Mammalian 15-lipoxygenases, which have been implicated in the differentiation of hematopoietic cells are commonly regarded as cytosolic enzymes. Studying the interaction of the purified rabbit ...reticulocyte 15-lipoxygenase with various types of biomembranes, we found that the enzyme binds to biomembranes when calcium is present in the incubation mixture. Under these conditions, an oxidation of the membrane lipids was observed. The membrane binding was reversible and led to an increase in the fatty acid oxygenase activity of the enzyme. To find out whether such a membrane binding also occurs in vivo, we investigated the intracellular localization of the enzyme in stimulated and resting hematopoietic cells by immunoelectron microscopy, cell fractionation studies and activity assays. In rabbit reticulocytes, the 15-lipoxygenase was localized in the cytosol, but also bound to intracellular membranes. This membrane binding was also reversible and the detection of specific lipoxygenase products in the membrane lipids indicated the in vivo activity of the enzyme on endogenous substrates. Immunoelectron microscopy showed that in interleukin-4 –treated monocytes, the 15-lipoxygenase was localized in the cytosol, but also at the inner side of the plasma membrane and at the cytosolic side of intracellular vesicles. Here again, cell fractionation studies confirmed the in vivo membrane binding of the enzyme. In human eosinophils, which constitutively express the 15-lipoxygenase, the membrane bound share of the enzyme was augmented when the cells were stimulated with calcium ionophore. Only under these conditions, specific lipoxygenase products were detected in the membrane lipids. These data suggest that in hematopoietic cells the cytosolic 15-lipoxygenase translocates reversibly to the cellular membranes. This translocation, which increases the fatty acid oxygenase activity of the enzyme, is calcium-dependent, but may not require a special docking protein.
Waiting time and practice organization in dermatology Krensel, Magdalene; Augustin, Matthias; Rosenbach, Thomas ...
Journal der Deutschen Dermatologischen Gesellschaft,
08/2015, Letnik:
13, Številka:
8
Journal Article
Apoptosis represents an active form of cell death that is involved in the control of tissue homeostasis and in the deletion of DNA-damaged cells. Because the product of the tumor suppressor gene p53 ...has been demonstrated to be crucial for the induction of apoptosis in certain cell types, the present study was aimed at elucidating its role in ultraviolet-induced apoptosis in HaCaT keratinocytes. After in vitro ultraviolet B irradiation, p53 protein levels were noted to increase prior to the induction of apoptosis in a time- and concentration-dependent fashion. This increase could not be inhibited by the protein synthesis inhibitor cycloheximide. Because HaCaT keratinocytes are known to bear two p53 point mutations and because it is unclear whether p53 in HaCaT cells is still functional regarding induction of apoptosis, HaCaT cells were stably transfected with wild-type p53 cDNA inserted into the expression vector pCMV-Neo-Bam in sense (pC53-SN3) and anti-sense (pC53-ASN) direction. After selection with geniticin, growing colonies were screened for the presence of the transfected cDNA constructs by polymerase chain reaction. Cell clones bearing the anti-sense product were further analyzed for p53 expression by western blotting. Clones showing reduced p53 protein levels were irradiated with ultraviolet B light, and there was a clear reduction of apoptosis in the pC53-ASN bearing cell clones compared with the parental HaCaT cells. These studies demonstrate that blocking mutated p53 can partially block apoptosis in HaCaT keratinocytes and furthermore can confirm the key role for p53 in ultraviolet-induced apoptosis in human keratinocytes. Moreover, HaCaT keratinocytes and their p53-transfectants provide a convenient model that allows for further detailed analyses of apoptosis-associated biochemical and molecular events in human keratinocytes.
Mutation of the hairless (hr) gene in mice causes severe abnormalities during the first hair follicle regression (catagen), resulting in complete baldness. Here, we further characterize how ...hairlessness develops in HRS/J hairless mouse skin (hr) by histology, histochemistry, immunohistology, and in situ hybridization. We show that, in hr skin, only two defined epithelial cell populations in the distal outer root sheath (ORS) retain their integrity, whereas the rest of the ORS disintegrates. The surviving distal ORS forms the characteristic utriculi, whereas the remnants of the bulge get isolated from other epithelial compartments, but retain the capacity to proliferate and to produce either columnar epithelial outgrowths or selected dermal cysts. Normal dermal papilla structures get lost during the development of hairlessness. Based on the patterns of keratin 17 mRNA and neural cell adhesion molecule antigen expression, and on the distribution of alkaline phosphatase activity, we propose that dermal cysts in hr skin arise from (i) the central ORS, (ii) bulge-derived cells, or (iii) the disintegrating proximal ORS under the influence of dermal papilla remnants. The hr mutation seems to disrupt the integrity of key functional tissue units in the hair follicle, possibly due to a dysregulation of normal, catagen-associated apoptosis and/or an impairment of cell adhesion, whereas the distal follicle epithelium (including its stem cell region) seems to be largely protected from this. Thus, hairless mice offer a unique model for dissecting the as yet obscure functional properties of the hr gene product in maintaining follicle integrity during normal catagen.
Zusammenfassung
Die topische Behandlung der Psoriasis und ihrer Sonderformen hat einen hohen Stellenwert im Praxisalltag. Sie ist Therapiestandard bei leichter Psoriasis und wird unterstützend auch ...bei mittelschwerer bis schwerer Psoriasis eingesetzt. Bei der Optimierung der Behandlung der Psoriasis spielt neben den geeigneten Wirkstoffen auch die Wahl der Galenik eine entscheidende Rolle. Die Weiterentwicklungen in diesem Bereich wurden in der 2017 publizierten Aktualisierung der S3‐Leitlinie nicht berücksichtigt. Der vorliegende Behandlungspfad wurde im Rahmen der PsoNet‐Sprecherkonferenz erarbeitet und durch die nationale Versorgungskonferenz Psoriasis bestätigt. Er stellt eine Illustration der aktuellen Optionen dar. Die Fachinformationen der genannten Präparate sind dabei stets zu berücksichtigen.
Die Festlegung von Therapiezielen mit dem Patienten ist obligat und adhärenzsteigernd. Dabei sollten die persönlichen Präferenzen und Vorerfahrungen des Patienten berücksichtigt werden. Goldstandard in der Initialphase ist die Fixkombination aus Calcipotriol (Cal) 50 μg/g und Betamethason‐Dipropionat (Bet) 0,5 mg/g 1x täglich über vier bis acht Wochen. Als Darreichungsform ist der Schaum am effektivsten, wobei die individuelle Wahl der Grundlage auch nach Patientenpräferenz erfolgen sollte.
In der Erhaltungsphase hat sich die 1–2x wöchentliche (proaktive) Anwendung dieser Fixkombination bewährt. In zweiter Linie können auch Vitamin D3 Analoga (Calcipotriol, Tacalcitol) und topische Corticosteroide als Monotherapie zur Anwendung kommen. Eine begleitende wirkstofffreie topische Basistherapie sollte regelhaft empfohlen werden. Bei besonderen Therapiesituationen werden spezifische Empfehlungen gegeben. Reicht eine alleinige Lokaltherapie nicht aus, sollte eine Therapieeskalation analog der S3‐Leitlinie zur Therapie der Psoriasis erfolgen.
Summary
Background
Current data from daily practice show that vitamin D
3
analogues, corticosteroids and their fixed combination products are used heterogeneously for topical long‐term treatment of ...psoriasis.
Aim
To evaluate scientific evidence about topical long‐term therapy with vitamin D
3
analogues, corticosteroids and their two‐compound‐products in psoriasis vulgaris and scalp psoriasis and to develop daily practice recommendations.
Methods
Systematic literature review via PubMed® and Embase® and informal expert consensus.
Results
The search strategy identified 21 relevant clinical trials. Best evidence regarding topical long term treatment was available for the two‐compound‐formulation containing calcipotriene and betamethasone. In a comparative trial in psoriasis vulgaris the two‐compound‐formulation showed superior tolerability and cost effectiveness compared to monotherapy. In scalp psoriasis the two‐compound‐gel was superior compared to calcipotriene monotherapy. Standardized and simplified treatment application modes resulted in a better clinical outcome comparing to on‐demand therapies.
Daily practice recommendations
Patients should be proactively involved in the choice of treatment, formulation and mode of application. Besides long‐term treatment with the two‐compound‐formulation other treatment regimens including calcipotriene monotherapy can also be considered. Due to a favorable risk‐benefit ratio in maintenance trials and due to better cost‐effectiveness the application of two‐compound‐products once or twice a week after initial therapy is recommended.
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