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Biomedical subjects

M Schönharting

Publications and source records attributed to M Schönharting.

At least 19 recordsLinked to original sources
PubMed2001

ICE/Caspase-1 inhibitors as novel anti-inflammatory drugs.

In recent years, several strategies that selectively inhibit pro-inflammatory cytokines, have yielded effective protein-based therapies for inflammatory disorders, validating the therapeutic hypothesis that intervention in cytokine signalling can provide clinical benefit. However, these protein-based products must be administered by injection, a constraint associated with inconvenience, adverse effects and expense for patients, caregivers and insurers. Besides interfering with the effects of cytokines such as TNF-alpha or IL-1beta that have already been produced, inhibition of pro-inflammatory cytokine production or signalling with low-molecular weight orally-active drugs would combine the convenience of conventional pharmaceuticals with the focused efficacy of the protein therapies. Reducing IL-1beta and IL-18 production by inhibition of IL-1beta converting enzyme (ICE, caspase-1) is one promising strategy because of the key roles of these cytokines in many inflammatory diseases. Pralnacasan, the first orally available, potent and selective ICE inhibitor to enter clinical trials, is currently under investigation in rheumatoid arthritis.

Animals↗
PubMed1997

Use of the methylxanthine derivative A802715 in transplantation immunology: II. In vivo experiments.

BACKGROUND: We have previously demonstrated in vitro that the methylxanthine derivative A802715 suppresses the cyclosporine (CsA)-resistant "signal two"-dependent pathway of T cell activation and hence acts synergistically with CsA. Here, this synergism was further investigated in vivo in rats. METHODS: Primary cardiac allografts were placed in the neck, and secondary grafts were transplanted intra-abdominally. A802715 was given orally for 30 days or by continuous intravenous infusion via a mini-osmotic pump for 2 weeks. CsA was given orally for up to 30 days. T cell responses were examined in vitro using mixed lymphocyte reaction, concanavalin A whole blood, and cell-mediated lympholysis assays. RESULTS: In a major histocompatibility complex incompatible WKAH-->PVG combination, neither oral CsA (7.5 mg/kg/day) nor oral A802715 (100 mg/kg/day) was able to prolong graft survival. However, a combination of both drugs, given at the same dose, sustained graft survival during treatment. A similar synergism was not obtained with pentoxifylline, another methylxanthine derivative. The synergism between A802715 and CsA could be further increased by using a continuous intravenous infusion of A802715, since (1) lower doses of A802715 (20 mg/kg/day) and CsA (5 mg/kg/day) could be used, and (2) six of seven grafts survived permanently. In a major histocompatibility complex compatible Wag/Rij-->R/A combination, similar synergistic effects and permanent graft survival could also be obtained by oral A802715 (100 mg/kg/day) in combination with a low dose of CsA (2.5 mg/kg/day). In both strain combinations, long-term survivors accepted donor-type but rejected third-party second grafts in the absence of immunosuppression. This specific tolerance was not related to clonal deletion nor anergy, as recipient lymphocytes proliferated normally in the anti-donor mixed lymphocyte reaction. Instead, a defect in generating specific cytotoxic T lymphocytes was involved. CONCLUSIONS: A802715 synergizes with CsA in vivo to induce specific transplantation tolerance and hence should be considered as a promising new immunosuppressant.

Administration, Oral↗
PubMed1997

Use of the methylxanthine derivative A802715 in transplantation immunology: I. Strong in vitro inhibitory effects on CD28-costimulated T cell activities.

BACKGROUND: Recently, methylxanthines such as pentoxifylline (PTX) were shown to be immunosuppressive in vitro. Unfortunately, when used in transplant patients, PTX was poorly active as an immunosuppressant. Here we report that the new methylxanthine derivative A802715 not only is more active than PTX, it also suppresses the cyclosporine (CsA)-resistant "signal two"-dependent pathway of T cell proliferation, making it an interesting drug to associate with CsA. METHODS: "Signal one"- and "signal two"-dependent T cell activation was investigated with purified human T cells stimulated with immobilized anti-CD3 or anti-CD28 monoclonal antibody (mAb) plus phorbol myristate acetate (PMA) or with a 3T6 mouse fibroblast cell line presenting anti-CD3 mAb on transfected human Fcgamma receptors II (FcgammaRII) in the presence or absence of transfected B7-1 (CD80) molecules. RESULTS: A802715 was more immunosuppressive in the mixed lymphocyte reaction (MLR) than PTX. A802715 dose-dependently suppressed polyclonal signal one-dependent T cell activation induced by anti-CD3 mAb/PMA. In addition, A802715 also suppressed signal two-dependent T cell proliferation induced by anti-CD28 mAb/PMA. The expression of the interleukin-2 receptor on T cells stimulated by anti-CD3 mAb presented on 3T6/FcgammaRII cells was equally well suppressed by A802715 and PTX. In contrast, interleukin-2 receptor or CD40L (gp39) expression by T cells after stimulation with the same anti-CD3 mAb- 3T6/FcgammaRII cells, but coexpressing transfected B7-1, was only suppressed by A802715. The anticipated synergism between A802715 and CsA was confirmed in MLR assays. Moreover, generation of cytotoxic T lymphocytes during MLR with Epstein-Barr virus-transformed B cells, which strongly express B7-1 and B7-2, was also inhibited by A802715. CONCLUSIONS: These in vitro data indicate that the A802715 (1) is a stronger immunosuppressant for T cells than PTX, (2) suppresses T cell activation pathways that are resistant to PTX or CsA, and (3) acts synergistically with CsA.

Animals↗
PubMed1993

In vitro immunomodulatory effects of pentoxifylline.

Pentoxifylline (PTX), a methylxanthine derivative and phosphodiesterase inhibitor, is known to influence production and/or function of some cytokines. We examined the effect of PTX on the in vitro expression of cytokine genes using endotoxin- or phytohaemagglutinin (PHA)-stimulated human blood mononuclear cells. The expression of tumour necrosis factor (TNF)alpha, TNF beta interleukin (IL)-2 and interferon (IFN)gamma was inhibited by PTX in a dose-dependent manner, whereas expression of IL-1 alpha, IL-1 beta, and IL-6 was unaffected at concentrations up to 300 microM of PTX. The amount of TNF beta mRNA in PHA-stimulated blood mononuclear cells was reduced by PTX. Finally, PTX stimulated PHA-induced cell proliferation whereas antigen-induced cell proliferation was inhibited in the presence of PTX. The PTX analogues HWA-138 and A-802715 inhibited TNF alpha mRNA expression from endotoxin-stimulated mononuclear cells. These data suggest that PTX-analogues affect the in vitro immune response at different target points and that the response depends upon the respective triggering mechanism(s).

Cells, Cultured↗
PubMed1993

Influence of a pentoxifylline-analogue on the granulocyte-mediated pulmonary mediator release and vascular reaction.

The influence of a novel pentoxifylline-analogue, HWA 138, on the polymorphonuclear neutrophil leukocyte (PMN)-mediated changes in pulmonary resistance and mediator release was investigated in the isolated perfused and ventilated rabbit lung model. Isolated, washed human granulocytes were injected into the pulmonary artery and stimulated by either 10(-6) mol/L N-formyl-L-leucin-methionyl-L-phenylalanine (FMP) or 3 x 10(-8) mol/L phorbol 12-myristate 13-acetate (PMA) in the presence or absence (controls) of HWA 138 (10(-4) mol/L). Shortly after granulocyte activation, there was a massive generation and release of thromboxane (> 110 pg/ml) and histamine (150-400 nmol/L), with an acute increase of pulmonary artery pressure (> 8 mmHg) in the control groups. Application of HWA 138 almost completely suppressed mediator formation and release as well as pulmonary vascular reaction in the FMP stimulated group. In contrast to this, HWA 138 was unable to influence either mediator release, the pulmonary pressure reaction or interstitial edema formation following PMA stimulation. In the present model, HWA 138 is supposed to be effective via granulocytes by decreasing mediator release, obviously due to burst reaction.

6-Ketoprostaglandin F1 alpha↗
PubMed1992

A novel xanthine derivative counteracting in vivo tumor necrosis factor alpha toxicity in mice.

The xanthine derivative A 802715 (1-(5-hydroxy-5-methyl)hexyl-3-methyl-7- propyl-xanthine, Hoechst AG) caused dose-dependent protection against lipopolysaccharide (LPS)-induced lethal shock in mice. In animals which had received the compound, the LPS-induced increase of serum tumor necrosis factor (TNF alpha) levels was not significantly affected. Protection against LPS-induced lethality was observed not only when A 802715 was given 1 hr before or simultaneously with LPS but also when administered 1 hr after LPS challenge. Administration of 200 mg/kg of the compound 1 hr before challenge also fully protected against lethal shock induced by intravenous administration of recombinant murine TNF alpha. It is concluded that A 802715 counteracts TNF alpha toxicity and that the drug bears the potential of therapeutic intervention in septic shock.

Animals↗
PubMed1988

The haemorheological and antithrombotic potential of pentoxifylline ('Trental'): a review.

Haemorheological knowledge achieved in the past decade has revealed the essential interactions of flow properties of blood with haemostatic, coagulation, and vessel wall mechanisms in blood flow disturbances. Fine tuning of these factors maintains the physiologically adequate perfusion of the nutritive microcirculation. Under pathological conditions, therefore, the most beneficial effect can be expected from the therapeutic approaches which, apart from the disturbed flow properties of the blood itself, improve also all the other factors involved. In consequence, it is suggested that treatment of circulatory disturbances should be directed not only at the reduction of enhanced red blood cell aggregation and improvement of impaired red blood cell deformability, but also at a diminuation of enhanced platelet and white cell hyperreactivity as well as at an amendment of hypercoagulability and of the affected endothelial and vessel wall systems. Experimental and clinical studies are reviewed to show that pentoxifylline meets these different requirements to a great extent. Its multi-functional pharmacological profile suggests new aspects in the treatment of circulatory disorders in many diseases and in the prevention of thrombotic events.

Animals↗
PubMed1978

A study of microsomal oxidative functions with the aid of a series of N-colchiceyl derivatives.

N-Colchiceyl derivatives are presented as a class of substances which, provided certain structural requirements are met, are oxidatively degraded by microsomal suspensions both at the nitrogen-linked side chain at ring C and at the oxygen-linked side chain(s) at Ring A. The chemical structures of unknown metabolites have been elucidated by comparison with authentic samples whose syntheses are described. Comparative studies indicate structure-dependent preferred sites for the introduction fo oxygen, whose extent correlates rather closely with the partition coefficient in the system n-octanol/ethanol/water. The results demonstrate, with the inclusion of some inhibition data, the suitability of N-colchiceyl derivatives for detailed investigations of microsomal degradative processes.

Animals↗
PubMed1977

[Binding of colchiceine to isolated gangliosides and ganglioside-containing membranes (author's transl)].

The binding of the alkaloid colchicine and its metabolite colchiceine to different membranes and gangliosides has been investigated. In contrast to colchicine, colchiceine binds to erythrocyte ghosts, plasma membranes of rat liver and heart muscle, and synaptosomes of rat brain. The binding properties of isolated gangliosides are analogous to those of the membranes investigated. On a molar basis the binding capacities of the gangliosides GT1, GD1a and GM1 for colchiceine are 7:4:1, respectively. The binding of alkaloid to ganglioside structures is diminished in the presence of EDTA and after pretreatment with neuraminidase, suggesting a specific, Ca2 -dependent interaction of colchiceine with gangliosides. The results are discussed with respect to the different biological activities of colchicine and its metabolite colchiceine.

Animals↗
PubMed1976

Metabolic transformation of colchicine, IV[1]. On the interaction of colchicine and colchiceine with sulfhydryl compounds.

The interaction of colchicine and one of its metabolites, O10-demethylcolchicine (colchiceine), with sulfhydryl compounds was studied in several experimental systems. Colchiceine protects reduced glutathione from oxidation by atmospheric oxygen. Inactivation of enzymes with catalytically essential sulfhydryl groups is prevented by colchiceine. In affinity chromatographic experiments, Agarose-bound colchiceine adsorbs sulfhydryl enzymes which may be eluted specifically by SH-compounds like mercaptoethanol. No such effects are shown by colchicine. The data demonstrate a novel type of biochemical reactivity in the metabolite colchiceine with potential biological relevance.

Adenosine Deaminase↗
PubMed1975

Metabolic transformation of colchicine, III. Inhibition of phosphatases by the metabolite O10-demethylcolchicine (colchiceine) and their reactivation by divalent cations.

Colchicine and some of its metabolites and derivatives were investigated regarding their inhibitory action against alkaline phosphatases from E. coli and calf intestine, and against acid phosphatase from potato. Colchicine itself was essentially ineffective, also its metabolites O2-demethyl- and O3-demethylcolchicine. The metabolite O10-demethylcolchicine (= colchiceine) was found to be a powerful, non-competitive inhibitor for all three phosphatases with Ki in the range of 0.45-6.0mM. Amongst the derivatives of colchicine, colchiceyltaurine proved to be a non-competitive inhibitor of acid phosphatase (Ki=3.0mM); desacetylcolchiceine behaved like colchiceine. The inhbitory actions of colchiceine and desacetylcholchiceine could be completely reversed by the addition of Mg2, Ca2, or Zn2, respectively. This interaction with divalent cations demonstrates a novel type of action of the metabolite colchiceine when compared with its mother alkaloid and is possibly of major biological significance.

Acid Phosphatase↗