Angiogenesis-regulating cytokines: activities and interactions.
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Animals↗
Biomedical subjects
J D Vassalli
Publications and source records attributed to J D Vassalli.
Protease nexin 1 in the murine kidney: glomerular localization and up-regulation in glomerulopathies.
Protease nexin 1 (PN-1), a potent serpin-class antiprotease, is thought to be synthesized in the murine kidney. However, neither the cellular localization of PN-1 synthesis nor its role has yet been defined. To address these questions, we determined by in situ hybridizations RNase protection assay and immunoblotting, the sites of PN-1 mRNA accumulation in normal mouse kidneys and the modulation of PN-1 expression in several pathological conditions. In normal kidneys, PN-1 mRNA was detected primarily in glomeruli, most likely in mesangial cells. The glomerular expression of PN-1 was substantially enhanced not only in lupus-like glomerulonephritis (induced by IgG3 monoclonal rheumatoid factors or occurring spontaneously in lupus-prone mice), but also in mild glomerular lesions associated with intracapillary thrombi induced by IgG3 anti-trinitrophenyl monoclonal antibodies. In contrast, no modulation of PN-1 mRNA levels was observed during the course of lipopolysaccharide-induced acute tubular necrosis. A constitutive PN-1 gene expression and its up-regulation during glomerular injury suggest a possible role for PN-1 in glomerular biology. In view of its high inhibitory activity towards thrombin, mesangial PN-1 may be involved in the control of glomerular coagulation following initial glomerular injuries.
Amyloid beta-Protein Precursor↗
Cuts and scrapes? Plasmin heals!
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Animals↗
Angiogenesis: a paradigm for balanced extracellular proteolysis during cell migration and morphogenesis.
Extracellular proteolysis is required for matrix degradation and the regulation of cytokine activity during angiogenesis, and this is dependent on a cohort of proteases and protease inhibitors produced by endothelial and nonendothelial cells. The plasminogen activator (PA)/plasmin system has been extensively investigated in these processes, and descriptive studies have demonstrated that urokinase-type PA (uPA), uPA receptor (uPAR) and PA inhibitor-1 (PAI-1) are expressed by endothelial cells during angiogenesis in vivo. In vitro studies have led to the notion that normal capillary morphogenesis is dependent on a protease-antiprotease equilibrium. These findings are discussed in the context of recent observations on uPA-, uPAR-, PAI-1 and plaminogen-deficient mice, in which developmental and physiological angiogenesis appear to occur normally. This has led to a reevaluation of the role of the PA/plasmin system during angiogenesis. In particular, these observations raise the possibility that the role of this system may be limited to situations in which endothelial cells encounter and must degrade fibrin in order to form new capillary sprouts.
Animals↗
TGF-beta 1 overexpression in murine pancreas induces chronic pancreatitis and, together with TNF-alpha, triggers insulin-dependent diabetes.
We have generated transgenic mice overexpressing TGF-beta 1 in pancreatic beta cells. This resulted in massive fibrosis of the pancreas; in adult mice, most of the acini were replaced by fibrotic and adipose tissues. A conspicuous disorganization of the islets of Langerhans was also observed; however, the number of beta cells was not decreased and the mice were normoglycemic. Backcrossing to transgenic mice overexpressing TNF-alpha in their islet beta cells (which also remain normoglycemic, (1)) yielded double transgenics, most of which became diabetic by the age of 4 months; histological analysis revealed a dramatic decrease in insulin-containing beta cells.
Amylases↗
Plasmin-catalyzed proteolysis in colorectal neoplasia.
The expression of different components of the plasminogen activator (PA)/plasmin system was explored in a series of colorectal neoplasia. We have found that urokinase (uPA) and urokinase receptor (uPA-R) gene expression is upregulated in adenomas and carcinomas, and that uPA/uPA-R production is confined to stromal cells in the proximity of epithelial proliferations. In addition, in adenomas, the focal increase in uPA mRNA is not systematically coupled to detectable enzymatic activity, whereas in carcinomas, uPA mRNA accumulation is consistently associated with detectable but variable levels of enzymatic activity. In contrast, in the tumor vasculature, tissue-type plasminogen activator-mediated proteolysis is considerably reduced when compared to normal mucosal and submucosal vessels; this reduction in plasmin formation appears to result from the highly increased production of plasminogen activator inhibitor type 1 by endothelial cells. Our observations demonstrate that colorectal neoplasia are associated with marked alterations in the extracellular proteolytic balance controlled by the PA/plasmin system. They show that contrasting disturbances in plasmin formation take place in distinct stromal compartments but not in epithelial cells, and that these disturbances are maximal during invasive neoplasia. Altogether, our results raise the possibility that alterations in plasmin formation should not be exclusively regarded as promoters of cancer cell invasiveness.
Adenocarcinoma↗
Translational control. Awakening dormant mRNAs.
The translational control of many maternal mRNAs in oocytes and early embryos relies on changes in poly(A) tail length; the factors controlling poly(A) tail length are being identified in a range of species.
Animals↗
Vascular endothelial growth factor increases urokinase receptor expression in vascular endothelial cells.
Vascular endothelial growth factor (VEGF) is a potent angiogenic factor and endothelial cell-specific mitogen that stimulates urokinase-type plasminogen activator (uPA) activity in vascular endothelial cells. Here, we report that VEGF increases the high affinity binding of uPA to the same cells and that this binding is prevented by a peptide corresponding to the uPA receptor (uPAR) binding growth factor-like domain of uPA. Ligand cross-linking, ligand blotting, and uPA-Sepharose affinity chromatography revealed an increase in a cell surface uPA binding protein that corresponds to the uPAR on the basis of its affinity for uPA, M(r) of 50,000-55,000, and phosphatidylinositol-specific phospholipase C sensitivity. By Scatchard analysis, VEGF increased the number of uPAR molecules by 2.8-3.5-fold and concomitantly decreased their affinity for uPA. By northern blotting uPAR mRNA was increased in a dose- and time-dependent manner in response to VEGF. Taken together, these findings demonstrate that VEGF-induced angiogenesis is accompanied by increased uPAR expression and uPA activity on the endothelial cell surface. These observations are consistent with the notion that the uPA-uPAR interaction facilitates cellular invasion.
Animals↗
Induction of plasminogen activator inhibitor type 1 in murine lupus-like glomerulonephritis.
Three major components of the plasminogen activators (PA)/plasmin system are synthesized physiologically in glomeruli, and can be involved in glomerular proteolysis and extracellular matrix metabolism: tissue-type PA (tPA), urokinase (uPA) and PA inhibitor type 1 (PAI-1). To explore the possible role of a dysregulation of the plasmin protease system in the development and progression of lupus-like glomerulonephritis, we studied the expression of the renal plasmin protease components during the course of the disease, either acute, induced by IgG3 monoclonal cryoglobulins, or chronic, occurring spontaneously in three different lupus-prone mice: (NZBxNZW)F1, BXSB and MRL-lpr/lpr. RNase protection assays and in situ hybridizations revealed a marked glomerular induction of PAI-1 mRNA abundance without any significant changes in renal tPA and uPA mRNA levels in the two different types of lupus-like glomerulonephritis. The overexpression of PAI-1 mRNA occurred in parallel with a significant decrease in glomerular tPA-catalyzed enzymatic activity as determined by zymographic analysis. In addition, a concomitant increase in glomerular expression of transforming growth factor beta 1 (TGF-beta 1) mRNA was observed. The demonstration of a close correlation between the PAI-1 and TGF-beta 1 mRNA levels and the severity of lupus-like glomerular lesions suggests that a pertubation of the glomerular PA/PAI balance, resulting from a marked TGF-beta 1-mediated induction of PAI-1 gene expression, plays an important role in the progression of lupus-like glomerular lesions, leading to glomerulosclerosis.
Animals↗
Ablation of islet endocrine cells by targeted expression of hormone-promoter-driven toxigenes.
Ontogenic relationships between the different types of endocrine cells in the islets of Langerhans were explored by generating transgenic mouse embryos in which cells transcribing the glucagon, insulin, or pancreatic polypeptide genes were destroyed through the promoter-targeted expression of the diphtheria toxin A chain. Embryos lacking glucagon- or insulin-containing cells did not exhibit alterations in the development of the nontargeted islet cell types, whereas embryos lacking pancreatic polypeptide gene-expressing cells also lacked pancreatic insulin- and somatostatin-containing cells. These results show that neither glucagon nor insulin gene-expressing cells are essential for the differentiation of the other islet endocrine-cell types. These results also suggest that pancreatic polypeptide gene-expressing cells are indispensable for the differentiation of islet beta and delta cells because the former produce a necessary paracrine or endocrine factor and/or operate through a cell-lineage relationship.
Animals↗
Plasminogen activation in melanocytic neoplasia.
A large body of experimental evidence suggests that plasminogen activators provide tumoral cells with efficient means to degrade extracellular matrix constituents and thereby facilitate their dissemination to distant sites. Melanocytic neoplasia encompass a spectrum of lesions exhibiting diverse clinical behavior that remain difficult to predict with current histopathological evaluations. Little information concerning the contribution of plasminogen activation in diagnostic specimens of human melanocytic tumors is presently available. We thus analyzed biopsy specimens of pigmented skin lesions by histological techniques that identify the cellular sites of synthesis of plasminogen activators and of their inhibitors and that localize the sites of plasminogen activators-catalyzed enzymatic activities. We found that urokinase-type plasminogen activators (uPA) and plasminogen activator inhibitor type 1 mRNAs accumulate in atypical nevocytes and in melanoma cells, but not in benign nevocytes. However, uPA-catalyzed proteolytic activity was detected exclusively in melanomas. These observations suggest that up-regulation of the uPA gene is an early feature of melanocyte transformation and that unbalanced enzyme/inhibitor activity is associated with the malignant phenotype. By supporting a role for uPA in melanoma invasiveness, they provide a novel tool for the evaluation of atypia in nevi.
Humans↗
Tumour biology. Membrane proteases in focus.
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Cell Membrane↗
Modulation of bovine microvascular endothelial cell proteolytic properties by inhibitors of angiogenesis.
A tightly controlled increase in extracellular proteolysis, restricted both in time and space, is an important component of the angiogenic process, while anti-proteolysis is effective in inhibiting angiogenesis. By focussing on the plasminogen activator (PA)-plasmin system, the objective of the present studies was to assess whether previously described inhibitors of angiogenesis modify bovine microvascular endothelial cell proteolytic properties. We demonstrate that although synthetic angiostatic steroids (U-24067 and U-42129), heparin, suramin, interferon alpha-2a, and retinoic acid are all inhibitors of in vitro angiogenesis, each of these agents has distinct effects on the plasminogen-dependent proteolytic system. Specifically, angiostatic steroids and interferon alpha-2a reduce urokinase-type PA (u-PA) and PA inhibitor-1 activity, while heparin and retinoic acid increase u-PA activity. Suramin reduces cell-associated u-PA activity and greatly increases PAI-1 production at doses which induce monolayer disruption. These findings demonstrate that a spectrum of alterations in extracellular proteolysis is associated with anti-angiogenesis, and that anti-angiogenesis and anti-proteolysis are not necessarily correlated. A reduction in extracellular proteolysis would be expected to reduce invasion, whereas an increase in proteolysis might modulate the activity of inhibitory cytokines, which in turn could reduce endothelial cell proliferation and migration and inhibit angiogenesis. The spectrum of effects on different elements of the PA system observed in response to the agents assessed suggests that the role of modulations in extracellular proteolytic activity in anti-angiogenesis is likely to be varied and complex.
Adrenal Cortex↗
A CD8+ T-lymphocyte-mediated and CD4+ T-lymphocyte-independent autoimmune diabetes of early onset in transgenic mice.
While transgenic mice expressing tumour necrosis factor-alpha under the control of the beta-cell-specific insulin promoter display a marked lymphocytic infiltration of the islets, they never develop insulin-dependent diabetes mellitus (IDDM). In striking contrast, "double" transgenic mice whose beta cells express both tumour necrosis factor-alpha as well as the co-stimulatory B7-1 molecule all develop IDDM at an early age. Furthermore, administration of anti-CD8 but not anti-CD4 immunoglobulins prevents diabetes onset. These results indicate that while tumour necrosis factor-alpha induced lymphocytic infiltration is not sufficient to effect beta-cell destruction, locally co-stimulated islet-infiltrating CD8+ T lymphocytes could play a critical role in the development of IDDM.
Animals↗
LPS induces major changes in the extracellular proteolytic balance in the murine kidney.
Recent investigations have shown that in the murine kidney urokinase (uPA) and tissue-type plasminogen activator (tPA) are synthesized and released in urine by tubular epithelial cells, raising the possibility that plasminogen activators (PAs) may be involved in the maintenance of patency and fluidity in renal tubules. To further investigate the contribution of the PA system in renal pathology, we have determined the effects of LPS on the renal production of PAs: we localized PA-catalyzed proteolysis by zymographic analysis of tissue sections and studied the accumulation of mRNAs for PAs and their inhibitors (PAI-1 and PAI-2) by in situ hybridization. Both a single and two injections of LPS induced a dramatic reduction in urinary and renal uPA enzymatic activity; this decrease in catalytic activity was attributable to a reduction in uPA mRNA levels in both proximal and distal tubules. By contrast, we noticed a marked increase of tPA mRNA content in glomerular cells which was not accompanied by a concomitant increase in tPA-mediated proteolytic activity. In addition, a major up-regulation in PAI-1 mRNA levels was observed throughout the kidney, while PAI-2 mRNA was not detectable in the kidneys of control or LPS-injected animals. Our investigations document the profound alterations of the PA/PAI balance in renal tissue following in vivo LPS administration. They suggest that imbalanced extracellular proteolysis might participate in the alterations of kidney function observed in septic shock.
Animals↗
TGF-beta 1 influences the relative development of the exocrine and endocrine pancreas in vitro.
Pancreatic rudiments from E12.5 mouse embryos undergo extensive development and differentiation when cultured in three-dimensional gels of extracellular matrix proteins for up to 12 days. Whereas collagen gels promote the formation of numerous exocrine acini and relatively small clusters of endocrine cells, in basement membrane (EHS) matrices the development of endocrine cells is dramatically favoured over that of acinar tissue. Buds embedded in a collagen gel contiguous to an EHS gel also fail to develop acini, suggesting the involvement of diffusible factor(s). Addition of cytokines to cultures of pancreatic buds in collagen gels modifies the relative proportions of the epithelial components of the gland. In the presence of EGF the proportion of the tissue occupied by ducts overrides that of acinar structures, whereas the endocrine portion of the tissue is not significantly modified. TGF-beta 1 partially mimicks the effect of EHS matrix in inhibiting the development of acinar tissue without decreasing the amount of ducts and mesenchyme; TGF-beta 1 also promotes the development of endocrine cells, in particular of insulin-containing beta cells and of cells expressing genes of the PP-fold family. These results show that cytokines can modulate the development of the pancreas and suggest a role for TGF-beta 1 in regulating the balance between the acinar and endocrine portions of the gland in vivo. More generally, they are compatible with the notion that, during organogenesis, cytokines act as paracrine factors responsible for the development and maintenance of appropriate proportions of different tissue constituents.
Animals↗
Prevention of systemic lupus erythematosus in autoimmune BXSB mice by a transgene encoding I-E alpha chain.
Males from the BXSB murine strain (H-2b) spontaneously develop an autoimmune syndrome with features of systemic lupus erythematosus (SLE), which results in part from the action of a mutant gene (Yaa) located on the Y chromosome. Like other H-2b mice, the BXSB strain does not express the class II major histocompatibility complex antigen, I-E. Here we report that the expression of I-E (E alpha dE beta b) in BXSB males bearing an E alpha d transgene prevents hypergammaglobulinemia, autoantibody production, and subsequent autoimmune glomerulonephritis. These transgenic mice bear on the majority of their B cells not only I-E molecules, but also an I-E alpha chain-derived peptide presented by a higher number of I-Ab molecules, as recognized by the Y-Ae monoclonal antibody. The I-E+ B cells appear less activated in vivo than the I-E- B cells, a minor population. This limited activation of the I-E+ B cells does not reflect a functional deficiency of this cell population, since it can be stimulated to IgM production in vitro by lipopolysaccharides at an even higher level than the I-E- B cell population. The development of the autoimmune syndrome in the transgenic and nontransgenic bone marrow chimeric mice argues against the possibility that the induction of regulatory T cells or clonal deletion of potential autoreactive T cells as a result of I-E expression is a mechanism of the protection conferred by the E alpha d transgene. We propose a novel mechanism by which the E alpha d transgene protects BXSB mice against SLE: overexpression of I-E alpha chains results in the generation of excessive amounts of a peptide displaying a high affinity to the I-Ab molecule, thereby competing with pathogenic autoantigen-derived peptides for presentation by B lymphocytes and preventing their excessive stimulation.
Animals↗
Processing of complex between urokinase and its type-2 inhibitor on the cell surface. A possible regulatory mechanism of urokinase activity.
Complexes between the urokinase-type plasminogen activator (uPA) and its type-2 inhibitor (PAI-2) are bound by a cell-surface receptor for uPA and rapidly cleaved into two fragments of 70 and 22 kDa. The 70-kDa fragment contains the active site of uPA and PAI-2, while the 22-kDa species was identified as the amino terminal fragment of uPA, that binds specifically to the receptor. When the experiment is performed at 4 degrees C, both fragments remain bound to the cell surface and can be eluted by acid treatment. We therefore postulate that after the binding of the uPA-PAI-2 complex, a new binding site for the 70-kDa species becomes available. This additional binding favours the cleavage of the complex into the 70-and 22-kDa fragments; the 70-kDa species is endocytosed or released, while the 22-kDa fragment remains on the cell surface to prevent the binding of intact uPA.
Cell Line↗