Background Allergic contact dermatitis (ACD) is the most common occupational disease. Although murine contact hypersensitivity provides a framework for understanding ACD, it carries important ...differences from its human counterpart. Unlike the contact hypersensitivity model, which is induced by potent sensitizers (ie, dinitrofluorobenzene), human ACD is induced by weak-to-moderate sensitizers (ie, nickel), which cannot induce reactions in mice. Distinct hapten-specific immune-polarizing responses to potent inducers were suggested in mice, with unclear relevance to human ACD. Objective We explored the possibility of distinct T-cell polarization responses in skin to common clinically relevant ACD allergens. Methods Gene-expression and cellular studies were performed on common allergens (ie, nickel, fragrance, and rubber) compared with petrolatum-occluded skin, using RT-PCR, gene arrays, and immunohistochemistry. Results Despite similar clinical reactions in all allergen groups, distinct immune polarizations characterized different allergens. Although the common ACD transcriptome consisted of 149 differentially expressed genes across all allergens versus petrolatum, a much larger gene set was uniquely altered by individual allergens. Nickel demonstrated the highest immune activation, with potent inductions of innate immunity, TH 1/TH 17 and a TH 22 component. Fragrance, and to a lesser extent rubber, demonstrated a strong TH 2 bias, some TH 22 polarization, and smaller TH 1/TH 17 contributions. Conclusions Our study offers new insights into the pathogenesis of ACD, expanding the understanding of T-cell activation and associated cytokines in allergen-reactive tissues. It is the first study that defines the common transcriptome of clinically relevant sensitizers in human skin and identifies unique pathways preferentially activated by different allergens, suggesting that ACD cannot be considered a single entity.
Background Genomic profiling of lesional and nonlesional skin of patients with atopic dermatitis (AD) using microarrays has led to increased understanding of AD and identification of novel ...therapeutic targets. However, the limitations of microarrays might decrease detection of AD genes. These limitations might be lessened with next-generation RNA sequencing (RNA-seq). Objective We sought to define the lesional AD transcriptome using RNA-seq and compare it using microarrays performed on the same cohort. Methods RNA-seq and microarrays were performed to identify differentially expressed genes (criteria: fold change, ≥2.0; false discovery rate ≤0.05) in lesional versus nonlesional skin from 18 patients with moderate-to-severe AD, with real-time PCR (RT-PCR) and immunohistochemistry used for validation. Results Both platforms showed robust disease transcriptomes and correlated well with RT-PCR. The common AD transcriptome identified by using both techniques contained 217 genes, including inflammatory ( S100A8/A9/A12, CXCL1 , and 2′-5′-oligoadenylate synthetase-like OASL ) and barrier ( MKi67 , keratin 16 K16 , and claudin 8 CLDN8 ) AD-related genes. Although fold change estimates determined by using RNA-seq showed somewhat better agreement with RT-PCR (intraclass correlation coefficient, 0.57 and 0.70 for microarrays and RNA-seq vs RT-PCR, respectively), bias was not eliminated. Among genes uniquely identified by using RNA-seq were triggering receptor expressed on myeloid cells 1 (TREM-1) signaling (eg, CCL2 , CCL3 , and single immunoglobulin domain IL1R1 related SIGIRR ) and IL-36 isoform genes. TREM-1 is a surface receptor implicated in innate and adaptive immunity that amplifies infection-related inflammation. Conclusions This is the first report of a lesional AD phenotype using RNA-seq and the first direct comparison between platforms in this disease. Both platforms robustly characterize the AD transcriptome. Through RNA-seq, we unraveled novel disease pathology, including increased expression of the novel TREM-1 pathway and the IL-36 cytokine in patients with AD.
Background The molecular signature of atopic dermatitis (AD) lesions is associated with TH 2 and TH 22 activation and epidermal alterations. However, the epidermal and dermal AD transcriptomes and ...their respective contributions to abnormalities in respective immune and barrier phenotypes are unknown. Objective We sought to establish the genomic profile of the epidermal and dermal compartments of lesional and nonlesional AD skin compared with normal skin. Methods Laser capture microdissection was performed to separate the epidermis and dermis of lesional and nonlesional skin from patients with AD and normal skin from healthy volunteers, followed by gene expression (microarrays and real-time PCR) and immunostaining studies. Results Our study identified novel immune and barrier genes, including the IL-34 cytokine and claudins 4 and 8, and showed increased detection of key AD genes usually undetectable on arrays (ie, IL22 , thymic stromal lymphopoietin TSLP , CCL22 , and CCL26 ). Overall, the combined epidermal and dermal transcriptomes enlarged the AD transcriptome, adding 674 upregulated and 405 downregulated differentially expressed genes between lesional and nonlesional skin to the AD transcriptome. We were also able to localize individual transcripts as primarily epidermal (defensin, beta 4A DEFB4A ) or dermal ( IL22 , cytotoxic T-lymphocyte antigen 4 CTLA4 , and CCR7 ) and link their expressions to possible cellular sources. Conclusions This is the first report that establishes robust epidermal and dermal genomic signatures of lesional and nonlesional AD skin and normal skin compared with whole tissues. These data establish the utility of laser capture microdissection to separate different compartments and cellular subsets in patients with AD, allowing localization of key barrier or immune molecules and enabling detection of gene products usually not detected on arrays.
Background Atopic dermatitis (AD) is the most common inflammatory disease. Evolving disease models link changes in epidermal growth and differentiation to TH 2/TH 22 cytokine activation. However, ...these models have not been tested by in vivo suppression of T-cell cytokines. Cyclosporine (CsA) is an immunosuppressant that is highly effective for severe disease, but its mechanism in AD skin lesions has not been studied. Objective We sought to establish the ability of a systemic immunosuppressant to modulate immune and epidermal alterations that form the pathogenic disease phenotype and to correlate changes with clinical improvement. Methods CsA's effects on AD skin pathology were evaluated by using gene expression and immunohistochemistry studies in baseline, week 2, and week 12 lesional and nonlesional biopsy specimens from 19 patients treated with 5 mg/kg/d CsA for 12 weeks. Results After 2 and 12 weeks of treatment, we observed significant reductions of 51% and 72%, respectively, in SCORAD scores. Clinical improvements were associated with significant gene expression changes in lesional but also nonlesional skin, particularly reductions in levels of TH 2-, TH 22-, and some TH 17-related molecules (ie, IL-13, IL-22, CCL17, S100As, and elafin/peptidase inhibitor 3), and modulation of epidermal hyperplasia and differentiation measures. Conclusions This is the first study that establishes a relationship between cytokine activation and molecular epidermal alterations, as well as correlations between disease biomarkers in the skin and clinical improvement. The reversal of the molecular phenotype with CsA and the associated biomarkers can serve as a reference for the successful modulation of tissue inflammation with specific immune antagonists in future studies, contributing to the understanding of the specific cytokines involved in epidermal pathology.
Background Atopic dermatitis (AD) is the most common inflammatory disease. The prevalence of allergic contact dermatitis to allergens (eg, fragrance) is higher in patients with AD, despite a trend ...toward weaker clinical allergic contact dermatitis reactions. The role of the AD skin phenotype in modulating allergic sensitization to common sensitizers has not been evaluated. Objective We sought to investigate whether patients with AD have altered tissue immune responses on allergen challenge. Methods Gene expression and immunohistochemistry studies were performed on biopsy specimens from 10 patients with AD and 14 patients without AD patch tested with common contact allergens (nickel, fragrance, and rubber). Results Although 1085 differentially expressed genes (DEGs) were commonly modulated in patch-tested skin from patients with AD and patients without AD versus control skin, 1185 DEGs were uniquely altered in skin from patients without AD, and only 246 DEGs were altered in skin from patients with AD. Although many inflammatory products (ie, matrix metalloproteinase 12/matrix metalloproteinase 1/S100A9) were upregulated in both groups, higher-magnitude changes and upregulation of interferon responses were evident only in the non-AD group. Stratification by allergen showed decreased expression of immune, TH 1-subset, and TH 2-subset genes in nickel-related AD responses, with increased TH 17/IL-23 skewing. Rubber/fragrance showed similar trends of lesser magnitude. Negative regulators showed higher expression in patients with AD. Conclusions Through contact sensitization, our study offers new insights into AD. Allergic immune reactions were globally attenuated and differentially polarized in patients with AD, with significant decreases in levels of TH 1 products, some increases in levels of TH 17 products, and inconsistent upregulation in levels of TH 2 products. The overall hyporesponsiveness in skin from patients with background AD might be explained by baseline immune abnormalities, such as increased TH 2, TH 17, and negative regulator levels compared with those seen in non-AD skin.
PDF