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INTRODUÇÃO: O conhecimento sobre os tipos celulares envolvidos na patogenia da urticária constitui um elemento essencial para a compreensão da fisiopatologia desta doença. Poucos autores têm dado atenção às interações entre mastócitos e dendrócitos da derme na urticária. Os objetivos deste estudo são orientados no sentido de descreverem-se os tipos de degranulação mastocitária na urticária aguda associada a medicamentos, e o de analisarem-se as interações entre dendrócitos da derme e mastócitos. MÉTODOS: Sete doentes com urticária aguda associada com medicamentos foram incluídos neste estudo. Foram obtidas biopsias cutâneas das lesões urticadas e da pele aparentemente normal destes doentes. Os quatorze fragmentos coletados foram divididos em duas partes (28 fragmentos): uma das partes foi enviada para processamento pela coloração de hematoxilina-eosina, para a coloração de Azul de Toluidina e reações de imunoistoquímica com anticorpos anti-CD34, antifator XIIIA (anti- FXIIIa) e antitriptase e o outro fragmento foi processado para uso na microscopia imunoeletrônica, utilizando-se anticorpos para triptase e FXIIIa, além de dupla imunomarcação com ouro com o uso de anticorpos antitriptase e anti-FXIIIa. RESULTADOS: células imunomarcadas com anticorpos anti-CD34 foram observadas de forma esparsa na derme superficial e de forma mais proeminente na derme reticular. Havia múltiplos dendrócitos dérmicos FXIIIa+ na derme superficial e média, dispersos nas regiões subepidérmicas e em torno doa vasos da derme, tanto na pele urticada com na pele aparentemente normal. O número destas células foi similar nos dois grupos de amostras. Não houve diferença estatística entre o número de células triptase-positivas na pele aparentemente normal e na pele urticada, em todos os doentes. Nós observamos mastócitos íntegros na maioria das amostras da pele aparentemente normal. Tanto as amostras de pele aparentemente normal quanto as amostras de pele urticada apresentavam mastócitos em processo de degranulação do tipo anafilático, com inúmeros grânulos extruídos. Após a dupla imunomarcação com ouro, na imuno-microscopia eletrônica de transmissão foram observadas partículas de ouro de 10 nm (FXIIIa) e 15 nm (Triptase) marcando concomitante os grânulos dos mastócitos indicando que tanto a triptase como o FXIIIa encontraram-se presentes nos grânulos destas células. De forma interessante, nós encontramos uma forte evidência de que grânulos contendo tanto FXIIIa, como triptase, extruídos dos mastócitos são fagocitados pelos dendrócitos da derme. CONCLUSÕES: na urticária aguda associada a medicamentos o padrão de degranulação observado foi do tipo anafilático. Este estudo constitui a primeira demonstração da expressão do FXIIIa nos grânulos intracitoplasmáticos e nos grânulos extruídos dos mastócitos, dispersos na matriz extracelular, nos doentes com urticária aguda associada a medicamentos. Outro fato inédito foi a demonstração da fagocitose dos grânulos extruídos dos mastócitos pelos dendrócitos da derme FXIIIa+ / BACKGROUND: The knowledge about the cell types involved in urticaria is an essential element for understanding the pathophysiology of this disease. Few authors have been attempting on interactions among mast cells and dermal dendrocytes in urticaria. The aims of this study are to describe the types of mast cell degranulation in drug-induced acute, besides to analyze the interactions between mast cell and dermal dendrocyte in urticaria. METHODS: Seven patients with drug-induced acute urticaria were enrolled in the study. We token skin biopsies of urticarial lesion and apparently normal skin. The fourteen fragments collected were divided into two parts (28 sections): one to haematoxylin-eosin stain, Toluidine blue stain and immunohistochemisty reactions with anti-CD34, anti-FXIIIa and anti-tryptase antibodies and other part to immunogold electron microscopy using single antibodies to tryptase and FXIIIa, besides double immunogold labelling with anti-tryptase and anti-FXIIIa. RESULTS: immunolabelled CD34+ cells were observed scattered in the superficial dermis and more prominent in the reticular dermis. There were multiple FXIIIa+ dermal dendrocytes in upper and mid dermis, dispersed in subepidermal areas and around blood vessels, both in apparently normal skin and urticarial lesion of drug-induced acute urticaria. The number of these cells was similar in both groups. There was no difference in tryptase positive cells number between apparently normal skin and urticarial lesions, in all patients. We observed intact mast cells in the majority of the sections of the apparently normal skin. Some sections demonstrated a few mast cells in degranulation process, in anaphylactic degranulation type. In urticarial lesions, several mast cells showed degranulation process, in anaphylactic degranulation type. After double immunogold staining, 10 nm (FXIIIa) and 15 nm (Tryptase) gold particles were seen together over the granules in mast cells indicating that tryptase and FXIIIa are each localized into granules of these cells. Interestingly, we found a strong evidence of than the exocytosed mast cell granules contents both FXIIIa and Tryptase immunolabelled are phagocytised by dermal dendrocytes. CONCLUSIONS: In drug-induced acute urticaria the degranulation pattern of mast cells found was composed by anaphylatic. This is the first report, in acute urtuicaria, concern of the expression of FXIIIa in the cytoplasmic mast cell and in extruded granules into extracellular matrix. Phagocytosis of the extruded mast cell granules by FXIIIa+ dermal dendrocytes in urticaria was observed

Indiana University-Purdue University Indianapolis (IUPUI) / In response to glucose, pancreatic islet beta cells secrete insulin in a biphasic manner, and both phases are diminished in type 2 diabetes. In beta cells, cortical F-actin beneath the plasma membrane (PM) prevents insulin granule access to the PM and glucose stimulates remodeling of this cortical F-actin to allow trafficking of insulin granules to the PM. Glucose stimulation activates the small GTPase Cdc42, which then activates p21-activated kinase 1 (PAK1); both Cdc42 and PAK1 are required for insulin secretion. In conjunction with Cdc42-PAK1 signaling, the SNARE protein Syntaxin 4 dissociates from F-actin to allow SNARE complex formation and insulin exocytosis. My central hypothesis is that, in the pancreatic beta cell, glucose signals through a Cdc42-PAK1-mediated pathway to remodel the F-actin cytoskeleton to mobilize insulin granules to SNARE docking sites at the PM to evoke glucose stimulated second phase insulin secretion. To investigate this, PAK1 was inhibited in MIN6 beta cells with IPA3 followed by live-cell imaging of F-actin remodeling using the F-actin probe, Lifeact-GFP. PAK1 inhibition prevented normal glucose-induced F-actin remodeling. PAK1 inhibition also prevented insulin granule accumulation at the PM in response to glucose. The ERK pathway was implicated, as glucose-stimulated ERK activation was decreased under PAK1-depleted conditions. Further study showed that inhibition of ERK impaired insulin secretion and cortical F-actin remodeling. One of the final steps of insulin secretion is the fusion of insulin granules with the PM which is facilitated by the SNARE proteins Syntaxin 4 on the PM and VAMP2 on the insulin granule. PAK1 activation was also found to be critical for Syntaxin 4-F-actin complex dynamics in beta cells, linking the Cdc42-PAK1 signaling pathway to SNARE-mediated exocytosis. Syntaxin 4 interacts with the F-actin severing protein Gelsolin, and in response to glucose Gelsolin dissociates from Syntaxin 4 in a calcium-dependent manner to allow Syntaxin 4 activation. Disrupting the interaction between Syntaxin 4 and Gelsolin aberrantly activates endogenous Syntaxin 4, elevating basal insulin secretion. Taken together, these results illustrate that signaling to F-actin remodeling is important for insulin secretion and that F-actin and its binding proteins can impact the final steps of insulin secretion.

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Die integralen Vesikelmembranproteine Synaptophysin und Synaptobrevin interagieren in adulten Neuronen. Zusätzlich bildet Synaptobrevin mit den Plasmamembranproteinen Syntaxin und synaptosome-associated protein 25kDa (SNAP25) den SNAP-Rezeptor (SNARE)-Proteinkomplex, der Voraussetzung für die Fusion zwischen synaptischen Vesikeln und präsynaptischer Membran ist. Mit Synaptophysin interagierendes Synaptobrevin bindet jedoch nicht an den SNARE-Proteinen. Es wird daher vermutet, dass der Synaptophysin/Synaptobrevin-Komplex eine Art Reservepool für Synaptobrevin bei erhöhter neuronaler Aktivität darstellt und die Verfügbarkeit von Synaptobrevin während der Exozytose reguliert. Mit verschiedenen Ansätzen wurde versucht, den auf dem Vesikel befindlichen Komplex genauer zu charakterisieren und in seiner Funktion näher zu beschreiben. Nach Stimulation mit exozytosevermittelnden Substanzen dissoziierte der Synaptophysin/ Synaptobrevin-Komplex, sowohl unter nativen Bedingungen als auch bei Blockierung des finalen Fusionsereignisses. Dieser Prozess war calciumabhängig, konnte jedoch nicht durch die direkte Wirkung von Calcium ausgelöst werden. Die Untersuchung des Komplexes mit Hilfe von clostridialen Neurotoxinen zeigte, dass Synaptobrevin bevorzugt in Bindung an Synaptophysin und als Dimer gespalten wurde. Die Spaltung des SNARE-Proteins SNAP25 hatte keinen Einfluss auf die Komplexbildung. Die Verringerung des Cholesterolgehaltes der Membran führte zur Abnahme der Interaktion von Synaptophysin und Synaptobrevin, umgekehrt zeigte sich ein Anstieg bei zusätzlicher Cholesterolapplikation. In weiteren Experimenten konnte der C-terminale Teil des Synaptobrevins als für die Bindung zu Synaptophysin entscheidende Abschnitt identifiziert werden. Weiterhin konnte die erfolgreiche Translokation von rekombinanten Konstrukten aus Botulinumtoxin D und einem angekoppelten funktionstüchtigen Protein ins Zytosol gezeigt werden. / The vesicle associated membrane proteins synaptophysin and synaptobrevin interact in ma-ture neurones. Additionally synaptobrevin forms a complex with the plasma membrane pro-teins syntaxin and synaptosome-associated protein 25kDa (SNAP25), better known as the SNAP-Receptor (SNARE) complex, which is a prerequisite for fusion of the presynaptic and vesicle membranes. These two protein complexes however are mutually exclusive. It is as-sumed that the synaptophysin/synaptobrevin complex resembles a reserve pool for synapto-brevin and regulates the availability of synaptobrevin for the fusion process in case of in-creased synaptic activity. Different approaches where chosen to characterize this protein complex and to examine its function in more detail. After excessive stimulation the synaptophysin/synaptobrevin complex dissociates, even when the final fusion process is blocked. This step was dependent on the presence of cal-cium, though it could not be triggered directly by calcium administration. When using clos-tridial neurotoxins, synaptobrevin was preferentially cleaved in its homodimeric form and in the complex with synaptophysin. Cleavage of SNAP25 had no effect on the complex forma-tion. Depletion of cholesterol content decreases the interaction of synaptophysin with synap-tobrevin, while cholesterol treatment increases interaction. Further experiments indicated that synaptophysin binds to the the carboxy-terminal transmembrane part of synaptobrevin. Fur-thermore it could be shown that proteins attached to botulinum toxin can be delivered to the cytosol of neuronal cells, being fully active.

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