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Biomedical subjects

K Resch

Publications and source records attributed to K Resch.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1988

Activation of glomerular mesangial cells by gram-negative bacterial cell wall components.

The cell walls of gram-negative bacteria contain several biologically active components, including lipopolysaccharide (LPS), lipoprotein, and protein 1. The effects of these individual components and a synthetic analog of lipoprotein, TPP, on several activation parameters of glomerular mesangial cells (MC) were examined. Prostaglandin secretion, synthesis of the autogrowth factor, mesangial interleukin-1 (IL-1), and new synthesis of cellular proteins were assessed as markers of MC activation. All bacterial cell wall components evaluated were active in varying degrees as stimulants of prostaglandin secretion. In general, PGE was the predominant product. TPP and protein 1 also induced substantial secretion of thromboxane. Each cell-wall component was effective in stimulating mesangial IL-1 secretion. The activation of MC was associated with the enhanced synthesis of many cellular proteins in addition to IL-1. Stimulation by these bacterial components was dependent on the state of the mesangial cell cycle, because nonproliferating cells did not respond to these factors. Activation of MC by gram-negative bacterial cell wall components, with release of vasoactive prostaglandins and peptide mitogens, may be responsible for some of the glomerular hemodynamic alterations and cellular proliferative events associated with sepsis or chronic bacterial infection.

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

Polyunsaturated fatty acids are enriched in the plasma membranes of mitogen-stimulated T-lymphocytes.

Plasma membranes were purified from T-lymphocytes from rabbit thymus stimulated with concanavalin A. Lipids were extracted and the fatty acid composition of the individual phospholipid species was determined by gas-liquid chromatography. Compared to the plasma membranes derived from control cells, the plasma membranes from mitogen-stimulated cells were enriched in polyunsaturated fatty acids. This increase in unsaturation was found in phosphatidylcholine, phosphatidylinositol and phosphatidylserine, while the fatty acid composition of phosphatidylethanolamine was not significantly altered. The phospholipid composition remained almost unchanged during the period of stimulation. The molar ratio cholesterol to phospholipid was decreased. These changes in the lipid composition of plasma membranes from mitogen-stimulated T-lymphocytes are discussed with regard to functional implications.

Animals↗
PubMed1987

The diacylglycerols dioctanoylglycerol and oleoylacetylglycerol enhance prostaglandin synthesis by inhibition of the lysophosphatide acyltransferase.

Prostanoids are synthesized by resident macrophages upon stimulation with diacylglycerols. Oleoylacetylglycerol and dioctanoylglycerol induced prostaglandin E and thromboxane synthesis in a time- and concentration-dependent manner. Both diacylglycerols inhibited the lysophosphatide acyltransferase, which is the key enzyme in the reacylation of arachidonic acid. By this mechanism the pool of free arachidonic acid available for prostanoid synthesis is increased. Both diacylglycerols were able to inhibit the membrane-bound lysophosphatide acyltransferase by a direct interaction independent of protein kinase C. Thus lysophosphatide acyltransferase could be shown to be a new target of these diacylglycerols, known as activators of protein kinase C.

Acyltransferases↗
PubMed1987

Separation of plasma membrane domains of calf thymocytes by affinity chromatography on ouabain-Sepharose.

Highly purified plasma membranes of calf thymocytes were fractionated by means of affinity chromatography on ouabain-Sepharose. By the method used two subfractions were obtained, one eluting freely from the affinity gel (MF1oua) and a second specifically retained by matrix-bound ouabain (MF2oua), with a total recovery of 95 per cent. Fractionation required the binding of matrix-bound ouabain to its plasma membrane receptor, i.e. (Na+ + K+)-ATPase. Increasing the temperature and binding time did not significantly alter the fractionation of plasma membranes into the two subfractions. Both plasma membrane subfractions separated by ouabain-Sepharose were of plasma membrane origin, as revealed by the identical specific activities of several membrane bound enzymes, gamma-glutamyl transpeptidase, alkaline phosphatase and Mg2+-ATPase in unseparated plasma membranes and in both subfractions, and by the identical amounts of the cytoskeletal protein actin in unseparated plasma membranes and subfractions. The plasma membrane subfractions MF1oua and MF2oua showed different structural and functional properties. In SDS-polyacrylamide gel electrophoresis polypeptides of 170, 150, 110, 94, 39, and 30 kDa were several-fold enriched in the adherent fraction, MF2oua. The phospholipid fatty acid composition of the plasma membrane subfractions proved to be different, as well. MF2oua contained significantly higher amounts of saturated fatty acids as compared to MF1oua. The specific activities of (Na+ + K+)-ATPase, Ca2+-ATPase and lysolecithin acyltransferase were highly enriched in the adherent fraction MF2oua, as compared to MF1oua. The data suggest that by the means of affinity chromatography on ouabain-Sepharose plasma membrane domains of the lymphocyte plasma membrane can be isolated, most probably implicated in the initiation of lymphocyte activation.

Animals↗
PubMed1987

Phospholipid-metabolism of a stimulated murine T cell clone.

The release of IP3 and the incorporation of arachidonic acid into phospholipids was measured in a stimulated murine alloantigen-specific, non-cytolytic T cell clone. While Concanavalin A provoked a sharp increase in IP3, Interleukin 2 had no effect on the production of IP3. An increased reacylation of phospholipids with arachidonic acid was seen within the first 4 hours after addition of Concanavalin A, while an effect upon Interleukin 2 was only observed after 8 hours of incubation with Interleukin 2. A similar retarded response to Interleukin 2 was observed in proliferation experiments. These retarded cell responses may be due to changed properties of IL 2 receptors induced by IL 2.

Animals↗
PubMed1987

Activation of glomerular mesangial cells by the terminal membrane attack complex of complement.

Treatment of cultured renal glomerular mesangial cells (MC) with nonlytic concentrations of the purified components (C5b-9) of the terminal membrane attack complex (MAC) of complement induced significant functional alterations characteristic of cellular activation. C5b-9-treated MC released large quantities of primarily vasodilatory prostaglandins. In addition, the secretion of an MC-derived auto-growth factor (MC interleukin 1) was greatly enhanced. Examination of the action of C5b-9 on MC phospholipid metabolism indicated that complement induced the activation of phospholipases, leading to quantitative changes in the fatty acid profile of MC membrane phospholipids. These findings demonstrate that cultured MC are highly responsive to nonlytic concentrations of the C5b-9 complex, and suggest that the mesangial deposition of the MAC in many forms of glomerular disease, with resultant cellular activation, may play a major role in the hemodynamic and cellular proliferative events characteristic of these disorders.

Animals↗
PubMed1987

The immunosuppressive activities of different cyclosporins are correlated to inhibition of the early membrane phospholipid metabolism in activated lymphocytes.

Recently, it could be shown that Cyclosporin A (CsA) inhibited the activation of T and B lymphocytes by interfering with an early step of the activation, namely the stimulation of the plasma membrane-bound lysophosphatide acyltransferase. In this report, we compared three CsA-derivatives, Dihydro-Cyclosporin C (Dihydro-CsC), "C9-O-Acetyl"-CsA (CsAAC), Cyclosporin H (CsH), regarding the inhibition of proliferation and the interference with the activation of the phospholipid metabolism. At concentrations below 1 microgram/ml, CsAAC and CsH had no effect on any parameter measured. Dihydro-CsC, however, closely resembled CsA: it inhibited the induction of DNA- and RNA-synthesis in T and B lymphocytes from mesenteric lymph nodes of rabbits. Similar to CsA, Dihydro-CsC also interfered with the enhanced incorporation of arachidonic acid into plasma membrane phospholipids by inhibiting the activation of the lysophosphatide acyltransferase. The close correlation between inhibition of proliferation and interferences with the phospholipid metabolism of the plasma membrane suggested that Dihydro-CsC as well as CsA interfered with an early step of lymphocyte activation at the level of the plasma membrane.

1-Acylglycerophosphocholine O-Acyltransferase↗