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Background: Pyoderma gangraenosum is an immune-mediated, inflammatory, neutrophilic dermatosis of unknown etiology, which represents one of the extraintestinal manifestations of inflammatory bowel disease. It is a rare disease that occurs in less than 1% of patients with inflammatory bowel disease and with the same ratio in patients with Crohn's disease and ulcerative colitis. Main observations: A 36-year-old woman was diagnosed with ulcerative colitis 6 years before admission to our dermatology department with an acute disseminated pyoderma gangraenosum with mucosal involvement, during a flare of ulcerative colitis. Disease progression was interrupted by intravenous administration of the tumor necrosis factor-α inhibitor infliximab at 5mg/kg at weeks 0, 2, and 6 (1st cycle) and every 8 weeks thereafter. Improvement of intestinal, skin and oral manifestations was evident already after the 1st cycle of treatment and has been maintained since (at least 16 months). Conclusions: This case report is one of very few on disseminated pyoderma gangraenosum with oral involvement complicating ulcerative colitis, where infliximab was shown to have a rapid efficacy on skin, mucosal and bowel symptoms. [ABSTRACT FROM AUTHOR]

Abstract: Mast cells are important players in innate immunity and mediate allergic responses. Upon stimulation, they release biologically active mediators including histamine, cytokines and lysosomal hydrolases. We used permeabilized rat basophilic leukaemia cells as model to identify R-SNAREs (soluble NSF (N-ethylmaleimide-sensitive fusion protein)) mediating exocytosis of hexosaminidase from mast cells. Of a complete set of recombinant mammalian R-SNAREs, only vesicle associated membrane protein (VAMP8)/endobrevin consistently blocked hexosaminidase release, which was also insensitive to treatment with clostridial neurotoxins. Thus, VAMP8, which also mediates fusion of late endosomes and lysosomes, plays a major role in hexosaminidase release, strengthening the view that mast cell granules share properties of both secretory granules and lysosomes. [Copyright &y& Elsevier]

The structure and mode of binding of the endoplasmic reticulum protein disulfide isomerase-related proteins to their substrates is currently a focus of intensive research. We have recently determined the crystal structure of the Drosophila melanogaster protein disulfide isomerase-related protein Wind and have described two essential substrate binding sites within the protein, one within the thioredoxin b-domain and another within the C-terminal D-domain. Although a mammalian ortholog of Wind (ERp29/28) is known, conflicting interpretations of its structure and putative function have been postulated. Here, we have provided evidence indicating that ERp29 is indeed similar in both structure and function to its Drosophila ortholog. Using a site-directed mutagenesis approach, we have demonstrated that homodimerization of the b-domains is significantly reduced in vitro upon replacement of key residues at the predicted dimerization interface. Investigation of Wind-ERp29 fusion constructs showed that mutants of the D-domain of ERp29 prevent transport of a substrate protein (Pipe) in a manner consistent with the presence of a discrete, conserved peptide binding site in the D-domain. Finally, we have highlighted the general applicability of these findings by showing that the D-domain of a redox-active disulfide isomerase, from the slime mold Dictyostelium discoideum, can also functionally replace the Wind D-domain in vivo. [ABSTRACT FROM AUTHOR]

Mast cells generate and release histamine during anaphylactic reactions, and there is pharmacological evidence that histamine regulates this process via specific receptors. Therefore, we examined human leukemic (HMC-1) and normal skin mast cells for the expression of all four currently known histamine receptors. Both cell types expressed H2 and H4 receptors at mRNA and protein levels, whereas H3 receptor specific mRNA and receptor protein was undetectable. Similarly, immunohistochemistry of cutaneous tissue showed an absence of H3 receptor in these cells. Despite transcription of mRNA, H1 receptor protein was only moderately expressed in HMC-1 cells and was virtually absent in skin mast cells. Furthermore, only H1, H2, and H4 receptors were detectable by Western blot analysis of HMC-1 cells. Radiolabeled histamine binding was strongly inhibited only by H2 (ranitidine)- and H3/H4 (FUB 108)-specific antagonists. Histamine-induced increase of cAMP was inhibited by the H2 receptor antagonist famotidine, whereas induction of IP3 was not observed, making signaling via the H1 receptor unlikely. These data show that human mast cells constitutively express primarily H2 and H4 receptors and that H2 receptors are functionally linked to cellular processes. They provide new insights into the mechanisms that govern auto- and paracrine histamine-induced mast cell functions. [ABSTRACT FROM AUTHOR]

Background: Urticarial vasculitis (UV) should be differentiated from chronic spontaneous urticaria (CSU) in patients initially presenting with recurrent wheals, although criteria for differential diagnosis remain ill‐defined. Objectives: To set the goals, define criteria and unmet needs in UV diagnosis and differential diagnosis with CSU, and explore the possibility of coexistence of both diseases. Methods: Thirteen experts experienced in UV research participated in a Delphi survey of European Academy of Allergy and Clinical Immunology taskforce. This Delphi survey involved three rounds of anonymous responses to n = 32 questions with the aim to aggregate the experts' opinions and to achieve consensus. Urticaria specialists (n = 130, most from Urticaria Centers of Reference and Excellence) evaluated the consensus statements and recommendations in the fourth and final round. Results: The panel agreed that essential criteria to guide a skin biopsy in patients with recurrent wheals should include at least one of the following features: wheal duration >24 h, bruising/postinflammatory hyperpigmentation, and systemic symptoms. Leukocytoclasia and fibrin deposits were identified as a minimum set of UV histological criteria. As agreed by the panel members, CSU and normocomplementemic UV (NUV) may coexist in some patients. Conclusions: The use of established criteria for the diagnosis and differential diagnosis of UV in patients with recurrent wheals can help guide the diagnostic approach and prompt earlier treatment. Further studies should investigate whether CSU and NUV are different entities or part of a disease spectrum. [ABSTRACT FROM AUTHOR]

Membrane fusion in the secretory pathway is mediated by soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins. Different fusion steps are thought to be effected by independent sets of SNAREs, but it is unclear whether specificity is determined by an intrinsic specificity of SNARE pairing or by upstream factors. Using a newly developed microscopy-based assay, we have investigated the SNARE specificity of homotypic early endosomal fusion. We show that early endosomes contain multiple sets of SNAREs, including, in addition to the putative early endosomal SNAREs, those involved in exocytosis and in fusion of late endosomes. We demonstrate that fusion is largely mediated by a complex formed by syntaxin 13, syntaxin 6, vti1a, and VAMP4, whereas the exocytic and late endosomal SNAREs play little or no role in the reaction. In contrast, proteoliposomes reconstituted with early endosomal SNAREs promiscuously fuse with liposomes containing exocytotic or late endosomal SNAREs. We conclude that the specificity of SNARE pairing does not suffice to determine the specificity of organelle fusion. [ABSTRACT FROM AUTHOR]

Summary Psoriasis is a chronic inflammatory skin disease in which epidermal hyperplasia results from the release of cytokines by infiltrating type 1 T cells. Up- regulation of endogenous interleukin-10 controls type 1 skin responses in animal models; however, interleukin-10 production is low in psoriatic lesions. Consistent with an important role of interleukin-10 in psoriasis, we and colleagues have recently demonstrated clinical efficacy of subcutaneous administration of recombinant interleukin-10 to affected patients. Here, we studied the effects of interleukin-10 on disease-related inflammatory pathways. Patients were treated with recombinant interleukin-10 over 6 wk in an open-label phase II clinical trial. Tissue was obtained before and after therapy and examined by histology/immunohistochemistry, in situ hybridization, and quantitative real-time reverse transcription–polymerase chain reaction. Ten of 14 patients showed a marked reduction of the clinical disease activity. The clinical response was associated with a significant decrease of cutaneous T cell infiltration and the lesional expression of type 1 cytokines interferon-γ and tumor necrosis factor-α. Interleukin-10 inhibited the epidermal interleukin-8 pathway by downregulating the expression of interleukin-8, its receptor CXCR2, and its inducer interleukin-17, and partially reversed the aberrant keratinocyte maturation defining psoriatic epidermal pathology. Remarkably, there was evidence that genetic factors are involved in the response to interleukin-10 as individual variations in the downregulation of tumor necrosis factor-α were related to the presence of polymorphisms in the tumor necrosis factor-α promoter. These data suggest that excessive production of type 1 cytokines in human skin disease can be counter-regulated by the administration of recombinant interleukin-10. Genotypic analysis may help to identify patients that will preferentially respond to interleukin-10 therapy. [ABSTRACT FROM AUTHOR]

Since mast cells and basophils are thought to play a central role in several types of cutaneous inflammatory and allergic reactions and since interleukin-6 (IL-6) is an important mediator in these processes, we have studied the ability of the human mast cell line HMC-1, the human basophilic cell line KU812 and human skin mast cells to produce IL-6. All three cell types proved to be potent sources of this cytokine after appropriate stimulation. Transcription of IL-6 mRNA was first detectable 2 h after stimulation with the ester phorbol myristate acetate (PMA) and the calcium ionophore A23187 in both cell lines, as evidenced by semiquantitative reverse transcriptase polymerase chain reaction analysis. Whereas resting cells did not produce IL-6 protein, PMA/A23187- stimulated cells released immunoreactive and biologically active IL-6, as demonstrated and quantitated by enzyme-linked immunosorbent assay and by the use of TEPC 1033 cells an IL-6-dependent murine plasmacytoma cell line. Stimulated KU812 cells secreted sevenfold more IL-6 (up to 15 ng/ml) than HMC-1 cells (up to 2.4 ng/ml). Immunoblotting of HMC-1- and KU812 cell-derived IL-6 revealed several IL-6 forms in the molecular weight range of 2l to 30 kDa. Immunoelectron microscopic studies of human skin biopsies provided evidence that unstimulated mast cells do not contain preformed IL-6 but accumulate IL-6 in cytoplasmic and extruded granules after IgE-dependent stimulation. These findings suggest that IL-6 secreted by human mast cells and basophils potentially contributes to allergic, other immunologically mediated and nonspecific inflammatory responses. [ABSTRACT FROM AUTHOR]