Exploratory Study of Intracutaneous Histamine Stimulation in Patient Populations with Chronic Pruritus.

Chronic pruritus can be a diagnostic sign of an underlying disease. In the intracutaneous histamine test, histamine (one of the best-known inducers of pruritus) may cause different reaction patterns depending on the underlying disease. The aim of this study was to determine if an intracutaneous injection of histamine can differentiate between the causes of chronic pruritus and thus be used as a diagnostic test in chronic pruritus of unknown aetiology. A total of 140 subjects with chronic pruritus with various dermatological, systemic or neurological diseases were included. The intracutaneous histamine test was performed once on each subject. Erythema, wheal and pruritus intensity were measured and analysed. Significantly greater wheal size was observed in patients with systemic or multifactorial causes. In general, there was a significant correlation between age and wheal size. Also, noticeable differences were found between males and females regarding pruritus and wheal size. In summary, the exact type of chronic pruritus could not be clearly determined based on the results of the intracutaneous histamine test. However, the results provide valuable insights into specific reaction patterns to experimental histamine-induced itch, e.g. sex-specific differences in the neurophysiology of pruritus, which should be considered in future studies.

Immune suppression via glucocorticoid-stimulated monocytes: a novel mechanism to cope with inflammation.

Glucocorticoids (GCs) are used as first-line therapies for generalized suppression of inflammation (e.g., allergies or autoimmune diseases), but their long-term use is limited by severe side effects. Our previous work revealed that GCs induced a stable anti-inflammatory phenotype in monocytes, the GC-stimulated monocytes (GCsMs) that we exploited for targeted GC-mediated therapeutic effects. We demonstrate that GCsMs interact with T cells in suppressing proliferation, as well as cytokine release of CD8(+) and, especially, CD4(+) T cells in vitro, and that they support generation of Foxp3(+) cells. Therefore, we tested their immunosuppressive potential in CD4(+) T cell-induced colitis in vivo. We found that injection of GCsMs into mice with severe colitis abolished the inflammation and resulted in significant clinical improvement within a few days. T cells recovered from GCsM-treated mice exhibited reduced secretion of proinflammatory cytokines IFN-γ and IL-17. Furthermore, clusters of Foxp3(+) CD4(+) T cells were detectable at local sites of inflammation in the colon. Thus, GCsMs are able to modify T cell responses in vitro and in vivo, as well as to downregulate and clinically cure severe T cell-mediated colitis.

The catabolite control protein E (CcpE) affects virulence determinant production and pathogenesis of Staphylococcus aureus.

Carbon metabolism and virulence determinant production are often linked in pathogenic bacteria, and several regulatory elements have been reported to mediate this linkage in Staphylococcus aureus. Previously, we described a novel protein, catabolite control protein E (CcpE) that functions as a regulator of the tricarboxylic acid cycle. Here we demonstrate that CcpE also regulates virulence determinant biosynthesis and pathogenesis. Specifically, deletion of ccpE in S. aureus strain Newman revealed that CcpE affects transcription of virulence factors such as capA, the first gene in the capsule biosynthetic operon; hla, encoding α-toxin; and psmα, encoding the phenol-soluble modulin cluster α. Electrophoretic mobility shift assays demonstrated that CcpE binds to the hla promoter. Mice challenged with S. aureus strain Newman or its isogenic ΔccpE derivative revealed increased disease severity in the ΔccpE mutant using two animal models; an acute lung infection model and a skin infection model. Complementation of the mutant with the ccpE wild-type allele restored all phenotypes, demonstrating that CcpE is negative regulator of virulence in S. aureus.

Epidermal expression of I-TAC (Cxcl11) instructs adaptive Th2-type immunity.

To decipher early promoters of the local microenvironment for Th2-type immunity, we wanted to identify gene patterns that were induced by Leishmania major in the infected skin of susceptible, Th2-prone BALB/c, but not of resistant, Th1-prone C57BL/6 mice. We found a marked up-regulation of the chemokine I-TAC (Cxcl11) during the first 2 d of infection in the epidermis of susceptible but not of resistant mice. Accordingly, local injection of I-TAC (2×1 µg) in resistant mice on the first day of infection resulted in a Th2-driven, sustained deterioration of disease and dramatically enhanced parasite levels. On the cellular level, I-TAC decreased IL-12 production by dendritic cells (DCs) in skin-draining lymph nodes and by DCs in vitro. Thus, we demonstrate for the first time that epidermis-derived I-TAC triggers a sustained Th2-response that determines the outcome of a complex immunological process.

Highly shifted proton MR imaging: cell tracking by using direct detection of paramagnetic compounds.

PURPOSE: To explore the feasibility of tracking thulium (Tm)-1,4,7,10-tetraazacyclododecane-α,α',α'',α'''-tetramethyl-1,4,7,10-tetraacetic acid (DOTMA)-labeled cells in vivo by means of highly shifted proton magnetic resonance (MR) imaging as a potential alternative to established cell-tracking methods. MATERIALS AND METHODS: All animal experiments were approved by the local ethics committee for animal experiments. Highly shifted proton MR imaging is based on the principle that the shifted resonances on Tm and dysprosium (Dy)-DOTMA can be detected separately from the tissue water signal at MR imaging with very short echo time and radial center-out readout (UTE, or "ultrashort echo time"). MR imaging of aqueous solutions and in mice in vivo was performed at 9.4 T. Human fibrosarcoma cells (HT-1080) and murine macrophages were labeled with different amounts of Tm-DOTMA. Labeled fibrosarcoma cells were injected subcutaneously into three mice. For cell tracking, labeled macrophages were administered intravenously into eight mice bearing local granulomatous inflammation. Three-dimensional UTE MR imaging was performed during 1 week. Macrophage viability and activity and fibrosarcoma cell viability were statistically analyzed by performing an unpaired two-tailed t test for labeled versus unlabeled cells by using data of at least six independent experiments. RESULTS: The strongly shifted MR lines of Tm- and Dy-DOTMA can be separated from the tissue water signal and from each other. A detection limit of about 25 µmol/L of Tm-DOTMA was calculated from in vitro MR measurements. A mean ± standard error of the mean intracellular uptake of (4.19 ± 0.88) × 10(9) (HT-1080) and (10.1 ± 3.0) × 10(10) (macrophages) of Tm-DOTMA molecules per cell was achieved. In vivo, Tm-DOTMA signal was detectable for 1 week in both tumors and macrophages, with a detection limit of approximately 10(4) HT-1080 and 600 macrophages. Histologic examination results and elemental bioimaging confirmed labeled cells as source of MR signal. CONCLUSION: Strongly shifted proton three-dimensional UTE MR imaging of Tm-DOTMA-labeled cells is a highly specific and sensitive tool for in vivo cell tracking.

Bacteria tracking by in vivo magnetic resonance imaging.

BACKGROUND: Different non-invasive real-time imaging techniques have been developed over the last decades to study bacterial pathogenic mechanisms in mouse models by following infections over a time course. In vivo investigations of bacterial infections previously relied mostly on bioluminescence imaging (BLI), which is able to localize metabolically active bacteria, but provides no data on the status of the involved organs in the infected host organism. In this study we established an in vivo imaging platform by magnetic resonance imaging (MRI) for tracking bacteria in mouse models of infection to study infection biology of clinically relevant bacteria. RESULTS: We have developed a method to label Gram-positive and Gram-negative bacteria with iron oxide nano particles and detected and pursued these with MRI. The key step for successful labeling was to manipulate the bacterial surface charge by producing electro-competent cells enabling charge interactions between the iron particles and the cell wall. Different particle sizes and coatings were tested for their ability to attach to the cell wall and possible labeling mechanisms were elaborated by comparing Gram-positive and -negative bacterial characteristics. With 5-nm citrate-coated particles an iron load of 0.015 ± 0.002 pg Fe/bacterial cell was achieved for Staphylococcus aureus. In both a subcutaneous and a systemic infection model induced by iron-labeled S. aureus bacteria, high resolution MR images allowed for bacterial tracking and provided information on the morphology of organs and the inflammatory response. CONCLUSION: Labeled with iron oxide particles, in vivo detection of small S. aureus colonies in infection models is feasible by MRI and provides a versatile tool to follow bacterial infections in vivo. The established cell labeling strategy can easily be transferred to other bacterial species and thus provides a conceptual advance in the field of molecular MRI.

Keratinocytes determine Th1 immunity during early experimental leishmaniasis.

Experimental leishmaniasis is an excellent model system for analyzing Th1/Th2 differentiation. Resistance to Leishmania (L.) major depends on the development of a L. major specific Th1 response, while Th2 differentiation results in susceptibility. There is growing evidence that the microenvironment of the early affected tissue delivers the initial triggers for Th-cell differentiation. To analyze this we studied differential gene expression in infected skin of resistant and susceptible mice 16h after parasite inoculation. Employing microarray technology, bioinformatics, laser-microdissection and in-situ-hybridization we found that the epidermis was the major source of immunomodulatory mediators. This epidermal gene induction was significantly stronger in resistant mice especially for several genes known to promote Th1 differentiation (IL-12, IL-1beta, osteopontin, IL-4) and for IL-6. Expression of these cytokines was temporally restricted to the crucial time of Th1/2 differentiation. Moreover, we revealed a stronger epidermal up-regulation of IL-6 in the epidermis of resistant mice. Accordingly, early local neutralization of IL-4 in resistant mice resulted in a Th2 switch and mice with a selective IL-6 deficiency in non-hematopoietic cells showed a Th2 switch and dramatic deterioration of disease. Thus, our data indicate for the first time that epidermal cytokine expression is a decisive factor in the generation of protective Th1 immunity and contributes to the outcome of infection with this important human pathogen.

CcpA Affects Infectivity of Staphylococcus aureus in a Hyperglycemic Environment.

Many bacteria regulate the expression of virulence factors via carbon catabolite responsive elements. In Gram-positive bacteria, the predominant mediator of carbon catabolite repression is the catabolite control protein A (CcpA). Hyperglycemia is a widespread disorder that predisposes individuals to an array of symptoms and an increased risk of infections. In hyperglycemic individuals, the bacterium Staphylococcus aureus causes serious, life-threatening infections. The importance of CcpA in regulating carbon catabolite repression in S. aureus suggests it may be important for infections in hyperglycemic individuals. To test this suggestion, hyperglycemic non-obese diabetic (NOD; blood glucose level ≥20 mM) mice were challenged with the mouse pathogenic S. aureus strain Newman and the isogenic ccpA deletion mutant (MST14), and the effects on infectivity were determined. Diabetic NOD mice challenged with the ccpA deletion mutant enhanced the symptoms of infection in an acute murine pneumonia model relative to the parental strain. Interestingly, when diabetic NOD mice were used in footpad or catheter infection models, infectivity of the ccpA mutant decreased relative to the parental strain. These differences greatly diminished when normoglycemic NOD mice (blood glucose level ≤ 10 mM) were used. These data suggest that CcpA is important for infectivity of S. aureus in hyperglycemic individuals.

Myeloid-related proteins 8 and 14 contribute to monosodium urate monohydrate crystal-induced inflammation in gout.

OBJECTIVE: Monosodium urate monohydrate (MSU) crystal-induced interleukin-1ß (IL-1ß) secretion is a critical factor in the pathogenesis of gout. However, without costimulation by a proIL-1ß-inducing factor, MSU crystals alone are insufficient to induce IL-1ß secretion. The responsible costimulatory factors that act as a priming endogenous signal in vivo are not yet known. We undertook this study to analyze the costimulatory properties of myeloid-related protein 8 (MRP-8) and MRP-14 (endogenous Toll-like receptor 4 [TLR-4] agonists) in MSU crystal-induced IL-1ß secretion and their relevance in gout. METHODS: MRP-8/MRP-14 was measured in paired serum and synovial fluid samples by enzyme-linked immunosorbent assay (ELISA) and localized in synovial tissue from gout patients by immunohistochemistry. Serum levels were correlated with disease activity, and MSU crystal-induced release of MRPs from human phagocytes was measured. Costimulatory effects of MRP-8 and MRP-14 on MSU crystal-induced IL-1ß secretion from phagocytes were analyzed in vitro by ELISA, Western blotting, and polymerase chain reaction. The impact of MRP was tested in vivo in a murine MSU crystal-induced peritonitis model. RESULTS: MRP-8/MRP-14 levels were elevated in the synovium, tophi, and serum of patients with gout and correlated with disease activity. MRP-8/MRP-14 was released by MSU crystal-activated phagocytes and increased MSU crystal-induced IL-1ß secretion in a TLR-4-dependent manner. Targeted deletion of MRP-14 in mice led to a moderately reduced response of MSU crystal-induced inflammation in vivo. CONCLUSION: MRP-8 and MRP-14, which are highly expressed in gout, are enhancers of MSU crystal-induced IL-1ß secretion in vitro and in vivo. These endogenous TLR-4 ligands released by activated phagocytes contribute to the maintenance of inflammation in gout.

Induction of an anti-inflammatory human monocyte subtype is a unique property of glucocorticoids, but can be modified by IL-6 and IL-10.

Glucocorticoids (GC) are the most widely used immunosuppressive agents in clinical medicine. Recently we showed that GC enhance survival of human monocytes and induce a specific anti-inflammatory monocyte subtype which actively induces resolution of inflammation. We now investigated if cytokines IL-4, IL-6 and IL-10, which, like GC, have mostly anti-inflammatory effects on macrophages, would have GC-like effects also on monocytes. Human monocytes were stimulated with either cytokine, GC or combination thereof, and resulting effects on apoptosis, adherence, migration, phagocytosis, ROS production and cell surface phenotype were determined. We found that IL-4, IL-6, and IL-10 had either less or different effects on various anti-inflammatory functions of monocytes compared to GC. As such, IL-4 and IL-6 alone did not delay apoptosis while IL-10 even enhanced it. However, IL-6 or IL-10 increased GC-mediated protection from apoptosis when applied together with GC. Thus, the potential of GC to induce anti-inflammatory human monocytes is unique and not mimicked by the investigated cytokines. However, IL-6 and IL-10 amplify GC-induced anti-inflammatory and pro-resolution mechanisms by enhancing survival of GC-induced monocytes and thus sustaining their function. This combined effect of GC and cytokines could be important for the physiological switch from amplification towards resolution phase of inflammation.

Staphylococcus aureus Panton-Valentine leukocidin induces an inflammatory response in human phagocytes via the NLRP3 inflammasome.

The Staphylococcus aureus pore-forming toxin PVL is most likely causative for life-threatening necrotizing infections, which are characterized by massive tissue inflammation and necrosis. Whereas the cytotoxic action of PVL on human neutrophils is already well established, the PVL effects on other sensitive cell types, such as monocytes and macrophages, are less clear. In this study, we used different types of human leukocytes (neutrophils, monocytes, macrophages, lymphocytes) to investigate cell-specific binding of PVL subunits and subsequent proinflammatory and cytotoxic effects. In all PVL-sensitive cells, we identified the binding of the subunit LukS-PV as the critical factor for PVL-induced cytotoxicity, which was followed by binding of LukF-PV. LukS-PV binds to monocytes, macrophages, and neutrophils but not to lymphocytes. Additionally, we showed that PVL binding to monocytes and macrophages leads to release of caspase-1-dependent proinflammatory cytokines IL-1ß and IL-18. PVL activates the NLRP3 inflammasome, a signaling complex of myeloid cells that is involved in caspase-1-dependent IL-1ß processing in response to pathogens and endogenous danger signals. Specific inhibition of this pathway at several steps significantly reduced inflammasome activation and subsequent pyronecrosis. Furthermore, we found that PAMPs and DAMPs derived from dying neutrophils can dramatically enhance this response by up-regulating pro-IL-1ß in monocytes/macrophages. This study analyzes a specific host signaling pathway that mediates PVL-induced inflammation and cytotoxicity, which has high relevance for CA-MRSA-associated and PVL-mediated pathogenic processes, such as necrotizing infections.

Subcutaneous infection with S. aureus in mice reveals association of resistance with influx of neutrophils and Th2 response.

Staphylococcus aureus is the leading cause of bacterial skin infection. Once it overcomes the epithelial barrier, it either remains locally controlled or spreads in the dermis causing soft tissue infection. These different courses depend not only on its virulence factors, but also on the immune response of the infected individual. The goal of this study was to identify host factors that influence different outcomes. We, therefore, established comparative analysis of subcutaneous footpad infection with S. aureus (SH1000) in different inbred mouse strains. We found that C57BL/6 mice are more susceptible than BALB/c and DBA/2 mice, reflected by significantly higher footpad swelling and bacterial load, as well as increased dissemination of bacteria into inguinal lymph nodes and kidneys. This susceptibility was associated with lower influx of polymorphonuclear leukocytes (PMNs), but higher secretion of CXCL-2. Remarkably, resistance correlated with S. aureus-specific Th2-cell response in BALB/c and DBA/2 mice, whereas susceptible C57BL/6 mice generated a Th1-cell response. As Th1 cells are able to induce release of CXCL-2, and as CXCL-2 is able to increase the survival of S. aureus within PMNs, interactions between PMNs and Th1 or Th2 cells need to be considered as important mechanisms of resistance in murine soft tissue infection with S. aureus.

LFA-1 contributes to signal I of T-cell activation and to the production of T(h)1 cytokines.

The beta(2) integrins are important for both transendothelial migration of leukocytes and T-cell activation during antigen presentation. In T cells, triggering of leukocyte functional antigen-1 (LFA-1) is required for full activation and T-helper (Th)1/Th2 differentiation. We used CD18-deficient (CD18(-/-)) mice to examine the role of LFA-1 in the activation of T cells. Compared with wild-type controls, CD18(-/-) T cells proliferated normally when stimulated with antibodies against CD3 and CD28, but secreted significantly less IFN-gamma and IL-2 than their wild-type counterparts. However, when T cells were stimulated with dendritic cells (DCs) that provide additional LFA-1 ligation, the proliferation of CD18(-/-) T cells was significantly reduced, whereas cytokine production remained impaired. The diminished proliferative capacity of CD18(-/-) T cells could be fully compensated for by additional triggering of the T-cell receptor, but not by additional stimulation through the costimulatory molecule, CD28. Thus, ligation of LFA-1 on T cells participates in regulation of Th1 cytokines in vivo. In addition, LFA-1 primarily exerts an effect as an enhancer of TCR signalling and does not facilitate classical costimulation.