT1R antagonist), or ACE2 overexpression. Furthermore, pretreatment with A‐779 (Ang‐(1–7) receptor antagonist) restored phosphorylation in N2AhACE2. These data suggest that ACE2 counteracts Ang‐II‐induced phosphorylation of p38 MAP kinase and Akt, by both, decreasing AT1R signaling and increasing Ang‐(1–7) receptor signaling in neurons. (Support: HL093178)

Angiotensin-(1-7) suppresses oxidative stress and improves glucose uptake via Mas receptor in adipocytes

Although reactive oxygen species (ROS) contribute to glucose intolerance induced by the renin-angiotensin system (RAS) is well documented, the role of the newly discovered pathway of RAS, angiotensin (Ang)-(1-7)/Mas axis, in this process remains unknown. Here, we examined the effect of Ang-(1-7) on oxidative stress and glucose uptake in adipocytes. We used primary cultured epididymal adipocytes from C57 mice to study Ang-(1-7) effects on glucose uptake. We also treated fully differentiated 3T3-L1 adipocytes with exogenous Ang-(1-7) or overexpression of angiotensin-converting enzyme 2 (ACE2) to induce endogenous generation of Ang-(1-7) to clarify its effects on ROS production. Intracellular ROS was measured by flow cytometry, dihydroethidium (DHE), and nitroblue tetrazolium assay. Levels of NADPH oxidase and adiponectin mRNA were measured by real-time PCR. Ang-(1-7) improved glucose uptake both in basal and insulin-stimulated states. ROS production was slightly but significantly decreased in adipocytes treated with Ang-(1-7). Additionally, Mas receptor antagonist D-Ala7-Ang-(1-7) (A779) reversed the effect of Ang-(1-7) on glucose uptake and oxidative stress. Furthermore, treatment of adipocytes with Ang-(1-7) decreased NADPH oxidase mRNA levels. We also found that oxidative stress induced by glucose oxidase-suppressed expression of adiponectin, an insulin-sensitive protein. However, the suppression of oxidative stress by Ang-(1-7) restored adiponectin expression, while A779 agonists these changes induced by Ang-(1-7). In conclusion, Ang-(1-7) can protect against oxidative stress and improve glucose metabolism in adipocytes. These results show that Ang-(1-7) is a novel target for the improvement of glucose metabolism by preventing oxidative stress.

Adipocyte-derived lipids increase angiotensin-converting enzyme (ACE) expression and modulate macrophage phenotype

Human monocytes/macrophages express the angiotensin-converting enzyme (ACE) but nothing is known about its role under physiological conditions. As adipose tissue contains resident macrophages that have been implicated in the generation of insulin resistance in expanding fat mass, we determined whether adipocytes release factors that affect ACE expression and function in monocytes. Incubation of human monocyte-derived macrophages with conditioned medium from freshly isolated human adipocytes (BMI=25.4±0.96) resulted in a 4-fold increase in ACE expression. The effect was insensitive to denaturation and different proteases but abolished after lipid extraction. mRNA levels of the major histocompatibility complex class II protein increased in parallel with ACE, whereas the expression of tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), interleukin (IL)-6, and cyclooxygenase-2 decreased. As a consequence of the reduction in MCP-1, monocyte recruitment was also attenuated. Moreover, adipocyte-conditioned medium prevented the interferon (IFN)-γ induced formation of TNF-α, IL-6, and MCP-1, all markers of classically-activated (M1 type) macrophages. The decrease in cytokine expression in adipocyte-conditioned medium-treated macrophages was sensitive to ACE silencing by small interfering RNA (siRNA). Accordingly, ACE overexpression in THP-1 cells mimicked the effect of adipocyte-conditioned medium. In both cell types, ACE inhibition failed to affect the changes induced by adipocyte conditioned-medium treatment and ACE overexpression. Thus, the modulation of macrophage polarization by ACE appears to be mediated independently of enzyme activity, probably via intracellular signaling. Interestingly, human macrophage ACE expression was also upregulated by IL-4 and IL-13, which promote the "alternative" activation of macrophages and decreased by LPS and IFN-γ. Mechanistically, adipocyte-conditioned medium stimulated the phosphorylation of the AMP-activated protein kinase and AMPK inhibition prevented the increase in ACE expression. Moreover, ACE expression was reduced in spleen derived-monocytes from AMPKα1(-/-) mice versus their wild-type littermates. These data indicate that mature adipocytes modulate the expression profile of macrophages by releasing lipid mediators that increase ACE expression via AMPK. This prevents the pro-inflammatory cytokine production by macrophages.

Angiotensin-converting Enzyme Overexpression in Mouse Myelomonocytic Cells Augments Resistance to Listeria and Methicillin-resistant Staphylococcus aureus

Gene targeting in ES cells was used to substitute control of angiotensin converting enzyme (ACE) expression from the endogenous promoter to the mouse c-fms promoter. The result is an animal model called ACE 10/10 in which ACE is overexpressed by monocytes, macrophages, and other myelomonocytic lineage cells. To study the immune response of these mice to bacterial infection, we challenged them with Listeria monocytogenes or methicillin-resistant Staphylococcus aureus (MRSA). ACE 10/10 mice have a significantly enhanced immune response to both bacteria in vivo and in vitro. For example, 5 days after Listeria infection, the spleen and liver of ACE 10/10 mice had 8.0- and 5.2-fold less bacteria than wild type mice (WT). In a model of MRSA skin infection, ACE 10/10 mice had 50-fold less bacteria than WT mice. Histologic examination showed a prominent infiltrate of ACE-positive mononuclear cells in the skin lesions from ACE 10/10. Increased bacterial resistance in ACE 10/10 is directly due to overexpression of ACE, as it is eliminated by an ACE inhibitor. Critical to increased immunity in ACE 10/10 is the overexpression of iNOS and reactive nitrogen intermediates, as inhibition of iNOS by the inhibitor 1400W eliminated all in vitro and in vivo differences in innate bacterial resistance between ACE 10/10 and WT mice. Increased resistance to MRSA was transferable by bone marrow transplantation. The overexpression of ACE and iNOS by myelomonocytic cells substantially boosts innate immunity and may represent a new means to address serious bacterial infections.

ACE2 Overexpression Ameliorates Left Ventricular Remodeling and Dysfunction in a Rat Model of Myocardial Infarction

The purpose of this study was to test the hypothesis that overexpression of angiotensin-converting enzyme 2 (ACE2) may favorably affect left ventricular (LV) remodeling and function after myocardial infarction (MI). The left anterior descending coronary artery was ligated to produce anterior MI in 100 Wistar-Kyoto rats that were randomly divided into Ad-ACE2, Ad-ACE2+A779, Ad-EGFP, model, and sham groups. Two weeks later, rats in the Ad-ACE2 and Ad-EGFP groups received direct intramyocardial injection of Ad-ACE2 and Ad-EGFP, respectively. Rats in the Ad-ACE2+A779 group received both intramyocardial injection of Ad-ACE2 and a continuous intravenous infusion of A779 for 15 days. LV volume and systolic function, the extent of myocardial fibrosis, and levels of ACE2, angiotensin II (Ang II), and collagen I protein expression were evaluated. Four weeks after ACE2 gene transfer, the Ad-ACE2 group showed reduced LV volume, extent of myocardial fibrosis, and expression levels of ACE, Ang II, and collagen I in the myocardium, and increased LV ejection fraction and levels of ACE2 activity and expression in comparison with the Ad-EGFP and model groups. These results suggest that ACE2 overexpression attenuated LV fibrosis and improved LV remodeling and systolic function. In conclusion, overexpression of ACE2 favorably affected the pathological process of LV remodeling after MI by inhibiting ACE activity, reducing AngII levels, and up-regulating Ang-(1-7) expression, thus providing a potential therapeutic target in the treatment of heart failure.

Secondary Prevention of CAD with ACE Inhibitors: A Struggle Between Life and Death of the Endothelium

Angiotensin-converting enzyme (ACE) inhibitors improve outcomes in patients with coronary artery disease (CAD), heart failure, and hypertension. This short review examines clinical evidence for such effects and the underlying mechanism of action. One potential mode of action for ACE inhibitors in CAD is blood pressure reduction. However, recent data suggest that the effects of ACE inhibitors on the endothelium may also be relevant in attenuating the progression of atherosclerosis. In CAD, chronic overexpression of tissue ACE disrupts the angiotensin II/bradykinin balance with a net result of endothelial dysfunction, mainly due to an increased rate of apoptosis. An imbalance between endothelial apoptosis (death) and its renewal from the bone marrow (life) causes discontinuity of the endothelial layer, favoring the initiation and progression of a biochemical sequence that leads to atherosclerosis, plaque rupture, and eventually acute coronary syndromes. There is clinical and experimental evidence that ACE inhibition improves the life and death cycle of the endothelium. By restoring the bradykinin/angiotensin II balance, ACE inhibition reduces the rate of endothelial apoptosis and experimental results suggest that ACE inhibition can also improve the production and mobilization of endothelial progenitor cells from bone marrow. We report our experience in this context with perindopril.

Intramuscular renin–angiotensin system is activated in human muscular dystrophy

To investigate the role of the muscular renin–angiotensin system (RAS) in human muscular dystrophy, we used immunohistochemistry and Western blotting to examine the cellular localization of angiotensin-converting enzyme (ACE), the angiotensin II type 1 receptor (AT1) and the angiotensin II type 2 receptor (AT2) in muscle biopsies from patients with Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), and congenital muscular dystrophy (CMD). In normal muscle, ACE was expressed in vascular endothelial cells and neuromuscular junctions (NMJs), whereas AT1 was immunolocalized to the smooth muscle cells of blood vessels and intramuscular nerve twigs. AT2 was immunolocalized in the smooth muscle cells of blood vessels. These findings suggest that the RAS has a functional role in peripheral nerves and NMJs. ACE and AT1, but AT2 immunoreactivity were increased markedly in dystrophic muscle as compared to controls. ACE and the AT1 were strongly expressed in the cytoplasm and nuclei of regenerating muscle fibers, fibroblasts, and in macrophages infiltrating necrotic fibers. Double immunolabeling revealed that activated fibroblasts in the endomysium and perimysium of DMD and CMD muscle were positive for ACE and AT1. Triple immunolabeling demonstrated that transforming growth factor-β1 (TGF-β1) and ACE were colocalized on the cytoplasm of activated fibroblasts in dystrophic muscle. Furthermore, Western blotting showed increases in the expression of AT1 and TGF-β1 protein in dystrophic muscle, which coincided with our immunohistochemical results. The overexpression of ACE and AT1 in dystrophic muscle would likely result in the increased production of Ang II, which may act on these cells in an autocrine manner via AT1. The activation of AT1 may induce fibrous tissue formation through overexpression of TGF-β1, which potently activates fibrogenesis and suppresses regeneration. In conclusion, our results imply that the intramuscular RAS–TGF-β1 pathway is activated in human muscular dystrophy and plays a role at least partly in the pathophysiology of this disease.

Onset of Experimental Severe Cardiac Fibrosis Is Mediated by Overexpression of Angiotensin-Converting Enzyme 2

Angiotensin-converting enzyme (ACE) 2 is a recently identified homologue of ACE. There is great interest in the therapeutic benefit for ACE2 overexpression in the heart. However, the role of ACE2 in the regulation of cardiac structure and function, as well as maintenance of systemic blood pressure, remains poorly understood. In cell culture, ACE2 overexpression led to markedly increased myocyte volume, assessed in primary rabbit myocytes. To assess ACE2 function in vivo, we used a recombinant adeno-associated virus 6 delivery system to provide 11-week overexpression of ACE2 in the myocardium of stroke-prone spontaneously hypertensive rats. ACE2, as well as the ACE inhibitor enalapril, significantly reduced systolic blood pressure. However, in the heart, ACE2 overexpression resulted in cardiac fibrosis, as assessed by histological analysis with concomitant deficits in ejection fraction and fractional shortening measured by echocardiography. Furthermore, global gene expression profiling demonstrated the activation of profibrotic pathways in the heart mediated by ACE2 gene delivery. This study demonstrates that sustained overexpression of ACE2 in the heart in vivo leads to the onset of severe fibrosis.

The Angiotensin Converting Enzyme 2/Ang-(1-7) Axis in the Heart

For decades, the literature has been inundated with evidence of the important role of the renin–angiotensin system (RAS) in cardiac remodeling and function with most in the field familiar with this classic, dogmatic story. The protease renin is synthesized and released from the kidney and acts on a circulating inactive peptide, angiotensinogen, produced by the liver, giving rise to angiotensin (Ang) I. Ang I is then transformed into the biologically active octapeptide, Ang II, through enzymatic cleavage by angiotensin-converting enzyme (ACE).1 Ang II is the main effector molecule of the RAS, acting in an endocrine, autocrine/paracrine, and intracrine hormone pathway on cardiac cells. Ang II binds and activates G protein–coupled receptors, the angiotensin type 1 (AT1R) and angiotensin type 2 (AT2R) receptors, to mediate its actions. Activation of AT1R mediates most of the cardiovascular responses attributed to Ang II (ie, vasoconstriction, mitogenic and hypertrophic effects, fibrosis, inflammation, and fluid retention). In contrast, AT2R activation may cause opposing physiological responses that are increased in several disease processes.2 Nearly 50 years after the discovery of ACE, a genomic based screening resulted in a characterization of ACE2, thus adding an unexpected twist into the well-known tale of the RAS.3,4 ACE2 is a carboxypeptidase that cleaves a single residue from Ang I to form Ang-(1-9), which is then converted to Ang-(1-7) by either ACE or neutral endopeptidases.3 This process is less efficient because of the requirement of 2 enzymatic processes. ACE2 …

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

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

Abstract 1088: Prevention of Connexin 43 (Cx43) Dephosphorylation is Associated with Reduced Ventricular Tachycardia in Cardiac-Specific Angiotensin Converting Enzyme (ACE) Overexpression Mice

Introduction: Connexin 43 (Cx43) is a major component of the ventricular gap junctional complex, which provides a low resistance pathway for electrical conduction between myocytes. Reduction of Cx43 amount of phosphorylation has been implicated in the pathogenesis of ventricular tachycardia (VT) and fibrillation. Cardiac-specific angiotensin converting enzyme overexpression mice (ACE 8/8) have slow conduction, show conduction blocks, are prone to VT and sudden death, and show profound reductions in Cx43 levels and phosphorylation. Therefore, we hypothesized that reversal of Cx43 changes, by preventing the renin-angiotensin system (RAS) activation, would reduce the arrhythmic risk in these animals. Methods: Prevention of RAS activation was accomplished by one of three methods: ACE 8/8 receiving an ACE inhibitor (captopril), ACE 8/8 mice treated with a specific angiotensin receptor type-1 blocker (losartan), and ACE 8/8 mice crossed with homozygote angiotensinogen null mice. Pooled results were compared to untreated ACE 8/8 littermates. Surface electrocardiography and invasive electrophysiological study with programmed ventricular stimulation were performed on ten-week old mice, and the hearts were extracted for immunoblotting. Results: VT was induced in 10 out of 12 untreated ACE 8/8 mice, but only in 3 out of 11 treated mice (p<0.02). Total Cx43 was not changed significantly in treated animals as compared to controls, but the ratio (P/NP) of phosphorylated Cx43 (bands P1 and P2 in immunoblot) to non-phosphorylated Cx43 (band P0) showed a trend toward increase in the treatment group (0.78±0.18 vs. 1.25±0.19; P=0.09). Dividing the mice into two groups, high-risk (inducible and/or spontaneous VT) versus low-risk (no VT), we observed a significant difference in P/NP ratio (0.75±0.12 in high-risk mice vs. 1.78±0.32 in low-risk, p<0.01). Discussion: Unexpectedly, disruption of RAS signaling did not increase total Cx43 levels in ACE 8/8 mice. On the other hand, the treatments increased phospho-Cx43, suggesting that RAS controls Cx43 phosphorylation but not total amount. Even in the presence of significantly depressed levels of Cx43, small changes in Cx43 phosphorylation were associated with a significant reduction in VT inducibility.

Cardiac-restricted angiotensin-converting enzyme overexpression causes conduction defects and connexin dysregulation

Renin-angiotensin (RAS) system activation is associated with an increased risk of sudden death. Previously, we used cardiac-restricted angiotensin-converting enzyme (ACE) overexpression to construct a mouse model of RAS activation. These ACE 8/8 mice die prematurely and abruptly. Here, we have investigated cardiac electrophysiological abnormalities that may contribute to early mortality in this model. In ACE 8/8 mice, surface ECG voltages are reduced. Intracardiac electrograms showed atrial and ventricular potential amplitudes of 11% and 24% compared with matched wild-type (WT) controls. The atrioventricular (AV), atrio-Hisian (AH), and Hisian-ventricular (HV) intervals were prolonged 2.8-, 2.6-, and 3.9-fold, respectively, in ACE 8/8 vs. WT mice. Various degrees of AV nodal block were present only in ACE 8/8 mice. Intracardiac electrophysiology studies demonstrated that WT and heterozygote (HZ) mice were noninducible, whereas 83% of ACE 8/8 mice demonstrated ventricular tachycardia with burst pacing. Atrial connexin 40 (Cx40) and connexin 43 (Cx43) protein levels, ventricular Cx43 protein level, atrial and ventricular Cx40 mRNA abundances, ventricular Cx43 mRNA abundance, and atrial and ventricular cardiac Na(+) channel (Scn5a) mRNA abundances were reduced in ACE 8/8 compared with WT mice. ACE 8/8 mice demonstrated ventricular Cx43 dephosphorylation. Atrial and ventricular L-type Ca(2+) channel, Kv4.2 K(+) channel alpha-subunit, and Cx45 mRNA abundances and the peak ventricular Na(+) current did not differ between the groups. In isolated heart preparations, a connexin blocker, 1-heptanol (0.5 mM), produced an electrophysiological phenotype similar to that seen in ACE 8/8 mice. Therefore, cardiac-specific ACE overexpression resulted in changes in connexins consistent with the phenotype of low-voltage electrical activity, conduction defects, and induced ventricular arrhythmia. These results may help explain the increased risk of arrhythmia in states of RAS activation such as heart failure.

Overexpression of Angiotensin-Converting Enzyme 2 in the Rostral Ventrolateral Medulla Causes Long-Term Decrease in Blood Pressure in the Spontaneously Hypertensive Rats

The rostral ventrolateral medulla (RVLM) is a relay point that provides supraspinal excitatory input to sympathetic preganglionic neurons in the regulation of blood pressure. The importance of the RVLM is further highlighted by observations that an increase of RVLM sensitivity to angiotensin II and enhanced sympathetic activity are associated with hypertension. Angiotensin-converting enzyme 2 (ACE2) has been shown to be central in maintaining the balance between vasoconstrictor activity of angiotensin II with vasoprotective action of angiotensin-(1-7) in the peripheral system. However, its role in central control of blood pressure in the RVLM is yet to be investigated. Thus, our objective in this study was to compare ACE2 expression in the RVLM of Wistar-Kyoto rats and spontaneously hypertensive rats and to determine whether RVLM ACE2 is involved in blood pressure control. ACE2 immunoreactivity was diffusely distributed in many cardiovascular regulatory neurons, including the RVLM. Western blot analysis revealed a 40% decrease in ACE2 in the RVLM of spontaneously hypertensive rat compared with Wistar-Kyoto rats. Lentiviral-mediated overexpression of ACE2 (lenti-ACE2) was used to determine whether a decrease in ACE2 in the RVLM is associated with hypertensive state. Bilateral injection of lenti-ACE2 resulted in a long-term expression of transgenic ACE2. This was associated with a decrease in mean arterial pressure exclusively in the spontaneously hypertensive rat (141+/-4 mm Hg in lenti-GFP versus 124+/-5 mm Hg in lenti-ACE2) and heart rate (304+/-7 bpm in lenti-GFP versus 285+/-5 bpm in lenti-ACE2). These observations demonstrate that overexpression of ACE2 overcomes its intrinsic decrease in the RVLM and decreases high blood pressure in the spontaneously hypertensive rat.

Prevention of angiotensin II-induced cardiac remodeling by angiotensin-(1–7)

Cardiac remodeling, which typically results from chronic hypertension or following an acute myocardial infarction, is a major risk factor for the development of heart failure and, ultimately, death. The renin-angiotensin system (RAS) has previously been established to play an important role in the progression of cardiac remodeling, and inhibition of a hyperactive RAS provides protection from cardiac remodeling and subsequent heart failure. Our previous studies have demonstrated that overexpression of angiotensin-converting enzyme 2 (ACE2) prevents cardiac remodeling and hypertrophy during chronic infusion of angiotensin II (ANG II). This, coupled with the knowledge that ACE2 is a key enzyme in the formation of ANG-(1-7), led us to hypothesize that chronic infusion of ANG-(1-7) would prevent cardiac remodeling induced by chronic infusion of ANG II. Infusion of ANG II into adult Sprague-Dawley rats resulted in significantly increased blood pressure, myocyte hypertrophy, and midmyocardial interstitial fibrosis. Coinfusion of ANG-(1-7) resulted in significant attenuations of myocyte hypertrophy and interstitial fibrosis, without significant effects on blood pressure. In a subgroup of animals also administered [d-Ala(7)]-ANG-(1-7) (A779), an antagonist to the reported receptor for ANG-(1-7), there was a tendency to attenuate the antiremodeling effects of ANG-(1-7). Chronic infusion of ANG II, with or without coinfusion of ANG-(1-7), had no effect on ANG II type 1 or type 2 receptor binding in cardiac tissue. Together, these findings indicate an antiremodeling role for ANG-(1-7) in cardiac tissue, which is not mediated through modulation of blood pressure or altered cardiac angiotensin receptor populations and may be at least partially mediated through an ANG-(1-7) receptor.

Myocardial dysfunction and neurohumoral activation without remodeling in left ventricle of monocrotaline-induced pulmonary hypertensive rats

In monocrotaline (MCT)-induced pulmonary hypertension (PH), only the right ventricle (RV) endures overload, but both ventricles are exposed to enhanced neuroendocrine stimulation. To assess whether in long-standing PH the left ventricular (LV) myocardium molecular/contractile phenotype can be disturbed, we evaluated myocardial function, histology, and gene expression of autocrine/paracrine systems in rats with severe PH 6 wk after subcutaneous injection of 60 mg/kg MCT. The overloaded RV underwent myocardial hypertrophy (P < 0.001) and fibrosis (P = 0.014) as well as increased expression of angiotensin-converting enzyme (ACE) (8-fold; P < 0.001), endothelin-1 (ET-1) (6-fold; P < 0.001), and type B natriuretic peptide (BNP) (15-fold; P < 0.001). Despite the similar upregulation of ET-1 (8-fold; P < 0.001) and overexpression of ACE (4-fold; P < 0.001) without BNP elevation, the nonoverloaded LV myocardium was neither hypertrophic nor fibrotic. LV indexes of contractility (P < 0.001) and relaxation (P = 0.03) were abnormal, however, and LV muscle strips from MCT-treated compared with sham rats presented negative (P = 0.003) force-frequency relationships (FFR). Despite higher ET-1 production, BQ-123 (ET(A) antagonist) did not alter LV MCT-treated muscle strip contractility distinctly (P = 0.005) from the negative inotropic effect exerted on shams. Chronic daily therapy with 250 mg/kg bosentan (dual endothelin receptor antagonist) after MCT injection not only attenuated RV hypertrophy and local neuroendocrine activation but also completely reverted FFR of LV muscle strips to positive values. In conclusion, the LV myocardium is altered in advanced MCT-induced PH, undergoing neuroendocrine activation and contractile dysfunction in the absence of hypertrophy or fibrosis. Neuroendocrine mediators, particularly ET-1, may participate in this functional deterioration.

Over-expression of angiotensin-converting enzyme (CD 143) on leukemic blasts as a clue for the activated local bone marrow RAS in AML

Local bone marrow renin-angiotensin system (RAS) is an autocrine-paracrine system affecting hematopoiesis. Angiotensin II type 1a (AT1a) receptors are present on the CD34+ hematopoietic stem cells. Angiotensin II stimulates the proliferation of bone marrow and umbilical cord blood hematopoietic progenitors. There are preliminary data that local RAS might also be involved in leukemogenesis. ACE hyper-function may lead to the acceleration of negative hematopoietic regulator peptide, AcSDKP, metabolism, which in turn lowers its level in the bone marrow micro-environment, finally removing the anti-proliferative effect of AcSDKP on the hematopoietic cells and blasts. Renin expression could have a role on the leukemia development and angiotensin may act as an autocrine growth factor for acute myeloid leukemia (AML) cells. The aim of this study is to search ACE (CD 143) surface antigen by flow-cytometric analyses on the leukemic blast cells taken from the bone marrow of the patients with AML. Bone marrow aspiration materials and peripheral blood samples were obtained from 11 patients with AML (eight males, three females; aged 46 (range 26–67) years) and six patients with non-malignant hematological disorders (four males, two females; aged 56 (range 22–71) years). ACE (CD 143) surface antigen was shown to be over-expressed in leukemic myeloid blast cells. ACE is positively correlated with bone marrow blast count. Elucidation of the pathological activity of the local RAS-mediated regulation of the leukemogenesis is both pathobiologically and clinically important, since the angiotensin peptides represent a molecular target in the disease management.

Potential of Gene Therapy Strategy for the Treatment of Hypertension

Hypertension is one of the most important risk factors for cardiovascular diseases (CVDs). CVD extends across all populations and represents the leading cause of morbidity and mortality in industrialized countries. Hypertension increases the risk of peripheral arterial disease, cardiomyopathy, stroke, and renal failure. The disease affects &50 million Americans and goes undetected in at least one third of the population. In spite of the tremendous progress made by pharmacotherapy in the management and control of hypertension, there has been a steady escalation in its prevalence during the last decade. This has led many to conclude that traditional pharmacotherapy has reached an intellectual plateau and that novel and innovative approaches must be sought for the treatment, control, and possible cure of hypertension. As a result, efforts of our group and those of many others have been diverted to explore the use of gene transfer and gene therapy strategies for a long-term control of hypertension. We have argued that gene therapy offers potentially significant improvements and benefits over the use of traditional pharmacotherapy: (1) noncompliance by patients can be significantly reduced or even eliminated because of the fact that a single treatment involving gene transfer could remain effective for months or even years; (2) side effects associated with pharmacotherapy can be minimized as a result of specific targeting of a therapeutic gene in a given tissue and optimally influencing cardiovascular pathophysiology on an individual patient basis; and (3) with its potential to produce long-term beneficial outcomes in end-organ damage, the gene therapy strategy could lead to a cure of hypertension and its related pathophysiology. It is noteworthy to mention that current pharmacotherapies are often unable to reverse end-organ damage associated with hypertension. In order for the gene therapy for hypertension to be successful, one must provide conceptual support of its efficacy in …

Up-regulation of angiotensin-converting enzyme (ACE) gene expression induces tubulointerstitial injury in reflux nephropathy.

Reflux nephropathy (RN) is the cause of end-stage renal failure in 3%-25% of children and 10%-15% of adults. Angiotensin-converting enzyme (ACE) converts the inactive decapeptide angiotensin I (Ang I) to the active octapeptide angiotensin II (Ang II), a potent vasoconstrictor. ACE is localized in highest concentrations on the luminal surface of endothelial cells, but is also found in several other cell types, including the epithelial cells of the proximal renal tubule. Recent studies have suggested that ACE increases production of the components of extracellular matrix (ECM) such as fibronectin (Fib) mediated through Ang II. Since RN is a primary tubulointerstitial disease, we hypothesized that local overexpression of ACE may induce renal fibrosis via up-regulation of Ang II. In this study, we investigated the expression of ACE in severely refluxing kidneys from eight patients (age range 6 months-14 years) with severe RN secondary to primary high-grade vesicoureteral reflux at nephrectomy. Control material included normal kidney specimens obtained from three adult patients during partial nephrectomy for an incidentaloma. Soluble enzyme immunohistochemistry was carried out using polyclonal antibodies to ACE and Fib. In-situ hybridization (ISH) was performed utilizing biotin-labelled antisense oligonucleotide probe. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to evaluate the relative amount of ACE mRNA. In the refluxing kidney, there was strong ACE immunoreactivity in the glomerulus and proximal tubules and moderate-to-strong immunoreactivity in the distal tubules accompanied by strong Fib immunoreactivity in the glomerulus, proximal tubule, and interstitial space. There was strong ACE mRNA expression in the glomerulus and proximal tubules and moderate expression in the distal tubules. In the control kidneys, homogeneous weak ACE immunoreactivity and mRNA expression was demonstrated only in the proximal tubules. RT-PCR showed strong ACE expression in the refluxing kidneys compared to controls. Up-regulation of ACE in RN accompanied by an increase in ECM in the tubulointerstitial space suggests that ACE is involved in the pathogenesis of the renal parenchymal damage in patients with RN. Pharmacologic blockade of ACE may be helpful in preventing the renal fibrosis associated with RN.