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Biomedical subjects

B Bonnekoh

Publications and source records attributed to B Bonnekoh.

68 records · Page 4Linked to original sources
PubMed1987

Epidermal cell growth-dependent arylhydrocarbon-hydroxylase (AHH) activity in vitro.

Cytochrome P-450-dependent arylhydrocarbon-hydroxylase (AHH) activity and inducibility by benzanthracene (BA) was measured in cultured guinea pig and human epidermal cells. Basal AHH-activity (AHHb) in guinea pig epidermal cells was much higher than in human epidermal cells. AHHb in guinea pig epidermal cells was directly related to the labeling index and decreased to the original level between the 5th and 7th day of cell culturing. On the other hand, the induction-ratio of AHH reached its maximum level when the number of cells began to rise (proliferation phase) and remained high at day 7 of the cell culture. These results suggest a cell growth dependent activity and inducibility of carcinogen-metabolizing enzymes, such as AHH, in isolated epidermal cells.

Adult↗
PubMed1986

[Epidermal cell cultures--significance for wound coverage in the human].

Epithelial sheets can be cultivated from isolated epidermal cells; in this way, it is possible to increase the cell number considerably. H. Green and co-workers were the first to make use of such epithelia for the autologous covering of burn wounds. We modified this method and report on our experiences with this technique in a patient with small skin defects.

Adult↗
PubMed1986

[In vitro model of the re-epithelialization of defects].

Epidermal cells taken from guinea pigs were cultured on collagen in order to study the processes comparable to reepithelialization of wounds by means of time-lapse cinematography and electron microscopy. Attachment and spreading of the cells are essential for the following cell proliferation. Immediately after seeding, the cells move in streams and rotate around their axes. Flattened cells show cytoplasmic streaming and ameboid movement as they continuously alter their shapes (10-25 microns/h). The cells actively form intercellular bridges, which favor the confluence of the cells. In the present study, the phases of attachment, intercellular association, and formation of colonies have been classified and related to the activity of the DNA synthesis, as it was indicated by 3H-thymidine incorporation.

Animals↗
PubMed1986

[Squamous epithelial cancer in lichen ruber hypertrophicus--a case report with a review of the literature].

Spinocellular carcinoma developed in a 19-year-old lesion of lichen ruber hypertrophicus of the lower leg. In the literature,24 cases of spinocellular carcinoma in lesions of cutaneous lichen ruber have been reported. X-ray and arsenic treatment has often preceded malignant transformation. Another risk factor seems to be the chronic hypertrophic type of lichen ruber located on the lower extremities.

Adult↗
PubMedDate not supplied

Optimized visualization and PCR reamplification of differentially displayed cDNA bands detected by silver staining in polyacrylamide gels as established in the model of dithranol-treated keratinocytes.

The differential display of cDNA species defined by a combination of so-called anchored and arbitrary primers has been acknowledged as a powerful complex strategy to identify differences in gene expression, and depends in its original version, inaugurated by P. Liang and A. B. Pardee in 1992, on the use of radioactive-labelled nucleotides. As a non-radioactive methodological alternative, we established the use of polyesterfilm-backed 10% polyacrylamide gels for horizontal differential-display electrophoresis under non-denaturing conditions, with subsequent detection of cDNA bands by an optimized, semi-automated silver staining omitting any fixation step. Polyacrylamide gel slices carrying the silvered cDNA species of interest were cut out, chopped, squashed and incubated in an ammonium acetate/EDTA solution at 37 degrees C overnight under vigorous shaking. This procedure resulted in a 70% average success rate for subsequent PCR reamplification with regard to the number of cDNAs harvested from the differential-display gel. Novel sequence data of three cDNA clones are communicated, which under these methodological conditions were selected to be up- or down-regulated, respectively, by antipsoriatic dithranol in cultured HaCaT keratinocytes.

Acrylic Resins↗
PubMedDate not supplied

Tazarotene induces epidermal cell differentiation in the mouse tail test used as an animal model for psoriasis.

Disturbed epidermal proliferation and keratinization are major features of psoriatic skin lesions. The so-called mouse tail test is known as an animal model to evaluate the antipsoriatic efficacy of topical drugs with regard to the induction of orthokeratosis. The purpose of the present study was to investigate the effect of tazarotene, a novel, receptor-specific retinoid, by the mouse tail test in a direct comparison to dithranol representing a classical topical antipsoriatic compound. The tails of CFLP mice were treated with tazarotene gel (0.1%, 0.05%), dithranol ointment (1.0%), tretinoin cream (0.05%) and methylcellulose (5%) hydrogel (vehicle control) for 2 weeks. Longitudinal histological sections were prepared from the tail skin, and the degree of orthokeratosis was determined by measuring the horizontal length of the fully developed granular layer within an individual scale in relation to its total length according to a method originally described by Bosman and co-authors. The degree of orthokeratosis was significantly (p < or = 0.05) increased by 0.1% tazarotene (87+/-20%), 1.0% dithranol (75+/-26%), 0.05% tazarotene (59+/-27%), and 0.05% tretinoin (23+/-13%) as compared to untreated (11+/-6%) and methylcellulose hydrogel-treated (13+/-6%) controls. Under the conditions of the mouse tail test, tazarotene showed a strong potency to induce orthokeratosis. With regard to clinically relevant concentrations this effect was even more pronounced than that observed for dithranol.

Animals↗
PubMedDate not supplied

Dithranol and dimethylfumarate suppress the interferon-gamma-induced up-regulation of cytokeratin 17 as a putative psoriasis autoantigen in vitro.

In psoriasis an etiopathogenetic vicious circle has been hypothesized in which disease manifestation is triggered by skin-specific autoantigen structures. Autoreactive T cells are supposed to mediate inflammation and hyperproliferation in the epidermopapillary compartment, positively feeding back the expression and accessibility of decisive antigen structures. Recently an epitope within cytokeratin 17 (K17) has been described as such a putative psoriasis autoantigen, which is moreover known to be up-regulated under the influence of proinflammatory interferon-gamma (IFN-gamma), which is abundantly detected in psoriatic plaques. The present study proposes an in vitro model for this presumptive IFN-gamma/K17 autoimmune loop, i.e. the incubation of hyperproliferative human HaCaT keratinocytes with 25 U IFN-gamma/ml for 72 h. This treatment led to a significant up-regulation of K17 protein expression (> or =300%) measured by flow immunocytometry as compared to the untreated control (100%, p < or = 0.05). Preincubation with a subcytotoxic and antiproliferative dithranol concentration as low as 0.3 microM for 2 h prior to the IFN-gamma exposure resulted in a K17 expression that was significantly lower than the IFN-gamma-induced K17 expression reference level. The IFN-gamma-induced K17 expression was also significantly lowered by coincubation with a subcytotoxic and nonantiproliferative concentration of 3 microM dimethylfumarate. The data indicate for dithranol and dimethylfumarate that a part of their antipsoriatic mode of action may be related to a direct down-regulation of putative psoriasis autoantigen structures.

Administration, Topical↗
PubMedDate not supplied

Perforin granule release from cytotoxic lymphocytes ex vivo is inhibited by ciclosporin but not by methotrexate.

The 70-kD plasma membrane pore-forming protein perforin is a key component of lymphocyte cytotoxicity mediated by lytic granules. It represents a major player in the regulation of various immune reactions like immunoglobulin synthesis, T-cell activation and homeostasis, and in the elimination of virus-infected and tumor cells. Dysregulation of the perforin-granule system, i.e. an increase of perforin-containing lymphocytes, was recently demonstrated in exacerbated psoriasis and generalized drug reactions. In contrast, in patients with exacerbated atopic dermatitis or unsymptomatic rhinitis allergica, a severe perforin depletion in cytotoxic T cells was demonstrated. In addition, these cells displayed a remarkable transport defect of lytic granules, i.e. a perforin hyperreleasability. Thus, the process of perforin-granule release may represent an attractive target for therapeutic immune modulation in various dermatological diseases. Ficoll isolated peripheral blood mononuclear cells (PBMCs) of healthy volunteers were preincubated with different concentrations of ciclosporin or methotrexate (MTX) for 1 h. A newly developed flow cytometry based perforin release assay was used to quantify the velocity of ionomycin/phorbol 12-myristate 13-acetate stimulated perforin-granule release in the presence or absence of pharmacological agents. The immunosuppressant MTX did not influence perforin-granule release. Ciclosporin, in contrast, was found to inhibit perforin-granule release significantly and dose dependently: whereas release from CD8(+) lymphocytes was almost maximal for the untreated control after 60 min (41% of CD8(+) perforin(+) cells at time zero), ciclosporin at 20, 4 and 2 microg/ml elevated the aforementioned parameter up to 73, 65 and 53%, respectively. Our data demonstrate that (i) perforin-granule release can be targeted efficiently by pharmacological agents which can be monitored directly in a newly developed perforin-granule release assay, and (ii) suppression of perforin-granule based cytotoxicity by ciclosporin might contribute to the beneficial therapeutic effects of this drug as an immunomodulating and immunosuppressant target.

Adult↗
PubMedDate not supplied

Interferon-gamma-dependent in vitro model for the putative keratin 17 autoimmune loop in psoriasis: exploration of pharmaco- and gene-therapeutic effects.

In 1999, A.S. Gudmundsdottir et al. have envisaged an epitope on keratin 17 (K17) as a putative psoriasis major autoantigen recognized by T cells. In a HaCaT keratinocyte model, we now demonstrate that IFN-gamma and to a less extent also TNF-alpha and TGF-alpha are able to induce K17 protein expression, in contrast to IL-1alpha, IL-1beta, IL-6, IL-8 and IL-18. This supports our hypothesis of an existing proinflammatory cytokine/K17 autoimmune loop as a presumptive positive feedback mechanism driving psoriasis etiopathogenesis. K17 overexpression was now found to also coincide with suppression of keratinocyte proliferation, e.g. induced by NF-kappa B inhibitors (Bay 11-7082 and Bay 11-7085), and thereby correlated hyperapoptosis to be encountered in psoriatic epidermis. Acitretin as an established antipsoriatic drug and the tyrosine kinase inhibitor imatinib decreased, whereas hydrocortisone as well as dexamethasone increased the IFN-gamma-induced K17 overexpression. The latter might be another mechanism explaining the well-known rebound phenomena after abrupt withdrawal of corticosteroids in psoriasis treatment. Finally, we defined a K17-directed and effective antisense oligodesoxynucleotide which may hold promise for future gene-therapeutic approaches in psoriasis.

Acitretin↗
PubMedDate not supplied

Up-regulated perforin expression of CD8+ blood lymphocytes in generalized non-anaphylactic drug eruptions and exacerbated psoriasis.

Perforin expressed in CD8+ cytotoxic T cells is known to mediate the lysis of target cells carrying microbial as well as tumor-associated antigens, and to be involved in autoimmune and transplant reactions. The aim of the present investigation was to study the role of perforin- and CD8-expressing effector lymphocytes from peripheral blood in patients with generalized inflammatory skin diseases. Mononuclear cells were separated from peripheral venous blood and permeabilized by 0.1% saponin. The co-expression of cytoplasmatic perforin and cell membrane-residing CD8 was determined in lymphocytes by immuno-flow cytometry. Patients affected by generalized macular-papular drug eruptions (n = 14), drug-unrelated acute urticaria (n = 10) and drug-independently exacerbated psoriasis (n = 11, PASI scores ranging from 25 to 35), as well as control individuals not affected by any inflammatory skin disease (n = 10) were enrolled. Additionally, n = 5 patients with drug-induced Stevens-Johnson syndrome (SJS) were included. The average proportion of CD8+ peripheral lymphocytes co-expressing perforin in generalized drug eruptions (68.8+/-24.9%) and exacerbated psoriasis (67.2+/-17.1%) differed significantly from the controls (43.5+/-11.6%; p 0. 05), whereas no significant difference for acute urticaria (58.2+/-23.1%) could be measured. In each of the 5 SJS patients treated by high dose systemic steroids the parameter substantially declined during the first 7 days after admission from an average value of 81. 6% down to 33.0%. Thus, as compared to controls we observed an increased perforin+ proportion of CD8+ lymphocytes in generalized drug eruptions and in exacerbated psoriasis but not in acute urticaria. Therefore the parameter showed some specificity as a marker of distinct inflammatory skin disorders, and proved to be useful in monitoring the disease activity of SJS under anti-inflammatory medication. Furthermore, the findings point to a possible crucial role of CD8+ lymphocytes in the pathogenesis of psoriasis.

Adult↗
PubMedDate not supplied

Keratinocyte lipid fluidity under the influence of cholesterols, hydrocortisones, "active lipid", tocopherol and retinoic acid--a fluorescence polarization study with regard to physiological and pathophysiological epidermopoiesis and its therapeutic accessibility.

Lipid fluidity of freshly isolated human (H) and guinea pig (GP) keratinocytes (K) was determined as the reciprocal of diphenylhexatriene (DPH) fluorescence polarization (P-value), the temperature being kept at 25 degrees C and cell density standardized to 550,000 per ml (level of statistical significance a less than 0.05). An experimental model involving short-term incubations (2.5 hours, 37 degrees C) of GPK in 1% ethanolic lipid solutions (15 mg lipid agent per ml ethanol) was set up to investigate accumulation a) of cholesterol due to terminal differentiation of keratinocytes and b) of cholesteryl sulfate due to the lack of steroid sulfatase activity in recessive X-linked ichthyosis (RXLI). In comparison to the control including 1% ethanol (P = 0.291 +/- 0.004), significant rigidifying effects were demonstrated for cholesteryl hemisuccinate (0.331 +/- 0.005) and cholesteryl sulfate (0.310 +/- 0.002). Correspondingly, a significant increase of the P-value was also induced by cholesteryl hemisuccinate in HK. Rigidification of GPK by a preincubation with cholesteryl sulfate (P = 0.306 +/- 0.002) could be antagonized by a subsequent short-term incubation with "active lipid (mixture 721)" (0.285 +/- 0.003, a less than 0.05) which may be relevant for future therapeutic strategies in RXLI. Other steran molecules such as hydrocortisone-21-hemisuccinate or hydrocortisone acetate did not affect lipid fluidity. With regard to the therapeutic potency of retinoids in epidermopoietic disorders, incubations of HK with all-trans-retinoic-acid were compared to those with also lipophilic vitamin E, i.e. d-alpha-tocopherol, for 2.5 hours at 37 degrees C using 1% DMSO as a solvent.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

The antipsoriatic dimethyl-fumarate suppresses interferon-gamma -induced ICAM-1 and HLA-DR expression on hyperproliferative keratinocytes. Quantification by a culture plate-directed APAAP-ELISA technique.

The derivatives of fumaric acid show antipsoriatic effects but details of the mechanism of action are largely unknown. The study focused on the effect of fumaric acid, dimethyl-fumarate, Zn-, Ca- and Mg-monoethyl-fumarate on the interferon-gamma (IFN-gamma)-induced expression of ICAM-1 and HLA-DR molecules on keratinocytes. Human hyperproliferative keratinocytes of the HaCaT cell line were exposed to IFN-gamma (10 U/ml) alone or in combination with fumaric acid and its derivatives for 48 hrs. The effect of fumarates was investigated semiquantitatively using the alkaline phosphatase-anti-alkaline phosphatase (APAAP) method. Subsequently, the effect of dimethyl-fumarate, the main component of "fumaric acid therapy", was evaluated quantitatively by means of an APAAP-ELISA technique. The semiquantitative evaluation revealed that in the micromolar dose range investigated only dimethyl-fumarate demonstrated substantial growth inhibition and down-regulation of the cell surface markers. In the quantitative evaluation, dimethyl-fumarate significantly (p</=0.05) suppressed the expression of ICAM-1 (84%) and HLA-DR (67%) on HaCaT keratinocytes at a subtoxic concentration of 4.0 microM as compared to untreated controls (100%). In contrast, concentrations of 4.0, 12 and 35 microM dimethyl-fumarate had no influence on the ICAM-1 and HLA-DR expression on IFN-gamma-exposed normal human epidermal keratinocytes in primary cultures. Thus, there is experimental evidence that dimethyl-fumarate may exert its antipsoriatic effect not only as an antiproliferative agent but also by down-regulation of ICAM-1 and HLA-DR molecules on hyperproliferative keratinocytes.

Cell Division↗