The transcriptome of hand eczema assessed by tape stripping.

BACKGROUND: No biomarkers have been identified that can classify subtypes of hand eczema (HE). Although skin biopsies represent the gold standard for investigations of the skin, the invasive technique is not favorable when investigating skin from sensitive areas. Recent advances in the use of skin-tape strips for molecular investigations enable noninvasive investigations of HE. OBJECTIVE: By using whole transcriptome sequencing (WTS), the molecular profile of HE according to different localizations on the hands, etiologies, and clinical/morphological subtypes was investigated. METHODS: Thirty adult, Danish HE patients, 12 with and 18 without concurrent atopic dermatitis (AD), as well as 16 controls were included. Tape strip samples were collected from lesional, nonlesional, and healthy skin. Total RNA was extracted and WTS was performed. RESULTS: The largest molecular difference of HE patients with and without AD was found in nonlesional skin areas and included a downregulation of CXCL8 for HE patients without AD. Differences between allergic and irritant contact dermatitis included epidermal biomarkers such as EPHA1. CONCLUSION: Skin tape strip samples could be used to assess the gene expression profile of HE on different localizations of the hands. The skin tape strip method identified new molecular markers that showed promising result for the identification of HE subtypes.

Unique molecular signatures typify skin inflammation induced by chemical allergens and irritants.

BACKGROUND: Skin exposure to chemicals may induce an inflammatory disease known as contact dermatitis (CD). Distinguishing the allergic and irritant forms of CD often proves challenging in the clinic. METHODS: To characterize the molecular signatures of chemical-induced skin inflammation, we conducted a comprehensive transcriptomic analysis on the skin lesions of 47 patients with positive patch tests to reference contact allergens and nonallergenic irritants. RESULTS: A clear segregation was observed between allergen- and irritant-induced gene profiles. Distinct modules pertaining to the epidermal compartment, metabolism, and proliferation were induced by both contact allergens and irritants; whereas only contact allergens prompted strong activation of adaptive immunity, notably of cytotoxic T-cell responses. Our results also confirmed that: (a) unique pathways characterize allergen- and irritant-induced dermatitis; (b) the intensity of the clinical reaction correlates with the magnitude of immune activation. Finally, using a machine-learning approach, we identified and validated several minimal combinations of biomarkers to distinguish contact allergy from irritation. CONCLUSION: These results highlight the value of molecular profiling of chemical-induced skin inflammation for improving the diagnosis of allergic versus irritant contact dermatitis.

Machine-learning-driven biomarker discovery for the discrimination between allergic and irritant contact dermatitis.

Contact dermatitis tremendously impacts the quality of life of suffering patients. Currently, diagnostic regimes rely on allergy testing, exposure specification, and follow-up visits; however, distinguishing the clinical phenotype of irritant and allergic contact dermatitis remains challenging. Employing integrative transcriptomic analysis and machine-learning approaches, we aimed to decipher disease-related signature genes to find suitable sets of biomarkers. A total of 89 positive patch-test reaction biopsies against four contact allergens and two irritants were analyzed via microarray. Coexpression network analysis and Random Forest classification were used to discover potential biomarkers and selected biomarker models were validated in an independent patient group. Differential gene-expression analysis identified major gene-expression changes depending on the stimulus. Random Forest classification identified CD47, BATF, FASLG, RGS16, SYNPO, SELE, PTPN7, WARS, PRC1, EXO1, RRM2, PBK, RAD54L, KIFC1, SPC25, PKMYT, HISTH1A, TPX2, DLGAP5, TPX2, CH25H, and IL37 as potential biomarkers to distinguish allergic and irritant contact dermatitis in human skin. Validation experiments and prediction performances on external testing datasets demonstrated potential applicability of the identified biomarker models in the clinic. Capitalizing on this knowledge, novel diagnostic tools can be developed to guide clinical diagnosis of contact allergies.

Filaggrin gene mutations in hand eczema patients in the Indian subcontinent: A prospective case-control study.

BACKGROUND: There are no Indian studies on the association between filaggrin gene (FLG) mutations and any dermatosis, including hand eczema. OBJECTIVES: To determine the prevalence of FLG mutations in Indian hand eczema patients, and examine associations between such mutations and any aetiological type of hand eczema. MATERIALS AND METHODS: A total of 163 patients and 86 controls were included. Patients were categorized into aetiological subtypes of hand eczema. FLG polymorphisms (S2889X, 2282del4, R501X, and Q2417X) were determined in patients and controls, and correlated with subtypes. RESULTS: The prevalences of FLG mutations were 33.7% in cases and 3.5% in controls. Mutations in S2889X constituted 96.4% of all FLG mutations. No carrier of R501X and Q2417X mutations was identified. Among 55 patients with mutations, irritant contact dermatitis (ICD) with or without atopy was found in 22 patients, allergic contact dermatitis (ACD) with or without atopy was found in 12, and idiopathic hand eczema was found in 12. There was a significant association of FLG mutations with ICD with or without atopy, ACD without atopy, and idiopathic subtypes. FLG mutations were associated with more severe hand eczema. CONCLUSIONS: S2889X mutation is commoner in patients than in controls. FLG polymorphisms are associated with specific subtypes of hand eczema and severe disease.

Associations Between Immune Phenotype and Inflammation in Murine Models of Irritant Contact Dermatitis.

Irritant contact dermatitis (ICD), the most common occupational cutaneous illness, is an acute inflammatory response caused by topical irritant exposure. Multiple factors are associated with the manifestation and severity of ICD and contribute to the lack of effective prophylactic and treatment strategies. To determine the pathomechanism of ICD caused by the irritants, benzalkonium chloride (BKC) and JP-8 jet fuel, 2 mouse strains, C57BL/6 and Balb/c, were assessed due to their differential immune predispositions. Dermatitis lesions were obtained for histological examination, cytokine protein expression analysis, and determination of immune cell infiltration via flow cytometric analysis. Following acute (3-day) BKC exposure C57BL/6 skin displayed increased neutrophils and expression of 19 distinct cytokines, but fewer dendritic cells and lower expression of IL-1α and IL-9 as compared with Balb/c skin. Following prolonged (7-day) exposure to BKC, inflammatory cell populations trended similar to 3-day exposure; however, only 6 distinct cytokines were higher in C57BL/6, whereas Balb/c displayed higher expression of IL-27, 28, and 31. Following acute JP-8 exposure, C57BL/6 skin displayed higher levels of γδ T cell infiltration, G and M-CSF expression, but lower populations of neutrophils, monocytes, and dendritic cells compared with Balb/c skin. As with BKC, skin inflammatory cell populations following 7-day JP-8 exposure trended similar to 3-day exposure. However, C57BL/6 skin displayed higher levels of IL-6 and LIF, whereas Balb/c showed increased IL-1ß, IL-27, G-CSF, TNFα, and 7 additional chemokines. These findings further define the pathology of ICD, partially explain individual variation of ICD, and offer insight into biomarkers for risk assessment.

Health-related quality of life in adult dermatitis patients stratified by filaggrin genotype.

BACKGROUND: Information concerning health-related quality of life (HRQoL) and comorbidities of adult dermatitis patients stratified by loss-of-function mutations in the filaggrin gene (FLG) is limited. OBJECTIVE: To investigate HRQoL, skin symptoms and comorbidities in adult FLG mutation carriers. METHODS: This cross-sectional study included patients diagnosed with atopic dermatitis and/or hand eczema (n = 520). Patients completed questionnaires about dermatitis, skin symptoms, HRQoL, and comorbidities, including actinic keratosis, and atopic and mental disorders. RESULTS: FLG mutations (R501X, 2282del4, and R2447X) were identified in 16.9% of patients, and were significantly associated not only with atopic dermatitis, but also independently with skin fissures on the fingers and heels, and self-reported actinic keratosis. Although FLG mutations were significantly associated with reduced HRQoL, as measured by use of the Dermatology Life Quality Index (DLQI), no association with self-reported anxiety or depression was identified. Notably, the highest median DLQI score, reflecting greater impairment, was reported by patients with both FLG mutations and atopic dermatitis. Overall, 19.7% of patients with both atopic dermatitis and FLG mutations reported a 'large or extremely large' impact on their lives; this represents twice the prevalence seen in patients with atopic dermatitis and wild-type FLG (9.6%). CONCLUSION: Patients with both atopic dermatitis and common FLG mutations are more frequently affected by reduced HRQoL.

Association of MHC region SNPs with irritant susceptibility in healthcare workers.

Irritant contact dermatitis is the most common work-related skin disease, especially affecting workers in "wet-work" occupations. This study was conducted to investigate the association between single nucleotide polymorphisms (SNPs) within the major histocompatibility complex (MHC) and skin irritant response in a group of healthcare workers. 585 volunteer healthcare workers were genotyped for MHC SNPs and patch tested with three different irritants: sodium lauryl sulfate (SLS), sodium hydroxide (NaOH) and benzalkonium chloride (BKC). Genotyping was performed using Illumina Goldengate MHC panels. A number of SNPs within the MHC Class I (OR2B3, TRIM31, TRIM10, TRIM40 and IER3), Class II (HLA-DPA1, HLA-DPB1) and Class III (C2) genes were associated (p < 0.001) with skin response to tested irritants in different genetic models. Linkage disequilibrium patterns and functional annotations identified two SNPs in the TRIM40 (rs1573298) and HLA-DPB1 (rs9277554) genes, with a potential impact on gene regulation. In addition, SNPs in PSMB9 (rs10046277 and ITPR3 (rs499384) were associated with hand dermatitis. The results are of interest as they demonstrate that genetic variations in inflammation-related genes within the MHC can influence chemical-induced skin irritation and may explain the connection between inflamed skin and propensity to subsequent allergic contact sensitization.

Contact dermatitis in the construction industry: the role of filaggrin loss-of-function mutations.

BACKGROUND: A high prevalence of contact dermatitis (CD) and respiratory symptoms has been observed in the construction industry, probably due to widespread exposure to irritants and allergens. It is unknown whether carriers of loss-of-function mutations in the gene encoding filaggrin (FLG), a known risk gene for eczema and asthma, are at increased risk. OBJECTIVES: To investigate associations of FLG mutations with CD and respiratory symptoms in Dutch construction workers. METHODS: A questionnaire including items on dermal and respiratory symptoms such as wheeze, shortness of breath and asthma was administered to construction workers. Total and specific serum IgE was analysed by enzyme immunoassays. Four FLG loss-of-function mutations were genotyped. CD was diagnosed by a team of a dermatologist and a clinical occupational medicine specialist using photographs of the subjects' hands and self-reported questionnaire data. RESULTS: Of the 506 participating workers, 6·3% carried at least one FLG mutation. Mild CD was diagnosed by the specialists in 34·0%, and severe CD in an additional 24·3%. CD was considered work related in 282 of 295 subjects (95·6%). Carriers of FLG variants had an increased risk of CD compared with subjects carrying wild-type alleles [mild CD: odds ratio (OR) 5·71, 95% confidence interval (CI) 1·63-20·06; severe CD: OR 8·26, 95% CI 2·32-29·39]. FLG variants and the presence of CD were not associated with respiratory symptoms and atopy. CONCLUSIONS: Contact dermatitis prevalence in construction workers is high. FLG loss-of-function mutations increase the risk of CD even further. FLG mutations were not associated with respiratory symptoms or atopy.

Decrease of serum adenine nucleotide hydrolysis in an irritant contact dermatitis mice model: potential P2X7R involvement.

Extracellular adenosine 5'-triphosphate (ATP) has significant effects on a variety of pathological conditions and it is the main physiological agonist of P2X7 purinergic receptor (P2X7R). It is known that ATP acting via purinergic receptors plays a relevant role on skin inflammation, and P2X7R is required to neutrophil recruitment in a mice model of irritant contact dermatitis (ICD).The present study investigated the effects of chemical irritant croton oil (CrO) upon ATP, ADP, and AMP hydrolysis in mice blood serum, and the potential involvement of P2X7R. The topical application CrO induced a decrease on soluble ATP/ADPase activities (~50 %), and the treatment with the selective P2X7R antagonist, A438079, reversed these effects to control level. Furthermore, we showed that CrO decreased cellular viability (52.6 % ± 3.9) in relation to the control and caused necrosis in keratinocytes (PI positive cells). The necrosis induced by CrO was prevented by the pre-treatment with the selective P2X7R antagonist A438079. The results presented herein suggest that CrO exerts an inhibitory effect on the activity of ATPDase in mouse serum, reinforcing the idea that ICD has a pathogenic mechanism dependent of CD39. Furthermore, it is tempting to suggest that P2X7R may act as a controller of the extracellular levels of ATP.

Skin reaction and regeneration after single sodium lauryl sulfate exposure stratified by filaggrin genotype and atopic dermatitis phenotype.

BACKGROUND: Filaggrin is key for the integrity of the stratum corneum. Mutations in the filaggrin gene (FLGnull) play a prominent role in atopic dermatitis (AD) pathogenesis. People with AD have increased susceptibility to irritants. However, little is known about the effect of filaggrin genotype and AD phenotype on irritant response and skin regeneration. OBJECTIVES: To investigate the role of FLGnull and AD groups for skin reaction and recovery after sodium lauryl sulfate (SLS) irritation. METHODS: This is a case-control study comprising 67 subjects, including healthy controls and patients with and without FLGnull and AD. Reactivity to different doses of SLS at 24, 48, 72 and 145 h after SLS application was measured by transepidermal water loss (TEWL) and laser Doppler flowmetry (LDF). Reactivity was assessed univariately and by pattern analysis. RESULTS: All patient groups showed a higher degree of skin-barrier disruption and inflammation than did controls in response to SLS. Assessing reactivity by the delta value of the area under the curve for both TEWL and LDF showed significant differences between healthy controls and those with the AD phenotype, irrespective of filaggrin mutation. The poorest regeneration was among those with the AD phenotype. The two AD phenotype groups were separated by multivariate technique, due to earlier inflammatory reactivity among subjects with FLGnullplus AD compared with the AD phenotype alone. CONCLUSIONS: Both skin reaction and regeneration were significantly different between the patient population and the healthy controls. Additionally, response severity and regeneration depended more on AD phenotype than on filaggrin genotype, whereas the response was more rapid among the FLGnullplus AD individuals.

Filaggrin loss-of-function mutations are not associated with atopic dermatitis that develops in late childhood or adulthood.

BACKGROUND: The influence of filaggrin gene (FLG) mutations on early- vs. late-onset development of atopic dermatitis (AD), allergic contact dermatitis (ACD) and chronic irritant contact dermatitis (CICD) is not completely understood. OBJECTIVES: To assess the association between FLG mutations and development of AD, ACD and CICD. METHODS: This study assessed 241 patients with AD. AD developed during infancy in 85 patients, during childhood in 79 patients (32 early and 47 late) and during adulthood in 77 patients. We also included 100 patients with ACD and 44 with CICD, as well as 164 healthy controls. Four prevalent FLG loss-of-function mutations were genotyped (R501X, 2282del4, R2447X and S3247X). RESULTS: The 2282del4 mutation was significantly associated with a greater risk of AD in the entire group [odds ratio (OR) 4·33, 95% confidence interval (CI) 1·26-14·96]. However, the 2282del4 mutation was associated only with AD that developed during infancy or in early childhood (≤ 8 years: OR 20·91, 95% CI 2·73-159·9), not with AD development in late childhood or adulthood (> 8 or > 18 years), or ACD or CICD. Similar associations were also observed for the combined 2282del4 or R501X genotype. Carriers of FLG mutations also experienced a longer duration of AD and required hospitalization more often. CONCLUSIONS: FLG mutations are associated with only the early onset of AD, not late onset. Other factors should receive attention in patients with late-onset AD.

Filaggrin loss-of-function mutations and atopic dermatitis as risk factors for hand eczema in apprentice nurses: part II of a prospective cohort study.

BACKGROUND/OBJECTIVES: Environmental exposure and personal susceptibility both contribute to the development of hand eczema. In this study, we investigated the effect of loss-of-function mutations in the filaggrin gene (FLG), atopic dermatitis and wet work exposure on the development of hand eczema in apprentice nurses. METHODS: Dutch apprentice nurses were genotyped for the four most common FLG mutations; atopic dermatitis and hand eczema history were assessed by questionnaire. Exposure and hand eczema during traineeships were assessed with diary cards. RESULTS: The prevalence of hand eczema during traineeships was higher among subjects with a history of hand eczema reported at inclusion. Hand washing during traineeships and at home increased the risk of hand eczema. After adjustment for the effects of exposure and FLG mutations, an odds ratio of 2.5 (90% confidence interval 1.7-3.7) was found for a history of atopic dermatitis. In this study, an increased risk of hand eczema conferred by FLG mutations could not be shown, but subjects with concomitant FLG mutations and atopic dermatitis showed the highest risk of hand eczema during traineeships. CONCLUSION: A history of atopic dermatitis, a history of hand eczema and wet work exposure were the most important factors increasing the risk of hand eczema during traineeships.

Carriers of filaggrin gene (FLG) mutations avoid professional exposure to irritants in adulthood.

BACKGROUND: Loss-of-function mutations in the filaggrin gene (FLG) are associated with xerosis, atopic dermatitis, and early onset of hand eczema. Irritant exposure is a risk factor for occupational hand eczema, and FLG mutations increase the risk of occupational irritant contact dermatitis on the hands in hospital cohorts. It is unknown whether FLG mutations affect the level of irritant exposure. OBJECTIVES: To evaluate whether exposure to occupational irritants was dependent on FLG mutations, atopic dermatitis, and age at hand eczema onset. METHODS: Randomly chosen Danish adults completed a questionnaire on general health and occupational exposures. Genotyping for FLG mutations (R501X, 2282del4, and R2447X) and patch testing were performed. RESULTS: Overall, 38.7% of subjects reported present or previous occupational exposure to irritants. Among individuals who reported hand eczema onset before entering their work life, 50.6% (45/89) of FLG non-mutation carriers became exposed to irritants, as compared with 28.6% (4/14) of heterozygous and 0% (0/6) of homozygous mutation carriers (p = 0.006). Avoidance was conspicuous among mutation carriers reporting childhood hand eczema and atopic dermatitis (odds ratio 0.08, 95% confidence interval 0.01-0.65). CONCLUSIONS: Carriers of FLG mutations who have had hand eczema onset in childhood avoid occupational exposure to irritants; the association is most marked with homozygous mutation status combined with atopic dermatitis.

Genotype-phenotype associations in filaggrin loss-of-function mutation carriers.

BACKGROUND: Loss-of-function mutations in the filaggrin gene (FLG) have been reported to be associated with specific phenotypic characteristics such as hyperlinearity and keratosis pilaris. OBJECTIVES: To study phenotypic features in patients with occupational irritant contact eczema of the hands in relation to FLG loss-of-function mutations. MATERIALS AND METHODS: In a prospective cohort study, genotype was determined for 459 study subjects for four FLG null alleles, and investigated for selected history, clinical and laboratory features. RESULTS: Overall, 68 patients showed a mutation in the FLG alleles R501X, R2447X, S3247X, and/or 2282del4. Flexural eczema, xerosis cutis, pityriasis alba, dirty neck, pulpitis sicca, hyperlinear palms, keratosis pilaris and family history of eczema were positively associated with FLG mutations (p < 0.05). Although we observed a statistically significant correlation with higher serum IgE in FLG mutation carriers, allergic rhinoconjunctivitis and allergic asthma were not over-represented in this group. CONCLUSION: This study shows further genotype-phenotype correlations in patients with occupational irritant contact eczema and FLG mutation carrier status. These features may help to identify those with FLG mutations on a specific phenotype basis.

Filaggrin mutations are strongly associated with contact sensitization in individuals with dermatitis.

BACKGROUND: Although heterozygous filaggrin gene (FLG) mutation carriers seem to have an increased risk of atopic, irritant and allergic nickel dermatitis, it remains unclear whether the risk of contact sensitization to allergens other than nickel is also elevated in FLG mutation carriers. OBJECTIVES: We hypothesized that heterozygous FLG mutation carriers who suffer from dermatitis will have strongly reduced or even absent filaggrin levels during episodes of inflammation, potentially increasing the penetration of contact allergens, and hence the risk of becoming sensitized. MATERIALS AND METHODS: During 2006-2008, 3335 randomly invited 18-69-year-old adult Danes participated in a general health examination, filled out a questionnaire, and were genotyped for the R501X and 2282del4 mutations in FLG. RESULTS: A logistic regression analysis restricted to individuals who reported atopic dermatitis and frequent episodes of hand eczema showed a strong association between FLG mutations and contact sensitization to allergens other than nickel (odds ratio 5.71; 95% confidence interval 1.31-24.94). In participants without dermatitis, no association was found between contact sensitization and FLG mutations. CONCLUSION: FLG mutation carriers with self-reported dermatitis have an increased risk of contact sensitization to substances other than nickel, whereas FLG mutations alone may not, or may only slightly, increase the risk of sensitization.

Impact of atopic dermatitis and loss-of-function mutations in the filaggrin gene on the development of occupational irritant contact dermatitis.

BACKGROUND: Atopic dermatitis (AD) and loss-of-function mutations in the filaggrin gene (FLG) are both associated with chronic irritant contact dermatitis (ICD). As FLG mutations also are a major risk factor for AD, it is not clear whether FLG mutations are an independent risk factor for ICD or whether the risk is mediated by AD. OBJECTIVES: To investigate the relative contribution and interaction of FLG mutations and AD in German patients with occupational ICD and controls (vocational school apprentices). METHODS: A total of 634 patients and 393 controls were genotyped for R501X, 2282del4, R2447X and S3247X. Current or past flexural eczema was used as an indicator of AD. RESULTS: FLG mutations were found in 15·9% of the patients with ICD and 8·3% of the controls, with a crude odds ratio (OR) of 2·09 [95% confidence interval (CI) 1·33-3·28] for the combined genotype. The adjusted OR for FLG mutations, corrected for AD, was 1·62 (95% CI 1·01-2·58). Subjects with AD were at approximately three times higher risk of developing ICD than controls (OR 2·89; 95% CI 2·09-3·99). There was no evidence of an interaction between these two risk factors. CONCLUSIONS: Our results indicate that both FLG mutations and AD increase the risk of ICD. Individuals with concurrent FLG mutations and AD are at the highest risk of developing ICD.