Antti Lauerma

IL-33 and ST2 in atopic dermatitis: expression profiles and modulation by triggering factors.

In the acute phase of atopic dermatitis (AD), T-helper type 2 (Th2) cytokines characterize the inflammatory response in the skin. IL-33 is a new tissue-derived cytokine, which is mainly expressed by cells of barrier tissues, and is known to activate Th2 lymphocytes, mast cells, and eosinophils. IL-33 signals through a receptor complex consisting of IL-33-specific receptor ST2 and a co-receptor IL-1RAcP. As IL-33 is known to promote Th2-type immunity, we examined expression profiles of IL-33 and its receptor components in human AD skin, in the murine model of AD, and in various cell models. We found increased expression of IL-33 and ST2 in AD skin after allergen or staphylococcal enterotoxin B (SEB) exposure, as well as in the skin of 22-week-old filaggrin-deficient mice. In addition, skin fibroblasts, HaCaT keratinocytes, primary macrophages, and HUVEC endothelial cells efficiently produced IL-33 in response to the combined stimulation of tumor necrosis factor-α and IFN-γ, which was further enhanced by a mimetic of double-stranded RNA. Finally, the increased expression of IL-33 and ST2 caused by irritant, allergen, or SEB challenge was suppressed by topical tacrolimus treatment. These results suggest an important role for IL-33-ST2 interaction in AD and highlight the fact that bacterial and viral infections may increase the production of IL-33.

MiR-155 is overexpressed in patients with atopic dermatitis and modulates T-cell proliferative responses by targeting cytotoxic T lymphocyte–associated antigen 4

BACKGROUND MicroRNAs (miRNAs) are short noncoding RNAs that suppress gene expression at the posttranscriptional level. Atopic dermatitis is a common chronic inflammatory skin disease characterized by the presence of activated T cells within the skin. OBJECTIVE We sought to explore the role of miRNAs in the pathogenesis of atopic dermatitis. METHODS Global miRNA expression in healthy and lesional skin of patients with atopic dermatitis was compared by using TaqMan MicroRNA Low Density Arrays. miR-155 expression in tissues and cells was quantified by means of quantitative real-time PCR. The cellular localization of miR-155 was analyzed by means of in situ hybridization. The regulation of cytotoxic T lymphocyte-associated antigen (CTLA-4) by miR-155 was investigated by using luciferase reporter assays and flow cytometry. CTLA-4 expression and functional assays were performed on T(H) cells overexpressing miR-155. RESULTS miR-155 was one of the highest-ranked upregulated miRNAs in patients with atopic dermatitis. In the skin miR-155 was predominantly expressed in infiltrating immune cells. miR-155 was upregulated during T-cell differentiation/activation and was markedly induced by T-cell activators in PBMCs in vitro and by superantigens and allergens in the skin in vivo. CTLA-4, an important negative regulator of T-cell activation, was identified as a direct target of miR-155. Overexpression of miR-155 in T(H) cells resulted in decreased CTLA-4 levels accompanied by an increased proliferative response. CONCLUSION miR-155 is significantly overexpressed in patients with atopic dermatitis and might contribute to chronic skin inflammation by increasing the proliferative response of T(H) cells through the downregulation of CTLA-4.

Transforming growth factor-beta/Smad3 signalling regulates inflammatory responses in a murine model of contact hypersensitivity.

Background  Transforming growth factor (TGF)‐β is an important modulator of immune functions and cellular responses, such as differentiation, proliferation, migration and apoptosis. The Smad proteins, which are intracellular TGF‐β signal transducers, mediate most actions of TGF‐β.

Foxp3+ Cells Control Th2 Responses in a Murine Model of Atopic Dermatitis

The role of Foxp3+ regulatory T (Treg) cells in atopic dermatitis (AD) is still unclear. In a murine AD model, the number of Foxp3+ cells increased in the allergen-exposed skin area and in the secondary lymphoid organs. Both Foxp3+ and Foxp3- IL-10+ T cells accumulated at the site of allergen exposure, and CD103+ effector/memory Foxp3+ Treg cells expanded gradually in the lymph nodes throughout the sensitization protocol. The depletion of Foxp3+ Treg cells led to significantly exacerbated skin inflammation, including increased recruitment of inflammatory cells and expression of T helper type 2 cytokines, as well as elevated serum IgE levels. The effect of depleting Treg cells during epicutaneous sensitization was mirrored off by a stronger inflammatory response also in the lungs following airway challenge. Thus, Treg cells have an important role in controlling AD-like inflammation and the transfer of allergic skin inflammation to the lungs.

Absence of CCR4 exacerbates skin inflammation in an oxazolone-induced contact hypersensitivity model.

Chemokine receptor CCR4 is expressed by Th2 cells and is involved in the recruitment of inflammatory cells into the skin. We studied the effects of CCR4 deficiency in the murine model of oxazolone-induced contact hypersensitivity in CCR4-/- and wild-type (WT) mice. The inflammatory response in the skin at 24  hours post-elicitation was stronger in CCR4-/- mice compared with WT, evidenced by increased ear swelling and inflammatory cell infiltration. In addition, the mRNA expression levels of several cytokines, chemokines, chemokine receptors, and selectins in the skin of CCR4-/- mice were significantly elevated compared with WT mice. Time kinetic experiments during the sensitization and elicitation phases revealed that the number of CD3+CD4+ cells in CCR4-/- mice remained high longer during the sensitization phase and increased more rapidly during the elicitation phase compared with WT mice. These data demonstrate that the absence of CCR4 results in enhanced secondary immune response during allergic skin inflammation.

ST2 Regulates Allergic Airway Inflammation and T-Cell Polarization in Epicutaneously Sensitized Mice

IL-33 is an inducer of proinflammatory and T-helper type 2 (Th2) cytokines, which have an important role in atopic dermatitis (AD) and allergic asthma. ST2 is a specific receptor for IL-33 and is expressed on Th2 cells, eosinophils and mast cells. A murine model of AD was used to characterize the role of ST2 in allergen-induced skin inflammation and allergic asthma. ST2-/- and wild-type (WT) mice were epicutaneously sensitized with ovalbumin (OVA) and staphylococcal enterotoxin B, and intranasally challenged with OVA. ST2-/- mice exhibited increased production of IFNγ and increased number of CD8(+) T cells in the sensitized skin and in the airways compared with WT mice. The number of eosinophils was decreased, and Th2 cytokines were downregulated in the airways of epicutaneously sensitized ST2-/- mice compared with WT controls. However, dermal eosinophil numbers were as in WT, and the levels of Th2 cytokines were even elevated in the sensitized skin of ST2-/- mice. ST2-/- mice had elevated numbers of neutrophils and macrophages and increased levels of proinflammatory cytokines in the sensitized skin. The role of ST2 differs between different target tissues: ST2 is dispensable for the development of Th2 response in the sensitized skin, whereas it is a main inducer of Th2 cytokines in asthmatic airways.

Toll-Like Receptor Activation during Cutaneous Allergen Sensitization Blocks Development of Asthma through IFN-Gamma-Dependent Mechanisms

Toll-like receptors (TLRs) are pattern-recognition receptors that have a pivotal role as primary sensors of microbial products and as initiators of innate and adaptive immune responses. We investigated the role of TLR2, TLR3, and TLR4 activation during cutaneous allergen sensitization in the modulation of allergic asthma. The results show that dermal exposure to TLR4 ligand lipopolysaccharide (LPS) or TLR2 ligand Pam3Cys suppresses asthmatic responses by reducing airway hyperreactivity, mucus production, Th2-type inflammation in the lungs, and IgE antibodies in serum in a dose-dependent manner. In contrast, TLR3 ligand Poly(I:C) did not protect the mice from asthmatic symptoms but reduced IgE and induced IgG2a in serum. LPS (especially) and Pam3Cys enhanced the activation of dermal dendritic cell (DCs) by increasing the expression of CD80 and CD86 but decreased DC numbers in draining lymph nodes at early time points. Later, these changes in DCs led to an increased number of CD8(+) T cells and enhanced the production of IFN-γ in bronchoalveolar lavage fluid. In conclusion, dermal exposure to LPS during sensitization modulates the asthmatic response by skewing the Th1/Th2 balance toward Th1 by stimulating the production of IFN-γ. These findings support the hygiene hypothesis and pinpoint the importance of dermal microbiome in the development of allergy and asthma.

The Temporal and Spatial Dynamics of Foxp3+ Treg Cell–Mediated Suppression during Contact Hypersensitivity Responses in a Murine Model

Regulatory T (Treg) cells suppress contact hypersensitivity (CHS) responses, but the dynamics, mode, and site of their action is not well characterized. We studied forkhead box P3+ (Foxp3+) Treg cells during the CHS response in conditional Foxp3 knockout depletion of regulatory T cell (DEREG) mice, where Foxp3+ cells can be transiently deleted by diphtheria toxin. The mice were sensitized and challenged with oxazolone, and Foxp3+ cells were depleted either during sensitization or elicitation. Treg cell depletion before sensitization led to significantly exacerbated and prolonged CHS responses. In contrast, depleting Treg cells during elicitation had no effect on the 24-hour response, but the response was significantly prolonged. In wild-type mice, the gradual resolution of the CHS response was accompanied by a similarly gradual accumulation of Foxp3+ Treg cells relative to T effector cells in the skin. This effect was not as marked in the Treg cell-depleted mice, suggesting that the skin is an important site of Treg cell activities during the resolution phase. Together, our results show that endogenous Foxp3+ Treg cell function is important during the sensitization and resolution phases, but their depletion just before elicitation does not have an effect on the CHS response during the first 24 hours after elicitation.

A local lymph node assay to analyse immunosuppressive effects of topically applied drugs

Topical glucocorticosteroids represent the mainstay of antiinflammatory therapy in the treatment of inflammatory skin diseases. Their clinical use, however, is limited by local and systemic side-effects. Thus, in dermatopharmacology there is a large demand for alternative non-steroidal antiinflammatories. Other than transplantation models, most of the frequently used in vivo test systems for assessment of drug-induced immunosuppression measure changes in inflammatory skin responses by means of skin erythema and edema after challenge of sensitized animals. The aim of this study was to develop an alternative mouse model to detect and analyse immunosuppressive effects of topically applied drugs. On the basis of a modified local lymph node assay, we analysed effects of topical hydrocortisone, dexamethasone, mometasone furoate and FK506 (tacrolimus) during the induction phase of contact hypersensitivity. On 4 consecutive days, NMRI mice were treated on the dorsal surfaces of both ears with increasing concentrations of test compound. During the last 3 days, the mice received in addition the contact sensitizer, oxazolone (1%). On day 5, draining auricular lymph nodes were removed in order to assess lymph node cell counts and perform flow cytometric analysis of lymph node cell subpopulations (CD4+/CD25+, Ia+/CD69+, Ia+/B220+). All test compounds proved to exert significant immunosuppressive effects after topical application, but showed differences in their immunomodulatory potential. In conclusion, the local lymph node assay serves as an appropriate model to characterize immunosuppressive effects of topically applied drugs by measuring immunologically relevant end-points.

Reduced work ability in middle-aged men with asthma from youth- a 20-year follow-up

We studied, whether asthma diagnosed in childhood or early adulthood affects work ability 20 years later. We used Finnish Defence Force registers, 1986-1990, to select: (1) conscripts with asthma to represent a mild/moderate asthma group (n=485), (2) asthmatics who were exempted from military service to represent a relatively severe asthma group (n=393) and (3) a control group (n 1500) without asthma. A questionnaire consisting of validated questions on asthma and work ability was sent out in 2009. A total of 54% of the men in the first study group, 44% of those in the second study group and 44% of the controls answered. The mean age of the participants was 41 (range 37-51). Self-assessed current work ability compared with lifetime best had decreased in 28.9% of the first asthma group, in 31.1% of the second asthma group, and in 19.7% of the controls (p = 0.0007). Current smoking (OR 2.5), only basic education (OR 2.6), being a manual worker (OR 2.7) and current severe asthma (OR 3.8) associated most strongly with decreased work ability among the asthmatics. Both mild and more severe asthma at the age of around 20 seems to be associated with reduced work ability in 40-year-old males.