scholarly journals Antagonistic effects of different members of the fibroblast and platelet-derived growth factor families on adipose conversion and NADPH-dependent H2O2 generation in 3T3 L1-cells

1995 ◽  
Vol 307 (2) ◽  
pp. 549-556 ◽  
Author(s):  
H I Krieger-Brauer ◽  
H Kather
Keyword(s):  
Growth Factor ◽  
Plasma Membranes ◽  
Platelet Derived Growth Factor ◽  
Fat Cell ◽  
Intact Cells ◽  
Antagonistic Effects ◽  
H2o2 Generation ◽  
Adipose Conversion ◽  
Generating System

3T3 L1-cells, which undergo adipose conversion in vitro, possess a stimulus-sensitive H2O2-generating system in their plasma membrane, and its properties are virtually identical with those of the insulin-sensitive human fat-cell oxidase [Krieger-Brauer and Kather (1992) J. Clin. Invest. 89, 1006-1013]. Insulin and insulin-like growth factor I were found to be active stimulators of NADPH-dependent H2O2 generation. Surprisingly, the acidic (a) and basic (b) isoforms of fibroblast growth factor (FGF) as well as the AA and BB homodimers of platelet-derived growth factor (PDGF) had antagonistic effects on NADPH-dependent H2O2 generation in plasma membranes which were parallelled by corresponding changes in H2O2 accumulation in intact cells. bFGF and PDGF BB (which inhibit NADPH-dependent H2O2 generation) prevented the adipose conversion of 3T3 L1-preadipocytes, and this effect could be reversed by exogenously supplied H2O2. Conversely, aFGF and PDGF AA, which stimulated H2O2 generation, accelerated adipocyte conversion in the presence of insulin and were adipogenic in themselves. Consistently, expression of the adipocyte phenotype induced by insulin, dexamethasone and isobutylmethylxanthine was enhanced in the presence of exogenous hypoxanthine/xanthine oxidase, whereas antioxidants, such as N-acetylcysteine or ascorbate, suppressed the process of differentiation. It is concluded that the H2O2 produced in response to hormones and cytokines may contribute to the development and maintenance of the differentiated state.

scholarly journals The stimulus-sensitive H2O2-generating system present in human fat-cell plasma membranes is multireceptor-linked and under antagonistic control by hormones and cytokines

1995 ◽  
Vol 307 (2) ◽  
pp. 543-548 ◽  
Author(s):  
H I Krieger-Brauer ◽  
H Kather
Keyword(s):  
Growth Factor ◽  
Plasma Membranes ◽  
Fat Cells ◽  
Inhibitory Effects ◽  
Fat Cell ◽  
Redox Equilibrium ◽  
Necrosis Factor Alpha ◽  
H2o2 Generation ◽  
Generating System ◽  
Antagonistic Control

Previous work demonstrated that human fat-cells possess a plasma-membrane-bound H2O2-generating system that is activated by insulin. Here we show that this system is under antagonistic control by various hormones and cytokines that typically act through several distinct receptor families. Similarly to insulin, oxytocin and tumour necrosis factor alpha acted as stimulators of NADPH-dependent H2O2 generation, whereas isoprenaline, a beta-adrenergic agonist, had inhibitory effects. Surprisingly, the acidic and basic isoforms of fibroblast growth factor as well as homodimeric platelet-derived growth factor AA and BB had antagonistic stimulatory and inhibitory effects on NADPH-dependent H2O2 generation. The agents tested acted at discrete ligand-specific receptors and their mechanisms of action were membrane-delimited and occurred in the absence of ATP. These findings implied that established pathways of signal transduction, including receptor kinases or second-messenger-dependent protein kinases A and C, were not involved and placed the stimulus-sensitive H2O2-generating system in a position comparable with adenylate cyclase. It was concluded that the stimulus-sensitive H2O2-generating system of human fat-cells meets all criteria of a universal signal-transducing system for hormones and cytokines that may link ligand binding to cell-surface receptors to changes in the intracellular redox equilibrium.

scholarly journals D-3 phosphoinositide metabolism in cells treated with platelet-derived growth factor

1996 ◽  
Vol 319 (3) ◽  
pp. 851-860 ◽  
Author(s):  
Craig C WHITEFORD ◽  
Christie BEST ◽  
Andrius KAZLAUSKAS ◽  
Emin T. ULUG
Keyword(s):  
Growth Factor ◽  
Kinase Inhibitor ◽  
Kinetic Studies ◽  
Platelet Derived Growth Factor ◽  
Phosphoinositide Metabolism ◽  
Intact Cells ◽  
Rapid Induction ◽  
Transient Activation ◽  
In Vitro Treatment

Despite extensive analysis of phosphoinositide 3-hydroxykinases (PI 3-kinases) at the molecular level, comparatively little is known about the mechanisms by which products of these enzymes exert their expected second-messenger functions. This study examines the metabolism of D-3 phosphoinositides in mouse Ph-N2 fibroblasts lacking the platelet-derived growth factor (PDGF) α-receptor. Treatment of these cultures with BB PDGF, but not AA PDGF, resulted in transient activation of PI 3-kinase activity measured in vitro. Treatment of myo-[3H]inositol-labelled Ph-N2 cells with BB PDGF resulted in the rapid induction of PtdIns(3,4)P2 and PtdIns(3,4,5)P3 and, to a smaller extent, PtdIns3P. The appearance of PtdIns(3,4,5)P3 preceded that of PtdIns(3,4)P2 and PtdIns3P after the addition of PDGF, suggesting that PtdIns(4,5)P2 is the preferred substrate of the agonist-stimulated PI 3-kinase in intact cells. Treatment of both resting and PDGF-stimulated cells with the fungal metabolite wortmannin resulted in pronounced, selective effects on the levels of all D-3 phosphoinositides. Kinetic studies with this PI 3-kinase inhibitor revealed the presence of at least two independent routes for the biosynthesis of D-3 phosphoinositides in PDGF-treated cells.

Basis of hematopoietic defects in platelet-derived growth factor (PDGF)-B and PDGF β-receptor null mice

Blood ◽  
2001 ◽  
Vol 97 (7) ◽  
pp. 1990-1998 ◽  
Author(s):  
Wolfgang E. Kaminski ◽  
Per Lindahl ◽  
Nancy L. Lin ◽  
Virginia C. Broudy ◽  
Jeffrey R. Crosby ◽  
...  
Keyword(s):  
Growth Factor ◽  
Fetal Liver ◽  
Liver Cells ◽  
Platelet Derived Growth Factor ◽  
Wild Type ◽  
Liver Growth ◽  
Hematologic Disorders ◽  
Fetal Liver Cells ◽  
Β Receptor

Abstract Platelet-derived growth factor (PDGF)-B and PDGF β-receptor (PDGFRβ) deficiency in mice is embryonic lethal and results in cardiovascular, renal, placental, and hematologic disorders. The hematologic disorders are described, and a correlation with hepatic hypocellularity is demonstrated. To explore possible causes, the colony-forming activity of fetal liver cells in vitro was assessed, and hematopoietic chimeras were demonstrated by the transplantation of mutant fetal liver cells into lethally irradiated recipients. It was found that mutant colony formation is equivalent to that of wild-type controls. Hematopoietic chimeras reconstituted with PDGF-B−/−, PDGFRβ−/−, or wild-type fetal liver cells show complete engraftment (greater than 98%) with donor granulocytes, monocytes, B cells, and T cells and display none of the cardiovascular or hematologic abnormalities seen in mutants. In mouse embryos, PDGF-B is expressed by vascular endothelial cells and megakaryocytes. After birth, expression is seen in macrophages and neurons. This study demonstrates that hematopoietic PDGF-B or PDGFRβ expression is not required for hematopoiesis or integrity of the cardiovascular system. It is argued that metabolic stress arising from mutant defects in the placenta, heart, or blood vessels may lead to impaired liver growth and decreased production of blood cells. The chimera models in this study will serve as valuable tools to test the role of PDGF in inflammatory and immune responses.

Platelet-derived growth factor (PDGF)-dependent association of phospholipase C-gamma with the PDGF receptor signaling complex

1990 ◽  
Vol 10 (5) ◽  
pp. 2359-2366
Author(s):  
D K Morrison ◽  
D R Kaplan ◽  
S G Rhee ◽  
L T Williams
Keyword(s):  
Growth Factor ◽  
Tyrosine Phosphorylation ◽  
Serine Phosphorylation ◽  
Platelet Derived Growth Factor ◽  
Pdgf Receptor ◽  
Wild Type ◽  
Receptor Proteins ◽  
Signaling Complex

We investigated the interaction of phospholipase C-gamma (PLC-gamma) with wild-type and mutant forms of the platelet-derived growth factor (PDGF) beta-receptor both in vivo and in vitro. After PDGF treatment of CHO cell lines expressing wild-type or either of two mutant (delta Ki and Y825F) PDGF receptors, PLC-gamma became tyrosine phosphorylated and associated with the receptor proteins. The receptor association and tyrosine phosphorylation of PLC-gamma correlated with the ability of these receptors to mediate ligand-induced phosphatidylinositol turnover. However, both the delta Ki and Y825F mutant receptors were deficient in transmitting mitogenic signals, suggesting that the PDGF-induced tyrosine phosphorylation and receptor association of PLC-gamma are not sufficient to account for the growth-stimulatory activity of PDGF. Wild-type and delta Ki mutant PDGF receptor proteins expressed with recombinant baculovirus vectors also associated in vitro with mammalian PLC-gamma. However, baculovirus-expressed c-fms, v-fms, c-src, and Raf-1 proteins failed to associate with PLC-gamma under similar conditions. Phosphatase treatment of the baculovirus-expressed PDGF receptor greatly decreased its association with PLC-gamma. This requirement for receptor phosphorylation was also observed in vivo, where PLC-gamma could not associate with a mutant PDGF receptor (K602A) defective in autophosphorylation. PLC-gamma also coimmunoprecipitated with two other putative receptor substrates, the serine-threonine kinase Raf-1 and the 85-kilodalton phosphatidylinositol-3' kinase, presumably through its association with the ligand-activated receptor. Furthermore, baculovirus-expressed Raf-1 phosphorylated purified PLC-gamma in vitro at sites which showed increased serine phosphorylation in vivo in response to PDGF. These results suggest that PDGF directly influences PLC activity by inducing the association of PLC-gamma with a receptor signaling complex, resulting in increased tyrosine and serine phosphorylation of PLC-gamma.

Cellular crosstalk mediated by platelet-derived growth factor BB and transforming growth factor β during hepatic injury activates hepatic stellate cells

2018 ◽  
Vol 96 (8) ◽  
pp. 728-741 ◽  
Author(s):  
Sowmya Mekala ◽  
SubbaRao V. Tulimilli ◽  
Ramasatyaveni Geesala ◽  
Kanakaraju Manupati ◽  
Neha R. Dhoke ◽  
...  
Keyword(s):  
Growth Factor ◽  
Hepatic Stellate Cells ◽  
Hepg2 Cells ◽  
Molecular Mechanisms ◽  
Transforming Growth Factor ◽  
Stellate Cells ◽  
Transforming Growth Factor Β ◽  
Platelet Derived Growth Factor ◽  
Hepatic Tissue

Apoptotic hepatocytes release factors that activate hepatic stellate cells (HSCs), thereby inducing hepatic fibrosis. In the present study, in vivo and in vitro injury models were established using acetaminophen, ethanol, carbon tetrachloride, or thioacetamide. Histology of hepatotoxicant-induced diseased hepatic tissue correlated with differential expression of fibrosis-related genes. A marked increase in co-staining of transforming growth factor β receptor type II (TGFRIIβ) – desmin or α-smooth muscle actin – platelet-derived growth factor receptor β (PDGFRβ), markers of activated HSCs, in liver sections of these hepatotoxicant-treated mice also depicted an increase in Annexin V – cytokeratin expressing hepatocytes. To understand the molecular mechanisms of disease pathology, in vitro experiments were designed using the conditioned medium (CM) of hepatotoxicant-treated HepG2 cells supplemented to HSCs. A significant increase in HSC proliferation, migration, and expression of fibrosis-related genes and protein was observed, thereby suggesting the characteristics of an activated phenotype. Treating HepG2 cells with hepatotoxicants resulted in a significant increase in mRNA expression of platelet-derived growth factor BB (PDGF-BB) and transforming growth factor β (TGFβ). CM supplemented to HSCs resulted in increased phosphorylation of PDGFRβ and TGFRIIβ along with its downstream effectors, extracellular signal-related kinase 1/2 and focal adhesion kinase. Neutralizing antibodies against PDGF-BB and TGFβ effectively perturbed the hepatotoxicant-treated HepG2 cell CM-induced activation of HSCs. This study suggests PDGF-BB and TGFβ as potential molecular targets for developing anti-fibrotic therapeutics.

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