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Martin Leverkus

Publications and source records attributed to Martin Leverkus.

25 records · Page 2Linked to original sources
PubMed2003

TRAIL-induced apoptosis and gene induction in HaCaT keratinocytes: differential contribution of TRAIL receptors 1 and 2.

Tumor necrosis factor related apoptosis-inducing ligand (TRAIL) exerts a potent cytotoxic activity especially against many tumor cell types such as transformed keratinocytes. The specific role of the different TRAIL receptors in this process, however, is unknown. In this report we examine the role the TRAIL receptors play in both the apoptotic and nonapoptotic responses of HaCaT keratinocytes to leucine zipper TRAIL (LZ-TRAIL). By employing receptor-specific blocking antibodies we demonstrate that TRAIL receptor 1 plays the primary role in mediating caspase activation and apoptosis in HaCaT cells. Furthermore, we show that this receptor mainly mediates nuclear factor kappaB activation and expression of the pro-inflammatory cytokine interleukin-8 and that nuclear factor kappaB activation is critically required for the induction of pro-inflammatory cytokines in response to LZ-TRAIL. Taken together, our data suggest that beside its potent pro-apoptotic role, LZ-TRAIL leads to pro-inflammatory responses that are mainly mediated by TRAIL receptor 1 in HaCaT keratinocytes.

Apoptosis↗
PubMed2003

[Benign course of malignant atrophic papulosis (Köhlmeier-Degos disease): lack of vessel occlusion as good prognostic sign?].

Morbus Köhlmeier-Degos is a rare systemic disease characterized by pathognomonic cutaneous lesions with typical histology. We report the case of a 22-year-old woman with a benign course of this disease and discuss therapeutical options. The patient presented with whitish papules on neck, trunk and extremities that slowly developed within seven months. Examination of the skin revealed about 20 papules of 2-5 mm size. The lesions were partly skin-colored, partly with an erythematous rim and showed a central porcelain-like atrophy. Histology showed an interface-dermatitis and a wedge-shaped mucin deposition with sclerosis of the upper reticular dermis. Organ manifestation was absent. The patient was started on a daily therapy of 300 mg acetyl salicylic acid. Over the course of 24 months single new lesions appeared at a reduced frequency. Apart from the malignant form of Morbus Köhlmeier-Degos there exists a benign course which may be successfully controlled with anti-platelet therapy. We speculate that the lack of vessel occlusion in the histology could be a hallmark of a benign form of this rare disease.

Diagnosis, Differential↗
PubMed2003

MHC class II-mediated apoptosis in dendritic cells: a role for membrane-associated and mitochondrial signaling pathways.

Cytotoxic elimination of dendritic cells (DC) in lymphoid tissue represents an important pathway of immune regulation. However, the mechanism of DC removal is still controversial since mature DC are insensitive to death receptor-mediated killing and other surface or soluble molecules mediating DC death in vivo have yet to be characterized. Class II ligation is the only known signal that induces rapid cell death in mature DC, thus our studies have now focused on the requirements for this cell death using the advantages of tools available for both the mouse and human systems. Anti-class II mAb could be grouped into (i) mAb that both bound to class II and caused class II-mediated cell death as well as (ii) those that bound to class II, but did not cause apoptosis. mAb binding stable class II dimers as well as those mAb recognizing either the alpha or beta chains of class II were found in both groups. Whereas class II-mediated death was enhanced by DC-DC homotypic interactions, DC clustering itself was insufficient to induce apoptosis. Although DC death could be inhibited by uncoupling actin filament bundling, the inhibition of various proteases, including the caspases, and protein transport mediators failed to inhibit class II-mediated cell death. Neither Bid, poly-ADP-ribose polymerase, caspases-3, -7 and -8 nor FLICE-inhibitory protein were found to be cleaved during class II apoptosis. Lastly, although class II mAb induced a rapid mitochondrial membrane depolarization in DC, cell death was not inhibited by Bcl-2 over-expression in DC. The independence of this form of apoptosis from protein or RNA synthesis, coupled to the rapidity of the mitochondrial depolarization and the lack of protection by Bcl-2, suggests that mature DC express pre-formed pro-apoptotic molecules that are involved in class II-mediated death.

Amino Acid Chloromethyl Ketones↗
PubMed2003

Proteasome inhibition results in TRAIL sensitization of primary keratinocytes by removing the resistance-mediating block of effector caspase maturation.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) exerts potent cytotoxic activity against transformed keratinocytes, whereas primary keratinocytes are relatively resistant. In several cell types, inhibition of the proteasome sensitizes for TRAIL-induced apoptosis by interference with NF-kappaB activation. Here we describe a novel intracellular mechanism of TRAIL resistance in primary cells and how this resistance is removed by proteasome inhibitors independent of NF-kappaB in primary human keratinocytes. This sensitization was not mediated at the receptor-proximal level of TRAIL DISC formation or caspase 8 activation but further downstream. Activation of caspase 3 was critical, as it only occurred when mitochondrial apoptotic pathways were activated, as reflected by Smac/DIABLO, HtrA2, and cytochrome c release. Smac/DIABLO and HtrA2 are needed to release the X-linked inhibitor-of-apoptosis protein (XIAP)-mediated block of full caspase 3 maturation. XIAP can effectively block caspase 3 maturation and, intriguingly, is highly expressed in primary but not in transformed keratinocytes. Ectopic XIAP expression in transformed keratinocytes resulted in increased resistance to TRAIL. Our data suggest that breaking of this resistance via proteasome inhibitors, which are potential anticancer drugs, may sensitize certain primary cells to TRAIL-induced apoptosis and could thereby complicate the clinical applicability of a combination of TRAIL receptor agonists with proteasome inhibitors.

Apoptosis↗
PubMed2002

Cicatricial pemphigoid with circulating IgA and IgG autoantibodies to the central portion of the BP180 ectodomain: beneficial effect of adjuvant therapy with high-dose intravenous immunoglobulin.

Cicatricial pemphigoid (CP) is an autoimmune subepidermal blistering disease characterized by deposits of IgG, IgA, or C3 at the cutaneous basement membrane zone. CP may present with considerable variation regarding age, morphology of lesions, and mucosal involvement, which may heal with or without scarring. We describe a patient with CP who presented with circulating IgA and IgG autoantibodies to the epidermal side of salt-split human skin. By immunoblot analysis, the patient's IgA reacted with the soluble ectodomain of BP180 (LAD-1). This reactivity was mainly directed to the central portion of the BP180 ectodomain, a site that, to date, has not been described as the target of IgA autoantibodies. Different immunosuppressive treatment regimens including steroids and mycophenolate mofetil did not control this patient's disease, and severe scarring of the conjunctivae occurred with impairment of vision. Addition of adjuvant intravenous immunoglobulin (1 g/kg body weight on 2 consecutive days) every 4 weeks led to a dramatic improvement of conjunctivitis and gingivitis. Clinical improvement correlated with the serum's IgA immunoblot reactivity against LAD-1. Further studies on a larger number of patients with CP should try to correlate the specificity of autoantibodies in CP with the response to certain therapeutic regimens.

Aged↗
PubMedDate not supplied

Reduced joining of DNA ends correlates with chromosomal instability in three melanoma cell lines.

Chromosomal instability plays a pivotal role in multistep carcinogenesis by facilitating the acquisition of the multiple genetic alterations necessary for malignant transformation. In order to study the role of abnormal DNA repair in malignant melanoma, we measured the ability of cell lines from malignant melanoma and that of primary melanocytes to process 4 different kinds of DNA damage (pyrimidine dimers, oxidative DNA lesions, replication errors, and DNA double-strand breaks) using 4 different plasmid assays. Based on the number of chromosomes, the DNA index, and the rates of spontaneous micronuclei, the chromosomal stability in primary melanocytes and the melanoma line LIBR was characterized as being high, intermediate in M1, and low in MeWo. Repair of UVB photoproducts, of oxidative DNA damage, and of replication errors was not impaired in any melanoma line. Using linearized shuttle vector plasmid pZ189, LIBR cells and primary melanocytes exhibited a high efficiency of joining overlapping DNA ends, reflecting proficient repair of DNA double-strand breaks. Joining efficiency was reduced slightly in M1 and 2.9-fold in MeWo. This indicates that in the melanoma cell lines studied here, an increase in chromosomal instability is accompanied by a pronounced impairment in the ability to join DNA ends. Although a small sample was studied, this raises the possibility that defects in DNA end joining may also contribute to genetic instability and chromosome aberrations in melanoma.

Chromosome Aberrations↗