Malene Hvid

IL-25 in Atopic Dermatitis: A Possible Link between Inflammation and Skin Barrier Dysfunction?

Atopic dermatitis (AD) is a common skin disease associated with a T(H)2 response and increased levels of T(H)2-associated cytokines and IgE. The mechanisms resulting in skewing the immune response in a T(H)2 direction in AD are not fully elucidated. However, such skewing has recently been associated with IL-25 in a murine model for allergic airway disease. The aim of this study was to investigate whether IL-25 may have a role in AD. We have identified IL-25-producing cells within the dermis of AD patients and propose that these cells are dendritic cells (DCs). This is supported by in vitro experiments that indicate that monocyte-derived DCs are capable of producing IL-25. As null mutations of filaggrin are associated with the development of an impaired skin barrier in AD, we investigated whether IL-25 affects filaggrin synthesis by keratinocytes. Using mRNA analysis, we have shown that IL-25 stimulation does indeed decrease filaggrin synthesis in cultured keratinocytes. These results suggest that IL-25 produced by DCs could have a dual role as both an inducer of the T(H)2 response and as an inhibitor of filaggrin synthesis, thereby directly affecting skin barrier function in AD patients.

Interleukin‐1 is the initiator of Fallopian tube destruction during Chlamydia trachomatis infection

Chlamydia trachomatis infection is associated with severe Fallopian tube tissue damage leading to tubal infertility and ectopic pregnancy. To explore the molecular mechanisms behind infection an ex vivo model was established from human Fallopian tubes and examined by scanning electron microscopy and immunohistochemistry. Extensive tissue destruction affecting especially ciliated cells was observed in C. trachomatis infected human Fallopian tube organ culture. Interleukin‐1 (IL‐1) produced by epithelial cells was detected after infection. Addition of IL‐1 receptor antagonist (IL‐1RA) completely eliminated tissue destruction induced by C. trachomatis. The anti‐inflammatory cytokine IL‐10 reduced the damaging effect of C. trachomatis infection, however, to a lesser extent than IL‐1RA. Furthermore, IL‐1 was found to induce IL‐8, a neutrophil attractant, using a signal transduction pathway involving p38 MAP kinase. Consequently, IL‐1 has the potential to generate a cellular infiltrate at the site of infection in vivo. Blocking the IL‐1 receptors by IL‐1RA eliminated tissue destruction and cytokine production. Hence, these studies show the importance of IL‐1 in initiating the tissue destruction observed in the Fallopian tube following C. trachomatis infection. Because leukocytes are absent in the ex vivo model, this study strongly indicates that IL‐1 is the initial proinflammatory cytokine activated by C. trachomatis infection.

Original ArticleIL-25 in Atopic Dermatitis: A Possible Link between Inflammation and Skin Barrier Dysfunction?

Atopic dermatitis (AD) is a common skin disease associated with a T(H)2 response and increased levels of T(H)2-associated cytokines and IgE. The mechanisms resulting in skewing the immune response in a T(H)2 direction in AD are not fully elucidated. However, such skewing has recently been associated with IL-25 in a murine model for allergic airway disease. The aim of this study was to investigate whether IL-25 may have a role in AD. We have identified IL-25-producing cells within the dermis of AD patients and propose that these cells are dendritic cells (DCs). This is supported by in vitro experiments that indicate that monocyte-derived DCs are capable of producing IL-25. As null mutations of filaggrin are associated with the development of an impaired skin barrier in AD, we investigated whether IL-25 affects filaggrin synthesis by keratinocytes. Using mRNA analysis, we have shown that IL-25 stimulation does indeed decrease filaggrin synthesis in cultured keratinocytes. These results suggest that IL-25 produced by DCs could have a dual role as both an inducer of the T(H)2 response and as an inhibitor of filaggrin synthesis, thereby directly affecting skin barrier function in AD patients.

Increased Interleukin 21 (IL-21) and IL-23 Are Associated with Increased Disease Activity and with Radiographic Status in Patients with Early Rheumatoid Arthritis

Objective. To investigate the levels of the T helper (Th)17-related cytokines interleukin 17A (IL-17A), IL-21, and IL-23 and their association with disease activity in rheumatoid arthritis (RA). Methods. In a longitudinal sample set from patients with early RA (< 6 months; n = 40), we measured the plasma cytokine levels of IL-17A, IL-21, and IL-23 and analyzed for correlation with disease activity in 28 joints (Disease Activity Score 28-joint count; DAS28), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and total Sharp score (TSS). In a transverse sample set of patients with chronic RA (> 8 years), using paired peripheral blood mononuclear cells and synovial fluid mononuclear cells, we investigated the cellular expression of IL-17A, IL-21, and IL-23R. Results. Patients with early-stage RA had significantly increased plasma levels of IL-21 and IL-23, but not IL-17A, compared to patients with chronic RA and healthy volunteer controls. Plasma levels of IL-21 and IL-23 after 12 months of treatment correlated with DAS28 and ESR, but not to TSS. Changes in IL-23 plasma levels from time of diagnosis to 12 months correlated with change in DAS28 and with TSS scores at 2 years. The numbers of CD4+ T cells producing IL-21 were significantly increased in the synovial fluid of patients with chronic RA, with only marginal coexpression of IL-21 and IL-17A. Conclusion. Our results show a significant association between plasma levels of IL-21 and IL-23 and disease activity in RA, supporting the hypothesis that IL-21 and IL-23 are important pathogenic factors of this disease.

Regulation of caspase 14 expression in keratinocytes by inflammatory cytokines – a possible link between reduced skin barrier function and inflammation?

Abstract:  Caspase 14 is a unique member of the cysteinyl aspartate‐specific proteinase family. Its expression is confined primarily to cornified epithelium such as the skin. Caspase 14 has been associated with the processing of filaggrin monomers and the development of natural moisturising factors of the skin, and thus, it could be speculated that caspase 14 dysregulation is implicated in the development of an impaired skin barrier function. We have investigated the regulation of caspase 14 transcription in cultured primary keratinocytes following stimulation with a number of factors present in inflamed skin, including TH1‐ and TH2‐associated cytokines in addition to LPS and peptidoglycan. In particular, we found that TH2‐associated cytokines reduced the caspase 14 mRNA level significantly. Furthermore, we found that the expression of caspase 14 was reduced in skin biopsies from patients with atopic dermatitis (AD), psoriasis and contact dermatitis, further supporting a role for this kinase in inflammatory skin conditions. Hence, the regulation of caspase 14 levels provides a possible link between impaired skin barrier function and inflammatory reactions in skin diseases such as AD and may offer an explanation to the skin barrier dysfunction in inflamed skin lesions.

Expression of MDC/CCL22 and its receptor CCR4 in rheumatoid arthritis, psoriatic arthritis and osteoarthritis

The pathogenesis of rheumatoid arthritis (RA) and psoriatic arthritis (PsA) involves an abnormal chemokine regulation. The chemokine receptor CCR4 is necessary for T cell migration to the skin. We, therefore, studied if CCR4 and its ligand macrophage-derived chemokine (MDC/CCL22) could participate in spreading the disease between skin and joints by examining RA, PsA and osteoarthritis (OA) patients. In synovial fluid from RA and PsA patients we observed a significantly higher MDC/CCL22 level compared to OA patients. Additionally, the MDC/CCL22 protein was found to be elevated in RA and PsA plasma compared to OA and healthy volunteers. Flow cytometry revealed that most CD4(+)CCR4(+) lymphocytes also co-expressed CD45RO. Neither the MDC/CCL22 level nor the expression of CCR4 correlated to CRP. Immunohistochemistry of the RA and OA synovial membrane demonstrated CCR4 to be expressed by mononuclear cells and endothelial cells. Our results show that MDC/CCL22 is present within the synovial membrane of RA and OA patients and in high amount in the synovial fluid of patients with RA and PsA. This will enable migration of CCR4 expressing memory cells supporting that MDC/CCR4 could play a role in attracting skin specific memory T cells to the joints.

TSLP, IL-31, IL-33 and sST2 are new biomarkers in endophenotypic profiling of adult and childhood atopic dermatitis.

Recent years have seen growing interest in identifying new biomarkers in atopic dermatitis (AD) that could serve as indicators of disease severity and predictors of treatment response.

A simple set of validation steps identifies and removes false results in a sandwich enzyme-linked immunosorbent assay caused by anti-animal IgG antibodies in plasma from arthritis patients

Rheumatoid arthritis (RA) and spondyloarthritis (SpA) are chronic diseases characterized by activation of the immune system and production of antibodies. Thus, rheumatoid factor, anti-animal IgG antibodies and heterophilic antibodies in plasma samples from arthritis patients can interfere with immunoassays such as sandwich enzyme-linked immunosorbent assay (ELISA) systems often used in arthritis research. However, standard methodologies on how to test for false results caused by these antibodies are lacking. The objective of this study was to design a simple set of steps to validate a sandwich ELISA before using it for measuring analytes in plasma from arthritis patients. An interleukin-24 (IL-24) sandwich ELISA system was prepared with a monoclonal mouse capture antibody and a polyclonal goat detection antibody and tested for interference by rheumatoid factor, anti-animal IgG antibodies and heterophilic antibodies. Plasma samples from 23 patients with RA and SpA were used. No differences were found between plasma samples measured in wells coated with anti-IL-24 specific antibody and in wells coated with isotype control antibody (false positive results), and recombinant human IL-24 was not recovered in spiked samples (false negative results). This interference was removed after preincubating the plasma samples from patients with arthritis with goat or bovine IgG, suggesting that anti-animal IgG antibodies found in the plasma of the arthritis patients caused the false results. Additional testing showed that the signal-to-noise ratio could be increased by titration of the capture and detection antibodies and by using the ELAST amplification system. Finally, the calculated concentration of IL-24 was increased in ethylenediaminetetraacetic acid (EDTA) plasma compared to heparin plasma and serum and decreased with repetitive freeze/thaw cycles of the samples illustrating how sample handling could additionally contribute to the variations reported by different laboratories in measurement of the same analyte. This study proposes a simple set of validation steps to evaluate and optimize a sandwich ELISA before using it for measuring analytes in plasma from arthritis patients. Anti-animal IgG antibodies are also present in healthy individuals, suggesting that validation of ELISA systems for measuring non-arthritis samples could also be improved by this simple set of validation steps.

TLR3 Ligand Polyinosinic:Polycytidylic Acid Induces IL-17A and IL-21 Synthesis in Human Th Cells

TLR3 and TLR9 recognize the pathogen-associated microbial patterns dsRNA and unmethylated DNA, respectively. The recent discovery that these receptors also recognize endogenous ligands from necrotic material has drawn increased attention to their involvement in autoimmunity. Th cell cytokines IL-17A and IL-21 have been assigned with pivotal roles in the regulation of such autoimmune diseases. IL-17A is the hallmark cytokine of the recently discovered proinflammatory Th cell subset TH17. By contrast, the expression of IL-21 does not seem to be limited to a single distinct Th cell subset. We investigated the expression of IL-17A and IL-21 in human CD4+ T cells in response to stimulation with the TLR3 ligand polyinosinic:polycytidylic acid (poly(I:C)) and the TLR9 ligand CpG. We discovered that poly(I:C) induced synthesis of both IL-17A and IL-21. Moreover, we found that poly(I:C) was able to drive the differentiation of naive Th cells into an IL-21 but not into an IL-17A-producing phenotype and did this without affecting the levels of transcription factors T-bet, GATA-3, or retinoic acid receptor-related orphan receptor C. Finally, we found that the IL-21-producing cells that were differentiated in response to poly(I:C) expressed the chemokine receptor CXCR3, which is important in the recruitment of T cells into inflamed joints in rheumatoid arthritis. This is the first report to show that the TLR3 ligand poly(I:C) can directly induce the synthesis of IL-17A and IL-21 and drive differentiation of human naive CD4+ T cells.

IL-25 Induces Both Inflammation and Skin Barrier Dysfunction in Atopic Dermatitis

Atopic dermatitis (AD) is a chronic relapsing skin disease characterized by having both an epidermal and a dermal component, shown as a barrier deficiency and inflammation. The mechanisms resulting in skewing the immune response in a Th2 direction in AD are still not fully elucidated. We suggest that IL-25 could be a major target in AD. IL-25 is produced by cells within the dermis of AD patients, and we suggest these to be dendritic cells (DCs). Furthermore, we show that IL-25 can inhibit filaggrin synthesis in keratinocytes. These results point towards a central role of IL-25 producing DCs that can induce both a Th2 response and inhibit filaggrin synthesis. We believe this strongly supports a role for IL-25 in AD, bridging the gap between inflammation and impaired skin barrier function.