Biomedical subjects

Markus Böhm

Publications and source records attributed to Markus Böhm.

32 records · Page 2Linked to original sources

PubMed2003

New insights into the functions of alpha-MSH and related peptides in the immune system.

There is a substantial body of evidence that the tridecapeptide alpha-melanocyte-stimulating hormone (alpha-MSH) functions as a mediator of immunity and inflammation. The immunomodulating capacity of alpha-MSH is primarily because of its effects on melanocortin receptor (MC-1R)-expressing monocytes, macrophages, and dendritic cells (DCs). alpha-MSH down-regulates the production of proinflammatory and immunomodulating cytokines (IL-1, IL-6, TNF-alpha, IL-2, IFN-gamma, IL-4, IL-13) as well as the expression of costimulatory molecules (CD86, CD40, ICAM-1) on antigen-presenting DCs. In contrast, the production of the cytokine synthesis inhibitor IL-10 is up-regulated by alpha-MSH. At the molecular level, these effects of alpha-MSH are mediated via the inhibition of the activation of transcription factors such as NFkappaB. Not only alpha-MSH but also its C-terminal tripeptide (alpha-MSH 11-13, KPV) was able to bind to MC-1R and to modulate the function of APCs. In vivo, using a mouse model of contact hypersensitivity (CHS) systemic and topical application of alpha-MSH or KPV inhibited the sensitization and the elicitation phase of CHS and was able to induce hapten-specific tolerance. To investigate the underlying mechanisms of tolerance induction, we have performed in vivo transfer experiments. Treatment of naive mice with bone marrow-derived immature haptenized and alpha-MSH-pulsed DCs resulted in a significant inhibition of CHS. Furthermore, tolerance induction was found to be mediated by the generation of CTLA4(+) and IL-10-producing T lymphocytes. The potent capacity of alpha-MSH to modulate the function of antigen-presenting cells (APCs) has been further supported in another experimental approach. In vitro, by activating APCs, alpha-MSH has been shown to modulate IgE production by IL-4 and anti-CD40 stimulated B lymphocytes. Moreover, in a murine model of allergic airway inflammation, systemic treatment with alpha-MSH resulted in a significant reduction of allergen-specific IgE production, eosinophil influx, and IL-4 production. These effects were mediated via IL-10 production, because IL-10 knockout mice were resistant to alpha-MSH treatment. Therefore, therapeutic application of alpha-MSH or related peptides (KPVs) as well as alpha-MSH/KPV-pulsed DCs may be a useful approach for the treatment of inflammatory, autoimmune, and allergic diseases in the future.

Animals↗

PubMed2003

Topical tacrolimus as a therapeutic adjunct in patients with cutaneous lupus erythematosus. A report of three cases.

The topical therapy of cutaneous lupus erythematosus (LE) consists mainly of corticosteroids which may lead to significant side effects when overused. We report the efficacy of topical tacrolimus as a therapeutic adjunct in 3 patients with cutaneous LE of the face. All patients, 1 with systemic LE and a malar rash, 1 with annular subacute cutaneous LE, the other with a papular variant of subacute cutaneous LE, experienced significant improvement following application of tacrolimus ointment. Treatment with topical tacrolimus was tolerated well without major side effects in all patients. The presented cases are in line with recent reports that topical tacrolimus may be effective in facial LE.

Administration, Cutaneous↗

PubMed2002

Conservation of the positions of metazoan introns from sponges to humans.

Sponges (phylum Porifera) are the phylogenetic oldest Metazoa still extant. They can be considered as reference animals (Urmetazoa) for the understanding of the evolutionary processes resulting in the creation of Metazoa in general and also for the metazoan gene organization in particular. In the marine sponge Suberites domuncula, genes encoding p38 and JNK kinases contain nine and twelve introns, respectively. Eight introns in both genes share the same positions and the identical phases. One p38 intron slipped for six bases and the JNK gene has three more introns. However, the sequences of the introns are not conserved and the introns in JNK gene are generally much longer. Introns interrupt most of the conserved kinase subdomains I-XI and are found in all three phases (0, 1 and 2). We analyzed in details p38 and JNK genes from human, Caenorhabditis elegans and Drosophila melanogaster and found in most genes introns at the positions identical to those in sponge genes. The exceptions are two p38 genes from D. melanogaster that have lost all introns in the coding sequence. The positions of 11 introns in each of four human p38 genes are fully conserved and ten introns occupy identical positions as the introns in sponge p38 or JNK genes. The same is true for nine, out of ten introns in the human JNK-1 gene. The introns in human p38 and JNK genes are on average more than ten times longer than corresponding introns in sponges. It was proposed that yeast HOG1-like kinases (from i.e. Saccharomyces cerevisiae and Emericella nidulans) and metazoan p38 and JNK kinases are orthologues. p38 and JNK genes were created after the split from fungi by the duplication and diversification of the HOG1-like progenitor gene. Our results further support the common origin of p38 and JNK genes and speak in favor of a very early time of duplication. The ancestral gene contained at least ten introns, which are still present at the very conserved positions in p38 and JNK genes of extant animals. Four of these introns are present at the same positions in the HOG-like gene in the fungus E. nidulans. The others probably entered the ancestral gene after the split of fungi, but before the duplication of the gene and before the creation of the common, urmetazoan progenitor of all multicellular animals. A second gene coding for an immune molecule is described, the allograft inflammatory factor, which likewise showed a highly conserved exon/intron structure in S. domuncula and in human. These data show that the intron/exon borders are highly conserved in genes from sponges to human.

Amino Acid Sequence↗

PubMed2002

Evolution of osmosensing signal transduction in Metazoa: stress-activated protein kinases p38 and JNK.

Sponges (Porifera) represent the most basal branch of the Metazoa alive today. We show that two central stress-activated protein kinases involved in the osmosensing pathway, p38 mitogen-activated protein kinase (MAPK) and JNK, can complement for the ancestral MAPK Hog1 in the yeast Saccharomyces cerevisiae. S. cerevisiae mutants lacking Hog1 (hog1-Delta 1) have been complemented with the sponge SDJNK and SDp38 genes. Western blotting has revealed that, after transformation, the hog1-Delta 1+ SDJNK(sense) and hog1-Delta 1+ SDp38(sense) clones express the sponge proteins. Functional studies have demonstrated that the complemented clones grow under hyperosmotic conditions (0.6 M NaCl). Furthermore, the expressed sponge kinases undergo phosphorylation in S. cerevisiae at 0.6 M NaCl. This report documents that the metazoan signal transduction kinases, p38 and JNK, which were originally derived from an common ancestor with yeast HOG1, have retained their function after their specification.

Animals↗

PubMed2002

Development of new hydrogen-bond descriptors and their application to comparative molecular field analyses.

Knowledge-based descriptors extracted from composite crystal-field environments in crystal data have been developed for the description of interaction properties of small molecules. Using SuperStar seven diverse probe atoms have been selected to reflect the most important physicochemical properties. The general application of these descriptors in comparative molecular field analysis has been investigated using a dataset of thermolysin inhibitors, and a comparison to the GRID program has been performed. We especially focused on hydrogen-bond donor and acceptor properties by selecting a carbonyl and amino group as suitable probes. Their performance has been compared to that of the hydrogen-bond descriptors presently implemented in CoMSIA (comparative molecular similarity indices analysis). The newly developed descriptors produced significantly improved statistics for the correlation analyses if they are exclusively applied or, even better, applied in combination with other CoMSIA descriptors. Two methodologically different approaches have been tested to approximate the developed descriptors. Both reduce significantly the required computational efforts in particular for large data sets. The graphical interpretation of the field contributions of hydrogen-bonding properties elucidates additional features compared to those obtained from the original CoMSIA method. They are of valuable support for the design of improved inhibitors.

Databases, Factual↗

PubMed2002

Non-thiol farnesyltransferase inhibitors: evaluation of different AA(X)-peptidomimetic substructures in combination with arylic cysteine replacements.

In the course of our studies on non-thiol farnesyltransferase inhibitors based on the 2, 5-diaminobenzophenone AAX-peptidomimetic substructure, we have developed the (4-nitrophenyl)butyryl (R(1)), the (2-naphthyl)acryloyl (R(2)), the 4-nitrocinnamoyl (R(3)), and the 5-(4-nitrophenyl)furylacryloyl (R(4)) groups as useful cysteine replacements. In this study, we combined these four groups with other AA(X)-peptidomimetic substructures (5-10: R = H) reported in the literature. The 5-(4-nitrophenyl)furylacryloyl moiety (R(4)) turned out to be the most useful non-thiol cysteine replacement yielding in all cases the most active inhibitors. By combination of this 5-(4-nitrophenyl) furylacryloyl moiety (R(4)) with the structurally simple AAX-peptidomimetics 4-aminobenzophenone (5) and 4-aminodiphenylsulfone (6) potent, readily accessible non-thiol farnesyltransferase inhibitors were obtained (IC(50) = 12 nMand 10 nM).

Acrylates↗

PubMed2002

Non-thiol farnesyltransferase inhibitors: structure-activity relationships of benzophenone-based bisubstrate analogue farnesyltransferase inhibitors.

Investigations on the structure-activity relationships of benzophenone-based bisubstrate analogue farnesyltransferase inhibitors yielded a bisubstrate analogue farnesyltransferase inhibitor lacking any prenylic or peptidic substructures with nanomolar activity. This represents a considerable progress in comparison to those non-prenylic, non-peptidic bisubstrate analogue farnesyltransferase inhibitors we have described before which utilized AAX-peptidomimetic substructures different from the benzophenone since those inhibitors displayed activity only in the micromolar range.

Alkyl and Aryl Transferases↗

PubMed2002

Non-thiol farnesyltransferase inhibitors: utilization of an aryl binding site by 5-arylacryloylaminobenzophenones.

We recently described a novel aryl binding site of farnesyltransferase. The 2-naphthylacryloyl residue was developed as an appropriate substituent for our benzophenone-based AAX-peptidomimetic capable of occupying this binding site, resulting in a non-thiol farnesyltransferase inhibitor with nanomolar activity. The activity of this inhibitor is readily explained on the basis of docking studies which show the 2-naphthyl residue fitting into the aryl binding site.

Alkyl and Aryl Transferases↗

PubMed2002

Expression of melanocortin-1 receptor in normal, malformed and neoplastic skin glands and hair follicles.

Melanocortin receptors (MC-Rs) are G-protein coupled receptors that mediate pleiotropic actions of melanocyte-stimulating hormones and adrenocorticotropin. There is increasing evidence that one of the five so far identified melanocortin receptors, i.e. melanocortin-1 receptor (MC-1R), has a more ubiquitous distribution in the skin than originally expected. In the present study, the expression of MC-1R in normal skin glands and hair follicles, various malformations and neoplasms with adnexal differentiation is described. Using an anti-MC-1R antibody directed against the amino acids 2-18 of the human MC-1R, specimens of normal healthy skin (n = 10) as well as hamartomas, cysts, hyperplasias, and benign or malignant neoplasms with eccrine, apocrine, sebaceous gland, and hair follicle differentiation (n = 98) were immunostained. MC-1R expression was widely preserved in various adnexal malformations and neoplasms as compared with normal skin and did not show major differences with regard to maturation of the neoplasms. The majority of adnexal epithelia showed an intracytoplasmically granular staining and, to a lesser extent, an intercellular staining pattern. Immunoelectron microscopical investigations revealed expression of MC-1R both along the cell surface and intracytoplasmically within tubular endosomes, the latter suggesting internalisation of the receptor. In conclusion, preserved MC-1R expression in adnexal epithelia suggests a functional role of proopiomelanocortin (POMC) in various malformations and neoplasms of the skin.

Apocrine Glands↗

PubMed2002

Interleukin-12 suppresses ultraviolet radiation-induced apoptosis by inducing DNA repair.

Induction of apoptosis of keratinocytes by ultraviolet (UV) radiation is a protective phenomenon relevant in limiting the survival of cells with irreparable DNA damage. Changes in UV-induced apoptosis may therefore have significant impact on photocarcinogenesis. We have found that the immunomodulatory cytokine IL-12 suppresses UV-mediated apoptosis of keratinocytes both in vitro and in vivo. IL-12 caused a remarkable reduction in UV-specific DNA lesions which was due to induction of DNA repair. In accordance with this, IL-12 induced the expression of particular components of the nucleotide-excision repair complex. Our results show that cytokines can protect cells from apoptosis induced by DNA-damaging UV radiation by inducing DNA repair, and that nucleotide-excision repair can be manipulated by cytokines.

Adjuvants, Immunologic↗

PubMed2002

Evidence for expression of melanocortin-1 receptor in human sebocytes in vitro and in situ.

Many lines of evidence indicate that the activity of sebaceous glands can be modulated by neuropeptides. Direct evidence in man, however, is still missing. We show that SZ95 sebocytes, an immortalized human sebaceous gland cell line, express receptors for alpha-melanocyte-stimulating hormone. Reverse transcription polymerase chain reaction with primers against the five melanocortin receptors and immunofluorescence studies using an antibody directed against a peptide corresponding to the amino acids 2-18 of the human melanocortin-1 receptor disclosed specific transcripts and immunoreactivity for melanocortin-1 receptor in these cells. Melanocortin-1 receptor expression was confirmed in sebocytes of normal human skin by immunohistochemistry. In contrast, no immunostaining for the melanocortin-5 receptor could be detected in sebocytes in situ, in accordance with the lack of specific transcripts for this melanocortin receptor in SZ95 sebocytes. As cytokines play an important role in the recruitment of inflammatory cells in acne and related disorders and alpha-melanocyte-stimulating hormone exerts immunomodulatory effects in many other cell types, we investigated the effect of alpha-melanocyte-stimulating hormone on interleukin-8 secretion by SZ95 sebocytes. Treatment with interleukin-1beta resulted in a marked increase in interleukin-8 release that was partially blocked by coincubation with alpha-melanocyte-stimulating hormone in a dose-dependent manner. Taken together, we show here that the melanocortin-1 receptor is expressed in vitro and in situ in human sebocytes. By modulating interleukin-8 secretion, alpha-melanocyte-stimulating hormone may act as a modulator of inflammatory responses in the pilosebaceous unit.

Cell Membrane↗

PubMed2002

Cutaneous hyperpigmentation induced by doxycycline: histochemical and ultrastructural examination, laser microprobe mass analysis, and cathodoluminescence.

Skin hyperpigmentation induced by minocycline is a well-recognized side effect of minocycline but has rarely been reported for other tetracyclines. Based on a previously reported unusual case of chronic doxycycline abuse in a psychotic patient, we have investigated the nature of the observed pigment changes in the same patient. Histopathologic investigation of lesional skin by light microscopy disclosed hyperpigmentation of the basal keratinocytes and pigment-laden histiocytes in the dermis and subcutaneous fat. Only the pigment in the histiocytes of the upper dermis was reactive for Fontana Masson stain and could be bleached by hydrogen peroxide. The other histiocytes contained iron and calcium deposits as shown by von Kossa and Perls staining as well as by laser microprobe mass analysis. Ultrastructurally, these histiocytes contained amorphous material within the cytoplasm and stored in lysosomal structures. Comparative cathodoluminescence disclosed the presence of doxycycline in affected skin by means of overlapping emission spectra between the patient's skin and pure doxycycline. Taken together, the histomorphologic and ultrastructural changes induced by doxycycline shared several features with cutaneous hyperpigmentation caused by minocycline. Our biophysical findings further suggest a direct deposition of doxycycline, probably chelated with iron and/or calcium, within the lesional skin. Based on the presented unique case and the reviewed literature, only suprapharmacologic doses of doxycycline may be sufficient to cause such pigment changes.

Adult↗

PubMedDate not supplied

A 3D QSAR study on a set of dopamine D4 receptor antagonists.

The molecular alignments obtained from a previously reported pharmacophore model have been employed in a three-dimensional quantitative structure-activity relationship (3D QSAR) study, to obtain a more detailed insight into the structure-activity relationships for D(2) and D(4) receptor antagonists. The frequently applied CoMFA method and the related CoMSIA method were used. Statistically significant models have been derived with these two methods, based on a set of 32 structurally diverse D(2) and D(4) receptor antagonists. The CoMSIA and the CoMFA methods produced equally good models expressed in terms of q(2) values. The predictive power of the derived models were demonstrated to be high. Graphical interpretation of the results, provided by the CoMSIA method, brings to light important structural features of the compounds related to either low- or high-affinity D(2) or D(4) antagonism. The results of the 3D QSAR studies indicate that bulky N-substituents decrease D(2) binding, whereas D(4) binding is enhanced. Electrostatically favorable and unfavorable regions exclusive to D(2) receptor binding were identified. Likewise, certain hydrogen-bond acceptors can be used to lower D(2) affinity. These observations may be exploited for the design of novel dopamine D(4) selective antagonists.

Dopamine D2 Receptor Antagonists↗

PubMedDate not supplied

3D QSAR selectivity analyses of carbonic anhydrase inhibitors: insights for the design of isozyme selective inhibitors.

A 3D QSAR selectivity analysis of carbonic anhydrase (CA) inhibitors using a data set of 87 CA inhibitors is reported. After ligand minimization in the binding pockets of CA I, CA II, and CA IV isoforms, selectivity CoMFA and CoMSIA 3D QSAR models have been derived by taking the affinity differences (DeltapKi) with respect to two CA isozymes as independent variables. Evaluation of the developed 3D QSAR selectivity models allows us to determine amino acids in the respective CA isozymes that possibly play a crucial role for selective inhibition of these isozymes. We further combined the ligand-based 3D QSAR models with the docking program AUTODOCK in order to screen for novel CA inhibitors. Correct binding modes are predicted for various CA inhibitors with respect to known crystal structures. Furthermore, in combination with the developed 3D QSAR models we could successfully estimate the affinity of CA inhibitors even in cases where the applied scoring function failed. This novel strategy to combine AUTODOCK poses with CoMFA/CoMSIA 3D QSAR models can be used as a guideline to assess the relevance of generated binding modes and to accurately predict the binding affinity of newly designed CA inhibitors that could play a crucial role in the treatment of pathologies such as tumors, obesity, or glaucoma.

Animals↗