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V Kaever

Publications and source records attributed to V Kaever.

At least 55 records · Page 3Linked to original sources
PubMed1990

Monokines and platelet-derived growth factor modulate prostanoid production in growth arrested, human mesangial cells.

Previous studies have demonstrated considerable prostanoid production by cultured proliferating rat mesangial cells (MC). In this study, human mesangial cells (HMC) were examined during serum-free culture in which the cells were reversibly growth arrested and did not suffer obvious irreversible functional changes. Non-stimulated cells released 2 to 10 pg/24 hr/micrograms cellular protein of PGE2, PGF2 alpha, 6-keto-PGF1 alpha, while TXB2 was not detectable. Stimulation with interleukin-1 beta (IL-1 beta) or tumor necrosis factor alpha (TNF alpha) induced up to 18-fold (IL-1 beta) or up to fourfold (TNF alpha) increases of prostanoid release. Combinations of the two monokines resulted in significant synergistic induction of PGE2 and 6-keto-PGF1 alpha up to 38 times that of control cells. Interleukin-6 (IL-6) and the HMC-mitogen, platelet-derived growth factor-BB (PDGF-BB) only induced marginal increases in HMC prostanoid generation. However, when PDGF-BB or -AB was combined with IL-1 beta or IL-6, prostanoid generation by HMC was synergistically increased up to 222-fold (IL-1 beta) or 12-fold (IL-6) above the control values, with the induction of PGE2 greater than 6-keto-PGF1 alpha greater than PGF2 alpha much greater than TXB2. In the case of IL-1 beta + PDGF-BB the induction of PGE2 release was at least partly due to the synergistic induction of cyclooxygenase activity. These findings demonstrate that both proliferating and reversibly growth arrested HMCs release prostaglandins in response to various inflammatory stimulators and combinations thereof. The findings support the important role of HMC in the regulation of glomerular hemodynamics during inflammatory processes.

Cell Division↗
PubMed1989

Prostaglandin E2 production is synergistically increased in cultured human glomerular mesangial cells by combinations of IL-1 and tumor necrosis factor-alpha 1.

Both IL-1 alpha and IL-1 beta and TNF-alpha induced a time- and dose-dependent release of authentic PGE2 from cultured human glomerular mesangial cells (HMC). This release became significant only after a 4- to 6-h lag phase, and was abolished by inhibition of protein synthesis, and was not related to cell proliferation. Combinations of IL-1 and TNF-alpha when added simultaneously to HMC resulted in a dose-dependent synergistic increase in PGE2 production. These stimulatory effects were specifically inhibited by anticytokine antibodies and the synergistic effect required the simultaneous presence of both IL-1 and TNF-alpha. Arachidonic acid (AA) release experiments and measurement of cyclooxygenase activity, revealed that while both were increased by IL-1 beta and TNF-alpha alone (IL-1 beta greater than TNF-alpha), combinations of IL-1 beta and TNF-alpha resulted in only additive increases in AA release and cyclooxygenase activity. Taken together, these data suggest that stimulation of PGE2 in HMC, by combinations of these cytokines, is not rate limited by AA release or cyclooxygenase activation, but may be related to the induction of the distal enzymes controlling specific PG synthesis.

Adult↗
PubMed1989

Regulation of prostaglandin synthesis by protein kinase C in mouse peritoneal macrophages.

Resident mouse peritoneal macrophages synthesized and released prostaglandins (PGs) when challenged with 12-O-tetradecanoylphorbol 13-acetate (TPA) or 1,2-dioctanoyl-sn-glycerol (DiC8). Both stimuli were found to activate Ca2+/phospholipid-dependent protein kinase C (PKC). 1-(5-Isoquinolinesulphonyl)-2-methylpiperazine ('H-7') and D-sphingosine, known to inhibit PKC by different mechanisms, were able to decrease the PKC activity of macrophages in a dose-dependent manner. Addition of either PKC inhibitor decreased PG synthesis and also the release of arachidonic acid (AA) from phospholipids induced by TPA or DiC8. Simultaneously TPA or DiC8 also decreased incorporation of free AA into membrane phospholipids of macrophages. AA incorporation could be restored, however, by pretreatment with the PKC inhibitors. Our results demonstrate an involvement of PKC in the regulation of PG synthesis in mouse peritoneal macrophages and provide further evidence that reacylation of released fatty acids may be an important regulatory step.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1989

Cholera toxin modulates the T cell antigen receptor/CD3 complex but not the CD2 molecule and inhibits signaling via both receptor structures in the human T cell lymphoma Jurkat.

The human T cell lymphoma Jurkat can be activated by stimuli directed either against the T cell antigen receptor-CD3 antigen complex (TcR/CD3) or the CD2 molecule. Stimulation of cells via the TcR/CD3-complex or via the CD2 molecule increases inositol phosphates and cytoplasmic free calcium. Pretreatment of Jurkat cells with cholera toxin leads to a decrease of TcR/CD3 expression on the surface of the cells, while the expression of CD2 is unaffected. In contrast to this distinct effect on the receptor expression, signaling via both pathways is inhibited by cholera toxin. The most convincing explanation for the cholera toxin-mediated inhibition of signaling is that cholera toxin interrupts the signaling pathways at a point where both, stimulation via TcR/CD3 and via CD2, use the same route. The earliest common point of the two signaling pathways, at least in the Jurkat cell line, seems to be the CD3 complex because after its down-regulation (and functional inactivation) both pathways of activation are interrupted.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1989

Differential effect of dexamethasone on the regulation of phospholipase A2 and prostanoid synthesis in undifferentiated and phorbolester-differentiated U937 cells.

The human undifferentiated histiocytic cell-line U937 can be induced to differentiate by incubation with 12-0-tetradecanoylphorbol-13-acetate (TPA) into macrophage-like cells. Dexamethasone reduced the prostaglandin production in TPA-differentiated U937 cells dose dependently, whereas undifferentiated U937 cells were dexamethasone insensitive. Concomitantly phospholipase A2, the enzyme liberating the prostaglandin precursor arachidonic acid, was inhibited by dexamethasone in TPA-differentiated but not in undifferentiated U937 cells. The activity of lysophosphatide acyltransferase, the key enzyme of fatty acid reacylation into phospholipids, remained unchanged both in undifferentiated and TPA-differentiated U937 cells. The data suggest that responsiveness to glucocorticoid-dependent regulation of prostanoid synthesis is acquired by cells of the monocyte-macrophage lineage late in differentiation.

Acyltransferases↗
PubMed1989

Virus-transformed macrophage-like cell line as tool for eicosanoid research.

The ability of a virus-transformed murine macrophage like cell line HA 38 to produce different eicosanoid metabolites was examined. HA 38 cells release similar amounts of prostaglandins and leukotrienes as did murine peritoneal macrophages in response to both physiological and non-physiological stimuli. Enzyme systems known to be involved in the regulation of eicosanoid synthesis are expressed. HA 38 cells thus are a well defined macrophage model system and are well suited to study eicosanoid synthesis in macrophages and effects of drugs on the prostaglandin and leukotriene synthesis pathways.

Animals↗
PubMed1989

Human monocytes convert leukotriene B4 to two dihydro-leukotriene B4-metabolites.

Human monocytes metabolize LTB4 by an additional pathway different from omega-oxidation. Reverse-phase high performance liquid chromatography showed four metabolites: 20-COOH-LTB4, 20-OH-LTB4 and two metabolites less polar than LTB4 with an UV maximum at 232 nm. Gas-chromatography mass-spectrometry showed nearly identical mass spectra for both metabolites. The main mass fragments of the two metabolites were increased by two mass units compared to LTB4. Our findings suggest that LTB4 had been reduced to a known and a new dihydro-metabolite of LTB4. Both metabolites together amounted to 85% of total metabolites. The remaining 15% were omega-oxidation products. Thus, the major pathway of LTB4 metabolism by human monocytes is reduction to dihydro-LTB4.

Chromatography, High Pressure Liquid↗
PubMed1989

Aluminium fluoride enhances phospholipase A2 activity and eicosanoid synthesis in macrophages.

Eicosanoid synthesis in macrophages is controlled by the availability of free arachidonic acid. Activation of the phospholipase A2 (PLA2) is an important mechanism leading to increased eicosanoid synthesis. In order to obtain further insight into the regulatory mechanisms of eicosanoid release, we incubated macrophages with the protein kinase C (PKC) activator dioctanoylglycerol (DiC8) or aluminium fluoride (AIF4-), a well-described activator of guanine nucleotide binding proteins (G-proteins). Arachidonic acid release, membrane-bound PLA2 activity and prostaglandin production in macrophages were enhanced by both substances in a time-dependent manner. Incubation with the phorbol ester TPA had no effect on the PLA2-activity. AIF4- elevated the cellular diacylglycerol content. The results suggest that activation of PLA2 and successive eicosanoid synthesis by AIF4- is mediated by direct activation of PLA2 by the AIF4(-)-induced generation of diacylglycerol.

Aluminum↗
PubMed1988

Biological properties of dihydro-leukotriene B4, an alternative leukotriene B4 metabolite.

Dihydro-leukotriene B4 (a 5,12-dihydroxy-eicosatrienoic acid) has been shown to be the primary metabolite of leukotriene B4 (LTB4) in a variety of cells other than human polymorphonuclear leukocytes (PMNLs). In this report we show that dihydro-LTB4 is significantly less active than LTB4 in different biological assay systems, i.e. leukocyte chemotaxis, chemokinesis, aggregation, adhesion to endothelium and superoxide anion production. This suggests that primary reduction constitutes a second so far unknown deactivation pathway for LTB4.

Cell Adhesion↗
PubMed1988

Cyclosporin A suppresses proliferation of renal mesangial cells in culture.

Rat glomerular mesangial cells were isolated and grown in culture for a prolonged period of time. The proliferation of these cells was suppressed by the immunosuppressivum Cyclosporin A (CSA) up to 75%, as measured by the incorporation of radiolabeled thymidine. This was dependent on the concentration of CSA used, being in the range of 125-2000 ng/ml. This effect was specific for CSA and other immunosuppressive derivatives thereof, while a non-immunosuppressive cyclosporin was ineffective. Neither the density of the cultures, nor the time of application had any influence on the susceptibility of the cells to CSA. The suppression of MC proliferation was proliferation was reversible after removal of CSA. These studies demonstrate a suppressive effect of Cyclosporin A on the proliferation of non-lymphocytic cells, the glomerular mesangial cells. This observation may help to explain the beneficial results reported with CSA in the treatment of some kidney diseases.

Animals↗
PubMed1988

Enhancement of eicosanoid synthesis in mouse peritoneal macrophages by the organic mercury compound thimerosal.

Availability of the common precursor arachidonic acid represents the fundamental prerequisite of the cellular eicosanoid synthesis. The amount of free arachidonic acid is regulated not only by phospholipases, which liberate this polyunsaturated fatty acid from lipid pools, but also by the reacylating enzyme acylCoA:lysophosphatide acyltransferase. We have previously shown (Goppelt-Strübe, G., C.-F. Körner, G. Hausmann, D. Gemsa, and K. Resch. Control of Prostanoid Synthesis: Role of Reincorporation of Released Precursor Fatty Acids. Prostaglandins 32:373. 1986.) that the organic mercury compound thimerosal in murine peritoneal macrophages inhibits arachidonic acid reincorporation into cellular lipids, thereby leading to an enhanced prostanoid synthesis. In this report we show that the production of leukotriene C4 was also increased after the addition of thimerosal to mouse peritoneal macrophages in a time and dose dependent manner. Concomitantly, thimerosal led to a significant rise of the intracellular calcium concentration as measured by fura-2 fluorescence. Simultaneous addition of thimerosal and indomethacin or exogeneous arachidonic acid to the cells resulted in a synergistic enhancement of leukotriene C4 synthesis. On the other hand, another sulfhydryl group blocking agent, ethacrynic acid, was found to be ineffective in increasing leukotriene C4 levels even in combination with exogeneous arachidonic acid. Thimerosal therefore provides a helpful tool in studying the basic regulatory mechanisms of the cellular leukotriene synthesis.

Animals↗
PubMed1988

Sulfhydryl reagents as model substances for eicosanoid research.

The rate of eicosanoid synthesis is controlled by the availability of free arachidonic acid. Recently we showed that inhibition of reacylation of liberated fatty acids by the sulfhydryl group-blocking agent thimerosal increased prostaglandin as well as leukotriene synthesis. In order to gain further insight into the basic regulatory mechanisms controlling cellular eicosanoid production, the effects of different sulfhydryl reagents on prostaglandin E2 synthesis in the macrophage-like cell line P388D1 were investigated. As these cells exhibit an enormous acyl turnover of cellular phospholipids even under basal conditions, any interference with their fatty acid deacylation-reacylation cycle should lead to a change in intracellular concentrations of the eicosanoid precursor arachidonic acid. Therefore, arachidonic acid release from prelabelled cells as well as arachidonic acid incorporation into different phospholipid species under the influence of mercuric chloride (HgCl2), ethylmercurithiosalicylate (thimerosal), p-hydroxymercuribenzoic acid (PHMB), 0-(3-hydroxymercuri-3-methoxypropyl)carbamoyl-phenoxyacetic acid (mersalyl), N-ethylmaleimide (NEM), and ethacrynic acid were examined. Additionally, direct effects of those substances on corresponding enzyme activities, i.e. phospholipase A2 (PLA2), acyl-CoA synthetase, and lysophospholipid acyltransferase (LAT), on glutathione levels, and on cell viability were estimated. The results demonstrate that the organic mercury compound thimerosal was the most effective in enhancing free arachidonic acid levels, and concomitantly prostaglandin E2 synthesis in P388D1 cells, as result of a rather selective inhibition of the fatty acid reacylating enzyme LAT.

Acyltransferases↗
PubMed1987

A novel metabolic pathway for leukotriene B4 in different cell types: primary reduction of a double bond.

Addition of leukotriene B4 together with trace amounts of tritiated leukotriene B4 to different cell types, such as bone marrow-derived macrophages, T-lymphocytes, mesangial cells or fibroblast tumor cells, led to the formation of several hitherto unknown degradation products within hours. None of them could be identified as 20-hydroxy- or 20-carboxyleukotriene B4, known to be produced by polymorphonuclear leukocytes. The primarily formed transient leukotriene B4 metabolite was less polar than leukotriene B4 and was detectable by measuring its ultraviolet absorbance at 232 nm or its radioactivity. Mass spectral analysis showed very similar fragmentation spectra of leukotriene B4 and its primary metabolite. The most abundant ion and the main fragments of the new metabolite were increased by two mass units compared to leukotriene B4. These observations suggest that, in a variety of cells, leukotriene B4 is first reduced to a 5,12-dihydroxyeicosatrienoic acid, which is further converted to secondary hydrophilic degradation products. This raises the question of the major route of leukotriene B4 metabolism in vivo.

Animals↗
PubMed1987

Arachidonic acid metabolism following aneurysm rupture. Evaluation of cerebrospinal fluid and serum concentration of 6-keto-prostaglandin F1 alpha and thromboxane B2 in patients with subarachnoid hemorrhage.

Experimental investigations have suggested an important role of arachidonic acid metabolites in the genesis of cerebral vasospasm following subarachnoid hemorrhage. In this clinical study the cerebrospinal fluid (CSF) and serum levels of the two main arachidonic acid metabolites prostacyclin and thromboxane A2 are evaluated by measuring their stable degradation products 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and thromboxane B2 (TXB2) using radioimmunoassay methods during the pre- and postoperative course in patients after aneurysm rupture. Although the serum levels of both substances do not seem to be important for the clinical course of the patients, the CSF concentrations of 6-keto-PGF1 alpha and TXB2 provide important data. A close correlation between the initial TXB2 level of the individual patient and the amount of blood in the basal cisterns as detected by computed tomography scan can be demonstrated. The predictive value of this additional information for the occurrence of cerebral angiospasm is discussed. Comparing the CSF levels of both metabolites the slight preoperative elevation of 6-keto-PGF1 alpha is significantly surmounted by an extraordinary rise in TXB2 concentration. Postoperatively, after cleavage of the basal cisterns there is a decline in the CSF levels of both substances. The pre- and postoperative clinical course in comparison to the CSF levels of 6-keto-PGF1 alpha and TXB2 is demonstrated in four patients. A nearly normal course of TXB2 and 6-keto-PGF1 alpha seems to be associated with an uneventful clinical course, whereas a high TXB2 level--whether occurring preoperatively or, even more important, as a secondary postoperative rise--seems to be associated with ischemic complications and neurological deterioration. It is suggested that pre- and postoperative monitoring of CSF levels of 6-keto-PGF1 alpha and especially TXB2 may serve as a possible indicator for the detection of patients at risk of developing cerebral vasospasm.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

Functional domains of the T lymphocyte plasma membrane: characterization of the polypeptide composition.

Highly purified plasma membranes from calf thymocytes were fractionated by affinity chromatography on Concanavalin A-Sepharose into two subfractions, one eluting freely from the affinity column (MF1) and a second being specifically retained (MF2). SDS-polyacrylamide-gel-electrophoresis revealed different polypeptide patterns of the two plasma membrane subfractions. Polypeptides of apparent molecular weights of 170, 150, 110, 94, 39, and 30 kDa were several-fold enriched in the adherent fraction, MF2. In contrast, several proteins in the 55-65 kDa range were preferentially recovered in the non-adherent fraction. Five Five of the six polypeptides, preferentially recovered in MF2 proved to be glycoproteins, the 39 kDa peptide was non-glycosilated. The differences in the amounts of the polypeptides specifically enriched in the adherent fraction MF2 became even more clear-cut when plasma membranes solubilized with non-ionic detergents (lysolecithin, ET-18-2H, Triton-X-100) were separated by affinity chromatography on Concanavalin A-Sepharose. The non-glycosilated peptide of apparent molecular weight of 39 kDa was recovered together with several glycoproteins in the adherent fraction, MF2, suggesting that not single glycoproteins, but plasma membrane domains were separated by Concanavalin A-Sepharose. Although the glycoproteins of the non-adherent fraction MF1 bound significant amounts of Concanavalin A, the major Concanavalin A binding glycoproteins were recovered in the adherent fraction, MF2. The plasma membrane subfractions showed also different functional properties, the specific activities [Na+ + K+]AT-Pase, Ca2+ ATPase and lysolecithin acyltransferase were several-fold enriched in the adherent fraction, MF2, as compared to MF1. The data suggest the existence of plasma membrane domains in the plasma membranes of thymocytes consisting of a different set of proteins, among others the major Concanavalin A binding glycoproteins with some membrane bound enzymes, probably implicated in the initiation of lymphocyte activation.

Animals↗
PubMed1986

A possible role of protein kinase C in regulating prostaglandin synthesis of mouse peritoneal macrophages.

The addition of the analogue of diacylglycerol, 1-oleoyl-2-acetylglycerol (OAG), to resident macrophages isolated from the peritoneal cavity of mice led to a dose and time dependent increase in the synthesis of prostaglandin E. This was likely due to an enhanced amount of arachidonic acid available for eicosanoid synthesis as OAG suppressed the incorporation of arachidonic acid into cellular phospholipids by inhibiting acyl-CoA:lysophosphatide acyltransferase. Since OAG has been shown to activate protein kinase C in various cells, these data lead us to suggest that synthesis of eicosanoids in peritoneal macrophages is mediated by the activation of protein kinase C.

Acyltransferases↗