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P Corvol

Publications and source records attributed to P Corvol.

At least 127 records · Page 7Linked to original sources
PubMed1996

Acute angiotensin-converting enzyme inhibition increases the plasma level of the natural stem cell regulator N-acetyl-seryl-aspartyl-lysyl-proline.

Angiotensin I-converting enzyme (ACE) has two homologous active NH2- and COOH-terminal domains and displays activity toward a broad range of substrates. The tetrapeptide N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) has been shown to be hydrolyzed in vitro by ACE and to be a preferential substrate for its NH2-terminal active site. This peptide is a regulatory factor of hematopoiesis which reversibly stem cells and normal early progenitors into S-phase. We found that a single oral dose of 50 mg of the ACE inhibitor, captopril, when administered to eight healthy subjects in a double-blind, crossover, placebo-controlled study, massively increased the plasma level of Ac-SDKP. ACE inhibition by captopril induced a 90-99% inhibition of in vitro [3H]Ac-SDKP hydrolysis and a long-lasting 5.5-fold (range: 4-8.5-fold) increase in the plasma levels of Ac-SDKP. These results demonstrate that Ac-SDKP is the first natural peptide hydrolyzed by the NH2-terminal domain of ACE not only in vitro but also in vivo, confirming that both catalytic sites of ACE are physiologically active. Our data suggest that ACE may also be implicated in the process of hematopoietic stem cell regulation, by permanently degrading this natural circulating inhibitor of cell entry into S-phase.

Administration, Oral↗
PubMed1996

Polar residues in the transmembrane domains of the type 1 angiotensin II receptor are required for binding and coupling. Reconstitution of the binding site by co-expression of two deficient mutants.

Type 1 angiotensin receptors (AT1) are G-protein coupled receptors, mediating the physiological actions of the vasoactive peptide angiotensin II. In this study, the roles of 7 amino acids of the rat AT1A receptor in ligand binding and signaling were investigated by performing functional assays of individual receptor mutants expressed in COS and Chinese hamster ovary cells. Substitutions of polar residues in the third transmembrane domain with Ala indicate that Ser105, Ser107, and Ser109 are not essential for maintenance of the angiotensin II binding site. Replacement of Asn111 or Ser115 does not alter the binding affinity for peptidic analogs, but modifies the ability of the receptor to interact with AT1 (DuP753)- or AT2 (CGP42112A)-specific ligands. These 2 residues are probably involved in determining the binding specificity for these analogs. The absence of G-protein coupling to the Ser115 mutant suggests that this residue, in addition to previously identified residues, Asp74 and Tyr292, participates in the receptor activation mechanism. Finally, Lys102 (third helix) and Lys199 (fifth helix) mutants do not bind angiotensin II or different analogs. Co-expression of these two deficient receptors permitted the restoration of a normal binding site. This effect was not due to homologous recombination of the cDNAs but to protein trans-complementation.

Amino Acid Sequence↗
PubMed1996

Evidence that renal and chorionic tissues contain similar nuclear binding proteins that recognize the human renin promoter.

This study examines whether the human renal cortex, the major renin producing site, contains nuclear factors that bind to the human renin proximal promoter. Footprint analysis of the human renin promoter region showed that human renal cortex cell nuclear extracts interacted with 6 putative cis-elements (the Ets domain-protein, a Pit-1 like binding site, a CRE sequence, an ARP-1 like binding site, an AGE3 like region, and a unknown consensus region, designated element C). Transient DNA transfection studies on chorionic cells implicated the CRE and Pit-1 consensus sites in the regulation of renin gene transcription by cAMP. Electromobility shift assays showed that renal proteins bind specifically to these sequences, and that one of them is CREB; two others seem to be Ets-1 and ARP-1. These results raise the possibility that the human renal cortex and human chorionic cells have the same trans-acting factors that bind to the proximal human renin promoter.

Base Sequence↗
PubMed1996

Angiotensin II type 2 receptor mRNA expression in the developing cardiopulmonary system of the rat.

Recent studies have shown that angiotensin II has a trophic action on the heart. The presence of two types of angiotensin II receptors, type 1 (AT1) and type 2 (AT2), has been reported in the rat heart. This in situ hybridization study describes the tissue and cell location of AT2 receptor mRNA in the developing rat cardiopulmonary system, from 15 days of gestation to adulthood. Expression of AT1A receptor mRNA was studied in parallel for direct comparison. The aortic arch and pulmonary artery expressed high levels of AT2 receptor mRNA from 15 days of gestation up until 15 days postpartum, whereas expression of this mRNA was observed only just before and after birth in the coronary arteries. AT2 receptor mRNA was not detected in any cardiac muscle of the fetus, neonate, or adult. The annulus of all four heart valves expressed AT2 mRNA from 21 days of gestation until 10 days postpartum, but no labeling was seen in the valve leaflets. The subendocardial atrial tissue showed a high level of AT2 receptor mRNA expression during the early postnatal period, but no expression was observed in the atrial myocytes from fetal stages to adulthood. The bronchi and trachea, but not the lung parenchyma, showed a high level of AT2 receptor mRNA expression starting from 17 days of gestation until 10 days postpartum. AT2 receptor mRNA expression in the cardiopulmonary system is therefore transient, developmentally regulated, and mostly located in vascular structures. By these three characteristics, its expression contrasts with that of AT1A, which is continuously expressed in the cardiac muscle to adulthood. This spatiotemporal pattern of expression of angiotensin II receptor mRNAs during development suggests a possible role for angiotensin II in organogenesis.

Age Factors↗
PubMed1996

Tissue-specific regulation of type 1 angiotensin II receptor mRNA levels in the rat.

Most of the biological effects of the renin-angiotensin system are mediated by the binding of angiotensin II (Ang II) to the type 1 Ang II (AT1) receptor, the predominant receptor subtype present after fetal life. To study tissue-specific regulation of the expression of the AT1 receptor in the rat, we altered activity of the renin-angiotensin system by feeding rats a low (0.07% NaCl), normal (0.3% NaCl), or high (7.5% NaCl) salt chow for 14 days; infusing Ang II (200 ng/kg per minute IP) or vehicle for 7 days; and administering an angiotensin-converting enzyme inhibitor (captopril, 100 mg/dL in the drinking water) or vehicle for 7 days. Renin, angiotensinogen, and total AT1 receptor mRNA levels were measured by slot-blot hybridization with cRNA probes, and AT1 receptor subtypes (A and B) were measured by reverse transcription-polymerase chain reaction in the presence of a cRNA internal standard. Plasma renin concentration and renal renin, renal and hepatic angiotensinogen, and hepatic AT1 receptor mRNA levels were all inversely related to salt intake; in contrast, renal AT1 receptor mRNA levels were significantly lower in rats fed low salt, a difference that was exclusively due to a decrease in the AT1A subtype. This difference did not appear to be mediated by a change in the circulating levels of Ang II, because Ang II infusion reduced plasma renin concentration and renal renin mRNA with no effect on either angiotensinogen or AT1 receptor mRNA levels in kidney or liver, renal Ang II receptor density (determined by in situ autoradiography) decreased, presumably via a posttranscriptional mechanism. Similarly, inhibition of Ang II generation with captopril increased plasma renin concentration and renal renin mRNA levels without altering renal or hepatic angiotensinogen mRNA or renal AT1 receptor mRNA levels. Thus, AT1 receptor gene expression is regulated in a tissue-specific manner that is distinct from other components of systemic and local renin-angiotensin systems and that appears to be mediated by a mechanism other than through changes in the circulating levels of Ang II.

Angiotensin II↗
PubMed1996

Selective recognition of M235T angiotensinogen variants and their determination in human plasma by monoclonal antibody-based immunoanalysis.

The common M235T mutation of human angiotensinogen has been shown to be associated with a 10-20% increase in plasma angiotensinOgen level and increased frequency of essential and pregnancy-induced hypertension. The detection of such a common factor in the plasma of individuals at risk could be a useful tool for modern molecular-based medicine. The recognition of M235T variants was investigated using four monoclonal antibodies (mAbs) directed against human angiotensinogen; two immunometric assays were developed. The first assay (using mAbS 7B2 and 4G3) allowed the direct determination of angiotensinogen concentrations and did not show a significant difference with the enzymatic measurement of angiotensinogen. The second assay (using mAbs 1H8 and 1C11) showed a fine distinction between the T235 mutant and M235 wild-type forms of angiotensinogen, with a greater affinity for the latter, as confirmed by biosensor BIAcore experiments. This assay was extremely sensitive in measuring the proportions of the M235 and T235 forms present in the test samples, the first time such a distinction has been achieved in the serpin family. The simple immunoanalysis of the plasma allowed the direct determination of the M235T genotype of the individual tested. Furthermore, it was shown that the T174M mutation, described as being in complete linkage disequilibrium with the M235T mutation, had no influence on these results. Moreover, this assay suggested the presence of the M235 and T235 angiotensinogens in approximately equal amounts in heterozygous plasmas. In conclusion, the immunometric assay described in this study should provide original tools for investigating the relationship between M235T genotype, plasma angiotensinogen levels, and regulation of blood pressure.

Angiotensinogen↗
PubMed1996

Angiotensin II receptors: protein and gene structures, expression and potential pathological involvements.

Two distinct types of cell-surface angiotensin II receptors (AT1 and AT2) have been defined pharmacologically and cDNAs encoding each type have been identified by expression cloning. These pharmacological studies showed the AT1 receptors to mediate all the known functions of angiotensin II in regulating salt and fluid homeostasis. Further complexity in the angiotensin II receptor system was revealed when homology cloning showed the existence of two AT1 subtypes in rodents and in situ hybridization and reverse transcription-polymerase chain reaction analyses showed their level of expression to be regulated differently in different tissues: AT1A is the principal receptor in the vessels, brain, kidney, lung, liver, adrenal gland and fetal pituitary, while AT1B predominates in the adult pituitary and is only expressed in specific regions of the adrenal gland (zona glomerulosa) and kidney (glomeruli). Expression of AT1A appears to be induced by angiotensin II in vascular smooth-muscle cells but is inhibited in the adrenal gland. Preliminary analysis of the AT1 promoters is also suggestive of a high degree of complexity in their regulation. Investigation of a potential role for altered AT1 receptor function has commenced at a genetic level in several diseases of the cardiovascular system. No mutations affecting the coding sequence have been identified in Conn adenoma and no linkage has been demonstrated with human hypertension by sib-pair analysis. None the less, certain polymorphisms that do not alter the protein structure have been found to be associated with hypertension and to occur at an increased frequency in conjunction with specific polymorphisms in the ACE gene in individuals at increased risk for myocardial infarction. Further characterization of the regions of the AT1 gene that regulate its expression are therefore needed. The physiological importance of the AT2 gene product still remains a matter of debate.

Amino Acid Sequence↗
PubMed1996

Early expression of all the components of the renin-angiotensin-system in human development.

Increasing evidence suggests that the renin-angiotensin system (RAS) is not only a potent regulator of blood pressure and fluid and electrolyte homeostasis, but that it also plays an important role in growth and differentiation in development as well as in pathological states. We, therefore, investigated the expression of all components of the RAS in the human embryo and fetus by in situ hybridization or immunohistochemistry. This study is the first to demonstrate the presence of all components of the RAS in very early human development (30-35 days of gestation). Angiotensinogen mRNA is expressed in very high amounts in the yolk sac, liver, and kidney, whereas renin mRNA and angiotensin-converting enzyme are expressed in the chorion, kidney, and heart, thus allowing fetal production of angiotensin II. This effector molecule of the RAS mediates its effects through binding to specific receptor types, AT1 and AT2. Both of these receptors are also expressed very early in development (24 days of gestation), suggesting a role for angiotensin II in organogenesis. Based on the expression pattern of these receptors, angiotensin II likely plays a role in the growth and differentiation of the kidney, adrenal gland, heart, and liver, all organs that are of major importance for the regulation of blood pressure later in life.

Adrenal Glands↗
PubMed1995

Comparative expression of vasopressin and angiotensin type-1 receptor mRNA in rat hypothalamic nuclei: a double in situ hybridization study.

Angiotensin II (Ang) injected intracerebroventricularly stimulates neurohypophyseal vasopressin (AVP) release into the peripheral circulation. As we have shown previously, central actions of Ang II in the rat forebrain are mediated by the AT1A receptor subtype. In the present paper, we attempted to clarify the cellular localization of the AT1A receptor mRNA in the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei, in order to reappraise the conflicting data on the nature of the angiotensin II receptor involved in Ang induced vasopressin release. For this purpose, double in situ hybridization was performed using a radioactive AT1A receptor riboprobe and a digoxygenin labeled AVP oligoprobe, and immunohistochemical localization of the glial marker glial fibrillary acidic protein (GFAP) on the same brain slice. The results show neuronal expression of AT1A receptor mRNA mainly in dorsal and medial parvocellular parts of the PVN, its localization in some magnocellular PVN neurons and the absence of its expression in AVP producing neurons either in the PVN or in the SON. Thus, while indirect evidence indicates the involvement of the AT1A receptor subtype in the regulation of CRH and oxytocin release, the stimulation of vasopressinergic neurons is likely due to indirect mechanisms, or to a yet unknown type of angiotensin receptor.

Animals↗
PubMed1995

Cell surface localization of proteolysis of human endothelial angiotensin I-converting enzyme. Effect of the amino-terminal domain in the solubilization process.

Angiotensin-converting enzyme (ACE) belongs to the type I class of ectoproteins and is solubilized by Chinese hamster ovary cells transfected with the full-length human ACE cDNA. ACE release in Chinese hamster ovary cells involves a proteolytic cleavage occurring in the carboxyl-terminal region, between Arg-1137 and Leu-1138. The subcellular localization of ACE proteolysis was established by pulse-chase experiments, cell surface immunolabeling, and biotinylation of radiolabeled mature proteins. The proteolysis of ACE takes place primarily at the plasma membrane. The solubilization of ACE is less than 2% within 1 h, is increased 2.4-fold by phorbol esters, but is not influenced by ionophores. An ACE mutant lacking the transmembrane domain and the cytosolic part (ACE delta COOH), is secreted at a faster rate without a carboxyl-terminal cleavage, and phorbol esters or ionophores have no effect on its rate of production in the medium. Therefore, the proteolysis of ACE is dependent on the presence of the membrane anchor and suggests that the secretase(s) involved is also membrane-associated. An ACE mutant lacking the amino-terminal domain (ACECF) is secreted 10-fold faster compared with wild-type ACE. The solubilization of ACECF occurs at the plasma membrane and is stimulated 2.7-fold by phorbol esters, and the cleavage site is localized between Arg-1227 and Val-1228. The amino-terminal domain of ACE slows down the proteolysis and seems to act as a "conformational inhibitor" of the proteolytic process, possibly via interactions with the "stalk" of ACE and the secretase(s) itself.

Amino Acid Sequence↗
PubMed1995

[New data on mineralocorticoid hormones. Physiopathological implications].

Our better understanding of the terminal steps of aldosterone production based on enzyme cloning has led to new clinical approaches to three aldosterone-related types of hypertension: mineralocorticoid excess, Liddle's disease and glucocorticoid-sensitive hyperaldosteronism. In all three cases, hypertension results from volume expansion due to increased reabsorption of sodium in the distal renal tube with decreased plasma renin activity and hypokaliaemia. Genetic testing now allows early diagnosis of these severe familial diseases and specific treatment. Although both glucocorticoid-sensitive hypertension and Liddle's disease are dominantly inherited diseases, other genes can also modulate the degree of volume expansion, hypokaliaemia and blood pressure levels within a given family. The degree of hypertension observed in a given individual results from the interactions between the expression of "hypertenser" and "hypotenser" genes. Recent progress raises the possibility that other similar genetic mechanisms exist in more common forms of primary hypertension. Systematic exploration of the renin-angiotensin-aldosterone system based on measurement of the renin/aldosterone ratio as proposed in the diagnosis of primary hyperaldosteronism will make it possible to determine whether there exists a relationship between these genes and the hypertension observed.

Aldosterone↗
PubMed1995

[Hyperaldosteronism sensitive to dexamethasone with adrenal adenoma. Clinical, biological and genetic study].

OBJECTIVES: Dexamethasone-sensitive hyperaldosteronism is associated with early onset hypertension and primary hyperaldosteronism. Diagnosis is difficult but can be improved by genetic testing for the mutant gene. METHODS: We collected the clinical, biological and genetic elements observed in a family with dexamethasone-sensible hyperaldosteronism. Complete data were obtained in 5 adult subjects with the disease. Degree of hypertension varied, more so in the second generations as did hypokaliaemia and hyperaldosteronism. In affected patients, there was a 10 to 50 fold increase in urinary 18-OH components and 18 oxocortisol. RESULTS: Single dose (1.5 mg) dexamethasone led to a greater than 80% drop in aldosterone levels in the blood and urine, confirming the abnormal effect of ACTH on mineralocorticoid secretion. At the dose of 1 mg/d for 10 weeks, dexamethasone lowered mean 24-H ambulatory arterial pressure (11.8/9.6 mmHg) and corrected for the hypokaliaemia (+0.54 mmol/l) and the hyperaldosteronism (mean decrease -36% and -75% in blood and urine respectively). An adrenal tumour was identified in hyperplasic glands in two subjects and a micronodular formation was identified in two others. The specific molecular diagnosis of the disease was done with Southern blotting. Among the 18 families in 3 generations, 8 carried a 11 beta OHase-aldosterone synthetase chimeric gene. This mutation cosegregates with hormonal abnormalities and confirms the autosomal dominant inheritance of the disease. CONCLUSION: The simplicity and rapidity of genetic testing allows early diagnosis of this disease among families with early onset hypertension and associated hyperaldosteronism with or without adrenal hyperplasia and/or a tumoral formation.

Adolescent↗
PubMed1995

Cloning and expression of an evolutionary conserved single-domain angiotensin converting enzyme from Drosophila melanogaster.

Mammalian somatic angiotensin converting enzyme (EC 3.4.15.1, ACE) consists of two highly homologous (N- and C-) domains encoded by a duplicated gene. We have identified an apparent single-domain (67 kDa) insect angiotensin converting enzyme (AnCE) in embryos of Drosophila melanogaster which converts angiotensin I to angiotensin II (Km, 365 microM), removes Phe-Arg from the C terminus of bradykinin (Km, 22 microM), and is inhibited by ACE inhibitors, captopril (IC50 = 1.1 x 10(-9) M) and trandolaprilat (IC50 = 1.6 x 10(-8) M). We also report the cloning and expression of a Drosophila AnCE cDNA which codes for a single-domain 615-amino acid protein with a predicted 17-amino acid signal peptide and regions with high levels of homology to both the N- and C-domains of mammalian somatic ACE, especially around the active site consensus sequence. Northern analysis identified a single 2.1-kilobase mRNA in Drosophila embryos, and Southern analysis of Drosophila genomic DNA indicates that the insect gene is not duplicated. When expressed in COS-7 cells, the AnCE protein is a secreted enzyme, which converts angiotensin I to angiotensin II and is inhibited by captopril (IC50 = 5.6 x 10(-9) M) and trandolaprilat (IC50 = 2 x 10(-8) M). The evolutionary significance of these results is discussed.

Amino Acid Sequence↗
PubMed1995

A mutation of angiotensinogen in a patient with preeclampsia leads to altered kinetics of the renin-angiotensin system.

Angiotensinogen exhibits genetic linkage to and association with essential hypertension and preeclampsia, a common hypertensive disorder of pregnancy; however, the polymorphisms detected thus far provide no functional clues. In a preeclamptic patient, we have identified a mutation leading to the replacement of leucine by phenylalanine at position 10 of mature angiotensinogen (L10F), the site of renin cleavage. Kinetic analyses of the enzymes of the renin-angiotensin system, using either model peptides or full-length substrates, show that this mutation significantly alters the reactions with both renin and angiotensin-converting enzyme. For the renin reaction on a full-length substrate, this substitution leads to a 10-fold decrease in Km (from 1.1 to 0.09 microM) and a 5-fold decrease in kcat (from 1.0 to 0.22 s-1); as a result, catalytic efficiency (kcat/Km) is increased by a factor of 2 (1.1 versus 2.4 microM-1 s-1). In the reaction of angiotensin-converting enzyme on angiotensin decapeptides, the substitution has no effect on Km (38.0 versus 30.0 microM), but increases kcat and catalytic efficiency > 2-fold (kcat = 15.0 versus 37.0 s-1; kcat/Km = 0.41 versus 1.23). The renin-angiotensin system, challenged by the profound physiological adaptations of pregnancy, is perturbed in preeclampsia; consequently, the L10F mutation may promote this condition in carrier subjects.

Angiotensinogen↗
PubMed1995

The hemoregulatory peptide N-acetyl-Ser-Asp-Lys-Pro is a natural and specific substrate of the N-terminal active site of human angiotensin-converting enzyme.

Angiotensin I-converting enzyme (ACE) is a zinc-dipeptidyl carboxypeptidase, which contains two similar domains, each possessing a functional active site. Respective involvement of each active site in the degradation of the circulating peptide N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP), a negative regulator of hematopoietic stem cell proliferation, was studied by using wild-type recombinant ACE and two full-length mutants containing a single functional site. Both the N- and C-active sites of ACE exhibit dipeptidyl activity toward AcSDKP, with Km values of 31 and 39 microM, respectively. However, the N-active site hydrolyzes the peptide 50 times faster compared with the C-active site, with kcat/Km values of 0.5 and 0.01 microM-1.s-1, respectively. The predominant role of the N-active site in AcSDKP hydrolysis was confirmed by the inhibition of hydrolysis using a monoclonal antibody specifically directed against the N-active site. The N-domain specificity for AcSDKP will aid the identification of specific inhibitors for this domain. This is the first report of a highly specific substrate for the N-active site of ACE, with kinetic constants in the range of physiological substrates, suggesting that ACE might be involved via its N-terminal active site in the in vivo regulation of the local concentration of this hemoregulatory peptide.

Amino Acid Sequence↗
PubMed1995

Lack of evidence for linkage of the endothelial cell nitric oxide synthase gene to essential hypertension.

BACKGROUND: The basal release of nitric oxide by the endothelium plays an important role in regulating blood flow and pressure and mediates most of the endothelium-dependent vasodilation. Impairment of nitric oxide production by specific inhibitors increases blood pressure in humans, and several reports suggest that hypertensive subjects have a blunted endothelium-dependent vasodilatation that might be secondary to decreased nitric oxide production from the vessel wall. METHODS AND RESULTS: To determine whether the endothelial nitric oxide synthase gene is involved in human essential hypertension, we identified informative biallelic and multiallelic markers of this locus and performed case-control and linkage studies in hypertensive subjects and normotensive control subjects. We used the affected sib pair method to test for potential linkage in 145 hypertensive pedigrees (269 sib pairs, 346 subjects) with a highly polymorphic marker of the nitric oxide synthase gene (polymorphism information content of 92%). There was no evidence for linkage among affected siblings. The 95% upper confidence limit of this value suggests that at most 1% of alleles in excess of expected are shared. We also identified two informative biallelic markers of this gene to perform a case-control study on white hypertensive and normotensive subjects. Similar genotype distributions between the two groups were noted for both markers. Estimated haplotype frequencies by maximum likelihood methods combining the two biallelic markers were also similar in both groups. CONCLUSIONS: These findings do not suggest that common molecular variants of the endothelial nitric oxide synthase gene are involved in essential hypertension.

Adult↗
PubMed1995

Molecular characterization of the mineralocorticoid receptor in pseudohypoaldosteronism.

Pseudohypoaldosteronism (PHA) is characterized by salt-wasting and failure to thrive in the newborn, accompanied by high urinary levels of sodium despite hyponatremia, hyperkalemia and metabolic acidosis, elevation of plasma renin activity, and high plasma aldosterone levels. PHA patients are resistant to mineralocorticoid administration, but their symptoms ameliorate after a period of sodium supplementation, which can be discontinued in older subjects. Binding studies performed on mononuclear leukocytes of the family members affected by the disease have shown the absence of binding of [3H]aldosterone to the mineralocorticoid receptor (MR) in mononuclear leukocytes in two siblings and a marked reduction in another sibling and the father, suggesting either the absence of MR or a defect in the ligand binding domain of the MR in these patients. Molecular analysis of the MR in the members of this family did not reveal any major rearrangement or deletion of the MR gene. In addition, no mutation was found in the entire MR coding sequence by RT-PCR and direct sequencing of MR mRNA, and the semiquantitative RT-PCR analysis of the MR mRNA of one affected patient failed to show any quantitative abnormality in MR expression. These results do not exclude a molecular abnormality present in the MR gene being responsible for PHA. However, they indicate that in this family PHA is not related to a modification of the MR primary structure or to a major abnormality in MR expression.

DNA, Complementary↗