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N Ardaillou

Publications and source records attributed to N Ardaillou.

At least 37 records · Page 2Linked to original sources
PubMed1992

[Mechanism of action and catabolism of atrial natriuretic factor in cultured human and animal kidney cells].

Cultures of renal cells from human or animal origins have allowed the modes of action and the degradation pathways of atrial natriuretic factor (ANF) to be characterized. Human glomerular mesangial and epithelial cells possess ANF receptors of both types, only clearance receptors (C) in mesangial cells, receptors with guanylate cyclase activity (A) and C receptors in epithelial cells which are, in addition, equipped with ectoenzymes rapidly degrading extracellular ANF. Epithelial cells which have been stimulated by ANF secrete cyclic guanosine monophosphate (cGMP) at their apical side. Vascular smooth muscle cells prepared from the rabbit renal cortex also possess A receptors of high affinity and C receptors. Neutral endopeptidase (NEP), an enzyme of which ANF is a specific substrate in the kidney, is expressed at the cell surface. Its expression is inhibited by factors present in the serum and is increased by glucocorticoids. Principal cells of the collecting duct are also a target for ANF via A and C receptors. Taken together, these studies demonstrate that the kidneys are sites both for the physiological effects and the degradation of ANF. Production of cGMP results in vasodilation in the renal cortex, increase of glomerular filtration rate and decrease of sodium reabsorption in the collecting duct. Degradation of ANF occurs via two different ways, its conversion into inactive peptides by NEP and its internalization after binding to C receptors.

Animals↗
PubMed1991

Receptor-mediated induction of aminopeptidase A (APA) of human glomerular epithelial cells (HGEC) by glucocorticoids.

Membrane-bound peptidases are critical regulators of peptide hormones. We therefore characterized aminopeptidase A (APA) activity in human glomerular epithelial cells (HGEC) and studied the control of its expression. APA, which splits off the N-terminal Asp from angiotensin II (AII), was present at the surface of HGECs (55% of the total enzyme). APA activity was calcium-dependent and was inhibited by amastatin. Treatment of HGECs by dexamethasone (DEX) increased ecto-APA activity in a dose- and time-dependent manner. Maximal increase of APA activity (x 2) occurred after treatment with 0.5 microM DEX for 5 days. HIgher concentrations (1-10 microM) of aldosterone (ALD) stimulated APA activity to a lesser extent (x 1.25). Actinomycin D and cycloheximide prevented and RU 38486, a glucocorticoid receptor antagonist, suppressed the DEX-induced increase in APA activity. These results indicate that AII availability at glomerular receptor sites may be reduced by DEX and suggest a role for glucocorticoids in AII-dependent changes of glomerular filtration rate.

Aldosterone↗
PubMed1991

Cyclic adenosine monophosphate-stimulating agents induce ecto-5'-nucleotidase activity and inhibit DNA synthesis in rat cultured mesangial cells.

The ecto-5'-nucleotidase activity of rat glomerular mesangial cells increases after exposure to prostaglandin E2 (PGE2) via cAMP stimulation (Savic et al., 1990, Immunology 70, 321). Therefore we examined whether other cAMP-stimulating agents had a similar effect. Forskolin (1 microM), PGE2 (10 microM), and isoproterenol (10 microM), three products stimulating rat mesangial cell adenylate cyclase activity, enhanced cAMP accumulation within 5 min and 5'-nucleotidase activity after a lag time of at least 24 h, 3-Isobutyl-1-methylxanthine (IBMX) and Ro 20-1724, two drugs inhibiting cAMP degradation, also stimulated cAMP accumulation and 5'-nucleotidase activity. The effects of these agents on 5'-nucleotidase activity were additive with those of the three products stimulating adenylate cyclase activity, except for Ro 20-1724 and forskolin which acted synergistically. Cycloheximide, a blocker of protein synthesis, suppressed the cAMP-dependent increase of 5'-nucleotidase activity. Because ecto-5'-nucleotidase activity is a marker of cell differentiation, the effect of the same cAMP-stimulating agents on cell proliferation was also studied. Forskolin, PGE2, and isoproterenol inhibited [3H]thymidine incorporation into rat mesangial cells in a dose-dependent manner. The same effect was obtained with IBMX (100 microM) and Ro 20-1724 (50 microM). Stimulation of 5'-nucleotidase activity and inhibition of [3H]thymidine incorporation occurred over the same range of concentrations for the various agonists tested. Taken together, these results indicate that expression of ecto-5'-nucleotidase in rat mesangial cells is induced by cAMP whatever the reason for its accumulation. The simultaneous inhibition of DNA synthesis may occur independently or be associated with the stimulation of 5'-nucleotidase expression.

5'-Nucleotidase↗
PubMed1990

Effect of prostaglandin E2 on proline uptake and protein synthesis by cultured human mesangial cells.

PGE2 production by glomeruli is increased in a variety of glomerular diseases. Potentially, this process may affect mesangial cell protein synthesis and mesangial cell growth. Thus studies have been undertaken, using cultured human mesangial cells, to assess the effects of PGE2 on proline uptake, protein synthesis and cell proliferation. In the presence of 140 mM NaCl, incubation of mesangial cells with 0.01 to 1 microM PGE2 for 72 hours resulted in a marked decrease of 14C proline uptake, but did not modify 14C leucine uptake. Substitution of choline to sodium inhibited 14C proline uptake by 85% which became independent of PGE2, indicating that this PG specifically altered sodium-dependent proline uptake. Inhibition of this component reached 35 to 50% with 1 microM PGE2. The inhibitory effect of PGE2 on sodium-dependent proline uptake required a lag time of 48 hours, and was suppressed by ouabain, an inhibitor of Na+, K+ ATPase activity. PGE2 did not modify the Vmax of the transport system (1.007 vs. 1.023 nmol/mg/min) but increased (P less than 0.01) its Km (1.179 vs. 0.823 mM). 8-bromo-cyclic AMP also inhibited sodium-independent proline uptake, and PGE2 markedly increased cyclic AMP production. Taken together, these results suggested that PGE2 acted via cyclic AMP stimulation. PGE2 under identical conditions (1 microM, 72 hr incubation) produced a decrease in collagen synthesis estimated by the relative rate of collagen production after incubation of mesangial cells with 14C proline (percentage of 14C radioactivity in collagenase-sensitive proteins over total proteins). PGE2 also diminished the intracellular free proline pool. More generally, PGE2 inhibited cell proliferation and cell total proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Division↗
PubMed1990

Induction of ecto-5'-nucleotidase of rat cultured mesangial cells by interleukin-1 beta and tumour necrosis factor-alpha.

Because ecto-5'-nucleotidase activity of rat glomerular mesangial cells has been shown to increase upon interaction with macrophages in vitro, it was examined whether interleukin-1 beta (IL-1 beta) and tumour necrosis factor-alpha (TNF-alpha), two macrophage-released cytokines, were responsible for this effect. IL-1 beta and TNF-alpha stimulated mesangial cell 5'-nucleotidase activity in a dose-dependent manner after treatment for 24 hr. Maximum increases reached 4.5 times and 1.7 times basal values for IL-1 beta (20 U/ml) and TNF-alpha (25 ng/ml), respectively. The effects of both cytokines were additive. Stimulation of 5'-nucleotidase by IL-1 beta and TNF-alpha was specific since the activity of other ectoenzymes, such as Mg2(+)-ATPase, was unchanged. Cycloheximide, a blocker of protein synthesis, suppressed the cytokine-dependent increase of 5'-nucleotidase activity. Cyclo-oxygenase inhibitors such as indomethacin and ibuprofen inhibited approximately 50% of the effects of both cytokines. Their inhibitory effect was abolished in the presence of prostaglandin E2 (PGE2). In addition, PGE2 itself produced a dose-related (0.1-10 microM) increase of 5'-nucleotidase activity with a maximum of 2.2 times basal value. Taken together, these results indicate that IL-1 beta, essentially, and TNF-alpha, to a lesser extent, regulate 5'-nucleotidase expression in the plasma membrane of cultured mesangial cells and that their effect depends in part on PGE2 synthesis. Therefore, macrophages, via their products of secretion acting on 5'-nucleotidase, could modulate adenosine production in the glomerular capillaries.

5'-Nucleotidase↗
PubMed1990

Genetic thrombocytopenia with an autosomal dominant transmission: a study of 54 cases.

On the basis of a retrospective study of 3,600 platelet kinetic studies, we have isolated 54 cases with chronic thrombocytopenia, a normal autologous and homologous platelet lifespan, and increased mean platelet volume without Döhle bodies, the absence of any functional platelet abnormalities, and a normal megakaryocyte count. These cases were either discovered during the first few years of life (i.e. constitutional) and/or were proven to be familial (autosomal dominant transmission). Previous treatments (corticosteroids, immunoglobulins, androgens, immunosuppressor agents, splenectomy) were not effective in any of these cases or in their relatives. A new syndrome can therefore be proposed which can be easily suspected in cases of early onset in life, increased platelet volume, failure of corticosteroids or evidence of a familial blood disorder. It can be proved when the autologous platelet life span is demonstrated to be normal in spite of a chronic thrombocytopenia and a normal megakaryocytic count. The recognition of this syndrome will avoid neonatal complications (cephal-hematomas), surgical complications, and the use of expensive and possibility harmful ineffective treatments, both in the propositus and in other abnormal family members. The syndrome is certainly frequent (54 families are presented here), but the diagnosis is often missed or delayed due to the low risk of hemorrhage. However, it is associated with a certain risk of leukemia (4 cases in 3 families).

Blood Platelets↗
PubMed1989

Quantification of collagen synthesis by cultured human glomerular cells.

This study examines the amount of total collagen and its different fractions synthesized by cultured human glomerular epithelial and mesangial cells. Two quantitative techniques were used, namely estimation of proline (Pro) plus hydroxyproline (Hyp) present in the collagenase-sensitive proteins and ELISA or RIA of the different types of collagen. In addition, the pattern of collagen synthesis for both cell types was further examined using immunofluorescence methods and polyacrylamide gel electrophoresis. Glomerular epithelial cells synthesized mainly type IV collagen and it was, for the better part, cell-associated. Mesangial cells synthesized approx. 4-times more collagen than epithelial cells. Type I collagen was predominant, but there were also type IV and III collagens. Secreted and cell-associated collagens were present in roughly equivalent amounts. In both cell lines 10-14% of the newly synthesized collagen had been degraded within the cells. These results provide quantitative data on collagen synthesis by human glomerular cells in vitro and represent the first necessary stage before studying which factors mediate the development of glomerular sclerosis.

Cells, Cultured↗
PubMed1989

Macrophages selectively stimulate ecto-5'-nucleotidase activity of cultured mesangial cells.

Because rat peritoneal macrophages exhibit a particular binding capacity to rat glomerular mesangial cells in vitro, we have studied the effect of macrophages on two plasma membrane enzymes, ecto-5'-nucleotidase and ecto-Mg2+ ATPase, or rat cultured mesangial cells. A marked increase of ecto-5'-nucleotidase activity was observed in cocultures of rat mesangial cells and peritoneal macrophages. In addition, macrophage-conditioned medium (MCM) produced a dose-dependent increase of mesangial cell ecto-5'-nucleotidase activity. In contrast, ecto-Mg2+ ATPase activity was unaffected. The effect of MCM on ecto-5'-nucleotidase activity was apparent after 24 hours and increased with time. Reversion was obtained by MCM withdrawal. Stimulation of ecto-5'-nucleotidase activity by MCM was inhibited by cycloheximide, which suggests that protein synthesis was required. Induction of enzyme activity by MCM depended in part on the presence of extracellular adenosine. The macrophage-released factor responsible for this effect was non-dialysable, heat-stable at 56 degrees C for 30 minutes but heat-inactivated at 100 degrees C for five minutes, inactivated in the presence of trypsin or protease V8, and adsorbed on charcoal. Its apparent molecular weight estimated by gel chromatography was close to 20 kD. MCM from resident macrophages was as potent as MCM from thioglycollate-elicited or zymosan-stimulated macrophages. This stimulatory effect was specific of macrophages since it was absent in the culture medium of rat fibroblasts or mouse thymocytes but present in that of mouse macrophages. These results suggest that peritoneal macrophages synthesize a factor which selectively stimulates ecto-5'-nucleotidase activity of glomerular mesangial cells.

5'-Nucleotidase↗
PubMed1989

Extra- and intracellular metabolism of platelet-activating factor by cultured mesangial cells.

Metabolism of platelet-activating factor (PAF) was examined in cultured mesangial cells from human and rat glomeruli. Human mesangial cells, similar to those from rat, generated PAF after A23187. Both human and rat mesangial cells rapidly hydrolyzed [3H]PAF to lyso-[3H]PAF, and reacylated it into 1-alkyl-2-acyl glycerophosphocholine. Extra- and intracellular metabolism of PAF was then analyzed separately. The majority of [3H]PAF metabolism occurred extracellularly and generated Lyso-[3H]PAF. Intracellularly generated lyso-PAF was rapidly converted to 1-alkyl-2-acyl glycerophosphocholine. Cells prelabeled with [3H]PAF released some [3H]PAF within minutes and then rapidly converted it to lyso-PAF extracellularly. Under control conditions no acetylhydrolase activity was released from cells into the buffer. Acetylhydrolase activity could, however, be released from cell surface into buffer by limited trypsinization, supporting its location on the outer cell membrane. The acetylhydrolase activity was different from phospholipase A2, since phosphatidylcholine was not a substrate for the enzyme. In summary our results show that both rat and human mesangial cells can generate and metabolize PAF. Acetylhydrolase for PAF is present intracellularly, but also and predominantly on the outer cell surface of cells. This ectoenzymatic acetylhydrolase activity may be important in the rapid inactivation of PAF presented to cells, thus protecting cells from deleterious effects of PAF.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1987

Angiotensin I-converting enzyme in isolated human glomeruli.

Angiotensin I-converting enzyme (ACE) activity was measured with hippurylhistidylleucine as a substrate in isolated human glomeruli. The mean level was 2.2 +/- 0.47 mIU/mg glomerular protein. S9780, a newly designed competitive inhibitor of ACE, inhibited this activity by 85% at 0.3 microM. [3H]S9780 specifically bound to isolated human glomeruli. The Kd value and the number of sites were 23 nM and 83 fmol/mg, respectively. The prodrug, S9490, and Captopril were less potent than S9780 in displacing [3H]S9780 from its binding sites. Angiotensin I had no effect. Binding of [3H]S9780 was inhibited after preincubation of the glomeruli with a specific polyclonal anti-human ACE antibody. These results demonstrate that ACE is present in human adult glomeruli.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1987

Identification and regulation of renin in human cultured mesangial cells.

Renin activity was measured in the incubation medium, and the cellular extract of human mesangial cells, which had been cultured in the presence of renin-free human plasma (three kidneys; 4-7 passages). Active renin and total renin obtained after trypsin treatment was estimated by radioimmunoassay of angiotensin I using renin-free human plasma as a substrate. Mesangial cell renin had characteristics similar to those of standard human renin; optimum enzymatic activity at pH 5.8, marked inhibition in the presence of two (monoclonal and polyclonal) human renin-specific antibodies and of SR 42128, a new potent statine-containing renin inhibitory peptide. The synthetic capability of the mesangial cells varied markedly with the original kidney (1-49 and 0.3-0.9 ng X h-1 X mg-1 for total renin in the medium and the cellular extract respectively). Renin was secreted mainly as inactive renin. Prostaglandin E2 (PGE2) and carba-prostaglandin I2 (PGI2) (a stable analogue) produced a dose-dependent (0.1-1.10 microM) increase in renin activity in both the cellular extract and the culture medium. Isoproterenol (200 microM) increased renin activity only in the medium. The effects of these agonists were more marked on inactive than on active renin. These results demonstrate that cultured human mesangial cells synthesize and release renin in a stable manner over a long period of culture, thus providing a useful tool for the in vitro study of renin secretion and its control.

Cells, Cultured↗
PubMed1986

Stimulation of cyclic GMP synthesis in human cultured glomerular cells by atrial natriuretic peptide.

Recently a stimulatory effect of atrial natriuretic peptide (ANP) on the particulate guanylate cyclase system has been reported in the glomeruli from different species. Using cultures of homogeneous human glomerular cell lines, we found that rat and human ANP stimulated markedly cGMP formation in epithelial cells with a threshold dose of 1 nM. A 20-fold increase was obtained at 5 microM. Stimulation was also present but less substantial (2-fold at 5 microM) in mesangial cells. cGMP was formed rapidly and released in the medium. ANP and sodium nitroprusside, an activator of soluble guanylate cyclase, had additive effects on cGMP formation. ANP did not inhibit cAMP formation in both cell lines. These results demonstrate that, at least in the human species, epithelial cells represent the main target of ANP in the glomerulus. Synthesis of cGMP in the glomerular epithelial cells in response to ANP also suggests that the excess of urinary cGMP produced by the kidney which is observed after ANP administration is of glomerular rather than of tubular origin.

Atrial Natriuretic Factor↗
PubMed1985

Stimulation of guanylate cyclase by atrial natriuretic factor in isolated human glomeruli.

A 23 amino acid synthetic peptide fragment of atrial natriuretic factor (ANF) stimulated guanylate cyclase activity in isolated human glomeruli in a concentration- and time-dependent manner. ANF activated particulate guanylate cyclase whereas it had no effect on soluble guanylate cyclase. These results demonstrate that the glomerulus is a target structure for ANF in humans. They also suggest that ANF-induced increase in glomerular filtration rate is due to a direct effect of this peptide on the glomerular cells mediated by activation of glomerular guanylate cyclase.

Atrial Natriuretic Factor↗
PubMed1985

Vasoconstrictor-evoked prostaglandin synthesis in cultured human mesangial cells.

We examined the influence of angiotensin II (ANG II), arginine vasopressin (AVP), and platelet activating factor (PAF) on prostaglandin (PG) synthesis and cell contractility in human glomerular mesangial cells in culture. Addition of sodium butyrate to the culture medium for 40 h significantly increased synthesis of both 6-keto-PGF1 alpha and PGE2 in the presence of exogenous arachidonic acid and of PGE2 under basal conditions. To optimize conditions in all further experiments, cells cultured with butyrate were studied. Under basal conditions, cultured mesangial cells produced predominantly 6-keto-PGF1 alpha and much less PGE2. Addition of either ANG II, AVP, or PAF all resulted in a rapid (within minutes) two- to threefold stimulation of 6-keto-PGF1 alpha and PGE2. Threshold stimulations were obtained at 10 pM for ANG II, 1 nM for AVP, and 10-100 pM for PAF. Preincubation of the cells with [Sar1,Ala8]ANG II, an antagonist of ANG II, inhibited ANG II-enhanced PG production, and preincubation with 1-desamino-8-D-arginine vasopressin, an antidiuretic analogue, blunted AVP-enhanced PG production. Under phase-contrast microscopy, PAF, ANG II, and, to a lesser degree, AVP caused decrease in cell surface area of mesangial cells cultured without butyrate at concentrations similar to those stimulating PG synthesis. Only PAF contracted cells cultured with butyrate, indicating attenuation of the vasoactive effects of ANG II and AVP when synthesis of PG was increased. However, a lower dose of PAF was only active when PG synthesis was inhibited, suggesting the same feedback mechanism for the three agonists.

Angiotensin II↗
PubMed1984

Solubilization of angiotensin II receptors in rat glomeruli.

125I-labelled angiotensin II (A II) specifically binds to solubilized receptors extracted from rat isolated glomeruli using CHAPS (3-[3-( cholamidopropyl ) dimethylammonio ]-1-propanesulfonate). The yield of solubilization of the binding sites was 3.3%. Equilibrium was reached after 15-20 min and specific binding represented 75% of total binding. Dissociation of the hormone-receptor complex after addition of an excess of A II was very slow in the presence of Ca2+ and Mg2+. [Sar1 Ala8] A II and [Sar1 Ile8] A II were more potent as competitive inhibitors of 125I-labelled A II than A II itself and its heptapeptide. These basic features of 125I-labelled A II binding to the extracted material were similar to those observed previously with untreated glomeruli.

1-Sarcosine-8-Isoleucine Angiotensin II↗
PubMed1983

Prostaglandin synthesis by human glomerular cells in culture.

PG synthesis by cultured human glomerular mesangial and epithelial cells incubated with [1- 14C] arachidonic acid was determined by radioimmunoassay (RIA) after high performance liquid chromatography purification. Both dissociated cells and cell monolayers were studied under basal conditions. PG synthesis by epithelial cells was undetectable. Mesangial cells produced low amounts of PGE2, PGF2 alpha and 6 keto-PGF1 alpha and no TXB2. We also examined the effects of several agents on PG synthesis in these two types of cells scraped away from their flasks using direct RIA. Arachidonic acid produced a slight stimulation only with mesangial cells whereas angiotensin II, cyclic AMP and calcium ionophore were inactive with both cell lines. Homogenization of the cells did not enhance the stimulatory effect of arachidonic acid. Alkalinization of the incubation medium produced an increase of PG production by mesangial cells. These results suggest that two types of human glomerular cells, particularly epithelial cells, possess low cyclooxygenase activity. The low capacity of human mesangial and epithelial cells to produce PG may have consequences for the endocrine control of the glomerular microcirculation in man.

Arachidonic Acid↗