Retinoic acid induction of human tissue-type plasminogen activator gene expression via a direct repeat element (DR5) located at -7 kilobases

All-trans-retinoic acid (RA) and retinoids induce synthesis of tissue-type plasminogen activator (t-PA) in endothelial and neuroblastoma cells in vitro and in rats in vivo. In HT1080 fibrosarcoma cells, induction of t-PA-related antigen secretion and t-PA mRNA steady state levels by RA were found to depend on de novo protein and mRNA synthesis. Fragments derived from the 5'-flanking region of the t-PA gene (+197 to -9578 base pairs (bp)) were linked to the chloramphenicol acetyltransferase gene. Transfection studies demonstrated that the region spanning bp -7145 to -9578 mediated induction by RA. A functional retinoic acid response element (RARE), consisting of a direct repeat of the GGGTCA motif spaced by 5 nucleotides (t-PA/DR5), was localized at -7.3 kilobases. The t-PA/DR5 element interacted with the heterodimer composed of retinoic acid receptor alpha and retinoid X receptor alpha in vitro, whereas its mutation abolished induction by RA in transient expression. In human EA.hy926 hybrid endothelial and in SK-N-SH neuroblastoma cells, the activity of t-PA/DR5 was found to be independent of the intervening sequence (-632 to -7144 bp) and of its distance from the transcription initiation site. Staurosporine, an inhibitor of protein kinase activity, inhibited induction by RA, suggesting that it required protein phosphorylation.

Ecto-5'-nucleotidase is expressed by pericytes and fibroblasts in the rat heart

Ecto-5'-nucleotidase is anchored at the outer surface of cell membranes and thus its reaction product adenosine is released into the extracellular space. Extracellular adenosine displays via specific receptors a wide range of physiological effects in heart. There are discrepancies in the literature concerning the distribution of ecto-5'-nucleotidase in heart. Since we suspected that these may be due to technical problems, in the present study on ecto-5'-nucleotidase in rat heart we attempted to circumvent some technical pitfalls. Good preservation of the tissue with open capillary lumina, providing a clear identification of endothelium, was obtained by perfusion fixation. At the light microscopic level, the distribution of ecto-5'-nucleotidase studied by enzyme histochemistry and immunohistochemistry using a monoclonal and a polyclonal antibody yielded congruent results. The enzyme was rather homogeneously distributed throughout the myocardium, with a slightly higher incidence of stained cells in the outer thirds than in the inner third of the wall. Consistently high levels of ecto-5'-nucleotidase were seen only in interstitial cells. The walls of large vessels and heart muscle cells were constantly negative for ecto-5'-nucleotidase. The endothelia of capillaries were mostly negative but a few profiles occasionally displayed a weak immunoreaction. The interstitial cells staining positive for ecto-5'-nucleotidase could be identified as pericytes and as fibroblasts according to their shapes and localizations. The immunoreactivity of fibroblasts was confirmed by electron microscopy. These data indicate that adenosine may be formed extracellularly in the interstitium of the myocardium, where it would have direct access to important targets such as myocytes, arterioles and nerve endings.

Immunohistochemical expression of inducible nitric oxide synthase (iNOS) in reversible endotoxic shock studied by a novel monoclonal antibody against rat iNOS

An antirat monoclonal antibody (mAb) against inducible nitric oxide synthase (iNOS), ANOS11, was used for immunohistochemistry to examine the expression of iNOS in various organs and tissues of adult rats in experimental endotoxic shock induced by lipopolysaccharide (LPS) injection. The phenotype of iNOS-expressed cells was also examined immunohistochemically using various mAbs. In control rats, very few cells were positive for ANOS11 except in the thymus. After intravenous injection of LPS, the number of iNOS-positive cells increased rapidly in almost all organs, except the thymus and brain, peaked 6 h after the injection, and decreased slowly. Of the numerous inflammatory cells that infiltrated the lungs, liver, and spleen after LPS injection, many were positive for ANOS11. Besides inflammatory cells, hepatocytes and endothelial cells of the aorta were also positive for ANOS11 but only around 6 h after injection. The cellular composition of iNOS-positive infiltrated cells changed along with the progression of endotoxic shock. At 4 to 6 h after injection, most iNOS-positive cells were considered polymorphonuclear leukocytes judging by their positive reactivity to OX42 and their nuclear morphology. The population of iNOS-positive macrophages positive for ED1 or ED2 increased with time. After 24 h, many iNOS-positive macrophages were found around the focal necrosis in the liver and spleen. These results indicate that the expression of iNOS in neutrophils, endothelial cells, and hepatocytes precedes that of macrophages in experimental endotoxic shock. The expression of iNOS in various cells and organs is closely associated with the progress and pathological changes of endotoxic shock.

Glutathione S-transferases and cytochrome P450 detoxifying enzyme distribution in human cerebral glioma

Malignant astrocytomas are frequently resistant to cytotoxic chemotherapy. A possible mechanism of chemoresistance is drug inactivation within malignant astrocytes by detoxifying enzymes (glutathione transferases (GST) and cytochrome P450's). The aim of this study was to assess whether there was differential expression of these detoxifying enzymes in the central nervous system and any relationship to histological grade (WHO) of the tumours. Immunostaining was performed in 30 consecutive glioma samples, using class specific polyclonal antibodies to subtypes of GST (pi, alpha, mu) and to human cytochrome P450 reductase. GST immunostaining was evident in astrocytes and endothelium but not neurones or oligodendrocytes in normal brain. Immunostaining for GST increased in intensity from well differentiated tumours to glioblastoma. Staining was least evident in surrounding normal brain, strong in reactive astrocytes and astrocytic tumour cells and very intense in gemistocytic and giant tumour cells. Small anaplastic tumour cells had very little GST staining. Where endothelial proliferation was evident, GST staining in endothelial cells was increased. Pi was always the predominant subclass, although GST alpha and mu were also expressed in some tumours. Cytochrome P450 reductase immunostaining was present in normal neurones and malignant astrocytes. Gemistocytic astrocytic tumour cells stained intensely. Further work is necessary to see if there is any correlation between immunostaining intensity survival or response to chemotherapy.

Invasive tumors induce c-ets1 transcription factor expression in adjacent stroma

The stroma reaction plays a central role in tumor growth, invasion and metastasis. Tumor growth is dependent on angiogenesis and requires the vascular supply provided by new capillary blood vessels of the stroma. The expression of the gene encoding the transcription factor c-ets1 is localized within fibroblasts and endothelial cells of the stromal compartment. This expression correlates with the accumulation of transcripts for potential target genes such as collagenase I and stromelysin I in stromal fibroblasts surrounding malignant cells in invasive tumors. We suggest that c-Ets1 protein might regulate the transcription of the genes coding for matrix-degrading proteases necessary for both angiogenesis and tumor invasion.

Effect of protamine on lipoprotein lipase and hepatic lipase in rats

The polycation protamine impedes the catabolism of triglyceride-rich lipoproteins and this has been suggested to be due to intravascular inactivation of lipoprotein lipase. We have made intravenous injections of protamine to rats and found that both lipoprotein lipase and hepatic lipase activities were released to plasma. The effect of protamine was more short-lived than that obtained by injection of heparin. The release of hepatic lipase by protamine was as effective as the release by heparin, while the amount of lipoprotein lipase released by protamine was only about one-tenth of that released by heparin. This was not due to inactivation of lipoprotein lipase, since injection of an excess of heparin 10 min after injection of protamine released as much lipoprotein lipase activity to plasma as in controls. The results in vivo differed from those obtained in model experiments in vitro. Protamine was able to almost quantitatively release both lipoprotein lipase and hepatic lipase from columns of heparin-agarose. The displacement was dependent on the total amount of protamine that had passed over the column, indicating that it was due to occupation by protamine of all available binding sites. Our results in vivo showed that the binding sites for lipoprotein lipase were not blocked as efficiently as those for hepatic lipase, indicating that the binding structures were not identical. It was concluded that the impaired turnover of lipoproteins by protamine probably was due to prevention of binding of the lipoproteins to endothelial cell surfaces rather than to impaired lipase function.

Rapid conversion to high xanthine oxidase activity in viable Kupffer cells during hypoxia

It has been widely postulated that the central mechanism of hepatic reperfusion injury involves the conversion, during ischemia, of the enzyme xanthine dehydrogenase (XDH) to its free radical-producing form, xanthine oxidase (XOD). However, this theory has been questioned because (a) XDH to XOD conversion in whole liver occurs very slowly; (b) the cellular distribution of XDH/XOD is unclear; and (c) the direct demonstration of XDH to XOD conversion in viable cells is lacking. In this paper, we address all three issues by measuring XDH to XOD conversion and cell viability in purified populations of hepatic endothelial cells (EC), Kupffer cells (KC), and hepatocytes (HEP). Although XDH/XOD activity on a cellular basis was greater in hepatocytes (0.92 +/- 0.12 mU/10(6) cells) than ECs (0.03 +/- 0.01) or KCs (0.12 +/- 0.04), XDH + XOD specific activity was similar in all three cell types (HEP 1.85 +/- 0.10 U/g protein; EC 1.69 +/- 0.54; KC 2.30 +/- 0.22). Over 150 min of warm (37 degrees C) or 24 h of cold (4 degrees C) hypoxia, percent XOD activity increased slowly in ECs, from 21 +/- 2% (basal) to 39 +/- 3% (warm) and 49 +/- 5% (cold) and in HEPs (29 +/- 2% to 38 +/- 3% and 49 +/- 2%), but converted significantly faster in KCs (28 +/- 3% to 91 +/- 7% and 94 +/- 4%). The dramatic changes in Kupffer cell XOD during cold hypoxia occurred despite only minor changes in cell viability. When hypoxic KCs were reoxygenated after 16 h of cold hypoxia, there was a marked increase in cell death that was significantly blocked by allopurinol. These data suggest that significant conversion to the free radical-producing state occurs within viable KCs, and that Kupffer cell XOD may play an important role in mediating reperfusion injury in the liver.

Neuronal and endothelial nitric oxide synthase immunoreactivity and NADPH-diaphorase staining in rat and human pancreas: influence of fixation

In this study, we wished to clarify the distribution and co-localization of nitric oxide synthase and NA-DPH-diaphorase (NADPH-d) in nerve cells, nerve fibres and parenchymal cells in exocrine and endocrine pancreas, and to assess the influence of fixation on the staining pattern obtained. For this purpose, we applied nitric oxide synthase immunocytochemistry and NADPH-d histochemistry to rat and human pancreas under different fixation conditions. Antibodies to neuronal and endothelial nitric oxide synthase were similarly applied. We found complete co-localization of neuronal nitric oxide synthase and NADPH-d in ganglion cells, and in nerve fibres around acini, excretory ducts, blood vessels and in islets of Langerhans of rat and human pancreas. Immunoreactivity for endothelial nitric oxide synthase was co-localized with NADPH-d in endothelial cells. However, in NADPH-d reactive islet and ductal epithelial cells we could detect neither brain nor endothelial nitric oxide synthase immunoreactivity with any fixation protocol applied. There were marked differences in NADPH-d staining of both neurons and parenchymal cells under different fixation conditions. These results indicate the existence of different types of NADPH-d, which are associated or not associated with nitric oxide synthase(s), and which are differently influenced by various fixation procedures in rat and human pancreas.

Endotoxin stimulates the expression of glucose-6-phosphate dehydrogenase in Kupffer and hepatic endothelial cells

The aim of the study was to elucidate the effect of lipopolysaccharide (LPS) administration in vivo (Escherichia coli endotoxin, 1 mg/kg body weight) on the expression and cellular activity of glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49), the rate-limiting enzyme of the hexose monophosphate shunt in hepatic cells. Under basal conditions, Kupffer cells displayed higher activity of G6PDH than endothelial or parenchymal cells. In vivo LPS treatments for 7 and 22 h resulted in 40 and 60% increases, respectively, in the cellular activity of G6PDH in Kupffer cells. G6PDH activity was increased by 140 and 90% after 7- and 22-h LPS treatments in endothelial cells. G6PDH activity in parenchymal cells prepared from animals after 22 h of LPS treatment was decreased by approximately 60% compared with that in cells from saline-injected animals. Total cellular RNA or protein extracts from these cells were analyzed by Northern or Western blots. Under basal conditions, G6PDH mRNA levels relative to total cellular RNA were higher in Kupffer than in endothelial cells and were not detectable in parenchyma cells. LPS injection caused a time-dependent increase in G6PDH mRNA expression in Kupffer and endothelial cells. Western blot analysis of Kupffer cell extracts also showed that LPS treatments caused markedly elevated expression of protein in these cells. These results show that endotoxemia results in marked induction of G6PDH in Kupffer and hepatic endothelial cells but has no such effect in the parenchymal cells. These findings also suggest that the elevated cellular expression of G6PDH is an important regulatory event in the adaptive responses of hepatic nonparenchymal cells to infections. The elevated expression of G6PDH may be important for support of the upregulated NADPH-dependent pathways, such as superoxide anion and nitric oxide production, macromolecular synthesis, or the maintenance of cellular glutathione status.

Expression of nitric oxide synthase immunoreactivity by interstitial cells of the canine proximal colon

A subpopulation of interstitial cells (ICs) are interposed between nerve terminals and smooth muscle cells in the gastrointestinal tract and may participate in neuromuscular transmission. These cells appear to be targets for NO released from enteric inhibitory nerves and respond to exogenous NO with: (i) an elevation in cGMP levels; (ii) an increase in intracellular Ca2+; (iii) and release of a diffusible substance that has tentatively been identified as NO. For the latter to be possible, ICs must express a constitutive isoform of NOS. This study characterized the expression of NOS-like immunoreactivity (NOS-LI) in ICs of the canine colon using 3 antibodies raised against the 2 known constitutive forms of NOS (i.e., neural (nNOS) and endothelial (eNOS) isoforms). Antibodies raised against cNOS and an antibody raised against rat cerebellar nNOS labeled ICs along the submucosal surface of the circular muscle layer (IC-SM), along the surface of septa that separate the circular muscle into fiber bundles (IC-SM), and in the myenteric region between the circular and longitudinal muscle layers (IC-MY). Another antibody raised against rat cerebellar nNOS failed to label ICs. Cultured IC-SM also expressed NOS-LI, suggesting that this feature of the IC phenotype survives culture conditions. Arteriolar endothelial cells in the canine colon were labeled with the same 2 antibodies that labeled ICs, suggesting there are significant structural similarities between NO synthases in ICs and endothelial cells. The data suggest that IC-SM and IC-MY express a constitutive form of NOS. Synthesis of NO by ICs may influence electrical rhythmicity and may serve to amplify and even propagate enteric inhibitory neurotransmission.

Establishment and characterization of an immortalized bovine glomerular endothelial cell line

Bovine subcultures (second passage) of glomerular endothelial cells (GEN) isolated from one-year-old kidney were successfully transfected by recombinant plasmids containing the simian virus (SV)-40 T antigen (Tag) using a lipofectin-mediated procedure. One cell clone was selected, propagated and characterized. This clone can be grown in RPMI 1640 medium supplemented with 10% fetal calf serum. The advantage of this cell line is the cultivation of bovine GEN without the addition of fibroblast growth factor or a coating of fibronectin or gelatin on the culture plate. More than 80 passages were achieved and the doubling time was 32 h. The Tag was easily identified in transfected-GEN by indirect immunofluorescence. These cells weakly expressed factor VIII-related antigen, slightly took up acetylated-low density lipoprotein and secreted a detectable amount of angiotensin-converting enzyme. Immunocytochemical staining for UAE-1 was also positive. Moreover, oncoproteins, such as Ki-67 and p53, were expressed in these cells. Cell cycle analysis by flow cytometry revealed that the percentages of G1, S, and G2/M stages in cycling transfected-GEN culture in RPMI 1640 medium supplemented with 10% fetal calf serum were 34%, 52.9%, and 13.1%, respectively. The conditioned medium from confluent transfected-GEN stimulated [3H]thymidine incorporation into glomerular mesangial cells. This cell line may provide a useful tool for examining modulators of mesangial cell growth. Thus this cell line is the first immortalized bovine GEN that retain the morphologic, phenotypic, and functional characteristics of bovine GEN.

Oxidants induce transcriptional activation of manganese superoxide dismutase in glomerular cells

Cultured rat glomerular mesangial and epithelial cells and bovine glomerular endothelial cells were exposed to various concentrations of hydrogen peroxide (H2O2). Mesangial cells treated with 10 to 100 microM H2O2 for 24 hours showed a two- to ninefold increase in Mn-SOD mRNA expression associated with significantly (P < 0.005) increased Mn-SOD activity (22.2 +/- 1.2 and 12.2 +/- 0.7 mu/mg protein for H2O2 100 microM treated and untreated cells, respectively). In contrast, expression of Cu-Zn SOD and beta-actin mRNA was not affected by H2O2. Induction of Mn-SOD mRNA by H2O2 was inhibited by actinomycin-D (4 microM) treatment. Glomerular endothelial cells also showed an increase in Mn-SOD mRNA expression following 100 microM H2O2 treatment, as did glomerular epithelial cells following treatment with 500 and 1000 microM H2O2 but not with 100 microM. Transcriptional activity of the Mn-SOD gene was assessed with a fusion reporter gene consisting of a luciferase gene (pGL2P) and a 1.2 kb fragment from the rat Mn-SOD genomic DNA (-806 to +408 bp of the transcription initiation site, -806:+408). The construct was transfected into rat glomerular mesangial and epithelial cells. Mesangial and epithelial cells transfected with pGL2P (-806:+408) and treated with H2O2 (100 microM and 1 mM for mesangial and epithelial cells, respectively) demonstrated some threefold increase in luciferase activity, whereas cells transfected with pGL2P lacking the Mn-SOD fragment did not show changes in luciferase activity following H2O2 treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Endothelial NOS and the blockade of LTP by NOS inhibitors in mice lacking neuronal NOS

Long-term potentiation (LTP) is a persistent increase in synaptic strength implicated in certain forms of learning and memory. In the CA1 region of the hippocampus, LTP is thought to involve the release of one or more retrograde messengers from the postsynaptic cell that act on the presynaptic terminal to enhance transmitter release. One candidate retrograde messenger is the membrane-permeant gas nitric oxide (NO), which in the brain is released after activation of the neuronal-specific NO synthase isoform (nNOS). To assess the importance of NO in hippocampal synaptic plasticity, LTP was examined in mice where the gene encoding nNOS was disrupted by gene targeting. In nNOS- mice, LTP induced by weak intensity tetanic stimulation was normal except for a slight reduction in comparison to that in wild-type mice and was blocked by NOS inhibitors, just as it was in wild-type mice. Immunocytochemical studies indicate that in the nNOS- mice as in wild-type mice, the endothelial form of NOS (eNOS) is expressed in CA1 neurons. These findings suggest that eNOS, rather than nNOS, generates NO within the postsynaptic cell during LTP.

Gene structure, polymorphism and mapping of the human endothelial nitric oxide synthase gene

Endothelium-derived relaxing factor (EDRF)/nitric oxide (NO) is synthesized from L-Arginine by the endothelial, constitutive, NO synthase. No facilitate genetic studies, we have cloned the human endothelial NO synthase gene and determined its structure. The gene is composed of 26 exons, ranging from 68 to 579 bp and spans 22 kb. We determined the transcription start point using human lung mRNA. No TATA-box was found at the expected distance from the transcription start point and several consensus sequences for transcription factors, including a shear-stress responsive element were identified in the 5'-flanking region. A highly polymorphic (CA) repeat within intron 13 was studied, allowing the precise genetic mapping of the gene to chromosome 7, within a 4 cM interval delimited by genethon markers AFM199Zd4 and AFM074Xg5.

Localization of Na+/K(+)-ATPase in the bovine corneal endothelium

A mouse monoclonal antibody has been used to localize Na+/K(+)-ATPase in the bovine corneal endothelium. The specificity of the antibody was demonstrated by reaction with a single protein of molecular mass 100 kDa on Western blots and immunoprecipitation of a complex consisting of 100 kDa and 50 kDa subunits. Treatment of the immunoprecipitated antigen with Peptide N-Glycanase F produced no change in the molecular mass of the 100 kDa protein, but resulted in a progressive decrease in the molecular mass of the 50 kDa subunit, to yield a core protein of molecular mass about 33 kDa. The pattern of deglycosylation suggested the presence of three N-linked glycans attached to the 33 kDa protein core. These results were consistent with the antibody being specific for the alpha subunit of the Na+/K(+)-ATPase. Immunocytochemical studies at the light and electron microscopic level demonstrated antibody binding to both the basal and lateral membranes of bovine corneal endothelial cells. This suggested a baso-lateral distribution of Na+/K(+)-ATPase in these cells, rather than the previously proposed lateral membrane-only distribution.

Induction of manganese superoxide dismutase by glucocorticoids in glomerular cells

Our previous in vivo study demonstrated that methylprednisolone (MP) activates glomerular antioxidant enzymes and attenuates glomerular oxidant injuries, including those in experimental nephrosis. The present study investigates the cellular mechanism of the MP-induced activation of antioxidant enzymes and their contribution to the attenuation of cellular oxidant toxicity. When bovine glomerular endothelial cells (GECs) were treated with 10 microM MP, cellular manganese superoxide dismutase (Mn-SOD, 3.95 +/- 0.33 mu/mg protein, M +/- SE) and catalase (1.64 +/- 0.06 k/mg protein) activities were significantly (P < 0.05) elevated above control GECs (2.23 +/- 0.43 mu/mg protein and 1.06 +/- 0.09 k/mg protein, respectively). When GECs pretreated with MP (10 microM 24 hrs) were exposed to xanthine (0.1 mM)+xanthine oxidase (5 mU/ml) for four hours, levels of specific membrane lipid peroxidation products, that is, phosphatidylcholine- and phosphatidylethanolamine-hydroperoxides, remained at levels 10 to 25% of those measured in non-MP-treated (xanthine/xanthine oxidase-exposed) control cells. Moreover, the degree of cell damage following exposure to the superoxide generating system, assessed by 51Cr release, was significantly attenuated in MP-treated cells (approximately 50% of MP-non-treated controls, N = 6). Thus, MP-treated GECs with elevated antioxidant enzyme activities by MP were more resistant to the toxic effect of reactive oxygen metabolites. The mechanism of antioxidant enzyme induction by MP was studied for Mn-SOD. MP was shown to enhance Mn-SOD mRNA in bovine GECs and rat glomerular mesangial cells (GMCs) in dose-dependent manners.(ABSTRACT TRUNCATED AT 250 WORDS)

Endothelial cells release casein kinase II--like activity capable of phosphorylating fibrinogen in response to thrombin

Rat liver endothelial cells cultivated in the absence of serum and activated with thrombin released up to 10% of the total protein kinase activity into the cell medium using casein or fibrinogen as the phosphate acceptor protein. The activity was partly inhibited by heparin, indicating that it was of the casein kinase II type. The release of kinase started directly after the addition of thrombin (2 NIH U/ml) to the media with two maxima; one after about 10 min and the second after around 30 min. The phosphorylating activity of media from cells incubated for longer times was less dependent on thrombin-induction which probably indicated the start of destruction of the cells. The results reported suggest that phosphorylation of fibrinogen could occur in the blood under acute phase conditions.

Induction and release of manganese superoxide dismutase from mitochondria of human umbilical vein endothelial cells by tumor necrosis factor-alpha and interleukin-1 alpha

The effects of tumor necrosis factor-alpha (TNF alpha) on cultured human umbilical vein endothelial cells (EC) and 2 cancer cell lines, A549 and ME180, were compared. The effects of interleukin-1 alpha (IL-1 alpha) on EC were also examined. While A549 cells were fairly resistant to the cytolytic effects of TNF alpha and IL-1 alpha, ME180 cells were sensitive. EC were also less sensitive to TNF alpha than ME180 cells, as judged by viability of individual cells and by the release of lactate dehydrogenase (LDH) into the medium. Both manganese superoxide dismutase (Mn-SOD) and its mRNA were markedly induced by these cytokines in EC and in A549 cells but not in ME180 cells. The levels of Mn-SOD in the conditioned medium of EC were markedly increased after stimulation with cytokines, whereas those in ME180 and A549 cells were relatively low. The amount of Mn-SOD released appears to be comparable to that from cells lysed due to the cytocidal effect of cytokines, as assessed by measuring intra- and extra-cellular LDH activity. These data suggest that, in vivo, the TNF alpha and IL-1 alpha produced by cancer cells and other cells may induce Mn-SOD in vascular endothelial cells as well as other host tissues, resulting in release of a relatively large amount of this protein into the serum.

Lung endothelial dipeptidyl peptidase IV is an adhesion molecule for lung-metastatic rat breast and prostate carcinoma cells

Attachment of circulating tumor cells to endothelial cell adhesion molecules restricted to select vascular compartments is thought to be responsible for site-specific metastasis. Lung-metastatic rat R3230AC-MET breast and RPC-2 prostate carcinoma cells bound outside-out endothelial cell membrane vesicles, prepared by perfusion of the rat lung vasculature with a low-strength formaldehyde solution, in significantly higher numbers than their nonmetastatic counterparts R3230AC-LR and RPC-LR. In contrast, vesicles derived from the vasculature of a nonmetastasized organ (e.g., hind leg muscle) showed no binding preference for either of the four tumor cell lines. Lung-derived endothelial vesicles were used here to generate mAbs against lung endothelial cell adhesion molecules. The first group of mice were actively immunized against lung endothelial vesicles, whereas the second group was injected with syngeneic mouse antiserum against leg endothelial vesicles before active immunization with lung endothelial vesicles. 17 hybridoma supernatants obtained from the two fusions bound lung vesicles with at least a 10-fold higher affinity than leg vesicles. Seven (four obtained by a passive/active immunization protocol) stained rat capillary endothelia. One mAb, mAb 8.6A3, inhibited specific adhesion of lung-derived vesicles to lung-metastatic breast and prostate carcinoma cells. Purification of the antigen (endothelial cell adhesion molecule) from rat lung extracts revealed a protein with a 110-kD mol wt. NH2-terminal sequencing established identity with dipeptidyl peptidase IV which had been reported to serve as a fibronectin-binding protein. These results indicate that vesicles obtained from in situ perfused organs are a convenient immunogen for the production of antibodies to compartment-specific endothelial cell surface molecules, and reinforce the concept that endothelial cell surface components are selectively recognized by circulating cancer cells during metastasis formation.

Genomic analysis and expression patterns reveal distinct genes for endothelial and brain nitric oxide synthase

Constitutively active nitric oxide synthases (NOS) are a unique class of NADPH-dependent, calcium/calmodulin-dependent enzymes that catalyze the conversion of L-arginine to nitric oxide and L-citrulline. However, little is known about the molecular similarities or differences between the two prototypical constitutive NOS enzymes, endothelial NOS (ECNOS) and brain NOS (bNOS). The aims of this study were to begin characterizing the gene structure and tissue distribution of messenger RNAs (mRNAs) for ECNOS and bNOS and to examine the immunological resemblance of the proteins by Western blotting. Full-length complementary DNAs (cDNAs) encoding bovine ECNOS and rat bNOS hybridized, under high stringency, to different-sized fragments of endonuclease-digested bovine, rat, and human genomic DNA. In addition, more than one fragment was detected with both cDNAs, suggesting that ECNOS and bNOS genes contained multiple introns. Tissue distribution of ECNOS mRNA (4.4 kb) and bNOS mRNA (9.5 kb) in the rat was detected by Northern blotting. Patterns among tissue extracts were strikingly different, with ECNOS mRNA being most abundant in aorta, heart, lung, kidney, adrenal gland, spinal cord, and urogenital tissues and bNOS mRNA most prominent in brain regions, intestine, stomach, spinal cord, adrenal gland, and aorta. Interestingly, ECNOS cDNA detected two equally abundant RNA transcripts (4.4 and 4.0 kb) in most brain regions tested, suggesting an alternative splicing of the ECNOS pre-mRNA. Western blotting, using an ECNOS monoclonal antibody, recognized ECNOS protein from native bovine endothelial cells, cultured bovine endothelial cells, and COS cells transfected with ECNOS cDNA but did not recognize purified bNOS.(ABSTRACT TRUNCATED AT 250 WORDS)

Redistribution of glomerular dipeptidyl peptidase type IV in experimental lupus nephritis. Demonstration of decreased enzyme activity at the ultrastructural level

BACKGROUND

In murine chronic graft-versus-host disease, an experimental model for lupus nephritis, autoantibodies against renal tubular epithelium can be found. Part of these antibodies are directed against a constituent of renal tubular epithelium, the enzyme Dipeptidyl peptidase IV (DPP IV). DPP IV is present on the cell membrane of glomerular epithelial and endothelial cells, and plays an important role in cell-extracellular matrix interactions. In mice and rats, administration of heterologous anti-DPP IV antibodies can induce proteinuria and podocyte effacement.

EXPERIMENTAL DESIGN

In this study, the glomerular DPP IV enzyme activity was investigated in the course of graft-versus-host disease in (C57BL/10 x DBA/2) F1 hybrids both by light- and electron microscopy using a DPP IV-specific substratum.

RESULTS

Light microscopical examination revealed an overall reduction of DPP IV activity and an altered distribution pattern in glomeruli as early as 4 weeks after induction of graft-versus-host disease. Immunofluorescence studies using anti-DPP IV antibodies showed actual redistribution, excluding antibody-mediated enzyme inactivation. Enzyme electron microscopy revealed an irregular deposition of reaction product characterized by a patchy, "moth eaten" appearance of the endothelial and epithelial membranes. This process occurred simultaneously with the development of albuminuria and preceded the effacement of epithelial foot processes. In control mice, DPP IV showed a continuous distribution along endothelial and podocyte membranes.

CONCLUSIONS

In view of these findings we postulate that impairment of the function of DPP IV as a non integrin adhesion molecule may be one of the causative factors underlying the structural and functional lesions observed in this model for lupus nephritis.

Evidence for a nucleotide receptor on adrenal medullary endothelial cells linked to phospholipase C and phospholipase D

1. We have investigated whether the 'atypical' P2-purinoceptor previously described on adrenal microvasculature endothelial cells is a nucleotide receptor (responds to pyrimidines and purines) and is linked to phospholipase D as well as phospholipase C. 2. Cultured bovine adrenal medullary endothelial (BAME) cells responded to the pyrimidine UTP, as well as the purines. The total [3H]-inositol phosphate responses were with a rank order of UTP > ATP- = adenosine 5'-O-(3-thio-triphosphate) (ATP gamma S) >> 2MeSATP. The selective P2x agonist beta, gamma-methylene ATP was inactive. 3. Construction of dose-response curves to ATP, ATP gamma S and UTP in the presence and absence of additional agonists showed that responses to ATP gamma S and UTP were not additive, nor were those to UTP and ATP. This suggests that purines and pyrmidines acted via a common nucleotide receptor. 4. 32P-labelled BAME cells, in the presence of butanol, produced [32P]-phosphatidylbutanol (PBut) when stimulated with ATP gamma S or the protein kinase C activator, tetradecanoyl phorbol acetate (TPA). 5. Cells labelled with [3H]-palmitate and stimulated in the presence of butanol generated [3H]-PBut with the same order of agonist potencies seen for inositol phosphate responses. 6. The protein kinase C inhibitor, Ro 31-8220, abolished TPA and agonist stimulation of [3H]-PBut production. 7. These observations, and our related studies on bovine aortic endothelial cells, provide the first demonstration of a phospholipase C linked nucleotide receptor on vascular endothelial cells. It is concluded that BAME cells express a nucleotide receptor linked to phospholipase C and phospholipase D, but that activation of phospholipase D is probably down-stream of phospholipase C.

Immunohistochemical detection of prostaglandin I2 synthase in various calcified tissue-forming cells in rat

Localization of prostaglandin (PG) I2 synthase immunoreactivity was examined in demineralized sections of rat pulpal, periodontal and skeletal tissues using isn-1, a monoclonal antibody raised against the enzyme. Various calcified tissue-forming cells, i.e. odontoblasts, osteoblasts, osteocytes, cementoblasts, cementocytes and chondrocytes, were similarly immunoreactive for PGI2 synthase, suggesting that they are capable of producing PGI2. In odontoblasts and chondrocytes, the reactivity increased gradually with maturation. Weak immunoreactivity was also observed in endothelial cells and fibroblast-like cells in pulpal and periodontal tissues. However, no reactivity was seen in ameloblasts. These results suggest the possible involvement of PGI2 in the regulation of the metabolism of various calcified tissues. Monoclonal antibodies such as isn-1 may become useful markers of the maturation of calcified tissue-forming cells of mesenchymal origin.

NYK/FLK-1: a putative receptor protein tyrosine kinase isolated from E10 embryonic neuroepithelium is expressed in endothelial cells of the developing embryo

A protein tyrosine kinase (NYK/FLK-1), bearing all the hallmarks of a growth factor receptor, has been isolated from a cDNA library generated from enriched populations of mouse day 10 embryonic neuroepithelium and from day 18 embryonic colon. Sequence analysis of cDNAs covering the entire coding region of this 5.7 kb mRNA predicted the presence of seven immunoglobulin-like domains in the extracellular region of this molecule. This feature, coupled with the detection of an insert domain bisecting the kinase domain of the predicted protein sequence, places NYK/FLK-1 firmly in the Platelet-derived Growth Factor Receptor-related class of molecules. NYK/FLK-1 is expressed at high levels in adult heart, lung, kidney, brain and skeletal muscle, but is also expressed at lower levels in most other adult tissues. In situ hybridization of day 12.5 embryo sections demonstrated NYK/FLK-1 mRNA expression in endothelial cells lining the dorsal aorta and intervertebral veins. In addition, expression was found in cells lining the capillary plexus which surrounds the developing neuroepithelium, and in the endothelial cells which are found within the embryonic lung, spleen, liver and metanephros.