Relationships between intermediate filaments and cell-specific functions in renal cell lines derived from transgenic mice harboring the temperature-sensitive T antigen

Four renal cell lines were derived from glomeruli, proximal, distal, and cortical collecting tubules microdissected from the kidneys of transgenic mice carrying the temperature-sensitive mutant of the simian virus 40 large T antigen under the control of the vimentin promoter. All four cell lines contained large T antigen in their nuclei, grew rapidly, and contained vimentin filaments when grown in serum-enriched medium at the permissive temperature of 33 degrees C. The glomerular cell line formed multiple layers of cells and contained smooth muscle actin and desmin filaments, features of mesangial cells. The three tubule cell lines formed monolayers of polarized cuboid cells separated by tight junctions and having a patchy distribution of cytokeratins K8-K18. A shift from 33 degrees C to the restrictive temperature (39.5 degrees C) stopped cell growth in all cell lines and caused profound changes in the content of intermediate filaments. Vimentin was still present in mesangial-like cells, but the proximal, distal, and collecting tubule cells contained uniform networks of cytokeratins K8-K18 and desmoplakin I and II around the cell peripheries. Potassium transport, mediated by Na+-K+ ATPase pumps and specific cAMP hormonal sensitivities, significantly increased in proximal, distal, and collecting tubule cells when shifted from 33 degrees C to 39.5 degrees C. Thus, the temperature-dependent inactivation of large T antigen, responsible for the arrest of cell growth, did not affect the phenotype of mesangial-like glomerular cells but induced some changes in the expression of intermediate filaments and restored, at least partially, the main parental cell-specific functions in proximal, distal, and collecting tubule cultured cells.

Cloning and functional expression of rat CLC-5, a chloride channel related to kidney disease

We have cloned a novel member of the CLC chloride channel family from rat brain, rCLC-5. The cDNA predicts a 83-kDa protein belonging to the branch including CLC-3 and CLC-4, with which it shares approximately 80% identity. Expression of rCLC-5 in Xenopus oocytes elicits novel anion currents. They are strongly outwardly rectifying and have a conductivity sequence of NO3- > Cl- > Br- > I- >> glutamate-. Although CLC-5 has consensus sites for phosphorylation by protein kinase A, raising the intracellular cAMP concentration had no effect on these currents. Currents were also unchanged when rCLC-5 was coexpressed with rCLC-3 and rCLC-4, either singly or in combination. rCLC-5 is expressed predominantly in kidney and also in brain, lung, and liver. Along the nephron, rCLC-5 message is detectable in all tubule segments investigated, but expression in the glomerulus and the S2 segment of the proximal tubule is low.

N-acetyl-beta-D-glucosaminidase (NAG) isoenzymes in primary cultures of rabbit kidney proximal tubule cells: a cellular model for studies on nephrotoxicity?

N-Acetyl-beta-D-glucosaminidase (NAG) isoenzyme profile in primary cultures of rabbit kidney proximal tubule cells was studied. Confluent cells had high levels of NAG activity, but ion exchange chromatography showed that the NAG isoenzyme profile in cultured cells was different from that of rabbit renal cortex homogenates and freshly isolated cells. Confluent cultured cells contained an atypical acidic isoform, absent in homogenates and freshly isolated cells in which the predominant isoform is NAG-A (a heterodimer alpha beta). The fact that this atypical isoform was able to hydrolyse the synthetic substrate 4-methylumbelliferyl-beta-N-acetylglucosaminide-6-sulphate indicated that it probably was an alpha-subunit homodimer. These results suggest subunit rearrangement within NAG polypeptide chains linked to down-regulation of beta-subunit production in cultured rabbit proximal cells. The change in isoenzyme profile in cultured cells may make it difficult to use primary cultures of rabbit proximal tubule cells to establish correlations between in vitro and in vivo studies using NAG isoenzymes as a nephrotoxicity index, as illustrated by the effects of gentamicin.

Cultured proximal cells derived from transgenic mouse provide a model to study drug toxicity

The effects of gentamicin on N-acetyl-beta-D-glucosaminidase (NAG) and acid phosphatase (AcP), two lysosomal enzymes present in proximal renal tubule cells, were studied in the PKSV-PCT cell line derived from proximal convoluted tubules from the kidney of a transgenic mouse carrying SV40 large T antigen under the control of the L-type pyruvate kinase gene. Gentamicin (400 micrograms/ml for 72 hr) did not alter cell viability, but significantly reduced cell growth and favored the formation of myeloid bodies. Gentamicin (50 to 800 micrograms/ml for 72 hr) decreased in a dose-dependent manner the cellular NAG in PKSV-PCT cells and stimulated its secretion by 20 to 60%. Chloroquine (50 to 100 microns) and ammonium chloride (NH4Cl, 30mM), two lysosomotropic amines known to stimulate the secretion of lysosomal enzymes in fibroblasts and macrophages, also stimulated secreted NAG in PKSV-PCT cells. However, the effect of chloroquine was less marked in PKSV-PCT cells than in cultured mouse 3T3 fibroblasts. Gentamicin induced lysosomal alkalinization but, in contrast to chloroquine and NH4Cl, the aminoside strongly stimulated the secretion of AcP. The secretion induced by gentamicin was nonpolarized, since the percentage of secreted NAG significantly increased from both the apical and basal sides of PKSV-PCT cells grown on permeable filters. Thus, these data suggest that gentamicin alters the secretion of NAG and AcP by a non-specific pathway and indicate that the PKSV-PCT cell line is a suitable system to examine the cellular action of drugs in kidney proximal tubule cells.

Transcription factors and aldolase B gene expression in microdissected renal proximal tubules and derived cell lines

Renal expression of the aldolase B isoenzyme and transcription factors previously shown to regulate the aldolase B gene promoter in the liver were analyzed in whole kidney, microdissected tubules, and the two PKSV-PCT and PKSV-PR proximal tubule cell lines derived from transgenic mice. Aldolase B gene expression appeared restricted to the proximal tubule, the site where HNF1 alpha, HNF1 beta, C/EBP alpha, and DBP transcripts were also abundant. Compared to the liver, another organ synthesizing aldolase B, proximal tubules from the kidney were characterized by the absence of HNF3 and the presence of higher ratio of HNF1 beta/HNF1 alpha transcripts. The same features were conserved in both PKSV-PCT and PKSV-PR proximal tubule cell lines. Transactivation experiments in PKSV-PCT cultured cells showed that HNF1 alpha, C/EBP alpha, and DBP behave as transactivators of the 190-bp aldolase B gene promoter, and that HNF1 beta had a low transactivating efficiency. HNF1 beta, as well as HNF3, antagonized the HNF1 alpha-dependent transactivation of the aldolase B promoter. The fact that both HNF1 beta and HNF3 factors play similar negative roles by competitively binding close to or on the HNF1 site could suggest that, in proximal tubule renal cells, HNF1 beta has the same attenuator effect on the aldolase B gene promoter as HNF3 in hepatocytes. Thus, these results indicate that such models of established renal tubule cell lines, which have conserved the same features of parental cells, represent valuable tools for studies of the regulation of genes expressed in proximal tubules of the kidney.

Role of F-actin in the activation of Na(+)-K(+)-Cl- cotransport by forskolin and vasopressin in mouse kidney cultured thick ascending limb cells

The influence of microtubules and F-actin on Na(+)-K(+)-Cl- cotransport was investigated in cultured cells derived from outer-medullary thick ascending limb tubules microdissected from the mouse kidney. The cultured cells contained Tamm-Horsfall protein, produced cAMP in response to dD-arginine vasopressin (dD-AVP), isoproterenol, prostaglandin E2 and forskolin (FK), and exhibited an ouabain-resistant furosemide-sensitive (Or-Fs) component of 86Rb+ influx mediated by the Na(+)-K(+)-Cl- cotransporter. Both FK and dD-AVP stimulated the Or-Fs component of Rb+ influx. Neither agent altered the tubulin and cytokeratin networks nor the shape of the tight junction using a specific anti-ZO-1 antibody. In contrast, they did induce a marked redistribution of F-actin to the periphery of the cells delineating the tight junctions. Preincubation of the cells with nocodazole, to disrupt microtubules, did not alter the FK- or dD-AVP-elicited Or-Fs Rb+ influx. In contrast, phalloidin and NBD-phallicidin, which stabilize F-actin, markedly impaired the stimulation of Na(+)-K(+)-Cl- cotransport by FK or dD-AVP, without affecting the Na(+)-K+ ATPase pumps and the rate constant of 36Cl- and 86Rb+ efflux. These results strongly suggested that cAMP-stimulated Na(+)-K(+)-Cl- cotransport is linked to F-actin in renal TAL cells.

Immortalization of multiple cell types from transgenic mice using a transgene containing the vimentin promoter and a conditional oncogene

Differentiated clonal cell lines were obtained from transgenic mice carrying a recombinant gene composed of DNA coding for a temperature-sensitive mutant of the simian virus large T antigen under the control of regulatory elements of the human vimentin gene. In response to mitogenic factors the vimentin promoter is activated in the presence of serum in almost all cultured cells independently of their origin. The expression of the T antigen could be controlled both at the level of transcription since the vimentin promoter is growth-regulated and at the level of the protein structure through the temperature stability of the T antigen. Indeed, the switch-off of the oncogene protein is obtained by serum deprivation of the culture and achieved with enhancement of the growth temperature. From transgenic mice several types of clonal differentiated cell lines were established and characterized including melanocytes, macrophages, mesangial, muscle, and endothelial cells. Melanocytes displayed melanin while endothelial cells from brain and heart expressed the related factor VIII and low density lipoprotein absorption capacities. Mesangial cells from kidney exhibited numerous desmosomes. Typical markers of macrophages from bone marrow were observed while skeletal muscle cells fused and contracted.

Two highly homologous members of the ClC chloride channel family in both rat and human kidney

We have cloned two closely related putative Cl- channels from both rat kidney (designated rClC-K1 and rClC-K2) and human kidney (hClC-Ka and hClC-Kb) by sequence homology to the ClC family of voltage-gated Cl- channels. While rClC-K1 is nearly identical to ClC-K1, a channel recently isolated by a similar strategy, rClC-K2 is 80% identical to rClC-K1 and is encoded by a different gene. hClC-Ka and hClC-Kb show approximately 90% identity, while being approximately 80% identical to the rat proteins. All ClC-K gene products are expressed predominantly in the kidney. While rClC-K1 is expressed strongly in the cortical thick ascending limb and the distal convoluted tubule, with minor expression in the S3 segment of the proximal tubule and the cortical collecting tubule, rClC-K2 is expressed in all segments of the nephron examined, including the glomerulus. Since they are related more closely to each other than to the rat proteins, hClC-Ka and hClC-Kb cannot be regarded as strict homologs of rClC-K1 or rClC-K2. After injection of ClC-K cRNAs into oocytes, corresponding proteins were made and glycosylated, though no additional Cl- currents were detectable. Glycosylation occurs between domains D8 and D9, leading to a revision of the transmembrane topology model for ClC channels.

Peptide YY receptors in the proximal tubule PKSV-PCT cell line derived from transgenic mice. Relation with cell growth

Receptors for peptide YY (PYY) were identified in the PKSV-PCT renal proximal tubule cell line, derived from transgenic mice (SV40 large T antigen under the control of the rat L-type pyruvate kinase 5'-regulatory sequence). Binding of [125I-Tyr36]monoiodo-PYY ([125I] PYY to cell was specific, saturable, and reversible. The order of potency for peptides for inhibiting [125I]PYY binding was: PYY > neuropeptide Y (NPY) = PYY (13-36) >> pancreatic polypeptide. A single class of receptors was observed with a Kd of 0.37 +/- 0.05 nM and a Bmax of 103 +/- 10 fmol/mg protein. After cross-linking, electrophoresis of covalent [125I]PYY-receptor complexes revealed a single band of M(r) 50,000. PYY receptors were exclusively present at the basolateral membrane surface of polarized cells and were coupled negatively to adenylylcyclase by a pertussis toxin-sensitive G protein. PKSV-PCT cell growth and T antigen expression could be modulated by D-glucose in the medium. PYY receptors were exclusively expressed in proliferative cells cultured in the presence of D-glucose. PYY receptors disappeared in the absence of D-glucose and were expressed again when proliferation was activated by reintroduction of D-glucose. PYY stimulated cell growth (17-26% increase) and promoted [methyl-3H]thymidine incorporation into DNA (64% increase; ED50 = 5 nM PYY) of cells grown in D-glucose-enriched medium. This latter effect of PYY was largely reversed by pretreatment of cells with pertussis toxin. These findings suggest that PYY receptors play a role in epithelial cell growth.

Functional properties of proximal tubule cell lines derived from transgenic mice harboring L-pyruvate kinase-SV40 (T) antigen hybrid gene

This study describes the functional characterization of two cell lines derived from the proximal convoluted (PKSV-PCT cells) and proximal straight (PKSV-PR) tubules microdissected out from kidneys of transgenic mice harboring the simian virus 40 (SV40) large T and small t antigens placed under the control of the rat L-type pyruvate kinase (L-PK) 5′ regulatory sequence. Both cell lines exhibited cellular cyclic AMP stimulated by parathormone (PTH) and calcitonin (CT) and a sodium-dependent glucose transporter. Uptake of the fluid-phase marker [3H]inulin showed that both cell lines grown on filters exhibited biphasic apical and basolateral endocytic rates. Results from Northern blot analysis indicate that the expression of the T antigen gene (Tag) is dependent on the concentration of D-glucose in the medium and show that the L-PK construct has maintained its capacity for up- or down-regulation by carbohydrates. Replacement of D-glucose by neoglucogenic substrates (lactate, oxaloacetate) blunted the expression of Tag transcripts and induced arrest of cell growth. Compared to cell grown in D-glucose-enriched medium, the hormonal sensitivities to PTH and CT and the sodium-dependent glucose uptake were unchanged whereas quiescent cells exhibited increased hydrolase content. Thus the proximal function has been preserved in these cultured cells derived from tissue-specific targeted oncogenesis in transgenic mice. As the expression of Tag transcripts is controlled by D-glucose, the structural and physiological characteristics of these cell lines can be studied in either quiescent or active growth conditions.

K+ fluxes mediated by Na(+)-K(+)-Cl- cotransport and Na(+)-K(+)-ATPase pumps in renal tubule cell lines transformed by wild-type and temperature-sensitive strains of Simian virus 40

The relative contributions of Na(+)-K(+)-ATPase pumps and Na(+)-K(+)-Cl- cotransport to total rubidium (Rb+) influx into primary cultures of renal tubule cells (PC.RC) and cells transformed either with the wild-type or a temperature-sensitive mutant of the simian virus 40 (SV40), were measured under various growth conditions. The Na(+)-K(+)-ATPase-mediated component represented 74% and 44-48% of total Rb+ influx into PC.RC and SV40-transformed cells, respectively. Proliferating transformed cells showed substantial ouabain-resistant bumetanide-sensitive (Or-Bs) Rb+ influx (41-45% of total) which indicated the presence of a Na(+)-K(+)-Cl- cotransport. The Or-Bs component of Rb+ influx was greatly reduced when temperature-sensitive transformed renal cells (RC.SVtsA58) grown in Petri dishes or on permeable filters were shifted from the permissive (33 degrees C) to the restrictive temperature (39.5 degrees C) to arrest cell growth. The ouabain-sensitive Rb+ influx mediated by the Na(+)-K(+)-ATPase, the total and amiloride-sensitive Na+ uptakes were not modified following inhibition of cell proliferation. A similar fall in the Or-Bs influx was obtained when renal tubule cells transformed by the wild-type SV40 (RC.SV) were incubated with the K+ channel blocker, tetraethylammonium (TEA) ion, which we had previously shown to arrest cell growth without affecting cell viability (Teulon et al.: J. Cell. Physiol., 151:113-125, 1992). Reinitiation of cell growth by removal of TEA or return to 33 degrees C of the temperature-sensitive cells restored the Or-Bs component of Rb influx. Taken together, these results indicate that the Na(+)-K(+)-Cl- cotransport activity is critically dependent on cell growth conditions.

Enhanced metabolism of arachidonic acid by macrophages from nonobese diabetic (NOD) mice

The inbred nonobese diabetic (NOD) mouse spontaneously develops an autoimmune diabetes, which is now recognized as an experimental model for human type I insulin-dependent diabetes mellitus (IDDM). The autoimmune reaction, specifically directed against pancreatic beta cells (insulitis), involves both macrophages and T lymphocytes. The study of the production of cyclooxygenase and lipoxygenase derivatives of arachidonic acid metabolism shows that in some conditions, and in particular in the presence of zymosan A, macrophages from NOD mice produced significantly more 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and leukotriene C4 (LTC4) than macrophages from age- and sex-matched C57BL/6 mice. Moreover, zymosan A-stimulated macrophages from NOD females produced significantly more LTC4 than did macrophages from NOD males. These results may be of interest, given the bidirectional relationship between the various cytokines involved in the destruction of beta cells of the islets of Langerhans and different eicosanoids.

Glomerular tissue factor stimulates thromboxane synthesis in human platelets via thrombin generation

We have investigated whether or not tissue factor (TF) which is present in the supernatant of isolated glomeruli, is responsible for the stimulatory activity of TXB2 production by isolated human platelets. Reconstituted TF stimulated TXB2 synthesis in platelets in a dose-dependent manner. This effect was potentiated in the presence of a mixture of the major fatty acids found in glomerular supernatants. Addition of a neutralizing anti-TF monoclonal antibody abolished both the procoagulant activity and the platelet-TXB2 stimulatory activity of reconstituted TF and of glomerular supernatants. Anti-factor VII/VIIa (F VII/VIIa) Fab inhibited in a dose-dependent manner the platelet-TXB2 stimulatory activity of an identical dilution of reconstituted TF and of glomerular supernatants, providing evidence that the functional complex TF. VIIa and not TF itself was the active agent. Pretreatment of platelets, TF or glomerular supernatant by hirudin, an inhibitor of thrombin, as well as by antithrombin III heparin, which inhibits both activated factor X and thrombin also markedly inhibited the synthesis of TXB2 by platelets in the presence of either TF or glomerular supernatant. Taken together, these results demonstrate that the stimulatory activity for TXB2 production by platelets which is released by the glomerular cells is attributable to TF. TF does not act directly. Its effect is mediated by thrombin which is formed de novo at the platelet surface in the presence of even traces of the plasma coagulation proteins associated with platelets. TXB2 formation in platelets correlates well with TF concentration in the glomerular supernatant. The possibility of a similar set of mechanisms associated with glomerular injury may require consideration.

Characterization of ANF receptors in cultured renal cortical vascular smooth muscle cells

Because atrial natriuretic factor (ANF) has been demonstrated to decrease resistances in cortical renal vessels in vivo, we studied 125I-ANF binding and ANF-dependent guanosine 3',5'-cyclic monophosphate (cGMP) production in subcultured vascular smooth muscle cells (VSMC) prepared from the rabbit renal cortex. 125I-ANF specific binding at 4 degrees C represented 70% of total binding and reached a plateau at 30-60 min. Equilibrium saturation binding curves suggested one group of high-affinity receptor sites (KD = 78 +/- 16 pM, Bmax = 45 +/- 11 fmol/mg) but were compatible with several groups exhibiting close binding parameters. ANF, [Ala7,Ala23]ANF (a linear analogue), and C-ANF-(4-23) (a ligand of C receptors) inhibited 125I-ANF binding at 37 degrees C with nearly similar potencies. In contrast, at 4 degrees C, complete or nearly complete inhibition of binding was obtained with ANF and linear ANF, the latter exhibiting the weakest potency, whereas C-ANF-(4-23) displaced only 35% of the tracer. ANF markedly stimulated cGMP accumulation, with a threshold concentration of 10 pM and a stimulation of 115 times basal value at 0.1 microM. Linear ANF was also stimulatory with a much weaker potency. Around 25% of 125I-ANF bound to cell surface was internalized at 37 degrees C. Phenylarsine oxide partially inhibited internalization as well as the inhibitory potency of C-ANF-(4-23) on 125I-ANF binding. As shown by high-performance liquid chromatography extracellular 125I-ANF was rapidly degraded at 37 degrees C into its 125I-COOH-terminal tripeptide and 125I-Tyr.(ABSTRACT TRUNCATED AT 250 WORDS)

Nordihydroguaiaretic acid inhibits urokinase synthesis by phorbol myristate acetate-stimulated LLC-PK1 cells

Protein kinase C (PKC) activation is regulated by Ca2+, phospholipids, diacylglycerol (DAG) and fatty acids. Phorbol myristate acetate (PMA) which mimics the effect of DAG on PKC induces transcriptional activation of the urokinase-type plasminogen activator (u-PA) gene in LLC-PK1 cells. We examined in the present work the relationships between PKC activity, fatty acids, and u-PA synthesis in this cell line. We showed that H7, an inhibitor of PKC, inhibited the PMA-induced u-PA synthesis by LLC-PK1 cells. PMA-induced u-PA synthesis was enhanced by eicosatetraynoic acid (ETYA), a competitive inhibitor of both the lipoxygenase and cyclooxygenase pathways and inhibited by nordihydroguaiaretic acid (NDGA), an inhibitor of the lipoxygenase pathway. Three other unrelated lipoxygenase inhibitors (phenidone 100 microM, BW755 50 microM and diethylcarbamazine 50 microM) had no effect on u-PA biosynthesis. Two polyunsaturated fatty acids other than ETYA, arachidonic acid and linoleic acid, also potentiated the PMA effect and a lipoxygenase derivative, 12 hydroxyeicosatetraenoic acid (12 HETE), did not modify the basal and PMA-stimulated u-PA syntheses. PKC activity purified from cytosol of LLC-PK1 cells was stimulated by addition of 16 nM PMA in vitro and this effect was blunted by simultaneous addition of 5 microM NDGA. By Northern blot analysis using a pig u-PA cDNA probe we found that PMA increased the steady state level of u-PA mRNA after 2 h of incubation and that NDGA inhibited this effect. These data suggest that NDGA inhibits PMA-stimulated PKC activity in intact cells leading to a decrease of u-PA mRNA level and u-PA biosynthesis in PMA-stimulated LLC-PK1 cells. Polyunsaturated fatty acids have opposite effects.

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.

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)

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.

Human glomeruli release fatty acids which stimulate thromboxane synthesis in platelets

The cell-free medium of isolated human glomeruli exhibited a procoagulant activity and stimulated thromboxane (TXB2) synthesis in human platelets in a dose-dependent manner. The amount of TXB2 measured was 16-fold higher than what could have been predicted (TXB2 synthesized by the platelets under control conditions plus TXB2 present in the glomerular supernatant). The lipid extract of the glomerular supernatant and its purified fraction including the fatty acids was still able to stimulate--although at a lesser degree--TXB2 synthesis in platelets. Stimulation was abolished after treatment of this fraction by charcoal or albumin. Gas chromatography/mass spectrometry analysis demonstrated the presence in the purified glomerular fraction of several long-chain saturated or monoenoic fatty acids at a total concentration of 80 microM with the following order of abundance: stearic, palmitic, myristic and oleic acids. Addition to human platelets of these same exogenous synthetic acids resulted in a dose-dependent stimulation of TX synthesis. It was maximum with three or four fatty acids tested in combination, but still present with myristic acid used separately. Arachidonic acid was absent in the glomerular supernatant. Thus the stimulation observed could not be related to a greater availability of substrate. Fatty acids did not act on platelets through a non-specific detergent effect since addition of high doses of detergents inhibited TXB2 formation in platelets. The combination of fatty acids from glomerular origin identified in the present study represents a novel factor involved in the control of intracapillary hemostasis, but different from the procoagulant activity common to many tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Production of 5-lipoxygenase pathway metabolites by peripheral leucocytes in capillary leak syndrome (Clarkson disease)

Periodic systemic capillary leak syndrome (Clarkson disease) is characterized by unexplained attacks of a marked increase in capillary permeability. As leukotrienes, derived from arachidonic acid via the 5-lipoxygenase pathway, enhance capillary permeability, we studied arachidonate metabolism in leucocytes of a patient with capillary leak syndrome. Leucocyte-platelet suspensions, prepared from blood collected from the patient during asymptomatic periods (n = 11) produced greater amounts of 5-hydroxyeicosatetraenoic acid (5-HETE) than control suspensions (P less than 0.05). Peripheral leucocytes, collected during attacks (n = 3) and studied without addition of A23187 released LTB4 in vitro but not sulphidopeptides leukotrienes. This result was never observed with leucocytes from control subjects or from the patient out of a crisis. These results suggest that in the patient, peripheral leucocytes could be stimulated by an unknown, as yet to be determined, endogenous factor to produce more 5-HETE and LTB4. Whether LTB4 plays a pathogenic role in the capillary leakage remains to be determined.

Synthesis of prostaglandins and lipoxygenase products by rat glomeruli during development

In glomeruli isolated from adult rats, arachidonic acid (C20:4) is metabolized through at least two different pathways: the lipoxygenase and the cyclooxygenase pathway, resulting in the synthesis of 12-hydroxyeicosatetraenoic acid (12-HETE) and four prostaglandins (PG) respectively. Because renal blood flow (RBF) and glomerular filtration rate (GFR) increase during development, and because C20:4 metabolites are implicated in their local regulation, the conversion of 3H-C20:4 was studied in 3 groups of rats; group A: 4 days old, 10 g; group B: 10 days old, 25 g; group C: 60 days old, 200 g. Glomeruli mechanically isolated from blanched kidneys were incubated with 5.4 X 10(-8) M 3H-C20:4. Lipoxygenase and cyclooxygenase products were extracted and resolved by high-performance liquid chromatography (HPLC); quantitative determination of PGs was performed by radioimmunoassay (RIA). The results are: (1) conversion of C20:4 to lipoxygenase product is predominant in comparison to cyclooxygenase products; (2) conversion of labeled C20:4 into 12-HETE is constant with age; (3) identified cyclooxygenase products, PGE2, and particularly PGF2 alpha are maximum in group B; (4) the variation of C20:4 metabolism during development suggest that these products may be involved in the maturation and the regulation of glomerular functions.

Bioconversion of leukotriene C4 by rat glomeruli and papilla

Since leukotriene C4 (LTC4) may be locally synthesized by bone marrow-derived cells infiltrating the kidney in inflammatory renal diseases we examined the in vitro metabolism of exogenously added [3H] LTC4 by rat glomeruli and papilla using radiometric HPLC. Homogenized as well as intact glomeruli converted [3H] LTC4 mainly into [3H] LTE4 (83%) and, at a smaller extent, into [3H] LTD4 (4%). Intact [3H] LTC4 represented 13% of the sum of radioactive leukotrienes. Addition of L-cysteine resulted in accumulation of LTD4. In contrast, there was nearly no conversion of [3H] LTC4 (87% intact) in the presence of homogenized papilla. The metabolism of [3H] LTC4 by the glomeruli was time- and temperature-dependent. The 10,000 g supernatant and pellet of homogenized glomeruli both retained the ability to metabolize [3H] LTC4. The papillary 10,000 g supernatant was inactive, as found for the total homogenate, whereas the papillary 10,000 g pellet separated from its supernatant could transform [3H] LTC4 into its metabolites, LTD4 and LTE4. Addition of increasing amounts of papillary 10,000 g supernatant to homogenized glomeruli progressively protected [3H] LTC4 from its bioconversion. These results demonstrate that both glomeruli and papilla possess the gamma-glutamyl transpeptidase and dipeptidase necessary to process LTC4. However, the enzyme activity of the papilla is unmasked only when the inhibitor present in the 10,000 g supernatant is separated from the enzyme present in the pellet.

Lipoxygenase products mediate the attachment of rat macrophages to glomeruli in vitro

Because there is an accumulation of macrophages in the Bowman's space during human and experimental glomerulonephritis, we have studied the binding of [3H]-uridine labeled macrophages to isolated glomeruli. Binding was related to the glomerular protein and macrophage concentrations, temperature, time of incubation, and was a saturable process. Macrophage adherence depended on glomerular lipoxygenase activity but not on glomerular cyclooxygenase activity since preincubation of glomeruli with nordihydroguaiaretic acid (NDGA) inhibited this phenomenon whereas preincubation with indomethacin was ineffective. Glomeruli interacted with macrophages in converting arachidonic acid (C20:4) to prostaglandins (PG) since productions of 6 keto-PGF1 alpha, TXB2, and PGD2 by glomeruli and macrophages incubated in combination were much greater than the sums of their respective productions by glomeruli and macrophages incubated separately. Macrophages were the source of the supplementary synthesis of PG which was abolished when these cells were pretreated with aspirin. Stimulation of macrophages by glomeruli was blunted by pretreatment of glomeruli with NDGA. Production of PG and of 12-HETE by macrophages was stimulated by a lipid extract of glomeruli containing the oxygenated metabolites of C20:4. Direct addition of 12-HPETE also stimulated macrophage functions. These data suggest that macrophage attachment to glomeruli and macrophage stimulation in the presence of glomeruli depend on glomerular lipoxygenase activity.

Increased prostaglandin production by glomeruli isolated from rats with streptozotocin-induced diabetes mellitus

Abnormalities in glomerular function have been observed frequently in the early stages of both clinical and experimental diabetes mellitus. Because prostaglandins (PGs) are present in the glomerulus and have profound effects on glomerular hemodynamics, and because abnormalities of PG metabolism have been noted in other tissues from diabetics, we studied PG biosynthesis in glomeruli obtained from rats in the early stages of experimental diabetes mellitus. Streptozotocin, 60 mg/kg, was administered intravenously to male Sprague-Dawley rats. Control rats received an equal volume of the vehicle. Glomeruli were isolated 9-23 d later. Production of eicosanoids was determined by two methods: by direct radioimmunoassay after incubation of glomeruli under basal conditions and in the presence of arachidonic acid (C20:4), 30 microM, and by radiometric high-performance liquid chromatography (HPLC) after incubation of glomeruli with [14C]C20:4. When assessed by radioimmunoassay, mean basal production of both prostaglandin E2 (PGE2) and prostaglandin F2 alpha (PGF2 alpha) was twofold greater in the diabetic animals whereas production of thromboxane B2 (TXB2) was not significantly greater than control. In response to C20:4, both PGE2 and PGF2 alpha were also greater in the diabetic animals, but these differences were not statistically significant. The increased rate of basal PG production did not appear to be related directly to the severity of the diabetic state as reflected by the degree of hyperglycemia at the time of sacrifice. In fact, the rates of glomerular PG production in the individual diabetic animals correlated inversely with the plasma glucose concentration. The increased rate of PG synthesis did not appear to be due to a nonspecific effect of streptozotocin inasmuch as glomerular PG production was not increased significantly in streptozotocin-treated rats which were made euglycemic by insulin therapy. Furthermore, addition of streptozotocin, 1-10 mM, to the incubation media had no effect on PGE2 production by normal glomeruli. PGE2 production by normal glomeruli was also not influenced by varying the glucose concentration in the incubation media over a range of 1-40 mM. When metabolism of [14C]C20:4 was evaluated by high-performance liquid chromatography conversion to labeled PGE2, PGF2 alpha, TXB2, and hydroxyheptadecatrienoic acid by diabetic glomeruli was two- to threefold greater compared with that in control glomeruli, whereas no significant difference in conversion to 12- and 15-hydroxyeicosatetraenoic acid occurred. These findings indicate that glomerular cyclooxygenase but not lipoxygenase activity was increased in the diabetic animals. A concomitant increase in glomerular phospholipase activity may also have been present to account for the more pronounced differences in PG production noted in the absence of exogenous unlabeled C20:4. These abnormalities in PG biosynthesis by diabetic glomeruli may contribute to the altered glomerular hemodynamics in this pathophysiologic setting.