Danuta Gutowska-Owsiak

A role for IL-25 and IL-33-driven type-2 innate lymphoid cells in atopic dermatitis.

Type 2 innate lymphoid cells promote skin inflammation in mice and men, in part by producing IL-5 and IL-13 in response to IL-33

IL-17 downregulates filaggrin and affects keratinocyte expression of genes associated with cellular adhesion.

Abstract:  Atopic eczema and psoriasis are common skin diseases. While it is well established that the pathogenesis of these diseases varies, both are characterized by impairment in epidermal barrier function and abnormal IL‐17 expression in the skin and peripheral blood. Recent findings indicated that filaggrin is essential during barrier formation and its insufficiency underlies the pathogenesis of atopic eczema. Filaggrin downregulation has also been reported in psoriasis. It is clear that Th1/Th2 bias influences expression of the protein, but an analysis of the effects of interleukin‐17 (IL‐17) on the expression of the protein and profilaggrin‐processing enzymes has not yet been reported. In addition, the effect of the cytokine on components of functional epidermal barrier, tight junctions and adhesion/desmosomal proteins, has not been elucidated. Keratinocytes were exposed to interleukin‐17A, and microarray analysis was performed. Filaggrin protein level was assessed by western blot. We have observed a significant decrease in profilaggrin mRNA level in interleukin‐17A‐exposed cultures (P = 0.008). Expression of processing enzymes was also altered, indicating an indirect effect of the cytokine on filaggrin production/degradation. Moreover, expression of many genes involved in cellular adhesion was also decreased. A significant downregulation of filaggrin at the protein level was detected by western blot in immortal and primary keratinocytes. Gene ontology analysis indicated changes in keratinization, epidermal differentiation and formation of the cornified envelope. We conclude that IL‐17A downregulates the expression of filaggrin and genes important for cellular adhesion which could affect epidermal barrier formation. This effect potentially contributes to barrier dysfunction and could become a possible therapeutic target.

Interleukin-22 downregulates filaggrin expression and affects expression of profilaggrin processing enzymes

Background  The identification of filaggrin mutations has contributed towards our understanding of hereditary factors associated with epidermal dysfunction observed in individuals with atopic eczema (AE). However, factors that predispose to acquired filaggrin modulation are not well understood. Interleukin (IL)‐22 is upregulated in lesional AE tissue, but its effects on filaggrin expression and genes associated with epidermal function have not yet been comprehensively addressed.

Psoriatic T cells recognize neolipid antigens generated by mast cell phospholipase delivered by exosomes and presented by CD1a

In psoriasis, IFN-α–stimulated mast cells release exosomes containing cytoplasmic PLA2 that are transferred to CD1a-expressing cells and generate neolipid antigens which induce the production of IL-22 and IL-17A by CD1a-reactive T cells.

The Epidermis as an Adjuvant

It is now clear that the epidermis has an active role in local immune responses in the skin. Keratinocytes are involved early in inflammation by providing first-line innate mechanisms and, in addition, can contribute to adaptive immune responses that may be associated with clinical disease. Moreover, keratinocytes are capable of enhancing and shaping the outcome of inflammation in response to stimuli and promoting particular types of immune bias. Through understanding the underlying mechanisms, the role of keratinocytes in disease pathogenesis will be further defined, which is likely to lead to the identification of potential targets for prophylactic or therapeutic intervention.

The Mucosal Immune Response to Laryngopharyngeal Reflux

RATIONALE Laryngopharyngeal reflux (LPR) affects up to 20% of Western populations. Although individual morbidity is usually moderate, treatment costs are high and there are associations with other diseases, including laryngeal cancer. To date, there have been no studies of the mucosal immune response to this common inflammatory disease. OBJECTIVES To determine the mucosal immune response to LPR. METHODS We performed a prospective immunologic study of laryngeal biopsies from patients with LPR and control subjects (n = 12 and 11, respectively), and of primary laryngeal epithelial cells in vitro. MEASUREMENTS AND MAIN RESULTS Quantitative multiple-color immunofluorescence, using antibodies for lymphocytes (CD4, CD8, CD3, CD79, CD161), granulocytes (CD68, EMBP), monocytic cells (CD68, major histocompatibility complex [MHC] class II), and classical and nonclassical MHC (I, II, beta(2)-microglobulin, CD1d). Univariate and multivariate analysis and colocalization measurements were applied. There was an increase in percentage area of mucosal CD8(+) cells in the epithelium (P < 0.005), whereas other leukocyte and granulocyte antigens were unchanged. Although epithelial MHC class I and II expression was unchanged by reflux, expression of the nonclassical MHC molecule CD1d increased (P < 0.05, luminal layers). In vitro, laryngeal epithelial cells constitutively expressed CD1d. CD1d and MHC I expression were inversely related in all subjects, in a pattern which appears to be unique to the upper airway. Colocalization of natural killer T (NKT) cells with CD1d increased in patients (P < 0.01). CONCLUSIONS These data indicate a role for the CD1d-NKT cell axis in response to LPR in humans. This represents a useful target for novel diagnostics and treatments in this common condition.

Filaggrin inhibits generation of CD1a neolipid antigens by house dust mite–derived phospholipase

Lack of the skin barrier protein filaggrin worsens atopic dermatitis by allergenic activation of CD1a-reactive T cells. Bringing atopic dermatitis up to scratch Targeted therapies are transforming medicine, but complex diseases such as atopic dermatitis are difficult to target. Now, Jarrett et al. report a mechanism that links two contributors to atopic dermatitis pathogenesis—cutaneous inflammation and barrier dysfunction. They found that house dust mite allergen phospholipase (PLA2) can induce neolipid antigens in human skin. These antigens can then be presented by the nonclassical MHC family member CD1a to CD1a-restricted T cells, which contribute to inflammation. The skin barrier protein filaggrin can inhibit PLA2 and decrease this inflammation. Indeed, individuals with filaggrin mutations experience severe atopic dermatitis. These data suggest that barrier dysfunction and inflammation may be linked, and support PLA2 as a target for atopic dermatitis. Atopic dermatitis is a common pruritic skin disease in which barrier dysfunction and cutaneous inflammation contribute to pathogenesis. Mechanisms underlying the associated inflammation are not fully understood, and although Langerhans cells expressing the nonclassical major histocompatibility complex (MHC) family member CD1a are known to be enriched within lesions, their role in clinical disease pathogenesis has not been studied. We observed that house dust mite (HDM) allergen generates neolipid antigens presented by CD1a to T cells in the blood and skin lesions of affected individuals. HDM-responsive CD1a-reactive T cells increased in frequency after birth in individuals with atopic dermatitis and showed rapid effector function, consistent with antigen-driven maturation. In HDM-challenged human skin, we observed phospholipase A2 (PLA2) activity in vivo. CD1a-reactive T cell activation was dependent on HDM-derived PLA2, and such cells infiltrated the skin after allergen challenge. Moreover, we observed that the skin barrier protein filaggrin, insufficiency of which is associated with atopic skin disease, inhibited PLA2 activity and decreased CD1a-reactive PLA2-generated neolipid-specific T cell activity from skin and blood. The most widely used classification schemes of hypersensitivity suggest that nonpeptide stimulants of T cells act as haptens that modify peptides or proteins; however, our results show that HDM proteins may also generate neolipid antigens that directly activate T cells. These data define PLA2 inhibition as a function of filaggrin, supporting PLA2 inhibition as a therapeutic approach.

Cytokine regulation of the epidermal barrier.

Studies published in recent years have highlighted the role of epidermal barrier defects in both atopic skin disease and the development of broader allergic manifestations. While genetic determinants of barrier function are important, it is clear that local acquired effects are also involved in disease pathogenesis. In this review, we aimed to summarize the known influences of cytokines abundantly expressed during atopic skin disease on components of epidermal barrier integrity and function.

Platelet Activating Factor Contributes to Vascular Leak in Acute Dengue Infection

Background Although plasma leakage is the hallmark of severe dengue infections, the factors that cause increased vascular permeability have not been identified. As platelet activating factor (PAF) is associated with an increase in vascular permeability in other diseases, we set out to investigate its role in acute dengue infection. Materials and Methods PAF levels were initially assessed in 25 patients with acute dengue infection to determine if they were increased in acute dengue. For investigation of the kinetics of PAF, serial PAF values were assessed in 36 patients. The effect of dengue serum on tight junction protein ZO-1 was determined by using human endothelial cell lines (HUVECs). The effect of dengue serum on and trans-endothelial resistance (TEER) was also measured on HUVECs. Results PAF levels were significantly higher in patients with acute dengue (n = 25; p = 0.001) when compared to healthy individuals (n = 12). In further investigation of the kinetics of PAF in serial blood samples of patients (n = 36), PAF levels rose just before the onset of the critical phase. PAF levels were significantly higher in patients with evidence of vascular leak throughout the course of the illness when compared to those with milder disease. Serum from patients with dengue significantly down-regulated expression of tight junction protein, ZO-1 (p = 0.004), HUVECs. This was significantly inhibited (p = 0.004) by use of a PAF receptor (PAFR) blocker. Serum from dengue patients also significantly reduced TEER and this reduction was also significantly (p = 0.02) inhibited by prior incubation with the PAFR blocker. Conclusion Our results suggest the PAF is likely to be playing a significant role in inducing vascular leak in acute dengue infection which offers a potential target for therapeutic intervention.

The histamine-synthesizing enzyme histidine decarboxylase is upregulated by keratinocytes in atopic skin

Histamine is an abundant mediator accumulating in the skin of atopic patients, where it is thought to be derived from immune cells. While keratinocytes express histidine decarboxylase (HDC), levels of the enzyme in normal or diseased epidermis and factors that influence its expression in human keratinocytes are not known.