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R Ardaillou

Publications and source records attributed to R Ardaillou.

At least 109 records · Page 6Linked to original sources
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

Dual effects of cyclosporine A on arachidonate metabolism by peritoneal macrophages. Phospholipase activation and partial thromboxane-synthase blockage.

Because the oxygenated metabolites of arachidonate synthesized by macrophages, particularly prostaglandins (PG)I2 and E2, thromboxane (TX)A2 and 12-hydroxyeicosatetraenoic acid (12-HETE) have been shown to modulate the immune response of T-cells, we tested the effect of cyclosporine A (CsA), a potent immunosuppressor agent, on arachidonate (AA) metabolism in cultured peritoneal rat macrophages. Endogenous AA release and 12-HETE synthesis were estimated by radiometric HPLC after prelabelling of macrophages with [3H]AA whereas PG were determined either by radiometric HPLC or by direct radioimmunoassay in the culture mediums. Exposure of prelabelled cells for 16 hr to CsA led to a large increase in the release of AA itself and of its oxygenated metabolites, PG and 12-HETE, indicating stimulation of phospholipase activity. This effect was time- and dose-dependent at concentrations of CsA between 2 and 50 microM. There was also a marked increase in the ratio PGI2/TX, suggesting, in addition to activation of phospholipase, a partial blockade of TX synthase. When macrophages were triggered by A 23187 calcium ionophore (2 microM) or opsonized zymosan (1 mg/ml), the only detectable effect of CsA was a strong and specific inhibition (50%) of TX synthesis. Addition of an excess of exogenous AA (5 micrograms/ml) to cells treated by CsA confirmed the fact that CsA acted by specifically blocking the transformation of AA into TX without affecting PGI2 or 12-HETE synthesis. These results demonstrate that CsA acts at two different levels: it promotes phospholipase activation on resting cells but simultaneously induces a partial blockade of TX-synthase. This latter effect predominates when cells are stimulated. The resulting change in the ratio PGI2/TX promotes immunosuppression to the expense of immunostimulation. This may represent one of the factors underlying the potent immunosuppressive role of CsA.

6-Ketoprostaglandin F1 alpha↗
PubMed1989

Modulation of renin synthesis by lipoxygenase products in cultured human mesangial cells.

Modulation of renin synthesis by lipoxygenase products has been studied in cultured human mesangial cells under basal conditions and in the presence of prostaglandin (PG) E2. Total renin and cyclic AMP productions were stimulated in a dose-dependent manner (0.1-10 microM) by PGE2. The stimulatory effect of PGE2 on renin production was inhibited by 12-hydroxyeicosatetraenoic acid (12-HETE) between 0.1 and 100 nM. Extracellular and intracellular renin were affected similarly. Neither basal and PGE2-dependent cyclic AMP nor basal cyclic GMP productions were modified. 15-Hydroxyeicosatetraenoic acid (15-HPETE), 12-hydroperoxyeicosatetraenoic acid (12-HPETE) and 15-hydroperoxyeicosatetraenoic acid (15-HPETE) had the same effects as 12-HETE. Intracellular calcium concentration was not modified in the presence of 12-HETE. Since oleyl-2-acetylglycerol (OAG), an analog of diacylglycerol, also inhibited PGE2-stimulated renin production, it is hypothesized that the effect of the lipoxygenase products is mediated via protein kinase C stimulation.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
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

Production of tumor necrosis factor by rat mesangial cells in response to bacterial lipopolysaccharide.

Tumor necrosis factor (TNF) is a cytokine which is produced by mononuclear phagocytes upon activation by bacterial lipopolysaccharide (LPS) and various other stimuli. In immune-mediated glomerulonephritis, infiltration of glomeruli by monocytes-macrophages is associated with production of TNF. The purpose of the present experiments was to determine whether mesangial cells could also contribute to glomerular TNF synthesis. TNF activity has been determined in the culture medium of rat mesangial cells using a L-929 fibroblast lytic assay. This activity was detectable only when the cells were exposed to LPS (0.1 to 10 micrograms/ml) and for periods longer than one hour. The cytotoxic factor was identified as TNF since: (1) the lytic activity was completely inhibited by an anti-mouse TNF polyclonal antibody and was associated with suppression of lipoprotein lipase activity in adipocytes; (2) its molecular weight (110,000 daltons) corresponded to that observed for murine TNF under non-denaturing conditions; and (3) mRNA encoding TNF was expressed by mesangial cells two hours after addition of LPS. To assess the mechanisms whereby TNF production was regulated, the role of prostaglandin E2 (PGE2) was determined. LPS caused a dose-dependent increase of PGE2 synthesis by mesangial cells. Treatment by indomethacin promoted a suppression of PGE2 production together with an increase of TNF synthesis, indicating that PGE2 acted in a negative feedback manner to regulate the production of TNF. Addition of PGE2 (0.1 to 300 nM) or 8-bromo cyclic AMP (0.1 to 100 microM) induced similar dose-dependent reductions of TNF synthesis. Thus the inhibitory effect of PGE2 probably required in part cyclic AMP accumulation.(ABSTRACT TRUNCATED AT 250 WORDS)

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1989

Leukotriene D4-induced proliferation of glomerular epithelial cells: PKC- and Na+-H+ exchanger-mediated response.

The growth-promoting effect of leukotriene D4 (LTD4) has been observed in a variety of cells, including human glomerular epithelial cells. The purpose of this study was to determine the mechanisms underlying this process. LTD4 induction of [3H]thymidine uptake in human glomerular epithelial cells was blocked by the LTD4 receptor antagonist L648,051 when added in a 50-fold excess and by pertussis toxin. Neither drug affected basal DNA synthesis. These results suggest that the LTD4-mediated signal transduction implies activation of a GTP-binding protein that is coupled to a specific receptor. The possible role of protein kinase C (PKC) activation was also studied. In the presence of the PKC inhibitor H-7 or after downregulation of PKC levels by chronic treatment with phorbol ester, stimulation of [3H]thymidine uptake by LTD4 was greatly inhibited. Moreover, treatment of the cells by LTD4 resulted in a time-dependent increase of cytosolic PKC activity, whereas addition of phorbol 12-myristate 13-acetate reduced this activity. Therefore PKC-dependent mechanisms are likely to mediate the growth-promoting effect of LTD4. Finally, three approaches were used to determine the potential role of the Na+-H+ exchanger. First, progressive removal of extracellular Na+ using N-methyl-D-glucamine+ as a substitute inhibited LTD4-induced [3H]thymidine uptake with a 50% inhibitory concentration (IC50) of 85 mM. Second, addition of amiloride reduced the LTD4 growth effect with an IC50 of 6.5 microM, whereas three amiloride analogues exhibited lower IC50 values in accordance with their greater affinity for the Na+-H+ exchanger.(ABSTRACT TRUNCATED AT 250 WORDS)

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1989

Physiological significance of increased levels of endogenous atrial natriuretic factor in human acute renal failure.

In twelve patients with acute renal failure, mean plasma levels of atrial natriuretic factor (ANF) and of its second messenger cGMP were found elevated at the early phase of the disease, but tended to return towards normal values at recovery. Variations of plasma ANF and cGMP were correlated significantly (p less than 0.05) with those of total blood volume. At the early phase of the disease, plasma ANF was also correlated with the excreted fraction of filtered sodium (FENa) (r = 0.95). Moreover, plasma ANF and FENa peaked concomitantly at the onset of the diuretic phase in the five patients who were not treated by diuretics or dialysis and were studied sequentially during the course of the disease. It is suggested that enhanced plasma ANF levels might reflect one of the mechanisms of adaptation controlling body fluid balance in acute renal failure.

Acute Kidney Injury↗
PubMed1988

Tumor necrosis factor stimulates prostaglandin production and cyclic AMP levels in rat cultured mesangial cells.

Human recombinant tumor necrosis factor-alpha (TNF) was found to stimulate the production of prostaglandins (PG) by cultured rat mesangial cells. This effect was demonstrable from 6 h, was dose dependent and affected the synthesis of PGE2, PGF2 alpha, and 6-keto-PGF1 alpha. It required both RNA and protein synthesis but was not associated with a modification of cell proliferation. TNF also stimulated adenosine 3'-5' cyclic monophosphate (cAMP) levels in the mesangial cell culture medium. Indomethacin suppressed the effect of TNF on PGs but only reduced that on cAMP, indicating that PG production partly mediates the increase in cAMP. These findings demonstrate that mesangial cells can be a target for TNF and that the mechanism of TNF action includes stimulation of both PG production and cAMP levels.

6-Ketoprostaglandin F1 alpha↗
PubMed1988

Influence of polymorphonuclear leukocytes on the metabolism of arachidonate in human platelets.

The effect of the association of purified polymorphonuclear leukocytes (PMNL) with platelets on arachidonic acid (AA) metabolism was studied in the presence of various concentrations of this fatty acid. Both thromboxane B2 (TXB2) and 12-hydroxy-eicosatetraenoic acid (12-HETE) were measured. In the presence of tracer doses of AA, addition of increasing amounts of PMNL to platelets inhibited in a concentration-dependent manner their 12-HETE and TXB2 production. This inhibition was not due to diversion of AA metabolism towards other pathways since, apart a negligible amount of 12,20-diHETE, no other product could be detected. Inhibition of platelet-TXB2 synthesis by PMNL persisted at increasing concentrations of AA below 16 microM. Above this concentration, TXB2 production by platelets incubated alone diminished progressively. Addition of PMNL blunted in part this inhibitory effect and even resulted, above 16 microM AA, in an increased production of TXB2. In contrast with what was observed for TXB2 formation, the inhibition of 12-HETE synthesis persisted when PMNL and platelets were coincubated in the presence of high doses of AA (163 microM). At this concentration, 15-HETE generation became apparent for each cell type incubated separately and was markedly enhanced in the coincubation studies. The present investigation demonstrates that the presence of PMNL modifies the metabolism of arachidonate by human platelets. Moreover, this cell-cell interaction markedly depends on the concentration of substrate. PMNL in excess may attenuate synthesis by platelets of their toxic products.

Arachidonic Acid↗
PubMed1988

Atrial natriuretic peptide and adaptation of sodium urinary excretion in patients with chronic renal failure.

1. In order to examine the potential role of endogenous atrial natriuretic peptide (ANP) in modulating the increased sodium excretion per nephron in chronic renal failure, we studied healthy subjects with normal renal function (group I) and patients with moderate (group II) or severe chronic renal failure (group III) before, during and after administration of an intravenous sodium load. All subjects had been on a controlled diet containing 120 mmol of sodium per day for 5 days before the study. 2. Under basal conditions, plasma ANP and fractional excretion of sodium (FENa) were highest in group III. Both parameters increased in response to the sodium load in the three groups studied (P less than 0.001). Changes with time differed from group to group (P less than 0.05), the more marked response for both parameters being observed in group III. After adjustment with respect to plasma ANP (analysis of covariance), FENa was no longer modified in response to the sodium load, whereas adjustment of FENa with respect to mean blood pressure was without consequence on the significance of its change with time. This demonstrates that plasma ANP, but not mean blood pressure, represents the main factor producing variation in FENa during and after the sodium load. 3. These results suggest an important role for plasma ANP in promoting adaptation of short-term sodium excretion in response to an acute sodium load in patients with chronic renal failure who ingest a normal sodium intake.

Adaptation, Physiological↗
PubMed1988

Plasma atrial natriuretic factor and cyclic GMP in mitral stenosis treated by balloon valvulotomy. Effect of atrial fibrillation.

To study the relation between plasma atrial natriuretic factor (ANF) and cardiac pressures, we measured plasma ANF in 24 patients with mitral stenosis 30 minutes before and 20 minutes after balloon mitral valvulotomy. All patients were without physical signs of congestive heart failure. Normal sinus rhythm was present in 15 (group 1), whereas the other nine (group 2) had permanent atrial fibrillation. There were no significant differences between groups for basal mean pressures in right atrium (RA), left atrium (LA), and pulmonary artery (PA). Valvulotomy resulted in a fall in both groups (p less than 0.001) in LA and PA mean pressures, whereas heart rate, cardiac index, and RA and aorta (AO) pressures did not change significantly. Basal ANF was not different in either group in RA (240 +/- 43 vs. 266 +/- 35 pg/ml) or AO (441 +/- 92 vs. 643 +/- 70 pg/ml) but tended to be higher in group 2 in LA (428 +/- 88 vs. 682 +/- 84 pg/ml; p = 0.059) and PA (488 +/- 93 vs. 759 +/- 92 pg/ml; p = 0.057). Plasma ANF was the highest in PA, and about 50% ANF was extracted in the systemic circulation. After valvulotomy, plasma ANF was greater (p less than 0.05) in group 2 (372 +/- 90, 755 +/- 152, 805 +/- 134, and 707 +/- 144 pg/ml) than in group 1 (206 +/- 36, 386 +/- 47, 429 +/- 66, and 421 +/- 49 pg/ml), regardless of the site of blood collection (RA, LA, PA, and AO, respectively). PA ANF was correlated with LA pressure (p less than 0.05) in group 1 before as well as after valvulotomy, whereas there was no such correlation in group 2. Cyclic GMP (cGMP) in LA was correlated (p less than 0.01) with PA ANF in group 1, and LA cGMP (10.0 +/- 1.2 and 9.1 +/- 1.8 pmol/ml in groups 1 and 2, respectively) was higher (p less than 0.05) than PA cGMP (9.1 +/- 1.0 and 8.0 +/- 1.5 pmol/ml in groups 1 and 2, respectively) before valvulotomy, which suggests the presence of ANF receptors in the pulmonary circulation. Taken together, these results indicate that in patients in sinus rhythm with mitral stenosis, there is an increase in ANF secretion depending on LA pressure. ANF secretion is also high in patients with mitral stenosis and atrial fibrillation but does not respond appropriately to changes in LA pressure.(ABSTRACT TRUNCATED AT 400 WORDS)

Aldosterone↗
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

Modulation of fibroblast proliferation by sulfidopeptide leukotrienes: effect of indomethacin.

Because infiltration of mononuclear cells and fibroblast proliferation are associated in chronic inflammatory lesions, we tested the hypothesis that leukotrienes (LT), a product of activated mononuclear cells, may modulate fibroblast growth. Proliferation of cultured human skin fibroblasts was estimated by [3H]thymidine incorporation and cell count at increasing concentrations (0.1 nM to 0.1 microM) of LTC4 or LTD4. LTC4 and LTD4 stimulated cell growth in a dose-dependent manner only in the presence of 50 microM indomethacin. Under similar conditions, LTE4 but not LTB4 (0.1 microM) was active. Both asynchronous, growing cells and synchronous, quiescent cells were sensitive to LT when prostaglandin (PG) synthesis was suppressed by indomethacin. Other blockers of cyclooxygenase such as ibuprofen and aspirin exhibited identical permissive activity, and the effect of indomethacin was totally abolished by addition of PGE2. LTC4 modified neither [3H]arachidonic acid release from prelabeled fibroblasts nor PGE2 production by fibroblasts. These results demonstrate that the sulfidopeptide LT stimulate fibroblast proliferation only when the endogenous synthesis of PG is blocked, but they do not enhance the synthesis of PG in their target cells showing no evidence for a negative feed-back loop. Nevertheless, it seems likely that the initiation and development of the fibrotic process in the different tissues depends in part on the local balance between PG and LT productions.

Adult↗