Subclinical immune responses to nickel in sensitized individuals-a dose-response study.

BACKGROUND: Nickel is the leading cause of contact allergy in Europe, with 14.5% of the adult population being sensitized. Despite regulations limiting nickel release from consumer items, the incidence and prevalence of nickel allergy remain high. OBJECTIVE: To investigate the clinical and subclinical immune response to low-dose nickel exposure on nickel pre-exposed skin to assess the adequacy of current regulatory limits. METHOD: Nickel-allergic and healthy controls were patch tested with nickel twice with a 3-4 weeks interval. The first exposure used the diagnostic concentration of 2000 µg/cm2 nickel sulphate, and the same skin areas were then re-exposed to 0.2, 0.5, 12.8 and 370 µg/cm2 nickel sulphate. After 48 h, the patch reactions were examined for clinical signs of eczema, and skin biopsies were collected. The transcriptomic immune profile was analysed with Nanostring nCounter and quantitative polymerase chain reaction. RESULTS: Two nickel-allergic participants (15%) had clinical reactions to the regulatory limiting doses for nickel (0.2/0.5 µg/cm2) following re-exposure. There was immune activation in all skin areas following re-exposure to nickel, predominantly mediated by up-regulation of cytokines and chemokines. In all nickel re-exposed skin areas, 81 genes were up-regulated independent from the clinical response. In skin areas exposed to 0.2 µg/cm2, 101 immune-related genes were differentially expressed, even when no clinical response was observed. Healthy controls showed up-regulation of three genes in response to nickel re-exposures without any clinical reactions. CONCLUSION: Immune activation can be induced in skin with local memory to nickel upon challenge with nickel doses within the regulatory limits. Our findings suggest that the regulatory limits in the European nickel regulation may not provide sufficient protection for consumers against low-dose exposures.

Metabolic re-programming of keratinocytes in response to contact allergens.

BACKGROUND: Allergic contact dermatitis (ACD) is a common skin disease caused by the recognition of haptens by the immune system. Keratinocytes play an important role in the initiation and facilitation of inflammatory responses in ACD. Immune responses are associated with major changes in metabolism. However, metabolic re-programming is not well studied in ACD; specifically, knowledge of metabolic alterations in structural cells is lacking. METHODS: Metabolic re-programming in ACD was studied using publicly available transcriptome datasets. Primary pooled keratinocytes and a keratinocyte cell line (HaCaT) were stimulated with contact allergens, and inflammatory responses and expression of metabolic markers were measured by qPCR and flow cytometry, respectively. RESULTS: ACD is characterized by metabolic re-programming with a metabolic profile similar to atopic dermatitis. Exposure to contact allergens causes a wide array of metabolic alterations. Stimulation of keratinocytes with contact allergens induced inflammatory responses typical for ACD and was associated with an up-regulation of proteins representative for glucose uptake, fatty acid metabolism, oxidative phosphorylation and to some extent arginine biosynthesis. Changes in these metabolic pathways were also observed when comparing lesional with non-lesional contact dermatitis skin. CONCLUSIONS: ACD is, similarly to other inflammatory skin diseases, characterized by metabolic re-programming. Contact allergen exposure induces expression of a wide array of metabolic pathways, which is at least in part mediated through metabolic re-programming of keratinocytes.

The junctional adhesion molecule-like protein (JAML) is important for the inflammatory response during contact hypersensitivity.

BACKGROUND: The junctional adhesion molecule-like protein (JAML) plays important roles in wound healing and activation of epidermal γδ T cells in mice. Whether JAML plays a role in contact hypersensitivity (CHS), the animal model of allergic contact dermatitis (ACD), is not known. METHODS: To examine the role of JAML in CHS, we used various mouse models of CHS in JAML knockout (KO) and wild-type (WT) mice. Furthermore, the expression of the JAML ligand coxsackievirus and adenovirus receptor (CXADR) on keratinocytes was accessed in vitro and in vivo. RESULTS: JAML KO mice had a diminished inflammatory response during both the sensitization and elicitation phase of CHS and had reduced numbers of CD8+ and CD4+ T cells in the epidermis. Furthermore, interferon γ (IFNγ), interleukin 1ß (IL-1ß) and CXCL10 production were significantly reduced in JAML KO mice during the elicitation phase. We found that CD8+ T cells express JAML and that JAML is essential for rapid flare-up responses to contact allergens. Finally, we show that keratinocytes up-regulate the JAML ligand CXADR following exposure to contact allergens. CONCLUSION: Our study is the first to show a central role of JAML in CHS and reveals a potential new target for the treatment of ACD in humans.

Skin Colonization with S. aureus Can Lead to Increased NLRP1 Inflammasome Activation in Patients with Atopic Dermatitis.

The role of NLRP1 inflammasome activation and subsequent production of IL-1 family cytokines in the development of atopic dermatitis (AD) is not clearly understood. Staphylococcus aureus is known to be associated with increased mRNA levels of IL1 family cytokines in the skin and more severe AD. In this study, the altered expression of IL-1 family cytokines and inflammasome-related genes was confirmed, and a positive relationship between mRNA levels of inflammasome sensor NLRP1 and IL1B or IL18 was determined. Enhanced expression of the NLRP1 and PYCARD proteins and increased caspase-1 activity were detected in the skin of patients with AD. The genetic association of IL18R1 and IL18RAP with AD was confirmed, and the involvement of various immune cell types was predicted using published GWAS and expression quantitative trait loci datasets. In keratinocytes, the inoculation with S. aureus led to the increased secretion of IL-1ß and IL-18, whereas small interfering RNA silencing of NLRP1 inhibited the production of these cytokines. Our results suggest that skin colonization with S. aureus may cause the activation of the NLRP1 inflammasome in keratinocytes, which leads to the secretion of IL-1ß and IL-18 and thereby may contribute to the pathogenesis of AD, particularly in the presence of genetic variations in the IL-18 pathway.

miRNA expression profiles of the perilesional skin of atopic dermatitis and psoriasis patients are highly similar.

Atopic dermatitis (AD) and psoriasis vulgaris (PV) are chronic inflammatory skin diseases with heterogeneous molecular backgrounds. MicroRNAs (miRNAs) contribute to either development or regulation of many immune system related diseases. Only few miRNA profiling studies are available for AD and no comparisons between AD and PV skin miRNA profiles have been performed recently. We conducted a miRNA profiling analysis of skin, as well as serum, from adult AD and PV patients and control individuals. 130 miRNAs were differentially expressed in AD skin, of which 77 were common differentially expressed in AD and PV. No differentially expressed miRNAs were detected in serum. Pathway analyses revealed differentially expressed miRNAs to potentially target immune-system related pathways, including TNF-α, IL-2/STAT4 and IL-6/JAK/STAT3. Additional genetic analysis of published AD GWAS dataset detected association of several target genes of differentially expressed miRNAs in skin. Moreover, miR-28-5p, miR-31-5p, miR-378a-3p and miR-203a were validated as upregulated in the skin of AD and PV patients. All validated miRNAs were reliable predictive markers for AD or PV. In conclusion, miRNA expression pattern in the skin of adult AD patients is highly similar to that of PV with multiple differentially expressed miRNAs potentially involved in the regulation of immune responses in AD and PV.

Impact of AHR Ligand TCDD on Human Embryonic Stem Cells and Early Differentiation.

Aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor, which mediates the effects of a variety of environmental stimuli in multiple tissues. Recent advances in AHR biology have underlined its importance in cells with high developmental potency, including pluripotent stem cells. Nonetheless, there is little data on AHR expression and its role during the initial stages of stem cell differentiation. The purpose of this study was to investigate the temporal pattern of AHR expression during directed differentiation of human embryonic stem cells (hESC) into neural progenitor, early mesoderm and definitive endoderm cells. Additionally, we investigated the effect of the AHR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the gene expression profile in hESCs and differentiated cells by RNA-seq, accompanied by identification of AHR binding sites by ChIP-seq and epigenetic landscape analysis by ATAC-seq. We showed that AHR is differentially regulated in distinct lineages. We provided evidence that TCDD alters gene expression patterns in hESCs and during early differentiation. Additionally, we identified novel potential AHR target genes, which expand our understanding on the role of this protein in different cell types.

NickFect type of cell-penetrating peptides present enhanced efficiency for microRNA-146a delivery into dendritic cells and during skin inflammation.

MicroRNAs (miRNAs) are post-transcriptional gene expression regulators with potential therapeutic applications. miR-146a is a negative regulator of inflammatory processes in both tissue-resident and specialized immune cells and may therefore have therapeutic effect in inflammatory skin diseases. PepFect (PF) and NickFect (NF) type of cell-penetrating peptides (CPPs) have previously been shown to deliver miRNA mimics and/or siRNAs into cell cultures and in vivo. Here, we first demonstrate that selected PF- and NF-type of CPPs support delivery of fluorescent labelled miRNA mimics into keratinocytes (KCs) and dendritic cells (DCs). Second, we show that both PF- and NF-miR-146a nanocomplexes were equally effective in KCs, while NFs were more efficient in DCs as assessed by downregulation of miR-146a-influenced genes. None of miRNA nanocomplexes with the tested CPPs influenced the viability of KCs and DCs nor caused activation of DCs according to CD86 and CD83 markers. Transmission electron microscopy analysis with Nanogold-labelled miR-146a mimics and assessment of endocytic trafficking pathways revealed endocytosis as an active route of delivery in both KCs and DCs for all tested CPPs. However, consistent with the higher efficiency, NF-delivered miR-146a was detected more often outside endosomes in DCs. Finally, pre-injection of NF71:miR-146a nanocomplexes was confirmed to suppress inflammatory responses in a mouse model of irritant contact dermatitis as shown by reduced ear swelling response and downregulation of pro-inflammatory cytokines, including IL-6, IL-1ß, IL-33 and TNF-α. In conclusion, NF71 efficiently delivers miRNA mimics into KCs as well as DCs, and therefore may have advantage in therapeutic delivery of miRNAs in case of inflammatory skin diseases.

SERPINB2 and miR-146a/b are coordinately regulated and act in the suppression of psoriasis-associated inflammatory responses in keratinocytes.

Psoriasis is a chronic inflammatory skin disease with numerous involved factors. miR-146a and miR-146b (miR-146a/b) are anti-inflammatory miRNAs that are increased in psoriatic skin. SERPINB2 has been shown to be upregulated in the inflammation and infections. Here we aimed to study the relationship between miR-146a/b and SERPINB2 and to delineate the role of SERPINB2 in association of plaque psoriasis. We report increased SERPINB2 expression in the skin of psoriasis patients, which was in a positive relationship with psoriasis severity and in a negative relationship with miR-146a/b in psoriatic lesions. In cultured keratinocytes, both cellular and secreted SERPINB2 levels were strongly induced in response to IFN-γ and TNF-α. Interestingly, SERPINB2 mRNA was downregulated by IL-17A and the combination of TNF-α and IL-17A at time points when miR-146a was increased. The predicted binding site for miR-146a/b in 3' untranslated region of SERPINB2 revealed no activity in luciferase assay, while siRNA silencing of miR-146a/b direct targets IRAK1 and CARD10 resulted in reduced expression of SERPINB2, suggesting that miR-146a/b indirectly control SERPINB2 expression in the skin. The siRNA silencing of SERPINB2 increased the expression of IL-8, CXCL5 and CCL5 and migration of neutrophils revealing its anti-inflammatory role in keratinocytes. Our data together suggest that SERPINB2 and miR-146a/b are part of disease-related network of molecules that are coordinately regulated and act in controlling the inflammatory responses in psoriatic skin.

miR-10a-5p is increased in atopic dermatitis and has capacity to inhibit keratinocyte proliferation.

BACKGROUND: miR-10a-5p has been shown to regulate cancer cell proliferation and invasiveness and endothelial cell inflammatory responses. The function of miR-10a-5p in the skin has not been previously studied. The aim of the current study was to examine miR-10a-5p expression, regulation, and function in keratinocytes (KCs) in association with atopic dermatitis (AD). METHODS: The expression of miR-10a-5p and its target genes was analyzed using RT-qPCR, mRNA array analysis, in situ hybridization, and immunofluorescence. The transfection of miRNA mimics, cell cycle distribution analysis, and luciferase assays was used to study miR-10a-5p functions in human primary KCs. RESULTS: miR-10a-5p was found to be upregulated in lesional skin from patients with AD and in proliferating KCs. Array and pathway analysis of IL-1ß-stimulated KCs revealed that miR-10a-5p inhibited many genes that affect cell cycle progression and only a few inflammation-related genes. Accordingly, fewer cells in S-phase and reduced proliferation were detected as characteristics of miR-10a-5p-transfected KCs. The influence of miR-10a-5p on cell proliferation was also evident in KCs induced by AD-related cytokines, including IL-4, IL-17, and IL-1ß, as measured by the capacity to strongly suppress the expression of the proliferation marker Ki-67. Among AD-related putative direct target genes, we verified hyaluronan synthase 3, a damage-associated positive regulator of KC migration and proliferation, as a direct target of miR-10a-5p. CONCLUSIONS: miR-10a-5p inhibits KC proliferation and directly targets hyaluronan synthase 3 and thereby may modulate AD-associated processes in the skin.

Lymphoid Stress Surveillance Response Contributes to Vitiligo Pathogenesis.

Vitiligo is a chronic multifactorial depigmentation disorder characterized by the destruction and functional loss of melanocytes. Although a direct cytotoxic T cell attack is thought to be responsible for melanocyte damage, the events leading to the loss of self-tolerance toward melanocytic antigens are not understood. This research aimed to identify novel cellular and molecular factors that participate in vitiligo pathogenesis through the application of gene expression and immunofluorescence analysis of skin biopsy samples along with immunophenotyping of circulating cells. Our study provides insights into the mechanisms involved in melanocyte destruction. The upregulation of stress-ligand MICA/MICB, recognized by activating receptors on innate and innate-like T cells, imply involvement of lymphoid stress surveillance responses in vitiligo lesions. A simultaneous increase in the expression of transcription factor EOMES that is characteristic for innate-like virtual memory T cells, suggest a similar scenario. Local lymphoid stress surveillance has been previously associated with the amplification of systemic humoral responses that were mirrored in our study by increased T follicular helper cells and switched memory B cell proportions in patients with active vitiligo. In addition, microtubule-associated protein light chain 3 staining was compatible with the activation of autophagy in keratinocytes and in the remaining melanocytes of vitiligo lesional skin.