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M Leist

Publications and source records attributed to M Leist.

83 records · Page 5Linked to original sources
PubMed1995

Concanavalin A-induced T-cell-mediated hepatic injury in mice: the role of tumor necrosis factor.

Concanavalin A activates T lymphocytes in vitro and causes T-cell-dependent hepatic injury in mice. T lymphocytes were previously identified as effector cells of concanavalin A-induced liver injury. Here we report that hepatic injury is characterized by apoptotic cell death. On concanavalin A challenge, the cytokines tumor necrosis factor-alpha (TNF alpha), interleukin-2, granulocyte macrophage-colony stimulating factor, and interferon-gamma were detectable in the circulation of the mice. Pretreatment of mice with anti-mouse TNF-alpha antiserum protected them from concanavalin A-induced liver injury. Nude mice failed to release TNF-alpha or interleukin-2 after concanavalin A challenge and were protected from liver injury. Lymph node cell transfer from responder mice to resistant nude mice resulted in susceptibility of the latter towards concanavalin A, i.e., to induction of cytokine release and hepatotoxicity. These experiments suggest that immunocompetent T cells play a pivotal role in concanavalin A-stimulated TNF-alpha release in vivo. After intravenous administration of fluorescein isothiocyanate-labeled concanavalin A to mice, the most fluorescence was found within the liver. In vitro, concanavalin A stimulation of separate cultures of mouse lymph node cells or nonparenchymal liver cells induced the release of minute amounts of TNF, whereas stimulation of cocultures of these cells resulted in production of substantial amounts of TNF-alpha. These findings may explain the hepatotropic effect of concanavalin A. In conclusion, T-cell-dependent concanavalin A-induced apoptotic liver injury in mice is related to immunological and cytokine-mediated disorders and possibly to autoreactive hepatic processes.

Animals↗
PubMed1995

Tolerance against tumor necrosis factor alpha (TNF)-induced hepatotoxicity in mice: the role of nitric oxide.

D-Galactosamine-sensitized mice challenged with tumor necrosis factor alpha (TNF) developed severe apoptotic and secondary necrotic liver injury as assessed by histology, measurement of cytosolic DNA fragments and determination of liver-specific enzymes in plasma. Pretreatment of mice with interleukin-1 beta (IL-1) resulted in elevated levels of nitrite/nitrate in serum and rendered mice insensitive towards TNF toxicity. Pharmacological doses of the nitric oxide (NO) donor sodium nitroprusside (SNP) also conferred complete protection against TNF toxicity, suggesting a possible link between IL-1- and NO-induced protection. However, NO-synthesis inhibition by NG-monomethyl-L-arginine failed to abrogate IL-1-induced tolerance against TNF toxicity. We conclude that IL-1 and NO protect against TNF-induced liver injury through distinct pathways.

Animals↗
PubMed1995

Novel urinary metabolite of alpha-tocopherol, 2,5,7,8-tetramethyl-2(2'-carboxyethyl)-6-hydroxychroman, as an indicator of an adequate vitamin E supply?

Previously, the metabolism of alpha-tocopherol was considered to involve the opening of the chroman structure because of its oxidation to tocopherylquinone. In contrast, we describe here 2,5,7,8-tetramethyl-2(2'-carboxyethyl)-6-hydroxychroman (alpha-CEHC) as the major urinary metabolite of alpha-tocopherol that appears in human urine after vitamin E supplementation. It is formed directly from alpha-tocopherol without previous oxidative splitting of the chroman ring. The correlation of alpha-tocopherol intake, plasma alpha-tocopherol concentrations, and urinary excretion of alpha-CEHC in human volunteers supplemented with RRR-alpha-tocopherol dosages ranging from 0 to 800 mg/d was examined. HPLC and gas chromatography-mass spectroscopy analysis revealed that alpha-CEHC was only excreted when a plasma threshold of 7-9 mumol alpha-tocopherol/g total lipid was exceeded. This concentration was obtained by a daily intake of approximately 50-150 mg alpha-tocopherol. We suggest that alpha-CEHC excretion indicates a saturated binding capacity of vitamin E in the plasma and thus may be considered to be a marker of optimum vitamin E intake.

Biomarkers↗
PubMed1995

Evidence that the granulocyte-specific antigen NC1 is identical with NA2.

The neutrophil-specific antigen NC1 is defined by an antibody in the serum of a mother who gave birth to a child with alloimmune neonatal neutropenia. NC1 has been reported to be associated with the neutrophil-specific antigen NA2, but the precise relation of NC1 and NA2 remained unclear. Therefore, we investigated the serum using the antigen capture assay MAIGA and the granulocyte (GIFT) and lymphocyte (LIFT) immunofluorescence tests. In GIFT, no NA association was observed. In LIFT, serum antibodies bound preferably to lymphocytes with the HLA antigens HLA-B7 and cross-reacting antigens. In MAIGA, an antibody specific for the NA2 variant of the granulocyte Fc gamma-receptor III was observed. The NA2 specificity was confirmed by testing granulocytes from 40 further different donors. This indicates that the NC1 and NA2 antigens are identical. A positive GIFT result but a negative one in LIFT using cells of an NA2-negative typed individual suggest the presence of an additional, non-NA2-specific granulocyte antibody.

Antibodies, Monoclonal↗
PubMed1995

Interleukin-1 and nitric oxide protect against tumor necrosis factor alpha-induced liver injury through distinct pathways.

Mice sensitized with D-galactosamine (GalN) and challenged with recombinant murine tumor necrosis factor alpha (TNF alpha) developed severe apoptotic and secondary necrotic liver injury as assessed by histology, measurement of cytosolic DNA fragments, and determination of liver specific enzymes in plasma. Pretreatment with recombinant human interleukin-1 beta (IL-1) rendered mice insensitive to this TNF alpha toxicity. Coadministration of the liver-specific transcriptional inhibitor GalN with IL-1 prevented the development of tolerance, implicating de novo synthesis of liver specific proteins in the induction of tolerance. Pretreatment of mice with IL-1 resulted in elevated levels of nitrite/nitrate in serum and in enhanced nitric oxide synthase (NOS) activity in liver cells isolated from these animals. In addition, pharmacological doses of the nitric oxide (NO) donor sodium nitroprusside conferred complete protection against TNF alpha-induced liver injury in galactosamine-sensitized mice, suggesting a possible link between IL-1- and NO-induced protection. However, prevention of NO-synthesis by NG-monomethyl-L-arginine (NMMA) did not abolish IL-1-induced tolerance to TNF alpha in vivo. Cytotoxicity of TNF alpha to isolated hepatocytes sensitized with actinomycin D (ActD) was not significantly altered by inhibition of endogenous nitrite release. Also, enhanced NO production elicited in vitro by glycerol trinitrate or ex vivo by pretreatment with IL-1 had no significant effect in this system. We conclude that IL-1- and NO-induced protection of mice against TNF alpha-mediated liver damage follow distinct pathways.

Animals↗
PubMed1995

Tumor necrosis factor-induced hepatocyte apoptosis precedes liver failure in experimental murine shock models.

We investigated the role of hepatocyte apoptosis in four different murine models of acute inflammatory liver failure. Liver damage induced in D-galactosamine-sensitized mice by endotoxin infection was initiated by processes typical of apoptosis, ie, chromatin condensation, DNA fragmentation, and formation of intracellular apoptotic bodies. DNA was cleaved into oligonucleosomal fragments in the liver before a significant rise of alanine aminotransferase in plasma occurred. Passive immunization against tumor necrosis factor (TNF) completely inhibited the injury caused by endotoxin. Direct injection of recombinant TNF-alpha also caused DNA fragmentation followed by alanine aminotransferase release into the plasma. Pretreatment of mice with interleukin-1 beta, which is known to suppress TNF-induced lethality, completely prevented apoptosis and liver failure in this model. These results demonstrate the causal role of TNF in endotoxin-induced hepatic apoptosis. TNF-inducible hepatocyte apoptosis in vivo was not only observed in D-galactosamine-sensitized mice, but also when the alternative transcriptional inhibitor actinomycin D was used. In mice injected with the TNF-inducing T cell mitogen concanavalin A, hepatic apoptosis was even noticed without requirement of additional sensitizers. We conclude that TNF-induced hepatocyte apoptosis is an early, general, and possibly causal event during experimental liver failure triggered by inflammatory stimuli.

Animals↗
PubMed1994

Murine hepatocyte apoptosis induced in vitro and in vivo by TNF-alpha requires transcriptional arrest.

Freshly isolated mouse hepatocytes were essentially insensitive to TNF-alpha cytotoxicity. However, TNF-alpha induced a concentration-dependent cell death in hepatocytes that had been pretreated with the transcriptional inhibitors actinomycin D (ActD), D-galactosamine, or alpha-amanitin. Unlike RNA synthesis inhibition, a translational block in the presence of cycloheximide (CHX) or puromycin did not sensitive hepatocytes to TNF. On the contrary, these agents prevented hepatocytotoxicity induced by ActD/TNF. Pretreatment with peroxides or glutathione depletors had no significant influence on TNF cytotoxicity. In vivo treatment of mice with ActD/TNF caused hepatic failure, which was significantly reduced by co-treatment with CHX. These findings demonstrate that protein synthesis is required for this mechanism of cell death. To test whether TNF may trigger an endogenous suicide program in hepatocytes, we examined whether DNA fragmentation preceded cell death. In the culture system, hepatocellular DNA fragmentation in the presence of ActD/TNF was observed several hours before lactate dehydrogenase release and was inhibited by CHX. Similar results were obtained in vivo. Chromatin condensation and the formation of apoptotic bodies were observed in livers from mice treated with ActD/TNF and significant DNA fragmentation was detected as early as 4 h after challenge. At this time, organ total glutathione content and plasma transaminase levels were not significantly different from those of untreated controls. The findings of this study demonstrate that direct hepatotoxicity of TNF-alpha is associated with an apoptotic mechanism that becomes manifest under the metabolic condition of arrested transcription and functional translation.

Animals↗
PubMed1992

Granulocyte colony-stimulating factor treatment protects rodents against lipopolysaccharide-induced toxicity via suppression of systemic tumor necrosis factor-alpha.

Pretreatment with recombinant human granulocyte CSF (G-CSF) protected mice in two different models of septic shock. Intravenous injection of 250 micrograms/kg G-CSF to mice prevented lethality induced by 5 mg/kg LPS. Injection of 50 micrograms/kg G-CSF protected galactosamine-sensitized mice against LPS-induced hepatitis. In either case, this protection was accompanied by a suppression of LPS-induced serum TNF activity. In contrast, when galactosamine-sensitized mice were pretreated with 50 micrograms/kg murine recombinant granulocyte/macrophage CSF instead of G-CSF and subsequently challenged with LPS, serum TNF activity was significantly enhanced and mortality was increased. The suppressive effect of G-CSF on LPS-induced TNF production was also demonstrated in rats. In vivo, no TNF was detectable in the blood of LPS-treated rats, which had been pretreated with G-CSF. Ex vivo, alveolar macrophages, bone marrow macrophages, Kupffer cells, or peritoneal macrophages prepared from G-CSF-treated rats produced significantly less TNF upon stimulation with LPS than corresponding populations from control rats. However, when these macrophage populations were incubated with G-CSF in vitro, LPS-induced TNF production was unaffected. These data suggest that the G-CSF-mediated suppression of TNF production is not a direct effect of G-CSF on macrophages. To examine whether, independent of the protection against LPS, G-CSF treatment still activated neutrophils, it was demonstrated that granulocytes from G-CSF-treated rats were primed for PMA-induced oxidative burst and for ionophore/arachidonic acid-stimulated lipoxygenase product formation. The experiments of this study support the notion that G-CSF is a negative feedback signal for macrophage-derived TNF-alpha production during Gram-negative sepsis.

Animals↗
PubMed1992

A cytosolic oxygenase activity involved in the bioactivation of 2-aminofluorene.

The contributions of the hepatic microsomal and cytosolic fractions in the metabolic activation of the promutagen 2-aminofluorene into mutagenic intermediates in the Ames test were investigated. Rat hepatic postmitochondrial, microsomal and cytosolic preparations could convert 2-aminofluorene to mutagens, the postmitochondrial preparation being the most and cytosol the least efficient. Pretreatment of the rats with Aroclor 1254 markedly enhanced the cytosol-mediated mutagenicity of the amine but increased microsomal- and postmitochrondrial-mediated mutagenicity only modestly. The cytosol-mediated mutagenicity of 2-aminofluorene was abolished by heat treatment and by incubation with proteinase K, but was unaffected by dialysis emphasising the protein nature of the cytosolic activation system. Oxygen radical generating systems and oxygen radical scavengers did not significantly influence the cytosol-mediated mutagenic response. Similarly incorporation of xanthine or allopurinol into the cytosolic activation system did not modulate the mutagenic response indicating no role for the molybdenum oxygenases. The cytosolic activation of 2-aminofluorene differed from that mediated by the microsomes in cofactor requirement, substrate specificity and sensitivity to DMSO and (+)-catechin. Further centrifugation of the cytosolic fraction to remove any microsomal contamination did not decrease the cytosolic activation of 2-aminofluorene. It is concluded that the hepatic cytosol contains an oxygenase activity capable of activating certain aromatic amines.

Animals↗
PubMedDate not supplied

Utilization of selenium from different chemical entities for selenoprotein biosynthesis by mammalian cell lines.

Four different cell lines (Hep G2, THP-1, EL 4 6.1, and ECV 304) were grown in a selenium-deficient standard medium (5% fetal calf serum in RPMI 1640 resulting in 5.5 nM selenium of unknown bioavailability) and supplemented with increasing concentration of selenium in the form of sodium selenite, selenomethionine and serum-bound selenium. The activities of two types of glutathione peroxidases (cGPx and PHGPx) were measured to estimate the availability of selenium for selenoprotein synthesis. Only sodium selenite between 1 and 100 nM was found to consistently induce GPx activity in all cell lines, whereas selenomethionine in equal concentrations was practically ineffective. Only THP-1 cells were able to utilize selenium from serum as efficiently as sodium selenite. PHGPx activity similarly responded to selenium supplementation, but was not increased in EL 4 6.1 cells. Our data demonstrate that conventional tissue culture media require selenium supplementation to guarantee adequate selenoprotein biosynthesis in cultured cells. The chemical nature of the selenium compound used for such supplement is as critical for in vitro cultivated cells as for dietary intake.

Animals↗