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E Fitzke

Publications and source records attributed to E Fitzke.

31 records · Page 2Linked to original sources
PubMed1992

Protein kinase C involved in zymosan-induced release of arachidonic acid and superoxide but not in calcium ionophore-elicited arachidonic acid release or formation of prostaglandin E2 from added arachidonate.

Zymosan and phorbol ester induced in liver macrophages the release of arachidonic acid, prostaglandin E2, and superoxide; the calcium ionophore A 23187 elicited a release of arachidonic acid and prostaglandin E2 but not of superoxide, and exogenously added arachidonic acid led to the formation of prostaglandin E2 only. The zymosan- and phorbol-ester-induced release of arachidonic acid, prostaglandin E2, and superoxide was dose-dependently inhibited by staurosporine and K252a, two inhibitors of protein kinase C, and by pretreatment of the cells with phorbol ester which desensitized protein kinase C. The release of arachidonic acid or prostaglandin E2 following the addition of A 23187 or arachidonic acid was not affected by these treatments. Zymosan and phorbol ester but not A 23187 or arachidonic acid induced a translocation of protein kinase C from the cytosol to membranes in intact cells. These results demonstrate an involvement of protein kinase C in the zymosan- and phorbol-ester-induced release of arachidonic acid, prostaglandin E2, and superoxide; the release of arachidonic acid and prostaglandin E2 elicited by A 23187 and the formation of prostaglandin E2 from exogenously added arachidonic acid, however, is independent of an activation of protein kinase C.

Alkaloids↗
PubMed1992

Human serum gangliosides in hypercholesterolemia, before and after extracorporeal elimination of LDL.

Total content, pattern and transport by lipoproteins of gangliosides have been studied in the sera of 10 patients with hypercholesterolemia and manifest cardiovascular disease. Half of the patients with hypercholesterolemia and 3 healthy controls were treated with heparin-induced extracorporeal LDL precipitation (HELP). In the sera of the untreated group total gangliosides and cholesterol were elevated about 2-fold. Ratios of normal ganglioside components were not altered and abnormal ganglioside species not detected. Treatment with HELP resulted in an almost selective removal of lipid-bound sialic acid carried on LDL. The re-increase of total serum gangliosides was strictly correlated to that of LDL-cholesterol and apolipoprotein B. Total gangliosides and ratios of individual components carried on single LDL- and HDL-particles were not altered by the HELP treatment. Our results indicate that gangliosides are excreted into the serum along with nascent apolipoprotein B-containing lipoproteins, which are of hepatic origin. In hypercholesterolemia excretion of gangliosides into the circulation is elevated and surplus of circulating gangliosides is bound to increased numbers of 'atherogenic' LDL. Biosynthesis of different ganglioside components, most probably by the liver, and total amount of gangliosides bound to lipoprotein particles seem not to be altered.

Adult↗
PubMed1991

RO 31-8220 and RO 31-7549 show improved selectivity for protein kinase C over staurosporine in macrophages.

Two new potent protein kinase C inhibitors, RO 31-8220 and RO 31-7549, and staurosporine were found to inhibit dose-dependently the phorbol ester-induced formation of prostaglandin E2 and superoxide in cultured liver macrophages. Prostaglandin E2 formation from exogenously added arachidonate was not affected by these compounds. The zymosan-induced formation of inositol phosphates was decreased by simultaneous addition of phorbol ester and was enhanced by prior desensitization of protein kinase C indicating that protein kinase C negatively modulates phospholipase C activation in these cells. While staurosporine suppressed almost totally the zymosan-induced formation of inositol RO 31-8220 and RO 31-7549 inhibited the protein kinase C-mediated effect on inositol phosphate formation, only. Phagocytosis of zymosan was not affected by RO 31-8220 and RO 31-7549 but was decreased by staurosporine. These results demonstrate that two new potent protein kinase C inhibitors, RO 31-8220 and RO 31-7549, are more selective in their actions as staurosporine and are useful tools to determine an involvement of protein kinase C in cellular systems.

Alkaloids↗
PubMed1991

Glucocorticoids inhibit formation of inositol phosphates in macrophages.

Glucocorticoids inhibited the zymosan-induced formation of inositol phosphates in macrophages. No inhibition was observed with progesterone. Inhibitors of protein (cycloheximide) and RNA (actinomycin D) synthesis exhibited similar inhibitory effects. The activity of phospholipase C in subcellular fractions was not altered by hormone treatment of the cells. However, the incorporation of inositol into membrane lipids was reduced by dexamethasone. These data indicate that glucocorticoids are able to inhibit the formation of inositol phosphates; the effect of the hormone is rather due to an inhibition of the incorporation of inositol in membrane lipids than to an inhibition of phospholipase C. The anti-inflammatory action of glucocorticoids may, therefore, also be attributed to their effect on the polyphosphoinositide cycle and inositol phosphate-mediated processes.

Animals↗
PubMed1991

Altered biosynthesis of gangliosides in developing biliary cirrhosis in the rat.

The biosynthesis of gangliosides was studied in developing biliary cirrhosis in rats 14, 28, and 42 days after bile duct obstruction. The total content and patterns of gangliosides in livers and sera, and the activity of six hepatic ganglioside synthases in a cell-free system were determined. Up to 7-fold increased synthase activities were strictly correlated in time and extent with increased total contents of gangliosides in liver and serum. In addition, altered patterns of serum gangliosides were observed. The results clearly demonstrate that the liver is the main source of elevated serum gangliosides in biliary cirrhosis in the rat. Increased hepatic biosynthesis and the secretion of gangliosides into the serum appear to be an important pathogenetic event. Alterations of hepatic enzyme activities indicate that GL2 and GM3 synthase regulate total hepatic ganglioside content. However, certain abnormalities in ganglioside patterns which were observed in the liver and sera of cirrhotic animals can not be explained by changes in hepatic enzyme activity. They indicate additional pathobiochemical mechanisms to be involved, e.g., altered hepatocellular processing and/or impaired secretion into bile.

Animals↗
PubMed1991

Activation of phospholipase C is not correlated to the formation of prostaglandins and superoxide in cultured rat liver macrophages.

This study evaluates the role of inositol phosphates as possible mediators of the activation of phospholipase A2 and NADPH oxidase in cultured rat liver macrophages. Inositol phosphate formation was achieved by zymosan, immune complexes, latex particles and calcium ionophore while the release of arachidonic acid and the formation of prostaglandin E2 was also elicited by phorbol ester and NaF, but not by latex particles; generation of superoxide was obtained by zymosan and phorbol ester only. The kinetics of the formation of inositol phosphates revealed that within the first few minutes after zymosan addition inositol trisphosphate was formed, followed by inositol bisphosphate and inositol monophosphate. Pre-treatment of the cells with dexamethasone or removal of extracellular calcium led to an inhibition of the zymosan-induced formation of inositol phosphates and prostaglandin E2 but had no effect on the generation of superoxide; inhibition of the Na+/H+ exchanger by removal of extracellular sodium ions led to a decrease of the zymosan-induced synthesis of prostaglandin E2, but did not affect the formation of inositol phosphates and superoxide. Pre-treatment of the cells with phorbol ester decreased the zymosan-induced synthesis of prostaglandin E2 and superoxide, but even enhanced the zymosan-induced formation of inositol phosphates. These data indicate that in cultured rat liver macrophages the formation of prostaglandins and superoxide cannot be correlated to an activation of phospholipase C.

Animals↗
PubMed1991

Effect of long-chain alkylamines on arachidonate metabolism in macrophages.

The two long-chain alkylamines RO 31-4493 and RO 31-4639 inhibit in a concentration-dependent manner the zymosan-induced release of arachidonic acid, the conversion of arachidonic acid into thromboxane, prostaglandin E2 and D2 and the uptake and incorporation of exogenously added arachidonate into membrane lipids of liver macrophages. The generation of superoxide and the formation of inositol phosphates is not influenced by both agents. These results suggest a rather specific interaction of RO 31-4493 and RO 31-4639 with enzymes involved in the cellular metabolism of arachidonic acid.

Amines↗
PubMed1990

Ganglioside biosynthesis in rat liver: different distribution of ganglioside synthases in hepatocytes, Kupffer cells, and sinusoidal endothelial cells.

The activities of five glycolipid-glycosyltransferases, GL2, GM3, GM2, GM1, and GD1a synthase, were determined in a cell-free system with homogenate protein of total rat liver, isolated hepatocytes, Kupffer cells, and sinusoidal endothelial cells. In rat liver parenchymal and nonparenchymal cells ganglioside synthases were distributed differently. Compared to hepatocytes, Kupffer cells expressed a nearly sevenfold greater activity of GM3 synthase, but only 14% of GM2, 19% of GM1, and 67% of GD1a synthase activity. Sinusoidal endothelial cells expressed a pattern of enzyme activities quite similar to that of Kupffer cells with the exception of higher GM2 synthase activity. Activity of GL2 synthase was distributed unifromly in parenchymal and nonparenchymal cells of rat liver, but differed by sex. It was 1 to 2 orders of magnitude below that of all the other ganglioside synthases investigated. The results indicate GL2 synthase regulates the total hepatic ganglioside content, and hepatocytes but not nonparenchymal liver cells have high enzymatic capacities to form a-series gangliosides more complex than GM3.

Animals↗
PubMed1990

Altered concentrations, patterns and distribution in lipoproteins of serum gangliosides in liver diseases of different etiologies.

Concentrations, patterns and distribution in different lipoprotein classes of human serum gangliosides were investigated in acute and chronic liver diseases of different etiologies. The total concentrations of gangliosides were moderately elevated in sera of patients with cirrhosis and acute B or NANB virus hepatitis, but almost 3-fold in those with severe cholestasis. Up to three unknown gangliosides appeared in the sera of six out of nine patients with alcoholic cirrhosis. They accounted for 11-27% of total serum gangliosides. In acute viral hepatitis very small amounts of these gangliosides were inconsistently detected. In severe cholestasis (bilirubin greater than 10 mg/dl) the distribution of serum gangliosides was altered in different lipoprotein classes including lipoprotein X (LP(x)). The results indicate that the liver produces serum gangliosides. The diseased liver is supposed to affect the total concentration, pattern and distribution of serum gangliosides in different lipoprotein classes as a result of at least two different pathogenetic events: the qualitative and quantitative alterations of their biosynthesis and secretion into the circulation (cirrhosis); and the alteration of lipoprotein metabolism following cholestasis.

Acute Disease↗
PubMed1989

Gangliosides in normal human serum. Concentration, pattern and transport by lipoproteins.

The total content and pattern of gangliosides were determined in the unfractionated sera of 11 healthy human adults and in isolated lipoproteins. The total content of lipid-bound sialic acid was 10.5 +/- 3.2 nmol/ml serum. The ganglioside profile consisted of more than ten different components. The major ganglioside was GM3, followed by GD3, GD1a, GM2, GT1b, MG-3 (sialosyllactoneotetraosylceramide), GD1b and GQ1b. Traces of four additional gangliosides could not be quantified reliably. Ganglioside patterns did not vary in sera taken from healthy adults of different age and sex. Approximately 98% of human serum gangliosides were transported by serum lipoproteins, predominantly by LDL (66%), followed by HDL (25%) and VLDL (7%). The quantitative distribution of individual gangliosides in VLDL and LDL was almost the same as that in the unfractionated serum; some differences existed with the ganglioside profile in HDL.

Adult↗
PubMed1981

Some properties of a new electrogenic transport system: the ammonium (methylammonium) carrier from Clostridium pasteurianum.

Clostridium pasteurianum is able to build up about 100-fold gradients of methylammonium across the cell membrane. Methylammonium enters the cell by means of a carrier as shown by the energy requirement, saturation kinetics and a pH profile with a narrow maximum between pH 6.2 and 6.8. The methyl ammonium transport (apparent Km = 150 microM, V = 100 mumol/min per g dry weight) is competitively inhibited by ammonium (apparent Ki = 9 microM). The low Ki value and the observation that methylammonium cannot serve as a carbon or nitrogen source for Cl. pasteurianum strongly indicate that ammonium rather than methylammonium is the natural substrate. Uncouplers and inhibitors of energy metabolism or of the membrane-bound ATPase inhibit transport. Cl. pasteurianum maintains a membrane potential (interior negative) in the range 80-130 mV. This membrane potential was identified as the energy source: the same agents that block transport also decrease the membrane potential, and artificial generation of a membrane potential (by addition of valinomycin to K+-loaded cells) induces concentrative uptake of methylammonium. Thus NH4+ (or CH3NH3+) must be the transported species. Digestion of the cell wall by lysozyme does not abolish the transport activity.

Biological Transport, Active↗
PubMedDate not supplied

Different regulation of the formation of intra- and extracellular oxygen radicals in macrophages.

The formation and accumulation of reactive oxygen species within liver macrophages and their release into the medium were determined by lucigenin-enhanced chemiluminescence, the reduction of cytochrome c, the formation of formazan from nitroblue tetrazolium and the fluorescence of 5- (and 6)-carboxy-2',7'-dichlorodihydrofluorescein. Zymosan, phorbol ester and fluoride induced the formation and accumulation of oxygen radicals intra- and extracellularly, ionomycin and lipopolysaccharide led to an intracellular accumulation of oxygen radicals, while after arachidonic acid and tumor necrosis factor-alpha, no reactive oxygen species were formed. While zymosan and phorbol ester predominantly induced the formation and release of superoxide, hydroperoxide was the main form released by fluoride. These results indicate that agents of different biological potencies induce reactive oxygen species within and/or outside liver macrophages and that different techniques must be used to detect different oxygen species within and outside cells.

Arachidonic Acid↗