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Biomedical subjects

K Resch

Publications and source records attributed to K Resch.

At least 109 records · Page 6Linked to original sources
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↗
PubMed1989

TPA-induced differentiation and adhesion of U937 cells: changes in ultrastructure, cytoskeletal organization and expression of cell surface antigens.

Incubation of the human promonocytic cell line U937 with 12-O-tetradecanoylphorbol-13-acetate (TPA) for 72 h resulted in differentiation into immature macrophage-like cells and was accompanied by marked morphological and functional changes. U937 cells which normally grow in suspension and show a smooth surface, extended pseudopodia and became adherent to each other and to the surface of the culture vessel. Concomitant with the TPA-induced adherence U937 cells ceased to proliferate. Our results show that phorbol ester-treated U937 cells exhibited markedly increased levels of fibronectin and of the cytoskeletal proteins actin, myosin and vimentin including a reorganization of actin and vimentin filaments. The induction of both cellular adherence and growth inhibition were accompanied by a significantly reduced level of cells expressing transferrin receptors and changes in cell surface antigen expression. Here, the expression of the leukocytefunction antigens (LFA-1), including CD11 and CD18 was markedly enhanced during phorbol ester-induced differentiation. TPA-treatment, however, failed to enhance the small amount of U937 cells expressing the monocyte/macrophage-specific CD14 antigen or expressing MHC class-II antigens. A detailed analysis of the CD14 cluster by 7 differential antibodies resulted in an induction of TM1, UCHM1, MEM15, My4, and 3C10, whereas the epitopes recognized by TM2 and Mo2 remained unaltered. Neither indomethacin nor interferon-gamma were capable of inducing a marked expression of these antigen epitopes in TPA-treated cells. Although these data demonstrate that during phorbol ester-induced differentiation U937 cells acquire many properties typically associated with macrophages, the failure to express marked levels of macrophage-specific cell surface antigens suggests a transition of U937 cells from a promonocytic to an immature macrophage intermediate state rather than into mature macrophage-like cells.

Antigens, Surface↗
PubMed1988

Phospholipase C in rabbit thymocytes: subcellular distribution and influences of calcium and GTP gamma S on the substrate dependence of cytosolic and plasma membrane-associated phospholipase C.

The subcellular distribution of phospholipase C (PLC) activity in rabbit thymocytes was examined by measuring the enzyme's activity in different subcellular fractions. PLC activity was determined using exogenously added [3H]PIP2 as substrate. Approx. 80% of the activity of the cell homogenate was found in the cytosolic fraction. A minor portion of PLC activity was attached to the particulate fraction. This membrane-associated PLC activity was found to be predominantly bound to the plasma membrane. Both PIP2-cleaving PLCs (the PLC associated with the plasma membrane and the PLC in the cytosol) exhibited maximum activity at pH 5. GTP gamma S stimulated the cytosolic and the membrane-bound PLC. As revealed by computer analysis of the substrate dependence of both basal and GTP gamma S-stimulated PLC activity, GTP gamma S enhanced the Vmax of the enzymes. Calcium, at a concentration of 1 mM, decreased PLC activity, as compared to a calcium concentration of 100 nM. The characteristic increase in Vmax induced by GTP gamma S was observed at a concentration of 1 mM calcium and was similar to that at 100 nM. These data suggest that the stimulatory effect of GTP gamma S is not due to an increased affinity of PLCs to calcium.

Animals↗
PubMed1988

Zinc increases the affinity of phorbol ester receptor in T lymphocytes.

In the primary structure of the major phorbol ester receptor, protein kinase C the presence of putative metal (zinc) binding sites has been suggested. We have demonstrated earlier that zinc activates protein kinase C and contributes to its binding to plasma membranes in T lymphocytes. Here we report that zinc increases the phorbol ester binding affinity of cytosolic protein kinase C. The effect of zinc on the membrane-bound enzyme is much less pronounced. Our results raise the possibility that cytosolic protein kinase C is a mixture of isoenzymes with different sensitivity towards zinc ions.

Animals↗
PubMed1988

Zinc can increase the activity of protein kinase C and contributes to its binding to plasma membranes in T lymphocytes.

In the primary structure of protein kinase C, the presence of a putative metal-binding site has been suggested (Parker, P.J., Coussens, L., Totty, N., Rhee, L., Young, S., Chen, E., Stabel, S., Waterfield, M.D., and Ullrich, A. (1986) Science 233, 853-859). In the present report, we demonstrate that the most abundant intracellular heavy metal, zinc, can increase the activity of cytosolic protein kinase C. Zinc reversibly binds the enzyme to plasma membranes, and it may contribute to the calcium-induced binding as well. The intracellular heavy metal chelator N,N,N',N'-tetrakis(2-pyridylmethyl) ethylenediamine prevents the phorbol ester- and antigen-induced translocation of protein kinase C. This effect can be totally reversed by the concomitant addition of Zn2+, while Fe2+ and Mn2+ are only partially counteractive. Our results suggest that zinc can activate protein kinase C and contributes to its binding to plasma membranes in T lymphocytes induced by Ca2+, phorbol ester, or antigen.

Animals↗
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

Two-chain structure of the interleukin 1 receptor.

By crosslinking radioiodinated recombinant human IL1 alpha to mouse EL4 thymoma cells we have identified in addition to the known IL1-binding proteins of 80 kDa, a second IL1-binding protein of about 40 kDa. This second binding protein could be demonstrated most easily when crosslinking to higher protein complexes was inhibited. This finding suggests that the IL1 receptor, similar to the receptor for other cytokines such as interleukin 2, is composed of a heterodimer, of which both polypeptides contribute to ligand binding.

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

Induction of responsiveness to IL 2 in Con A-stimulated rat lymphoid cells requires synergistic action of IL 1 and the accessory cell membrane.

Rat spleen or lymph node cells stimulated with Con A and cultured at a low density of 1 x 10(5) cells per ml proliferated in response to IL 2-containing supernatants and thus expressed receptors for IL 2. Cells depleted of accessory cells either by passage over a glassbead-column or by treatment with the lysosomotropic agent leucine methyl ester (Leu-OMe) did not proliferate in response to IL 2-containing supernatants. The diminished proliferative response after adherent cell depletion could be reconstituted by the addition of peritoneal exudate cells (PEC). Reconstitution could also be achieved by synergistic action of IL 1 and paraformaldehyde-fixed peritoneal exudate cells, indicating an important role for the accessory cell membrane in the induction of IL 2-mediated proliferation.

Animals↗
PubMed1988

Interleukin 1 and the glomerular mesangium. III. IL-1-dependent stimulation of mesangial cell protein kinase activity.

Interleukin 1 (IL-1) exerts a number of biologic actions upon cultured glomerular mesangial cells (MC). These include stimulation of cellular proliferation and induction of prostaglandin and type IV collagenase secretion. It was determined that this activity, as with other polypeptide growth factors, was associated with the activation of specific MC plasma membrane protein kinases. Plasma membranes from cycling MC were incubated with purified IL-1 and (32P) ATP in the absence of calcium and cyclic nucleotides. Macrophage IL-1 stimulated the rapid phosphorylation of several plasma membrane proteins, the most significant of which were 52-55 kd, 46 kd, and 20 kd in size. Macrophage IL-1 induced specific membrane phosphorylation in concentrations as low as 1.5 x 10(-12) M, an effect obtained with equivalent concentrations of purified MC IL-1. The 46 kd phosphoprotein, which was the most prominent, was alkali-resistant and contained phosphotyrosine when examined by phosphoamino acid analysis. The 52-55 kd and 20 kd phosphoproteins were alkali-labile and contained phosphoserine. The 46 kd phosphoprotein was the major phosphoprotein recovered from Con A-Sepharose and IL-1 affinity columns. Induction of plasma membrane-associated protein kinase activity may represent one mechanism whereby IL-1 initiates mesangial cellular activation.

Animals↗
PubMed1988

Influence of blood volume on cerebrospinal fluid levels of arachidonic acid metabolites after subarachnoid hemorrhage: experimental study on the pathogenesis of cerebral vasospasm.

Based on accumulating data indicating the important role of arachidonic acid metabolites in the pathogenesis of cerebral vasospasm, we examined the influence of alterations in blood volume on the cerebrospinal fluid (CSF) level of the subarachnoid hemorrhage (SAH). Three separate injections of autologous blood into the cisterna magna of dogs within subarachnoid hemorrhage (SAH). Three separate injections of autologous blood into the cisterna magna of dogs within 72 hours were performed. Three experimental groups were formed, with an overall injected blood volume of 6, 9, and 12 ml. Arterial spasm was verified by comparison of the angiographic diameter of the basilar artery on Day 8 vs. Day 1. Additionally, light microscopic, scanning and transmission electron microscopic, and freeze cracking technique examinations of the basilar artery demonstrated the typical morphological features of proliferative vasculopathy. Increasing the volume of experimental SAH led to a linear decrease of the mean vessel diameter from 45% to 53% and finally to 75% of normal. Parallel to the reduction of angiographic vessel lumen, a volume-dependent significant increase of all three eicosanoids was demonstrated. A deficiency of prostacyclin concentration during the course of the experiment was not observed. Despite highly elevated CSF levels of vasodilating prostacyclin, however, severe angiographic constriction of the basilar artery occurred in the presence of high concentrations of TXA2 and PGE2. It is concluded that increasing volumes of SAH led to a concomitant release of arachidonic acid metabolites during posthemorrhagic clot lysis. From our data, it seems questionable whether a prostacyclin deficiency is an important underlying factor for the development of cerebral spasm.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗